http://www.python.org/dev/buildbot/all/builders/x86 FreeBSD 6.4 3.x/builds/1570/steps/test/logs/stdio

"""
[ 29/356] test_signal
Fatal error 'mutex is on list' at line 540 in file /usr/src/lib/libpthread/thread/thr_mutex.c (errno = 22)
test test_signal failed -- Traceback (most recent call last):
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd/build/Lib/test/test_signal.py", line 669, in test_sigwait_thread
    self.check_sigwait(test, signal.SIGUSR1)
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd/build/Lib/test/test_signal.py", line 632, in check_sigwait
    self.assertEqual(os.waitpid(pid, 0), (pid, 0))
AssertionError: Tuples differ: (50592, 134) != (50592, 0)

First differing element 1:
134
0

- (50592, 134)
?         ^^^

+ (50592, 0)
?         ^
"""


Fatal error 'mutex is on list' at line 540 in file /usr/src/lib/libpthread/thread/thr_mutex.c (errno = 22)

In a multi-threaded program, we're only allowed to call async-safe functions between fork() and exec() in the child process (well, taken literaly this means we shouldn't run Python at all after fork...). It looks like FreeBSD 6.4 doesn't like new threads after fork() :
http://unix.derkeiler.com/Mailing-Lists/FreeBSD/hackers/2008-03/msg00108.html

test_sigwait_thread should either be skipped on FreeBSD 6 (it seems to pass on FreeBSD 7), or removed altogether.