linux-kernel - Re: recent -git: BUG in free_thread

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Date:	Fri, 8 Aug 2008 20:46:21 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	paulmck@...ux.vnet.ibm.com
Cc:	"Suresh Siddha" <suresh.b.siddha@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: recent -git: BUG in free_thread_xstate

On Fri, Aug 1, 2008 at 11:10 PM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
> On Wed, Jul 23, 2008 at 01:31:09PM -0700, Suresh Siddha wrote:
>> On Wed, Jul 23, 2008 at 01:07:04PM -0700, Vegard Nossum wrote:
>> > Hi,
>> >
>> > I just got this on c010b2f76c3032e48097a6eef291d8593d5d79a6 (-git from
>> > yesterday):
>>
>> Do you see this in 2.6.26 aswell? I suspect it is coming from post 2.6.26
>> changes.
>>
>> >
>> > BUG: unable to handle kernel paging request at 00664381
>> > IP: [<c010b274>] free_thread_xstate+0x4/0x30
>> ...
>>
>> > EIP is at arch/x86/kernel/process.c:36:
>> >
>> >         if (tsk->thread.xstate) {
>> >
>>
>> It looks like the kernel stack of that process got corrupted, corrupting the
>> task pointer in thread_info. Can you send us your config file?
>
> I would also like to see the config file.

Hi,

I'm sorry for the late reply.

I copied you because I saw some RCU entry in the stack trace, but it
is almost definitely not a problem with (core or "leaf") RCU code.
Sometimes it also happens that people will say "oh, I recognize this
problem, the patch has been posted here and here", etc.

It seems to be a problem with either netpoll, netconsole, or the
8139too driver. I find a UDP packet in the task_struct slab, and the
stacktrace with RCU entries come from unrelated, unfortunate callbacks
that stumbled upon the corruption.

My config, if you are still interested, can be found here:
http://userweb.kernel.org/~vegard/bugs/20080724-fork/config

I don't know if the problem persists with the latest -git, it is now a
while since I last tested, but I've checked kernels back to 2.6.20, so
the problem has existed for a long time.


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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