[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.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	*
	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.
	11	*
	12	* This Original Code and all software distributed under the License are
	13	* distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
	14	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
	15	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
	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.
	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>
	63	#include <sys/proc.h>
	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	\
94	simple_unlock(&lkp->lk_interlock); \
95	for (i = lock_wait_time; i > 0; i--) \
96	if (!(wanted)) \
97	break; \
98	simple_lock(&lkp->lk_interlock); \
99	} \
100	if (!(wanted)) \
101	break;
102
103	#else /* NCPUS == 1 */
104
105	/*
106	* It is an error to spin on a uniprocessor as nothing will ever cause
107	* the simple lock to clear while we are executing.
108	*/
109	#define PAUSE(lkp, wanted)
110
111	#endif /* NCPUS == 1 */
112
113	/*
114	* Acquire a resource.
115	*/
116	#define ACQUIRE(lkp, error, extflags, wanted) \
117	PAUSE(lkp, wanted); \
118	for (error = 0; wanted; ) { \
119	(lkp)->lk_waitcount++; \
120	simple_unlock(&(lkp)->lk_interlock); \
121	error = tsleep((void *)lkp, (lkp)->lk_prio, \
122	(lkp)->lk_wmesg, (lkp)->lk_timo); \
123	simple_lock(&(lkp)->lk_interlock); \
124	(lkp)->lk_waitcount--; \
125	if (error) \
126	break; \
127	if ((extflags) & LK_SLEEPFAIL) { \
128	error = ENOLCK; \
129	break; \
130	} \
131	}
132
133	/*
134	* Initialize a lock; required before use.
135	*/
136	void
137	lockinit(lkp, prio, wmesg, timo, flags)
138	struct lock__bsd__ *lkp;
139	int prio;
140	char *wmesg;
141	int timo;
142	int flags;
143	{
144
145	bzero(lkp, sizeof(struct lock__bsd__));
146	simple_lock_init(&lkp->lk_interlock);
147	lkp->lk_flags = flags & LK_EXTFLG_MASK;
148	lkp->lk_prio = prio;
149	lkp->lk_timo = timo;
150	lkp->lk_wmesg = wmesg;
151	lkp->lk_lockholder = LK_NOPROC;
152	lkp->lk_lockthread = 0;
153	}
154
155	/*
156	* Determine the status of a lock.
157	*/
158	int
159	lockstatus(lkp)
160	struct lock__bsd__ *lkp;
161	{
162	int lock_type = 0;
163
164	simple_lock(&lkp->lk_interlock);
165	if (lkp->lk_exclusivecount != 0)
166	lock_type = LK_EXCLUSIVE;
167	else if (lkp->lk_sharecount != 0)
168	lock_type = LK_SHARED;
169	simple_unlock(&lkp->lk_interlock);
170	return (lock_type);
171	}
172
173	/*
174	* Set, change, or release a lock.
175	*
176	* Shared requests increment the shared count. Exclusive requests set the
177	* LK_WANT_EXCL flag (preventing further shared locks), and wait for already
178	* accepted shared locks and shared-to-exclusive upgrades to go away.
179	*/
180	int
181	lockmgr(lkp, flags, interlkp, p)
182	struct lock__bsd__ *lkp;
183	u_int flags;
184	simple_lock_t interlkp;
185	struct proc *p;
186	{
187	int error;
188	pid_t pid;
189	int extflags;
190	void *self;
191
192	error = 0; self = current_thread();
193	if (p)
194	pid = p->p_pid;
195	else
196	pid = LK_KERNPROC;
197	simple_lock(&lkp->lk_interlock);
198	if (flags & LK_INTERLOCK)
199	simple_unlock(interlkp);
200	extflags = (flags \| lkp->lk_flags) & LK_EXTFLG_MASK;
201	#if 0
202	/*
203	* Once a lock has drained, the LK_DRAINING flag is set and an
204	* exclusive lock is returned. The only valid operation thereafter
205	* is a single release of that exclusive lock. This final release
206	* clears the LK_DRAINING flag and sets the LK_DRAINED flag. Any
207	* further requests of any sort will result in a panic. The bits
208	* selected for these two flags are chosen so that they will be set
209	* in memory that is freed (freed memory is filled with 0xdeadbeef).
210	* The final release is permitted to give a new lease on life to
211	* the lock by specifying LK_REENABLE.
212	*/
213	if (lkp->lk_flags & (LK_DRAINING\|LK_DRAINED)) {
214	if (lkp->lk_flags & LK_DRAINED)
215	panic("lockmgr: using decommissioned lock");
216	if ((flags & LK_TYPE_MASK) != LK_RELEASE \|\|
217	(lkp->lk_lockholder != pid && lkp->lk_lockthread != self)
218	panic("lockmgr: non-release on draining lock: %d\n",
219	flags & LK_TYPE_MASK);
220	lkp->lk_flags &= ~LK_DRAINING;
221	if ((flags & LK_REENABLE) == 0)
222	lkp->lk_flags \|= LK_DRAINED;
223	}
224	#endif
225
226	switch (flags & LK_TYPE_MASK) {
227
228	case LK_SHARED:
229	if (lkp->lk_lockholder != pid \|\| lkp->lk_lockthread != self) {
230	/*
231	* If just polling, check to see if we will block.
