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

   1 /* sem_timedwait -- wait on a semaphore.  Generic futex-using version.
   2    Copyright (C) 2003 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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <errno.h>
  22 #include <sysdep.h>
  23 #include <lowlevellock.h>
  24 #include <internaltypes.h>
  25 #include <semaphore.h>
  26
  27 #include <pthreadP.h>
  28 #include <shlib-compat.h>
  29
  30
  31 int
  32 sem_timedwait (sem_t *sem, const struct timespec *abstime)
  33 {
  34   /* First check for cancellation.  */
  35   CANCELLATION_P (THREAD_SELF);
  36
  37   int *futex = (int *) sem;
  38   int val;
  39   int err;
  40
  41   if (*futex > 0)
  42     {
  43       val = atomic_decrement_if_positive (futex);
  44       if (val > 0)
  45         return 0;
  46     }
  47
  48   err = -EINVAL;
  49   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  50     goto error_return;
  51
  52   do
  53     {
  54       struct timeval tv;
  55       struct timespec rt;
  56       int sec, nsec;
  57
  58       /* Get the current time.  */
  59       __gettimeofday (&tv, NULL);
  60
  61       /* Compute relative timeout.  */
  62       sec = abstime->tv_sec - tv.tv_sec;
  63       nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  64       if (nsec < 0)
  65         {
  66           nsec += 1000000000;
  67           --sec;
  68         }
  69
  70       /* Already timed out?  */
  71       err = -ETIMEDOUT;
  72       if (sec < 0)
  73         goto error_return;
  74
  75       /* Do wait.  */
  76       rt.tv_sec = sec;
  77       rt.tv_nsec = nsec;
  78
  79       /* Enable asynchronous cancellation.  Required by the standard.  */
  80       int oldtype = __pthread_enable_asynccancel ();
  81
  82       err = lll_futex_timed_wait (futex, 0, &rt);
  83
  84       /* Disable asynchronous cancellation.  */
  85       __pthread_disable_asynccancel (oldtype);
  86
  87       if (err != 0 && err != -EWOULDBLOCK)
  88         goto error_return;
  89
  90       val = atomic_decrement_if_positive (futex);
  91     }
  92   while (val <= 0);
  93
  94   return 0;
  95
  96  error_return:
  97   __set_errno (-err);
  98   return -1;
  99 }