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test_signal: Signal handling on the Tru64 buildbot 

appears to be utterly insane.  Plug some theoretical
insecurities in the test script:

- Verify that the SIGALRM handler was actually installed.

- Don't call alarm() before the handler is installed.

- Move everything that can fail inside the try/finally,
  so the test cleans up after itself more often.

- Try sending all the expected signals in
  force_test_exit(), not just SIGALRM.  Since that was
  fixed to actually send SIGALRM (instead of invisibly
  dying with an AttributeError), we've seen that sending
  SIGALRM alone does not stop this from hanging.

- Move the "kill the child" business into the finally
  clause, so the child doesn't survive test failure
  to send SIGALRM to other tests later (there are also
  baffling SIGALRM-related failures in test_socket).

- Cancel the alarm in the finally clause -- if the
  test dies early, we again don't want SIGALRM showing
  up to confuse a later test.

Alas, this still relies on timing luck wrt the spawned
script that sends the test signals, but it's hard to see
how waiting for seconds can so often be so unlucky.

test_threadedsignals:  curiously, this test never fails
on Tru64, but doesn't normally signal SIGALRM.  Anyway,
fixed an obvious (but probably inconsequential) logic
error.
This commit is contained in:
Tim Peters 2006-08-12 04:42:47 +00:00
parent ebcf8759bb
commit 1742f3331f
2 changed files with 88 additions and 68 deletions
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128
Lib/test/test_signal.py
View File

