===================================================================
@@ -1056,6 +1056,7 @@ struct sched_class {
void (*enqueue_task) (struct rq *rq, struct task_struct *p, int flags);
void (*dequeue_task) (struct rq *rq, struct task_struct *p, int flags);
void (*yield_task) (struct rq *rq);
+ int (*yield_to_task) (struct task_struct *p, int preempt);
void (*check_preempt_curr) (struct rq *rq, struct task_struct *p, int flags);
===================================================================
@@ -5327,6 +5327,62 @@ void __sched yield(void)
}
EXPORT_SYMBOL(yield);
+/**
+ * yield_to - yield the current processor to another thread in
+ * your thread group, or accelerate that thread toward the
+ * processor it's on.
+ *
+ * It's the caller's job to ensure that the target task struct
+ * can't go away on us before we can do any checks.
+ */
+void __sched yield_to(struct task_struct *p, int preempt)
+{
+ struct task_struct *curr = current;
+ struct rq *rq, *p_rq;
+ unsigned long flags;
+ int yield = 0;
+
+ local_irq_save(flags);
+ rq = this_rq();
+
+again:
+ p_rq = task_rq(p);
+ double_rq_lock(rq, p_rq);
+ while (task_rq(p) != p_rq) {
+ double_rq_unlock(rq, p_rq);
+ goto again;
+ }
+
+ if (!curr->sched_class->yield_to_task)
+ goto out;
+
+ if (curr->sched_class != p->sched_class)
+ goto out;
+
+ if (task_running(p_rq, p) || p->state)
+ goto out;
+
+ if (!same_thread_group(p, curr))
+ goto out;
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+ if (task_group(p) != task_group(curr))
+ goto out;
+#endif
+
+ yield = curr->sched_class->yield_to_task(p, preempt);
+
+out:
+ double_rq_unlock(rq, p_rq);
+ local_irq_restore(flags);
+
+ if (yield) {
+ set_current_state(TASK_RUNNING);
+ schedule();
+ }
+}
+EXPORT_SYMBOL_GPL(yield_to);
+
/*
* This task is about to go to sleep on IO. Increment rq->nr_iowait so
* that process accounting knows that this is a task in IO wait state.
===================================================================
@@ -1337,6 +1337,57 @@ static void yield_task_fair(struct rq *r
}
#ifdef CONFIG_SMP
+static void pull_task(struct rq *src_rq, struct task_struct *p,
+ struct rq *this_rq, int this_cpu);
+#endif
+
+static int yield_to_task_fair(struct task_struct *p, int preempt)
+{
+ struct sched_entity *se = ¤t->se;
+ struct sched_entity *pse = &p->se;
+ struct cfs_rq *cfs_rq = cfs_rq_of(se);
+ struct cfs_rq *p_cfs_rq = cfs_rq_of(pse);
+ int local = cfs_rq == p_cfs_rq;
+ int this_cpu = smp_processor_id();
+
+ if (!pse->on_rq)
+ return 0;
+
+#ifdef CONFIG_SMP
+ /*
+ * If this yield is important enough to want to preempt instead
+ * of only dropping a ->next hint, we're alone, and the target
+ * is not alone, pull the target to this cpu.
+ *
+ * NOTE: the target may be alone in it's cfs_rq if another class
+ * task or another task group is currently executing on it's cpu.
+ * In this case, we still pull, to accelerate it toward the cpu.
+ */
+ if (!local && preempt && cfs_rq->nr_running == 1 &&
+ cpumask_test_cpu(this_cpu, &p->cpus_allowed)) {
+ pull_task(task_rq(p), p, this_rq(), this_cpu);
+ p_cfs_rq = cfs_rq_of(pse);
+ local = 1;
+ }
+#endif
+
+ /* We know whether we want to preempt or not, but are we allowed? */
+ preempt &= same_thread_group(p, task_of(p_cfs_rq->curr));
+
+ if (local)
+ clear_buddies(cfs_rq, se);
+ else if (preempt) {
+ clear_buddies(p_cfs_rq, p_cfs_rq->curr);
+ resched_task(task_of(p_cfs_rq->curr));
+ }
+
+ /* Tell the scheduler that we'd really like pse to run next. */
+ p_cfs_rq->next = pse;
+
+ return local;
+}
+
+#ifdef CONFIG_SMP
static void task_waking_fair(struct rq *rq, struct task_struct *p)
{
@@ -4143,6 +4194,7 @@ static const struct sched_class fair_sch
.enqueue_task = enqueue_task_fair,
.dequeue_task = dequeue_task_fair,
.yield_task = yield_task_fair,
+ .yield_to_task = yield_to_task_fair,
.check_preempt_curr = check_preempt_wakeup,