Re: Beepcore-c-users digest, Vol 1 #62 - 2 msgs

mtr2 <[email protected]> Wed, 23 Oct 2002 06:36:57 -0700
Newsgroups	gmane.network.beep.beepcore.c.general
Message-ID	<[email protected]>
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> Today's Topics:
>
>    1. Re: why yield? (William J. Mills)
>    2. Re: why yield? (Doug Royer)
>
> --__--__--
>
> Message: 1
> Date: Mon, 21 Oct 2002 13:37:10 -0700
> From: "William J. Mills" <[email protected]>
> To: Chris Hanson <[email protected]>
> Cc: [email protected]
> Subject: Re: [Beepcore-c-users] why yield?
>
> I think it has to do with forcing a yield to the other threads in the
> case that the poll grabs the CPU.  Not sure though what the specific
> cases are where we needed this.  Might be a holdover from previous
> thread/race debuggig or it might be current and needed.
>
> -bill
>
> On Mon, Oct 21, 2002 at 10:53:12AM -0400, Chris Hanson wrote:
> > I am puzzled by the YIELD() in the code below from tcp_bp_listen().
> > (I've edited the code below to remove the win32 conditionalizations.)
> > Can someone explain why there's any reason to YIELD() here?  It seems
> > to me that the program simply loops back to poll(), which will block
> > if there isn't any input.
> >
> > ----------------------------------------
> >     do {
> >         int   msecs = 5;
> >
> >         if (poll(ready, 1, msecs) <= 0)
> >         {
> >             if (TERMINATE) {
> >                 return NULL;
> >             }
> >             YIELD();
> >             continue;
> >         }
> > ----------------------------------------
> >
> >
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> Message: 2
> Date: Mon, 21 Oct 2002 16:31:12 -0600
> From: Doug Royer <[email protected]>
> Reply-To: [email protected]
> To: [email protected]
> Subject: Re: [Beepcore-c-users] why yield?
>
> This is a cryptographically signed message in MIME format.
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> --------------ms080908000206020902030503
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>
> On POSIX system, I think the 'poll()' must do a 'pthread_testcancel()'
> and should be ASYNC-SAFE, so perhaps the YIELD() is for non-POSIX
> implementations.
>
> William J. Mills wrote:
> > I think it has to do with forcing a yield to the other threads in the
> > case that the poll grabs the CPU.  Not sure though what the specific
> > cases are where we needed this.  Might be a holdover from previous
> > thread/race debuggig or it might be current and needed.
> >
> > -bill
> >
> >
> >
> > On Mon, Oct 21, 2002 at 10:53:12AM -0400, Chris Hanson wrote:
> >
> >>I am puzzled by the YIELD() in the code below from tcp_bp_listen().
> >>(I've edited the code below to remove the win32 conditionalizations.)
> >>Can someone explain why there's any reason to YIELD() here?  It seems
> >>to me that the program simply loops back to poll(), which will block
> >>if there isn't any input.
> >>
> >>----------------------------------------
> >>    do {
> >>        int   msecs = 5;
> >>
> >>        if (poll(ready, 1, msecs) <= 0)
> >>        {
> >>            if (TERMINATE) {
> >>                return NULL;
> >>            }
> >>            YIELD();
> >>            continue;
> >>        }
> >>----------------------------------------
> >>
> >>
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> --
> -
> Doug Royer                       Work: (208)612-INET
> [email protected]                   Fax:  (866)594-8574
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> http://Royer.com/People/Doug
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This transport engine for beep once could be configured to run a group of
threads where each thread can run the code in question.   For example, each
thread call's the poll command where each thread handles x number of file
descriptors, where the YIELD macro would be called if there was nothing to do.
Looks like MAX_POLL_THREADS is now always 1 so your right, the YIELD it is not
needed or should only be called if MAX_POLL_THREADS is more than 1.

MarkTRichardson - mtr2.




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