linuxthreads/sysdeps/sparc/sparc32/sparcv9/pspinlock.c

   1 /* POSIX spinlock implementation.  SPARC v9 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 /* This implementation is similar to the one used in the Linux kernel.  */
  26 int
  27 __pthread_spin_lock (pthread_spinlock_t *lock)
  28 {
  29   asm volatile
  30     ("1: ldstub  [%0], %%g2\n"
  31      "   brnz,pn %%g2, 2f\n"
  32      "    membar #StoreLoad | #StoreStore\n"
  33      ".subsection 2\n"
  34      "2: ldub    [%0], %%g2\n"
  35      "   brnz,pt %%g2, 2b\n"
  36      "    membar #LoadLoad\n"
  37      "   b,a,pt  %%xcc, 1b\n"
  38      ".previous"
  39      : /* no outputs */
  40      : "r" (lock)
  41      : "g2", "memory");
  42   return 0;
  43 }
  44 weak_alias (__pthread_spin_lock, pthread_spin_lock)
  45
  46
  47 int
  48 __pthread_spin_trylock (pthread_spinlock_t *lock)
  49 {
  50   int result;
  51   asm volatile
  52     ("ldstub [%1], %0\n"
  53      "membar #StoreLoad | #StoreStore"
  54      : "=r" (result)
  55      : "r" (lock)
  56      : "memory");
  57   return result == 0 ? 0 : EBUSY;
  58 }
  59 weak_alias (__pthread_spin_trylock, pthread_spin_trylock)
  60
  61
  62 int
  63 __pthread_spin_unlock (pthread_spinlock_t *lock)
  64 {
  65   asm volatile
  66     ("membar #StoreStore | #LoadStore\n"
  67      "stb    %%g0, [%0]"
  68      :
  69      : "r" (lock)
  70      : "memory");
  71   return 0;
  72 }
  73 weak_alias (__pthread_spin_unlock, pthread_spin_unlock)
  74
  75
  76 int
  77 __pthread_spin_init (pthread_spinlock_t *lock, int pshared)
  78 {
  79   /* We can ignore the `pshared' parameter.  Since we are busy-waiting
  80      all processes which can access the memory location `lock' points
  81      to can use the spinlock.  */
  82   *lock = 0;
  83   return 0;
  84 }
  85 weak_alias (__pthread_spin_init, pthread_spin_init)
  86
  87
  88 int
  89 __pthread_spin_destroy (pthread_spinlock_t *lock)
  90 {
  91   /* Nothing to do.  */
  92   return 0;
  93 }
  94 weak_alias (__pthread_spin_destroy, pthread_spin_destroy)