From: Tejun Heo <tj@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
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>
Subject: Re: regression 4.4: deadlock in with cgroup percpu_rwsem
Date: Mon, 25 Jan 2016 14:38:36 -0500 [thread overview]
Message-ID: <20160125193836.GH3628@mtj.duckdns.org> (raw)
In-Reply-To: <20160125084942.GA7354@lst.de>
Hello, Christoph.
On Mon, Jan 25, 2016 at 09:49:42AM +0100, Christoph Hellwig wrote:
> FYI, my use case was also related to percpu-ref. The percpu ref API
> is unfortunately really hard to use and will almost always involve
> a work queue due to the complex interaction between percpu_ref_kill
> and percpu_ref_exit. One thing that would help a lot of callers would
That's interesting. Can you please elaborate on how kill and exit
interact to make things complex?
> be a percpu_ref_exit_sync that kills the ref and waits for all references
> to go away synchronously.
That shouldn't be difficult to implement. One minor concern is that
it's almost guaranteed that there will be cases where the
synchronicity is exposed to userland. Anyways, can you please
describe the use case?
Thanks.
--
tejun
next prev parent reply other threads:[~2016-01-25 19:38 UTC|newest]
Thread overview: 46+ 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
2016-01-25 8:49 ` Christoph Hellwig
2016-01-25 19:38 ` Tejun Heo [this message]
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
2016-01-19 17:18 ` [PATCH cgroup/for-4.5-fixes] cpuset: make mm migration asynchronous Tejun Heo
2016-01-22 14:24 ` Christian Borntraeger
2016-01-22 15:22 ` Tejun Heo
2016-01-22 15:45 ` Christian Borntraeger
2016-01-22 15:47 ` Tejun Heo
2016-01-22 15:23 ` Tejun Heo
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 20:32 ` [PATCH 2/2] cgroup: make sure a parent css isn't freed " Tejun Heo
2016-01-22 15:45 ` [PATCH v2 " Tejun Heo
2016-01-21 21:24 ` [PATCH 1/2] cgroup: make sure a parent css isn't offlined " Peter Zijlstra
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
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