FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_lock.c
1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2008 Attilio Rao <attilio@FreeBSD.org>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice(s), this list of conditions and the following disclaimer as
12 * the first lines of this file unmodified other than the possible
13 * addition of one or more copyright notices.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice(s), this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
19 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
24 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
25 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
28 * DAMAGE.
29 */
30
31 #include "opt_ddb.h"
32 #include "opt_hwpmc_hooks.h"
33
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD: releng/12.0/sys/kern/kern_lock.c 336267 2018-07-13 22:40:14Z mjg $");
36
37 #include <sys/param.h>
38 #include <sys/kdb.h>
39 #include <sys/ktr.h>
40 #include <sys/lock.h>
41 #include <sys/lock_profile.h>
42 #include <sys/lockmgr.h>
43 #include <sys/mutex.h>
44 #include <sys/proc.h>
45 #include <sys/sleepqueue.h>
46 #ifdef DEBUG_LOCKS
47 #include <sys/stack.h>
48 #endif
49 #include <sys/sysctl.h>
50 #include <sys/systm.h>
51
52 #include <machine/cpu.h>
53
54 #ifdef DDB
55 #include <ddb/ddb.h>
56 #endif
57
58 #ifdef HWPMC_HOOKS
59 #include <sys/pmckern.h>
60 PMC_SOFT_DECLARE( , , lock, failed);
61 #endif
62
63 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
64 (LK_ADAPTIVE | LK_NOSHARE));
65 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
66 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
67
68 #define SQ_EXCLUSIVE_QUEUE 0
69 #define SQ_SHARED_QUEUE 1
70
71 #ifndef INVARIANTS
72 #define _lockmgr_assert(lk, what, file, line)
73 #endif
74
75 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++)
76 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--)
77
78 #ifndef DEBUG_LOCKS
79 #define STACK_PRINT(lk)
80 #define STACK_SAVE(lk)
81 #define STACK_ZERO(lk)
82 #else
83 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
84 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack)
85 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack)
86 #endif
87
88 #define LOCK_LOG2(lk, string, arg1, arg2) \
89 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
90 CTR2(KTR_LOCK, (string), (arg1), (arg2))
91 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \
92 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
93 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
94
95 #define GIANT_DECLARE \
96 int _i = 0; \
97 WITNESS_SAVE_DECL(Giant)
98 #define GIANT_RESTORE() do { \
99 if (_i > 0) { \
100 while (_i--) \
101 mtx_lock(&Giant); \
102 WITNESS_RESTORE(&Giant.lock_object, Giant); \
103 } \
104 } while (0)
105 #define GIANT_SAVE() do { \
106 if (mtx_owned(&Giant)) { \
107 WITNESS_SAVE(&Giant.lock_object, Giant); \
108 while (mtx_owned(&Giant)) { \
109 _i++; \
110 mtx_unlock(&Giant); \
111 } \
112 } \
113 } while (0)
114
115 static bool __always_inline
116 LK_CAN_SHARE(uintptr_t x, int flags, bool fp)
117 {
118
119 if ((x & (LK_SHARE | LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) ==
120 LK_SHARE)
121 return (true);
122 if (fp || (!(x & LK_SHARE)))
123 return (false);
124 if ((curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) ||
125 (curthread->td_pflags & TDP_DEADLKTREAT))
126 return (true);
127 return (false);
128 }
129
130 #define LK_TRYOP(x) \
131 ((x) & LK_NOWAIT)
132
133 #define LK_CAN_WITNESS(x) \
134 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
135 #define LK_TRYWIT(x) \
136 (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
137
138 #define LK_CAN_ADAPT(lk, f) \
139 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \
140 ((f) & LK_SLEEPFAIL) == 0)
141
142 #define lockmgr_disowned(lk) \
143 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
144
145 #define lockmgr_xlocked_v(v) \
146 (((v) & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
147
148 #define lockmgr_xlocked(lk) lockmgr_xlocked_v((lk)->lk_lock)
149
150 static void assert_lockmgr(const struct lock_object *lock, int how);
151 #ifdef DDB
152 static void db_show_lockmgr(const struct lock_object *lock);
153 #endif
154 static void lock_lockmgr(struct lock_object *lock, uintptr_t how);
155 #ifdef KDTRACE_HOOKS
156 static int owner_lockmgr(const struct lock_object *lock,
157 struct thread **owner);
158 #endif
159 static uintptr_t unlock_lockmgr(struct lock_object *lock);
160
161 struct lock_class lock_class_lockmgr = {
162 .lc_name = "lockmgr",
163 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
164 .lc_assert = assert_lockmgr,
165 #ifdef DDB
166 .lc_ddb_show = db_show_lockmgr,
167 #endif
168 .lc_lock = lock_lockmgr,
169 .lc_unlock = unlock_lockmgr,
170 #ifdef KDTRACE_HOOKS
171 .lc_owner = owner_lockmgr,
172 #endif
173 };
174
175 struct lockmgr_wait {
176 const char *iwmesg;
177 int ipri;
178 int itimo;
179 };
180
181 static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp,
182 int flags, bool fp);
183 static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp);
184
185 static void
186 lockmgr_exit(u_int flags, struct lock_object *ilk, int wakeup_swapper)
187 {
188 struct lock_class *class;
189
190 if (flags & LK_INTERLOCK) {
191 class = LOCK_CLASS(ilk);
192 class->lc_unlock(ilk);
193 }
194
195 if (__predict_false(wakeup_swapper))
196 kick_proc0();
197 }
198
199 static void
200 lockmgr_note_shared_acquire(struct lock *lk, int contested,
201 uint64_t waittime, const char *file, int line, int flags)
202 {
203
204 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime,
205 file, line);
206 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line);
207 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line);
208 TD_LOCKS_INC(curthread);
209 TD_SLOCKS_INC(curthread);
210 STACK_SAVE(lk);
211 }
212
213 static void
214 lockmgr_note_shared_release(struct lock *lk, const char *file, int line)
215 {
216
217 lock_profile_release_lock(&lk->lock_object);
218 WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
219 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
220 TD_LOCKS_DEC(curthread);
221 TD_SLOCKS_DEC(curthread);
222 }
223
224 static void
225 lockmgr_note_exclusive_acquire(struct lock *lk, int contested,
226 uint64_t waittime, const char *file, int line, int flags)
227 {
228
229 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime,
230 file, line);
231 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
232 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file,
233 line);
234 TD_LOCKS_INC(curthread);
235 STACK_SAVE(lk);
236 }
237
238 static void
239 lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line)
240 {
241
242 lock_profile_release_lock(&lk->lock_object);
243 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file,
244 line);
245 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
246 TD_LOCKS_DEC(curthread);
247 }
248
249 static __inline struct thread *
250 lockmgr_xholder(const struct lock *lk)
251 {
252 uintptr_t x;
253
254 x = lk->lk_lock;
255 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
256 }
257
258 /*
259 * It assumes sleepq_lock held and returns with this one unheld.
260 * It also assumes the generic interlock is sane and previously checked.
261 * If LK_INTERLOCK is specified the interlock is not reacquired after the
262 * sleep.
263 */
264 static __inline int
265 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
266 const char *wmesg, int pri, int timo, int queue)
267 {
268 GIANT_DECLARE;
269 struct lock_class *class;
270 int catch, error;
271
272 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
273 catch = pri & PCATCH;
274 pri &= PRIMASK;
275 error = 0;
276
277 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
278 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
279
280 if (flags & LK_INTERLOCK)
281 class->lc_unlock(ilk);
282 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0)
283 lk->lk_exslpfail++;
284 GIANT_SAVE();
285 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
286 SLEEPQ_INTERRUPTIBLE : 0), queue);
287 if ((flags & LK_TIMELOCK) && timo)
288 sleepq_set_timeout(&lk->lock_object, timo);
289
290 /*
291 * Decisional switch for real sleeping.
292 */
293 if ((flags & LK_TIMELOCK) && timo && catch)
294 error = sleepq_timedwait_sig(&lk->lock_object, pri);
295 else if ((flags & LK_TIMELOCK) && timo)
296 error = sleepq_timedwait(&lk->lock_object, pri);
297 else if (catch)
298 error = sleepq_wait_sig(&lk->lock_object, pri);
299 else
300 sleepq_wait(&lk->lock_object, pri);
301 GIANT_RESTORE();
302 if ((flags & LK_SLEEPFAIL) && error == 0)
303 error = ENOLCK;
304
305 return (error);
306 }
307
308 static __inline int
309 wakeupshlk(struct lock *lk, const char *file, int line)
310 {
311 uintptr_t v, x, orig_x;
312 u_int realexslp;
313 int queue, wakeup_swapper;
314
315 wakeup_swapper = 0;
316 for (;;) {
317 x = lk->lk_lock;
318 if (lockmgr_sunlock_try(lk, &x))
319 break;
320
321 /*
322 * We should have a sharer with waiters, so enter the hard
323 * path in order to handle wakeups correctly.
324 */
325 sleepq_lock(&lk->lock_object);
326 orig_x = lk->lk_lock;
327 retry_sleepq:
328 x = orig_x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
329 v = LK_UNLOCKED;
330
331 /*
332 * If the lock has exclusive waiters, give them preference in
333 * order to avoid deadlock with shared runners up.
334 * If interruptible sleeps left the exclusive queue empty
335 * avoid a starvation for the threads sleeping on the shared
336 * queue by giving them precedence and cleaning up the
337 * exclusive waiters bit anyway.
338 * Please note that lk_exslpfail count may be lying about
339 * the real number of waiters with the LK_SLEEPFAIL flag on
340 * because they may be used in conjunction with interruptible
341 * sleeps so lk_exslpfail might be considered an 'upper limit'
342 * bound, including the edge cases.
343 */
344 realexslp = sleepq_sleepcnt(&lk->lock_object,
345 SQ_EXCLUSIVE_QUEUE);
346 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
347 if (lk->lk_exslpfail < realexslp) {
348 lk->lk_exslpfail = 0;
349 queue = SQ_EXCLUSIVE_QUEUE;
350 v |= (x & LK_SHARED_WAITERS);
351 } else {
352 lk->lk_exslpfail = 0;
353 LOCK_LOG2(lk,
354 "%s: %p has only LK_SLEEPFAIL sleepers",
355 __func__, lk);
356 LOCK_LOG2(lk,
357 "%s: %p waking up threads on the exclusive queue",
358 __func__, lk);
359 wakeup_swapper =
360 sleepq_broadcast(&lk->lock_object,
361 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
362 queue = SQ_SHARED_QUEUE;
363 }
364
365 } else {
366
367 /*
368 * Exclusive waiters sleeping with LK_SLEEPFAIL on
369 * and using interruptible sleeps/timeout may have
370 * left spourious lk_exslpfail counts on, so clean
371 * it up anyway.
372 */
373 lk->lk_exslpfail = 0;
374 queue = SQ_SHARED_QUEUE;
375 }
376
377 if (lockmgr_sunlock_try(lk, &orig_x)) {
378 sleepq_release(&lk->lock_object);
379 break;
380 }
381
382 x |= LK_SHARERS_LOCK(1);
383 if (!atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, v)) {
384 orig_x = x;
385 goto retry_sleepq;
386 }
387 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
388 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
389 "exclusive");
390 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
391 0, queue);
392 sleepq_release(&lk->lock_object);
393 break;
394 }
395
396 lockmgr_note_shared_release(lk, file, line);
397 return (wakeup_swapper);
398 }
399
400 static void
401 assert_lockmgr(const struct lock_object *lock, int what)
402 {
403
404 panic("lockmgr locks do not support assertions");
405 }
406
407 static void
408 lock_lockmgr(struct lock_object *lock, uintptr_t how)
409 {
410
411 panic("lockmgr locks do not support sleep interlocking");
412 }
413
414 static uintptr_t
415 unlock_lockmgr(struct lock_object *lock)
416 {
417
418 panic("lockmgr locks do not support sleep interlocking");
419 }
420
421 #ifdef KDTRACE_HOOKS
422 static int
423 owner_lockmgr(const struct lock_object *lock, struct thread **owner)
424 {
425
426 panic("lockmgr locks do not support owner inquiring");
427 }
428 #endif
429
430 void
431 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
432 {
433 int iflags;
434
435 MPASS((flags & ~LK_INIT_MASK) == 0);
436 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
437 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
438 &lk->lk_lock));
439
440 iflags = LO_SLEEPABLE | LO_UPGRADABLE;
441 if (flags & LK_CANRECURSE)
442 iflags |= LO_RECURSABLE;
443 if ((flags & LK_NODUP) == 0)
444 iflags |= LO_DUPOK;
445 if (flags & LK_NOPROFILE)
446 iflags |= LO_NOPROFILE;
447 if ((flags & LK_NOWITNESS) == 0)
448 iflags |= LO_WITNESS;
449 if (flags & LK_QUIET)
450 iflags |= LO_QUIET;
451 if (flags & LK_IS_VNODE)
452 iflags |= LO_IS_VNODE;
453 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
454
455 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
456 lk->lk_lock = LK_UNLOCKED;
457 lk->lk_recurse = 0;
458 lk->lk_exslpfail = 0;
459 lk->lk_timo = timo;
460 lk->lk_pri = pri;
461 STACK_ZERO(lk);
462 }
463
464 /*
465 * XXX: Gross hacks to manipulate external lock flags after
466 * initialization. Used for certain vnode and buf locks.
467 */
468 void
469 lockallowshare(struct lock *lk)
470 {
471
472 lockmgr_assert(lk, KA_XLOCKED);
473 lk->lock_object.lo_flags &= ~LK_NOSHARE;
474 }
475
476 void
477 lockdisableshare(struct lock *lk)
478 {
479
480 lockmgr_assert(lk, KA_XLOCKED);
481 lk->lock_object.lo_flags |= LK_NOSHARE;
482 }
483
484 void
485 lockallowrecurse(struct lock *lk)
486 {
487
488 lockmgr_assert(lk, KA_XLOCKED);
489 lk->lock_object.lo_flags |= LO_RECURSABLE;
490 }
491
492 void
493 lockdisablerecurse(struct lock *lk)
494 {
495
496 lockmgr_assert(lk, KA_XLOCKED);
497 lk->lock_object.lo_flags &= ~LO_RECURSABLE;
498 }
499
500 void
501 lockdestroy(struct lock *lk)
502 {
503
504 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
505 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
506 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
507 lock_destroy(&lk->lock_object);
508 }
509
510 static bool __always_inline
511 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags, bool fp)
512 {
513
514 /*
515 * If no other thread has an exclusive lock, or
516 * no exclusive waiter is present, bump the count of
517 * sharers. Since we have to preserve the state of
518 * waiters, if we fail to acquire the shared lock
519 * loop back and retry.
520 */
521 *xp = lk->lk_lock;
522 while (LK_CAN_SHARE(*xp, flags, fp)) {
523 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp,
524 *xp + LK_ONE_SHARER)) {
525 return (true);
526 }
527 }
528 return (false);
529 }
530
531 static bool __always_inline
532 lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp)
533 {
534
535 for (;;) {
536 if (LK_SHARERS(*xp) > 1 || !(*xp & LK_ALL_WAITERS)) {
537 if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp,
538 *xp - LK_ONE_SHARER))
539 return (true);
540 continue;
541 }
542 break;
543 }
544 return (false);
545 }
546
547 static __noinline int
548 lockmgr_slock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
549 const char *file, int line, struct lockmgr_wait *lwa)
550 {
551 uintptr_t tid, x;
552 int error = 0;
553 const char *iwmesg;
554 int ipri, itimo;
555
556 #ifdef LOCK_PROFILING
557 uint64_t waittime = 0;
558 int contested = 0;
559 #endif
560
561 if (__predict_false(panicstr != NULL))
562 goto out;
563
564 tid = (uintptr_t)curthread;
565
566 if (LK_CAN_WITNESS(flags))
567 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
568 file, line, flags & LK_INTERLOCK ? ilk : NULL);
569 for (;;) {
570 if (lockmgr_slock_try(lk, &x, flags, false))
571 break;
572 #ifdef HWPMC_HOOKS
573 PMC_SOFT_CALL( , , lock, failed);
574 #endif
575 lock_profile_obtain_lock_failed(&lk->lock_object,
576 &contested, &waittime);
577
578 /*
579 * If the lock is already held by curthread in
580 * exclusive way avoid a deadlock.
581 */
582 if (LK_HOLDER(x) == tid) {
583 LOCK_LOG2(lk,
584 "%s: %p already held in exclusive mode",
585 __func__, lk);
586 error = EDEADLK;
587 break;
588 }
589
590 /*
591 * If the lock is expected to not sleep just give up
592 * and return.
593 */
594 if (LK_TRYOP(flags)) {
595 LOCK_LOG2(lk, "%s: %p fails the try operation",
596 __func__, lk);
597 error = EBUSY;
598 break;
599 }
600
601 /*
602 * Acquire the sleepqueue chain lock because we
603 * probabilly will need to manipulate waiters flags.
604 */
605 sleepq_lock(&lk->lock_object);
606 x = lk->lk_lock;
607 retry_sleepq:
608
609 /*
610 * if the lock can be acquired in shared mode, try
611 * again.
612 */
613 if (LK_CAN_SHARE(x, flags, false)) {
614 sleepq_release(&lk->lock_object);
615 continue;
616 }
617
618 /*
619 * Try to set the LK_SHARED_WAITERS flag. If we fail,
620 * loop back and retry.
621 */
622 if ((x & LK_SHARED_WAITERS) == 0) {
623 if (!atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
624 x | LK_SHARED_WAITERS)) {
625 goto retry_sleepq;
626 }
627 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
628 __func__, lk);
629 }
630
631 if (lwa == NULL) {
632 iwmesg = lk->lock_object.lo_name;
633 ipri = lk->lk_pri;
634 itimo = lk->lk_timo;
635 } else {
636 iwmesg = lwa->iwmesg;
637 ipri = lwa->ipri;
638 itimo = lwa->itimo;
639 }
640
641 /*
642 * As far as we have been unable to acquire the
643 * shared lock and the shared waiters flag is set,
644 * we will sleep.
645 */
646 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
647 SQ_SHARED_QUEUE);
648 flags &= ~LK_INTERLOCK;
649 if (error) {
650 LOCK_LOG3(lk,
651 "%s: interrupted sleep for %p with %d",
652 __func__, lk, error);
653 break;
654 }
655 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
656 __func__, lk);
657 }
658 if (error == 0) {
659 #ifdef LOCK_PROFILING
660 lockmgr_note_shared_acquire(lk, contested, waittime,
661 file, line, flags);
662 #else
663 lockmgr_note_shared_acquire(lk, 0, 0, file, line,
664 flags);
665 #endif
666 }
667
668 out:
669 lockmgr_exit(flags, ilk, 0);
670 return (error);
671 }
672
673 static __noinline int
674 lockmgr_xlock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
675 const char *file, int line, struct lockmgr_wait *lwa)
676 {
677 struct lock_class *class;
678 uintptr_t tid, x, v;
679 int error = 0;
680 const char *iwmesg;
681 int ipri, itimo;
682
683 #ifdef LOCK_PROFILING
684 uint64_t waittime = 0;
685 int contested = 0;
686 #endif
687
688 if (__predict_false(panicstr != NULL))
689 goto out;
690
691 tid = (uintptr_t)curthread;
692
693 if (LK_CAN_WITNESS(flags))
694 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
695 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
696 ilk : NULL);
697
698 /*
699 * If curthread already holds the lock and this one is
700 * allowed to recurse, simply recurse on it.
701 */
702 if (lockmgr_xlocked(lk)) {
703 if ((flags & LK_CANRECURSE) == 0 &&
704 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
705 /*
706 * If the lock is expected to not panic just
707 * give up and return.
708 */
709 if (LK_TRYOP(flags)) {
710 LOCK_LOG2(lk,
711 "%s: %p fails the try operation",
712 __func__, lk);
713 error = EBUSY;
714 goto out;
715 }
716 if (flags & LK_INTERLOCK) {
717 class = LOCK_CLASS(ilk);
718 class->lc_unlock(ilk);
719 }
720 panic("%s: recursing on non recursive lockmgr %p "
721 "@ %s:%d\n", __func__, lk, file, line);
722 }
723 lk->lk_recurse++;
724 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
725 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
726 lk->lk_recurse, file, line);
727 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
728 LK_TRYWIT(flags), file, line);
729 TD_LOCKS_INC(curthread);
730 goto out;
731 }
732
733 for (;;) {
734 if (lk->lk_lock == LK_UNLOCKED &&
735 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
736 break;
737 #ifdef HWPMC_HOOKS
738 PMC_SOFT_CALL( , , lock, failed);
739 #endif
740 lock_profile_obtain_lock_failed(&lk->lock_object,
741 &contested, &waittime);
742
743 /*
744 * If the lock is expected to not sleep just give up
745 * and return.
746 */
747 if (LK_TRYOP(flags)) {
748 LOCK_LOG2(lk, "%s: %p fails the try operation",
749 __func__, lk);
750 error = EBUSY;
751 break;
752 }
753
754 /*
755 * Acquire the sleepqueue chain lock because we
756 * probabilly will need to manipulate waiters flags.
757 */
758 sleepq_lock(&lk->lock_object);
759 x = lk->lk_lock;
760 retry_sleepq:
761
762 /*
763 * if the lock has been released while we spun on
764 * the sleepqueue chain lock just try again.
765 */
766 if (x == LK_UNLOCKED) {
767 sleepq_release(&lk->lock_object);
768 continue;
769 }
770
771 /*
772 * The lock can be in the state where there is a
773 * pending queue of waiters, but still no owner.
774 * This happens when the lock is contested and an
775 * owner is going to claim the lock.
776 * If curthread is the one successfully acquiring it
777 * claim lock ownership and return, preserving waiters
778 * flags.
779 */
780 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
781 if ((x & ~v) == LK_UNLOCKED) {
782 v &= ~LK_EXCLUSIVE_SPINNERS;
783 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
784 tid | v)) {
785 sleepq_release(&lk->lock_object);
786 LOCK_LOG2(lk,
787 "%s: %p claimed by a new writer",
788 __func__, lk);
789 break;
790 }
791 goto retry_sleepq;
792 }
793
794 /*
795 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
796 * fail, loop back and retry.
797 */
798 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
799 if (!atomic_fcmpset_ptr(&lk->lk_lock, &x,
800 x | LK_EXCLUSIVE_WAITERS)) {
801 goto retry_sleepq;
802 }
803 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
804 __func__, lk);
805 }
806
807 if (lwa == NULL) {
808 iwmesg = lk->lock_object.lo_name;
809 ipri = lk->lk_pri;
810 itimo = lk->lk_timo;
811 } else {
812 iwmesg = lwa->iwmesg;
813 ipri = lwa->ipri;
814 itimo = lwa->itimo;
815 }
816
817 /*
818 * As far as we have been unable to acquire the
819 * exclusive lock and the exclusive waiters flag
820 * is set, we will sleep.
821 */
822 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
823 SQ_EXCLUSIVE_QUEUE);
824 flags &= ~LK_INTERLOCK;
825 if (error) {
826 LOCK_LOG3(lk,
827 "%s: interrupted sleep for %p with %d",
828 __func__, lk, error);
829 break;
830 }
831 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
832 __func__, lk);
833 }
834 if (error == 0) {
835 #ifdef LOCK_PROFILING
836 lockmgr_note_exclusive_acquire(lk, contested, waittime,
837 file, line, flags);
838 #else
839 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
840 flags);
841 #endif
842 }
843
844 out:
845 lockmgr_exit(flags, ilk, 0);
846 return (error);
847 }
848
849 static __noinline int
850 lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk,
851 const char *file, int line, struct lockmgr_wait *lwa)
852 {
853 uintptr_t tid, x, v;
854 int error = 0;
855 int wakeup_swapper = 0;
856 int op;
857
858 if (__predict_false(panicstr != NULL))
859 goto out;
860
861 tid = (uintptr_t)curthread;
862
863 _lockmgr_assert(lk, KA_SLOCKED, file, line);
864 v = lk->lk_lock;
865 x = v & LK_ALL_WAITERS;
866 v &= LK_EXCLUSIVE_SPINNERS;
867
868 /*
869 * Try to switch from one shared lock to an exclusive one.
870 * We need to preserve waiters flags during the operation.
871 */
872 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
873 tid | x)) {
874 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
875 line);
876 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
877 LK_TRYWIT(flags), file, line);
878 TD_SLOCKS_DEC(curthread);
879 goto out;
880 }
881
882 op = flags & LK_TYPE_MASK;
883
884 /*
885 * In LK_TRYUPGRADE mode, do not drop the lock,
886 * returning EBUSY instead.
887 */
888 if (op == LK_TRYUPGRADE) {
889 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
890 __func__, lk);
891 error = EBUSY;
892 goto out;
893 }
894
895 /*
896 * We have been unable to succeed in upgrading, so just
897 * give up the shared lock.
898 */
899 wakeup_swapper |= wakeupshlk(lk, file, line);
900 error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa);
901 flags &= ~LK_INTERLOCK;
902 out:
903 lockmgr_exit(flags, ilk, wakeup_swapper);
904 return (error);
905 }
906
907 int
908 lockmgr_lock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk,
909 const char *file, int line)
910 {
911 struct lock_class *class;
912 uintptr_t x, tid;
913 u_int op;
914 bool locked;
915
916 if (__predict_false(panicstr != NULL))
917 return (0);
918
919 op = flags & LK_TYPE_MASK;
920 locked = false;
921 switch (op) {
922 case LK_SHARED:
923 if (LK_CAN_WITNESS(flags))
924 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
925 file, line, flags & LK_INTERLOCK ? ilk : NULL);
926 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE))
927 break;
928 if (lockmgr_slock_try(lk, &x, flags, true)) {
929 lockmgr_note_shared_acquire(lk, 0, 0,
930 file, line, flags);
931 locked = true;
932 } else {
933 return (lockmgr_slock_hard(lk, flags, ilk, file, line,
934 NULL));
935 }
936 break;
937 case LK_EXCLUSIVE:
938 if (LK_CAN_WITNESS(flags))
939 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
940 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
941 ilk : NULL);
942 tid = (uintptr_t)curthread;
943 if (lk->lk_lock == LK_UNLOCKED &&
944 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
945 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
946 flags);
947 locked = true;
948 } else {
949 return (lockmgr_xlock_hard(lk, flags, ilk, file, line,
950 NULL));
951 }
952 break;
953 case LK_UPGRADE:
954 case LK_TRYUPGRADE:
955 return (lockmgr_upgrade(lk, flags, ilk, file, line, NULL));
956 default:
957 break;
958 }
959 if (__predict_true(locked)) {
960 if (__predict_false(flags & LK_INTERLOCK)) {
961 class = LOCK_CLASS(ilk);
962 class->lc_unlock(ilk);
963 }
964 return (0);
965 } else {
966 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT,
967 LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line));
968 }
969 }
970
971 static __noinline int
972 lockmgr_sunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
973 const char *file, int line)
974
975 {
976 int wakeup_swapper = 0;
977
978 if (__predict_false(panicstr != NULL))
979 goto out;
980
981 wakeup_swapper = wakeupshlk(lk, file, line);
982
983 out:
984 lockmgr_exit(flags, ilk, wakeup_swapper);
985 return (0);
986 }
987
988 static __noinline int
989 lockmgr_xunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
990 const char *file, int line)
991 {
992 uintptr_t tid, v;
993 int wakeup_swapper = 0;
994 u_int realexslp;
995 int queue;
996
997 if (__predict_false(panicstr != NULL))
998 goto out;
999
1000 tid = (uintptr_t)curthread;
1001
1002 /*
1003 * As first option, treact the lock as if it has not
1004 * any waiter.
1005 * Fix-up the tid var if the lock has been disowned.
1006 */
1007 if (LK_HOLDER(x) == LK_KERNPROC)
1008 tid = LK_KERNPROC;
1009 else {
1010 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1011 TD_LOCKS_DEC(curthread);
1012 }
1013 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
1014
1015 /*
1016 * The lock is held in exclusive mode.
1017 * If the lock is recursed also, then unrecurse it.
1018 */
1019 if (lockmgr_xlocked_v(x) && lockmgr_recursed(lk)) {
1020 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk);
1021 lk->lk_recurse--;
1022 goto out;
1023 }
1024 if (tid != LK_KERNPROC)
1025 lock_profile_release_lock(&lk->lock_object);
1026
1027 if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED))
1028 goto out;
1029
1030 sleepq_lock(&lk->lock_object);
1031 x = lk->lk_lock;
1032 v = LK_UNLOCKED;
1033
1034 /*
1035 * If the lock has exclusive waiters, give them
1036 * preference in order to avoid deadlock with
1037 * shared runners up.
1038 * If interruptible sleeps left the exclusive queue
1039 * empty avoid a starvation for the threads sleeping
1040 * on the shared queue by giving them precedence
1041 * and cleaning up the exclusive waiters bit anyway.
1042 * Please note that lk_exslpfail count may be lying
1043 * about the real number of waiters with the
1044 * LK_SLEEPFAIL flag on because they may be used in
1045 * conjunction with interruptible sleeps so
1046 * lk_exslpfail might be considered an 'upper limit'
1047 * bound, including the edge cases.
1048 */
1049 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1050 realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE);
1051 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
1052 if (lk->lk_exslpfail < realexslp) {
1053 lk->lk_exslpfail = 0;
1054 queue = SQ_EXCLUSIVE_QUEUE;
1055 v |= (x & LK_SHARED_WAITERS);
1056 } else {
1057 lk->lk_exslpfail = 0;
1058 LOCK_LOG2(lk,
1059 "%s: %p has only LK_SLEEPFAIL sleepers",
1060 __func__, lk);
1061 LOCK_LOG2(lk,
1062 "%s: %p waking up threads on the exclusive queue",
1063 __func__, lk);
1064 wakeup_swapper = sleepq_broadcast(&lk->lock_object,
1065 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1066 queue = SQ_SHARED_QUEUE;
1067 }
1068 } else {
1069
1070 /*
1071 * Exclusive waiters sleeping with LK_SLEEPFAIL
1072 * on and using interruptible sleeps/timeout
1073 * may have left spourious lk_exslpfail counts
1074 * on, so clean it up anyway.
1075 */
1076 lk->lk_exslpfail = 0;
1077 queue = SQ_SHARED_QUEUE;
1078 }
1079
1080 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
1081 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
1082 "exclusive");
1083 atomic_store_rel_ptr(&lk->lk_lock, v);
1084 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue);
1085 sleepq_release(&lk->lock_object);
1086
1087 out:
1088 lockmgr_exit(flags, ilk, wakeup_swapper);
1089 return (0);
1090 }
1091
1092 int
1093 lockmgr_unlock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk)
1094 {
1095 struct lock_class *class;
1096 uintptr_t x, tid;
1097 const char *file;
1098 int line;
1099
1100 if (__predict_false(panicstr != NULL))
1101 return (0);
1102
1103 file = __FILE__;
1104 line = __LINE__;
1105
1106 _lockmgr_assert(lk, KA_LOCKED, file, line);
1107 x = lk->lk_lock;
1108 if (__predict_true(x & LK_SHARE) != 0) {
1109 if (lockmgr_sunlock_try(lk, &x)) {
1110 lockmgr_note_shared_release(lk, file, line);
1111 } else {
1112 return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line));
1113 }
1114 } else {
1115 tid = (uintptr_t)curthread;
1116 if (!lockmgr_recursed(lk) &&
1117 atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) {
1118 lockmgr_note_exclusive_release(lk, file, line);
1119 } else {
1120 return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line));
1121 }
1122 }
1123 if (__predict_false(flags & LK_INTERLOCK)) {
1124 class = LOCK_CLASS(ilk);
1125 class->lc_unlock(ilk);
1126 }
1127 return (0);
1128 }
1129
1130 int
1131 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
1132 const char *wmesg, int pri, int timo, const char *file, int line)
1133 {
1134 GIANT_DECLARE;
1135 struct lockmgr_wait lwa;
1136 struct lock_class *class;
1137 const char *iwmesg;
1138 uintptr_t tid, v, x;
1139 u_int op, realexslp;
1140 int error, ipri, itimo, queue, wakeup_swapper;
1141 #ifdef LOCK_PROFILING
1142 uint64_t waittime = 0;
1143 int contested = 0;
1144 #endif
1145
1146 if (panicstr != NULL)
1147 return (0);
1148
1149 error = 0;
1150 tid = (uintptr_t)curthread;
1151 op = (flags & LK_TYPE_MASK);
1152 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
1153 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
1154 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
1155
1156 lwa.iwmesg = iwmesg;
1157 lwa.ipri = ipri;
1158 lwa.itimo = itimo;
1159
1160 MPASS((flags & ~LK_TOTAL_MASK) == 0);
1161 KASSERT((op & (op - 1)) == 0,
1162 ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
1163 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
1164 (op != LK_DOWNGRADE && op != LK_RELEASE),
1165 ("%s: Invalid flags in regard of the operation desired @ %s:%d",
1166 __func__, file, line));
1167 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
1168 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
1169 __func__, file, line));
1170 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
1171 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread,
1172 lk->lock_object.lo_name, file, line));
1173
1174 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
1175
1176 if (lk->lock_object.lo_flags & LK_NOSHARE) {
1177 switch (op) {
1178 case LK_SHARED:
1179 op = LK_EXCLUSIVE;
1180 break;
1181 case LK_UPGRADE:
1182 case LK_TRYUPGRADE:
1183 case LK_DOWNGRADE:
1184 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
1185 file, line);
1186 if (flags & LK_INTERLOCK)
1187 class->lc_unlock(ilk);
1188 return (0);
1189 }
1190 }
1191
1192 wakeup_swapper = 0;
1193 switch (op) {
1194 case LK_SHARED:
1195 return (lockmgr_slock_hard(lk, flags, ilk, file, line, &lwa));
1196 break;
1197 case LK_UPGRADE:
1198 case LK_TRYUPGRADE:
1199 return (lockmgr_upgrade(lk, flags, ilk, file, line, &lwa));
1200 break;
1201 case LK_EXCLUSIVE:
1202 return (lockmgr_xlock_hard(lk, flags, ilk, file, line, &lwa));
1203 break;
1204 case LK_DOWNGRADE:
1205 _lockmgr_assert(lk, KA_XLOCKED, file, line);
1206 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
1207 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
1208
1209 /*
1210 * Panic if the lock is recursed.
1211 */
1212 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
1213 if (flags & LK_INTERLOCK)
1214 class->lc_unlock(ilk);
1215 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n",
1216 __func__, iwmesg, file, line);
1217 }
1218 TD_SLOCKS_INC(curthread);
1219
1220 /*
1221 * In order to preserve waiters flags, just spin.
1222 */
1223 for (;;) {
1224 x = lk->lk_lock;
1225 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1226 x &= LK_ALL_WAITERS;
1227 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1228 LK_SHARERS_LOCK(1) | x))
1229 break;
1230 cpu_spinwait();
1231 }
1232 break;
1233 case LK_RELEASE:
1234 _lockmgr_assert(lk, KA_LOCKED, file, line);
1235 x = lk->lk_lock;
1236
1237 if (__predict_true(x & LK_SHARE) != 0) {
1238 return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line));
1239 } else {
1240 return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line));
1241 }
1242 break;
1243 case LK_DRAIN:
1244 if (LK_CAN_WITNESS(flags))
1245 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1246 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
1247 ilk : NULL);
1248
1249 /*
1250 * Trying to drain a lock we already own will result in a
1251 * deadlock.
1252 */
1253 if (lockmgr_xlocked(lk)) {
1254 if (flags & LK_INTERLOCK)
1255 class->lc_unlock(ilk);
1256 panic("%s: draining %s with the lock held @ %s:%d\n",
1257 __func__, iwmesg, file, line);
1258 }
1259
1260 for (;;) {
1261 if (lk->lk_lock == LK_UNLOCKED &&
1262 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
1263 break;
1264
1265 #ifdef HWPMC_HOOKS
1266 PMC_SOFT_CALL( , , lock, failed);
1267 #endif
1268 lock_profile_obtain_lock_failed(&lk->lock_object,
1269 &contested, &waittime);
1270
1271 /*
1272 * If the lock is expected to not sleep just give up
1273 * and return.
1274 */
1275 if (LK_TRYOP(flags)) {
1276 LOCK_LOG2(lk, "%s: %p fails the try operation",
1277 __func__, lk);
1278 error = EBUSY;
1279 break;
1280 }
1281
1282 /*
1283 * Acquire the sleepqueue chain lock because we
1284 * probabilly will need to manipulate waiters flags.
1285 */
1286 sleepq_lock(&lk->lock_object);
1287 x = lk->lk_lock;
1288
1289 /*
1290 * if the lock has been released while we spun on
1291 * the sleepqueue chain lock just try again.
1292 */
1293 if (x == LK_UNLOCKED) {
1294 sleepq_release(&lk->lock_object);
1295 continue;
1296 }
1297
1298 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1299 if ((x & ~v) == LK_UNLOCKED) {
1300 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1301
1302 /*
1303 * If interruptible sleeps left the exclusive
1304 * queue empty avoid a starvation for the
1305 * threads sleeping on the shared queue by
1306 * giving them precedence and cleaning up the
1307 * exclusive waiters bit anyway.
1308 * Please note that lk_exslpfail count may be
1309 * lying about the real number of waiters with
1310 * the LK_SLEEPFAIL flag on because they may
1311 * be used in conjunction with interruptible
1312 * sleeps so lk_exslpfail might be considered
1313 * an 'upper limit' bound, including the edge
1314 * cases.
1315 */
1316 if (v & LK_EXCLUSIVE_WAITERS) {
1317 queue = SQ_EXCLUSIVE_QUEUE;
1318 v &= ~LK_EXCLUSIVE_WAITERS;
1319 } else {
1320
1321 /*
1322 * Exclusive waiters sleeping with
1323 * LK_SLEEPFAIL on and using
1324 * interruptible sleeps/timeout may
1325 * have left spourious lk_exslpfail
1326 * counts on, so clean it up anyway.
1327 */
1328 MPASS(v & LK_SHARED_WAITERS);
1329 lk->lk_exslpfail = 0;
1330 queue = SQ_SHARED_QUEUE;
1331 v &= ~LK_SHARED_WAITERS;
1332 }
1333 if (queue == SQ_EXCLUSIVE_QUEUE) {
1334 realexslp =
1335 sleepq_sleepcnt(&lk->lock_object,
1336 SQ_EXCLUSIVE_QUEUE);
1337 if (lk->lk_exslpfail >= realexslp) {
1338 lk->lk_exslpfail = 0;
1339 queue = SQ_SHARED_QUEUE;
1340 v &= ~LK_SHARED_WAITERS;
1341 if (realexslp != 0) {
1342 LOCK_LOG2(lk,
1343 "%s: %p has only LK_SLEEPFAIL sleepers",
1344 __func__, lk);
1345 LOCK_LOG2(lk,
1346 "%s: %p waking up threads on the exclusive queue",
1347 __func__, lk);
1348 wakeup_swapper =
1349 sleepq_broadcast(
1350 &lk->lock_object,
1351 SLEEPQ_LK, 0,
1352 SQ_EXCLUSIVE_QUEUE);
1353 }
1354 } else
1355 lk->lk_exslpfail = 0;
1356 }
1357 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1358 sleepq_release(&lk->lock_object);
1359 continue;
1360 }
1361 LOCK_LOG3(lk,
1362 "%s: %p waking up all threads on the %s queue",
1363 __func__, lk, queue == SQ_SHARED_QUEUE ?
1364 "shared" : "exclusive");
1365 wakeup_swapper |= sleepq_broadcast(
1366 &lk->lock_object, SLEEPQ_LK, 0, queue);
1367
1368 /*
1369 * If shared waiters have been woken up we need
1370 * to wait for one of them to acquire the lock
1371 * before to set the exclusive waiters in
1372 * order to avoid a deadlock.
1373 */
1374 if (queue == SQ_SHARED_QUEUE) {
1375 for (v = lk->lk_lock;
1376 (v & LK_SHARE) && !LK_SHARERS(v);
1377 v = lk->lk_lock)
1378 cpu_spinwait();
1379 }
1380 }
1381
1382 /*
1383 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
1384 * fail, loop back and retry.
1385 */
1386 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1387 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1388 x | LK_EXCLUSIVE_WAITERS)) {
1389 sleepq_release(&lk->lock_object);
1390 continue;
1391 }
1392 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1393 __func__, lk);
1394 }
1395
1396 /*
1397 * As far as we have been unable to acquire the
1398 * exclusive lock and the exclusive waiters flag
1399 * is set, we will sleep.
1400 */
1401 if (flags & LK_INTERLOCK) {
1402 class->lc_unlock(ilk);
1403 flags &= ~LK_INTERLOCK;
1404 }
1405 GIANT_SAVE();
1406 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1407 SQ_EXCLUSIVE_QUEUE);
1408 sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1409 GIANT_RESTORE();
1410 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1411 __func__, lk);
1412 }
1413
1414 if (error == 0) {
1415 lock_profile_obtain_lock_success(&lk->lock_object,
1416 contested, waittime, file, line);
1417 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1418 lk->lk_recurse, file, line);
1419 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1420 LK_TRYWIT(flags), file, line);
1421 TD_LOCKS_INC(curthread);
1422 STACK_SAVE(lk);
1423 }
1424 break;
1425 default:
1426 if (flags & LK_INTERLOCK)
1427 class->lc_unlock(ilk);
1428 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1429 }
1430
1431 if (flags & LK_INTERLOCK)
1432 class->lc_unlock(ilk);
1433 if (wakeup_swapper)
1434 kick_proc0();
1435
1436 return (error);
1437 }
1438
1439 void
1440 _lockmgr_disown(struct lock *lk, const char *file, int line)
1441 {
1442 uintptr_t tid, x;
1443
1444 if (SCHEDULER_STOPPED())
1445 return;
1446
1447 tid = (uintptr_t)curthread;
1448 _lockmgr_assert(lk, KA_XLOCKED, file, line);
1449
1450 /*
1451 * Panic if the lock is recursed.
1452 */
1453 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk))
1454 panic("%s: disown a recursed lockmgr @ %s:%d\n",
1455 __func__, file, line);
1456
1457 /*
1458 * If the owner is already LK_KERNPROC just skip the whole operation.
1459 */
1460 if (LK_HOLDER(lk->lk_lock) != tid)
1461 return;
1462 lock_profile_release_lock(&lk->lock_object);
1463 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1464 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1465 TD_LOCKS_DEC(curthread);
1466 STACK_SAVE(lk);
1467
1468 /*
1469 * In order to preserve waiters flags, just spin.
