linux-kernel - Re: kernfs/rtc: circular dependency between kernfs and ops

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Date:	Mon, 31 Mar 2014 14:19:23 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Alessandro Zummo <a.zummo@...ertech.it>
CC:	Sasha Levin <sasha.levin@...cle.com>, Tejun Heo <tj@...nel.org>,
	Greg KH <greg@...ah.com>, rtc-linux@...glegroups.com,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: kernfs/rtc: circular dependency between kernfs and ops_lock

On 03/31/2014 02:03 PM, Alessandro Zummo wrote:
> On Mon, 31 Mar 2014 13:07:10 +0200
> Lars-Peter Clausen <lars@...afoo.de> wrote:
>
>> It doesn't really matter where it is unregistered. device_unregister() will
>> (somewhere down it's callchain) take the kernfs lock, hence it must be
>> callled with the rtc mutex being held.
>
>   Maybe device_remove_attrs could be called in the rtc base class,
>   before the device removal?
>

Just move the device_unregister() call outside the lock. I think the only 
thing that needs to be protected is the ops = NULL assignment. Moving the 
unregister after the unlock also means that the extra 
get_device()/put_device() pair can be removed.
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