librt/timer_create.c

   1 /*
   2  * timer_create.c - create a per-process timer.
   3  */
   4
   5 #include <stddef.h>
   6 #include <errno.h>
   7 #include <signal.h>
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <time.h>
  11 #include <sys/syscall.h>
  12
  13 #include "kernel-posix-timers.h"
  14
  15 #ifdef __NR_timer_create
  16
  17 #define __NR___syscall_timer_create __NR_timer_create
  18 static __inline__ _syscall3(int, __syscall_timer_create, clockid_t, clock_id,
  19                         struct sigevent *, evp, kernel_timer_t *, ktimerid);
  20
  21 /* Create a per-process timer */
  22 int timer_create(clockid_t clock_id, struct sigevent *evp, timer_t * timerid)
  23 {
  24         int retval;
  25         kernel_timer_t ktimerid;
  26         struct sigevent default_evp;
  27         struct timer *newp;
  28
  29         if (evp == NULL) {
  30                 /*
  31                  * The kernel has to pass up the timer ID which is a userlevel object.
  32                  * Therefore we cannot leave it up to the kernel to determine it.
  33                  */
  34                 default_evp.sigev_notify = SIGEV_SIGNAL;
  35                 default_evp.sigev_signo = SIGALRM;
  36                 evp = &default_evp;
  37         }
  38
  39         /* Notification via a thread is not supported yet */
  40         if (__builtin_expect(evp->sigev_notify == SIGEV_THREAD, 1))
  41                 return -1;
  42
  43         /*
  44          * We avoid allocating too much memory by basically using
  45          * struct timer as a derived class with the first two elements
  46          * being in the superclass. We only need these two elements here.
  47          */
  48         newp = malloc(offsetof(struct timer, thrfunc));
  49         if (newp == NULL)
  50                 return -1;      /* No memory */
  51         default_evp.sigev_value.sival_ptr = newp;
  52
  53         retval = __syscall_timer_create(clock_id, evp, &ktimerid);
  54         if (retval != -1) {
  55                 newp->sigev_notify = evp->sigev_notify;
  56                 newp->ktimerid = ktimerid;
  57
  58                 *timerid = (timer_t) newp;
  59         } else {
  60                 /* Cannot allocate the timer, fail */
  61                 free(newp);
  62                 retval = -1;
  63         }
  64
  65         return retval;
  66 }
  67
  68 #endif