Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Pull RCU changes from Paul E. McKenney: - Dynticks updates, consolidating open-coded counter accesses into a well-defined API - SRCU updates: Simplify algorithm, add formal verification - Documentation updates - Miscellaneous fixes - Torture-test updates Signed-off-by: Ingo Molnar <mingo@kernel.org>
author: Ingo Molnar <mingo@kernel.org> 2017-01-31 01:45:42 -0500
committer: Ingo Molnar <mingo@kernel.org> 2017-01-31 01:45:42 -0500
commit: a8709fa4a06d4af5f86e3660839531cbe0f2a19b (patch)
tree: 4deb2947a93294e4771265a60c508598a98cb494
parent: f9a42e0d58cf0fe3d902e63d4582f2ea4cd2bb8b (diff)
parent: 31945aa9f14085c81cb3257e51bb210698b78626 (diff)
88 files changed, 7150 insertions, 300 deletions
diff --git a/Documentation/RCU/Design/Data-Structures/Data-Structures.html b/Documentation/RCU/Design/Data-Structures/Data-Structures.html
index 7eb47ac25ad7..d583c653a703 100644
--- a/Documentation/RCU/Design/Data-Structures/Data-Structures.html
+++ b/Documentation/RCU/Design/Data-Structures/Data-Structures.html
@@ -4,7 +4,7 @@
        <head><title>A Tour Through TREE_RCU's Data Structures [LWN.net]</title>
        <meta HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
-           <p>January 27, 2016</p>
+           <p>December 18, 2016</p>
           <p>This article was contributed by Paul E.&nbsp;McKenney</p>
 <h3>Introduction</h3>
@@ -31,9 +31,6 @@ to each other.
        Accessor Functions</a>
 </ol>
-At the end we have the
-<a href="#Answers to Quick Quizzes">answers to the quick quizzes</a>.
 <h3><a name="Data-Structure Relationships">Data-Structure Relationships</a></h3>
 <p>RCU is for all intents and purposes a large state machine, and its
diff --git a/Documentation/RCU/Design/Expedited-Grace-Periods/ExpRCUFlow.svg b/Documentation/RCU/Design/Expedited-Grace-Periods/ExpRCUFlow.svg
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diff --git a/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html b/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html
new file mode 100644
index 000000000000..7a3194c5559a
--- /dev/null
+++ b/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html
@@ -0,0 +1,626 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
+        "http://www.w3.org/TR/html4/loose.dtd">
+        <html>
+        <head><title>A Tour Through TREE_RCU's Expedited Grace Periods</title>
+        <meta HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
+<h2>Introduction</h2>
+This document describes RCU's expedited grace periods.
+Unlike RCU's normal grace periods, which accept long latencies to attain
+high efficiency and minimal disturbance, expedited grace periods accept
+lower efficiency and significant disturbance to attain shorter latencies.
+<p>
+There are three flavors of RCU (RCU-bh, RCU-preempt, and RCU-sched),
+but only two flavors of expedited grace periods because the RCU-bh
+expedited grace period maps onto the RCU-sched expedited grace period.
+Each of the remaining two implementations is covered in its own section.
+<ol>
+<li>    <a href="#Expedited Grace Period Design">
+        Expedited Grace Period Design</a>
+<li>    <a href="#RCU-preempt Expedited Grace Periods">
+        RCU-preempt Expedited Grace Periods</a>
+<li>    <a href="#RCU-sched Expedited Grace Periods">
+        RCU-sched Expedited Grace Periods</a>
+<li>    <a href="#Expedited Grace Period and CPU Hotplug">
+        Expedited Grace Period and CPU Hotplug</a>
+<li>    <a href="#Expedited Grace Period Refinements">
+        Expedited Grace Period Refinements</a>
+</ol>
+<h2><a name="Expedited Grace Period Design">
+Expedited Grace Period Design</a></h2>
+<p>
+The expedited RCU grace periods cannot be accused of being subtle,
+given that they for all intents and purposes hammer every CPU that
+has not yet provided a quiescent state for the current expedited
+grace period.
+The one saving grace is that the hammer has grown a bit smaller
+over time:  The old call to <tt>try_stop_cpus()</tt> has been
+replaced with a set of calls to <tt>smp_call_function_single()</tt>,
+each of which results in an IPI to the target CPU.
+The corresponding handler function checks the CPU's state, motivating
+a faster quiescent state where possible, and triggering a report
+of that quiescent state.
+As always for RCU, once everything has spent some time in a quiescent
+state, the expedited grace period has completed.
+<p>
+The details of the <tt>smp_call_function_single()</tt> handler's
+operation depend on the RCU flavor, as described in the following
+sections.
+<h2><a name="RCU-preempt Expedited Grace Periods">
+RCU-preempt Expedited Grace Periods</a></h2>
+<p>
+The overall flow of the handling of a given CPU by an RCU-preempt
+expedited grace period is shown in the following diagram:
+<p><img src="ExpRCUFlow.svg" alt="ExpRCUFlow.svg" width="55%">
+<p>
+The solid arrows denote direct action, for example, a function call.
+The dotted arrows denote indirect action, for example, an IPI
+or a state that is reached after some time.
+<p>
+If a given CPU is offline or idle, <tt>synchronize_rcu_expedited()</tt>
+will ignore it because idle and offline CPUs are already residing
+in quiescent states.
+Otherwise, the expedited grace period will use
+<tt>smp_call_function_single()</tt> to send the CPU an IPI, which
+is handled by <tt>sync_rcu_exp_handler()</tt>.
+<p>
+However, because this is preemptible RCU, <tt>sync_rcu_exp_handler()</tt>
+can check to see if the CPU is currently running in an RCU read-side
+critical section.
+If not, the handler can immediately report a quiescent state.
+Otherwise, it sets flags so that the outermost <tt>rcu_read_unlock()</tt>
+invocation will provide the needed quiescent-state report.
+This flag-setting avoids the previous forced preemption of all
+CPUs that might have RCU read-side critical sections.
+In addition, this flag-setting is done so as to avoid increasing
+the overhead of the common-case fastpath through the scheduler.
+<p>
+Again because this is preemptible RCU, an RCU read-side critical section
+can be preempted.
+When that happens, RCU will enqueue the task, which will the continue to
+block the current expedited grace period until it resumes and finds its
+outermost <tt>rcu_read_unlock()</tt>.
+The CPU will report a quiescent state just after enqueuing the task because
+the CPU is no longer blocking the grace period.
+It is instead the preempted task doing the blocking.
+The list of blocked tasks is managed by <tt>rcu_preempt_ctxt_queue()</tt>,
+which is called from <tt>rcu_preempt_note_context_switch()</tt>, which
+in turn is called from <tt>rcu_note_context_switch()</tt>, which in
+turn is called from the scheduler.
+<table>
+<tr><th>&nbsp;</th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+        Why not just have the expedited grace period check the
+        state of all the CPUs?
+        After all, that would avoid all those real-time-unfriendly IPIs.
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+        Because we want the RCU read-side critical sections to run fast,
+        which means no memory barriers.
+        Therefore, it is not possible to safely check the state from some
+        other CPU.
+        And even if it was possible to safely check the state, it would
+        still be necessary to IPI the CPU to safely interact with the
+        upcoming <tt>rcu_read_unlock()</tt> invocation, which means that
+        the remote state testing would not help the worst-case
+        latency that real-time applications care about.
+        <p><font color="ffffff">One way to prevent your real-time
+        application from getting hit with these IPIs is to
+        build your kernel with <tt>CONFIG_NO_HZ_FULL=y</tt>.
+        RCU would then perceive the CPU running your application
+        as being idle, and it would be able to safely detect that
+        state without needing to IPI the CPU.
+</font></td></tr>
+<tr><td>&nbsp;</td></tr>
+</table>
+<p>
+Please note that this is just the overall flow:
+Additional complications can arise due to races with CPUs going idle
+or offline, among other things.
+<h2><a name="RCU-sched Expedited Grace Periods">
+RCU-sched Expedited Grace Periods</a></h2>
+<p>
+The overall flow of the handling of a given CPU by an RCU-sched
+expedited grace period is shown in the following diagram:
+<p><img src="ExpSchedFlow.svg" alt="ExpSchedFlow.svg" width="55%">
+<p>
+As with RCU-preempt's <tt>synchronize_rcu_expedited()</tt>,
+<tt>synchronize_sched_expedited()</tt> ignores offline and
+idle CPUs, again because they are in remotely detectable
+quiescent states.
+However, the <tt>synchronize_rcu_expedited()</tt> handler
+is <tt>sync_sched_exp_handler()</tt>, and because the
+<tt>rcu_read_lock_sched()</tt> and <tt>rcu_read_unlock_sched()</tt>
+leave no trace of their invocation, in general it is not possible to tell
+whether or not the current CPU is in an RCU read-side critical section.
+The best that <tt>sync_sched_exp_handler()</tt> can do is to check
+for idle, on the off-chance that the CPU went idle while the IPI
+was in flight.
+If the CPU is idle, then tt>sync_sched_exp_handler()</tt> reports
+the quiescent state.
+<p>
+Otherwise, the handler invokes <tt>resched_cpu()</tt>, which forces
+a future context switch.
+At the time of the context switch, the CPU reports the quiescent state.
+Should the CPU go offline first, it will report the quiescent state
+at that time.
+<h2><a name="Expedited Grace Period and CPU Hotplug">
+Expedited Grace Period and CPU Hotplug</a></h2>
+<p>
+The expedited nature of expedited grace periods require a much tighter
+interaction with CPU hotplug operations than is required for normal
+grace periods.
+In addition, attempting to IPI offline CPUs will result in splats, but
+failing to IPI online CPUs can result in too-short grace periods.
+Neither option is acceptable in production kernels.
+<p>
+The interaction between expedited grace periods and CPU hotplug operations
+is carried out at several levels:
+<ol>
+<li>    The number of CPUs that have ever been online is tracked
+        by the <tt>rcu_state</tt> structure's <tt>-&gt;ncpus</tt>
+        field.
+        The <tt>rcu_state</tt> structure's <tt>-&gt;ncpus_snap</tt>
+        field tracks the number of CPUs that have ever been online
+        at the beginning of an RCU expedited grace period.
+        Note that this number never decreases, at least in the absence
+        of a time machine.
+<li>    The identities of the CPUs that have ever been online is
+        tracked by the <tt>rcu_node</tt> structure's
+        <tt>-&gt;expmaskinitnext</tt> field.
+        The <tt>rcu_node</tt> structure's <tt>-&gt;expmaskinit</tt>
+        field tracks the identities of the CPUs that were online
+        at least once at the beginning of the most recent RCU
+        expedited grace period.
+        The <tt>rcu_state</tt> structure's <tt>-&gt;ncpus</tt> and
+        <tt>-&gt;ncpus_snap</tt> fields are used to detect when
+        new CPUs have come online for the first time, that is,
+        when the <tt>rcu_node</tt> structure's <tt>-&gt;expmaskinitnext</tt>
+        field has changed since the beginning of the last RCU
+        expedited grace period, which triggers an update of each
+        <tt>rcu_node</tt> structure's <tt>-&gt;expmaskinit</tt>
+        field from its <tt>-&gt;expmaskinitnext</tt> field.
+<li>    Each <tt>rcu_node</tt> structure's <tt>-&gt;expmaskinit</tt>
+        field is used to initialize that structure's
+        <tt>-&gt;expmask</tt> at the beginning of each RCU
+        expedited grace period.
+        This means that only those CPUs that have been online at least
+        once will be considered for a given grace period.
+<li>    Any CPU that goes offline will clear its bit in its leaf
+        <tt>rcu_node</tt> structure's <tt>-&gt;qsmaskinitnext</tt>
+        field, so any CPU with that bit clear can safely be ignored.
+        However, it is possible for a CPU coming online or going offline
+        to have this bit set for some time while <tt>cpu_online</tt>
+        returns <tt>false</tt>.
+<li>    For each non-idle CPU that RCU believes is currently online, the grace
+        period invokes <tt>smp_call_function_single()</tt>.
+        If this succeeds, the CPU was fully online.
+        Failure indicates that the CPU is in the process of coming online
+        or going offline, in which case it is necessary to wait for a
+        short time period and try again.
+        The purpose of this wait (or series of waits, as the case may be)
+        is to permit a concurrent CPU-hotplug operation to complete.
+<li>    In the case of RCU-sched, one of the last acts of an outgoing CPU
+        is to invoke <tt>rcu_report_dead()</tt>, which
+        reports a quiescent state for that CPU.
+        However, this is likely paranoia-induced redundancy. <!-- @@@ -->
+</ol>
+<table>
+<tr><th>&nbsp;</th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+        Why all the dancing around with multiple counters and masks
+        tracking CPUs that were once online?
+        Why not just have a single set of masks tracking the currently
+        online CPUs and be done with it?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+        Maintaining single set of masks tracking the online CPUs <i>sounds</i>
+        easier, at least until you try working out all the race conditions
+        between grace-period initialization and CPU-hotplug operations.
+        For example, suppose initialization is progressing down the
+        tree while a CPU-offline operation is progressing up the tree.
+        This situation can result in bits set at the top of the tree
+        that have no counterparts at the bottom of the tree.
+        Those bits will never be cleared, which will result in
+        grace-period hangs.
+        In short, that way lies madness, to say nothing of a great many
+        bugs, hangs, and deadlocks.
+        <p><font color="ffffff">
+        In contrast, the current multi-mask multi-counter scheme ensures
+        that grace-period initialization will always see consistent masks
+        up and down the tree, which brings significant simplifications
+        over the single-mask method.
+        <p><font color="ffffff">
+        This is an instance of
+        <a href="http://www.cs.columbia.edu/~library/TR-repository/reports/reports-1992/cucs-039-92.ps.gz"><font color="ffffff">
+        deferring work in order to avoid synchronization</a>.
+        Lazily recording CPU-hotplug events at the beginning of the next
+        grace period greatly simplifies maintenance of the CPU-tracking
+        bitmasks in the <tt>rcu_node</tt> tree.
+</font></td></tr>
+<tr><td>&nbsp;</td></tr>
+</table>
+<h2><a name="Expedited Grace Period Refinements">
+Expedited Grace Period Refinements</a></h2>
+<ol>
+<li>    <a href="#Idle-CPU Checks">Idle-CPU checks</a>.
+<li>    <a href="#Batching via Sequence Counter">
+        Batching via sequence counter</a>.
+<li>    <a href="#Funnel Locking and Wait/Wakeup">
+        Funnel locking and wait/wakeup</a>.
+<li>    <a href="#Use of Workqueues">Use of Workqueues</a>.
+<li>    <a href="#Stall Warnings">Stall warnings</a>.
+</ol>
+<h3><a name="Idle-CPU Checks">Idle-CPU Checks</a></h3>
+<p>
+Each expedited grace period checks for idle CPUs when initially forming
+the mask of CPUs to be IPIed and again just before IPIing a CPU
+(both checks are carried out by <tt>sync_rcu_exp_select_cpus()</tt>).
+If the CPU is idle at any time between those two times, the CPU will
+not be IPIed.
+Instead, the task pushing the grace period forward will include the
+idle CPUs in the mask passed to <tt>rcu_report_exp_cpu_mult()</tt>.
+<p>
+For RCU-sched, there is an additional check for idle in the IPI
+handler, <tt>sync_sched_exp_handler()</tt>.
+If the IPI has interrupted the idle loop, then
+<tt>sync_sched_exp_handler()</tt> invokes <tt>rcu_report_exp_rdp()</tt>
+to report the corresponding quiescent state.
+<p>
+For RCU-preempt, there is no specific check for idle in the
+IPI handler (<tt>sync_rcu_exp_handler()</tt>), but because
+RCU read-side critical sections are not permitted within the
+idle loop, if <tt>sync_rcu_exp_handler()</tt> sees that the CPU is within
+RCU read-side critical section, the CPU cannot possibly be idle.
+Otherwise, <tt>sync_rcu_exp_handler()</tt> invokes
+<tt>rcu_report_exp_rdp()</tt> to report the corresponding quiescent
+state, regardless of whether or not that quiescent state was due to
+the CPU being idle.
+<p>
+In summary, RCU expedited grace periods check for idle when building
+the bitmask of CPUs that must be IPIed, just before sending each IPI,
+and (either explicitly or implicitly) within the IPI handler.
+<h3><a name="Batching via Sequence Counter">
+Batching via Sequence Counter</a></h3>
+<p>
+If each grace-period request was carried out separately, expedited
+grace periods would have abysmal scalability and
+problematic high-load characteristics.
+Because each grace-period operation can serve an unlimited number of
+updates, it is important to <i>batch</i> requests, so that a single
+expedited grace-period operation will cover all requests in the
+corresponding batch.
+<p>
+This batching is controlled by a sequence counter named
+<tt>-&gt;expedited_sequence</tt> in the <tt>rcu_state</tt> structure.
+This counter has an odd value when there is an expedited grace period
+in progress and an even value otherwise, so that dividing the counter
+value by two gives the number of completed grace periods.
+During any given update request, the counter must transition from
+even to odd and then back to even, thus indicating that a grace
+period has elapsed.
+Therefore, if the initial value of the counter is <tt>s</tt>,
+the updater must wait until the counter reaches at least the
+value <tt>(s+3)&amp;~0x1</tt>.
+This counter is managed by the following access functions:
+<ol>
+<li>    <tt>rcu_exp_gp_seq_start()</tt>, which marks the start of
+        an expedited grace period.
+<li>    <tt>rcu_exp_gp_seq_end()</tt>, which marks the end of an
+        expedited grace period.
+<li>    <tt>rcu_exp_gp_seq_snap()</tt>, which obtains a snapshot of
+        the counter.
+<li>    <tt>rcu_exp_gp_seq_done()</tt>, which returns <tt>true</tt>
+        if a full expedited grace period has elapsed since the
+        corresponding call to <tt>rcu_exp_gp_seq_snap()</tt>.
+</ol>
+<p>
+Again, only one request in a given batch need actually carry out
+a grace-period operation, which means there must be an efficient
+way to identify which of many concurrent reqeusts will initiate
+the grace period, and that there be an efficient way for the
+remaining requests to wait for that grace period to complete.
+However, that is the topic of the next section.
+<h3><a name="Funnel Locking and Wait/Wakeup">
+Funnel Locking and Wait/Wakeup</a></h3>
+<p>
+The natural way to sort out which of a batch of updaters will initiate
+the expedited grace period is to use the <tt>rcu_node</tt> combining
+tree, as implemented by the <tt>exp_funnel_lock()</tt> function.
