xref: /freebsd/sys/kern/kern_lock.c (revision be6847d729bd8482b4de6c7a665cfe7124f8c9a0)
19454b2d8SWarner Losh /*-
253bf4bb2SPeter Wemm  * Copyright (c) 1995
353bf4bb2SPeter Wemm  *	The Regents of the University of California.  All rights reserved.
453bf4bb2SPeter Wemm  *
503e9c6c1SJohn Dyson  * Copyright (C) 1997
603e9c6c1SJohn Dyson  *	John S. Dyson.  All rights reserved.
703e9c6c1SJohn Dyson  *
853bf4bb2SPeter Wemm  * This code contains ideas from software contributed to Berkeley by
953bf4bb2SPeter Wemm  * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
1053bf4bb2SPeter Wemm  * System project at Carnegie-Mellon University.
1153bf4bb2SPeter Wemm  *
1253bf4bb2SPeter Wemm  * Redistribution and use in source and binary forms, with or without
1353bf4bb2SPeter Wemm  * modification, are permitted provided that the following conditions
1453bf4bb2SPeter Wemm  * are met:
1553bf4bb2SPeter Wemm  * 1. Redistributions of source code must retain the above copyright
1653bf4bb2SPeter Wemm  *    notice, this list of conditions and the following disclaimer.
1753bf4bb2SPeter Wemm  * 2. Redistributions in binary form must reproduce the above copyright
1853bf4bb2SPeter Wemm  *    notice, this list of conditions and the following disclaimer in the
1953bf4bb2SPeter Wemm  *    documentation and/or other materials provided with the distribution.
2053bf4bb2SPeter Wemm  * 3. All advertising materials mentioning features or use of this software
2153bf4bb2SPeter Wemm  *    must display the following acknowledgement:
2253bf4bb2SPeter Wemm  *	This product includes software developed by the University of
2353bf4bb2SPeter Wemm  *	California, Berkeley and its contributors.
2453bf4bb2SPeter Wemm  * 4. Neither the name of the University nor the names of its contributors
2553bf4bb2SPeter Wemm  *    may be used to endorse or promote products derived from this software
2653bf4bb2SPeter Wemm  *    without specific prior written permission.
2753bf4bb2SPeter Wemm  *
2853bf4bb2SPeter Wemm  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
2953bf4bb2SPeter Wemm  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
3053bf4bb2SPeter Wemm  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
3153bf4bb2SPeter Wemm  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
3253bf4bb2SPeter Wemm  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
3353bf4bb2SPeter Wemm  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
3453bf4bb2SPeter Wemm  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
3553bf4bb2SPeter Wemm  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
3653bf4bb2SPeter Wemm  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
3753bf4bb2SPeter Wemm  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
3853bf4bb2SPeter Wemm  * SUCH DAMAGE.
3953bf4bb2SPeter Wemm  *
4053bf4bb2SPeter Wemm  *	@(#)kern_lock.c	8.18 (Berkeley) 5/21/95
4153bf4bb2SPeter Wemm  */
4253bf4bb2SPeter Wemm 
43677b542eSDavid E. O'Brien #include <sys/cdefs.h>
44677b542eSDavid E. O'Brien __FBSDID("$FreeBSD$");
45677b542eSDavid E. O'Brien 
46be6847d7SJohn Baldwin #include "opt_ddb.h"
47be6847d7SJohn Baldwin 
4853bf4bb2SPeter Wemm #include <sys/param.h>
49c30bf5c3SRobert Watson #include <sys/kdb.h>
509722d88fSJason Evans #include <sys/kernel.h>
5161d80e90SJohn Baldwin #include <sys/ktr.h>
5253bf4bb2SPeter Wemm #include <sys/lock.h>
538302d183SBruce Evans #include <sys/lockmgr.h>
54d8881ca3SJohn Baldwin #include <sys/mutex.h>
558302d183SBruce Evans #include <sys/proc.h>
564bdb9b11SPeter Wemm #include <sys/systm.h>
57e8ddb61dSJeff Roberson #ifdef DEBUG_LOCKS
58e8ddb61dSJeff Roberson #include <sys/stack.h>
59e8ddb61dSJeff Roberson #endif
6053bf4bb2SPeter Wemm 
61be6847d7SJohn Baldwin #ifdef DDB
62be6847d7SJohn Baldwin #include <ddb/ddb.h>
63be6847d7SJohn Baldwin #endif
64be6847d7SJohn Baldwin 
6553bf4bb2SPeter Wemm /*
6653bf4bb2SPeter Wemm  * Locking primitives implementation.
6753bf4bb2SPeter Wemm  * Locks provide shared/exclusive sychronization.
