From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
To: Jiri Kosina <jkosina@suse.cz>
Cc: "Paul E. McKenney" <paul.mckenney@linaro.org>,
Josh Triplett <josh@joshtriplett.org>,
linux-kernel@vger.kernel.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: Lockdep complains about commit 1331e7a1bb ("rcu: Remove _rcu_barrier() dependency on __stop_machine()")
Date: Wed, 03 Oct 2012 09:05:31 +0530 [thread overview]
Message-ID: <506BB283.4010800@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.LNX.2.00.1210030008590.23544@pobox.suse.cz>
On 10/03/2012 03:47 AM, Jiri Kosina wrote:
> On Wed, 3 Oct 2012, Srivatsa S. Bhat wrote:
>
>> I don't see how this circular locking dependency can occur.. If you are using SLUB,
>> kmem_cache_destroy() releases slab_mutex before it calls rcu_barrier(). If you are
>> using SLAB, kmem_cache_destroy() wraps its whole operation inside get/put_online_cpus(),
>> which means, it cannot run concurrently with a hotplug operation such as cpu_up(). So, I'm
>> rather puzzled at this lockdep splat..
>
> I am using SLAB here.
>
> The scenario I think is very well possible:
>
>
> CPU 0 CPU 1
> kmem_cache_destroy()
What about the get_online_cpus() right here at CPU0 before
calling mutex_lock(slab_mutex)? How can the cpu_up() proceed
on CPU1?? I still don't get it... :(
(kmem_cache_destroy() uses get/put_online_cpus() around acquiring
and releasing slab_mutex).
Regards,
Srivatsa S. Bhat
> mutex_lock(slab_mutex)
> _cpu_up()
> cpu_hotplug_begin()
> mutex_lock(cpu_hotplug.lock)
> rcu_barrier()
> _rcu_barrier()
> get_online_cpus()
> mutex_lock(cpu_hotplug.lock)
> (blocks, CPU 1 has the mutex)
> __cpu_notify()
> mutex_lock(slab_mutex)
>
> Deadlock.
>
> Right?
>
next prev parent reply other threads:[~2012-10-03 3:36 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-02 16:14 Lockdep complains about commit 1331e7a1bb ("rcu: Remove _rcu_barrier() dependency on __stop_machine()") Jiri Kosina
2012-10-02 17:01 ` Paul E. McKenney
2012-10-02 21:27 ` Jiri Kosina
2012-10-02 21:49 ` Jiri Kosina
2012-10-02 21:58 ` Jiri Kosina
2012-10-02 23:31 ` Paul E. McKenney
2012-10-02 23:48 ` Jiri Kosina
2012-10-03 0:15 ` Paul E. McKenney
2012-10-03 0:45 ` [PATCH] mm, slab: release slab_mutex earlier in kmem_cache_destroy() (was Re: Lockdep complains about commit 1331e7a1bb ("rcu: Remove _rcu_barrier() dependency on __stop_machine()")) Jiri Kosina
2012-10-03 0:45 ` Jiri Kosina
2012-10-03 3:41 ` Paul E. McKenney
2012-10-03 3:41 ` Paul E. McKenney
2012-10-03 3:50 ` Srivatsa S. Bhat
2012-10-03 3:50 ` Srivatsa S. Bhat
2012-10-03 6:08 ` Srivatsa S. Bhat
2012-10-03 6:08 ` Srivatsa S. Bhat
2012-10-03 8:21 ` Srivatsa S. Bhat
2012-10-03 8:21 ` Srivatsa S. Bhat
2012-10-03 9:46 ` [PATCH v2] [RFC] mm, slab: release slab_mutex earlier in kmem_cache_destroy() Jiri Kosina
2012-10-03 9:46 ` Jiri Kosina
2012-10-03 12:22 ` Srivatsa S. Bhat
2012-10-03 12:22 ` Srivatsa S. Bhat
2012-10-03 12:53 ` [PATCH] CPU hotplug, debug: Detect imbalance between get_online_cpus() and put_online_cpus() Srivatsa S. Bhat
2012-10-03 12:53 ` Srivatsa S. Bhat
2012-10-03 21:13 ` Andrew Morton
2012-10-03 21:13 ` Andrew Morton
2012-10-04 6:16 ` Srivatsa S. Bhat
2012-10-04 6:16 ` Srivatsa S. Bhat
2012-10-05 3:24 ` Yasuaki Ishimatsu
2012-10-05 3:24 ` Yasuaki Ishimatsu
2012-10-05 5:35 ` Srivatsa S. Bhat
2012-10-05 5:35 ` Srivatsa S. Bhat
2012-10-03 14:50 ` [PATCH v2] [RFC] mm, slab: release slab_mutex earlier in kmem_cache_destroy() Paul E. McKenney
2012-10-03 14:50 ` Paul E. McKenney
2012-10-03 14:55 ` Srivatsa S. Bhat
2012-10-03 14:55 ` Srivatsa S. Bhat
2012-10-03 16:00 ` Paul E. McKenney
2012-10-03 16:00 ` Paul E. McKenney
2012-10-03 14:17 ` Christoph Lameter
2012-10-03 14:17 ` Christoph Lameter
2012-10-03 14:15 ` [PATCH] mm, slab: release slab_mutex earlier in kmem_cache_destroy() (was Re: Lockdep complains about commit 1331e7a1bb ("rcu: Remove _rcu_barrier() dependency on __stop_machine()")) Christoph Lameter
2012-10-03 14:15 ` Christoph Lameter
2012-10-03 14:34 ` [PATCH v3] mm, slab: release slab_mutex earlier in kmem_cache_destroy() Jiri Kosina
2012-10-03 14:34 ` Jiri Kosina
2012-10-03 15:00 ` Srivatsa S. Bhat
2012-10-03 15:00 ` Srivatsa S. Bhat
2012-10-03 15:05 ` [PATCH v4] " Jiri Kosina
2012-10-03 15:05 ` Jiri Kosina
2012-10-03 15:49 ` Srivatsa S. Bhat
2012-10-03 15:49 ` Srivatsa S. Bhat
2012-10-03 18:49 ` David Rientjes
2012-10-03 18:49 ` David Rientjes
2012-10-08 7:26 ` [PATCH] [RESEND] " Jiri Kosina
2012-10-08 7:26 ` Jiri Kosina
2012-10-10 6:27 ` Pekka Enberg
2012-10-10 6:27 ` Pekka Enberg
2012-10-03 3:59 ` Lockdep complains about commit 1331e7a1bb ("rcu: Remove _rcu_barrier() dependency on __stop_machine()") Srivatsa S. Bhat
2012-10-03 4:07 ` Paul E. McKenney
2012-10-03 4:15 ` Srivatsa S. Bhat
2012-10-02 20:39 ` Srivatsa S. Bhat
2012-10-02 22:17 ` Jiri Kosina
2012-10-03 3:35 ` Srivatsa S. Bhat [this message]
2012-10-03 3:44 ` Paul E. McKenney
2012-10-03 4:04 ` Srivatsa S. Bhat
2012-10-03 7:43 ` Jiri Kosina
2012-10-03 8:11 ` Srivatsa S. Bhat
2012-10-03 8:19 ` Jiri Kosina
2012-10-03 8:30 ` Srivatsa S. Bhat
2012-10-03 9:24 ` Jiri Kosina
2012-10-03 9:58 ` Srivatsa S. Bhat
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=506BB283.4010800@linux.vnet.ibm.com \
--to=srivatsa.bhat@linux.vnet.ibm.com \
--cc=jkosina@suse.cz \
--cc=josh@joshtriplett.org \
--cc=linux-kernel@vger.kernel.org \
--cc=paul.mckenney@linaro.org \
--cc=paulmck@linux.vnet.ibm.com \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.