+The first updater corresponding to a given grace period arriving
+at a given <tt>rcu_node</tt> structure records its desired grace-period
+sequence number in the <tt>-&gt;exp_seq_rq</tt> field and moves up
+to the next level in the tree.
+Otherwise, if the <tt>-&gt;exp_seq_rq</tt> field already contains
+the sequence number for the desired grace period or some later one,
+the updater blocks on one of four wait queues in the
+<tt>-&gt;exp_wq[]</tt> array, using the second-from-bottom
+and third-from bottom bits as an index.
+An <tt>-&gt;exp_lock</tt> field in the <tt>rcu_node</tt> structure
+synchronizes access to these fields.
+<p>
+An empty <tt>rcu_node</tt> tree is shown in the following diagram,
+with the white cells representing the <tt>-&gt;exp_seq_rq</tt> field
+and the red cells representing the elements of the
+<tt>-&gt;exp_wq[]</tt> array.
+<p><img src="Funnel0.svg" alt="Funnel0.svg" width="75%">
+<p>
+The next diagram shows the situation after the arrival of Task&nbsp;A
+and Task&nbsp;B at the leftmost and rightmost leaf <tt>rcu_node</tt>
+structures, respectively.
+The current value of the <tt>rcu_state</tt> structure's
+<tt>-&gt;expedited_sequence</tt> field is zero, so adding three and
+clearing the bottom bit results in the value two, which both tasks
+record in the <tt>-&gt;exp_seq_rq</tt> field of their respective
+<tt>rcu_node</tt> structures:
+<p><img src="Funnel1.svg" alt="Funnel1.svg" width="75%">
+<p>
+Each of Tasks&nbsp;A and&nbsp;B will move up to the root
+<tt>rcu_node</tt> structure.
+Suppose that Task&nbsp;A wins, recording its desired grace-period sequence
+number and resulting in the state shown below:
+<p><img src="Funnel2.svg" alt="Funnel2.svg" width="75%">
+<p>
+Task&nbsp;A now advances to initiate a new grace period, while Task&nbsp;B
+moves up to the root <tt>rcu_node</tt> structure, and, seeing that
+its desired sequence number is already recorded, blocks on
+<tt>-&gt;exp_wq[1]</tt>.
+<table>
+<tr><th>&nbsp;</th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+        Why <tt>-&gt;exp_wq[1]</tt>?
+        Given that the value of these tasks' desired sequence number is
+        two, so shouldn't they instead block on <tt>-&gt;exp_wq[2]</tt>?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+        No.
+        <p><font color="ffffff">
+        Recall that the bottom bit of the desired sequence number indicates
+        whether or not a grace period is currently in progress.
+        It is therefore necessary to shift the sequence number right one
+        bit position to obtain the number of the grace period.
+        This results in <tt>-&gt;exp_wq[1]</tt>.
+</font></td></tr>
+<tr><td>&nbsp;</td></tr>
+</table>
+<p>
+If Tasks&nbsp;C and&nbsp;D also arrive at this point, they will compute the
+same desired grace-period sequence number, and see that both leaf
+<tt>rcu_node</tt> structures already have that value recorded.
+They will therefore block on their respective <tt>rcu_node</tt>
+structures' <tt>-&gt;exp_wq[1]</tt> fields, as shown below:
+<p><img src="Funnel3.svg" alt="Funnel3.svg" width="75%">
+<p>
+Task&nbsp;A now acquires the <tt>rcu_state</tt> structure's
+<tt>-&gt;exp_mutex</tt> and initiates the grace period, which
+increments <tt>-&gt;expedited_sequence</tt>.
+Therefore, if Tasks&nbsp;E and&nbsp;F arrive, they will compute
+a desired sequence number of 4 and will record this value as
+shown below:
+<p><img src="Funnel4.svg" alt="Funnel4.svg" width="75%">
+<p>
+Tasks&nbsp;E and&nbsp;F will propagate up the <tt>rcu_node</tt>
+combining tree, with Task&nbsp;F blocking on the root <tt>rcu_node</tt>
+structure and Task&nbsp;E wait for Task&nbsp;A to finish so that
+it can start the next grace period.
+The resulting state is as shown below:
+<p><img src="Funnel5.svg" alt="Funnel5.svg" width="75%">
+<p>
+Once the grace period completes, Task&nbsp;A
+starts waking up the tasks waiting for this grace period to complete,
+increments the <tt>-&gt;expedited_sequence</tt>,
+acquires the <tt>-&gt;exp_wake_mutex</tt> and then releases the
+<tt>-&gt;exp_mutex</tt>.
+This results in the following state:
+<p><img src="Funnel6.svg" alt="Funnel6.svg" width="75%">
+<p>
+Task&nbsp;E can then acquire <tt>-&gt;exp_mutex</tt> and increment
+<tt>-&gt;expedited_sequence</tt> to the value three.
+If new tasks&nbsp;G and&nbsp;H arrive and moves up the combining tree at the
+same time, the state will be as follows:
+<p><img src="Funnel7.svg" alt="Funnel7.svg" width="75%">
+<p>
+Note that three of the root <tt>rcu_node</tt> structure's
+waitqueues are now occupied.
+However, at some point, Task&nbsp;A will wake up the
+tasks blocked on the <tt>-&gt;exp_wq</tt> waitqueues, resulting
+in the following state:
+<p><img src="Funnel8.svg" alt="Funnel8.svg" width="75%">
+<p>
+Execution will continue with Tasks&nbsp;E and&nbsp;H completing
+their grace periods and carrying out their wakeups.
+<table>
+<tr><th>&nbsp;</th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+        What happens if Task&nbsp;A takes so long to do its wakeups
+        that Task&nbsp;E's grace period completes?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+        Then Task&nbsp;E will block on the <tt>-&gt;exp_wake_mutex</tt>,
+        which will also prevent it from releasing <tt>-&gt;exp_mutex</tt>,
+        which in turn will prevent the next grace period from starting.
+        This last is important in preventing overflow of the
+        <tt>-&gt;exp_wq[]</tt> array.
+</font></td></tr>
+<tr><td>&nbsp;</td></tr>
+</table>
+<h3><a name="Use of Workqueues">Use of Workqueues</a></h3>
+<p>
+In earlier implementations, the task requesting the expedited
+grace period also drove it to completion.
+This straightforward approach had the disadvantage of needing to
+account for signals sent to user tasks,
+so more recent implemementations use the Linux kernel's
+<a href="https://www.kernel.org/doc/Documentation/workqueue.txt">workqueues</a>.
+<p>
+The requesting task still does counter snapshotting and funnel-lock
+processing, but the task reaching the top of the funnel lock
+does a <tt>schedule_work()</tt> (from <tt>_synchronize_rcu_expedited()</tt>
+so that a workqueue kthread does the actual grace-period processing.
+Because workqueue kthreads do not accept signals, grace-period-wait
+processing need not allow for signals.
+In addition, this approach allows wakeups for the previous expedited
+grace period to be overlapped with processing for the next expedited
+grace period.
+Because there are only four sets of waitqueues, it is necessary to
+ensure that the previous grace period's wakeups complete before the
+next grace period's wakeups start.
+This is handled by having the <tt>-&gt;exp_mutex</tt>
+guard expedited grace-period processing and the
+<tt>-&gt;exp_wake_mutex</tt> guard wakeups.
+The key point is that the <tt>-&gt;exp_mutex</tt> is not released
+until the first wakeup is complete, which means that the
+<tt>-&gt;exp_wake_mutex</tt> has already been acquired at that point.
+This approach ensures that the previous grace period's wakeups can
+be carried out while the current grace period is in process, but
+that these wakeups will complete before the next grace period starts.
+This means that only three waitqueues are required, guaranteeing that
+the four that are provided are sufficient.
+<h3><a name="Stall Warnings">Stall Warnings</a></h3>
+<p>
+Expediting grace periods does nothing to speed things up when RCU
+readers take too long, and therefore expedited grace periods check
+for stalls just as normal grace periods do.
+<table>
+<tr><th>&nbsp;</th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+        But why not just let the normal grace-period machinery
+        detect the stalls, given that a given reader must block
+        both normal and expedited grace periods?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+        Because it is quite possible that at a given time there
+        is no normal grace period in progress, in which case the
+        normal grace period cannot emit a stall warning.
+</font></td></tr>
+<tr><td>&nbsp;</td></tr>
+</table>
+The <tt>synchronize_sched_expedited_wait()</tt> function loops waiting
+for the expedited grace period to end, but with a timeout set to the
+current RCU CPU stall-warning time.
+If this time is exceeded, any CPUs or <tt>rcu_node</tt> structures
+blocking the current grace period are printed.
+Each stall warning results in another pass through the loop, but the
+second and subsequent passes use longer stall times.
+<h3><a name="Summary">
+Summary</a></h3>
+<p>
+Expedited grace periods use a sequence-number approach to promote
+batching, so that a single grace-period operation can serve numerous
+requests.
+A funnel lock is used to efficiently identify the one task out of
+a concurrent group that will request the grace period.
+All members of the group will block on waitqueues provided in
+the <tt>rcu_node</tt> structure.
+The actual grace-period processing is carried out by a workqueue.
+<p>
+CPU-hotplug operations are noted lazily in order to prevent the need
+for tight synchronization between expedited grace periods and
+CPU-hotplug operations.
+The dyntick-idle counters are used to avoid sending IPIs to idle CPUs,
+at least in the common case.
+RCU-preempt and RCU-sched use different IPI handlers and different
+code to respond to the state changes carried out by those handlers,
+but otherwise use common code.
+<p>
+Quiescent states are tracked using the <tt>rcu_node</tt> tree,
+and once all necessary quiescent states have been reported,
+all tasks waiting on this expedited grace period are awakened.
+A pair of mutexes are used to allow one grace period's wakeups
+to proceed concurrently with the next grace period's processing.
+<p>
+This combination of mechanisms allows expedited grace periods to
+run reasonably efficiently.
+However, for non-time-critical tasks, normal grace periods should be
+used instead because their longer duration permits much higher
+degrees of batching, and thus much lower per-request overheads.
+</body></html>
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diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html
index 39bcb74ea733..21593496aca6 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.html
+++ b/Documentation/RCU/Design/Requirements/Requirements.html
@@ -1480,7 +1480,7 @@ speed-of-light delays if nothing else.
 <p>
 Furthermore, uncertainty about external state is inherent in many cases.
-For example, a pair of veternarians might use heartbeat to determine
+For example, a pair of veterinarians might use heartbeat to determine
 whether or not a given cat was alive.
 But how long should they wait after the last heartbeat to decide that
 the cat is in fact dead?
@@ -1489,9 +1489,9 @@ mean that a relaxed cat would be considered to cycle between death
 and life more than 100 times per minute.
 Moreover, just as with human beings, a cat's heart might stop for
 some period of time, so the exact wait period is a judgment call.
-One of our pair of veternarians might wait 30 seconds before pronouncing
+One of our pair of veterinarians might wait 30 seconds before pronouncing
 the cat dead, while the other might insist on waiting a full minute.
-The two veternarians would then disagree on the state of the cat during
+The two veterinarians would then disagree on the state of the cat during
 the final 30 seconds of the minute following the last heartbeat.
 <p>
@@ -1945,7 +1945,7 @@ guard against mishaps and misuse:
 <ol>
 <li>    It is all too easy to forget to use <tt>rcu_read_lock()</tt>
        everywhere that it is needed, so kernels built with
-        <tt>CONFIG_PROVE_RCU=y</tt> will spat if
+        <tt>CONFIG_PROVE_RCU=y</tt> will splat if
        <tt>rcu_dereference()</tt> is used outside of an
        RCU read-side critical section.
        Update-side code can use <tt>rcu_dereference_protected()</tt>,
@@ -2421,7 +2421,7 @@ However, there are some restrictions on the code placed within
 <li>    Blocking is prohibited.
        In practice, this is not a serious restriction given that idle
        tasks are prohibited from blocking to begin with.
-<li>    Although nesting <tt>RCU_NONIDLE()</tt> is permited, they cannot
+<li>    Although nesting <tt>RCU_NONIDLE()</tt> is permitted, they cannot
        nest indefinitely deeply.
        However, given that they can be nested on the order of a million
        deep, even on 32-bit systems, this should not be a serious
@@ -2885,7 +2885,7 @@ APIs for defining and initializing <tt>srcu_struct</tt> structures.
 <h3><a name="Tasks RCU">Tasks RCU</a></h3>
 <p>
-Some forms of tracing use &ldquo;tramopolines&rdquo; to handle the
+Some forms of tracing use &ldquo;trampolines&rdquo; to handle the
 binary rewriting required to install different types of probes.
 It would be good to be able to free old trampolines, which sounds
 like a job for some form of RCU.
diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt
index 00a3a38b375a..6549012033f9 100644
--- a/Documentation/RCU/trace.txt
+++ b/Documentation/RCU/trace.txt
@@ -237,7 +237,7 @@ o	"ktl" is the low-order 16 bits (in hexadecimal) of the count of
 The output of "cat rcu/rcu_preempt/rcuexp" looks as follows:
-s=21872 wd1=0 wd2=0 wd3=5 n=0 enq=0 sc=21872
+s=21872 wd1=0 wd2=0 wd3=5 enq=0 sc=21872
 These fields are as follows:
@@ -249,9 +249,6 @@ o	"wd1", "wd2", and "wd3" are the number of times that an attempt
        completed an expedited grace period that satisfies the attempted
        request.  "Our work is done."
-o       "n" is number of times that a concurrent CPU-hotplug operation
-        forced a fallback to a normal grace period.
 o       "enq" is the number of quiescent states still outstanding.
 o       "sc" is the number of times that the attempt to start a
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index be7c0d9506b1..110745e7d61f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3278,6 +3278,13 @@
                        Lazy RCU callbacks are those which RCU can
                        prove do nothing more than free memory.
+        rcutree.rcu_kick_kthreads= [KNL]
+                        Cause the grace-period kthread to get an extra
+                        wake_up() if it sleeps three times longer than
+                        it should at force-quiescent-state time.
+                        This wake_up() will be accompanied by a
+                        WARN_ONCE() splat and an ftrace_dump().
        rcuperf.gp_exp= [KNL]
                        Measure performance of expedited synchronous
                        grace-period primitives.
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index ba818ecce6f9..d2b0a8d81258 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -640,6 +640,10 @@ See also the subsection on "Cache Coherency" for a more thorough example.
 CONTROL DEPENDENCIES
 --------------------
+Control dependencies can be a bit tricky because current compilers do
+not understand them.  The purpose of this section is to help you prevent
+the compiler's ignorance from breaking your code.
 A load-load control dependency requires a full read memory barrier, not
 simply a data dependency barrier to make it work correctly.  Consider the
 following bit of code:
@@ -667,14 +671,15 @@ for load-store control dependencies, as in the following example:
        q = READ_ONCE(a);
        if (q) {
-                WRITE_ONCE(b, p);
+                WRITE_ONCE(b, 1);
        }
-Control dependencies pair normally with other types of barriers.  That
+Control dependencies pair normally with other types of barriers.
-said, please note that READ_ONCE() is not optional! Without the
+That said, please note that neither READ_ONCE() nor WRITE_ONCE()
-READ_ONCE(), the compiler might combine the load from 'a' with other
+are optional! Without the READ_ONCE(), the compiler might combine the
-loads from 'a', and the store to 'b' with other stores to 'b', with
+load from 'a' with other loads from 'a'.  Without the WRITE_ONCE(),
-possible highly counterintuitive effects on ordering.
+the compiler might combine the store to 'b' with other stores to 'b'.
+Either can result in highly counterintuitive effects on ordering.
 Worse yet, if the compiler is able to prove (say) that the value of
 variable 'a' is always non-zero, it would be well within its rights
@@ -682,7 +687,7 @@ to optimize the original example by eliminating the "if" statement
 as follows:
        q = a;
-        b = p;  /* BUG: Compiler and CPU can both reorder!!! */
+        b = 1;  /* BUG: Compiler and CPU can both reorder!!! */
 So don't leave out the READ_ONCE().
@@ -692,11 +697,11 @@ branches of the "if" statement as follows:
        q = READ_ONCE(a);
        if (q) {
                barrier();
-                WRITE_ONCE(b, p);
+                WRITE_ONCE(b, 1);
                do_something();
        } else {
                barrier();
-                WRITE_ONCE(b, p);
+                WRITE_ONCE(b, 1);
                do_something_else();
        }
@@ -705,12 +710,12 @@ optimization levels:
        q = READ_ONCE(a);
        barrier();
-        WRITE_ONCE(b, p);  /* BUG: No ordering vs. load from a!!! */
+        WRITE_ONCE(b, 1);  /* BUG: No ordering vs. load from a!!! */
        if (q) {
-                /* WRITE_ONCE(b, p); -- moved up, BUG!!! */
+                /* WRITE_ONCE(b, 1); -- moved up, BUG!!! */
                do_something();
        } else {
-                /* WRITE_ONCE(b, p); -- moved up, BUG!!! */
+                /* WRITE_ONCE(b, 1); -- moved up, BUG!!! */
                do_something_else();
        }
@@ -723,10 +728,10 @@ memory barriers, for example, smp_store_release():
        q = READ_ONCE(a);
        if (q) {
-                smp_store_release(&b, p);
+                smp_store_release(&b, 1);
                do_something();
        } else {
-                smp_store_release(&b, p);
+                smp_store_release(&b, 1);
                do_something_else();
        }
@@ -735,10 +740,10 @@ ordering is guaranteed only when the stores differ, for example:
        q = READ_ONCE(a);
        if (q) {
-                WRITE_ONCE(b, p);
+                WRITE_ONCE(b, 1);
                do_something();
        } else {
-                WRITE_ONCE(b, r);
+                WRITE_ONCE(b, 2);
                do_something_else();
        }
@@ -751,10 +756,10 @@ the needed conditional.  For example:
        q = READ_ONCE(a);
        if (q % MAX) {
-                WRITE_ONCE(b, p);
+                WRITE_ONCE(b, 1);
                do_something();
        } else {
-                WRITE_ONCE(b, r);
+                WRITE_ONCE(b, 2);
                do_something_else();
        }
@@ -763,7 +768,7 @@ equal to zero, in which case the compiler is within its rights to
 transform the above code into the following:
        q = READ_ONCE(a);
-        WRITE_ONCE(b, p);
+        WRITE_ONCE(b, 1);
        do_something_else();
 Given this transformation, the CPU is not required to respect the ordering
@@ -776,10 +781,10 @@ one, perhaps as follows:
        q = READ_ONCE(a);
        BUILD_BUG_ON(MAX <= 1); /* Order load from a with store to b. */
        if (q % MAX) {
-                WRITE_ONCE(b, p);
+                WRITE_ONCE(b, 1);
                do_something();
        } else {
-                WRITE_ONCE(b, r);
+                WRITE_ONCE(b, 2);
                do_something_else();
        }
@@ -812,30 +817,28 @@ not necessarily apply to code following the if-statement:
        q = READ_ONCE(a);
        if (q) {
-                WRITE_ONCE(b, p);
+                WRITE_ONCE(b, 1);
        } else {
-                WRITE_ONCE(b, r);
+                WRITE_ONCE(b, 2);
        }
-        WRITE_ONCE(c, 1);  /* BUG: No ordering against the read from "a". */
+        WRITE_ONCE(c, 1);  /* BUG: No ordering against the read from 'a'. */
 It is tempting to argue that there in fact is ordering because the
 compiler cannot reorder volatile accesses and also cannot reorder
-the writes to "b" with the condition.  Unfortunately for this line
+the writes to 'b' with the condition.  Unfortunately for this line
-of reasoning, the compiler might compile the two writes to "b" as
+of reasoning, the compiler might compile the two writes to 'b' as
 conditional-move instructions, as in this fanciful pseudo-assembly
 language:
        ld r1,a
-        ld r2,p
-        ld r3,r
        cmp r1,$0
-        cmov,ne r4,r2
+        cmov,ne r4,$1
-        cmov,eq r4,r3
+        cmov,eq r4,$2
        st r4,b
        st $1,c
 A weakly ordered CPU would have no dependency of any sort between the load
-from "a" and the store to "c".  The control dependencies would extend
+from 'a' and the store to 'c'.  The control dependencies would extend
 only to the pair of cmov instructions and the store depending on them.
