I added a timeout of 30 minutes to regrtest. On "x86 FreeBSD 7.2 3.x" and "x86 FreeBSD 3.x" buildbot, test_sendall_interrupted() of test_socket does timeout after 30 minutes:
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...
[201/354] test_socket
Thread 0x28401040:
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/test/test_socket.py", line 729 in check_sendall_interrupted
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/test/test_socket.py", line 740 in test_sendall_interrupted
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/unittest/case.py", line 387 in _executeTestPart
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/unittest/case.py", line 442 in run
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/unittest/case.py", line 494 in __call__
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/unittest/suite.py", line 105 in run
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/unittest/suite.py", line 67 in __call__
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/unittest/suite.py", line 105 in run
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/unittest/suite.py", line 67 in __call__
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/test/support.py", line 1078 in run
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/test/support.py", line 1166 in _run_suite
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/test/support.py", line 1192 in run_unittest
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd7/build/Lib/test/test_socket.py", line 2052 in test_main
  File "./Lib/test/regrtest.py", line 1032 in runtest_inner
  File "./Lib/test/regrtest.py", line 826 in runtest
  File "./Lib/test/regrtest.py", line 650 in main
  File "./Lib/test/regrtest.py", line 1607 in <module>
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http://www.python.org/dev/buildbot/all/builders/x86%20FreeBSD%207.2%203.x/builds/1644/steps/test/logs/stdio
another example:
http://www.python.org/dev/buildbot/all/builders/x86%20FreeBSD%203.x/builds/1344/steps/test/logs/stdio

It looks like the test should be done in less than 5 seconds. Extract of the code (with_timeout=False for test_sendall_interrupted):
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def check_sendall_interrupted(self, with_timeout):
        # socketpair() is not stricly required, but it makes things easier.
        if not hasattr(signal, 'alarm') or not hasattr(socket, 'socketpair'):
            self.skipTest("signal.alarm and socket.socketpair required for this test")
        # Our signal handlers clobber the C errno by calling a math function
        # with an invalid domain value.
        def ok_handler(*args):
            self.assertRaises(ValueError, math.acosh, 0)
        def raising_handler(*args):
            self.assertRaises(ValueError, math.acosh, 0)
            1 // 0
        c, s = socket.socketpair()
        old_alarm = signal.signal(signal.SIGALRM, raising_handler)
        try:
            if with_timeout:
                # Just above the one second minimum for signal.alarm
                c.settimeout(1.5)
            with self.assertRaises(ZeroDivisionError):
                signal.alarm(1)
                c.sendall(b"x" * (1024**2)) <~~~~ HERE
            if with_timeout:
                signal.signal(signal.SIGALRM, ok_handler)
                signal.alarm(1)
                self.assertRaises(socket.timeout, c.sendall, b"x" * (1024**2))
        finally:
            signal.signal(signal.SIGALRM, old_alarm)
            c.close()
            s.close()
-------------------------
I suppose that sendall() should be interrupted by SIGALRM. sendall() calls PyErr_CheckSignals() after each system call to send(), and exits with an error if PyErr_CheckSignals() returns NULL. If send() fails with EINTR error, sendall() retries calls send() again (in a loop).

I don't know if this hang is new or not, and if it is (or not) a border effect of the timeout feature of regrtest...

But test_signal don't always fail, it looks like a race condition.