pthread_t互斥锁的设置范围

关于Linux 线程pthread_join的用法

Linux系统pthread_join用于挂起当前线程（调用pthread_join的线程），直到thread指定的线程终止运行为止，当前线程才继续执行。

案例代码： /******************************************* **????Name:pthread_join.c **????用于Linux下多线程学习 **????案例解释线程的暂停和结束 **????Author:admin **????Date:2015/8/11??????? **????Copyright?(c)?2015,All?Rights?Reserved! ********************************************** #include?<pthread.h> #include?<unistd.h> #include?<stdio.h> void?*thread(void?*str) { ????int?i; ????//不调用pthread_join线程函数 ????for?(i?=?0;?i?<?10;?++i) ????{ ????????sleep(2); ????????printf(?"This?in?the?thread?:?%d "?,?i?); ????} ????return?NULL; } int?main() { ????pthread_t?pth; ????int?i; ????int?ret?=?pthread_create(&pth,?NULL,?thread,?(void?*)(i)); ????//调用pthread_join线程函数 ????pthread_join(pth,?NULL); ????for?(i?=?0;?i?<?10;?++i) ????{ ????????sleep(1); ????????printf(?"This?in?the?main?:?%d "?,?i?); ????} ????return?0; }通过Linux下shell命令执行上面的案例代码： [root@localhost?src]#??pthread_join.c?-lpthread [root@localhost?src]#?./a.out This?in?the?main?:?0 This?in?the?thread?:?0 This?in?the?main?:?1 This?in?the?main?:?2 This?in?the?thread?:?1 This?in?the?main?:?3 This?in?the?main?:?4 This?in?the?thread?:?2 This?in?the?main?:?5 This?in?the?main?:?6 This?in?the?thread?:?3 This?in?the?main?:?7 This?in?the?main?:?8 This?in?the?thread?:?4 This?in?the?main?:?9子线程还没有执行完毕，main函数已经退出，那么子线程也就退出了，“pthread_join(pth,?NULL);”函数起作用。

[root@localhost?src]#??pthread_join.c?-lpthread [root@localhost?src]#?./a.out This?in?the?thread?:?0 This?in?the?thread?:?1 This?in?the?thread?:?2 This?in?the?thread?:?3 This?in?the?thread?:?4 This?in?the?thread?:?5 This?in?the?thread?:?6 This?in?the?thread?:?7 This?in?the?thread?:?8 This?in?the?thread?:?9 This?in?the?main?:?0 This?in?the?main?:?1 This?in?the?main?:?2 This?in?the?main?:?3 This?in?the?main?:?4 This?in?the?main?:?5 This?in?the?main?:?6 This?in?the?main?:?7 This?in?the?main?:?8 This?in?the?main?:?9这说明pthread_join函数的调用者在等待子线程退出后才继续执行。

linux线程同步的互斥锁(mutex)到底怎么用的》？谢谢

互斥锁(mutex) 通过锁机制实现线程间的同步。

1、初始化锁。

在Linux下，线程的互斥量数据类型是pthread_mutex_t。

在使用前,要对它进行初始化。

2、静态分配：pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; 3、动态分配：int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutex_attr_t *mutexattr); 4、加锁。

对共享资源的访问，要对互斥量进行加锁，如果互斥量已经上了锁，调用线程会阻塞，直到互斥量被解锁。

????int?pthread_mutex_lock(pthread_mutex?*mutex); ????int?pthread_mutex_trylock(pthread_mutex_t?*mutex); ????解锁。

在完成了对共享资源的访问后，要对互斥量进行解锁。

????int?pthread_mutex_unlock(pthread_mutex_t?*mutex); ????销毁锁。

锁在是使用完成后，需要进行销毁以释放资源。

????int?pthread_mutex_destroy(pthread_mutex?*mutex); ????#include?<cstdio>?? ????#include?<cstdlib>?? ????#include?<unistd.h>?? ????#include?<pthread.h>?? ????#include?"iostream"?? ????using?namespace?std;?? ????pthread_mutex_t?mutex?=?PTHREAD_MUTEX_INITIALIZER;?? ????int?tmp;?? ????void*?thread(void?*arg)?? ????{?? ????????cout?<<?"thread?id?is?"?<<?pthread_self()?<<?endl;?? ????????pthread_mutex_lock(&mutex);?? ????????tmp?=?12;?? ????????cout?<<?"Now?a?is?"?<<?tmp?<<?endl;?? ????????pthread_mutex_unlock(&mutex);?? ????????return?NULL;?? ????}?? ????int?main()?? ????{?? ????????pthread_t?id;?? ????????cout?<<?"main?thread?id?is?"?<<?pthread_self()?<<?endl;?? ????????tmp?=?3;?? ????????cout?<<?"In?main?func?tmp?=?"?<<?tmp?<<?endl;?? ????????if?(!pthread_create(&id,?NULL,?thread,?NULL))?? ????????{?? ????????????cout?<<?"Create?thread?ess!"?<<?endl;?? ????????}?? ????????else?? ????????{?? ????????????cout?<<?"Create?thread?failed!"?<<?endl;?? ????????}?? ????????pthread_join(id,?NULL);?? ????????pthread_mutex_destroy(&mutex);?? ????????return?0;?? ????}?? ????//编译：g++?-o?thread?testthread.cpp?-lpthread

互斥锁的设置范围

pthread_mutexattr_setpshared(3C)可用来设置互斥锁变量的作用域。

pthread_mutexattr_setpshared 语法 int pthread_mutexattr_setpshared(pthread_mutexattr_t *mattr, int pshared); #include <pthread.h> pthread_mutexattr_t mattr; int ret; ret = pthread_mutexattr_init(&mattr);/* * resetting to its default value: private */ ret = pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_PRIVATE); 互斥锁变量可以是进程专用的（进程内）变量，也可以是系统范围内的（进程间）变量。

要在多个进程中的线程之间共享互斥锁，可以在共享内存中创建互斥锁，并将pshared属性设置为 PTHREAD_PROCESS_SHARED。

此行为与最初的 Solaris 线程实现中mutex_init()中的 USYNC_PROCESS 标志等效。

如果互斥锁的pshared属性设置为 PTHREAD_PROCESS_PRIVATE，则仅有那些由同一个进程创建的线程才能够处理该互斥锁。