Commit 62716ea0 authored Feb 23, 2016 by Tejun Heo

cgroup: use ->subtree_control when testing no internal process rule



No internal process rule is enforced by cgroup_migrate_prepare_dst()
during process migration.  It tests whether the target cgroup's
->child_subsys_mask is zero which is different from "subtree_control"
write path which tests ->subtree_control.  This hasn't mattered
because up until now, both ->child_subsys_mask and ->subtree_control
are zero or non-zero at the same time.  However, with the planned
addition of implicit controllers, this will no longer be true.

This patch prepares for the change by making
cgorup_migrate_prepare_dst() test ->subtree_control instead.

Signed-off-by: Tejun Heo <tj@kernel.org>

parent f17fc25f

kernel/cgroup.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -2527,11 +2527,11 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
		lockdep_assert_held(&cgroup_mutex);

		/*
		* Except for the root, subtree_ss_mask must be zero for a cgroup
		* Except for the root, subtree_control must be zero for a cgroup
		* with tasks so that child cgroups don't compete against tasks.
		*/
		if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && cgroup_parent(dst_cgrp) &&
		dst_cgrp->subtree_ss_mask)
		dst_cgrp->subtree_control)
		return -EBUSY;

		/* look up the dst cset for each src cset and link it to src */

Admin message