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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: 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>
hifive-unleashed-5.1
Jason Baron 2014-07-02 15:52:44 +00:00 committed by Ingo Molnar
parent 6e76ea8a82
commit 5cd08fbfdb
1 changed files with 5 additions and 0 deletions
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5
kernel/sched/core.c
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@ -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;