Re: [PATCH] fb: move mutex_init to framebuffer_alloc()

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

On Wed, Jul 08, 2009 at 05:42:25PM +0800, Wu Zhangjin wrote:
> On Wed, 2009-07-01 at 18:26 +0200, Daniel Mack wrote:
> > In 537a1bf05, a per-fbinfo mutex was added and framebuffer drivers were
> > adopted accordingly. This new lock is currently initialized in
> > register_framebuffer().
> > 
> > The mx3fb driver takes this lock in mx3fb_map_video_memory() _before_
> > register_framebuffer() is called and hence crashes the system very
> > early.
> > 
> > Moving this mutex_init() to framebuffer_alloc() solves this and also
> > seems a lot more straight forward.
> > 
> 
> but this may introduce deadlock to some _old_ drivers which have not
> used framebuffer_alloc to allocate fb_info structure.
> 
> to avoid deadlock, these drivers need to change kmalloc to
> framebuffer_alloc, otherwise, they need to add their own mutexes
> initialization source code:
> 		mutex_init(&info->lock);	mutex_init(&info->mm_lock);
> 
> here is only a record for the _old_ drivers' maintainers. hope they can
> get this info from google or find this commit: 
> 
Yes, I'm going through and gradually converting all of the outstanding
drivers (both old and new) over to framebuffer_alloc(). The old ones are
a bit more tedious given all of the casting games they play. I should
have the outstanding ones finished tomorrow.