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_mprof.h"
42 #include "opt_mutex_wake_all.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
63 #include <machine/atomic.h>
64 #include <machine/bus.h>
65 #include <machine/clock.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 /*
76 * Force MUTEX_WAKE_ALL for now.
77 * single thread wakeup needs fixes to avoid race conditions with
78 * priority inheritance.
79 */
80 #ifndef MUTEX_WAKE_ALL
81 #define MUTEX_WAKE_ALL
82 #endif
83
84 /*
85 * Internal utility macros.
86 */
87 #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
88
89 #define mtx_owner(m) (mtx_unowned((m)) ? NULL \
90 : (struct thread *)((m)->mtx_lock & MTX_FLAGMASK))
91
92 #ifdef DDB
93 static void db_show_mtx(struct lock_object *lock);
94 #endif
95
96 /*
97 * Lock classes for sleep and spin mutexes.
98 */
99 struct lock_class lock_class_mtx_sleep = {
100 "sleep mutex",
101 LC_SLEEPLOCK | LC_RECURSABLE,
102 #ifdef DDB
103 db_show_mtx
104 #endif
105 };
106 struct lock_class lock_class_mtx_spin = {
107 "spin mutex",
108 LC_SPINLOCK | LC_RECURSABLE,
109 #ifdef DDB
110 db_show_mtx
111 #endif
112 };
113
114 /*
115 * System-wide mutexes
116 */
117 struct mtx sched_lock;
118 struct mtx Giant;
119
120 #ifdef MUTEX_PROFILING
121 SYSCTL_NODE(_debug, OID_AUTO, mutex, CTLFLAG_RD, NULL, "mutex debugging");
122 SYSCTL_NODE(_debug_mutex, OID_AUTO, prof, CTLFLAG_RD, NULL, "mutex profiling");
123 static int mutex_prof_enable = 0;
124 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, enable, CTLFLAG_RW,
125 &mutex_prof_enable, 0, "Enable tracing of mutex holdtime");
126
127 struct mutex_prof {
128 const char *name;
129 const char *file;
130 int line;
131 uintmax_t cnt_max;
132 uintmax_t cnt_tot;
133 uintmax_t cnt_cur;
134 uintmax_t cnt_contest_holding;
135 uintmax_t cnt_contest_locking;
136 struct mutex_prof *next;
137 };
138
139 /*
140 * mprof_buf is a static pool of profiling records to avoid possible
141 * reentrance of the memory allocation functions.
142 *
143 * Note: NUM_MPROF_BUFFERS must be smaller than MPROF_HASH_SIZE.
144 */
145 #ifdef MPROF_BUFFERS
146 #define NUM_MPROF_BUFFERS MPROF_BUFFERS
147 #else
148 #define NUM_MPROF_BUFFERS 1000
149 #endif
150 static struct mutex_prof mprof_buf[NUM_MPROF_BUFFERS];
151 static int first_free_mprof_buf;
152 #ifndef MPROF_HASH_SIZE
153 #define MPROF_HASH_SIZE 1009
154 #endif
155 #if NUM_MPROF_BUFFERS >= MPROF_HASH_SIZE
156 #error MPROF_BUFFERS must be larger than MPROF_HASH_SIZE
157 #endif
158 static struct mutex_prof *mprof_hash[MPROF_HASH_SIZE];
159 /* SWAG: sbuf size = avg stat. line size * number of locks */
160 #define MPROF_SBUF_SIZE 256 * 400
161
162 static int mutex_prof_acquisitions;
163 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, acquisitions, CTLFLAG_RD,
164 &mutex_prof_acquisitions, 0, "Number of mutex acquistions recorded");
165 static int mutex_prof_records;
166 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, records, CTLFLAG_RD,
167 &mutex_prof_records, 0, "Number of profiling records");
168 static int mutex_prof_maxrecords = NUM_MPROF_BUFFERS;
169 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, maxrecords, CTLFLAG_RD,
170 &mutex_prof_maxrecords, 0, "Maximum number of profiling records");
171 static int mutex_prof_rejected;
172 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, rejected, CTLFLAG_RD,
173 &mutex_prof_rejected, 0, "Number of rejected profiling records");
174 static int mutex_prof_hashsize = MPROF_HASH_SIZE;
175 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, hashsize, CTLFLAG_RD,
176 &mutex_prof_hashsize, 0, "Hash size");
177 static int mutex_prof_collisions = 0;
178 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, collisions, CTLFLAG_RD,
179 &mutex_prof_collisions, 0, "Number of hash collisions");
180
181 /*
182 * mprof_mtx protects the profiling buffers and the hash.