6853bf4bb2SPeter Wemm  */
6953bf4bb2SPeter Wemm 
70f158df07SJeff Roberson #define	COUNT(td, x)	if ((td)) (td)->td_locks += (x)
7199448ed1SJohn Dyson #define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \
7299448ed1SJohn Dyson 	LK_SHARE_NONZERO | LK_WAIT_NONZERO)
7399448ed1SJohn Dyson 
74c6964d3bSKirk McKusick static int acquire(struct lock **lkpp, int extflags, int wanted);
7599448ed1SJohn Dyson static int acquiredrain(struct lock *lkp, int extflags) ;
7603e9c6c1SJohn Dyson 
77a96ab770SJeff Roberson static __inline void
78f158df07SJeff Roberson sharelock(struct thread *td, struct lock *lkp, int incr) {
7903e9c6c1SJohn Dyson 	lkp->lk_flags |= LK_SHARE_NONZERO;
8003e9c6c1SJohn Dyson 	lkp->lk_sharecount += incr;
81f158df07SJeff Roberson 	COUNT(td, incr);
8203e9c6c1SJohn Dyson }
8303e9c6c1SJohn Dyson 
84a96ab770SJeff Roberson static __inline void
85f158df07SJeff Roberson shareunlock(struct thread *td, struct lock *lkp, int decr) {
86219cbf59SEivind Eklund 
875526d2d9SEivind Eklund 	KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr"));
8803e9c6c1SJohn Dyson 
89f158df07SJeff Roberson 	COUNT(td, -decr);
909b2e5badSJohn Dyson 	if (lkp->lk_sharecount == decr) {
9103e9c6c1SJohn Dyson 		lkp->lk_flags &= ~LK_SHARE_NONZERO;
929b2e5badSJohn Dyson 		if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) {
939b2e5badSJohn Dyson 			wakeup(lkp);
949b2e5badSJohn Dyson 		}
959b2e5badSJohn Dyson 		lkp->lk_sharecount = 0;
969b2e5badSJohn Dyson 	} else {
979b2e5badSJohn Dyson 		lkp->lk_sharecount -= decr;
989b2e5badSJohn Dyson 	}
9903e9c6c1SJohn Dyson }
10003e9c6c1SJohn Dyson 
10103e9c6c1SJohn Dyson static int
10241bd6c15SJeff Roberson acquire(struct lock **lkpp, int extflags, int wanted)
10341bd6c15SJeff Roberson {
104c6964d3bSKirk McKusick 	struct lock *lkp = *lkpp;
10520728d8fSJeff Roberson 	int error;
106c06394f5SJohn Baldwin 	CTR3(KTR_LOCK,
107ff381670SRobert Watson 	    "acquire(): lkp == %p, extflags == 0x%x, wanted == 0x%x",
108a18b1f1dSJason Evans 	    lkp, extflags, wanted);
109a18b1f1dSJason Evans 
11020728d8fSJeff Roberson 	if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted))
11103e9c6c1SJohn Dyson 		return EBUSY;
11220728d8fSJeff Roberson 	error = 0;
11303e9c6c1SJohn Dyson 	while ((lkp->lk_flags & wanted) != 0) {
11420728d8fSJeff Roberson 		CTR2(KTR_LOCK,
11520728d8fSJeff Roberson 		    "acquire(): lkp == %p, lk_flags == 0x%x sleeping",
11620728d8fSJeff Roberson 		    lkp, lkp->lk_flags);
11703e9c6c1SJohn Dyson 		lkp->lk_flags |= LK_WAIT_NONZERO;
11803e9c6c1SJohn Dyson 		lkp->lk_waitcount++;
11996fde7daSJake Burkholder 		error = msleep(lkp, lkp->lk_interlock, lkp->lk_prio,
12023b59018SMatthew Dillon 		    lkp->lk_wmesg,
12123b59018SMatthew Dillon 		    ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
1229b2e5badSJohn Dyson 		lkp->lk_waitcount--;
12320728d8fSJeff Roberson 		if (lkp->lk_waitcount == 0)
12420728d8fSJeff Roberson 			lkp->lk_flags &= ~LK_WAIT_NONZERO;
12520728d8fSJeff Roberson 		if (error)
12620728d8fSJeff Roberson 			break;
12703e9c6c1SJohn Dyson 		if (extflags & LK_SLEEPFAIL) {
12820728d8fSJeff Roberson 			error = ENOLCK;
12920728d8fSJeff Roberson 			break;
13003e9c6c1SJohn Dyson 		}
131c6964d3bSKirk McKusick 		if (lkp->lk_newlock != NULL) {
132c6964d3bSKirk McKusick 			mtx_lock(lkp->lk_newlock->lk_interlock);
133c6964d3bSKirk McKusick 			mtx_unlock(lkp->lk_interlock);
134c6964d3bSKirk McKusick 			if (lkp->lk_waitcount == 0)
135c6964d3bSKirk McKusick 				wakeup((void *)(&lkp->lk_newlock));
136c6964d3bSKirk McKusick 			*lkpp = lkp = lkp->lk_newlock;
137c6964d3bSKirk McKusick 		}
13803e9c6c1SJohn Dyson 	}
13920728d8fSJeff Roberson 	mtx_assert(lkp->lk_interlock, MA_OWNED);
14020728d8fSJeff Roberson 	return (error);
14103e9c6c1SJohn Dyson }
14203e9c6c1SJohn Dyson 
14353bf4bb2SPeter Wemm /*
14453bf4bb2SPeter Wemm  * Set, change, or release a lock.
14553bf4bb2SPeter Wemm  *
14653bf4bb2SPeter Wemm  * Shared requests increment the shared count. Exclusive requests set the
14753bf4bb2SPeter Wemm  * LK_WANT_EXCL flag (preventing further shared locks), and wait for already
14853bf4bb2SPeter Wemm  * accepted shared locks and shared-to-exclusive upgrades to go away.
