Re: [BUG] drivers/video/sis: deadlock introduced by "fbdev: add mutex for fb_mmap locking"

[Paul Mundt <lethal@linux-sh.org>]

On Sun, Jul 05, 2009 at 07:56:56AM -0700, Linus Torvalds wrote:
> 
> 
> On Sun, 5 Jul 2009, Paul Mundt wrote:
> >                     break;
> >     fb_info->node = i;
> >     mutex_init(&fb_info->lock);
> > -   mutex_init(&fb_info->mm_lock);
> 
> Why not "lock" as well?
> 
I had that initially, but matroxfb will break if we do that, and
presently nothing cares about trying to take ->lock that early on.

->mm_lock was a special case as the lock/unlock pairs were sprinkled
around well before initialization, while in the ->lock case all of the
lock/unlock pairs are handled internally by the fbmem code (at least a
quick grep does not show any drivers using it on their own).