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glibc  2.9
machine-lock.h
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00001 /* Machine-specific definition for spin locks.  Alpha version.
00002    Copyright (C) 1994, 1997, 2007 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #ifndef _MACHINE_LOCK_H
00021 #define       _MACHINE_LOCK_H
00022 
00023 /* The type of a spin lock variable.  */
00024 
00025 typedef __volatile long int __spin_lock_t;
00026 
00027 /* Value to initialize `__spin_lock_t' variables to.  */
00028 
00029 #define       __SPIN_LOCK_INITIALIZER     0L
00030 
00031 
00032 #ifndef _EXTERN_INLINE
00033 #define _EXTERN_INLINE __extern_inline
00034 #endif
00035 
00036 /* Unlock LOCK.  */
00037 
00038 _EXTERN_INLINE void
00039 __spin_unlock (__spin_lock_t *__lock)
00040 {
00041   __asm__ __volatile__ ("mb; stq $31, %0; mb"
00042                      : "=m" (__lock));
00043 }
00044 
00045 /* Try to lock LOCK; return nonzero if we locked it, zero if another has.  */
00046 
00047 _EXTERN_INLINE int
00048 __spin_try_lock (register __spin_lock_t *__lock)
00049 {
00050   register long int __rtn, __tmp;
00051 
00052   do
00053     {
00054       __asm__ __volatile__ ("mb; ldq_l %0,%1" /* Load lock value into TMP.  */
00055                          : "=r" (__tmp) : "m" (*__lock));
00056       __rtn = 2;            /* Load locked value into RTN.  */
00057       if (__tmp)
00058        /* The lock is already taken.  */
00059        return 0;
00060 
00061       /* The lock is not taken; try to get it now.  */
00062       __asm__ __volatile__ ("stq_c %0,%1"
00063                          : "=r" (__rtn), "=m" (*__lock)
00064                          : "0" (__rtn), "1" (*__lock));
00065       /* RTN is clear if stq_c was interrupted; loop to try the lock again.  */
00066    } while (! __rtn);
00067   /* RTN is now nonzero; we have the lock.  */
00068   return __rtn;
00069 }
00070 
00071 /* Return nonzero if LOCK is locked.  */
00072 
00073 _EXTERN_INLINE int
00074 __spin_lock_locked (__spin_lock_t *__lock)
00075 {
00076   return *__lock != 0;
00077 }
00078 
00079 
00080 #endif /* machine-lock.h */