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#!/usr/bin/python3
import errno
import fcntl
import os
import signal
import struct
import time
def handler(signum, frame):
pass
def lock_two(f1, f2):
lockdata = struct.pack('hhllhh', fcntl.F_WRLCK, 0, 0, 10, 0, 0)
fcntl.fcntl(f1, fcntl.F_SETLKW, lockdata)
time.sleep(10)
# don't wait forever
signal.signal(signal.SIGALRM, handler)
signal.alarm(10)
exitcode = 0
try:
fcntl.fcntl(f2, fcntl.F_SETLKW, lockdata)
except IOError as e:
if e.errno == errno.EDEADLK:
exitcode = 1
elif e.errno == errno.EINTR:
exitcode = 2
else:
exitcode = 3
os._exit(exitcode)
def main():
pid1 = os.fork()
if pid1 == 0:
f1 = open("testfile1", 'w')
f2 = open("testfile2", 'w')
lock_two(f1, f2)
pid2 = os.fork()
if pid2 == 0:
f1 = open("testfile2", 'w')
f2 = open("testfile3", 'w')
lock_two(f1, f2)
pid3 = os.fork()
if pid3 == 0:
f1 = open("testfile3", 'w')
f2 = open("testfile1", 'w')
lock_two(f1, f2)
deadlk_count = 0
i = 0
while i < 3:
pid, status = os.wait()
exitcode = status >> 8
if exitcode == 1:
deadlk_count += 1
elif exitcode != 0:
raise RuntimeError("unexpect exit code of child")
i += 1
if deadlk_count != 1:
raise RuntimeError("unexpect count of EDEADLK")
print('ok')
main()
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