On 2019-07-27 00:56:35 [-0500], Scott Wood wrote:
> With the changes to migrate disabling, ->set_cpus_allowed() no longer
> gets deferred until migrate_enable(). To avoid releasing the bandwidth
> while the task may still be executing on the old CPU, move the subtraction
> to ->migrate_task_rq().
I assume this is still valid for the !RT case.
Could someone from the scheduler/DL department please comment on this
one?
> Signed-off-by: Scott Wood <swood@xxxxxxxxxx>
> ---
> kernel/sched/deadline.c | 67 +++++++++++++++++++++++--------------------------
> 1 file changed, 31 insertions(+), 36 deletions(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index c18be51f7608..2f18d0cf1b56 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1606,14 +1606,42 @@ static void yield_task_dl(struct rq *rq)
> return cpu;
> }
>
> +static void free_old_cpuset_bw_dl(struct rq *rq, struct task_struct *p)
> +{
> + struct root_domain *src_rd = rq->rd;
> +
> + /*
> + * Migrating a SCHED_DEADLINE task between exclusive
> + * cpusets (different root_domains) entails a bandwidth
> + * update. We already made space for us in the destination
> + * domain (see cpuset_can_attach()).
> + */
> + if (!cpumask_intersects(src_rd->span, p->cpus_ptr)) {
> + struct dl_bw *src_dl_b;
> +
> + src_dl_b = dl_bw_of(cpu_of(rq));
> + /*
> + * We now free resources of the root_domain we are migrating
> + * off. In the worst case, sched_setattr() may temporary fail
> + * until we complete the update.
> + */
> + raw_spin_lock(&src_dl_b->lock);
> + __dl_sub(src_dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
> + raw_spin_unlock(&src_dl_b->lock);
> + }
> +}
> +
> static void migrate_task_rq_dl(struct task_struct *p, int new_cpu __maybe_unused)
> {
> struct rq *rq;
>
> - if (p->state != TASK_WAKING)
> + rq = task_rq(p);
> +
> + if (p->state != TASK_WAKING) {
> + free_old_cpuset_bw_dl(rq, p);
> return;
> + }
>
> - rq = task_rq(p);
> /*
> * Since p->state == TASK_WAKING, set_task_cpu() has been called
> * from try_to_wake_up(). Hence, p->pi_lock is locked, but
> @@ -2220,39 +2248,6 @@ static void task_woken_dl(struct rq *rq, struct task_struct *p)
> }
> }
>
> -static void set_cpus_allowed_dl(struct task_struct *p,
> - const struct cpumask *new_mask)
> -{
> - struct root_domain *src_rd;
> - struct rq *rq;
> -
> - BUG_ON(!dl_task(p));
> -
> - rq = task_rq(p);
> - src_rd = rq->rd;
> - /*
> - * Migrating a SCHED_DEADLINE task between exclusive
> - * cpusets (different root_domains) entails a bandwidth
> - * update. We already made space for us in the destination
> - * domain (see cpuset_can_attach()).
> - */
> - if (!cpumask_intersects(src_rd->span, new_mask)) {
> - struct dl_bw *src_dl_b;
> -
> - src_dl_b = dl_bw_of(cpu_of(rq));
> - /*
> - * We now free resources of the root_domain we are migrating
> - * off. In the worst case, sched_setattr() may temporary fail
> - * until we complete the update.
> - */
> - raw_spin_lock(&src_dl_b->lock);
> - __dl_sub(src_dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
> - raw_spin_unlock(&src_dl_b->lock);
> - }
> -
> - set_cpus_allowed_common(p, new_mask);
> -}
> -
> /* Assumes rq->lock is held */
> static void rq_online_dl(struct rq *rq)
> {
> @@ -2407,7 +2402,7 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
> #ifdef CONFIG_SMP
> .select_task_rq = select_task_rq_dl,
> .migrate_task_rq = migrate_task_rq_dl,
> - .set_cpus_allowed = set_cpus_allowed_dl,
> + .set_cpus_allowed = set_cpus_allowed_common,
> .rq_online = rq_online_dl,
> .rq_offline = rq_offline_dl,
> .task_woken = task_woken_dl,
> --
> 1.8.3.1
>
Sebastian
