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此時互斥鎖的作用，只有在時間足夠的情況下才能體現(xiàn)出來，即有時線程內(nèi)需要延時； 否則只有第一個線程不斷解鎖和獲鎖，別的線程在第一個線程執(zhí)行完前無法獲得互斥鎖。 三 pthread_join pthread_exit 函數(shù)pthread_join用來等待一個線程的結(jié)束。函數(shù)原型為： extern int pthread_join __P ((pthread_t __th, void **__thread_return)); 第一個參數(shù)為被等待的線程標識符，第二個參數(shù)為一個用戶定義的指針，它可以用來存儲被等待線程的返回值。這個函數(shù)是一個線程阻塞的函數(shù)，調(diào)用它的函數(shù)將 一直等待到被等待的線程結(jié)束為止，當(dāng)函數(shù)返回時，被等待線程的資源被收回。一個線程的結(jié)束有兩種途徑，一種是象我們上面的例子一樣，函數(shù)結(jié)束了，調(diào)用它的 線程也就結(jié)束了；另一種方式是通過函數(shù)pthread_exit來實現(xiàn)。它的函數(shù)原型為： extern void pthread_exit __P ((void *__retval)) __attribute__ ((__noreturn__)); 唯一的參數(shù)是函數(shù)的返回代碼，只要pthread_join中的第二個參數(shù)thread_return不是NULL，這個值將被傳遞給 thread_return。最后要說明的是，一個線程不能被多個線程等待，否則第一個接收到信號的線程成功返回，其余調(diào)用pthread_join的線 程則返回錯誤代碼ESRCH。 在這一節(jié)里，我們編寫了一個最簡單的線程，并掌握了最常用的三個函數(shù)pthread_create，pthread_join和pthread_exit。下面，我們來了解線程的一些常用屬性以及如何設(shè)置這些屬性。 /////////////////////////////////////////////////////////////////////////// 源程序： /*thread_example.c : c multiple thread programming in linux */ #include #include #include #include #define MAX1 10 #define MAX2 30 pthread_t thread[2]; pthread_mutex_t mut; int number=0, i; void *thread1() { printf ("thread1 : I'm thread 1\n"); for (i = 0; i < MAX1; i++) { printf("thread1 : number = %d i=%d\n",number,i); pthread_mutex_lock(&mut); number++; pthread_mutex_unlock(&mut); sleep(2); } printf("thread1 :Is main function waiting for me acomplishing task? \n"); pthread_exit(NULL); } void *thread2() { printf("thread2 : I'm thread 2\n"); for (i = 0; i < MAX2; i++) { printf("thread2 : number = %d i=%d\n",number,i); pthread_mutex_lock(&mut); number++; pthread_mutex_unlock(&mut); sleep(3); } printf("thread2 :Is main function waiting for me to acomplish task ?\n"); pthread_exit(NULL); } void thread_create(void) { int temp; memset(&thread, 0, sizeof(thread)); //comment1 /*創(chuàng)建線程*/ if((temp = pthread_create(&thread[0], NULL, thread1, NULL)) != 0) //comment2 printf("線程1創(chuàng)建失敗!\n"); else printf("Thread 1 is established\n"); if((temp = pthread_create(&thread[1], NULL, thread2, NULL)) != 0) //comment3 printf("線程2創(chuàng)建失敗"); else printf("Thread 2 is established\n"); } void thread_wait(void) { /*等待線程結(jié)束*/ if(thread[0] !=0) { //comment4 pthread_join(thread[0],NULL); printf("Thread 1 is over \n"); } if(thread[1] !=0) { //comment5 pthread_join(thread[1],NULL); printf("Thread 2 is over\n"); } } int main() { /*用默認屬性初始化互斥鎖*/ pthread_mutex_init(&mut,NULL); printf("I am the main funtion,and I am establishing threads. Ha-ha\n"); thread_create(); printf("I am the main funtion,and I am waiting for thread to accomplish task. Ha-ha\n"); thread_wait(); return 0; } /////////////////////////////////////////////////////////// 執(zhí)行情況1(linux終端)： [root@localhost root]# gcc -o joint joint.c -lpthread [root@localhost root]# ./joint I am the main funtion,and I am establishing threads. Ha-ha thread1 : I'm thread 1 thread1 : number = 0 i=0 Thread 1 is established thread2 : I'm thread 2 thread2 : number = 1 i=0 Thread 2 is established I am the main funtion,and I am waiting for thread to accomplish task. Ha-ha thread1 : number = 2 i=1 thread2 : number = 3 i=2 thread1 : number = 4 i=3 thread2 : number = 5 i=4 thread1 : number = 6 i=5 thread1 : number = 7 i=6 thread2 : number = 8 i=7 thread1 : number = 9 i=8 thread2 : number = 10 i=9 thread1 :Is main function waiting for me acomplishing task? Thread 1 is over thread2 : number = 11 i=11 thread2 : number = 12 i=12 thread2 : number = 13 i=13 thread2 : number = 14 i=14 thread2 : number = 15 i=15 thread2 : number = 16 i=16 thread2 : number = 17 i=17 thread2 : number = 18 i=18 thread2 : number = 19 i=19 thread2 : number = 20 i=20 thread2 : number = 21 i=21 thread2 : number = 22 i=22 thread2 : number = 23 i=23 thread2 : number = 24 i=24 thread2 : number = 25 i=25 thread2 : number = 26 i=26 thread2 : number = 27 i=27 thread2 : number = 28 i=28 thread2 : number = 29 i=29 thread2 :Is main function waiting for me to acomplish task ? Thread 2 is over |
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