nptl/sysdeps/unix/sysv/linux/sem_timedwait.c

   1 /* sem_timedwait -- wait on a semaphore.  Generic futex-using version.
   2    Copyright (C) 2003-2013 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
  26 #include <pthreadP.h>
  27 #include <shlib-compat.h>
  28
  29
  30 extern void __sem_wait_cleanup (void *arg) attribute_hidden;
  31
  32 /* This is in a seperate function in order to make sure gcc
  33    puts the call site into an exception region, and thus the
  34    cleanups get properly run.  */
  35 static int
  36 __attribute__ ((noinline))
  37 do_futex_timed_wait (struct new_sem *isem, struct timespec *rt)
  38 {
  39   int err, oldtype = __pthread_enable_asynccancel ();
  40
  41   err = lll_futex_timed_wait (&isem->value, 0, rt,
  42                               isem->private ^ FUTEX_PRIVATE_FLAG);
  43
  44   __pthread_disable_asynccancel (oldtype);
  45   return err;
  46 }
  47
  48 int
  49 sem_timedwait (sem_t *sem, const struct timespec *abstime)
  50 {
  51   struct new_sem *isem = (struct new_sem *) sem;
  52   int err;
  53
  54   if (atomic_decrement_if_positive (&isem->value) > 0)
  55     return 0;
  56
  57   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  58     {
  59       __set_errno (EINVAL);
  60       return -1;
  61     }
  62
  63   atomic_increment (&isem->nwaiters);
  64
  65   pthread_cleanup_push (__sem_wait_cleanup, isem);
  66
  67   while (1)
  68     {
  69       struct timeval tv;
  70       struct timespec rt;
  71       int sec, nsec;
  72
  73       /* Get the current time.  */
  74       __gettimeofday (&tv, NULL);
  75
  76       /* Compute relative timeout.  */
  77       sec = abstime->tv_sec - tv.tv_sec;
  78       nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  79       if (nsec < 0)
  80         {
  81           nsec += 1000000000;
  82           --sec;
  83         }
  84
  85       /* Already timed out?  */
  86       if (sec < 0)
  87         {
  88           __set_errno (ETIMEDOUT);
  89           err = -1;
  90           break;
  91         }
  92
  93       /* Do wait.  */
  94       rt.tv_sec = sec;
  95       rt.tv_nsec = nsec;
  96       err = do_futex_timed_wait(isem, &rt);
  97       if (err != 0 && err != -EWOULDBLOCK)
  98         {
  99           __set_errno (-err);
 100           err = -1;
 101           break;
 102         }
 103
 104       if (atomic_decrement_if_positive (&isem->value) > 0)
 105         {
 106           err = 0;
 107           break;
 108         }
 109     }
 110
 111   pthread_cleanup_pop (0);
 112
 113   atomic_decrement (&isem->nwaiters);
 114
 115   return err;
 116 }