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

/*
 * Copyright (c) 2000-2001 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
 * 
 * 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. 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_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.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;						\
									\
			simple_unlock(&lkp->lk_interlock);		\
			for (i = lock_wait_time; i > 0; i--)		\
				if (!(wanted))				\
					break;				\
			simple_lock(&lkp->lk_interlock);		\
		}							\
		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++;					\
		simple_unlock(&(lkp)->lk_interlock);			\
		error = tsleep((void *)lkp, (lkp)->lk_prio,		\
		    (lkp)->lk_wmesg, (lkp)->lk_timo);			\
		simple_lock(&(lkp)->lk_interlock);			\
		(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;
	char *wmesg;
	int timo;
	int flags;
{

	bzero(lkp, sizeof(struct lock__bsd__));
	simple_lock_init(&lkp->lk_interlock);
	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;

	simple_lock(&lkp->lk_interlock);
	if (lkp->lk_exclusivecount != 0)
		lock_type = LK_EXCLUSIVE;
	else if (lkp->lk_sharecount != 0)
		lock_type = LK_SHARED;
	simple_unlock(&lkp->lk_interlock);
	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;
	simple_lock_t 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;
	simple_lock(&lkp->lk_interlock);
	if (flags & LK_INTERLOCK)
		simple_unlock(interlkp);
	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;
			simple_unlock(&lkp->lk_interlock);
			if (error = tsleep((void *)&lkp->lk_flags, lkp->lk_prio,
			    lkp->lk_wmesg, lkp->lk_timo))
				return (error);
			if ((extflags) & LK_SLEEPFAIL)
				return (ENOLCK);
			simple_lock(&lkp->lk_interlock);
		}
		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:
		simple_unlock(&lkp->lk_interlock);
		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);
	}
	simple_unlock(&lkp->lk_interlock);
	return (error);
}

/*
 * Print out information about state of a lock. Used by VOP_PRINT
 * routines to display ststus about contained locks.
 */
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	*
d7e50217	6	* Copyright (c) 1999-2003 Apple Computer, Inc. All Rights Reserved.
1c79356b	7	*
d7e50217 A	8	* This file contains Original Code and/or Modifications of Original Code
	9	* as defined in and that are subject to the Apple Public Source License
	10	* Version 2.0 (the 'License'). You may not use this file except in
	11	* compliance with the License. Please obtain a copy of the License at
	12	* http://www.opensource.apple.com/apsl/ and read it before using this
	13	* file.
	14	*
	15	* The Original Code and all software distributed under the License are
	16	* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
1c79356b A	17	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
1c79356b A	18	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
d7e50217 A	19	* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
	20	* Please see the License for the specific language governing rights and
	21	* limitations under the License.
1c79356b A	22	*
	23	* @APPLE_LICENSE_HEADER_END@
	24	*/
	25	/* Copyright (c) 1995, 1997 Apple Computer, Inc. All Rights Reserved */
	26	/*
	27	* Copyright (c) 1995
	28	* The Regents of the University of California. All rights reserved.
	29	*
	30	* This code contains ideas from software contributed to Berkeley by
	31	* Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
	32	* System project at Carnegie-Mellon University.
	33	*
	34	* Redistribution and use in source and binary forms, with or without
	35	* modification, are permitted provided that the following conditions
	36	* are met:
	37	* 1. Redistributions of source code must retain the above copyright
	38	* notice, this list of conditions and the following disclaimer.
	39	* 2. Redistributions in binary form must reproduce the above copyright
	40	* notice, this list of conditions and the following disclaimer in the
	41	* documentation and/or other materials provided with the distribution.
	42	* 3. All advertising materials mentioning features or use of this software
	43	* must display the following acknowledgement:
	44	* This product includes software developed by the University of
	45	* California, Berkeley and its contributors.
	46	* 4. Neither the name of the University nor the names of its contributors
	47	* may be used to endorse or promote products derived from this software
	48	* without specific prior written permission.
	49	*
	50	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	51	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	52	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	53	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	54	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	55	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	56	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	57	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	58	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	59	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	60	* SUCH DAMAGE.
	61	*
	62	* @(#)kern_lock.c 8.18 (Berkeley) 5/21/95
	63	*/
	64
	65	#include <sys/param.h>
	66	#include <sys/proc.h>
	67	#include <sys/lock.h>
	68	#include <kern/cpu_number.h>
	69	#include <kern/thread.h>
	70
	71	#include <mach/mach_types.h>
	72
	73	/*
	74	* Locking primitives implementation.
	75	* Locks provide shared/exclusive sychronization.
	76	*/
	77
	78	#if 0
	79	#define COUNT(p, x) if (p) (p)->p_locks += (x)
	80	#else
	81	#define COUNT(p, x)
	82	#endif
	83
	84	#if NCPUS > 1
	85
86	/*
87	* For multiprocessor system, try spin lock first.
88	*
89	* This should be inline expanded below, but we cannot have #if
90	* inside a multiline define.
91	*/
92	int lock_wait_time = 100;
93	#define PAUSE(lkp, wanted) \
94	if (lock_wait_time > 0) { \
95	int i; \
96	\
97	simple_unlock(&lkp->lk_interlock); \
98	for (i = lock_wait_time; i > 0; i--) \
99	if (!(wanted)) \
100	break; \
101	simple_lock(&lkp->lk_interlock); \
102	} \
103	if (!(wanted)) \
104	break;
105
106	#else /* NCPUS == 1 */
107
108	/*
109	* It is an error to spin on a uniprocessor as nothing will ever cause
110	* the simple lock to clear while we are executing.
111	*/
112	#define PAUSE(lkp, wanted)
113
114	#endif /* NCPUS == 1 */
115
116	/*
117	* Acquire a resource.
118	*/
119	#define ACQUIRE(lkp, error, extflags, wanted) \
120	PAUSE(lkp, wanted); \
121	for (error = 0; wanted; ) { \
122	(lkp)->lk_waitcount++; \
123	simple_unlock(&(lkp)->lk_interlock); \
124	error = tsleep((void *)lkp, (lkp)->lk_prio, \
125	(lkp)->lk_wmesg, (lkp)->lk_timo); \
126	simple_lock(&(lkp)->lk_interlock); \
127	(lkp)->lk_waitcount--; \
128	if (error) \
129	break; \
130	if ((extflags) & LK_SLEEPFAIL) { \
131	error = ENOLCK; \
132	break; \
133	} \
134	}
135
136	/*
137	* Initialize a lock; required before use.
138	*/
139	void
140	lockinit(lkp, prio, wmesg, timo, flags)
141	struct lock__bsd__ *lkp;
142	int prio;
143	char *wmesg;
144	int timo;
145	int flags;
146	{
147
148	bzero(lkp, sizeof(struct lock__bsd__));
149	simple_lock_init(&lkp->lk_interlock);
150	lkp->lk_flags = flags & LK_EXTFLG_MASK;
151	lkp->lk_prio = prio;
152	lkp->lk_timo = timo;
153	lkp->lk_wmesg = wmesg;
154	lkp->lk_lockholder = LK_NOPROC;
155	lkp->lk_lockthread = 0;
156	}
157
158	/*
159	* Determine the status of a lock.
160	*/
161	int
162	lockstatus(lkp)
163	struct lock__bsd__ *lkp;
164	{
165	int lock_type = 0;
166
167	simple_lock(&lkp->lk_interlock);
168	if (lkp->lk_exclusivecount != 0)
169	lock_type = LK_EXCLUSIVE;
170	else if (lkp->lk_sharecount != 0)
171	lock_type = LK_SHARED;
172	simple_unlock(&lkp->lk_interlock);
173	return (lock_type);
174	}
175
176	/*
177	* Set, change, or release a lock.
178	*
179	* Shared requests increment the shared count. Exclusive requests set the
180	* LK_WANT_EXCL flag (preventing further shared locks), and wait for already
181	* accepted shared locks and shared-to-exclusive upgrades to go away.
182	*/
183	int
184	lockmgr(lkp, flags, interlkp, p)
185	struct lock__bsd__ *lkp;
186	u_int flags;
187	simple_lock_t interlkp;
188	struct proc *p;
189	{
190	int error;
191	pid_t pid;
192	int extflags;
193	void *self;
194
195	error = 0; self = current_thread();
196	if (p)
197	pid = p->p_pid;
198	else
199	pid = LK_KERNPROC;
200	simple_lock(&lkp->lk_interlock);
201	if (flags & LK_INTERLOCK)
202	simple_unlock(interlkp);
203	extflags = (flags \| lkp->lk_flags) & LK_EXTFLG_MASK;
204	#if 0
205	/*
206	* Once a lock has drained, the LK_DRAINING flag is set and an
207	* exclusive lock is returned. The only valid operation thereafter
208	* is a single release of that exclusive lock. This final release
209	* clears the LK_DRAINING flag and sets the LK_DRAINED flag. Any
210	* further requests of any sort will result in a panic. The bits
211	* selected for these two flags are chosen so that they will be set
212	* in memory that is freed (freed memory is filled with 0xdeadbeef).
213	* The final release is permitted to give a new lease on life to
214	* the lock by specifying LK_REENABLE.
215	*/
216	if (lkp->lk_flags & (LK_DRAINING\|LK_DRAINED)) {
217	if (lkp->lk_flags & LK_DRAINED)
218	panic("lockmgr: using decommissioned lock");
219	if ((flags & LK_TYPE_MASK) != LK_RELEASE \|\|
220	(lkp->lk_lockholder != pid && lkp->lk_lockthread != self)
221	panic("lockmgr: non-release on draining lock: %d\n",
222	flags & LK_TYPE_MASK);
223	lkp->lk_flags &= ~LK_DRAINING;
224	if ((flags & LK_REENABLE) == 0)
225	lkp->lk_flags \|= LK_DRAINED;
226	}
227	#endif
228
229	switch (flags & LK_TYPE_MASK) {
230
231	case LK_SHARED:
232	if (lkp->lk_lockholder != pid \|\| lkp->lk_lockthread != self) {
233	/*
234	* If just polling, check to see if we will block.
235	*/
236	if ((extflags & LK_NOWAIT) && (lkp->lk_flags &
237	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE))) {
238	error = EBUSY;
239	break;
240	}
241	/*
242	* Wait for exclusive locks and upgrades to clear.
243	*/
244	ACQUIRE(lkp, error, extflags, lkp->lk_flags &
245	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE));
246	if (error)
247	break;
248	lkp->lk_sharecount++;
249	COUNT(p, 1);
250	break;
251	}
252	/*
253	* We hold an exclusive lock, so downgrade it to shared.
254	* An alternative would be to fail with EDEADLK.
255	*/
256	lkp->lk_sharecount++;
257	COUNT(p, 1);
258	/* fall into downgrade */
259
260	case LK_DOWNGRADE:
261	if (lkp->lk_lockholder != pid \|\|
262	lkp->lk_lockthread != self \|\|
263	lkp->lk_exclusivecount == 0)
264	panic("lockmgr: not holding exclusive lock");
265	lkp->lk_sharecount += lkp->lk_exclusivecount;
266	lkp->lk_exclusivecount = 0;
267	lkp->lk_flags &= ~LK_HAVE_EXCL;
268	lkp->lk_lockholder = LK_NOPROC;
269	lkp->lk_lockthread = 0;
270	if (lkp->lk_waitcount)
271	wakeup((void *)lkp);
272	break;
273
274	case LK_EXCLUPGRADE:
275	/*
276	* If another process is ahead of us to get an upgrade,
277	* then we want to fail rather than have an intervening
278	* exclusive access.
279	*/
280	if (lkp->lk_flags & LK_WANT_UPGRADE) {
281	lkp->lk_sharecount--;
282	COUNT(p, -1);
283	error = EBUSY;
284	break;
285	}
286	/* fall into normal upgrade */
287
288	case LK_UPGRADE:
289	/*
290	* Upgrade a shared lock to an exclusive one. If another
291	* shared lock has already requested an upgrade to an
292	* exclusive lock, our shared lock is released and an
293	* exclusive lock is requested (which will be granted
294	* after the upgrade). If we return an error, the file
295	* will always be unlocked.
296	*/
297	if ((lkp->lk_lockholder == pid &&
298	lkp->lk_lockthread == self) \|\|
299	lkp->lk_sharecount <= 0)
300	panic("lockmgr: upgrade exclusive lock");
301	lkp->lk_sharecount--;
302	COUNT(p, -1);
303	/*
304	* If we are just polling, check to see if we will block.
305	*/
306	if ((extflags & LK_NOWAIT) &&
307	((lkp->lk_flags & LK_WANT_UPGRADE) \|\|
308	lkp->lk_sharecount > 1)) {
309	error = EBUSY;
310	break;
311	}
312	if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
313	/*
314	* We are first shared lock to request an upgrade, so
315	* request upgrade and wait for the shared count to
316	* drop to zero, then take exclusive lock.
317	*/
318	lkp->lk_flags \|= LK_WANT_UPGRADE;
319	ACQUIRE(lkp, error, extflags, lkp->lk_sharecount);
320	lkp->lk_flags &= ~LK_WANT_UPGRADE;
321	if (error)
322	break;
323	lkp->lk_flags \|= LK_HAVE_EXCL;
324	lkp->lk_lockholder = pid;
325	lkp->lk_lockthread = self;
326	if (lkp->lk_exclusivecount != 0)
327	panic("lockmgr: non-zero exclusive count");
328	lkp->lk_exclusivecount = 1;
329	COUNT(p, 1);
330	break;
331	}
332	/*
333	* Someone else has requested upgrade. Release our shared
334	* lock, awaken upgrade requestor if we are the last shared
335	* lock, then request an exclusive lock.
336	*/
337	if (lkp->lk_sharecount == 0 && lkp->lk_waitcount)
338	wakeup((void *)lkp);
339	/* fall into exclusive request */
340
341	case LK_EXCLUSIVE:
342	if (lkp->lk_lockholder == pid && lkp->lk_lockthread == self) {
343	/*
344	* Recursive lock.
345	*/
346	if ((extflags & LK_CANRECURSE) == 0)
347	panic("lockmgr: locking against myself");
348	lkp->lk_exclusivecount++;
349	COUNT(p, 1);
350	break;
351	}
352	/*
353	* If we are just polling, check to see if we will sleep.
354	*/
355	if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
356	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
357	lkp->lk_sharecount != 0)) {
358	error = EBUSY;
359	break;
360	}
361	/*
362	* Try to acquire the want_exclusive flag.
363	*/
364	ACQUIRE(lkp, error, extflags, lkp->lk_flags &
365	(LK_HAVE_EXCL \| LK_WANT_EXCL));
366	if (error)
367	break;
368	lkp->lk_flags \|= LK_WANT_EXCL;
369	/*
370	* Wait for shared locks and upgrades to finish.
371	*/
372	ACQUIRE(lkp, error, extflags, lkp->lk_sharecount != 0 \|\|
373	(lkp->lk_flags & LK_WANT_UPGRADE));
374	lkp->lk_flags &= ~LK_WANT_EXCL;
375	if (error)
376	break;
377	lkp->lk_flags \|= LK_HAVE_EXCL;
378	lkp->lk_lockholder = pid;
379	lkp->lk_lockthread = self;
380	if (lkp->lk_exclusivecount != 0)
381	panic("lockmgr: non-zero exclusive count");
382	lkp->lk_exclusivecount = 1;
383	COUNT(p, 1);
384	break;
385
386	case LK_RELEASE:
387	if (lkp->lk_exclusivecount != 0) {
388	if (pid != lkp->lk_lockholder \|\|
389	lkp->lk_lockthread != self)
0b4e3aa0 A	390	panic("lockmgr: pid %d, thread 0x%8x,"
	391	" not exclusive lock holder pid %d"
	392	" thread 0x%8x unlocking, exclusive count %d",
	393	pid, self, lkp->lk_lockholder,
	394	lkp->lk_lockthread, lkp->lk_exclusivecount);
1c79356b A	395	lkp->lk_exclusivecount--;
	396	COUNT(p, -1);
	397	if (lkp->lk_exclusivecount == 0) {
	398	lkp->lk_flags &= ~LK_HAVE_EXCL;
	399	lkp->lk_lockholder = LK_NOPROC;
	400	lkp->lk_lockthread = 0;
	401	}
	402	} else if (lkp->lk_sharecount != 0) {
	403	lkp->lk_sharecount--;
	404	COUNT(p, -1);
	405	}
	406	if (lkp->lk_waitcount)
	407	wakeup((void *)lkp);
	408	break;
	409
	410	case LK_DRAIN:
	411	/*
	412	* Check that we do not already hold the lock, as it can
	413	* never drain if we do. Unfortunately, we have no way to
	414	* check for holding a shared lock, but at least we can
	415	* check for an exclusive one.
	416	*/
	417	if (lkp->lk_lockholder == pid && lkp->lk_lockthread == self)
	418	panic("lockmgr: draining against myself");
	419	/*
	420	* If we are just polling, check to see if we will sleep.
	421	*/
	422	if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
	423	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
	424	lkp->lk_sharecount != 0 \|\| lkp->lk_waitcount != 0)) {
	425	error = EBUSY;
	426	break;
	427	}
	428	PAUSE(lkp, ((lkp->lk_flags &
	429	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
	430	lkp->lk_sharecount != 0 \|\| lkp->lk_waitcount != 0));
	431	for (error = 0; ((lkp->lk_flags &
	432	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
	433	lkp->lk_sharecount != 0 \|\| lkp->lk_waitcount != 0); ) {
	434	lkp->lk_flags \|= LK_WAITDRAIN;
	435	simple_unlock(&lkp->lk_interlock);
	436	if (error = tsleep((void *)&lkp->lk_flags, lkp->lk_prio,
	437	lkp->lk_wmesg, lkp->lk_timo))
	438	return (error);
	439	if ((extflags) & LK_SLEEPFAIL)
	440	return (ENOLCK);
	441	simple_lock(&lkp->lk_interlock);
	442	}
	443	lkp->lk_flags \|= LK_DRAINING \| LK_HAVE_EXCL;
	444	lkp->lk_lockholder = pid;
	445	lkp->lk_lockthread = self;
	446	lkp->lk_exclusivecount = 1;
	447	COUNT(p, 1);
	448	break;
	449
	450	default:
	451	simple_unlock(&lkp->lk_interlock);
	452	panic("lockmgr: unknown locktype request %d",
	453	flags & LK_TYPE_MASK);
	454	/* NOTREACHED */
	455	}
	456	if ((lkp->lk_flags & LK_WAITDRAIN) && ((lkp->lk_flags &
	457	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) == 0 &&
	458	lkp->lk_sharecount == 0 && lkp->lk_waitcount == 0)) {
459	lkp->lk_flags &= ~LK_WAITDRAIN;
460	wakeup((void *)&lkp->lk_flags);
461	}
462	simple_unlock(&lkp->lk_interlock);
463	return (error);
464	}
465
466	/*
467	* Print out information about state of a lock. Used by VOP_PRINT
468	* routines to display ststus about contained locks.
469	*/
470	lockmgr_printinfo(lkp)
471	struct lock__bsd__ *lkp;
472	{
473
474	if (lkp->lk_sharecount)
475	printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
476	lkp->lk_sharecount);
477	else if (lkp->lk_flags & LK_HAVE_EXCL)
478	printf(" lock type %s: EXCL (count %d) by pid %d",
479	lkp->lk_wmesg, lkp->lk_exclusivecount, lkp->lk_lockholder);
480	if (lkp->lk_waitcount > 0)
481	printf(" with %d pending", lkp->lk_waitcount);
482	}