On Thu, 15 Feb 2007, Andrew Morton wrote:

On Fri, 16 Feb 2007 08:43:37 +1100
Benjamin Herrenschmidt [off-list ref] wrote:

quoted

On Thu, 2007-02-15 at 18:50 +0100, Christoph Hellwig wrote:

quoted

On Thu, Feb 15, 2007 at 04:23:02PM +0100, Geert.Uytterhoeven@sonycom.com wrote:

quoted

+	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.

As modular ps3fb is not yet supported, this trivial testing is not that
trivial...

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);

Thanks! We don't wait on ext_flip, though, but I see your point. Updated patch
will follow.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- Sony Network and Software Technology Center Europe (NSCE)
Geert.Uytterhoeven@sonycom.com ------- The Corporate Village, Da Vincilaan 7-D1
Voice +32-2-7008453 Fax +32-2-7008622 ---------------- B-1935 Zaventem, Belgium

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