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| author | Tejun Heo <tj@kernel.org> | 2015-10-15 20:41:51 (GMT) |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2015-10-15 20:41:51 (GMT) |
| commit | 91486f61f486662c27ef86dd910f875832e3a5de (patch) | |
| tree | 19c2bbe7e0bfd8115147d883b47b4978e090048b /kernel/cgroup.c | |
| parent | 2ceb231b0ab0e3d700c5f7c839273bfeecbefe3b (diff) | |
| download | linux-91486f61f486662c27ef86dd910f875832e3a5de.tar.xz | |
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.c | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index ea87340..61ee85d 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; /* |