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authorTejun Heo <tj@kernel.org>2018-04-26 14:29:06 -0700
committerTejun Heo <tj@kernel.org>2018-04-26 14:29:06 -0700
commitc43c5ea75fd53cae3c8b63e1a27efc4cff6508d3 (patch)
tree9144ead9ae1b39efb3382edc7f025f9eff75a319 /kernel/cgroup/rstat.c
parent9a9e97b2f1f27ec70e3c138a790bd5627747d868 (diff)
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>
Diffstat (limited to 'kernel/cgroup/rstat.c')
-rw-r--r--kernel/cgroup/rstat.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index a4901e20735a..d503d1a9007c 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -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.