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perf: Fix branch stack refcount leak on callchain init failure

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On callchain buffers allocation failure, free_event() is
called and all the accounting performed in perf_event_alloc()
for that event is cancelled.

But if the event has branch stack sampling, it is unaccounted
as well from the branch stack sampling events refcounts.

This is a bug because this accounting is performed after the
callchain buffer allocation. As a result, the branch stack sampling
events refcount can become negative.

To fix this, move the branch stack event accounting before the
callchain buffer allocation.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1374539466-4799-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Frederic Weisbecker 2013-07-23 02:30:59 +02:00 committed by Ingo Molnar
parent 7d9ffa8961
commit 6050cb0b0b
1 changed files with 6 additions and 6 deletions
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12
kernel/events/core.c
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@ -6567,6 +6567,12 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
atomic_inc(&nr_comm_events);
if (event->attr.task)
atomic_inc(&nr_task_events);
if (has_branch_stack(event)) {
static_key_slow_inc(&perf_sched_events.key);
if (!(event->attach_state & PERF_ATTACH_TASK))
atomic_inc(&per_cpu(perf_branch_stack_events,
event->cpu));
}
if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) {
err = get_callchain_buffers();
if (err) {
@ -6574,12 +6580,6 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
return ERR_PTR(err);
}
}
if (has_branch_stack(event)) {
static_key_slow_inc(&perf_sched_events.key);
if (!(event->attach_state & PERF_ATTACH_TASK))
atomic_inc(&per_cpu(perf_branch_stack_events,
event->cpu));
}
}
return event;