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fbmem: fix fb_info->lock and mm->mmap_sem circular locking dependency

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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 <arvidjaar@mail.ru>
Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrea Righi
2009-03-31 15:25:18 -07:00
committed by Linus Torvalds
parent 8636a9240c
commit 66c1ca0190
4 changed files with 70 additions and 20 deletions
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3
drivers/video/backlight/backlight.c
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@@ -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;
}