[apple/xnu.git] / bsd / kern / kern_lock.c

/*
 * Copyright (c) 2000-2001 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This 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 OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995, 1997 Apple Computer, Inc. All Rights Reserved */
/* 
 * 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.
 *
 *	@(#)kern_lock.c	8.18 (Berkeley) 5/21/95
 */

#include <sys/param.h>
#include <sys/proc_internal.h>
#include <sys/lock.h>
#include <kern/cpu_number.h>
#include <kern/thread.h>

#include <mach/mach_types.h>

/*
 * Locking primitives implementation.
 * Locks provide shared/exclusive sychronization.
 */

#if 0
#define COUNT(p, x) if (p) (p)->p_locks += (x)
#else
#define COUNT(p, x)
#endif

#if NCPUS > 1

/*
 * For multiprocessor system, try spin lock first.
 *
 * This should be inline expanded below, but we cannot have #if
 * inside a multiline define.
 */
int lock_wait_time = 100;
#define PAUSE(lkp, wanted)						\
		if (lock_wait_time > 0) {				\
			int i;						\
									\
			for (i = lock_wait_time; i > 0; i--)		\
				if (!(wanted))				\
					break;				\
		}							\
		if (!(wanted))						\
			break;

#else /* NCPUS == 1 */

/*
 * It is an error to spin on a uniprocessor as nothing will ever cause
 * the simple lock to clear while we are executing.
 */
#define PAUSE(lkp, wanted)

#endif /* NCPUS == 1 */

/*
 * Acquire a resource.
 */
#define ACQUIRE(lkp, error, extflags, wanted)				\
	PAUSE(lkp, wanted);						\
	for (error = 0; wanted; ) {					\
		(lkp)->lk_waitcount++;					\
		error = tsleep((void *)lkp, (lkp)->lk_prio,		\
		    (lkp)->lk_wmesg, (lkp)->lk_timo);			\
		(lkp)->lk_waitcount--;					\
		if (error)						\
			break;						\
		if ((extflags) & LK_SLEEPFAIL) {			\
			error = ENOLCK;					\
			break;						\
		}							\
	}

/*
 * Initialize a lock; required before use.
 */
void
lockinit(lkp, prio, wmesg, timo, flags)
	struct lock__bsd__ *lkp;
	int prio;
	const char *wmesg;
	int timo;
	int flags;
{

	bzero(lkp, sizeof(struct lock__bsd__));
	lkp->lk_flags = flags & LK_EXTFLG_MASK;
	lkp->lk_prio = prio;
	lkp->lk_timo = timo;
	lkp->lk_wmesg = wmesg;
	lkp->lk_lockholder = LK_NOPROC;
	lkp->lk_lockthread = 0;
}

/*
 * Determine the status of a lock.
 */
int
lockstatus(lkp)
	struct lock__bsd__ *lkp;
{
	int lock_type = 0;

	if (lkp->lk_exclusivecount != 0)
		lock_type = LK_EXCLUSIVE;
	else if (lkp->lk_sharecount != 0)
		lock_type = LK_SHARED;
	return (lock_type);
}

/*
 * Set, change, or release a lock.
 *
 * Shared requests increment the shared count. Exclusive requests set the
 * LK_WANT_EXCL flag (preventing further shared locks), and wait for already
 * accepted shared locks and shared-to-exclusive upgrades to go away.
 */
int
lockmgr(lkp, flags, interlkp, p)
	struct lock__bsd__ *lkp;
	u_int flags;
	void * interlkp;
	struct proc *p;
{
	int error;
	pid_t pid;
	int extflags;
	void *self;