232	*/
233	if ((extflags & LK_NOWAIT) && (lkp->lk_flags &
234	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE))) {
235	error = EBUSY;
236	break;
237	}
238	/*
239	* Wait for exclusive locks and upgrades to clear.
240	*/
241	ACQUIRE(lkp, error, extflags, lkp->lk_flags &
242	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE));
243	if (error)
244	break;
245	lkp->lk_sharecount++;
246	COUNT(p, 1);
247	break;
248	}
249	/*
250	* We hold an exclusive lock, so downgrade it to shared.
251	* An alternative would be to fail with EDEADLK.
252	*/
253	lkp->lk_sharecount++;
254	COUNT(p, 1);
255	/* fall into downgrade */
256
257	case LK_DOWNGRADE:
258	if (lkp->lk_lockholder != pid \|\|
259	lkp->lk_lockthread != self \|\|
260	lkp->lk_exclusivecount == 0)
261	panic("lockmgr: not holding exclusive lock");
262	lkp->lk_sharecount += lkp->lk_exclusivecount;
263	lkp->lk_exclusivecount = 0;
264	lkp->lk_flags &= ~LK_HAVE_EXCL;
265	lkp->lk_lockholder = LK_NOPROC;
266	lkp->lk_lockthread = 0;
267	if (lkp->lk_waitcount)
268	wakeup((void *)lkp);
269	break;
270
271	case LK_EXCLUPGRADE:
272	/*
273	* If another process is ahead of us to get an upgrade,
274	* then we want to fail rather than have an intervening
275	* exclusive access.
276	*/
277	if (lkp->lk_flags & LK_WANT_UPGRADE) {
278	lkp->lk_sharecount--;
279	COUNT(p, -1);
280	error = EBUSY;
281	break;
282	}
283	/* fall into normal upgrade */
284
285	case LK_UPGRADE:
286	/*
287	* Upgrade a shared lock to an exclusive one. If another
288	* shared lock has already requested an upgrade to an
289	* exclusive lock, our shared lock is released and an
290	* exclusive lock is requested (which will be granted
291	* after the upgrade). If we return an error, the file
292	* will always be unlocked.
293	*/
294	if ((lkp->lk_lockholder == pid &&
295	lkp->lk_lockthread == self) \|\|
296	lkp->lk_sharecount <= 0)
297	panic("lockmgr: upgrade exclusive lock");
298	lkp->lk_sharecount--;
299	COUNT(p, -1);
300	/*
301	* If we are just polling, check to see if we will block.
302	*/
303	if ((extflags & LK_NOWAIT) &&
304	((lkp->lk_flags & LK_WANT_UPGRADE) \|\|
305	lkp->lk_sharecount > 1)) {
306	error = EBUSY;
307	break;
308	}
309	if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
310	/*
311	* We are first shared lock to request an upgrade, so
312	* request upgrade and wait for the shared count to
313	* drop to zero, then take exclusive lock.
314	*/
315	lkp->lk_flags \|= LK_WANT_UPGRADE;
316	ACQUIRE(lkp, error, extflags, lkp->lk_sharecount);
317	lkp->lk_flags &= ~LK_WANT_UPGRADE;
318	if (error)
319	break;
320	lkp->lk_flags \|= LK_HAVE_EXCL;
321	lkp->lk_lockholder = pid;
322	lkp->lk_lockthread = self;
323	if (lkp->lk_exclusivecount != 0)
324	panic("lockmgr: non-zero exclusive count");
325	lkp->lk_exclusivecount = 1;
326	COUNT(p, 1);
327	break;
328	}
329	/*
330	* Someone else has requested upgrade. Release our shared
331	* lock, awaken upgrade requestor if we are the last shared
332	* lock, then request an exclusive lock.
333	*/
334	if (lkp->lk_sharecount == 0 && lkp->lk_waitcount)
335	wakeup((void *)lkp);
336	/* fall into exclusive request */
337
338	case LK_EXCLUSIVE:
339	if (lkp->lk_lockholder == pid && lkp->lk_lockthread == self) {
340	/*
341	* Recursive lock.
342	*/
343	if ((extflags & LK_CANRECURSE) == 0)
344	panic("lockmgr: locking against myself");
345	lkp->lk_exclusivecount++;
346	COUNT(p, 1);
347	break;
348	}
349	/*
350	* If we are just polling, check to see if we will sleep.
351	*/
352	if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
353	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
354	lkp->lk_sharecount != 0)) {
355	error = EBUSY;
356	break;
357	}
358	/*
359	* Try to acquire the want_exclusive flag.
360	*/
361	ACQUIRE(lkp, error, extflags, lkp->lk_flags &
362	(LK_HAVE_EXCL \| LK_WANT_EXCL));
363	if (error)
364	break;
365	lkp->lk_flags \|= LK_WANT_EXCL;
366	/*
367	* Wait for shared locks and upgrades to finish.
