网页设计的优缺点,济南关键词优化费用情况,wordpress now 1.5,wordpress 免登陆接口三种关系#xff1a;互斥#xff0c;同步#xff0c;互斥和同步 两类角色:生产者#xff0c;消费者#xff08;线程#xff09; 一个交易场所#xff1a;生产者消费者共享的区域
卖苹果的模型
dish上面只有一个苹果买家必须要等卖家把苹果放到dish上才可以去买苹果。…三种关系互斥同步互斥和同步 两类角色:生产者消费者线程 一个交易场所生产者消费者共享的区域
卖苹果的模型
dish上面只有一个苹果买家必须要等卖家把苹果放到dish上才可以去买苹果。卖家必须等待买家把苹果买走才可以生产苹果pthread_mutex_lock(mutex); 和pthread_mutex_unlock(mutex); 成对出现里面的操作为一个原子操作pthread_cond_wait(empty,mutex);内部有一个加锁解锁操作过程详解 苹果为0初始化时苹果为0买家在pthread_cond_wait(empty,mutex); 开始等待卖家不进入while循环生产苹果后发出pthread_cond_signal(empty);让正在因dish上苹果为0的买家停止等待pthread_cond_wait(empty,mutex);苹果为1当一个卖家进入pthread_mutex_lock(mutex); 但是发现苹果为1时就在while循环处等待pthread_cond_wait(empty,mutex);直到买家发出信号 pthread_cond_signal(full);卖家停止等待此时苹果为0跳出while循环开始生产苹果。生产苹果后发出pthread_cond_signal(empty);让正在因dish上苹果为0的买家停止等待pthread_cond_wait(empty,mutex); 这样这个过程就结束了 *
#include stdio.h
#include unistd.h
#include stdlib.h
#include pthread.hint dish 0;
pthread_cond_t full;
pthread_cond_t empty;
pthread_mutex_t mutex;void * consumer(void * arg)
{int id (int)arg;while(1){pthread_mutex_lock(mutex);//上锁while(dish 0){//买家发现没有苹果开始等待pthread_cond_wait(empty,mutex);}usleep(100000);dish 0;printf(consumer %d get an apple!!\n, id);//给卖家发送信号pthread_cond_signal(full);pthread_mutex_unlock(mutex);//解锁}return NULL;
}void * product(void *arg)
{int id (int)arg;while(1){pthread_mutex_lock(mutex); while(dish 1){pthread_cond_wait(full,mutex);}dish 1;printf(producer %d put an apple!!\n, id); pthread_cond_signal(empty);pthread_mutex_unlock(mutex);}return NULL;
}int main()
{pthread_t tid;int set ;//初始化pthread_cond_init(full,NULL);pthread_cond_init(empty,NULL);pthread_mutex_init(mutex,NULL);//四个卖家生产苹果for(int i 0;i4;i){pthread_create(tid,NULL,product,(void *)i);}//四个买家买苹果for(int i 0;i4;i){pthread_create(tid,NULL,consumer,(void *)i);}//等待thread标识的线程终止防止僵尸进程产生pthread_join(tid,NULL);//销毁所有资源pthread_cond_destroy(full);pthread_cond_destroy(empty);pthread_mutex_destroy(mutex);
}
如果对于互斥量含义尚不清楚建议阅读Linux/UNIX系统编程手册
pthread_mutex_t
pthread_mutex_init
pthread_mutex_lock
pthread_mutex_unlock
pthread_mutex_destroy
模型采取Linux/UNIX系统编程手册 这个模型很好也把概念讲清楚了加了中文注释
生产者
s pthread_mutex_lock(mtx);
if (s ! 0)errExitEN(s, pthread_mutex_lock);avail; /*这是一个原子操作 */s pthread_mutex_unlock(mtx);
if (s ! 0)errExitEN(s, pthread_mutex_unlock);s pthread_cond_signal(cond); /* 唤醒消费者 */
if (s ! 0)errExitEN(s, pthread_cond_signal);
消费者
s pthread_mutex_lock(mtx);
if (s ! 0)errExitEN(s, pthread_mutex_lock);while (avail 0){ s pthread_cond_wait(cond, mtx);if (s ! 0)errExitEN(s, pthread_cond_wait);
}
完整代码
#include time.h
#include pthread.h
#include tlpi_hdr.hstatic pthread_mutex_t mtx PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t cond PTHREAD_COND_INITIALIZER;static int avail 0;static void *
threadFunc(void *arg)
{int cnt atoi((char *) arg);int s, j;for (j 0; j cnt; j) {sleep(1);/* Code to produce a unit omitted */s pthread_mutex_lock(mtx);if (s ! 0)errExitEN(s, pthread_mutex_lock);avail; /* Let consumer know another unit is available */s pthread_mutex_unlock(mtx);if (s ! 0)errExitEN(s, pthread_mutex_unlock);s pthread_cond_signal(cond); /* Wake sleeping consumer */if (s ! 0)errExitEN(s, pthread_cond_signal);}return NULL;
}int
main(int argc, char *argv[])
{pthread_t tid;int s, j;int totRequired; /* Total number of units that all threadswill produce */int numConsumed; /* Total units so far consumed */Boolean done;time_t t;t time(NULL);/* Create all threads */totRequired 0;for (j 1; j argc; j) {totRequired atoi(argv[j]);s pthread_create(tid, NULL, threadFunc, argv[j]);if (s ! 0)errExitEN(s, pthread_create);}/* Loop to consume available units */numConsumed 0;done FALSE;for (;;) {s pthread_mutex_lock(mtx);if (s ! 0)errExitEN(s, pthread_mutex_lock);while (avail 0) { /* Wait for something to consume */s pthread_cond_wait(cond, mtx);if (s ! 0)errExitEN(s, pthread_cond_wait);}/* At this point, mtx is locked... */while (avail 0) { /* Consume all available units *//* Do something with produced unit */numConsumed ;avail--;printf(T%ld: numConsumed%d\n, (long) (time(NULL) - t),numConsumed);done numConsumed totRequired;}s pthread_mutex_unlock(mtx);if (s ! 0)errExitEN(s, pthread_mutex_unlock);if (done)break;/* Perhaps do other work here that does not require mutex lock */}exit(EXIT_SUCCESS);
}
