netdev - Re: [next] unix stream crashes

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Date:	Sat, 3 Sep 2011 06:32:56 +0200
From:	Sedat Dilek <sedat.dilek@...glemail.com>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
Cc:	Valdis.Kletnieks@...edu, Jiri Slaby <jirislaby@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	ML netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [next] unix stream crashes

On Sat, Sep 3, 2011 at 1:55 AM, Tim Chen <tim.c.chen@...ux.intel.com> wrote:
> On Fri, 2011-09-02 at 12:12 -0400, Valdis.Kletnieks@...edu wrote:
>> On Thu, 01 Sep 2011 18:40:45 PDT, Tim Chen said:
>>
>> > Yes, Jiri's log does indicate that something went wrong when releasing
>> > the skb, most likely due to changes in the pid and credentials ref
>> > count.  Unfortunately, I cannot duplicate the problem on my system.  Any
>> > info on your system to help me debug will be appreciated.  I'll try to
>> > take another look at the patch tomorrow.
>>
>> Dell Latitude E6500, Core2 T8700 processor, x86_64 kernel, a slightly mangled
>> Fedora Rawhide userspace.  I'd not be surprised if there's an idiocyncratic
>> setting in my .config that makes the bug crawl out of the woodwork on my box,
>> so I'm attaching the .config in case it provides some enlightenment.
>>
>> If you want me to try a debugging or test patch, let me know...
>
> Valdis,
>
> I've tried your config on a few different machines but I'm still not
> able to reproduce the problem.  Can you help me narrow things down?
> Please revert my original patch.  I've separated my original changes
> into two parts.  Try apply only the recv_scm.patch attached and try to
> boot.  Then apply only the send_scm.patch without the rcv_scm.patch and
> repeat.  Let me know which patch causes the boot problem.
>
> I'll like to isolate the problem to either the send path or receive
> path. My suspicion is the error handling portion of the send path is not
> quite right but I haven't yet found any issues after reviewing the
> patch.
>
> Thanks.
>
> Tim
>

Hi,

base for my testing was linux-next (next-20110826) which contains
first time the culprit commit.
I have tested on an i386 Debian/sid system, my kernel-config is attached.

BAD #1: next-20110826

GOOD #1: next-20110826 + Revert-patch

GOOD #2: next-20110826 + Revert-patch + scm_recv.patch

BAD #2: next-20110826 + Revert-patch + scm_send.patch

With BAD #2 I have seen a NULL derefence (*pde = 00000000) arosing
from kmem_cache_alloc_trace().
( Sorry, no digicam here for a screenshot. )

Hope this helps you.

Feel free to send me further patches and/or add a
Reported-by/Tested-by/Bisected-by if you like.

- Sedat -

View attachment "0001-Revert-Scm-Remove-unnecessary-pid-credential-referen.patch" of type "text/x-diff" (5901 bytes)

Download attachment "config-3.1.0-rc3-next20110826.3-686-small" of type "application/octet-stream" (88965 bytes)