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Date: Fri, 20 Jan 2012 08:49:57 -0600 (CST)
From: Christoph Lameter <cl@linux.com>
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To: "Eric W. Biederman" <ebiederm@xmission.com>
cc: Eric Dumazet <eric.dumazet@gmail.com>,
        Sasha Levin <levinsasha928@gmail.com>, Dave Jones <davej@redhat.com>,
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        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>, netfilter-devel@vger.kernel.org,
        netdev <netdev@vger.kernel.org>
Subject: Re: Hung task when calling clone() due to netfilter/slab
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On Thu, 19 Jan 2012, Eric W. Biederman wrote:

> On the flip side removing from sysfs with locks held must be done
> carefully, and as a default I would recommend not to hold locks over
> removing things from sysfs.  As removal blocks waiting for all of the
> callers into sysfs those sysfs attributes to complete.
>
> It looks like you are ok on the removal because none of the sysfs
> attributes appear to take the slub_lock, just /proc/slabinfo.  But
> it does look like playing with fire.

Ok then I guess my last patch is needed to make sysfs operations safe.

It may be good to audit the kernel for locks being held while calling
sysfs functions. Isnt there a lockdep check that ensures that no locks are
held?