sysdeps/mach/alpha/machine-lock.h

   1 /* Machine-specific definition for spin locks.  Alpha version.
   2    Copyright (C) 1994, 1997, 2007 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #ifndef _MACHINE_LOCK_H
  21 #define _MACHINE_LOCK_H
  22
  23 /* The type of a spin lock variable.  */
  24
  25 typedef __volatile long int __spin_lock_t;
  26
  27 /* Value to initialize `__spin_lock_t' variables to.  */
  28
  29 #define __SPIN_LOCK_INITIALIZER 0L
  30
  31
  32 #ifndef _EXTERN_INLINE
  33 #define _EXTERN_INLINE __extern_inline
  34 #endif
  35
  36 /* Unlock LOCK.  */
  37
  38 _EXTERN_INLINE void
  39 __spin_unlock (__spin_lock_t *__lock)
  40 {
  41   __asm__ __volatile__ ("mb; stq $31, %0; mb"
  42                         : "=m" (__lock));
  43 }
  44
  45 /* Try to lock LOCK; return nonzero if we locked it, zero if another has.  */
  46
  47 _EXTERN_INLINE int
  48 __spin_try_lock (register __spin_lock_t *__lock)
  49 {
  50   register long int __rtn, __tmp;
  51
  52   do
  53     {
  54       __asm__ __volatile__ ("mb; ldq_l %0,%1" /* Load lock value into TMP.  */
  55                             : "=r" (__tmp) : "m" (*__lock));
  56       __rtn = 2;                /* Load locked value into RTN.  */
  57       if (__tmp)
  58         /* The lock is already taken.  */
  59         return 0;
  60
  61       /* The lock is not taken; try to get it now.  */
  62       __asm__ __volatile__ ("stq_c %0,%1"
  63                             : "=r" (__rtn), "=m" (*__lock)
  64                             : "0" (__rtn), "1" (*__lock));
  65       /* RTN is clear if stq_c was interrupted; loop to try the lock again.  */
  66    } while (! __rtn);
  67   /* RTN is now nonzero; we have the lock.  */
  68   return __rtn;
  69 }
  70
  71 /* Return nonzero if LOCK is locked.  */
  72
  73 _EXTERN_INLINE int
  74 __spin_lock_locked (__spin_lock_t *__lock)
  75 {
  76   return *__lock != 0;
  77 }
  78
  79
  80 #endif /* machine-lock.h */