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 3.4-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-3.4 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
@@ -368,6 +368,8 @@ 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_cgroup_events says at least one
@@ -391,9 +393,10 @@ 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-3.4/perf-clarify-perf_cpu_context-active_pmu-usage-by-renaming.patch
queue-3.4/perf-fix-perf_cgroup_switch-for-sw-events.patch
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