1 /*-
2 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. Berkeley Software Design Inc's name may not be used to endorse or
13 * promote products derived from this software without specific prior
14 * written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
29 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
30 */
31
32 /*
33 * Machine independent bits of mutex implementation.
34 */
35
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
38
39 #include "opt_adaptive_mutexes.h"
40 #include "opt_ddb.h"
41 #include "opt_global.h"
42 #include "opt_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 * Return the mutex address when the lock cookie address is provided.
87 * This functionality assumes that struct mtx* have a member named mtx_lock.
88 */
89 #define mtxlock2mtx(c) (__containerof(c, struct mtx, mtx_lock))
90
91 /*
92 * Internal utility macros.
93 */
94 #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
95
96 #define mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED)
97
98 #define mtx_owner(m) ((struct thread *)((m)->mtx_lock & ~MTX_FLAGMASK))
99
100 static void assert_mtx(const struct lock_object *lock, int what);
101 #ifdef DDB
102 static void db_show_mtx(const struct lock_object *lock);
103 #endif
104 static void lock_mtx(struct lock_object *lock, uintptr_t how);
105 static void lock_spin(struct lock_object *lock, uintptr_t how);
106 #ifdef KDTRACE_HOOKS
107 static int owner_mtx(const struct lock_object *lock,
108 struct thread **owner);
109 #endif
110 static uintptr_t unlock_mtx(struct lock_object *lock);
111 static uintptr_t unlock_spin(struct lock_object *lock);
112
113 /*
114 * Lock classes for sleep and spin mutexes.
115 */
116 struct lock_class lock_class_mtx_sleep = {
117 .lc_name = "sleep mutex",
118 .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE,
119 .lc_assert = assert_mtx,
120 #ifdef DDB
121 .lc_ddb_show = db_show_mtx,
122 #endif
123 .lc_lock = lock_mtx,
124 .lc_unlock = unlock_mtx,
125 #ifdef KDTRACE_HOOKS
126 .lc_owner = owner_mtx,
127 #endif
128 };
129 struct lock_class lock_class_mtx_spin = {
130 .lc_name = "spin mutex",
131 .lc_flags = LC_SPINLOCK | LC_RECURSABLE,
132 .lc_assert = assert_mtx,
133 #ifdef DDB
134 .lc_ddb_show = db_show_mtx,
135 #endif
136 .lc_lock = lock_spin,
137 .lc_unlock = unlock_spin,
138 #ifdef KDTRACE_HOOKS
139 .lc_owner = owner_mtx,
140 #endif
141 };
142
143 /*
144 * System-wide mutexes
145 */
146 struct mtx blocked_lock;
147 struct mtx Giant;
148
149 void
assert_mtx(const struct lock_object * lock,int what)150 assert_mtx(const struct lock_object *lock, int what)
151 {
152
153 mtx_assert((const struct mtx *)lock, what);
154 }
155
156 void
lock_mtx(struct lock_object * lock,uintptr_t how)157 lock_mtx(struct lock_object *lock, uintptr_t how)
158 {
159
160 mtx_lock((struct mtx *)lock);
161 }
162
163 void
lock_spin(struct lock_object * lock,uintptr_t how)164 lock_spin(struct lock_object *lock, uintptr_t how)
165 {
166
167 panic("spin locks can only use msleep_spin");
168 }
169
170 uintptr_t
unlock_mtx(struct lock_object * lock)171 unlock_mtx(struct lock_object *lock)
172 {
173 struct mtx *m;
174
175 m = (struct mtx *)lock;
176 mtx_assert(m, MA_OWNED | MA_NOTRECURSED);
177 mtx_unlock(m);
178 return (0);
179 }
180
181 uintptr_t
unlock_spin(struct lock_object * lock)182 unlock_spin(struct lock_object *lock)
183 {
184
185 panic("spin locks can only use msleep_spin");
186 }
187
188 #ifdef KDTRACE_HOOKS
189 int
owner_mtx(const struct lock_object * lock,struct thread ** owner)190 owner_mtx(const struct lock_object *lock, struct thread **owner)
191 {
192 const struct mtx *m = (const struct mtx *)lock;
193
194 *owner = mtx_owner(m);
195 return (mtx_unowned(m) == 0);
196 }
197 #endif
198
199 /*
200 * Function versions of the inlined __mtx_* macros. These are used by
201 * modules and can also be called from assembly language if needed.
