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 #include "opt_global.h"
48
49 #include <sys/param.h>
50 #include <sys/kdb.h>
51 #include <sys/kernel.h>
52 #include <sys/ktr.h>
53 #include <sys/lock.h>
54 #include <sys/lockmgr.h>
55 #include <sys/mutex.h>
56 #include <sys/proc.h>
57 #include <sys/systm.h>
58 #include <sys/lock_profile.h>
59 #ifdef DEBUG_LOCKS
60 #include <sys/stack.h>
61 #endif
62
63 #ifdef DDB
64 #include <ddb/ddb.h>
65 static void db_show_lockmgr(struct lock_object *lock);
66 #endif
67 static void lock_lockmgr(struct lock_object *lock, int how);
68 static int unlock_lockmgr(struct lock_object *lock);
69
70 struct lock_class lock_class_lockmgr = {
71 .lc_name = "lockmgr",
72 .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE,
73 #ifdef DDB
74 .lc_ddb_show = db_show_lockmgr,
75 #endif
76 .lc_lock = lock_lockmgr,
77 .lc_unlock = unlock_lockmgr,
78 };
79
80 /*
81 * Locking primitives implementation.
82 * Locks provide shared/exclusive sychronization.
83 */
84
85 void
86 lock_lockmgr(struct lock_object *lock, int how)
87 {
88
89 panic("lockmgr locks do not support sleep interlocking");
90 }
91
92 int
93 unlock_lockmgr(struct lock_object *lock)
94 {
95
96 panic("lockmgr locks do not support sleep interlocking");
97 }
98
99 #define COUNT(td, x) if ((td)) (td)->td_locks += (x)
100 #define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \
101 LK_SHARE_NONZERO | LK_WAIT_NONZERO)
102
103 static int acquire(struct lock **lkpp, int extflags, int wanted, int *contested, uint64_t *waittime);
104 static int acquiredrain(struct lock *lkp, int extflags) ;
105
106 static __inline void
107 sharelock(struct thread *td, struct lock *lkp, int incr) {
108 lkp->lk_flags |= LK_SHARE_NONZERO;
109 lkp->lk_sharecount += incr;
110 COUNT(td, incr);
111 }
112
113 static __inline void
114 shareunlock(struct thread *td, struct lock *lkp, int decr) {
115
116 KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr"));
117
118 COUNT(td, -decr);
119 if (lkp->lk_sharecount == decr) {
120 lkp->lk_flags &= ~LK_SHARE_NONZERO;
121 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) {
122 wakeup(lkp);
123 }
124 lkp->lk_sharecount = 0;
125 } else {
126 lkp->lk_sharecount -= decr;
127 }
128 }
129
130 static int
131 acquire(struct lock **lkpp, int extflags, int wanted, int *contested, uint64_t *waittime)
132 {
133 struct lock *lkp = *lkpp;
134 int error;
135 CTR3(KTR_LOCK,
136 "acquire(): lkp == %p, extflags == 0x%x, wanted == 0x%x",
137 lkp, extflags, wanted);
138
139 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted))
140 return EBUSY;
141 error = 0;
142 if ((lkp->lk_flags & wanted) != 0)
143 lock_profile_obtain_lock_failed(&lkp->lk_object, contested, waittime);
144
145 while ((lkp->lk_flags & wanted) != 0) {
146 CTR2(KTR_LOCK,
147 "acquire(): lkp == %p, lk_flags == 0x%x sleeping",
148 lkp, lkp->lk_flags);
149 lkp->lk_flags |= LK_WAIT_NONZERO;
150 lkp->lk_waitcount++;
151 error = msleep(lkp, lkp->lk_interlock, lkp->lk_prio,
152 lkp->lk_wmesg,
153 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
154 lkp->lk_waitcount--;
155 if (lkp->lk_waitcount == 0)
156 lkp->lk_flags &= ~LK_WAIT_NONZERO;
157 if (error)
158 break;
159 if (extflags & LK_SLEEPFAIL) {
160 error = ENOLCK;
161 break;
162 }
163 if (lkp->lk_newlock != NULL) {
164 mtx_lock(lkp->lk_newlock->lk_interlock);
165 mtx_unlock(lkp->lk_interlock);
166 if (lkp->lk_waitcount == 0)
167 wakeup((void *)(&lkp->lk_newlock));
168 *lkpp = lkp = lkp->lk_newlock;
169 }
170 }
171 mtx_assert(lkp->lk_interlock, MA_OWNED);
172 return (error);
173 }
174
175 /*
176 * Set, change, or release a lock.