368	*/
369	ACQUIRE(lkp, error, extflags, lkp->lk_sharecount != 0 \|\|
370	(lkp->lk_flags & LK_WANT_UPGRADE));
371	lkp->lk_flags &= ~LK_WANT_EXCL;
372	if (error)
373	break;
374	lkp->lk_flags \|= LK_HAVE_EXCL;
375	lkp->lk_lockholder = pid;
376	lkp->lk_lockthread = self;
377	if (lkp->lk_exclusivecount != 0)
378	panic("lockmgr: non-zero exclusive count");
379	lkp->lk_exclusivecount = 1;
380	COUNT(p, 1);
381	break;
382
383	case LK_RELEASE:
384	if (lkp->lk_exclusivecount != 0) {
385	if (pid != lkp->lk_lockholder \|\|
386	lkp->lk_lockthread != self)
0b4e3aa0 A	387	panic("lockmgr: pid %d, thread 0x%8x,"
	388	" not exclusive lock holder pid %d"
	389	" thread 0x%8x unlocking, exclusive count %d",
	390	pid, self, lkp->lk_lockholder,
	391	lkp->lk_lockthread, lkp->lk_exclusivecount);
1c79356b A	392	lkp->lk_exclusivecount--;
	393	COUNT(p, -1);
	394	if (lkp->lk_exclusivecount == 0) {
	395	lkp->lk_flags &= ~LK_HAVE_EXCL;
	396	lkp->lk_lockholder = LK_NOPROC;
	397	lkp->lk_lockthread = 0;
	398	}
	399	} else if (lkp->lk_sharecount != 0) {
	400	lkp->lk_sharecount--;
	401	COUNT(p, -1);
	402	}
	403	if (lkp->lk_waitcount)
	404	wakeup((void *)lkp);
	405	break;
	406
	407	case LK_DRAIN:
	408	/*
	409	* Check that we do not already hold the lock, as it can
	410	* never drain if we do. Unfortunately, we have no way to
	411	* check for holding a shared lock, but at least we can
	412	* check for an exclusive one.
	413	*/
	414	if (lkp->lk_lockholder == pid && lkp->lk_lockthread == self)
	415	panic("lockmgr: draining against myself");
	416	/*
	417	* If we are just polling, check to see if we will sleep.
	418	*/
	419	if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
	420	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
	421	lkp->lk_sharecount != 0 \|\| lkp->lk_waitcount != 0)) {
	422	error = EBUSY;
	423	break;
	424	}
	425	PAUSE(lkp, ((lkp->lk_flags &
	426	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
	427	lkp->lk_sharecount != 0 \|\| lkp->lk_waitcount != 0));
	428	for (error = 0; ((lkp->lk_flags &
	429	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) \|\|
	430	lkp->lk_sharecount != 0 \|\| lkp->lk_waitcount != 0); ) {
	431	lkp->lk_flags \|= LK_WAITDRAIN;
	432	simple_unlock(&lkp->lk_interlock);
	433	if (error = tsleep((void *)&lkp->lk_flags, lkp->lk_prio,
	434	lkp->lk_wmesg, lkp->lk_timo))
	435	return (error);
	436	if ((extflags) & LK_SLEEPFAIL)
	437	return (ENOLCK);
	438	simple_lock(&lkp->lk_interlock);
	439	}
	440	lkp->lk_flags \|= LK_DRAINING \| LK_HAVE_EXCL;
	441	lkp->lk_lockholder = pid;
	442	lkp->lk_lockthread = self;
	443	lkp->lk_exclusivecount = 1;
	444	COUNT(p, 1);
	445	break;
	446
	447	default:
	448	simple_unlock(&lkp->lk_interlock);
	449	panic("lockmgr: unknown locktype request %d",
	450	flags & LK_TYPE_MASK);
	451	/* NOTREACHED */
	452	}
	453	if ((lkp->lk_flags & LK_WAITDRAIN) && ((lkp->lk_flags &
	454	(LK_HAVE_EXCL \| LK_WANT_EXCL \| LK_WANT_UPGRADE)) == 0 &&
	455	lkp->lk_sharecount == 0 && lkp->lk_waitcount == 0)) {
456	lkp->lk_flags &= ~LK_WAITDRAIN;
457	wakeup((void *)&lkp->lk_flags);
458	}
459	simple_unlock(&lkp->lk_interlock);
460	return (error);
461	}
462
463	/*
464	* Print out information about state of a lock. Used by VOP_PRINT
465	* routines to display ststus about contained locks.
466	*/
467	lockmgr_printinfo(lkp)
468	struct lock__bsd__ *lkp;
469	{
470
471	if (lkp->lk_sharecount)
472	printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
473	lkp->lk_sharecount);
474	else if (lkp->lk_flags & LK_HAVE_EXCL)
475	printf(" lock type %s: EXCL (count %d) by pid %d",
476	lkp->lk_wmesg, lkp->lk_exclusivecount, lkp->lk_lockholder);
477	if (lkp->lk_waitcount > 0)
478	printf(" with %d pending", lkp->lk_waitcount);
479	}