From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Lameter <cl@linux.com>
Subject: Re: netfilter: Hung task
Date: Mon, 19 Mar 2012 11:31:47 -0500 (CDT)
Message-ID: <alpine.DEB.2.00.1203191129440.20196@router.home>
References: <CA+1xoqfCTXxXsbfUjttuOVutyD_FzYS8PoOoAOOtB72P8SwdVg@mail.gmail.com> <20120318141943.GA28850@1984> <CA+1xoqcQYqCgQb=1M5PVkm=6SBhV2oJxJ2CtBp=gAvZM36Kc2Q@mail.gmail.com> <20120319002811.GA30408@1984> <alpine.DEB.2.00.1203190854560.16879@router.home>
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Cc: Pablo Neira Ayuso <pablo@netfilter.org>, kaber@trash.net,
	davem@davemloft.net, Dave Jones <davej@redhat.com>,
	netfilter-devel@vger.kernel.org,
	"linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>,
	netdev@vger.kernel.org
To: Sasha Levin <levinsasha928@gmail.com>
Return-path: <netfilter-devel-owner@vger.kernel.org>
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On Mon, 19 Mar 2012, Sasha Levin wrote:

> On Mon, Mar 19, 2012 at 3:56 PM, Christoph Lameter <cl@linux.com> wrote:
> > This is sually something causing memory corruption. Please enable
> > debugging to get backtrace that help to debutg this. CONFIG_SLUB_DEBUG_ON
> > will do the trick or passing "slub_debug" on the kernel command line.
>
> The kernel was compiled with SLUB_DEBUG_ON, there's nothing coming out
> of the slub before that hang message, nor after it.

Ok looking at the backtrace: This is kmem_cache_destroy and not the usual
failure following a pointer in alloc / free.

netfilter calls kmem_cache_destroy which calls into sysfs functions and
there the hang occurs.

Did you try to see if lockdep can detect any serialization problems ?

Is kmem_cache_destroy called with any locks held? Interrupts off?