fb: convert lock/unlock_kernel() into local fb mutex

Change lock_kernel()/unlock_kernel() to local fb mutex.  Each frame buffer
instance has its own mutex.

The one line try_to_load() function is unrolled to request_module() in two
places for readability.

[righi.andrea@gmail.com: fb: fix NULL pointer BUG dereference in fb_open()]
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/fb.h b/include/linux/fb.h
index 531ccd5f5960..75a81eaf3430 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -808,6 +808,7 @@ struct fb_tile_ops {
 struct fb_info {
         int node;
         int flags;
+        struct mutex lock;              /* Lock for open/release/ioctl funcs */
         struct fb_var_screeninfo var;   /* Current var */
         struct fb_fix_screeninfo fix;   /* Current fix */
         struct fb_monspecs monspecs;    /* Current Monitor specs */