rcu: Remove debugfs tracing

RCU's debugfs tracing used to be the only reasonable low-level debug
information available, but ftrace and event tracing has since surpassed
the RCU debugfs level of usefulness.  This commit therefore removes
RCU's debugfs tracing.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

3 files changed, 1 insertions, 538 deletions

diff --git a/Documentation/RCU/00-INDEX b/Documentation/RCU/00-INDEX
index 1672573b037a..f46980c060aa 100644
--- a/Documentation/RCU/00-INDEX
+++ b/Documentation/RCU/00-INDEX
@@ -28,8 +28,6 @@ stallwarn.txt
         - RCU CPU stall warnings (module parameter rcu_cpu_stall_suppress)
 torture.txt
         - RCU Torture Test Operation (CONFIG_RCU_TORTURE_TEST)
-trace.txt
-        - CONFIG_RCU_TRACE debugfs files and formats
 UP.txt
         - RCU on Uniprocessor Systems
 whatisRCU.txt
diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html
index 0e6550a8c926..95b30fa25d56 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.html
+++ b/Documentation/RCU/Design/Requirements/Requirements.html
@@ -2034,7 +2034,7 @@ guard against mishaps and misuse:
         some other synchronization mechanism, for example, reference
         counting.
 <li>    In kernels built with <tt>CONFIG_RCU_TRACE=y</tt>, RCU-related
-        information is provided via both debugfs and event tracing.
+        information is provided via event tracing.
 <li>    Open-coded use of <tt>rcu_assign_pointer()</tt> and
         <tt>rcu_dereference()</tt> to create typical linked
         data structures can be surprisingly error-prone.
diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt
deleted file mode 100644
index 6549012033f9..000000000000
--- a/Documentation/RCU/trace.txt
+++ /dev/null
@@ -1,535 +0,0 @@
-CONFIG_RCU_TRACE debugfs Files and Formats
-
-
-The rcutree and rcutiny implementations of RCU provide debugfs trace
-output that summarizes counters and state.  This information is useful for
-debugging RCU itself, and can sometimes also help to debug abuses of RCU.
-The following sections describe the debugfs files and formats, first
-for rcutree and next for rcutiny.
-
-
-CONFIG_TREE_RCU and CONFIG_PREEMPT_RCU debugfs Files and Formats
-
-These implementations of RCU provide several debugfs directories under the
-top-level directory "rcu":
-
-rcu/rcu_bh
-rcu/rcu_preempt
-rcu/rcu_sched
-
-Each directory contains files for the corresponding flavor of RCU.
-Note that rcu/rcu_preempt is only present for CONFIG_PREEMPT_RCU.
-For CONFIG_TREE_RCU, the RCU flavor maps onto the RCU-sched flavor,
-so that activity for both appears in rcu/rcu_sched.
-
-In addition, the following file appears in the top-level directory:
-rcu/rcutorture.  This file displays rcutorture test progress.  The output
-of "cat rcu/rcutorture" looks as follows:
-
-rcutorture test sequence: 0 (test in progress)
-rcutorture update version number: 615
-
-The first line shows the number of rcutorture tests that have completed
-since boot.  If a test is currently running, the "(test in progress)"
-string will appear as shown above.  The second line shows the number of
-update cycles that the current test has started, or zero if there is
-no test in progress.
-
-
-Within each flavor directory (rcu/rcu_bh, rcu/rcu_sched, and possibly
-also rcu/rcu_preempt) the following files will be present:
-
-rcudata:
-        Displays fields in struct rcu_data.
-rcuexp:
-        Displays statistics for expedited grace periods.
-rcugp:
-        Displays grace-period counters.
-rcuhier:
-        Displays the struct rcu_node hierarchy.
-rcu_pending:
-        Displays counts of the reasons rcu_pending() decided that RCU had
-        work to do.
-rcuboost:
-        Displays RCU boosting statistics.  Only present if
-        CONFIG_RCU_BOOST=y.
