FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_mutex.c
1 /*-
2 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. Berkeley Software Design Inc's name may not be used to endorse or
13 * promote products derived from this software without specific prior
14 * written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
29 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
30 */
31
32 /*
33 * Machine independent bits of mutex implementation.
34 */
35
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
38
39 #include "opt_adaptive_mutexes.h"
40 #include "opt_ddb.h"
41 #include "opt_global.h"
42 #include "opt_sched.h"
43
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/bus.h>
47 #include <sys/conf.h>
48 #include <sys/kdb.h>
49 #include <sys/kernel.h>
50 #include <sys/ktr.h>
51 #include <sys/lock.h>
52 #include <sys/malloc.h>
53 #include <sys/mutex.h>
54 #include <sys/proc.h>
55 #include <sys/resourcevar.h>
56 #include <sys/sched.h>
57 #include <sys/sbuf.h>
58 #include <sys/sysctl.h>
59 #include <sys/turnstile.h>
60 #include <sys/vmmeter.h>
61 #include <sys/lock_profile.h>
62
63 #include <machine/atomic.h>
64 #include <machine/bus.h>
65 #include <machine/cpu.h>
66
67 #include <ddb/ddb.h>
68
69 #include <fs/devfs/devfs_int.h>
70
71 #include <vm/vm.h>
72 #include <vm/vm_extern.h>
73
74 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
75 #define ADAPTIVE_MUTEXES
76 #endif
77
78 /*
79 * Internal utility macros.
80 */
81 #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
82
83 #define mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED)
84
85 #define mtx_owner(m) ((struct thread *)((m)->mtx_lock & ~MTX_FLAGMASK))
86
87 #ifdef DDB
88 static void db_show_mtx(struct lock_object *lock);
89 #endif
90 static void lock_mtx(struct lock_object *lock, int how);
91 static void lock_spin(struct lock_object *lock, int how);
92 static int unlock_mtx(struct lock_object *lock);
93 static int unlock_spin(struct lock_object *lock);
94
95 /*
96 * Lock classes for sleep and spin mutexes.
97 */
98 struct lock_class lock_class_mtx_sleep = {
99 .lc_name = "sleep mutex",
100 .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE,
101 #ifdef DDB
102 .lc_ddb_show = db_show_mtx,
103 #endif
104 .lc_lock = lock_mtx,
105 .lc_unlock = unlock_mtx,
106 };
107 struct lock_class lock_class_mtx_spin = {
108 .lc_name = "spin mutex",
109 .lc_flags = LC_SPINLOCK | LC_RECURSABLE,
110 #ifdef DDB
111 .lc_ddb_show = db_show_mtx,
112 #endif
113 .lc_lock = lock_spin,
114 .lc_unlock = unlock_spin,
115 };
116
117 /*
118 * System-wide mutexes
119 */
120 struct mtx blocked_lock;
121 struct mtx Giant;
122
123 #ifdef LOCK_PROFILING
124 static inline void lock_profile_init(void)
125 {
126 int i;
127 /* Initialize the mutex profiling locks */
128 for (i = 0; i < LPROF_LOCK_SIZE; i++) {
129 mtx_init(&lprof_locks[i], "mprof lock",
130 NULL, MTX_SPIN|MTX_QUIET|MTX_NOPROFILE);
131 }
132 }
133 #else
134 static inline void lock_profile_init(void) {;}
135 #endif
136
137 void
138 lock_mtx(struct lock_object *lock, int how)
139 {
140
141 mtx_lock((struct mtx *)lock);
142 }
143
144 void
145 lock_spin(struct lock_object *lock, int how)
146 {
147
148 panic("spin locks can only use msleep_spin");
149 }
150
151 int
152 unlock_mtx(struct lock_object *lock)
153 {
154 struct mtx *m;
155
156 m = (struct mtx *)lock;
157 mtx_assert(m, MA_OWNED | MA_NOTRECURSED);
158 mtx_unlock(m);
159 return (0);
160 }
161
162 int
163 unlock_spin(struct lock_object *lock)
164 {
165
166 panic("spin locks can only use msleep_spin");
167 }
168
169 /*
170 * Function versions of the inlined __mtx_* macros. These are used by
171 * modules and can also be called from assembly language if needed.