 In short, control dependencies apply only to the stores in the then-clause
 and else-clause of the if-statement in question (including functions
@@ -843,7 +846,7 @@ invoked by those two clauses), not to code following that if-statement.
 Finally, control dependencies do -not- provide transitivity.  This is
 demonstrated by two related examples, with the initial values of
-x and y both being zero:
+'x' and 'y' both being zero:
        CPU 0                     CPU 1
        =======================   =======================
@@ -915,6 +918,9 @@ In summary:
  (*) Control dependencies do -not- provide transitivity.  If you
      need transitivity, use smp_mb().
+  (*) Compilers do not understand control dependencies.  It is therefore
+      your job to ensure that they do not break your code.
 SMP BARRIER PAIRING
 -------------------
diff --git a/include/linux/llist.h b/include/linux/llist.h
index fd4ca0b4fe0f..171baa90f6f6 100644
--- a/include/linux/llist.h
+++ b/include/linux/llist.h
@@ -3,28 +3,33 @@
 /*
 * Lock-less NULL terminated single linked list
 *
- * If there are multiple producers and multiple consumers, llist_add
+ * Cases where locking is not needed:
- * can be used in producers and llist_del_all can be used in
+ * If there are multiple producers and multiple consumers, llist_add can be
- * consumers.  They can work simultaneously without lock.  But
+ * used in producers and llist_del_all can be used in consumers simultaneously
- * llist_del_first can not be used here.  Because llist_del_first
+ * without locking. Also a single consumer can use llist_del_first while
- * depends on list->first->next does not changed if list->first is not
+ * multiple producers simultaneously use llist_add, without any locking.
- * changed during its operation, but llist_del_first, llist_add,
+ *
- * llist_add (or llist_del_all, llist_add, llist_add) sequence in
+ * Cases where locking is needed:
- * another consumer may violate that.
+ * If we have multiple consumers with llist_del_first used in one consumer, and
- *
+ * llist_del_first or llist_del_all used in other consumers, then a lock is
- * If there are multiple producers and one consumer, llist_add can be
+ * needed.  This is because llist_del_first depends on list->first->next not
- * used in producers and llist_del_all or llist_del_first can be used
+ * changing, but without lock protection, there's no way to be sure about that
- * in the consumer.
+ * if a preemption happens in the middle of the delete operation and on being
- *
+ * preempted back, the list->first is the same as before causing the cmpxchg in
- * This can be summarized as follow:
+ * llist_del_first to succeed. For example, while a llist_del_first operation
+ * is in progress in one consumer, then a llist_del_first, llist_add,
+ * llist_add (or llist_del_all, llist_add, llist_add) sequence in another
+ * consumer may cause violations.
+ *
+ * This can be summarized as follows:
 *
 *           |   add    | del_first |  del_all
 * add       |    -     |     -     |     -
 * del_first |          |     L     |     L
 * del_all   |          |           |     -
 *
- * Where "-" stands for no lock is needed, while "L" stands for lock
+ * Where, a particular row's operation can happen concurrently with a column's
- * is needed.
+ * operation, with "-" being no lock needed, while "L" being lock is needed.
 *
 * The list entries deleted via llist_del_all can be traversed with
 * traversing function such as llist_for_each etc.  But the list
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 01f71e1d2e94..6ade6a52d9d4 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -1161,5 +1161,17 @@ do { \
                ftrace_dump(oops_dump_mode); \
 } while (0)
+/*
+ * Place this after a lock-acquisition primitive to guarantee that
+ * an UNLOCK+LOCK pair acts as a full barrier.  This guarantee applies
+ * if the UNLOCK and LOCK are executed by the same CPU or if the
+ * UNLOCK and LOCK operate on the same lock variable.
+ */
+#ifdef CONFIG_PPC
+#define smp_mb__after_unlock_lock()     smp_mb()  /* Full ordering for lock. */
+#else /* #ifdef CONFIG_PPC */
+#define smp_mb__after_unlock_lock()     do { } while (0)
+#endif /* #else #ifdef CONFIG_PPC */
 #endif /* __LINUX_RCUPDATE_H */
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index ac81e4063b40..4f9b2fa2173d 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -27,6 +27,12 @@
 #include <linux/cache.h>
+struct rcu_dynticks;
+static inline int rcu_dynticks_snap(struct rcu_dynticks *rdtp)
+{
+        return 0;
+}
 static inline unsigned long get_state_synchronize_rcu(void)
 {
        return 0;
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index dc8eb63c6568..a598cf3ac70c 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -33,9 +33,9 @@
 #include <linux/rcupdate.h>
 #include <linux/workqueue.h>
-struct srcu_struct_array {
+struct srcu_array {
-        unsigned long c[2];
+        unsigned long lock_count[2];
-        unsigned long seq[2];
+        unsigned long unlock_count[2];
 };
 struct rcu_batch {
@@ -46,7 +46,7 @@ struct rcu_batch {
 struct srcu_struct {
        unsigned long completed;
-        struct srcu_struct_array __percpu *per_cpu_ref;
+        struct srcu_array __percpu *per_cpu_ref;
        spinlock_t queue_lock; /* protect ->batch_queue, ->running */
        bool running;
        /* callbacks just queued */
@@ -118,7 +118,7 @@ void process_srcu(struct work_struct *work);
 * See include/linux/percpu-defs.h for the rules on per-CPU variables.
 */
 #define __DEFINE_SRCU(name, is_static)                                  \
-        static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
+        static DEFINE_PER_CPU(struct srcu_array, name##_srcu_array);\
        is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
 #define DEFINE_SRCU(name)               __DEFINE_SRCU(name, /* not static */)
 #define DEFINE_STATIC_SRCU(name)        __DEFINE_SRCU(name, static)
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 9d4f9b3a2b7b..e3facb356838 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -385,11 +385,11 @@ TRACE_EVENT(rcu_quiescent_state_report,
 /*
 * Tracepoint for quiescent states detected by force_quiescent_state().
- * These trace events include the type of RCU, the grace-period number
+ * These trace events include the type of RCU, the grace-period number that
- * that was blocked by the CPU, the CPU itself, and the type of quiescent
+ * was blocked by the CPU, the CPU itself, and the type of quiescent state,
- * state, which can be "dti" for dyntick-idle mode, "ofl" for CPU offline,
+ * which can be "dti" for dyntick-idle mode, "ofl" for CPU offline, "kick"
- * or "kick" when kicking a CPU that has been in dyntick-idle mode for
+ * when kicking a CPU that has been in dyntick-idle mode for too long, or
- * too long.
+ * "rqc" if the CPU got a quiescent state via its rcu_qs_ctr.
 */
 TRACE_EVENT(rcu_fqs,
diff --git a/init/Kconfig b/init/Kconfig
index e1a937348a3e..b40774578f29 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -529,7 +529,6 @@ config SRCU
 config TASKS_RCU
        bool
        default n
-        depends on !UML
        select SRCU
        help
          This option enables a task-based RCU implementation that uses
@@ -781,19 +780,6 @@ config RCU_NOCB_CPU_ALL
 endchoice
-config RCU_EXPEDITE_BOOT
-        bool
-        default n
-        help
-          This option enables expedited grace periods at boot time,
-          as if rcu_expedite_gp() had been invoked early in boot.
-          The corresponding rcu_unexpedite_gp() is invoked from
-          rcu_end_inkernel_boot(), which is intended to be invoked
-          at the end of the kernel-only boot sequence, just before
-          init is exec'ed.
-          Accept the default if unsure.
 endmenu # "RCU Subsystem"
 config BUILD_BIN2C
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 7c38f8f3d97b..d9a698e8458f 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4412,13 +4412,13 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
 #endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
        /* Note: the following can be executed concurrently, so be careful. */
        printk("\n");
-        printk("===============================\n");
+        pr_err("===============================\n");
-        printk("[ INFO: suspicious RCU usage. ]\n");
+        pr_err("[ ERR: suspicious RCU usage.  ]\n");
        print_kernel_ident();
-        printk("-------------------------------\n");
+        pr_err("-------------------------------\n");
-        printk("%s:%d %s!\n", file, line, s);
+        pr_err("%s:%d %s!\n", file, line, s);
-        printk("\nother info that might help us debug this:\n\n");
+        pr_err("\nother info that might help us debug this:\n\n");
-        printk("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
+        pr_err("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
               !rcu_lockdep_current_cpu_online()
                        ? "RCU used illegally from offline CPU!\n"
                        : !rcu_is_watching()
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index f8c5af52a131..d3de04b12f8c 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -780,6 +780,10 @@ static void lock_torture_cleanup(void)
        else
                lock_torture_print_module_parms(cxt.cur_ops,
                                                "End of test: SUCCESS");
+        kfree(cxt.lwsa);
+        kfree(cxt.lrsa);
 end:
        torture_cleanup_end();
 }
@@ -924,6 +928,8 @@ static int __init lock_torture_init(void)
                                       GFP_KERNEL);
                if (reader_tasks == NULL) {
                        VERBOSE_TOROUT_ERRSTRING("reader_tasks: Out of memory");
+                        kfree(writer_tasks);
+                        writer_tasks = NULL;
                        firsterr = -ENOMEM;
                        goto unwind;
                }
diff --git a/kernel/membarrier.c b/kernel/membarrier.c
index 536c727a56e9..9f9284f37f8d 100644
--- a/kernel/membarrier.c
+++ b/kernel/membarrier.c
@@ -16,6 +16,7 @@
 #include <linux/syscalls.h>
 #include <linux/membarrier.h>
+#include <linux/tick.h>
 /*
 * Bitmask made from a "or" of all commands within enum membarrier_cmd,
@@ -51,6 +52,9 @@
 */
 SYSCALL_DEFINE2(membarrier, int, cmd, int, flags)
 {
+        /* MEMBARRIER_CMD_SHARED is not compatible with nohz_full. */
+        if (tick_nohz_full_enabled())
+                return -ENOSYS;
        if (unlikely(flags))
                return -EINVAL;
        switch (cmd) {
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 87c51225ceec..d81345be730e 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -564,10 +564,25 @@ static void srcu_torture_stats(void)
        pr_alert("%s%s per-CPU(idx=%d):",
                 torture_type, TORTURE_FLAG, idx);
        for_each_possible_cpu(cpu) {
+                unsigned long l0, l1;
+                unsigned long u0, u1;
                long c0, c1;
+                struct srcu_array *counts = per_cpu_ptr(srcu_ctlp->per_cpu_ref, cpu);
-                c0 = (long)per_cpu_ptr(srcu_ctlp->per_cpu_ref, cpu)->c[!idx];
+                u0 = counts->unlock_count[!idx];
-                c1 = (long)per_cpu_ptr(srcu_ctlp->per_cpu_ref, cpu)->c[idx];
+                u1 = counts->unlock_count[idx];
+                /*
+                 * Make sure that a lock is always counted if the corresponding
+                 * unlock is counted.
+                 */
+                smp_rmb();
+                l0 = counts->lock_count[!idx];
+                l1 = counts->lock_count[idx];
+                c0 = l0 - u0;
+                c1 = l1 - u1;
                pr_cont(" %d(%ld,%ld)", cpu, c0, c1);
        }
        pr_cont("\n");
diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
index 9b9cdd549caa..e773129c8b08 100644
--- a/kernel/rcu/srcu.c
+++ b/kernel/rcu/srcu.c
@@ -106,7 +106,7 @@ static int init_srcu_struct_fields(struct srcu_struct *sp)
        rcu_batch_init(&sp->batch_check1);
        rcu_batch_init(&sp->batch_done);
        INIT_DELAYED_WORK(&sp->work, process_srcu);
-        sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);
+        sp->per_cpu_ref = alloc_percpu(struct srcu_array);
        return sp->per_cpu_ref ? 0 : -ENOMEM;
 }
@@ -141,114 +141,77 @@ EXPORT_SYMBOL_GPL(init_srcu_struct);
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 /*
- * Returns approximate total of the readers' ->seq[] values for the
+ * Returns approximate total of the readers' ->lock_count[] values for the
 * rank of per-CPU counters specified by idx.
 */
-static unsigned long srcu_readers_seq_idx(struct srcu_struct *sp, int idx)
+static unsigned long srcu_readers_lock_idx(struct srcu_struct *sp, int idx)
 {
        int cpu;
        unsigned long sum = 0;
-        unsigned long t;
        for_each_possible_cpu(cpu) {
-                t = READ_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->seq[idx]);
+                struct srcu_array *cpuc = per_cpu_ptr(sp->per_cpu_ref, cpu);
-                sum += t;
+                sum += READ_ONCE(cpuc->lock_count[idx]);
        }
        return sum;
 }
 /*
- * Returns approximate number of readers active on the specified rank
+ * Returns approximate total of the readers' ->unlock_count[] values for the
- * of the per-CPU ->c[] counters.
+ * rank of per-CPU counters specified by idx.
 */
-static unsigned long srcu_readers_active_idx(struct srcu_struct *sp, int idx)
+static unsigned long srcu_readers_unlock_idx(struct srcu_struct *sp, int idx)
 {
        int cpu;
        unsigned long sum = 0;
-        unsigned long t;
        for_each_possible_cpu(cpu) {
-                t = READ_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[idx]);
+                struct srcu_array *cpuc = per_cpu_ptr(sp->per_cpu_ref, cpu);
-                sum += t;
+                sum += READ_ONCE(cpuc->unlock_count[idx]);
        }
        return sum;
 }
 /*
 * Return true if the number of pre-existing readers is determined to
- * be stably zero.  An example unstable zero can occur if the call
+ * be zero.
- * to srcu_readers_active_idx() misses an __srcu_read_lock() increment,
- * but due to task migration, sees the corresponding __srcu_read_unlock()
- * decrement.  This can happen because srcu_readers_active_idx() takes
- * time to sum the array, and might in fact be interrupted or preempted
- * partway through the summation.
 */
 static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx)
 {
-        unsigned long seq;
+        unsigned long unlocks;
-        seq = srcu_readers_seq_idx(sp, idx);
+        unlocks = srcu_readers_unlock_idx(sp, idx);
        /*
-         * The following smp_mb() A pairs with the smp_mb() B located in
+         * Make sure that a lock is always counted if the corresponding unlock
-         * __srcu_read_lock().  This pairing ensures that if an
+         * is counted. Needs to be a smp_mb() as the read side may contain a
-         * __srcu_read_lock() increments its counter after the summation
+         * read from a variable that is written to before the synchronize_srcu()
-         * in srcu_readers_active_idx(), then the corresponding SRCU read-side
+         * in the write side. In this case smp_mb()s A and B act like the store
-         * critical section will see any changes made prior to the start
+         * buffering pattern.
-         * of the current SRCU grace period.
         *
-         * Also, if the above call to srcu_readers_seq_idx() saw the
+         * This smp_mb() also pairs with smp_mb() C to prevent accesses after the
-         * increment of ->seq[], then the call to srcu_readers_active_idx()
+         * synchronize_srcu() from being executed before the grace period ends.
-         * must see the increment of ->c[].
         */
        smp_mb(); /* A */
        /*
-         * Note that srcu_readers_active_idx() can incorrectly return
+         * If the locks are the same as the unlocks, then there must have
-         * zero even though there is a pre-existing reader throughout.
+         * been no readers on this index at some time in between. This does not
-         * To see this, suppose that task A is in a very long SRCU
+         * mean that there are no more readers, as one could have read the
-         * read-side critical section that started on CPU 0, and that
+         * current index but not have incremented the lock counter yet.
-         * no other reader exists, so that the sum of the counters
-         * is equal to one.  Then suppose that task B starts executing
-         * srcu_readers_active_idx(), summing up to CPU 1, and then that
-         * task C starts reading on CPU 0, so that its increment is not
-         * summed, but finishes reading on CPU 2, so that its decrement
-         * -is- summed.  Then when task B completes its sum, it will
-         * incorrectly get zero, despite the fact that task A has been
-         * in its SRCU read-side critical section the whole time.
-         *
-         * We therefore do a validation step should srcu_readers_active_idx()
-         * return zero.
-         */
-        if (srcu_readers_active_idx(sp, idx) != 0)
-                return false;
-        /*
-         * The remainder of this function is the validation step.
-         * The following smp_mb() D pairs with the smp_mb() C in
-         * __srcu_read_unlock().  If the __srcu_read_unlock() was seen
-         * by srcu_readers_active_idx() above, then any destructive
-         * operation performed after the grace period will happen after
-         * the corresponding SRCU read-side critical section.
         *
-         * Note that there can be at most NR_CPUS worth of readers using
+         * Possible bug: There is no guarantee that there haven't been ULONG_MAX
-         * the old index, which is not enough to overflow even a 32-bit
+         * increments of ->lock_count[] since the unlocks were counted, meaning
-         * integer.  (Yes, this does mean that systems having more than
+         * that this could return true even if there are still active readers.
-         * a billion or so CPUs need to be 64-bit systems.)  Therefore,
+         * Since there are no memory barriers around srcu_flip(), the CPU is not
-         * the sum of the ->seq[] counters cannot possibly overflow.
+         * required to increment ->completed before running
-         * Therefore, the only way that the return values of the two
+         * srcu_readers_unlock_idx(), which means that there could be an
-         * calls to srcu_readers_seq_idx() can be equal is if there were
+         * arbitrarily large number of critical sections that execute after
-         * no increments of the corresponding rank of ->seq[] counts
+         * srcu_readers_unlock_idx() but use the old value of ->completed.
-         * in the interim.  But the missed-increment scenario laid out
-         * above includes an increment of the ->seq[] counter by
-         * the corresponding __srcu_read_lock().  Therefore, if this
-         * scenario occurs, the return values from the two calls to
-         * srcu_readers_seq_idx() will differ, and thus the validation
-         * step below suffices.
         */
-        smp_mb(); /* D */
+        return srcu_readers_lock_idx(sp, idx) == unlocks;
-        return srcu_readers_seq_idx(sp, idx) == seq;
 }
 /**
@@ -266,8 +229,12 @@ static bool srcu_readers_active(struct srcu_struct *sp)
        unsigned long sum = 0;
        for_each_possible_cpu(cpu) {
-                sum += READ_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[0]);
+                struct srcu_array *cpuc = per_cpu_ptr(sp->per_cpu_ref, cpu);
-                sum += READ_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[1]);
+                sum += READ_ONCE(cpuc->lock_count[0]);
+                sum += READ_ONCE(cpuc->lock_count[1]);
+                sum -= READ_ONCE(cpuc->unlock_count[0]);
+                sum -= READ_ONCE(cpuc->unlock_count[1]);
        }
        return sum;
 }
@@ -298,9 +265,8 @@ int __srcu_read_lock(struct srcu_struct *sp)
        int idx;
        idx = READ_ONCE(sp->completed) & 0x1;
-        __this_cpu_inc(sp->per_cpu_ref->c[idx]);
+        __this_cpu_inc(sp->per_cpu_ref->lock_count[idx]);
        smp_mb(); /* B */  /* Avoid leaking the critical section. */
-        __this_cpu_inc(sp->per_cpu_ref->seq[idx]);
        return idx;
 }
 EXPORT_SYMBOL_GPL(__srcu_read_lock);
@@ -314,7 +280,7 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock);
 void __srcu_read_unlock(struct srcu_struct *sp, int idx)
 {
        smp_mb(); /* C */  /* Avoid leaking the critical section. */
-        this_cpu_dec(sp->per_cpu_ref->c[idx]);
+        this_cpu_inc(sp->per_cpu_ref->unlock_count[idx]);
 }
 EXPORT_SYMBOL_GPL(__srcu_read_unlock);
@@ -349,12 +315,21 @@ static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount)
 /*
 * Increment the ->completed counter so that future SRCU readers will
- * use the other rank of the ->c[] and ->seq[] arrays.  This allows
+ * use the other rank of the ->(un)lock_count[] arrays.  This allows
 * us to wait for pre-existing readers in a starvation-free manner.
 */
 static void srcu_flip(struct srcu_struct *sp)
 {
-        sp->completed++;
+        WRITE_ONCE(sp->completed, sp->completed + 1);
+        /*
+         * Ensure that if the updater misses an __srcu_read_unlock()
+         * increment, that task's next __srcu_read_lock() will see the
+         * above counter update.  Note that both this memory barrier
+         * and the one in srcu_readers_active_idx_check() provide the
+         * guarantee for __srcu_read_lock().
+         */
+        smp_mb(); /* D */  /* Pairs with C. */
 }
 /*
@@ -392,6 +367,7 @@ void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
        head->next = NULL;
        head->func = func;
        spin_lock_irqsave(&sp->queue_lock, flags);
+        smp_mb__after_unlock_lock(); /* Caller's prior accesses before GP. */
        rcu_batch_queue(&sp->batch_queue, head);
        if (!sp->running) {
                sp->running = true;
@@ -425,6 +401,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
        head->next = NULL;
        head->func = wakeme_after_rcu;
        spin_lock_irq(&sp->queue_lock);
+        smp_mb__after_unlock_lock(); /* Caller's prior accesses before GP. */
        if (!sp->running) {
                /* steal the processing owner */
                sp->running = true;
@@ -444,8 +421,11 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
                spin_unlock_irq(&sp->queue_lock);
        }
-        if (!done)
+        if (!done) {
                wait_for_completion(&rcu.completion);
+                smp_mb(); /* Caller's later accesses after GP. */
+        }
 }
 /**
@@ -613,7 +593,8 @@ static void srcu_advance_batches(struct srcu_struct *sp, int trycount)
 /*
 * Invoke a limited number of SRCU callbacks that have passed through
 * their grace period.  If there are more to do, SRCU will reschedule
- * the workqueue.
+ * the workqueue.  Note that needed memory barriers have been executed
+ * in this task's context by srcu_readers_active_idx_check().
 */
 static void srcu_invoke_callbacks(struct srcu_struct *sp)
 {
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index b23a4d076f3d..fa6a48d3917b 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -41,8 +41,6 @@
 /* Forward declarations for tiny_plugin.h. */
 struct rcu_ctrlblk;
-static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp);
-static void rcu_process_callbacks(struct softirq_action *unused);
 static void __call_rcu(struct rcu_head *head,
                       rcu_callback_t func,
                       struct rcu_ctrlblk *rcp);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index cb4e2056ccf3..d80e0d2f68c6 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -281,6 +281,116 @@ static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
 #endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
 };
+/*
+ * Record entry into an extended quiescent state.  This is only to be
+ * called when not already in an extended quiescent state.
+ */
+static void rcu_dynticks_eqs_enter(void)
+{
+        struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+        int special;
+        /*
+         * CPUs seeing atomic_inc_return() must see prior RCU read-side
+         * critical sections, and we also must force ordering with the
+         * next idle sojourn.
+         */
+        special = atomic_inc_return(&rdtp->dynticks);
+        WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && special & 0x1);
+}
+/*
+ * Record exit from an extended quiescent state.  This is only to be
+ * called from an extended quiescent state.
+ */
+static void rcu_dynticks_eqs_exit(void)
+{
+        struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+        int special;
+        /*
+         * CPUs seeing atomic_inc_return() must see prior idle sojourns,
+         * and we also must force ordering with the next RCU read-side
+         * critical section.
+         */
+        special = atomic_inc_return(&rdtp->dynticks);
+        WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(special & 0x1));
+}
+/*
+ * Reset the current CPU's ->dynticks counter to indicate that the
+ * newly onlined CPU is no longer in an extended quiescent state.
+ * This will either leave the counter unchanged, or increment it
+ * to the next non-quiescent value.
+ *
+ * The non-atomic test/increment sequence works because the upper bits
+ * of the ->dynticks counter are manipulated only by the corresponding CPU,
+ * or when the corresponding CPU is offline.
+ */
+static void rcu_dynticks_eqs_online(void)
+{
+        struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+        if (atomic_read(&rdtp->dynticks) & 0x1)
+                return;
+        atomic_add(0x1, &rdtp->dynticks);
+}
+/*
+ * Is the current CPU in an extended quiescent state?
+ *
+ * No ordering, as we are sampling CPU-local information.
+ */
+bool rcu_dynticks_curr_cpu_in_eqs(void)
+{
+        struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+        return !(atomic_read(&rdtp->dynticks) & 0x1);
+}
+/*
+ * Snapshot the ->dynticks counter with full ordering so as to allow
+ * stable comparison of this counter with past and future snapshots.
+ */
+int rcu_dynticks_snap(struct rcu_dynticks *rdtp)
+{
+        int snap = atomic_add_return(0, &rdtp->dynticks);
+        return snap;
+}
+/*
+ * Return true if the snapshot returned from rcu_dynticks_snap()
+ * indicates that RCU is in an extended quiescent state.
+ */
+static bool rcu_dynticks_in_eqs(int snap)
+{
+        return !(snap & 0x1);
+}
+/*
+ * Return true if the CPU corresponding to the specified rcu_dynticks
+ * structure has spent some time in an extended quiescent state since
+ * rcu_dynticks_snap() returned the specified snapshot.
+ */
+static bool rcu_dynticks_in_eqs_since(struct rcu_dynticks *rdtp, int snap)
+{
+        return snap != rcu_dynticks_snap(rdtp);
+}
+/*
+ * Do a double-increment of the ->dynticks counter to emulate a
+ * momentary idle-CPU quiescent state.
+ */
+static void rcu_dynticks_momentary_idle(void)
+{
+        struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+        int special = atomic_add_return(2, &rdtp->dynticks);
+        /* It is illegal to call this from idle state. */
+        WARN_ON_ONCE(!(special & 0x1));
+}
 DEFINE_PER_CPU_SHARED_ALIGNED(unsigned long, rcu_qs_ctr);
 EXPORT_PER_CPU_SYMBOL_GPL(rcu_qs_ctr);
@@ -300,7 +410,6 @@ EXPORT_PER_CPU_SYMBOL_GPL(rcu_qs_ctr);
 static void rcu_momentary_dyntick_idle(void)
 {
        struct rcu_data *rdp;
-        struct rcu_dynticks *rdtp;
        int resched_mask;
        struct rcu_state *rsp;
@@ -327,10 +436,7 @@ static void rcu_momentary_dyntick_idle(void)
                 * quiescent state, with no need for this CPU to do anything
                 * further.
                 */
-                rdtp = this_cpu_ptr(&rcu_dynticks);
+                rcu_dynticks_momentary_idle();
-                smp_mb__before_atomic(); /* Earlier stuff before QS. */
-                atomic_add(2, &rdtp->dynticks);  /* QS. */
-                smp_mb__after_atomic(); /* Later stuff after QS. */
                break;
        }
 }
@@ -611,7 +717,7 @@ static int
 cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
 {
        return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] &&
-               rdp->nxttail[RCU_DONE_TAIL] != NULL;
+               rdp->nxttail[RCU_NEXT_TAIL] != NULL;
 }
 /*
@@ -673,7 +779,7 @@ static void rcu_eqs_enter_common(long long oldval, bool user)
 {
        struct rcu_state *rsp;
        struct rcu_data *rdp;
-        struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+        RCU_TRACE(struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);)
        trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting);
        if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
@@ -692,12 +798,7 @@ static void rcu_eqs_enter_common(long long oldval, bool user)
                do_nocb_deferred_wakeup(rdp);
        }
        rcu_prepare_for_idle();
-        /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
+        rcu_dynticks_eqs_enter();
-        smp_mb__before_atomic();  /* See above. */
-        atomic_inc(&rdtp->dynticks);
-        smp_mb__after_atomic();  /* Force ordering with next sojourn. */
-        WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
-                     atomic_read(&rdtp->dynticks) & 0x1);
        rcu_dynticks_task_enter();
        /*
@@ -826,15 +927,10 @@ void rcu_irq_exit_irqson(void)
 */
 static void rcu_eqs_exit_common(long long oldval, int user)
 {
-        struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+        RCU_TRACE(struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);)
        rcu_dynticks_task_exit();
-        smp_mb__before_atomic();  /* Force ordering w/previous sojourn. */
+        rcu_dynticks_eqs_exit();
-        atomic_inc(&rdtp->dynticks);
-        /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
-        smp_mb__after_atomic();  /* See above. */
-        WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
-                     !(atomic_read(&rdtp->dynticks) & 0x1));
        rcu_cleanup_after_idle();
        trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting);
        if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
@@ -980,12 +1076,8 @@ void rcu_nmi_enter(void)
         * to be in the outermost NMI handler that interrupted an RCU-idle
         * period (observation due to Andy Lutomirski).
         */
-        if (!(atomic_read(&rdtp->dynticks) & 0x1)) {
+        if (rcu_dynticks_curr_cpu_in_eqs()) {
-                smp_mb__before_atomic();  /* Force delay from prior write. */
+                rcu_dynticks_eqs_exit();
-                atomic_inc(&rdtp->dynticks);
-                /* atomic_inc() before later RCU read-side crit sects */
-                smp_mb__after_atomic();  /* See above. */
-                WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
                incby = 1;
        }
        rdtp->dynticks_nmi_nesting += incby;
@@ -1010,7 +1102,7 @@ void rcu_nmi_exit(void)
         * to us!)
         */
        WARN_ON_ONCE(rdtp->dynticks_nmi_nesting <= 0);
-        WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
+        WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());
        /*
         * If the nesting level is not 1, the CPU wasn't RCU-idle, so
@@ -1023,11 +1115,7 @@ void rcu_nmi_exit(void)
        /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
        rdtp->dynticks_nmi_nesting = 0;
-        /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
+        rcu_dynticks_eqs_enter();
-        smp_mb__before_atomic();  /* See above. */
-        atomic_inc(&rdtp->dynticks);
-        smp_mb__after_atomic();  /* Force delay to next write. */
-        WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
 }
 /**
@@ -1040,7 +1128,7 @@ void rcu_nmi_exit(void)
 */
 bool notrace __rcu_is_watching(void)
 {
-        return atomic_read(this_cpu_ptr(&rcu_dynticks.dynticks)) & 0x1;
+        return !rcu_dynticks_curr_cpu_in_eqs();
 }
 /**
@@ -1123,9 +1211,9 @@ static int rcu_is_cpu_rrupt_from_idle(void)
 static int dyntick_save_progress_counter(struct rcu_data *rdp,
                                         bool *isidle, unsigned long *maxj)
 {
-        rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
+        rdp->dynticks_snap = rcu_dynticks_snap(rdp->dynticks);
        rcu_sysidle_check_cpu(rdp, isidle, maxj);
-        if ((rdp->dynticks_snap & 0x1) == 0) {
+        if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) {
                trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
                if (ULONG_CMP_LT(READ_ONCE(rdp->gpnum) + ULONG_MAX / 4,
                                 rdp->mynode->gpnum))
@@ -1144,12 +1232,10 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp,
 static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
                                    bool *isidle, unsigned long *maxj)
 {
-        unsigned int curr;
+        unsigned long jtsq;
        int *rcrmp;
-        unsigned int snap;
+        unsigned long rjtsc;
+        struct rcu_node *rnp;
-        curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks);
-        snap = (unsigned int)rdp->dynticks_snap;
        /*
         * If the CPU passed through or entered a dynticks idle phase with
@@ -1159,27 +1245,39 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
         * read-side critical section that started before the beginning
         * of the current RCU grace period.
         */
-        if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) {
+        if (rcu_dynticks_in_eqs_since(rdp->dynticks, rdp->dynticks_snap)) {
                trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
                rdp->dynticks_fqs++;
                return 1;
        }
+        /* Compute and saturate jiffies_till_sched_qs. */
+        jtsq = jiffies_till_sched_qs;
+        rjtsc = rcu_jiffies_till_stall_check();
+        if (jtsq > rjtsc / 2) {
+                WRITE_ONCE(jiffies_till_sched_qs, rjtsc);
+                jtsq = rjtsc / 2;
+        } else if (jtsq < 1) {
+                WRITE_ONCE(jiffies_till_sched_qs, 1);
+                jtsq = 1;
+        }
        /*
-         * Check for the CPU being offline, but only if the grace period
+         * Has this CPU encountered a cond_resched_rcu_qs() since the
-         * is old enough.  We don't need to worry about the CPU changing
+         * beginning of the grace period?  For this to be the case,
-         * state: If we see it offline even once, it has been through a
+         * the CPU has to have noticed the current grace period.  This
-         * quiescent state.
+         * might not be the case for nohz_full CPUs looping in the kernel.
-         *
-         * The reason for insisting that the grace period be at least
-         * one jiffy old is that CPUs that are not quite online and that
-         * have just gone offline can still execute RCU read-side critical
-         * sections.
         */
-        if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies))
+        rnp = rdp->mynode;
-                return 0;  /* Grace period is not old enough. */
+        if (time_after(jiffies, rdp->rsp->gp_start + jtsq) &&
-        barrier();
+            READ_ONCE(rdp->rcu_qs_ctr_snap) != per_cpu(rcu_qs_ctr, rdp->cpu) &&
-        if (cpu_is_offline(rdp->cpu)) {
+            READ_ONCE(rdp->gpnum) == rnp->gpnum && !rdp->gpwrap) {
+                trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("rqc"));
+                return 1;
+        }
+        /* Check for the CPU being offline. */
+        if (!(rdp->grpmask & rcu_rnp_online_cpus(rnp))) {
                trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("ofl"));
                rdp->offline_fqs++;
                return 1;
@@ -1207,9 +1305,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
         * warning delay.
         */
        rcrmp = &per_cpu(rcu_sched_qs_mask, rdp->cpu);
-        if (ULONG_CMP_GE(jiffies,
+        if (time_after(jiffies, rdp->rsp->gp_start + jtsq) ||
-                         rdp->rsp->gp_start + jiffies_till_sched_qs) ||
+            time_after(jiffies, rdp->rsp->jiffies_resched)) {
-            ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) {
                if (!(READ_ONCE(*rcrmp) & rdp->rsp->flavor_mask)) {
                        WRITE_ONCE(rdp->cond_resched_completed,
                                   READ_ONCE(rdp->mynode->completed));
@@ -1220,11 +1317,12 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
                rdp->rsp->jiffies_resched += 5; /* Re-enable beating. */
        }
-        /* And if it has been a really long time, kick the CPU as well. */
+        /*
-        if (ULONG_CMP_GE(jiffies,
+         * If more than halfway to RCU CPU stall-warning time, do
-                         rdp->rsp->gp_start + 2 * jiffies_till_sched_qs) ||
+         * a resched_cpu() to try to loosen things up a bit.
-            ULONG_CMP_GE(jiffies, rdp->rsp->gp_start + jiffies_till_sched_qs))
+         */
-                resched_cpu(rdp->cpu);  /* Force CPU into scheduler. */
+        if (jiffies - rdp->rsp->gp_start > rcu_jiffies_till_stall_check() / 2)
+                resched_cpu(rdp->cpu);
        return 0;
 }
@@ -1277,7 +1375,10 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
 }
 /*
- * Dump stacks of all tasks running on stalled CPUs.
+ * Dump stacks of all tasks running on stalled CPUs.  First try using
+ * NMIs, but fall back to manual remote stack tracing on architectures
+ * that don't support NMI-based stack dumps.  The NMI-triggered stack
+ * traces are more accurate because they are printed by the target CPU.
