ocl: silence warning in case of async cleanup

- OpenCL kernel cleanup processing is asynchronous and can be called even after forced clFinish()
- buffers are released later in asynchronous mode
- silence these false positive cases for asynchronous cleanup

modules/core/src/umatrix.cpp

@@ -80,6 +80,7 @@ UMatData::~UMatData()
     CV_Assert(mapcount == 0);
     data = origdata = 0;
     size = 0;
+    bool isAsyncCleanup = !!(flags & UMatData::ASYNC_CLEANUP);
     flags = 0;
     handle = 0;
     userdata = 0;
@@ -106,7 +107,7 @@ UMatData::~UMatData()
             showWarn = true;
         if (zero_Ref && zero_URef) // oops, we need to free resources
         {
-            showWarn = true;
+            showWarn = !isAsyncCleanup;
             // simulate UMat::deallocate
             u->currAllocator->deallocate(u);
         }

modules/core/test/test_umat.cpp

@@ -1154,6 +1154,30 @@ TEST(UMat, map_unmap_counting)
 }
 
 
+static void process_with_async_cleanup(Mat& frame)
+{
+    UMat blurResult;
+    {
+        UMat umat_buffer = frame.getUMat(ACCESS_READ);
+        cv::blur(umat_buffer, blurResult, Size(3, 3));  // UMat doesn't support inplace, this call is not synchronized
+    }
+    Mat result;
+    blurResult.copyTo(result);
+    swap(result, frame);
+    // umat_buffer cleanup is done asynchronously, silence warning about original 'frame' cleanup here (through 'result')
+    // - release input 'frame' (as 'result')
+    // - release 'umat_buffer' asynchronously and silence warning about "parent" buffer (in debug builds)
+}
+TEST(UMat, async_cleanup_without_call_chain_warning)
+{
+    Mat frame(Size(640, 480), CV_8UC1, Scalar::all(128));
+    for (int i = 0; i < 10; i++)
+    {
+        process_with_async_cleanup(frame);
+    }
+}
+
+
 ///////////// oclCleanupCallback threadsafe check (#5062) /////////////////////
 
 // Case 1: reuse of old src Mat in OCL pipe. Hard to catch!