177 *
178 * Shared requests increment the shared count. Exclusive requests set the
179 * LK_WANT_EXCL flag (preventing further shared locks), and wait for already
180 * accepted shared locks and shared-to-exclusive upgrades to go away.
181 */
182 int
183 _lockmgr(struct lock *lkp, u_int flags, struct mtx *interlkp,
184 struct thread *td, char *file, int line)
185
186 {
187 int error;
188 struct thread *thr;
189 int extflags, lockflags;
190 int contested = 0;
191 uint64_t waitstart = 0;
192
193 error = 0;
194 if (td == NULL)
195 thr = LK_KERNPROC;
196 else
197 thr = td;
198
199 if ((flags & LK_INTERNAL) == 0)
200 mtx_lock(lkp->lk_interlock);
201 CTR6(KTR_LOCK,
202 "lockmgr(): lkp == %p (lk_wmesg == \"%s\"), owner == %p, exclusivecount == %d, flags == 0x%x, "
203 "td == %p", lkp, lkp->lk_wmesg, lkp->lk_lockholder,
204 lkp->lk_exclusivecount, flags, td);
205 #ifdef DEBUG_LOCKS
206 {
207 struct stack stack; /* XXX */
208 stack_save(&stack);
209 CTRSTACK(KTR_LOCK, &stack, 0, 1);
210 }
211 #endif
212
213 if (flags & LK_INTERLOCK) {
214 mtx_assert(interlkp, MA_OWNED | MA_NOTRECURSED);
215 mtx_unlock(interlkp);
216 }
217
218 if ((flags & (LK_NOWAIT|LK_RELEASE)) == 0)
219 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK,
220 &lkp->lk_interlock->lock_object,
221 "Acquiring lockmgr lock \"%s\"", lkp->lk_wmesg);
222
223 if (panicstr != NULL) {
224 mtx_unlock(lkp->lk_interlock);
225 return (0);
226 }
227 if ((lkp->lk_flags & LK_NOSHARE) &&
228 (flags & LK_TYPE_MASK) == LK_SHARED) {
229 flags &= ~LK_TYPE_MASK;
230 flags |= LK_EXCLUSIVE;
231 }
232 extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
233
234 switch (flags & LK_TYPE_MASK) {
235
236 case LK_SHARED:
237 /*
238 * If we are not the exclusive lock holder, we have to block
239 * while there is an exclusive lock holder or while an
240 * exclusive lock request or upgrade request is in progress.
241 *
242 * However, if TDP_DEADLKTREAT is set, we override exclusive
243 * lock requests or upgrade requests ( but not the exclusive
244 * lock itself ).
245 */
246 if (lkp->lk_lockholder != thr) {
247 lockflags = LK_HAVE_EXCL;
248 if (td != NULL && !(td->td_pflags & TDP_DEADLKTREAT))
249 lockflags |= LK_WANT_EXCL | LK_WANT_UPGRADE;
250 error = acquire(&lkp, extflags, lockflags, &contested, &waitstart);
251 if (error)
252 break;
253 sharelock(td, lkp, 1);
254 if (lkp->lk_sharecount == 1)
255 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line);
256
257 #if defined(DEBUG_LOCKS)
258 stack_save(&lkp->lk_stack);
259 #endif
260 break;
261 }
262 /*
263 * We hold an exclusive lock, so downgrade it to shared.
264 * An alternative would be to fail with EDEADLK.
