Patch "perf: Fix perf_cgroup_switch for sw-events" has been added to the 3.0-stable tree

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This is a note to let you know that I've just added the patch titled

    perf: Fix perf_cgroup_switch for sw-events

to the 3.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     perf-fix-perf_cgroup_switch-for-sw-events.patch
and it can be found in the queue-3.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 95cf59ea72331d0093010543b8951bb43f262cac Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Date: Tue, 2 Oct 2012 15:41:23 +0200
Subject: perf: Fix perf_cgroup_switch for sw-events

From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>

commit 95cf59ea72331d0093010543b8951bb43f262cac upstream.

Jiri reported that he could trigger the WARN_ON_ONCE() in
perf_cgroup_switch() using sw-events. This is because sw-events share
a cpuctx with multiple PMUs.

Use the ->unique_pmu pointer to limit the pmu iteration to unique
cpuctx instances.

Reported-and-Tested-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-so7wi2zf3jjzrwcutm2mkz0j@xxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/events/core.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -342,6 +342,8 @@ void perf_cgroup_switch(struct task_stru
 	list_for_each_entry_rcu(pmu, &pmus, entry) {
 
 		cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
+		if (cpuctx->unique_pmu != pmu)
+			continue; /* ensure we process each cpuctx once */
 
 		perf_pmu_disable(cpuctx->ctx.pmu);
 
@@ -365,9 +367,10 @@ void perf_cgroup_switch(struct task_stru
 
 			if (mode & PERF_CGROUP_SWIN) {
 				WARN_ON_ONCE(cpuctx->cgrp);
-				/* set cgrp before ctxsw in to
-				 * allow event_filter_match() to not
-				 * have to pass task around
+				/*
+				 * set cgrp before ctxsw in to allow
+				 * event_filter_match() to not have to pass
+				 * task around
 				 */
 				cpuctx->cgrp = perf_cgroup_from_task(task);
 				cpu_ctx_sched_in(cpuctx, EVENT_ALL, task);


Patches currently in stable-queue which might be from a.p.zijlstra@xxxxxxxxx are

queue-3.0/perf-clarify-perf_cpu_context-active_pmu-usage-by-renaming.patch
queue-3.0/perf-fix-perf_cgroup_switch-for-sw-events.patch
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