linux-kernel - Re: [PATCH] signals: work around random wakeups in sigsuspend()

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Message-ID: <56A8FD4F.5080708@oracle.com>
Date:	Wed, 27 Jan 2016 12:24:31 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, mingo@...nel.org
Subject: Re: [PATCH] signals: work around random wakeups in sigsuspend()

On 01/27/2016 03:44 AM, Peter Zijlstra wrote:
> On Tue, Jan 26, 2016 at 10:10:09PM +0100, Oleg Nesterov wrote:
> 
>> And, ironically, there is another more serious "reverse" problem ;) sigsuspend()
>> orany other user of -ERESTARTNOHAND can "miss" the signal, in a sense that the
>> kernel can wrongly restart this syscall after return from signal handler. This
>> is not trivial to fix..
> 
> So I'm not entirely sure I get what you mean there. But it did get me to
> look at the patch again:
> 
> +       while (!signal_pending(current)) {
> +               __set_current_state(TASK_INTERRUPTIBLE);
> +               schedule();
> +       }
> 
> That should very much be:
> 
> 	for (;;) {
> 		set_current_state(TASK_INTERRUPTIBLE);
> 		if (signal_pending(current))
> 			break;
> 		schedule();
> 	}
> 	__set_current_state(TASK_RUNNING);

Should that be the case for sys_pause() too?


Thanks,
Sasha