Cooperative POSIX threads?

Cooperative POSIX threads?

[Marius Vollmer]

Hi,

I noticed that signal delivery does not really work when using coop
threads together with the LinuxThreads compatability workaround (i.e,
when configured --with-threads=coop and --enable-linuxthreads)

While pondering what to do, I thought about the following:

Let's make another thread suport option, "coop-pthreads" that will use
pthreads for implementing threads but will rig it so that all threads
that use Guile are executing cooperatively.

There will be new C functions that will bring a thread into Guile
land, and make it leave again.  While a thread is in Guile land, it
can call Guile functions, etc.  When it is outside, it can't.  Threads
created by Guile itself will start in Guile land.  scm_boot_guile and
scm_init_guile will do the right thing, but I'm not yure yet what that
is for scm_init_guile.

We will need these Guile entering and leaving functions anyway when we
want external threads to use Guile since we need to know about the
relevant stack segments.  Those functions can take care that only one
thread is in Guile land at the same time.

Later the coop restriction can be lifted, when Guile itself can
survive this.

Thoughts?

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Re: Cooperative POSIX threads?

[Mikael Djurfeldt]

Marius Vollmer <mvo@zagadka.ping.de> writes:

> I noticed that signal delivery does not really work when using coop
> threads together with the LinuxThreads compatability workaround (i.e,
> when configured --with-threads=coop and --enable-linuxthreads)

Just curious: In what sense doesn't it work?


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Re: Cooperative POSIX threads?

[Marius Vollmer]

Mikael Djurfeldt <mdj@kvast.blakulla.net> writes:

> Marius Vollmer <mvo@zagadka.ping.de> writes:
> 
> > I noticed that signal delivery does not really work when using coop
> > threads together with the LinuxThreads compatability workaround (i.e,
> > when configured --with-threads=coop and --enable-linuxthreads)
> 
> Just curious: In what sense doesn't it work?

It segfaults when there is more than one thread running.  Try

  guile> (begin-thread (let loop () (loop)))
  guile>

and then hitting C-c.

Maybe this is easy to solve (maybe it's a readline problem), but I'm
currently so enthused by my coop-pthread plan that I'd rather hack on
that... :-) Should give me enough opportunity to practice pthread
debugging.

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Re: Cooperative POSIX threads?

[Mikael Djurfeldt]

Marius Vollmer <mvo@zagadka.ping.de> writes:

> Mikael Djurfeldt <mdj@kvast.blakulla.net> writes:
> 
> > Marius Vollmer <mvo@zagadka.ping.de> writes:
> > 
> > > I noticed that signal delivery does not really work when using coop
> > > threads together with the LinuxThreads compatability workaround (i.e,
> > > when configured --with-threads=coop and --enable-linuxthreads)
> > 
> > Just curious: In what sense doesn't it work?
> 
> It segfaults when there is more than one thread running.  Try
> 
>   guile> (begin-thread (let loop () (loop)))
>   guile>
> 
> and then hitting C-c.

Sigh... this has worked before.  But when testing it, it occurs even
in version 1.4.

> Maybe this is easy to solve (maybe it's a readline problem), but I'm
> currently so enthused by my coop-pthread plan that I'd rather hack on
> that... :-) Should give me enough opportunity to practice pthread
> debugging.

:-)

Sounds good to me.

Mikael


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Re: Cooperative POSIX threads?

[Rob Browning]

Marius Vollmer <mvo@zagadka.ping.de> writes:

> I noticed that signal delivery does not really work when using coop
> threads together with the LinuxThreads compatability workaround (i.e,
> when configured --with-threads=coop and --enable-linuxthreads)
>
> While pondering what to do, I thought about the following:
>
> Let's make another thread suport option, "coop-pthreads" that will use
> pthreads for implementing threads but will rig it so that all threads
> that use Guile are executing cooperatively.

At this point, how many platforms are there that support libqthreads
and guile, but not posix threads?  If there aren't any and presuming
your idea works out, could we just drop qthreads in favor of posix
threads?  What would be the tradeoffs?

(I'd love to get rid of the qthread per-platform special-casing in
 debian/rules.)

-- 
Rob Browning
rlb @defaultvalue.org, @linuxdevel.com, and @debian.org
Previously @cs.utexas.edu
GPG=1C58 8B2C FB5E 3F64 EA5C  64AE 78FE E5FE F0CB A0AD


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