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authorLinus Torvalds <torvalds@linux-foundation.org>2011-05-28 12:56:32 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-05-28 12:56:32 -0700
commit1ba4b8cb94e59b17fd0142a509eb583695c36db6 (patch)
treee42d1967025670401758d32964a5fa048f59f10a /Documentation
parentc4a227d89f758e582fd167bb15245f2704de99ef (diff)
parentcc3ce5176d83cd8ae1134f86e208ea758d6cb78e (diff)
Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: rcu: Start RCU kthreads in TASK_INTERRUPTIBLE state rcu: Remove waitqueue usage for cpu, node, and boost kthreads rcu: Avoid acquiring rcu_node locks in timer functions atomic: Add atomic_or() Documentation: Add statistics about nested locks rcu: Decrease memory-barrier usage based on semi-formal proof rcu: Make rcu_enter_nohz() pay attention to nesting rcu: Don't do reschedule unless in irq rcu: Remove old memory barriers from rcu_process_callbacks() rcu: Add memory barriers rcu: Fix unpaired rcu_irq_enter() from locking selftests
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/RCU/trace.txt17
-rw-r--r--Documentation/lockstat.txt36
2 files changed, 39 insertions, 14 deletions
diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt
index c078ad48f7a1..8173cec473aa 100644
--- a/Documentation/RCU/trace.txt
+++ b/Documentation/RCU/trace.txt
@@ -99,18 +99,11 @@ o "qp" indicates that RCU still expects a quiescent state from
o "dt" is the current value of the dyntick counter that is incremented
when entering or leaving dynticks idle state, either by the
- scheduler or by irq. The number after the "/" is the interrupt
- nesting depth when in dyntick-idle state, or one greater than
- the interrupt-nesting depth otherwise.
-
- This field is displayed only for CONFIG_NO_HZ kernels.
-
-o "dn" is the current value of the dyntick counter that is incremented
- when entering or leaving dynticks idle state via NMI. If both
- the "dt" and "dn" values are even, then this CPU is in dynticks
- idle mode and may be ignored by RCU. If either of these two
- counters is odd, then RCU must be alert to the possibility of
- an RCU read-side critical section running on this CPU.
+ scheduler or by irq. This number is even if the CPU is in
+ dyntick idle mode and odd otherwise. The number after the first
+ "/" is the interrupt nesting depth when in dyntick-idle state,
+ or one greater than the interrupt-nesting depth otherwise.
+ The number after the second "/" is the NMI nesting depth.
This field is displayed only for CONFIG_NO_HZ kernels.
diff --git a/Documentation/lockstat.txt b/Documentation/lockstat.txt
index 9c0a80d17a23..cef00d42ed5b 100644
--- a/Documentation/lockstat.txt
+++ b/Documentation/lockstat.txt
@@ -12,8 +12,9 @@ Because things like lock contention can severely impact performance.
- HOW
Lockdep already has hooks in the lock functions and maps lock instances to
-lock classes. We build on that. The graph below shows the relation between
-the lock functions and the various hooks therein.
+lock classes. We build on that (see Documentation/lockdep-design.txt).
+The graph below shows the relation between the lock functions and the various
+hooks therein.
__acquire
|
@@ -128,6 +129,37 @@ points are the points we're contending with.
The integer part of the time values is in us.
+Dealing with nested locks, subclasses may appear:
+
+32...............................................................................................................................................................................................
+33
+34 &rq->lock: 13128 13128 0.43 190.53 103881.26 97454 3453404 0.00 401.11 13224683.11
+35 ---------
+36 &rq->lock 645 [<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
+37 &rq->lock 297 [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+38 &rq->lock 360 [<ffffffff8103c4c5>] select_task_rq_fair+0x1f0/0x74a
+39 &rq->lock 428 [<ffffffff81045f98>] scheduler_tick+0x46/0x1fb
+40 ---------
+41 &rq->lock 77 [<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
+42 &rq->lock 174 [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+43 &rq->lock 4715 [<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
+44 &rq->lock 893 [<ffffffff81340524>] schedule+0x157/0x7b8
+45
+46...............................................................................................................................................................................................
+47
+48 &rq->lock/1: 11526 11488 0.33 388.73 136294.31 21461 38404 0.00 37.93 109388.53
+49 -----------
+50 &rq->lock/1 11526 [<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
+51 -----------
+52 &rq->lock/1 5645 [<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
+53 &rq->lock/1 1224 [<ffffffff81340524>] schedule+0x157/0x7b8
+54 &rq->lock/1 4336 [<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
+55 &rq->lock/1 181 [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+
+Line 48 shows statistics for the second subclass (/1) of &rq->lock class
+(subclass starts from 0), since in this case, as line 50 suggests,
+double_rq_lock actually acquires a nested lock of two spinlocks.
+
View the top contending locks:
# grep : /proc/lock_stat | head