linux-kernel - Re: [RFC PATCH v5 1/2] Use lock_device_hotplug() in cpu_probe_store() and cpu_release

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Message-ID: <20140425122822.GA20460@htj.dyndns.org>
Date:	Fri, 25 Apr 2014 08:28:22 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Li Zhong <zhong@...ux.vnet.ibm.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, gregkh@...uxfoundation.org,
	rafael.j.wysocki@...el.com, toshi.kani@...com
Subject: Re: [RFC PATCH v5 1/2] Use lock_device_hotplug() in
 cpu_probe_store() and cpu_release_store()

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.  Alright,
thanks a lot for the explanation.

-- 
tejun
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