From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Wed, 2 Feb 2011 12:19:09 +0000 (+0100)
Subject: perf: Cure task_oncpu_function_call() races
X-Git-Tag: v2.6.39-rc1~510^2~93
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fe4b04fa31a6dcf4358aa84cf81e5a7fd079469b;p=pandora-kernel.git

perf: Cure task_oncpu_function_call() races

Oleg reported that on architectures with
__ARCH_WANT_INTERRUPTS_ON_CTXSW the IPI from
task_oncpu_function_call() can land before perf_event_task_sched_in()
and cause interesting situations for eg. perf_install_in_context().

This patch reworks the task_oncpu_function_call() interface to give a
more usable primitive as well as rework all its users to hopefully be
more obvious as well as remove the races.

While looking at the code I also found a number of races against
perf_event_task_sched_out() which can flip contexts between tasks so
plug those too.

Reported-and-reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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