FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_lock.c
1 /*-
2 * Copyright (c) 2008 Attilio Rao <attilio@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice(s), this list of conditions and the following disclaimer as
10 * the first lines of this file unmodified other than the possible
11 * addition of one or more copyright notices.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice(s), this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
20 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
22 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
23 * 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 SUCH
26 * DAMAGE.
27 */
28
29 #include "opt_adaptive_lockmgrs.h"
30 #include "opt_ddb.h"
31 #include "opt_hwpmc_hooks.h"
32
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD: releng/11.2/sys/kern/kern_lock.c 315375 2017-03-16 06:14:33Z mjg $");
35
36 #include <sys/param.h>
37 #include <sys/kdb.h>
38 #include <sys/ktr.h>
39 #include <sys/lock.h>
40 #include <sys/lock_profile.h>
41 #include <sys/lockmgr.h>
42 #include <sys/mutex.h>
43 #include <sys/proc.h>
44 #include <sys/sleepqueue.h>
45 #ifdef DEBUG_LOCKS
46 #include <sys/stack.h>
47 #endif
48 #include <sys/sysctl.h>
49 #include <sys/systm.h>
50
51 #include <machine/cpu.h>
52
53 #ifdef DDB
54 #include <ddb/ddb.h>
55 #endif
56
57 #ifdef HWPMC_HOOKS
58 #include <sys/pmckern.h>
59 PMC_SOFT_DECLARE( , , lock, failed);
60 #endif
61
62 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
63 (LK_ADAPTIVE | LK_NOSHARE));
64 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
65 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
66
67 #define SQ_EXCLUSIVE_QUEUE 0
68 #define SQ_SHARED_QUEUE 1
69
70 #ifndef INVARIANTS
71 #define _lockmgr_assert(lk, what, file, line)
72 #endif
73
74 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++)
75 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--)
76
77 #ifndef DEBUG_LOCKS
78 #define STACK_PRINT(lk)
79 #define STACK_SAVE(lk)
80 #define STACK_ZERO(lk)
81 #else
82 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
83 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack)
84 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack)
85 #endif
86
87 #define LOCK_LOG2(lk, string, arg1, arg2) \
88 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
89 CTR2(KTR_LOCK, (string), (arg1), (arg2))
90 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \
91 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
92 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
93
94 #define GIANT_DECLARE \
95 int _i = 0; \
96 WITNESS_SAVE_DECL(Giant)
97 #define GIANT_RESTORE() do { \
98 if (_i > 0) { \
99 while (_i--) \
100 mtx_lock(&Giant); \
101 WITNESS_RESTORE(&Giant.lock_object, Giant); \
102 } \
103 } while (0)
104 #define GIANT_SAVE() do { \
105 if (mtx_owned(&Giant)) { \
106 WITNESS_SAVE(&Giant.lock_object, Giant); \
107 while (mtx_owned(&Giant)) { \
108 _i++; \
109 mtx_unlock(&Giant); \
110 } \
111 } \
112 } while (0)
113
114 #define LK_CAN_SHARE(x, flags) \
115 (((x) & LK_SHARE) && \
116 (((x) & (LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) == 0 || \
117 (curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) || \
118 (curthread->td_pflags & TDP_DEADLKTREAT)))
119 #define LK_TRYOP(x) \
120 ((x) & LK_NOWAIT)
121
122 #define LK_CAN_WITNESS(x) \
123 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
124 #define LK_TRYWIT(x) \
125 (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
126
127 #define LK_CAN_ADAPT(lk, f) \
128 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \
129 ((f) & LK_SLEEPFAIL) == 0)
130
131 #define lockmgr_disowned(lk) \
132 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
133
134 #define lockmgr_xlocked(lk) \
135 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
136
137 static void assert_lockmgr(const struct lock_object *lock, int how);
138 #ifdef DDB
139 static void db_show_lockmgr(const struct lock_object *lock);
140 #endif
141 static void lock_lockmgr(struct lock_object *lock, uintptr_t how);
142 #ifdef KDTRACE_HOOKS
143 static int owner_lockmgr(const struct lock_object *lock,
144 struct thread **owner);
145 #endif
146 static uintptr_t unlock_lockmgr(struct lock_object *lock);
147
148 struct lock_class lock_class_lockmgr = {
149 .lc_name = "lockmgr",
150 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
151 .lc_assert = assert_lockmgr,
152 #ifdef DDB
153 .lc_ddb_show = db_show_lockmgr,
154 #endif
155 .lc_lock = lock_lockmgr,
156 .lc_unlock = unlock_lockmgr,
157 #ifdef KDTRACE_HOOKS
158 .lc_owner = owner_lockmgr,
159 #endif
160 };
161
162 #ifdef ADAPTIVE_LOCKMGRS
163 static u_int alk_retries = 10;
164 static u_int alk_loops = 10000;
165 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL,
166 "lockmgr debugging");
167 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, "");
168 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, "");
169 #endif
170
171 static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp,
172 int flags);
173 static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t x);
174
175 static void
176 lockmgr_note_shared_acquire(struct lock *lk, int contested,
177 uint64_t waittime, const char *file, int line, int flags)
178 {
179
180 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime,
181 file, line);
182 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line);
183 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line);
184 TD_LOCKS_INC(curthread);
185 TD_SLOCKS_INC(curthread);
186 STACK_SAVE(lk);
187 }
188
189 static void
190 lockmgr_note_shared_release(struct lock *lk, const char *file, int line)
191 {
192
193 lock_profile_release_lock(&lk->lock_object);
194 WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
195 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
196 TD_LOCKS_DEC(curthread);
197 TD_SLOCKS_DEC(curthread);
198 }
199
200 static void
201 lockmgr_note_exclusive_acquire(struct lock *lk, int contested,
202 uint64_t waittime, const char *file, int line, int flags)
203 {
204
205 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime,
206 file, line);
207 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
208 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file,
209 line);
210 TD_LOCKS_INC(curthread);
211 STACK_SAVE(lk);
212 }
213
214 static void
215 lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line)
216 {
217
218 lock_profile_release_lock(&lk->lock_object);
219 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file,
220 line);
221 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
222 TD_LOCKS_DEC(curthread);
223 }
224
225 static void
226 lockmgr_note_exclusive_upgrade(struct lock *lk, const char *file, int line,
227 int flags)
228 {
229
230 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
231 line);
232 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
233 LK_TRYWIT(flags), file, line);
234 TD_SLOCKS_DEC(curthread);
235 }
236
237 static __inline struct thread *
238 lockmgr_xholder(const struct lock *lk)
239 {
240 uintptr_t x;
241
242 x = lk->lk_lock;
243 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
244 }
245
246 /*
247 * It assumes sleepq_lock held and returns with this one unheld.
248 * It also assumes the generic interlock is sane and previously checked.
