6.12-stable review patch. If anyone has any objections, please let me know.
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From: Waiman Long longman@redhat.com
[ Upstream commit 39b5ef791d109dd54c7c2e6e87933edfcc0ad1ac ]
Commit ec5fbdfb99d1 ("cgroup/cpuset: Enable update_tasks_cpumask() on top_cpuset") enabled us to pull CPUs dedicated to child partitions from tasks in top_cpuset by ignoring per cpu kthreads. However, there can be other kthreads that are not per cpu but have PF_NO_SETAFFINITY flag set to indicate that we shouldn't mess with their CPU affinity. For other kthreads, their affinity will be changed to skip CPUs dedicated to child partitions whether it is an isolating or a scheduling one.
As all the per cpu kthreads have PF_NO_SETAFFINITY set, the PF_NO_SETAFFINITY tasks are essentially a superset of per cpu kthreads. Fix this issue by dropping the kthread_is_per_cpu() check and checking the PF_NO_SETAFFINITY flag instead.
Fixes: ec5fbdfb99d1 ("cgroup/cpuset: Enable update_tasks_cpumask() on top_cpuset") Signed-off-by: Waiman Long longman@redhat.com Acked-by: Frederic Weisbecker frederic@kernel.org Signed-off-by: Tejun Heo tj@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/cgroup/cpuset.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index c709a05023cd9..d1fb4bfbbd4c3 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1100,9 +1100,11 @@ void cpuset_update_tasks_cpumask(struct cpuset *cs, struct cpumask *new_cpus)
if (top_cs) { /* - * Percpu kthreads in top_cpuset are ignored + * PF_NO_SETAFFINITY tasks are ignored. + * All per cpu kthreads should have PF_NO_SETAFFINITY + * flag set, see kthread_set_per_cpu(). */ - if (kthread_is_per_cpu(task)) + if (task->flags & PF_NO_SETAFFINITY) continue; cpumask_andnot(new_cpus, possible_mask, subpartitions_cpus); } else {