linux-kernel - Re: [PATCH] psmouse: run kpsmoused only while needed

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Message-Id: <20090202230335.9e31c97f.akpm@linux-foundation.org>
Date:	Mon, 2 Feb 2009 23:03:35 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	dmitry.torokhov@...il.com, dtor@...l.ru,
	linux-kernel@...r.kernel.org, mingo@...e.hu,
	linux-input@...r.kernel.org,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [PATCH] psmouse: run kpsmoused only while needed

On Thu, 29 Jan 2009 00:08:39 +0100 Frederic Weisbecker <fweisbec@...il.com> wrote:

> > > @@ -1131,7 +1155,13 @@ static void psmouse_disconnect(struct serio *serio)
> > >  
> > >  	/* make sure we don't have a resync in progress */
> > >  	mutex_unlock(&psmouse_mutex);
> > > -	flush_workqueue(kpsmoused_wq);
> > > +
> > > +	prepare_to_wait(&psmouse->recync_pending_queue, &wait,
> > > +				TASK_UNINTERRUPTIBLE);
> > > +	if (atomic_read(&psmouse->nb_recync_pending))
> > > +		schedule();
> > > +	finish_wait(&psmouse->recync_pending_queue, &wait);
> > 
> > So... we're requiring that nb_recync_pending is zero at this stage?
> > 
> > I wonder if the code manages to do that.  A little WARN_ON(), maybe?
> > 
> > >  	mutex_lock(&psmouse_mutex);
> > >  
> > 
> 
> After reading how work the async jobs (kernel/async.c), I think it would be better
> to actually use it instead of creating a thread through a workqueue and wait for a
> counter to be zero to be sure all is flushed.
> 
> The async functions provide local execution and synchronisation domains through special cookies,
> which means long tasks of mouse resync will not starve other works.
> 
> What do you think about it?

Yes, it would be better to use the async infrastructure.

If only to see how the code ends up looking - it _should_ be simpler/cleaner
than the open-coded implementation.  If it isn't, we should ask the async code
"why not?".
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