Messages in this thread | | | From | Waiman Long <> | Subject | Re: [PATCH 1/2] cgroup: Fix incorrect warning from cgroup_apply_control_disable() | Date | Mon, 13 Sep 2021 14:46:05 -0400 |
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On 9/13/21 2:45 PM, Tejun Heo wrote: > On Mon, Sep 13, 2021 at 02:43:44PM -0400, Waiman Long wrote: >>> The problem with percpu_ref_is_dying() is the fact that it becomes true >>> after percpu_ref_exit() is called in css_free_rwork_fn() which has an >>> RCU delay. If you want to catch the fact that kill_css() has been >>> called, we can check the CSS_DYING flag which is set in kill_css() by >>> commit 33c35aa481786 ("cgroup: Prevent kill_css() from being called more >>> than once"). Will that be an acceptable alternative? >> Something like >> >> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c >> index 881ce1470beb..851e54800ad8 100644 >> --- a/kernel/cgroup/cgroup.c >> +++ b/kernel/cgroup/cgroup.c >> @@ -3140,6 +3140,9 @@ static void cgroup_apply_control_disable(struct cgroup >> *cg >> if (!css) >> continue; >> >> + if (css->flags & CSS_DYING) >> + continue; >> + > So, I don't think this would be correct. It is assumed that there are no > dying csses when control reaches this point. The right fix is making sure > that remount path clears up dying csses before calling into this path.
Thanks for the suggestion. I will look into that.
Cheers, Longman
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