Messages in this thread Patch in this message | | | Date | Tue, 22 Jul 2008 10:06:10 -0400 | From | Gregory Haskins <> | Subject | Re: [PATCH] cpu hotplug, sched:Introduce cpu_active_map and redoscheddomainmanagment (take 2) |
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Max Krasnyansky wrote: > Greg, correct me if I'm wrong but we seem to have exact same issue with the > rq->rq->online map. Lets take "cpu going down" for example. We're clearing > rq->rd->online bit on DYING event, but nothing AFAICS prevents another cpu > calling rebuild_sched_domains()->partition_sched_domains() in the middle of > the hotplug sequence. > partition_sched_domains() will happily reset rd->rq->online mask and things > will fail. I'm talking about this path > > __build_sched_domains() -> cpu_attach_domain() -> rq_attach_root() > ... > cpu_set(rq->cpu, rd->span); > if (cpu_isset(rq->cpu, cpu_online_map)) > set_rq_online(rq); > ... > >
I think you are right, but wouldn't s/online/active above fix that as well? The active_map didnt exist at the time that code went in initially ;)
> -- > > btw Why didn't we convert sched*.c to use rq->rd->online when it was > introduced ? ie Instead of using cpu_online_map directly. > I think things were converted where they made sense to convert. But we also had a different goal at that time, so perhaps something was missed. If you think something else should be converted, please point it out.
In the meantime, I would suggest we consider this patch on top of yours (applies to tip/sched/devel):
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sched: Fully integrate cpus_active_map and root-domain code Signed-off-by: Gregory Haskins <ghaskins@novell.com>
diff --git a/kernel/sched.c b/kernel/sched.c index 62b1b8e..99ba70d 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -6611,7 +6611,7 @@ static void rq_attach_root(struct rq *rq, struct root_domain *rd) rq->rd = rd; cpu_set(rq->cpu, rd->span); - if (cpu_isset(rq->cpu, cpu_online_map)) + if (cpu_isset(rq->cpu, cpu_active_map)) set_rq_online(rq); spin_unlock_irqrestore(&rq->lock, flags); diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 7f70026..2bae8de 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1004,7 +1004,7 @@ static void yield_task_fair(struct rq *rq) * search starts with cpus closest then further out as needed, * so we always favor a closer, idle cpu. * Domains may include CPUs that are not usable for migration, - * hence we need to mask them out (cpu_active_map) + * hence we need to mask them out (rq->rd->online) * * Returns the CPU we should wake onto. */ @@ -1032,7 +1032,7 @@ static int wake_idle(int cpu, struct task_struct *p) || ((sd->flags & SD_WAKE_IDLE_FAR) && !task_hot(p, task_rq(p)->clock, sd))) { cpus_and(tmp, sd->span, p->cpus_allowed); - cpus_and(tmp, tmp, cpu_active_map); + cpus_and(tmp, tmp, task_rq(p)->rd->online); for_each_cpu_mask(i, tmp) { if (idle_cpu(i)) { if (i != task_cpu(p)) { diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 24621ce..d93169d 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -936,13 +936,6 @@ static int find_lowest_rq(struct task_struct *task) return -1; /* No targets found */ /* - * Only consider CPUs that are usable for migration. - * I guess we might want to change cpupri_find() to ignore those - * in the first place. - */ - cpus_and(*lowest_mask, *lowest_mask, cpu_active_map); - - /* * At this point we have built a mask of cpus representing the * lowest priority tasks in the system. Now we want to elect * the best one based on our affinity and topology. -------------- Regards, -Greg
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