Re: [Linux-fbdev-devel] [PATCH] add mutex to fbdev for fb_mmap locking

[Linus T. <tor...@li...>]

On Sun, 31 May 2009, Krzysztof Helt wrote:
>  
>  static int atafb_get_fix(struct fb_fix_screeninfo *fix, struct fb_info *info)
> +__acquires(&info->mm_lock)
> +__releases(&info->mm_lock)

Btw, you shouldn't do this when things nest "correctly" - sparse will see 
the fact that the function acquires and releases a lock and is perfectly 
happy.

The extra annotations are helpful only if you have a function that does 
something _unexpected_ to a lock, like first releasing it and then 
re-aqcuiring it, or releasing it without acquiring it at all. Then the 
extra annotations (a) tell sparse not to complain about odd locking, and 
(b) act as visual notification to users that this function drops a lock in 
the middle.

I haven't actually looked at the patch yet, I just reacted to this part of 
it.

		Linus