249 * If LK_INTERLOCK is specified the interlock is not reacquired after the
250 * sleep.
251 */
252 static __inline int
253 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
254 const char *wmesg, int pri, int timo, int queue)
255 {
256 GIANT_DECLARE;
257 struct lock_class *class;
258 int catch, error;
259
260 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
261 catch = pri & PCATCH;
262 pri &= PRIMASK;
263 error = 0;
264
265 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
266 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
267
268 if (flags & LK_INTERLOCK)
269 class->lc_unlock(ilk);
270 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0)
271 lk->lk_exslpfail++;
272 GIANT_SAVE();
273 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
274 SLEEPQ_INTERRUPTIBLE : 0), queue);
275 if ((flags & LK_TIMELOCK) && timo)
276 sleepq_set_timeout(&lk->lock_object, timo);
277
278 /*
279 * Decisional switch for real sleeping.
280 */
281 if ((flags & LK_TIMELOCK) && timo && catch)
282 error = sleepq_timedwait_sig(&lk->lock_object, pri);
283 else if ((flags & LK_TIMELOCK) && timo)
284 error = sleepq_timedwait(&lk->lock_object, pri);
285 else if (catch)
286 error = sleepq_wait_sig(&lk->lock_object, pri);
287 else
288 sleepq_wait(&lk->lock_object, pri);
289 GIANT_RESTORE();
290 if ((flags & LK_SLEEPFAIL) && error == 0)
291 error = ENOLCK;
292
293 return (error);
294 }
295
296 static __inline int
297 wakeupshlk(struct lock *lk, const char *file, int line)
298 {
299 uintptr_t v, x;
300 u_int realexslp;
301 int queue, wakeup_swapper;
302
303 wakeup_swapper = 0;
304 for (;;) {
305 x = lk->lk_lock;
306 if (lockmgr_sunlock_try(lk, x))
307 break;
308
309 /*
310 * We should have a sharer with waiters, so enter the hard
311 * path in order to handle wakeups correctly.
312 */
313 sleepq_lock(&lk->lock_object);
314 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
315 v = LK_UNLOCKED;
316
317 /*
318 * If the lock has exclusive waiters, give them preference in
319 * order to avoid deadlock with shared runners up.
320 * If interruptible sleeps left the exclusive queue empty
321 * avoid a starvation for the threads sleeping on the shared
322 * queue by giving them precedence and cleaning up the
323 * exclusive waiters bit anyway.
324 * Please note that lk_exslpfail count may be lying about
325 * the real number of waiters with the LK_SLEEPFAIL flag on
326 * because they may be used in conjunction with interruptible
327 * sleeps so lk_exslpfail might be considered an 'upper limit'
328 * bound, including the edge cases.
329 */
330 realexslp = sleepq_sleepcnt(&lk->lock_object,
331 SQ_EXCLUSIVE_QUEUE);
332 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
333 if (lk->lk_exslpfail < realexslp) {
334 lk->lk_exslpfail = 0;
335 queue = SQ_EXCLUSIVE_QUEUE;
336 v |= (x & LK_SHARED_WAITERS);
337 } else {
338 lk->lk_exslpfail = 0;
339 LOCK_LOG2(lk,
340 "%s: %p has only LK_SLEEPFAIL sleepers",
341 __func__, lk);
342 LOCK_LOG2(lk,
343 "%s: %p waking up threads on the exclusive queue",
344 __func__, lk);
345 wakeup_swapper =
346 sleepq_broadcast(&lk->lock_object,
347 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
348 queue = SQ_SHARED_QUEUE;
349 }
350
351 } else {
352
353 /*
354 * Exclusive waiters sleeping with LK_SLEEPFAIL on
355 * and using interruptible sleeps/timeout may have
356 * left spourious lk_exslpfail counts on, so clean
357 * it up anyway.
358 */
359 lk->lk_exslpfail = 0;
360 queue = SQ_SHARED_QUEUE;
361 }
362
363 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x,
364 v)) {
365 sleepq_release(&lk->lock_object);
366 continue;
367 }
368 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
369 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
370 "exclusive");
371 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
372 0, queue);
373 sleepq_release(&lk->lock_object);
374 break;
375 }
376
377 lockmgr_note_shared_release(lk, file, line);
378 return (wakeup_swapper);
379 }
380
381 static void
382 assert_lockmgr(const struct lock_object *lock, int what)
383 {
384
385 panic("lockmgr locks do not support assertions");
386 }
387
388 static void
389 lock_lockmgr(struct lock_object *lock, uintptr_t how)
390 {
391
392 panic("lockmgr locks do not support sleep interlocking");
393 }
394
395 static uintptr_t
396 unlock_lockmgr(struct lock_object *lock)
397 {
398
399 panic("lockmgr locks do not support sleep interlocking");
400 }
401
402 #ifdef KDTRACE_HOOKS
403 static int
404 owner_lockmgr(const struct lock_object *lock, struct thread **owner)
405 {
406
407 panic("lockmgr locks do not support owner inquiring");
408 }
409 #endif
410
411 void
412 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
413 {
414 int iflags;
415
416 MPASS((flags & ~LK_INIT_MASK) == 0);
417 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
418 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
419 &lk->lk_lock));
420
421 iflags = LO_SLEEPABLE | LO_UPGRADABLE;
422 if (flags & LK_CANRECURSE)
423 iflags |= LO_RECURSABLE;
424 if ((flags & LK_NODUP) == 0)
425 iflags |= LO_DUPOK;
426 if (flags & LK_NOPROFILE)
427 iflags |= LO_NOPROFILE;
428 if ((flags & LK_NOWITNESS) == 0)
429 iflags |= LO_WITNESS;
430 if (flags & LK_QUIET)
431 iflags |= LO_QUIET;
432 if (flags & LK_IS_VNODE)
433 iflags |= LO_IS_VNODE;
434 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
435
436 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
437 lk->lk_lock = LK_UNLOCKED;
438 lk->lk_recurse = 0;
439 lk->lk_exslpfail = 0;
440 lk->lk_timo = timo;
441 lk->lk_pri = pri;
442 STACK_ZERO(lk);
443 }
444
445 /*
446 * XXX: Gross hacks to manipulate external lock flags after
447 * initialization. Used for certain vnode and buf locks.
