Subj : Question : usage of conditional variables.
To   : comp.programming.threads
From : Jamie
Date : Wed Jun 08 2005 06:22 pm

Hi there,

I am quite new to multi-threaded programming, and I am now trying to
make two threads and communicate with each other by using conditional
variables. However, I got stuck in a problem. If anyone give me any
idea, I would really appreciate it!!


Program Summary:
  1) Making two threads (tA, tB)
  2) tA send a conditional signal to tB
  3) tB recv a conditional signal
  4) tB send a conditional signal to tA
  5) tA recv a conditional signal
  6) repeat through 2 to 5.

Issue:
 I tried to run this program with a set of mutex & conditional variable
and also two sets of mutex & conditional variables(one for tA->tB, the
other for tB->tA). But same issue happened.
I ran it on VMWare and it's quite slow. When I run around 300 loop, it
looks working well, it works as the order I expected. However, when I
increase the number of loop more than that, the order get tangled and
it looks waiting a signal forever and don't get a signal at all..

Should it be guaranted that pthread_cond_wait() is called before
pthread_cond_signal() is called?

.