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Issue #9573: os.fork now works when triggered as a side effect of import (the wisdom of actually relying on this remains questionable!)

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This commit is contained in:
Nick Coghlan 2010-12-02 04:11:46 +00:00
parent d2bb830edc
commit b2ddf7979d
3 changed files with 57 additions and 5 deletions
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46
Lib/test/test_fork1.py
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@ -8,13 +8,14 @@ import sys
import time
from test.fork_wait import ForkWait
from test.support import run_unittest, reap_children, get_attribute, import_module
from test.support import (run_unittest, reap_children, get_attribute,
import_module, verbose)
threading = import_module('threading')
# Skip test if fork does not exist.
get_attribute(os, 'fork')
class ForkTest(ForkWait):
def wait_impl(self, cpid):
for i in range(10):
@ -28,7 +29,8 @@ class ForkTest(ForkWait):
self.assertEqual(spid, cpid)
self.assertEqual(status, 0, "cause = %d, exit = %d" % (status&0xff, status>>8))
def test_import_lock_fork(self):
def test_threaded_import_lock_fork(self):
"""Check fork() in main thread works while a subthread is doing an import"""
import_started = threading.Event()
fake_module_name = "fake test module"
partial_module = "partial"
@ -45,11 +47,16 @@ class ForkTest(ForkWait):
import_started.wait()
pid = os.fork()
try:
# PyOS_BeforeFork should have waited for the import to complete
# before forking, so the child can recreate the import lock
# correctly, but also won't see a partially initialised module
if not pid:
m = __import__(fake_module_name)
if m == complete_module:
os._exit(0)
else:
if verbose > 1:
print("Child encountered partial module")
os._exit(1)
else:
t.join()
@ -63,6 +70,39 @@ class ForkTest(ForkWait):
except OSError:
pass
def test_nested_import_lock_fork(self):
"""Check fork() in main thread works while the main thread is doing an import"""
# Issue 9573: this used to trigger RuntimeError in the child process
def fork_with_import_lock(level):
release = 0
in_child = False
try:
try:
for i in range(level):
imp.acquire_lock()
release += 1
pid = os.fork()
in_child = not pid
finally:
for i in range(release):
imp.release_lock()
except RuntimeError:
if in_child:
if verbose > 1:
print("RuntimeError in child")
os._exit(1)
raise
if in_child:
os._exit(0)
self.wait_impl(pid)
# Check this works with various levels of nested
# import in the main thread
for level in range(5):
fork_with_import_lock(level)
def test_main():
run_unittest(ForkTest)
reap_children()