华南理工大学研究生课程(操作系统与系统编程)讲义06 Thread.ppt

Thread Benefits of thread Simplify handle event Share memory and file descriptors Throughput can be improved Improved response time Process items - Address space-?? Global variables-?? Open files,-????Current working directory-????Timers-????Signals-????Semaphores-????Accounting information-????User and group Ids Thread items - Thread ID- Program counter - Stack (for local variables and return addresses)- State-? Register set- Priority-? Errno Thread Identification A thread ID is represented by the pthread_t data type - Linux 2.4.22 : unsigned long integer - Solaris 9 : unsigned integer. - FreeBSD 5.2.1 and Mac OS X 10.3 : pointer to the pthread structure for the pthread_t data type. int pthread_equal(pthread_t tid1, pthread_t tid2) pthread_t pthread_self(void) Thread Creation Additional threads created by pthread_create function:#include pthread.h?int pthread_create ( pthread_t *tid, const pthread_attr_t *attr, void * (*func) (void *), void *arg);-? tid is the thread ID (returned by the call)-??attr attributes: initial stack size, priority, should be a daemon thread or notspecify these attributes by initializing a pthread_attr_t variable.default:NULL ?-?func:address of thread start function. -? arg points to a set of parameters to be passed to the function when it is called.?return value from pthread functions is either 0: OK, positive number (Exxx): Example of thread pthread_t ntid; void printids(const char *s) { pid_t pid; pthread_t tid; pid = getpid(); tid = pthread_self(); printf(%s pid %u tid %u (0x%x)\n, s, (unsigned int)pid, (unsigned int)tid, (unsigned int)tid); } void * thr_fn(void *arg) { printids(new thread: ); return((void *)0); } Example of thread int main(void) { int err; err = pthread_create(ntid, NULL, thr_fn, NULL); if (err != 0) err_quit(cant create thread: %s\n, strerror(err)); printids(main thread:); sleep(1); exit(0); } Re