操作系统原理4章节(2158KB).ppt

Chapter 4: Threads Overview Multithreading Models Threading Issues Windows XP Threads Linux Threads Java Threads Windows Threads API Pthreads Operating System Concepts Pthreads a POSIX standard (IEEE 1003.1c) API for thread creation and synchronization. API specifies behavior of the thread library, implementation is up to development of the library. Common in UNIX operating systems. Operating System Concepts pthread_create pthread_t *tid handle of created thread const pthread_attr_t *attr attributes of thread to be created void *(*function) (void*) function to be mapped to thread void *arg single argument to function Operating System Concepts int pthread_create(tid, attr, function, arg); pthread_create explained spawn a thread running the function thread handle returned via pthread_t structure specify NULL to use default attributes single argument sent to function If no argument to function, specify NULL check error codes! Operating System Concepts EAGAIN – insufficient resources to create thread EINVAL – invalid attribute Threads states pthread threads have two states joinable and detached threads are joinable by default Resources are kept until pthread_join can be reset with attribute or API call detached thread can not be joined resources can be reclaimed at termination cannot reset to be joinable Operating System Concepts Waiting for a thread pthread_t *tid handle of joinable thread void **val_ptr exit value returned by joined thread Operating System Concepts int pthread_join(tid, val_ptr); pthread_join explained calling thread waits for the thread with handle tid to terminate only one thread can be joined thread must be joinable exit value is returned from joined thread Type returned is (void *) use NULL if no return value expected Operating System Concepts ESRCH –thread not found EINVAL – thread not joinable Example: Multiple threads #include stdio.h #include pthread.h const int numThreads = 4; void *helloFunc(void * pArg) { printf(Hello Thread\n); } ma