linux-kernel - Re: [Bug 11046] New: Kernel bug in mm/bootmem.c on Sparc machines

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Message-ID: <877ibb7abh.fsf@saeurebad.de>
Date:	Thu, 24 Jul 2008 14:09:38 +0200
From:	Johannes Weiner <hannes@...urebad.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	David Miller <davem@...emloft.net>, sparclinux@...r.kernel.org,
	bugme-daemon@...zilla.kernel.org, lomp0101@....net,
	linux-kernel@...r.kernel.org
Subject: Re: [Bug 11046] New: Kernel bug in mm/bootmem.c on Sparc machines

Hi,

Andrew Morton <akpm@...ux-foundation.org> writes:

> On Wed, 23 Jul 2008 20:25:33 -0700 (PDT) David Miller <davem@...emloft.net> wrote:
>
>> From: Andrew Morton <akpm@...ux-foundation.org>
>> Date: Sun, 6 Jul 2008 13:20:49 -0700
>> 
>> > On Sun,  6 Jul 2008 13:02:28 -0700 (PDT) bugme-daemon@...zilla.kernel.org wrote:
>> > 
>> > > http://bugzilla.kernel.org/show_bug.cgi?id=11046
>>  ...
>> > > Here is the BUG:
>> > > 
>> > > [    0.000000] PROMLIB: Sun IEEE Boot Prom 'OBP 4.11.5 2003/11/12 10:40'
>> > > [    0.000000] PROMLIB: Root node compatible: 
>> > > [    0.000000] Linux version 2.6.25.10 (root@...rc1) (gcc version 4.1.2
>> > > 20061115 (prerelease) (Debian 4.1.1-21)) #5 SMP Sun Jul 6 21:05:42 CEST 2008
>> > > [    0.000000] console [earlyprom0] enabled
>> > > [    0.000000] ARCH: SUN4U
>> > > [    0.000000] Ethernet address: 00:03:ba:7a:f3:d6
>> > > [    0.000000] Kernel: Using 2 locked TLB entries for main kernel image.
>> > > [    0.000000] Remapping the kernel... done.
>> > > [    0.000000] kernel BUG at mm/bootmem.c:125!
>> 
>> This can only happen if you attach a zero-sized initrd to the kernel.
>> 
>> I see platforms like x86 sometimes have explicit checks for a zero
>> size to guard reserve_bootmem() and similar calls, but if that's what
>> callers are all going to do doesn't it make better sense for
>> reserve_bootmem_core() to just return instead of BUG on a zero size
>> argument?
>
> Sounds logical.
>
> Johannes just rewrote the bootmem code, but from a quick read it
> appears that this behaviour has been retained.

In the new version, zero sized ranges are okay for reservation and
freeing.  It still bugs on allocation, though.

> So if we're going to change it in 2.6.26, we'll need a separate patch.

	Hannes
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