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video: sm501fb: Early initialization of mm_lock mutex.

Commit 537a1bf (fbdev: add mutex for
fb_mmap locking) introduces a ->mm_lock mutex for protecting smem
assignments. Unfortunately in the case of sm501fb these happen quite
early in the initialization code, well before the mutex_init() that takes
place in register_framebuffer(), leading to:

   Badness at kernel/mutex.c:207

   Pid : 1, Comm:          swapper
   CPU : 0                 Not tainted  (2.6.31-rc1-00284-g529ba0d-dirty #2273)

   PC is at __mutex_lock_slowpath+0x72/0x1bc
   PR is at __mutex_lock_slowpath+0x66/0x1bc

matroxfb appears to have the same issue and has solved it with an early
mutex_init(), so we do the same for sm501fb.

Signed-off-by: Paul Mundt <>
Cc: Krzysztof Helt <>
Signed-off-by: Linus Torvalds <>
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Paul Mundt authored and torvalds committed Jul 3, 2009
1 parent de481ba commit f50bf2b2f5e83b794e0bdb2f3f589f55ef0d52d0
Showing with 2 additions and 0 deletions.
  1. +2 −0 drivers/video/sm501fb.c
@@ -1624,6 +1624,8 @@ static int __devinit sm501fb_start_one(struct sm501fb_info *info,
if (!fbi)
return 0;
+ mutex_init(&info->fb[head]->mm_lock);
ret = sm501fb_init_fb(info->fb[head], head, drvname);
if (ret) {
dev_err(info->dev, "cannot initialise fb %s\n", drvname);

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