Re: [PATCH 4/5] sched/deadline: Rebuild root domain accounting after every update

[Waiman Long <llong@redhat.com>]

On 3/4/25 10:17 AM, Waiman Long wrote:
> On 3/4/25 3:40 AM, Juri Lelli wrote:
>> Rebuilding of root domains accounting information (total_bw) is
>> currently broken on some cases, e.g. suspend/resume on aarch64. Problem
>> is that the way we keep track of domain changes and try to add bandwidth
>> back is convoluted and fragile.
>>
>> Fix it by simplify things by making sure bandwidth accounting is cleared
>> and completely restored after root domains changes (after root domains
>> are again stable).
>>
>> Reported-by: Jon Hunter <jonathanh@nvidia.com>
>> Fixes: 53916d5fd3c0 ("sched/deadline: Check bandwidth overflow 
>> earlier for hotplug")
>> Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
>> ---
>>   include/linux/sched/deadline.h |  4 ++++
>>   include/linux/sched/topology.h |  2 ++
>>   kernel/cgroup/cpuset.c         | 16 +++++++++-------
>>   kernel/sched/deadline.c        | 16 ++++++++++------
>>   kernel/sched/topology.c        |  1 +
>>   5 files changed, 26 insertions(+), 13 deletions(-)
>>
>> diff --git a/include/linux/sched/deadline.h 
>> b/include/linux/sched/deadline.h
>> index 6ec578600b24..a780068aa1a5 100644
>> --- a/include/linux/sched/deadline.h
>> +++ b/include/linux/sched/deadline.h
>> @@ -34,6 +34,10 @@ static inline bool dl_time_before(u64 a, u64 b)
>>   struct root_domain;
>>   extern void dl_add_task_root_domain(struct task_struct *p);
>>   extern void dl_clear_root_domain(struct root_domain *rd);
>> +extern void dl_clear_root_domain_cpu(int cpu);
>> +
>> +extern u64 dl_cookie;
>> +extern bool dl_bw_visited(int cpu, u64 gen);
>>     #endif /* CONFIG_SMP */
>>   diff --git a/include/linux/sched/topology.h 
>> b/include/linux/sched/topology.h
>> index 7f3dbafe1817..1622232bd08b 100644
>> --- a/include/linux/sched/topology.h
>> +++ b/include/linux/sched/topology.h
>> @@ -166,6 +166,8 @@ static inline struct cpumask 
>> *sched_domain_span(struct sched_domain *sd)
>>       return to_cpumask(sd->span);
>>   }
>>   +extern void dl_rebuild_rd_accounting(void);
>> +
>>   extern void partition_sched_domains_locked(int ndoms_new,
>>                          cpumask_var_t doms_new[],
>>                          struct sched_domain_attr *dattr_new);

BTW, dl_rebuild_rd_accounting() is defined only if CONFIG_CPUSETS is 
defined. I think you should move that declaration to cpuset.h and define 
a proper wrapper in the else part.

Cheers,
Longman