nptl/lowlevellock.c

   1 /* 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 <errno.h>
  21 #include <sysdep.h>
  22 #include <lowlevellock.h>
  23 #include <sys/time.h>
  24 #include <atomic.h>
  25
  26 void
  27 __lll_lock_wait_private (int *futex)
  28 {
  29   if (*futex == 2)
  30     lll_futex_wait (futex, 2, LLL_PRIVATE); /* Wait if *futex == 2.  */
  31
  32   while (atomic_exchange_acq (futex, 2) != 0)
  33     lll_futex_wait (futex, 2, LLL_PRIVATE); /* Wait if *futex == 2.  */
  34 }
  35
  36
  37 /* This function doesn't get included in libc.  */
  38 #if IS_IN (libpthread)
  39 void
  40 __lll_lock_wait (int *futex, int private)
  41 {
  42   if (*futex == 2)
  43     lll_futex_wait (futex, 2, private); /* Wait if *futex == 2.  */
  44
  45   while (atomic_exchange_acq (futex, 2) != 0)
  46     lll_futex_wait (futex, 2, private); /* Wait if *futex == 2.  */
  47 }
  48 #endif