-
-The output of "cat rcu/rcu_preempt/rcudata" looks as follows:
-
-  0!c=30455 g=30456 cnq=1/0:1 dt=126535/140000000000000/0 df=2002 of=4 ql=0/0 qs=N... b=10 ci=74572 nci=0 co=1131 ca=716
-  1!c=30719 g=30720 cnq=1/0:0 dt=132007/140000000000000/0 df=1874 of=10 ql=0/0 qs=N... b=10 ci=123209 nci=0 co=685 ca=982
-  2!c=30150 g=30151 cnq=1/1:1 dt=138537/140000000000000/0 df=1707 of=8 ql=0/0 qs=N... b=10 ci=80132 nci=0 co=1328 ca=1458
-  3 c=31249 g=31250 cnq=1/1:0 dt=107255/140000000000000/0 df=1749 of=6 ql=0/450 qs=NRW. b=10 ci=151700 nci=0 co=509 ca=622
-  4!c=29502 g=29503 cnq=1/0:1 dt=83647/140000000000000/0 df=965 of=5 ql=0/0 qs=N... b=10 ci=65643 nci=0 co=1373 ca=1521
-  5 c=31201 g=31202 cnq=1/0:1 dt=70422/0/0 df=535 of=7 ql=0/0 qs=.... b=10 ci=58500 nci=0 co=764 ca=698
-  6!c=30253 g=30254 cnq=1/0:1 dt=95363/140000000000000/0 df=780 of=5 ql=0/0 qs=N... b=10 ci=100607 nci=0 co=1414 ca=1353
-  7 c=31178 g=31178 cnq=1/0:0 dt=91536/0/0 df=547 of=4 ql=0/0 qs=.... b=10 ci=109819 nci=0 co=1115 ca=969
-
-This file has one line per CPU, or eight for this 8-CPU system.
-The fields are as follows:
-
-o       The number at the beginning of each line is the CPU number.
-        CPUs numbers followed by an exclamation mark are offline,
-        but have been online at least once since boot.  There will be
-        no output for CPUs that have never been online, which can be
-        a good thing in the surprisingly common case where NR_CPUS is
-        substantially larger than the number of actual CPUs.
-
-o       "c" is the count of grace periods that this CPU believes have
-        completed.  Offlined CPUs and CPUs in dynticks idle mode may lag
-        quite a ways behind, for example, CPU 4 under "rcu_sched" above,
-        which has been offline through 16 RCU grace periods.  It is not
-        unusual to see offline CPUs lagging by thousands of grace periods.
-        Note that although the grace-period number is an unsigned long,
-        it is printed out as a signed long to allow more human-friendly
-        representation near boot time.
-
-o       "g" is the count of grace periods that this CPU believes have
-        started.  Again, offlined CPUs and CPUs in dynticks idle mode
-        may lag behind.  If the "c" and "g" values are equal, this CPU
-        has already reported a quiescent state for the last RCU grace
-        period that it is aware of, otherwise, the CPU believes that it
-        owes RCU a quiescent state.
-
-o       "pq" indicates that this CPU has passed through a quiescent state
-        for the current grace period.  It is possible for "pq" to be
-        "1" and "c" different than "g", which indicates that although
-        the CPU has passed through a quiescent state, either (1) this
-        CPU has not yet reported that fact, (2) some other CPU has not
-        yet reported for this grace period, or (3) both.
-
-o       "qp" indicates that RCU still expects a quiescent state from
-        this CPU.  Offlined CPUs and CPUs in dyntick idle mode might
-        well have qp=1, which is OK: RCU is still ignoring them.