202 */
203 void
__mtx_lock_flags(volatile uintptr_t * c,int opts,const char * file,int line)204 __mtx_lock_flags(volatile uintptr_t *c, int opts, const char *file, int line)
205 {
206 struct mtx *m;
207
208 if (SCHEDULER_STOPPED())
209 return;
210
211 m = mtxlock2mtx(c);
212
213 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
214 ("mtx_lock() by idle thread %p on sleep mutex %s @ %s:%d",
215 curthread, m->lock_object.lo_name, file, line));
216 KASSERT(m->mtx_lock != MTX_DESTROYED,
217 ("mtx_lock() of destroyed mutex @ %s:%d", file, line));
218 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
219 ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
220 file, line));
221 WITNESS_CHECKORDER(&m->lock_object, (opts & ~MTX_RECURSE) |
222 LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
223
224 __mtx_lock(m, curthread, opts, file, line);
225 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
226 line);
227 WITNESS_LOCK(&m->lock_object, (opts & ~MTX_RECURSE) | LOP_EXCLUSIVE,
228 file, line);
229 curthread->td_locks++;
230 }
231
232 void
__mtx_unlock_flags(volatile uintptr_t * c,int opts,const char * file,int line)233 __mtx_unlock_flags(volatile uintptr_t *c, int opts, const char *file, int line)
234 {
235 struct mtx *m;
236
237 if (SCHEDULER_STOPPED())
238 return;
239
240 m = mtxlock2mtx(c);
241
242 KASSERT(m->mtx_lock != MTX_DESTROYED,
243 ("mtx_unlock() of destroyed mutex @ %s:%d", file, line));
244 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
245 ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
246 file, line));
247 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
248 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
249 line);
250 mtx_assert(m, MA_OWNED);
251
252 if (m->mtx_recurse == 0)
253 LOCKSTAT_PROFILE_RELEASE_LOCK(LS_MTX_UNLOCK_RELEASE, m);
254 __mtx_unlock(m, curthread, opts, file, line);
255 curthread->td_locks--;
256 }
257
258 void
__mtx_lock_spin_flags(volatile uintptr_t * c,int opts,const char * file,int line)259 __mtx_lock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
260 int line)
261 {
262 struct mtx *m;
263
264 if (SCHEDULER_STOPPED())
265 return;
266
267 m = mtxlock2mtx(c);
268
269 KASSERT(m->mtx_lock != MTX_DESTROYED,
270 ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line));
271 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
272 ("mtx_lock_spin() of sleep mutex %s @ %s:%d",
273 m->lock_object.lo_name, file, line));
274 if (mtx_owned(m))
275 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
276 (opts & MTX_RECURSE) != 0,
277 ("mtx_lock_spin: recursed on non-recursive mutex %s @ %s:%d\n",
278 m->lock_object.lo_name, file, line));
279 opts &= ~MTX_RECURSE;
280 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
281 file, line, NULL);
282 __mtx_lock_spin(m, curthread, opts, file, line);
283 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
284 line);
285 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
286 }
287
288 void
__mtx_unlock_spin_flags(volatile uintptr_t * c,int opts,const char * file,int line)289 __mtx_unlock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
290 int line)
291 {
292 struct mtx *m;
293
294 if (SCHEDULER_STOPPED())
295 return;
296
297 m = mtxlock2mtx(c);
298
299 KASSERT(m->mtx_lock != MTX_DESTROYED,
300 ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line));
301 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
302 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d",
303 m->lock_object.lo_name, file, line));
304 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
305 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
306 line);
307 mtx_assert(m, MA_OWNED);
308
309 __mtx_unlock_spin(m);
310 }
311
312 /*
313 * The important part of mtx_trylock{,_flags}()
314 * Tries to acquire lock `m.' If this function is called on a mutex that
315 * is already owned, it will recursively acquire the lock.
