glibc/sysdeps/mach/alpha/machine-lock.h

/* Machine-specific definition for spin locks.  Alpha version.
   Copyright (C) 1994, 1997, 2007 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#ifndef _MACHINE_LOCK_H
#define	_MACHINE_LOCK_H

/* The type of a spin lock variable.  */

typedef __volatile long int __spin_lock_t;

/* Value to initialize `__spin_lock_t' variables to.  */

#define	__SPIN_LOCK_INITIALIZER	0L


#ifndef _EXTERN_INLINE
#define _EXTERN_INLINE __extern_inline
#endif

/* Unlock LOCK.  */

_EXTERN_INLINE void
__spin_unlock (__spin_lock_t *__lock)
{
  __asm__ __volatile__ ("mb; stq $31, %0; mb"
			: "=m" (__lock));
}

/* Try to lock LOCK; return nonzero if we locked it, zero if another has.  */

_EXTERN_INLINE int
__spin_try_lock (register __spin_lock_t *__lock)
{
  register long int __rtn, __tmp;

  do
    {
      __asm__ __volatile__ ("mb; ldq_l %0,%1" /* Load lock value into TMP.  */
			    : "=r" (__tmp) : "m" (*__lock));
      __rtn = 2;		/* Load locked value into RTN.  */
      if (__tmp)
	/* The lock is already taken.  */
	return 0;

      /* The lock is not taken; try to get it now.  */
      __asm__ __volatile__ ("stq_c %0,%1"
			    : "=r" (__rtn), "=m" (*__lock)
			    : "0" (__rtn), "1" (*__lock));
      /* RTN is clear if stq_c was interrupted; loop to try the lock again.  */
   } while (! __rtn);
  /* RTN is now nonzero; we have the lock.  */
  return __rtn;
}

/* Return nonzero if LOCK is locked.  */

_EXTERN_INLINE int
__spin_lock_locked (__spin_lock_t *__lock)
{
  return *__lock != 0;
}


#endif /* machine-lock.h */