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From: Russell Leighton <russell.leighton@247media.com>
To: Michael Rothwell <rothwell@holly-springs.nc.us>
Cc: linux-kernel@vger.kernel.org
Subject: Coroutines [was Re: threading question]
Date: Sat, 16 Jun 2001 17:30:55 -0400	[thread overview]
Message-ID: <3B2BD00F.E8CEBF0B@247media.com> (raw)
In-Reply-To: <E15BHrC-0008Ba-00@the-village.bc.nu>  <3B2BA68D.984A2808@247media.com> <992718405.913.0.camel@gromit>



Any chance this or the equiv could become part of glibc?

This seems a very handy abstraction,  in many apps
threads would then really only be needed for true parallelism.


Michael Rothwell wrote:

> Try this:
>
> http://lecker.essen.de/~froese/coro/
>
> -M
>
> On 16 Jun 2001 14:33:50 -0400, Russell Leighton wrote:
> >
> > Is there a user-space implemenation (library?) for coroutines that would work from C?
> >
> >
> > Alan Cox wrote:
> >
> > > > Can you provide any info and/or examples of co-routines? I'm curious to
> > > > see a good example of co-routines' "betterness."
> > >
> > > With co-routines you don't need
> > >
> > >         8K of kernel stack
> > >         Scheduler overhead
> > >         Fancy locking
> > >
> > > You don't get the automatic thread switching stuff though.
> > >
> > > So you might get code that reads like this (note that aio_ stuff works rather
> > > well combined with co-routines as it fixes a lack of asynchronicity in the
> > > unix disk I/O world)
> > >
> > >         select(....)
> > >
> > >         if(FD_ISSET(copier_fd))
> > >                 run_coroutine(&copier_state);
> > >
> > >         ...
> > >
> > > and the copier might be something like
> > >
> > >         while(1)
> > >         {
> > >                 // Yes 1 at a time is dumb but this is an example..
> > >                 // Yes Im ignoring EOF for this
> > >                 if(read(copier_fd, buf[bufptr], 1)==-1)
> > >                 {
> > >                         if(errno==-EWOULDBLOCK)
> > >                         {
> > >                                 coroutine_return();
> > >                                 continue;
> > >                         }
> > >                 }
> > >                 if(bufptr==255  || buf[bufptr]=='\n')
> > >                 {
> > >                         run_coroutine(run_command, buf);
> > >                         bufptr=0;
> > >                 }
> > >                 else
> > >                         bufptr++;
> > >         }
> > >
> > > it lets you express a state machine as a set of multiple such small state
> > > machines instead.  run_coroutine() will continue a routine where it last
> > > coroutine_return()'d from. Thus in the above case we are expressing read
> > > bytes until you see a new line cleanly - not mangled in with keeping state
> > > in global structures but by using natural C local variables and code flow
> > >
> > > Alan
> > >
> > > -
> > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > > the body of a message to majordomo@vger.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > > Please read the FAQ at  http://www.tux.org/lkml/
> >
> > --
> > ---------------------------------------------------
> > Russell Leighton    russell.leighton@247media.com
> > ---------------------------------------------------
> >
> >
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> --
> Michael Rothwell
> rothwell@holly-springs.nc.us



--
---------------------------------------------------
Russell Leighton    russell.leighton@247media.com
---------------------------------------------------



  reply	other threads:[~2001-06-16 21:28 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2001-06-12 18:24 threading question ognen
2001-06-12 18:39 ` Davide Libenzi
2001-06-12 18:57 ` from dmesg: kernel BUG at inode.c:486 Olivier Sessink
2001-06-12 18:58 ` threading question Christoph Hellwig
2001-06-12 19:07   ` ognen
2001-06-12 19:15     ` Kip Macy
2001-06-12 19:29       ` Christoph Hellwig
2001-06-12 19:15     ` Christoph Hellwig
2001-06-13 12:20     ` Kurt Garloff
2001-06-13 13:35       ` J . A . Magallon
2001-06-13 14:17         ` Philips
2001-06-13 15:06           ` ognen
2001-06-12 21:44   ` Davide Libenzi
2001-06-12 21:48     ` ognen
2001-06-14 18:15       ` Alan Cox
2001-06-14 22:42         ` threading question (results after thread pooling) ognen
2001-06-14 23:00           ` Mike Castle
2001-06-12 21:58     ` threading question Albert D. Cahalan
2001-06-12 23:48       ` J . A . Magallon
2001-06-12 19:06 ` Kip Macy
2001-06-12 19:14   ` Alexander Viro
2001-06-12 19:25     ` Russell Leighton
2001-06-12 23:27       ` Mike Castle
2001-06-13 17:31   ` bert hubert
2001-06-14  6:45     ` Helge Hafting
2001-06-14 18:28   ` Alan Cox
2001-06-14 19:01     ` bert hubert
2001-06-14 19:22       ` Russell Leighton
2001-06-15 11:29       ` Anil Kumar
2001-06-14 23:05     ` J . A . Magallon
2001-06-16 14:16     ` Michael Rothwell
2001-06-16 15:19       ` Alan Cox
2001-06-16 18:33         ` Russell Leighton
2001-06-16 19:06         ` Michael Rothwell
2001-06-16 21:30           ` Russell Leighton [this message]
2001-06-12 22:41 ` Pavel Machek

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