5 files changed, 41 insertions, 8 deletions

diff --git a/src/mailman/core/runner.py b/src/mailman/core/runner.py
index 757d8837e..9f8094153 100644
--- a/src/mailman/core/runner.py
+++ b/src/mailman/core/runner.py
@@ -31,7 +31,8 @@ from mailman.core.logging import reopen
 from mailman.core.switchboard import Switchboard
 from mailman.interfaces.languages import ILanguageManager
 from mailman.interfaces.listmanager import IListManager
-from mailman.interfaces.runner import IRunner, RunnerCrashEvent
+from mailman.interfaces.runner import (
+    IRunner, RunnerCrashEvent, RunnerInterrupt)
 from mailman.utilities.string import expand
 from public import public
 from zope.component import getUtility
@@ -98,6 +99,16 @@ class Runner:
         elif signum == signal.SIGHUP:
             reopen()
             rlog.info('%s runner caught SIGHUP.  Reopening logs.', self.name)
+        # As of Python 3.5, PEP 475 gets in our way.  Runners with long
+        # time.sleep()'s in their _snooze() method (e.g. the retry runner) will
+        # have their system call implemented time.sleep() automatically retried
+        # at the C layer.  The only reliable way to prevent this is to raise an
+        # exception in the signal handler.  The standard run() method
+        # automatically suppresses this exception, meaning, it's caught and
+        # ignored, but effectively breaks the run() loop, which is just what we
+        # want.  Runners which implement their own run() method must be
+        # prepared to catch RunnerInterrupts, usually also ignoring them.
+        raise RunnerInterrupt
 
     def set_signals(self):
         """See `IRunner`."""
@@ -113,7 +124,7 @@ class Runner:
     def run(self):
         """See `IRunner`."""
         # Start the main loop for this runner.
-        with suppress(KeyboardInterrupt):
+        with suppress(KeyboardInterrupt, RunnerInterrupt):
             while True:
                 # Once through the loop that processes all the files in the
                 # queue directory.
diff --git a/src/mailman/docs/NEWS.rst b/src/mailman/docs/NEWS.rst
index 5736c1354..dfe71755f 100644
--- a/src/mailman/docs/NEWS.rst
+++ b/src/mailman/docs/NEWS.rst
@@ -106,6 +106,8 @@ Bugs
  * Messages were shunted when non-ASCII characters appeared in a mailing
    list's description.  Given by Mark Sapiro.  (Closes: #215)
  * Fix confirmation of unsubscription requests.  (Closes: #294)
+ * Fix ``mailman stop`` not stopping some runners due to PEP 475 interaction.
+   (Closes: #255)
 
 Configuration
 -------------
diff --git a/src/mailman/interfaces/runner.py b/src/mailman/interfaces/runner.py
index 12a7e49ad..f85c759c1 100644
--- a/src/mailman/interfaces/runner.py
+++ b/src/mailman/interfaces/runner.py
@@ -34,6 +34,19 @@ class RunnerCrashEvent:
 
 
 @public
+class RunnerInterrupt(Exception):
+    """A runner received a system call interrupting signal.
+
+    PEP 475 automatically, and at the C layer, retries system calls such as
+    time.sleep().  This can mean runners with long sleeps in their _snooze()
+    method won't actually exit.  This exception is always raised in Mailman's
+    runner signal handlers to prevent this behavior.  Runners that implement
+    their own .run() method must be prepared to handle this, usually by
+    ignoring it.
+    """
+
+
+@public
 class IRunner(Interface):
     """The runner."""
 
diff --git a/src/mailman/runners/lmtp.py b/src/mailman/runners/lmtp.py
index b5c7bbb1f..f24107bd7 100644
--- a/src/mailman/runners/lmtp.py
+++ b/src/mailman/runners/lmtp.py
@@ -40,12 +40,14 @@ import logging
 
 from aiosmtpd.controller import Controller
 from aiosmtpd.lmtp import LMTP
+from contextlib import suppress
 from email.utils import parseaddr
 from mailman.config import config
 from mailman.core.runner import Runner
 from mailman.database.transaction import transactional
 from mailman.email.message import Message
 from mailman.interfaces.listmanager import IListManager
+from mailman.interfaces.runner import RunnerInterrupt
 from mailman.utilities.datetime import now
 from mailman.utilities.email import add_message_hash
 from public import public
@@ -240,7 +242,8 @@ class LMTPRunner(Runner):
 
     def run(self):
         """See `IRunner`."""
-        self.lmtp.start()
-        while not self._stop:
-            self._snooze(0)
-        self.lmtp.stop()
+        with suppress(RunnerInterrupt):
+            self.lmtp.start()
+            while not self._stop:
+                self._snooze(0)
+            self.lmtp.stop()
diff --git a/src/mailman/runners/rest.py b/src/mailman/runners/rest.py
index a93d164c1..7758972ed 100644
--- a/src/mailman/runners/rest.py
+++ b/src/mailman/runners/rest.py
@@ -21,7 +21,9 @@ import signal
 import logging
 import threading
 
+from contextlib import suppress
 from mailman.core.runner import Runner
+from mailman.interfaces.runner import RunnerInterrupt
 from mailman.rest.wsgiapp import make_server
 from public import public
 
@@ -59,10 +61,12 @@ class RESTRunner(Runner):
 
     def run(self):
         """See `IRunner`."""
-        self._server.serve_forever()
+        with suppress(RunnerInterrupt):
+            self._server.serve_forever()
 
     def signal_handler(self, signum, frame):
-        super().signal_handler(signum, frame)
+        with suppress(RunnerInterrupt):
+            super().signal_handler(signum, frame)
         if signum in (signal.SIGTERM, signal.SIGINT, signal.SIGUSR1):
             # Set the flag that will terminate the TCPserver loop.
             self._event.set()