448 */
449 void
450 lockallowshare(struct lock *lk)
451 {
452
453 lockmgr_assert(lk, KA_XLOCKED);
454 lk->lock_object.lo_flags &= ~LK_NOSHARE;
455 }
456
457 void
458 lockdisableshare(struct lock *lk)
459 {
460
461 lockmgr_assert(lk, KA_XLOCKED);
462 lk->lock_object.lo_flags |= LK_NOSHARE;
463 }
464
465 void
466 lockallowrecurse(struct lock *lk)
467 {
468
469 lockmgr_assert(lk, KA_XLOCKED);
470 lk->lock_object.lo_flags |= LO_RECURSABLE;
471 }
472
473 void
474 lockdisablerecurse(struct lock *lk)
475 {
476
477 lockmgr_assert(lk, KA_XLOCKED);
478 lk->lock_object.lo_flags &= ~LO_RECURSABLE;
479 }
480
481 void
482 lockdestroy(struct lock *lk)
483 {
484
485 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
486 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
487 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
488 lock_destroy(&lk->lock_object);
489 }
490
491 static bool __always_inline
492 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags)
493 {
494
495 /*
496 * If no other thread has an exclusive lock, or
497 * no exclusive waiter is present, bump the count of
498 * sharers. Since we have to preserve the state of
499 * waiters, if we fail to acquire the shared lock
500 * loop back and retry.
501 */
502 *xp = lk->lk_lock;
503 while (LK_CAN_SHARE(*xp, flags)) {
504 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp,
505 *xp + LK_ONE_SHARER)) {
506 return (true);
507 }
508 }
509 return (false);
510 }
511
512 static bool __always_inline
513 lockmgr_sunlock_try(struct lock *lk, uintptr_t x)
514 {
515
516 for (;;) {
517 /*
518 * If there is more than one shared lock held, just drop one
519 * and return.
520 */
521 if (LK_SHARERS(x) > 1) {
522 if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &x,
523 x - LK_ONE_SHARER))
524 return (true);
525 continue;
526 }
527
528 /*
529 * If there are not waiters on the exclusive queue, drop the
530 * lock quickly.
531 */
532 if ((x & LK_ALL_WAITERS) == 0) {
533 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) ==
534 LK_SHARERS_LOCK(1));
535 if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &x,
536 LK_UNLOCKED))
537 return (true);
538 continue;
539 }
540 break;
541 }
542 return (false);
543 }
544
545 int
546 lockmgr_lock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk,
547 const char *file, int line)
548 {
549 struct lock_class *class;
550 uintptr_t x, v, tid;
551 u_int op;
552 bool locked;
553
554 op = flags & LK_TYPE_MASK;
555 locked = false;
556 switch (op) {
557 case LK_SHARED:
558 if (LK_CAN_WITNESS(flags))
559 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
560 file, line, flags & LK_INTERLOCK ? ilk : NULL);
561 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE))
562 break;
563 if (lockmgr_slock_try(lk, &x, flags)) {
564 lockmgr_note_shared_acquire(lk, 0, 0,
565 file, line, flags);
566 locked = true;
567 }
568 break;
569 case LK_EXCLUSIVE:
570 if (LK_CAN_WITNESS(flags))
571 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
572 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
573 ilk : NULL);
574 tid = (uintptr_t)curthread;
575 if (lk->lk_lock == LK_UNLOCKED &&
576 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
577 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
578 flags);
579 locked = true;
580 }
581 break;
582 case LK_UPGRADE:
583 case LK_TRYUPGRADE:
584 _lockmgr_assert(lk, KA_SLOCKED, file, line);
585 tid = (uintptr_t)curthread;
586 v = lk->lk_lock;
587 x = v & LK_ALL_WAITERS;
588 v &= LK_EXCLUSIVE_SPINNERS;
589 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
590 tid | x)) {
591 lockmgr_note_exclusive_upgrade(lk, file, line, flags);
592 locked = true;
593 }
594 break;
595 default:
596 break;
597 }
598 if (__predict_true(locked)) {
599 if (__predict_false(flags & LK_INTERLOCK)) {
600 class = LOCK_CLASS(ilk);
601 class->lc_unlock(ilk);
602 }
603 return (0);
604 } else {
605 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT,
606 LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line));
607 }
608 }
609
610 int
611 lockmgr_unlock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk)
612 {
613 struct lock_class *class;
614 uintptr_t x, tid;
615 bool unlocked;
616 const char *file;
617 int line;
618
619 file = __FILE__;
620 line = __LINE__;
621
622 _lockmgr_assert(lk, KA_LOCKED, file, line);
623 unlocked = false;
624 x = lk->lk_lock;
625 if (__predict_true(x & LK_SHARE) != 0) {
626 if (lockmgr_sunlock_try(lk, x)) {
627 lockmgr_note_shared_release(lk, file, line);
628 unlocked = true;
629 }
630 } else {
631 tid = (uintptr_t)curthread;
632 if (!lockmgr_recursed(lk) &&
633 atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) {
634 lockmgr_note_exclusive_release(lk, file, line);
635 unlocked = true;
636 }
637 }
638 if (__predict_true(unlocked)) {
639 if (__predict_false(flags & LK_INTERLOCK)) {
640 class = LOCK_CLASS(ilk);
641 class->lc_unlock(ilk);
642 }
643 return (0);
644 } else {
645 return (__lockmgr_args(lk, flags | LK_RELEASE, ilk, LK_WMESG_DEFAULT,
646 LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, LOCK_FILE, LOCK_LINE));
647 }
648 }
649
650 int
651 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
652 const char *wmesg, int pri, int timo, const char *file, int line)
653 {
654 GIANT_DECLARE;
655 struct lock_class *class;
656 const char *iwmesg;
657 uintptr_t tid, v, x;
658 u_int op, realexslp;
659 int error, ipri, itimo, queue, wakeup_swapper;
660 #ifdef LOCK_PROFILING
661 uint64_t waittime = 0;
662 int contested = 0;
663 #endif
664 #ifdef ADAPTIVE_LOCKMGRS
665 volatile struct thread *owner;
666 u_int i, spintries = 0;
667 #endif
668
669 error = 0;
670 tid = (uintptr_t)curthread;
671 op = (flags & LK_TYPE_MASK);
672 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
673 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
674 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
675
676 MPASS((flags & ~LK_TOTAL_MASK) == 0);
677 KASSERT((op & (op - 1)) == 0,
678 ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
679 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
680 (op != LK_DOWNGRADE && op != LK_RELEASE),
681 ("%s: Invalid flags in regard of the operation desired @ %s:%d",
682 __func__, file, line));
683 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
684 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
685 __func__, file, line));
686 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
687 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread,
688 lk->lock_object.lo_name, file, line));
689
690 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
691 if (panicstr != NULL) {
692 if (flags & LK_INTERLOCK)
693 class->lc_unlock(ilk);
694 return (0);
695 }
696
697 if (lk->lock_object.lo_flags & LK_NOSHARE) {
698 switch (op) {
699 case LK_SHARED:
700 op = LK_EXCLUSIVE;
701 break;
702 case LK_UPGRADE:
703 case LK_TRYUPGRADE:
704 case LK_DOWNGRADE:
705 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
706 file, line);
707 if (flags & LK_INTERLOCK)
708 class->lc_unlock(ilk);
709 return (0);
710 }
711 }
712
713 wakeup_swapper = 0;
714 switch (op) {
715 case LK_SHARED:
716 if (LK_CAN_WITNESS(flags))
717 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
718 file, line, flags & LK_INTERLOCK ? ilk : NULL);
719 for (;;) {
720 if (lockmgr_slock_try(lk, &x, flags))
721 break;
722 #ifdef HWPMC_HOOKS
723 PMC_SOFT_CALL( , , lock, failed);
724 #endif
725 lock_profile_obtain_lock_failed(&lk->lock_object,
726 &contested, &waittime);
727
728 /*
729 * If the lock is already held by curthread in
730 * exclusive way avoid a deadlock.
