linux-kernel - Re: [PATCH] rcu_sched_grace_period: kill the bogus flush

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Date:	Sun, 3 May 2009 16:36:08 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, mingo@...e.hu
Subject: Re: [PATCH] rcu_sched_grace_period: kill the bogus flush_signals()

On Sun, May 03, 2009 at 11:11:18PM +0200, Oleg Nesterov wrote:
> 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.

Good point!!!

Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> Signed-off-by: Oleg Nesterov <oleg@...hat.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());
> 
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