316 */
317 int
_mtx_trylock_flags_(volatile uintptr_t * c,int opts,const char * file,int line)318 _mtx_trylock_flags_(volatile uintptr_t *c, int opts, const char *file, int line)
319 {
320 struct mtx *m;
321 #ifdef LOCK_PROFILING
322 uint64_t waittime = 0;
323 int contested = 0;
324 #endif
325 int rval;
326
327 if (SCHEDULER_STOPPED())
328 return (1);
329
330 m = mtxlock2mtx(c);
331
332 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
333 ("mtx_trylock() by idle thread %p on sleep mutex %s @ %s:%d",
334 curthread, m->lock_object.lo_name, file, line));
335 KASSERT(m->mtx_lock != MTX_DESTROYED,
336 ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
337 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
338 ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
339 file, line));
340
341 if (mtx_owned(m) && ((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
342 (opts & MTX_RECURSE) != 0)) {
343 m->mtx_recurse++;
344 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
345 rval = 1;
346 } else
347 rval = _mtx_obtain_lock(m, (uintptr_t)curthread);
348 opts &= ~MTX_RECURSE;
349
350 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line);
351 if (rval) {
352 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
353 file, line);
354 curthread->td_locks++;
355 if (m->mtx_recurse == 0)
356 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE,
357 m, contested, waittime, file, line);
358
359 }
360
361 return (rval);
362 }
363
364 /*
365 * __mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
366 *
367 * We call this if the lock is either contested (i.e. we need to go to
368 * sleep waiting for it), or if we need to recurse on it.
369 */
370 void
__mtx_lock_sleep(volatile uintptr_t * c,uintptr_t tid,int opts,const char * file,int line)371 __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t tid, int opts,
372 const char *file, int line)
373 {
374 struct mtx *m;
375 struct turnstile *ts;
376 uintptr_t v;
377 #ifdef ADAPTIVE_MUTEXES
378 volatile struct thread *owner;
379 #endif
380 #ifdef KTR
381 int cont_logged = 0;
382 #endif
383 #ifdef LOCK_PROFILING
384 int contested = 0;
385 uint64_t waittime = 0;
386 #endif
387 #ifdef KDTRACE_HOOKS
388 uint64_t spin_cnt = 0;
389 uint64_t sleep_cnt = 0;
390 int64_t sleep_time = 0;
391 #endif
392
393 if (SCHEDULER_STOPPED())
394 return;
395
396 m = mtxlock2mtx(c);
397
398 if (mtx_owned(m)) {
399 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
400 (opts & MTX_RECURSE) != 0,
401 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
402 m->lock_object.lo_name, file, line));
403 opts &= ~MTX_RECURSE;
404 m->mtx_recurse++;
405 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
406 if (LOCK_LOG_TEST(&m->lock_object, opts))
407 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
408 return;
409 }
410 opts &= ~MTX_RECURSE;
411
412 #ifdef HWPMC_HOOKS
413 PMC_SOFT_CALL( , , lock, failed);
414 #endif
415 lock_profile_obtain_lock_failed(&m->lock_object,
416 &contested, &waittime);
417 if (LOCK_LOG_TEST(&m->lock_object, opts))
418 CTR4(KTR_LOCK,
419 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
420 m->lock_object.lo_name, (void *)m->mtx_lock, file, line);
421
422 while (!_mtx_obtain_lock(m, tid)) {
423 #ifdef KDTRACE_HOOKS
424 spin_cnt++;
425 #endif
426 #ifdef ADAPTIVE_MUTEXES
427 /*
428 * If the owner is running on another CPU, spin until the
429 * owner stops running or the state of the lock changes.