14953bf4bb2SPeter Wemm  */
15053bf4bb2SPeter Wemm int
151b40ce416SJulian Elischer lockmgr(lkp, flags, interlkp, td)
152248fcb66SSteve Passe 	struct lock *lkp;
15353bf4bb2SPeter Wemm 	u_int flags;
154a18b1f1dSJason Evans 	struct mtx *interlkp;
155b40ce416SJulian Elischer 	struct thread *td;
15653bf4bb2SPeter Wemm {
15753bf4bb2SPeter Wemm 	int error;
158822ded67SJulian Elischer 	struct thread *thr;
159635962afSJohn Baldwin 	int extflags, lockflags;
16053bf4bb2SPeter Wemm 
16153bf4bb2SPeter Wemm 	error = 0;
162b40ce416SJulian Elischer 	if (td == NULL)
163822ded67SJulian Elischer 		thr = LK_KERNPROC;
164891e0f24SJohn Dyson 	else
165822ded67SJulian Elischer 		thr = td;
16603e9c6c1SJohn Dyson 
16717661e5aSJeff Roberson 	if ((flags & LK_INTERNAL) == 0)
1689ed346baSBosko Milekic 		mtx_lock(lkp->lk_interlock);
16941bd6c15SJeff Roberson 	CTR6(KTR_LOCK,
17041bd6c15SJeff Roberson 	    "lockmgr(): lkp == %p (lk_wmesg == \"%s\"), owner == %p, exclusivecount == %d, flags == 0x%x, "
17141bd6c15SJeff Roberson 	    "td == %p", lkp, lkp->lk_wmesg, lkp->lk_lockholder,
17241bd6c15SJeff Roberson 	    lkp->lk_exclusivecount, flags, td);
173e8ddb61dSJeff Roberson #ifdef DEBUG_LOCKS
174e8ddb61dSJeff Roberson 	{
175e8ddb61dSJeff Roberson 		struct stack stack; /* XXX */
176e8ddb61dSJeff Roberson 		stack_save(&stack);
177e37a4994SPawel Jakub Dawidek 		CTRSTACK(KTR_LOCK, &stack, 0, 1);
178e8ddb61dSJeff Roberson 	}
17941bd6c15SJeff Roberson #endif
18041bd6c15SJeff Roberson 
18198689e1eSAlfred Perlstein 	if (flags & LK_INTERLOCK) {
1826157b69fSAlfred Perlstein 		mtx_assert(interlkp, MA_OWNED | MA_NOTRECURSED);
1839ed346baSBosko Milekic 		mtx_unlock(interlkp);
18498689e1eSAlfred Perlstein 	}
18503e9c6c1SJohn Dyson 
18617661e5aSJeff Roberson 	if ((flags & (LK_NOWAIT|LK_RELEASE)) == 0)
18726306795SJohn Baldwin 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK,
18826306795SJohn Baldwin 		    &lkp->lk_interlock->mtx_object,
18926306795SJohn Baldwin 		    "Acquiring lockmgr lock \"%s\"", lkp->lk_wmesg);
19017661e5aSJeff Roberson 
1913f085c22SJohn Baldwin 	if (panicstr != NULL) {
1923f085c22SJohn Baldwin 		mtx_unlock(lkp->lk_interlock);
1933f085c22SJohn Baldwin 		return (0);
1943f085c22SJohn Baldwin 	}
195c4c0ec5bSJeff Roberson 	if ((lkp->lk_flags & LK_NOSHARE) &&
196c4c0ec5bSJeff Roberson 	    (flags & LK_TYPE_MASK) == LK_SHARED) {
197c4c0ec5bSJeff Roberson 		flags &= ~LK_TYPE_MASK;
198c4c0ec5bSJeff Roberson 		flags |= LK_EXCLUSIVE;
199c4c0ec5bSJeff Roberson 	}
20053bf4bb2SPeter Wemm 	extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
20153bf4bb2SPeter Wemm 
20253bf4bb2SPeter Wemm 	switch (flags & LK_TYPE_MASK) {
20353bf4bb2SPeter Wemm 
20453bf4bb2SPeter Wemm 	case LK_SHARED:
205beef8a36SJulian Elischer 		/*
206beef8a36SJulian Elischer 		 * If we are not the exclusive lock holder, we have to block
207beef8a36SJulian Elischer 		 * while there is an exclusive lock holder or while an
208beef8a36SJulian Elischer 		 * exclusive lock request or upgrade request is in progress.
209beef8a36SJulian Elischer 		 *
210fa2a4d05STim J. Robbins 		 * However, if TDP_DEADLKTREAT is set, we override exclusive
211beef8a36SJulian Elischer 		 * lock requests or upgrade requests ( but not the exclusive
212beef8a36SJulian Elischer 		 * lock itself ).
213beef8a36SJulian Elischer 		 */
214822ded67SJulian Elischer 		if (lkp->lk_lockholder != thr) {
215635962afSJohn Baldwin 			lockflags = LK_HAVE_EXCL;
216fa2a4d05STim J. Robbins 			if (td != NULL && !(td->td_pflags & TDP_DEADLKTREAT))
217bce98419SJohn Baldwin 				lockflags |= LK_WANT_EXCL | LK_WANT_UPGRADE;
218c6964d3bSKirk McKusick 			error = acquire(&lkp, extflags, lockflags);
21953bf4bb2SPeter Wemm 			if (error)
22053bf4bb2SPeter Wemm 				break;
221f158df07SJeff Roberson 			sharelock(td, lkp, 1);
2227181624aSJeff Roberson #if defined(DEBUG_LOCKS)
2237499fd8dSJeff Roberson 			stack_save(&lkp->lk_stack);
2247181624aSJeff Roberson #endif
22553bf4bb2SPeter Wemm 			break;
22653bf4bb2SPeter Wemm 		}
22753bf4bb2SPeter Wemm 		/*
22853bf4bb2SPeter Wemm 		 * We hold an exclusive lock, so downgrade it to shared.
22953bf4bb2SPeter Wemm 		 * An alternative would be to fail with EDEADLK.
