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: releng/8.2/sys/kern/kern_mutex.c 208261 2010-05-18 10:24:23Z attilio $");
38
39 #include "opt_adaptive_mutexes.h"
40 #include "opt_ddb.h"
41 #include "opt_global.h"
42 #include "opt_kdtrace.h"
43 #include "opt_sched.h"
44
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/bus.h>
48 #include <sys/conf.h>
49 #include <sys/kdb.h>
50 #include <sys/kernel.h>
51 #include <sys/ktr.h>
52 #include <sys/lock.h>
53 #include <sys/malloc.h>
54 #include <sys/mutex.h>
55 #include <sys/proc.h>
56 #include <sys/resourcevar.h>
57 #include <sys/sched.h>
58 #include <sys/sbuf.h>
59 #include <sys/sysctl.h>
60 #include <sys/turnstile.h>
61 #include <sys/vmmeter.h>
62 #include <sys/lock_profile.h>
63
64 #include <machine/atomic.h>
65 #include <machine/bus.h>
66 #include <machine/cpu.h>
67
68 #include <ddb/ddb.h>
69
70 #include <fs/devfs/devfs_int.h>
71
72 #include <vm/vm.h>
73 #include <vm/vm_extern.h>
74
75 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
76 #define ADAPTIVE_MUTEXES
77 #endif
78
79 /*
80 * Internal utility macros.
81 */
82 #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
83
84 #define mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED)
85
86 #define mtx_owner(m) ((struct thread *)((m)->mtx_lock & ~MTX_FLAGMASK))
87
88 static void assert_mtx(struct lock_object *lock, int what);
89 #ifdef DDB
90 static void db_show_mtx(struct lock_object *lock);
91 #endif
92 static void lock_mtx(struct lock_object *lock, int how);
93 static void lock_spin(struct lock_object *lock, int how);
94 #ifdef KDTRACE_HOOKS
95 static int owner_mtx(struct lock_object *lock, struct thread **owner);
96 #endif
97 static int unlock_mtx(struct lock_object *lock);
98 static int unlock_spin(struct lock_object *lock);
99
100 /*
101 * Lock classes for sleep and spin mutexes.
102 */
103 struct lock_class lock_class_mtx_sleep = {
104 .lc_name = "sleep mutex",
105 .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE,
106 .lc_assert = assert_mtx,
107 #ifdef DDB
108 .lc_ddb_show = db_show_mtx,
109 #endif
110 .lc_lock = lock_mtx,
111 .lc_unlock = unlock_mtx,
112 #ifdef KDTRACE_HOOKS
113 .lc_owner = owner_mtx,
114 #endif
115 };
116 struct lock_class lock_class_mtx_spin = {
117 .lc_name = "spin mutex",
118 .lc_flags = LC_SPINLOCK | LC_RECURSABLE,
119 .lc_assert = assert_mtx,
120 #ifdef DDB
121 .lc_ddb_show = db_show_mtx,
122 #endif
123 .lc_lock = lock_spin,
124 .lc_unlock = unlock_spin,
125 #ifdef KDTRACE_HOOKS
126 .lc_owner = owner_mtx,
127 #endif
128 };
129
130 /*
131 * System-wide mutexes
132 */
133 struct mtx blocked_lock;
134 struct mtx Giant;
135
136 void
137 assert_mtx(struct lock_object *lock, int what)
138 {
139
140 mtx_assert((struct mtx *)lock, what);
141 }
142
143 void
144 lock_mtx(struct lock_object *lock, int how)
145 {
146
147 mtx_lock((struct mtx *)lock);
148 }
149
150 void
151 lock_spin(struct lock_object *lock, int how)
152 {
153
154 panic("spin locks can only use msleep_spin");
155 }
156
157 int
158 unlock_mtx(struct lock_object *lock)
159 {
160 struct mtx *m;
161
162 m = (struct mtx *)lock;
163 mtx_assert(m, MA_OWNED | MA_NOTRECURSED);
164 mtx_unlock(m);
165 return (0);
166 }
167
168 int
169 unlock_spin(struct lock_object *lock)
170 {
171
172 panic("spin locks can only use msleep_spin");
173 }
174
175 #ifdef KDTRACE_HOOKS
176 int
177 owner_mtx(struct lock_object *lock, struct thread **owner)
178 {
179 struct mtx *m = (struct mtx *)lock;
180
181 *owner = mtx_owner(m);
182 return (mtx_unowned(m) == 0);
183 }
184 #endif
185
186 /*
187 * Function versions of the inlined __mtx_* macros. These are used by
188 * modules and can also be called from assembly language if needed.
