POSIX的只執行一次的pthread_once

POSIX的只執行一次的pthread_once

1. #ifdef WIN32
2. #include <windows.h>
3. #define SLEEP(ms) Sleep(ms)
4. #else if defined(LINUX)
5. #include <stdio.h>
6. #define SLEEP(ms) sleep(ms)
7. #endif
9. #include <cassert>
10. #include <pthread.h>
12. // 取出線程的ID
13. int GetThreadID()
14. {
15. #ifdef WIN32
16. return (int)pthread_getw32threadhandle_np( pthread_self() );
17. #else if defined(LINUX)
18. return (int)pthread_self();
19. #endif
20. }
22. // 該靜態變量被所有線程使用
23. static int s_nThreadResult = 0;
25. static pthread_once_t once = PTHREAD_ONCE_INIT;
27. // 該初始化函數，我在多線程下只想執行一次
28. void thread_init()
29. {
30. s_nThreadResult = -1;
31. printf("[Child %0.4x] looping i(%0.8x)\n", GetThreadID(), s_nThreadResult);
32. }
34. void * theThread(void * param)
35. {
36. // 通過once的控制，thread_init只會被執行一次
37. pthread_once(&once, &thread_init);
38. printf("[Child %0.4x] looping i(%0.8x)\n", GetThreadID(), s_nThreadResult);
40. s_nThreadResult ++;
41. pthread_exit(&s_nThreadResult);
43. return NULL;
44. }
46. int main(int argc, char* argv[])
47. {
48. pthread_t tid1, tid2;
49. pthread_create(&tid1, NULL, &theThread, NULL);
50. pthread_create(&tid2, NULL, &theThread, NULL);
52. // 無論是否休眠，兩個子線程最終都會被主線程join到
53. // 因為兩個子線程都是默認的PTHREAD_CREATE_JOINABLE類型
54. //SLEEP(3);
56. void * status = NULL;
57. int rc = pthread_join(tid1, &status);
58. assert(rc == 0 && "pthread_join 1", rc);
59. if (status != PTHREAD_CANCELED && status != NULL)
60. {
61. printf("Returned value from thread: %d\n", *(int *)status);
62. }
64. rc = pthread_join(tid2, &status);
65. assert(rc == 0 && "pthread_join 2", rc);
66. if (status != PTHREAD_CANCELED && status != NULL)
67. {
68. printf("Returned value from thread: %d\n", *(int *)status);
69. }
71. return 0;
72. }