sysdeps/nacl/lll_timedlock_wait.c

   1 /* Timed low level locking for pthread library.  NaCl version.
   2    Copyright (C) 2015-2016 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <atomic.h>
  21 #include <errno.h>
  22 #include <lowlevellock.h>
  23 #include <sys/time.h>
  24
  25
  26 /* This behaves the same as the generic version in nptl/.  It's simpler
  27    because it doesn't need to convert an absolute timeout to a relative
  28    one (and back again in the lll_futex_timed_wait macro).  */
  29
  30 int
  31 __lll_timedlock_wait (int *futex, const struct timespec *abstime, int private)
  32 {
  33   /* Reject invalid timeouts.  */
  34   if (__glibc_unlikely (abstime->tv_nsec < 0)
  35       || __glibc_unlikely (abstime->tv_nsec >= 1000000000))
  36     return EINVAL;
  37
  38   /* Try locking.  */
  39   while (atomic_exchange_acq (futex, 2) != 0)
  40     {
  41       /* If *futex == 2, wait until woken or timeout.  */
  42       int err = __nacl_irt_futex.futex_wait_abs ((volatile int *) futex, 2,
  43                                                  abstime);
  44       if (err != 0)
  45         {
  46           if (__glibc_likely (err == ETIMEDOUT))
  47             return err;
  48           assert (err == EAGAIN);
  49         }
  50     }
  51
  52   return 0;
  53 }