Commit c43c5ea7 authored Apr 26, 2018 by Tejun Heo

cgroup: Make cgroup_rstat_updated() ready for root cgroup usage



cgroup_rstat_updated() ensures that the cgroup's rstat is linked to
the parent.  If there's no parent, it never gets linked and the
function ends up grabbing and releasing the cgroup_rstat_lock each
time for no reason which can be expensive.

This hasn't been a problem till now because nobody was calling the
function for the root cgroup but rstat is gonna be exposed to
controllers and use cases, so let's get ready.  Make
cgroup_rstat_updated() an no-op for the root cgroup.

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

parent 9a9e97b2

kernel/cgroup/rstat.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -27,6 +27,10 @@ void cgroup_rstat_updated(struct cgroup *cgrp, int cpu)
		struct cgroup *parent;
		unsigned long flags;

		/* nothing to do for root */
		if (!cgroup_parent(cgrp))
		return;

		/*
		* Paired with the one in cgroup_rstat_cpu_pop_upated(). Either we
		* see NULL updated_next or they see our updated stat.

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