Commit | Line | Data |
---|---|---|
920dae64 AT |
1 | # This is a variant of the very old (early 90's) file |
2 | # Demo/threads/bug.py. It simply provokes a number of threads into | |
3 | # trying to import the same module "at the same time". | |
4 | # There are no pleasant failure modes -- most likely is that Python | |
5 | # complains several times about module random having no attribute | |
6 | # randrange, and then Python hangs. | |
7 | ||
8 | import thread | |
9 | from test.test_support import verbose, TestSkipped | |
10 | ||
11 | critical_section = thread.allocate_lock() | |
12 | done = thread.allocate_lock() | |
13 | ||
14 | def task(): | |
15 | global N, critical_section, done | |
16 | import random | |
17 | x = random.randrange(1, 3) | |
18 | critical_section.acquire() | |
19 | N -= 1 | |
20 | # Must release critical_section before releasing done, else the main | |
21 | # thread can exit and set critical_section to None as part of global | |
22 | # teardown; then critical_section.release() raises AttributeError. | |
23 | finished = N == 0 | |
24 | critical_section.release() | |
25 | if finished: | |
26 | done.release() | |
27 | ||
28 | # Tricky: When regrtest imports this module, the thread running regrtest | |
29 | # grabs the import lock and won't let go of it until this module returns. | |
30 | # All other threads attempting an import hang for the duration. Since | |
31 | # this test spawns threads that do little *but* import, we can't do that | |
32 | # successfully until after this module finishes importing and regrtest | |
33 | # regains control. To make this work, a special case was added to | |
34 | # regrtest to invoke a module's "test_main" function (if any) after | |
35 | # importing it. | |
36 | ||
37 | def test_main(): # magic name! see above | |
38 | global N, done | |
39 | ||
40 | import imp | |
41 | if imp.lock_held(): | |
42 | # This triggers on, e.g., from test import autotest. | |
43 | raise TestSkipped("can't run when import lock is held") | |
44 | ||
45 | done.acquire() | |
46 | for N in (20, 50) * 3: | |
47 | if verbose: | |
48 | print "Trying", N, "threads ...", | |
49 | for i in range(N): | |
50 | thread.start_new_thread(task, ()) | |
51 | done.acquire() | |
52 | if verbose: | |
53 | print "OK." | |
54 | done.release() | |
55 | ||
56 | if __name__ == "__main__": | |
57 | test_main() |