265 */
266 sharelock(td, lkp, 1);
267 if (lkp->lk_sharecount == 1)
268 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line);
269 /* FALLTHROUGH downgrade */
270
271 case LK_DOWNGRADE:
272 KASSERT(lkp->lk_lockholder == thr && lkp->lk_exclusivecount != 0,
273 ("lockmgr: not holding exclusive lock "
274 "(owner thread (%p) != thread (%p), exlcnt (%d) != 0",
275 lkp->lk_lockholder, thr, lkp->lk_exclusivecount));
276 sharelock(td, lkp, lkp->lk_exclusivecount);
277 COUNT(td, -lkp->lk_exclusivecount);
278 lkp->lk_exclusivecount = 0;
279 lkp->lk_flags &= ~LK_HAVE_EXCL;
280 lkp->lk_lockholder = LK_NOPROC;
281 if (lkp->lk_waitcount)
282 wakeup((void *)lkp);
283 break;
284
285 case LK_EXCLUPGRADE:
286 /*
287 * If another process is ahead of us to get an upgrade,
288 * then we want to fail rather than have an intervening
289 * exclusive access.
290 */
291 if (lkp->lk_flags & LK_WANT_UPGRADE) {
292 shareunlock(td, lkp, 1);
293 error = EBUSY;
294 break;
295 }
296 /* FALLTHROUGH normal upgrade */
297
298 case LK_UPGRADE:
299 /*
300 * Upgrade a shared lock to an exclusive one. If another
301 * shared lock has already requested an upgrade to an
302 * exclusive lock, our shared lock is released and an
303 * exclusive lock is requested (which will be granted
304 * after the upgrade). If we return an error, the file
305 * will always be unlocked.
306 */
307 if (lkp->lk_lockholder == thr)
308 panic("lockmgr: upgrade exclusive lock");
309 if (lkp->lk_sharecount <= 0)
310 panic("lockmgr: upgrade without shared");
311 shareunlock(td, lkp, 1);
312 if (lkp->lk_sharecount == 0)
313 lock_profile_release_lock(&lkp->lk_object);
314 /*
315 * If we are just polling, check to see if we will block.
316 */
317 if ((extflags & LK_NOWAIT) &&
318 ((lkp->lk_flags & LK_WANT_UPGRADE) ||
319 lkp->lk_sharecount > 1)) {
320 error = EBUSY;
321 break;
322 }
323 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
324 /*
325 * We are first shared lock to request an upgrade, so
326 * request upgrade and wait for the shared count to
327 * drop to zero, then take exclusive lock.
328 */
329 lkp->lk_flags |= LK_WANT_UPGRADE;
330 error = acquire(&lkp, extflags, LK_SHARE_NONZERO, &contested, &waitstart);
331 lkp->lk_flags &= ~LK_WANT_UPGRADE;
332
333 if (error) {
334 if ((lkp->lk_flags & ( LK_WANT_EXCL | LK_WAIT_NONZERO)) == (LK_WANT_EXCL | LK_WAIT_NONZERO))
335 wakeup((void *)lkp);
336 break;
337 }
338 if (lkp->lk_exclusivecount != 0)
339 panic("lockmgr: non-zero exclusive count");
340 lkp->lk_flags |= LK_HAVE_EXCL;
341 lkp->lk_lockholder = thr;
342 lkp->lk_exclusivecount = 1;
343 COUNT(td, 1);
344 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line);
345 #if defined(DEBUG_LOCKS)
346 stack_save(&lkp->lk_stack);
347 #endif
348 break;
349 }
350 /*
351 * Someone else has requested upgrade. Release our shared
352 * lock, awaken upgrade requestor if we are the last shared
353 * lock, then request an exclusive lock.
354 */
355 if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) ==
356 LK_WAIT_NONZERO)
357 wakeup((void *)lkp);
358 /* FALLTHROUGH exclusive request */
359
360 case LK_EXCLUSIVE:
361 if (lkp->lk_lockholder == thr && thr != LK_KERNPROC) {
362 /*
363 * Recursive lock.
364 */
365 if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0)
366 panic("lockmgr: locking against myself");
367 if ((extflags & LK_CANRECURSE) != 0) {
368 lkp->lk_exclusivecount++;
369 COUNT(td, 1);
370 break;
371 }
372 }
373 /*
374 * If we are just polling, check to see if we will sleep.
375 */
376 if ((extflags & LK_NOWAIT) &&
377 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO))) {
378 error = EBUSY;
379 break;
380 }
381 /*
382 * Try to acquire the want_exclusive flag.
383 */
384 error = acquire(&lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL), &contested, &waitstart);
385 if (error)
386 break;
387 lkp->lk_flags |= LK_WANT_EXCL;
388 /*
389 * Wait for shared locks and upgrades to finish.
390 */
391 error = acquire(&lkp, extflags, LK_HAVE_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO, &contested, &waitstart);
392 lkp->lk_flags &= ~LK_WANT_EXCL;
393 if (error) {
394 if (lkp->lk_flags & LK_WAIT_NONZERO)
395 wakeup((void *)lkp);
396 break;
397 }
398 lkp->lk_flags |= LK_HAVE_EXCL;
399 lkp->lk_lockholder = thr;
400 if (lkp->lk_exclusivecount != 0)
401 panic("lockmgr: non-zero exclusive count");
402 lkp->lk_exclusivecount = 1;
403 COUNT(td, 1);
404 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line);
405 #if defined(DEBUG_LOCKS)
406 stack_save(&lkp->lk_stack);
407 #endif
408 break;
409
410 case LK_RELEASE:
411 if (lkp->lk_exclusivecount != 0) {
412 if (lkp->lk_lockholder != thr &&
413 lkp->lk_lockholder != LK_KERNPROC) {
414 panic("lockmgr: thread %p, not %s %p unlocking",
415 thr, "exclusive lock holder",
416 lkp->lk_lockholder);
417 }
418 if (lkp->lk_lockholder != LK_KERNPROC)
419 COUNT(td, -1);
420 if (lkp->lk_exclusivecount == 1) {
421 lkp->lk_flags &= ~LK_HAVE_EXCL;
422 lkp->lk_lockholder = LK_NOPROC;
423 lkp->lk_exclusivecount = 0;
424 lock_profile_release_lock(&lkp->lk_object);
425 } else {
426 lkp->lk_exclusivecount--;
427 }
428 } else if (lkp->lk_flags & LK_SHARE_NONZERO)
429 shareunlock(td, lkp, 1);
430 else {
431 printf("lockmgr: thread %p unlocking unheld lock\n",
432 thr);
433 kdb_backtrace();
434 }
435
436 if (lkp->lk_flags & LK_WAIT_NONZERO)
437 wakeup((void *)lkp);
438 break;
439
440 case LK_DRAIN:
441 /*
442 * Check that we do not already hold the lock, as it can
443 * never drain if we do. Unfortunately, we have no way to
444 * check for holding a shared lock, but at least we can
445 * check for an exclusive one.
446 */
447 if (lkp->lk_lockholder == thr)
448 panic("lockmgr: draining against myself");
449
450 error = acquiredrain(lkp, extflags);
451 if (error)
452 break;
453 lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL;
454 lkp->lk_lockholder = thr;
455 lkp->lk_exclusivecount = 1;
456 COUNT(td, 1);
457 #if defined(DEBUG_LOCKS)
458 stack_save(&lkp->lk_stack);
459 #endif
460 break;
461
462 default:
463 mtx_unlock(lkp->lk_interlock);
464 panic("lockmgr: unknown locktype request %d",
465 flags & LK_TYPE_MASK);
466 /* NOTREACHED */
467 }
468 if ((lkp->lk_flags & LK_WAITDRAIN) &&
469 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE |
470 LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) {
471 lkp->lk_flags &= ~LK_WAITDRAIN;
472 wakeup((void *)&lkp->lk_flags);
473 }
474 mtx_unlock(lkp->lk_interlock);
475 return (error);
476 }
477
478 static int
479 acquiredrain(struct lock *lkp, int extflags) {
480 int error;
481
482 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) {
483 return EBUSY;
484 }
485 while (lkp->lk_flags & LK_ALL) {
486 lkp->lk_flags |= LK_WAITDRAIN;
487 error = msleep(&lkp->lk_flags, lkp->lk_interlock, lkp->lk_prio,
488 lkp->lk_wmesg,
489 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
490 if (error)
491 return error;
492 if (extflags & LK_SLEEPFAIL) {
493 return ENOLCK;
494 }
495 }
496 return 0;
497 }
498
499 /*
500 * Transfer any waiting processes from one lock to another.
501 */
502 void
503 transferlockers(from, to)
504 struct lock *from;
505 struct lock *to;
506 {
507
508 KASSERT(from != to, ("lock transfer to self"));
509 KASSERT((from->lk_flags&LK_WAITDRAIN) == 0, ("transfer draining lock"));
510
511 mtx_lock(from->lk_interlock);
512 if (from->lk_waitcount == 0) {
513 mtx_unlock(from->lk_interlock);
514 return;
515 }
516 from->lk_newlock = to;
517 wakeup((void *)from);
518 msleep(&from->lk_newlock, from->lk_interlock, from->lk_prio,
519 "lkxfer", 0);
520 from->lk_newlock = NULL;
521 from->lk_flags &= ~(LK_WANT_EXCL | LK_WANT_UPGRADE);
522 KASSERT(from->lk_waitcount == 0, ("active lock"));
523 mtx_unlock(from->lk_interlock);
524 }
525
526
527 /*
528 * Initialize a lock; required before use.
529 */
530 void
531 lockinit(lkp, prio, wmesg, timo, flags)
532 struct lock *lkp;
533 int prio;
534 const char *wmesg;
535 int timo;
536 int flags;
537 {
538 CTR5(KTR_LOCK, "lockinit(): lkp == %p, prio == %d, wmesg == \"%s\", "
539 "timo == %d, flags = 0x%x\n", lkp, prio, wmesg, timo, flags);
540
541 lkp->lk_interlock = mtx_pool_alloc(mtxpool_lockbuilder);
542 lkp->lk_flags = (flags & LK_EXTFLG_MASK);
543 lkp->lk_sharecount = 0;
544 lkp->lk_waitcount = 0;
545 lkp->lk_exclusivecount = 0;
546 lkp->lk_prio = prio;
547 lkp->lk_timo = timo;
548 lkp->lk_lockholder = LK_NOPROC;
549 lkp->lk_newlock = NULL;
550 #ifdef DEBUG_LOCKS
551 stack_zero(&lkp->lk_stack);
552 #endif
553 lock_init(&lkp->lk_object, &lock_class_lockmgr, wmesg, NULL,
554 LO_RECURSABLE | LO_SLEEPABLE | LO_UPGRADABLE);
555 }
556
557 /*
558 * Destroy a lock.
559 */
560 void
561 lockdestroy(lkp)
562 struct lock *lkp;
563 {
564
565 CTR2(KTR_LOCK, "lockdestroy(): lkp == %p (lk_wmesg == \"%s\")",
566 lkp, lkp->lk_wmesg);
567 lock_destroy(&lkp->lk_object);
568 }
569
570 /*
571 * Determine the status of a lock.
572 */
573 int
574 lockstatus(lkp, td)
575 struct lock *lkp;
576 struct thread *td;
577 {
578 int lock_type = 0;
579 int interlocked;
580
581 if (!kdb_active) {
582 interlocked = 1;
583 mtx_lock(lkp->lk_interlock);
584 } else
585 interlocked = 0;
586 if (lkp->lk_exclusivecount != 0) {
587 if (td == NULL || lkp->lk_lockholder == td)
588 lock_type = LK_EXCLUSIVE;
589 else
590 lock_type = LK_EXCLOTHER;
591 } else if (lkp->lk_sharecount != 0)
592 lock_type = LK_SHARED;
593 if (interlocked)
594 mtx_unlock(lkp->lk_interlock);
595 return (lock_type);
596 }
597
598 /*
599 * Determine the number of holders of a lock.
600 */
601 int
602 lockcount(lkp)
603 struct lock *lkp;
604 {
605 int count;
606
607 mtx_lock(lkp->lk_interlock);
608 count = lkp->lk_exclusivecount + lkp->lk_sharecount;
609 mtx_unlock(lkp->lk_interlock);
610 return (count);
611 }
612
613 /*
614 * Determine the number of waiters on a lock.