189 */
190 void
191 _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line)
192 {
193
194 MPASS(curthread != NULL);
195 KASSERT(m->mtx_lock != MTX_DESTROYED,
196 ("mtx_lock() of destroyed mutex @ %s:%d", file, line));
197 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
198 ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
199 file, line));
200 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
201 file, line, NULL);
202
203 _get_sleep_lock(m, curthread, opts, file, line);
204 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
205 line);
206 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
207 curthread->td_locks++;
208 }
209
210 void
211 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line)
212 {
213 MPASS(curthread != NULL);
214 KASSERT(m->mtx_lock != MTX_DESTROYED,
215 ("mtx_unlock() of destroyed mutex @ %s:%d", file, line));
216 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
217 ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
218 file, line));
219 curthread->td_locks--;
220 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
221 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
222 line);
223 mtx_assert(m, MA_OWNED);
224
225 if (m->mtx_recurse == 0)
226 LOCKSTAT_PROFILE_RELEASE_LOCK(LS_MTX_UNLOCK_RELEASE, m);
227 _rel_sleep_lock(m, curthread, opts, file, line);
228 }
229
230 void
231 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line)
232 {
233
234 MPASS(curthread != NULL);
235 KASSERT(m->mtx_lock != MTX_DESTROYED,
236 ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line));
237 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
238 ("mtx_lock_spin() of sleep mutex %s @ %s:%d",
239 m->lock_object.lo_name, file, line));
240 if (mtx_owned(m))
241 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
242 ("mtx_lock_spin: recursed on non-recursive mutex %s @ %s:%d\n",
243 m->lock_object.lo_name, file, line));
244 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
245 file, line, NULL);
246 _get_spin_lock(m, curthread, opts, file, line);
247 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
248 line);
249 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
250 }
251
252 void
253 _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line)
254 {
255
256 MPASS(curthread != NULL);
257 KASSERT(m->mtx_lock != MTX_DESTROYED,
258 ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line));
259 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
260 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d",
261 m->lock_object.lo_name, file, line));
262 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
263 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
264 line);
265 mtx_assert(m, MA_OWNED);
266
267 _rel_spin_lock(m);
268 }
269
270 /*
271 * The important part of mtx_trylock{,_flags}()
272 * Tries to acquire lock `m.' If this function is called on a mutex that
273 * is already owned, it will recursively acquire the lock.
274 */
275 int
276 _mtx_trylock(struct mtx *m, int opts, const char *file, int line)
277 {
278 #ifdef LOCK_PROFILING
279 uint64_t waittime = 0;
280 int contested = 0;
281 #endif
282 int rval;
283
284 MPASS(curthread != NULL);
285 KASSERT(m->mtx_lock != MTX_DESTROYED,
286 ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
287 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
288 ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
289 file, line));
290
291 if (mtx_owned(m) && (m->lock_object.lo_flags & LO_RECURSABLE) != 0) {
292 m->mtx_recurse++;
293 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
294 rval = 1;
295 } else
296 rval = _obtain_lock(m, (uintptr_t)curthread);
297
298 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line);
299 if (rval) {
300 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
301 file, line);
302 curthread->td_locks++;
303 if (m->mtx_recurse == 0)
304 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE,
305 m, contested, waittime, file, line);
306
307 }
308
309 return (rval);
310 }
311
312 /*
313 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
314 *
315 * We call this if the lock is either contested (i.e. we need to go to
316 * sleep waiting for it), or if we need to recurse on it.