731 */
732 if (LK_HOLDER(x) == tid) {
733 LOCK_LOG2(lk,
734 "%s: %p already held in exclusive mode",
735 __func__, lk);
736 error = EDEADLK;
737 break;
738 }
739
740 /*
741 * If the lock is expected to not sleep just give up
742 * and return.
743 */
744 if (LK_TRYOP(flags)) {
745 LOCK_LOG2(lk, "%s: %p fails the try operation",
746 __func__, lk);
747 error = EBUSY;
748 break;
749 }
750
751 #ifdef ADAPTIVE_LOCKMGRS
752 /*
753 * If the owner is running on another CPU, spin until
754 * the owner stops running or the state of the lock
755 * changes. We need a double-state handle here
756 * because for a failed acquisition the lock can be
757 * either held in exclusive mode or shared mode
758 * (for the writer starvation avoidance technique).
759 */
760 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
761 LK_HOLDER(x) != LK_KERNPROC) {
762 owner = (struct thread *)LK_HOLDER(x);
763 if (LOCK_LOG_TEST(&lk->lock_object, 0))
764 CTR3(KTR_LOCK,
765 "%s: spinning on %p held by %p",
766 __func__, lk, owner);
767 KTR_STATE1(KTR_SCHED, "thread",
768 sched_tdname(td), "spinning",
769 "lockname:\"%s\"", lk->lock_object.lo_name);
770
771 /*
772 * If we are holding also an interlock drop it
773 * in order to avoid a deadlock if the lockmgr
774 * owner is adaptively spinning on the
775 * interlock itself.
776 */
777 if (flags & LK_INTERLOCK) {
778 class->lc_unlock(ilk);
779 flags &= ~LK_INTERLOCK;
780 }
781 GIANT_SAVE();
782 while (LK_HOLDER(lk->lk_lock) ==
783 (uintptr_t)owner && TD_IS_RUNNING(owner))
784 cpu_spinwait();
785 KTR_STATE0(KTR_SCHED, "thread",
786 sched_tdname(td), "running");
787 GIANT_RESTORE();
788 continue;
789 } else if (LK_CAN_ADAPT(lk, flags) &&
790 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
791 spintries < alk_retries) {
792 KTR_STATE1(KTR_SCHED, "thread",
793 sched_tdname(td), "spinning",
794 "lockname:\"%s\"", lk->lock_object.lo_name);
795 if (flags & LK_INTERLOCK) {
796 class->lc_unlock(ilk);
797 flags &= ~LK_INTERLOCK;
798 }
799 GIANT_SAVE();
800 spintries++;
801 for (i = 0; i < alk_loops; i++) {
802 if (LOCK_LOG_TEST(&lk->lock_object, 0))
803 CTR4(KTR_LOCK,
804 "%s: shared spinning on %p with %u and %u",
805 __func__, lk, spintries, i);
806 x = lk->lk_lock;
807 if ((x & LK_SHARE) == 0 ||
808 LK_CAN_SHARE(x, flags) != 0)
809 break;
810 cpu_spinwait();
811 }
812 KTR_STATE0(KTR_SCHED, "thread",
813 sched_tdname(td), "running");
814 GIANT_RESTORE();
815 if (i != alk_loops)
816 continue;
817 }
818 #endif
819
820 /*
821 * Acquire the sleepqueue chain lock because we
822 * probabilly will need to manipulate waiters flags.
823 */
824 sleepq_lock(&lk->lock_object);
825 x = lk->lk_lock;
826
827 /*
828 * if the lock can be acquired in shared mode, try
829 * again.
830 */
831 if (LK_CAN_SHARE(x, flags)) {
832 sleepq_release(&lk->lock_object);
833 continue;
834 }
835
836 #ifdef ADAPTIVE_LOCKMGRS
837 /*
838 * The current lock owner might have started executing
839 * on another CPU (or the lock could have changed
840 * owner) while we were waiting on the turnstile
841 * chain lock. If so, drop the turnstile lock and try
842 * again.
843 */
844 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
845 LK_HOLDER(x) != LK_KERNPROC) {
846 owner = (struct thread *)LK_HOLDER(x);
847 if (TD_IS_RUNNING(owner)) {
848 sleepq_release(&lk->lock_object);
849 continue;
850 }
851 }
852 #endif
853
854 /*
855 * Try to set the LK_SHARED_WAITERS flag. If we fail,
856 * loop back and retry.
857 */
858 if ((x & LK_SHARED_WAITERS) == 0) {
859 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x,
860 x | LK_SHARED_WAITERS)) {
861 sleepq_release(&lk->lock_object);
862 continue;
863 }
864 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
865 __func__, lk);
866 }
867
868 /*
869 * As far as we have been unable to acquire the
870 * shared lock and the shared waiters flag is set,
871 * we will sleep.
872 */
873 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
874 SQ_SHARED_QUEUE);
875 flags &= ~LK_INTERLOCK;
876 if (error) {
877 LOCK_LOG3(lk,
878 "%s: interrupted sleep for %p with %d",
879 __func__, lk, error);
880 break;
881 }
882 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
883 __func__, lk);
884 }
885 if (error == 0) {
886 #ifdef LOCK_PROFILING
887 lockmgr_note_shared_acquire(lk, contested, waittime,
888 file, line, flags);
889 #else
890 lockmgr_note_shared_acquire(lk, 0, 0, file, line,
891 flags);
892 #endif
893 }
894 break;
895 case LK_UPGRADE:
896 case LK_TRYUPGRADE:
897 _lockmgr_assert(lk, KA_SLOCKED, file, line);
898 v = lk->lk_lock;
899 x = v & LK_ALL_WAITERS;
900 v &= LK_EXCLUSIVE_SPINNERS;
901
902 /*
903 * Try to switch from one shared lock to an exclusive one.
904 * We need to preserve waiters flags during the operation.
905 */
906 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
907 tid | x)) {
908 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
909 line);
910 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
911 LK_TRYWIT(flags), file, line);
912 TD_SLOCKS_DEC(curthread);
913 break;
914 }
915
916 /*
917 * In LK_TRYUPGRADE mode, do not drop the lock,
918 * returning EBUSY instead.
919 */
920 if (op == LK_TRYUPGRADE) {
921 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
922 __func__, lk);
923 error = EBUSY;
924 break;
925 }
926
927 /*
928 * We have been unable to succeed in upgrading, so just
929 * give up the shared lock.
