workqueue: add system_freezeable_wq

Add system wide freezeable workqueue.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>

include/linux/workqueue.h

@@ -286,11 +286,15 @@ enum {
  * any specific CPU, not concurrency managed, and all queued works are
  * executed immediately as long as max_active limit is not reached and
  * resources are available.
+ *
+ * system_freezeable_wq is equivalent to system_wq except that it's
+ * freezeable.
  */
 extern struct workqueue_struct *system_wq;
 extern struct workqueue_struct *system_long_wq;
 extern struct workqueue_struct *system_nrt_wq;
 extern struct workqueue_struct *system_unbound_wq;
+extern struct workqueue_struct *system_freezeable_wq;
 
 extern struct workqueue_struct *
 __alloc_workqueue_key(const char *name, unsigned int flags, int max_active,

kernel/workqueue.c

@@ -249,10 +249,12 @@ struct workqueue_struct *system_wq __read_mostly;
 struct workqueue_struct *system_long_wq __read_mostly;
 struct workqueue_struct *system_nrt_wq __read_mostly;
 struct workqueue_struct *system_unbound_wq __read_mostly;
+struct workqueue_struct *system_freezeable_wq __read_mostly;
 EXPORT_SYMBOL_GPL(system_wq);
 EXPORT_SYMBOL_GPL(system_long_wq);
 EXPORT_SYMBOL_GPL(system_nrt_wq);
 EXPORT_SYMBOL_GPL(system_unbound_wq);
+EXPORT_SYMBOL_GPL(system_freezeable_wq);
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/workqueue.h>
@@ -3764,8 +3766,10 @@ static int __init init_workqueues(void)
 	system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
 	system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
 					    WQ_UNBOUND_MAX_ACTIVE);
+	system_freezeable_wq = alloc_workqueue("events_freezeable",
+					       WQ_FREEZEABLE, 0);
 	BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
-	       !system_unbound_wq);
+	       !system_unbound_wq || !system_freezeable_wq);
 	return 0;
 }
 early_initcall(init_workqueues);