ptrace: annotate lock context change on exit_ptrace()

exit_ptrace() releases and regrabs tasklist_lock but was missing proper
annotation.  Add it.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index f34d798..4afd9b8 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -329,6 +329,8 @@
  * and reacquire the lock.
  */
 void exit_ptrace(struct task_struct *tracer)
+	__releases(&tasklist_lock)
+	__acquires(&tasklist_lock)
 {
 	struct task_struct *p, *n;
 	LIST_HEAD(ptrace_dead);