linux-kernel - [PATCH] move file->f_op->open out of mutex (misc_mtx) in misc

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Date:	Tue,  6 Jan 2015 08:34:07 +0800
From:	xiaomin1 <xiaoming.wang@...el.com>
To:	arnd@...db.de, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org, chuansheng.liu@...el.com
Cc:	xiaomin1 <xiaoming.wang@...el.com>,
	Zhang Dongxing <dongxing.zhang@...el.com>
Subject: [PATCH] move file->f_op->open out of mutex (misc_mtx) in misc_open

misc_mtx was used to mutex misc_list.
But file->f_op->open may be blocked by downloading
firmware in some devices' open.
So move file->f_op->open out of mutex (misc_mtx)
in misc_open to avoid this block.
It also make code more efficiency.

Signed-off-by: Zhang Dongxing <dongxing.zhang@...el.com>
Signed-off-by: xiaoming wang <xiaoming.wang@...el.com>
---
 drivers/char/misc.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index ffa97d2..289c59e 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -144,7 +144,8 @@ static int misc_open(struct inode * inode, struct file * file)
 	replace_fops(file, new_fops);
 	if (file->f_op->open) {
 		file->private_data = c;
-		err = file->f_op->open(inode,file);
+		mutex_unlock(&misc_mtx);
+		return file->f_op->open(inode,file);
 	}
 fail:
 	mutex_unlock(&misc_mtx);
-- 
1.7.9.5

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