一入 Java 深似海 系列 第四期 第一节 POSIX Thread

一入 Java 深似海 系列课程 - 第四期 第一节：POSIX Thread 小马哥 mercyblitz 一入 Java 深似海 系列课程 讲师信息 小马哥，Java 劝退师，Apache 和 Spring Cloud 等知名开源 架构成员。 微信：mercyblitz-1985 GitHub： 课件资源： lessons/ 博客：https:/mercyblitz.github.io/ 一入 Java 深似海 系列课程 小马哥书籍预售 Spring Boot 编程思想 - 核心篇 以 Spring Boot 2.0 为讨论的主线，讨论的范围将涵盖 Spring Boot 1.x 的所有版本，以及所关联的 Spring Framework 版本 场景分析：掌握技术选型 系统学习：拒绝浅尝辄止 重视规范：了解发展趋势 源码解读：理解设计思想 实战演练：巩固学习成果 主要议题 POSIX Thread 简介 POSIX Thread 基础 API POSIX Thread 同步 API 课程总结 下期预告 POSIX Thread 简介 POSIX Thread POSIX 简介 POSIX stands for Portable Operating System Interface for UNIX POSIX is thus not an implementation of UNIX but rather specifi cations of the APIs available for UNIX implementations. The standards in POSIX are specifi ed by the IEEE. POSIX Thread POSIX Thread 介绍 The POSIX thread libraries are a standards based thread API for C/C+. It allows one to spawn a new concurrent process fl ow. It is most effective on multi-processor or multi-core systems where the process fl ow can be scheduled to run on another processor thus gaining speed through parallel or distributed processing.Threads require less overhead than forking or spawning a new process because the system does not initialize a new system virtual memory space and environment for the process. While most effective on a multiprocessor system, gains are also found on uniprocessor systems which exploit latency in I/O and other system functions which may halt process execution. POSIX Thread POSIX Thread 介绍 POSIX Threads are described by three parts: Functions for runnning threads Functions for synchronizing threads Functions for scheduling threads POSIX Thread 线程基础 同进程中的线程 进程指令（Process instructions） 打开的文件描述（FD） 信号和信号处理（signals and signal handlers） 当前工作目录（current working directory） POSIX Thread 线程基础 线程特有的 线程ID（Thread ID） 寄存器集合、栈指针（set of registers, stack pointer） 局部变量栈和返回地址（stack for local variables, return addresses） POSIX Thread 线程基础 线程特有的 信号掩码（signal mask） 优先级（priority） 返回值（Return value: errno） POSIX Thread 基础 API POSIX Thread 基础 API 核心 API - 创建线程 pthread_create Java API - new Thread(Runnable) POSIX Thread 基础 API 核心 API - 线程属性（pthread_attr_t） pthread_attr_* 状态：是否可 JOIN，默认值 PTHREAD_CREATE_JOINABLE 调度策略：是否实时，默认值 范围：内核（PTHREAD_SCOPE_SYSTEM）、用户（PTHREAD_SCOPE_PROCESS） 栈：地址和大小 POSIX Thread 基础 API 核心 API - 线程执行结束 pthread_join Java API - Thread#join() POSIX Thread 基础 API 核心 API - 终止线程 等待函数执行完毕 void pthread_exit(void* value) Java API - Thread#exit()（非公开方法） int pthread_cancel(pthread_t thread) Java API - Thread#stop()（不推荐方法） POSIX Thread 同步 API POSIX Thread 同步 API 线程同步 三大原语（primitives） 互斥（Mutex） 条件变量（Condition variable） 屏障（Barriers） POSIX Thread 同步 API 互斥（Mutex） A POSIX Threads mutex is a lock with a sleep queue and not a spin lock. 类型：pthread_mutex_t 函数： pthread_mutex_init - used to create mutex attribute objects respectively. pthread_mutex_destroy - used to free a mutex object which is no longer needed. POSIX Thread 同步 API 互斥（Mutex） 函数（续）： pthread_mutex_lock - is used by a thread to acquire a lock on the specifi ed mutex variable. If the mutex is already locked by another thread, this call will block the calling thread until the mutex is unlocked. pthread_mutex_trylock - will attempt to lock a mutex. However, if the mutex is already locked, the routine will return immediately with a busy error code. This routine may be useful in preventing deadlock conditions, as in a priority-inversion situation. POSIX Thread 同步 API 互斥（Mutex） 函数（续）： pthread_mutex_unlock - will unlock a mutex if called by the owning thread. Calling this routine is required after a thread has completed its use of protected data if other threads are to acquire the mutex for their work with the protected data. An error will be returned if: If the mutex was already unlocked If the mutex is owned by another thread POSIX Thread 同步 API 条件变量（Condition variable） A condition variable lets a thread wait for something to happen in the future, and another thread to inform it that it has happened. 类型：pthread_cond_t PO