linuxthreads/sysdeps/sh/pspinlock.c

   1 /* POSIX spinlock implementation.  SH version.
   2    Copyright (C) 2000, 2001 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 int
  25 __pthread_spin_lock (pthread_spinlock_t *lock)
  26 {
  27   unsigned int val;
  28
  29   do
  30     asm volatile ("tas.b @%1; movt %0"
  31                   : "=r" (val)
  32                   : "r" (lock)
  33                   : "memory");
  34   while (val == 0);
  35
  36   return 0;
  37 }
  38 weak_alias (__pthread_spin_lock, pthread_spin_lock)
  39
  40
  41 int
  42 __pthread_spin_trylock (pthread_spinlock_t *lock)
  43 {
  44   unsigned int val;
  45
  46   asm volatile ("tas.b @%1; movt %0"
  47                 : "=r" (val)
  48                 : "r" (lock)
  49                 : "memory");
  50   return val ? 0 : EBUSY;
  51 }
  52 weak_alias (__pthread_spin_trylock, pthread_spin_trylock)
  53
  54
  55 int
  56 __pthread_spin_unlock (pthread_spinlock_t *lock)
  57 {
  58   return *lock = 0;
  59 }
  60 weak_alias (__pthread_spin_unlock, pthread_spin_unlock)
  61
  62
  63 int
  64 __pthread_spin_init (pthread_spinlock_t *lock, int pshared)
  65 {
  66   /* We can ignore the `pshared' parameter.  Since we are busy-waiting
  67      all processes which can access the memory location `lock' points
  68      to can use the spinlock.  */
  69   return *lock = 0;
  70 }
  71 weak_alias (__pthread_spin_init, pthread_spin_init)
  72
  73
  74 int
  75 __pthread_spin_destroy (pthread_spinlock_t *lock)
  76 {
  77   /* Nothing to do.  */
  78   return 0;
  79 }
  80 weak_alias (__pthread_spin_destroy, pthread_spin_destroy)