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| author | Peter Zijlstra <peterz@infradead.org> | 2016-08-30 10:15:03 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-09-05 11:55:00 +0200 |
| commit | 58763148758057ffc447bf990321d3ea86d199a0 (patch) | |
| tree | bdd43eb58b713c04495250eaa834819655bfdf0f /kernel/events/core.c | |
| parent | Linux 4.8-rc5 (diff) | |
| download | linux-58763148758057ffc447bf990321d3ea86d199a0.tar.xz linux-58763148758057ffc447bf990321d3ea86d199a0.zip | |
perf/core: Remove WARN from perf_event_read()
This effectively reverts commit:
71e7bc2bab77 ("perf/core: Check return value of the perf_event_read() IPI")
... and puts in a comment explaining why we ignore the return value.
Reported-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David Carrillo-Cisneros <davidcc@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 71e7bc2bab77 ("perf/core: Check return value of the perf_event_read() IPI")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events/core.c')
| -rw-r--r-- | kernel/events/core.c | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 3cfabdf7b942..07ac8596a728 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3549,10 +3549,18 @@ static int perf_event_read(struct perf_event *event, bool group) .group = group, .ret = 0, }; - ret = smp_call_function_single(event->oncpu, __perf_event_read, &data, 1); - /* The event must have been read from an online CPU: */ - WARN_ON_ONCE(ret); - ret = ret ? : data.ret; + /* + * Purposely ignore the smp_call_function_single() return + * value. + * + * If event->oncpu isn't a valid CPU it means the event got + * scheduled out and that will have updated the event count. + * + * Therefore, either way, we'll have an up-to-date event count + * after this. + */ + (void)smp_call_function_single(event->oncpu, __perf_event_read, &data, 1); + ret = data.ret; } else if (event->state == PERF_EVENT_STATE_INACTIVE) { struct perf_event_context *ctx = event->ctx; unsigned long flags; |