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authorPeter Zijlstra <peterz@infradead.org>2016-08-30 10:15:03 +0200
committerIngo Molnar <mingo@kernel.org>2016-09-05 11:55:00 +0200
commit58763148758057ffc447bf990321d3ea86d199a0 (patch)
treebdd43eb58b713c04495250eaa834819655bfdf0f /kernel
parentc6935931c1894ff857616ff8549b61236a19148f (diff)
downloadlinux-stericsson-58763148758057ffc447bf990321d3ea86d199a0.tar.gz
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')
-rw-r--r--kernel/events/core.c16
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;