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Re: cause of early indigo2 crash

To: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Subject: Re: cause of early indigo2 crash
From: Florian Lohoff <flo@rfc822.org>
Date: Thu, 6 Apr 2000 12:08:31 +0200
Cc: linux@cthulhu.engr.sgi.com
In-reply-to: <Pine.GSO.4.10.10004061050160.28032-100000@dandelion.sonytel.be>; from Geert Uytterhoeven on Thu, Apr 06, 2000 at 10:51:17AM +0200
Organization: rfc822 - pure communication
References: <20000405223413.B996@paradigm.rfc822.org> <Pine.GSO.4.10.10004061050160.28032-100000@dandelion.sonytel.be>
Sender: owner-linuxmips@oss.sgi.com
On Thu, Apr 06, 2000 at 10:51:17AM +0200, Geert Uytterhoeven wrote:
> > scsi::resize_dma_pool: WARNING, dma_sectors=0, wanted=48, scaling
> >        WARNING, not enough memory, pool not expanded
> > Unable to handle kernel paging request at virtual address 00000000, epc == 
> > 880cc668, ra == 880cc5d8
> > [...]
>   ^^^^^
> What's here? Usually it tells the function where it crashes.

:) I dont have an System.map available - But i think i know the cause
of the crash - I think the arch/mips/arc/memory.c forgets to
allocate/not-free the memory the kernel - I dont think the ARC Prom is
able to mark the kernel memory different - But i cant see a location
where it explicitly reserves/allocates the kernel pages. Dec and ddb
to something like free_bootmem(bootmap,&_end,size-_end) - Nothing
like that in the arc things ... They free all memory segments
the ARC Prom gives back as "MEMTYPE_FREE" (arc_contigm, arc_freem)
and then it just takes the largest segment (there are 2 segments 
- before and after the arc-prom segment) and installs the bootmem-map
in there. The next alloc and memset causes the crash as it allocates
from 88002000 which is the end of the mem map - My suspicion is (Which
ill try tonight) that the memory map with 2 pages is that small
that is just overwrites parts of the kernel with no effect - The next alloc
and memset is 4MB - This destroys the kernel completely and though causes
a crash.

> I see these panics sometimes as well. Where does the crash happen? Please
> lookup in System.map.

Ill do tonight

Flo
-- 
Florian Lohoff          flo@rfc822.org                  +49-subject-2-change
"Technology is a constant battle between manufacturers producing bigger and
more idiot-proof systems and nature producing bigger and better idiots."


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