我写了一个简单的程序解决读者作家问题使用信号量.它在
Linux操作系统上运行完美,但是当我在Mac OSX上运行它时,我会得到意想不到的结果,我不知道为什么.
我的计划:
#include <semaphore.h> #include <sys/types.h> #include <stdio.h> #include <pthread.h> #include <unistd.h> void* function1(void* val); void* function2(void* val); // shared values volatile int X; volatile int Y; // declare semaphores sem_t s1; sem_t s2; main() { void* status; pthread_t thread1; pthread_t thread2; srand(time(NULL)); // initialize semaphores to zero sem_init(&s1,0); sem_init(&s2,0); pthread_create(&thread1,NULL,function1,NULL); pthread_create(&thread2,function2,NULL); pthread_join(thread1,&status); pthread_join(thread2,&status); sem_destroy(&s1); sem_destroy(&s2); } void* function1(void* val) { while(1) { X = rand()%1000; // write printf("After thread ID A writes to X,X = %d\n",X); sem_post(&s1); // signal sem_wait(&s2); // wait printf("After thread ID A reads from Y,Y = %d\n",Y); // read sleep(3); } } void* function2(void* val) { while(1) { sem_wait(&s1); // wait printf("After thread ID B reads from X,X); // read Y = rand()%1000; // write printf("After thread ID B write to Y,Y); sem_post(&s2); // signal sleep(3); } }
我在Linux上收到的输出(应该是什么样的):
After thread ID A writes to X,X = 100 After thread ID B reads from X,X = 100 After thread ID B write to Y,Y = 234 After thread ID A reads from Y,Y = 234 ...
Mac OSX上的输出(意外):
After thread ID A writes to X,X = 253 After thread ID A reads from Y,Y = 0 After thread ID B reads from X,X = 253 After thread ID B write to Y,Y = 728 ...
解决方法
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