linux-kernel - [bug] Fixing mutex_lock() under held spinlock

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Message-ID: <20100729132223.GA19715@albatros>
Date:	Thu, 29 Jul 2010 17:22:23 +0400
From:	Vasiliy Kulikov <segooon@...il.com>
To:	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>,
	David Woodhouse <David.Woodhouse@...el.com>,
	Nicolas Pitre <nico@...xnic.net>,
	Hans-Christian Egtvedt <hans-christian.egtvedt@...el.com>,
	Jiri Slaby <jslaby@...e.cz>,
	Stefani Seibold <stefani@...bold.net>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Cc:	kernel-janitors@...r.kernel.org
Subject: [bug] Fixing mutex_lock() under held spinlock

Hi,

I've found that cfi_cmdset and lpddr_cmds call mutex_lock() under held
spinlock(). Maybe it was designed as a special locking scheme, so I
don't try to fix it as I might create new complex locking problem.


--- ./drivers/mtd/chips/cfi_cmdset_0001.c	2010-07-06 16:45:43.000000000 +0400
+++ /tmp/cocci-output-8818-2d9c62-cfi_cmdset_0001.c	2010-07-29 16:30:47.000000000 +0400
@@ -959,14 +959,12 @@ static void put_chip(struct map_info *ma
 
 	if (chip->priv) {
 		struct flchip_shared *shared = chip->priv;
-		spin_lock(&shared->lock);
 		if (shared->writing == chip && chip->oldstate == FL_READY) {
 			/* We own the ability to write, but we're done */
 			shared->writing = shared->erasing;
 			if (shared->writing && shared->writing != chip) {
 				/* give back ownership to who we loaned it from */
 				struct flchip *loaner = shared->writing;
-				mutex_lock(&loaner->mutex);
 				spin_unlock(&shared->lock);
 				mutex_unlock(&chip->mutex);
 				put_chip(map, loaner, loaner->start);
--- ./drivers/mtd/lpddr/lpddr_cmds.c	2010-07-06 16:45:43.000000000 +0400
+++ /tmp/cocci-output-8953-56b3dd-lpddr_cmds.c	2010-07-29 16:30:57.000000000 +0400
@@ -348,14 +348,12 @@ static void put_chip(struct map_info *ma
 {
 	if (chip->priv) {
 		struct flchip_shared *shared = chip->priv;
-		spin_lock(&shared->lock);
 		if (shared->writing == chip && chip->oldstate == FL_READY) {
 			/* We own the ability to write, but we're done */
 			shared->writing = shared->erasing;
 			if (shared->writing && shared->writing != chip) {
 				/* give back the ownership */
 				struct flchip *loaner = shared->writing;
-				mutex_lock(&loaner->mutex);
 				spin_unlock(&shared->lock);
 				mutex_unlock(&chip->mutex);
 				put_chip(map, loaner);


thanks,
Vasiliy
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