[SYCL] Fix coverity hits in queue & graph

sycl/source/detail/graph/graph_impl.cpp

@@ -327,7 +327,7 @@ graph_impl::graph_impl(const sycl::context &SyclContext,
 
 graph_impl::~graph_impl() {
   try {
-    clearQueues();
+    clearQueues(false /*Needs lock*/);
     for (auto &MemObj : MMemObjs) {
       MemObj->markNoLongerBeingUsedInGraph();
     }
@@ -564,17 +564,21 @@ void graph_impl::removeQueue(sycl::detail::queue_impl &RecordingQueue) {
   MRecordingQueues.erase(RecordingQueue.weak_from_this());
 }
 
-bool graph_impl::clearQueues() {
-  bool AnyQueuesCleared = false;
-  for (auto &Queue : MRecordingQueues) {
+void graph_impl::clearQueues(bool NeedsLock) {
+  graph_impl::RecQueuesStorage SwappedQueues;
+  {
+    graph_impl::WriteLock Guard(MMutex, std::defer_lock);
+    if (NeedsLock) {
+      Guard.lock();
+    }
+    std::swap(MRecordingQueues, SwappedQueues);
+  }
+
+  for (auto &Queue : SwappedQueues) {
     if (auto ValidQueue = Queue.lock(); ValidQueue) {
       ValidQueue->setCommandGraph(nullptr);
-      AnyQueuesCleared = true;
     }
   }
-  MRecordingQueues.clear();
-
-  return AnyQueuesCleared;
 }
 
 bool graph_impl::checkForCycles() {
@@ -1970,8 +1974,7 @@ void modifiable_command_graph::begin_recording(
 }
 
 void modifiable_command_graph::end_recording() {
-  graph_impl::WriteLock Lock(impl->MMutex);
-  impl->clearQueues();
+  impl->clearQueues(true /*Needs lock*/);
 }
 
 void modifiable_command_graph::end_recording(queue &RecordingQueue) {

sycl/source/detail/graph/graph_impl.hpp

@@ -190,9 +190,7 @@ class graph_impl : public std::enable_shared_from_this<graph_impl> {
 
   /// Remove all queues which are recording to this graph, also sets all queues
   /// cleared back to the executing state.
-  ///
-  /// @return True if any queues were removed.
-  bool clearQueues();
+  void clearQueues(bool NeedsLock);
 
   /// Associate a sycl event with a node in the graph.
   /// @param EventImpl Event to associate with a node in map.
@@ -561,10 +559,12 @@ class graph_impl : public std::enable_shared_from_this<graph_impl> {
   /// Device associated with this graph. All graph nodes will execute on this
   /// device.
   sycl::device MDevice;
+
+  using RecQueuesStorage =
+      std::set<std::weak_ptr<sycl::detail::queue_impl>,
+               std::owner_less<std::weak_ptr<sycl::detail::queue_impl>>>;
   /// Unique set of queues which are currently recording to this graph.
-  std::set<std::weak_ptr<sycl::detail::queue_impl>,
-           std::owner_less<std::weak_ptr<sycl::detail::queue_impl>>>
-      MRecordingQueues;
+  RecQueuesStorage MRecordingQueues;
   /// Map of events to their associated recorded nodes.
   std::unordered_map<std::shared_ptr<sycl::detail::event_impl>, node_impl *>
       MEventsMap;

sycl/source/detail/queue_impl.hpp

@@ -602,7 +602,8 @@ class queue_impl : public std::enable_shared_from_this<queue_impl> {
                                bool CallerNeedsEvent);
 
   void setCommandGraphUnlocked(
-      std::shared_ptr<ext::oneapi::experimental::detail::graph_impl> Graph) {
+      const std::shared_ptr<ext::oneapi::experimental::detail::graph_impl>
+          &Graph) {
     MGraph = Graph;
     MExtGraphDeps.reset();
 
@@ -614,7 +615,8 @@ class queue_impl : public std::enable_shared_from_this<queue_impl> {
   }
 
   void setCommandGraph(
-      std::shared_ptr<ext::oneapi::experimental::detail::graph_impl> Graph) {
+      const std::shared_ptr<ext::oneapi::experimental::detail::graph_impl>
+          &Graph) {
     std::lock_guard<std::mutex> Lock(MMutex);
     setCommandGraphUnlocked(Graph);
   }