 */
 static void rcu_dump_cpu_stacks(struct rcu_state *rsp)
 {
@@ -1287,11 +1388,10 @@ static void rcu_dump_cpu_stacks(struct rcu_state *rsp)
        rcu_for_each_leaf_node(rsp, rnp) {
                raw_spin_lock_irqsave_rcu_node(rnp, flags);
-                if (rnp->qsmask != 0) {
+                for_each_leaf_node_possible_cpu(rnp, cpu)
-                        for_each_leaf_node_possible_cpu(rnp, cpu)
+                        if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu))
-                                if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu))
+                                if (!trigger_single_cpu_backtrace(cpu))
                                        dump_cpu_task(cpu);
-                }
                raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
        }
 }
@@ -1379,6 +1479,9 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
               (long)rsp->gpnum, (long)rsp->completed, totqlen);
        if (ndetected) {
                rcu_dump_cpu_stacks(rsp);
+                /* Complain about tasks blocking the grace period. */
+                rcu_print_detail_task_stall(rsp);
        } else {
                if (READ_ONCE(rsp->gpnum) != gpnum ||
                    READ_ONCE(rsp->completed) == gpnum) {
@@ -1395,9 +1498,6 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
                }
        }
-        /* Complain about tasks blocking the grace period. */
-        rcu_print_detail_task_stall(rsp);
        rcu_check_gp_kthread_starvation(rsp);
        panic_on_rcu_stall();
@@ -2467,10 +2567,8 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
        rnp = rdp->mynode;
        raw_spin_lock_irqsave_rcu_node(rnp, flags);
-        if ((rdp->cpu_no_qs.b.norm &&
+        if (rdp->cpu_no_qs.b.norm || rdp->gpnum != rnp->gpnum ||
-             rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) ||
+            rnp->completed == rnp->gpnum || rdp->gpwrap) {
-            rdp->gpnum != rnp->gpnum || rnp->completed == rnp->gpnum ||
-            rdp->gpwrap) {
                /*
                 * The grace period in which this quiescent state was
@@ -2525,8 +2623,7 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
         * Was there a quiescent state since the beginning of the grace
         * period? If no, then exit and wait for the next call.
         */
-        if (rdp->cpu_no_qs.b.norm &&
+        if (rdp->cpu_no_qs.b.norm)
-            rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr))
                return;
        /*
@@ -3480,9 +3577,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
            rdp->core_needs_qs && rdp->cpu_no_qs.b.norm &&
            rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) {
                rdp->n_rp_core_needs_qs++;
-        } else if (rdp->core_needs_qs &&
+        } else if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm) {
-                   (!rdp->cpu_no_qs.b.norm ||
-                    rdp->rcu_qs_ctr_snap != __this_cpu_read(rcu_qs_ctr))) {
                rdp->n_rp_report_qs++;
                return 1;
        }
@@ -3748,7 +3843,7 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
        rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
        rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
        WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
-        WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
+        WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp->dynticks)));
        rdp->cpu = cpu;
        rdp->rsp = rsp;
        rcu_boot_init_nocb_percpu_data(rdp);
@@ -3765,7 +3860,6 @@ static void
 rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
 {
        unsigned long flags;
-        unsigned long mask;
        struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
        struct rcu_node *rnp = rcu_get_root(rsp);
@@ -3778,8 +3872,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
                init_callback_list(rdp);  /* Re-enable callbacks on this CPU. */
        rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
        rcu_sysidle_init_percpu_data(rdp->dynticks);
-        atomic_set(&rdp->dynticks->dynticks,
+        rcu_dynticks_eqs_online();
-                   (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
        raw_spin_unlock_rcu_node(rnp);          /* irqs remain disabled. */
        /*
@@ -3788,7 +3881,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
         * of the next grace period.
         */
        rnp = rdp->mynode;
-        mask = rdp->grpmask;
        raw_spin_lock_rcu_node(rnp);            /* irqs already disabled. */
        if (!rdp->beenonline)
                WRITE_ONCE(rsp->ncpus, READ_ONCE(rsp->ncpus) + 1);
@@ -3872,7 +3964,7 @@ void rcu_cpu_starting(unsigned int cpu)
        struct rcu_state *rsp;
        for_each_rcu_flavor(rsp) {
-                rdp = this_cpu_ptr(rsp->rda);
+                rdp = per_cpu_ptr(rsp->rda, cpu);
                rnp = rdp->mynode;
                mask = rdp->grpmask;
                raw_spin_lock_irqsave_rcu_node(rnp, flags);
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index fe98dd24adf8..b60f2b6caa14 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -521,7 +521,6 @@ struct rcu_state {
        struct mutex exp_mutex;                 /* Serialize expedited GP. */
        struct mutex exp_wake_mutex;            /* Serialize wakeup. */
        unsigned long expedited_sequence;       /* Take a ticket. */
-        atomic_long_t expedited_normal;         /* # fallbacks to normal. */
        atomic_t expedited_need_qs;             /* # CPUs left to check in. */
        struct swait_queue_head expedited_wq;   /* Wait for check-ins. */
        int ncpus_snap;                         /* # CPUs seen last time. */
@@ -595,6 +594,8 @@ extern struct rcu_state rcu_bh_state;
 extern struct rcu_state rcu_preempt_state;
 #endif /* #ifdef CONFIG_PREEMPT_RCU */
+int rcu_dynticks_snap(struct rcu_dynticks *rdtp);
 #ifdef CONFIG_RCU_BOOST
 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
 DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
@@ -688,18 +689,6 @@ static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
 #endif /* #ifdef CONFIG_RCU_TRACE */
 /*
- * Place this after a lock-acquisition primitive to guarantee that
- * an UNLOCK+LOCK pair act as a full barrier.  This guarantee applies
- * if the UNLOCK and LOCK are executed by the same CPU or if the
- * UNLOCK and LOCK operate on the same lock variable.
- */
-#ifdef CONFIG_PPC
-#define smp_mb__after_unlock_lock()     smp_mb()  /* Full ordering for lock. */
-#else /* #ifdef CONFIG_PPC */
-#define smp_mb__after_unlock_lock()     do { } while (0)
-#endif /* #else #ifdef CONFIG_PPC */
-/*
 * Wrappers for the rcu_node::lock acquire and release.
 *
 * Because the rcu_nodes form a tree, the tree traversal locking will observe
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index e59e1849b89a..a7b639ccd46e 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -20,16 +20,26 @@
 * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 */
-/* Wrapper functions for expedited grace periods.  */
+/*
+ * Record the start of an expedited grace period.
+ */
 static void rcu_exp_gp_seq_start(struct rcu_state *rsp)
 {
        rcu_seq_start(&rsp->expedited_sequence);
 }
+/*
+ * Record the end of an expedited grace period.
+ */
 static void rcu_exp_gp_seq_end(struct rcu_state *rsp)
 {
        rcu_seq_end(&rsp->expedited_sequence);
        smp_mb(); /* Ensure that consecutive grace periods serialize. */
 }
+/*
+ * Take a snapshot of the expedited-grace-period counter.
+ */
 static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp)
 {
        unsigned long s;
@@ -39,6 +49,12 @@ static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp)
        trace_rcu_exp_grace_period(rsp->name, s, TPS("snap"));
        return s;
 }
+/*
+ * Given a counter snapshot from rcu_exp_gp_seq_snap(), return true
+ * if a full expedited grace period has elapsed since that snapshot
+ * was taken.
+ */
 static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
 {
        return rcu_seq_done(&rsp->expedited_sequence, s);
@@ -356,12 +372,11 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
                mask_ofl_test = 0;
                for_each_leaf_node_possible_cpu(rnp, cpu) {
                        struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
-                        struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
                        rdp->exp_dynticks_snap =
-                                atomic_add_return(0, &rdtp->dynticks);
+                                rcu_dynticks_snap(rdp->dynticks);
                        if (raw_smp_processor_id() == cpu ||
-                            !(rdp->exp_dynticks_snap & 0x1) ||
+                            rcu_dynticks_in_eqs(rdp->exp_dynticks_snap) ||
                            !(rnp->qsmaskinitnext & rdp->grpmask))
                                mask_ofl_test |= rdp->grpmask;
                }
@@ -380,13 +395,12 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
                for_each_leaf_node_possible_cpu(rnp, cpu) {
                        unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
                        struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
-                        struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
                        if (!(mask_ofl_ipi & mask))
                                continue;
 retry_ipi:
-                        if (atomic_add_return(0, &rdtp->dynticks) !=
+                        if (rcu_dynticks_in_eqs_since(rdp->dynticks,
-                            rdp->exp_dynticks_snap) {
+                                                      rdp->exp_dynticks_snap)) {
                                mask_ofl_test |= mask;
                                continue;
                        }
@@ -623,6 +637,11 @@ void synchronize_sched_expedited(void)
 {
        struct rcu_state *rsp = &rcu_sched_state;
+        RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
+                         lock_is_held(&rcu_lock_map) ||
+                         lock_is_held(&rcu_sched_lock_map),
+                         "Illegal synchronize_sched_expedited() in RCU read-side critical section");
        /* If only one CPU, this is automatically a grace period. */
        if (rcu_blocking_is_gp())
                return;
@@ -692,6 +711,11 @@ void synchronize_rcu_expedited(void)
 {
        struct rcu_state *rsp = rcu_state_p;
+        RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
+                         lock_is_held(&rcu_lock_map) ||
+                         lock_is_held(&rcu_sched_lock_map),
+                         "Illegal synchronize_rcu_expedited() in RCU read-side critical section");
        if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
                return;
        _synchronize_rcu_expedited(rsp, sync_rcu_exp_handler);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 56583e764ebf..a240f3308be6 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1643,7 +1643,7 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)
               "o."[!!(rdp->grpmask & rdp->mynode->qsmaskinit)],
               "N."[!!(rdp->grpmask & rdp->mynode->qsmaskinitnext)],
               ticks_value, ticks_title,
-               atomic_read(&rdtp->dynticks) & 0xfff,
+               rcu_dynticks_snap(rdtp) & 0xfff,
               rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting,
               rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
               READ_ONCE(rsp->n_force_qs) - rsp->n_force_qs_gpstart,
@@ -2366,8 +2366,9 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp)
        }
        /*
-         * Each pass through this loop sets up one rcu_data structure and
+         * Each pass through this loop sets up one rcu_data structure.
-         * spawns one rcu_nocb_kthread().
+         * Should the corresponding CPU come online in the future, then
+         * we will spawn the needed set of rcu_nocb_kthread() kthreads.
         */
        for_each_cpu(cpu, rcu_nocb_mask) {
                rdp = per_cpu_ptr(rsp->rda, cpu);
diff --git a/kernel/rcu/tree_trace.c b/kernel/rcu/tree_trace.c
index b1f28972872c..8751a748499a 100644
--- a/kernel/rcu/tree_trace.c
+++ b/kernel/rcu/tree_trace.c
@@ -124,7 +124,7 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
                   rdp->rcu_qs_ctr_snap == per_cpu(rcu_qs_ctr, rdp->cpu),
                   rdp->core_needs_qs);
        seq_printf(m, " dt=%d/%llx/%d df=%lu",
-                   atomic_read(&rdp->dynticks->dynticks),
+                   rcu_dynticks_snap(rdp->dynticks),
                   rdp->dynticks->dynticks_nesting,
                   rdp->dynticks->dynticks_nmi_nesting,
                   rdp->dynticks_fqs);
@@ -194,9 +194,8 @@ static int show_rcuexp(struct seq_file *m, void *v)
                s2 += atomic_long_read(&rdp->exp_workdone2);
                s3 += atomic_long_read(&rdp->exp_workdone3);
        }
-        seq_printf(m, "s=%lu wd0=%lu wd1=%lu wd2=%lu wd3=%lu n=%lu enq=%d sc=%lu\n",
+        seq_printf(m, "s=%lu wd0=%lu wd1=%lu wd2=%lu wd3=%lu enq=%d sc=%lu\n",
                   rsp->expedited_sequence, s0, s1, s2, s3,
-                   atomic_long_read(&rsp->expedited_normal),
                   atomic_read(&rsp->expedited_need_qs),
                   rsp->expedited_sequence / 2);
        return 0;
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 4f6db7e6a117..9e03db9ea9c0 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -132,8 +132,7 @@ bool rcu_gp_is_normal(void)
 }
 EXPORT_SYMBOL_GPL(rcu_gp_is_normal);
-static atomic_t rcu_expedited_nesting =
+static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1);
-        ATOMIC_INIT(IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT) ? 1 : 0);
 /*
 * Should normal grace-period primitives be expedited?  Intended for
@@ -182,8 +181,7 @@ EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
 */
 void rcu_end_inkernel_boot(void)
 {
-        if (IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT))
+        rcu_unexpedite_gp();
-                rcu_unexpedite_gp();
        if (rcu_normal_after_boot)
                WRITE_ONCE(rcu_normal, 1);
 }
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index eb9e9a7870fa..9db831439aa2 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1450,6 +1450,7 @@ config RCU_CPU_STALL_TIMEOUT
 config RCU_TRACE
        bool "Enable tracing for RCU"
        depends on DEBUG_KERNEL
+        default y if TREE_RCU
        select TRACE_CLOCK
        help
          This option provides tracing in RCU which presents stats
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/CFcommon b/tools/testing/selftests/rcutorture/configs/rcu/CFcommon
index f824b4c9d9d9..d2d2a86139db 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/CFcommon
+++ b/tools/testing/selftests/rcutorture/configs/rcu/CFcommon
@@ -1,5 +1,2 @@
 CONFIG_RCU_TORTURE_TEST=y
 CONFIG_PRINTK_TIME=y
-CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
-CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TINY01 b/tools/testing/selftests/rcutorture/configs/rcu/TINY01
index 0a63e073a00c..6db705e55487 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TINY01
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TINY01
@@ -7,6 +7,7 @@ CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
 CONFIG_RCU_TRACE=n
+#CHECK#CONFIG_RCU_STALL_COMMON=n
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_PREEMPT_COUNT=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TINY02 b/tools/testing/selftests/rcutorture/configs/rcu/TINY02
index f1892e0371c9..a59f7686e219 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TINY02
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TINY02
@@ -8,7 +8,8 @@ CONFIG_NO_HZ_IDLE=n
 CONFIG_NO_HZ_FULL=n
 CONFIG_RCU_TRACE=y
 CONFIG_PROVE_LOCKING=y
+CONFIG_PROVE_RCU_REPEATEDLY=y
 #CHECK#CONFIG_PROVE_RCU=y
 CONFIG_DEBUG_LOCK_ALLOC=y
-CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
+CONFIG_DEBUG_OBJECTS_RCU_HEAD=y
 CONFIG_PREEMPT_COUNT=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE01 b/tools/testing/selftests/rcutorture/configs/rcu/TREE01
index f572b873c620..359cb258f639 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE01
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE01
@@ -16,3 +16,6 @@ CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
+CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE02 b/tools/testing/selftests/rcutorture/configs/rcu/TREE02
index ef6a22c44dea..c1ab5926568b 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE02
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE02
@@ -20,3 +20,7 @@ CONFIG_PROVE_LOCKING=n
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
+CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y
+CONFIG_DEBUG_OBJECTS_RCU_HEAD=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE03 b/tools/testing/selftests/rcutorture/configs/rcu/TREE03
index 7a17c503b382..3b93ee544e70 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE03
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE03
@@ -17,3 +17,6 @@ CONFIG_RCU_BOOST=y
 CONFIG_RCU_KTHREAD_PRIO=2
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
+CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE04 b/tools/testing/selftests/rcutorture/configs/rcu/TREE04
index 17cbe098b115..5af758e783c7 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE04
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE04
@@ -19,3 +19,7 @@ CONFIG_RCU_NOCB_CPU=n
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
+CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y
+CONFIG_RCU_EQS_DEBUG=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE05 b/tools/testing/selftests/rcutorture/configs/rcu/TREE05
index 1257d3227b1e..d4cdc0d74e16 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE05
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE05
@@ -19,3 +19,6 @@ CONFIG_PROVE_LOCKING=y
 #CHECK#CONFIG_PROVE_RCU=y
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
+CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE06 b/tools/testing/selftests/rcutorture/configs/rcu/TREE06
index d3e456b74cbe..4cb02bd28f08 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE06
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE06
@@ -20,3 +20,6 @@ CONFIG_PROVE_LOCKING=y
 #CHECK#CONFIG_PROVE_RCU=y
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=y
 CONFIG_RCU_EXPERT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
+CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE07 b/tools/testing/selftests/rcutorture/configs/rcu/TREE07
index 3956b4131f72..b12a3ea1867e 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE07
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE07
@@ -19,3 +19,6 @@ CONFIG_RCU_NOCB_CPU=n
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
+CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
+CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE08 b/tools/testing/selftests/rcutorture/configs/rcu/TREE08
index bb9b0c1a23c2..099cc63c6a3b 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE08
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE08
@@ -17,8 +17,8 @@ CONFIG_RCU_FANOUT_LEAF=2
 CONFIG_RCU_NOCB_CPU=y
 CONFIG_RCU_NOCB_CPU_ALL=y
 CONFIG_DEBUG_LOCK_ALLOC=n
-CONFIG_PROVE_LOCKING=y
+CONFIG_PROVE_LOCKING=n
-#CHECK#CONFIG_PROVE_RCU=y
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
+CONFIG_RCU_EQS_DEBUG=y
diff --git a/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
index 4e2b1893d40d..364801b1a230 100644
--- a/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
+++ b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
@@ -14,6 +14,7 @@ CONFIG_NO_HZ_FULL_SYSIDLE -- Do one.
 CONFIG_PREEMPT -- Do half.  (First three and #8.)
 CONFIG_PROVE_LOCKING -- Do several, covering CONFIG_DEBUG_LOCK_ALLOC=y and not.
 CONFIG_PROVE_RCU -- Hardwired to CONFIG_PROVE_LOCKING.
+CONFIG_PROVE_RCU_REPEATEDLY -- Do one.
 CONFIG_RCU_BOOST -- one of PREEMPT_RCU.
 CONFIG_RCU_KTHREAD_PRIO -- set to 2 for _BOOST testing.
 CONFIG_RCU_FANOUT -- Cover hierarchy, but overlap with others.
@@ -25,7 +26,12 @@ CONFIG_RCU_NOCB_CPU_NONE -- Do one.
 CONFIG_RCU_NOCB_CPU_ZERO -- Do one.
 CONFIG_RCU_TRACE -- Do half.
 CONFIG_SMP -- Need one !SMP for PREEMPT_RCU.
-!RCU_EXPERT -- Do a few, but these have to be vanilla configurations.
+CONFIG_RCU_EXPERT=n -- Do a few, but these have to be vanilla configurations.
+CONFIG_RCU_EQS_DEBUG -- Do at least one for CONFIG_NO_HZ_FULL and not.
+CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP -- Do for all but a couple TREE scenarios.
