4进程同步与通信详解.ppt

VxWorks进程同步 互斥 /* create a binary semaphore that is initially full */ semMutex = semBCreate (SEM_Q_PRIORITY, SEM_FULL);? semTake (semMutex, WAIT_FOREVER); ... /* critical region, accessible only by one task at a time */ semGive (semMutex); VxWorks进程同步 同步 init () { intConnect (..., eventInterruptSvcRout, ...); semSync = semBCreate (SEM_Q_FIFO, SEM_EMPTY); taskSpawn (..., task1); }? ? VxWorks进程同步 同步(cont.) ? task1 () { ... semTake (semSync, WAIT_FOREVER); /* wait for event*/ ... /* process event */ }? ? eventInterruptSvcRout () { ... semGive (semSync); /* let task 1 process event */ ... } VxWorks进程同步 在vxworks中实现管程思想 建立一个进程对临界资源进行操作 其它进程向该进程发送消息，请求操作 管理进程 monitorprocess() { for(;;) { msgQReceive (…) switch(cmd){…} } } VxWorks进程同步 其它进程 otherprocess() { … cmd=… msgQSend (…cmd…) … } 阅读材料 蒋静等，操作系统原理、技术与编程,第6章 Abraham S.,Operating System Concepts,chapter 7 尤晋元等，Windows操作系统原理，第3章 VxWorks程序设计 作业 P94 2,3,5,6,7,8,9,10 The sleeping_barber Problem:A barbershop consists of a waiting room with n chairs and the barber room containing the barber chair.if there are no customers to be served,the barber goes to sleep.if a customer enters the barbershop and all chairs are ocupied,then the customer leaves the shop.if the barber is busy but chairs are available,then the customer sits in a free chair.if the barber is asleep,the customer wakes up the barber. 作业 Baber: var chairs:semaphore:=n; m:interger:=0; barbersleep:semarphore:=0; mutex:semaphore:=1; begin repeat wait(barbersleep); … until false end 作业 Customer: var chairs:semaphore:=n; m:interger:=0; barbersleep:semarphore:=1; begin wait(mutext); if m = n begin signal(mutex);leave;end m=m+1; signal(mutex);