183 */
184 static struct mtx mprof_mtx;
185 MTX_SYSINIT(mprof, &mprof_mtx, "mutex profiling lock", MTX_SPIN | MTX_QUIET);
186
187 static u_int64_t
188 nanoseconds(void)
189 {
190 struct timespec tv;
191
192 nanotime(&tv);
193 return (tv.tv_sec * (u_int64_t)1000000000 + tv.tv_nsec);
194 }
195
196 static int
197 dump_mutex_prof_stats(SYSCTL_HANDLER_ARGS)
198 {
199 struct sbuf *sb;
200 int error, i;
201 static int multiplier = 1;
202
203 if (first_free_mprof_buf == 0)
204 return (SYSCTL_OUT(req, "No locking recorded",
205 sizeof("No locking recorded")));
206
207 retry_sbufops:
208 sb = sbuf_new(NULL, NULL, MPROF_SBUF_SIZE * multiplier, SBUF_FIXEDLEN);
209 sbuf_printf(sb, "\n%6s %12s %11s %5s %12s %12s %s\n",
210 "max", "total", "count", "avg", "cnt_hold", "cnt_lock", "name");
211 /*
212 * XXX this spinlock seems to be by far the largest perpetrator
213 * of spinlock latency (1.6 msec on an Athlon1600 was recorded
214 * even before I pessimized it further by moving the average
215 * computation here).
216 */
217 mtx_lock_spin(&mprof_mtx);
218 for (i = 0; i < first_free_mprof_buf; ++i) {
219 sbuf_printf(sb, "%6ju %12ju %11ju %5ju %12ju %12ju %s:%d (%s)\n",
220 mprof_buf[i].cnt_max / 1000,
221 mprof_buf[i].cnt_tot / 1000,
222 mprof_buf[i].cnt_cur,
223 mprof_buf[i].cnt_cur == 0 ? (uintmax_t)0 :
224 mprof_buf[i].cnt_tot / (mprof_buf[i].cnt_cur * 1000),
225 mprof_buf[i].cnt_contest_holding,
226 mprof_buf[i].cnt_contest_locking,
227 mprof_buf[i].file, mprof_buf[i].line, mprof_buf[i].name);
228 if (sbuf_overflowed(sb)) {
229 mtx_unlock_spin(&mprof_mtx);
230 sbuf_delete(sb);
231 multiplier++;
232 goto retry_sbufops;
233 }
234 }
235 mtx_unlock_spin(&mprof_mtx);
236 sbuf_finish(sb);
237 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
238 sbuf_delete(sb);
239 return (error);
240 }
241 SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
242 NULL, 0, dump_mutex_prof_stats, "A", "Mutex profiling statistics");
243
244 static int
245 reset_mutex_prof_stats(SYSCTL_HANDLER_ARGS)
246 {
247 int error, v;
248
249 if (first_free_mprof_buf == 0)
250 return (0);
251
252 v = 0;
253 error = sysctl_handle_int(oidp, &v, 0, req);
254 if (error)
255 return (error);
256 if (req->newptr == NULL)
257 return (error);
258 if (v == 0)
259 return (0);
260
261 mtx_lock_spin(&mprof_mtx);
262 bzero(mprof_buf, sizeof(*mprof_buf) * first_free_mprof_buf);
263 bzero(mprof_hash, sizeof(struct mtx *) * MPROF_HASH_SIZE);
264 first_free_mprof_buf = 0;
265 mtx_unlock_spin(&mprof_mtx);
266 return (0);
267 }
268 SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
269 NULL, 0, reset_mutex_prof_stats, "I", "Reset mutex profiling statistics");
270 #endif
271
272 /*
273 * Function versions of the inlined __mtx_* macros. These are used by
274 * modules and can also be called from assembly language if needed.
