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>

1 files changed, 7 insertions, 6 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index ba0ee0d34545..8da004bbc8db 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1972,13 +1972,14 @@ 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;
 }
 
@@ -2056,7 +2057,7 @@ 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);
 }
 
@@ -6389,7 +6390,7 @@ void task_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);
         }
@@ -6433,7 +6434,7 @@ 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:
@@ -10522,7 +10523,7 @@ 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);
 }