615 */
616 int
617 lockwaiters(lkp)
618 struct lock *lkp;
619 {
620 int count;
621
622 mtx_lock(lkp->lk_interlock);
623 count = lkp->lk_waitcount;
624 mtx_unlock(lkp->lk_interlock);
625 return (count);
626 }
627
628 /*
629 * Print out information about state of a lock. Used by VOP_PRINT
630 * routines to display status about contained locks.
631 */
632 void
633 lockmgr_printinfo(lkp)
634 struct lock *lkp;
635 {
636
637 if (lkp->lk_sharecount)
638 printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
639 lkp->lk_sharecount);
640 else if (lkp->lk_flags & LK_HAVE_EXCL)
641 printf(" lock type %s: EXCL (count %d) by thread %p (pid %d)",
642 lkp->lk_wmesg, lkp->lk_exclusivecount,
643 lkp->lk_lockholder, lkp->lk_lockholder->td_proc->p_pid);
644 if (lkp->lk_waitcount > 0)
645 printf(" with %d pending", lkp->lk_waitcount);
646 #ifdef DEBUG_LOCKS
647 stack_print_ddb(&lkp->lk_stack);
648 #endif
649 }
650
651 #ifdef DDB
652 /*
653 * Check to see if a thread that is blocked on a sleep queue is actually
654 * blocked on a 'struct lock'. If so, output some details and return true.
655 * If the lock has an exclusive owner, return that in *ownerp.
656 */
657 int
658 lockmgr_chain(struct thread *td, struct thread **ownerp)
659 {
660 struct lock *lkp;
661
662 lkp = td->td_wchan;
663
664 /* Simple test to see if wchan points to a lockmgr lock. */
665 if (LOCK_CLASS(&lkp->lk_object) == &lock_class_lockmgr &&
666 lkp->lk_wmesg == td->td_wmesg)
667 goto ok;
668
669 /*
670 * If this thread is doing a DRAIN, then it would be asleep on
671 * &lkp->lk_flags rather than lkp.
672 */
673 lkp = (struct lock *)((char *)td->td_wchan -
674 offsetof(struct lock, lk_flags));
675 if (LOCK_CLASS(&lkp->lk_object) == &lock_class_lockmgr &&
676 lkp->lk_wmesg == td->td_wmesg && (lkp->lk_flags & LK_WAITDRAIN))
677 goto ok;
678
679 /* Doen't seem to be a lockmgr lock. */
680 return (0);
681
682 ok:
683 /* Ok, we think we have a lockmgr lock, so output some details. */
684 db_printf("blocked on lk \"%s\" ", lkp->lk_wmesg);
685 if (lkp->lk_sharecount) {
686 db_printf("SHARED (count %d)\n", lkp->lk_sharecount);
687 *ownerp = NULL;
688 } else {
689 db_printf("EXCL (count %d)\n", lkp->lk_exclusivecount);
690 *ownerp = lkp->lk_lockholder;
691 }
692 return (1);
693 }
694
695 void
696 db_show_lockmgr(struct lock_object *lock)
697 {
698 struct thread *td;
699 struct lock *lkp;
700
701 lkp = (struct lock *)lock;
702
703 db_printf(" lock type: %s\n", lkp->lk_wmesg);
704 db_printf(" state: ");
705 if (lkp->lk_sharecount)
706 db_printf("SHARED (count %d)\n", lkp->lk_sharecount);
707 else if (lkp->lk_flags & LK_HAVE_EXCL) {
708 td = lkp->lk_lockholder;
709 db_printf("EXCL (count %d) %p ", lkp->lk_exclusivecount, td);
710 db_printf("(tid %d, pid %d, \"%s\")\n", td->td_tid,
711 td->td_proc->p_pid, td->td_proc->p_comm);
712 } else
713 db_printf("UNLOCKED\n");
714 if (lkp->lk_waitcount > 0)
715 db_printf(" waiters: %d\n", lkp->lk_waitcount);
716 }
717 #endif
Cache object: e3aeca2bc720fd9868ef012523037a93
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