2 files changed, 19 insertions, 2 deletions
diff --git a/base/message_pump_libevent.cc b/base/message_pump_libevent.cc
index a940081..e6d2cea 100644
--- a/base/message_pump_libevent.cc
+++ b/base/message_pump_libevent.cc
@@ -171,6 +171,23 @@ bool MessagePumpLibevent::WatchFileDescriptor(int fd,
     should_delete_event = false;
     // Ownership is transferred to the controller.
     evt.reset(new event);
+  } else {
+    // It's illegal to use this function to listen on 2 separate fds with the
+    // same |controller|.
+    if (EVENT_FD(evt.get()) != fd) {
+      NOTREACHED() << "FDs don't match" << EVENT_FD(evt.get()) << "!=" << fd;
+      return false;
+    }
+
+    // Make sure we don't pick up any funky internal libevent masks.
+    int old_interest_mask = evt.get()->ev_events &
+        (EV_READ | EV_WRITE | EV_PERSIST);
+
+    // Combine old/new event masks.
+    event_mask |= old_interest_mask;
+
+    // Must disarm the event before we can reuse it.
+    event_del(evt.get());
   }
 
   // Set current interest mask and message pump for this event.
diff --git a/base/message_pump_libevent.h b/base/message_pump_libevent.h
index a2a4e1c..8e2f77c 100644
--- a/base/message_pump_libevent.h
+++ b/base/message_pump_libevent.h
@@ -68,9 +68,9 @@ class MessagePumpLibevent : public MessagePump {
   };
 
   // Have the current thread's message loop watch for a a situation in which
-  // reading/writing to the FD can be performed without Blocking.
+  // reading/writing to the FD can be performed without blocking.
   // Callers must provide a preallocated FileDescriptorWatcher object which
-  // can later be used to manage the Lifetime of this event.
+  // can later be used to manage the lifetime of this event.
   // If a FileDescriptorWatcher is passed in which is already attached to
   // an event, then the effect is cumulative i.e. after the call |controller|
   // will watch both the previous event and the new one.