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The nr_deadline_tasks variable in the cpuset structure was introduced by commit6c24849f55("sched/cpuset: Keep track of SCHED_DEADLINE task in cpusets"). It is reported by sashiko [1] that nr_deadline_tasks can currently be modified by inc_dl_tasks_cs() under rq->lock and by cpuset_attach() under cpuset_mutex. So if both updates happen simultaneously, the nr_deadline_tasks variable can be corrupted leading to incorrect operations down the road. Fix that by changing its type to atomic_t so that nr_deadline_tasks are always atomically updated. This fix patch is a low hanging fruit. It can handle some of the races between a concurrent sched_setscheduler() and cpuset_can_attach()/cpuset_attach() calls, but not all of them like the other issue raised by sashiko [2]. This will be handled hopefully in a future follow up patch. [1] https://sashiko.dev/#/patchset/20260626181923.133658-1-longman%40redhat.com [2] https://sashiko.dev/#/patchset/20260630033344.352702-1-longman%40redhat.com Fixes:6c24849f55("sched/cpuset: Keep track of SCHED_DEADLINE task in cpusets") Reviewed-by: Ridong Chen <ridong.chen@linux.dev> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org>