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Commit 5cd08fbf authored by Jason Baron's avatar Jason Baron Committed by Ingo Molnar
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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: default avatarAndi Kleen <andi@firstfloor.org>
Signed-off-by: default avatarJason Baron <jbaron@akamai.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 6e76ea8a

kernel/sched/core.c

+5 −0
Original line number Diff line number Diff line
@@ -245,6 +245,7 @@ sched_feat_write(struct file *filp, const char __user *ubuf, 
	char buf[64];

	char *cmp;

	int i;

	struct inode *inode;



	if (cnt > 63)

		cnt = 63;
@@ -255,7 +256,11 @@ sched_feat_write(struct file *filp, const char __user *ubuf, 
	buf[cnt] = 0;

	cmp = strstrip(buf);



	/* Ensure the static_key remains in a consistent state */

	inode = file_inode(filp);

	mutex_lock(&inode->i_mutex);

	i = sched_feat_set(cmp);

	mutex_unlock(&inode->i_mutex);

	if (i == __SCHED_FEAT_NR)

		return -EINVAL;