summaryrefslogtreecommitdiffstats
path: root/sys/kern/kern_mutex.c
blob: 58f25331eb97030b9457eaebc6da01df7ed1fa73 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
/*-
 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Berkeley Software Design Inc's name may not be used to endorse or
 *    promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
 *	and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
 */

/*
 * Machine independent bits of mutex implementation.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_adaptive_mutexes.h"
#include "opt_ddb.h"
#include "opt_global.h"
#include "opt_sched.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/conf.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/sbuf.h>
#include <sys/sysctl.h>
#include <sys/turnstile.h>
#include <sys/vmmeter.h>
#include <sys/lock_profile.h>

#include <machine/atomic.h>
#include <machine/bus.h>
#include <machine/cpu.h>

#include <ddb/ddb.h>

#include <fs/devfs/devfs_int.h>

#include <vm/vm.h>
#include <vm/vm_extern.h>

#if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
#define	ADAPTIVE_MUTEXES
#endif

/*
 * Internal utility macros.
 */
#define mtx_unowned(m)	((m)->mtx_lock == MTX_UNOWNED)

#define	mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED)

#define	mtx_owner(m)	((struct thread *)((m)->mtx_lock & ~MTX_FLAGMASK))

#ifdef DDB
static void	db_show_mtx(struct lock_object *lock);
#endif
static void	lock_mtx(struct lock_object *lock, int how);
static void	lock_spin(struct lock_object *lock, int how);
static int	unlock_mtx(struct lock_object *lock);
static int	unlock_spin(struct lock_object *lock);

/*
 * Lock classes for sleep and spin mutexes.
 */
struct lock_class lock_class_mtx_sleep = {
	.lc_name = "sleep mutex",
	.lc_flags = LC_SLEEPLOCK | LC_RECURSABLE,
#ifdef DDB
	.lc_ddb_show = db_show_mtx,
#endif
	.lc_lock = lock_mtx,
	.lc_unlock = unlock_mtx,
};
struct lock_class lock_class_mtx_spin = {
	.lc_name = "spin mutex",
	.lc_flags = LC_SPINLOCK | LC_RECURSABLE,
#ifdef DDB
	.lc_ddb_show = db_show_mtx,
#endif
	.lc_lock = lock_spin,
	.lc_unlock = unlock_spin,
};

/*
 * System-wide mutexes
 */
struct mtx blocked_lock;
struct mtx Giant;

#ifdef LOCK_PROFILING
static inline void lock_profile_init(void)
{
        int i;
        /* Initialize the mutex profiling locks */
        for (i = 0; i < LPROF_LOCK_SIZE; i++) {
                mtx_init(&lprof_locks[i], "mprof lock",
                    NULL, MTX_SPIN|MTX_QUIET|MTX_NOPROFILE);
        }
}
#else
static inline void lock_profile_init(void) {;}
#endif

void
lock_mtx(struct lock_object *lock, int how)
{

	mtx_lock((struct mtx *)lock);
}

void
lock_spin(struct lock_object *lock, int how)
{

	panic("spin locks can only use msleep_spin");
}

int
unlock_mtx(struct lock_object *lock)
{
	struct mtx *m;

	m = (struct mtx *)lock;
	mtx_assert(m, MA_OWNED | MA_NOTRECURSED);
	mtx_unlock(m);
	return (0);
}

int
unlock_spin(struct lock_object *lock)
{

	panic("spin locks can only use msleep_spin");
}

/*
 * Function versions of the inlined __mtx_* macros.  These are used by
 * modules and can also be called from assembly language if needed.
 */
void
_mtx_lock_flags(struct mtx *m, int opts, const char *file, int line)
{

	MPASS(curthread != NULL);
	KASSERT(m->mtx_lock != MTX_DESTROYED,
	    ("mtx_lock() of destroyed mutex @ %s:%d", file, line));
	KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
	    ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
	    file, line));
	WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
	    file, line);

	_get_sleep_lock(m, curthread, opts, file, line);
	LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
	    line);
	WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
	curthread->td_locks++;
}

void
_mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line)
{
	MPASS(curthread != NULL);
	KASSERT(m->mtx_lock != MTX_DESTROYED,
	    ("mtx_unlock() of destroyed mutex @ %s:%d", file, line));
	KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
	    ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
	    file, line));
	curthread->td_locks--;
	WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
	LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
	    line);
	mtx_assert(m, MA_OWNED);

	if (m->mtx_recurse == 0)
		lock_profile_release_lock(&m->lock_object);
	_rel_sleep_lock(m, curthread, opts, file, line);
}

void
_mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line)
{
	
	MPASS(curthread != NULL);
	KASSERT(m->mtx_lock != MTX_DESTROYED,
	    ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line));
	KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
	    ("mtx_lock_spin() of sleep mutex %s @ %s:%d",
	    m->lock_object.lo_name, file, line));
	WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
	    file, line);
	_get_spin_lock(m, curthread, opts, file, line);
	LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
	    line);
	WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
}

void
_mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line)
{

	MPASS(curthread != NULL);
	KASSERT(m->mtx_lock != MTX_DESTROYED,
	    ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line));
	KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
	    ("mtx_unlock_spin() of sleep mutex %s @ %s:%d",
	    m->lock_object.lo_name, file, line));
	WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
	LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
	    line);
	mtx_assert(m, MA_OWNED);

	_rel_spin_lock(m);
}

/*
 * The important part of mtx_trylock{,_flags}()
 * Tries to acquire lock `m.'  If this function is called on a mutex that
 * is already owned, it will recursively acquire the lock.
 */
int
_mtx_trylock(struct mtx *m, int opts, const char *file, int line)
{
	int rval, contested = 0;
	uint64_t waittime = 0;
	
	MPASS(curthread != NULL);
	KASSERT(m->mtx_lock != MTX_DESTROYED,
	    ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
	KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
	    ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
	    file, line));

	if (mtx_owned(m) && (m->lock_object.lo_flags & LO_RECURSABLE) != 0) {
		m->mtx_recurse++;
		atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
		rval = 1;
	} else
		rval = _obtain_lock(m, (uintptr_t)curthread);

	LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line);
	if (rval) {
		WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
		    file, line);
		curthread->td_locks++;
		if (m->mtx_recurse == 0)
			lock_profile_obtain_lock_success(&m->lock_object, contested,
			    waittime, file, line);

	}

	return (rval);
}

/*
 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
 *
 * We call this if the lock is either contested (i.e. we need to go to
 * sleep waiting for it), or if we need to recurse on it.
 */
void
_mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file,
    int line)
{
	struct turnstile *ts;
#ifdef ADAPTIVE_MUTEXES
	volatile struct thread *owner;
#endif
#ifdef KTR
	int cont_logged = 0;
#endif
	int contested = 0;
	uint64_t waittime = 0;
	uintptr_t v;
	
	if (mtx_owned(m)) {
		KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
	    ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
		    m->lock_object.lo_name, file, line));
		m->mtx_recurse++;
		atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
		if (LOCK_LOG_TEST(&m->lock_object, opts))
			CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
		return;
	}

	lock_profile_obtain_lock_failed(&m->lock_object,
		    &contested, &waittime);
	if (LOCK_LOG_TEST(&m->lock_object, opts))
		CTR4(KTR_LOCK,
		    "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
		    m->lock_object.lo_name, (void *)m->mtx_lock, file, line);

	while (!_obtain_lock(m, tid)) { 
		ts = turnstile_trywait(&m->lock_object);
		v = m->mtx_lock;

		/*
		 * Check if the lock has been released while spinning for
		 * the turnstile chain lock.
		 */
		if (v == MTX_UNOWNED) {
			turnstile_cancel(ts);
			cpu_spinwait();
			continue;
		}

		MPASS(v != MTX_CONTESTED);

		/*
		 * If the mutex isn't already contested and a failure occurs
		 * setting the contested bit, the mutex was either released
		 * or the state of the MTX_RECURSED bit changed.
		 */
		if ((v & MTX_CONTESTED) == 0 &&
		    !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) {
			turnstile_cancel(ts);
			cpu_spinwait();
			continue;
		}

#ifdef ADAPTIVE_MUTEXES
		/*
		 * If the current owner of the lock is executing on another
		 * CPU, spin instead of blocking.
		 */
		owner = (struct thread *)(v & ~MTX_FLAGMASK);
#ifdef ADAPTIVE_GIANT
		if (TD_IS_RUNNING(owner)) 
#else
		if (m != &Giant && TD_IS_RUNNING(owner)) 
#endif
		{
			turnstile_cancel(ts);
			while (mtx_owner(m) == owner && TD_IS_RUNNING(owner)) {
				cpu_spinwait();
			}
			continue;
		}
#endif	/* ADAPTIVE_MUTEXES */

		/*
		 * We definitely must sleep for this lock.
		 */
		mtx_assert(m, MA_NOTOWNED);

#ifdef KTR
		if (!cont_logged) {
			CTR6(KTR_CONTENTION,
			    "contention: %p at %s:%d wants %s, taken by %s:%d",
			    (void *)tid, file, line, m->lock_object.lo_name,
			    WITNESS_FILE(&m->lock_object),
			    WITNESS_LINE(&m->lock_object));
			cont_logged = 1;
		}
#endif

		/*
		 * Block on the turnstile.
		 */
		turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE);
	}
#ifdef KTR
	if (cont_logged) {
		CTR4(KTR_CONTENTION,
		    "contention end: %s acquired by %p at %s:%d",
		    m->lock_object.lo_name, (void *)tid, file, line);
	}
#endif
	lock_profile_obtain_lock_success(&m->lock_object, contested,	
	    waittime, (file), (line));					
}

static void
_mtx_lock_spin_failed(struct mtx *m)
{
	struct thread *td;

	td = mtx_owner(m);

	/* If the mutex is unlocked, try again. */
	if (td == NULL)
		return;

	printf( "spin lock %p (%s) held by %p (tid %d) too long\n",
	    m, m->lock_object.lo_name, td, td->td_tid);
#ifdef WITNESS
	witness_display_spinlock(&m->lock_object, td);
#endif
	panic("spin lock held too long");
}

#ifdef SMP
/*
 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock.
 *
 * This is only called if we need to actually spin for the lock. Recursion
 * is handled inline.
 */
void
_mtx_lock_spin(struct mtx *m, uintptr_t tid, int opts, const char *file,
    int line)
{
	int i = 0, contested = 0;
	uint64_t waittime = 0;
	
	if (LOCK_LOG_TEST(&m->lock_object, opts))
		CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);

	lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime);
	while (!_obtain_lock(m, tid)) {

		/* Give interrupts a chance while we spin. */
		spinlock_exit();
		while (m->mtx_lock != MTX_UNOWNED) {
			if (i++ < 10000000) {
				cpu_spinwait();
				continue;
			}
			if (i < 60000000 || kdb_active || panicstr != NULL)
				DELAY(1);
			else
				_mtx_lock_spin_failed(m);
			cpu_spinwait();
		}
		spinlock_enter();
	}

	if (LOCK_LOG_TEST(&m->lock_object, opts))
		CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);

	lock_profile_obtain_lock_success(&m->lock_object, contested,	
	    waittime, (file), (line));
}
#endif /* SMP */

void
_thread_lock_flags(struct thread *td, int opts, const char *file, int line)
{
	struct mtx *m;
	uintptr_t tid;
	int i, contested;
	uint64_t waittime;

	
	contested = i = 0;
	waittime = 0;
	tid = (uintptr_t)curthread;
	for (;;) {
retry:
		spinlock_enter();
		m = td->td_lock;
		WITNESS_CHECKORDER(&m->lock_object,
		    opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line);
		while (!_obtain_lock(m, tid)) {
			if (m->mtx_lock == tid) {
				m->mtx_recurse++;
				break;
			}
			lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime);
			/* Give interrupts a chance while we spin. */
			spinlock_exit();
			while (m->mtx_lock != MTX_UNOWNED) {
				if (i++ < 10000000)
					cpu_spinwait();
				else if (i < 60000000 ||
				    kdb_active || panicstr != NULL)
					DELAY(1);
				else
					_mtx_lock_spin_failed(m);
				cpu_spinwait();
				if (m != td->td_lock)
					goto retry;
			}
			spinlock_enter();
		}
		if (m == td->td_lock)
			break;
		_rel_spin_lock(m);	/* does spinlock_exit() */
	}
	lock_profile_obtain_lock_success(&m->lock_object, contested,	
	    waittime, (file), (line));
	WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
}

struct mtx *
thread_lock_block(struct thread *td)
{
	struct mtx *lock;

