CPSC 313: Intro to Computer Systems. POSIX Threads. Latency Hiding / Multiprogramming (covered earlier) Ease of Programming (covered now)

Transcription

1 Why Threads? Latency Hiding / Multiprogramming (covered earlier) Ease of Programming (covered now) (R&R, Chapter 12) Thread Management Thread Safety Thread Attributes Why Threads? Latency Hiding / Multiprogramming (covered earlier) Ease of Programming (covered now) (R&R, Chapter 12) Thread Management Thread Safety Thread Attributes 1

2 Why Threads? Many interactive applications run in loops. For example, an interactive game. Reference [B.O. Gallmeister, POSIX.4, Programming for the Real World, O Reilly&Assoc., Inc.] Why Threads? Many interactive applications run in loops. For example, an interactive game. Reference [B.O. Gallmeister, POSIX.4, Programming for the Real World, O Reilly&Assoc., Inc.] 2

3 Why Threads? Many interactive applications run in loops. For example, an interactive game. It ain t over yet! What about compute-intensive operations, like AI, video compression? How about Signal Handlers? Suddenly, application is getting complex! Reference [B.O. Gallmeister, POSIX.4, Programming for the Real World, O Reilly&Assoc., Inc.] Reading the Mouse read_mouse() { 3

4 Reading the Mouse (II) fork() Separate Process int main() { read_mouse() { Reading the Mouse (III) Separate Thread read_mouse() { 4

5 The Thread and its Creation /* The Mouse Input Function */ void * read_mouse() { char buf[bufsize]; ssize_t nbytes; for (;;) { if ((nbytes = read_from_mouse(buf,bufsize)) <= 0) break; dosomething_with(buf, nbytes); /* Recompute Player Position return */ NULL; The Thread and its Creation #include <pthread.h> /* The Mouse Input Function */ int error; pthread_t tid; void * read_mouse() { char buf[bufsize]; ssize_t nbytes; if (error = pthread_create(&tid, for (;;) NULL, { read_mouse, NULL)) perror( Failed to create if read_mouse ((nbytes thread ); = read_from_mouse(buf,bufsize)) <= 0) break; dosomething_with(buf, nbytes); return NULL; <- Handled by separate thread! 5

6 Thread Management pthread_cancel (terminate another thread) pthread_create (create a thread) pthread_detach (have thread release res s) pthread_equal (two thread id s equal?) pthread_exit (exit a thread) pthread_kill (send a signal to a thread) pthread_join (wait for a thread) pthread_self (what is my id?) Thread Management pthread_cancel (terminate another thread) pthread_create (create a thread) pthread_detach (have thread release res s) pthread_equal (two thread id s equal?) pthread_exit (exit a thread) pthread_kill (send a signal to a thread) int pthread_create(pthread_t *restrict thread, pthread_join (wait for a thread) const pthread_attr_t * restrict attr, pthread_self (what is my id?) void *(*start_routine)(void *), void *restrict arg) 6

7 Thread Attributes atribute objects state stack scheduling pthread_attr_destroy pthread_attr_init pthread_attr_getdetachstate pthread_attr_setdetachstate pthread_attr_getguardsize pthread_attr_setguardsize pthread_attr_getstack pthread_attr_setstack pthread_attr_getinheritedsched pthread_attr_setinheritedsched pthread_attr_getschedparam pthread_attr_setschedparam pthread_attr_getschedpolicy pthread_attr_setschedpolicy pthread_attr_getscope pthread_attr_setscope Thread Attributes: State atribute objects state stack scheduling pthread_attr_destroy pthread_attr_init pthread_attr_getdetachstate pthread_attr_setdetachstate pthread_attr_getguardsize pthread_attr_setguardsize Detached threads release pthread_attr_getstackresources when terminate. pthread_attr_setstack Attached states hold on to pthread_attr_getinheritedsched resources until parent thread pthread_attr_setinheritedsched calls pthread_join. pthread_attr_getschedparam pthread_attr_setschedparam pthread_attr_getschedpolicy pthread_attr_setschedpolicy pthread_attr_getscope pthread_attr_setscope 7

8 Thread Attributes: Stack atribute objects state stack scheduling pthread_attr_destroy pthread_attr_init pthread_attr_getdetachstate pthread_attr_setdetachstate pthread_attr_getguardsize pthread_attr_setguardsize pthread_attr_getstack pthread_attr_setstack pthread_attr_getinheritedsched pthread_attr_setinheritedsched setstack defines location and size pthread_attr_getschedparam of stack. pthread_attr_setschedparam setguardsize allocates additional pthread_attr_getschedpolicy memory. If the thread overflows pthread_attr_setschedpolicy into this extra memory, an error pthread_attr_getscope is generated. pthread_attr_setscope Thread Attributes: Scheduling atribute objects pthread_attr_destroy PTHREAD_INHERIT_SCHED pthread_attr_init defines that scheduling parameters are inherited from parent thread. (as opposed to state pthread_attr_getdetachstate PTHREAD_EXPLICIT_SCHED). pthread_attr_setdetachstate Scheduling policies: SCHED_FIFO, SCHED_RR, stack SCHED_SPORADIC, pthread_attr_getguardsize SCHED_OTHER, pthread_attr_setguardsize contention scope defines whether process competes at pthread_attr_getstack process level or at system level for resources. pthread_attr_setstack scheduling pthread_attr_getinheritedsched pthread_attr_setinheritedsched pthread_attr_getschedparam pthread_attr_setschedparam pthread_attr_getschedpolicy pthread_attr_setschedpolicy pthread_attr_getscope pthread_attr_setscope 8