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| author | Tejun Heo <tj@kernel.org> | 2018-04-26 23:29:06 +0200 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2018-04-26 23:29:06 +0200 |
| commit | c43c5ea75fd53cae3c8b63e1a27efc4cff6508d3 (patch) | |
| tree | 9144ead9ae1b39efb3382edc7f025f9eff75a319 /kernel/cgroup | |
| parent | cgroup: Add memory barriers to plug cgroup_rstat_updated() race window (diff) | |
| download | linux-c43c5ea75fd53cae3c8b63e1a27efc4cff6508d3.tar.xz linux-c43c5ea75fd53cae3c8b63e1a27efc4cff6508d3.zip | |
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')
| -rw-r--r-- | kernel/cgroup/rstat.c | 4 |
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. |