+CONFIG_RCU_TORTURE_TEST_SLOW_INIT -- Do for all but a couple TREE scenarios.
+CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT -- Do for all but a couple TREE scenarios.
 RCU-bh: Do one with PREEMPT and one with !PREEMPT.
 RCU-sched: Do one with PREEMPT but not BOOST.
@@ -72,7 +78,30 @@ CONFIG_RCU_TORTURE_TEST_RUNNABLE
        Always used in KVM testing.
+CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
+CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY
+CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
+        Inspection suffices, ignore.
 CONFIG_PREEMPT_RCU
 CONFIG_TREE_RCU
+CONFIG_TINY_RCU
+        These are controlled by CONFIG_PREEMPT and/or CONFIG_SMP.
+CONFIG_SPARSE_RCU_POINTER
+        Makes sense only for sparse runs, not for kernel builds.
+CONFIG_SRCU
+CONFIG_TASKS_RCU
+        Selected by CONFIG_RCU_TORTURE_TEST, so cannot disable.
+CONFIG_RCU_TRACE
+        Implied by CONFIG_RCU_TRACE for Tree RCU.
-        These are controlled by CONFIG_PREEMPT.
+boot parameters ignored: TBD
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/.gitignore b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/.gitignore
new file mode 100644
index 000000000000..712a3d41a325
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/.gitignore
@@ -0,0 +1 @@
+srcu.c
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/Makefile b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/Makefile
new file mode 100644
index 000000000000..16b01559fa55
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/Makefile
@@ -0,0 +1,16 @@
+all: srcu.c store_buffering
+LINUX_SOURCE = ../../../../../..
+modified_srcu_input = $(LINUX_SOURCE)/include/linux/srcu.h \
+                      $(LINUX_SOURCE)/kernel/rcu/srcu.c
+modified_srcu_output = include/linux/srcu.h srcu.c
+include/linux/srcu.h: srcu.c
+srcu.c: modify_srcu.awk Makefile $(modified_srcu_input)
+        awk -f modify_srcu.awk $(modified_srcu_input) $(modified_srcu_output)
+store_buffering:
+        @cd tests/store_buffering; make
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/delay.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/delay.h
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/delay.h
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/export.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/export.h
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/export.h
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/mutex.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/mutex.h
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/mutex.h
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/percpu.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/percpu.h
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/percpu.h
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/preempt.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/preempt.h
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/preempt.h
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/rcupdate.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/rcupdate.h
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/rcupdate.h
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/sched.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/sched.h
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/sched.h
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/smp.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/smp.h
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/smp.h
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/workqueue.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/workqueue.h
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/linux/workqueue.h
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/uapi/linux/types.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/uapi/linux/types.h
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/empty_includes/uapi/linux/types.h
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/.gitignore b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/.gitignore
new file mode 100644
index 000000000000..1d016e66980a
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/.gitignore
@@ -0,0 +1 @@
+srcu.h
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/kconfig.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/kconfig.h
new file mode 100644
index 000000000000..f2860dd1b407
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/kconfig.h
@@ -0,0 +1 @@
+#include <LINUX_SOURCE/linux/kconfig.h>
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/types.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/types.h
new file mode 100644
index 000000000000..4a3d538fef12
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/types.h
@@ -0,0 +1,155 @@
+/*
+ * This header has been modifies to remove definitions of types that
+ * are defined in standard userspace headers or are problematic for some
+ * other reason.
+ */
+#ifndef _LINUX_TYPES_H
+#define _LINUX_TYPES_H
+#define __EXPORTED_HEADERS__
+#include <uapi/linux/types.h>
+#ifndef __ASSEMBLY__
+#define DECLARE_BITMAP(name, bits) \
+        unsigned long name[BITS_TO_LONGS(bits)]
+typedef __u32 __kernel_dev_t;
+/* bsd */
+typedef unsigned char           u_char;
+typedef unsigned short          u_short;
+typedef unsigned int            u_int;
+typedef unsigned long           u_long;
+/* sysv */
+typedef unsigned char           unchar;
+typedef unsigned short          ushort;
+typedef unsigned int            uint;
+typedef unsigned long           ulong;
+#ifndef __BIT_TYPES_DEFINED__
+#define __BIT_TYPES_DEFINED__
+typedef         __u8            u_int8_t;
+typedef         __s8            int8_t;
+typedef         __u16           u_int16_t;
+typedef         __s16           int16_t;
+typedef         __u32           u_int32_t;
+typedef         __s32           int32_t;
+#endif /* !(__BIT_TYPES_DEFINED__) */
+typedef         __u8            uint8_t;
+typedef         __u16           uint16_t;
+typedef         __u32           uint32_t;
+/* this is a special 64bit data type that is 8-byte aligned */
+#define aligned_u64 __u64 __attribute__((aligned(8)))
+#define aligned_be64 __be64 __attribute__((aligned(8)))
+#define aligned_le64 __le64 __attribute__((aligned(8)))
+/**
+ * The type used for indexing onto a disc or disc partition.
+ *
+ * Linux always considers sectors to be 512 bytes long independently
+ * of the devices real block size.
+ *
+ * blkcnt_t is the type of the inode's block count.
+ */
+#ifdef CONFIG_LBDAF
+typedef u64 sector_t;
+#else
+typedef unsigned long sector_t;
+#endif
+/*
+ * The type of an index into the pagecache.
+ */
+#define pgoff_t unsigned long
+/*
+ * A dma_addr_t can hold any valid DMA address, i.e., any address returned
+ * by the DMA API.
+ *
+ * If the DMA API only uses 32-bit addresses, dma_addr_t need only be 32
+ * bits wide.  Bus addresses, e.g., PCI BARs, may be wider than 32 bits,
+ * but drivers do memory-mapped I/O to ioremapped kernel virtual addresses,
+ * so they don't care about the size of the actual bus addresses.
+ */
+#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
+typedef u64 dma_addr_t;
+#else
+typedef u32 dma_addr_t;
+#endif
+#ifdef CONFIG_PHYS_ADDR_T_64BIT
+typedef u64 phys_addr_t;
+#else
+typedef u32 phys_addr_t;
+#endif
+typedef phys_addr_t resource_size_t;
+/*
+ * This type is the placeholder for a hardware interrupt number. It has to be
+ * big enough to enclose whatever representation is used by a given platform.
+ */
+typedef unsigned long irq_hw_number_t;
+typedef struct {
+        int counter;
+} atomic_t;
+#ifdef CONFIG_64BIT
+typedef struct {
+        long counter;
+} atomic64_t;
+#endif
+struct list_head {
+        struct list_head *next, *prev;
+};
+struct hlist_head {
+        struct hlist_node *first;
+};
+struct hlist_node {
+        struct hlist_node *next, **pprev;
+};
+/**
+ * struct callback_head - callback structure for use with RCU and task_work
+ * @next: next update requests in a list
+ * @func: actual update function to call after the grace period.
+ *
+ * The struct is aligned to size of pointer. On most architectures it happens
+ * naturally due ABI requirements, but some architectures (like CRIS) have
+ * weird ABI and we need to ask it explicitly.
+ *
+ * The alignment is required to guarantee that bits 0 and 1 of @next will be
+ * clear under normal conditions -- as long as we use call_rcu(),
+ * call_rcu_bh(), call_rcu_sched(), or call_srcu() to queue callback.
+ *
+ * This guarantee is important for few reasons:
+ *  - future call_rcu_lazy() will make use of lower bits in the pointer;
+ *  - the structure shares storage spacer in struct page with @compound_head,
+ *    which encode PageTail() in bit 0. The guarantee is needed to avoid
+ *    false-positive PageTail().
+ */
+struct callback_head {
+        struct callback_head *next;
+        void (*func)(struct callback_head *head);
+} __attribute__((aligned(sizeof(void *))));
+#define rcu_head callback_head
+typedef void (*rcu_callback_t)(struct rcu_head *head);
+typedef void (*call_rcu_func_t)(struct rcu_head *head, rcu_callback_t func);
+/* clocksource cycle base type */
+typedef u64 cycle_t;
+#endif /*  __ASSEMBLY__ */
+#endif /* _LINUX_TYPES_H */
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/modify_srcu.awk b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/modify_srcu.awk
new file mode 100755
index 000000000000..8ff89043d0a9
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/modify_srcu.awk
@@ -0,0 +1,375 @@
+#!/bin/awk -f
+# Modify SRCU for formal verification. The first argument should be srcu.h and
+# the second should be srcu.c. Outputs modified srcu.h and srcu.c into the
+# current directory.
+BEGIN {
+        if (ARGC != 5) {
+                print "Usange: input.h input.c output.h output.c" > "/dev/stderr";
+                exit 1;
+        }
+        h_output = ARGV[3];
+        c_output = ARGV[4];
+        ARGC = 3;
+        # Tokenize using FS and not RS as FS supports regular expressions. Each
+        # record is one line of source, except that backslashed lines are
+        # combined. Comments are treated as field separators, as are quotes.
+        quote_regexp="\"([^\\\\\"]|\\\\.)*\"";
+        comment_regexp="\\/\\*([^*]|\\*+[^*/])*\\*\\/|\\/\\/.*(\n|$)";
+        FS="([ \\\\\t\n\v\f;,.=(){}+*/<>&|^-]|\\[|\\]|" comment_regexp "|" quote_regexp ")+";
+        inside_srcu_struct = 0;
+        inside_srcu_init_def = 0;
+        srcu_init_param_name = "";
+        in_macro = 0;
+        brace_nesting = 0;
+        paren_nesting = 0;
+        # Allow the manipulation of the last field separator after has been
+        # seen.
+        last_fs = "";
+        # Whether the last field separator was intended to be output.
+        last_fs_print = 0;
+        # rcu_batches stores the initialization for each instance of struct
+        # rcu_batch
+        in_comment = 0;
+        outputfile = "";
+}
+{
+        prev_outputfile = outputfile;
+        if (FILENAME ~ /\.h$/) {
+                outputfile = h_output;
+                if (FNR != NR) {
+                        print "Incorrect file order" > "/dev/stderr";
+                        exit 1;
+                }
+        }
+        else
+                outputfile = c_output;
+        if (prev_outputfile && outputfile != prev_outputfile) {
+                new_outputfile = outputfile;
+                outputfile = prev_outputfile;
+                update_fieldsep("", 0);
+                outputfile = new_outputfile;
+        }
+}
+# Combine the next line into $0.
+function combine_line() {
+        ret = getline next_line;
+        if (ret == 0) {
+                # Don't allow two consecutive getlines at the end of the file
+                if (eof_found) {
+                        print "Error: expected more input." > "/dev/stderr";
+                        exit 1;
+                } else {
+                        eof_found = 1;
+                }
+        } else if (ret == -1) {
+                print "Error reading next line of file" FILENAME > "/dev/stderr";
+                exit 1;
+        }
+        $0 = $0 "\n" next_line;
+}
+# Combine backslashed lines and multiline comments.
+function combine_backslashes() {
+        while (/\\$|\/\*([^*]|\*+[^*\/])*\**$/) {
+                combine_line();
+        }
+}
+function read_line() {
+        combine_line();
+        combine_backslashes();
+}
+# Print out field separators and update variables that depend on them. Only
+# print if p is true. Call with sep="" and p=0 to print out the last field
+# separator.
+function update_fieldsep(sep, p) {
+        # Count braces
+        sep_tmp = sep;
+        gsub(quote_regexp "|" comment_regexp, "", sep_tmp);
+        while (1)
+        {
+                if (sub("[^{}()]*\\{", "", sep_tmp)) {
+                        brace_nesting++;
+                        continue;
+                }
+                if (sub("[^{}()]*\\}", "", sep_tmp)) {
+                        brace_nesting--;
+                        if (brace_nesting < 0) {
+                                print "Unbalanced braces!" > "/dev/stderr";
+                                exit 1;
+                        }
+                        continue;
+                }
+                if (sub("[^{}()]*\\(", "", sep_tmp)) {
+                        paren_nesting++;
+                        continue;
+                }
+                if (sub("[^{}()]*\\)", "", sep_tmp)) {
+                        paren_nesting--;
+                        if (paren_nesting < 0) {
+                                print "Unbalanced parenthesis!" > "/dev/stderr";
+                                exit 1;
+                        }
+                        continue;
+                }
+                break;
+        }
+        if (last_fs_print)
+                printf("%s", last_fs) > outputfile;
+        last_fs = sep;
+        last_fs_print = p;
+}
+# Shifts the fields down by n positions. Calls next if there are no more. If p
+# is true then print out field separators.
+function shift_fields(n, p) {
+        do {
+                if (match($0, FS) > 0) {
+                        update_fieldsep(substr($0, RSTART, RLENGTH), p);
+                        if (RSTART + RLENGTH <= length())
+                                $0 = substr($0, RSTART + RLENGTH);
+                        else
+                                $0 = "";
+                } else {
+                        update_fieldsep("", 0);
+                        print "" > outputfile;
+                        next;
+                }
+        } while (--n > 0);
+}
+# Shifts and prints the first n fields.
+function print_fields(n) {
+        do {
+                update_fieldsep("", 0);
+                printf("%s", $1) > outputfile;
+                shift_fields(1, 1);
+        } while (--n > 0);
+}
+{
+        combine_backslashes();
+}
+# Print leading FS
+{
+        if (match($0, "^(" FS ")+") > 0) {
+                update_fieldsep(substr($0, RSTART, RLENGTH), 1);
+                if (RSTART + RLENGTH <= length())
+                        $0 = substr($0, RSTART + RLENGTH);
+                else
+                        $0 = "";
+        }
+}
+# Parse the line.
+{
+        while (NF > 0) {
+                if ($1 == "struct" && NF < 3) {
+                        read_line();
+                        continue;
+                }
+                if (FILENAME ~ /\.h$/ && !inside_srcu_struct &&
+                    brace_nesting == 0 && paren_nesting == 0 &&
+                    $1 == "struct" && $2 == "srcu_struct" &&
+                    $0 ~ "^struct(" FS ")+srcu_struct(" FS ")+\\{") {
+                        inside_srcu_struct = 1;
+                        print_fields(2);
+                        continue;
+                }
+                if (inside_srcu_struct && brace_nesting == 0 &&
+                    paren_nesting == 0) {
+                        inside_srcu_struct = 0;
+                        update_fieldsep("", 0);
+                        for (name in rcu_batches)
+                                print "extern struct rcu_batch " name ";" > outputfile;
+                }
+                if (inside_srcu_struct && $1 == "struct" && $2 == "rcu_batch") {
+                        # Move rcu_batches outside of the struct.
+                        rcu_batches[$3] = "";
+                        shift_fields(3, 1);
+                        sub(/;[[:space:]]*$/, "", last_fs);
+                        continue;
+                }
+                if (FILENAME ~ /\.h$/ && !inside_srcu_init_def &&
+                    $1 == "#define" && $2 == "__SRCU_STRUCT_INIT") {
+                        inside_srcu_init_def = 1;
+                        srcu_init_param_name = $3;
+                        in_macro = 1;
+                        print_fields(3);
+                        continue;
+                }
+                if (inside_srcu_init_def && brace_nesting == 0 &&
+                    paren_nesting == 0) {
+                        inside_srcu_init_def = 0;
+                        in_macro = 0;
+                        continue;
+                }
+                if (inside_srcu_init_def && brace_nesting == 1 &&
+                    paren_nesting == 0 && last_fs ~ /\.[[:space:]]*$/ &&
+                    $1 ~ /^[[:alnum:]_]+$/) {
+                        name = $1;
+                        if (name in rcu_batches) {
+                                # Remove the dot.
+                                sub(/\.[[:space:]]*$/, "", last_fs);
+                                old_record = $0;
+                                do
+                                        shift_fields(1, 0);
+                                while (last_fs !~ /,/ || paren_nesting > 0);
+                                end_loc = length(old_record) - length($0);
+                                end_loc += index(last_fs, ",") - length(last_fs);
+                                last_fs = substr(last_fs, index(last_fs, ",") + 1);
+                                last_fs_print = 1;
+                                match(old_record, "^"name"("FS")+=");
+                                start_loc = RSTART + RLENGTH;
+                                len = end_loc - start_loc;
+                                initializer = substr(old_record, start_loc, len);
+                                gsub(srcu_init_param_name "\\.", "", initializer);
+                                rcu_batches[name] = initializer;
+                                continue;
+                        }
+                }
+                # Don't include a nonexistent file
+                if (!in_macro && $1 == "#include" && /^#include[[:space:]]+"rcu\.h"/) {
+                        update_fieldsep("", 0);
+                        next;
+                }
+                # Ignore most preprocessor stuff.
+                if (!in_macro && $1 ~ /#/) {
+                        break;
+                }
+                if (brace_nesting > 0 && $1 ~ "^[[:alnum:]_]+$" && NF < 2) {
+                        read_line();
+                        continue;
+                }
+                if (brace_nesting > 0 &&
+                    $0 ~ "^[[:alnum:]_]+[[:space:]]*(\\.|->)[[:space:]]*[[:alnum:]_]+" &&
+                    $2 in rcu_batches) {
+                        # Make uses of rcu_batches global. Somewhat unreliable.
+                        shift_fields(1, 0);
+                        print_fields(1);
+                        continue;
+                }
+                if ($1 == "static" && NF < 3) {
+                        read_line();
+                        continue;
+                }
+                if ($1 == "static" && ($2 == "bool" && $3 == "try_check_zero" ||
+                                       $2 == "void" && $3 == "srcu_flip")) {
+                        shift_fields(1, 1);
+                        print_fields(2);
+                        continue;
+                }
+                # Distinguish between read-side and write-side memory barriers.
+                if ($1 == "smp_mb" && NF < 2) {
+                        read_line();
+                        continue;
+                }
+                if (match($0, /^smp_mb[[:space:]();\/*]*[[:alnum:]]/)) {
+                        barrier_letter = substr($0, RLENGTH, 1);
+                        if (barrier_letter ~ /A|D/)
+                                new_barrier_name = "sync_smp_mb";
+                        else if (barrier_letter ~ /B|C/)
+                                new_barrier_name = "rs_smp_mb";
+                        else {
+                                print "Unrecognized memory barrier." > "/dev/null";
+                                exit 1;
+                        }
+                        shift_fields(1, 1);
+                        printf("%s", new_barrier_name) > outputfile;
+                        continue;
+                }
+                # Skip definition of rcu_synchronize, since it is already
+                # defined in misc.h. Only present in old versions of srcu.