430 */
431 v = m->mtx_lock;
432 if (v != MTX_UNOWNED) {
433 owner = (struct thread *)(v & ~MTX_FLAGMASK);
434 if (TD_IS_RUNNING(owner)) {
435 if (LOCK_LOG_TEST(&m->lock_object, 0))
436 CTR3(KTR_LOCK,
437 "%s: spinning on %p held by %p",
438 __func__, m, owner);
439 KTR_STATE1(KTR_SCHED, "thread",
440 sched_tdname((struct thread *)tid),
441 "spinning", "lockname:\"%s\"",
442 m->lock_object.lo_name);
443 while (mtx_owner(m) == owner &&
444 TD_IS_RUNNING(owner)) {
445 cpu_spinwait();
446 #ifdef KDTRACE_HOOKS
447 spin_cnt++;
448 #endif
449 }
450 KTR_STATE0(KTR_SCHED, "thread",
451 sched_tdname((struct thread *)tid),
452 "running");
453 continue;
454 }
455 }
456 #endif
457
458 ts = turnstile_trywait(&m->lock_object);
459 v = m->mtx_lock;
460
461 /*
462 * Check if the lock has been released while spinning for
463 * the turnstile chain lock.
464 */
465 if (v == MTX_UNOWNED) {
466 turnstile_cancel(ts);
467 continue;
468 }
469
470 #ifdef ADAPTIVE_MUTEXES
471 /*
472 * The current lock owner might have started executing
473 * on another CPU (or the lock could have changed
474 * owners) while we were waiting on the turnstile
475 * chain lock. If so, drop the turnstile lock and try
476 * again.
477 */
478 owner = (struct thread *)(v & ~MTX_FLAGMASK);
479 if (TD_IS_RUNNING(owner)) {
480 turnstile_cancel(ts);
481 continue;
482 }
483 #endif
484
485 /*
486 * If the mutex isn't already contested and a failure occurs
487 * setting the contested bit, the mutex was either released
488 * or the state of the MTX_RECURSED bit changed.
489 */
490 if ((v & MTX_CONTESTED) == 0 &&
491 !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) {
492 turnstile_cancel(ts);
493 continue;
494 }
495
496 /*
497 * We definitely must sleep for this lock.
498 */
499 mtx_assert(m, MA_NOTOWNED);
500
501 #ifdef KTR
502 if (!cont_logged) {
503 CTR6(KTR_CONTENTION,
504 "contention: %p at %s:%d wants %s, taken by %s:%d",
505 (void *)tid, file, line, m->lock_object.lo_name,
506 WITNESS_FILE(&m->lock_object),
507 WITNESS_LINE(&m->lock_object));
508 cont_logged = 1;
509 }
510 #endif
511
512 /*
513 * Block on the turnstile.
514 */
515 #ifdef KDTRACE_HOOKS
516 sleep_time -= lockstat_nsecs();
517 #endif
518 turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE);
519 #ifdef KDTRACE_HOOKS
520 sleep_time += lockstat_nsecs();
521 sleep_cnt++;
522 #endif
523 }
524 #ifdef KTR
525 if (cont_logged) {
526 CTR4(KTR_CONTENTION,
527 "contention end: %s acquired by %p at %s:%d",
528 m->lock_object.lo_name, (void *)tid, file, line);
529 }
530 #endif
531 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE, m, contested,
532 waittime, file, line);
533 #ifdef KDTRACE_HOOKS
534 if (sleep_time)
535 LOCKSTAT_RECORD1(LS_MTX_LOCK_BLOCK, m, sleep_time);
536
537 /*
538 * Only record the loops spinning and not sleeping.
