Gidday Michael,
IIRC, I had an issue left:
I see a major deficiency in your code. Unless I am mistaken, the global
variable <done> and <cleanup_pop_arg> are accessed from two different
threads.
True.
Following the POSIX memory model, you need mutex to synchronize the
visibility.
Please educate me about the POSIX memory model ;-). Say some more
here please. Are you meaning that the change made in main are not
guaranteed to visible in the other thread, unless I use a
synchronization mechanism? (or, perhaps, a barrier?)
Oh, that's a long story. Tomorrow perhaps (I just came home, and I guess
Antje would like to spend some time with me...)
Please refer to St Butenhof's bible "Programming with POSIX Threads",
§3.4, pp88-95.
An excerpt can be found at:
http://markmail.org/message/24zdwjjkbe4dqz5o
Basically:
1) the values you write prior to pthread_create(3) can be seen in the
new thread.
2) the values you write prior to mutex_unlock(3) can be seen in any
thread that locks later the same mutex.
3) the values you write prior to terminating a thread can be seen in the
thread that joins.
4) the values you write prior to pthread_cond_{signal,broadcast}(3) can
be seen by any thread that is awakened.
Failing to comply these rules may cause your program to fail in very
subtle ways on multi-processors machine. Even if I may save here and
there a mutex; I apply those rules religiously (but, yeah, I am a
Pthreads fanatic ;-)
HTH,
Loïc.
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