1# GPU/CPU内存访问同步操作开发指南 (C/C++) 2<!--Kit: ArkGraphics 2D--> 3<!--Subsystem: Graphics--> 4<!--Owner: @Felix-fangyang; @li_hui180; @dingpy--> 5<!--Designer: @conan13234--> 6<!--Tester: @nobuggers--> 7<!--Adviser: @ge-yafang--> 8## 场景介绍 9 10NativeFence是提供**同步管理fenceFd**的模块。开发者可以通过`NativeFence`接口实现对fenceFd阻塞指定时间、永久阻塞、关闭和检查fenceFd是否有效等操作。 11 12## 接口说明 13 14| 接口名 | 描述 | 15| -------- | -------- | 16| OH_NativeFence_IsValid (int fenceFd) | 检查fenceFd是否有效。 | 17| OH_NativeFence_Wait (int fenceFd, uint32_t timeout) | 阻塞传入的fenceFd，最大阻塞时间由超时参数决定。 | 18| OH_NativeFence_WaitForever (int fenceFd) | 永久阻塞传入的fenceFd。 | 19| OH_NativeFence_Close (int fenceFd) | 关闭fenceFd。 | 20 21详细的接口说明请参考[NativeFence](../reference/apis-arkgraphics2d/capi-nativefence.md)。 22 23## 开发步骤 24 25以下步骤描述了如何使用`NativeFence`提供的Native API接口。 26 27**添加动态链接库** 28 29CMakeLists.txt中添加以下lib。 30```txt 31libnative_fence.so 32``` 33 34**头文件** 35```c++ 36#include <native_fence/native_fence.h> 37#include <cstring> 38#include <iostream> 39#include <linux/sync_file.h> 40#include <signal.h> 41#include <sys/signalfd.h> 42#include <unistd.h> 43``` 441. **通过signalfd创建fenceFd**。 45 ```c++ 46 sigset_t mask; 47 sigemptyset(&mask); 48 sigprocmask(SIG_BLOCK, &mask, NULL); 49 50 int fenceFd = signalfd(-1, &mask, 0); 51 ``` 52 532. **判断传入的fenceFd是否合法**。 54 ```c++ 55 // 检查fenceFd是否有效 56 bool isValid = OH_NativeFence_IsValid(fenceFd); 57 if (!isValid) { 58 std::cout << "fenceFd is invalid" << std::endl; 59 } 60 ``` 61 623. **调用OH_NativeFence_Wait阻塞接口**。 63 ```c++ 64 constexpr uint32_t TIMEOUT_MS = 5000; 65 bool resultWait = OH_NativeFence_Wait(fenceFd, TIMEOUT_MS); 66 if (!resultWait) { 67 std::cout << "OH_NativeFence_Wait Failed" << std::endl; 68 } 69 ``` 70 714. **调用OH_NativeFence_WaitForever阻塞接口**。 72 ```c++ 73 bool resultWaitForever = OH_NativeFence_WaitForever(fenceFd); 74 if (!resultWaitForever) { 75 std::cout << "OH_NativeFence_WaitForever Failed" << std::endl; 76 } 77 ``` 78 795. **GPU或CPU进行信号触发signal，通知fenceFd解除阻塞**。 80 816. **关闭fenceFd**。 82 ```c++ 83 OH_NativeFence_Close(fenceFd); 84 ```