23053bf4bb2SPeter Wemm 		 */
231f158df07SJeff Roberson 		sharelock(td, lkp, 1);
23293b0017fSPhilippe Charnier 		/* FALLTHROUGH downgrade */
23353bf4bb2SPeter Wemm 
23453bf4bb2SPeter Wemm 	case LK_DOWNGRADE:
235822ded67SJulian Elischer 		KASSERT(lkp->lk_lockholder == thr && lkp->lk_exclusivecount != 0,
2361375ed7eSAlfred Perlstein 			("lockmgr: not holding exclusive lock "
237822ded67SJulian Elischer 			"(owner thread (%p) != thread (%p), exlcnt (%d) != 0",
238822ded67SJulian Elischer 			lkp->lk_lockholder, thr, lkp->lk_exclusivecount));
239f158df07SJeff Roberson 		sharelock(td, lkp, lkp->lk_exclusivecount);
240f158df07SJeff Roberson 		COUNT(td, -lkp->lk_exclusivecount);
24153bf4bb2SPeter Wemm 		lkp->lk_exclusivecount = 0;
24253bf4bb2SPeter Wemm 		lkp->lk_flags &= ~LK_HAVE_EXCL;
2436f8132a8SJulian Elischer 		lkp->lk_lockholder = LK_NOPROC;
24453bf4bb2SPeter Wemm 		if (lkp->lk_waitcount)
24553bf4bb2SPeter Wemm 			wakeup((void *)lkp);
24653bf4bb2SPeter Wemm 		break;
24753bf4bb2SPeter Wemm 
24853bf4bb2SPeter Wemm 	case LK_EXCLUPGRADE:
24953bf4bb2SPeter Wemm 		/*
25053bf4bb2SPeter Wemm 		 * If another process is ahead of us to get an upgrade,
25153bf4bb2SPeter Wemm 		 * then we want to fail rather than have an intervening
25253bf4bb2SPeter Wemm 		 * exclusive access.
25353bf4bb2SPeter Wemm 		 */
25453bf4bb2SPeter Wemm 		if (lkp->lk_flags & LK_WANT_UPGRADE) {
255f158df07SJeff Roberson 			shareunlock(td, lkp, 1);
25653bf4bb2SPeter Wemm 			error = EBUSY;
25753bf4bb2SPeter Wemm 			break;
25853bf4bb2SPeter Wemm 		}
25993b0017fSPhilippe Charnier 		/* FALLTHROUGH normal upgrade */
26053bf4bb2SPeter Wemm 
26153bf4bb2SPeter Wemm 	case LK_UPGRADE:
26253bf4bb2SPeter Wemm 		/*
26353bf4bb2SPeter Wemm 		 * Upgrade a shared lock to an exclusive one. If another
26453bf4bb2SPeter Wemm 		 * shared lock has already requested an upgrade to an
26553bf4bb2SPeter Wemm 		 * exclusive lock, our shared lock is released and an
26653bf4bb2SPeter Wemm 		 * exclusive lock is requested (which will be granted
26753bf4bb2SPeter Wemm 		 * after the upgrade). If we return an error, the file
26853bf4bb2SPeter Wemm 		 * will always be unlocked.
26953bf4bb2SPeter Wemm 		 */
270436901a8SJeff Roberson 		if (lkp->lk_lockholder == thr)
27153bf4bb2SPeter Wemm 			panic("lockmgr: upgrade exclusive lock");
272436901a8SJeff Roberson 		if (lkp->lk_sharecount <= 0)
273436901a8SJeff Roberson 			panic("lockmgr: upgrade without shared");
274f158df07SJeff Roberson 		shareunlock(td, lkp, 1);
27553bf4bb2SPeter Wemm 		/*
27653bf4bb2SPeter Wemm 		 * If we are just polling, check to see if we will block.
27753bf4bb2SPeter Wemm 		 */
27853bf4bb2SPeter Wemm 		if ((extflags & LK_NOWAIT) &&
27953bf4bb2SPeter Wemm 		    ((lkp->lk_flags & LK_WANT_UPGRADE) ||
28053bf4bb2SPeter Wemm 		     lkp->lk_sharecount > 1)) {
28153bf4bb2SPeter Wemm 			error = EBUSY;
28253bf4bb2SPeter Wemm 			break;
28353bf4bb2SPeter Wemm 		}
28453bf4bb2SPeter Wemm 		if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
28553bf4bb2SPeter Wemm 			/*
28653bf4bb2SPeter Wemm 			 * We are first shared lock to request an upgrade, so
28753bf4bb2SPeter Wemm 			 * request upgrade and wait for the shared count to
28853bf4bb2SPeter Wemm 			 * drop to zero, then take exclusive lock.
28953bf4bb2SPeter Wemm 			 */
29053bf4bb2SPeter Wemm 			lkp->lk_flags |= LK_WANT_UPGRADE;
291c6964d3bSKirk McKusick 			error = acquire(&lkp, extflags, LK_SHARE_NONZERO);
29253bf4bb2SPeter Wemm 			lkp->lk_flags &= ~LK_WANT_UPGRADE;
2939b2e5badSJohn Dyson 
2944cef6d5aSAlexander Kabaev 			if (error) {
2954cef6d5aSAlexander Kabaev 			         if ((lkp->lk_flags & ( LK_WANT_EXCL | LK_WAIT_NONZERO)) == (LK_WANT_EXCL | LK_WAIT_NONZERO))
2964cef6d5aSAlexander Kabaev 			                   wakeup((void *)lkp);
29753bf4bb2SPeter Wemm 			         break;
2984cef6d5aSAlexander Kabaev 			}
29953bf4bb2SPeter Wemm 			if (lkp->lk_exclusivecount != 0)
30053bf4bb2SPeter Wemm 				panic("lockmgr: non-zero exclusive count");
301d8b8e875SPaul Saab 			lkp->lk_flags |= LK_HAVE_EXCL;
302d8b8e875SPaul Saab 			lkp->lk_lockholder = thr;
30353bf4bb2SPeter Wemm 			lkp->lk_exclusivecount = 1;
304f158df07SJeff Roberson 			COUNT(td, 1);
30515a1057cSEivind Eklund #if defined(DEBUG_LOCKS)
3067499fd8dSJeff Roberson 			stack_save(&lkp->lk_stack);
30715a1057cSEivind Eklund #endif
30853bf4bb2SPeter Wemm 			break;
30953bf4bb2SPeter Wemm 		}
31053bf4bb2SPeter Wemm 		/*
31153bf4bb2SPeter Wemm 		 * Someone else has requested upgrade. Release our shared
31253bf4bb2SPeter Wemm 		 * lock, awaken upgrade requestor if we are the last shared
31353bf4bb2SPeter Wemm 		 * lock, then request an exclusive lock.
