[PATCH/RFC v2 2/6] workqueue: introduce create_rt_workqueue

[Heiko Carstens <heiko.carstens@de.ibm.com>]

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From: Heiko Carstens <heiko.carstens@de.ibm.com>

create_rt_workqueue will create a real time prioritized workqueue.
This is needed for the conversion of stop_machine to a workqueue based
implementation.
This patch adds yet another parameter to __create_workqueue_key to tell
it that we want an rt workqueue.
However it looks like we rather should have something like "int type"
instead of singlethread, freezable and rt.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
---
 include/linux/workqueue.h |   18 ++++++++++--------
 kernel/workqueue.c        |    7 ++++++-
 2 files changed, 16 insertions(+), 9 deletions(-)

Index: linux-2.6/include/linux/workqueue.h
===================================================================
--- linux-2.6.orig/include/linux/workqueue.h
+++ linux-2.6/include/linux/workqueue.h
@@ -149,11 +149,11 @@ struct execute_work {
 
 extern struct workqueue_struct *
 __create_workqueue_key(const char *name, int singlethread,
-		       int freezeable, struct lock_class_key *key,
+		       int freezeable, int rt, struct lock_class_key *key,
 		       const char *lock_name);
 
 #ifdef CONFIG_LOCKDEP
-#define __create_workqueue(name, singlethread, freezeable)	\
+#define __create_workqueue(name, singlethread, freezeable, rt)	\
 ({								\
 	static struct lock_class_key __key;			\
 	const char *__lock_name;				\
@@ -164,17 +164,19 @@ __create_workqueue_key(const char *name,
 		__lock_name = #name;				\
 								\
 	__create_workqueue_key((name), (singlethread),		\
-			       (freezeable), &__key,		\
+			       (freezeable), (rt), &__key,	\
 			       __lock_name);			\
 })
 #else
-#define __create_workqueue(name, singlethread, freezeable)	\
-	__create_workqueue_key((name), (singlethread), (freezeable), NULL, NULL)
+#define __create_workqueue(name, singlethread, freezeable, rt)	\
+	__create_workqueue_key((name), (singlethread), (freezeable), (rt), \
+			       NULL, NULL)
 #endif
 
-#define create_workqueue(name) __create_workqueue((name), 0, 0)
-#define create_freezeable_workqueue(name) __create_workqueue((name), 1, 1)
-#define create_singlethread_workqueue(name) __create_workqueue((name), 1, 0)
+#define create_workqueue(name) __create_workqueue((name), 0, 0, 0)
+#define create_rt_workqueue(name) __create_workqueue((name), 0, 0, 1)
+#define create_freezeable_workqueue(name) __create_workqueue((name), 1, 1, 0)
+#define create_singlethread_workqueue(name) __create_workqueue((name), 1, 0, 0)
 
 extern void destroy_workqueue(struct workqueue_struct *wq);
 
Index: linux-2.6/kernel/workqueue.c
===================================================================
--- linux-2.6.orig/kernel/workqueue.c
+++ linux-2.6/kernel/workqueue.c
@@ -62,6 +62,7 @@ struct workqueue_struct {
 	const char *name;
 	int singlethread;
 	int freezeable;		/* Freeze threads during suspend */
+	int rt;
 #ifdef CONFIG_LOCKDEP
 	struct lockdep_map lockdep_map;
 #endif
@@ -766,6 +767,7 @@ init_cpu_workqueue(struct workqueue_stru
 
 static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 {
+	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 	struct workqueue_struct *wq = cwq->wq;
 	const char *fmt = is_single_threaded(wq) ? "%s" : "%s/%d";
 	struct task_struct *p;
@@ -781,7 +783,8 @@ static int create_workqueue_thread(struc
 	 */
 	if (IS_ERR(p))
 		return PTR_ERR(p);
-
+	if (cwq->wq->rt)
+		sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
 	cwq->thread = p;
 
 	return 0;
@@ -801,6 +804,7 @@ static void start_workqueue_thread(struc
 struct workqueue_struct *__create_workqueue_key(const char *name,
 						int singlethread,
 						int freezeable,
+						int rt,
 						struct lock_class_key *key,
 						const char *lock_name)
 {
@@ -822,6 +826,7 @@ struct workqueue_struct *__create_workqu
 	lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
 	wq->singlethread = singlethread;
 	wq->freezeable = freezeable;
+	wq->rt = rt;
 	INIT_LIST_HEAD(&wq->list);
 
 	if (singlethread) {

--