-
-o       "dt" is the current value of the dyntick counter that is incremented
-        when entering or leaving idle, either due to a context switch or
-        due to an interrupt.  This number is even if the CPU is in idle
-        from RCU's viewpoint and odd otherwise.  The number after the
-        first "/" is the interrupt nesting depth when in idle state,
-        or a large number added to the interrupt-nesting depth when
-        running a non-idle task.  Some architectures do not accurately
-        count interrupt nesting when running in non-idle kernel context,
-        which can result in interesting anomalies such as negative
-        interrupt-nesting levels.  The number after the second "/"
-        is the NMI nesting depth.
-
-o       "df" is the number of times that some other CPU has forced a
-        quiescent state on behalf of this CPU due to this CPU being in
-        idle state.
-
-o       "of" is the number of times that some other CPU has forced a
-        quiescent state on behalf of this CPU due to this CPU being
-        offline.  In a perfect world, this might never happen, but it
-        turns out that offlining and onlining a CPU can take several grace
-        periods, and so there is likely to be an extended period of time
-        when RCU believes that the CPU is online when it really is not.
-        Please note that erring in the other direction (RCU believing a
-        CPU is offline when it is really alive and kicking) is a fatal
-        error, so it makes sense to err conservatively.
-
-o       "ql" is the number of RCU callbacks currently residing on
-        this CPU.  The first number is the number of "lazy" callbacks
-        that are known to RCU to only be freeing memory, and the number
-        after the "/" is the total number of callbacks, lazy or not.
-        These counters count callbacks regardless of what phase of
-        grace-period processing that they are in (new, waiting for
-        grace period to start, waiting for grace period to end, ready
-        to invoke).
-
-o       "qs" gives an indication of the state of the callback queue
-        with four characters:
-
-        "N"     Indicates that there are callbacks queued that are not
-                ready to be handled by the next grace period, and thus
-                will be handled by the grace period following the next
-                one.
-
-        "R"     Indicates that there are callbacks queued that are
-                ready to be handled by the next grace period.
-
-        "W"     Indicates that there are callbacks queued that are
-                waiting on the current grace period.
-
-        "D"     Indicates that there are callbacks queued that have
-                already been handled by a prior grace period, and are
-                thus waiting to be invoked.  Note that callbacks in
-                the process of being invoked are not counted here.
-                Callbacks in the process of being invoked are those
-                that have been removed from the rcu_data structures
-                queues by rcu_do_batch(), but which have not yet been
-                invoked.
-
-        If there are no callbacks in a given one of the above states,
-        the corresponding character is replaced by ".".
-
-o       "b" is the batch limit for this CPU.  If more than this number
-        of RCU callbacks is ready to invoke, then the remainder will
-        be deferred.
-
-o       "ci" is the number of RCU callbacks that have been invoked for
-        this CPU.  Note that ci+nci+ql is the number of callbacks that have
-        been registered in absence of CPU-hotplug activity.
-
-o       "nci" is the number of RCU callbacks that have been offloaded from
-        this CPU.  This will always be zero unless the kernel was built
-        with CONFIG_RCU_NOCB_CPU=y and the "rcu_nocbs=" kernel boot
-        parameter was specified.
-
-o       "co" is the number of RCU callbacks that have been orphaned due to
-        this CPU going offline.  These orphaned callbacks have been moved
-        to an arbitrarily chosen online CPU.
-
-o       "ca" is the number of RCU callbacks that have been adopted by this
-        CPU due to other CPUs going offline.  Note that ci+co-ca+ql is
-        the number of RCU callbacks registered on this CPU.
