Prevent possible race conditions in scheduler.

src/schedule.py

@@ -32,8 +32,11 @@ Schedule plugin with a subclass of drivers.IrcDriver in order to be run as a
 Supybot driver.
 """
 
+from __future__ import with_statement
+
 import time
 import heapq
+from threading import Lock
 
 import supybot.log as log
 import supybot.world as world
@@ -61,8 +64,10 @@ class Schedule(drivers.IrcDriver):
         self.schedule = []
         self.events = {}
         self.counter = 0
+        self.lock = Lock()
 
     def reset(self):
+        with self.lock:
             self.events.clear()
             self.schedule[:] = []
         # We don't reset the counter here because if someone has held an id of
@@ -82,6 +87,7 @@ class Schedule(drivers.IrcDriver):
             self.counter += 1
         assert name not in self.events, \
                'An event with the same name has already been scheduled.'
+        with self.lock:
             self.events[name] = f
             heapq.heappush(self.schedule, mytuple((t, name, args, kwargs)))
         return name
@@ -89,12 +95,13 @@ class Schedule(drivers.IrcDriver):
     def removeEvent(self, name):
         """Removes the event with the given name from the schedule."""
         f = self.events.pop(name)
-        self.schedule = [x for x in self.schedule if f != name]
         # We must heapify here because the heap property may not be preserved
         # by the above list comprehension.  We could, conceivably, just mark
         # the elements of the heap as removed and ignore them when we heappop,
         # but that would only save a constant factor (we're already linear for
         # the listcomp) so I'm not worried about it right now.
+        with self.lock:
+            self.schedule = [x for x in self.schedule if f != name]
             heapq.heapify(self.schedule)
         return f
 
@@ -123,6 +130,7 @@ class Schedule(drivers.IrcDriver):
                       'why do we continue to live?')
             time.sleep(1) # We're the only driver; let's pause to think.
         while self.schedule and self.schedule[0][0] < time.time():
+            with self.lock:
                 (t, name, args, kwargs) = heapq.heappop(self.schedule)
                 f = self.events[name]
             del self.events[name]