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Commit e3703f8c authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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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: default avatarDrew Richardson <drew.richardson@arm.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 26e61e89

kernel/events/core.c

+6 −6
Original line number Diff line number Diff line
@@ -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) { }