Commit-ID: a15b12ac36ad4e7b856a4ae54937ae26a51aebad
Gitweb: http://git.kernel.org/tip/a15b12ac36ad4e7b856a4ae54937ae26a51aebad
Author: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
AuthorDate: Fri, 12 Sep 2014 15:03:34 +0400
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 19 Sep 2014 12:35:21 +0200
sched: Do not stop cpu in set_cpus_allowed_ptr() if task is not running
If a task is queued but not running on it rq, we can simply migrate
it without migration thread and switching of context.
Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1410519814.3569.7.camel@tkhai
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/core.c | 47 ++++++++++++++++++++++++++++++++---------------
1 file changed, 32 insertions(+), 15 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5536397..4b1ddeb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4629,6 +4629,33 @@ void init_idle(struct task_struct *idle, int cpu)
}
#ifdef CONFIG_SMP
+/*
+ * move_queued_task - move a queued task to new rq.
+ *
+ * Returns (locked) new rq. Old rq's lock is released.
+ */
+static struct rq *move_queued_task(struct task_struct *p, int new_cpu)
+{
+ struct rq *rq = task_rq(p);
+
+ lockdep_assert_held(&rq->lock);
+
+ dequeue_task(rq, p, 0);
+ p->on_rq = TASK_ON_RQ_MIGRATING;
+ set_task_cpu(p, new_cpu);
+ raw_spin_unlock(&rq->lock);
+
+ rq = cpu_rq(new_cpu);
+
+ raw_spin_lock(&rq->lock);
+ BUG_ON(task_cpu(p) != new_cpu);
+ p->on_rq = TASK_ON_RQ_QUEUED;
+ enqueue_task(rq, p, 0);
+ check_preempt_curr(rq, p, 0);
+
+ return rq;
+}
+
void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
{
if (p->sched_class && p->sched_class->set_cpus_allowed)
@@ -4685,14 +4712,15 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
goto out;
dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);
- if (task_on_rq_queued(p) || p->state == TASK_WAKING) {
+ if (task_running(rq, p) || p->state == TASK_WAKING) {
struct migration_arg arg = { p, dest_cpu };
/* Need help from migration thread: drop lock and wait. */
task_rq_unlock(rq, p, &flags);
stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
tlb_migrate_finish(p->mm);
return 0;
- }
+ } else if (task_on_rq_queued(p))
+ rq = move_queued_task(p, dest_cpu);
out:
task_rq_unlock(rq, p, &flags);
@@ -4735,19 +4763,8 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
* If we're not on a rq, the next wake-up will ensure we're
* placed properly.
*/
- if (task_on_rq_queued(p)) {
- dequeue_task(rq, p, 0);
- p->on_rq = TASK_ON_RQ_MIGRATING;
- set_task_cpu(p, dest_cpu);
- raw_spin_unlock(&rq->lock);
-
- rq = cpu_rq(dest_cpu);
- raw_spin_lock(&rq->lock);
- BUG_ON(task_rq(p) != rq);
- p->on_rq = TASK_ON_RQ_QUEUED;
- enqueue_task(rq, p, 0);
- check_preempt_curr(rq, p, 0);
- }
+ if (task_on_rq_queued(p))
+ rq = move_queued_task(p, dest_cpu);
done:
ret = 1;
fail:
--
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