Fix deadlock between content storage and asset that is being updated during load

#2621

Source/Engine/Content/Assets/Material.cpp

@@ -187,6 +187,9 @@ Asset::LoadResult Material::load()
 #endif
     )
     {
+        // Guard file with the lock during shader generation (prevents FlaxStorage::Tick from messing with the file)
+        auto lock = Storage->Lock();
+
         // Prepare
         MaterialGenerator generator;
         generator.Error.Bind(&OnGeneratorError);

Source/Engine/Content/Storage/ContentStorageManager.cpp

@@ -252,6 +252,7 @@ void ContentStorageSystem::Job(int32 index)
 {
     PROFILE_CPU_NAMED("ContentStorage.Job");
 
+    const double time = Platform::GetTimeSeconds();
     ScopeLock lock(Locker);
     for (auto i = StorageMap.Begin(); i.IsNotEnd(); ++i)
     {
@@ -271,7 +272,7 @@ void ContentStorageSystem::Job(int32 index)
         }
         else
         {
-            storage->Tick();
+            storage->Tick(time);
         }
     }
 }

Source/Engine/Content/Storage/FlaxStorage.cpp

@@ -1398,19 +1398,18 @@ void FlaxStorage::Dispose()
     _version = 0;
 }
 
-void FlaxStorage::Tick()
+void FlaxStorage::Tick(double time)
 {
-    // Check if chunks are locked
+    // Skip if file is in use
     if (Platform::AtomicRead(&_chunksLock) != 0)
         return;
 
-    const double now = Platform::GetTimeSeconds();
     bool wasAnyUsed = false;
     const float unusedDataChunksLifetime = ContentStorageManager::UnusedDataChunksLifetime.GetTotalSeconds();
     for (int32 i = 0; i < _chunks.Count(); i++)
     {
         auto chunk = _chunks.Get()[i];
-        const bool wasUsed = (now - chunk->LastAccessTime) < unusedDataChunksLifetime;
+        const bool wasUsed = (time - chunk->LastAccessTime) < unusedDataChunksLifetime;
         if (!wasUsed && chunk->IsLoaded())
         {
             chunk->Unload();
@@ -1418,7 +1417,7 @@ void FlaxStorage::Tick()
         wasAnyUsed |= wasUsed;
     }
 
-    // Release file handles in none of chunks was not used
+    // Release file handles in none of chunks is in use
     if (!wasAnyUsed && Platform::AtomicRead(&_chunksLock) == 0)
     {
         CloseFileHandles();

Source/Engine/Content/Storage/FlaxStorage.h

@@ -416,7 +416,7 @@ public:
     /// <summary>
     /// Ticks this instance.
     /// </summary>
-    void Tick();
+    void Tick(double time);
 
 #if USE_EDITOR
     void OnRename(const StringView& newPath);