FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_lock.c
1 /*-
2 * Copyright (c) 1995
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Copyright (C) 1997
6 * John S. Dyson. All rights reserved.
7 *
8 * This code contains ideas from software contributed to Berkeley by
9 * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
10 * System project at Carnegie-Mellon University.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Berkeley and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
39 *
40 * @(#)kern_lock.c 8.18 (Berkeley) 5/21/95
41 */
42
43 #include <sys/cdefs.h>
44 __FBSDID("$FreeBSD$");
45
46 #include "opt_ddb.h"
47
48 #include <sys/param.h>
49 #include <sys/kdb.h>
50 #include <sys/kernel.h>
51 #include <sys/ktr.h>
52 #include <sys/lock.h>
53 #include <sys/lockmgr.h>
54 #include <sys/mutex.h>
55 #include <sys/proc.h>
56 #include <sys/systm.h>
57 #ifdef DEBUG_LOCKS
58 #include <sys/stack.h>
59 #endif
60
61 #ifdef DDB
62 #include <ddb/ddb.h>
63 #endif
64
65 /*
66 * Locking primitives implementation.
67 * Locks provide shared/exclusive sychronization.
68 */
69
70 #define COUNT(td, x) if ((td)) (td)->td_locks += (x)
71 #define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \
72 LK_SHARE_NONZERO | LK_WAIT_NONZERO)
73
74 static int acquire(struct lock **lkpp, int extflags, int wanted);
75 static int acquiredrain(struct lock *lkp, int extflags) ;
76
77 static __inline void
78 sharelock(struct thread *td, struct lock *lkp, int incr) {
79 lkp->lk_flags |= LK_SHARE_NONZERO;
80 lkp->lk_sharecount += incr;
81 COUNT(td, incr);
82 }
83
84 static __inline void
85 shareunlock(struct thread *td, struct lock *lkp, int decr) {
86
87 KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr"));
88
89 COUNT(td, -decr);
90 if (lkp->lk_sharecount == decr) {
91 lkp->lk_flags &= ~LK_SHARE_NONZERO;
92 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) {
93 wakeup(lkp);
94 }
95 lkp->lk_sharecount = 0;
96 } else {
97 lkp->lk_sharecount -= decr;
98 }
99 }
100
101 static int
102 acquire(struct lock **lkpp, int extflags, int wanted)
103 {
104 struct lock *lkp = *lkpp;
105 int error;
106 CTR3(KTR_LOCK,
107 "acquire(): lkp == %p, extflags == 0x%x, wanted == 0x%x",
108 lkp, extflags, wanted);
109
110 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted))
111 return EBUSY;
112 error = 0;
113 while ((lkp->lk_flags & wanted) != 0) {
114 CTR2(KTR_LOCK,
115 "acquire(): lkp == %p, lk_flags == 0x%x sleeping",
116 lkp, lkp->lk_flags);
117 lkp->lk_flags |= LK_WAIT_NONZERO;
118 lkp->lk_waitcount++;
119 error = msleep(lkp, lkp->lk_interlock, lkp->lk_prio,
120 lkp->lk_wmesg,
121 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
122 lkp->lk_waitcount--;
123 if (lkp->lk_waitcount == 0)
124 lkp->lk_flags &= ~LK_WAIT_NONZERO;
125 if (error)
126 break;
127 if (extflags & LK_SLEEPFAIL) {
128 error = ENOLCK;
129 break;
130 }
131 if (lkp->lk_newlock != NULL) {
132 mtx_lock(lkp->lk_newlock->lk_interlock);
133 mtx_unlock(lkp->lk_interlock);
134 if (lkp->lk_waitcount == 0)
135 wakeup((void *)(&lkp->lk_newlock));
136 *lkpp = lkp = lkp->lk_newlock;
137 }
138 }
139 mtx_assert(lkp->lk_interlock, MA_OWNED);
140 return (error);
141 }
142
143 /*
144 * Set, change, or release a lock.
145 *
146 * Shared requests increment the shared count. Exclusive requests set the
147 * LK_WANT_EXCL flag (preventing further shared locks), and wait for already
148 * accepted shared locks and shared-to-exclusive upgrades to go away.
