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

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Message-Id: <200701311114.55685.oliver@neukum.org>
Date:	Wed, 31 Jan 2007 11:14:44 +0100 (MET)
From:	Oliver Neukum <oliver@...kum.org>
To:	Pavel Machek <pavel@....cz>
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()

Am Mittwoch, 31. Januar 2007 10:36 schrieb Pavel Machek:
> 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.

What about URBs in flight which are waited for with TASK_INTERRUPTIBLE?

> > 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.

What happens to tasks in TASK_INTERRUPTIBLE which are frozen?
Are they interrupted and frozen?

	Regards
		Oliver
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