mutex: Don't spin when the owner CPU is offline or other weird cases

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Due to recent load-balancer changes that delay the task migration to
the next wakeup, the adaptive mutex spinning ends up in a live lock
when the owner's CPU gets offlined because the cpu_online() check
lives before the owner running check.

This patch changes mutex_spin_on_owner() to return 0 (don't spin) in
any case where we aren't sure about the owner struct validity or CPU
number, and if the said CPU is offline. There is no point going back &
re-evaluate spinning in corner cases like that, let's just go to
sleep.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1271212509.13059.135.camel@pasglop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

...

This commit is contained in:

Benjamin Herrenschmidt 2010-04-16 23:20:00 +02:00 • committed by Ingo Molnar

parent d5a30458a9

commit 4b40221048

1 changed files with 4 additions and 4 deletions

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kernel/sched.c

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