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/*
* Copyright (c) 1997 John Birrell <jb@cimlogic.com.au>.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by John Birrell.
* 4. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $Id: uthread_spinlock.c,v 1.2 1998/05/05 21:47:58 jb Exp $
*
*/
#include <stdio.h>
#include <sched.h>
#include <unistd.h>
#include <pthread.h>
#include <string.h>
#include "spinlock.h"
#include "pthread_private.h"
/*
* Lock a location for the running thread. Yield to allow other
* threads to run if this thread is blocked because the lock is
* not available. Note that this function does not sleep. It
* assumes that the lock will be available very soon.
*/
void
_spinlock(volatile long * volatile lck)
{
do {
/*
* Allow other threads to run if the lock is not
* available:
*/
while (*lck != 0) {
/* Check if already locked by the running thread: */
if (*lck == (long) _thread_run) {
char str[40];
snprintf(str,sizeof(str),"Warning: Thread %p attempted to lock %p which it had already locked!\n",_thread_run,lck);
_thread_sys_write(2,str,strlen(str));
return;
}
/* Give up the time slice: */
sched_yield();
}
/*
* Try to grab the lock and loop if another thread grabs
* it before we do.
*/
} while(_atomic_lock(lck,(long) _thread_run));
}
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