1470 */
1471 for (;;) {
1472 x = lk->lk_lock;
1473 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1474 x &= LK_ALL_WAITERS;
1475 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1476 LK_KERNPROC | x))
1477 return;
1478 cpu_spinwait();
1479 }
1480 }
1481
1482 void
1483 lockmgr_printinfo(const struct lock *lk)
1484 {
1485 struct thread *td;
1486 uintptr_t x;
1487
1488 if (lk->lk_lock == LK_UNLOCKED)
1489 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1490 else if (lk->lk_lock & LK_SHARE)
1491 printf("lock type %s: SHARED (count %ju)\n",
1492 lk->lock_object.lo_name,
1493 (uintmax_t)LK_SHARERS(lk->lk_lock));
1494 else {
1495 td = lockmgr_xholder(lk);
1496 if (td == (struct thread *)LK_KERNPROC)
1497 printf("lock type %s: EXCL by KERNPROC\n",
1498 lk->lock_object.lo_name);
1499 else
1500 printf("lock type %s: EXCL by thread %p "
1501 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name,
1502 td, td->td_proc->p_pid, td->td_proc->p_comm,
1503 td->td_tid);
1504 }
1505
1506 x = lk->lk_lock;
1507 if (x & LK_EXCLUSIVE_WAITERS)
1508 printf(" with exclusive waiters pending\n");
1509 if (x & LK_SHARED_WAITERS)
1510 printf(" with shared waiters pending\n");
1511 if (x & LK_EXCLUSIVE_SPINNERS)
1512 printf(" with exclusive spinners pending\n");
1513
1514 STACK_PRINT(lk);
1515 }
1516
1517 int
1518 lockstatus(const struct lock *lk)
1519 {
1520 uintptr_t v, x;
1521 int ret;
1522
1523 ret = LK_SHARED;
1524 x = lk->lk_lock;
1525 v = LK_HOLDER(x);
1526
1527 if ((x & LK_SHARE) == 0) {
1528 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1529 ret = LK_EXCLUSIVE;
1530 else
1531 ret = LK_EXCLOTHER;
1532 } else if (x == LK_UNLOCKED)
1533 ret = 0;
1534
1535 return (ret);
1536 }
1537
1538 #ifdef INVARIANT_SUPPORT
1539
1540 FEATURE(invariant_support,
1541 "Support for modules compiled with INVARIANTS option");
1542
1543 #ifndef INVARIANTS
1544 #undef _lockmgr_assert
1545 #endif
1546
1547 void
1548 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line)
1549 {
1550 int slocked = 0;
1551
1552 if (panicstr != NULL)
1553 return;
1554 switch (what) {
1555 case KA_SLOCKED:
1556 case KA_SLOCKED | KA_NOTRECURSED:
1557 case KA_SLOCKED | KA_RECURSED:
1558 slocked = 1;
1559 case KA_LOCKED:
1560 case KA_LOCKED | KA_NOTRECURSED:
1561 case KA_LOCKED | KA_RECURSED:
1562 #ifdef WITNESS
1563
1564 /*
1565 * We cannot trust WITNESS if the lock is held in exclusive
1566 * mode and a call to lockmgr_disown() happened.
1567 * Workaround this skipping the check if the lock is held in
1568 * exclusive mode even for the KA_LOCKED case.
1569 */
1570 if (slocked || (lk->lk_lock & LK_SHARE)) {
1571 witness_assert(&lk->lock_object, what, file, line);
1572 break;
1573 }
1574 #endif
1575 if (lk->lk_lock == LK_UNLOCKED ||
1576 ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1577 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1578 panic("Lock %s not %slocked @ %s:%d\n",
1579 lk->lock_object.lo_name, slocked ? "share" : "",
1580 file, line);
1581
1582 if ((lk->lk_lock & LK_SHARE) == 0) {
1583 if (lockmgr_recursed(lk)) {
1584 if (what & KA_NOTRECURSED)
1585 panic("Lock %s recursed @ %s:%d\n",
1586 lk->lock_object.lo_name, file,
1587 line);
1588 } else if (what & KA_RECURSED)
1589 panic("Lock %s not recursed @ %s:%d\n",
1590 lk->lock_object.lo_name, file, line);
1591 }
1592 break;
1593 case KA_XLOCKED:
1594 case KA_XLOCKED | KA_NOTRECURSED:
1595 case KA_XLOCKED | KA_RECURSED:
1596 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1597 panic("Lock %s not exclusively locked @ %s:%d\n",
1598 lk->lock_object.lo_name, file, line);
1599 if (lockmgr_recursed(lk)) {
1600 if (what & KA_NOTRECURSED)
1601 panic("Lock %s recursed @ %s:%d\n",
1602 lk->lock_object.lo_name, file, line);
1603 } else if (what & KA_RECURSED)
1604 panic("Lock %s not recursed @ %s:%d\n",
1605 lk->lock_object.lo_name, file, line);
1606 break;
1607 case KA_UNLOCKED:
1608 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1609 panic("Lock %s exclusively locked @ %s:%d\n",
1610 lk->lock_object.lo_name, file, line);
1611 break;
1612 default:
1613 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1614 line);
1615 }
1616 }
1617 #endif
1618
1619 #ifdef DDB
1620 int
1621 lockmgr_chain(struct thread *td, struct thread **ownerp)
1622 {
1623 struct lock *lk;
1624
1625 lk = td->td_wchan;
1626
1627 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1628 return (0);
1629 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1630 if (lk->lk_lock & LK_SHARE)
1631 db_printf("SHARED (count %ju)\n",
1632 (uintmax_t)LK_SHARERS(lk->lk_lock));
1633 else
1634 db_printf("EXCL\n");
1635 *ownerp = lockmgr_xholder(lk);
1636
1637 return (1);
1638 }
1639
1640 static void
1641 db_show_lockmgr(const struct lock_object *lock)
1642 {
1643 struct thread *td;
1644 const struct lock *lk;
1645
1646 lk = (const struct lock *)lock;
1647
1648 db_printf(" state: ");
1649 if (lk->lk_lock == LK_UNLOCKED)
1650 db_printf("UNLOCKED\n");
1651 else if (lk->lk_lock & LK_SHARE)
1652 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1653 else {
1654 td = lockmgr_xholder(lk);
1655 if (td == (struct thread *)LK_KERNPROC)
1656 db_printf("XLOCK: LK_KERNPROC\n");
1657 else
1658 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1659 td->td_tid, td->td_proc->p_pid,
1660 td->td_proc->p_comm);
1661 if (lockmgr_recursed(lk))
1662 db_printf(" recursed: %d\n", lk->lk_recurse);
1663 }
1664 db_printf(" waiters: ");
1665 switch (lk->lk_lock & LK_ALL_WAITERS) {
1666 case LK_SHARED_WAITERS:
1667 db_printf("shared\n");
1668 break;
1669 case LK_EXCLUSIVE_WAITERS:
1670 db_printf("exclusive\n");
1671 break;
1672 case LK_ALL_WAITERS:
1673 db_printf("shared and exclusive\n");
1674 break;
1675 default:
1676 db_printf("none\n");
1677 }
1678 db_printf(" spinners: ");
1679 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1680 db_printf("exclusive\n");
1681 else
1682 db_printf("none\n");
1683 }
1684 #endif
Cache object: bbca2ee5e84f9934b0f328e95f008e29
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