/* * Copyright (c) 2000-2004 Silicon Graphics, Inc.  All Rights Reserved. * * This program is free software; you can redistribute it and/or modify it * under the terms of version 2 of the GNU General Public License as * published by the Free Software Foundation. * * This program is distributed in the hope that it would be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. * * Further, this software is distributed without any warranty that it is * free of the rightful claim of any third person regarding infringement * or the like.  Any license provided herein, whether implied or * otherwise, applies only to this software file.  Patent licenses, if * any, provided herein do not apply to combinations of this program with * other software, or any other product whatsoever. * * You should have received a copy of the GNU General Public License along * with this program; if not, write the Free Software Foundation, Inc., 59 * Temple Place - Suite 330, Boston MA 02111-1307, USA. * * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy, * Mountain View, CA  94043, or: * * http://www.sgi.com * * For further information regarding this notice, see: * * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/ */#ifndef __XFS_SUPPORT_MRLOCK_H__#define __XFS_SUPPORT_MRLOCK_H__#include <linux/rwsem.h>enum { MR_NONE, MR_ACCESS, MR_UPDATE };typedef struct {	struct rw_semaphore	mr_lock;	int			mr_writer;} mrlock_t;#define mrinit(mrp, name)	\	( (mrp)->mr_writer = 0, init_rwsem(&(mrp)->mr_lock) )#define mrlock_init(mrp, t,n,s)	mrinit(mrp, n)#define mrfree(mrp)		do { } while (0)#define mraccess(mrp)		mraccessf(mrp, 0)#define mrupdate(mrp)		mrupdatef(mrp, 0)static inline void mraccessf(mrlock_t *mrp, int flags){	down_read(&mrp->mr_lock);}static inline void mrupdatef(mrlock_t *mrp, int flags){	down_write(&mrp->mr_lock);	mrp->mr_writer = 1;}static inline int mrtryaccess(mrlock_t *mrp){	return down_read_trylock(&mrp->mr_lock);}static inline int mrtryupdate(mrlock_t *mrp){	if (!down_write_trylock(&mrp->mr_lock))		return 0;	mrp->mr_writer = 1;	return 1;}static inline void mrunlock(mrlock_t *mrp){	if (mrp->mr_writer) {		mrp->mr_writer = 0;		up_write(&mrp->mr_lock);	} else {		up_read(&mrp->mr_lock);	}}static inline void mrdemote(mrlock_t *mrp){	mrp->mr_writer = 0;	downgrade_write(&mrp->mr_lock);}#ifdef DEBUG/* * Debug-only routine, without some platform-specific asm code, we can * now only answer requests regarding whether we hold the lock for write * (reader state is outside our visibility, we only track writer state). * Note: means !ismrlocked would give false positivies, so don't do that. */static inline int ismrlocked(mrlock_t *mrp, int type){	if (mrp && type == MR_UPDATE)		return mrp->mr_writer;	return 1;}#endif#endif /* __XFS_SUPPORT_MRLOCK_H__ */