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| author | Peter Zijlstra <peterz@infradead.org> | 2015-01-29 14:44:34 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-02-04 08:07:12 +0100 |
| commit | a83fe28e2e45392464858a96745db26ac73670c8 (patch) | |
| tree | f5512a81ef46a14319e1600079b36e9cea11ee90 /kernel/events | |
| parent | 8f95b435b62522aed3381aaea920de8d09ccabf3 (diff) | |
| download | linux-a83fe28e2e45392464858a96745db26ac73670c8.tar.bz2 | |
perf: Fix put_event() ctx lock
So what I suspect; but I'm in zombie mode today it seems; is that while
I initially thought that it was impossible for ctx to change when
refcount dropped to 0, I now suspect its possible.
Note that until perf_remove_from_context() the event is still active and
visible on the lists. So a concurrent sys_perf_event_open() from another
task into this task can race.
Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Stephane Eranian <eranian@gmail.com>
Cc: mark.rutland@arm.com
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20150129134434.GB26304@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/core.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 142dbabc1615..f773fa13d7c2 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -947,7 +947,8 @@ static void put_ctx(struct perf_event_context *ctx) * perf_event::mmap_mutex * mmap_sem */ -static struct perf_event_context *perf_event_ctx_lock(struct perf_event *event) +static struct perf_event_context * +perf_event_ctx_lock_nested(struct perf_event *event, int nesting) { struct perf_event_context *ctx; @@ -960,7 +961,7 @@ again: } rcu_read_unlock(); - mutex_lock(&ctx->mutex); + mutex_lock_nested(&ctx->mutex, nesting); if (event->ctx != ctx) { mutex_unlock(&ctx->mutex); put_ctx(ctx); @@ -970,6 +971,12 @@ again: return ctx; } +static inline struct perf_event_context * +perf_event_ctx_lock(struct perf_event *event) +{ + return perf_event_ctx_lock_nested(event, 0); +} + static void perf_event_ctx_unlock(struct perf_event *event, struct perf_event_context *ctx) { @@ -3572,7 +3579,7 @@ static void perf_remove_from_owner(struct perf_event *event) */ static void put_event(struct perf_event *event) { - struct perf_event_context *ctx = event->ctx; + struct perf_event_context *ctx; if (!atomic_long_dec_and_test(&event->refcount)) return; @@ -3580,7 +3587,6 @@ static void put_event(struct perf_event *event) if (!is_kernel_event(event)) perf_remove_from_owner(event); - WARN_ON_ONCE(ctx->parent_ctx); /* * There are two ways this annotation is useful: * @@ -3593,7 +3599,8 @@ static void put_event(struct perf_event *event) * the last filedesc died, so there is no possibility * to trigger the AB-BA case. */ - mutex_lock_nested(&ctx->mutex, SINGLE_DEPTH_NESTING); + ctx = perf_event_ctx_lock_nested(event, SINGLE_DEPTH_NESTING); + WARN_ON_ONCE(ctx->parent_ctx); perf_remove_from_context(event, true); mutex_unlock(&ctx->mutex); |