From 66c1ca019078220dc1bf968f2bb18421100ef147 Mon Sep 17 00:00:00 2001 From: Andrea Righi Date: Tue, 31 Mar 2009 15:25:18 -0700 Subject: fbmem: fix fb_info->lock and mm->mmap_sem circular locking dependency Fix a circular locking dependency in the frame buffer console driver pushing down the mutex fb_info->lock. Circular locking dependecies occur calling the blocking fb_notifier_call_chain() with fb_info->lock held. Notifier callbacks can try to acquire mm->mmap_sem, while fb_mmap() acquires the locks in the reverse order mm->mmap_sem => fb_info->lock. Tested-by: Andrey Borzenkov Signed-off-by: Andrea Righi Cc: Geert Uytterhoeven Cc: Krzysztof Helt Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/video/backlight/backlight.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'drivers/video/backlight/backlight.c') diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 157057c79ca3..dd37cbcaf8ce 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -35,6 +35,8 @@ static int fb_notifier_callback(struct notifier_block *self, return 0; bd = container_of(self, struct backlight_device, fb_notif); + if (!lock_fb_info(evdata->info)) + return -ENODEV; mutex_lock(&bd->ops_lock); if (bd->ops) if (!bd->ops->check_fb || @@ -47,6 +49,7 @@ static int fb_notifier_callback(struct notifier_block *self, backlight_update_status(bd); } mutex_unlock(&bd->ops_lock); + unlock_fb_info(evdata->info); return 0; } -- cgit v1.2.2