[Linux-fbdev-devel] [PATCH 1/4 (updated)] ps3fb: thread updates

[Geert Uytterhoeven]

On Fri, 16 Feb 2007, Geert Uytterhoeven wrote:
> On Fri, 16 Feb 2007, Christoph Hellwig wrote:
> > > +	DEFINE_WAIT(wait);
> > > +	DECLARE_WAIT_QUEUE_HEAD(wq);
> > > +
> > > +	while (!kthread_should_stop()) {
> > > +		prepare_to_wait(&wq, &wait, TASK_INTERRUPTIBLE);
> > > +		if (!ps3fb.is_kicked)
> > > +			schedule();
> > > +		finish_wait(&wq, &wait);
> > > +		ps3fb.is_kicked = 0;
> > > +		ps3fb_sync(0);	/* single buffer */
> > 
> > should probably be just:
> > 
> > 	while (!kthread_should_stop()) {
> > 		ps3fb_sync(0);
> > 		schedule();
> > 	}
> > 
> > given that you don't need a waitqueue and a spurious wakeup here
> > seems harmless.
> 
> Not always. If flipping is disabled, or external flip is enabled, you don't
> want a spurious flip.

Looks like the waitqueue is needed. Without it ps3fbd runs at 100% CPU and +15
million loops per second.

Gr{oetje,eeting}s,

						Geert

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Geert Uytterhoeven -- Sony Network and Software Technology Center Europe (NSCE)
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