lib/timer.c

   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 */