[patch 1/4] ps3fb: thread updates
Andrew Morton
akpm at linux-foundation.org
Fri Feb 16 11:59:16 EST 2007
On Fri, 16 Feb 2007 08:43:37 +1100
Benjamin Herrenschmidt <benh at kernel.crashing.org> wrote:
> On Thu, 2007-02-15 at 18:50 +0100, Christoph Hellwig wrote:
> > On Thu, Feb 15, 2007 at 04:23:02PM +0100, Geert.Uytterhoeven at sonycom.com wrote:
> > > + do {
> > > + try_to_freeze();
> > > + error = down_interruptible(&ps3fb.sem);
> > > + if (!error && !atomic_read(&ps3fb.ext_flip))
> > > ps3fb_sync(0); /* single buffer */
> >
> > this still can deadlock when calling kthread_stop. You really want
> > to use wake_up_process to kick this thread or use a workqueue.
>
> kthread_stop does wake_up_process no ? However, that might not get you
> out of interruptible if you don't also have signal_pending...
>
No, it won't get you out of down_interruptible(). But the code would have
failed trivial testing so perhaps we're missing something.
It seems crufty to use semaphores in this manner. afaict all we're doing
here is poking a kernel thread and asking it to do a bit of work. The
standard way of doing this is to go to sleep on a waitqueue_head.
DEFINE_WAIT(wait);
while (!kthread_should_stop()) {
prepare_to_wait(&wq, &wait, TASK_INTERRUPTIBLE);
if (!atomic_read(&ps3fb.ext_flip))
schedule();
finish_wait(&wq, &wait);
if (!atomic_read(&ps3fb.ext_flip))
WARN_ON(1);
else
ps3fb_sync(0);
}
and, elsewhere,
atomic_inc(&ps3fb.ext_flip);
wake_up_process(my_kernel_therad);
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