Linux多线程之优先级

本人转载的　Linux多线程编程（一）和　linux多线程编程（五）解决我的 如下问题：

１、多线程的作用：　即什么情况考虑使用多线程？

２、多线程的创建：　默认参数创建即可！pthread_create(&tid,NULL,(void *)thread_func,NULL);

３、多线程的同步：　掌握互斥，条件 　两种同步方式即可！

下表来自于：http://www.ibm.com/developerworks/cn/linux/l-cn-mthreadps/index.html

表 1. 线程函数列表

对象	操作	Linux Pthread API	Windows SDK 库对应 API
线程	创建	pthread_create	CreateThread
	退出	pthread_exit	ThreadExit
	等待	pthread_join	WaitForSingleObject
互斥锁	创建	pthread_mutex_init	CreateMutex
	销毁	pthread_mutex_destroy	CloseHandle
	加锁	pthread_mutex_lock	WaitForSingleObject
	解锁	pthread_mutex_unlock	ReleaseMutex
条件	创建	pthread_cond_init	CreateEvent
	销毁	pthread_cond_destroy	CloseHandle
	触发	pthread_cond_signal	SetEvent
	广播	pthread_cond_broadcast	SetEvent / ResetEvent
	等待	pthread_cond_wait / pthread_cond_timedwait	SingleObjectAndWait

但我还有一个问题：

４、主线程是否比默认创建的线程优先级更高？

我用如下测试代码及运行结果说明问题：

#include
#include
#include
#include

void Thread_1()
{
  printf("%s  pid :0x%x, tid :0x%x \n",__func__,  getpid(), (int)pthread_self());  
  
  int i=0,j=0;

  while(1)
  {
    for(j=1;j<5000000;j++)
    {
    }
    //sleep(1);　// 删除sleep,每个线程都全力运行！
    i++;
    printf("%s,  %d\n", __func__, i);
  }
}


void Thread_2()
{
  printf("%s  pid :0x%x, tid :0x%x \n",__func__,  getpid(), (int)pthread_self());  
  
  int i=0,j=0;

  while(1)
  {
    for(j=1;j<5000000;j++)
    {
    }
    //sleep(1);
    i++;
    printf("%s,  %d\n", __func__, i);
  }
}


void Thread_3()
{
  printf("%s  pid :0x%x, tid :0x%x \n",__func__,  getpid(), (int)pthread_self());  
  
  int i=0,j=0;

  while(1)
  {
    for(j=1;j<5000000;j++)
    {
    }
    //sleep(1);
    i++;
    printf("%s,  %d\n", __func__, i);
  }
}


void Thread_main()
{
  printf("%s  pid :0x%x, tid :0x%x \n",__func__,  getpid(), (int)pthread_self());  
  
  int i=0,j=0;

  while(1)
  {
    for(j=1;j<5000000;j++)
    {
    }
    //sleep(1);
    i++;
    printf("%s,  %d\n", __func__, i);
  }
}
int main()
{
  pthread_t ppid1,ppid2,ppid3;
  printf("%s  pid :0x%x, tid :0x%x \n",__func__,  getpid(), (int)pthread_self());  

  pthread_create(&ppid1,NULL,(void *)Thread_1,NULL);
  pthread_create(&ppid2,NULL,(void *)Thread_2,NULL);
  pthread_create(&ppid3,NULL,(void *)Thread_3,NULL);

  Thread_main(); 

  return 0;
}

编译执行结果如下：

$ gcc test.c -lpthread

$ ./a.out 

删除sleep,每个线程都全力运行！

运行结果可以看出：主线程没有明显的级别优先。

应避免使用“父线程”和“子线程”的说法

main  pid :0x71c5, tid :0x65bfa720 
Thread_2  pid :0x71c5, tid :0x64c4b700 
Thread_main  pid :0x71c5, tid :0x65bfa720 
Thread_1  pid :0x71c5, tid :0x6544c700 
Thread_3  pid :0x71c5, tid :0x6444a700 
Thread_main,  1
Thread_3,  1
Thread_1,  1
Thread_2,  1
Thread_main,  2
Thread_3,  2
Thread_1,  2
Thread_main,  3
Thread_2,  2
Thread_3,  3
Thread_main,  4
Thread_1,  3
Thread_2,  3
Thread_main,  5
Thread_3,  4
Thread_1,  4
Thread_main,  6
Thread_2,  4
Thread_3,  5
Thread_main,  7
Thread_1,  5
Thread_2,  5
Thread_3,  6
Thread_main,  8
Thread_1,  6
Thread_2,  6
Thread_main,  9
Thread_3,  7
Thread_1,  7
Thread_main,  10
Thread_2,  7
Thread_3,  8
Thread_main,  11
Thread_1,  8
Thread_2,  8
Thread_main,  12
Thread_3,  9
Thread_1,  9
Thread_2,  9
Thread_main,  13
Thread_3,  10
Thread_1,  10
Thread_main,  14
Thread_2,  10
Thread_3,  11
Thread_1,  11
Thread_main,  15
Thread_2,  11
Thread_3,  12
Thread_main,  16
Thread_1,  12
Thread_2,  12
Thread_main,  17
Thread_3,  13
Thread_2,  13
Thread_main,  18
Thread_3,  14
Thread_1,  13
Thread_2,  14
Thread_main,  19
Thread_3,  15
Thread_1,  14
Thread_2,  15
Thread_main,  20
Thread_3,  16
Thread_main,  21
Thread_2,  16
Thread_1,  15
Thread_main,  22
Thread_3,  17
Thread_2,  17
Thread_main,  23
Thread_1,  16
Thread_3,  18
Thread_2,  18
Thread_main,  24
Thread_1,  17
Thread_2,  19
Thread_3,  19
Thread_main,  25
Thread_3,  20
Thread_2,  20
Thread_main,  26
Thread_1,  18
Thread_main,  27
Thread_2,  21
Thread_3,  21
Thread_1,  19
Thread_main,  28
Thread_2,  22
Thread_3,  22
Thread_main,  29
Thread_1,  20
Thread_3,  23
Thread_2,  23
Thread_main,  30
Thread_1,  21
Thread_2,  24
Thread_3,  24
Thread_main,  31
Thread_1,  22
Thread_main,  32
Thread_3,  25
Thread_2,  25
Thread_main,  33
Thread_1,  23
Thread_2,  26
Thread_3,  26
Thread_main,  34
Thread_1,  24
Thread_3,  27
Thread_2,  27
Thread_main,  35
Thread_1,  25
Thread_2,  28
Thread_main,  36
Thread_3,  28
Thread_main,  37
Thread_1,  26
Thread_3,  29
Thread_2,  29
Thread_main,  38
Thread_1,  27
Thread_3,  30
Thread_main,  39

..........

Thread_main,  3736
Thread_2,  3671
Thread_1,  2888
Thread_main,  3737
Thread_3,  2840
Thread_2,  3672