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authorTejun Heo <tj@kernel.org>2015-10-15 16:41:51 -0400
committerTejun Heo <tj@kernel.org>2015-10-15 16:41:51 -0400
commit91486f61f486662c27ef86dd910f875832e3a5de (patch)
tree19c2bbe7e0bfd8115147d883b47b4978e090048b /kernel/cgroup.c
parent2ceb231b0ab0e3d700c5f7c839273bfeecbefe3b (diff)
cgroup: make cgroup_destroy_locked() test cgroup_is_populated()
cgroup_destroy_locked() currently tests whether any css_sets are associated to reject removal if the cgroup contains tasks. This works because a css_set's refcnt converges with the number of tasks linked to it and thus there's no css_set linked to a cgroup if it doesn't have any live tasks. To help tracking resource usage of zombie tasks, putting the ref of css_set will be separated from disassociating the task from the css_set which means that a cgroup may have css_sets linked to it even when it doesn't have any live tasks. This patch updates cgroup_destroy_locked() so that it tests cgroup_is_populated(), which counts the number of populated css_sets, instead of whether cgrp->cset_links is empty to determine whether the cgroup is populated or not. This ensures that rmdirs won't be incorrectly rejected for cgroups which only contain zombie tasks. Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c11
1 files changed, 5 insertions, 6 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index ea87340af871..61ee85ded6ae 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4998,16 +4998,15 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
{
struct cgroup_subsys_state *css;
- bool empty;
int ssid;
lockdep_assert_held(&cgroup_mutex);
- /* css_set_rwsem synchronizes access to ->cset_links */
- down_read(&css_set_rwsem);
- empty = list_empty(&cgrp->cset_links);
- up_read(&css_set_rwsem);
- if (!empty)
+ /*
+ * Only migration can raise populated from zero and we're already
+ * holding cgroup_mutex.
+ */
+ if (cgroup_is_populated(cgrp))
return -EBUSY;
/*