glibc/sysdeps/mach/i386/machine-lock.h

/* Machine-specific definition for spin locks.  i386 version.
   Copyright (C) 1994-2022 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, see
   <https://www.gnu.org/licenses/>.  */

#ifndef _MACHINE_LOCK_H
#define	_MACHINE_LOCK_H

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

typedef volatile int __spin_lock_t;

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

#define	__SPIN_LOCK_INITIALIZER	0


#ifndef _EXTERN_INLINE
#define _EXTERN_INLINE __extern_inline
#endif

/* Unlock LOCK.  */

extern void __spin_unlock (__spin_lock_t *__lock);

#if defined __USE_EXTERN_INLINES && defined _LIBC
_EXTERN_INLINE void
__spin_unlock (__spin_lock_t *__lock)
{
   register int __unlocked;
   __asm__ __volatile ("xchgl %0, %1"
		       : "=&r" (__unlocked), "=m" (*__lock) : "0" (0)
		       : "memory");
}
#endif

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

extern int __spin_try_lock (__spin_lock_t *__lock);

#if defined __USE_EXTERN_INLINES && defined _LIBC
_EXTERN_INLINE int
__spin_try_lock (__spin_lock_t *__lock)
{
  register int __locked;
  __asm__ __volatile ("xchgl %0, %1"
		      : "=&r" (__locked), "=m" (*__lock) : "0" (1)
		      : "memory");
  return !__locked;
}
#endif

/* Return nonzero if LOCK is locked.  */

extern int __spin_lock_locked (__spin_lock_t *__lock);

#if defined __USE_EXTERN_INLINES && defined _LIBC
_EXTERN_INLINE int
__spin_lock_locked (__spin_lock_t *__lock)
{
  return *__lock != 0;
}
#endif


#endif /* machine-lock.h */