930 */
931 wakeup_swapper |= wakeupshlk(lk, file, line);
932
933 /* FALLTHROUGH */
934 case LK_EXCLUSIVE:
935 if (LK_CAN_WITNESS(flags))
936 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
937 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
938 ilk : NULL);
939
940 /*
941 * If curthread already holds the lock and this one is
942 * allowed to recurse, simply recurse on it.
943 */
944 if (lockmgr_xlocked(lk)) {
945 if ((flags & LK_CANRECURSE) == 0 &&
946 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
947
948 /*
949 * If the lock is expected to not panic just
950 * give up and return.
951 */
952 if (LK_TRYOP(flags)) {
953 LOCK_LOG2(lk,
954 "%s: %p fails the try operation",
955 __func__, lk);
956 error = EBUSY;
957 break;
958 }
959 if (flags & LK_INTERLOCK)
960 class->lc_unlock(ilk);
961 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n",
962 __func__, iwmesg, file, line);
963 }
964 lk->lk_recurse++;
965 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
966 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
967 lk->lk_recurse, file, line);
968 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
969 LK_TRYWIT(flags), file, line);
970 TD_LOCKS_INC(curthread);
971 break;
972 }
973
974 for (;;) {
975 if (lk->lk_lock == LK_UNLOCKED &&
976 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
977 break;
978 #ifdef HWPMC_HOOKS
979 PMC_SOFT_CALL( , , lock, failed);
980 #endif
981 lock_profile_obtain_lock_failed(&lk->lock_object,
982 &contested, &waittime);
983
984 /*
985 * If the lock is expected to not sleep just give up
986 * and return.
987 */
988 if (LK_TRYOP(flags)) {
989 LOCK_LOG2(lk, "%s: %p fails the try operation",
990 __func__, lk);
991 error = EBUSY;
992 break;
993 }
994
995 #ifdef ADAPTIVE_LOCKMGRS
996 /*
997 * If the owner is running on another CPU, spin until
998 * the owner stops running or the state of the lock
999 * changes.
1000 */
1001 x = lk->lk_lock;
1002 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
1003 LK_HOLDER(x) != LK_KERNPROC) {
1004 owner = (struct thread *)LK_HOLDER(x);
1005 if (LOCK_LOG_TEST(&lk->lock_object, 0))
1006 CTR3(KTR_LOCK,
1007 "%s: spinning on %p held by %p",
1008 __func__, lk, owner);
1009 KTR_STATE1(KTR_SCHED, "thread",
1010 sched_tdname(td), "spinning",
1011 "lockname:\"%s\"", lk->lock_object.lo_name);
1012
1013 /*
1014 * If we are holding also an interlock drop it
1015 * in order to avoid a deadlock if the lockmgr
1016 * owner is adaptively spinning on the
1017 * interlock itself.
1018 */
1019 if (flags & LK_INTERLOCK) {
1020 class->lc_unlock(ilk);
1021 flags &= ~LK_INTERLOCK;
1022 }
1023 GIANT_SAVE();
1024 while (LK_HOLDER(lk->lk_lock) ==
1025 (uintptr_t)owner && TD_IS_RUNNING(owner))
1026 cpu_spinwait();
1027 KTR_STATE0(KTR_SCHED, "thread",
1028 sched_tdname(td), "running");
1029 GIANT_RESTORE();
1030 continue;
1031 } else if (LK_CAN_ADAPT(lk, flags) &&
1032 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
1033 spintries < alk_retries) {
1034 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 &&
1035 !atomic_cmpset_ptr(&lk->lk_lock, x,
1036 x | LK_EXCLUSIVE_SPINNERS))
1037 continue;
1038 KTR_STATE1(KTR_SCHED, "thread",
1039 sched_tdname(td), "spinning",
1040 "lockname:\"%s\"", lk->lock_object.lo_name);
1041 if (flags & LK_INTERLOCK) {
1042 class->lc_unlock(ilk);
1043 flags &= ~LK_INTERLOCK;
1044 }
1045 GIANT_SAVE();
1046 spintries++;
1047 for (i = 0; i < alk_loops; i++) {
1048 if (LOCK_LOG_TEST(&lk->lock_object, 0))
1049 CTR4(KTR_LOCK,
1050 "%s: shared spinning on %p with %u and %u",
1051 __func__, lk, spintries, i);
1052 if ((lk->lk_lock &
1053 LK_EXCLUSIVE_SPINNERS) == 0)
1054 break;
1055 cpu_spinwait();
1056 }
1057 KTR_STATE0(KTR_SCHED, "thread",
1058 sched_tdname(td), "running");
1059 GIANT_RESTORE();
1060 if (i != alk_loops)
1061 continue;
1062 }
1063 #endif
1064
1065 /*
1066 * Acquire the sleepqueue chain lock because we
1067 * probabilly will need to manipulate waiters flags.
1068 */
1069 sleepq_lock(&lk->lock_object);
1070 x = lk->lk_lock;
1071
1072 /*
1073 * if the lock has been released while we spun on
1074 * the sleepqueue chain lock just try again.
1075 */
1076 if (x == LK_UNLOCKED) {
1077 sleepq_release(&lk->lock_object);
1078 continue;
1079 }
1080
1081 #ifdef ADAPTIVE_LOCKMGRS
1082 /*
1083 * The current lock owner might have started executing
1084 * on another CPU (or the lock could have changed
1085 * owner) while we were waiting on the turnstile
1086 * chain lock. If so, drop the turnstile lock and try
1087 * again.
1088 */
1089 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
1090 LK_HOLDER(x) != LK_KERNPROC) {
1091 owner = (struct thread *)LK_HOLDER(x);
1092 if (TD_IS_RUNNING(owner)) {
1093 sleepq_release(&lk->lock_object);
1094 continue;
1095 }
1096 }
1097 #endif
1098
1099 /*
1100 * The lock can be in the state where there is a
1101 * pending queue of waiters, but still no owner.
1102 * This happens when the lock is contested and an
1103 * owner is going to claim the lock.
1104 * If curthread is the one successfully acquiring it
1105 * claim lock ownership and return, preserving waiters
1106 * flags.
1107 */
1108 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1109 if ((x & ~v) == LK_UNLOCKED) {
1110 v &= ~LK_EXCLUSIVE_SPINNERS;
1111 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
1112 tid | v)) {
1113 sleepq_release(&lk->lock_object);
1114 LOCK_LOG2(lk,
1115 "%s: %p claimed by a new writer",
1116 __func__, lk);
1117 break;
1118 }
1119 sleepq_release(&lk->lock_object);
1120 continue;
1121 }
1122
1123 /*
1124 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
1125 * fail, loop back and retry.
1126 */
1127 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1128 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1129 x | LK_EXCLUSIVE_WAITERS)) {
1130 sleepq_release(&lk->lock_object);
1131 continue;
1132 }
1133 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
1134 __func__, lk);
1135 }
1136
1137 /*
1138 * As far as we have been unable to acquire the
1139 * exclusive lock and the exclusive waiters flag
1140 * is set, we will sleep.
1141 */
1142 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
1143 SQ_EXCLUSIVE_QUEUE);
1144 flags &= ~LK_INTERLOCK;
1145 if (error) {
1146 LOCK_LOG3(lk,
1147 "%s: interrupted sleep for %p with %d",
1148 __func__, lk, error);
1149 break;
1150 }
1151 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1152 __func__, lk);
1153 }
1154 if (error == 0) {
1155 #ifdef LOCK_PROFILING
1156 lockmgr_note_exclusive_acquire(lk, contested, waittime,
1157 file, line, flags);
1158 #else
1159 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
1160 flags);
1161 #endif
1162 }
1163 break;
1164 case LK_DOWNGRADE:
1165 _lockmgr_assert(lk, KA_XLOCKED, file, line);
1166 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
1167 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
1168
1169 /*
1170 * Panic if the lock is recursed.
1171 */
1172 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
1173 if (flags & LK_INTERLOCK)
1174 class->lc_unlock(ilk);
1175 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n",
1176 __func__, iwmesg, file, line);
1177 }
1178 TD_SLOCKS_INC(curthread);
1179
1180 /*
1181 * In order to preserve waiters flags, just spin.
1182 */
1183 for (;;) {
1184 x = lk->lk_lock;
1185 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1186 x &= LK_ALL_WAITERS;
1187 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1188 LK_SHARERS_LOCK(1) | x))
1189 break;
1190 cpu_spinwait();
1191 }
1192 break;
1193 case LK_RELEASE:
1194 _lockmgr_assert(lk, KA_LOCKED, file, line);
1195 x = lk->lk_lock;
1196
1197 if ((x & LK_SHARE) == 0) {
1198
1199 /*
1200 * As first option, treact the lock as if it has not
1201 * any waiter.
1202 * Fix-up the tid var if the lock has been disowned.
1203 */
1204 if (LK_HOLDER(x) == LK_KERNPROC)
1205 tid = LK_KERNPROC;
1206 else {
1207 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE,
1208 file, line);
1209 TD_LOCKS_DEC(curthread);
1210 }
1211 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0,
1212 lk->lk_recurse, file, line);
1213
1214 /*
1215 * The lock is held in exclusive mode.
1216 * If the lock is recursed also, then unrecurse it.
1217 */
1218 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
1219 LOCK_LOG2(lk, "%s: %p unrecursing", __func__,
1220 lk);
1221 lk->lk_recurse--;
1222 break;
1223 }
1224 if (tid != LK_KERNPROC)
1225 lock_profile_release_lock(&lk->lock_object);
1226
1227 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid,
1228 LK_UNLOCKED))
1229 break;
1230
1231 sleepq_lock(&lk->lock_object);
1232 x = lk->lk_lock;
1233 v = LK_UNLOCKED;
1234
1235 /*
1236 * If the lock has exclusive waiters, give them
1237 * preference in order to avoid deadlock with
1238 * shared runners up.
1239 * If interruptible sleeps left the exclusive queue
1240 * empty avoid a starvation for the threads sleeping
1241 * on the shared queue by giving them precedence
1242 * and cleaning up the exclusive waiters bit anyway.
1243 * Please note that lk_exslpfail count may be lying
1244 * about the real number of waiters with the
1245 * LK_SLEEPFAIL flag on because they may be used in
1246 * conjunction with interruptible sleeps so
1247 * lk_exslpfail might be considered an 'upper limit'
1248 * bound, including the edge cases.
1249 */
1250 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1251 realexslp = sleepq_sleepcnt(&lk->lock_object,
1252 SQ_EXCLUSIVE_QUEUE);
1253 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
1254 if (lk->lk_exslpfail < realexslp) {
1255 lk->lk_exslpfail = 0;
1256 queue = SQ_EXCLUSIVE_QUEUE;
1257 v |= (x & LK_SHARED_WAITERS);
1258 } else {
1259 lk->lk_exslpfail = 0;
1260 LOCK_LOG2(lk,
1261 "%s: %p has only LK_SLEEPFAIL sleepers",
1262 __func__, lk);
1263 LOCK_LOG2(lk,
1264 "%s: %p waking up threads on the exclusive queue",
1265 __func__, lk);
1266 wakeup_swapper =
1267 sleepq_broadcast(&lk->lock_object,
1268 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1269 queue = SQ_SHARED_QUEUE;
1270 }
1271 } else {
1272
1273 /*
1274 * Exclusive waiters sleeping with LK_SLEEPFAIL
1275 * on and using interruptible sleeps/timeout
1276 * may have left spourious lk_exslpfail counts
1277 * on, so clean it up anyway.
1278 */
1279 lk->lk_exslpfail = 0;
1280 queue = SQ_SHARED_QUEUE;
1281 }
1282
1283 LOCK_LOG3(lk,
1284 "%s: %p waking up threads on the %s queue",
1285 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
1286 "exclusive");
1287 atomic_store_rel_ptr(&lk->lk_lock, v);
1288 wakeup_swapper |= sleepq_broadcast(&lk->lock_object,
1289 SLEEPQ_LK, 0, queue);
1290 sleepq_release(&lk->lock_object);
1291 break;
1292 } else
1293 wakeup_swapper = wakeupshlk(lk, file, line);
1294 break;
1295 case LK_DRAIN:
1296 if (LK_CAN_WITNESS(flags))
1297 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1298 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
1299 ilk : NULL);
1300
1301 /*
1302 * Trying to drain a lock we already own will result in a
1303 * deadlock.
1304 */
1305 if (lockmgr_xlocked(lk)) {
1306 if (flags & LK_INTERLOCK)
1307 class->lc_unlock(ilk);
1308 panic("%s: draining %s with the lock held @ %s:%d\n",
1309 __func__, iwmesg, file, line);
1310 }
1311
1312 for (;;) {
1313 if (lk->lk_lock == LK_UNLOCKED &&
1314 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
1315 break;
1316
1317 #ifdef HWPMC_HOOKS
1318 PMC_SOFT_CALL( , , lock, failed);
1319 #endif
1320 lock_profile_obtain_lock_failed(&lk->lock_object,
1321 &contested, &waittime);
1322
1323 /*
1324 * If the lock is expected to not sleep just give up
1325 * and return.
1326 */
1327 if (LK_TRYOP(flags)) {
1328 LOCK_LOG2(lk, "%s: %p fails the try operation",
1329 __func__, lk);
1330 error = EBUSY;
1331 break;
1332 }
1333
1334 /*
1335 * Acquire the sleepqueue chain lock because we
1336 * probabilly will need to manipulate waiters flags.