31453bf4bb2SPeter Wemm 		 */
31503e9c6c1SJohn Dyson 		if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) ==
31603e9c6c1SJohn Dyson 			LK_WAIT_NONZERO)
31753bf4bb2SPeter Wemm 			wakeup((void *)lkp);
31893b0017fSPhilippe Charnier 		/* FALLTHROUGH exclusive request */
31953bf4bb2SPeter Wemm 
32053bf4bb2SPeter Wemm 	case LK_EXCLUSIVE:
321822ded67SJulian Elischer 		if (lkp->lk_lockholder == thr && thr != LK_KERNPROC) {
32253bf4bb2SPeter Wemm 			/*
32353bf4bb2SPeter Wemm 			 *	Recursive lock.
32453bf4bb2SPeter Wemm 			 */
32533638e93SKirk McKusick 			if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0)
32653bf4bb2SPeter Wemm 				panic("lockmgr: locking against myself");
32733638e93SKirk McKusick 			if ((extflags & LK_CANRECURSE) != 0) {
32853bf4bb2SPeter Wemm 				lkp->lk_exclusivecount++;
329f158df07SJeff Roberson 				COUNT(td, 1);
33053bf4bb2SPeter Wemm 				break;
33153bf4bb2SPeter Wemm 			}
33233638e93SKirk McKusick 		}
33353bf4bb2SPeter Wemm 		/*
33453bf4bb2SPeter Wemm 		 * If we are just polling, check to see if we will sleep.
33553bf4bb2SPeter Wemm 		 */
33603e9c6c1SJohn Dyson 		if ((extflags & LK_NOWAIT) &&
33703e9c6c1SJohn Dyson 		    (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO))) {
33853bf4bb2SPeter Wemm 			error = EBUSY;
33953bf4bb2SPeter Wemm 			break;
34053bf4bb2SPeter Wemm 		}
34153bf4bb2SPeter Wemm 		/*
34253bf4bb2SPeter Wemm 		 * Try to acquire the want_exclusive flag.
34353bf4bb2SPeter Wemm 		 */
344cffdaf2dSAlexander Kabaev 		error = acquire(&lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL));
34553bf4bb2SPeter Wemm 		if (error)
34653bf4bb2SPeter Wemm 			break;
34753bf4bb2SPeter Wemm 		lkp->lk_flags |= LK_WANT_EXCL;
34853bf4bb2SPeter Wemm 		/*
34953bf4bb2SPeter Wemm 		 * Wait for shared locks and upgrades to finish.
35053bf4bb2SPeter Wemm 		 */
3514cef6d5aSAlexander Kabaev 		error = acquire(&lkp, extflags, LK_HAVE_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO);
35253bf4bb2SPeter Wemm 		lkp->lk_flags &= ~LK_WANT_EXCL;
3534cef6d5aSAlexander Kabaev 		if (error) {
3544cef6d5aSAlexander Kabaev 			if (lkp->lk_flags & LK_WAIT_NONZERO)
3554cef6d5aSAlexander Kabaev 			         wakeup((void *)lkp);
35653bf4bb2SPeter Wemm 			break;
3574cef6d5aSAlexander Kabaev 		}
35853bf4bb2SPeter Wemm 		lkp->lk_flags |= LK_HAVE_EXCL;
359822ded67SJulian Elischer 		lkp->lk_lockholder = thr;
36053bf4bb2SPeter Wemm 		if (lkp->lk_exclusivecount != 0)
36153bf4bb2SPeter Wemm 			panic("lockmgr: non-zero exclusive count");
36253bf4bb2SPeter Wemm 		lkp->lk_exclusivecount = 1;
363f158df07SJeff Roberson 		COUNT(td, 1);
36415a1057cSEivind Eklund #if defined(DEBUG_LOCKS)
3657499fd8dSJeff Roberson 		stack_save(&lkp->lk_stack);
36615a1057cSEivind Eklund #endif
36753bf4bb2SPeter Wemm 		break;
36853bf4bb2SPeter Wemm 
36953bf4bb2SPeter Wemm 	case LK_RELEASE:
37053bf4bb2SPeter Wemm 		if (lkp->lk_exclusivecount != 0) {
371822ded67SJulian Elischer 			if (lkp->lk_lockholder != thr &&
372e701df7dSMatthew Dillon 			    lkp->lk_lockholder != LK_KERNPROC) {
373822ded67SJulian Elischer 				panic("lockmgr: thread %p, not %s %p unlocking",
374822ded67SJulian Elischer 				    thr, "exclusive lock holder",
37553bf4bb2SPeter Wemm 				    lkp->lk_lockholder);
376e701df7dSMatthew Dillon 			}
377f158df07SJeff Roberson 			if (lkp->lk_lockholder != LK_KERNPROC)
378f158df07SJeff Roberson 				COUNT(td, -1);
3799b2e5badSJohn Dyson 			if (lkp->lk_exclusivecount == 1) {
38053bf4bb2SPeter Wemm 				lkp->lk_flags &= ~LK_HAVE_EXCL;
38153bf4bb2SPeter Wemm 				lkp->lk_lockholder = LK_NOPROC;
3829b2e5badSJohn Dyson 				lkp->lk_exclusivecount = 0;
3839b2e5badSJohn Dyson 			} else {
