From cmascott@world.std.com  Wed Jul  1 15:43:05 1998
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From: cmascott@world.std.com
Reply-To: cmascott@world.std.com
To: FreeBSD-gnats-submit@freebsd.org
Subject: Kernel freezes, gdb, high memory load
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>Number:         7141
>Category:       kern
>Synopsis:       Kernel freezes, gdb, high memory load
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Jul  1 15:50:01 PDT 1998
>Closed-Date:    Thu Aug 6 23:40:43 PDT 1998
>Last-Modified:  Thu Aug  6 23:41:14 PDT 1998
>Originator:     Carl Mascott
>Release:        FreeBSD 2.2.6-RELEASE i386
>Organization:
>Environment:

FreeBSD europa.my.pc 2.2.6-RELEASE
FreeBSD 2.2.6-RELEASE #0: Fri Jun 19 22:08:12 EDT 1998
     cem@europa.my.pc:/usr/src/sys/compile/EUR980619  i386

(GENERIC kernel with unused drivers deleted, Voxware sound
blaster driver added)

P90, 32 MB RAM, 96 MB swap, Adaptec 2940, 2 SCSI drives

SW running at time of freeze:

3 xterm's
olvwm
gdb
program being debugged (calctool)
root csh on console

>Description:

I built a debugging version of libxview.a.  The library
has ~20 MB of symbol information.  I linked a small
program (calctool) with the library and started to debug
the program with gdb.  I set a breakpoint and started
the program.  The program ran to the breakpoint.  I
then continued the program and the kernel froze.

During the following few minutes there was no disk
activity and the keyboard and mouse buttons were
dead.  I couldn't switch VT's.  I couldn't reboot
with CTL-ALT-DEL.  The only clue that the kernel
had not crashed was that the mouse cursor was still
following the mouse.  I finally had to shut the
power off (no reset switch).

After rebooting I checked /var/log/messages to see
if the kernel wrote something about the problem,
but it didn't.

This could well be the first time I did anything that
required more memory than the machine's physical RAM.

I have seen temporary freezes before when searching
a large (~500K) document in Netscape Communicator 4.04,
but during those freezes the mouse cursor wasn't
following the mouse.  Those freezes lasted 10-20
seconds.

>How-To-Repeat:

Unsure.  Seems to be a VM problem.  Try creating a
memory load that exceeds physical RAM.  If it is a
VM problem, the less RAM the machine had, the more
likely it would be for the problem to occur.

>Fix:
	
Unknown.

>Release-Note:
>Audit-Trail:
State-Changed-From-To: open->feedback 
State-Changed-By: phk 
State-Changed-When: Wed Jul 1 22:39:20 PDT 1998 
State-Changed-Why:  

1. Are you sure your swapdevice is configured and works (swapinfo(1)) 

2. Can you reproduce it ? 

3. Can you compile DDB into the kernel and reproduce it from the console 
and try to break into the debugger (Ctrl+Alt+Esc) and send us the output 
from a "trace" command ? 


From: Poul-Henning Kamp <phk@critter.freebsd.dk>
To: freebsd-gnats-submit@freebsd.org
Cc:  Subject: Re: kern/7141
Date: Sat, 04 Jul 1998 23:07:30 +0200

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 Date: Sat, 4 Jul 1998 16:26:31 -0400 (EDT)
 From: Carl Mascott <cmascott@world.std.com>
 Message-Id: <199807042026.QAA00325@europa.my.pc>
 To: phk@FreeBSD.ORG
 Subject: Re: kern/7141
 X-UIDL: bfc34456bf3e3ffe3de2fea2b1af13a8
 
 > 1. Are you sure your swapdevice is configured and works (swapinfo(1))
 
 Device      1K-blocks     Used    Avail Capacity  Type
 /dev/sd0s2b     98304     9376    88864    10%    Interleaved
 
 > 2. Can you reproduce it ?
 
 Alas, no.  I didn't write down where I set the breakpoint.
 I tried gdb on calctool again with a few different breakpoints
 and couldn't reproduce the freeze.
 
 I also wrote a test program called memhog that allocates
 however many megabytes you tell it to from the command line.
 When the system runs out of RAM you can see the swap disk
 activity.  This test program runs fine.  When run as root
 in single-user mode it is able to allocate 63 MB.
 
 > 3. Can you compile DDB into the kernel and reproduce it from the console
 >    and try to break into the debugger (Ctrl+Alt+Esc) and send us the output
 >    from a "trace" command ?
 
 Even if I could reproduce the freeze this would not do any
 good.  As I said, when the kernel freezes the keyboard is
 dead.  Even CTL-ALT-DEL doesn't work.  It would be impossible
 to get into the debugger.
 
 
 Since I can't reproduce this myself I certainly can't tell
 you how to reproduce it.  I guess there is nothing more
 you can do about this problem at this time.
 
 
 ------- End of Forwarded Message
 
State-Changed-From-To: feedback->closed 
State-Changed-By: phk 
State-Changed-When: Thu Aug 6 23:40:43 PDT 1998 
State-Changed-Why:  
ireproducible 
>Unformatted:
