From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@quanstro.net>
Date: Sun, 30 May 2010 12:30:05 -0400
To: xigh@bouyapop.org, 9fans@9fans.net
Message-ID: <455a9b599b32a95fdfa5ae79083ae99a@kw.quanstro.net>
In-Reply-To: <4C028B75.8080701@bouyapop.org>
References: <416156.63571.qm@web83915.mail.sp1.yahoo.com>
	<4C028B75.8080701@bouyapop.org>
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Subject: Re: [9fans] crashing 9vx
Topicbox-Message-UUID: 2d93e5ca-ead6-11e9-9d60-3106f5b1d025

On Sun May 30 12:00:25 EDT 2010, xigh@bouyapop.org wrote:
> You also have to recompile vx library.
>
> Phil
>
> Brian L. Stuart wrote:
> >> OK, somebody sent a hint that it
> >> might make sense to take the -O3 out
> >> of the make flags. Done.
> >>
> >> Result: I can now get through this command:
> >> hget -v http://plan9.bell-labs.com/plan9/download/plan9.iso.bz2>/tmp/iso.bz2
> >> |[2]aux/statusbar plan9.iso
> >>
> >> without an explosion.
> >>
> >
> > This is weird.  I just built 9vx on FreeBSD without
> > the -O3.  But instead of being more stable, that
> > one crashed on startup, like Charles reported.
> > Namely:
> >
> > 9vx panic: user fault: signo=11 addr=3850cb67 [useraddr=cb67] read=1 eip=80b973c esp=493ffac0
> > aborting, to dump core.
> >
> > With the -O3, the crashes are rare, and seem to be
> > associated with heavy I/O.

you may be right, but it seems too easy to blame gcc.
a better fit for the facts so far would seem to me that
9vx' locking is broken.  the optimization may just put
more pressure on broken locking.

putting a couple of prints in the startup will also change
timing.  if you can eliminate or cause a crash by adding
or removing prints, then you can be sure that there is a
locking/timing problem in 9vx.  although that doesn't prove
that gcc is blameless, it would be a reasonable assumption.

- erik