149 */
150 int
151 lockmgr(lkp, flags, interlkp, td)
152 struct lock *lkp;
153 u_int flags;
154 struct mtx *interlkp;
155 struct thread *td;
156 {
157 int error;
158 struct thread *thr;
159 int extflags, lockflags;
160
161 error = 0;
162 if (td == NULL)
163 thr = LK_KERNPROC;
164 else
165 thr = td;
166
167 if ((flags & LK_INTERNAL) == 0)
168 mtx_lock(lkp->lk_interlock);
169 CTR6(KTR_LOCK,
170 "lockmgr(): lkp == %p (lk_wmesg == \"%s\"), owner == %p, exclusivecount == %d, flags == 0x%x, "
171 "td == %p", lkp, lkp->lk_wmesg, lkp->lk_lockholder,
172 lkp->lk_exclusivecount, flags, td);
173 #ifdef DEBUG_LOCKS
174 {
175 struct stack stack; /* XXX */
176 stack_save(&stack);
177 CTRSTACK(KTR_LOCK, &stack, 0, 1);
178 }
179 #endif
180
181 if (flags & LK_INTERLOCK) {
182 mtx_assert(interlkp, MA_OWNED | MA_NOTRECURSED);
183 mtx_unlock(interlkp);
184 }
185
186 if ((flags & (LK_NOWAIT|LK_RELEASE)) == 0)
187 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK,
188 &lkp->lk_interlock->mtx_object,
189 "Acquiring lockmgr lock \"%s\"", lkp->lk_wmesg);
190
191 if (panicstr != NULL) {
192 mtx_unlock(lkp->lk_interlock);
193 return (0);
194 }
195 if ((lkp->lk_flags & LK_NOSHARE) &&
196 (flags & LK_TYPE_MASK) == LK_SHARED) {
197 flags &= ~LK_TYPE_MASK;
198 flags |= LK_EXCLUSIVE;
199 }
200 extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
201
202 switch (flags & LK_TYPE_MASK) {
203
204 case LK_SHARED:
205 /*
206 * If we are not the exclusive lock holder, we have to block
207 * while there is an exclusive lock holder or while an
208 * exclusive lock request or upgrade request is in progress.
209 *
210 * However, if TDP_DEADLKTREAT is set, we override exclusive
211 * lock requests or upgrade requests ( but not the exclusive
212 * lock itself ).
213 */
214 if (lkp->lk_lockholder != thr) {
215 lockflags = LK_HAVE_EXCL;
216 if (td != NULL && !(td->td_pflags & TDP_DEADLKTREAT))
217 lockflags |= LK_WANT_EXCL | LK_WANT_UPGRADE;
218 error = acquire(&lkp, extflags, lockflags);
219 if (error)
220 break;
221 sharelock(td, lkp, 1);
222 #if defined(DEBUG_LOCKS)
223 stack_save(&lkp->lk_stack);
224 #endif
225 break;
226 }
227 /*
228 * We hold an exclusive lock, so downgrade it to shared.
229 * An alternative would be to fail with EDEADLK.
230 */
231 sharelock(td, lkp, 1);
232 /* FALLTHROUGH downgrade */
233
234 case LK_DOWNGRADE:
235 KASSERT(lkp->lk_lockholder == thr && lkp->lk_exclusivecount != 0,
236 ("lockmgr: not holding exclusive lock "
237 "(owner thread (%p) != thread (%p), exlcnt (%d) != 0",
238 lkp->lk_lockholder, thr, lkp->lk_exclusivecount));
239 sharelock(td, lkp, lkp->lk_exclusivecount);
240 COUNT(td, -lkp->lk_exclusivecount);
241 lkp->lk_exclusivecount = 0;
242 lkp->lk_flags &= ~LK_HAVE_EXCL;
243 lkp->lk_lockholder = LK_NOPROC;
244 if (lkp->lk_waitcount)
245 wakeup((void *)lkp);
246 break;
247
248 case LK_EXCLUPGRADE:
249 /*
250 * If another process is ahead of us to get an upgrade,
251 * then we want to fail rather than have an intervening
252 * exclusive access.
253 */
254 if (lkp->lk_flags & LK_WANT_UPGRADE) {
255 shareunlock(td, lkp, 1);
256 error = EBUSY;
257 break;
258 }
259 /* FALLTHROUGH normal upgrade */
260
261 case LK_UPGRADE:
262 /*
263 * Upgrade a shared lock to an exclusive one. If another
264 * shared lock has already requested an upgrade to an
265 * exclusive lock, our shared lock is released and an
266 * exclusive lock is requested (which will be granted
267 * after the upgrade). If we return an error, the file
268 * will always be unlocked.
269 */
270 if (lkp->lk_lockholder == thr)
271 panic("lockmgr: upgrade exclusive lock");
272 if (lkp->lk_sharecount <= 0)
273 panic("lockmgr: upgrade without shared");
274 shareunlock(td, lkp, 1);
275 /*
276 * If we are just polling, check to see if we will block.