-
-
-Kernels compiled with CONFIG_RCU_BOOST=y display the following from
-/debug/rcu/rcu_preempt/rcudata:
-
-  0!c=12865 g=12866 cnq=1/0:1 dt=83113/140000000000000/0 df=288 of=11 ql=0/0 qs=N... kt=0/O ktl=944 b=10 ci=60709 nci=0 co=748 ca=871
-  1 c=14407 g=14408 cnq=1/0:0 dt=100679/140000000000000/0 df=378 of=7 ql=0/119 qs=NRW. kt=0/W ktl=9b6 b=10 ci=109740 nci=0 co=589 ca=485
-  2 c=14407 g=14408 cnq=1/0:0 dt=105486/0/0 df=90 of=9 ql=0/89 qs=NRW. kt=0/W ktl=c0c b=10 ci=83113 nci=0 co=533 ca=490
-  3 c=14407 g=14408 cnq=1/0:0 dt=107138/0/0 df=142 of=8 ql=0/188 qs=NRW. kt=0/W ktl=b96 b=10 ci=121114 nci=0 co=426 ca=290
-  4 c=14405 g=14406 cnq=1/0:1 dt=50238/0/0 df=706 of=7 ql=0/0 qs=.... kt=0/W ktl=812 b=10 ci=34929 nci=0 co=643 ca=114
-  5!c=14168 g=14169 cnq=1/0:0 dt=45465/140000000000000/0 df=161 of=11 ql=0/0 qs=N... kt=0/O ktl=b4d b=10 ci=47712 nci=0 co=677 ca=722
-  6 c=14404 g=14405 cnq=1/0:0 dt=59454/0/0 df=94 of=6 ql=0/0 qs=.... kt=0/W ktl=e57 b=10 ci=55597 nci=0 co=701 ca=811
-  7 c=14407 g=14408 cnq=1/0:1 dt=68850/0/0 df=31 of=8 ql=0/0 qs=.... kt=0/W ktl=14bd b=10 ci=77475 nci=0 co=508 ca=1042
-
-This is similar to the output discussed above, but contains the following
-additional fields:
-
-o       "kt" is the per-CPU kernel-thread state.  The digit preceding
-        the first slash is zero if there is no work pending and 1
-        otherwise.  The character between the first pair of slashes is
-        as follows:
-
-        "S"     The kernel thread is stopped, in other words, all
-                CPUs corresponding to this rcu_node structure are
-                offline.
-
-        "R"     The kernel thread is running.
-
-        "W"     The kernel thread is waiting because there is no work
-                for it to do.
-
-        "O"     The kernel thread is waiting because it has been
-                forced off of its designated CPU or because its
-                ->cpus_allowed mask permits it to run on other than
-                its designated CPU.
-
-        "Y"     The kernel thread is yielding to avoid hogging CPU.
-
-        "?"     Unknown value, indicates a bug.
-
-        The number after the final slash is the CPU that the kthread
-        is actually running on.
-
-        This field is displayed only for CONFIG_RCU_BOOST kernels.
-
-o       "ktl" is the low-order 16 bits (in hexadecimal) of the count of
-        the number of times that this CPU's per-CPU kthread has gone
-        through its loop servicing invoke_rcu_cpu_kthread() requests.
-
-        This field is displayed only for CONFIG_RCU_BOOST kernels.
-
-
-The output of "cat rcu/rcu_preempt/rcuexp" looks as follows:
-
-s=21872 wd1=0 wd2=0 wd3=5 enq=0 sc=21872
-
-These fields are as follows:
-
-o       "s" is the sequence number, with an odd number indicating that
-        an expedited grace period is in progress.
-
-o       "wd1", "wd2", and "wd3" are the number of times that an attempt
-        to start an expedited grace period found that someone else had
-        completed an expedited grace period that satisfies the attempted
-        request.  "Our work is done."
-
-o       "enq" is the number of quiescent states still outstanding.
-
-o       "sc" is the number of times that the attempt to start a
-        new expedited grace period succeeded.
-
-
-The output of "cat rcu/rcu_preempt/rcugp" looks as follows:
-
-completed=31249  gpnum=31250  age=1  max=18
-
-These fields are taken from the rcu_state structure, and are as follows:
-
-o       "completed" is the number of grace periods that have completed.
-        It is comparable to the "c" field from rcu/rcudata in that a
-        CPU whose "c" field matches the value of "completed" is aware
-        that the corresponding RCU grace period has completed.
