Revert "Avoid lock for last queued command"

This reverts commit dc4e09a63a.

Reason for revert: <INSERT REASONING HERE>

Change-Id: Ie10442c9447f010bb90c679b6cffca5b48b8d054

rocclr/platform/commandqueue.hpp

@@ -126,6 +126,7 @@ class CommandQueue : public RuntimeObject {
         rtCUs_(rtCUs),
         priority_(priority),
         queueLock_("CommandQueue::queueLock"),
+        lastCmdLock_("LastQueuedCommand"),
         device_(device),
         context_(context),
         cuMask_(cuMask){}
@@ -134,6 +135,7 @@ class CommandQueue : public RuntimeObject {
   uint rtCUs_;                        //!< The number of used RT compute units
   Priority priority_;                 //!< Queue priority
   Monitor queueLock_;                 //!< Lock protecting the queue
+  Monitor lastCmdLock_;               //!< Lock protecting the last queued command
   Device& device_;                    //!< The device
   SharedReference<Context> context_;  //!< The context of this command queue
   const std::vector<uint32_t>& cuMask_;  //!< The CU mask
@@ -185,7 +187,7 @@ class HostQueue : public CommandQueue {
  private:
   ConcurrentLinkedQueue<Command*> queue_;  //!< The queue.
 
-  std::atomic<Command*> lastEnqueueCommand_;  //!< The last submitted command
+  Command* lastEnqueueCommand_;  //!< The last submitted command
 
   //! Await commands and execute them as they become ready.
   void loop(device::VirtualDevice* virtualDevice);