perf/core: Fix perf_event_read()

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perf_event_read() has a number of issues regarding the timekeeping bits.

 - The IPI didn't update group times when it found INACTIVE

 - The direct call would not re-check ->state after taking ctx->lock
   which can result in ->count and timestamps getting out of sync.

And we can make use of the ordering introduced for perf_event_stop()
to make it more accurate for ACTIVE.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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Peter Zijlstra 2017-09-05 16:26:44 +02:00 • committed by Ingo Molnar

parent 7f0ec32526

commit 0c1cbc18df

1 changed files with 39 additions and 16 deletions

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kernel/events/core.c

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