diff options
| author | Roman Gushchin <guro@fb.com> | 2019-04-19 10:03:03 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-05-31 06:45:03 -0700 |
| commit | eab336b76e6b6ac17903cc3a6d204885f84a2a2d (patch) | |
| tree | 169d02fa6177fd9d163f7a4270e366af1b89c1b4 /include | |
| parent | d6c68321e7856a247672205a33a61f6c668ac070 (diff) | |
cgroup: protect cgroup->nr_(dying_)descendants by css_set_lock
[ Upstream commit 4dcabece4c3a9f9522127be12cc12cc120399b2f ]
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
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include')
| -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 120d1d40704b..319c07305500 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -348,6 +348,11 @@ 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; |