def test_trashcan_threads(self):
# Issue #13992: trashcan mechanism should be thread-safe
NESTING = 60
N_THREADS = 2
def sleeper_gen():
"""A generator that releases the GIL when closed or dealloc'ed."""
try:
yield
finally:
time.sleep(0.000001)
class C(list):
# Appending to a list is atomic, which avoids the use of a lock.
inits = []
dels = []
def __init__(self, alist):
self[:] = alist
C.inits.append(None)
def __del__(self):
# This __del__ is called by subtype_dealloc().
C.dels.append(None)
# `g` will release the GIL when garbage-collected. This
# helps assert subtype_dealloc's behaviour when threads
# switch in the middle of it.
g = sleeper_gen()
next(g)
# Now that __del__ is finished, subtype_dealloc will proceed
# to call list_dealloc, which also uses the trashcan mechanism.
def make_nested():
"""Create a sufficiently nested container object so that the
trashcan mechanism is invoked when deallocating it."""
x = C([])
for i in range(NESTING):
x = [C([x])]
del x
def run_thread():
"""Exercise make_nested() in a loop."""
while not exit:
make_nested()
old_switchinterval = sys.getswitchinterval()
sys.setswitchinterval(1e-5)
try:
exit = []
threads = []
for i in range(N_THREADS):
t = threading.Thread(target=run_thread)
threads.append(t)
with start_threads(threads, lambda: exit.append(1)):
time.sleep(1.0)
finally:
sys.setswitchinterval(old_switchinterval)
gc.collect()
self.assertEqual(len(C.inits), len(C.dels))
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