	error = 0; self = current_thread();
	if (p)
		pid = p->p_pid;
	else
		pid = LK_KERNPROC;
	extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
#if 0
	/*
	 * Once a lock has drained, the LK_DRAINING flag is set and an
	 * exclusive lock is returned. The only valid operation thereafter
	 * is a single release of that exclusive lock. This final release
	 * clears the LK_DRAINING flag and sets the LK_DRAINED flag. Any
	 * further requests of any sort will result in a panic. The bits
	 * selected for these two flags are chosen so that they will be set
	 * in memory that is freed (freed memory is filled with 0xdeadbeef).
	 * The final release is permitted to give a new lease on life to
	 * the lock by specifying LK_REENABLE.
	 */
	if (lkp->lk_flags & (LK_DRAINING|LK_DRAINED)) {
		if (lkp->lk_flags & LK_DRAINED)
			panic("lockmgr: using decommissioned lock");
		if ((flags & LK_TYPE_MASK) != LK_RELEASE ||
		    (lkp->lk_lockholder != pid && lkp->lk_lockthread != self)
			panic("lockmgr: non-release on draining lock: %d\n",
			    flags & LK_TYPE_MASK);
		lkp->lk_flags &= ~LK_DRAINING;
		if ((flags & LK_REENABLE) == 0)
			lkp->lk_flags |= LK_DRAINED;
	}
#endif

	switch (flags & LK_TYPE_MASK) {

	case LK_SHARED:
		if (lkp->lk_lockholder != pid || lkp->lk_lockthread != self) {
			/*
			 * If just polling, check to see if we will block.
			 */
			if ((extflags & LK_NOWAIT) && (lkp->lk_flags &
			    (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE))) {
				error = EBUSY;
				break;
			}
			/*
			 * Wait for exclusive locks and upgrades to clear.
			 */
			ACQUIRE(lkp, error, extflags, lkp->lk_flags &
			    (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE));
			if (error)
				break;
			lkp->lk_sharecount++;
			COUNT(p, 1);
			break;
		}
		/*
		 * We hold an exclusive lock, so downgrade it to shared.
		 * An alternative would be to fail with EDEADLK.
		 */
		lkp->lk_sharecount++;
		COUNT(p, 1);
		/* fall into downgrade */

	case LK_DOWNGRADE:
		if (lkp->lk_lockholder != pid ||
				lkp->lk_lockthread != self ||
					lkp->lk_exclusivecount == 0)
			panic("lockmgr: not holding exclusive lock");
		lkp->lk_sharecount += lkp->lk_exclusivecount;
		lkp->lk_exclusivecount = 0;
		lkp->lk_flags &= ~LK_HAVE_EXCL;
		lkp->lk_lockholder = LK_NOPROC;
		lkp->lk_lockthread = 0;
		if (lkp->lk_waitcount)
			wakeup((void *)lkp);
		break;

	case LK_EXCLUPGRADE:
		/*
		 * If another process is ahead of us to get an upgrade,
		 * then we want to fail rather than have an intervening
		 * exclusive access.
		 */
		if (lkp->lk_flags & LK_WANT_UPGRADE) {
			lkp->lk_sharecount--;
			COUNT(p, -1);
			error = EBUSY;
			break;
		}
		/* fall into normal upgrade */

	case LK_UPGRADE:
		/*
		 * Upgrade a shared lock to an exclusive one. If another
		 * shared lock has already requested an upgrade to an
		 * exclusive lock, our shared lock is released and an
		 * exclusive lock is requested (which will be granted
		 * after the upgrade). If we return an error, the file
		 * will always be unlocked.
		 */
		if ((lkp->lk_lockholder == pid &&
				lkp->lk_lockthread == self) ||
						lkp->lk_sharecount <= 0)
			panic("lockmgr: upgrade exclusive lock");
		lkp->lk_sharecount--;
		COUNT(p, -1);
		/*
		 * If we are just polling, check to see if we will block.
		 */
		if ((extflags & LK_NOWAIT) &&
		    ((lkp->lk_flags & LK_WANT_UPGRADE) ||
		     lkp->lk_sharecount > 1)) {
			error = EBUSY;
			break;
		}
		if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
			/*
			 * We are first shared lock to request an upgrade, so
			 * request upgrade and wait for the shared count to
			 * drop to zero, then take exclusive lock.
			 */
			lkp->lk_flags |= LK_WANT_UPGRADE;
			ACQUIRE(lkp, error, extflags, lkp->lk_sharecount);
			lkp->lk_flags &= ~LK_WANT_UPGRADE;
			if (error)
				break;
			lkp->lk_flags |= LK_HAVE_EXCL;
			lkp->lk_lockholder = pid;
			lkp->lk_lockthread = self;
			if (lkp->lk_exclusivecount != 0)
				panic("lockmgr: non-zero exclusive count");
			lkp->lk_exclusivecount = 1;
			COUNT(p, 1);
			break;
		}
		/*
		 * Someone else has requested upgrade. Release our shared
		 * lock, awaken upgrade requestor if we are the last shared
		 * lock, then request an exclusive lock.
		 */
		if (lkp->lk_sharecount == 0 && lkp->lk_waitcount)
			wakeup((void *)lkp);
		/* fall into exclusive request */

