linux-kernel - [PATCH] [drivers/video/fb] Eliminate recursive mutex in compat fb ioctl path

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Message-Id: <1225696010-6574-1-git-send-email-keithp@keithp.com>
Date:	Sun,  2 Nov 2008 23:06:50 -0800
From:	Keith Packard <keithp@...thp.com>
To:	linux-kernel@...r.kernel.org
Cc:	Keith Packard <keithp@...thp.com>
Subject: [PATCH] [drivers/video/fb] Eliminate recursive mutex in compat fb ioctl path

fb_compat_ioctl grabbed the fb mutex and then called fb_ioctl, which also
grabs the same mutex. I traced through all existing fb_compat_ioctl
functions in the various fb drivers and found that they also transform their
arguments and call the native fb_ioctl function. So, it is correct to just
remove the mutex_lock/mutex_unlock pair in the top-level compat path.

Signed-off-by: Keith Packard <keithp@...thp.com>
---
 drivers/video/fbmem.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index cd5f20d..548cf26 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -1253,7 +1253,6 @@ fb_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	struct fb_ops *fb = info->fbops;
 	long ret = -ENOIOCTLCMD;
 
-	mutex_lock(&info->lock);
 	switch(cmd) {
 	case FBIOGET_VSCREENINFO:
 	case FBIOPUT_VSCREENINFO:
@@ -1279,7 +1278,6 @@ fb_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 			ret = fb->fb_compat_ioctl(info, cmd, arg);
 		break;
 	}
-	mutex_unlock(&info->lock);
 	return ret;
 }
 #endif
-- 
1.5.6.5

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