Commit 58763148 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar

perf/core: Remove WARN from perf_event_read()

This effectively reverts commit:

  71e7bc2b ("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: default avatarVegard Nossum <>
Signed-off-by: default avatarPeter Zijlstra (Intel) <>
Cc: David Carrillo-Cisneros <>
Cc: Jiri Olsa <>
Cc: Linus Torvalds <>
Cc: Peter Zijlstra <>
Cc: Thomas Gleixner <>
Fixes: 71e7bc2b ("perf/core: Check return value of the perf_event_read() IPI")
Signed-off-by: default avatarIngo Molnar <>
parent c6935931
......@@ -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: */
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;
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