workqueue: introduce create_rt_workqueue

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>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>

2 files changed, 16 insertions, 9 deletions

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 5c158c477ac7..89a5a1231ffb 100644
--- a/include/linux/workqueue.h
+++ b/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, int singlethread,
                 __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);
 
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 714afad46539..f928f2a87b9b 100644
--- a/kernel/workqueue.c
+++ b/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_struct *wq, int cpu)
 
 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(struct cpu_workqueue_struct *cwq, int cpu)
          */
         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(struct cpu_workqueue_struct *cwq, int cpu)
 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_workqueue_key(const char *name,
         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) {