From: Jason Baron <jbaron@akamai.com>
Date: Wed, 2 Jul 2014 15:52:44 +0000 (+0000)
Subject: sched: Fix static_key race with sched_feat()
X-Git-Tag: omap-for-v3.17/fixes-against-rc2~177^2~8
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5cd08fbfdb6baa9fe98f530b76898fc5725a6289;p=pandora-kernel.git

sched: Fix static_key race with sched_feat()

As pointed out by Andi Kleen, the usage of static keys can be racy in
sched_feat_disable() vs. sched_feat_enable(). Currently, we first check the
value of keys->enabled, and subsequently update the branch direction. This,
can be racy and can potentially leave the keys in an inconsistent state.

Take the i_mutex around these calls to resolve the race.

Reported-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Jason Baron <jbaron@akamai.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/9d7780c83db26683955cd01e6bc654ee2586e67f.1404315388.git.jbaron@akamai.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---

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