[PATCH] rcu_sched_grace_period: kill the bogus flush_signals()

[Oleg Nesterov <oleg@redhat.com>]

As a kernel thread, rcu_sched_grace_period() runs with all signals ignored.
It can never receive a signal even if it sleeps in TASK_INTERRUPTIBLE, it
needs the explicit allow_signal() to be visible for signals.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>

--- PTRACE/kernel/rcupreempt.c~	2009-04-09 00:39:10.000000000 +0200
+++ PTRACE/kernel/rcupreempt.c	2009-05-03 02:17:11.000000000 +0200
@@ -1356,17 +1356,11 @@ static int rcu_sched_grace_period(void *
 
 		rcu_ctrlblk.sched_sleep = rcu_sched_sleeping;
 		spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags);
-		ret = 0;
+		ret = 0; /* unused */
 		__wait_event_interruptible(rcu_ctrlblk.sched_wq,
 			rcu_ctrlblk.sched_sleep != rcu_sched_sleeping,
 			ret);
 
-		/*
-		 * Signals would prevent us from sleeping, and we cannot
-		 * do much with them in any case.  So flush them.
-		 */
-		if (ret)
-			flush_signals(current);
 		couldsleepnext = 0;
 
 	} while (!kthread_should_stop());