nptl/sem_timedwait.c

   1 /* sem_timedwait -- wait on a semaphore.  Generic futex-using version.
   2    Copyright (C) 2003-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <errno.h>
  21 #include <sysdep.h>
  22 #include <lowlevellock.h>
  23 #include <internaltypes.h>
  24 #include <semaphore.h>
  25 #include <sys/time.h>
  26
  27 #include <pthreadP.h>
  28 #include <shlib-compat.h>
  29
  30
  31 extern void __sem_wait_cleanup (void *arg) attribute_hidden;
  32
  33 /* This is in a seperate function in order to make sure gcc
  34    puts the call site into an exception region, and thus the
  35    cleanups get properly run.  */
  36 static int
  37 __attribute__ ((noinline))
  38 do_futex_timed_wait (struct new_sem *isem, struct timespec *rt)
  39 {
  40   int err, oldtype = __pthread_enable_asynccancel ();
  41
  42   err = lll_futex_timed_wait (&isem->value, 0, rt,
  43                               isem->private ^ FUTEX_PRIVATE_FLAG);
  44
  45   __pthread_disable_asynccancel (oldtype);
  46   return err;
  47 }
  48
  49 int
  50 sem_timedwait (sem_t *sem, const struct timespec *abstime)
  51 {
  52   struct new_sem *isem = (struct new_sem *) sem;
  53   int err;
  54
  55   if (atomic_decrement_if_positive (&isem->value) > 0)
  56     return 0;
  57
  58   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  59     {
  60       __set_errno (EINVAL);
  61       return -1;
  62     }
  63
  64   atomic_increment (&isem->nwaiters);
  65
  66   pthread_cleanup_push (__sem_wait_cleanup, isem);
  67
  68   while (1)
  69     {
  70       struct timeval tv;
  71       struct timespec rt;
  72       int sec, nsec;
  73
  74       /* Get the current time.  */
  75       __gettimeofday (&tv, NULL);
  76
  77       /* Compute relative timeout.  */
  78       sec = abstime->tv_sec - tv.tv_sec;
  79       nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  80       if (nsec < 0)
  81         {
  82           nsec += 1000000000;
  83           --sec;
  84         }
  85
  86       /* Already timed out?  */
  87       if (sec < 0)
  88         {
  89           __set_errno (ETIMEDOUT);
  90           err = -1;
  91           break;
  92         }
  93
  94       /* Do wait.  */
  95       rt.tv_sec = sec;
  96       rt.tv_nsec = nsec;
  97       err = do_futex_timed_wait(isem, &rt);
  98       if (err != 0 && err != -EWOULDBLOCK)
  99         {
 100           __set_errno (-err);
 101           err = -1;
 102           break;
 103         }
 104
 105       if (atomic_decrement_if_positive (&isem->value) > 0)
 106         {
 107           err = 0;
 108           break;
 109         }
 110     }
 111
 112   pthread_cleanup_pop (0);
 113
 114   atomic_decrement (&isem->nwaiters);
 115
 116   return err;
 117 }