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

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Message-ID: <20140224120427.6394d5dd@linux.lan.towertech.it>
Date:	Mon, 24 Feb 2014 12:04:27 +0100
From:	Alessandro Zummo <a.zummo@...ertech.it>
To:	Tejun Heo <tj@...nel.org>
Cc:	Sasha Levin <sasha.levin@...cle.com>, 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 Sat, 22 Feb 2014 15:52:17 -0500
Tejun Heo <tj@...nel.org> wrote:

> The problem is rtc_device_unregister().  It grabs rtc->ops_lock and
> then tries to remove the sysfs files.  Some of those sysfs file
> implementations acquire rtc->ops_lock, so it of course can lead to
> deadlocks.  One can't try to delete a sysfs file which acquires a lock
> while holding the same lock.

 Pretty interesting indeed. One option would be to remove
 the sys files before acquiring the lock. But I wonder
 if this could lead to other issues.

-- 

 Best regards,

 Alessandro Zummo,
  Tower Technologies - Torino, Italy

  http://www.towertech.it

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