linux-kernel - Re: [linux-pm] question on resume()

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Message-ID: <20070131093653.GA19643@elf.ucw.cz>
Date:	Wed, 31 Jan 2007 10:36:53 +0100
From:	Pavel Machek <pavel@....cz>
To:	Oliver Neukum <oneukum@...e.de>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oliver@...kum.name>,
	pm list <linux-pm@...ts.osdl.org>, linux-kernel@...r.kernel.org
Subject: Re: [linux-pm] question on resume()

Hi!

> > Yes, it will.  The process freezer can only return success if there are no more
> > TASK_UNINTERRUPTIBLE tasks.  Otherwise it fails (after a timeout).
> 
> So, this means, on suspend():
> 
> 1. Don't worry about TASK_UNINTERRUPTIBLE
> 2. Do worry about TASK_INTERRUPTIBLE
> We have to cease IO and must not call wake_up_interruptible()

"cease IO"? No, I believe it is enough not to start new I/O. Userspace
is frozen at that point, it can't ask you to do I/O.

> Isn't that a race until suspend() is called?

I do not think so.

> On resume():
> 
> 1. Don't worry about TASK_UNINTERRUPTIBLE
> 2. Do not restart IO that may call wake_up_interruptible()
> 
> When do we restart such IO?

We reuse signal handling code to do that for us. It is same situation
as when someone signals task doing I/O.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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