--- xnu/xnu-3248.50.21/iokit/Kernel/IOSharedDataQueue.cpp
+++ xnu/xnu-2782.1.97/iokit/Kernel/IOSharedDataQueue.cpp
@@ -99,11 +99,10 @@
     if (dataQueue == 0) {
         return false;
     }
-    bzero(dataQueue, allocSize);
 
     dataQueue->queueSize    = size;
-//  dataQueue->head         = 0;
-//  dataQueue->tail         = 0;
+    dataQueue->head         = 0;
+    dataQueue->tail         = 0;
 
     if (!setQueueSize(size)) {
         return false;
@@ -111,14 +110,7 @@
     
     appendix            = (IODataQueueAppendix *)((UInt8 *)dataQueue + size + DATA_QUEUE_MEMORY_HEADER_SIZE);
     appendix->version   = 0;
-
-    if (!notifyMsg) {
-        notifyMsg = IOMalloc(sizeof(mach_msg_header_t));
-        if (!notifyMsg)
-            return false;
-    }
-    bzero(notifyMsg, sizeof(mach_msg_header_t));
-
+    notifyMsg           = &(appendix->msgh);
     setNotificationPort(MACH_PORT_NULL);
 
     return true;
@@ -129,10 +121,6 @@
     if (dataQueue) {
         IOFreeAligned(dataQueue, round_page(getQueueSize() + DATA_QUEUE_MEMORY_HEADER_SIZE + DATA_QUEUE_MEMORY_APPENDIX_SIZE));
         dataQueue = NULL;
-        if (notifyMsg) {
-            IOFree(notifyMsg, sizeof(mach_msg_header_t));
-            notifyMsg = NULL;
-        }
     }
 
     if (_reserved) {
@@ -204,7 +192,7 @@
         return false;
     }
     // Check for underflow of (getQueueSize() - tail)
-    if (getQueueSize() < tail || getQueueSize() < head) {
+    if (getQueueSize() < tail) {
         return false;
     }