Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU update from Ingo Molnar:
 "The major features of this tree are:

     1. A first version of no-callbacks CPUs.  This version prohibits
        offlining CPU 0, but only when enabled via CONFIG_RCU_NOCB_CPU=y.
        Relaxing this constraint is in progress, but not yet ready
        for prime time.  These commits were posted to LKML at
        https://lkml.org/lkml/2012/10/30/724.

     2. Changes to SRCU that allows statically initialized srcu_struct
        structures.  These commits were posted to LKML at
        https://lkml.org/lkml/2012/10/30/296.

     3. Restructuring of RCU's debugfs output.  These commits were posted
        to LKML at https://lkml.org/lkml/2012/10/30/341.

     4. Additional CPU-hotplug/RCU improvements, posted to LKML at
        https://lkml.org/lkml/2012/10/30/327.
        Note that the commit eliminating __stop_machine() was judged to
        be too-high of risk, so is deferred to 3.9.

     5. Changes to RCU's idle interface, most notably a new module
        parameter that redirects normal grace-period operations to
        their expedited equivalents.  These were posted to LKML at
        https://lkml.org/lkml/2012/10/30/739.

     6. Additional diagnostics for RCU's CPU stall warning facility,
        posted to LKML at https://lkml.org/lkml/2012/10/30/315.
        The most notable change reduces the
        default RCU CPU stall-warning time from 60 seconds to 21 seconds,
        so that it once again happens sooner than the softlockup timeout.

     7. Documentation updates, which were posted to LKML at
        https://lkml.org/lkml/2012/10/30/280.
        A couple of late-breaking changes were posted at
        https://lkml.org/lkml/2012/11/16/634 and
        https://lkml.org/lkml/2012/11/16/547.

     8. Miscellaneous fixes, which were posted to LKML at
        https://lkml.org/lkml/2012/10/30/309.

     9. Finally, a fix for an lockdep-RCU splat was posted to LKML
        at https://lkml.org/lkml/2012/11/7/486."

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (49 commits)
  context_tracking: New context tracking susbsystem
  sched: Mark RCU reader in sched_show_task()
  rcu: Separate accounting of callbacks from callback-free CPUs
  rcu: Add callback-free CPUs
  rcu: Add documentation for the new rcuexp debugfs trace file
  rcu: Update documentation for TREE_RCU debugfs tracing
  rcu: Reduce default RCU CPU stall warning timeout
  rcu: Fix TINY_RCU rcu_is_cpu_rrupt_from_idle check
  rcu: Clarify memory-ordering properties of grace-period primitives
  rcu: Add new rcutorture module parameters to start/end test messages
  rcu: Remove list_for_each_continue_rcu()
  rcu: Fix batch-limit size problem
  rcu: Add tracing for synchronize_sched_expedited()
  rcu: Remove old debugfs interfaces and also RCU flavor name
  rcu: split 'rcuhier' to each flavor
  rcu: split 'rcugp' to each flavor
  rcu: split 'rcuboost' to each flavor
  rcu: split 'rcubarrier' to each flavor
  rcu: Fix tracing formatting
  rcu: Remove the interface "rcudata.csv"
  ...

39 files changed, 1493 insertions, 628 deletions

diff --git a/Documentation/RCU/RTFP.txt b/Documentation/RCU/RTFP.txt
index 7c1dfb19fc40..7f40c72a9c51 100644
--- a/Documentation/RCU/RTFP.txt
+++ b/Documentation/RCU/RTFP.txt
@@ -186,7 +186,7 @@ Bibtex Entries
 
 @article{Kung80
 ,author="H. T. Kung and Q. Lehman"
-,title="Concurrent Maintenance of Binary Search Trees"
+,title="Concurrent Manipulation of Binary Search Trees"
 ,Year="1980"
 ,Month="September"
 ,journal="ACM Transactions on Database Systems"
diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt
index cdb20d41a44a..31ef8fe07f82 100644
--- a/Documentation/RCU/checklist.txt
+++ b/Documentation/RCU/checklist.txt
@@ -271,15 +271,14 @@ over a rather long period of time, but improvements are always welcome!
         The same cautions apply to call_rcu_bh() and call_rcu_sched().
 
 9.      All RCU list-traversal primitives, which include
-        rcu_dereference(), list_for_each_entry_rcu(),
-        list_for_each_continue_rcu(), and list_for_each_safe_rcu(),
-        must be either within an RCU read-side critical section or
-        must be protected by appropriate update-side locks.  RCU
-        read-side critical sections are delimited by rcu_read_lock()
-        and rcu_read_unlock(), or by similar primitives such as
-        rcu_read_lock_bh() and rcu_read_unlock_bh(), in which case
-        the matching rcu_dereference() primitive must be used in order
-        to keep lockdep happy, in this case, rcu_dereference_bh().
+        rcu_dereference(), list_for_each_entry_rcu(), and
+        list_for_each_safe_rcu(), must be either within an RCU read-side
+        critical section or must be protected by appropriate update-side
+        locks.  RCU read-side critical sections are delimited by
+        rcu_read_lock() and rcu_read_unlock(), or by similar primitives
+        such as rcu_read_lock_bh() and rcu_read_unlock_bh(), in which
+        case the matching rcu_dereference() primitive must be used in
+        order to keep lockdep happy, in this case, rcu_dereference_bh().
 
         The reason that it is permissible to use RCU list-traversal
         primitives when the update-side lock is held is that doing so
diff --git a/Documentation/RCU/listRCU.txt b/Documentation/RCU/listRCU.txt
index 4349c1487e91..adb5a3782846 100644
--- a/Documentation/RCU/listRCU.txt
+++ b/Documentation/RCU/listRCU.txt
@@ -205,7 +205,7 @@ RCU ("read-copy update") its name.  The RCU code is as follows:
                                 audit_copy_rule(&ne->rule, &e->rule);
                                 ne->rule.action = newaction;
                                 ne->rule.file_count = newfield_count;
-                                list_replace_rcu(e, ne);
+                                list_replace_rcu(&e->list, &ne->list);
                                 call_rcu(&e->rcu, audit_free_rule);
                                 return 0;
                         }
diff --git a/Documentation/RCU/rcuref.txt b/Documentation/RCU/rcuref.txt
index 4202ad093130..141d531aa14b 100644
--- a/Documentation/RCU/rcuref.txt
+++ b/Documentation/RCU/rcuref.txt
@@ -20,7 +20,7 @@ release_referenced()			delete()
 {                                       {
     ...                                     write_lock(&list_lock);
     atomic_dec(&el->rc, relfunc)            ...
-    ...                                     delete_element
+    ...                                     remove_element
 }                                           write_unlock(&list_lock);
                                             ...
                                             if (atomic_dec_and_test(&el->rc))
@@ -52,7 +52,7 @@ release_referenced()			delete()
 {                                       {
     ...                                     spin_lock(&list_lock);
     if (atomic_dec_and_test(&el->rc))       ...
-        call_rcu(&el->head, el_free);       delete_element
+        call_rcu(&el->head, el_free);       remove_element
     ...                                     spin_unlock(&list_lock);
 }                                           ...
                                             if (atomic_dec_and_test(&el->rc))
@@ -64,3 +64,60 @@ Sometimes, a reference to the element needs to be obtained in the
 update (write) stream.  In such cases, atomic_inc_not_zero() might be
 overkill, since we hold the update-side spinlock.  One might instead
 use atomic_inc() in such cases.
+
+It is not always convenient to deal with "FAIL" in the
+search_and_reference() code path.  In such cases, the
+atomic_dec_and_test() may be moved from delete() to el_free()
+as follows:
+
+1.                                      2.
+add()                                   search_and_reference()
+{                                       {
+    alloc_object                            rcu_read_lock();
+    ...                                     search_for_element
+    atomic_set(&el->rc, 1);                 atomic_inc(&el->rc);
+    spin_lock(&list_lock);                  ...
+
+    add_element                             rcu_read_unlock();
+    ...                                 }
+    spin_unlock(&list_lock);            4.
+}                                       delete()
+3.                                      {
+release_referenced()                        spin_lock(&list_lock);
+{                                           ...
+    ...                                     remove_element
+    if (atomic_dec_and_test(&el->rc))       spin_unlock(&list_lock);
+        kfree(el);                          ...
+    ...                                     call_rcu(&el->head, el_free);
+}                                           ...
+5.                                      }
+void el_free(struct rcu_head *rhp)
+{
+    release_referenced();
+}