lib/timer.c

   1 /*
   2  * Please, don't add this file to libcommon because timers requires
   3  * -lrt on systems with old libc (and probably also -lpthread for static
   4  *  build).
   5  */
   6 #include <time.h>
   7 #include <signal.h>
   8 #include <sys/time.h>
   9
  10 #include "c.h"
  11 #include "timer.h"
  12
  13 /*
  14  * Note the timeout is used for the first signal, then the signal is send
  15  * repeatedly in interval ~1% of the original timeout to avoid race in signal
  16  * handling -- for example you want to use timer to define timeout for a
  17  * syscall:
  18  *
  19  *       setup_timer()
  20  *       syscall()
  21  *       cancel_timer()
  22  *
  23  * if the timeout is too short than it's possible that the signal is delivered
  24  * before application enter the syscall function. For this reason timer send
  25  * the signal repeatedly.
  26  *
  27  * The applications need to ensure that they can tolerate multiple signal
  28  * deliveries.
  29  */
  30 #ifdef HAVE_TIMER_CREATE
  31 int setup_timer(struct ul_timer *timer,
  32                 struct itimerval *timeout,
  33                 void (*timeout_handler)(int, siginfo_t *, void *))
  34 {
  35         time_t sec = timeout->it_value.tv_sec;
  36         long usec = timeout->it_value.tv_usec;
  37         struct sigaction sig_a;
  38         static struct sigevent sig_e = {
  39                 .sigev_notify = SIGEV_SIGNAL,
  40                 .sigev_signo = SIGALRM
  41         };
  42         struct itimerspec val = {
  43                 .it_value.tv_sec = sec,
  44                 .it_value.tv_nsec = usec * 1000,
  45                 .it_interval.tv_sec = sec / 100,
  46                 .it_interval.tv_nsec = (sec ? sec % 100 : 1) * 10*1000*1000
  47         };
  48
  49         if (sigemptyset(&sig_a.sa_mask))
  50                 return 1;
  51
  52         sig_a.sa_flags = SA_SIGINFO;
  53         sig_a.sa_sigaction = timeout_handler;
  54
  55         if (sigaction(SIGALRM, &sig_a, NULL))
  56                 return 1;
  57         if (timer_create(CLOCK_MONOTONIC, &sig_e, &timer->t_id))
  58                 return 1;
  59         if (timer_settime(timer->t_id, 0, &val, NULL))
  60                 return 1;
  61         return 0;
  62 }
  63 void cancel_timer(struct ul_timer *timer)
  64 {
  65         timer_delete(timer->t_id);
  66 }
  67
  68 #else /* !HAVE_TIMER_CREATE */
  69
  70 int setup_timer(struct ul_timer *timer,
  71                 struct itimerval *timeout,
  72                 void (*timeout_handler)(int, siginfo_t *, void *))
  73 {
  74         struct sigaction sa;
  75
  76         memset(&sa, 0, sizeof sa);
  77         memset(timer, 0, sizeof(*timer));
  78
  79         sa.sa_flags = SA_SIGINFO | SA_RESETHAND;
  80         sa.sa_sigaction = timeout_handler;
  81
  82         if (sigaction(SIGALRM, &sa, &timer->old_sa))
  83                 return 1;
  84         if (setitimer(ITIMER_REAL, timeout, &timer->old_timer) != 0)
  85                 return 1;
  86         return 0;
  87 }
  88
  89 void cancel_timer(struct ul_timer *timer)
  90 {
  91         setitimer(ITIMER_REAL, &timer->old_timer, NULL);
  92         sigaction(SIGALRM, &timer->old_sa, NULL);
  93
  94 }
  95 #endif /* !HAVE_TIMER_CREATE */