Re: threading question

[Michael Rothwell <rothwell@holly-springs.nc.us>]

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