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| author | Tejun Heo <tj@kernel.org> | 2017-07-23 08:18:26 -0400 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2017-07-25 13:15:29 -0400 |
| commit | 918a8c2c4ea4fab8b7855b8da48bbaf0a733ebb0 (patch) | |
| tree | 55b740ec2319dc2a358e86a6b0323a6a71786a5c | |
| parent | 7a0cf0e74ab6cfd8e561f5f12860d4ff8844905a (diff) | |
| download | linux-918a8c2c4ea4fab8b7855b8da48bbaf0a733ebb0.tar.gz linux-918a8c2c4ea4fab8b7855b8da48bbaf0a733ebb0.tar.bz2 linux-918a8c2c4ea4fab8b7855b8da48bbaf0a733ebb0.zip | |
cgroup: remove unnecessary empty check when enabling threaded mode
cgroup_enable_threaded() checks that the cgroup doesn't have any tasks
or children and fails the operation if so. This test is unnecessary
because the first part is already checked by
cgroup_can_be_thread_root() and the latter is unnecessary. The latter
actually cause a behavioral oddity. Please consider the following
hierarchy. All cgroups are domains.
A
/ \
B C
\
D
If B is made threaded, C and D becomes invalid domains. Due to the no
children restriction, threaded mode can't be enabled on C. For C and
D, the only thing the user can do is removal.
There is no reason for this restriction. Remove it.
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
| -rw-r--r-- | Documentation/cgroup-v2.txt | 5 | ||||
| -rw-r--r-- | kernel/cgroup/cgroup.c | 7 |
2 files changed, 3 insertions, 9 deletions
diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt index cb9ea281ab72..dec5afdaa36d 100644 --- a/Documentation/cgroup-v2.txt +++ b/Documentation/cgroup-v2.txt @@ -274,8 +274,9 @@ thread mode, the following conditions must be met. - As the cgroup will join the parent's resource domain. The parent must either be a valid (threaded) domain or a threaded cgroup. -- The cgroup must be empty. No enabled controllers, child cgroups or - processes. +- When the parent is an unthreaded domain, it must not have any domain + controllers enabled or populated domain children. The root is + exempt from this requirement. Topology-wise, a cgroup can be in an invalid state. Please consider the following toplogy:: diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index e9a377dc5bdb..e0a558c4d358 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -3147,13 +3147,6 @@ static int cgroup_enable_threaded(struct cgroup *cgrp) return -EOPNOTSUPP; /* - * Allow enabling thread mode only on empty cgroups to avoid - * implicit migrations and recursive operations. - */ - if (cgroup_has_tasks(cgrp) || css_has_online_children(&cgrp->self)) - return -EBUSY; - - /* * The following shouldn't cause actual migrations and should * always succeed. */ |