線程的條件變量實例

情景1：

Jack開著一輛出租車來到一個網站停車。看見沒人就走了。過段時間。Susan來到網站準備乘車。可是沒有來，于是就等著。過了一會Mike開著車來到了這個網站，Sunsan就上了Mike的車走了。如圖所看到的：

程序實現該情景：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>pthread_cond_t taxicond = PTHREAD_COND_INITIALIZER;
pthread_mutex_t taximutex = PTHREAD_MUTEX_INITIALIZER;void *traveler_arrive(void *name)
{char *p = (char *)name;printf ("Travelr: %s need a taxi now!\n", p);pthread_mutex_lock(&taximutex);pthread_cond_wait(&taxicond, &taximutex);pthread_mutex_unlock(&taximutex);printf ("traveler: %s now got a taxi!\n", p);pthread_exit(NULL);
}void *taxi_arrive(void *name)
{char *p = (char *)name;printf ("Taxi: %s arrives.\n", p);pthread_cond_signal(&taxicond);pthread_exit(NULL);
}int main (int argc, char **argv)
{char *name;pthread_t thread;pthread_attr_t threadattr;pthread_attr_init(&threadattr);name = "Jack";pthread_create(&thread, &threadattr, taxi_arrive, name);sleep(1);name = "Susan";pthread_create(&thread, &threadattr, traveler_arrive, name);sleep(1);name = "Mike";pthread_create(&thread, &threadattr, taxi_arrive, name);sleep(1);return 0;
} /* ----- End of main() ----- */

情景2：

Jack開著一輛出租車來到一個網站停車，看見沒人就等著。過段時間，Susan來到網站準備乘車看見了Jack的出租車，于是就上去了。過了一會Mike開著車來到了這個網站，看見沒人救等著。

如圖所看到的：

程序實現該情景：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>int travelercount = 0;
pthread_cond_t taxicond = PTHREAD_COND_INITIALIZER;
pthread_mutex_t taximutex = PTHREAD_MUTEX_INITIALIZER;void *traveler_arrive(void *name)
{char *p = (char *)name;pthread_mutex_lock(&taximutex);printf ("traveler: %s need a taxi now!\n", p);travelercount++;pthread_cond_wait(&taxicond, &taximutex);pthread_mutex_unlock(&taximutex);printf ("traveler: %s now got a taxi!\n", p);pthread_exit(NULL);
}void *taxi_arrive(void *name)
{char *p = (char *)name;printf ("Taxi: %s arrives.\n", p);for(;;){if(travelercount){pthread_cond_signal(&taxicond);travelercount--;break;}}pthread_exit(NULL);
}int main (int argc, char **argv)
{char *name;pthread_t thread;pthread_attr_t threadattr;pthread_attr_init(&threadattr);name = "Jack";pthread_create(&thread, &threadattr, taxi_arrive, name);sleep(1);name = "Susan";pthread_create(&thread, &threadattr, traveler_arrive, name);sleep(3);name = "Mike";pthread_create(&thread, &threadattr, taxi_arrive, name);sleep(4);return 0;
} /* ----- End of main() ----- */

author: fulinux

E-mail: fulinux@sina.com

blog: blog.csdn.net/fulinus