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: stable/9/sys/kern/kern_mutex.c 285760 2015-07-21 17:19:03Z markj $");
38
39 #include "opt_adaptive_mutexes.h"
40 #include "opt_ddb.h"
41 #include "opt_global.h"
42 #include "opt_hwpmc_hooks.h"
43 #include "opt_kdtrace.h"
44 #include "opt_sched.h"
45
46 #include <sys/param.h>
47 #include <sys/systm.h>
48 #include <sys/bus.h>
49 #include <sys/conf.h>
50 #include <sys/kdb.h>
51 #include <sys/kernel.h>
52 #include <sys/ktr.h>
53 #include <sys/lock.h>
54 #include <sys/malloc.h>
55 #include <sys/mutex.h>
56 #include <sys/proc.h>
57 #include <sys/resourcevar.h>
58 #include <sys/sched.h>
59 #include <sys/sbuf.h>
60 #include <sys/sysctl.h>
61 #include <sys/turnstile.h>
62 #include <sys/vmmeter.h>
63 #include <sys/lock_profile.h>
64
65 #include <machine/atomic.h>
66 #include <machine/bus.h>
67 #include <machine/cpu.h>
68
69 #include <ddb/ddb.h>
70
71 #include <fs/devfs/devfs_int.h>
72
73 #include <vm/vm.h>
74 #include <vm/vm_extern.h>
75
76 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
77 #define ADAPTIVE_MUTEXES
78 #endif
79
80 #ifdef HWPMC_HOOKS
81 #include <sys/pmckern.h>
82 PMC_SOFT_DEFINE( , , lock, failed);
83 #endif
84
85 /*
86 * Internal utility macros.
87 */
88 #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
89
90 #define mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED)
91
92 #define mtx_owner(m) ((struct thread *)((m)->mtx_lock & ~MTX_FLAGMASK))
93
94 static void assert_mtx(struct lock_object *lock, int what);
95 #ifdef DDB
96 static void db_show_mtx(struct lock_object *lock);
97 #endif
98 static void lock_mtx(struct lock_object *lock, int how);
99 static void lock_spin(struct lock_object *lock, int how);
100 #ifdef KDTRACE_HOOKS
101 static int owner_mtx(struct lock_object *lock, struct thread **owner);
102 #endif
103 static int unlock_mtx(struct lock_object *lock);
104 static int unlock_spin(struct lock_object *lock);
105
106 /*
107 * Lock classes for sleep and spin mutexes.
108 */
109 struct lock_class lock_class_mtx_sleep = {
110 .lc_name = "sleep mutex",
111 .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE,
112 .lc_assert = assert_mtx,
113 #ifdef DDB
114 .lc_ddb_show = db_show_mtx,
115 #endif
116 .lc_lock = lock_mtx,
117 .lc_unlock = unlock_mtx,
118 #ifdef KDTRACE_HOOKS
119 .lc_owner = owner_mtx,
120 #endif
121 };
122 struct lock_class lock_class_mtx_spin = {
123 .lc_name = "spin mutex",
124 .lc_flags = LC_SPINLOCK | LC_RECURSABLE,
125 .lc_assert = assert_mtx,
126 #ifdef DDB
127 .lc_ddb_show = db_show_mtx,
128 #endif
129 .lc_lock = lock_spin,
130 .lc_unlock = unlock_spin,
131 #ifdef KDTRACE_HOOKS
132 .lc_owner = owner_mtx,
133 #endif
134 };
135
136 /*
137 * System-wide mutexes
138 */
139 struct mtx blocked_lock;
140 struct mtx Giant;
141
142 void
assert_mtx(struct lock_object * lock,int what)143 assert_mtx(struct lock_object *lock, int what)
144 {
145
146 mtx_assert((struct mtx *)lock, what);
147 }
148
149 void
lock_mtx(struct lock_object * lock,int how)150 lock_mtx(struct lock_object *lock, int how)
151 {
152
153 mtx_lock((struct mtx *)lock);
154 }
155
156 void
lock_spin(struct lock_object * lock,int how)157 lock_spin(struct lock_object *lock, int how)
158 {
159
160 panic("spin locks can only use msleep_spin");
161 }
162
163 int
unlock_mtx(struct lock_object * lock)164 unlock_mtx(struct lock_object *lock)
165 {
166 struct mtx *m;
167
168 m = (struct mtx *)lock;
169 mtx_assert(m, MA_OWNED | MA_NOTRECURSED);
170 mtx_unlock(m);
171 return (0);
172 }
173
174 int
unlock_spin(struct lock_object * lock)175 unlock_spin(struct lock_object *lock)
176 {
177
178 panic("spin locks can only use msleep_spin");
179 }
180
181 #ifdef KDTRACE_HOOKS
182 int
owner_mtx(struct lock_object * lock,struct thread ** owner)183 owner_mtx(struct lock_object *lock, struct thread **owner)
184 {
185 struct mtx *m = (struct mtx *)lock;
186
187 *owner = mtx_owner(m);
188 return (mtx_unowned(m) == 0);
189 }
190 #endif
191
192 /*
193 * Function versions of the inlined __mtx_* macros. These are used by
194 * modules and can also be called from assembly language if needed.
195 */
196 void
_mtx_lock_flags(struct mtx * m,int opts,const char * file,int line)197 _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line)
198 {
199
200 if (SCHEDULER_STOPPED())
201 return;
202 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
203 ("mtx_lock() by idle thread %p on sleep mutex %s @ %s:%d",
204 curthread, m->lock_object.lo_name, file, line));
205 KASSERT(m->mtx_lock != MTX_DESTROYED,
206 ("mtx_lock() of destroyed mutex @ %s:%d", file, line));
207 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
208 ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
209 file, line));
210 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
211 file, line, NULL);
212
213 __mtx_lock(m, curthread, opts, file, line);
214 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
215 line);
216 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
217 curthread->td_locks++;
218 }
219
220 void
_mtx_unlock_flags(struct mtx * m,int opts,const char * file,int line)221 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line)
222 {
223
224 if (SCHEDULER_STOPPED())
225 return;
226 KASSERT(m->mtx_lock != MTX_DESTROYED,
227 ("mtx_unlock() of destroyed mutex @ %s:%d", file, line));
228 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
229 ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
230 file, line));
231 curthread->td_locks--;
232 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
233 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
234 line);
235 mtx_assert(m, MA_OWNED);
236
237 if (m->mtx_recurse == 0)
238 LOCKSTAT_PROFILE_RELEASE_LOCK(LS_MTX_UNLOCK_RELEASE, m);
239 __mtx_unlock(m, curthread, opts, file, line);
240 }
241
242 void
_mtx_lock_spin_flags(struct mtx * m,int opts,const char * file,int line)243 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line)
244 {
245
246 if (SCHEDULER_STOPPED())
247 return;
248 KASSERT(m->mtx_lock != MTX_DESTROYED,
249 ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line));
250 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
251 ("mtx_lock_spin() of sleep mutex %s @ %s:%d",
252 m->lock_object.lo_name, file, line));
253 if (mtx_owned(m))
254 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
255 ("mtx_lock_spin: recursed on non-recursive mutex %s @ %s:%d\n",
256 m->lock_object.lo_name, file, line));
257 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
258 file, line, NULL);
259 __mtx_lock_spin(m, curthread, opts, file, line);
260 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
261 line);
262 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
263 }
264
265 void
_mtx_unlock_spin_flags(struct mtx * m,int opts,const char * file,int line)266 _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line)
267 {
268
269 if (SCHEDULER_STOPPED())
270 return;
271 KASSERT(m->mtx_lock != MTX_DESTROYED,
272 ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line));
273 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
274 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d",
275 m->lock_object.lo_name, file, line));
276 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
277 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
278 line);
279 mtx_assert(m, MA_OWNED);
280
281 __mtx_unlock_spin(m);
282 }
283
284 /*
285 * The important part of mtx_trylock{,_flags}()
286 * Tries to acquire lock `m.' If this function is called on a mutex that
287 * is already owned, it will recursively acquire the lock.
288 */
289 int
_mtx_trylock(struct mtx * m,int opts,const char * file,int line)290 _mtx_trylock(struct mtx *m, int opts, const char *file, int line)
291 {
292 #ifdef LOCK_PROFILING
293 uint64_t waittime = 0;
294 int contested = 0;
295 #endif
296 int rval;
297
298 if (SCHEDULER_STOPPED())
299 return (1);
300
301 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
302 ("mtx_trylock() by idle thread %p on sleep mutex %s @ %s:%d",
303 curthread, m->lock_object.lo_name, file, line));
304 KASSERT(m->mtx_lock != MTX_DESTROYED,
305 ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
306 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
307 ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
308 file, line));
309
310 if (mtx_owned(m) && (m->lock_object.lo_flags & LO_RECURSABLE) != 0) {
311 m->mtx_recurse++;
312 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
313 rval = 1;
314 } else
315 rval = _mtx_obtain_lock(m, (uintptr_t)curthread);
316
317 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line);
318 if (rval) {
319 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
320 file, line);
321 curthread->td_locks++;
322 if (m->mtx_recurse == 0)
323 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE,
324 m, contested, waittime, file, line);
325
326 }
327
328 return (rval);
329 }
330
331 /*
332 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
333 *
334 * We call this if the lock is either contested (i.e. we need to go to
335 * sleep waiting for it), or if we need to recurse on it.
336 */
337 void
_mtx_lock_sleep(struct mtx * m,uintptr_t tid,int opts,const char * file,int line)338 _mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file,
339 int line)
340 {
341 struct turnstile *ts;
342 uintptr_t v;
343 #ifdef ADAPTIVE_MUTEXES
344 volatile struct thread *owner;
345 #endif
346 #ifdef KTR
347 int cont_logged = 0;
348 #endif
349 #ifdef LOCK_PROFILING
350 int contested = 0;
351 uint64_t waittime = 0;
352 #endif
353 #ifdef KDTRACE_HOOKS
354 uint64_t spin_cnt = 0;
355 uint64_t sleep_cnt = 0;
356 int64_t sleep_time = 0;
357 int64_t all_time = 0;
358 #endif
359
360 if (SCHEDULER_STOPPED())
361 return;
362
363 if (mtx_owned(m)) {
364 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
365 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
366 m->lock_object.lo_name, file, line));
367 m->mtx_recurse++;
368 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
369 if (LOCK_LOG_TEST(&m->lock_object, opts))
370 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
371 return;
372 }
373
374 #ifdef HWPMC_HOOKS
375 PMC_SOFT_CALL( , , lock, failed);
376 #endif
377 lock_profile_obtain_lock_failed(&m->lock_object,
378 &contested, &waittime);
379 if (LOCK_LOG_TEST(&m->lock_object, opts))
380 CTR4(KTR_LOCK,
381 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
382 m->lock_object.lo_name, (void *)m->mtx_lock, file, line);
383 #ifdef KDTRACE_HOOKS
384 all_time -= lockstat_nsecs(&m->lock_object);
385 #endif
386
387 while (!_mtx_obtain_lock(m, tid)) {
388 #ifdef KDTRACE_HOOKS
389 spin_cnt++;
390 #endif
391 #ifdef ADAPTIVE_MUTEXES
392 /*
393 * If the owner is running on another CPU, spin until the
394 * owner stops running or the state of the lock changes.
395 */
396 v = m->mtx_lock;
397 if (v != MTX_UNOWNED) {
398 owner = (struct thread *)(v & ~MTX_FLAGMASK);
399 if (TD_IS_RUNNING(owner)) {
400 if (LOCK_LOG_TEST(&m->lock_object, 0))
401 CTR3(KTR_LOCK,
402 "%s: spinning on %p held by %p",
403 __func__, m, owner);
404 while (mtx_owner(m) == owner &&
405 TD_IS_RUNNING(owner)) {
406 cpu_spinwait();
407 #ifdef KDTRACE_HOOKS
408 spin_cnt++;
409 #endif
410 }
411 continue;
412 }
413 }
414 #endif
415
416 ts = turnstile_trywait(&m->lock_object);
417 v = m->mtx_lock;
418
419 /*
420 * Check if the lock has been released while spinning for
421 * the turnstile chain lock.
422 */
423 if (v == MTX_UNOWNED) {
424 turnstile_cancel(ts);
425 continue;
426 }
427
428 #ifdef ADAPTIVE_MUTEXES
429 /*
430 * The current lock owner might have started executing
431 * on another CPU (or the lock could have changed
432 * owners) while we were waiting on the turnstile
433 * chain lock. If so, drop the turnstile lock and try
434 * again.
435 */
436 owner = (struct thread *)(v & ~MTX_FLAGMASK);
437 if (TD_IS_RUNNING(owner)) {
438 turnstile_cancel(ts);
439 continue;
440 }
441 #endif
442
443 /*
444 * If the mutex isn't already contested and a failure occurs
445 * setting the contested bit, the mutex was either released
446 * or the state of the MTX_RECURSED bit changed.
447 */
448 if ((v & MTX_CONTESTED) == 0 &&
449 !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) {
450 turnstile_cancel(ts);
451 continue;
452 }
453
454 /*
455 * We definitely must sleep for this lock.
456 */
457 mtx_assert(m, MA_NOTOWNED);
458
459 #ifdef KTR
460 if (!cont_logged) {
461 CTR6(KTR_CONTENTION,
462 "contention: %p at %s:%d wants %s, taken by %s:%d",
463 (void *)tid, file, line, m->lock_object.lo_name,
464 WITNESS_FILE(&m->lock_object),
465 WITNESS_LINE(&m->lock_object));
466 cont_logged = 1;
467 }
468 #endif
469
470 /*
471 * Block on the turnstile.
472 */
473 #ifdef KDTRACE_HOOKS
474 sleep_time -= lockstat_nsecs(&m->lock_object);
475 #endif
476 turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE);
477 #ifdef KDTRACE_HOOKS
478 sleep_time += lockstat_nsecs(&m->lock_object);
479 sleep_cnt++;
480 #endif
481 }
482 #ifdef KDTRACE_HOOKS
483 all_time += lockstat_nsecs(&m->lock_object);
484 #endif
485 #ifdef KTR
486 if (cont_logged) {
487 CTR4(KTR_CONTENTION,
488 "contention end: %s acquired by %p at %s:%d",
489 m->lock_object.lo_name, (void *)tid, file, line);
490 }
491 #endif
492 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE, m, contested,
493 waittime, file, line);
494 #ifdef KDTRACE_HOOKS
495 if (sleep_time)
496 LOCKSTAT_RECORD1(LS_MTX_LOCK_BLOCK, m, sleep_time);
497
498 /*
499 * Only record the loops spinning and not sleeping.
500 */
501 if (spin_cnt > sleep_cnt)
502 LOCKSTAT_RECORD1(LS_MTX_LOCK_SPIN, m, (all_time - sleep_time));
503 #endif
504 }
505
506 static void
_mtx_lock_spin_failed(struct mtx * m)507 _mtx_lock_spin_failed(struct mtx *m)
508 {
509 struct thread *td;
510
511 td = mtx_owner(m);
512
513 /* If the mutex is unlocked, try again. */
514 if (td == NULL)
515 return;
516
517 printf( "spin lock %p (%s) held by %p (tid %d) too long\n",
518 m, m->lock_object.lo_name, td, td->td_tid);
519 #ifdef WITNESS
520 witness_display_spinlock(&m->lock_object, td, printf);
521 #endif
522 panic("spin lock held too long");
523 }
524
525 #ifdef SMP
526 /*
527 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock.
528 *
529 * This is only called if we need to actually spin for the lock. Recursion
530 * is handled inline.
531 */
532 void
_mtx_lock_spin(struct mtx * m,uintptr_t tid,int opts,const char * file,int line)533 _mtx_lock_spin(struct mtx *m, uintptr_t tid, int opts, const char *file,
534 int line)
535 {
536 int i = 0;
537 #ifdef LOCK_PROFILING
538 int contested = 0;
539 uint64_t waittime = 0;
540 #endif
541 #ifdef KDTRACE_HOOKS
542 int64_t spin_time = 0;
543 #endif
544
545 if (SCHEDULER_STOPPED())
546 return;
547
548 if (LOCK_LOG_TEST(&m->lock_object, opts))
549 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
550
551 #ifdef HWPMC_HOOKS
552 PMC_SOFT_CALL( , , lock, failed);
553 #endif
554 lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime);
555 #ifdef KDTRACE_HOOKS
556 spin_time -= lockstat_nsecs(&m->lock_object);
557 #endif
558 while (!_mtx_obtain_lock(m, tid)) {
559
560 /* Give interrupts a chance while we spin. */
561 spinlock_exit();
562 while (m->mtx_lock != MTX_UNOWNED) {
563 if (i++ < 10000000) {
564 cpu_spinwait();
565 continue;
566 }
567 if (i < 60000000 || kdb_active || panicstr != NULL)
568 DELAY(1);
569 else
570 _mtx_lock_spin_failed(m);
571 cpu_spinwait();
572 }
573 spinlock_enter();
574 }
575 #ifdef KDTRACE_HOOKS
576 spin_time += lockstat_nsecs(&m->lock_object);
577 #endif
578
579 if (LOCK_LOG_TEST(&m->lock_object, opts))
580 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
581
582 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE, m,
583 contested, waittime, (file), (line));
584 #ifdef KDTRACE_HOOKS
585 if (spin_time != 0)
586 LOCKSTAT_RECORD1(LS_MTX_SPIN_LOCK_SPIN, m, spin_time);
587 #endif
588 }
589 #endif /* SMP */
590
591 void
_thread_lock_flags(struct thread * td,int opts,const char * file,int line)592 _thread_lock_flags(struct thread *td, int opts, const char *file, int line)
593 {
594 struct mtx *m;
595 uintptr_t tid;
596 int i;
597 #ifdef LOCK_PROFILING
598 int contested = 0;
599 uint64_t waittime = 0;
600 #endif
601 #ifdef KDTRACE_HOOKS
602 int64_t spin_time = 0;
603 #endif
604
605 i = 0;
606 tid = (uintptr_t)curthread;
607
608 if (SCHEDULER_STOPPED())
609 return;
610
611 #ifdef KDTRACE_HOOKS
612 spin_time -= lockstat_nsecs(&td->td_lock->lock_object);
613 #endif
614 for (;;) {
615 retry:
616 spinlock_enter();
617 m = td->td_lock;
618 KASSERT(m->mtx_lock != MTX_DESTROYED,
619 ("thread_lock() of destroyed mutex @ %s:%d", file, line));
620 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
621 ("thread_lock() of sleep mutex %s @ %s:%d",
622 m->lock_object.lo_name, file, line));
623 if (mtx_owned(m))
624 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
625 ("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n",
626 m->lock_object.lo_name, file, line));
627 WITNESS_CHECKORDER(&m->lock_object,
628 opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
629 while (!_mtx_obtain_lock(m, tid)) {
630 if (m->mtx_lock == tid) {
631 m->mtx_recurse++;
632 break;
633 }
634 #ifdef HWPMC_HOOKS
635 PMC_SOFT_CALL( , , lock, failed);
636 #endif
637 lock_profile_obtain_lock_failed(&m->lock_object,
638 &contested, &waittime);
639 /* Give interrupts a chance while we spin. */
640 spinlock_exit();
641 while (m->mtx_lock != MTX_UNOWNED) {
642 if (i++ < 10000000)
643 cpu_spinwait();
644 else if (i < 60000000 ||
645 kdb_active || panicstr != NULL)
646 DELAY(1);
647 else
648 _mtx_lock_spin_failed(m);
649 cpu_spinwait();
650 if (m != td->td_lock)
651 goto retry;
652 }
653 spinlock_enter();
654 }
655 if (m == td->td_lock)
656 break;
657 __mtx_unlock_spin(m); /* does spinlock_exit() */
658 }
659 #ifdef KDTRACE_HOOKS
660 spin_time += lockstat_nsecs(&m->lock_object);
661 #endif
662 if (m->mtx_recurse == 0)
663 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE,
664 m, contested, waittime, (file), (line));
665 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
666 line);
667 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
668 LOCKSTAT_RECORD1(LS_THREAD_LOCK_SPIN, m, spin_time);
669 }
670
671 struct mtx *
thread_lock_block(struct thread * td)672 thread_lock_block(struct thread *td)
673 {
674 struct mtx *lock;
675
676 THREAD_LOCK_ASSERT(td, MA_OWNED);
677 lock = td->td_lock;
678 td->td_lock = &blocked_lock;
679 mtx_unlock_spin(lock);
680
681 return (lock);
682 }
683
684 void
thread_lock_unblock(struct thread * td,struct mtx * new)685 thread_lock_unblock(struct thread *td, struct mtx *new)
686 {
687 mtx_assert(new, MA_OWNED);
688 MPASS(td->td_lock == &blocked_lock);
689 atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new);
690 }
691
692 void
thread_lock_set(struct thread * td,struct mtx * new)693 thread_lock_set(struct thread *td, struct mtx *new)
694 {
695 struct mtx *lock;
696
697 mtx_assert(new, MA_OWNED);
698 THREAD_LOCK_ASSERT(td, MA_OWNED);
699 lock = td->td_lock;
700 td->td_lock = new;
701 mtx_unlock_spin(lock);
702 }
703
704 /*
705 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
706 *
707 * We are only called here if the lock is recursed or contested (i.e. we
708 * need to wake up a blocked thread).
709 */
710 void
_mtx_unlock_sleep(struct mtx * m,int opts,const char * file,int line)711 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line)
712 {
713 struct turnstile *ts;
714
715 if (SCHEDULER_STOPPED())
716 return;
717
718 if (mtx_recursed(m)) {
719 if (--(m->mtx_recurse) == 0)
720 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
721 if (LOCK_LOG_TEST(&m->lock_object, opts))
722 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
723 return;
724 }
725
726 /*
727 * We have to lock the chain before the turnstile so this turnstile
728 * can be removed from the hash list if it is empty.
729 */
730 turnstile_chain_lock(&m->lock_object);
731 ts = turnstile_lookup(&m->lock_object);
732 if (LOCK_LOG_TEST(&m->lock_object, opts))
733 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);
734 MPASS(ts != NULL);
735 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
736 _mtx_release_lock_quick(m);
737
738 /*
739 * This turnstile is now no longer associated with the mutex. We can
740 * unlock the chain lock so a new turnstile may take it's place.
741 */
742 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
743 turnstile_chain_unlock(&m->lock_object);
744 }
745
746 /*
747 * All the unlocking of MTX_SPIN locks is done inline.
748 * See the __mtx_unlock_spin() macro for the details.
749 */
750
751 /*
752 * The backing function for the INVARIANTS-enabled mtx_assert()
753 */
754 #ifdef INVARIANT_SUPPORT
755 void
_mtx_assert(struct mtx * m,int what,const char * file,int line)756 _mtx_assert(struct mtx *m, int what, const char *file, int line)
757 {
758
759 if (panicstr != NULL || dumping)
760 return;
761 switch (what) {
762 case MA_OWNED:
763 case MA_OWNED | MA_RECURSED:
764 case MA_OWNED | MA_NOTRECURSED:
765 if (!mtx_owned(m))
766 panic("mutex %s not owned at %s:%d",
767 m->lock_object.lo_name, file, line);
768 if (mtx_recursed(m)) {
769 if ((what & MA_NOTRECURSED) != 0)
770 panic("mutex %s recursed at %s:%d",
771 m->lock_object.lo_name, file, line);
772 } else if ((what & MA_RECURSED) != 0) {
773 panic("mutex %s unrecursed at %s:%d",
774 m->lock_object.lo_name, file, line);
775 }
776 break;
777 case MA_NOTOWNED:
778 if (mtx_owned(m))
779 panic("mutex %s owned at %s:%d",
780 m->lock_object.lo_name, file, line);
781 break;
782 default:
783 panic("unknown mtx_assert at %s:%d", file, line);
784 }
785 }
786 #endif
787
788 /*
789 * The MUTEX_DEBUG-enabled mtx_validate()
790 *
791 * Most of these checks have been moved off into the LO_INITIALIZED flag
792 * maintained by the witness code.
793 */
794 #ifdef MUTEX_DEBUG
795
796 void mtx_validate(struct mtx *);
797
798 void
mtx_validate(struct mtx * m)799 mtx_validate(struct mtx *m)
800 {
801
802 /*
803 * XXX: When kernacc() does not require Giant we can reenable this check
804 */
805 #ifdef notyet
806 /*
807 * Can't call kernacc() from early init386(), especially when
808 * initializing Giant mutex, because some stuff in kernacc()
809 * requires Giant itself.
810 */
811 if (!cold)
812 if (!kernacc((caddr_t)m, sizeof(m),
813 VM_PROT_READ | VM_PROT_WRITE))
814 panic("Can't read and write to mutex %p", m);
815 #endif
816 }
817 #endif
818
819 /*
820 * General init routine used by the MTX_SYSINIT() macro.
821 */
822 void
mtx_sysinit(void * arg)823 mtx_sysinit(void *arg)
824 {
825 struct mtx_args *margs = arg;
826
827 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts);
828 }
829
830 /*
831 * Mutex initialization routine; initialize lock `m' of type contained in
832 * `opts' with options contained in `opts' and name `name.' The optional
833 * lock type `type' is used as a general lock category name for use with
834 * witness.
835 */
836 void
mtx_init(struct mtx * m,const char * name,const char * type,int opts)837 mtx_init(struct mtx *m, const char *name, const char *type, int opts)
838 {
839 struct lock_class *class;
840 int flags;
841
842 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
843 MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0);
844 ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock,
845 ("%s: mtx_lock not aligned for %s: %p", __func__, name,
846 &m->mtx_lock));
847
848 #ifdef MUTEX_DEBUG
849 /* Diagnostic and error correction */
850 mtx_validate(m);
851 #endif
852
853 /* Determine lock class and lock flags. */
854 if (opts & MTX_SPIN)
855 class = &lock_class_mtx_spin;
856 else
857 class = &lock_class_mtx_sleep;
858 flags = 0;
859 if (opts & MTX_QUIET)
860 flags |= LO_QUIET;
861 if (opts & MTX_RECURSE)
862 flags |= LO_RECURSABLE;
863 if ((opts & MTX_NOWITNESS) == 0)
864 flags |= LO_WITNESS;
865 if (opts & MTX_DUPOK)
866 flags |= LO_DUPOK;
867 if (opts & MTX_NOPROFILE)
868 flags |= LO_NOPROFILE;
869
870 /* Initialize mutex. */
871 m->mtx_lock = MTX_UNOWNED;
872 m->mtx_recurse = 0;
873
874 lock_init(&m->lock_object, class, name, type, flags);
875 }
876
877 /*
878 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be
879 * passed in as a flag here because if the corresponding mtx_init() was
880 * called with MTX_QUIET set, then it will already be set in the mutex's
881 * flags.
882 */
883 void
mtx_destroy(struct mtx * m)884 mtx_destroy(struct mtx *m)
885 {
886
887 if (!mtx_owned(m))
888 MPASS(mtx_unowned(m));
889 else {
890 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);
891
892 /* Perform the non-mtx related part of mtx_unlock_spin(). */
893 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin)
894 spinlock_exit();
895 else
896 curthread->td_locks--;
897
898 lock_profile_release_lock(&m->lock_object);
899 /* Tell witness this isn't locked to make it happy. */
900 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__,
901 __LINE__);
902 }
903
904 m->mtx_lock = MTX_DESTROYED;
905 lock_destroy(&m->lock_object);
906 }
907
908 /*
909 * Intialize the mutex code and system mutexes. This is called from the MD
910 * startup code prior to mi_startup(). The per-CPU data space needs to be
911 * setup before this is called.
912 */
913 void
mutex_init(void)914 mutex_init(void)
915 {
916
917 /* Setup turnstiles so that sleep mutexes work. */
918 init_turnstiles();
919
920 /*
921 * Initialize mutexes.
922 */
923 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE);
924 mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN);
925 blocked_lock.mtx_lock = 0xdeadc0de; /* Always blocked. */
926 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK);
927 mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN | MTX_RECURSE);
928 mtx_init(&devmtx, "cdev", NULL, MTX_DEF);
929 mtx_lock(&Giant);
930 }
931
932 #ifdef DDB
933 void
db_show_mtx(struct lock_object * lock)934 db_show_mtx(struct lock_object *lock)
935 {
936 struct thread *td;
937 struct mtx *m;
938
939 m = (struct mtx *)lock;
940
941 db_printf(" flags: {");
942 if (LOCK_CLASS(lock) == &lock_class_mtx_spin)
943 db_printf("SPIN");
944 else
945 db_printf("DEF");
946 if (m->lock_object.lo_flags & LO_RECURSABLE)
947 db_printf(", RECURSE");
948 if (m->lock_object.lo_flags & LO_DUPOK)
949 db_printf(", DUPOK");
950 db_printf("}\n");
951 db_printf(" state: {");
952 if (mtx_unowned(m))
953 db_printf("UNOWNED");
954 else if (mtx_destroyed(m))
955 db_printf("DESTROYED");
956 else {
957 db_printf("OWNED");
958 if (m->mtx_lock & MTX_CONTESTED)
959 db_printf(", CONTESTED");
960 if (m->mtx_lock & MTX_RECURSED)
961 db_printf(", RECURSED");
962 }
963 db_printf("}\n");
964 if (!mtx_unowned(m) && !mtx_destroyed(m)) {
965 td = mtx_owner(m);
966 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td,
967 td->td_tid, td->td_proc->p_pid, td->td_name);
968 if (mtx_recursed(m))
969 db_printf(" recursed: %d\n", m->mtx_recurse);
970 }
971 }
972 #endif
973