[工学]多核程序设计5版本2.pptVIP

Chapter 5 Linux Multi-thread Programming李素科北京大学软件与微电子学院2007 What is a thread? A thread is an independent sequence of execution of program code inside a UNIX process A thread is often called a lightweight process – but it is NOT a process (something smaller than a process) Why Threads? Do concurrent control more efficiently Use fork() to create a process: is expensive, usually the child process need copy the whole context from the parent process. Inter-process communication is expensive and difficult. OS does more effort to switch process contexts. Creating a thread Threads use and exist within the process resources, so creating a thread is faster than creating a process. Inter-thread communication is easy, usually we can use global variable or struct to share data between threads. OS switches thread contexts easier than process contexts. Shared or Not Shared between thread and process Shared process instruction most data(A thread can have its own private data) open files signal handlers and signal dispositions current working directory user and group ID Not shared thread ID set of registers (including pc and sp) stack signal mask priority What are Pthreads? IEEE POSIX standard p1003.1c (Pthreads) specifies the APIs and the way other POSIX interfaces deal with threads Pthreads are defined as a set of C language programming types and procedure calls i.e. Create a new thread: #include pthread.h int pthread_create(pthread_t * thread, pthread_attr_t * attr, void * (*start_routine)(void *), void * arg); We want to link a pthread application in Linux , we need libpthread library. so, you can compile file with -lpthread flag # gcc xxxx.c -o xxxx -lpthread Creating Threads #include pthread.h int pthread_create(pthread_t * thread, pthread_attr_t * attr, void *(*start_routine)(void *), void * arg); Waiting For the Termination of Threads #include pthread.h int pthread_join(pthread_t th, void **thread_r