3849b2e5badSJohn Dyson 				lkp->lk_exclusivecount--;
38553bf4bb2SPeter Wemm 			}
3861b367556SJason Evans 		} else if (lkp->lk_flags & LK_SHARE_NONZERO)
387f158df07SJeff Roberson 			shareunlock(td, lkp, 1);
3881f71de49SSuleiman Souhlal 		else  {
3891f71de49SSuleiman Souhlal 			printf("lockmgr: thread %p unlocking unheld lock\n",
3901f71de49SSuleiman Souhlal 			    thr);
3911f71de49SSuleiman Souhlal 			kdb_backtrace();
3921f71de49SSuleiman Souhlal 		}
3931f71de49SSuleiman Souhlal 
39403e9c6c1SJohn Dyson 		if (lkp->lk_flags & LK_WAIT_NONZERO)
39553bf4bb2SPeter Wemm 			wakeup((void *)lkp);
39653bf4bb2SPeter Wemm 		break;
39753bf4bb2SPeter Wemm 
39853bf4bb2SPeter Wemm 	case LK_DRAIN:
39953bf4bb2SPeter Wemm 		/*
40053bf4bb2SPeter Wemm 		 * Check that we do not already hold the lock, as it can
40153bf4bb2SPeter Wemm 		 * never drain if we do. Unfortunately, we have no way to
40253bf4bb2SPeter Wemm 		 * check for holding a shared lock, but at least we can
40353bf4bb2SPeter Wemm 		 * check for an exclusive one.
40453bf4bb2SPeter Wemm 		 */
405822ded67SJulian Elischer 		if (lkp->lk_lockholder == thr)
40653bf4bb2SPeter Wemm 			panic("lockmgr: draining against myself");
40703e9c6c1SJohn Dyson 
40803e9c6c1SJohn Dyson 		error = acquiredrain(lkp, extflags);
40903e9c6c1SJohn Dyson 		if (error)
41053bf4bb2SPeter Wemm 			break;
41153bf4bb2SPeter Wemm 		lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL;
412822ded67SJulian Elischer 		lkp->lk_lockholder = thr;
41353bf4bb2SPeter Wemm 		lkp->lk_exclusivecount = 1;
414f158df07SJeff Roberson 		COUNT(td, 1);
41515a1057cSEivind Eklund #if defined(DEBUG_LOCKS)
4167499fd8dSJeff Roberson 		stack_save(&lkp->lk_stack);
41715a1057cSEivind Eklund #endif
41853bf4bb2SPeter Wemm 		break;
41953bf4bb2SPeter Wemm 
42053bf4bb2SPeter Wemm 	default:
4219ed346baSBosko Milekic 		mtx_unlock(lkp->lk_interlock);
42253bf4bb2SPeter Wemm 		panic("lockmgr: unknown locktype request %d",
42353bf4bb2SPeter Wemm 		    flags & LK_TYPE_MASK);
42453bf4bb2SPeter Wemm 		/* NOTREACHED */
42553bf4bb2SPeter Wemm 	}
42603e9c6c1SJohn Dyson 	if ((lkp->lk_flags & LK_WAITDRAIN) &&
42703e9c6c1SJohn Dyson 	    (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE |
42803e9c6c1SJohn Dyson 		LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) {
42953bf4bb2SPeter Wemm 		lkp->lk_flags &= ~LK_WAITDRAIN;
43053bf4bb2SPeter Wemm 		wakeup((void *)&lkp->lk_flags);
43153bf4bb2SPeter Wemm 	}
4329ed346baSBosko Milekic 	mtx_unlock(lkp->lk_interlock);
43353bf4bb2SPeter Wemm 	return (error);
43453bf4bb2SPeter Wemm }
43553bf4bb2SPeter Wemm 
43699448ed1SJohn Dyson static int
43799448ed1SJohn Dyson acquiredrain(struct lock *lkp, int extflags) {
43899448ed1SJohn Dyson 	int error;
43999448ed1SJohn Dyson 
44099448ed1SJohn Dyson 	if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) {
44199448ed1SJohn Dyson 		return EBUSY;
44299448ed1SJohn Dyson 	}
44399448ed1SJohn Dyson 	while (lkp->lk_flags & LK_ALL) {
44499448ed1SJohn Dyson 		lkp->lk_flags |= LK_WAITDRAIN;
44596fde7daSJake Burkholder 		error = msleep(&lkp->lk_flags, lkp->lk_interlock, lkp->lk_prio,
44623b59018SMatthew Dillon 			lkp->lk_wmesg,
44723b59018SMatthew Dillon 			((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
44899448ed1SJohn Dyson 		if (error)
44999448ed1SJohn Dyson 			return error;
45099448ed1SJohn Dyson 		if (extflags & LK_SLEEPFAIL) {
45199448ed1SJohn Dyson 			return ENOLCK;
45299448ed1SJohn Dyson 		}
45399448ed1SJohn Dyson 	}
45499448ed1SJohn Dyson 	return 0;
45599448ed1SJohn Dyson }
45699448ed1SJohn Dyson 
45799448ed1SJohn Dyson /*
458c6964d3bSKirk McKusick  * Transfer any waiting processes from one lock to another.
