nptl/lll_timedlock_wait.c

   1 /* Timed low level locking for pthread library.  Generic futex-using version.
   2    Copyright (C) 2003-2017 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 <atomic.h>
  21 #include <errno.h>
  22 #include <lowlevellock.h>
  23 #include <sys/time.h>
  24
  25
  26 int
  27 __lll_timedlock_wait (int *futex, const struct timespec *abstime, int private)
  28 {
  29   /* Reject invalid timeouts.  */
  30   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  31     return EINVAL;
  32
  33   /* Try locking.  */
  34   while (atomic_exchange_acq (futex, 2) != 0)
  35     {
  36       struct timeval tv;
  37
  38       /* Get the current time.  */
  39       (void) __gettimeofday (&tv, NULL);
  40
  41       /* Compute relative timeout.  */
  42       struct timespec rt;
  43       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
  44       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  45       if (rt.tv_nsec < 0)
  46         {
  47           rt.tv_nsec += 1000000000;
  48           --rt.tv_sec;
  49         }
  50
  51       if (rt.tv_sec < 0)
  52         return ETIMEDOUT;
  53
  54       /* If *futex == 2, wait until woken or timeout.  */
  55       lll_futex_timed_wait (futex, 2, &rt, private);
  56     }
  57
  58   return 0;
  59 }