linux-kernel - Re: [KDUMP] Ignore spurious IPI

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Date:	Thu, 24 Mar 2011 17:25:18 -0400
From:	Takao Indoh <indou.takao@...fujitsu.com>
To:	Milton Miller <miltonm@....com>
Cc:	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org
Subject: Re: [KDUMP] Ignore spurious IPI

On Thu, 24 Mar 2011 08:20:32 -0600, Milton Miller wrote:

>On Wed, 23 Mar 2011 about 18:40:12 -0000, Takao Indoh wrote:
>> Hi all,
>> 
>> I found a problem that kdump(2nd kernel) sometimes hangs up. It seems
>> that system panic occurs as follows.
>..
>> (2)
>> A pending IPI from 1st kernel comes after unmasking interrupts at the
>> following point.
>> 
>> asmlinkage void __init start_kernel(void)
>> {
>> (snip)
>>     time_init();
>>     profile_init();
>>     if (!irqs_disabled())
>>             printk(KERN_CRIT "start_kernel(): bug: interrupts were "
>>                              "enabled early\n");
>>     early_boot_irqs_disabled = false;
>>     local_irq_enable(); <=======================================HERE
>> 
>> (3)
>> Kernel tries to handle the interrupt, but some data structures are not
>> initialized yet at this point. As a result, in the
>> generic_smp_call_function_single_interrupt(), NULL pointer dereference
>> occurs when list_replace_init() tries to access &q->list.next.
>> 
>[tried to match lapic timer interrupt]
>> Any comments?
>
>So this occurs because unlike device interrupts, this vector has the action
>defined statically and no per-interrupt disable on your architecture?

I think there is not per-interrupt disable for IPI.

>If so, just initialize the data structure earlier -- change
>init_call_single_data from early_initcall to an explict call after the
>per-cpu areas are initialized.

That makes sense. I'll do this, thanks.

Thanks,
Takao Indoh


>
>milton
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