539 */
540 if (spin_cnt > sleep_cnt)
541 LOCKSTAT_RECORD1(LS_MTX_LOCK_SPIN, m, (spin_cnt - sleep_cnt));
542 #endif
543 }
544
545 static void
_mtx_lock_spin_failed(struct mtx * m)546 _mtx_lock_spin_failed(struct mtx *m)
547 {
548 struct thread *td;
549
550 td = mtx_owner(m);
551
552 /* If the mutex is unlocked, try again. */
553 if (td == NULL)
554 return;
555
556 printf( "spin lock %p (%s) held by %p (tid %d) too long\n",
557 m, m->lock_object.lo_name, td, td->td_tid);
558 #ifdef WITNESS
559 witness_display_spinlock(&m->lock_object, td, printf);
560 #endif
561 panic("spin lock held too long");
562 }
563
564 #ifdef SMP
565 /*
566 * _mtx_lock_spin_cookie: the tougher part of acquiring an MTX_SPIN lock.
567 *
568 * This is only called if we need to actually spin for the lock. Recursion
569 * is handled inline.
570 */
571 void
_mtx_lock_spin_cookie(volatile uintptr_t * c,uintptr_t tid,int opts,const char * file,int line)572 _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t tid, int opts,
573 const char *file, int line)
574 {
575 struct mtx *m;
576 int i = 0;
577 #ifdef LOCK_PROFILING
578 int contested = 0;
579 uint64_t waittime = 0;
580 #endif
581
582 if (SCHEDULER_STOPPED())
583 return;
584
585 m = mtxlock2mtx(c);
586
587 if (LOCK_LOG_TEST(&m->lock_object, opts))
588 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
589 KTR_STATE1(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
590 "spinning", "lockname:\"%s\"", m->lock_object.lo_name);
591
592 #ifdef HWPMC_HOOKS
593 PMC_SOFT_CALL( , , lock, failed);
594 #endif
595 lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime);
596 while (!_mtx_obtain_lock(m, tid)) {
597
598 /* Give interrupts a chance while we spin. */
599 spinlock_exit();
600 while (m->mtx_lock != MTX_UNOWNED) {
601 if (i++ < 10000000) {
602 cpu_spinwait();
603 continue;
604 }
605 if (i < 60000000 || kdb_active || panicstr != NULL)
606 DELAY(1);
607 else
608 _mtx_lock_spin_failed(m);
609 cpu_spinwait();
610 }
611 spinlock_enter();
612 }
613
614 if (LOCK_LOG_TEST(&m->lock_object, opts))
615 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
616 KTR_STATE0(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
617 "running");
618
619 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE, m,
620 contested, waittime, (file), (line));
621 LOCKSTAT_RECORD1(LS_MTX_SPIN_LOCK_SPIN, m, i);
622 }
623 #endif /* SMP */
624
625 void
thread_lock_flags_(struct thread * td,int opts,const char * file,int line)626 thread_lock_flags_(struct thread *td, int opts, const char *file, int line)
627 {
628 struct mtx *m;
629 uintptr_t tid;
630 int i;
631 #ifdef LOCK_PROFILING
632 int contested = 0;
633 uint64_t waittime = 0;
634 #endif
635 #ifdef KDTRACE_HOOKS
636 uint64_t spin_cnt = 0;
637 #endif
638
639 i = 0;
640 tid = (uintptr_t)curthread;
641
642 if (SCHEDULER_STOPPED())
643 return;
644
645 for (;;) {
646 retry:
647 spinlock_enter();
648 m = td->td_lock;
649 KASSERT(m->mtx_lock != MTX_DESTROYED,
650 ("thread_lock() of destroyed mutex @ %s:%d", file, line));
651 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
652 ("thread_lock() of sleep mutex %s @ %s:%d",
653 m->lock_object.lo_name, file, line));
654 if (mtx_owned(m))
655 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
656 ("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n",
657 m->lock_object.lo_name, file, line));
658 WITNESS_CHECKORDER(&m->lock_object,
659 opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
660 while (!_mtx_obtain_lock(m, tid)) {
661 #ifdef KDTRACE_HOOKS
662 spin_cnt++;