172 */
173 void
174 _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line)
175 {
176
177 MPASS(curthread != NULL);
178 KASSERT(m->mtx_lock != MTX_DESTROYED,
179 ("mtx_lock() of destroyed mutex @ %s:%d", file, line));
180 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
181 ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
182 file, line));
183 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
184 file, line);
185
186 _get_sleep_lock(m, curthread, opts, file, line);
187 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
188 line);
189 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
190 curthread->td_locks++;
191 }
192
193 void
194 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line)
195 {
196 MPASS(curthread != NULL);
197 KASSERT(m->mtx_lock != MTX_DESTROYED,
198 ("mtx_unlock() of destroyed mutex @ %s:%d", file, line));
199 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
200 ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
201 file, line));
202 curthread->td_locks--;
203 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
204 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
205 line);
206 mtx_assert(m, MA_OWNED);
207
208 if (m->mtx_recurse == 0)
209 lock_profile_release_lock(&m->lock_object);
210 _rel_sleep_lock(m, curthread, opts, file, line);
211 }
212
213 void
214 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line)
215 {
216
217 MPASS(curthread != NULL);
218 KASSERT(m->mtx_lock != MTX_DESTROYED,
219 ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line));
220 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
221 ("mtx_lock_spin() of sleep mutex %s @ %s:%d",
222 m->lock_object.lo_name, file, line));
223 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
224 file, line);
225 _get_spin_lock(m, curthread, opts, file, line);
226 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
227 line);
228 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
229 }
230
231 void
232 _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line)
233 {
234
235 MPASS(curthread != NULL);
236 KASSERT(m->mtx_lock != MTX_DESTROYED,
237 ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line));
238 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
239 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d",
240 m->lock_object.lo_name, file, line));
241 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
242 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
243 line);
244 mtx_assert(m, MA_OWNED);
245
246 _rel_spin_lock(m);
247 }
248
249 /*
250 * The important part of mtx_trylock{,_flags}()
251 * Tries to acquire lock `m.' If this function is called on a mutex that
252 * is already owned, it will recursively acquire the lock.
253 */
254 int
255 _mtx_trylock(struct mtx *m, int opts, const char *file, int line)
256 {
257 int rval, contested = 0;
258 uint64_t waittime = 0;
259
260 MPASS(curthread != NULL);
261 KASSERT(m->mtx_lock != MTX_DESTROYED,
262 ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
263 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
264 ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
265 file, line));
266
267 if (mtx_owned(m) && (m->lock_object.lo_flags & LO_RECURSABLE) != 0) {
268 m->mtx_recurse++;
269 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
270 rval = 1;
271 } else
272 rval = _obtain_lock(m, (uintptr_t)curthread);
273
274 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line);
275 if (rval) {
276 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
277 file, line);
278 curthread->td_locks++;
279 if (m->mtx_recurse == 0)
280 lock_profile_obtain_lock_success(&m->lock_object, contested,
281 waittime, file, line);
282
283 }
284
285 return (rval);
286 }
287
288 /*
289 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
290 *
291 * We call this if the lock is either contested (i.e. we need to go to
292 * sleep waiting for it), or if we need to recurse on it.
293 */
294 void
295 _mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file,
296 int line)
297 {
298 struct turnstile *ts;
299 #ifdef ADAPTIVE_MUTEXES
300 volatile struct thread *owner;
301 #endif
302 #ifdef KTR
303 int cont_logged = 0;
304 #endif
305 int contested = 0;
306 uint64_t waittime = 0;
307 uintptr_t v;
308
309 if (mtx_owned(m)) {
310 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
311 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
312 m->lock_object.lo_name, file, line));
313 m->mtx_recurse++;
314 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
315 if (LOCK_LOG_TEST(&m->lock_object, opts))
316 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
317 return;
318 }
319
320 lock_profile_obtain_lock_failed(&m->lock_object,
321 &contested, &waittime);
322 if (LOCK_LOG_TEST(&m->lock_object, opts))
323 CTR4(KTR_LOCK,
324 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
325 m->lock_object.lo_name, (void *)m->mtx_lock, file, line);
326
327 while (!_obtain_lock(m, tid)) {
328 #ifdef ADAPTIVE_MUTEXES
329 /*
330 * If the owner is running on another CPU, spin until the
331 * owner stops running or the state of the lock changes.
