From: Oleg Nesterov <oleg@redhat.com>
Date: Mon, 15 Mar 2010 09:10:23 +0000 (+0100)
Subject: sched: _cpu_down(): Don't play with current->cpus_allowed
X-Git-Tag: v2.6.35-rc1~521^2~24
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6a1bdc1b577ebcb65f6603c57f8347309bc4ab13;p=pandora-kernel.git

sched: _cpu_down(): Don't play with current->cpus_allowed

_cpu_down() changes the current task's affinity and then recovers it at
the end. The problems are well known: we can't restore old_allowed if it
was bound to the now-dead-cpu, and we can race with the userspace which
can change cpu-affinity during unplug.

_cpu_down() should not play with current->cpus_allowed at all. Instead,
take_cpu_down() can migrate the caller of _cpu_down() after __cpu_disable()
removes the dying cpu from cpu_online_mask.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100315091023.GA9148@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

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