663 #endif
664 if (m->mtx_lock == tid) {
665 m->mtx_recurse++;
666 break;
667 }
668 #ifdef HWPMC_HOOKS
669 PMC_SOFT_CALL( , , lock, failed);
670 #endif
671 lock_profile_obtain_lock_failed(&m->lock_object,
672 &contested, &waittime);
673 /* Give interrupts a chance while we spin. */
674 spinlock_exit();
675 while (m->mtx_lock != MTX_UNOWNED) {
676 if (i++ < 10000000)
677 cpu_spinwait();
678 else if (i < 60000000 ||
679 kdb_active || panicstr != NULL)
680 DELAY(1);
681 else
682 _mtx_lock_spin_failed(m);
683 cpu_spinwait();
684 if (m != td->td_lock)
685 goto retry;
686 }
687 spinlock_enter();
688 }
689 if (m == td->td_lock)
690 break;
691 __mtx_unlock_spin(m); /* does spinlock_exit() */
692 #ifdef KDTRACE_HOOKS
693 spin_cnt++;
694 #endif
695 }
696 if (m->mtx_recurse == 0)
697 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE,
698 m, contested, waittime, (file), (line));
699 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
700 line);
701 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
702 LOCKSTAT_RECORD1(LS_THREAD_LOCK_SPIN, m, spin_cnt);
703 }
704
705 struct mtx *
thread_lock_block(struct thread * td)706 thread_lock_block(struct thread *td)
707 {
708 struct mtx *lock;
709
710 THREAD_LOCK_ASSERT(td, MA_OWNED);
711 lock = td->td_lock;
712 td->td_lock = &blocked_lock;
713 mtx_unlock_spin(lock);
714
715 return (lock);
716 }
717
718 void
thread_lock_unblock(struct thread * td,struct mtx * new)719 thread_lock_unblock(struct thread *td, struct mtx *new)
720 {
721 mtx_assert(new, MA_OWNED);
722 MPASS(td->td_lock == &blocked_lock);
723 atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new);
724 }
725
726 void
thread_lock_set(struct thread * td,struct mtx * new)727 thread_lock_set(struct thread *td, struct mtx *new)
728 {
729 struct mtx *lock;
730
731 mtx_assert(new, MA_OWNED);
732 THREAD_LOCK_ASSERT(td, MA_OWNED);
733 lock = td->td_lock;
734 td->td_lock = new;
735 mtx_unlock_spin(lock);
736 }
737
738 /*
739 * __mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
740 *
741 * We are only called here if the lock is recursed or contested (i.e. we
742 * need to wake up a blocked thread).
743 */
744 void
__mtx_unlock_sleep(volatile uintptr_t * c,int opts,const char * file,int line)745 __mtx_unlock_sleep(volatile uintptr_t *c, int opts, const char *file, int line)
746 {
747 struct mtx *m;
748 struct turnstile *ts;
749
750 if (SCHEDULER_STOPPED())
751 return;
752
753 m = mtxlock2mtx(c);
754
755 if (mtx_recursed(m)) {
756 if (--(m->mtx_recurse) == 0)
757 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
758 if (LOCK_LOG_TEST(&m->lock_object, opts))
759 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
760 return;
761 }
762
763 /*
764 * We have to lock the chain before the turnstile so this turnstile
765 * can be removed from the hash list if it is empty.
766 */
767 turnstile_chain_lock(&m->lock_object);
768 ts = turnstile_lookup(&m->lock_object);
769 if (LOCK_LOG_TEST(&m->lock_object, opts))
770 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);
771 MPASS(ts != NULL);
772 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
773 _mtx_release_lock_quick(m);
774
775 /*
776 * This turnstile is now no longer associated with the mutex. We can
777 * unlock the chain lock so a new turnstile may take it's place.
778 */
779 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
780 turnstile_chain_unlock(&m->lock_object);
781 }
782
783 /*
784 * All the unlocking of MTX_SPIN locks is done inline.
785 * See the __mtx_unlock_spin() macro for the details.
