[5753] in Athena Bugs
workaround for emacs lossage on pmax
daemon@ATHENA.MIT.EDU (raeburn@ATHENA.MIT.EDU)
Thu Aug 16 22:20:47 1990
From: raeburn@ATHENA.MIT.EDU
To: bugs@ATHENA.MIT.EDU
Date: Thu, 16 Aug 90 22:20:28 EDT
I get the "segmentation fault" problem more often than not, and ran into the
panic mentioned just tonight when I logged in (and started emacs among other
things). Any chance this can get into pmax 7.1, since it's such a frequent
problem?
-- Ken
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From: Mark W. Eichin <eichin@ATHENA.MIT.EDU>
Message-Id: <9008162222.AA19779@E40-008-9.MIT.EDU>
To: Ken Raeburn <raeburn@ATHENA.MIT.EDU>, Marc Horowitz <marc@ATHENA.MIT.EDU>
Subject: emacs and the PMAX
Seen on the FAQ posted to bug-gnu-emacs recently... does this mean
anything for us? That panic is the one that hit in the middle nof the
backup this week, wasn't it? _Mark_
Q: Why does Emacs occasionally cause segmentation faults and machine
panics on my DECstation 3100?
Bruce Cole <cole@dip.cs.wisc.edu> writes:
> We're running emacs 18.54 on an Ultrix Risc Decsystem 5400. Three times
> we've had the machine hang with the following message:
>
> panic: tblmod on invalid pte
>
> Ultrix support tells us this is caused by emacs. Has anyone experienced
> this? DEC says it only happens on RISC boxes.
This is due to a MIPS specific Ultrix kernel bug. I sent DEC a description
of the bug with a bug fix. The Kernel bug manifests itself with emacs
since emacs uses a non-standard data start address on Ultrix MIPS machines.
I haven't often seen emacs cause MIPS machines to panic. Usually you just
see one of the following errors when you try to start up emacs:
segmentation fault (core dumped)
emacs: Bad address
Out of memory
data size rlimit exceeded, pid 6523, process tcsh (for example)
Until DEC fixes their kernel, you can avoid the bug by changing the data
start address used by emacs.
> I have built two newer versions of gnu emacs and it still happens. I should
> also mention that these faults happen quite rarely to some users (I may see
> it once a month), while other users see it a few times a week or even daily!
The problem only occurs when a MIPS machine is doing a lot of paging. Users
who don't cause their workstation to page will not see this problem.
Patch to GNU Emacs 18.55:
*** m-pmax.h Thu Jun 8 11:53:55 1989
--- m-pmax.h.new Mon Jul 9 10:21:21 1990
***************
*** 1,3 ****
--- 1,7 ----
#include "m-mips.h"
#undef LIBS_MACHINE
#undef BIG_ENDIAN
+ #undef LD_SWITCH_MACHINE
+ #undef DATA_START
+ #define DATA_START 0x10000000
+ #define DATA_SEG_BITS 0x10000000
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