Programming with POSIX® Threads

14 * thread, each time the timer expires.

15 *

16 * When the timer has expired 5 times, the main thread will

17 * be awakened, and will terminate the program.

18 */

19 void

20 timer_thread (void *arg)

21 {

22 int status;

23

24 status = pthread_mutex_lock (&mutex);

25 if (status != 0)

26  err_abort (status, "Lock mutex");

27 if (++counter >= 5) {

28  status = pthread_cond_signal (&cond);

29  if (status != 0)

30  err_abort (status, "Signal condition");

31 }

32 status = pthread_mutex_unlock (&mutex);

33 if (status != 0)

34  err_abort (status, "Unlock mutex");

35

36 printf ("Timer %d\n", counter);

37 }

38

39 main( )

40 {

41 int status;

42 struct itimerspec ts;

43 struct sigevent se;

44

45 #ifdef sun

46 fprintf (

47 stderr,

48 "This program cannot compile on Solaris 2.5.\n"

49 "To build and run on Solaris 2.6, remove the\n"

50 "\"#ifdef sun\" block in main().\n");

51 #else

52 /*

53 * Set the sigevent structure to cause the signal to be

54 * delivered by creating a new thread.

55 */

56 se.sigev_notify = SIGEV_THREAD;

57 se.sigev_value.sival_ptr = &timer_id;

58 se.sigev_notify_function = timer_thread;

59 se.sigev_notify_attributes = NULL;

60

61 /*

62 * Specify a repeating timer that fires every 5 seconds.

63 */

64 ts.it_value.tv_sec = 5;

65 ts.it_value.tv_nsec = 0;

66 ts.it_interval.tv_sec = 5;

67 ts.it_interval.tv_nsec = 0;

68

69 DPRINTF (("Creating timer\n"));

70 status = timer_create(CLOCK_REALTIME, &se, &timer_id);

71 if (status == -1)

72  errno_abort ("Create timer");

73

74 DPRINTF ((

75  "Setting timer %d for 5-second expiration...\n", timer_id));

76 status = timer_settime(timer_id, 0, &ts, 0);

77 if (status == -1)

78  errno_abort ("Set timer");

79

80 status = pthread_mutex_lock (&mutex);

81 if (status != 0)

82  err_abort (status, "Lock mutex");

83 while (counter < 5) {

84  status = pthread_cond_wait (&cond, &mutex);

85  if (status != 0)

86  err_abort (status, "Wait on condition");

87 }

88 status = pthread_mutex_unlock (&mutex);

89 if (status != 0)

90 err_abort (status, "Unlock mutex");

91

92 #endif /* Sun */

93 return 0;

94 }

6.6.6 Semaphores: synchronizing with a signal-catching function

#ifdef _POSIX_SEMAPHORES

int sem_init (sem_t *sem, int pshared, unsigned int value);

int sem_destroy (sem_t *sem);

int sem_wait (sem_t*sem);

int sem_trywake (sem_t *sem);

int sem_post (sem_t *sem);

int sem_getvalue (sem_t *sem, int *sval);

#endif