jump_label: jump_label_inc may return before the code is patched

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/[email protected] Cc: [email protected] Cc: Peter Zijlstra <[email protected]> Acked-by: Jason Baron <[email protected]> Signed-off-by: Gleb Natapov <[email protected]> Signed-off-by: Steven Rostedt <[email protected]>
progmanos · Dec 5, 2011 · bbbf7af · bbbf7af
1 parent c7c6ec8
commit bbbf7af
Showing 1 changed file with 2 additions and 1 deletion.
diff --git 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();
 }