From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
"linux-kernel@vger.kernel.org >> Linux Kernel Mailing List"
<linux-kernel@vger.kernel.org>,
linux-s390 <linux-s390@vger.kernel.org>,
KVM list <kvm@vger.kernel.org>, Oleg Nesterov <oleg@redhat.com>,
hch@lst.de
Subject: Re: regression 4.4: deadlock in with cgroup percpu_rwsem
Date: Fri, 22 Jan 2016 18:03:13 -0800 [thread overview]
Message-ID: <20160123020313.GA4915@linux.vnet.ibm.com> (raw)
In-Reply-To: <20160120153007.GC5157@mtj.duckdns.org>
On Wed, Jan 20, 2016 at 10:30:07AM -0500, Tejun Heo wrote:
> Hello,
>
> On Wed, Jan 20, 2016 at 11:47:58AM +0100, Peter Zijlstra wrote:
> > TJ, is css_offline guaranteed to be called in hierarchical order? I
>
> No, they aren't. The ancestors of a css are guaranteed to stay around
> until css_free is called on the css and that's the only ordering
> guarantee.
>
> > got properly lost in the whole cgroup destroy code. There's endless
> > workqueues and rcu callbacks there.
>
> Yeah, it's hairy. I wondered about adding support for bouncing to
> workqueue in both percpu_ref and rcu which would make things easier to
> follow. Not sure how often this pattern happens tho.
This came up recently offlist for call_rcu(), so that a call to (say)
call_rcu_schedule_work() would do a schedule_work() after a grace period
elapsed, invoking the function passed in to call_rcu_schedule_work().
There are several existing cases that do this, so special-casing it seems
worthwhile. Perhaps something vaguely similar would work for percpu_ref.
Thanx, Paul
next prev parent reply other threads:[~2016-01-23 2:03 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-14 11:19 regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger
2016-01-14 13:38 ` Christian Borntraeger
2016-01-14 14:04 ` Nikolay Borisov
2016-01-14 14:08 ` Christian Borntraeger
2016-01-14 14:27 ` Nikolay Borisov
2016-01-14 17:15 ` Christian Borntraeger
2016-01-14 19:56 ` Tejun Heo
2016-01-15 7:30 ` Christian Borntraeger
2016-01-15 15:13 ` Christian Borntraeger
2016-01-18 18:32 ` Peter Zijlstra
2016-01-18 18:48 ` Christian Borntraeger
2016-01-19 9:55 ` Heiko Carstens
2016-01-19 19:36 ` Christian Borntraeger
2016-01-19 19:38 ` Tejun Heo
2016-01-20 7:07 ` Heiko Carstens
2016-01-20 10:15 ` Christian Borntraeger
2016-01-20 10:30 ` Peter Zijlstra
2016-01-20 10:47 ` Peter Zijlstra
2016-01-20 15:30 ` Tejun Heo
2016-01-20 16:04 ` Tejun Heo
2016-01-20 16:49 ` Peter Zijlstra
2016-01-20 16:56 ` Tejun Heo
2016-01-23 2:03 ` Paul E. McKenney [this message]
2016-01-25 8:49 ` Christoph Hellwig
2016-01-25 19:38 ` Tejun Heo
2016-01-26 14:51 ` Christoph Hellwig
2016-01-26 15:28 ` Tejun Heo
2016-01-26 16:41 ` Christoph Hellwig
2016-01-20 10:53 ` Peter Zijlstra
2016-01-21 8:23 ` Christian Borntraeger
2016-01-21 9:27 ` Peter Zijlstra
2016-01-15 16:40 ` Tejun Heo
[not found] ` <20160115164023.GH3520-qYNAdHglDFBN0TnZuCh8vA@public.gmane.org>
2016-01-19 17:18 ` [PATCH cgroup/for-4.5-fixes] cpuset: make mm migration asynchronous Tejun Heo
2016-01-19 17:18 ` Tejun Heo
2016-01-22 14:24 ` Christian Borntraeger
2016-01-22 15:22 ` Tejun Heo
[not found] ` <20160122152232.GB32380-piEFEHQLUPpN0TnZuCh8vA@public.gmane.org>
2016-01-22 15:45 ` Christian Borntraeger
2016-01-22 15:45 ` Christian Borntraeger
2016-01-22 15:47 ` Tejun Heo
[not found] ` <20160119171841.GP3520-qYNAdHglDFBN0TnZuCh8vA@public.gmane.org>
2016-01-22 15:23 ` Tejun Heo
2016-01-22 15:23 ` Tejun Heo
[not found] ` <5698A023.9070703-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>
2016-01-21 20:31 ` [PATCH 1/2] cgroup: make sure a parent css isn't offlined before its children Tejun Heo
2016-01-21 20:31 ` Tejun Heo
2016-01-21 20:32 ` [PATCH 2/2] cgroup: make sure a parent css isn't freed " Tejun Heo
2016-01-22 15:45 ` [PATCH v2 " Tejun Heo
2016-01-22 15:45 ` Tejun Heo
[not found] ` <20160121203111.GF5157-qYNAdHglDFBN0TnZuCh8vA@public.gmane.org>
2016-01-21 21:24 ` [PATCH 1/2] cgroup: make sure a parent css isn't offlined " Peter Zijlstra
2016-01-21 21:24 ` Peter Zijlstra
[not found] ` <20160121212416.GL6357-ndre7Fmf5hadTX5a5knrm8zTDFooKrT+cvkQGrU6aU0@public.gmane.org>
2016-01-21 21:28 ` Tejun Heo
2016-01-21 21:28 ` Tejun Heo
2016-01-22 8:18 ` Christian Borntraeger
2016-02-29 11:13 ` [tip:sched/core] sched/cgroup: Fix cgroup entity load tracking tear-down tip-bot for Peter Zijlstra
2016-01-22 15:45 ` [PATCH v2 1/2] cgroup: make sure a parent css isn't offlined before its children Tejun Heo
2016-01-22 15:45 ` Tejun Heo
2016-01-22 15:45 ` Tejun Heo
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