src/time/timer_create.c

   1 #include <time.h>
   2 #include "pthread_impl.h"
   3
   4 struct ksigevent {
   5         union sigval sigev_value;
   6         int sigev_signo;
   7         int sigev_notify;
   8         int sigev_tid;
   9 };
  10
  11 struct start_args {
  12         pthread_barrier_t b;
  13         struct sigevent *sev;
  14 };
  15
  16 void __sigtimer_handler(pthread_t self)
  17 {
  18         int st;
  19         void (*notify)(union sigval) = (void (*)(union sigval))self->start;
  20         union sigval val = { .sival_ptr = self->start_arg };
  21
  22         pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &st);
  23         notify(val);
  24         pthread_setcancelstate(st, 0);
  25 }
  26
  27 static void cleanup(void *p)
  28 {
  29         pthread_t self = p;
  30         __syscall(SYS_timer_delete, self->result);
  31 }
  32
  33 static void *start(void *arg)
  34 {
  35         pthread_t self = __pthread_self();
  36         struct start_args *args = arg;
  37
  38         /* Reuse no-longer-needed thread structure fields to avoid
  39          * needing the timer address in the signal handler. */
  40         self->start = (void *(*)(void *))args->sev->sigev_notify_function;
  41         self->start_arg = args->sev->sigev_value.sival_ptr;
  42         self->result = (void *)-1;
  43
  44         pthread_cleanup_push(cleanup, self);
  45         pthread_barrier_wait(&args->b);
  46         pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, 0);
  47         /* Loop on async-signal-safe cancellation point */
  48         for (;;) sleep(1);
  49         pthread_cleanup_pop(0);
  50         return 0;
  51 }
  52
  53 int timer_create(clockid_t clk, struct sigevent *evp, timer_t *res)
  54 {
  55         struct sigevent sev = {
  56                 .sigev_notify = SIGEV_SIGNAL,
  57                 .sigev_signo = SIGALRM
  58         };
  59         pthread_t td;
  60         pthread_attr_t attr;
  61         int r;
  62         struct start_args args;
  63         timer_t t;
  64         struct ksigevent ksev;
  65         int timerid;
  66
  67         if (evp) sev = *evp;
  68
  69         switch (sev.sigev_notify) {
  70         case SIGEV_NONE:
  71         case SIGEV_SIGNAL:
  72                 ksev.sigev_value = evp ? sev.sigev_value
  73                         : (union sigval){.sival_ptr=t};
  74                 ksev.sigev_signo = sev.sigev_signo;
  75                 ksev.sigev_notify = sev.sigev_notify;
  76                 ksev.sigev_tid = 0;
  77                 if (syscall(SYS_timer_create, clk, &ksev, &timerid) < 0)
  78                         return -1;
  79                 *res = (void *)(2*timerid+1);
  80                 break;
  81         case SIGEV_THREAD:
  82                 if (sev.sigev_notify_attributes)
  83                         attr = *sev.sigev_notify_attributes;
  84                 else
  85                         pthread_attr_init(&attr);
  86                 pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
  87                 pthread_barrier_init(&args.b, 0, 2);
  88                 args.sev = &sev;
  89                 r = pthread_create(&td, &attr, start, &args);
  90                 if (r) {
  91                         errno = r;
  92                         return -1;
  93                 }
  94                 ksev.sigev_value.sival_ptr = 0;
  95                 ksev.sigev_signo = SIGCANCEL;
  96                 ksev.sigev_notify = 4; /* SIGEV_THREAD_ID */
  97                 ksev.sigev_tid = td->tid;
  98                 r = syscall(SYS_timer_create, clk, &ksev, &timerid);
  99                 pthread_barrier_wait(&args.b);
 100                 if (r < 0) {
 101                         pthread_cancel(td);
 102                         return -1;
 103                 }
 104                 td->result = (void *)timerid;
 105                 *res = td;
 106                 break;
 107         default:
 108                 errno = EINVAL;
 109                 return -1;
 110         }
 111
 112         return 0;
 113 }