+                if (brace_nesting == 0 && paren_nesting == 0 &&
+                    $1 == "struct" && $2 == "rcu_synchronize" &&
+                    $0 ~ "^struct(" FS ")+rcu_synchronize(" FS ")+\\{") {
+                        shift_fields(2, 0);
+                        while (brace_nesting) {
+                                if (NF < 2)
+                                        read_line();
+                                shift_fields(1, 0);
+                        }
+                }
+                # Skip definition of wakeme_after_rcu for the same reason
+                if (brace_nesting == 0 && $1 == "static" && $2 == "void" &&
+                    $3 == "wakeme_after_rcu") {
+                        while (NF < 5)
+                                read_line();
+                        shift_fields(3, 0);
+                        do {
+                                while (NF < 3)
+                                        read_line();
+                                shift_fields(1, 0);
+                        } while (paren_nesting || brace_nesting);
+                }
+                if ($1 ~ /^(unsigned|long)$/ && NF < 3) {
+                        read_line();
+                        continue;
+                }
+                # Give srcu_batches_completed the correct type for old SRCU.
+                if (brace_nesting == 0 && $1 == "long" &&
+                    $2 == "srcu_batches_completed") {
+                        update_fieldsep("", 0);
+                        printf("unsigned ") > outputfile;
+                        print_fields(2);
+                        continue;
+                }
+                if (brace_nesting == 0 && $1 == "unsigned" && $2 == "long" &&
+                    $3 == "srcu_batches_completed") {
+                        print_fields(3);
+                        continue;
+                }
+                # Just print out the input code by default.
+                print_fields(1);
+        }
+        update_fieldsep("", 0);
+        print > outputfile;
+        next;
+}
+END {
+        update_fieldsep("", 0);
+        if (brace_nesting != 0) {
+                print "Unbalanced braces!" > "/dev/stderr";
+                exit 1;
+        }
+        # Define the rcu_batches
+        for (name in rcu_batches)
+                print "struct rcu_batch " name " = " rcu_batches[name] ";" > c_output;
+}
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/assume.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/assume.h
new file mode 100644
index 000000000000..a64955447995
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/assume.h
@@ -0,0 +1,16 @@
+#ifndef ASSUME_H
+#define ASSUME_H
+/* Provide an assumption macro that can be disabled for gcc. */
+#ifdef RUN
+#define assume(x) \
+        do { \
+                /* Evaluate x to suppress warnings. */ \
+                (void) (x); \
+        } while (0)
+#else
+#define assume(x) __CPROVER_assume(x)
+#endif
+#endif
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/barriers.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/barriers.h
new file mode 100644
index 000000000000..6687acc08e6d
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/barriers.h
@@ -0,0 +1,41 @@
+#ifndef BARRIERS_H
+#define BARRIERS_H
+#define barrier() __asm__ __volatile__("" : : : "memory")
+#ifdef RUN
+#define smp_mb() __sync_synchronize()
+#define smp_mb__after_unlock_lock() __sync_synchronize()
+#else
+/*
+ * Copied from CBMC's implementation of __sync_synchronize(), which
+ * seems to be disabled by default.
+ */
+#define smp_mb() __CPROVER_fence("WWfence", "RRfence", "RWfence", "WRfence", \
+                                 "WWcumul", "RRcumul", "RWcumul", "WRcumul")
+#define smp_mb__after_unlock_lock() __CPROVER_fence("WWfence", "RRfence", "RWfence", "WRfence", \
+                                    "WWcumul", "RRcumul", "RWcumul", "WRcumul")
+#endif
+/*
+ * Allow memory barriers to be disabled in either the read or write side
+ * of SRCU individually.
+ */
+#ifndef NO_SYNC_SMP_MB
+#define sync_smp_mb() smp_mb()
+#else
+#define sync_smp_mb() do {} while (0)
+#endif
+#ifndef NO_READ_SIDE_SMP_MB
+#define rs_smp_mb() smp_mb()
+#else
+#define rs_smp_mb() do {} while (0)
+#endif
+#define ACCESS_ONCE(x) (*(volatile typeof(x) *) &(x))
+#define READ_ONCE(x) ACCESS_ONCE(x)
+#define WRITE_ONCE(x, val) (ACCESS_ONCE(x) = (val))
+#endif
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/bug_on.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/bug_on.h
new file mode 100644
index 000000000000..2a80e91f78e7
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/bug_on.h
@@ -0,0 +1,13 @@
+#ifndef BUG_ON_H
+#define BUG_ON_H
+#include <assert.h>
+#define BUG() assert(0)
+#define BUG_ON(x) assert(!(x))
+/* Does it make sense to treat warnings as errors? */
+#define WARN() BUG()
+#define WARN_ON(x) (BUG_ON(x), false)
+#endif
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/combined_source.c b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/combined_source.c
new file mode 100644
index 000000000000..29eb5d2697ed
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/combined_source.c
@@ -0,0 +1,13 @@
+#include <config.h>
+/* Include all source files. */
+#include "include_srcu.c"
+#include "preempt.c"
+#include "misc.c"
+/* Used by test.c files */
+#include <pthread.h>
+#include <stdlib.h>
+#include <linux/srcu.h>
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/config.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/config.h
new file mode 100644
index 000000000000..a60038aeea7a
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/config.h
@@ -0,0 +1,27 @@
+/* "Cheater" definitions based on restricted Kconfig choices. */
+#undef CONFIG_TINY_RCU
+#undef __CHECKER__
+#undef CONFIG_DEBUG_LOCK_ALLOC
+#undef CONFIG_DEBUG_OBJECTS_RCU_HEAD
+#undef CONFIG_HOTPLUG_CPU
+#undef CONFIG_MODULES
+#undef CONFIG_NO_HZ_FULL_SYSIDLE
+#undef CONFIG_PREEMPT_COUNT
+#undef CONFIG_PREEMPT_RCU
+#undef CONFIG_PROVE_RCU
+#undef CONFIG_RCU_NOCB_CPU
+#undef CONFIG_RCU_NOCB_CPU_ALL
+#undef CONFIG_RCU_STALL_COMMON
+#undef CONFIG_RCU_TRACE
+#undef CONFIG_RCU_USER_QS
+#undef CONFIG_TASKS_RCU
+#define CONFIG_TREE_RCU
+#define CONFIG_GENERIC_ATOMIC64
+#if NR_CPUS > 1
+#define CONFIG_SMP
+#else
+#undef CONFIG_SMP
+#endif
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/include_srcu.c b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/include_srcu.c
new file mode 100644
index 000000000000..5ec582a53018
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/include_srcu.c
@@ -0,0 +1,31 @@
+#include <config.h>
+#include <assert.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <pthread.h>
+#include <stddef.h>
+#include <string.h>
+#include <sys/types.h>
+#include "int_typedefs.h"
+#include "barriers.h"
+#include "bug_on.h"
+#include "locks.h"
+#include "misc.h"
+#include "preempt.h"
+#include "percpu.h"
+#include "workqueues.h"
+#ifdef USE_SIMPLE_SYNC_SRCU
+#define synchronize_srcu(sp) synchronize_srcu_original(sp)
+#endif
+#include <srcu.c>
+#ifdef USE_SIMPLE_SYNC_SRCU
+#undef synchronize_srcu
+#include "simple_sync_srcu.c"
+#endif
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/int_typedefs.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/int_typedefs.h
new file mode 100644
index 000000000000..3aad63917858
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/int_typedefs.h
@@ -0,0 +1,33 @@
+#ifndef INT_TYPEDEFS_H
+#define INT_TYPEDEFS_H
+#include <inttypes.h>
+typedef int8_t s8;
+typedef uint8_t u8;
+typedef int16_t s16;
+typedef uint16_t u16;
+typedef int32_t s32;
+typedef uint32_t u32;
+typedef int64_t s64;
+typedef uint64_t u64;
+typedef int8_t __s8;
+typedef uint8_t __u8;
+typedef int16_t __s16;
+typedef uint16_t __u16;
+typedef int32_t __s32;
+typedef uint32_t __u32;
+typedef int64_t __s64;
+typedef uint64_t __u64;
+#define S8_C(x) INT8_C(x)
+#define U8_C(x) UINT8_C(x)
+#define S16_C(x) INT16_C(x)
+#define U16_C(x) UINT16_C(x)
+#define S32_C(x) INT32_C(x)
+#define U32_C(x) UINT32_C(x)
+#define S64_C(x) INT64_C(x)
+#define U64_C(x) UINT64_C(x)
+#endif
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/locks.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/locks.h
new file mode 100644
index 000000000000..356004665576
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/locks.h
@@ -0,0 +1,220 @@
+#ifndef LOCKS_H
+#define LOCKS_H
+#include <limits.h>
+#include <pthread.h>
+#include <stdbool.h>
+#include "assume.h"
+#include "bug_on.h"
+#include "preempt.h"
+int nondet_int(void);
+#define __acquire(x)
+#define __acquires(x)
+#define __release(x)
+#define __releases(x)
+/* Only use one lock mechanism. Select which one. */
+#ifdef PTHREAD_LOCK
+struct lock_impl {
+        pthread_mutex_t mutex;
+};
+static inline void lock_impl_lock(struct lock_impl *lock)
+{
+        BUG_ON(pthread_mutex_lock(&lock->mutex));
+}
+static inline void lock_impl_unlock(struct lock_impl *lock)
+{
+        BUG_ON(pthread_mutex_unlock(&lock->mutex));
+}
+static inline bool lock_impl_trylock(struct lock_impl *lock)
+{
+        int err = pthread_mutex_trylock(&lock->mutex);
+        if (!err)
+                return true;
+        else if (err == EBUSY)
+                return false;
+        BUG();
+}
+static inline void lock_impl_init(struct lock_impl *lock)
+{
+        pthread_mutex_init(&lock->mutex, NULL);
+}
+#define LOCK_IMPL_INITIALIZER {.mutex = PTHREAD_MUTEX_INITIALIZER}
+#else /* !defined(PTHREAD_LOCK) */
+/* Spinlock that assumes that it always gets the lock immediately. */
+struct lock_impl {
+        bool locked;
+};
+static inline bool lock_impl_trylock(struct lock_impl *lock)
+{
+#ifdef RUN
+        /* TODO: Should this be a test and set? */
+        return __sync_bool_compare_and_swap(&lock->locked, false, true);
+#else
+        __CPROVER_atomic_begin();
+        bool old_locked = lock->locked;
+        lock->locked = true;
+        __CPROVER_atomic_end();
+        /* Minimal barrier to prevent accesses leaking out of lock. */
+        __CPROVER_fence("RRfence", "RWfence");
+        return !old_locked;
+#endif
+}
+static inline void lock_impl_lock(struct lock_impl *lock)
+{
+        /*
+         * CBMC doesn't support busy waiting, so just assume that the
+         * lock is available.
+         */
+        assume(lock_impl_trylock(lock));
+        /*
+         * If the lock was already held by this thread then the assumption
+         * is unsatisfiable (deadlock).
+         */
+}
+static inline void lock_impl_unlock(struct lock_impl *lock)
+{
+#ifdef RUN
+        BUG_ON(!__sync_bool_compare_and_swap(&lock->locked, true, false));
+#else
+        /* Minimal barrier to prevent accesses leaking out of lock. */
+        __CPROVER_fence("RWfence", "WWfence");
+        __CPROVER_atomic_begin();
+        bool old_locked = lock->locked;
+        lock->locked = false;
+        __CPROVER_atomic_end();
+        BUG_ON(!old_locked);
+#endif
+}
+static inline void lock_impl_init(struct lock_impl *lock)
+{
+        lock->locked = false;
+}
+#define LOCK_IMPL_INITIALIZER {.locked = false}
+#endif /* !defined(PTHREAD_LOCK) */
+/*
+ * Implement spinlocks using the lock mechanism. Wrap the lock to prevent mixing
+ * locks of different types.
+ */
+typedef struct {
+        struct lock_impl internal_lock;
+} spinlock_t;
+#define SPIN_LOCK_UNLOCKED {.internal_lock = LOCK_IMPL_INITIALIZER}
+#define __SPIN_LOCK_UNLOCKED(x) SPIN_LOCK_UNLOCKED
+#define DEFINE_SPINLOCK(x) spinlock_t x = SPIN_LOCK_UNLOCKED
+static inline void spin_lock_init(spinlock_t *lock)
+{
+        lock_impl_init(&lock->internal_lock);
+}
+static inline void spin_lock(spinlock_t *lock)
+{
+        /*
+         * Spin locks also need to be removed in order to eliminate all
+         * memory barriers. They are only used by the write side anyway.
+         */
+#ifndef NO_SYNC_SMP_MB
+        preempt_disable();
+        lock_impl_lock(&lock->internal_lock);
+#endif
+}
+static inline void spin_unlock(spinlock_t *lock)
+{
+#ifndef NO_SYNC_SMP_MB
+        lock_impl_unlock(&lock->internal_lock);
+        preempt_enable();
+#endif
+}
+/* Don't bother with interrupts */
+#define spin_lock_irq(lock) spin_lock(lock)
+#define spin_unlock_irq(lock) spin_unlock(lock)
+#define spin_lock_irqsave(lock, flags) spin_lock(lock)
+#define spin_unlock_irqrestore(lock, flags) spin_unlock(lock)
+/*
+ * This is supposed to return an int, but I think that a bool should work as
+ * well.
+ */
+static inline bool spin_trylock(spinlock_t *lock)
+{
+#ifndef NO_SYNC_SMP_MB
+        preempt_disable();
+        return lock_impl_trylock(&lock->internal_lock);
+#else
+        return true;
+#endif
+}
+struct completion {
+        /* Hopefuly this won't overflow. */
+        unsigned int count;
+};
+#define COMPLETION_INITIALIZER(x) {.count = 0}
+#define DECLARE_COMPLETION(x) struct completion x = COMPLETION_INITIALIZER(x)
+#define DECLARE_COMPLETION_ONSTACK(x) DECLARE_COMPLETION(x)
+static inline void init_completion(struct completion *c)
+{
+        c->count = 0;
+}
+static inline void wait_for_completion(struct completion *c)
+{
+        unsigned int prev_count = __sync_fetch_and_sub(&c->count, 1);
+        assume(prev_count);
+}
+static inline void complete(struct completion *c)
+{
+        unsigned int prev_count = __sync_fetch_and_add(&c->count, 1);
+        BUG_ON(prev_count == UINT_MAX);
+}
+/* This function probably isn't very useful for CBMC. */
+static inline bool try_wait_for_completion(struct completion *c)
+{
+        BUG();
+}
+static inline bool completion_done(struct completion *c)
+{
+        return c->count;
+}
+/* TODO: Implement complete_all */
+static inline void complete_all(struct completion *c)
+{
+        BUG();
+}
+#endif
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/misc.c b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/misc.c
new file mode 100644
index 000000000000..ca892e3b2351
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/misc.c
@@ -0,0 +1,11 @@
+#include <config.h>
+#include "misc.h"
+#include "bug_on.h"
+struct rcu_head;
+void wakeme_after_rcu(struct rcu_head *head)
+{
+        BUG();
+}
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/misc.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/misc.h
new file mode 100644
index 000000000000..aca50030f954
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/misc.h
@@ -0,0 +1,58 @@
+#ifndef MISC_H
+#define MISC_H
+#include "assume.h"
+#include "int_typedefs.h"
+#include "locks.h"
+#include <linux/types.h>
+/* Probably won't need to deal with bottom halves. */
+static inline void local_bh_disable(void) {}
+static inline void local_bh_enable(void) {}
+#define MODULE_ALIAS(X)
+#define module_param(...)
+#define EXPORT_SYMBOL_GPL(x)
+#define container_of(ptr, type, member) ({                      \
+        const typeof(((type *)0)->member) *__mptr = (ptr);      \
+        (type *)((char *)__mptr - offsetof(type, member));      \
+})
+#ifndef USE_SIMPLE_SYNC_SRCU
+/* Abuse udelay to make sure that busy loops terminate. */
+#define udelay(x) assume(0)
+#else
+/* The simple custom synchronize_srcu is ok with try_check_zero failing. */
+#define udelay(x) do { } while (0)
+#endif
+#define trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
+        do { } while (0)
+#define notrace
+/* Avoid including rcupdate.h */
+struct rcu_synchronize {
+        struct rcu_head head;
+        struct completion completion;
+};
+void wakeme_after_rcu(struct rcu_head *head);
+#define rcu_lock_acquire(a) do { } while (0)
+#define rcu_lock_release(a) do { } while (0)
+#define rcu_lockdep_assert(c, s) do { } while (0)
+#define RCU_LOCKDEP_WARN(c, s) do { } while (0)
+/* Let CBMC non-deterministically choose switch between normal and expedited. */
+bool rcu_gp_is_normal(void);
+bool rcu_gp_is_expedited(void);
+/* Do the same for old versions of rcu. */
+#define rcu_expedited (rcu_gp_is_expedited())
+#endif
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/percpu.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/percpu.h
new file mode 100644
index 000000000000..3de5a49de49b
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/percpu.h
@@ -0,0 +1,92 @@
+#ifndef PERCPU_H
+#define PERCPU_H
+#include <stddef.h>
+#include "bug_on.h"
+#include "preempt.h"
+#define __percpu
+/* Maximum size of any percpu data. */
+#define PERCPU_OFFSET (4 * sizeof(long))
+/* Ignore alignment, as CBMC doesn't care about false sharing. */
+#define alloc_percpu(type) __alloc_percpu(sizeof(type), 1)
+static inline void *__alloc_percpu(size_t size, size_t align)
+{
+        BUG();
+        return NULL;
+}
+static inline void free_percpu(void *ptr)
+{
+        BUG();
+}
+#define per_cpu_ptr(ptr, cpu) \
+        ((typeof(ptr)) ((char *) (ptr) + PERCPU_OFFSET * cpu))
+#define __this_cpu_inc(pcp) __this_cpu_add(pcp, 1)
+#define __this_cpu_dec(pcp) __this_cpu_sub(pcp, 1)
+#define __this_cpu_sub(pcp, n) __this_cpu_add(pcp, -(typeof(pcp)) (n))
+#define this_cpu_inc(pcp) this_cpu_add(pcp, 1)
+#define this_cpu_dec(pcp) this_cpu_sub(pcp, 1)
+#define this_cpu_sub(pcp, n) this_cpu_add(pcp, -(typeof(pcp)) (n))
+/* Make CBMC use atomics to work around bug. */
+#ifdef RUN
+#define THIS_CPU_ADD_HELPER(ptr, x) (*(ptr) += (x))
+#else
+/*
+ * Split the atomic into a read and a write so that it has the least
+ * possible ordering.
