perf_counter: update mmap() counter read, take 2

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Update the userspace read method.

Paul noted that:
 - userspace cannot observe ->lock & 1 on the same cpu.
 - we need a barrier() between reading ->lock and ->index
   to ensure we read them in that prticular order.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090406094517.368446033@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

...

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Peter Zijlstra 2009-04-06 11:44:59 +02:00 • committed by Ingo Molnar

parent 92f22a3865

commit a2e87d06dd

1 changed files with 10 additions and 14 deletions

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include/linux/perf_counter.h

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