277 */
278 if ((extflags & LK_NOWAIT) &&
279 ((lkp->lk_flags & LK_WANT_UPGRADE) ||
280 lkp->lk_sharecount > 1)) {
281 error = EBUSY;
282 break;
283 }
284 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
285 /*
286 * We are first shared lock to request an upgrade, so
287 * request upgrade and wait for the shared count to
288 * drop to zero, then take exclusive lock.
289 */
290 lkp->lk_flags |= LK_WANT_UPGRADE;
291 error = acquire(&lkp, extflags, LK_SHARE_NONZERO);
292 lkp->lk_flags &= ~LK_WANT_UPGRADE;
293
294 if (error) {
295 if ((lkp->lk_flags & ( LK_WANT_EXCL | LK_WAIT_NONZERO)) == (LK_WANT_EXCL | LK_WAIT_NONZERO))
296 wakeup((void *)lkp);
297 break;
298 }
299 if (lkp->lk_exclusivecount != 0)
300 panic("lockmgr: non-zero exclusive count");
301 lkp->lk_flags |= LK_HAVE_EXCL;
302 lkp->lk_lockholder = thr;
303 lkp->lk_exclusivecount = 1;
304 COUNT(td, 1);
305 #if defined(DEBUG_LOCKS)
306 stack_save(&lkp->lk_stack);
307 #endif
308 break;
309 }
310 /*
311 * Someone else has requested upgrade. Release our shared
312 * lock, awaken upgrade requestor if we are the last shared
313 * lock, then request an exclusive lock.
314 */
315 if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) ==
316 LK_WAIT_NONZERO)
317 wakeup((void *)lkp);
318 /* FALLTHROUGH exclusive request */
319
320 case LK_EXCLUSIVE:
321 if (lkp->lk_lockholder == thr && thr != LK_KERNPROC) {
322 /*
323 * Recursive lock.
324 */
325 if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0)
326 panic("lockmgr: locking against myself");
327 if ((extflags & LK_CANRECURSE) != 0) {
328 lkp->lk_exclusivecount++;
329 COUNT(td, 1);
330 break;
331 }
332 }
333 /*
334 * If we are just polling, check to see if we will sleep.
335 */
336 if ((extflags & LK_NOWAIT) &&
337 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO))) {
338 error = EBUSY;
339 break;
340 }
341 /*
342 * Try to acquire the want_exclusive flag.
343 */
344 error = acquire(&lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL));
345 if (error)
346 break;
347 lkp->lk_flags |= LK_WANT_EXCL;
348 /*
349 * Wait for shared locks and upgrades to finish.
350 */
351 error = acquire(&lkp, extflags, LK_HAVE_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO);
352 lkp->lk_flags &= ~LK_WANT_EXCL;
353 if (error) {
354 if (lkp->lk_flags & LK_WAIT_NONZERO)
355 wakeup((void *)lkp);
356 break;
357 }
358 lkp->lk_flags |= LK_HAVE_EXCL;
359 lkp->lk_lockholder = thr;
360 if (lkp->lk_exclusivecount != 0)
361 panic("lockmgr: non-zero exclusive count");
362 lkp->lk_exclusivecount = 1;
363 COUNT(td, 1);
364 #if defined(DEBUG_LOCKS)
365 stack_save(&lkp->lk_stack);
366 #endif
367 break;
368
369 case LK_RELEASE:
370 if (lkp->lk_exclusivecount != 0) {
371 if (lkp->lk_lockholder != thr &&
372 lkp->lk_lockholder != LK_KERNPROC) {
373 panic("lockmgr: thread %p, not %s %p unlocking",
374 thr, "exclusive lock holder",
375 lkp->lk_lockholder);
376 }
377 if (lkp->lk_lockholder != LK_KERNPROC)
378 COUNT(td, -1);
379 if (lkp->lk_exclusivecount == 1) {
380 lkp->lk_flags &= ~LK_HAVE_EXCL;
381 lkp->lk_lockholder = LK_NOPROC;
382 lkp->lk_exclusivecount = 0;
383 } else {
384 lkp->lk_exclusivecount--;
385 }
386 } else if (lkp->lk_flags & LK_SHARE_NONZERO)
387 shareunlock(td, lkp, 1);
388 if (lkp->lk_flags & LK_WAIT_NONZERO)
389 wakeup((void *)lkp);
390 break;
391
392 case LK_DRAIN:
393 /*
394 * Check that we do not already hold the lock, as it can
395 * never drain if we do. Unfortunately, we have no way to
396 * check for holding a shared lock, but at least we can
397 * check for an exclusive one.
398 */
399 if (lkp->lk_lockholder == thr)
400 panic("lockmgr: draining against myself");
401
402 error = acquiredrain(lkp, extflags);
403 if (error)
404 break;
405 lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL;
406 lkp->lk_lockholder = thr;
407 lkp->lk_exclusivecount = 1;
408 COUNT(td, 1);
409 #if defined(DEBUG_LOCKS)
410 stack_save(&lkp->lk_stack);
411 #endif
412 break;
413
414 default:
415 mtx_unlock(lkp->lk_interlock);
416 panic("lockmgr: unknown locktype request %d",
417 flags & LK_TYPE_MASK);
418 /* NOTREACHED */
419 }
420 if ((lkp->lk_flags & LK_WAITDRAIN) &&
421 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE |
422 LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) {
423 lkp->lk_flags &= ~LK_WAITDRAIN;
424 wakeup((void *)&lkp->lk_flags);
425 }
426 mtx_unlock(lkp->lk_interlock);
427 return (error);
428 }
429
430 static int
431 acquiredrain(struct lock *lkp, int extflags) {
432 int error;
433
434 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) {
435 return EBUSY;
436 }
437 while (lkp->lk_flags & LK_ALL) {
438 lkp->lk_flags |= LK_WAITDRAIN;
439 error = msleep(&lkp->lk_flags, lkp->lk_interlock, lkp->lk_prio,
440 lkp->lk_wmesg,
441 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
442 if (error)
443 return error;
444 if (extflags & LK_SLEEPFAIL) {
445 return ENOLCK;
446 }
447 }
448 return 0;
449 }
450
451 /*
452 * Transfer any waiting processes from one lock to another.
453 */
454 void
455 transferlockers(from, to)
456 struct lock *from;
457 struct lock *to;
458 {
459
460 KASSERT(from != to, ("lock transfer to self"));
461 KASSERT((from->lk_flags&LK_WAITDRAIN) == 0, ("transfer draining lock"));
462
463 mtx_lock(from->lk_interlock);
464 if (from->lk_waitcount == 0) {
465 mtx_unlock(from->lk_interlock);
466 return;
467 }
468 from->lk_newlock = to;
469 wakeup((void *)from);
470 msleep(&from->lk_newlock, from->lk_interlock, from->lk_prio,
471 "lkxfer", 0);
472 from->lk_newlock = NULL;
473 from->lk_flags &= ~(LK_WANT_EXCL | LK_WANT_UPGRADE);
474 KASSERT(from->lk_waitcount == 0, ("active lock"));
475 mtx_unlock(from->lk_interlock);
476 }
477
478
479 /*
480 * Initialize a lock; required before use.
481 */
482 void
483 lockinit(lkp, prio, wmesg, timo, flags)
484 struct lock *lkp;
485 int prio;
486 const char *wmesg;
487 int timo;
488 int flags;
489 {
490 CTR5(KTR_LOCK, "lockinit(): lkp == %p, prio == %d, wmesg == \"%s\", "
491 "timo == %d, flags = 0x%x\n", lkp, prio, wmesg, timo, flags);
492
493 lkp->lk_interlock = mtx_pool_alloc(mtxpool_lockbuilder);
494 lkp->lk_flags = (flags & LK_EXTFLG_MASK);
495 lkp->lk_sharecount = 0;
496 lkp->lk_waitcount = 0;
497 lkp->lk_exclusivecount = 0;
498 lkp->lk_prio = prio;
499 lkp->lk_wmesg = wmesg;
500 lkp->lk_timo = timo;
501 lkp->lk_lockholder = LK_NOPROC;
502 lkp->lk_newlock = NULL;
503 #ifdef DEBUG_LOCKS
504 stack_zero(&lkp->lk_stack);
505 #endif
506 }
507
508 /*
509 * Destroy a lock.
510 */
511 void
512 lockdestroy(lkp)
513 struct lock *lkp;
514 {
515 CTR2(KTR_LOCK, "lockdestroy(): lkp == %p (lk_wmesg == \"%s\")",
516 lkp, lkp->lk_wmesg);
517 }
518
519 /*
520 * Determine the status of a lock.
521 */
522 int
523 lockstatus(lkp, td)
524 struct lock *lkp;
525 struct thread *td;
526 {
527 int lock_type = 0;
528 int interlocked;
529
530 if (!kdb_active) {
531 interlocked = 1;
532 mtx_lock(lkp->lk_interlock);
533 } else
534 interlocked = 0;
535 if (lkp->lk_exclusivecount != 0) {
536 if (td == NULL || lkp->lk_lockholder == td)
537 lock_type = LK_EXCLUSIVE;
538 else
539 lock_type = LK_EXCLOTHER;
540 } else if (lkp->lk_sharecount != 0)
541 lock_type = LK_SHARED;
542 if (interlocked)
543 mtx_unlock(lkp->lk_interlock);
544 return (lock_type);
545 }
546
547 /*
548 * Determine the number of holders of a lock.
549 */
550 int
551 lockcount(lkp)
552 struct lock *lkp;
553 {
554 int count;
555
556 mtx_lock(lkp->lk_interlock);
557 count = lkp->lk_exclusivecount + lkp->lk_sharecount;
558 mtx_unlock(lkp->lk_interlock);
559 return (count);
560 }
561
562 /*
563 * Determine the number of waiters on a lock.
564 */
565 int
566 lockwaiters(lkp)
567 struct lock *lkp;
568 {
569 int count;
570
571 mtx_lock(lkp->lk_interlock);
572 count = lkp->lk_waitcount;
573 mtx_unlock(lkp->lk_interlock);
574 return (count);
575 }
576
577 /*
578 * Print out information about state of a lock. Used by VOP_PRINT
579 * routines to display status about contained locks.
580 */
581 void
582 lockmgr_printinfo(lkp)
583 struct lock *lkp;
584 {
585
586 if (lkp->lk_sharecount)
587 printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
588 lkp->lk_sharecount);
589 else if (lkp->lk_flags & LK_HAVE_EXCL)
590 printf(" lock type %s: EXCL (count %d) by thread %p (pid %d)",
591 lkp->lk_wmesg, lkp->lk_exclusivecount,
592 lkp->lk_lockholder, lkp->lk_lockholder->td_proc->p_pid);
593 if (lkp->lk_waitcount > 0)
594 printf(" with %d pending", lkp->lk_waitcount);
595 #ifdef DEBUG_LOCKS
596 stack_print(&lkp->lk_stack);
597 #endif
598 }
599
600 #ifdef DDB
601 /*
602 * Check to see if a thread that is blocked on a sleep queue is actually
603 * blocked on a 'struct lock'. If so, output some details and return true.
604 * If the lock has an exclusive owner, return that in *ownerp.
605 */
606 int
607 lockmgr_chain(struct thread *td, struct thread **ownerp)
608 {
609 struct lock *lkp;
610
611 lkp = td->td_wchan;
612
613 /* Simple test to see if wchan points to a lockmgr lock. */
614 if (lkp->lk_wmesg == td->td_wmesg)
615 goto ok;
616
617 /*
618 * If this thread is doing a DRAIN, then it would be asleep on
619 * &lkp->lk_flags rather than lkp.
620 */
621 lkp = (struct lock *)((char *)td->td_wchan -
622 offsetof(struct lock, lk_flags));
623 if (lkp->lk_wmesg == td->td_wmesg && (lkp->lk_flags & LK_WAITDRAIN))
624 goto ok;
625
626 /* Doen't seem to be a lockmgr lock. */
627 return (0);
628
629 ok:
630 /* Ok, we think we have a lockmgr lock, so output some details. */
631 db_printf("blocked on lk \"%s\" ", lkp->lk_wmesg);
632 if (lkp->lk_sharecount) {
633 db_printf("SHARED (count %d)\n", lkp->lk_sharecount);
634 *ownerp = NULL;
635 } else {
636 db_printf("EXCL (count %d)\n", lkp->lk_exclusivecount);
637 *ownerp = lkp->lk_lockholder;
638 }
639 return (1);
640 }
641
642 DB_SHOW_COMMAND(lockmgr, db_show_lockmgr)
643 {
644 struct thread *td;
645 struct lock *lkp;
646
647 if (!have_addr)
648 return;
649 lkp = (struct lock *)addr;
650
651 db_printf("lock type: %s\n", lkp->lk_wmesg);
652 db_printf("state: ");
653 if (lkp->lk_sharecount)
654 db_printf("SHARED (count %d)\n", lkp->lk_sharecount);
655 else if (lkp->lk_flags & LK_HAVE_EXCL) {
656 td = lkp->lk_lockholder;
657 db_printf("EXCL (count %d) %p ", lkp->lk_exclusivecount, td);
658 db_printf("(tid %d, pid %d, \"%s\")\n", td->td_tid,
659 td->td_proc->p_pid, td->td_proc->p_comm);
660 } else
661 db_printf("UNLOCKED\n");
662 if (lkp->lk_waitcount > 0)
663 db_printf("waiters: %d\n", lkp->lk_waitcount);
664 }
665 #endif
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