linux-kernel - Re: 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff

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Message-ID: <20080423174006.GA2739@elte.hu>
Date:	Wed, 23 Apr 2008 19:40:06 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Zdenek Kabelac <zdenek.kabelac@...il.com>,
	Jiri Slaby <jirislaby@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, paulmck@...ux.vnet.ibm.com,
	David Miller <davem@...emloft.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-ext4@...r.kernel.org, herbert@...dor.apana.org.au,
	Pekka Enberg <penberg@...helsinki.fi>,
	Christoph Lameter <clameter@....com>
Subject: Re: 2.6.25-git2: BUG: unable to handle kernel paging request at
	ffffffffffffffff


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> >  CPU: L2 cache: 4096K
> >  CPU: Physical Processor ID: 0
> >  CPU: Processor Core ID: 1
> >  x86: PAT support disabled.
> >  SPIN IRQ ALREADY DISABLED
> >  Pid: 0, comm: swapper Not tainted 2.6.25 #57
> > 
> >  Call Trace:
> >   [_spin_lock_irq+126/128] _spin_lock_irq+0x7e/0x80
> >   [lock_ipi_call_lock+16/32] lock_ipi_call_lock+0x10/0x20
> >  CPU1: Intel(R) Core(TM)2 Duo CPU     T7500  @ 2.20GHz
> > [start_secondary+68/206] start_secondary+0x44/0xce
> 
> This is indeed an interesting issue: arch/x86/kernel/smpboot.c does an 
> IPI call to start_secondary, and yes, it looks suspicious to have that 
> lock_ipi_call_lock there (and in particular the unlock_ipi_call_lock 
> that enables interrupts within it). Ingo?

hm, irqs already disabled isnt bad in itself and it happens all the 
time. The irq enabling in unlock_ipi_call_lock() should be OK.

Any race with irqs there should at most result in a hung or crashed 
bootup, not in any memory corruption i believe.

	Ingo
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