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

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 24 Jul 2008 14:09:38 +0200 Johannes Weiner <hannes@saeurebad.de> wrote:

> Hi,
> 
> Andrew Morton <akpm@linux-foundation.org> writes:
> 
> > On Wed, 23 Jul 2008 20:25:33 -0700 (PDT) David Miller <davem@davemloft.net> wrote:
> >
> >> From: Andrew Morton <akpm@linux-foundation.org>
> >> Date: Sun, 6 Jul 2008 13:20:49 -0700
> >> 
> >> > On Sun,  6 Jul 2008 13:02:28 -0700 (PDT) bugme-daemon@bugzilla.kernel.org wrote:
> >> > 
> >> > > http://bugzilla.kernel.org/show_bug.cgi?id\x11046
> >>  ...
> >> > > 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@sparc1) (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.
> 

Interesting.  So from Dave's patch (which changes only
reserve_bootmem_core() and free_bootmem_core()), it sounds like we
have already fixed 2.6.27?

In which case David's 2.6.26 patch is a "minimal backport".