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glibc  2.9
pspinlock.c
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00001 /* POSIX spinlock implementation.  Arm version.
00002    Copyright (C) 2000 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 License as
00007    published by the Free Software Foundation; either version 2.1 of the
00008    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; see the file COPYING.LIB.  If not,
00017    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
00018    Boston, MA 02111-1307, USA.  */
00019 
00020 #include <errno.h>
00021 #include <pthread.h>
00022 #include "internals.h"
00023 
00024 
00025 int
00026 __pthread_spin_lock (pthread_spinlock_t *lock)
00027 {
00028   unsigned int val;
00029 
00030   do
00031     asm volatile ("swp %0, %1, [%2]"
00032                 : "=r" (val)
00033                 : "0" (1), "r" (lock)
00034                 : "memory");
00035   while (val != 0);
00036 
00037   return 0;
00038 }
00039 weak_alias (__pthread_spin_lock, pthread_spin_lock)
00040 
00041 
00042 int
00043 __pthread_spin_trylock (pthread_spinlock_t *lock)
00044 {
00045   unsigned int val;
00046 
00047   asm volatile ("swp %0, %1, [%2]"
00048               : "=r" (val)
00049               : "0" (1), "r" (lock)
00050               : "memory");
00051 
00052   return val ? EBUSY : 0;
00053 }
00054 weak_alias (__pthread_spin_trylock, pthread_spin_trylock)
00055 
00056 
00057 int
00058 __pthread_spin_unlock (pthread_spinlock_t *lock)
00059 {
00060   return *lock = 0;
00061 }
00062 weak_alias (__pthread_spin_unlock, pthread_spin_unlock)
00063 
00064 
00065 int
00066 __pthread_spin_init (pthread_spinlock_t *lock, int pshared)
00067 {
00068   /* We can ignore the `pshared' parameter.  Since we are busy-waiting
00069      all processes which can access the memory location `lock' points
00070      to can use the spinlock.  */
00071   return *lock = 0;
00072 }
00073 weak_alias (__pthread_spin_init, pthread_spin_init)
00074 
00075 
00076 int
00077 __pthread_spin_destroy (pthread_spinlock_t *lock)
00078 {
00079   /* Nothing to do.  */
00080   return 0;
00081 }
00082 weak_alias (__pthread_spin_destroy, pthread_spin_destroy)