332 */
333 v = m->mtx_lock;
334 if (v != MTX_UNOWNED) {
335 owner = (struct thread *)(v & ~MTX_FLAGMASK);
336 #ifdef ADAPTIVE_GIANT
337 if (TD_IS_RUNNING(owner)) {
338 #else
339 if (m != &Giant && TD_IS_RUNNING(owner)) {
340 #endif
341 if (LOCK_LOG_TEST(&m->lock_object, 0))
342 CTR3(KTR_LOCK,
343 "%s: spinning on %p held by %p",
344 __func__, m, owner);
345 while (mtx_owner(m) == owner &&
346 TD_IS_RUNNING(owner))
347 cpu_spinwait();
348 continue;
349 }
350 }
351 #endif
352
353 ts = turnstile_trywait(&m->lock_object);
354 v = m->mtx_lock;
355
356 /*
357 * Check if the lock has been released while spinning for
358 * the turnstile chain lock.
359 */
360 if (v == MTX_UNOWNED) {
361 turnstile_cancel(ts);
362 cpu_spinwait();
363 continue;
364 }
365
366 MPASS(v != MTX_CONTESTED);
367
368 #ifdef ADAPTIVE_MUTEXES
369 /*
370 * If the current owner of the lock is executing on another
371 * CPU quit the hard path and try to spin.
372 */
373 owner = (struct thread *)(v & ~MTX_FLAGMASK);
374 #ifdef ADAPTIVE_GIANT
375 if (TD_IS_RUNNING(owner)) {
376 #else
377 if (m != &Giant && TD_IS_RUNNING(owner)) {
378 #endif
379 turnstile_cancel(ts);
380 cpu_spinwait();
381 continue;
382 }
383 #endif
384
385 /*
386 * If the mutex isn't already contested and a failure occurs
387 * setting the contested bit, the mutex was either released
388 * or the state of the MTX_RECURSED bit changed.
389 */
390 if ((v & MTX_CONTESTED) == 0 &&
391 !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) {
392 turnstile_cancel(ts);
393 cpu_spinwait();
394 continue;
395 }
396
397 /*
398 * We definitely must sleep for this lock.
399 */
400 mtx_assert(m, MA_NOTOWNED);
401
402 #ifdef KTR
403 if (!cont_logged) {
404 CTR6(KTR_CONTENTION,
405 "contention: %p at %s:%d wants %s, taken by %s:%d",
406 (void *)tid, file, line, m->lock_object.lo_name,
407 WITNESS_FILE(&m->lock_object),
408 WITNESS_LINE(&m->lock_object));
409 cont_logged = 1;
410 }
411 #endif
412
413 /*
414 * Block on the turnstile.
415 */
416 turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE);
417 }
418 #ifdef KTR
419 if (cont_logged) {
420 CTR4(KTR_CONTENTION,
421 "contention end: %s acquired by %p at %s:%d",
422 m->lock_object.lo_name, (void *)tid, file, line);
423 }
424 #endif
425 lock_profile_obtain_lock_success(&m->lock_object, contested,
426 waittime, (file), (line));
427 }
428
429 static void
430 _mtx_lock_spin_failed(struct mtx *m)
431 {
432 struct thread *td;
433
434 td = mtx_owner(m);
435
436 /* If the mutex is unlocked, try again. */
437 if (td == NULL)
438 return;
439
440 printf( "spin lock %p (%s) held by %p (tid %d) too long\n",
441 m, m->lock_object.lo_name, td, td->td_tid);
442 #ifdef WITNESS
443 witness_display_spinlock(&m->lock_object, td);
444 #endif
445 panic("spin lock held too long");
446 }
447
448 #ifdef SMP
449 /*
450 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock.
