signals: annotate lock_task_sighand()

lock_task_sighand() grabs sighand->siglock in case of returning non-NULL
but unlock_task_sighand() releases it unconditionally.  This leads sparse
to complain about the lock context imbalance.  Rename and wrap
lock_task_sighand() using __cond_lock() macro to make sparse happy.

Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 919562c3d6b7..e921409b85a9 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1105,7 +1105,8 @@ int zap_other_threads(struct task_struct *p)
         return count;
 }
 
-struct sighand_struct *lock_task_sighand(struct task_struct *tsk, unsigned long *flags)
+struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
+                                           unsigned long *flags)
 {
         struct sighand_struct *sighand;