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#!/usr/bin/python3
from contextlib import contextmanager
import errno
import fcntl
import signal
import struct
@contextmanager
def timeout(seconds):
def timeout_handler(signum, frame):
raise InterruptedError
orig_handler = signal.signal(signal.SIGALRM, timeout_handler)
try:
signal.alarm(seconds)
yield
finally:
signal.alarm(0)
signal.signal(signal.SIGALRM, orig_handler)
"""
introduced by Linux 3.15
"""
fcntl.F_OFD_GETLK = 36
fcntl.F_OFD_SETLK = 37
fcntl.F_OFD_SETLKW = 38
def main():
f1 = open("testfile", 'w')
f2 = open("testfile", 'w')
fcntl.flock(f1, fcntl.LOCK_SH | fcntl.LOCK_NB)
"""
is flock interruptible?
"""
with timeout(5):
try:
fcntl.flock(f2, fcntl.LOCK_EX)
except InterruptedError:
pass
else:
raise RuntimeError("expect flock to block")
fcntl.flock(f1, fcntl.LOCK_UN)
lockdata = struct.pack('hhllhh', fcntl.F_WRLCK, 0, 0, 10, 0, 0)
try:
fcntl.fcntl(f1, fcntl.F_OFD_SETLK, lockdata)
except IOError as e:
if e.errno != errno.EINVAL:
raise
else:
print('kernel does not support fcntl.F_OFD_SETLK')
return
lockdata = struct.pack('hhllhh', fcntl.F_WRLCK, 0, 10, 10, 0, 0)
fcntl.fcntl(f2, fcntl.F_OFD_SETLK, lockdata)
"""
is posix lock interruptible?
"""
with timeout(5):
try:
lockdata = struct.pack('hhllhh', fcntl.F_WRLCK, 0, 0, 0, 0, 0)
fcntl.fcntl(f2, fcntl.F_OFD_SETLKW, lockdata)
except InterruptedError:
pass
else:
raise RuntimeError("expect posix lock to block")
"""
file handler 2 should still hold lock on 10~10
"""
try:
lockdata = struct.pack('hhllhh', fcntl.F_WRLCK, 0, 10, 10, 0, 0)
fcntl.fcntl(f1, fcntl.F_OFD_SETLK, lockdata)
except IOError as e:
if e.errno == errno.EAGAIN:
pass
else:
raise RuntimeError("expect file handler 2 to hold lock on 10~10")
lockdata = struct.pack('hhllhh', fcntl.F_UNLCK, 0, 0, 0, 0, 0)
fcntl.fcntl(f1, fcntl.F_OFD_SETLK, lockdata)
fcntl.fcntl(f2, fcntl.F_OFD_SETLK, lockdata)
print('ok')
main()
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