451 *
452 * This is only called if we need to actually spin for the lock. Recursion
453 * is handled inline.
454 */
455 void
456 _mtx_lock_spin(struct mtx *m, uintptr_t tid, int opts, const char *file,
457 int line)
458 {
459 int i = 0, contested = 0;
460 uint64_t waittime = 0;
461
462 if (LOCK_LOG_TEST(&m->lock_object, opts))
463 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
464
465 lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime);
466 while (!_obtain_lock(m, tid)) {
467
468 /* Give interrupts a chance while we spin. */
469 spinlock_exit();
470 while (m->mtx_lock != MTX_UNOWNED) {
471 if (i++ < 10000000) {
472 cpu_spinwait();
473 continue;
474 }
475 if (i < 60000000 || kdb_active || panicstr != NULL)
476 DELAY(1);
477 else
478 _mtx_lock_spin_failed(m);
479 cpu_spinwait();
480 }
481 spinlock_enter();
482 }
483
484 if (LOCK_LOG_TEST(&m->lock_object, opts))
485 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
486
487 lock_profile_obtain_lock_success(&m->lock_object, contested,
488 waittime, (file), (line));
489 }
490 #endif /* SMP */
491
492 void
493 _thread_lock_flags(struct thread *td, int opts, const char *file, int line)
494 {
495 struct mtx *m;
496 uintptr_t tid;
497 int i, contested;
498 uint64_t waittime;
499
500
501 contested = i = 0;
502 waittime = 0;
503 tid = (uintptr_t)curthread;
504 for (;;) {
505 retry:
506 spinlock_enter();
507 m = td->td_lock;
508 WITNESS_CHECKORDER(&m->lock_object,
509 opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line);
510 while (!_obtain_lock(m, tid)) {
511 if (m->mtx_lock == tid) {
512 m->mtx_recurse++;
513 break;
514 }
515 lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime);
516 /* Give interrupts a chance while we spin. */
517 spinlock_exit();
518 while (m->mtx_lock != MTX_UNOWNED) {
519 if (i++ < 10000000)
520 cpu_spinwait();
521 else if (i < 60000000 ||
522 kdb_active || panicstr != NULL)
523 DELAY(1);
524 else
525 _mtx_lock_spin_failed(m);
526 cpu_spinwait();
527 if (m != td->td_lock)
528 goto retry;
529 }
530 spinlock_enter();
531 }
532 if (m == td->td_lock)
533 break;
534 _rel_spin_lock(m); /* does spinlock_exit() */
535 }
536 lock_profile_obtain_lock_success(&m->lock_object, contested,
537 waittime, (file), (line));
538 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
539 }
540
541 struct mtx *
542 thread_lock_block(struct thread *td)
543 {
544 struct mtx *lock;
545
546 spinlock_enter();
547 THREAD_LOCK_ASSERT(td, MA_OWNED);
548 lock = td->td_lock;
549 td->td_lock = &blocked_lock;
550 mtx_unlock_spin(lock);
551
552 return (lock);
553 }
554
555 void
556 thread_lock_unblock(struct thread *td, struct mtx *new)
557 {
558 mtx_assert(new, MA_OWNED);
559 MPASS(td->td_lock == &blocked_lock);
560 atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new);
561 spinlock_exit();
562 }
563
564 void
565 thread_lock_set(struct thread *td, struct mtx *new)
566 {
567 struct mtx *lock;
568
569 mtx_assert(new, MA_OWNED);
570 THREAD_LOCK_ASSERT(td, MA_OWNED);
571 lock = td->td_lock;
572 td->td_lock = new;
573 mtx_unlock_spin(lock);
574 }
575
576 /*
577 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
578 *
579 * We are only called here if the lock is recursed or contested (i.e. we
580 * need to wake up a blocked thread).
