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-rw-r--r--kernel/sched_rt.c119
1 files changed, 101 insertions, 18 deletions
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index b0b6ea4..fe9da60 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -49,6 +49,24 @@ static void update_rt_migration(struct rq *rq)
rq->rt.overloaded = 0;
}
}
+
+static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
+{
+ plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
+ plist_node_init(&p->pushable_tasks, p->prio);
+ plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
+}
+
+static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
+{
+ plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
+}
+
+#else
+
+#define enqueue_pushable_task(rq, p) do { } while (0)
+#define dequeue_pushable_task(rq, p) do { } while (0)
+
#endif /* CONFIG_SMP */
static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
@@ -751,6 +769,9 @@ static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
enqueue_rt_entity(rt_se);
+ if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
+ enqueue_pushable_task(rq, p);
+
inc_cpu_load(rq, p->se.load.weight);
}
@@ -761,6 +782,8 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
update_curr_rt(rq);
dequeue_rt_entity(rt_se);
+ dequeue_pushable_task(rq, p);
+
dec_cpu_load(rq, p->se.load.weight);
}
@@ -911,7 +934,7 @@ static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
return next;
}
-static struct task_struct *pick_next_task_rt(struct rq *rq)
+static struct task_struct *_pick_next_task_rt(struct rq *rq)
{
struct sched_rt_entity *rt_se;
struct task_struct *p;
@@ -933,6 +956,18 @@ static struct task_struct *pick_next_task_rt(struct rq *rq)
p = rt_task_of(rt_se);
p->se.exec_start = rq->clock;
+
+ return p;
+}
+
+static struct task_struct *pick_next_task_rt(struct rq *rq)
+{
+ struct task_struct *p = _pick_next_task_rt(rq);
+
+ /* The running task is never eligible for pushing */
+ if (p)
+ dequeue_pushable_task(rq, p);
+
return p;
}
@@ -940,6 +975,13 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
{
update_curr_rt(rq);
p->se.exec_start = 0;
+
+ /*
+ * The previous task needs to be made eligible for pushing
+ * if it is still active
+ */
+ if (p->se.on_rq && p->rt.nr_cpus_allowed > 1)
+ enqueue_pushable_task(rq, p);
}
#ifdef CONFIG_SMP
@@ -1116,6 +1158,31 @@ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
return lowest_rq;
}
+static inline int has_pushable_tasks(struct rq *rq)
+{
+ return !plist_head_empty(&rq->rt.pushable_tasks);
+}
+
+static struct task_struct *pick_next_pushable_task(struct rq *rq)
+{
+ struct task_struct *p;
+
+ if (!has_pushable_tasks(rq))
+ return NULL;
+
+ p = plist_first_entry(&rq->rt.pushable_tasks,
+ struct task_struct, pushable_tasks);
+
+ BUG_ON(rq->cpu != task_cpu(p));
+ BUG_ON(task_current(rq, p));
+ BUG_ON(p->rt.nr_cpus_allowed <= 1);
+
+ BUG_ON(!p->se.on_rq);
+ BUG_ON(!rt_task(p));
+
+ return p;
+}
+
/*
* If the current CPU has more than one RT task, see if the non
* running task can migrate over to a CPU that is running a task
@@ -1125,13 +1192,12 @@ static int push_rt_task(struct rq *rq)
{
struct task_struct *next_task;
struct rq *lowest_rq;
- int ret = 0;
int paranoid = RT_MAX_TRIES;
if (!rq->rt.overloaded)
return 0;
- next_task = pick_next_highest_task_rt(rq, -1);
+ next_task = pick_next_pushable_task(rq);
if (!next_task)
return 0;
@@ -1163,12 +1229,19 @@ static int push_rt_task(struct rq *rq)
* so it is possible that next_task has changed.
* If it has, then try again.
*/
- task = pick_next_highest_task_rt(rq, -1);
+ task = pick_next_pushable_task(rq);
if (unlikely(task != next_task) && task && paranoid--) {
put_task_struct(next_task);
next_task = task;
goto retry;
}
+
+ /*
+ * Once we have failed to push this task, we will not
+ * try again, since the other cpus will pull from us
+ * when they are ready
+ */
+ dequeue_pushable_task(rq, next_task);
goto out;
}
@@ -1180,23 +1253,12 @@ static int push_rt_task(struct rq *rq)
double_unlock_balance(rq, lowest_rq);
- ret = 1;
out:
put_task_struct(next_task);
- return ret;
+ return 1;
}
-/*
- * TODO: Currently we just use the second highest prio task on
- * the queue, and stop when it can't migrate (or there's
- * no more RT tasks). There may be a case where a lower
- * priority RT task has a different affinity than the
- * higher RT task. In this case the lower RT task could
- * possibly be able to migrate where as the higher priority
- * RT task could not. We currently ignore this issue.
- * Enhancements are welcome!
- */
static void push_rt_tasks(struct rq *rq)
{
/* push_rt_task will return true if it moved an RT */
@@ -1295,7 +1357,7 @@ static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
*/
static int needs_post_schedule_rt(struct rq *rq)
{
- return rq->rt.overloaded ? 1 : 0;
+ return has_pushable_tasks(rq);
}
static void post_schedule_rt(struct rq *rq)
@@ -1317,7 +1379,7 @@ static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
{
if (!task_running(rq, p) &&
!test_tsk_need_resched(rq->curr) &&
- rq->rt.overloaded &&
+ has_pushable_tasks(rq) &&
p->rt.nr_cpus_allowed > 1)
push_rt_tasks(rq);
}
@@ -1354,6 +1416,24 @@ static void set_cpus_allowed_rt(struct task_struct *p,
if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
struct rq *rq = task_rq(p);
+ if (!task_current(rq, p)) {
+ /*
+ * Make sure we dequeue this task from the pushable list
+ * before going further. It will either remain off of
+ * the list because we are no longer pushable, or it
+ * will be requeued.
+ */
+ if (p->rt.nr_cpus_allowed > 1)
+ dequeue_pushable_task(rq, p);
+
+ /*
+ * Requeue if our weight is changing and still > 1
+ */
+ if (weight > 1)
+ enqueue_pushable_task(rq, p);
+
+ }
+
if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
rq->rt.rt_nr_migratory++;
} else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
@@ -1538,6 +1618,9 @@ static void set_curr_task_rt(struct rq *rq)
struct task_struct *p = rq->curr;
p->se.exec_start = rq->clock;
+
+ /* The running task is never eligible for pushing */
+ dequeue_pushable_task(rq, p);
}
static const struct sched_class rt_sched_class = {
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