459c6964d3bSKirk McKusick  */
460c6964d3bSKirk McKusick void
461c6964d3bSKirk McKusick transferlockers(from, to)
462c6964d3bSKirk McKusick 	struct lock *from;
463c6964d3bSKirk McKusick 	struct lock *to;
464c6964d3bSKirk McKusick {
465c6964d3bSKirk McKusick 
466c6964d3bSKirk McKusick 	KASSERT(from != to, ("lock transfer to self"));
467c6964d3bSKirk McKusick 	KASSERT((from->lk_flags&LK_WAITDRAIN) == 0, ("transfer draining lock"));
468f5f0da0aSJeff Roberson 
469f5f0da0aSJeff Roberson 	mtx_lock(from->lk_interlock);
470f5f0da0aSJeff Roberson 	if (from->lk_waitcount == 0) {
471f5f0da0aSJeff Roberson 		mtx_unlock(from->lk_interlock);
472c6964d3bSKirk McKusick 		return;
473f5f0da0aSJeff Roberson 	}
474c6964d3bSKirk McKusick 	from->lk_newlock = to;
475c6964d3bSKirk McKusick 	wakeup((void *)from);
476f5f0da0aSJeff Roberson 	msleep(&from->lk_newlock, from->lk_interlock, from->lk_prio,
477f5f0da0aSJeff Roberson 	    "lkxfer", 0);
478c6964d3bSKirk McKusick 	from->lk_newlock = NULL;
479c6964d3bSKirk McKusick 	from->lk_flags &= ~(LK_WANT_EXCL | LK_WANT_UPGRADE);
480c6964d3bSKirk McKusick 	KASSERT(from->lk_waitcount == 0, ("active lock"));
481f5f0da0aSJeff Roberson 	mtx_unlock(from->lk_interlock);
482c6964d3bSKirk McKusick }
483c6964d3bSKirk McKusick 
484c6964d3bSKirk McKusick 
485c6964d3bSKirk McKusick /*
48699448ed1SJohn Dyson  * Initialize a lock; required before use.
48799448ed1SJohn Dyson  */
48899448ed1SJohn Dyson void
48999448ed1SJohn Dyson lockinit(lkp, prio, wmesg, timo, flags)
49099448ed1SJohn Dyson 	struct lock *lkp;
49199448ed1SJohn Dyson 	int prio;
49204858e7eSEivind Eklund 	const char *wmesg;
49399448ed1SJohn Dyson 	int timo;
49499448ed1SJohn Dyson 	int flags;
49599448ed1SJohn Dyson {
496c06394f5SJohn Baldwin 	CTR5(KTR_LOCK, "lockinit(): lkp == %p, prio == %d, wmesg == \"%s\", "
497a18b1f1dSJason Evans 	    "timo == %d, flags = 0x%x\n", lkp, prio, wmesg, timo, flags);
49899448ed1SJohn Dyson 
499857d9c60SDon Lewis 	lkp->lk_interlock = mtx_pool_alloc(mtxpool_lockbuilder);
5009722d88fSJason Evans 	lkp->lk_flags = (flags & LK_EXTFLG_MASK);
50199448ed1SJohn Dyson 	lkp->lk_sharecount = 0;
50299448ed1SJohn Dyson 	lkp->lk_waitcount = 0;
50399448ed1SJohn Dyson 	lkp->lk_exclusivecount = 0;
50499448ed1SJohn Dyson 	lkp->lk_prio = prio;
50599448ed1SJohn Dyson 	lkp->lk_wmesg = wmesg;
50699448ed1SJohn Dyson 	lkp->lk_timo = timo;
50799448ed1SJohn Dyson 	lkp->lk_lockholder = LK_NOPROC;
508c6964d3bSKirk McKusick 	lkp->lk_newlock = NULL;
5093a096f6cSKirk McKusick #ifdef DEBUG_LOCKS
5107499fd8dSJeff Roberson 	stack_zero(&lkp->lk_stack);
5113a096f6cSKirk McKusick #endif
51299448ed1SJohn Dyson }
51399448ed1SJohn Dyson 
51499448ed1SJohn Dyson /*
515a18b1f1dSJason Evans  * Destroy a lock.
516a18b1f1dSJason Evans  */
517a18b1f1dSJason Evans void
518a18b1f1dSJason Evans lockdestroy(lkp)
519a18b1f1dSJason Evans 	struct lock *lkp;
520a18b1f1dSJason Evans {
521c06394f5SJohn Baldwin 	CTR2(KTR_LOCK, "lockdestroy(): lkp == %p (lk_wmesg == \"%s\")",
522a18b1f1dSJason Evans 	    lkp, lkp->lk_wmesg);
523a18b1f1dSJason Evans }
524a18b1f1dSJason Evans 
525a18b1f1dSJason Evans /*
52699448ed1SJohn Dyson  * Determine the status of a lock.