581 */
582 void
583 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line)
584 {
585 struct turnstile *ts;
586
587 if (mtx_recursed(m)) {
588 if (--(m->mtx_recurse) == 0)
589 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
590 if (LOCK_LOG_TEST(&m->lock_object, opts))
591 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
592 return;
593 }
594
595 /*
596 * We have to lock the chain before the turnstile so this turnstile
597 * can be removed from the hash list if it is empty.
598 */
599 turnstile_chain_lock(&m->lock_object);
600 ts = turnstile_lookup(&m->lock_object);
601 if (LOCK_LOG_TEST(&m->lock_object, opts))
602 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);
603
604 MPASS(ts != NULL);
605 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
606 _release_lock_quick(m);
607 /*
608 * This turnstile is now no longer associated with the mutex. We can
609 * unlock the chain lock so a new turnstile may take it's place.
610 */
611 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
612 turnstile_chain_unlock(&m->lock_object);
613 }
614
615 /*
616 * All the unlocking of MTX_SPIN locks is done inline.
617 * See the _rel_spin_lock() macro for the details.
618 */
619
620 /*
621 * The backing function for the INVARIANTS-enabled mtx_assert()
622 */
623 #ifdef INVARIANT_SUPPORT
624 void
625 _mtx_assert(struct mtx *m, int what, const char *file, int line)
626 {
627
628 if (panicstr != NULL || dumping)
629 return;
630 switch (what) {
631 case MA_OWNED:
632 case MA_OWNED | MA_RECURSED:
633 case MA_OWNED | MA_NOTRECURSED:
634 if (!mtx_owned(m))
635 panic("mutex %s not owned at %s:%d",
636 m->lock_object.lo_name, file, line);
637 if (mtx_recursed(m)) {
638 if ((what & MA_NOTRECURSED) != 0)
639 panic("mutex %s recursed at %s:%d",
640 m->lock_object.lo_name, file, line);
641 } else if ((what & MA_RECURSED) != 0) {
642 panic("mutex %s unrecursed at %s:%d",
643 m->lock_object.lo_name, file, line);
644 }
645 break;
646 case MA_NOTOWNED:
647 if (mtx_owned(m))
648 panic("mutex %s owned at %s:%d",
649 m->lock_object.lo_name, file, line);
650 break;
651 default:
652 panic("unknown mtx_assert at %s:%d", file, line);
653 }
654 }
655 #endif
656
657 /*
658 * The MUTEX_DEBUG-enabled mtx_validate()
659 *
660 * Most of these checks have been moved off into the LO_INITIALIZED flag
661 * maintained by the witness code.
662 */
663 #ifdef MUTEX_DEBUG
664
665 void mtx_validate(struct mtx *);
666
667 void
668 mtx_validate(struct mtx *m)
669 {
670
671 /*
672 * XXX: When kernacc() does not require Giant we can reenable this check
673 */
674 #ifdef notyet
675 /*
676 * Can't call kernacc() from early init386(), especially when
677 * initializing Giant mutex, because some stuff in kernacc()
678 * requires Giant itself.
679 */
680 if (!cold)
681 if (!kernacc((caddr_t)m, sizeof(m),
682 VM_PROT_READ | VM_PROT_WRITE))
683 panic("Can't read and write to mutex %p", m);
684 #endif
685 }
686 #endif
687
688 /*
689 * General init routine used by the MTX_SYSINIT() macro.
690 */
691 void
692 mtx_sysinit(void *arg)
693 {
694 struct mtx_args *margs = arg;
695
696 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts);
697 }
698
699 /*
700 * Mutex initialization routine; initialize lock `m' of type contained in
701 * `opts' with options contained in `opts' and name `name.' The optional
702 * lock type `type' is used as a general lock category name for use with
703 * witness.
