Re: [9fans] thread confusion

[Axel Belinfante <Axel.Belinfante@cs.utwente.nl>]

> But leave the proc alone and figure out the pipe close
> bug instead.  The most likely problem is that you haven't
> actually closed the other side of the pipe completely.
> For example, maybe you have forked a child who inherited
> a copy of that fd, and that child is holding the pipe up.

the problem seems to be that at both ends of the pipe
a read is 'hanging'.
(one from tlsClient, and one from my own pipe reader proc)
If I in this situation close (both ends of) the pipe,
it doesn't work.

I have tried to mimic the situation in a small
test program, and there I found:

if I first close one randomly chosen end of the pipe,
and then do a zero-length write at the other end and
then close that end, it works.
It also works if I first close one end of the pipe,
and then do the zero-length write and close at the
other end.

is this a correct procedure, or would another be preferred?




> Programming with notes or signals is asking for trouble.

I do use a timer, by having a proc that repeatedly sleeps
and decrements a counter, and when the counter reaches
zero it sends a (nil) timeout message on a channel.
in alts I not only wait for the io channels but
also for the timer timeout channel.

the question is how to start and reset the timer.
I have been thinking about using channels for that
too, but that seems deadlock prone: how to avoid
the case where I want to send a reset message to
the timer when the timer wants to send an expiration
message to me?
could I work around that by having a timer thread
in the same process with the main thread(s) that use it,
and a separate clock proc (process) that does regular
sleeps to generate regular tick messages?
the timer thread forever does an alt to
 - receive timer start message (contains timer and timeout value)
 - receive timer reset message (contains timer)
 - receive tick message, triggers decrement of counters
   and sending of timeout message if counter reaches zero
the clock proc forever sleeps and sends tick messages
to the timer thread.


Axel.