linux-kernel - [PATCH] video: sm501fb: Early initialization of mm

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Date:	Fri, 3 Jul 2009 15:45:56 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	Krzysztof Helt <krzysztof.h1@...pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] video: sm501fb: Early initialization of mm_lock mutex.

Commit 537a1bf059fa312355696fa6db80726e655e7f17 (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:

------------[ cut here ]------------
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 <lethal@...ux-sh.org>
Cc: Krzysztof Helt <krzysztof.h1@...pl>

---

 drivers/video/sm501fb.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/video/sm501fb.c b/drivers/video/sm501fb.c
index 98f24f0..16d4f4c 100644
--- a/drivers/video/sm501fb.c
+++ b/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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