317 */
318 void
319 _mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file,
320 int line)
321 {
322 struct turnstile *ts;
323 uintptr_t v;
324 #ifdef ADAPTIVE_MUTEXES
325 volatile struct thread *owner;
326 #endif
327 #ifdef KTR
328 int cont_logged = 0;
329 #endif
330 #ifdef LOCK_PROFILING
331 int contested = 0;
332 uint64_t waittime = 0;
333 #endif
334 #ifdef KDTRACE_HOOKS
335 uint64_t spin_cnt = 0;
336 uint64_t sleep_cnt = 0;
337 int64_t sleep_time = 0;
338 #endif
339
340 if (mtx_owned(m)) {
341 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
342 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
343 m->lock_object.lo_name, file, line));
344 m->mtx_recurse++;
345 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
346 if (LOCK_LOG_TEST(&m->lock_object, opts))
347 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
348 return;
349 }
350
351 lock_profile_obtain_lock_failed(&m->lock_object,
352 &contested, &waittime);
353 if (LOCK_LOG_TEST(&m->lock_object, opts))
354 CTR4(KTR_LOCK,
355 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
356 m->lock_object.lo_name, (void *)m->mtx_lock, file, line);
357
358 while (!_obtain_lock(m, tid)) {
359 #ifdef KDTRACE_HOOKS
360 spin_cnt++;
361 #endif
362 #ifdef ADAPTIVE_MUTEXES
363 /*
364 * If the owner is running on another CPU, spin until the
365 * owner stops running or the state of the lock changes.
366 */
367 v = m->mtx_lock;
368 if (v != MTX_UNOWNED) {
369 owner = (struct thread *)(v & ~MTX_FLAGMASK);
370 if (TD_IS_RUNNING(owner)) {
371 if (LOCK_LOG_TEST(&m->lock_object, 0))
372 CTR3(KTR_LOCK,
373 "%s: spinning on %p held by %p",
374 __func__, m, owner);
375 while (mtx_owner(m) == owner &&
376 TD_IS_RUNNING(owner)) {
377 cpu_spinwait();
378 #ifdef KDTRACE_HOOKS
379 spin_cnt++;
380 #endif
381 }
382 continue;
383 }
384 }
385 #endif
386
387 ts = turnstile_trywait(&m->lock_object);
388 v = m->mtx_lock;
389
390 /*
391 * Check if the lock has been released while spinning for
392 * the turnstile chain lock.
393 */
394 if (v == MTX_UNOWNED) {
395 turnstile_cancel(ts);
396 continue;
397 }
398
399 #ifdef ADAPTIVE_MUTEXES
400 /*
401 * The current lock owner might have started executing
402 * on another CPU (or the lock could have changed
403 * owners) while we were waiting on the turnstile
404 * chain lock. If so, drop the turnstile lock and try
405 * again.
406 */
407 owner = (struct thread *)(v & ~MTX_FLAGMASK);
408 if (TD_IS_RUNNING(owner)) {
409 turnstile_cancel(ts);
410 continue;
411 }
412 #endif
413
414 /*
415 * If the mutex isn't already contested and a failure occurs
416 * setting the contested bit, the mutex was either released
417 * or the state of the MTX_RECURSED bit changed.
418 */
419 if ((v & MTX_CONTESTED) == 0 &&
420 !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) {
421 turnstile_cancel(ts);
422 continue;
423 }
424
425 /*
426 * We definitely must sleep for this lock.
427 */
428 mtx_assert(m, MA_NOTOWNED);
429
430 #ifdef KTR
431 if (!cont_logged) {
432 CTR6(KTR_CONTENTION,
433 "contention: %p at %s:%d wants %s, taken by %s:%d",
434 (void *)tid, file, line, m->lock_object.lo_name,
435 WITNESS_FILE(&m->lock_object),
436 WITNESS_LINE(&m->lock_object));
437 cont_logged = 1;
438 }
439 #endif
440
441 /*
442 * Block on the turnstile.
443 */
444 #ifdef KDTRACE_HOOKS
445 sleep_time -= lockstat_nsecs();
446 #endif
447 turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE);
448 #ifdef KDTRACE_HOOKS
449 sleep_time += lockstat_nsecs();
450 sleep_cnt++;
451 #endif
452 }
453 #ifdef KTR
454 if (cont_logged) {
455 CTR4(KTR_CONTENTION,
456 "contention end: %s acquired by %p at %s:%d",
457 m->lock_object.lo_name, (void *)tid, file, line);
458 }
459 #endif
460 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE, m, contested,
461 waittime, file, line);
462 #ifdef KDTRACE_HOOKS
463 if (sleep_time)
464 LOCKSTAT_RECORD1(LS_MTX_LOCK_BLOCK, m, sleep_time);
465
466 /*
467 * Only record the loops spinning and not sleeping.
