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: <20140421223804.GD22730@htj.dyndns.org>
Date:	Mon, 21 Apr 2014 18:38:04 -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()

Hello,

On Mon, Apr 21, 2014 at 05:20:59PM +0800, Li Zhong wrote:
> While auditing the usage of lock_device_hotplug_sysfs() for implementing
> it in another way in following patch, it seems to me that the code here
> is to add/remove device, and the files probe/release for cpu bus
> themselves won't be removed. 
> 
> So it seems to me there is no s_active related deadlock here, and we
> could just use lock_device_hotplug().

It may still cause issue if offlining ends up removing sysfs files or
gets involved with the same lock used during cpu hot[un]plug
operations (e.g. offlining racing against cpu hotunplug) and offlining
a cpu does remove files.  Has this change been tested?

Thanks.

-- 
tejun
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