1  /* Machine-specific definition for spin locks.  x86 version.
       2     Copyright (C) 1994-2023 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
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the 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; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #ifndef _MACHINE_LOCK_H
      20  #define	_MACHINE_LOCK_H
      21  
      22  /* The type of a spin lock variable.  */
      23  
      24  typedef volatile int __spin_lock_t;
      25  
      26  /* Value to initialize `__spin_lock_t' variables to.  */
      27  
      28  #define	__SPIN_LOCK_INITIALIZER	0
      29  
      30  
      31  #ifndef _EXTERN_INLINE
      32  #define _EXTERN_INLINE __extern_inline
      33  #endif
      34  
      35  /* Unlock LOCK.  */
      36  
      37  extern void __spin_unlock (__spin_lock_t *__lock);
      38  
      39  #if defined __USE_EXTERN_INLINES && defined _LIBC
      40  _EXTERN_INLINE void
      41  __spin_unlock (__spin_lock_t *__lock)
      42  {
      43     register int __unlocked;
      44     __asm__ __volatile ("xchgl %0, %1"
      45  		       : "=&r" (__unlocked), "=m" (*__lock) : "0" (0)
      46  		       : "memory");
      47  }
      48  #endif
      49  
      50  /* Try to lock LOCK; return nonzero if we locked it, zero if another has.  */
      51  
      52  extern int __spin_try_lock (__spin_lock_t *__lock);
      53  
      54  #if defined __USE_EXTERN_INLINES && defined _LIBC
      55  _EXTERN_INLINE int
      56  __spin_try_lock (__spin_lock_t *__lock)
      57  {
      58    register int __locked;
      59    __asm__ __volatile ("xchgl %0, %1"
      60  		      : "=&r" (__locked), "=m" (*__lock) : "0" (1)
      61  		      : "memory");
      62    return !__locked;
      63  }
      64  #endif
      65  
      66  /* Return nonzero if LOCK is locked.  */
      67  
      68  extern int __spin_lock_locked (__spin_lock_t *__lock);
      69  
      70  #if defined __USE_EXTERN_INLINES && defined _LIBC
      71  _EXTERN_INLINE int
      72  __spin_lock_locked (__spin_lock_t *__lock)
      73  {
      74    return *__lock != 0;
      75  }
      76  #endif
      77  
      78  
      79  #endif /* machine-lock.h */