From 6c253510495d25b8178f53e67c1b7d9655ab5fdf Mon Sep 17 00:00:00 2001
From: Tomoaki Teshima <tomoaki.teshima@gmail.com>
Date: Thu, 15 Mar 2018 18:40:05 +0900
Subject: [PATCH] make the asynchronous call to NPP safe   * Stop calling
 nppSetStream

---
 modules/core/include/opencv2/core/private.cuda.hpp | 6 ++++--
 modules/cudaarithm/src/reductions.cpp              | 2 --
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/modules/core/include/opencv2/core/private.cuda.hpp b/modules/core/include/opencv2/core/private.cuda.hpp
index cea280b122..003ff126ba 100644
--- a/modules/core/include/opencv2/core/private.cuda.hpp
+++ b/modules/core/include/opencv2/core/private.cuda.hpp
@@ -108,6 +108,8 @@ static inline void throw_no_cuda() { CV_Error(cv::Error::GpuNotSupported, "The l
 
 #else // HAVE_CUDA
 
+#define nppSafeSetStream(oldStream, newStream) { if(oldStream != newStream) { cudaStreamSynchronize(oldStream); nppSetStream(newStream); } }
+
 static inline void throw_no_cuda() { CV_Error(cv::Error::StsNotImplemented, "The called functionality is disabled for current build or platform"); }
 
 namespace cv { namespace cuda
@@ -139,13 +141,13 @@ namespace cv { namespace cuda
         inline explicit NppStreamHandler(Stream& newStream)
         {
             oldStream = nppGetStream();
-            nppSetStream(StreamAccessor::getStream(newStream));
+            nppSafeSetStream(oldStream, StreamAccessor::getStream(newStream));
         }
 
         inline explicit NppStreamHandler(cudaStream_t newStream)
         {
             oldStream = nppGetStream();
-            nppSetStream(newStream);
+            nppSafeSetStream(oldStream, newStream);
         }
 
         inline ~NppStreamHandler()
diff --git a/modules/cudaarithm/src/reductions.cpp b/modules/cudaarithm/src/reductions.cpp
index 50185b161e..1adf05fe1a 100644
--- a/modules/cudaarithm/src/reductions.cpp
+++ b/modules/cudaarithm/src/reductions.cpp
@@ -157,8 +157,6 @@ void cv::cuda::meanStdDev(InputArray _src, OutputArray _dst, Stream& stream)
     BufferPool pool(stream);
     GpuMat buf = pool.getBuffer(1, bufSize, CV_8UC1);
 
-    NppStreamHandler h(StreamAccessor::getStream(stream));
-
     nppSafeCall( nppiMean_StdDev_8u_C1R(src.ptr<Npp8u>(), static_cast<int>(src.step), sz, buf.ptr<Npp8u>(), dst.ptr<Npp64f>(), dst.ptr<Npp64f>() + 1) );
 
     syncOutput(dst, _dst, stream);