add xtest_signal.py which reproduces SIGCHLD being missed (fixed in...

add xtest_signal.py which reproduces SIGCHLD being missed (fixed in https://bitbucket.org/denis/gevent/changeset/adb8b5ac698c)

greentest/xtest_signal.py

+"""This is the extract from test_signal.py that runs forever until it fails.
+
+It reproduces the bug where SIGCHLD either not delivered or somehow lost and thus
+if libev does not poll waitpid() periodically, popen.wait() blocks forever.
+
+The patch that fixes it: https://bitbucket.org/denis/gevent/changeset/adb8b5ac698c
+Comment out the lines in ev.c that start the timer if you want to see for yourself.
+
+Reproduced on my machine (Linux 3.0.0-16-generic) with backend epoll and select.
+
+With signalfd enabled (GEVENT_BACKEND=signalfd) it seems to work OK or at least takes
+much longer to reproduce.
+"""
+import gevent
+from contextlib import closing
+import gc
+import pickle
+from gevent import select
+import signal
+from gevent import subprocess
+import traceback
+import sys
+import os
+
+gc.disable()
+
+MAIN_PID = os.getpid()
+
+
+def handlerA(signum, frame):
+    pass
+
+
+MAX_DURATION = 10
+
+
+def run_test():
+    signal.signal(signal.SIGHUP, handlerA)
+    pid = os.getpid()
+    child = subprocess.Popen(['kill', '-HUP', str(pid)])
+    child.wait()  # << this is where it blocks
+
+
+def test_main():
+    # This function spawns a child process to insulate the main
+    # test-running process from all the signals. It then
+    # communicates with that child process over a pipe and
+    # re-raises information about any exceptions the child
+    # throws. The real work happens in self.run_test().
+    os_done_r, os_done_w = os.pipe()
+    with closing(os.fdopen(os_done_r)) as done_r, \
+         closing(os.fdopen(os_done_w, 'w')) as done_w:
+        child = gevent.fork()
+        if child == 0:
+            # In the child process; run the test and report results
+            # through the pipe.
+            try:
+                done_r.close()
+                # Have to close done_w again here because
+                # exit_subprocess() will skip the enclosing with block.
+                with closing(done_w):
+                    try:
+                        run_test()
+                    except:
+                        pickle.dump(traceback.format_exc(), done_w)
+                    else:
+                        pickle.dump(None, done_w)
+            except:
+                print 'Uh oh, raised from pickle.'
+                traceback.print_exc()
+            finally:
+                os._exit(0)
+
+        done_w.close()
+        # Block for up to MAX_DURATION seconds for the test to finish.
+        r, w, x = select.select([done_r], [], [], MAX_DURATION)
+        if done_r in r:
+            tb = pickle.load(done_r)
+            assert not tb, tb
+        else:
+            os.kill(child, signal.SIGKILL)
+            assert False, 'Test deadlocked after %d seconds.' % MAX_DURATION
+
+
+if __name__ == "__main__":
+    print gevent.get_hub()
+    while True:
+        test_main()
+        sys.stderr.write('.')