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

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Date:	Wed, 23 Jul 2008 23:45:32 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
Cc:	"Suresh Siddha" <suresh.b.siddha@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Subject: Re: recent -git: BUG in free_thread_xstate

On Wed, Jul 23, 2008 at 11:35 PM, Dmitry Adamushko
<dmitry.adamushko@...il.com> wrote:
> 2008/7/23 Dmitry Adamushko <dmitry.adamushko@...il.com>:
>> 2008/7/23 Vegard Nossum <vegard.nossum@...il.com>:
>>> ------------[ cut here ]------------
>>> WARNING: at kernel/sched_fair.c:815 hrtick_start_fair+0x158/0x170()
>>
>> that's interesting. As a first step and if it's easily reproducible,
>> would you try something like below?
>
> If not, maybe object files are still in-tact? Just to see where
> exactly in schedule() it crashed so maybe we may get an idea on what
> was a result of next = pick_next_task(rq, prev);

Yes, indeed. You mean this part?

BUG: unable to handle kernel paging request at c0804358
IP: [<c057e38d>] schedule+0x1ed/0x850
*pde = 3780e163 *pte = 00804162
Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
Pid: 5575, comm: migration/1 Tainted: G        W (2.6.26 #1)
EIP: 0060:[<c057e38d>] EFLAGS: 00010086 CPU: 1
EIP is at schedule+0x1ed/0x850
EAX: c0803f00 EBX: 00000001 ECX: f4d10000 EDX: 00450008
ESI: f4c91fe0 EDI: c0803f00 EBP: f4c85fa0 ESP: f4c85f3c

$ addr2line -e vmlinux -i c057e38d
kernel/sched_stats.h:164
kernel/sched_stats.h:236
kernel/sched_stats.h:242
kernel/sched.c:4191

(Keep in mind that the line numbers are for v2.6.26.)

Looks to be this line (kernel/sched.c):

                sched_info_switch(prev, next);

or for kernel/sched_stats.h:164:

        unsigned long long now = task_rq(t)->clock, delta = 0;

..I'm not sure how much information this is?

Most likely the task_struct just got corrupted, like for the xstate
crashes... Should I still try the patch? :-)


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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