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commit111cd11bbcupstream. Turns out percpu_cpuset_rwsem - commit1243dc518c("cgroup/cpuset: Convert cpuset_mutex to percpu_rwsem") - wasn't such a brilliant idea, as it has been reported to cause slowdowns in workloads that need to change cpuset configuration frequently and it is also not implementing priority inheritance (which causes troubles with realtime workloads). Convert percpu_cpuset_rwsem back to regular cpuset_mutex. Also grab it only for SCHED_DEADLINE tasks (other policies don't care about stable cpusets anyway). Signed-off-by: Juri Lelli <juri.lelli@redhat.com> Reviewed-by: Waiman Long <longman@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org> [ Fix conflict in kernel/cgroup/cpuset.c due to pulling new functions or comment that don't exist on 5.10 or the usage of different cpu hotplug lock whenever replacing the rwsem with mutex. Remove BUG_ON() for rwsem that doesn't exist on mainline. ] Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>