| From e3703f8cdfcf39c25c4338c3ad8e68891cca3731 Mon Sep 17 00:00:00 2001 |
| From: Peter Zijlstra <peterz@infradead.org> |
| Date: Mon, 24 Feb 2014 12:06:12 +0100 |
| Subject: perf: Fix hotplug splat |
| |
| From: Peter Zijlstra <peterz@infradead.org> |
| |
| commit e3703f8cdfcf39c25c4338c3ad8e68891cca3731 upstream. |
| |
| 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> |
| Link: http://lkml.kernel.org/n/tip-k6v5wundvusvcseqj1si0oz0@git.kernel.org |
| Signed-off-by: Ingo Molnar <mingo@kernel.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| kernel/events/core.c | 12 ++++++------ |
| 1 file changed, 6 insertions(+), 6 deletions(-) |
| |
| --- a/kernel/events/core.c |
| +++ b/kernel/events/core.c |
| @@ -7833,14 +7833,14 @@ static void perf_pmu_rotate_stop(struct |
| 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) |
| @@ -7864,11 +7864,11 @@ 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) { } |