From: Li Zhong <zhong@linux.vnet.ibm.com>
To: Tejun Heo <tj@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
gregkh@linuxfoundation.org, rafael.j.wysocki@intel.com,
toshi.kani@hp.com
Subject: Re: [RFC PATCH v5 1/2] Use lock_device_hotplug() in cpu_probe_store() and cpu_release_store()
Date: Mon, 28 Apr 2014 08:51:35 +0800 [thread overview]
Message-ID: <1398646295.3046.30.camel@ThinkPad-T5421> (raw)
In-Reply-To: <20140425122822.GA20460@htj.dyndns.org>
On Fri, 2014-04-25 at 08:28 -0400, Tejun Heo wrote:
> On Fri, Apr 25, 2014 at 09:56:10AM +0800, Li Zhong wrote:
> > > A nests cpu subsys mutex under s_active of the online node. B nests
> > > s_active of the online node under the cpu subsys mutex. What am I
> > > missing?
> >
> > From the above two chain, I think the problem is cpu_subsys_mutex and
> > s_active(online), which is the deadlock we are trying to solve in patch
>
> Yeap, that one was what I was thinking about.
>
> > #2. I seems to me s_active(release) here doesn't have lock issues?
>
> And your patch doesn't change the situation for online.
I'm a little confused here...
To clarify for this patch(#1):
Currently(before patch#2), the s_active(online) and cpu subsys mutex
deadlock is solved by lock_device_hotplug_sysfs(). (lockdep warnings are
still there, so we want to change the implementation of
lock_device_hotplug_sysfs() in patch #2 to take out of s_active_online,
instead of device_hotplug_lock, which is grabbed before cpu subsys
mutex).
But here, for the probe/release, I think we really don't need to use
this _sysfs() version.
So it is replaced with lock_device_hotplug() directly to avoid two
unnecessary conversions of lock_device_hotplug_sysfs(), that otherwise
need to be done in patch #2.
Thanks, Zhong
> Alright,
> thanks a lot for the explanation.
>
prev parent reply other threads:[~2014-04-28 0:51 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-10 9:18 [RFC PATCH] Suppress a device hot remove related lockdep warning Li Zhong
2014-04-10 13:31 ` Tejun Heo
2014-04-11 4:10 ` [RFC PATCH v2] Use kernfs_break_active_protection() for device online store callbacks Li Zhong
2014-04-11 10:26 ` Tejun Heo
2014-04-14 7:47 ` [RFC PATCH v3] " Li Zhong
2014-04-14 20:13 ` Tejun Heo
2014-04-15 2:44 ` Li Zhong
2014-04-15 14:50 ` Tejun Heo
2014-04-16 1:41 ` Li Zhong
2014-04-16 15:17 ` Tejun Heo
2014-04-17 3:05 ` Li Zhong
2014-04-17 15:06 ` Tejun Heo
2014-04-17 6:50 ` [RFC PATCH v4] " Li Zhong
2014-04-17 15:17 ` Tejun Heo
2014-04-18 8:33 ` Li Zhong
2014-04-21 9:20 ` [RFC PATCH v5 1/2] Use lock_device_hotplug() in cpu_probe_store() and cpu_release_store() Li Zhong
2014-04-21 9:23 ` [RFC PATCH v5 2/2] Use kernfs_break_active_protection() for device online store callbacks Li Zhong
2014-04-21 22:46 ` Tejun Heo
2014-04-22 3:34 ` Li Zhong
2014-04-22 10:11 ` Rafael J. Wysocki
2014-04-23 1:50 ` Li Zhong
2014-04-23 10:54 ` Rafael J. Wysocki
2014-04-24 1:13 ` Li Zhong
2014-04-22 20:44 ` Tejun Heo
2014-04-22 22:21 ` Rafael J. Wysocki
2014-04-23 14:23 ` Tejun Heo
2014-04-23 16:12 ` Rafael J. Wysocki
2014-04-23 16:52 ` Tejun Heo
2014-04-24 8:59 ` Li Zhong
2014-04-24 10:02 ` Rafael J. Wysocki
2014-04-25 1:46 ` Li Zhong
2014-04-25 12:47 ` Rafael J. Wysocki
2014-04-28 1:49 ` Li Zhong
2014-04-23 5:03 ` Li Zhong
2014-04-23 10:58 ` Rafael J. Wysocki
2014-04-24 1:33 ` Li Zhong
2014-05-09 8:35 ` Li Zhong
2014-05-09 8:40 ` [RFC PATCH v6 1/2 ] Use lock_device_hotplug() in cpu_probe_store() and cpu_release_store() Li Zhong
2014-05-09 8:40 ` [RFC PATCH v6 2/2] Implement lock_device_hotplug_sysfs() by breaking active protection Li Zhong
2014-04-21 22:38 ` [RFC PATCH v5 1/2] Use lock_device_hotplug() in cpu_probe_store() and cpu_release_store() Tejun Heo
2014-04-22 2:29 ` Li Zhong
2014-04-22 20:40 ` Tejun Heo
2014-04-23 2:00 ` Li Zhong
2014-04-23 14:39 ` Tejun Heo
2014-04-24 8:37 ` Li Zhong
2014-04-24 14:32 ` Tejun Heo
2014-04-25 1:56 ` Li Zhong
2014-04-25 12:28 ` Tejun Heo
2014-04-28 0:51 ` Li Zhong [this message]
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