-
-o       "gpnum" is the number of grace periods that have started.  It is
-        similarly comparable to the "g" field from rcu/rcudata in that
-        a CPU whose "g" field matches the value of "gpnum" is aware that
-        the corresponding RCU grace period has started.
-
-        If these two fields are equal, then there is no grace period
-        in progress, in other words, RCU is idle.  On the other hand,
-        if the two fields differ (as they are above), then an RCU grace
-        period is in progress.
-
-o       "age" is the number of jiffies that the current grace period
-        has extended for, or zero if there is no grace period currently
-        in effect.
-
-o       "max" is the age in jiffies of the longest-duration grace period
-        thus far.
-
-The output of "cat rcu/rcu_preempt/rcuhier" looks as follows:
-
-c=14407 g=14408 s=0 jfq=2 j=c863 nfqs=12040/nfqsng=0(12040) fqlh=1051 oqlen=0/0
-3/3 ..>. 0:7 ^0
-e/e ..>. 0:3 ^0    d/d ..>. 4:7 ^1
-
-The fields are as follows:
-
-o       "c" is exactly the same as "completed" under rcu/rcu_preempt/rcugp.
-
-o       "g" is exactly the same as "gpnum" under rcu/rcu_preempt/rcugp.
-
-o       "s" is the current state of the force_quiescent_state()
-        state machine.
-
-o       "jfq" is the number of jiffies remaining for this grace period
-        before force_quiescent_state() is invoked to help push things
-        along.  Note that CPUs in idle mode throughout the grace period
-        will not report on their own, but rather must be check by some
-        other CPU via force_quiescent_state().
-
-o       "j" is the low-order four hex digits of the jiffies counter.
-        Yes, Paul did run into a number of problems that turned out to
-        be due to the jiffies counter no longer counting.  Why do you ask?
-
-o       "nfqs" is the number of calls to force_quiescent_state() since
-        boot.
-
-o       "nfqsng" is the number of useless calls to force_quiescent_state(),
-        where there wasn't actually a grace period active.  This can
-        no longer happen due to grace-period processing being pushed
-        into a kthread.  The number in parentheses is the difference
-        between "nfqs" and "nfqsng", or the number of times that
-        force_quiescent_state() actually did some real work.
-
-o       "fqlh" is the number of calls to force_quiescent_state() that
-        exited immediately (without even being counted in nfqs above)
-        due to contention on ->fqslock.
-
-o       Each element of the form "3/3 ..>. 0:7 ^0" represents one rcu_node
-        structure.  Each line represents one level of the hierarchy,
-        from root to leaves.  It is best to think of the rcu_data
-        structures as forming yet another level after the leaves.
-        Note that there might be either one, two, three, or even four
-        levels of rcu_node structures, depending on the relationship
-        between CONFIG_RCU_FANOUT, CONFIG_RCU_FANOUT_LEAF (possibly
-        adjusted using the rcu_fanout_leaf kernel boot parameter), and
-        CONFIG_NR_CPUS (possibly adjusted using the nr_cpu_ids count of
-        possible CPUs for the booting hardware).
-
-        o       The numbers separated by the "/" are the qsmask followed
-                by the qsmaskinit.  The qsmask will have one bit
-                set for each entity in the next lower level that has
-                not yet checked in for the current grace period ("e"
-                indicating CPUs 5, 6, and 7 in the example above).
-                The qsmaskinit will have one bit for each entity that is
-                currently expected to check in during each grace period.
-                The value of qsmaskinit is assigned to that of qsmask
-                at the beginning of each grace period.
-
-        o       The characters separated by the ">" indicate the state
-                of the blocked-tasks lists.  A "G" preceding the ">"
-                indicates that at least one task blocked in an RCU
-                read-side critical section blocks the current grace
-                period, while a "E" preceding the ">" indicates that
-                at least one task blocked in an RCU read-side critical
-                section blocks the current expedited grace period.
