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"""PyUnit testing that threads honor our signal semantics"""
import unittest
import signal
import os
import sys
from test.support import run_unittest, import_module
thread = import_module('_thread')
import time
if sys.platform[:3] in ('win', 'os2') or sys.platform=='riscos':
raise unittest.SkipTest("Can't test signal on %s" % sys.platform)
process_pid = os.getpid()
signalled_all=thread.allocate_lock()
# Issue #11223: Locks are implemented using a mutex and a condition variable of
# the pthread library on FreeBSD6. POSIX condition variables cannot be
# interrupted by signals (see pthread_cond_wait manual page).
USING_PTHREAD_COND = (sys.platform == 'freebsd6')
def registerSignals(for_usr1, for_usr2, for_alrm):
usr1 = signal.signal(signal.SIGUSR1, for_usr1)
usr2 = signal.signal(signal.SIGUSR2, for_usr2)
alrm = signal.signal(signal.SIGALRM, for_alrm)
return usr1, usr2, alrm
# The signal handler. Just note that the signal occurred and
# from who.
def handle_signals(sig,frame):
signal_blackboard[sig]['tripped'] += 1
signal_blackboard[sig]['tripped_by'] = thread.get_ident()
# a function that will be spawned as a separate thread.
def send_signals():
os.kill(process_pid, signal.SIGUSR1)
os.kill(process_pid, signal.SIGUSR2)
signalled_all.release()
class ThreadSignals(unittest.TestCase):
def test_signals(self):
# Test signal handling semantics of threads.
# We spawn a thread, have the thread send two signals, and
# wait for it to finish. Check that we got both signals
# and that they were run by the main thread.
signalled_all.acquire()
self.spawnSignallingThread()
signalled_all.acquire()
# the signals that we asked the kernel to send
# will come back, but we don't know when.
# (it might even be after the thread exits
# and might be out of order.) If we haven't seen
# the signals yet, send yet another signal and
# wait for it return.
if signal_blackboard[signal.SIGUSR1]['tripped'] == 0 \
or signal_blackboard[signal.SIGUSR2]['tripped'] == 0:
signal.alarm(1)
signal.pause()
signal.alarm(0)
self.assertEqual( signal_blackboard[signal.SIGUSR1]['tripped'], 1)
self.assertEqual( signal_blackboard[signal.SIGUSR1]['tripped_by'],
thread.get_ident())
self.assertEqual( signal_blackboard[signal.SIGUSR2]['tripped'], 1)
self.assertEqual( signal_blackboard[signal.SIGUSR2]['tripped_by'],
thread.get_ident())
signalled_all.release()
def spawnSignallingThread(self):
thread.start_new_thread(send_signals, ())
def alarm_interrupt(self, sig, frame):
raise KeyboardInterrupt
@unittest.skipIf(USING_PTHREAD_COND,
'POSIX condition variables cannot be interrupted')
def test_lock_acquire_interruption(self):
# Mimic receiving a SIGINT (KeyboardInterrupt) with SIGALRM while stuck
# in a deadlock.
# XXX this test can fail when the legacy (non-semaphore) implementation
# of locks is used in thread_pthread.h, see issue #11223.
oldalrm = signal.signal(signal.SIGALRM, self.alarm_interrupt)
try:
lock = thread.allocate_lock()
lock.acquire()
signal.alarm(1)
t1 = time.time()
self.assertRaises(KeyboardInterrupt, lock.acquire, timeout=5)
dt = time.time() - t1
# Checking that KeyboardInterrupt was raised is not sufficient.
# We want to assert that lock.acquire() was interrupted because
# of the signal, not that the signal handler was called immediately
# after timeout return of lock.acquire() (which can fool assertRaises).
self.assertLess(dt, 3.0)
finally:
signal.signal(signal.SIGALRM, oldalrm)
@unittest.skipIf(USING_PTHREAD_COND,
'POSIX condition variables cannot be interrupted')
def test_rlock_acquire_interruption(self):
