linux-kernel - Re: Hung task when calling clone() due to netfilter/slab

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Message-ID: <alpine.DEB.2.00.1201200848040.25882@router.home>
Date:	Fri, 20 Jan 2012 08:49:57 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Sasha Levin <levinsasha928@...il.com>,
	Dave Jones <davej@...hat.com>, davem <davem@...emloft.net>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>, kaber@...sh.net,
	pablo@...filter.org, linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, netfilter-devel@...r.kernel.org,
	netdev <netdev@...r.kernel.org>
Subject: Re: Hung task when calling clone() due to netfilter/slab

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?


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