From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Thu, 26 May 2011 12:21:33 +0000 (+0200)
Subject: sched: Fix ttwu() for __ARCH_WANT_INTERRUPTS_ON_CTXSW
X-Git-Tag: v3.0-rc1~23^2~2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d6aa8f85f16379d42c147b22b59e33b67f9ff466;p=pandora-kernel.git

sched: Fix ttwu() for __ARCH_WANT_INTERRUPTS_ON_CTXSW

Marc reported that e4a52bcb9 (sched: Remove rq->lock from the first
half of ttwu()) broke his ARM-SMP machine. Now ARM is one of the few
__ARCH_WANT_INTERRUPTS_ON_CTXSW users, so that exception in the ttwu()
code was suspect.

Yong found that the interrupt could hit after context_switch() changes
current but before it clears p->on_cpu, if that interrupt were to
attempt a wake-up of p we would indeed find ourselves spinning in IRQ
context.

Fix this by reverting to the old behaviour for this situation and
perform a full remote wake-up.

Cc: Frank Rowand <frank.rowand@am.sony.com>
Cc: Yong Zhang <yong.zhang0@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Reported-by: Marc Zyngier <Marc.Zyngier@arm.com>
Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

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