@ -6,6 +6,8 @@ import os, sys, time
if sys.platform[:3] in ('win', 'os2') or sys.platform=='riscos':
raise TestSkipped, "Can't test signal on %s" % sys.platform
MAX_DURATION = 20 # Entire test should last at most 20 sec.
if verbose:
x = '-x'
else:
@ -34,7 +36,7 @@ def handlerA(*args):
global a_called
a_called = True
if verbose:
print "handlerA", args
print "handlerA invoked", args
class HandlerBCalled(Exception):
pass
@ -43,97 +45,103 @@ def handlerB(*args):
global b_called
b_called = True
if verbose:
print "handlerB", args
print "handlerB invoked", args
raise HandlerBCalled, args
MAX_DURATION = 20
signal.alarm(MAX_DURATION) # Entire test should last at most 20 sec.
# Set up a child to send signals to us (the parent) after waiting long
# enough to receive the alarm. It seems we miss the alarm for some
# reason. This will hopefully stop the hangs on Tru64/Alpha.
# Alas, it doesn't. Tru64 appears to miss all the signals at times, or
# seemingly random subsets of them, and nothing done in force_test_exit
# so far has actually helped.
def force_test_exit():
# Sigh, both imports seem necessary to avoid errors.
import os
fork_pid = os.fork()
if fork_pid:
# In parent.
return fork_pid
# In child.
import os, time
try:
# Wait 5 seconds longer than the expected alarm to give enough
# time for the normal sequence of events to occur. This is
# just a stop-gap to try to prevent the test from hanging.
time.sleep(MAX_DURATION + 5)
print >> sys.__stdout__, ' child should not have to kill parent'
for signame in "SIGHUP", "SIGUSR1", "SIGUSR2", "SIGALRM":
os.kill(pid, getattr(signal, signame))
print >> sys.__stdout__, " child sent", signame, "to", pid
time.sleep(1)
finally:
os._exit(0)
# Install handlers.
hup = signal.signal(signal.SIGHUP, handlerA)
usr1 = signal.signal(signal.SIGUSR1, handlerB)
usr2 = signal.signal(signal.SIGUSR2, signal.SIG_IGN)
alrm = signal.signal(signal.SIGALRM, signal.default_int_handler)
try:
signal.alarm(MAX_DURATION)
vereq(signal.getsignal(signal.SIGHUP), handlerA)
vereq(signal.getsignal(signal.SIGUSR1), handlerB)
vereq(signal.getsignal(signal.SIGUSR2), signal.SIG_IGN)
vereq(signal.getsignal(signal.SIGALRM), signal.default_int_handler)
# Try to ensure this test exits even if there is some problem with alarm.
# Tru64/Alpha often hangs and is ultimately killed by the buildbot.
fork_pid = force_test_exit()
try:
signal.signal(4242, handlerB)
raise TestFailed, 'expected ValueError for invalid signal # to signal()'
signal.getsignal(4242)
raise TestFailed('expected ValueError for invalid signal # to '
'getsignal()')
except ValueError:
pass
try:
signal.getsignal(4242)
raise TestFailed, 'expected ValueError for invalid signal # to getsignal()'
signal.signal(4242, handlerB)
raise TestFailed('expected ValueError for invalid signal # to '
'signal()')
except ValueError:
pass
try:
signal.signal(signal.SIGUSR1, None)
raise TestFailed, 'expected TypeError for non-callable'
raise TestFailed('expected TypeError for non-callable')
except TypeError:
pass
# Set up a child to send an alarm signal to us (the parent) after waiting
# long enough to receive the alarm. It seems we miss the alarm for some
# reason. This will hopefully stop the hangs on Tru64/Alpha.
def force_test_exit():
# Sigh, both imports seem necessary to avoid errors.
import os
fork_pid = os.fork()
if fork_pid == 0:
# In child
import os, time
try:
# Wait 5 seconds longer than the expected alarm to give enough
# time for the normal sequence of events to occur. This is
# just a stop-gap to prevent the test from hanging.
time.sleep(MAX_DURATION + 5)
print >> sys.__stdout__, ' child should not have to kill parent'
for i in range(3):
os.kill(pid, signal.SIGALRM)
print >> sys.__stdout__, " child sent SIGALRM to", pid
finally:
os._exit(0)
# In parent (or error)
return fork_pid
try:
# Launch an external script to send us signals.
# We expect the external script to:
# send HUP, which invokes handlerA to set a_called
# send USR1, which invokes handlerB to set b_called and raise
# HandlerBCalled
# send USR2, which is ignored
#
# Then we expect the alarm to go off, and its handler raises
# KeyboardInterrupt, finally getting us out of the loop.
os.system(script)
# Try to ensure this test exits even if there is some problem with alarm.
# Tru64/Alpha sometimes hangs and is ultimately killed by the buildbot.
fork_pid = force_test_exit()
print "starting pause() loop..."
try:
if verbose:
print "starting pause() loop..."
while 1:
try:
if verbose:
print "call pause()..."
try:
signal.pause()
if verbose:
print "pause() returned"
except HandlerBCalled:
if verbose:
print "HandlerBCalled exception caught"
else:
pass
except KeyboardInterrupt:
if verbose:
print "KeyboardInterrupt (assume the alarm() went off)"
# Forcibly kill the child we created to ping us if there was a test error.
try:
# Make sure we don't kill ourself if there was a fork error.
if fork_pid > 0:
os.kill(fork_pid, signal.SIGKILL)
except:
# If the child killed us, it has probably exited. Killing a
# non-existant process will raise an error which we don't care about.
pass
print "KeyboardInterrupt (the alarm() went off)"
if not a_called:
print 'HandlerA not called'
@ -142,6 +150,18 @@ try:
print 'HandlerB not called'
finally:
# Forcibly kill the child we created to ping us if there was a test error.
try:
# Make sure we don't kill ourself if there was a fork error.
if fork_pid > 0:
os.kill(fork_pid, signal.SIGKILL)
except:
# If the child killed us, it has probably exited. Killing a
# non-existent process will raise an error which we don't care about.
pass
# Restore handlers.
signal.alarm(0) # cancel alarm in case we died early
signal.signal(signal.SIGHUP, hup)
signal.signal(signal.SIGUSR1, usr1)
signal.signal(signal.SIGUSR2, usr2)

2
Lib/test/test_threadsignals.py
View File

@ -49,7 +49,7 @@ class ThreadSignals(unittest.TestCase):
# and might be out of order.) If we haven't seen
# the signals yet, send yet another signal and
# wait for it return.
if signal_blackboard[signal.SIGUSR2]['tripped'] == 0 \
if signal_blackboard[signal.SIGUSR1]['tripped'] == 0 \
or signal_blackboard[signal.SIGUSR2]['tripped'] == 0:
signal.alarm(1)
signal.pause()