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[3.11.y.z,extended,stable] Patch "dm delay: fix a possible deadlock due to shared workqueue" has been added to staging queue

Message ID 1387361944-21163-1-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques Dec. 18, 2013, 10:19 a.m. UTC 
This is a note to let you know that I have just added a patch titled

    dm delay: fix a possible deadlock due to shared workqueue

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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From b4e7fe957a788b08c3bdfe4ff87ba5ed1ca6d3e2 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Fri, 15 Nov 2013 16:12:20 -0500
Subject: dm delay: fix a possible deadlock due to shared workqueue

commit 718822c1c112dc99e0c72c8968ee1db9d9d910f0 upstream.

The dm-delay target uses a shared workqueue for multiple instances.  This
can cause deadlock if two or more dm-delay targets are stacked on the top
of each other.

This patch changes dm-delay to use a per-instance workqueue.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 drivers/md/dm-delay.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

--
1.8.3.2
diff mbox

Patch

diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c
index 496d5f3..2f91d6d 100644
--- a/drivers/md/dm-delay.c
+++ b/drivers/md/dm-delay.c
@@ -20,6 +20,7 @@ 
 struct delay_c {
 	struct timer_list delay_timer;
 	struct mutex timer_lock;
+	struct workqueue_struct *kdelayd_wq;
 	struct work_struct flush_expired_bios;
 	struct list_head delayed_bios;
 	atomic_t may_delay;
@@ -45,14 +46,13 @@  struct dm_delay_info {

 static DEFINE_MUTEX(delayed_bios_lock);

-static struct workqueue_struct *kdelayd_wq;
 static struct kmem_cache *delayed_cache;

 static void handle_delayed_timer(unsigned long data)
 {
 	struct delay_c *dc = (struct delay_c *)data;

-	queue_work(kdelayd_wq, &dc->flush_expired_bios);
+	queue_work(dc->kdelayd_wq, &dc->flush_expired_bios);
 }

 static void queue_timeout(struct delay_c *dc, unsigned long expires)
@@ -191,6 +191,12 @@  out:
 		goto bad_dev_write;
 	}

+	dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
+	if (!dc->kdelayd_wq) {
+		DMERR("Couldn't start kdelayd");
+		goto bad_queue;
+	}
+
 	setup_timer(&dc->delay_timer, handle_delayed_timer, (unsigned long)dc);

 	INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
@@ -203,6 +209,8 @@  out:
 	ti->private = dc;
 	return 0;

+bad_queue:
+	mempool_destroy(dc->delayed_pool);
 bad_dev_write:
 	if (dc->dev_write)
 		dm_put_device(ti, dc->dev_write);
@@ -217,7 +225,7 @@  static void delay_dtr(struct dm_target *ti)
 {
 	struct delay_c *dc = ti->private;

-	flush_workqueue(kdelayd_wq);
+	destroy_workqueue(dc->kdelayd_wq);

 	dm_put_device(ti, dc->dev_read);

@@ -350,12 +358,6 @@  static int __init dm_delay_init(void)
 {
 	int r = -ENOMEM;

-	kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
-	if (!kdelayd_wq) {
-		DMERR("Couldn't start kdelayd");
-		goto bad_queue;
-	}
-
 	delayed_cache = KMEM_CACHE(dm_delay_info, 0);
 	if (!delayed_cache) {
 		DMERR("Couldn't create delayed bio cache.");
@@ -373,8 +375,6 @@  static int __init dm_delay_init(void)
 bad_register:
 	kmem_cache_destroy(delayed_cache);
 bad_memcache:
-	destroy_workqueue(kdelayd_wq);
-bad_queue:
 	return r;
 }

@@ -382,7 +382,6 @@  static void __exit dm_delay_exit(void)
 {
 	dm_unregister_target(&delay_target);
 	kmem_cache_destroy(delayed_cache);
-	destroy_workqueue(kdelayd_wq);
 }

 /* Module hooks */