Commit a1a01793 authored by Waiman Long's avatar Waiman Long Committed by Tejun Heo
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cgroup/cpuset: Consistently compute effective_xcpus in update_cpumasks_hier() 



Since commit f62a5d39 ("cgroup/cpuset: Remove remote_partition_check()
& make update_cpumasks_hier() handle remote partition"), the
compute_effective_exclusive_cpumask() helper was extended to
strip exclusive CPUs from siblings when computing effective_xcpus
(cpuset.cpus.exclusive.effective). This helper was later renamed to
compute_excpus() in commit 86bbbd1f ("cpuset: Refactor exclusive
CPU mask computation logic").

This helper is supposed to be used consistently to compute
effective_xcpus. However, there is an exception within the callback
critical section in update_cpumasks_hier() when exclusive_cpus of a
valid partition root is empty. This can cause effective_xcpus value to
differ depending on where exactly it is last computed. Fix this by using
compute_excpus() in this case to give a consistent result.

Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Reviewed-by: default avatarChen Ridong <chenridong@huawei.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 18bc2425

kernel/cgroup/cpuset.c

+5 −9
Original line number Diff line number Diff line
@@ -2168,17 +2168,13 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, 
		spin_lock_irq(&callback_lock);

		cpumask_copy(cp->effective_cpus, tmp->new_cpus);

		cp->partition_root_state = new_prs;

		if (!cpumask_empty(cp->exclusive_cpus) && (cp != cs))

			compute_excpus(cp, cp->effective_xcpus);



		/*

		 * Make sure effective_xcpus is properly set for a valid

		 * partition root.

		 * Need to compute effective_xcpus if either exclusive_cpus

		 * is non-empty or it is a valid partition root.

		 */

		if ((new_prs > 0) && cpumask_empty(cp->exclusive_cpus))

			cpumask_and(cp->effective_xcpus,

				    cp->cpus_allowed, parent->effective_xcpus);

		else if (new_prs < 0)

		if ((new_prs > 0) || !cpumask_empty(cp->exclusive_cpus))

			compute_excpus(cp, cp->effective_xcpus);

		if (new_prs <= 0)

			reset_partition_data(cp);

		spin_unlock_irq(&callback_lock);