52799448ed1SJohn Dyson  */
52899448ed1SJohn Dyson int
529b40ce416SJulian Elischer lockstatus(lkp, td)
53099448ed1SJohn Dyson 	struct lock *lkp;
531b40ce416SJulian Elischer 	struct thread *td;
53299448ed1SJohn Dyson {
53399448ed1SJohn Dyson 	int lock_type = 0;
5342b59d50cSRobert Watson 	int interlocked;
53599448ed1SJohn Dyson 
5362b59d50cSRobert Watson 	if (!kdb_active) {
5372b59d50cSRobert Watson 		interlocked = 1;
5389ed346baSBosko Milekic 		mtx_lock(lkp->lk_interlock);
5392b59d50cSRobert Watson 	} else
5402b59d50cSRobert Watson 		interlocked = 0;
5416bdfe06aSEivind Eklund 	if (lkp->lk_exclusivecount != 0) {
542822ded67SJulian Elischer 		if (td == NULL || lkp->lk_lockholder == td)
54399448ed1SJohn Dyson 			lock_type = LK_EXCLUSIVE;
5446bdfe06aSEivind Eklund 		else
5456bdfe06aSEivind Eklund 			lock_type = LK_EXCLOTHER;
5466bdfe06aSEivind Eklund 	} else if (lkp->lk_sharecount != 0)
54799448ed1SJohn Dyson 		lock_type = LK_SHARED;
5482b59d50cSRobert Watson 	if (interlocked)
5499ed346baSBosko Milekic 		mtx_unlock(lkp->lk_interlock);
55099448ed1SJohn Dyson 	return (lock_type);
55199448ed1SJohn Dyson }
55299448ed1SJohn Dyson 
55353bf4bb2SPeter Wemm /*
55467812eacSKirk McKusick  * Determine the number of holders of a lock.
55567812eacSKirk McKusick  */
55667812eacSKirk McKusick int
55767812eacSKirk McKusick lockcount(lkp)
55867812eacSKirk McKusick 	struct lock *lkp;
55967812eacSKirk McKusick {
56067812eacSKirk McKusick 	int count;
56167812eacSKirk McKusick 
5629ed346baSBosko Milekic 	mtx_lock(lkp->lk_interlock);
56367812eacSKirk McKusick 	count = lkp->lk_exclusivecount + lkp->lk_sharecount;
5649ed346baSBosko Milekic 	mtx_unlock(lkp->lk_interlock);
56567812eacSKirk McKusick 	return (count);
56667812eacSKirk McKusick }
56767812eacSKirk McKusick 
56867812eacSKirk McKusick /*
56953bf4bb2SPeter Wemm  * Print out information about state of a lock. Used by VOP_PRINT
5700e61ac7bSPoul-Henning Kamp  * routines to display status about contained locks.
57153bf4bb2SPeter Wemm  */
572a1ce9d5cSPeter Wemm void
57353bf4bb2SPeter Wemm lockmgr_printinfo(lkp)
57453bf4bb2SPeter Wemm 	struct lock *lkp;
57553bf4bb2SPeter Wemm {
57653bf4bb2SPeter Wemm 
57753bf4bb2SPeter Wemm 	if (lkp->lk_sharecount)
57853bf4bb2SPeter Wemm 		printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
57953bf4bb2SPeter Wemm 		    lkp->lk_sharecount);
58053bf4bb2SPeter Wemm 	else if (lkp->lk_flags & LK_HAVE_EXCL)
581c969c60cSAlexander Kabaev 		printf(" lock type %s: EXCL (count %d) by thread %p (pid %d)",
582c969c60cSAlexander Kabaev 		    lkp->lk_wmesg, lkp->lk_exclusivecount,
583c969c60cSAlexander Kabaev 		    lkp->lk_lockholder, lkp->lk_lockholder->td_proc->p_pid);
58453bf4bb2SPeter Wemm 	if (lkp->lk_waitcount > 0)
58553bf4bb2SPeter Wemm 		printf(" with %d pending", lkp->lk_waitcount);
5867499fd8dSJeff Roberson #ifdef DEBUG_LOCKS
5877499fd8dSJeff Roberson 	stack_print(&lkp->lk_stack);
5887499fd8dSJeff Roberson #endif
58953bf4bb2SPeter Wemm }
590be6847d7SJohn Baldwin 
591be6847d7SJohn Baldwin #ifdef DDB
592be6847d7SJohn Baldwin DB_SHOW_COMMAND(lockmgr, db_show_lockmgr)
593be6847d7SJohn Baldwin {
594be6847d7SJohn Baldwin 	struct thread *td;
595be6847d7SJohn Baldwin 	struct lock *lkp;
596be6847d7SJohn Baldwin 
597be6847d7SJohn Baldwin 	if (!have_addr)
598be6847d7SJohn Baldwin 		return;
599be6847d7SJohn Baldwin 	lkp = (struct lock *)addr;
600be6847d7SJohn Baldwin 
601be6847d7SJohn Baldwin 	db_printf("lock type: %s\n", lkp->lk_wmesg);
602be6847d7SJohn Baldwin 	db_printf("state: ");
603be6847d7SJohn Baldwin 	if (lkp->lk_sharecount)
604be6847d7SJohn Baldwin 		db_printf("SHARED (count %d)\n", lkp->lk_sharecount);
605be6847d7SJohn Baldwin 	else if (lkp->lk_flags & LK_HAVE_EXCL) {
606be6847d7SJohn Baldwin 		td = lkp->lk_lockholder;
607be6847d7SJohn Baldwin 		db_printf("EXCL (count %d) %p ", lkp->lk_exclusivecount, td);
608be6847d7SJohn Baldwin 		db_printf("(tid %d, pid %d, \"%s\")\n", td->td_tid,
609be6847d7SJohn Baldwin 		    td->td_proc->p_pid, td->td_proc->p_comm);
610be6847d7SJohn Baldwin 	} else
611be6847d7SJohn Baldwin 		db_printf("UNLOCKED\n");
612be6847d7SJohn Baldwin 	if (lkp->lk_waitcount > 0)
613be6847d7SJohn Baldwin 		db_printf("waiters: %d\n", lkp->lk_waitcount);
614be6847d7SJohn Baldwin }
615be6847d7SJohn Baldwin #endif
616