On Thu, Jun 05, 2014 at 06:54:35PM +0800, Lai Jiangshan wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 268a45e..d05a5a1 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1474,20 +1474,24 @@ static int ttwu_remote(struct task_struct *p, int
> wake_flags)
> }
>
> #ifdef CONFIG_SMP
> -static void sched_ttwu_pending(void)
> +static void sched_ttwu_pending_locked(struct rq *rq)
> {
> - struct rq *rq = this_rq();
> struct llist_node *llist = llist_del_all(&rq->wake_list);
> struct task_struct *p;
>
> - raw_spin_lock(&rq->lock);
> -
> while (llist) {
> p = llist_entry(llist, struct task_struct, wake_entry);
> llist = llist_next(llist);
> ttwu_do_activate(rq, p, 0);
> }
> +}
>
> +static void sched_ttwu_pending(void)
> +{
> + struct rq *rq = this_rq();
> +
> + raw_spin_lock(&rq->lock);
> + sched_ttwu_pending_locked(rq);
> raw_spin_unlock(&rq->lock);
> }
OK, so this won't apply to a recent kernel.
> @@ -4530,6 +4534,11 @@ 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);
> +
> + /* Ensure it is on rq for migration if it is waking */
> + if (p->state == TASK_WAKING)
> + sched_ttwu_pending_locked(rq);
So I would really rather like to avoid this if possible, its doing full
remote queueing, exactly what we tried to avoid.
> +
> if (p->on_rq) {
> struct migration_arg arg = { p, dest_cpu };
> /* Need help from migration thread: drop lock and wait. */
> @@ -4576,6 +4585,10 @@ static int __migrate_task(struct task_struct *p, int
> src_cpu, int dest_cpu)
> if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
> goto fail;
>
> + /* Ensure it is on rq for migration if it is waking */
> + if (p->state == TASK_WAKING)
> + sched_ttwu_pending_locked(rq_src);
> +
> /*
> * If we're not on a rq, the next wake-up will ensure we're
> * placed properly.
Oh man, another variant.. why did you change it again? And without
explanation for why you changed it.
I don't see a reason to call sched_ttwu_pending() with rq->lock held,
seeing as how we append to that list without it held.
I'm still thinking the previous version is good, can you explain why you
changed it?
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