468 */
469 if (spin_cnt > sleep_cnt)
470 LOCKSTAT_RECORD1(LS_MTX_LOCK_SPIN, m, (spin_cnt - sleep_cnt));
471 #endif
472 }
473
474 static void
475 _mtx_lock_spin_failed(struct mtx *m)
476 {
477 struct thread *td;
478
479 td = mtx_owner(m);
480
481 /* If the mutex is unlocked, try again. */
482 if (td == NULL)
483 return;
484
485 printf( "spin lock %p (%s) held by %p (tid %d) too long\n",
486 m, m->lock_object.lo_name, td, td->td_tid);
487 #ifdef WITNESS
488 witness_display_spinlock(&m->lock_object, td, printf);
489 #endif
490 panic("spin lock held too long");
491 }
492
493 #ifdef SMP
494 /*
495 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock.
496 *
497 * This is only called if we need to actually spin for the lock. Recursion
498 * is handled inline.
499 */
500 void
501 _mtx_lock_spin(struct mtx *m, uintptr_t tid, int opts, const char *file,
502 int line)
503 {
504 int i = 0;
505 #ifdef LOCK_PROFILING
506 int contested = 0;
507 uint64_t waittime = 0;
508 #endif
509
510 if (LOCK_LOG_TEST(&m->lock_object, opts))
511 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
512
513 lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime);
514 while (!_obtain_lock(m, tid)) {
515
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 continue;
522 }
523 if (i < 60000000 || kdb_active || panicstr != NULL)
524 DELAY(1);
525 else
526 _mtx_lock_spin_failed(m);
527 cpu_spinwait();
528 }
529 spinlock_enter();
530 }
531
532 if (LOCK_LOG_TEST(&m->lock_object, opts))
533 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
534
535 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE, m,
536 contested, waittime, (file), (line));
537 LOCKSTAT_RECORD1(LS_MTX_SPIN_LOCK_SPIN, m, i);
538 }
539 #endif /* SMP */
540
541 void
542 _thread_lock_flags(struct thread *td, int opts, const char *file, int line)
543 {
544 struct mtx *m;
545 uintptr_t tid;
546 int i;
547 #ifdef LOCK_PROFILING
548 int contested = 0;
549 uint64_t waittime = 0;
550 #endif
551 #ifdef KDTRACE_HOOKS
552 uint64_t spin_cnt = 0;
553 #endif
554
555 i = 0;
556 tid = (uintptr_t)curthread;
557 for (;;) {
558 retry:
559 spinlock_enter();
560 m = td->td_lock;
561 KASSERT(m->mtx_lock != MTX_DESTROYED,
562 ("thread_lock() of destroyed mutex @ %s:%d", file, line));
563 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
564 ("thread_lock() of sleep mutex %s @ %s:%d",
565 m->lock_object.lo_name, file, line));
566 if (mtx_owned(m))
567 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
568 ("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n",
569 m->lock_object.lo_name, file, line));
570 WITNESS_CHECKORDER(&m->lock_object,
571 opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
572 while (!_obtain_lock(m, tid)) {
573 #ifdef KDTRACE_HOOKS
574 spin_cnt++;
575 #endif
576 if (m->mtx_lock == tid) {
577 m->mtx_recurse++;
578 break;
579 }
580 lock_profile_obtain_lock_failed(&m->lock_object,
581 &contested, &waittime);
582 /* Give interrupts a chance while we spin. */
583 spinlock_exit();
584 while (m->mtx_lock != MTX_UNOWNED) {
585 if (i++ < 10000000)
586 cpu_spinwait();
587 else if (i < 60000000 ||
588 kdb_active || panicstr != NULL)
589 DELAY(1);
590 else
591 _mtx_lock_spin_failed(m);
592 cpu_spinwait();
593 if (m != td->td_lock)
594 goto retry;
595 }
596 spinlock_enter();
597 }
598 if (m == td->td_lock)
599 break;
600 _rel_spin_lock(m); /* does spinlock_exit() */
601 #ifdef KDTRACE_HOOKS
602 spin_cnt++;
603 #endif
604 }
605 if (m->mtx_recurse == 0)
606 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE,
607 m, contested, waittime, (file), (line));
608 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
609 line);
610 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
611 LOCKSTAT_RECORD1(LS_THREAD_LOCK_SPIN, m, spin_cnt);
612 }
613
614 struct mtx *
615 thread_lock_block(struct thread *td)
616 {
617 struct mtx *lock;
618
619 THREAD_LOCK_ASSERT(td, MA_OWNED);
620 lock = td->td_lock;
621 td->td_lock = &blocked_lock;
622 mtx_unlock_spin(lock);
623
624 return (lock);
625 }
626
627 void
628 thread_lock_unblock(struct thread *td, struct mtx *new)
629 {
630 mtx_assert(new, MA_OWNED);
631 MPASS(td->td_lock == &blocked_lock);
632 atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new);
633 }
634
635 void
636 thread_lock_set(struct thread *td, struct mtx *new)
637 {
638 struct mtx *lock;
639
640 mtx_assert(new, MA_OWNED);
641 THREAD_LOCK_ASSERT(td, MA_OWNED);
642 lock = td->td_lock;
643 td->td_lock = new;
644 mtx_unlock_spin(lock);
645 }
646
647 /*
648 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
649 *
650 * We are only called here if the lock is recursed or contested (i.e. we
651 * need to wake up a blocked thread).
