do_wait() wakeup optimization: shift security_task_wait() from eligible_child() to wait_consider_task()

Preparation, no functional changes.

eligible_child() has a single caller, wait_consider_task(). We can move
security_task_wait() out from eligible_child(), this allows us to use it
for filtered wake_up().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ratan Nalumasu <rnalumasu@gmail.com>
Cc: Vitaly Mayatskikh <vmayatsk@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/exit.c

@@ -1112,8 +1112,6 @@ static struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
 
 static int eligible_child(struct wait_opts *wo, struct task_struct *p)
 {
-	int err;
-
 	if (wo->wo_type < PIDTYPE_MAX) {
 		if (task_pid_type(p, wo->wo_type) != wo->wo_pid)
 			return 0;
@@ -1128,10 +1126,6 @@ static int eligible_child(struct wait_opts *wo, struct task_struct *p)
 	    && !(wo->wo_flags & __WALL))
 		return 0;
 
-	err = security_task_wait(p);
-	if (err)
-		return err;
-
 	return 1;
 }
 
@@ -1492,6 +1486,7 @@ static int wait_consider_task(struct wait_opts *wo, struct task_struct *parent,
 	if (!ret)
 		return ret;
 
+	ret = security_task_wait(p);
 	if (unlikely(ret < 0)) {
 		/*
 		 * If we have not yet seen any eligible child,