linuxthreads/sysdeps/arm/pspinlock.c

   1 /* POSIX spinlock implementation.  Arm version.
   2    Copyright (C) 2000 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 License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    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; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <pthread.h>
  22 #include "internals.h"
  23
  24
  25 int
  26 __pthread_spin_lock (pthread_spinlock_t *lock)
  27 {
  28   unsigned int val;
  29
  30   do
  31     asm volatile ("swp %0, %1, [%2]"
  32                   : "=r" (val)
  33                   : "0" (1), "r" (lock)
  34                   : "memory");
  35   while (val != 0);
  36
  37   return 0;
  38 }
  39 weak_alias (__pthread_spin_lock, pthread_spin_lock)
  40
  41
  42 int
  43 __pthread_spin_trylock (pthread_spinlock_t *lock)
  44 {
  45   unsigned int val;
  46
  47   asm volatile ("swp %0, %1, [%2]"
  48                 : "=r" (val)
  49                 : "0" (1), "r" (lock)
  50                 : "memory");
  51
  52   return val ? EBUSY : 0;
  53 }
  54 weak_alias (__pthread_spin_trylock, pthread_spin_trylock)
  55
  56
  57 int
  58 __pthread_spin_unlock (pthread_spinlock_t *lock)
  59 {
  60   return *lock = 0;
  61 }
  62 weak_alias (__pthread_spin_unlock, pthread_spin_unlock)
  63
  64
  65 int
  66 __pthread_spin_init (pthread_spinlock_t *lock, int pshared)
  67 {
  68   /* We can ignore the `pshared' parameter.  Since we are busy-waiting
  69      all processes which can access the memory location `lock' points
  70      to can use the spinlock.  */
  71   return *lock = 0;
  72 }
  73 weak_alias (__pthread_spin_init, pthread_spin_init)
  74
  75
  76 int
  77 __pthread_spin_destroy (pthread_spinlock_t *lock)
  78 {
  79   /* Nothing to do.  */
  80   return 0;
  81 }
  82 weak_alias (__pthread_spin_destroy, pthread_spin_destroy)