[PATCH wq/for-3.18] workqueue: apply __WQ_ORDERED to create_singlethread_workqueue()

[Tejun Heo <theo@redhat.com>]

>From e141deffe6a30cfe7dd6ad97f21afa85b80ca3ac Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Sat, 13 Sep 2014 04:14:30 +0900

create_singlethread_workqueue() is a compat interface for singled
threaded workqueue which maps to ordered workqueue w/ rescuer in the
current implementation.  create_singlethread_workqueue() currently
implemented by invoking alloc_workqueue() w/ appropriate parameters.

8719dceae2f9 ("workqueue: reject adjusting max_active or applying
attrs to ordered workqueues") introduced __WQ_ORDERED to protect
ordered workqueues against dynamic attribute changes which can break
ordering guarantees but forgot to apply it to
create_singlethread_workqueue().  While this can be potentially
dangerous, this isn't a problem in practice given the existing uses of
dynamic attribute changes.

Let's make create_singlethread_workqueue() wrap
alloc_ordered_workqueue() instead so that it inherits __WQ_ORDERED and
can implicitly track future ordered_workqueue changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Mike Anderson <mike.anderson@us.ibm.com>
Cc: Gustavo Luiz Duarte <gduarte@redhat.com>
Cc: Tomas Henzl <thenzl@redhat.com>
---
Applied to wq/for-3.18.

Thanks.

 include/linux/workqueue.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index a0cc2e9..b996e6cd 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -419,7 +419,7 @@ __alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active,
 	alloc_workqueue("%s", WQ_FREEZABLE | WQ_UNBOUND | WQ_MEM_RECLAIM, \
 			1, (name))
 #define create_singlethread_workqueue(name)				\
-	alloc_workqueue("%s", WQ_UNBOUND | WQ_MEM_RECLAIM, 1, (name))
+	alloc_ordered_workqueue("%s", WQ_MEM_RECLAIM, name)
 
 extern void destroy_workqueue(struct workqueue_struct *wq);
 
-- 
1.9.3