Linux多線程──主線程和子線程分別循環一定次數

子線程循環 10 次，接著主線程循環 100 次，接著又回到子線程循環 10 次，接著再回到主線程又循環 100 次，如此循環50次，試寫出代碼。

要注意條件變量的自動復位問題。參看這篇文章：Linux 的多線程編程的高效開發經驗 http://www.linuxidc.com/Linux/2009-04/19615.htm

代碼：

1. #include <pthread.h>
2. #include <stdio.h>
4. // 互斥鎖，條件變量
5. pthread_mutex_t mutex;
6. pthread_cond_t cond;
8. // 循環次數
9. int main_count = 0;
10. int subthread_count = 0;
12. // 線程等待標志
13. bool main_thread_wait_flag = false;
14. bool subthread_wait_flag = false;
16. void main_thread_func();
17. void *subthread_func(void *arg);
19. int main(int argc, char **argv)
20. {
21. pthread_t tid;
23. pthread_mutex_init(&mutex, NULL);
24. pthread_cond_init(&cond, NULL);
26. pthread_create(&tid, NULL, subthread_func, NULL);
27. main_thread_func();
28. pthread_join(tid, NULL);
30. return 0;
31. }
33. void main_thread_func()
34. {
35. while (true)
36. {
37. pthread_mutex_lock(&mutex);
38. main_thread_wait_flag = true;
39. pthread_cond_wait(&cond, &mutex);
40. main_thread_wait_flag = false;
41. pthread_mutex_unlock(&mutex);
43. for (int i = 1; i <= 100; ++i)
44. {
45. fprintf(stdout, "main thread: %d\n", i);
46. }
49. while (true)
50. {
51. pthread_mutex_lock(&mutex);
52. if (true == subthread_wait_flag)
53. {
54. pthread_cond_signal(&cond);
55. pthread_mutex_unlock(&mutex);
56. break;
57. }
58. pthread_mutex_unlock(&mutex);
59. }
61. ++main_count;
62. if (main_count >= 50)
63. {
64. fprintf(stdout, "main thread loop 50 times\n");
65. break;
66. }
67. }
68. }
70. void *subthread_func(void *arg)
71. {
72. while (true)
73. {
74. for (int i = 1; i <= 10; ++i)
75. {
76. fprintf(stdout, "subthread: %d\n", i);
77. }
79. while (true)
80. {
81. pthread_mutex_lock(&mutex);
82. if (true == main_thread_wait_flag)
83. {
84. pthread_cond_signal(&cond);
85. pthread_mutex_unlock(&mutex);
86. break;
87. }
88. pthread_mutex_unlock(&mutex);
89. }
90. pthread_mutex_lock(&mutex);
91. subthread_wait_flag = true;
92. pthread_cond_wait(&cond, &mutex);
93. subthread_wait_flag = false;
94. pthread_mutex_unlock(&mutex);
96. ++subthread_count;
97. if (subthread_count >= 50)
98. {
99. fprintf(stdout, "subthread loop 50 times\n");
100. break;
101. }
102. }
103. return (void *)0;
104. }