On 10/03/25 20:16, Waiman Long wrote: > On 3/10/25 3:18 PM, Waiman Long wrote: > > > > 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() > > > > > > ? Good catch. Guess I didn't notice while testing with LOCKDEP as I was never able to hit this call path on my systems. > > 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. > > Actually, partition_sched_domains() is called with the special arguments (1, > NULL, NULL) to reset the domain to a single one. So perhaps something like > the following will be enough to avoid this problem. I think this would work, as we will still rebuild the accounting after last CPU comes back from suspend. The thing I am still not sure about is what we want to do in case we have DEADLINE tasks around, since with this I belive we would be ignoring them and let suspend proceed.
