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Re: How is pthread_self() implemented?
Will Bryant wrote:
John Bossom's original design also allows for pre-existing Win32 threads
to use any POSIX routines, and therefore fully interact with POSIX
threads, by creating a one-time-only on-the-fly detached POSIX thread
handle for the Win32 thread.
So it is safe to use all pthreads-win32 functions from threads not created
using the pthreads interface? I have an application where nearly all of the
code only needs to use standard windows threads, but there are a couple of
condition variables that I'd like to be able to use...
Note that non-POSIX threads are regarded by pthreads-win32 as detached
and deferred-cancelable initially. However, I don't think there's any
reason a non-POSIX thread can't subsequently change it's cancelability
type. There's no way it can make itself joinable though. Apart from
that, just about everything should work.
In particular, for condition variables I haven't proven the following
but I believe it should all work properly. And since this should work,
then so should POSIX read-write locks. Note that you odn't need to
explicitly call pthread_self() unless you need the POSIX thread handle.
Any routine that needs it internally will cause the POSIX handle to be
created implicitly.
// Global
pthread_t posixGuest[MAX_GUESTS];
pthread_mutex_t CVLock = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t CV = PTHREAD_COND_INITIALIZER;
int champaigneChilled = 0;
int cakeIced = 0;
int chaos = 0;
int mayhem = 0;
long guest = 0;
// Thread A (Win32 or POSIX thread):
// Party guest thread
...
if ((guest = InterLockedIncremement(&guest)) >= MAX_GUESTS)
return(gateCrasher);
posixGuest[guest] = pthread_self(); // Only needed sometimes e.g.
see thread D
// Mingle
pthread_mutex_lock(&CVLock);
pthread_cleanup_push(pthread_mutex_unlock(&CVLock));
while ( ! (champaigneChilled && cakeIced ) ) {
pthread_cond_wait(&CV, &CVLock);
}
pthread_cleanup_pop(1);
toastBirthdaySubject();
eatCake();
...
// Thread B (Win32 or POSIX thread):
// Ice cake thread
...
cakeIced = 1;
pthread_cond_broadcast(&CV);
...
// Thread C (Win32 or POSIX thread):
// Chill champaigne thread
...
champaigeChilled = 1;
pthread_cond_broadcast(&CV);
...
// Thread D (Win32 or POSIX thread):
// Monitor party thread
...
if (chaos && meyhem) {
// Evict our guests
for (i = 0; i < MAX_GUESTS && pthread_kill(posixGuest[i], 0) ==
0; i++)
pthread_cancel(posixGuest[i]);
}
...
Regards.
Ross