lock.h

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/* 
 * Copyright (c) 1995
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code contains ideas from software contributed to Berkeley by
 * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
 * System project at Carnegie-Mellon University.
 *
 * 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 the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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.
 *
 *	@(#)lock.h	8.12 (Berkeley) 5/19/95
 * $Id: lock.h,v 1.13 1999/01/20 14:49:12 eivind Exp $
 */

#ifndef	_LOCK_H_
#define	_LOCK_H_


#include <machine/lock.h>

/*
 * The general lock structure.  Provides for multiple shared locks,
 * upgrading from shared to exclusive, and sleeping until the lock
 * can be gained. The simple locks are defined in <machine/param.h>.
 */
struct lock {
	struct	simplelock lk_interlock; /* lock on remaining fields */
	u_int	lk_flags;		/* see below */
	int	lk_sharecount;		/* # of accepted shared locks */
	int	lk_waitcount;		/* # of processes sleeping for lock */
	short	lk_exclusivecount;	/* # of recursive exclusive locks */
	short	lk_prio;		/* priority at which to sleep */
	char	*lk_wmesg;		/* resource sleeping (for tsleep) */
	int	lk_timo;		/* maximum sleep time (for tsleep) */
	pid_t	lk_lockholder;		/* pid of exclusive lock holder */
#ifdef	DEBUG_LOCKS
	const char *lk_filename;
	const char *lk_lockername;
	int     lk_lineno;
#endif
};
/*
 * Lock request types:
 *   LK_SHARED - get one of many possible shared locks. If a process
 *	holding an exclusive lock requests a shared lock, the exclusive
 *	lock(s) will be downgraded to shared locks.
 *   LK_EXCLUSIVE - stop further shared locks, when they are cleared,
 *	grant a pending upgrade if it exists, then grant an exclusive
 *	lock. Only one exclusive lock may exist at a time, except that
 *	a process holding an exclusive lock may get additional exclusive
 *	locks if it explicitly sets the LK_CANRECURSE flag in the lock
 *	request, or if the LK_CANRECUSE flag was set when the lock was
 *	initialized.
 *   LK_UPGRADE - the process must hold a shared lock that it wants to
 *	have upgraded to an exclusive lock. Other processes may get
 *	exclusive access to the resource between the time that the upgrade
 *	is requested and the time that it is granted.
 *   LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
 *	have upgraded to an exclusive lock. If the request succeeds, no
 *	other processes will have gotten exclusive access to the resource
 *	between the time that the upgrade is requested and the time that
 *	it is granted. However, if another process has already requested
 *	an upgrade, the request will fail (see error returns below).
 *   LK_DOWNGRADE - the process must hold an exclusive lock that it wants
 *	to have downgraded to a shared lock. If the process holds multiple
 *	(recursive) exclusive locks, they will all be downgraded to shared
 *	locks.
 *   LK_RELEASE - release one instance of a lock.
 *   LK_DRAIN - wait for all activity on the lock to end, then mark it
 *	decommissioned. This feature is used before freeing a lock that
 *	is part of a piece of memory that is about to be freed.
 *
 * These are flags that are passed to the lockmgr routine.
 */
#define LK_TYPE_MASK	0x0000000f	/* type of lock sought */
#define LK_SHARED	0x00000001	/* shared lock */
#define LK_EXCLUSIVE	0x00000002	/* exclusive lock */
#define LK_UPGRADE	0x00000003	/* shared-to-exclusive upgrade */
#define LK_EXCLUPGRADE	0x00000004	/* first shared-to-exclusive upgrade */
#define LK_DOWNGRADE	0x00000005	/* exclusive-to-shared downgrade */
#define LK_RELEASE	0x00000006	/* release any type of lock */
#define LK_DRAIN	0x00000007	/* wait for all lock activity to end */
/*
 * External lock flags.
 *
 * The first three flags may be set in lock_init to set their mode permanently,
 * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
 * set only at the release of a lock obtained by drain.
 */
#define LK_EXTFLG_MASK	0x01000070	/* mask of external flags */
#define LK_NOWAIT	0x00000010	/* do not sleep to await lock */
#define LK_SLEEPFAIL	0x00000020	/* sleep, then return failure */
#define LK_CANRECURSE	0x00000040	/* allow recursive exclusive lock */
#define LK_REENABLE	0x00000080	/* lock is be reenabled after drain */
#define	LK_NOPAUSE	0x01000000	/* no spinloop */
/*
 * Internal lock flags.
 *
 * These flags are used internally to the lock manager.
 */
#define LK_WANT_UPGRADE	0x00000100	/* waiting for share-to-excl upgrade */
#define LK_WANT_EXCL	0x00000200	/* exclusive lock sought */
#define LK_HAVE_EXCL	0x00000400	/* exclusive lock obtained */
#define LK_WAITDRAIN	0x00000800	/* process waiting for lock to drain */
#define LK_DRAINING	0x00004000	/* lock is being drained */
#define LK_DRAINED	0x00008000	/* lock has been decommissioned */
/*
 * Control flags
 *
 * Non-persistent external flags.
 */
#define LK_INTERLOCK	0x00010000 /* unlock passed simple lock after
				   getting lk_interlock */
#define LK_RETRY	0x00020000 /* vn_lock: retry until locked */
#define	LK_NOOBJ	0x00040000 /* vget: don't create object */

