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

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Message-Id: <smp-ipi-supurious-single-kdump@mdm.bga.com>
Date:	Thu, 24 Mar 2011 08:20:32 -0600
From:	Milton Miller <miltonm@....com>
To:	Takao Indoh <indou.takao@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org
Subject: Re: [KDUMP] Ignore spurious IPI

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?


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.

milton
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