275 */
276 void
277 _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line)
278 {
279
280 MPASS(curthread != NULL);
281 KASSERT(m->mtx_lock != MTX_DESTROYED,
282 ("mtx_lock() of destroyed mutex @ %s:%d", file, line));
283 KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_sleep,
284 ("mtx_lock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name,
285 file, line));
286 WITNESS_CHECKORDER(&m->mtx_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
287 file, line);
288 _get_sleep_lock(m, curthread, opts, file, line);
289 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file,
290 line);
291 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
292 curthread->td_locks++;
293 #ifdef MUTEX_PROFILING
294 /* don't reset the timer when/if recursing */
295 if (m->mtx_acqtime == 0) {
296 m->mtx_filename = file;
297 m->mtx_lineno = line;
298 m->mtx_acqtime = mutex_prof_enable ? nanoseconds() : 0;
299 ++mutex_prof_acquisitions;
300 }
301 #endif
302 }
303
304 void
305 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line)
306 {
307
308 MPASS(curthread != NULL);
309 KASSERT(m->mtx_lock != MTX_DESTROYED,
310 ("mtx_unlock() of destroyed mutex @ %s:%d", file, line));
311 KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_sleep,
312 ("mtx_unlock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name,
313 file, line));
314 curthread->td_locks--;
315 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
316 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file,
317 line);
318 mtx_assert(m, MA_OWNED);
319 #ifdef MUTEX_PROFILING
320 if (m->mtx_acqtime != 0) {
321 static const char *unknown = "(unknown)";
322 struct mutex_prof *mpp;
323 u_int64_t acqtime, now;
324 const char *p, *q;
325 volatile u_int hash;
326
327 now = nanoseconds();
328 acqtime = m->mtx_acqtime;
329 m->mtx_acqtime = 0;
330 if (now <= acqtime)
331 goto out;
332 for (p = m->mtx_filename;
333 p != NULL && strncmp(p, "../", 3) == 0; p += 3)
334 /* nothing */ ;
335 if (p == NULL || *p == '\0')
336 p = unknown;
337 for (hash = m->mtx_lineno, q = p; *q != '\0'; ++q)
338 hash = (hash * 2 + *q) % MPROF_HASH_SIZE;
339 mtx_lock_spin(&mprof_mtx);
340 for (mpp = mprof_hash[hash]; mpp != NULL; mpp = mpp->next)
341 if (mpp->line == m->mtx_lineno &&
342 strcmp(mpp->file, p) == 0)
343 break;
344 if (mpp == NULL) {
345 /* Just exit if we cannot get a trace buffer */
346 if (first_free_mprof_buf >= NUM_MPROF_BUFFERS) {
347 ++mutex_prof_rejected;
348 goto unlock;
349 }
350 mpp = &mprof_buf[first_free_mprof_buf++];
351 mpp->name = mtx_name(m);
352 mpp->file = p;
353 mpp->line = m->mtx_lineno;
354 mpp->next = mprof_hash[hash];
355 if (mprof_hash[hash] != NULL)
356 ++mutex_prof_collisions;
357 mprof_hash[hash] = mpp;
358 ++mutex_prof_records;
359 }
360 /*
361 * Record if the mutex has been held longer now than ever
362 * before.
363 */
364 if (now - acqtime > mpp->cnt_max)
365 mpp->cnt_max = now - acqtime;
366 mpp->cnt_tot += now - acqtime;
367 mpp->cnt_cur++;
368 /*
369 * There's a small race, really we should cmpxchg
370 * 0 with the current value, but that would bill
371 * the contention to the wrong lock instance if
372 * it followed this also.
373 */
374 mpp->cnt_contest_holding += m->mtx_contest_holding;
375 m->mtx_contest_holding = 0;
376 mpp->cnt_contest_locking += m->mtx_contest_locking;
377 m->mtx_contest_locking = 0;
378 unlock:
379 mtx_unlock_spin(&mprof_mtx);
380 }
381 out:
382 #endif
383 _rel_sleep_lock(m, curthread, opts, file, line);
384 }
385
386 void
387 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line)
388 {
389
390 MPASS(curthread != NULL);
391 KASSERT(m->mtx_lock != MTX_DESTROYED,
392 ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line));
393 KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_spin,
394 ("mtx_lock_spin() of sleep mutex %s @ %s:%d",
395 m->mtx_object.lo_name, file, line));
396 WITNESS_CHECKORDER(&m->mtx_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
397 file, line);
398 _get_spin_lock(m, curthread, opts, file, line);
399 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file,
400 line);
401 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
402 }
403
404 void
405 _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line)
406 {
407
408 MPASS(curthread != NULL);
409 KASSERT(m->mtx_lock != MTX_DESTROYED,
410 ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line));
411 KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_spin,
412 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d",
413 m->mtx_object.lo_name, file, line));
414 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
415 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file,
416 line);
417 mtx_assert(m, MA_OWNED);
418 _rel_spin_lock(m);
419 }
420
421 /*
422 * The important part of mtx_trylock{,_flags}()
423 * Tries to acquire lock `m.' If this function is called on a mutex that
424 * is already owned, it will recursively acquire the lock.
425 */
426 int
427 _mtx_trylock(struct mtx *m, int opts, const char *file, int line)
428 {
429 int rval;
430
431 MPASS(curthread != NULL);
432 KASSERT(m->mtx_lock != MTX_DESTROYED,
433 ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
434 KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_sleep,
435 ("mtx_trylock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name,
436 file, line));
437
438 if (mtx_owned(m) && (m->mtx_object.lo_flags & LO_RECURSABLE) != 0) {
439 m->mtx_recurse++;
440 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
441 rval = 1;
442 } else
443 rval = _obtain_lock(m, (uintptr_t)curthread);
444
445 LOCK_LOG_TRY("LOCK", &m->mtx_object, opts, rval, file, line);
446 if (rval) {
447 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
448 file, line);
449 curthread->td_locks++;
450 }
451
452 return (rval);
453 }
454
455 /*
456 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
457 *
458 * We call this if the lock is either contested (i.e. we need to go to
459 * sleep waiting for it), or if we need to recurse on it.
460 */
461 void
462 _mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file,
463 int line)
464 {
465 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
466 volatile struct thread *owner;
467 #endif
468 uintptr_t v;
469 #ifdef KTR
470 int cont_logged = 0;
471 #endif
472 #ifdef MUTEX_PROFILING
473 int contested;
474 #endif
475
476 if (mtx_owned(m)) {
477 KASSERT((m->mtx_object.lo_flags & LO_RECURSABLE) != 0,
478 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
479 m->mtx_object.lo_name, file, line));
480 m->mtx_recurse++;
481 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
482 if (LOCK_LOG_TEST(&m->mtx_object, opts))
483 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
484 return;
485 }
486
487 if (LOCK_LOG_TEST(&m->mtx_object, opts))
488 CTR4(KTR_LOCK,
489 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
490 m->mtx_object.lo_name, (void *)m->mtx_lock, file, line);
491
492 #ifdef MUTEX_PROFILING
493 contested = 0;
494 #endif
495 while (!_obtain_lock(m, tid)) {
496 #ifdef MUTEX_PROFILING
497 contested = 1;
498 atomic_add_int(&m->mtx_contest_holding, 1);
499 #endif
500 turnstile_lock(&m->mtx_object);
501 v = m->mtx_lock;
502
503 /*
504 * Check if the lock has been released while spinning for
505 * the turnstile chain lock.
506 */
507 if (v == MTX_UNOWNED) {
508 turnstile_release(&m->mtx_object);
509 cpu_spinwait();
510 continue;
511 }
512
513 #ifdef MUTEX_WAKE_ALL
514 MPASS(v != MTX_CONTESTED);
515 #else
516 /*
517 * The mutex was marked contested on release. This means that
518 * there are other threads blocked on it. Grab ownership of
519 * it and propagate its priority to the current thread if
520 * necessary.
521 */
522 if (v == MTX_CONTESTED) {
523 m->mtx_lock = tid | MTX_CONTESTED;
524 turnstile_claim(&m->mtx_object);
525 break;
526 }
527 #endif
528
529 /*
530 * If the mutex isn't already contested and a failure occurs
531 * setting the contested bit, the mutex was either released
532 * or the state of the MTX_RECURSED bit changed.
533 */
534 if ((v & MTX_CONTESTED) == 0 &&
535 !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) {
536 turnstile_release(&m->mtx_object);
537 cpu_spinwait();
538 continue;
539 }
540
541 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
542 /*
543 * If the current owner of the lock is executing on another
544 * CPU, spin instead of blocking.
545 */
546 owner = (struct thread *)(v & MTX_FLAGMASK);
547 #ifdef ADAPTIVE_GIANT
548 if (TD_IS_RUNNING(owner)) {
549 #else
550 if (m != &Giant && TD_IS_RUNNING(owner)) {
551 #endif
552 turnstile_release(&m->mtx_object);
553 while (mtx_owner(m) == owner && TD_IS_RUNNING(owner)) {
554 cpu_spinwait();
555 }
556 continue;
557 }
558 #endif /* SMP && !NO_ADAPTIVE_MUTEXES */
559
560 /*
561 * We definitely must sleep for this lock.
562 */
563 mtx_assert(m, MA_NOTOWNED);
564
565 #ifdef KTR
566 if (!cont_logged) {
567 CTR6(KTR_CONTENTION,
568 "contention: %p at %s:%d wants %s, taken by %s:%d",
569 (void *)tid, file, line, m->mtx_object.lo_name,
570 WITNESS_FILE(&m->mtx_object),
571 WITNESS_LINE(&m->mtx_object));
572 cont_logged = 1;
573 }
574 #endif
575
576 /*
577 * Block on the turnstile.
578 */
579 turnstile_wait(&m->mtx_object, mtx_owner(m),
580 TS_EXCLUSIVE_QUEUE);
581 }
582
583 #ifdef KTR
584 if (cont_logged) {
585 CTR4(KTR_CONTENTION,
586 "contention end: %s acquired by %p at %s:%d",
587 m->mtx_object.lo_name, (void *)tid, file, line);
588 }
589 #endif
590 #ifdef MUTEX_PROFILING
591 if (contested)
592 m->mtx_contest_locking++;
593 m->mtx_contest_holding = 0;
594 #endif
595 return;
596 }
597
598 #ifdef SMP
599 /*
600 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock.
601 *
602 * This is only called if we need to actually spin for the lock. Recursion
603 * is handled inline.
604 */
605 void
606 _mtx_lock_spin(struct mtx *m, uintptr_t tid, int opts, const char *file,
607 int line)
608 {
609 int i = 0;
610
611 if (LOCK_LOG_TEST(&m->mtx_object, opts))
612 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
613
614 for (;;) {
615 if (_obtain_lock(m, tid))
616 break;
617
618 /* Give interrupts a chance while we spin. */
619 spinlock_exit();
620 while (m->mtx_lock != MTX_UNOWNED) {
621 if (i++ < 10000000) {
622 cpu_spinwait();
623 continue;
624 }
625 if (i < 60000000)
626 DELAY(1);
627 else if (!kdb_active && !panicstr) {
628 printf("spin lock %s held by %p for > 5 seconds\n",
629 m->mtx_object.lo_name, (void *)m->mtx_lock);
630 #ifdef WITNESS
631 witness_display_spinlock(&m->mtx_object,
632 mtx_owner(m));
633 #endif
634 panic("spin lock held too long");
635 }
636 cpu_spinwait();
637 }
638 spinlock_enter();
639 }
640
641 if (LOCK_LOG_TEST(&m->mtx_object, opts))
642 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
643
644 return;
645 }
646 #endif /* SMP */
647
648 /*
649 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
650 *
651 * We are only called here if the lock is recursed or contested (i.e. we
652 * need to wake up a blocked thread).
653 */
654 void
655 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line)
656 {
657 struct turnstile *ts;
658 #ifndef PREEMPTION
659 struct thread *td, *td1;
660 #endif
661
662 if (mtx_recursed(m)) {
663 if (--(m->mtx_recurse) == 0)
664 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
665 if (LOCK_LOG_TEST(&m->mtx_object, opts))
666 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
667 return;
668 }
669
670 turnstile_lock(&m->mtx_object);
671 ts = turnstile_lookup(&m->mtx_object);
672 if (LOCK_LOG_TEST(&m->mtx_object, opts))
673 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);
674
675 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
676 if (ts == NULL) {
677 _release_lock_quick(m);
678 if (LOCK_LOG_TEST(&m->mtx_object, opts))
679 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p no sleepers", m);
680 turnstile_release(&m->mtx_object);
681 return;
682 }
683 #else
684 MPASS(ts != NULL);
685 #endif
686 #ifndef PREEMPTION
687 /* XXX */
688 td1 = turnstile_head(ts, TS_EXCLUSIVE_QUEUE);
689 #endif
690 #ifdef MUTEX_WAKE_ALL
691 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
692 _release_lock_quick(m);
693 #else
694 if (turnstile_signal(ts, TS_EXCLUSIVE_QUEUE)) {
695 _release_lock_quick(m);
696 if (LOCK_LOG_TEST(&m->mtx_object, opts))
697 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m);
698 } else {
699 m->mtx_lock = MTX_CONTESTED;
700 if (LOCK_LOG_TEST(&m->mtx_object, opts))
701 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p still contested",
702 m);
703 }
704 #endif
705 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
706
707 #ifndef PREEMPTION
708 /*
709 * XXX: This is just a hack until preemption is done. However,
710 * once preemption is done we need to either wrap the
711 * turnstile_signal() and release of the actual lock in an
712 * extra critical section or change the preemption code to
713 * always just set a flag and never do instant-preempts.
714 */
715 td = curthread;
716 if (td->td_critnest > 0 || td1->td_priority >= td->td_priority)
717 return;
718 mtx_lock_spin(&sched_lock);
719 if (!TD_IS_RUNNING(td1)) {
720 #ifdef notyet
721 if (td->td_ithd != NULL) {
722 struct ithd *it = td->td_ithd;
723
724 if (it->it_interrupted) {
725 if (LOCK_LOG_TEST(&m->mtx_object, opts))
726 CTR2(KTR_LOCK,
727 "_mtx_unlock_sleep: %p interrupted %p",
728 it, it->it_interrupted);
729 intr_thd_fixup(it);
730 }
731 }
732 #endif
733 if (LOCK_LOG_TEST(&m->mtx_object, opts))
734 CTR2(KTR_LOCK,
735 "_mtx_unlock_sleep: %p switching out lock=%p", m,
736 (void *)m->mtx_lock);
737
738 mi_switch(SW_INVOL, NULL);
739 if (LOCK_LOG_TEST(&m->mtx_object, opts))
740 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p",
741 m, (void *)m->mtx_lock);
742 }
743 mtx_unlock_spin(&sched_lock);
744 #endif
745
746 return;
747 }
748
749 /*
750 * All the unlocking of MTX_SPIN locks is done inline.
751 * See the _rel_spin_lock() macro for the details.
752 */
753
754 /*
755 * The backing function for the INVARIANTS-enabled mtx_assert()
756 */
757 #ifdef INVARIANT_SUPPORT
758 void
759 _mtx_assert(struct mtx *m, int what, const char *file, int line)
760 {
761
762 if (panicstr != NULL || dumping)
763 return;
764 switch (what) {
765 case MA_OWNED:
766 case MA_OWNED | MA_RECURSED:
767 case MA_OWNED | MA_NOTRECURSED:
768 if (!mtx_owned(m))
769 panic("mutex %s not owned at %s:%d",
770 m->mtx_object.lo_name, file, line);
771 if (mtx_recursed(m)) {
772 if ((what & MA_NOTRECURSED) != 0)
773 panic("mutex %s recursed at %s:%d",
774 m->mtx_object.lo_name, file, line);
775 } else if ((what & MA_RECURSED) != 0) {
776 panic("mutex %s unrecursed at %s:%d",
777 m->mtx_object.lo_name, file, line);
778 }
779 break;
780 case MA_NOTOWNED:
781 if (mtx_owned(m))
782 panic("mutex %s owned at %s:%d",
783 m->mtx_object.lo_name, file, line);
784 break;
785 default:
786 panic("unknown mtx_assert at %s:%d", file, line);
787 }
788 }
789 #endif
790
791 /*
792 * The MUTEX_DEBUG-enabled mtx_validate()
793 *
794 * Most of these checks have been moved off into the LO_INITIALIZED flag
795 * maintained by the witness code.
796 */
797 #ifdef MUTEX_DEBUG
798
799 void mtx_validate(struct mtx *);
800
801 void
802 mtx_validate(struct mtx *m)
803 {
804
805 /*
806 * XXX: When kernacc() does not require Giant we can reenable this check
807 */
808 #ifdef notyet
809 /*
810 * XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly
811 * we can re-enable the kernacc() checks.
812 */
813 #ifndef __alpha__
814 /*
815 * Can't call kernacc() from early init386(), especially when
816 * initializing Giant mutex, because some stuff in kernacc()
817 * requires Giant itself.
818 */
819 if (!cold)
820 if (!kernacc((caddr_t)m, sizeof(m),
821 VM_PROT_READ | VM_PROT_WRITE))
822 panic("Can't read and write to mutex %p", m);
823 #endif
824 #endif
825 }
826 #endif
827
828 /*
829 * General init routine used by the MTX_SYSINIT() macro.
830 */
831 void
832 mtx_sysinit(void *arg)
833 {
834 struct mtx_args *margs = arg;
835
836 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts);
837 }
838
839 /*
840 * Mutex initialization routine; initialize lock `m' of type contained in
841 * `opts' with options contained in `opts' and name `name.' The optional
842 * lock type `type' is used as a general lock category name for use with
843 * witness.
