1  /*
       2   * No copyright is claimed.  This code is in the public domain; do with
       3   * it what you wish.
       4   *
       5   * Please, don't add this file to libcommon because timers requires
       6   * -lrt on systems with old libc (and probably also -lpthread for static
       7   *  build).
       8   */
       9  #include <time.h>
      10  #include <signal.h>
      11  #include <sys/time.h>
      12  
      13  #include "c.h"
      14  #include "timer.h"
      15  
      16  /*
      17   * Note the timeout is used for the first signal, then the signal is send
      18   * repeatedly in interval ~1% of the original timeout to avoid race in signal
      19   * handling -- for example you want to use timer to define timeout for a
      20   * syscall:
      21   *
      22   *	 setup_timer()
      23   *	 syscall()
      24   *	 cancel_timer()
      25   *
      26   * if the timeout is too short than it's possible that the signal is delivered
      27   * before application enter the syscall function. For this reason timer send
      28   * the signal repeatedly.
      29   *
      30   * The applications need to ensure that they can tolerate multiple signal
      31   * deliveries.
      32   */
      33  #ifdef HAVE_TIMER_CREATE
      34  int setup_timer(struct ul_timer *timer,
      35  		struct itimerval *timeout,
      36  		void (*timeout_handler)(int, siginfo_t *, void *))
      37  {
      38  	time_t sec = timeout->it_value.tv_sec;
      39  	long usec = timeout->it_value.tv_usec;
      40  	struct sigaction sig_a;
      41  	static struct sigevent sig_e = {
      42  		.sigev_notify = SIGEV_SIGNAL,
      43  		.sigev_signo = SIGALRM
      44  	};
      45  	struct itimerspec val = {
      46  		.it_value.tv_sec = sec,
      47  		.it_value.tv_nsec = usec * 1000,
      48  		.it_interval.tv_sec = sec / 100,
      49  		.it_interval.tv_nsec = (sec ? sec % 100 : 1) * 10*1000*1000
      50  	};
      51  
      52  	if (sigemptyset(&sig_a.sa_mask))
      53  		return 1;
      54  
      55  	sig_a.sa_flags = SA_SIGINFO;
      56  	sig_a.sa_sigaction = timeout_handler;
      57  
      58  	if (sigaction(SIGALRM, &sig_a, NULL))
      59  		return 1;
      60  	if (timer_create(CLOCK_MONOTONIC, &sig_e, &timer->t_id))
      61  		return 1;
      62  	if (timer_settime(timer->t_id, 0, &val, NULL))
      63  		return 1;
      64  	return 0;
      65  }
      66  void cancel_timer(struct ul_timer *timer)
      67  {
      68  	timer_delete(timer->t_id);
      69  }
      70  
      71  #else /* !HAVE_TIMER_CREATE */
      72  
      73  int setup_timer(struct ul_timer *timer,
      74  		struct itimerval *timeout,
      75  		void (*timeout_handler)(int, siginfo_t *, void *))
      76  {
      77  	struct sigaction sa;
      78  
      79  	memset(&sa, 0, sizeof sa);
      80  	memset(timer, 0, sizeof(*timer));
      81  
      82  	sa.sa_flags = SA_SIGINFO | SA_RESETHAND;
      83  	sa.sa_sigaction = timeout_handler;
      84  
      85  	if (sigaction(SIGALRM, &sa, &timer->old_sa))
      86  		return 1;
      87  	if (setitimer(ITIMER_REAL, timeout, &timer->old_timer) != 0)
      88  		return 1;
      89  	return 0;
      90  }
      91  
      92  void cancel_timer(struct ul_timer *timer)
      93  {
      94  	setitimer(ITIMER_REAL, &timer->old_timer, NULL);
      95          sigaction(SIGALRM, &timer->old_sa, NULL);
      96  
      97  }
      98  #endif /* !HAVE_TIMER_CREATE */