	case LK_EXCLUSIVE:
		if (lkp->lk_lockholder == pid && lkp->lk_lockthread == self) {
			/*
			 *	Recursive lock.
			 */
			if ((extflags & LK_CANRECURSE) == 0)
				panic("lockmgr: locking against myself");
			lkp->lk_exclusivecount++;
			COUNT(p, 1);
			break;
		}
		/*
		 * If we are just polling, check to see if we will sleep.
		 */
		if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
		     (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
		     lkp->lk_sharecount != 0)) {
			error = EBUSY;
			break;
		}
		/*
		 * Try to acquire the want_exclusive flag.
		 */
		ACQUIRE(lkp, error, extflags, lkp->lk_flags &
		    (LK_HAVE_EXCL | LK_WANT_EXCL));
		if (error)
			break;
		lkp->lk_flags |= LK_WANT_EXCL;
		/*
		 * Wait for shared locks and upgrades to finish.
		 */
		ACQUIRE(lkp, error, extflags, lkp->lk_sharecount != 0 ||
		       (lkp->lk_flags & LK_WANT_UPGRADE));
		lkp->lk_flags &= ~LK_WANT_EXCL;
		if (error)
			break;
		lkp->lk_flags |= LK_HAVE_EXCL;
		lkp->lk_lockholder = pid;
		lkp->lk_lockthread = self;
		if (lkp->lk_exclusivecount != 0)
			panic("lockmgr: non-zero exclusive count");
		lkp->lk_exclusivecount = 1;
		COUNT(p, 1);
		break;

	case LK_RELEASE:
		if (lkp->lk_exclusivecount != 0) {
			if (pid != lkp->lk_lockholder ||
					lkp->lk_lockthread != self)
				panic("lockmgr: pid %d, thread 0x%8x,"
					" not exclusive lock holder pid %d"
					" thread 0x%8x unlocking, exclusive count %d",
				    pid, self, lkp->lk_lockholder,
					lkp->lk_lockthread, lkp->lk_exclusivecount);
			lkp->lk_exclusivecount--;
			COUNT(p, -1);
			if (lkp->lk_exclusivecount == 0) {
				lkp->lk_flags &= ~LK_HAVE_EXCL;
				lkp->lk_lockholder = LK_NOPROC;
				lkp->lk_lockthread = 0;
			}
		} else if (lkp->lk_sharecount != 0) {
			lkp->lk_sharecount--;
			COUNT(p, -1);
		}
		if (lkp->lk_waitcount)
			wakeup((void *)lkp);
		break;

	case LK_DRAIN:
		/*
		 * Check that we do not already hold the lock, as it can 
		 * never drain if we do. Unfortunately, we have no way to
		 * check for holding a shared lock, but at least we can
		 * check for an exclusive one.
		 */
		if (lkp->lk_lockholder == pid && lkp->lk_lockthread == self)
			panic("lockmgr: draining against myself");
		/*
		 * If we are just polling, check to see if we will sleep.
		 */
		if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
		     (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
		     lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0)) {
			error = EBUSY;
			break;
		}
		PAUSE(lkp, ((lkp->lk_flags &
		     (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
		     lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0));
		for (error = 0; ((lkp->lk_flags &
		     (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
		     lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0); ) {
			lkp->lk_flags |= LK_WAITDRAIN;
			if (error = tsleep((void *)&lkp->lk_flags, lkp->lk_prio,
			    lkp->lk_wmesg, lkp->lk_timo))
				return (error);
			if ((extflags) & LK_SLEEPFAIL)
				return (ENOLCK);
		}
		lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL;
		lkp->lk_lockholder = pid;
		lkp->lk_lockthread = self;
		lkp->lk_exclusivecount = 1;
		COUNT(p, 1);
		break;