844 */
845 void
846 mtx_init(struct mtx *m, const char *name, const char *type, int opts)
847 {
848 struct lock_class *class;
849 int flags;
850
851 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
852 MTX_NOWITNESS | MTX_DUPOK)) == 0);
853
854 #ifdef MUTEX_DEBUG
855 /* Diagnostic and error correction */
856 mtx_validate(m);
857 #endif
858
859 /* Determine lock class and lock flags. */
860 if (opts & MTX_SPIN)
861 class = &lock_class_mtx_spin;
862 else
863 class = &lock_class_mtx_sleep;
864 flags = 0;
865 if (opts & MTX_QUIET)
866 flags |= LO_QUIET;
867 if (opts & MTX_RECURSE)
868 flags |= LO_RECURSABLE;
869 if ((opts & MTX_NOWITNESS) == 0)
870 flags |= LO_WITNESS;
871 if (opts & MTX_DUPOK)
872 flags |= LO_DUPOK;
873
874 /* Initialize mutex. */
875 m->mtx_lock = MTX_UNOWNED;
876 m->mtx_recurse = 0;
877 #ifdef MUTEX_PROFILING
878 m->mtx_acqtime = 0;
879 m->mtx_filename = NULL;
880 m->mtx_lineno = 0;
881 m->mtx_contest_holding = 0;
882 m->mtx_contest_locking = 0;
883 #endif
884
885 lock_init(&m->mtx_object, class, name, type, flags);
886 }
887
888 /*
889 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be
890 * passed in as a flag here because if the corresponding mtx_init() was
891 * called with MTX_QUIET set, then it will already be set in the mutex's
892 * flags.
893 */
894 void
895 mtx_destroy(struct mtx *m)
896 {
897
898 if (!mtx_owned(m))
899 MPASS(mtx_unowned(m));
900 else {
901 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);
902
903 /* Perform the non-mtx related part of mtx_unlock_spin(). */
904 if (LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_spin)
905 spinlock_exit();
906 else
907 curthread->td_locks--;
908
909 /* Tell witness this isn't locked to make it happy. */
910 WITNESS_UNLOCK(&m->mtx_object, LOP_EXCLUSIVE, __FILE__,
911 __LINE__);
912 }
913
914 m->mtx_lock = MTX_DESTROYED;
915 lock_destroy(&m->mtx_object);
916 }
917
918 /*
919 * Intialize the mutex code and system mutexes. This is called from the MD
920 * startup code prior to mi_startup(). The per-CPU data space needs to be
921 * setup before this is called.
922 */
923 void
924 mutex_init(void)
925 {
926
927 /* Setup turnstiles so that sleep mutexes work. */
928 init_turnstiles();
929
930 /*
931 * Initialize mutexes.
932 */
933 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE);
934 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE);
935 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK);
936 mtx_init(&devmtx, "cdev", NULL, MTX_DEF);
937 mtx_lock(&Giant);
938 }
939
940 #ifdef DDB
941 void
942 db_show_mtx(struct lock_object *lock)
943 {
944 struct thread *td;
945 struct mtx *m;
946
947 m = (struct mtx *)lock;
948
949 db_printf(" flags: {");
950 if (LOCK_CLASS(lock) == &lock_class_mtx_spin)
951 db_printf("SPIN");
952 else
953 db_printf("DEF");
954 if (m->mtx_object.lo_flags & LO_RECURSABLE)
955 db_printf(", RECURSE");
956 if (m->mtx_object.lo_flags & LO_DUPOK)
957 db_printf(", DUPOK");
958 db_printf("}\n");
959 db_printf(" state: {");
960 if (mtx_unowned(m))
961 db_printf("UNOWNED");
962 else {
963 db_printf("OWNED");
964 if (m->mtx_lock & MTX_CONTESTED)
965 db_printf(", CONTESTED");
966 if (m->mtx_lock & MTX_RECURSED)
967 db_printf(", RECURSED");
968 }
969 db_printf("}\n");
970 if (!mtx_unowned(m)) {
971 td = mtx_owner(m);
972 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td,
973 td->td_tid, td->td_proc->p_pid, td->td_proc->p_comm);
974 if (mtx_recursed(m))
975 db_printf(" recursed: %d\n", m->mtx_recurse);
976 }
977 }
978 #endif
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