652 */
653 void
654 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line)
655 {
656 struct turnstile *ts;
657
658 if (mtx_recursed(m)) {
659 if (--(m->mtx_recurse) == 0)
660 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
661 if (LOCK_LOG_TEST(&m->lock_object, opts))
662 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
663 return;
664 }
665
666 /*
667 * We have to lock the chain before the turnstile so this turnstile
668 * can be removed from the hash list if it is empty.
669 */
670 turnstile_chain_lock(&m->lock_object);
671 ts = turnstile_lookup(&m->lock_object);
672 if (LOCK_LOG_TEST(&m->lock_object, opts))
673 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);
674 MPASS(ts != NULL);
675 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
676 _release_lock_quick(m);
677
678 /*
679 * This turnstile is now no longer associated with the mutex. We can
680 * unlock the chain lock so a new turnstile may take it's place.
681 */
682 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
683 turnstile_chain_unlock(&m->lock_object);
684 }
685
686 /*
687 * All the unlocking of MTX_SPIN locks is done inline.
688 * See the _rel_spin_lock() macro for the details.
689 */
690
691 /*
692 * The backing function for the INVARIANTS-enabled mtx_assert()
693 */
694 #ifdef INVARIANT_SUPPORT
695 void
696 _mtx_assert(struct mtx *m, int what, const char *file, int line)
697 {
698
699 if (panicstr != NULL || dumping)
700 return;
701 switch (what) {
702 case MA_OWNED:
703 case MA_OWNED | MA_RECURSED:
704 case MA_OWNED | MA_NOTRECURSED:
705 if (!mtx_owned(m))
706 panic("mutex %s not owned at %s:%d",
707 m->lock_object.lo_name, file, line);
708 if (mtx_recursed(m)) {
709 if ((what & MA_NOTRECURSED) != 0)
710 panic("mutex %s recursed at %s:%d",
711 m->lock_object.lo_name, file, line);
712 } else if ((what & MA_RECURSED) != 0) {
713 panic("mutex %s unrecursed at %s:%d",
714 m->lock_object.lo_name, file, line);
715 }
716 break;
717 case MA_NOTOWNED:
718 if (mtx_owned(m))
719 panic("mutex %s owned at %s:%d",
720 m->lock_object.lo_name, file, line);
721 break;
722 default:
723 panic("unknown mtx_assert at %s:%d", file, line);
724 }
725 }
726 #endif
727
728 /*
729 * The MUTEX_DEBUG-enabled mtx_validate()
730 *
731 * Most of these checks have been moved off into the LO_INITIALIZED flag
732 * maintained by the witness code.
733 */
734 #ifdef MUTEX_DEBUG
735
736 void mtx_validate(struct mtx *);
737
738 void
739 mtx_validate(struct mtx *m)
740 {
741
742 /*
743 * XXX: When kernacc() does not require Giant we can reenable this check
744 */
745 #ifdef notyet
746 /*
747 * Can't call kernacc() from early init386(), especially when
748 * initializing Giant mutex, because some stuff in kernacc()
749 * requires Giant itself.
750 */
751 if (!cold)
752 if (!kernacc((caddr_t)m, sizeof(m),
753 VM_PROT_READ | VM_PROT_WRITE))
754 panic("Can't read and write to mutex %p", m);
755 #endif
756 }
757 #endif
758
759 /*
760 * General init routine used by the MTX_SYSINIT() macro.
761 */
762 void
763 mtx_sysinit(void *arg)
764 {
765 struct mtx_args *margs = arg;
766
767 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts);
768 }
769
770 /*
771 * Mutex initialization routine; initialize lock `m' of type contained in
772 * `opts' with options contained in `opts' and name `name.' The optional
773 * lock type `type' is used as a general lock category name for use with
774 * witness.