1337 */
1338 sleepq_lock(&lk->lock_object);
1339 x = lk->lk_lock;
1340
1341 /*
1342 * if the lock has been released while we spun on
1343 * the sleepqueue chain lock just try again.
1344 */
1345 if (x == LK_UNLOCKED) {
1346 sleepq_release(&lk->lock_object);
1347 continue;
1348 }
1349
1350 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1351 if ((x & ~v) == LK_UNLOCKED) {
1352 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1353
1354 /*
1355 * If interruptible sleeps left the exclusive
1356 * queue empty avoid a starvation for the
1357 * threads sleeping on the shared queue by
1358 * giving them precedence and cleaning up the
1359 * exclusive waiters bit anyway.
1360 * Please note that lk_exslpfail count may be
1361 * lying about the real number of waiters with
1362 * the LK_SLEEPFAIL flag on because they may
1363 * be used in conjunction with interruptible
1364 * sleeps so lk_exslpfail might be considered
1365 * an 'upper limit' bound, including the edge
1366 * cases.
1367 */
1368 if (v & LK_EXCLUSIVE_WAITERS) {
1369 queue = SQ_EXCLUSIVE_QUEUE;
1370 v &= ~LK_EXCLUSIVE_WAITERS;
1371 } else {
1372
1373 /*
1374 * Exclusive waiters sleeping with
1375 * LK_SLEEPFAIL on and using
1376 * interruptible sleeps/timeout may
1377 * have left spourious lk_exslpfail
1378 * counts on, so clean it up anyway.
1379 */
1380 MPASS(v & LK_SHARED_WAITERS);
1381 lk->lk_exslpfail = 0;
1382 queue = SQ_SHARED_QUEUE;
1383 v &= ~LK_SHARED_WAITERS;
1384 }
1385 if (queue == SQ_EXCLUSIVE_QUEUE) {
1386 realexslp =
1387 sleepq_sleepcnt(&lk->lock_object,
1388 SQ_EXCLUSIVE_QUEUE);
1389 if (lk->lk_exslpfail >= realexslp) {
1390 lk->lk_exslpfail = 0;
1391 queue = SQ_SHARED_QUEUE;
1392 v &= ~LK_SHARED_WAITERS;
1393 if (realexslp != 0) {
1394 LOCK_LOG2(lk,
1395 "%s: %p has only LK_SLEEPFAIL sleepers",
1396 __func__, lk);
1397 LOCK_LOG2(lk,
1398 "%s: %p waking up threads on the exclusive queue",
1399 __func__, lk);
1400 wakeup_swapper =
1401 sleepq_broadcast(
1402 &lk->lock_object,
1403 SLEEPQ_LK, 0,
1404 SQ_EXCLUSIVE_QUEUE);
1405 }
1406 } else
1407 lk->lk_exslpfail = 0;
1408 }
1409 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1410 sleepq_release(&lk->lock_object);
1411 continue;
1412 }
1413 LOCK_LOG3(lk,
1414 "%s: %p waking up all threads on the %s queue",
1415 __func__, lk, queue == SQ_SHARED_QUEUE ?
1416 "shared" : "exclusive");
1417 wakeup_swapper |= sleepq_broadcast(
1418 &lk->lock_object, SLEEPQ_LK, 0, queue);
1419
1420 /*
1421 * If shared waiters have been woken up we need
1422 * to wait for one of them to acquire the lock
1423 * before to set the exclusive waiters in
1424 * order to avoid a deadlock.
1425 */
1426 if (queue == SQ_SHARED_QUEUE) {
1427 for (v = lk->lk_lock;
1428 (v & LK_SHARE) && !LK_SHARERS(v);
1429 v = lk->lk_lock)
1430 cpu_spinwait();
1431 }
1432 }
1433
1434 /*
1435 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
1436 * fail, loop back and retry.
1437 */
1438 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1439 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1440 x | LK_EXCLUSIVE_WAITERS)) {
1441 sleepq_release(&lk->lock_object);
1442 continue;
1443 }
1444 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1445 __func__, lk);
1446 }
1447
1448 /*
1449 * As far as we have been unable to acquire the
1450 * exclusive lock and the exclusive waiters flag
1451 * is set, we will sleep.
1452 */
1453 if (flags & LK_INTERLOCK) {
1454 class->lc_unlock(ilk);
1455 flags &= ~LK_INTERLOCK;
1456 }
1457 GIANT_SAVE();
1458 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1459 SQ_EXCLUSIVE_QUEUE);
1460 sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1461 GIANT_RESTORE();
1462 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1463 __func__, lk);
1464 }
1465
1466 if (error == 0) {
1467 lock_profile_obtain_lock_success(&lk->lock_object,
1468 contested, waittime, file, line);
1469 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1470 lk->lk_recurse, file, line);
1471 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1472 LK_TRYWIT(flags), file, line);
1473 TD_LOCKS_INC(curthread);
1474 STACK_SAVE(lk);
1475 }
1476 break;
1477 default:
1478 if (flags & LK_INTERLOCK)
1479 class->lc_unlock(ilk);
1480 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1481 }
1482
1483 if (flags & LK_INTERLOCK)
1484 class->lc_unlock(ilk);
1485 if (wakeup_swapper)
1486 kick_proc0();
1487
1488 return (error);
1489 }
1490
1491 void
1492 _lockmgr_disown(struct lock *lk, const char *file, int line)
1493 {
1494 uintptr_t tid, x;
1495
1496 if (SCHEDULER_STOPPED())
1497 return;
1498
1499 tid = (uintptr_t)curthread;
1500 _lockmgr_assert(lk, KA_XLOCKED, file, line);
1501
1502 /*
1503 * Panic if the lock is recursed.
1504 */
1505 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk))
1506 panic("%s: disown a recursed lockmgr @ %s:%d\n",
1507 __func__, file, line);
1508
1509 /*
1510 * If the owner is already LK_KERNPROC just skip the whole operation.
1511 */
1512 if (LK_HOLDER(lk->lk_lock) != tid)
1513 return;
1514 lock_profile_release_lock(&lk->lock_object);
1515 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1516 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1517 TD_LOCKS_DEC(curthread);
1518 STACK_SAVE(lk);
1519
1520 /*
1521 * In order to preserve waiters flags, just spin.
