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]>

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index bbdfe2a462a088b210d5792c674b215274b1b39b..66ff7109f6970ca63cb4aa9bf6b4800d69ef2f3a 100644 (file)
--- 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();
 }