【发布时间】：2016-07-22 05:14:29
【问题描述】：
以下代码在 Nvidia 驱动程序 361.91（及更早版本）下运行良好（Windows 7，Nvidia GTX 750 Ti），但在 364.72 和 368.69 等较新版本上运行良好。现在 glFinish 仅在调用 clEnqueueReleaseGLObjects 后才阻止程序的执行。在责怪驱动程序之前，我怀疑我的 OpenCL/OpenGL 互操作方式有问题，所以这里是重现问题的整个小程序的代码，问题在最后：
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <SDL.h>
#include <gl/glew.h>
#include <SDL_opengl.h>
#include <gl/glut.h>
#pragma comment (lib, "C:\\Program Files\\NVIDIA GPU Computing Toolkit\\CUDA\\v7.5\\lib\\x64\\OpenCL.lib")
#include <CL/cl.h>
#include <CL/cl_gl.h>
cl_int init_cl_context(cl_context *context, cl_command_queue *command_queue)
{
cl_int i, ret, pf_index=-1;
cl_platform_id platform_id[16];
cl_device_id device_id[16];
cl_uint ret_num_platforms;
cl_uint ret_num_devices;
ret = clGetPlatformIDs(sizeof(platform_id)/sizeof(*platform_id), platform_id, &ret_num_platforms); // get all the platforms
for (i=0; i<ret_num_platforms; i++) // go through all the platforms
{
ret = clGetDeviceIDs(platform_id[i], CL_DEVICE_TYPE_GPU, sizeof(device_id)/sizeof(*device_id), device_id, &ret_num_devices); // get all the suitable GPU devices
if (ret_num_devices > 0) // stop trying platforms when a suitable device is found
{
pf_index = i;
break;
}
}
cl_context_properties properties[] = { CL_GL_CONTEXT_KHR, (cl_context_properties)wglGetCurrentContext(), CL_WGL_HDC_KHR, (cl_context_properties)wglGetCurrentDC(), CL_CONTEXT_PLATFORM, (cl_context_properties)platform_id[pf_index], 0 };
*context = clCreateContextFromType(properties, CL_DEVICE_TYPE_GPU, NULL, NULL, &ret);
*command_queue = clCreateCommandQueue(*context, device_id[0], 0*CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE | 0*CL_QUEUE_PROFILING_ENABLE, &ret);
return ret;
}
int main(int argc, char *argv[])
{
cl_int ret=0;
int w = 800, h = 600;
SDL_Window *window;
SDL_Renderer *renderer;
cl_context context;
cl_command_queue command_queue;
cl_mem cltex; // CL buffer of type image_2d_t pointing to the GL texture
uint32_t gltex; // ID of the GL texture for cltex
//**** Init SDL, OpenGL/glew ****
SDL_Init(SDL_INIT_TIMER | SDL_INIT_VIDEO | SDL_INIT_AUDIO);
window = SDL_CreateWindow ("Title", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, w, h, SDL_WINDOW_OPENGL);
SDL_GetWindowSize(window, &w, &h);
SDL_GL_CreateContext(window);
glewExperimental = 1;
glewInit();
renderer = SDL_CreateRenderer(window, -1, 0*SDL_RENDERER_PRESENTVSYNC);
//-------------------------------
ret = init_cl_context(&context, &command_queue); // initialise the CL context to match GL as to make the interop possible
// create an OpenGL 2D texture normally
glEnable(GL_TEXTURE_2D);
glGenTextures(1, &gltex); // generate the texture ID
glBindTexture(GL_TEXTURE_2D, gltex); // binding the texture
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0); // specify texture dimensions, format etc
cltex = clCreateFromGLTexture(context, CL_MEM_WRITE_ONLY, GL_TEXTURE_2D, 0, gltex, &ret); // Creating the OpenCL image corresponding to the texture (once)
ret = clFinish(command_queue);
//glFinish(); // this works fine
ret = clEnqueueReleaseGLObjects(command_queue, 1, &cltex, 0, 0, NULL); // release the ownership from CL back to GL
clFinish(command_queue);
glFlush();
printf("This blocks the execution forever:\n");
glFinish(); // this blocks everything
printf("This never gets printed\n");
return 0;
}
在我更大的程序（有完全相同的问题）中，在驱动程序更新之前，一切都运行良好，现在甚至在更新之前编译的二进制文件也显示出与上述相同的冻结。为了便于阅读，我删除了对返回码的检查，但是在这个小程序和更大的程序中，根本没有报告任何问题。而且我看不出我可能做的任何明显错误...
【问题讨论】：
-
作为旁注，glFinish 在技术上不能保证永远返回，除非之前调用 glFlush，保证在“有限时间内”执行。只有少数供应商足够笨拙，不会在每次完成时都进行隐式冲洗。错误的代码可能从此过上幸福的生活……
-
我终于再次尝试了最新的驱动程序并添加了 glFlush() 但遗憾的是它仍然挂起。