linux-kernel - Re: [PATCH v3] sched: cpuset: Don't rebuild root domains on suspend-resume

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Date:   Mon, 13 Mar 2023 18:10:49 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Juri Lelli <juri.lelli@...hat.com>,
        Qais Yousef <qyousef@...alina.io>
Cc:     Hao Luo <haoluo@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>, tj@...nel.org,
        linux-kernel@...r.kernel.org, luca.abeni@...tannapisa.it,
        claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
        bristot@...hat.com, mathieu.poirier@...aro.org,
        cgroups@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Wei Wang <wvw@...gle.com>, Rick Yiu <rickyiu@...gle.com>,
        Quentin Perret <qperret@...gle.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Sudeep Holla <sudeep.holla@....com>,
        Zefan Li <lizefan.x@...edance.com>, linux-s390@...r.kernel.org,
        x86@...nel.org
Subject: Re: [PATCH v3] sched: cpuset: Don't rebuild root domains on
 suspend-resume

On 13/03/2023 17:37, Juri Lelli wrote:
> On 11/03/23 18:51, Qais Yousef wrote:
>> On 03/09/23 14:23, Hao Luo wrote:
>>> On Wed, Mar 8, 2023 at 10:55 PM Juri Lelli <juri.lelli@...hat.com> wrote:
>>>>
>>>> On 08/03/23 10:01, Hao Luo wrote:
>>>>> On Wed, Mar 8, 2023 at 2:20 AM Juri Lelli <juri.lelli@...hat.com> wrote:
>>>>>>
>>>>>> On 01/03/23 17:03, Qais Yousef wrote:
>>>>>>> On 03/01/23 15:26, Juri Lelli wrote:

[...]

>> Yeah I am working on 5.10 too (this will need to be backported to 5.10 and 5.15
>> ultimately) and had the same crash because task is NULL.
>>
>> Fixed it this way which I think what you intended to do Juri? It moves the
>> check for dl_task(task) inside cgroup_taskset_for_each() loop.
>>
>> 	diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> 	index 83a8943467fb..06d6bb68d86b 100644
>> 	--- a/kernel/cgroup/cpuset.c
>> 	+++ b/kernel/cgroup/cpuset.c
>> 	@@ -2495,11 +2495,11 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
>> 			ret = security_task_setscheduler(task);
>> 			if (ret)
>> 				goto out_unlock;
>> 	-       }
>> 	 
>> 	-       if (dl_task(task)) {
>> 	-               cs->deadline_tasks++;
>> 	-               cpuset_attach_old_cs->deadline_tasks--;
>> 	+               if (dl_task(task)) {
>> 	+                       cs->deadline_tasks++;
>> 	+                       cpuset_attach_old_cs->deadline_tasks--;
>> 	+               }
>> 		}
>> 	 
>> 		/*
> 
> Duh, indeed.
> 
>> Like Hao I don't have any deadline tasks in the system. With the fix above
>> I don't notice the delay on suspend resume using your patches.
> 
> OK, cool.
> 
>> If you want any debug; please feel free to add them into your branch so I can
>> run with that and give you the log.
> 
> Will need to find time to run some tests with DEADLINE tasks, yeah.
> Maybe Dietmar, since you reported as well the issue above with your
> testing, you could help with testing DEADLINE?

Ah, now I see! It's the same issue I saw. And it's not specifically
related to DL tasks. Any tasks which you move into a cpuset will trigger
this.
Yeah, can do some DL tests later on this fix.