-                A "T" character following the ">" indicates that at
-                least one task is blocked within an RCU read-side
-                critical section, regardless of whether any current
-                grace period (expedited or normal) is inconvenienced.
-                A "." character appears if the corresponding condition
-                does not hold, so that "..>." indicates that no tasks
-                are blocked.  In contrast, "GE>T" indicates maximal
-                inconvenience from blocked tasks.  CONFIG_TREE_RCU
-                builds of the kernel will always show "..>.".
-
-        o       The numbers separated by the ":" are the range of CPUs
-                served by this struct rcu_node.  This can be helpful
-                in working out how the hierarchy is wired together.
-
-                For example, the example rcu_node structure shown above
-                has "0:7", indicating that it covers CPUs 0 through 7.
-
-        o       The number after the "^" indicates the bit in the
-                next higher level rcu_node structure that this rcu_node
-                structure corresponds to.  For example, the "d/d ..>. 4:7
-                ^1" has a "1" in this position, indicating that it
-                corresponds to the "1" bit in the "3" shown in the
-                "3/3 ..>. 0:7 ^0" entry on the next level up.
-
-
-The output of "cat rcu/rcu_sched/rcu_pending" looks as follows:
-
-  0!np=26111 qsp=29 rpq=5386 cbr=1 cng=570 gpc=3674 gps=577 nn=15903 ndw=0
-  1!np=28913 qsp=35 rpq=6097 cbr=1 cng=448 gpc=3700 gps=554 nn=18113 ndw=0
-  2!np=32740 qsp=37 rpq=6202 cbr=0 cng=476 gpc=4627 gps=546 nn=20889 ndw=0
-  3 np=23679 qsp=22 rpq=5044 cbr=1 cng=415 gpc=3403 gps=347 nn=14469 ndw=0
-  4!np=30714 qsp=4 rpq=5574 cbr=0 cng=528 gpc=3931 gps=639 nn=20042 ndw=0
-  5 np=28910 qsp=2 rpq=5246 cbr=0 cng=428 gpc=4105 gps=709 nn=18422 ndw=0
-  6!np=38648 qsp=5 rpq=7076 cbr=0 cng=840 gpc=4072 gps=961 nn=25699 ndw=0
-  7 np=37275 qsp=2 rpq=6873 cbr=0 cng=868 gpc=3416 gps=971 nn=25147 ndw=0
-
-The fields are as follows:
-
-o       The leading number is the CPU number, with "!" indicating
-        an offline CPU.
-
-o       "np" is the number of times that __rcu_pending() has been invoked
-        for the corresponding flavor of RCU.
-
-o       "qsp" is the number of times that the RCU was waiting for a
-        quiescent state from this CPU.
-
-o       "rpq" is the number of times that the CPU had passed through
-        a quiescent state, but not yet reported it to RCU.
-
-o       "cbr" is the number of times that this CPU had RCU callbacks
-        that had passed through a grace period, and were thus ready
-        to be invoked.
-
-o       "cng" is the number of times that this CPU needed another
-        grace period while RCU was idle.
-
-o       "gpc" is the number of times that an old grace period had
-        completed, but this CPU was not yet aware of it.
-
-o       "gps" is the number of times that a new grace period had started,
-        but this CPU was not yet aware of it.
-
-o       "ndw" is the number of times that a wakeup of an rcuo
-        callback-offload kthread had to be deferred in order to avoid
-        deadlock.
-
-o       "nn" is the number of times that this CPU needed nothing.
-
-
-The output of "cat rcu/rcuboost" looks as follows:
-
-0:3 tasks=.... kt=W ntb=0 neb=0 nnb=0 j=c864 bt=c894
-    balk: nt=0 egt=4695 bt=0 nb=0 ny=56 nos=0
-4:7 tasks=.... kt=W ntb=0 neb=0 nnb=0 j=c864 bt=c894
-    balk: nt=0 egt=6541 bt=0 nb=0 ny=126 nos=0
-
-This information is output only for rcu_preempt.  Each two-line entry
-corresponds to a leaf rcu_node structure.  The fields are as follows:
-
-o       "n:m" is the CPU-number range for the corresponding two-line
-        entry.  In the sample output above, the first entry covers
-        CPUs zero through three and the second entry covers CPUs four
-        through seven.
