Programs using threading tend to lock up consistently -- it seems that some
threads are either never unblocked, or they never exit. Same code on rhl-7.3
(python2) runs without locking issues. Could this be caused by NPTL?

Here is the code I'm using:

#!/usr/bin/python2 -tt
import threading
import socket
import random

class TestThread(threading.Thread):
    def __init__(self, ip, semaphore):
        threading.Thread.__init__(self)
        self.ip = ip
        self.semaphore = semaphore
        
    def run(self):
        self.semaphore.acquire()
        try:
            host = socket.gethostbyaddr(self.ip)
            self.host = host[0]
        except:
            self.host = self.ip
        print '%s resolves to %s' % (self.ip, self.host)
        self.semaphore.release()

semaphore = threading.Semaphore(50)

threads = []
for i in range(0, 100):
    a = random.randint(1, 250)
    b = random.randint(1, 250)
    ip = '152.3.%d.%d' % (a, b)
    t = TestThread(ip, semaphore)
    threads.append(t)
    t.start()

hosts = {}
for t in threads:
    t.join()
    hosts[t.ip] = t.host

print 'Results:'
print hosts