Getting Squeak to stop hanging on file I/O (and to start blocking threads on serial)?

David T. Lewis lewis at
Sat Apr 13 18:11:30 UTC 2002

On Sat, Apr 13, 2002 at 08:51:48AM -0700, Ned Konz wrote:
> On Saturday 13 April 2002 07:37 am, David T. Lewis wrote:
> > Yes, I would like to see this done, but I'm not sure about using
> > timeouts to implement it.
> I wasn't suggesting using timeouts to implement it. I just thought 
> that providing access to the native OS serial character/minimum read 
> API (on Unix, VMIN, VTIME in termios; there are corresponding 
> controls in Windows) could give better fine-tuning.

Ah, right. That sounds good.

> > The generalized aio support which Lex added to the Unix VM provides
> > the necessary underpinnings for Unix platforms. I not sure how it
> > would be done for Windows, Mac and RiscOS, but I'm sure that a
> > reading of the tcl source will provide the necessary clues.
> Perhaps the aio support would work on those platforms. It just uses 
> select(); isn't this pretty generally available? Ruby, for instance, 
> works on at least Unix and windows and never blocks the entire 
> process on file I/O. I remember that Windows' select() is specific to 
> sockets, but there is a wait for event there.

I'm not sure how it's done on non-unix platforms. Chances are that tcl,
Ruby, Perl and such have all figured it out. Hmmm, must be on one of
these CDROM's someplace... I'll have to look around.

> > In OSProcess for Windows, I'm struggling with trying to implement
> > nonblocking pipes, and it's just plain ugly (I have something
> > working, but I'm still getting occasional Windows crashes in
> > testing). If there is a way to do a read with timeout on a Win32
> > anonymous pipe, please enlighten me before I embarrass myself
> > further.
> Couldn't you just start another thread and do a non-blocking read on 
> the pipe, then signal a (Windows) semaphore? You could then do 
> WaitForMultipleEvents on all the semaphores...

That's similar to what I'm doing. Start a Win32 thread that does a
read, then Interpreter>>signalSemaphoreWithIndex when the read completes.
It works, but it's complicated and (pending further debugging) unreliable.
Debugging it frequently consists of turning off the computer, rebooting,
and trying something different. Grump.


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