1522 */
1523 for (;;) {
1524 x = lk->lk_lock;
1525 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1526 x &= LK_ALL_WAITERS;
1527 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1528 LK_KERNPROC | x))
1529 return;
1530 cpu_spinwait();
1531 }
1532 }
1533
1534 void
1535 lockmgr_printinfo(const struct lock *lk)
1536 {
1537 struct thread *td;
1538 uintptr_t x;
1539
1540 if (lk->lk_lock == LK_UNLOCKED)
1541 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1542 else if (lk->lk_lock & LK_SHARE)
1543 printf("lock type %s: SHARED (count %ju)\n",
1544 lk->lock_object.lo_name,
1545 (uintmax_t)LK_SHARERS(lk->lk_lock));
1546 else {
1547 td = lockmgr_xholder(lk);
1548 if (td == (struct thread *)LK_KERNPROC)
1549 printf("lock type %s: EXCL by KERNPROC\n",
1550 lk->lock_object.lo_name);
1551 else
1552 printf("lock type %s: EXCL by thread %p "
1553 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name,
1554 td, td->td_proc->p_pid, td->td_proc->p_comm,
1555 td->td_tid);
1556 }
1557
1558 x = lk->lk_lock;
1559 if (x & LK_EXCLUSIVE_WAITERS)
1560 printf(" with exclusive waiters pending\n");
1561 if (x & LK_SHARED_WAITERS)
1562 printf(" with shared waiters pending\n");
1563 if (x & LK_EXCLUSIVE_SPINNERS)
1564 printf(" with exclusive spinners pending\n");
1565
1566 STACK_PRINT(lk);
1567 }
1568
1569 int
1570 lockstatus(const struct lock *lk)
1571 {
1572 uintptr_t v, x;
1573 int ret;
1574
1575 ret = LK_SHARED;
1576 x = lk->lk_lock;
1577 v = LK_HOLDER(x);
1578
1579 if ((x & LK_SHARE) == 0) {
1580 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1581 ret = LK_EXCLUSIVE;
1582 else
1583 ret = LK_EXCLOTHER;
1584 } else if (x == LK_UNLOCKED)
1585 ret = 0;
1586
1587 return (ret);
1588 }
1589
1590 #ifdef INVARIANT_SUPPORT
1591
1592 FEATURE(invariant_support,
1593 "Support for modules compiled with INVARIANTS option");
1594
1595 #ifndef INVARIANTS
1596 #undef _lockmgr_assert
1597 #endif
1598
1599 void
1600 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line)
1601 {
1602 int slocked = 0;
1603
1604 if (panicstr != NULL)
1605 return;
1606 switch (what) {
1607 case KA_SLOCKED:
1608 case KA_SLOCKED | KA_NOTRECURSED:
1609 case KA_SLOCKED | KA_RECURSED:
1610 slocked = 1;
1611 case KA_LOCKED:
1612 case KA_LOCKED | KA_NOTRECURSED:
1613 case KA_LOCKED | KA_RECURSED:
1614 #ifdef WITNESS
1615
1616 /*
1617 * We cannot trust WITNESS if the lock is held in exclusive
1618 * mode and a call to lockmgr_disown() happened.
1619 * Workaround this skipping the check if the lock is held in
1620 * exclusive mode even for the KA_LOCKED case.
1621 */
1622 if (slocked || (lk->lk_lock & LK_SHARE)) {
1623 witness_assert(&lk->lock_object, what, file, line);
1624 break;
1625 }
1626 #endif
1627 if (lk->lk_lock == LK_UNLOCKED ||
1628 ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1629 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1630 panic("Lock %s not %slocked @ %s:%d\n",
1631 lk->lock_object.lo_name, slocked ? "share" : "",
1632 file, line);
1633
1634 if ((lk->lk_lock & LK_SHARE) == 0) {
1635 if (lockmgr_recursed(lk)) {
1636 if (what & KA_NOTRECURSED)
1637 panic("Lock %s recursed @ %s:%d\n",
1638 lk->lock_object.lo_name, file,
1639 line);
1640 } else if (what & KA_RECURSED)
1641 panic("Lock %s not recursed @ %s:%d\n",
1642 lk->lock_object.lo_name, file, line);
1643 }
1644 break;
1645 case KA_XLOCKED:
1646 case KA_XLOCKED | KA_NOTRECURSED:
1647 case KA_XLOCKED | KA_RECURSED:
1648 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1649 panic("Lock %s not exclusively locked @ %s:%d\n",
1650 lk->lock_object.lo_name, file, line);
1651 if (lockmgr_recursed(lk)) {
1652 if (what & KA_NOTRECURSED)
1653 panic("Lock %s recursed @ %s:%d\n",
1654 lk->lock_object.lo_name, file, line);
1655 } else if (what & KA_RECURSED)
1656 panic("Lock %s not recursed @ %s:%d\n",
1657 lk->lock_object.lo_name, file, line);
1658 break;
1659 case KA_UNLOCKED:
1660 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1661 panic("Lock %s exclusively locked @ %s:%d\n",
1662 lk->lock_object.lo_name, file, line);
1663 break;
1664 default:
1665 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1666 line);
1667 }
1668 }
1669 #endif
1670
1671 #ifdef DDB
1672 int
1673 lockmgr_chain(struct thread *td, struct thread **ownerp)
1674 {
1675 struct lock *lk;
1676
1677 lk = td->td_wchan;
1678
1679 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1680 return (0);
1681 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1682 if (lk->lk_lock & LK_SHARE)
1683 db_printf("SHARED (count %ju)\n",
1684 (uintmax_t)LK_SHARERS(lk->lk_lock));
1685 else
1686 db_printf("EXCL\n");
1687 *ownerp = lockmgr_xholder(lk);
1688
1689 return (1);
1690 }
1691
1692 static void
1693 db_show_lockmgr(const struct lock_object *lock)
1694 {
1695 struct thread *td;
1696 const struct lock *lk;
1697
1698 lk = (const struct lock *)lock;
1699
1700 db_printf(" state: ");
1701 if (lk->lk_lock == LK_UNLOCKED)
1702 db_printf("UNLOCKED\n");
1703 else if (lk->lk_lock & LK_SHARE)
1704 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1705 else {
1706 td = lockmgr_xholder(lk);
1707 if (td == (struct thread *)LK_KERNPROC)
1708 db_printf("XLOCK: LK_KERNPROC\n");
1709 else
1710 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1711 td->td_tid, td->td_proc->p_pid,
1712 td->td_proc->p_comm);
1713 if (lockmgr_recursed(lk))
1714 db_printf(" recursed: %d\n", lk->lk_recurse);
1715 }
1716 db_printf(" waiters: ");
1717 switch (lk->lk_lock & LK_ALL_WAITERS) {
1718 case LK_SHARED_WAITERS:
1719 db_printf("shared\n");
1720 break;
1721 case LK_EXCLUSIVE_WAITERS:
1722 db_printf("exclusive\n");
1723 break;
1724 case LK_ALL_WAITERS:
1725 db_printf("shared and exclusive\n");
1726 break;
1727 default:
1728 db_printf("none\n");
1729 }
1730 db_printf(" spinners: ");
1731 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1732 db_printf("exclusive\n");
1733 else
1734 db_printf("none\n");
1735 }
1736 #endif
Cache object: 5359162bce31abd8ff1e17df50d61d32
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