--- xnu/xnu-201.5/iokit/Kernel/IOWorkLoop.cpp
+++ xnu/xnu-517.7.7/iokit/Kernel/IOWorkLoop.cpp
@@ -59,10 +59,6 @@
 
 void IOWorkLoop::launchThreadMain(void *self)
 {
-    register thread_t mythread = current_thread();
-
-    // Make sure that this thread always has a kernel stack
-    stack_privilege(mythread);
     thread_set_cont_arg((int) self);
     threadMainContinuation();
 }
@@ -107,7 +103,7 @@
     IOWorkLoop *me = new IOWorkLoop;
 
     if (me && !me->init()) {
-        me->free();
+        me->release();
         return 0;
     }
 
@@ -298,13 +294,8 @@
 	    assert_wait((void *) &workToDo, false);
 	    IOSimpleLockUnlockEnableInterrupt(workToDoLock, is);
 
-#if defined (__i386__)
-	    thread_block(0);
-	    continue;
-#else
 	    thread_set_cont_arg((int) this);
 	    thread_block(&threadMainContinuation);
-#endif
 	    /* NOTREACHED */
 	}
 
@@ -321,7 +312,7 @@
 exitThread:
     workThread = 0;	// Say we don't have a loop and free ourselves
     free();
-    IOExitThread(0);
+    IOExitThread();
 }
 
 IOThread IOWorkLoop::getThread() const
@@ -376,8 +367,8 @@
 }
 
 IOReturn IOWorkLoop::runAction(Action inAction, OSObject *target,
-                                  void *arg0 = 0, void *arg1 = 0,
-                                  void *arg2 = 0, void *arg3 = 0)
+                                  void *arg0, void *arg1,
+                                  void *arg2, void *arg3)
 {
     IOReturn res;
 
@@ -398,43 +389,48 @@
     switch (command)
     {
     case mAddEvent:
-	SETP(&fFlags, kLoopRestart);
-        inEvent->retain();
-        inEvent->setWorkLoop(this);
-        inEvent->setNext(0);
-
-        if (!eventChain)
-            eventChain = inEvent;
-        else {
-            IOEventSource *event, *next;
-
-            for (event = eventChain; (next = event->getNext()); event = next)
-                ;
-            event->setNext(inEvent);
+        if (!inEvent->getWorkLoop()) {
+            SETP(&fFlags, kLoopRestart);
+
+            inEvent->retain();
+            inEvent->setWorkLoop(this);
+            inEvent->setNext(0);
+    
+            if (!eventChain)
+                eventChain = inEvent;
+            else {
+                IOEventSource *event, *next;
+    
+                for (event = eventChain; (next = event->getNext()); event = next)
+                    ;
+                event->setNext(inEvent);
+            }
         }
         break;
 
     case mRemoveEvent:
-        if (eventChain == inEvent)
-            eventChain = inEvent->getNext();
-        else {
-            IOEventSource *event, *next;
-
-            event = eventChain;
-            while ((next = event->getNext()) && next != inEvent)
-                event = next;
-
-            if (!next) {
-                res = kIOReturnBadArgument;
-                break;
+        if (inEvent->getWorkLoop()) {
+            if (eventChain == inEvent)
+                eventChain = inEvent->getNext();
+            else {
+                IOEventSource *event, *next;
+    
+                event = eventChain;
+                while ((next = event->getNext()) && next != inEvent)
+                    event = next;
+    
+                if (!next) {
+                    res = kIOReturnBadArgument;
+                    break;
+                }
+                event->setNext(inEvent->getNext());
             }
-            event->setNext(inEvent->getNext());
+    
+            inEvent->setWorkLoop(0);
+            inEvent->setNext(0);
+            inEvent->release();
+            SETP(&fFlags, kLoopRestart);
         }
-
-        inEvent->setWorkLoop(0);
-        inEvent->setNext(0);
-        inEvent->release();
-	SETP(&fFlags, kLoopRestart);
         break;
 
     default: