Question

I’m trying to load cuda driver api functions on runtime with dlsym, and i have encountered a strange error. I have this code that runs smoothly on my system ( compiled with nvcc etc ) :

#include <cuda.h>
#include <stdio.h>

int main(int argc,char *argv[]){

  if(argc<3){
    printf("Usage: ./test.cu <ptx_file> <cuda_device>\n");
    exit(0);
  }

  // Error code
  CUresult error;

  // My number
  unsigned int h_var=7;

  // Initialize driver API
  error = cuInit(0);
  if((int)error!=0){
    printf("Error! cuInit returned: %d\n",(int)error); 
    exit(0);
  }

  // Get Cuda Device and give handle
  CUdevice cu_device;
  error = cuDeviceGet(&cu_device,atoi(argv[2]));
  if((int)error!=0){
    printf("Error! cuDeviceGet returned: %d\n",(int)error);
    exit(0);
  }

  // Create context to run on device 
  CUcontext cu_context;
  error = cuCtxCreate(&cu_context, 0, cu_device);
  if((int)error!=0){
    printf("Error! cuCtxCreate returned: %d\n",(int)error);
    exit(0);
  }

  // Load ptx code
  CUmodule cu_module;
  error = cuModuleLoad(&cu_module,argv[1]);
  if((int)error!=0){
    printf("Error! cuModuleLoad returned: %d\n",(int)error);
    exit(0);
  }

  // Get kernel function
  CUfunction func;
  error = cuModuleGetFunction(&func,cu_module,"testing"); 
  if((int)error!=0){
    printf("Error! cuModuleGetFunction returned: %d\n",(int)error);
    exit(0);
  }

  CUdeviceptr var;

  // Allocate device memory
  unsigned int size = sizeof(unsigned int);
  error = cuMemAlloc(&var, size);
  if((int)error!=0){
    printf("Error! cuMemAlloc returned: %d\n",(int)error);
    exit(0);
  }

  // Copy variable to host
  error = cuMemcpyHtoD(var,&h_var,size);
  if((int)error!=0){
    printf("Error! cuMemcpyHtoD returned: %d\n",(int)error);
    exit(0);
  }

  // Lauch kernel
  void *args[] = {&var};
  error = cuLaunchKernel(func, 1, 1, 1, 1, 1, 1, 0, NULL, args, NULL);
  if((int)error!=0){
    printf("Error! cuLaunchKernel returned: %d\n",(int)error);
    exit(0);
  }

  // Get result to host
  error = cuMemcpyDtoH(&h_var,var,size);
  if((int)error!=0){
    printf("Error! cuMemcpyDtoH returned: %d\n",(int)error);
    exit(0);
  }

  // Free device memory
  error = cuMemFree(var);
  if((int)error!=0){
    printf("Error! cuMemFree returned: %d\n",(int)error);
    exit(0);
  }

  // Destroy context
  error = cuCtxDestroy(cu_context);
  if((int)error!=0){
    printf("Error! cuCtxDestroy returned: %d\n",(int)error);
    exit(0);
  }

  // Print result
  printf("var: %d\n",h_var);
}

with a ptx code written by me: (it’s a simple addition, just to test that it works)

.version 1.4
.target sm_10, map_f64_to_f32

.entry testing (
  .param .u64 mynum)
{

  .reg .u64 %r;
  .reg .u64 %i;
  ld.param.u64 %r,[mynum];
  ld.global.u64 %i,[%r];
  add.u64 %i,%i,3;
  st.global.u64 [%r+0],%i;
  exit;

}

So far so good. Then i took the code and loaded every function with dlsym like this:

  /* Lauch kernel */
  void *args[] = {&var};
  int (*_cuLaunchKernel)( void *, unsigned int, unsigned int, unsigned int, unsigned int, unsigned int, unsigned int, unsigned int, void *, void **, void ** );
  *(void **)(&_cuLaunchKernel) = dlsym(dlhandle, "cuLaunchKernel");
  (*_cuLaunchKernel)(cu_func,1 , 1, 1, 1, 1, 1, 0, NULL, args, NULL);


 /* Get result to host  */
  int (*_cuMemcpyDtoH)( void *, void *, size_t );
  *(void **)(&_cuMemcpyDtoH) = dlsym(dlhandle, "cuMemcpyHtoD");
  error = (*_cuMemcpyDtoH)(&h_var,var,size);

( The rest of the code is in the same logic ). All of my functions return with 0, which means everything went ok, except the last one _cuMemcpyDtoH , which returns error 1 ( = cudaErrorMissingConfiguration ). Can someone explain what this error means, and why it occurs? Is there a way to solve it? And why it shows up when i load the functions on runtime?

Thanks.

My system:
nvcc release 4.1
GPU : GTX 480
NVRM version: NVIDIA UNIX x86_64 Kernel Module 285.05.32
GCC version: gcc version 4.5.2 (Ubuntu/Linaro 4.5.2-8ubuntu4)

Answer 1

For driver API that you are using, erorr code 1 means CUDA_ERROR_INVALID_VALUE

The reason for this error is:

*(void **)(&_cuMemcpyDtoH) = dlsym(dlhandle, "cuMemcpyHtoD");

— you are trying to use the wrong function: HtoD instead of DtoH.