cpython/Lib/test/test_fork1.py

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"""This test checks for correct fork() behavior.
We want fork1() semantics -- only the forking thread survives in the
child after a fork().
On some systems (e.g. Solaris without posix threads) we find that all
active threads survive in the child after a fork(); this is an error.
"""
import os, sys, time, thread
LONGSLEEP = 2
SHORTSLEEP = 0.5
NUM_THREADS = 4
alive = {}
def f(id):
while 1:
alive[id] = os.getpid()
try:
time.sleep(SHORTSLEEP)
except IOError:
pass
def main():
for i in range(NUM_THREADS):
thread.start_new(f, (i,))
time.sleep(LONGSLEEP)
a = alive.keys()
a.sort()
assert a == range(NUM_THREADS)
prefork_lives = alive.copy()
cpid = os.fork()
if cpid == 0:
# Child
time.sleep(LONGSLEEP)
n = 0
for key in alive.keys():
if alive[key] != prefork_lives[key]:
n = n+1
os._exit(n)
else:
# Parent
spid, status = os.waitpid(cpid, 0)
assert spid == cpid
assert status == 0, "cause = %d, exit = %d" % (status&0xff, status>>8)
main()