+ */
+#define THIS_CPU_ADD_HELPER(ptr, x) \
+        do { \
+                typeof(ptr) this_cpu_add_helper_ptr = (ptr); \
+                typeof(ptr) this_cpu_add_helper_x = (x); \
+                typeof(*ptr) this_cpu_add_helper_temp; \
+                __CPROVER_atomic_begin(); \
+                this_cpu_add_helper_temp = *(this_cpu_add_helper_ptr); \
+                __CPROVER_atomic_end(); \
+                this_cpu_add_helper_temp += this_cpu_add_helper_x; \
+                __CPROVER_atomic_begin(); \
+                *(this_cpu_add_helper_ptr) = this_cpu_add_helper_temp; \
+                __CPROVER_atomic_end(); \
+        } while (0)
+#endif
+/*
+ * For some reason CBMC needs an atomic operation even though this is percpu
+ * data.
+ */
+#define __this_cpu_add(pcp, n) \
+        do { \
+                BUG_ON(preemptible()); \
+                THIS_CPU_ADD_HELPER(per_cpu_ptr(&(pcp), thread_cpu_id), \
+                                    (typeof(pcp)) (n)); \
+        } while (0)
+#define this_cpu_add(pcp, n) \
+        do { \
+                int this_cpu_add_impl_cpu = get_cpu(); \
+                THIS_CPU_ADD_HELPER(per_cpu_ptr(&(pcp), this_cpu_add_impl_cpu), \
+                                    (typeof(pcp)) (n)); \
+                put_cpu(); \
+        } while (0)
+/*
+ * This will cause a compiler warning because of the cast from char[][] to
+ * type*. This will cause a compile time error if type is too big.
+ */
+#define DEFINE_PER_CPU(type, name) \
+        char name[NR_CPUS][PERCPU_OFFSET]; \
+        typedef char percpu_too_big_##name \
+                [sizeof(type) > PERCPU_OFFSET ? -1 : 1]
+#define for_each_possible_cpu(cpu) \
+        for ((cpu) = 0; (cpu) < NR_CPUS; ++(cpu))
+#endif
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/preempt.c b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/preempt.c
new file mode 100644
index 000000000000..4f1b068e9b7a
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/preempt.c
@@ -0,0 +1,78 @@
+#include <config.h>
+#include "preempt.h"
+#include "assume.h"
+#include "locks.h"
+/* Support NR_CPUS of at most 64 */
+#define CPU_PREEMPTION_LOCKS_INIT0 LOCK_IMPL_INITIALIZER
+#define CPU_PREEMPTION_LOCKS_INIT1 \
+        CPU_PREEMPTION_LOCKS_INIT0, CPU_PREEMPTION_LOCKS_INIT0
+#define CPU_PREEMPTION_LOCKS_INIT2 \
+        CPU_PREEMPTION_LOCKS_INIT1, CPU_PREEMPTION_LOCKS_INIT1
+#define CPU_PREEMPTION_LOCKS_INIT3 \
+        CPU_PREEMPTION_LOCKS_INIT2, CPU_PREEMPTION_LOCKS_INIT2
+#define CPU_PREEMPTION_LOCKS_INIT4 \
+        CPU_PREEMPTION_LOCKS_INIT3, CPU_PREEMPTION_LOCKS_INIT3
+#define CPU_PREEMPTION_LOCKS_INIT5 \
+        CPU_PREEMPTION_LOCKS_INIT4, CPU_PREEMPTION_LOCKS_INIT4
+/*
+ * Simulate disabling preemption by locking a particular cpu. NR_CPUS
+ * should be the actual number of cpus, not just the maximum.
+ */
+struct lock_impl cpu_preemption_locks[NR_CPUS] = {
+        CPU_PREEMPTION_LOCKS_INIT0
+#if (NR_CPUS - 1) & 1
+        , CPU_PREEMPTION_LOCKS_INIT0
+#endif
+#if (NR_CPUS - 1) & 2
+        , CPU_PREEMPTION_LOCKS_INIT1
+#endif
+#if (NR_CPUS - 1) & 4
+        , CPU_PREEMPTION_LOCKS_INIT2
+#endif
+#if (NR_CPUS - 1) & 8
+        , CPU_PREEMPTION_LOCKS_INIT3
+#endif
+#if (NR_CPUS - 1) & 16
+        , CPU_PREEMPTION_LOCKS_INIT4
+#endif
+#if (NR_CPUS - 1) & 32
+        , CPU_PREEMPTION_LOCKS_INIT5
+#endif
+};
+#undef CPU_PREEMPTION_LOCKS_INIT0
+#undef CPU_PREEMPTION_LOCKS_INIT1
+#undef CPU_PREEMPTION_LOCKS_INIT2
+#undef CPU_PREEMPTION_LOCKS_INIT3
+#undef CPU_PREEMPTION_LOCKS_INIT4
+#undef CPU_PREEMPTION_LOCKS_INIT5
+__thread int thread_cpu_id;
+__thread int preempt_disable_count;
+void preempt_disable(void)
+{
+        BUG_ON(preempt_disable_count < 0 || preempt_disable_count == INT_MAX);
+        if (preempt_disable_count++)
+                return;
+        thread_cpu_id = nondet_int();
+        assume(thread_cpu_id >= 0);
+        assume(thread_cpu_id < NR_CPUS);
+        lock_impl_lock(&cpu_preemption_locks[thread_cpu_id]);
+}
+void preempt_enable(void)
+{
+        BUG_ON(preempt_disable_count < 1);
+        if (--preempt_disable_count)
+                return;
+        lock_impl_unlock(&cpu_preemption_locks[thread_cpu_id]);
+}
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/preempt.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/preempt.h
new file mode 100644
index 000000000000..2f95ee0e4dd5
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/preempt.h
@@ -0,0 +1,58 @@
+#ifndef PREEMPT_H
+#define PREEMPT_H
+#include <stdbool.h>
+#include "bug_on.h"
+/* This flag contains garbage if preempt_disable_count is 0. */
+extern __thread int thread_cpu_id;
+/* Support recursive preemption disabling. */
+extern __thread int preempt_disable_count;
+void preempt_disable(void);
+void preempt_enable(void);
+static inline void preempt_disable_notrace(void)
+{
+        preempt_disable();
+}
+static inline void preempt_enable_no_resched(void)
+{
+        preempt_enable();
+}
+static inline void preempt_enable_notrace(void)
+{
+        preempt_enable();
+}
+static inline int preempt_count(void)
+{
+        return preempt_disable_count;
+}
+static inline bool preemptible(void)
+{
+        return !preempt_count();
+}
+static inline int get_cpu(void)
+{
+        preempt_disable();
+        return thread_cpu_id;
+}
+static inline void put_cpu(void)
+{
+        preempt_enable();
+}
+static inline void might_sleep(void)
+{
+        BUG_ON(preempt_disable_count);
+}
+#endif
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/simple_sync_srcu.c b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/simple_sync_srcu.c
new file mode 100644
index 000000000000..ac9cbc62b411
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/simple_sync_srcu.c
@@ -0,0 +1,50 @@
+#include <config.h>
+#include <assert.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <pthread.h>
+#include <stddef.h>
+#include <string.h>
+#include <sys/types.h>
+#include "int_typedefs.h"
+#include "barriers.h"
+#include "bug_on.h"
+#include "locks.h"
+#include "misc.h"
+#include "preempt.h"
+#include "percpu.h"
+#include "workqueues.h"
+#include <linux/srcu.h>
+/* Functions needed from modify_srcu.c */
+bool try_check_zero(struct srcu_struct *sp, int idx, int trycount);
+void srcu_flip(struct srcu_struct *sp);
+/* Simpler implementation of synchronize_srcu that ignores batching. */
+void synchronize_srcu(struct srcu_struct *sp)
+{
+        int idx;
+        /*
+         * This code assumes that try_check_zero will succeed anyway,
+         * so there is no point in multiple tries.
+         */
+        const int trycount = 1;
+        might_sleep();
+        /* Ignore the lock, as multiple writers aren't working yet anyway. */
+        idx = 1 ^ (sp->completed & 1);
+        /* For comments see srcu_advance_batches. */
+        assume(try_check_zero(sp, idx, trycount));
+        srcu_flip(sp);
+        assume(try_check_zero(sp, idx^1, trycount));
+}
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/workqueues.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/workqueues.h
new file mode 100644
index 000000000000..e58c8dfd3e90
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/workqueues.h
@@ -0,0 +1,102 @@
+#ifndef WORKQUEUES_H
+#define WORKQUEUES_H
+#include <stdbool.h>
+#include "barriers.h"
+#include "bug_on.h"
+#include "int_typedefs.h"
+#include <linux/types.h>
+/* Stub workqueue implementation. */
+struct work_struct;
+typedef void (*work_func_t)(struct work_struct *work);
+void delayed_work_timer_fn(unsigned long __data);
+struct work_struct {
+/*      atomic_long_t data; */
+        unsigned long data;
+        struct list_head entry;
+        work_func_t func;
+#ifdef CONFIG_LOCKDEP
+        struct lockdep_map lockdep_map;
+#endif
+};
+struct timer_list {
+        struct hlist_node       entry;
+        unsigned long           expires;
+        void                    (*function)(unsigned long);
+        unsigned long           data;
+        u32                     flags;
+        int                     slack;
+};
+struct delayed_work {
+        struct work_struct work;
+        struct timer_list timer;
+        /* target workqueue and CPU ->timer uses to queue ->work */
+        struct workqueue_struct *wq;
+        int cpu;
+};
+static inline bool schedule_work(struct work_struct *work)
+{
+        BUG();
+        return true;
+}
+static inline bool schedule_work_on(int cpu, struct work_struct *work)
+{
+        BUG();
+        return true;
+}
+static inline bool queue_work(struct workqueue_struct *wq,
+                              struct work_struct *work)
+{
+        BUG();
+        return true;
+}
+static inline bool queue_delayed_work(struct workqueue_struct *wq,
+                                      struct delayed_work *dwork,
+                                      unsigned long delay)
+{
+        BUG();
+        return true;
+}
+#define INIT_WORK(w, f) \
+        do { \
+                (w)->data = 0; \
+                (w)->func = (f); \
+        } while (0)
+#define INIT_DELAYED_WORK(w, f) INIT_WORK(&(w)->work, (f))
+#define __WORK_INITIALIZER(n, f) { \
+                .data = 0, \
+                .entry = { &(n).entry, &(n).entry }, \
+                .func = f \
+        }
+/* Don't bother initializing timer. */
+#define __DELAYED_WORK_INITIALIZER(n, f, tflags) { \
+        .work = __WORK_INITIALIZER((n).work, (f)), \
+        }
+#define DECLARE_WORK(n, f) \
+        struct workqueue_struct n = __WORK_INITIALIZER
+#define DECLARE_DELAYED_WORK(n, f) \
+        struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f, 0)
+#define system_power_efficient_wq ((struct workqueue_struct *) NULL)
+#endif
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/.gitignore b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/.gitignore
new file mode 100644
index 000000000000..f47cb2045f13
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/.gitignore
@@ -0,0 +1 @@
+*.out
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/Makefile b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/Makefile
new file mode 100644
index 000000000000..3a3aee149225
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/Makefile
@@ -0,0 +1,11 @@
+CBMC_FLAGS = -I../.. -I../../src -I../../include -I../../empty_includes -32 -pointer-check -mm pso
+all:
+        for i in ./*.pass; do \
+                echo $$i ; \
+                CBMC_FLAGS="$(CBMC_FLAGS)" sh ../test_script.sh --should-pass $$i > $$i.out 2>&1 ; \
+        done
+        for i in ./*.fail; do \
+                echo $$i ; \
+                CBMC_FLAGS="$(CBMC_FLAGS)" sh ../test_script.sh --should-fail $$i > $$i.out 2>&1 ; \
+        done
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/assert_end.fail b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/assert_end.fail
new file mode 100644
index 000000000000..40c8075919d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/assert_end.fail
@@ -0,0 +1 @@
+test_cbmc_options="-DASSERT_END"
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/force.fail b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/force.fail
new file mode 100644
index 000000000000..ada5baf0b60d
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/force.fail
@@ -0,0 +1 @@
+test_cbmc_options="-DFORCE_FAILURE"
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/force2.fail b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/force2.fail
new file mode 100644
index 000000000000..8fe00c8db466
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/force2.fail
@@ -0,0 +1 @@
+test_cbmc_options="-DFORCE_FAILURE_2"
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/force3.fail b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/force3.fail
new file mode 100644
index 000000000000..612ed6772844
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/force3.fail
@@ -0,0 +1 @@
+test_cbmc_options="-DFORCE_FAILURE_3"
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/main.pass b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/main.pass
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/main.pass
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/test.c b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/test.c
new file mode 100644
index 000000000000..470b1105a112
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/test.c
@@ -0,0 +1,72 @@
+#include <src/combined_source.c>
+int x;
+int y;
+int __unbuffered_tpr_x;
+int __unbuffered_tpr_y;
+DEFINE_SRCU(ss);
+void rcu_reader(void)
+{
+        int idx;
+#ifndef FORCE_FAILURE_3
+        idx = srcu_read_lock(&ss);
+#endif
+        might_sleep();
+        __unbuffered_tpr_y = READ_ONCE(y);
+#ifdef FORCE_FAILURE
+        srcu_read_unlock(&ss, idx);
+        idx = srcu_read_lock(&ss);
+#endif
+        WRITE_ONCE(x, 1);
+#ifndef FORCE_FAILURE_3
+        srcu_read_unlock(&ss, idx);
+#endif
+        might_sleep();
+}
+void *thread_update(void *arg)
+{
+        WRITE_ONCE(y, 1);
+#ifndef FORCE_FAILURE_2
+        synchronize_srcu(&ss);
+#endif
+        might_sleep();
+        __unbuffered_tpr_x = READ_ONCE(x);
+        return NULL;
+}
+void *thread_process_reader(void *arg)
+{
+        rcu_reader();
+        return NULL;
+}
+int main(int argc, char *argv[])
+{
+        pthread_t tu;
+        pthread_t tpr;
+        if (pthread_create(&tu, NULL, thread_update, NULL))
+                abort();
+        if (pthread_create(&tpr, NULL, thread_process_reader, NULL))
+                abort();
+        if (pthread_join(tu, NULL))
+                abort();
+        if (pthread_join(tpr, NULL))
+                abort();
+        assert(__unbuffered_tpr_y != 0 || __unbuffered_tpr_x != 0);
+#ifdef ASSERT_END
+        assert(0);
+#endif
+        return 0;
+}
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/test_script.sh b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/test_script.sh
new file mode 100755
index 000000000000..d1545972a0fa
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/test_script.sh
@@ -0,0 +1,102 @@
+#!/bin/sh
+# This script expects a mode (either --should-pass or --should-fail) followed by
+# an input file. The script uses the following environment variables. The test C
+# source file is expected to be named test.c in the directory containing the
+# input file.
+#
+# CBMC: The command to run CBMC. Default: cbmc
+# CBMC_FLAGS: Additional flags to pass to CBMC
+# NR_CPUS: Number of cpus to run tests with. Default specified by the test
+# SYNC_SRCU_MODE: Choose implementation of synchronize_srcu. Defaults to simple.
+#                 kernel: Version included in the linux kernel source.
+#                 simple: Use try_check_zero directly.
+#
+# The input file is a script that is sourced by this file. It can define any of
+# the following variables to configure the test.
+#
+# test_cbmc_options: Extra options to pass to CBMC.
+# min_cpus_fail: Minimum number of CPUs (NR_CPUS) for verification to fail.
+#                The test is expected to pass if it is run with fewer. (Only
+#                useful for .fail files)
+# default_cpus: Quantity of CPUs to use for the test, if not specified on the
+#               command line. Default: Larger of 2 and MIN_CPUS_FAIL.
+set -e
+if test "$#" -ne 2; then
+        echo "Expected one option followed by an input file" 1>&2
+        exit 99
+fi
+if test "x$1" = "x--should-pass"; then
+        should_pass="yes"
+elif test "x$1" = "x--should-fail"; then
+        should_pass="no"
+else
+        echo "Unrecognized argument '$1'" 1>&2
+        # Exit code 99 indicates a hard error.
+        exit 99
+fi
+CBMC=${CBMC:-cbmc}
+SYNC_SRCU_MODE=${SYNC_SRCU_MODE:-simple}
+case ${SYNC_SRCU_MODE} in
+kernel) sync_srcu_mode_flags="" ;;
+simple) sync_srcu_mode_flags="-DUSE_SIMPLE_SYNC_SRCU" ;;
+*)
+        echo "Unrecognized argument '${SYNC_SRCU_MODE}'" 1>&2
+        exit 99
+        ;;
+esac
+min_cpus_fail=1
+c_file=`dirname "$2"`/test.c
+# Source the input file.
+. $2
+if test ${min_cpus_fail} -gt 2; then
+        default_default_cpus=${min_cpus_fail}
+else
+        default_default_cpus=2
+fi
+default_cpus=${default_cpus:-${default_default_cpus}}
+cpus=${NR_CPUS:-${default_cpus}}
+# Check if there are two few cpus to make the test fail.
+if test $cpus -lt ${min_cpus_fail:-0}; then
+        should_pass="yes"
+fi
+cbmc_opts="-DNR_CPUS=${cpus} ${sync_srcu_mode_flags} ${test_cbmc_options} ${CBMC_FLAGS}"
+echo "Running CBMC: ${CBMC} ${cbmc_opts} ${c_file}"
+if ${CBMC} ${cbmc_opts} "${c_file}"; then
+        # Verification successful. Make sure that it was supposed to verify.
+        test "x${should_pass}" = xyes
+else
+        cbmc_exit_status=$?
+        # An exit status of 10 indicates a failed verification.
+        # (see cbmc_parse_optionst::do_bmc in the CBMC source code)
+        if test ${cbmc_exit_status} -eq 10 && test "x${should_pass}" = xno; then
+                :
+        else
+                echo "CBMC returned ${cbmc_exit_status} exit status" 1>&2
+                # Parse errors have exit status 6. Any other type of error
+                # should be considered a hard error.
+                if test ${cbmc_exit_status} -ne 6 && \
+                   test ${cbmc_exit_status} -ne 10; then
+                        exit 99
+                else
+                        exit 1
+                fi
+        fi
+fi
author	Ingo Molnar <mingo@kernel.org>	2017-01-31 01:45:42 -0500
committer	Ingo Molnar <mingo@kernel.org>	2017-01-31 01:45:42 -0500
commit	a8709fa4a06d4af5f86e3660839531cbe0f2a19b (patch)
tree	4deb2947a93294e4771265a60c508598a98cb494
parent	f9a42e0d58cf0fe3d902e63d4582f2ea4cd2bb8b (diff)
parent	31945aa9f14085c81cb3257e51bb210698b78626 (diff)