1. 信号量
Linux提供了控制线程执行和访问代码临界区域的方法。其中最基本的两种办法是信号量和互斥量。
关于互斥量，笔者在Linux互斥量中介绍
本文只介绍semaphore.h 相关的信号量的简单的操作。关于信号量在笔者其他博客里有详细介绍。
Linux还有其他共享内存的方法。
2. 信号量相关函数
# include <semaphore.h >
int sem_init(sem_t *sem, int pshared, unsigned int value); //创建信号量
int sem_post(sem_t *sem); // +1操作
int sem_wait(sem_t *sem); // -1操作
int sem_destroy（sem_t *sem）; //销毁
3. 程序代码：
/***************************************
* @file semaphore.c
* @brief 线程信号量
* @author Windeal
* @date 2013/08/06
***************************************/
# include <stdlib.h >
# include <stdio.h >
# include <unistd.h >
# include <string.h >
# include <pthread.h >
# include <semaphore.h >
# define WORK_SIZE 1024 //
char work_area[WORK_SIZE];
sem_t bin_sem;
void *thread_function( void * arg);
int main( int argc, char * argv [ ])
{
int ret ;
void * thread_result;
pthread_t a_thread;
ret = sem_init( &bin_sem, 0, 0); //初始化信号量为0
if (ret != 0) {
perror( "sem_init() is failed!\n");
exit(EXIT_FAILURE);
}
ret = pthread_create( &a_thread, NULL, thread_function, NULL);
if (ret != 0) {
perror( "thread create failed!\n");
exit(EXIT_FAILURE);
}
printf( "Enter 'end' to finish!\n");
while (strncmp( "end", work_area, 3) != 0) {
fgets(work_area, WORK_SIZE, stdin);
sem_post( &bin_sem); // 信号量+ 1 操作
}
printf( "Waitint for thread join\n");
ret = pthread_join(a_thread, &thread_result);
if (ret != 0) {
perror( "thread_join failed!\n");
exit(EXIT_FAILURE);
}
printf( "thread join()\n");
sem_destroy( &bin_sem);
exit(EXIT_FAILURE);
}
void *thread_function( void * arg){
sem_wait( &bin_sem); // 信号量- 1 操作
while (strncmp( "end", work_area, 3) != 0){
printf( "you input %d charactor \n", strlen(work_area) - 1);
sem_wait( &bin_sem); // 信号量- 1 操作
}
pthread_exit(NULL);
}
* @file semaphore.c
* @brief 线程信号量
* @author Windeal
* @date 2013/08/06
***************************************/
# include <stdlib.h >
# include <stdio.h >
# include <unistd.h >
# include <string.h >
# include <pthread.h >
# include <semaphore.h >
# define WORK_SIZE 1024 //
char work_area[WORK_SIZE];
sem_t bin_sem;
void *thread_function( void * arg);
int main( int argc, char * argv [ ])
{
int ret ;
void * thread_result;
pthread_t a_thread;
ret = sem_init( &bin_sem, 0, 0); //初始化信号量为0
if (ret != 0) {
perror( "sem_init() is failed!\n");
exit(EXIT_FAILURE);
}
ret = pthread_create( &a_thread, NULL, thread_function, NULL);
if (ret != 0) {
perror( "thread create failed!\n");
exit(EXIT_FAILURE);
}
printf( "Enter 'end' to finish!\n");
while (strncmp( "end", work_area, 3) != 0) {
fgets(work_area, WORK_SIZE, stdin);
sem_post( &bin_sem); // 信号量+ 1 操作
}
printf( "Waitint for thread join\n");
ret = pthread_join(a_thread, &thread_result);
if (ret != 0) {
perror( "thread_join failed!\n");
exit(EXIT_FAILURE);
}
printf( "thread join()\n");
sem_destroy( &bin_sem);
exit(EXIT_FAILURE);
}
void *thread_function( void * arg){
sem_wait( &bin_sem); // 信号量- 1 操作
while (strncmp( "end", work_area, 3) != 0){
printf( "you input %d charactor \n", strlen(work_area) - 1);
sem_wait( &bin_sem); // 信号量- 1 操作
}
pthread_exit(NULL);
}
运行结果：