/*
 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
 */
#define	LK_SHARE_NONZERO 0x00100000
#define	LK_WAIT_NONZERO  0x00200000

/*
 * Lock return status.
 *
 * Successfully obtained locks return 0. Locks will always succeed
 * unless one of the following is true:
 *	LK_FORCEUPGRADE is requested and some other process has already
 *	    requested a lock upgrade (returns EBUSY).
 *	LK_WAIT is set and a sleep would be required (returns EBUSY).
 *	LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
 *	PCATCH is set in lock priority and a signal arrives (returns
 *	    either EINTR or ERESTART if system calls is to be restarted).
 *	Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
 * A failed lock attempt always returns a non-zero error value. No lock
 * is held after an error return (in particular, a failed LK_UPGRADE
 * or LK_FORCEUPGRADE will have released its shared access lock).
 */

/*
 * Indicator that no process holds exclusive lock
 */
#define LK_KERNPROC ((pid_t) -2)
#define LK_NOPROC ((pid_t) -1)

void dumplockinfo(struct lock *lkp);
struct proc;

void	lockinit __P((struct lock *, int prio, char *wmesg, int timo,
			int flags));
#ifdef DEBUG_LOCKS
int	debuglockmgr __P((struct lock *, u_int flags,
			struct simplelock *, struct proc *p,
			const char *,
			const char *,
			int));
#define lockmgr(lockp, flags, slockp, proc) \
	debuglockmgr((lockp), (flags), (slockp), (proc), \
	    "lockmgr", __FILE__, __LINE__)
#else
int	lockmgr __P((struct lock *, u_int flags,
			struct simplelock *, struct proc *p));
#endif
void	lockmgr_printinfo __P((struct lock *));
int	lockstatus __P((struct lock *));

#ifdef SIMPLELOCK_DEBUG
void _simple_unlock __P((struct simplelock *alp, const char *, int));
#define simple_unlock(alp) _simple_unlock(alp, __FILE__, __LINE__)
int _simple_lock_try __P((struct simplelock *alp, const char *, int));
#define simple_lock_try(alp) _simple_lock_try(alp, __FILE__, __LINE__)
void _simple_lock __P((struct simplelock *alp, const char *, int));
#define simple_lock(alp) _simple_lock(alp, __FILE__, __LINE__)
void simple_lock_init __P((struct simplelock *alp));
#else /* !SIMPLELOCK_DEBUG */
#if NCPUS == 1 /* no multiprocessor locking is necessary */
#define	NULL_SIMPLELOCKS
#define	simple_lock_init(alp)
#define	simple_lock(alp)
#define	simple_lock_try(alp)	(1)	/* always succeeds */
#define	simple_unlock(alp)
#endif /* NCPUS == 1 */
#endif /* !SIMPLELOCK_DEBUG */

#endif /* !_LOCK_H_ */