Prevent concurrent modification of host list

Limelight/Network/DiscoveryManager.m

@@ -77,9 +77,12 @@
     Log(LOG_I, @"Starting discovery");
     shouldDiscover = YES;
     [_mdnsMan searchForHosts];
+    
+    @synchronized (_hostQueue) {
         for (TemporaryHost* host in _hostQueue) {
             [_opQueue addOperation:[self createWorkerForHost:host]];
         }
+    }
 }
 
 - (void) stopDiscovery {
@@ -141,21 +144,26 @@
         return NO;
     }
     else {
+        @synchronized (_hostQueue) {
             [_hostQueue addObject:host];
             if (shouldDiscover) {
                 [_opQueue addOperation:[self createWorkerForHost:host]];
             }
+        }
         return YES;
     }
 }
 
 - (void) removeHostFromDiscovery:(TemporaryHost *)host {
+    @synchronized (_hostQueue) {
         for (DiscoveryWorker* worker in [_opQueue operations]) {
             if ([worker getHost] == host) {
                 [worker cancel];
             }
         }
+        
         [_hostQueue removeObject:host];
+    }
 }
 
 // Override from MDNSCallback - called in a worker thread
@@ -167,18 +175,22 @@
     [worker discoverHost];
     if ([self addHostToDiscovery:host]) {
         Log(LOG_I, @"Found new host through MDNS: %@:", host.name);
-        [self->_callback updateAllHosts:self->_hostQueue];
+        @synchronized (_hostQueue) {
+            [_callback updateAllHosts:_hostQueue];
+        }
     } else {
         Log(LOG_D, @"Found existing host through MDNS: %@", host.name);
     }
 }
 
 - (TemporaryHost*) getHostInDiscovery:(NSString*)uuidString {
+    @synchronized (_hostQueue) {
         for (TemporaryHost* discoveredHost in _hostQueue) {
             if (discoveredHost.uuid.length > 0 && [discoveredHost.uuid isEqualToString:uuidString]) {
                 return discoveredHost;
             }
         }
+    }
     return nil;
 }