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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libc/] [sys/] [linux/] [linuxthreads/] [machine/] [i386/] [pspinlock.c] - Blame information for rev 207

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1 207 jeremybenn
/* POSIX spinlock implementation.  x86 version.
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   Copyright (C) 2000 Free Software Foundation, Inc.
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   This file is part of the GNU C Library.
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   The GNU C Library is free software; you can redistribute it and/or
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   modify it under the terms of the GNU Library General Public License as
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   published by the Free Software Foundation; either version 2 of the
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   License, or (at your option) any later version.
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   The GNU C Library is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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   Library General Public License for more details.
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   You should have received a copy of the GNU Library General Public
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   License along with the GNU C Library; see the file COPYING.LIB.  If not,
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   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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   Boston, MA 02111-1307, USA.  */
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#include <errno.h>
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#include <pthread.h>
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#include "internals.h"
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/* This implementation is similar to the one used in the Linux kernel.
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   But the kernel is byte instructions for the memory access.  This is
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   faster but unusable here.  The problem is that only 128
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   threads/processes could use the spinlock at the same time.  If (by
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   a design error in the program) a thread/process would hold the
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   spinlock for a time long enough to accumulate 128 waiting
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   processes, the next one will find a positive value in the spinlock
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   and assume it is unlocked.  We cannot accept that.  */
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int
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__pthread_spin_lock (pthread_spinlock_t *lock)
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{
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  asm volatile
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    ("\n"
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     "1:\n\t"
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     "lock; decl %0\n\t"
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     "js 2f\n\t"
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     ".section .text.spinlock,\"ax\"\n"
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     "2:\n\t"
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     "cmpl $0,%0\n\t"
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     "rep; nop\n\t"
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     "jle 2b\n\t"
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     "jmp 1b\n\t"
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     ".previous"
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     : "=m" (*lock));
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  return 0;
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}
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weak_alias (__pthread_spin_lock, pthread_spin_lock)
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int
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__pthread_spin_trylock (pthread_spinlock_t *lock)
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{
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  int oldval;
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  asm volatile
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    ("xchgl %0,%1"
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     : "=r" (oldval), "=m" (*lock)
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     : "0" (0));
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  return oldval > 0 ? 0 : EBUSY;
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}
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weak_alias (__pthread_spin_trylock, pthread_spin_trylock)
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int
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__pthread_spin_unlock (pthread_spinlock_t *lock)
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{
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  asm volatile
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    ("movl $1,%0"
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     : "=m" (*lock));
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  return 0;
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}
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weak_alias (__pthread_spin_unlock, pthread_spin_unlock)
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int
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__pthread_spin_init (pthread_spinlock_t *lock, int pshared)
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{
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  /* We can ignore the `pshared' parameter.  Since we are busy-waiting
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     all processes which can access the memory location `lock' points
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     to can use the spinlock.  */
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  *lock = 1;
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  return 0;
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}
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weak_alias (__pthread_spin_init, pthread_spin_init)
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int
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__pthread_spin_destroy (pthread_spinlock_t *lock)
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{
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  /* Nothing to do.  */
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  return 0;
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}
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weak_alias (__pthread_spin_destroy, pthread_spin_destroy)

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