diff options
| author | Roman Gushchin <guro@fb.com> | 2019-04-19 10:03:03 -0700 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2019-04-19 11:26:48 -0700 |
| commit | 4dcabece4c3a9f9522127be12cc12cc120399b2f (patch) | |
| tree | 0d985b3d1232ff76e67a0ac07213e4c8e4ab4a7b /include/linux/cgroup-defs.h | |
| parent | aade7f9efba098859681f8e88d81a5b44ad09b12 (diff) | |
cgroup: protect cgroup->nr_(dying_)descendants by css_set_lock
The number of descendant cgroups and the number of dying
descendant cgroups are currently synchronized using the cgroup_mutex.
The number of descendant cgroups will be required by the cgroup v2
freezer, which will use it to determine if a cgroup is frozen
(depending on total number of descendants and number of frozen
descendants). It's not always acceptable to grab the cgroup_mutex,
especially from quite hot paths (e.g. exit()).
To avoid this, let's additionally synchronize these counters using
the css_set_lock.
So, it's safe to read these counters with either cgroup_mutex or
css_set_lock locked, and for changing both locks should be acquired.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: kernel-team@fb.com
Diffstat (limited to 'include/linux/cgroup-defs.h')
| -rw-r--r-- | include/linux/cgroup-defs.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 1c70803e9f77..7d57890cec67 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -349,6 +349,11 @@ struct cgroup { * Dying cgroups are cgroups which were deleted by a user, * but are still existing because someone else is holding a reference. * max_descendants is a maximum allowed number of descent cgroups. + * + * nr_descendants and nr_dying_descendants are protected + * by cgroup_mutex and css_set_lock. It's fine to read them holding + * any of cgroup_mutex and css_set_lock; for writing both locks + * should be held. */ int nr_descendants; int nr_dying_descendants; |