sched: Extend enqueue_task to allow head queueing

The ability of enqueueing a task to the head of a SCHED_FIFO priority
list is required to fix some violations of POSIX scheduling policy.

Extend the related functions with a "head" argument.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Carsten Emde <cbe@osadl.org>
Tested-by: Mathias Weber <mathias.weber.mw1@roche.com>
LKML-Reference: <20100120171629.734886007@linutronix.de>

4 files changed, 13 insertions, 9 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8b079735ae5f..b35c0c7130c8 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1067,7 +1067,8 @@ struct sched_domain;
 struct sched_class {
         const struct sched_class *next;
 
-        void (*enqueue_task) (struct rq *rq, struct task_struct *p, int wakeup);
+        void (*enqueue_task) (struct rq *rq, struct task_struct *p, int wakeup,
+                              bool head);
         void (*dequeue_task) (struct rq *rq, struct task_struct *p, int sleep);
         void (*yield_task) (struct rq *rq);
 
diff --git a/kernel/sched.c b/kernel/sched.c
index 41e76d325648..f47560ff3346 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1856,13 +1856,14 @@ static void update_avg(u64 *avg, u64 sample)
         *avg += diff >> 3;
 }
 
-static void enqueue_task(struct rq *rq, struct task_struct *p, int wakeup)
+static void
+enqueue_task(struct rq *rq, struct task_struct *p, int wakeup, bool head)
 {
         if (wakeup)
                 p->se.start_runtime = p->se.sum_exec_runtime;
 
         sched_info_queued(p);
-        p->sched_class->enqueue_task(rq, p, wakeup);
+        p->sched_class->enqueue_task(rq, p, wakeup, head);
         p->se.on_rq = 1;
 }
 
@@ -1892,7 +1893,7 @@ static void activate_task(struct rq *rq, struct task_struct *p, int wakeup)
         if (task_contributes_to_load(p))
                 rq->nr_uninterruptible--;
 
-        enqueue_task(rq, p, wakeup);
+        enqueue_task(rq, p, wakeup, false);
         inc_nr_running(rq);
 }
 
@@ -4236,7 +4237,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
         if (running)
                 p->sched_class->set_curr_task(rq);
         if (on_rq) {
-                enqueue_task(rq, p, 0);
+                enqueue_task(rq, p, 0, false);
 
                 check_class_changed(rq, p, prev_class, oldprio, running);
         }
@@ -4280,7 +4281,7 @@ void set_user_nice(struct task_struct *p, long nice)
         delta = p->prio - old_prio;
 
         if (on_rq) {
-                enqueue_task(rq, p, 0);
+                enqueue_task(rq, p, 0, false);
                 /*
                  * If the task increased its priority or is running and
                  * lowered its priority, then reschedule its CPU:
@@ -8230,7 +8231,7 @@ void sched_move_task(struct task_struct *tsk)
         if (unlikely(running))
                 tsk->sched_class->set_curr_task(rq);
         if (on_rq)
-                enqueue_task(rq, tsk, 0);
+                enqueue_task(rq, tsk, 0, false);
 
         task_rq_unlock(rq, &flags);
 }
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 22231ccb2f98..0e7a7af9cf8b 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1053,7 +1053,8 @@ static inline void hrtick_update(struct rq *rq)
  * increased. Here we update the fair scheduling stats and
  * then put the task into the rbtree:
  */
-static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
+static void
+enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup, bool head)
 {
         struct cfs_rq *cfs_rq;
         struct sched_entity *se = &p->se;
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 502bb614e40a..38076dabb44a 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -878,7 +878,8 @@ static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
 /*
  * Adding/removing a task to/from a priority array:
  */
-static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
+static void
+enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup, bool head)
 {
         struct sched_rt_entity *rt_se = &p->rt;