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From "Evgueni Brevnov" <evgueni.brev...@gmail.com>
Subject Re: [drlvm] HARMONY-1582 - invocation API for DRLVM CHECKPOINT
Date Fri, 29 Sep 2006 08:30:29 GMT
Weldon that's cool if you review the patch. Regarding enable/disable
switching. I agree here such bugs are quite hard to fix. Actually I
think it is a good indicator that you found 25 (don't remember
exactly) enable/disable switching. It was really suspicious if you
hadn't find any disabled region :-)

I will update the patch as with respect to your recommendations very soon....

Evgueni

On 9/29/06, Tim Ellison <t.p.ellison@gmail.com> wrote:
> IMHO Weldon is making a perfectly reasonable request.  If he is willing
> to look through the patch in detail then waiting a day or two on
> progressing other items is well worth it.
>
> Just my 2c.
>
> Tim
>
> Weldon Washburn wrote:
> > On 9/28/06, Evgueni Brevnov <evgueni.brevnov@gmail.com> wrote:
> >>
> >> I suppose two days silence means that there is no objects (maybe
> >> interest) against proposed patch. I would suggest to commit it ASAP.
> >> It really works! There are some cases when current VM crashes but the
> >> patch fixes it. I can work on bringing cunit tests to live as soon as
> >> the patch is committed.... This is just my understanding.
> >
> >
> > Sorry for not being clear.  I had asked in another thread for a readable
> > diff.  As I said before, hacking around with gc enable/disable without
> > careful review is a great way to introduce all sorts of hard to
> > diagnose intermittant threading/gc bugs.  The existing "build test" does
> > not
> > even come close to stressing threading/gc.  Its hard to say if this patch
> > really works at this point.
> >
> > I request a decent diff and 24 hours for Andrey Cherneyshev and me to
> > review.  I think the following will work:
> >
> > "svn diff  --diff-cmd diff.exe  -x  -w  -x  -B"
> >
> >
> > Thanks
> >> Evgueni
> >>
> >> On 9/28/06, Geir Magnusson Jr. <geir@pobox.com> wrote:
> >> > So where are we here?
> >> >
> >> > On Sep 28, 2006, at 12:41 AM, Evgueni Brevnov wrote:
> >> >
> >> > > On 9/28/06, Weldon Washburn <weldonwjw@gmail.com> wrote:
> >> > >> On 9/26/06, Evgueni Brevnov <evgueni.brevnov@gmail.com>
wrote:
> >> > >> >
> >> > >> > On 9/27/06, Andrey Chernyshev <a.y.chernyshev@gmail.com>
wrote:
> >> > >> > > (3)
> >> > >> > > One more lock is added - hythread_lib_lock. How is that
differ
> >> > >> from
> >> > >> > > the hythread_global_lock that we already have? Each
extra lock
> >> > >> to the
> >> > >> > > system may add more possibilities for deadlocks, as
well as can
> >> > >> > > negatively impact the scalability (unless some of the
existing
> >> > >> locks
> >> > >> > > are split).
> >> > >> > hythread_lib_lock acquires exactly the same lock as
> >> > >> > hythread_global_lock. Probably I miss something but we need
to be
> >> > >> > compatible with IBM threading library now. This library has
such
> >> > >> > function. That's why I added it. Sounds right?
> >> > >>
> >> > >>
> >> > >> Well,  this sort of, kind of sounds right but not quite.  Its
a
> >> > >> little more
> >> > >> subtle than being compatible with IBM threading library.  The
> >> > >> first goal is
> >> > >> to identify the parts of IBM threading library that are JVM
> >> > >> independent.  It
> >> > >> makes sense for DRLVM to be compatible with the independent
> >> > >> parts.   This
> >> > >> should be a nobrainer.
> >> > >>
> >> > >> The parts of IBM threading library that assume a specific JVM
> >> > >> implementation
> >> > >> will be a problem.  We will need to find a solution that is
> >> > >> endorsed by all
> >> > >> the stakeholders (including J9 folks).  The hythread_global_lock
> >> > >> falls into
> >> > >> this category.  For starts, I would like to see a concise
> >> > >> description from
> >> > >> the portlib owners on what hythread_global_lock protects, which
> >> > >> locks have
> >> > >> to be held before grabbing this lock, are there any restrictions
> >> > >> on what
> >> > >> system calls can be made while holding this lock (like sleep or
> >> > >> wait), etc.
> >> > >
> >> > > Weldon, I completely agree with what your are saying. It's common
> >> > > problem of current hythread that should be resolved some how. I just
> >> > > go inline with current implementation and added two missing
> >> functions.
> >> > > Missing these can lead to the same problems as with hythread_exit
> >> > > discussed  in another thread "[drlvm] [launcher] Executable hangs".
> >> > >
> >> > >>
> >> > >> To get a better idea what's in the patch.diff, I printed it out.
> >> > >> Its 120+
> >> > >> pages.  Quite a big patch!  Most of it looks like straight forward
> >> > >> JNI
> >> > >> interface glue.  There are some tricky parts.  I would like to
> >> > >> know the
> >> > >> design review process for these parts.  Using grep, I found 20
> >> > >> locations
> >> > >> where ...suspend_enable... and ...suspend_disable... have been
> >> > >> added.  And
> >> > >> 25 locations where enable/disable have been removed.  Failure
in
> >> > >> this logic
> >> > >> can lead to incorrect reference pointer enumeration.  These are
> >> > >> probably the
> >> > >> hardest bugs to find.  Please tell us who has looked at this code
> >> > >> in depth.
> >> > > Only me and you :-) Honetsly I think it happpens now....
> >> > >
> >> > >> Are there any known design flaws in it?
> >> > > I can think of two possible problems we may want to discuss.
> >> > > 1) Should native threads have "daemon" status or its completely java
> >> > > notion? This is TM related thing.
> >> > > 2) Should we attach thread to VM before attaching it to TM by calling
> >> > > jthread_atatch OR jthread_attach should callback VM to attach a
> >> thread
> >> > > to it? I didn't change original design of TM here ...... it
> >> implements
> >> > > second choice.
> >> > >
> >> > >>
> >> > >> I also notice APIs called tmn_suspend_enable(),
> >> > >> hythread_suspend_enable()
> >> > >> -- are these simply different names for the same binary
> >> > >> executible.  Or
> >> > >> different binaries that do the same thing??
> >> > >
> >> > > No, this is not just different names. tm_suspend_enable asserts that
> >> > > thread is in disabled state before calling hythread_suspend_enable
> >> (in
> >> > > debug mode only).
> >> > >
> >> > > Thanks
> >> > > Evgueni
> >> > >>
> >> > >>
> >> > >> --
> >> > >> > Weldon Washburn
> >> > >> > Intel Middleware Products Division
> >> > >>
> >> > >>
> >> > >
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> >>
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> >
> >
>
> --
>
> Tim Ellison (t.p.ellison@gmail.com)
> IBM Java technology centre, UK.
>
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