linux-kernel - Re: [RFC][PATCH 2/2] Freezer: Try to handle killable tasks

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Message-Id: <200805072035.57450.rjw@sisk.pl>
Date:	Wed, 7 May 2008 20:35:55 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Pavel Machek <pavel@...e.cz>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, Len Brown <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Matt Helsley <matthltc@...ibm.com>,
	Cedric Le Goater <clg@...ibm.com>,
	Paul Menage <menage@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Liam Howlett <howlett@...il.com>
Subject: Re: [RFC][PATCH 2/2] Freezer: Try to handle killable tasks

On Wednesday, 7 of May 2008, Matthew Wilcox wrote:
> On Wed, May 07, 2008 at 11:41:50AM +0200, Pavel Machek wrote:
> > > @@ -182,6 +183,8 @@ __mutex_lock_common(struct mutex *lock, 
> > >  		/* didnt get the lock, go to sleep: */
> > >  		spin_unlock_mutex(&lock->wait_lock, flags);
> > >  		schedule();
> > > +		if (state == TASK_KILLABLE)
> > > +			try_to_freeze();
> > >  		spin_lock_mutex(&lock->wait_lock, flags);
> > >  	}
> > >  
> > 
> > I'm not comfortable with this one. Can the task be killable, but still
> > hold some _other_ mutex? (and then release it only if it actually gets
> > the signal?)
> 
> Yes, that's exactly what's supposed to happen.

The question, though, is whether there is a driver that will try to lock this
mutex in its .suspend() or .resume() callback.  If there is one, TASK_KILLABLE
won't help the freezer indeed.

Thanks,
Rafael
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