	default:
		panic("lockmgr: unknown locktype request %d",
		    flags & LK_TYPE_MASK);
		/* NOTREACHED */
	}
	if ((lkp->lk_flags & LK_WAITDRAIN) && ((lkp->lk_flags &
	     (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) == 0 &&
	     lkp->lk_sharecount == 0 && lkp->lk_waitcount == 0)) {
		lkp->lk_flags &= ~LK_WAITDRAIN;
		wakeup((void *)&lkp->lk_flags);
	}
	return (error);
}

/*
 * Print out information about state of a lock. Used by VOP_PRINT
 * routines to display ststus about contained locks.
 */
void
lockmgr_printinfo(lkp)
	struct lock__bsd__ *lkp;
{

	if (lkp->lk_sharecount)
		printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
		    lkp->lk_sharecount);
	else if (lkp->lk_flags & LK_HAVE_EXCL)
		printf(" lock type %s: EXCL (count %d) by pid %d",
		    lkp->lk_wmesg, lkp->lk_exclusivecount, lkp->lk_lockholder);
	if (lkp->lk_waitcount > 0)
		printf(" with %d pending", lkp->lk_waitcount);
}
Commit	Line	Data
1c79356b	1	/*
0b4e3aa0	2	* Copyright (c) 2000-2001 Apple Computer, Inc. All rights reserved.
1c79356b A	3	*
	4	* @APPLE_LICENSE_HEADER_START@
	5	*
e5568f75 A	6	* The contents of this file constitute Original Code as defined in and
	7	* are subject to the Apple Public Source License Version 1.1 (the
	8	* "License"). You may not use this file except in compliance with the
	9	* License. Please obtain a copy of the License at
	10	* http://www.apple.com/publicsource and read it before using this file.
1c79356b	11	*
e5568f75 A	12	* This Original Code and all software distributed under the License are
e5568f75 A	13	* distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
1c79356b A	14	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
1c79356b A	15	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
e5568f75 A	16	* FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
	17	* License for the specific language governing rights and limitations
	18	* under the License.
1c79356b A	19	*
	20	* @APPLE_LICENSE_HEADER_END@
	21	*/
	22	/* Copyright (c) 1995, 1997 Apple Computer, Inc. All Rights Reserved */
	23	/*
	24	* Copyright (c) 1995
	25	* The Regents of the University of California. All rights reserved.
	26	*
	27	* This code contains ideas from software contributed to Berkeley by
	28	* Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
	29	* System project at Carnegie-Mellon University.
	30	*
	31	* Redistribution and use in source and binary forms, with or without
	32	* modification, are permitted provided that the following conditions
	33	* are met:
	34	* 1. Redistributions of source code must retain the above copyright
	35	* notice, this list of conditions and the following disclaimer.
	36	* 2. Redistributions in binary form must reproduce the above copyright
	37	* notice, this list of conditions and the following disclaimer in the
	38	* documentation and/or other materials provided with the distribution.
	39	* 3. All advertising materials mentioning features or use of this software
	40	* must display the following acknowledgement:
	41	* This product includes software developed by the University of
	42	* California, Berkeley and its contributors.
	43	* 4. Neither the name of the University nor the names of its contributors
	44	* may be used to endorse or promote products derived from this software
	45	* without specific prior written permission.
	46	*
	47	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	48	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	49	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	50	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	51	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	52	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	53	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	54	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	55	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	56	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	57	* SUCH DAMAGE.
	58	*
	59	* @(#)kern_lock.c 8.18 (Berkeley) 5/21/95
	60	*/
	61
	62	#include <sys/param.h>
91447636	63	#include <sys/proc_internal.h>
1c79356b A	64	#include <sys/lock.h>
	65	#include <kern/cpu_number.h>
	66	#include <kern/thread.h>
	67
	68	#include <mach/mach_types.h>
	69
	70	/*
	71	* Locking primitives implementation.
	72	* Locks provide shared/exclusive sychronization.
	73	*/
	74
	75	#if 0
	76	#define COUNT(p, x) if (p) (p)->p_locks += (x)
	77	#else
	78	#define COUNT(p, x)
	79	#endif
	80
	81	#if NCPUS > 1
	82
	83	/*
	84	* For multiprocessor system, try spin lock first.
	85	*
	86	* This should be inline expanded below, but we cannot have #if
	87	* inside a multiline define.
	88	*/
	89	int lock_wait_time = 100;
	90	#define PAUSE(lkp, wanted) \
	91	if (lock_wait_time > 0) { \
	92	int i; \
	93	\
1c79356b A	94	for (i = lock_wait_time; i > 0; i--) \
	95	if (!(wanted)) \
	96	break; \
1c79356b A	97	} \
	98	if (!(wanted)) \
	99	break;
	100
	101	#else /* NCPUS == 1 */
	102
	103	/*
	104	* It is an error to spin on a uniprocessor as nothing will ever cause
	105	* the simple lock to clear while we are executing.
	106	*/
	107	#define PAUSE(lkp, wanted)
	108
	109	#endif /* NCPUS == 1 */
	110
	111	/*
	112	* Acquire a resource.
	113	*/
	114	#define ACQUIRE(lkp, error, extflags, wanted) \
	115	PAUSE(lkp, wanted); \
	116	for (error = 0; wanted; ) { \
	117	(lkp)->lk_waitcount++; \
1c79356b A	118	error = tsleep((void *)lkp, (lkp)->lk_prio, \
1c79356b A	119	(lkp)->lk_wmesg, (lkp)->lk_timo); \
1c79356b A	120	(lkp)->lk_waitcount--; \
	121	if (error) \
	122	break; \
	123	if ((extflags) & LK_SLEEPFAIL) { \
	124	error = ENOLCK; \
	125	break; \
	126	} \
	127	}
	128
	129	/*
	130	* Initialize a lock; required before use.
	131	*/
	132	void
	133	lockinit(lkp, prio, wmesg, timo, flags)
	134	struct lock__bsd__ *lkp;
	135	int prio;
91447636	136	const char *wmesg;
1c79356b A	137	int timo;
	138	int flags;
	139	{
	140
	141	bzero(lkp, sizeof(struct lock__bsd__));
1c79356b A	142	lkp->lk_flags = flags & LK_EXTFLG_MASK;
	143	lkp->lk_prio = prio;
	144	lkp->lk_timo = timo;
	145	lkp->lk_wmesg = wmesg;
	146	lkp->lk_lockholder = LK_NOPROC;
	147	lkp->lk_lockthread = 0;
	148	}
	149
	150	/*
	151	* Determine the status of a lock.
	152	*/
	153	int
	154	lockstatus(lkp)
	155	struct lock__bsd__ *lkp;
	156	{
	157	int lock_type = 0;
	158
1c79356b A	159	if (lkp->lk_exclusivecount != 0)
	160	lock_type = LK_EXCLUSIVE;
	161	else if (lkp->lk_sharecount != 0)
	162	lock_type = LK_SHARED;
1c79356b A	163	return (lock_type);
	164	}
	165
	166	/*
	167	* Set, change, or release a lock.
	168	*
	169	* Shared requests increment the shared count. Exclusive requests set the
	170	* LK_WANT_EXCL flag (preventing further shared locks), and wait for already
	171	* accepted shared locks and shared-to-exclusive upgrades to go away.
	172	*/
	173	int
	174	lockmgr(lkp, flags, interlkp, p)
	175	struct lock__bsd__ *lkp;
	176	u_int flags;
91447636	177	void * interlkp;
1c79356b A	178	struct proc *p;
	179	{
	180	int error;
	181	pid_t pid;
	182	int extflags;
	183	void *self;
	184
91447636	185	error = 0; self = current_thread();
1c79356b A	186	if (p)
	187	pid = p->p_pid;
	188	else
	189	pid = LK_KERNPROC;
1c79356b A	190	extflags = (flags \| lkp->lk_flags) & LK_EXTFLG_MASK;
	191	#if 0
	192	/*
	193	* Once a lock has drained, the LK_DRAINING flag is set and an
	194	* exclusive lock is returned. The only valid operation thereafter
	195	* is a single release of that exclusive lock. This final release
	196	* clears the LK_DRAINING flag and sets the LK_DRAINED flag. Any
	197	* further requests of any sort will result in a panic. The bits
	198	* selected for these two flags are chosen so that they will be set
	199	* in memory that is freed (freed memory is filled with 0xdeadbeef).
	200	* The final release is permitted to give a new lease on life to
	201	* the lock by specifying LK_REENABLE.
	202	*/
	203	if (lkp->lk_flags & (LK_DRAINING\|LK_DRAINED)) {
	204	if (lkp->lk_flags & LK_DRAINED)
	205	panic("lockmgr: using decommissioned lock");
	206	if ((flags & LK_TYPE_MASK) != LK_RELEASE \|\|
	207	(lkp->lk_lockholder != pid && lkp->lk_lockthread != self)
	208	panic("lockmgr: non-release on draining lock: %d\n",
	209	flags & LK_TYPE_MASK);
	210	lkp->lk_flags &= ~LK_DRAINING;
	211	if ((flags & LK_REENABLE) == 0)
	212	lkp->lk_flags \|= LK_DRAINED;
	213	}
	214	#endif
	215
	216	switch (flags & LK_TYPE_MASK) {
	217
	218	case LK_SHARED:
	219	if (lkp->lk_lockholder != pid \|\| lkp->lk_lockthread != self) {
	220	/*
	221	* If just polling, check to see if we will block.
	222	*/
	223	if ((extflags & LK_NOWAIT) && (lkp->lk_flags &
	224	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE))) {
	225	error = EBUSY;
	226	break;
	227	}
	228	/*
	229	* Wait for exclusive locks and upgrades to clear.
	230	*/
	231	ACQUIRE(lkp, error, extflags, lkp->lk_flags &
	232	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE));
	233	if (error)
	234	break;
	235	lkp->lk_sharecount++;
	236	COUNT(p, 1);
	237	break;
	238	}
	239	/*
	240	* We hold an exclusive lock, so downgrade it to shared.
	241	* An alternative would be to fail with EDEADLK.
	242	*/
	243	lkp->lk_sharecount++;
	244	COUNT(p, 1);
	245	/* fall into downgrade */
	246
	247	case LK_DOWNGRADE:
	248	if (lkp->lk_lockholder != pid \|\|
	249	lkp->lk_lockthread != self \|\|
	250	lkp->lk_exclusivecount == 0)
	251	panic("lockmgr: not holding exclusive lock");
	252	lkp->lk_sharecount += lkp->lk_exclusivecount;
	253	lkp->lk_exclusivecount = 0;
254	lkp->lk_flags &= ~LK_HAVE_EXCL;
255	lkp->lk_lockholder = LK_NOPROC;
256	lkp->lk_lockthread = 0;
257	if (lkp->lk_waitcount)
258	wakeup((void *)lkp);
259	break;
260
261	case LK_EXCLUPGRADE:
262	/*
263	* If another process is ahead of us to get an upgrade,
264	* then we want to fail rather than have an intervening
265	* exclusive access.
266	*/
267	if (lkp->lk_flags & LK_WANT_UPGRADE) {
268	lkp->lk_sharecount--;
269	COUNT(p, -1);
270	error = EBUSY;
271	break;
272	}
273	/* fall into normal upgrade */
274
275	case LK_UPGRADE:
276	/*
277	* Upgrade a shared lock to an exclusive one. If another
278	* shared lock has already requested an upgrade to an
279	* exclusive lock, our shared lock is released and an
280	* exclusive lock is requested (which will be granted
281	* after the upgrade). If we return an error, the file
282	* will always be unlocked.
283	*/
284	if ((lkp->lk_lockholder == pid &&
285	lkp->lk_lockthread == self) \|\|
286	lkp->lk_sharecount <= 0)
287	panic("lockmgr: upgrade exclusive lock");
288	lkp->lk_sharecount--;
289	COUNT(p, -1);
290	/*
291	* If we are just polling, check to see if we will block.
292	*/
293	if ((extflags & LK_NOWAIT) &&
294	((lkp->lk_flags & LK_WANT_UPGRADE) \|\|
295	lkp->lk_sharecount > 1)) {
296	error = EBUSY;
297	break;
298	}
299	if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
300	/*
301	* We are first shared lock to request an upgrade, so
302	* request upgrade and wait for the shared count to
303	* drop to zero, then take exclusive lock.
304	*/
305	lkp->lk_flags \|= LK_WANT_UPGRADE;
306	ACQUIRE(lkp, error, extflags, lkp->lk_sharecount);
307	lkp->lk_flags &= ~LK_WANT_UPGRADE;
308	if (error)
309	break;
310	lkp->lk_flags \|= LK_HAVE_EXCL;
311	lkp->lk_lockholder = pid;
312	lkp->lk_lockthread = self;
313	if (lkp->lk_exclusivecount != 0)
314	panic("lockmgr: non-zero exclusive count");
315	lkp->lk_exclusivecount = 1;
316	COUNT(p, 1);
317	break;
318	}
319	/*
320	* Someone else has requested upgrade. Release our shared
321	* lock, awaken upgrade requestor if we are the last shared
322	* lock, then request an exclusive lock.
323	*/
324	if (lkp->lk_sharecount == 0 && lkp->lk_waitcount)
325	wakeup((void *)lkp);
326	/* fall into exclusive request */
327
328	case LK_EXCLUSIVE:
329	if (lkp->lk_lockholder == pid && lkp->lk_lockthread == self) {
330	/*
331	* Recursive lock.
332	*/
333	if ((extflags & LK_CANRECURSE) == 0)
334	panic("lockmgr: locking against myself");
335	lkp->lk_exclusivecount++;
336	COUNT(p, 1);
337	break;
338	}
339	/*
340	* If we are just polling, check to see if we will sleep.
341	*/
342	if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
343	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
344	lkp->lk_sharecount != 0)) {
345	error = EBUSY;
346	break;
347	}
348	/*
349	* Try to acquire the want_exclusive flag.
350	*/
351	ACQUIRE(lkp, error, extflags, lkp->lk_flags &
352	(LK_HAVE_EXCL \| LK_WANT_EXCL));
353	if (error)
354	break;
355	lkp->lk_flags \|= LK_WANT_EXCL;
356	/*
357	* Wait for shared locks and upgrades to finish.
358	*/
359	ACQUIRE(lkp, error, extflags, lkp->lk_sharecount != 0 \|\|
360	(lkp->lk_flags & LK_WANT_UPGRADE));
361	lkp->lk_flags &= ~LK_WANT_EXCL;
362	if (error)
363	break;
364	lkp->lk_flags \|= LK_HAVE_EXCL;
365	lkp->lk_lockholder = pid;
366	lkp->lk_lockthread = self;
367	if (lkp->lk_exclusivecount != 0)
368	panic("lockmgr: non-zero exclusive count");
369	lkp->lk_exclusivecount = 1;
370	COUNT(p, 1);
371	break;
372
373	case LK_RELEASE:
374	if (lkp->lk_exclusivecount != 0) {
375	if (pid != lkp->lk_lockholder \|\|
376	lkp->lk_lockthread != self)
0b4e3aa0 A	377	panic("lockmgr: pid %d, thread 0x%8x,"
	378	" not exclusive lock holder pid %d"
	379	" thread 0x%8x unlocking, exclusive count %d",
	380	pid, self, lkp->lk_lockholder,
	381	lkp->lk_lockthread, lkp->lk_exclusivecount);
1c79356b A	382	lkp->lk_exclusivecount--;
	383	COUNT(p, -1);
	384	if (lkp->lk_exclusivecount == 0) {
	385	lkp->lk_flags &= ~LK_HAVE_EXCL;
	386	lkp->lk_lockholder = LK_NOPROC;
	387	lkp->lk_lockthread = 0;
	388	}
	389	} else if (lkp->lk_sharecount != 0) {
	390	lkp->lk_sharecount--;
	391	COUNT(p, -1);
	392	}
	393	if (lkp->lk_waitcount)
	394	wakeup((void *)lkp);
	395	break;
	396
	397	case LK_DRAIN:
	398	/*
	399	* Check that we do not already hold the lock, as it can
	400	* never drain if we do. Unfortunately, we have no way to
	401	* check for holding a shared lock, but at least we can
	402	* check for an exclusive one.
	403	*/
	404	if (lkp->lk_lockholder == pid && lkp->lk_lockthread == self)
	405	panic("lockmgr: draining against myself");
	406	/*
	407	* If we are just polling, check to see if we will sleep.
	408	*/
	409	if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
	410	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
	411	lkp->lk_sharecount != 0 \|\| lkp->lk_waitcount != 0)) {
	412	error = EBUSY;
	413	break;
	414	}
	415	PAUSE(lkp, ((lkp->lk_flags &
	416	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
	417	lkp->lk_sharecount != 0 \|\| lkp->lk_waitcount != 0));
	418	for (error = 0; ((lkp->lk_flags &
	419	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
	420	lkp->lk_sharecount != 0 \|\| lkp->lk_waitcount != 0); ) {
	421	lkp->lk_flags \|= LK_WAITDRAIN;
1c79356b A	422	if (error = tsleep((void *)&lkp->lk_flags, lkp->lk_prio,
	423	lkp->lk_wmesg, lkp->lk_timo))
	424	return (error);
	425	if ((extflags) & LK_SLEEPFAIL)
	426	return (ENOLCK);
1c79356b A	427	}
	428	lkp->lk_flags \|= LK_DRAINING \| LK_HAVE_EXCL;
	429	lkp->lk_lockholder = pid;
	430	lkp->lk_lockthread = self;
	431	lkp->lk_exclusivecount = 1;
	432	COUNT(p, 1);
	433	break;
	434
	435	default:
1c79356b A	436	panic("lockmgr: unknown locktype request %d",
	437	flags & LK_TYPE_MASK);
	438	/* NOTREACHED */
	439	}
	440	if ((lkp->lk_flags & LK_WAITDRAIN) && ((lkp->lk_flags &
	441	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) == 0 &&
	442	lkp->lk_sharecount == 0 && lkp->lk_waitcount == 0)) {
	443	lkp->lk_flags &= ~LK_WAITDRAIN;
	444	wakeup((void *)&lkp->lk_flags);
	445	}
1c79356b A	446	return (error);
	447	}
	448
	449	/*
	450	* Print out information about state of a lock. Used by VOP_PRINT
	451	* routines to display ststus about contained locks.
	452	*/
91447636	453	void
1c79356b A	454	lockmgr_printinfo(lkp)
	455	struct lock__bsd__ *lkp;
	456	{
	457
	458	if (lkp->lk_sharecount)
	459	printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
	460	lkp->lk_sharecount);
	461	else if (lkp->lk_flags & LK_HAVE_EXCL)
	462	printf(" lock type %s: EXCL (count %d) by pid %d",
	463	lkp->lk_wmesg, lkp->lk_exclusivecount, lkp->lk_lockholder);
	464	if (lkp->lk_waitcount > 0)
	465	printf(" with %d pending", lkp->lk_waitcount);
	466	}