	spinlock_enter();
	THREAD_LOCK_ASSERT(td, MA_OWNED);
	lock = td->td_lock;
	td->td_lock = &blocked_lock;
	mtx_unlock_spin(lock);

	return (lock);
}

void
thread_lock_unblock(struct thread *td, struct mtx *new)
{
	mtx_assert(new, MA_OWNED);
	MPASS(td->td_lock == &blocked_lock);
	atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new);
	spinlock_exit();
}

void
thread_lock_set(struct thread *td, struct mtx *new)
{
	struct mtx *lock;

	mtx_assert(new, MA_OWNED);
	THREAD_LOCK_ASSERT(td, MA_OWNED);
	lock = td->td_lock;
	td->td_lock = new;
	mtx_unlock_spin(lock);
}

/*
 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
 *
 * We are only called here if the lock is recursed or contested (i.e. we
 * need to wake up a blocked thread).
 */
void
_mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line)
{
	struct turnstile *ts;

	if (mtx_recursed(m)) {
		if (--(m->mtx_recurse) == 0)
			atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
		if (LOCK_LOG_TEST(&m->lock_object, opts))
			CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
		return;
	}

	/*
	 * We have to lock the chain before the turnstile so this turnstile
	 * can be removed from the hash list if it is empty.
	 */
	turnstile_chain_lock(&m->lock_object);
	ts = turnstile_lookup(&m->lock_object);
	if (LOCK_LOG_TEST(&m->lock_object, opts))
		CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);

#ifdef ADAPTIVE_MUTEXES
	if (ts == NULL) {
		_release_lock_quick(m);
		if (LOCK_LOG_TEST(&m->lock_object, opts))
			CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p no sleepers", m);
		turnstile_chain_unlock(&m->lock_object);
		return;
	}
#else
	MPASS(ts != NULL);
#endif
	turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
	_release_lock_quick(m);
	/*
	 * This turnstile is now no longer associated with the mutex.  We can
	 * unlock the chain lock so a new turnstile may take it's place.
	 */
	turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
	turnstile_chain_unlock(&m->lock_object);
}

/*
 * All the unlocking of MTX_SPIN locks is done inline.
 * See the _rel_spin_lock() macro for the details.
 */

/*
 * The backing function for the INVARIANTS-enabled mtx_assert()
 */
#ifdef INVARIANT_SUPPORT
void
_mtx_assert(struct mtx *m, int what, const char *file, int line)
{

	if (panicstr != NULL || dumping)
		return;
	switch (what) {
	case MA_OWNED:
	case MA_OWNED | MA_RECURSED:
	case MA_OWNED | MA_NOTRECURSED:
		if (!mtx_owned(m))
			panic("mutex %s not owned at %s:%d",
			    m->lock_object.lo_name, file, line);
		if (mtx_recursed(m)) {
			if ((what & MA_NOTRECURSED) != 0)
				panic("mutex %s recursed at %s:%d",
				    m->lock_object.lo_name, file, line);
		} else if ((what & MA_RECURSED) != 0) {
			panic("mutex %s unrecursed at %s:%d",
			    m->lock_object.lo_name, file, line);
		}
		break;
	case MA_NOTOWNED:
		if (mtx_owned(m))
			panic("mutex %s owned at %s:%d",
			    m->lock_object.lo_name, file, line);
		break;
	default:
		panic("unknown mtx_assert at %s:%d", file, line);
	}
}
#endif

/*
 * The MUTEX_DEBUG-enabled mtx_validate()
 *
 * Most of these checks have been moved off into the LO_INITIALIZED flag
 * maintained by the witness code.
 */
#ifdef MUTEX_DEBUG

void	mtx_validate(struct mtx *);

void
mtx_validate(struct mtx *m)
{

/*
 * XXX: When kernacc() does not require Giant we can reenable this check
 */
#ifdef notyet
	/*
	 * Can't call kernacc() from early init386(), especially when
	 * initializing Giant mutex, because some stuff in kernacc()
	 * requires Giant itself.
	 */
	if (!cold)
		if (!kernacc((caddr_t)m, sizeof(m),
		    VM_PROT_READ | VM_PROT_WRITE))
			panic("Can't read and write to mutex %p", m);
#endif
}
#endif

