日期:2014-05-16 浏览次数:20644 次
linux的多线程,其实就是clone系统调用的实现的(共享文件等)
首先看个具体的例子:
#include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <unistd.h> #include <string.h> #include <sched.h> #include <errno.h> void *print_message_function( void *ptr ); int main() { pthread_t thread1, thread2; const char *message1 = "Thread 1"; const char *message2 = "Thread 2"; int iret1, iret2; /* Create independent threads each of which will execute function */ iret1 = pthread_create( &thread1, NULL, print_message_function, (void*) message1); iret2 = pthread_create( &thread2, NULL, print_message_function, (void*) message2); /* Wait till threads are complete before main continues. Unless we */ /* wait we run the risk of executing an exit which will terminate */ /* the process and all threads before the threads have completed. */ pthread_join( thread1, NULL); pthread_join( thread2, NULL); printf("Thread 1 returns: %d\n",iret1); printf("Thread 2 returns: %d\n",iret2); for(;;) { usleep(250*1000); } return 0; } void *print_message_function( void *ptr ) { char *message; for(;;) { message = (char *) ptr; printf("%s \n", message); usleep(3*250*1000); } return 0; }
此时一共有三个进程在跑(相对于kernel来说,只有进程的概念)
一般情况是,一个进程在/proc 目录下就对应一个,以该进程ID号名字的
文件目录,该目录下保存着该进程的所有信息。
但是对应,所谓的多线程,它的目录结构该会这么样呢?
假如该程序名为:thread
$
top -t | grep thread
PID TID PR CPU% S VSS RSS PCY UID Thread Proc
31694 31694 0 0% S 3008K 416K root thread system/bin/thread
31694 31695 0 0% S 3008K 416K root thread system/bin/thread
31694 31696 0 0% S 3008K 416K root thread system/bin/thread
可知他们对应于一个进程ID号,而在此目录下,分别在有其他三个线程目录信息:
proc/31694/task # ls
31694
31695
31696