# Mimic receiving a SIGINT (KeyboardInterrupt) with SIGALRM while stuck
# in a deadlock.
# XXX this test can fail when the legacy (non-semaphore) implementation
# of locks is used in thread_pthread.h, see issue #11223.
oldalrm = signal.signal(signal.SIGALRM, self.alarm_interrupt)
try:
rlock = thread.RLock()
# For reentrant locks, the initial acquisition must be in another
# thread.
def other_thread():
rlock.acquire()
thread.start_new_thread(other_thread, ())
# Wait until we can't acquire it without blocking...
while rlock.acquire(blocking=False):
rlock.release()
time.sleep(0.01)
signal.alarm(1)
t1 = time.time()
self.assertRaises(KeyboardInterrupt, rlock.acquire, timeout=5)
dt = time.time() - t1
# See rationale above in test_lock_acquire_interruption
self.assertLess(dt, 3.0)
finally:
signal.signal(signal.SIGALRM, oldalrm)
def acquire_retries_on_intr(self, lock):
self.sig_recvd = False
def my_handler(signal, frame):
self.sig_recvd = True
old_handler = signal.signal(signal.SIGUSR1, my_handler)
try:
def other_thread():
# Acquire the lock in a non-main thread, so this test works for
# RLocks.
lock.acquire()
# Wait until the main thread is blocked in the lock acquire, and
# then wake it up with this.
time.sleep(0.5)
os.kill(process_pid, signal.SIGUSR1)
# Let the main thread take the interrupt, handle it, and retry
# the lock acquisition. Then we'll let it run.
time.sleep(0.5)
lock.release()
thread.start_new_thread(other_thread, ())
# Wait until we can't acquire it without blocking...
while lock.acquire(blocking=False):
lock.release()
time.sleep(0.01)
result = lock.acquire() # Block while we receive a signal.
self.assertTrue(self.sig_recvd)
self.assertTrue(result)
finally:
signal.signal(signal.SIGUSR1, old_handler)
def test_lock_acquire_retries_on_intr(self):
self.acquire_retries_on_intr(thread.allocate_lock())
def test_rlock_acquire_retries_on_intr(self):
self.acquire_retries_on_intr(thread.RLock())
def test_interrupted_timed_acquire(self):
# Test to make sure we recompute lock acquisition timeouts when we
# receive a signal. Check this by repeatedly interrupting a lock
# acquire in the main thread, and make sure that the lock acquire times
# out after the right amount of time.
# NOTE: this test only behaves as expected if C signals get delivered
# to the main thread. Otherwise lock.acquire() itself doesn't get
# interrupted and the test trivially succeeds.
self.start = None
self.end = None
self.sigs_recvd = 0
done = thread.allocate_lock()
done.acquire()
lock = thread.allocate_lock()
lock.acquire()
def my_handler(signum, frame):
self.sigs_recvd += 1
old_handler = signal.signal(signal.SIGUSR1, my_handler)
try:
def timed_acquire():
self.start = time.time()
lock.acquire(timeout=0.5)
self.end = time.time()
def send_signals():
for _ in range(40):
time.sleep(0.02)
os.kill(process_pid, signal.SIGUSR1)
done.release()
# Send the signals from the non-main thread, since the main thread
# is the only one that can process signals.
thread.start_new_thread(send_signals, ())
timed_acquire()
# Wait for thread to finish
done.acquire()
# This allows for some timing and scheduling imprecision
self.assertLess(self.end - self.start, 2.0)
self.assertGreater(self.end - self.start, 0.3)
# If the signal is received several times before PyErr_CheckSignals()
# is called, the handler will get called less than 40 times. Just
# check it's been called at least once.
self.assertGreater(self.sigs_recvd, 0)
finally:
signal.signal(signal.SIGUSR1, old_handler)
def test_main():
global signal_blackboard
signal_blackboard = { signal.SIGUSR1 : {'tripped': 0, 'tripped_by': 0 },
signal.SIGUSR2 : {'tripped': 0, 'tripped_by': 0 },
signal.SIGALRM : {'tripped': 0, 'tripped_by': 0 } }
oldsigs = registerSignals(handle_signals, handle_signals, handle_signals)
try:
run_unittest(ThreadSignals)
finally:
registerSignals(*oldsigs)
if __name__ == '__main__':
test_main()
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