signal: use current->state helpers

Call __set_current_state() instead of assigning the new state directly.
These interfaces also aid CONFIG_DEBUG_ATOMIC_SLEEP environments, keeping
track of who changed the state.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

@@ -3550,7 +3550,7 @@ SYSCALL_DEFINE2(signal, int, sig, __sighandler_t, handler)
 SYSCALL_DEFINE0(pause)
 {
 	while (!signal_pending(current)) {
-		current->state = TASK_INTERRUPTIBLE;
+		__set_current_state(TASK_INTERRUPTIBLE);
 		schedule();
 	}
 	return -ERESTARTNOHAND;
@@ -3563,7 +3563,7 @@ int sigsuspend(sigset_t *set)
 	current->saved_sigmask = current->blocked;
 	set_current_blocked(set);
 
-	current->state = TASK_INTERRUPTIBLE;
+	__set_current_state(TASK_INTERRUPTIBLE);
 	schedule();
 	set_restore_sigmask();
 	return -ERESTARTNOHAND;