linuxthreads/sysdeps/ia64/pspinlock.c

   1 /* POSIX spinlock implementation.  ia64 version.
   2    Copyright (C) 2000, 2003 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Jes Sorensen <jes@linuxcare.com>
   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 License as
   8    published by the Free Software Foundation; either version 2.1 of the
   9    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; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <errno.h>
  22 #include <pthread.h>
  23 #include "internals.h"
  24 #include <ia64intrin.h>
  25
  26 /* This implementation is inspired by the implementation used in the
  27    Linux kernel. */
  28
  29 int
  30 __pthread_spin_lock (pthread_spinlock_t *lock)
  31 {
  32   int *p = (int *) lock;
  33
  34   while (__builtin_expect (__sync_val_compare_and_swap_si (p, 0, 1), 0))
  35     {
  36       /* Spin without using the atomic instruction.  */
  37       do
  38         __asm __volatile ("" : : : "memory");
  39       while (*p);
  40     }
  41   return 0;
  42 }
  43 weak_alias (__pthread_spin_lock, pthread_spin_lock)
  44
  45
  46 int
  47 __pthread_spin_trylock (pthread_spinlock_t *lock)
  48 {
  49   return __sync_val_compare_and_swap_si ((int *) lock, 0, 1) == 0 ? 0 : EBUSY;
  50 }
  51 weak_alias (__pthread_spin_trylock, pthread_spin_trylock)
  52
  53
  54 int
  55 __pthread_spin_unlock (pthread_spinlock_t *lock)
  56 {
  57   return *lock = 0;
  58 }
  59 weak_alias (__pthread_spin_unlock, pthread_spin_unlock)
  60
  61
  62 int
  63 __pthread_spin_init (pthread_spinlock_t *lock, int pshared)
  64 {
  65   /* We can ignore the `pshared' parameter.  Since we are busy-waiting
  66      all processes which can access the memory location `lock' points
  67      to can use the spinlock.  */
  68   return *lock = 0;
  69 }
  70 weak_alias (__pthread_spin_init, pthread_spin_init)
  71
  72
  73 int
  74 __pthread_spin_destroy (pthread_spinlock_t *lock)
  75 {
  76   /* Nothing to do.  */
  77   return 0;
  78 }
  79 weak_alias (__pthread_spin_destroy, pthread_spin_destroy)