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authorGleb Natapov <gleb@redhat.com>2011-10-18 19:55:51 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2011-12-09 08:55:54 -0800
commitcf246087a19a4958fba3123d21f1359b6177ddb5 (patch)
tree9d857d9ddf07d826bb2718ceff8b80dfb210bb4e
parent6bdf07f3dd1c2874792bb07cd84d4210cbc15ca7 (diff)
downloadlwn-cf246087a19a4958fba3123d21f1359b6177ddb5.tar.gz
lwn-cf246087a19a4958fba3123d21f1359b6177ddb5.zip
jump_label: jump_label_inc may return before the code is patched
commit bbbf7af4bf8fc69bc751818cf30521080fa47dcb upstream. If cpu A calls jump_label_inc() just after atomic_add_return() is called by cpu B, atomic_inc_not_zero() will return value greater then zero and jump_label_inc() will return to a caller before jump_label_update() finishes its job on cpu B. Link: http://lkml.kernel.org/r/20111018175551.GH17571@redhat.com Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Jason Baron <jbaron@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--kernel/jump_label.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index a8ce45097f3d..e6f1f24ad577 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -66,8 +66,9 @@ void jump_label_inc(struct jump_label_key *key)
return;
jump_label_lock();
- if (atomic_add_return(1, &key->enabled) == 1)
+ if (atomic_read(&key->enabled) == 0)
jump_label_update(key, JUMP_LABEL_ENABLE);
+ atomic_inc(&key->enabled);
jump_label_unlock();
}