[Vm-dev] Re: [squeak-dev] Re: [Pharo-project] new Cog VMs

[Eliot Miranda]

Hi Igor,  Hi All,

On Sun, Jan 2, 2011 at 4:11 PM, Igor Stasenko <siguctua at gmail.com> wrote:

> On 3 January 2011 00:15, Eliot Miranda <eliot.miranda at gmail.com> wrote:
> > Hi Martin, Hi All,
> >     so find new VMs in VM.r2341/.  The linux crashes (certainly the one
> you
> > suffered from Martin) seem to be caused by an optimization bug (but they
> > could be caused by bad code generation, creating something that assumes
> > ordering constraints which C doesn't guarantee).  I suspect the former
> > because I don't see the crash when running exactly the same VM and image
> > from a different directory; provoking the crash requires a particular
> path
> > (go figure; I haven't pinned this down yet).
> > So my "fix" is preventing a complex function being inlined into the main
> > interpreter loop, removing the sources of some warnings, and lowering the
> > optimization level of the gcc3x-cointerp.c file to -O1 from -O2 (my build
> > environment, CentOS Linux 5.3, uses gcc 4.1.2).  I'm not proud of this
> > "fix".  I've violated the Deutsch criterion by not diagnosing the cause
> of
> > the bug so I can't stand behind this fix; it's a hack that appears to
> work
> > and may have merely pushed the real bug further underground.  Alas I
> don't
> > have time to do a better job. Hopefully it'll get those of you on linux
> > going again.
>
> Eliot, if you remember, i also had crash issues on linux, and pinned down
> it to
> removing optimization from <something>heartbeat.c while keeping
> gcc3x-cointerp.c to use
>  same optimization flags as for rest of files.
>

Indeed, quite right.  I happened to add a flag to turn off the heartbeat so
I could debug the crash Matthew was seeing in starting up
Squeak4.2-10856-beta.image (since single-stepping through machine code
always gets interrupted by the heartbeat, it being an interval timer) and lo
and behold the bug went away.  This is very worrying because it appears to
imply that there's a serious bug in the linux kernel/gcc since delivering a
software interrupt shouldn't corrupt registers, but it clearly does.  I'll
try and pass it by someone who's an expert in this area.

Anyway, now find a new linux VM in
VM.r2346/<http://www.mirandabanda.org/files/Cog/VM/VM.r2346/> that
seems fine with the interpreter and the cogit compiled at -02 but the
heartbeat compiled at -O2.  Running this VM on CentOS 5.3 under Parallels I
get
    2839 run, 2796 passes, 7 expected failures, 24 failures, 11 errors, 0
unexpected passes
for the full test suite in Squeak4.2-10856-beta.image.

So have at it.

best
Eliot


> I will start coding cmake config for Cog during next week and will be
> able to check my previous
> observations again.
>
> > best
> > Eliot
> > On Sat, Jan 1, 2011 at 11:16 PM, <mkobetic at gmail.com> wrote:
>
> --
> Best regards,
> Igor Stasenko AKA sig.
>
>
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