786 */
787
788 /*
789 * The backing function for the INVARIANTS-enabled mtx_assert()
790 */
791 #ifdef INVARIANT_SUPPORT
792 void
__mtx_assert(const volatile uintptr_t * c,int what,const char * file,int line)793 __mtx_assert(const volatile uintptr_t *c, int what, const char *file, int line)
794 {
795 const struct mtx *m;
796
797 if (panicstr != NULL || dumping)
798 return;
799
800 m = mtxlock2mtx(c);
801
802 switch (what) {
803 case MA_OWNED:
804 case MA_OWNED | MA_RECURSED:
805 case MA_OWNED | MA_NOTRECURSED:
806 if (!mtx_owned(m))
807 panic("mutex %s not owned at %s:%d",
808 m->lock_object.lo_name, file, line);
809 if (mtx_recursed(m)) {
810 if ((what & MA_NOTRECURSED) != 0)
811 panic("mutex %s recursed at %s:%d",
812 m->lock_object.lo_name, file, line);
813 } else if ((what & MA_RECURSED) != 0) {
814 panic("mutex %s unrecursed at %s:%d",
815 m->lock_object.lo_name, file, line);
816 }
817 break;
818 case MA_NOTOWNED:
819 if (mtx_owned(m))
820 panic("mutex %s owned at %s:%d",
821 m->lock_object.lo_name, file, line);
822 break;
823 default:
824 panic("unknown mtx_assert at %s:%d", file, line);
825 }
826 }
827 #endif
828
829 /*
830 * The MUTEX_DEBUG-enabled mtx_validate()
831 *
832 * Most of these checks have been moved off into the LO_INITIALIZED flag
833 * maintained by the witness code.
834 */
835 #ifdef MUTEX_DEBUG
836
837 void mtx_validate(struct mtx *);
838
839 void
mtx_validate(struct mtx * m)840 mtx_validate(struct mtx *m)
841 {
842
843 /*
844 * XXX: When kernacc() does not require Giant we can reenable this check
845 */
846 #ifdef notyet
847 /*
848 * Can't call kernacc() from early init386(), especially when
849 * initializing Giant mutex, because some stuff in kernacc()
850 * requires Giant itself.
851 */
852 if (!cold)
853 if (!kernacc((caddr_t)m, sizeof(m),
854 VM_PROT_READ | VM_PROT_WRITE))
855 panic("Can't read and write to mutex %p", m);
856 #endif
857 }
858 #endif
859
860 /*
861 * General init routine used by the MTX_SYSINIT() macro.
862 */
863 void
mtx_sysinit(void * arg)864 mtx_sysinit(void *arg)
865 {
866 struct mtx_args *margs = arg;
867
868 mtx_init((struct mtx *)margs->ma_mtx, margs->ma_desc, NULL,
869 margs->ma_opts);
870 }
871
872 /*
873 * Mutex initialization routine; initialize lock `m' of type contained in
874 * `opts' with options contained in `opts' and name `name.' The optional
875 * lock type `type' is used as a general lock category name for use with
876 * witness.
877 */
878 void
_mtx_init(volatile uintptr_t * c,const char * name,const char * type,int opts)879 _mtx_init(volatile uintptr_t *c, const char *name, const char *type, int opts)
880 {
881 struct mtx *m;
882 struct lock_class *class;
883 int flags;
884
885 m = mtxlock2mtx(c);
886
887 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
888 MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0);
889 ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock,
890 ("%s: mtx_lock not aligned for %s: %p", __func__, name,
891 &m->mtx_lock));
892
893 #ifdef MUTEX_DEBUG
894 /* Diagnostic and error correction */
895 mtx_validate(m);
896 #endif
897
898 /* Determine lock class and lock flags. */
899 if (opts & MTX_SPIN)
900 class = &lock_class_mtx_spin;
901 else
902 class = &lock_class_mtx_sleep;
903 flags = 0;
904 if (opts & MTX_QUIET)
905 flags |= LO_QUIET;
906 if (opts & MTX_RECURSE)
907 flags |= LO_RECURSABLE;
908 if ((opts & MTX_NOWITNESS) == 0)
909 flags |= LO_WITNESS;
910 if (opts & MTX_DUPOK)
911 flags |= LO_DUPOK;
912 if (opts & MTX_NOPROFILE)
913 flags |= LO_NOPROFILE;
914
915 /* Initialize mutex. */
916 lock_init(&m->lock_object, class, name, type, flags);
917
918 m->mtx_lock = MTX_UNOWNED;
919 m->mtx_recurse = 0;
920 }
921
922 /*
923 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be
924 * passed in as a flag here because if the corresponding mtx_init() was
925 * called with MTX_QUIET set, then it will already be set in the mutex's
926 * flags.
927 */
928 void
_mtx_destroy(volatile uintptr_t * c)929 _mtx_destroy(volatile uintptr_t *c)
930 {
931 struct mtx *m;
932
933 m = mtxlock2mtx(c);
934
935 if (!mtx_owned(m))
936 MPASS(mtx_unowned(m));
937 else {
938 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);
939
940 /* Perform the non-mtx related part of mtx_unlock_spin(). */
941 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin)
942 spinlock_exit();
943 else
944 curthread->td_locks--;
945
946 lock_profile_release_lock(&m->lock_object);
947 /* Tell witness this isn't locked to make it happy. */
948 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__,
949 __LINE__);
950 }
951
952 m->mtx_lock = MTX_DESTROYED;
953 lock_destroy(&m->lock_object);
954 }
955
956 /*
957 * Intialize the mutex code and system mutexes. This is called from the MD
958 * startup code prior to mi_startup(). The per-CPU data space needs to be
959 * setup before this is called.
960 */
961 void
mutex_init(void)962 mutex_init(void)
963 {
964
965 /* Setup turnstiles so that sleep mutexes work. */
966 init_turnstiles();
967
968 /*
969 * Initialize mutexes.
970 */
971 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE);
972 mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN);
973 blocked_lock.mtx_lock = 0xdeadc0de; /* Always blocked. */
974 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK);
975 mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN | MTX_RECURSE);
976 mtx_init(&devmtx, "cdev", NULL, MTX_DEF);
977 mtx_lock(&Giant);
978 }
979
980 #ifdef DDB
981 void
db_show_mtx(const struct lock_object * lock)982 db_show_mtx(const struct lock_object *lock)
983 {
984 struct thread *td;
985 const struct mtx *m;
986
987 m = (const struct mtx *)lock;
988
989 db_printf(" flags: {");
990 if (LOCK_CLASS(lock) == &lock_class_mtx_spin)
991 db_printf("SPIN");
992 else
993 db_printf("DEF");
994 if (m->lock_object.lo_flags & LO_RECURSABLE)
995 db_printf(", RECURSE");
996 if (m->lock_object.lo_flags & LO_DUPOK)
997 db_printf(", DUPOK");
998 db_printf("}\n");
999 db_printf(" state: {");
1000 if (mtx_unowned(m))
1001 db_printf("UNOWNED");
1002 else if (mtx_destroyed(m))
1003 db_printf("DESTROYED");
1004 else {
1005 db_printf("OWNED");
1006 if (m->mtx_lock & MTX_CONTESTED)
1007 db_printf(", CONTESTED");
1008 if (m->mtx_lock & MTX_RECURSED)
1009 db_printf(", RECURSED");
1010 }
1011 db_printf("}\n");
1012 if (!mtx_unowned(m) && !mtx_destroyed(m)) {
1013 td = mtx_owner(m);
1014 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td,
1015 td->td_tid, td->td_proc->p_pid, td->td_name);
1016 if (mtx_recursed(m))
1017 db_printf(" recursed: %d\n", m->mtx_recurse);
1018 }
1019 }
1020 #endif
1021