Refs #627. Fix support for multi-threads with CUDA 7.0

Author: Rolf vandeVaart

opal/mca/common/cuda/common_cuda.c

@@ -1739,19 +1739,19 @@ static int mca_common_cuda_is_gpu_buffer(const void *pUserBuf, opal_convertor_t
     int res;
     CUmemorytype memType = 0;
     CUdeviceptr dbuf = (CUdeviceptr)pUserBuf;
-    CUcontext ctx = NULL;
+    CUcontext ctx = NULL, memCtx = NULL;
 #if OPAL_CUDA_GET_ATTRIBUTES
     uint32_t isManaged = 0;
     /* With CUDA 7.0, we can get multiple attributes with a single call */
     CUpointer_attribute attributes[3] = {CU_POINTER_ATTRIBUTE_MEMORY_TYPE,
                                          CU_POINTER_ATTRIBUTE_CONTEXT,
                                          CU_POINTER_ATTRIBUTE_IS_MANAGED};
-    void *attrdata[] = {(void *)&memType, (void *)&ctx, (void *)&isManaged};
+    void *attrdata[] = {(void *)&memType, (void *)&memCtx, (void *)&isManaged};
 
     res = cuFunc.cuPointerGetAttributes(3, attributes, attrdata, dbuf);
     OPAL_OUTPUT_VERBOSE((101, mca_common_cuda_output,
                         "dbuf=%p, memType=%d, ctx=%p, isManaged=%d, res=%d",
-                         (void *)dbuf, (int)memType, (void *)ctx, isManaged, res));
+                         (void *)dbuf, (int)memType, (void *)memCtx, isManaged, res));
 
     /* Mark unified memory buffers with a flag.  This will allow all unified
      * memory to be forced through host buffers.  Note that this memory can
@@ -1787,6 +1787,7 @@ static int mca_common_cuda_is_gpu_buffer(const void *pUserBuf, opal_convertor_t
     }
     /* Must be a device pointer */
     assert(memType == CU_MEMORYTYPE_DEVICE);
+#endif /* OPAL_CUDA_GET_ATTRIBUTES */
 
     /* This piece of code was added in to handle in a case involving
      * OMP threads.  The user had initialized CUDA and then spawned
@@ -1797,25 +1798,25 @@ static int mca_common_cuda_is_gpu_buffer(const void *pUserBuf, opal_convertor_t
      * and set the current context to that.  It is rare that we will not
      * have a context. */
     res = cuFunc.cuCtxGetCurrent(&ctx);
-#endif /* OPAL_CUDA_GET_ATTRIBUTES */
     if (OPAL_UNLIKELY(NULL == ctx)) {
         if (CUDA_SUCCESS == res) {
-            res = cuFunc.cuPointerGetAttribute(&ctx,
+#if !OPAL_CUDA_GET_ATTRIBUTES
+            res = cuFunc.cuPointerGetAttribute(&memCtx,
                                                CU_POINTER_ATTRIBUTE_CONTEXT, dbuf);
             if (res != CUDA_SUCCESS) {
                 opal_output(0, "CUDA: error calling cuPointerGetAttribute: "
                             "res=%d, ptr=%p aborting...", res, pUserBuf);
                 return OPAL_ERROR;
+            }
+#endif /* OPAL_CUDA_GET_ATTRIBUTES */
+            res = cuFunc.cuCtxSetCurrent(memCtx);
+            if (res != CUDA_SUCCESS) {
+                opal_output(0, "CUDA: error calling cuCtxSetCurrent: "
+                            "res=%d, ptr=%p aborting...", res, pUserBuf);
+                return OPAL_ERROR;
             } else {
-                res = cuFunc.cuCtxSetCurrent(ctx);
-                if (res != CUDA_SUCCESS) {
-                    opal_output(0, "CUDA: error calling cuCtxSetCurrent: "
-                                "res=%d, ptr=%p aborting...", res, pUserBuf);
-                    return OPAL_ERROR;
-                } else {
-                    opal_output_verbose(10, mca_common_cuda_output,
-                                        "CUDA: cuCtxSetCurrent passed: ptr=%p", pUserBuf);
-                }
+                opal_output_verbose(10, mca_common_cuda_output,
+                                    "CUDA: cuCtxSetCurrent passed: ptr=%p", pUserBuf);
             }
         } else {
             /* Print error and proceed */