/*
 * General init routine used by the MTX_SYSINIT() macro.
 */
void
mtx_sysinit(void *arg)
{
	struct mtx_args *margs = arg;

	mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts);
}

/*
 * Mutex initialization routine; initialize lock `m' of type contained in
 * `opts' with options contained in `opts' and name `name.'  The optional
 * lock type `type' is used as a general lock category name for use with
 * witness.
 */
void
mtx_init(struct mtx *m, const char *name, const char *type, int opts)
{
	struct lock_class *class;
	int flags;

	MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
		MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0);

#ifdef MUTEX_DEBUG
	/* Diagnostic and error correction */
	mtx_validate(m);
#endif

	/* Determine lock class and lock flags. */
	if (opts & MTX_SPIN)
		class = &lock_class_mtx_spin;
	else
		class = &lock_class_mtx_sleep;
	flags = 0;
	if (opts & MTX_QUIET)
		flags |= LO_QUIET;
	if (opts & MTX_RECURSE)
		flags |= LO_RECURSABLE;
	if ((opts & MTX_NOWITNESS) == 0)
		flags |= LO_WITNESS;
	if (opts & MTX_DUPOK)
		flags |= LO_DUPOK;
	if (opts & MTX_NOPROFILE)
		flags |= LO_NOPROFILE;

	/* Initialize mutex. */
	m->mtx_lock = MTX_UNOWNED;
	m->mtx_recurse = 0;

	lock_init(&m->lock_object, class, name, type, flags);
}

/*
 * Remove lock `m' from all_mtx queue.  We don't allow MTX_QUIET to be
 * passed in as a flag here because if the corresponding mtx_init() was
 * called with MTX_QUIET set, then it will already be set in the mutex's
 * flags.
 */
void
mtx_destroy(struct mtx *m)
{

	if (!mtx_owned(m))
		MPASS(mtx_unowned(m));
	else {
		MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);

		/* Perform the non-mtx related part of mtx_unlock_spin(). */
		if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin)
			spinlock_exit();
		else
			curthread->td_locks--;

		/* Tell witness this isn't locked to make it happy. */
		WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__,
		    __LINE__);
	}

	m->mtx_lock = MTX_DESTROYED;
	lock_destroy(&m->lock_object);
}

/*
 * Intialize the mutex code and system mutexes.  This is called from the MD
 * startup code prior to mi_startup().  The per-CPU data space needs to be
 * setup before this is called.
 */
void
mutex_init(void)
{

	/* Setup turnstiles so that sleep mutexes work. */
	init_turnstiles();

	/*
	 * Initialize mutexes.
	 */
	mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE);
	mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN);
	blocked_lock.mtx_lock = 0xdeadc0de;	/* Always blocked. */
	mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK);
	mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN | MTX_RECURSE);
	mtx_init(&devmtx, "cdev", NULL, MTX_DEF);
	mtx_lock(&Giant);
	
	lock_profile_init();
}

#ifdef DDB
void
db_show_mtx(struct lock_object *lock)
{
	struct thread *td;
	struct mtx *m;

	m = (struct mtx *)lock;

	db_printf(" flags: {");
	if (LOCK_CLASS(lock) == &lock_class_mtx_spin)
		db_printf("SPIN");
	else
		db_printf("DEF");
	if (m->lock_object.lo_flags & LO_RECURSABLE)
		db_printf(", RECURSE");
	if (m->lock_object.lo_flags & LO_DUPOK)
		db_printf(", DUPOK");
	db_printf("}\n");
	db_printf(" state: {");
	if (mtx_unowned(m))
		db_printf("UNOWNED");
	else if (mtx_destroyed(m))
		db_printf("DESTROYED");
	else {
		db_printf("OWNED");
		if (m->mtx_lock & MTX_CONTESTED)
			db_printf(", CONTESTED");
		if (m->mtx_lock & MTX_RECURSED)
			db_printf(", RECURSED");
	}
	db_printf("}\n");
	if (!mtx_unowned(m) && !mtx_destroyed(m)) {
		td = mtx_owner(m);
		db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td,
		    td->td_tid, td->td_proc->p_pid, td->td_proc->p_comm);
		if (mtx_recursed(m))
			db_printf(" recursed: %d\n", m->mtx_recurse);
	}
}
#endif
OpenPOWER on IntegriCloud