Reference engine from chunk via weak pointer

include/mxnet/ndarray.h

@@ -850,15 +850,20 @@ class NDArray {
     mxnet::ShapeVector aux_shapes;
     /*! \brief Reference to the storage to ensure proper destruct order */
     std::shared_ptr<Storage> storage_ref_;
+    /*! \brief Reference to the engine to ensure we cleanup without calling a destructed engine */
+    std::weak_ptr<Engine> engine_ref_;
 
-    /*! \brief default cosntructor */
+
+    /*! \brief default constructor */
     Chunk() : static_data(true), delay_alloc(false),
-              storage_ref_(Storage::_GetSharedRef()) {}
+              storage_ref_(Storage::_GetSharedRef()),
+              engine_ref_(Engine::_GetSharedRef()) {}
 
     /*! \brief construct a new chunk */
     Chunk(mxnet::TShape shape, Context ctx_, bool delay_alloc_, int dtype)
         : static_data(false), delay_alloc(true), ctx(ctx_),
-          storage_ref_(Storage::_GetSharedRef()) {
+          storage_ref_(Storage::_GetSharedRef()),
+          engine_ref_(Engine::_GetSharedRef()) {
       auto size = shape.Size();
       storage_shape = shape;
       var = Engine::Get()->NewVariable();
@@ -869,7 +874,8 @@ class NDArray {
 
     Chunk(const TBlob &data, int dev_id)
         : static_data(true), delay_alloc(false),
-          storage_ref_(Storage::_GetSharedRef()) {
+          storage_ref_(Storage::_GetSharedRef()),
+          engine_ref_(Engine::_GetSharedRef()) {
       CHECK(storage_type == kDefaultStorage);
       var = Engine::Get()->NewVariable();
       if (data.dev_mask() == cpu::kDevMask) {
@@ -887,7 +893,8 @@ class NDArray {
 
     Chunk(int shared_pid, int shared_id, const mxnet::TShape& shape, int dtype)
         : static_data(false), delay_alloc(false),
-          storage_ref_(Storage::_GetSharedRef()) {
+          storage_ref_(Storage::_GetSharedRef()),
+          engine_ref_(Engine::_GetSharedRef()) {
       var = Engine::Get()->NewVariable();
       ctx = Context::CPUShared(0);
       shandle.size = shape.Size() * mshadow::mshadow_sizeof(dtype);
@@ -903,7 +910,8 @@ class NDArray {
           const mxnet::ShapeVector &aux_shapes_)
         : static_data(false), delay_alloc(delay_alloc_), storage_type(storage_type_),
           aux_types(aux_types_), ctx(ctx_), storage_shape(storage_shape_),
-          aux_shapes(aux_shapes_), storage_ref_(Storage::_GetSharedRef()) {
+          aux_shapes(aux_shapes_), storage_ref_(Storage::_GetSharedRef()),
+          engine_ref_(Engine::_GetSharedRef()) {
       shandle.ctx = ctx;
       var = Engine::Get()->NewVariable();
       // aux_handles always reflect the correct number of aux data
@@ -921,7 +929,7 @@ class NDArray {
     Chunk(const NDArrayStorageType storage_type_, const TBlob &data,
           const std::vector<TBlob> &aux_data, int dev_id)
         : static_data(true), delay_alloc(false), storage_type(storage_type_),
-          storage_ref_(Storage::_GetSharedRef()) {
+          storage_ref_(Storage::_GetSharedRef()), engine_ref_(Engine::_GetSharedRef()) {
       using namespace mshadow;
       CHECK_NE(storage_type, kDefaultStorage);
       // init var

src/ndarray/ndarray.cc

@@ -113,20 +113,22 @@ NDArray::Chunk::~Chunk() {
   // We want to delete mkldnn memory after deleting the variable.
   mem.mem = this->mkl_mem_;
 #endif
-  Engine::Get()->DeleteVariable([mem, skip_free](RunContext s) {
-    if (skip_free == false) {
+  if (auto engine = engine_ref_.lock()) {
+    engine->DeleteVariable([mem, skip_free](RunContext s) {
+      if (skip_free == false) {
 #if MXNET_USE_MKLDNN == 1
-      if (mem.mem) {
-        CHECK_LE(mem.mem->GetSize(), mem.h.size);
-        CHECK_EQ(mem.mem->GetDataHandle(), mem.h.dptr);
-      }
+        if (mem.mem) {
+          CHECK_LE(mem.mem->GetSize(), mem.h.size);
+          CHECK_EQ(mem.mem->GetDataHandle(), mem.h.dptr);
+        }
 #endif
-      Storage::Get()->Free(mem.h);
-      for (const auto& aux : mem.aux_h) {
-        Storage::Get()->Free(aux);
+        Storage::Get()->Free(mem.h);
+        for (const auto &aux : mem.aux_h) {
+          Storage::Get()->Free(aux);
+        }
       }
-    }
-  }, shandle.ctx, var);
+    }, shandle.ctx, var);
+  }
 }
 
 void NDArray::Chunk::CheckAndAllocData(const mxnet::TShape &shape, int dtype) {