704 */
705 void
706 mtx_init(struct mtx *m, const char *name, const char *type, int opts)
707 {
708 struct lock_class *class;
709 int flags;
710
711 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
712 MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0);
713
714 #ifdef MUTEX_DEBUG
715 /* Diagnostic and error correction */
716 mtx_validate(m);
717 #endif
718
719 /* Determine lock class and lock flags. */
720 if (opts & MTX_SPIN)
721 class = &lock_class_mtx_spin;
722 else
723 class = &lock_class_mtx_sleep;
724 flags = 0;
725 if (opts & MTX_QUIET)
726 flags |= LO_QUIET;
727 if (opts & MTX_RECURSE)
728 flags |= LO_RECURSABLE;
729 if ((opts & MTX_NOWITNESS) == 0)
730 flags |= LO_WITNESS;
731 if (opts & MTX_DUPOK)
732 flags |= LO_DUPOK;
733 if (opts & MTX_NOPROFILE)
734 flags |= LO_NOPROFILE;
735
736 /* Initialize mutex. */
737 m->mtx_lock = MTX_UNOWNED;
738 m->mtx_recurse = 0;
739
740 lock_init(&m->lock_object, class, name, type, flags);
741 }
742
743 /*
744 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be
745 * passed in as a flag here because if the corresponding mtx_init() was
746 * called with MTX_QUIET set, then it will already be set in the mutex's
747 * flags.
748 */
749 void
750 mtx_destroy(struct mtx *m)
751 {
752
753 if (!mtx_owned(m))
754 MPASS(mtx_unowned(m));
755 else {
756 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);
757
758 /* Perform the non-mtx related part of mtx_unlock_spin(). */
759 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin)
760 spinlock_exit();
761 else
762 curthread->td_locks--;
763
764 /* Tell witness this isn't locked to make it happy. */
765 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__,
766 __LINE__);
767 }
768
769 m->mtx_lock = MTX_DESTROYED;
770 lock_destroy(&m->lock_object);
771 }
772
773 /*
774 * Intialize the mutex code and system mutexes. This is called from the MD
775 * startup code prior to mi_startup(). The per-CPU data space needs to be
776 * setup before this is called.
777 */
778 void
779 mutex_init(void)
780 {
781
782 /* Setup turnstiles so that sleep mutexes work. */
783 init_turnstiles();
784
785 /*
786 * Initialize mutexes.
787 */
788 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE);
789 mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN);
790 blocked_lock.mtx_lock = 0xdeadc0de; /* Always blocked. */
791 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK);
792 mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN | MTX_RECURSE);
793 mtx_init(&devmtx, "cdev", NULL, MTX_DEF);
794 mtx_lock(&Giant);
795
796 lock_profile_init();
797 }
798
799 #ifdef DDB
800 void
801 db_show_mtx(struct lock_object *lock)
802 {
803 struct thread *td;
804 struct mtx *m;
805
806 m = (struct mtx *)lock;
807
808 db_printf(" flags: {");
809 if (LOCK_CLASS(lock) == &lock_class_mtx_spin)
810 db_printf("SPIN");
811 else
812 db_printf("DEF");
813 if (m->lock_object.lo_flags & LO_RECURSABLE)
814 db_printf(", RECURSE");
815 if (m->lock_object.lo_flags & LO_DUPOK)
816 db_printf(", DUPOK");
817 db_printf("}\n");
818 db_printf(" state: {");
819 if (mtx_unowned(m))
820 db_printf("UNOWNED");
821 else if (mtx_destroyed(m))
822 db_printf("DESTROYED");
823 else {
824 db_printf("OWNED");
825 if (m->mtx_lock & MTX_CONTESTED)
826 db_printf(", CONTESTED");
827 if (m->mtx_lock & MTX_RECURSED)
828 db_printf(", RECURSED");
829 }
830 db_printf("}\n");
831 if (!mtx_unowned(m) && !mtx_destroyed(m)) {
832 td = mtx_owner(m);
833 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td,
834 td->td_tid, td->td_proc->p_pid, td->td_proc->p_comm);
835 if (mtx_recursed(m))
836 db_printf(" recursed: %d\n", m->mtx_recurse);
837 }
838 }
839 #endif
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