From: Michal Hocko <mhocko@suse.cz>
To: Tejun Heo <tj@kernel.org>
Cc: cgroups@vger.kernel.org, Li Zefan <lizefan@huawei.com>,
Anton Vorontsov <anton.vorontsov@linaro.org>,
Johannes Weiner <hannes@cmpxchg.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
linux-mm@kvack.org
Subject: Re: [PATCH 1/3] vmpressure: document why css_get/put is not necessary for work queue based signaling
Date: Mon, 15 Jul 2013 12:27:58 +0200 [thread overview]
Message-ID: <20130715102758.GC26199@dhcp22.suse.cz> (raw)
In-Reply-To: <20130712184836.GC23680@mtj.dyndns.org>
On Fri 12-07-13 11:48:36, Tejun Heo wrote:
> On Fri, Jul 12, 2013 at 11:24:56AM +0200, Michal Hocko wrote:
> > Cgroup events are unregistered from the workqueue context by
> > cgroup_event_remove scheduled by cgroup_destroy_locked (when a cgroup is
> > removed by rmdir).
> >
> > cgroup_event_remove removes the eventfd wait queue from the work
> > queue, then it unregisters all the registered events and finally
> > puts a reference to the cgroup dentry. css_free which triggers memcg
> > deallocation is called after the last reference is dropped.
> >
> > The scheduled vmpressure work item either happens before
> > cgroup_event_remove or it is not triggered at all so it always happen
> > _before_ the last dput thus css_free.
>
> I don't follow what the above has to do with ensuring work item
> execution is finished before the underlying data structure is
> released. How are the above relevant? What am I missing here?
OK, it seems I managed to confuse myself. I thought that
remove_wait_queue(event->wqh, &event->wait) called from
cgroup_event_remove guarantee that vmpr event would go away with that
workqueue. But now that I am looking at it, vmpr->work seems to be
living in a completely independent queue.
> > This patch just documents this trickiness.
>
> This doesn't have to be tricky at all. It's a *completely* routine
> thing. Would you please stop making it one?
Fair enough. I will repost the series shortly.
--
Michal Hocko
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2013-07-15 10:28 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20130710184254.GA16979@mtj.dyndns.org>
[not found] ` <20130711083110.GC21667@dhcp22.suse.cz>
[not found] ` <51DE701C.6010800@huawei.com>
[not found] ` <20130711092542.GD21667@dhcp22.suse.cz>
[not found] ` <51DE7AAF.6070004@huawei.com>
2013-07-11 9:33 ` [PATCH v2] vmpressure: make sure memcg stays alive until all users are signaled Michal Hocko
2013-07-11 15:44 ` Tejun Heo
2013-07-11 16:22 ` Michal Hocko
2013-07-11 16:32 ` Tejun Heo
2013-07-12 8:40 ` Michal Hocko
2013-07-12 9:20 ` Li Zefan
2013-07-12 9:29 ` Michal Hocko
2013-07-12 9:54 ` Li Zefan
2013-07-12 10:37 ` Michal Hocko
2013-07-15 3:07 ` Li Zefan
2013-07-15 9:20 ` Michal Hocko
2013-07-15 9:53 ` Li Zefan
2013-07-12 9:24 ` [PATCH 1/3] vmpressure: document why css_get/put is not necessary for work queue based signaling Michal Hocko
2013-07-12 9:24 ` [PATCH 2/3] vmpressure: change vmpressure::sr_lock to spinlock Michal Hocko
2013-07-12 9:24 ` [PATCH 3/3] vmpressure: do not check for pending work to prevent from new work Michal Hocko
2013-07-12 18:48 ` [PATCH 1/3] vmpressure: document why css_get/put is not necessary for work queue based signaling Tejun Heo
2013-07-15 10:27 ` Michal Hocko [this message]
2013-07-12 18:34 ` [PATCH v2] vmpressure: make sure memcg stays alive until all users are signaled Tejun Heo
2013-07-12 18:40 ` Tejun Heo
2013-07-12 6:03 ` Li Zefan
2013-07-15 10:30 ` [PATCH v3 1/3] vmpressure: change vmpressure::sr_lock to spinlock Michal Hocko
2013-07-15 10:30 ` [PATCH v3 2/3] vmpressure: do not check for pending work to prevent from new work Michal Hocko
2013-07-15 10:30 ` [PATCH v3 3/3] vmpressure: Make sure there are no events queued after memcg is offlined Michal Hocko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130715102758.GC26199@dhcp22.suse.cz \
--to=mhocko@suse.cz \
--cc=anton.vorontsov@linaro.org \
--cc=cgroups@vger.kernel.org \
--cc=hannes@cmpxchg.org \
--cc=kamezawa.hiroyu@jp.fujitsu.com \
--cc=kosaki.motohiro@jp.fujitsu.com \
--cc=linux-mm@kvack.org \
--cc=lizefan@huawei.com \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).