Commit 2bdfd282 authored by Waiman Long's avatar Waiman Long Committed by Tejun Heo
Browse files

cgroup/cpuset: Fix "suspicious RCU usage" lockdep warning 



It was found that a "suspicious RCU usage" lockdep warning was issued
with the rcu_read_lock() call in update_sibling_cpumasks().  It is
because the update_cpumasks_hier() function may sleep. So we have
to release the RCU lock, call update_cpumasks_hier() and reacquire
it afterward.

Also add a percpu_rwsem_assert_held() in update_sibling_cpumasks()
instead of stating that in the comment.

Fixes: 4716909c ("cpuset: Track cpusets that use parent's effective_cpus")
Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Tested-by: default avatarPhil Auld <pauld@redhat.com>
Reviewed-by: default avatarPhil Auld <pauld@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 24f60085

kernel/cgroup/cpuset.c

+10 −0
Original line number Diff line number Diff line
@@ -1550,10 +1550,15 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs, 
	struct cpuset *sibling;

	struct cgroup_subsys_state *pos_css;



	percpu_rwsem_assert_held(&cpuset_rwsem);



	/*

	 * Check all its siblings and call update_cpumasks_hier()

	 * if their use_parent_ecpus flag is set in order for them

	 * to use the right effective_cpus value.

	 *

	 * The update_cpumasks_hier() function may sleep. So we have to

	 * release the RCU read lock before calling it.

	 */

	rcu_read_lock();

	cpuset_for_each_child(sibling, pos_css, parent) {
@@ -1561,8 +1566,13 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs, 
			continue;

		if (!sibling->use_parent_ecpus)

			continue;

		if (!css_tryget_online(&sibling->css))

			continue;



		rcu_read_unlock();

		update_cpumasks_hier(sibling, tmp);

		rcu_read_lock();

		css_put(&sibling->css);

	}

	rcu_read_unlock();

}