powerbook/radeon PM problem

[Johannes Berg]

On Sun, 2007-02-04 at 15:47 +1100, Benjamin Herrenschmidt wrote:

> Yeah well, it's -supposed- to be taken by the resume function, but the
> early resume path is a hack that runs -really- early (so you get a
> screen back for debugging). I should find a way to silence those stupid
> warnings...

Yes, I agree that the semaphore that the comment talks about won't ever
be taken anyway. The warning actually comes from the notifier chain that
is used there, of course.

> > I'm totally unsure what the correct fix for this is.
> 
> None other than removing the early wakeup hack :-(

Actually, looking at the code again... fb_notifier_list is a blocking
notifier list. This could be converted to a raw one without any locking,
and we could require that callers of fb_register_client,
fb_unregister_client and fb_notifier_call_chain hold the console
semaphore while calling.
Then, some callers in drivers/video/fbmem.c would need to be updated,
but since fb_set_suspend already requires the semaphore to be held it
wouldn't acquire it again, of course.

We'd still abuse fb_set_suspend here by calling it without the semaphore
held, but we know that nobody else can hold it at that time so that'd be
ok.

Just a thought.

johannes
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