| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Tue, 11 Nov 2014 21:07:09 +0800
From: Wanpeng Li <kernellwp@...il.com>
To: Kirill Tkhai <ktkhai@...allels.com>,
Wanpeng Li <wanpeng.li@...ux.intel.com>
CC: Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] sched/deadline: support dl task migration during cpu
hotplug
Hi Kirill,
On 11/11/14, 7:10 PM, Kirill Tkhai wrote:
> В Вт, 11/11/2014 в 10:30 +0800, Wanpeng Li пишет:
>> I observe that dl task can't be migrated to other cpus during cpu hotplug, in
>> addition, task may/may not be running again if cpu is added back. The root cause
>> which I found is that dl task will be throtted and removed from dl rq after
>> comsuming all budget, which leads to stop task can't pick it up from dl rq and
>> migrate to other cpus during hotplug.
>>
>> The method to reproduce:
>> schedtool -E -t 50000:100000 -e ./test
>> Actually test is just a simple for loop. Then observe which cpu the test
>> task is on.
>> echo 0 > /sys/devices/system/cpu/cpuN/online
>>
>> This patch fix it by push the task to another cpu in dl_task_timer() if
>> rq is offline.
>>
>> Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
> I'm still thinking we don't have to guarantee any "deadlines" during cpu hotplug...
> But, if speaking about this way:
>
>> ---
>> v3 -> v4:
>> * use tsk_cpus_allowed wrapper
>> * fix compile error
>> v2 -> v3:
>> * don't get_task_struct
>> * if cannot preempt any rq, fallback to pick any online cpus
>> * use cpu_active_mask as original later_mask if cpu is offline
>> v1 -> v2:
>> * push the task to another cpu in dl_task_timer() if rq is offline.
>>
>>
>> kernel/sched/deadline.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++---
>> 1 file changed, 48 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>> index 00324af..e0fbba4 100644
>> --- a/kernel/sched/deadline.c
>> +++ b/kernel/sched/deadline.c
>> @@ -487,6 +487,7 @@ static int start_dl_timer(struct sched_dl_entity *dl_se, bool boosted)
>> return hrtimer_active(&dl_se->dl_timer);
>> }
>>
>> +static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq);
>> /*
>> * This is the bandwidth enforcement timer callback. If here, we know
>> * a task is not on its dl_rq, since the fact that the timer was running
>> @@ -538,6 +539,46 @@ again:
>> update_rq_clock(rq);
>> dl_se->dl_throttled = 0;
>> dl_se->dl_yielded = 0;
>> +
>> + /*
>> + * So if we find that the rq the task was on is no longer
>> + * available, we need to select a new rq.
>> + */
>> + if (!rq->online) {
>> + struct rq *later_rq = NULL;
>> +
>> + raw_spin_unlock(&rq->lock);
>> +
>> + later_rq = find_lock_later_rq(p, rq);
> find_lock_later_rq() expects that rq is locked.
>
> The comment near its head confuses a reader. It locks newly found rq.
Sorry for my bad, what's you think should be changed?
Regards,
Wanpeng Li
>
>> +
>> + if (!later_rq) {
>> + int cpu;
>> +
>> + /*
>> + * If cannot preempt any rq, fallback to pick any
>> + * online cpu.
>> + */
>> + for_each_cpu(cpu, tsk_cpus_allowed(p))
>> + if (cpu_online(cpu))
>> + later_rq = cpu_rq(cpu);
>> + if (!later_rq) {
>> + pr_warn("fail to find any online and task "
>> + "will never come back to us\n");
>> + goto out;
>> + }
>> + }
>> +
>> + deactivate_task(rq, p, 0);
>> + set_task_cpu(p, later_rq->cpu);
>> + activate_task(later_rq, p, 0);
>> +
>> + resched_curr(later_rq);
>> +
>> + double_unlock_balance(rq, later_rq);
> double_unlock_balance() unlocks later_rq only.
>
>> +
>> + goto out;
>> + }
>> +
>> if (task_on_rq_queued(p)) {
>> enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
>> if (dl_task(rq->curr))
>> @@ -555,7 +596,7 @@ again:
>> }
>> unlock:
>> raw_spin_unlock(&rq->lock);
>> -
>> +out:
>> return HRTIMER_NORESTART;
>> }
>>
>> @@ -1185,8 +1226,12 @@ static int find_later_rq(struct task_struct *task)
>> * We have to consider system topology and task affinity
>> * first, then we can look for a suitable cpu.
>> */
>> - cpumask_copy(later_mask, task_rq(task)->rd->span);
>> - cpumask_and(later_mask, later_mask, cpu_active_mask);
>> + if (likely(task_rq(task)->online)) {
>> + cpumask_copy(later_mask, task_rq(task)->rd->span);
>> + cpumask_and(later_mask, later_mask, cpu_active_mask);
>> + } else
>> + /* for offline cpus we have a singleton rd */
>> + cpumask_copy(later_mask, cpu_active_mask);
>> cpumask_and(later_mask, later_mask, &task->cpus_allowed);
>> best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
>> task, later_mask);
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists