Programming with POSIX® Threads

14 * "interrupted" flag (the main thread's wait predicate) and signal a

15 * condition variable. The main thread will exit.

16 */

17 void *signal_waiter (void *arg)

18 {

19 int sig_number;

20 int signal_count = 0;

21 int status;

22

23 while (1) {

24  sigwait (&signal_set, &sig_number);

25  if (sig_number == SIGINT) {

26  printf ("Got SIGINT (%d of 5)\n", signal_count+l);

27  if (++signal_count >= 5) {

28  status = pthread_mutex_lock (&mutex);

29  if (status != 0)

30  err_abort (status, "Lock mutex");

31  interrupted = 1;

32  status = pthread_cond_signal (&cond);

33  if (status != 0)

34  err_abort (status, "Signal condition");

35  status = pthread_mutex_unlock (&mutex);

36  if (status != 0)

37  err_abort (status, "Unlock mutex");

38  break;

39  }

40 }

41 }

42 return NULL;

43 }

44

45 int main (int argc, char *argv[])

46 {

47 pthread_t signal_thread_id;

48 int status;

49

50 /*

51 * Start by masking the "interesting" signal, SIGINT in the

52 * initial thread. Because all threads inherit the signal mask

53 * from their creator, all threads in the process will have

54 * SIGINT masked unless one explicitly unmasks it. The

55 * semantics of sigwait requires that all threads (including

56 * the thread calling sigwait) have the signal masked, for

57 * reliable operation. Otherwise, a signal that arrives

58 * while the sigwaiter is not blocked in sigwait might be

59 * delivered to another thread.

60 */

61 sigemptyset (&signal_set);

62 sigaddset (&signal_set, SIGINT);

63 status = pthread_sigmask (SIG_BLOCK, &signal_set, NULL);

64 if (status != 0)

65  err_abort (status, "Set signal mask"); 66

67 /*

68 * Create the sigwait thread.

69 */

70 status = pthread_create (&signal_thread_id, NULL,

71  signal_waiter, NULL);

72 if (status != 0)

73  err_abort (status, "Create sigwaiter");

74

75 /*

76 * Wait for the sigwait thread to receive SIGINT and signal

77 * the condition variable.

78 */

79 status = pthread_mutex_lock (&mutex);

80 if (status != 0)

81  err_abort (status, "Lock mutex");

82 while (!interrupted) {

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

84  if (status != 0)

85  err_abort (status, "Wait for interrupt");

86 }

87 status = pthread_mutex_unlock (&mutex);

88 if (status != 0)

89  err_abort (status, "Unlock mutex");

90 printf ("Main terminating with SIGINT\n");

91 return 0;

92 }

6.6.5 SIGEV_THREAD