Re: [PATCH v3 4/8] sched/deadline: Rebuild root domain accounting after every update

[Waiman Long <llong@redhat.com>]

On 3/10/25 2:54 PM, Dietmar Eggemann wrote:
> On 10/03/2025 10:37, Juri Lelli wrote:
>> Rebuilding of root domains accounting information (total_bw) is
>> currently broken on some cases, e.g. suspend/resume on aarch64. Problem
> Nit: Couldn't spot any arch dependency here. I guess it was just tested
> on Arm64 platforms so far.
>
> [...]
>
>> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
>> index 44093339761c..363ad268a25b 100644
>> --- a/kernel/sched/topology.c
>> +++ b/kernel/sched/topology.c
>> @@ -2791,6 +2791,7 @@ void partition_sched_domains_locked(int ndoms_new, cpumask_var_t doms_new[],
>>   	ndoms_cur = ndoms_new;
>>   
>>   	update_sched_domain_debugfs();
>> +	dl_rebuild_rd_accounting();
> Won't dl_rebuild_rd_accounting()'s lockdep_assert_held(&cpuset_mutex)
> barf when called via cpuhp's:
>
> sched_cpu_deactivate()
>
>    cpuset_cpu_inactive()
>
>      partition_sched_domains()
>
>        partition_sched_domains_locked()
>
>          dl_rebuild_rd_accounting()
>
> ?
>
> [...]

Right. If cpuhp_tasks_frozen is true, partition_sched_domains() will be 
called without holding cpuset mutex.

Well, I think we will need an additional wrapper in cpuset.c that 
acquires the cpuset_mutex first before calling partition_sched_domains() 
and use the new wrapper in these cases.

Cheers,
Longman