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

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 <vegard.nossum@gmail.com>
Signed-off-by: default avatarPeter 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: 71e7bc2b ("perf/core: Check return value of the perf_event_read() IPI")
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c6935931

kernel/events/core.c

+12 −4
Original line number Diff line number Diff line
@@ -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;