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perf: Fix hotplug splat 

Drew Richardson reported that he could make the kernel go *boom* when hotplugging
while having perf events active.

It turned out that when you have a group event, the code in
__perf_event_exit_context() fails to remove the group siblings from
the context.

We then proceed with destroying and freeing the event, and when you
re-plug the CPU and try and add another event to that CPU, things go
*boom* because you've still got dead entries there.

Reported-by: Drew Richardson <drew.richardson@arm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/n/tip-k6v5wundvusvcseqj1si0oz0@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2014-02-24 12:06:12 +01:00 committed by Ingo Molnar
parent 26e61e8939
commit e3703f8cdf
1 changed files with 6 additions and 6 deletions
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12
kernel/events/core.c
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@ -7856,14 +7856,14 @@ static void perf_pmu_rotate_stop(struct pmu *pmu)
static void __perf_event_exit_context(void *__info)
{
struct perf_event_context *ctx = __info;
struct perf_event *event, *tmp;
struct perf_event *event;
perf_pmu_rotate_stop(ctx->pmu);
list_for_each_entry_safe(event, tmp, &ctx->pinned_groups, group_entry)
__perf_remove_from_context(event);
list_for_each_entry_safe(event, tmp, &ctx->flexible_groups, group_entry)
rcu_read_lock();
list_for_each_entry_rcu(event, &ctx->event_list, event_entry)
__perf_remove_from_context(event);
rcu_read_unlock();
}
static void perf_event_exit_cpu_context(int cpu)
@ -7887,11 +7887,11 @@ static void perf_event_exit_cpu(int cpu)
{
struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);
perf_event_exit_cpu_context(cpu);
mutex_lock(&swhash->hlist_mutex);
swevent_hlist_release(swhash);
mutex_unlock(&swhash->hlist_mutex);
perf_event_exit_cpu_context(cpu);
}
#else
static inline void perf_event_exit_cpu(int cpu) { }