From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Tadeusz Struk <tadeusz.struk-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: "Michal Koutný" <mkoutny-IBi9RG/b67k@public.gmane.org>,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
"Zefan Li" <lizefan.x-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>,
"Johannes Weiner"
<hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
"Bui Quang Minh"
<minhquangbui99-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 2/2] cgroup: Use separate work structs on css release path
Date: Wed, 1 Jun 2022 14:29:23 -1000 [thread overview]
Message-ID: <YpgEY/lJbLidLOhc@slm.duckdns.org> (raw)
In-Reply-To: <416dc60a-f0e5-7d05-1613-3cd0ca415768-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
On Wed, Jun 01, 2022 at 05:26:34PM -0700, Tadeusz Struk wrote:
> Ok the problem is that
>
> 1. kill_css() triggers css_killed_ref_fn(), which enqueues &css->destroy_work on cgroup_destroy_wq
> 2. Last put_css() calls css_release(), which enqueues &css->destroy_work on cgroup_destroy_wq
>
> We have two instances of the same work struct enqueued on the same WQ (cgroup_destroy_wq),
> which causes "BUG: corrupted list in insert_work"
#2 shouldn't be happening before kill_ref_fn() is done with the css. If what
you're saying is happening, what's broken is the fact that the refcnt is
reaching 0 prematurely.
> So I think the easiest way to solve this would be to have two separate work_structs,
> one for the killed_ref path and css_release path as in:
If you do that, you'd just be racing the free path against the kill path and
the css might get freed while the kill path is still accessing it.
Thanks.
--
tejun
next prev parent reply other threads:[~2022-06-02 0:29 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-25 15:15 [PATCH 0/2] cgroup_subsys_state lifecycle fixups Michal Koutný
[not found] ` <20220525151517.8430-1-mkoutny-IBi9RG/b67k@public.gmane.org>
2022-05-25 15:15 ` [PATCH 1/2] cgroup: Wait for cgroup_subsys_state offlining on unmount Michal Koutný
2022-05-25 15:15 ` [PATCH 2/2] cgroup: Use separate work structs on css release path Michal Koutný
[not found] ` <20220525151517.8430-3-mkoutny-IBi9RG/b67k@public.gmane.org>
2022-05-25 16:14 ` Michal Koutný
[not found] ` <20220525161455.GA16134-9OudH3eul5jcvrawFnH+a6VXKuFTiq87@public.gmane.org>
2022-05-26 9:56 ` Michal Koutný
2022-05-26 18:15 ` Tejun Heo
[not found] ` <Yo/DtjEU/kYr190u-NiLfg/pYEd1N0TnZuCh8vA@public.gmane.org>
2022-05-27 16:39 ` Tadeusz Struk
[not found] ` <904ef8af-13a5-e566-b760-74519f70fa62-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2022-05-27 16:54 ` Michal Koutný
[not found] ` <20220527165429.GJ11007-9OudH3eul5jcvrawFnH+a6VXKuFTiq87@public.gmane.org>
2022-05-27 17:23 ` Tejun Heo
2022-06-01 23:13 ` Tadeusz Struk
[not found] ` <0babd7df-bdef-9edc-3682-1144bc0c2d2b-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2022-06-01 23:20 ` Tejun Heo
[not found] ` <Ypf0VnKUMiuRgZqT-NiLfg/pYEd1N0TnZuCh8vA@public.gmane.org>
2022-06-01 23:37 ` Tadeusz Struk
[not found] ` <1fb4d8d7-ccc0-b020-715e-38c2dfd94c23-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2022-06-01 23:43 ` Tejun Heo
[not found] ` <Ypf5jpI7dSmpi4W0-NiLfg/pYEd1N0TnZuCh8vA@public.gmane.org>
2022-06-02 0:00 ` Tadeusz Struk
[not found] ` <c3bd8e63-7204-f86d-8efa-254db71185fc-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2022-06-02 0:07 ` Tejun Heo
[not found] ` <Ypf/MpwzByOrSp6A-NiLfg/pYEd1N0TnZuCh8vA@public.gmane.org>
2022-06-02 0:26 ` Tadeusz Struk
[not found] ` <416dc60a-f0e5-7d05-1613-3cd0ca415768-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2022-06-02 0:29 ` Tejun Heo [this message]
[not found] ` <YpgEY/lJbLidLOhc-NiLfg/pYEd1N0TnZuCh8vA@public.gmane.org>
2022-06-02 0:40 ` Tadeusz Struk
[not found] ` <0fd1c3fd-fa86-dbed-f3f0-74c91b1efa11-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2022-06-02 11:47 ` Michal Koutný
[not found] ` <20220602114705.GB21320-9OudH3eul5jcvrawFnH+a6VXKuFTiq87@public.gmane.org>
2022-06-02 14:28 ` Tadeusz Struk
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