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From: Matthew Wilcox <willy@infradead.org>
To: Ian Kent <raven@themaw.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
	autofs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] autofs4: Use wait_event_killable
Date: Mon, 19 Mar 2018 20:12:02 -0700	[thread overview]
Message-ID: <20180320031202.GA22556@bombadil.infradead.org> (raw)
In-Reply-To: <7dae3cc8-bad1-ec18-bcf1-ae91a87f74fa@themaw.net>

On Tue, Mar 20, 2018 at 09:58:59AM +0800, Ian Kent wrote:
> On 20/03/18 03:16, Matthew Wilcox wrote:
> > From: Matthew Wilcox <mawilcox@microsoft.com>
> > This playing with signals to allow only fatal signals appears to predate
> > the introduction of wait_event_killable(), and I'm fairly sure that
> > wait_event_killable is what was meant to happen here.
> 
> Predates is an understatement, this is really, really old code.
> Do I need to forward this to Al or Andrew?

Looks like Andrew usually picks these up directly.  Here's the line
he'll want:

Link: http://lkml.kernel.org/r/20180319191609.23880-1-willy@infradead.org

> > Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
> Signed-off-by: Ian Kent <raven@themaw.net>


> > +	wait_event_killable(wq->queue, wq->name.name == NULL);
> 
> The wait event code looks like this will wake up on most any unmasked signal.
> But my assumption is that TASK_KILLABLE tasks are only forwarded specific
> signals ...
> 
> Is that right or am I missing something?

The signal code is gnarly.  As far as I can decipher it, a fatal
signal is always turned into SIGKILL (in complete_signal()), and the
task is woken.  For a task sleeping in TASK_KILLABLE, signal_wake_up()
passes TASK_WAKEKILL to signal_wake_up_state() if the signal is SIGKILL.
TASK_KILLABLE sets (TASK_WAKEKILL | TASK_UNINTERRUPTIBLE) so it will be
woken in order to die.

If the signal being sent isn't sig_fatal(), then we don't wake the task.
The signal will still be in the pending set, so it can notice when
exiting to userspace, but it won't be woken.

      reply	other threads:[~2018-03-20  3:12 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-19 19:16 Matthew Wilcox
2018-03-19 19:25 ` David Rientjes
2018-03-19 19:30   ` Matthew Wilcox
2018-03-20  2:42   ` Ian Kent
2018-03-20  1:58 ` Ian Kent
2018-03-20  3:12   ` Matthew Wilcox [this message]

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