-
-o       "tasks=TNEB" gives the state of the various segments of the
-        rnp->blocked_tasks list:
-
-        "T"     This indicates that there are some tasks that blocked
-                while running on one of the corresponding CPUs while
-                in an RCU read-side critical section.
-
-        "N"     This indicates that some of the blocked tasks are preventing
-                the current normal (non-expedited) grace period from
-                completing.
-
-        "E"     This indicates that some of the blocked tasks are preventing
-                the current expedited grace period from completing.
-
-        "B"     This indicates that some of the blocked tasks are in
-                need of RCU priority boosting.
-
-        Each character is replaced with "." if the corresponding
-        condition does not hold.
-
-o       "kt" is the state of the RCU priority-boosting kernel
-        thread associated with the corresponding rcu_node structure.
-        The state can be one of the following:
-
-        "S"     The kernel thread is stopped, in other words, all
-                CPUs corresponding to this rcu_node structure are
-                offline.
-
-        "R"     The kernel thread is running.
-
-        "W"     The kernel thread is waiting because there is no work
-                for it to do.
-
-        "Y"     The kernel thread is yielding to avoid hogging CPU.
-
-        "?"     Unknown value, indicates a bug.
-
-o       "ntb" is the number of tasks boosted.
-
-o       "neb" is the number of tasks boosted in order to complete an
-        expedited grace period.
-
-o       "nnb" is the number of tasks boosted in order to complete a
-        normal (non-expedited) grace period.  When boosting a task
-        that was blocking both an expedited and a normal grace period,
-        it is counted against the expedited total above.
-
-o       "j" is the low-order 16 bits of the jiffies counter in
-        hexadecimal.
-
-o       "bt" is the low-order 16 bits of the value that the jiffies
-        counter will have when we next start boosting, assuming that
-        the current grace period does not end beforehand.  This is
-        also in hexadecimal.
-
-o       "balk: nt" counts the number of times we didn't boost (in
-        other words, we balked) even though it was time to boost because
-        there were no blocked tasks to boost.  This situation occurs
-        when there is one blocked task on one rcu_node structure and
-        none on some other rcu_node structure.
-
-o       "egt" counts the number of times we balked because although
-        there were blocked tasks, none of them were blocking the
-        current grace period, whether expedited or otherwise.
-
-o       "bt" counts the number of times we balked because boosting
-        had already been initiated for the current grace period.
-
-o       "nb" counts the number of times we balked because there
-        was at least one task blocking the current non-expedited grace
-        period that never had blocked.  If it is already running, it
-        just won't help to boost its priority!
-
-o       "ny" counts the number of times we balked because it was
-        not yet time to start boosting.
-
-o       "nos" counts the number of times we balked for other
-        reasons, e.g., the grace period ended first.
-
-
-CONFIG_TINY_RCU debugfs Files and Formats
-
-These implementations of RCU provides a single debugfs file under the
-top-level directory RCU, namely rcu/rcudata, which displays fields in
-rcu_bh_ctrlblk and rcu_sched_ctrlblk.
-
-The output of "cat rcu/rcudata" is as follows:
-
-rcu_sched: qlen: 0
-rcu_bh: qlen: 0
-
-This is split into rcu_sched and rcu_bh sections.  The field is as
-follows:
-
-o       "qlen" is the number of RCU callbacks currently waiting either
-        for an RCU grace period or waiting to be invoked.  This is the
-        only field present for rcu_sched and rcu_bh, due to the
-        short-circuiting of grace period in those two cases.