perf/core: Fix perf_event_read()
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>
1 file changed