/*
 * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_OSREFERENCE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code 
 * as defined in and that are subject to the Apple Public Source License 
 * Version 2.0 (the 'License'). You may not use this file except in 
 * compliance with the License.  The rights granted to you under the 
 * License may not be used to create, or enable the creation or 
 * redistribution of, unlawful or unlicensed copies of an Apple operating 
 * system, or to circumvent, violate, or enable the circumvention or 
 * violation of, any terms of an Apple operating system software license 
 * agreement.
 *
 * Please obtain a copy of the License at 
 * http://www.opensource.apple.com/apsl/ and read it before using this 
 * file.
 *
 * The Original Code and all software distributed under the License are 
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 
 * Please see the License for the specific language governing rights and 
 * limitations under the License.
 *
 * @APPLE_LICENSE_OSREFERENCE_HEADER_END@
 */
/*
 * Copyright (c) 1998 Apple Computer, Inc.  All rights reserved. 
 *
 * HISTORY
 *
 */

/* 	Copyright (c) 1992 NeXT Computer, Inc.  All rights reserved. 
 *
 * EventShmemLock.h -	Shared memory area locks for use between the
 *			WindowServer and the Event Driver.
 *
 *
 * HISTORY
 * 29 April 1992    Mike Paquette at NeXT
 *      Created. 
 *
 * Multiprocessor locks used within the shared memory area between the
 * kernel and event system.  These must work in both user and kernel mode.
 * The locks are defined in an include file so they get exported to the local
 * include file area.
 *
 * This is basically a ripoff of the spin locks under the cthreads packages.
 */

#ifndef _IOKIT_IOSHAREDLOCKIMP_H
#define _IOKIT_IOSHAREDLOCKIMP_H

#include <architecture/i386/asm_help.h>

/* 
 * void
 * ev_lock(p)
 *	int *p;
 *
 * Lock the lock pointed to by p.  Spin (possibly forever) until the next
 * lock is available.
 */
	TEXT

#ifndef KERNEL
LEAF(_ev_lock, 0)
LEAF(_IOSpinLock, 0)
	movl		4(%esp), %ecx
0:
	xorl		%eax, %eax
	rep
	nop		/* pause for hyperthreaded CPU's */
	lock
	cmpxchgl	%ecx, (%ecx)
	jne		0b
	ret
END(_ev_lock)
#endif

/*
 * void
 * ev_unlock(p)
 *	int *p;
 *
 * Unlock the lock pointed to by p.
 */
LEAF(_ev_unlock, 0)
LEAF(_IOSpinUnlock, 0)
	movl		4(%esp), %ecx
	movl		$0, (%ecx)
	ret
END(_ev_unlock)



/*
 * int
 * ev_try_lock(p)
 *	int *p;
 *
 * Try to lock p.  Return zero if not successful.
 */

LEAF(_ev_try_lock, 0)
LEAF(_IOTrySpinLock, 0)
        movl            4(%esp), %ecx 
	xorl		%eax, %eax
        lock
        cmpxchgl        %ecx, (%ecx)
	jne	1f
	movl	$1, %eax		/* yes */
	ret
1:
	xorl	%eax, %eax		/* no */
END(_ev_try_lock)


#endif /* ! _IOKIT_IOSHAREDLOCKIMP_H */
