zoukankan      html  css  js  c++  java
  • sched_yield()函数

    这个函数可以使用另一个级别等于或高于当前线程的线程先运行。如果没有符合条件的线程,那么这个函数将会立刻返回然后继续执行当前线程的程序。
    
    下面这个例子中,只是使用了 sched_yield这个函数,其实就实际效果上,并未体现出其真正的意义,主要旨在体会用法。 
    
    #define _MULTI_THREADED 
    #include <pthread.h> 
    #include <stdio.h> 
    #include <errno.h> 
    #define checkResults(string, val) { \ 
    
    if(val){ \ printf("Failed with %d at %s", val, string); \ 
    
    exit(1); \ } \ } #define LOOPCONSTANT 1000 #define THREADS 3 
    
    pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; int i,j,k,l; 
    
    void *threadfunc(void *parm) 
    
    { int loop = 0; int localProcessingCompleted = 0; int numberOfLocalProcessingBursts = 0; int processingCompletedThisBurst = 0; int rc; 
    
    printf("Entered secondary thread\n"); 
    
    for (loop=0; loop<LOOPCONSTANT; ++loop) { rc = pthread_mutex_lock(&mutex); checkResults("pthread_mutex_lock()\n", rc); /* Perform some not so important processing */ i++, j++, k++, l++;
    
     rc = pthread_mutex_unlock(&mutex); checkResults("pthread_mutex_unlock()\n", rc); 
    
     
    
    /* This work is not too important. Also, we just released a lock and would like to ensure that other threads get a chance in a more co-operative manner. This is an admittedly contrived example with no real purpose for doing the sched_yield(). */
    
     sched_yield(); } printf("Finished secondary thread\n"); return NULL; 
    
    } 
    
    int main(int argc, char **argv) 
    
    { pthread_t threadid[THREADS]; int rc=0; int loop=0; 
    
    printf("Enter Testcase - %s\n", argv[0]); 
    
     rc = pthread_mutex_lock(&mutex); checkResults("pthread_mutex_lock()\n", rc); 
    
    printf("Creating %d threads\n", THREADS); 
    
    for (loop=0; loop<THREADS; ++loop) { rc = pthread_create(&threadid[loop], NULL, threadfunc, NULL); checkResults("pthread_create()\n", rc);
    
     }
    
     sleep(1); rc = pthread_mutex_unlock(&mutex); checkResults("pthread_mutex_unlock()\n", rc); 
    
    printf("Wait for results\n"); 
    
    for (loop=0; loop<THREADS; ++loop) { rc = pthread_join(threadid[loop], NULL); checkResults("pthread_join()\n", rc);
    
     } 
    
    pthread_mutex_destroy(&mutex); 
    
    printf("Main completed\n"); return 0; }

  • 相关阅读:
    「Poetize10」封印一击
    「Poetize10」能量获取
    vijosP1499炸毁燃料库
    BZOJ3550: [ONTAK2010]Vacation
    总结#3--一类最小割问题
    BZOJ1976: [BeiJing2010组队]能量魔方 Cube
    BZOJ2132: 圈地计划
    BZOJ2127: happiness
    BZOJ1754: [Usaco2005 qua]Bull Math
    920. 会议室
  • 原文地址:https://www.cnblogs.com/yuzaipiaofei/p/4124631.html
Copyright © 2011-2022 走看看