linux-kernel - Re: v2.6.26-rc9: kernel BUG at kernel/sched.c:5858!

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Date:	Fri, 11 Jul 2008 19:51:34 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
Cc:	Yanmin <yanmin_zhang@...ux.intel.com>,
	"Rusty Russell" <rusty@...tcorp.com.au>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"Dhaval Giani" <dhaval@...ux.vnet.ibm.com>,
	"Gautham R Shenoy" <ego@...ibm.com>,
	"Heiko Carstens" <heiko.carstens@...ibm.com>, miaox@...fujitsu.com,
	"Lai Jiangshan" <laijs@...fujitsu.com>,
	"Avi Kivity" <avi@...ranet.com>, linux-kernel@...r.kernel.org
Subject: Re: v2.6.26-rc9: kernel BUG at kernel/sched.c:5858!

On Fri, Jul 11, 2008 at 1:04 PM, Vegard Nossum <vegard.nossum@...il.com> wrote:
> On Fri, Jul 11, 2008 at 11:02 AM, Dmitry Adamushko
> <dmitry.adamushko@...il.com> wrote:
>> Vegard,
>>
>>
>> regarding the first crash. Would you please run your test with the
>> following debugging patch and let me know its output?
>>
>> The apperance of " * [ pid ] comm (name), orig_cpu() ... " means we
>> hit a problematic case (with Miao Xie's patch it shouldn't crash).
>>
>> I see that you have CONFIG_SCHED_DEBUG=y so I'm also interested in
>> messages from sched_domain_debug() - "CPU# attaching ...". IOW, all
>> the kernel messages appearing while a cpu is going down and up.
[...]

> Ok, now I tested it on my laptop (sorry, no serial console :-)) and I

Now I tested using serial console, but nothing new:

CPU0 attaching NULL sched-domain.
CPU1 attaching NULL sched-domain.
CPU0 attaching sched-domain:
 domain 0: span 0-1
  groups: 0 1
  domain 1: span 0-1
   groups: 0-1
CPU1 attaching sched-domain:
 domain 0: span 0-1
  groups: 1 0
  domain 1: span 0-1
   groups: 0-1
 * [ 7 ] comm (ksoftirqd/1), orig_cpu (1), dst_cpu (1), cpu (1)
CPU 1 is now offline
 * [ 1228 ] comm (kjournald), orig_cpu (0), dst_cpu (0), cpu (0)
 * [ 3113 ] comm (klogd), orig_cpu (0), dst_cpu (0), cpu (0)
BUG: spinlock recursion on CPU#0, syslogd/3110

and here the output stops. I find this REALLY strange, look at the
spinlock recursion code:

        printk(KERN_EMERG "BUG: spinlock %s on CPU#%d, %s/%d\n",
                msg, raw_smp_processor_id(),
                current->comm, task_pid_nr(current));
        printk(KERN_EMERG " lock: %p, .magic: %08x, .owner: %s/%d, "
                        ".owner_cpu: %d\n",
                lock, lock->magic,
                owner ? owner->comm : "<none>",
                owner ? task_pid_nr(owner) : -1,
                lock->owner_cpu);

why would it not be able to print the second line?


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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