775 */
776 void
777 mtx_init(struct mtx *m, const char *name, const char *type, int opts)
778 {
779 struct lock_class *class;
780 int flags;
781
782 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
783 MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0);
784 ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock,
785 ("%s: mtx_lock not aligned for %s: %p", __func__, name,
786 &m->mtx_lock));
787
788 #ifdef MUTEX_DEBUG
789 /* Diagnostic and error correction */
790 mtx_validate(m);
791 #endif
792
793 /* Determine lock class and lock flags. */
794 if (opts & MTX_SPIN)
795 class = &lock_class_mtx_spin;
796 else
797 class = &lock_class_mtx_sleep;
798 flags = 0;
799 if (opts & MTX_QUIET)
800 flags |= LO_QUIET;
801 if (opts & MTX_RECURSE)
802 flags |= LO_RECURSABLE;
803 if ((opts & MTX_NOWITNESS) == 0)
804 flags |= LO_WITNESS;
805 if (opts & MTX_DUPOK)
806 flags |= LO_DUPOK;
807 if (opts & MTX_NOPROFILE)
808 flags |= LO_NOPROFILE;
809
810 /* Initialize mutex. */
811 m->mtx_lock = MTX_UNOWNED;
812 m->mtx_recurse = 0;
813
814 lock_init(&m->lock_object, class, name, type, flags);
815 }
816
817 /*
818 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be
819 * passed in as a flag here because if the corresponding mtx_init() was
820 * called with MTX_QUIET set, then it will already be set in the mutex's
821 * flags.
822 */
823 void
824 mtx_destroy(struct mtx *m)
825 {
826
827 if (!mtx_owned(m))
828 MPASS(mtx_unowned(m));
829 else {
830 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);
831
832 /* Perform the non-mtx related part of mtx_unlock_spin(). */
833 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin)
834 spinlock_exit();
835 else
836 curthread->td_locks--;
837
838 lock_profile_release_lock(&m->lock_object);
839 /* Tell witness this isn't locked to make it happy. */
840 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__,
841 __LINE__);
842 }
843
844 m->mtx_lock = MTX_DESTROYED;
845 lock_destroy(&m->lock_object);
846 }
847
848 /*
849 * Intialize the mutex code and system mutexes. This is called from the MD
850 * startup code prior to mi_startup(). The per-CPU data space needs to be
851 * setup before this is called.
852 */
853 void
854 mutex_init(void)
855 {
856
857 /* Setup turnstiles so that sleep mutexes work. */
858 init_turnstiles();
859
860 /*
861 * Initialize mutexes.
862 */
863 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE);
864 mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN);
865 blocked_lock.mtx_lock = 0xdeadc0de; /* Always blocked. */
866 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK);
867 mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN | MTX_RECURSE);
868 mtx_init(&devmtx, "cdev", NULL, MTX_DEF);
869 mtx_lock(&Giant);
870 }
871
872 #ifdef DDB
873 void
874 db_show_mtx(struct lock_object *lock)
875 {
876 struct thread *td;
877 struct mtx *m;
878
879 m = (struct mtx *)lock;
880
881 db_printf(" flags: {");
882 if (LOCK_CLASS(lock) == &lock_class_mtx_spin)
883 db_printf("SPIN");
884 else
885 db_printf("DEF");
886 if (m->lock_object.lo_flags & LO_RECURSABLE)
887 db_printf(", RECURSE");
888 if (m->lock_object.lo_flags & LO_DUPOK)
889 db_printf(", DUPOK");
890 db_printf("}\n");
891 db_printf(" state: {");
892 if (mtx_unowned(m))
893 db_printf("UNOWNED");
894 else if (mtx_destroyed(m))
895 db_printf("DESTROYED");
896 else {
897 db_printf("OWNED");
898 if (m->mtx_lock & MTX_CONTESTED)
899 db_printf(", CONTESTED");
900 if (m->mtx_lock & MTX_RECURSED)
901 db_printf(", RECURSED");
902 }
903 db_printf("}\n");
904 if (!mtx_unowned(m) && !mtx_destroyed(m)) {
905 td = mtx_owner(m);
906 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td,
907 td->td_tid, td->td_proc->p_pid, td->td_name);
908 if (mtx_recursed(m))
909 db_printf(" recursed: %d\n", m->mtx_recurse);
910 }
911 }
912 #endif
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