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: stable/12/sys/kern/kern_lock.c 352046 2019-09-08 20:53:29Z markj $");
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/lockstat.h>
44 #include <sys/mutex.h>
45 #include <sys/proc.h>
46 #include <sys/sleepqueue.h>
47 #ifdef DEBUG_LOCKS
48 #include <sys/stack.h>
49 #endif
50 #include <sys/sysctl.h>
51 #include <sys/systm.h>
52
53 #include <machine/cpu.h>
54
55 #ifdef DDB
56 #include <ddb/ddb.h>
57 #endif
58
59 #ifdef HWPMC_HOOKS
60 #include <sys/pmckern.h>
61 PMC_SOFT_DECLARE( , , lock, failed);
62 #endif
63
64 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
65 (LK_ADAPTIVE | LK_NOSHARE));
66 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
67 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
68
69 #define SQ_EXCLUSIVE_QUEUE 0
70 #define SQ_SHARED_QUEUE 1
71
72 #ifndef INVARIANTS
73 #define _lockmgr_assert(lk, what, file, line)
74 #endif
75
76 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++)
77 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--)
78
79 #ifndef DEBUG_LOCKS
80 #define STACK_PRINT(lk)
81 #define STACK_SAVE(lk)
82 #define STACK_ZERO(lk)
83 #else
84 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
85 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack)
86 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack)
87 #endif
88
89 #define LOCK_LOG2(lk, string, arg1, arg2) \
90 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
91 CTR2(KTR_LOCK, (string), (arg1), (arg2))
92 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \
93 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
94 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
95
96 #define GIANT_DECLARE \
97 int _i = 0; \
98 WITNESS_SAVE_DECL(Giant)
99 #define GIANT_RESTORE() do { \
100 if (_i > 0) { \
101 while (_i--) \
102 mtx_lock(&Giant); \
103 WITNESS_RESTORE(&Giant.lock_object, Giant); \
104 } \
105 } while (0)
106 #define GIANT_SAVE() do { \
107 if (mtx_owned(&Giant)) { \
108 WITNESS_SAVE(&Giant.lock_object, Giant); \
109 while (mtx_owned(&Giant)) { \
110 _i++; \
111 mtx_unlock(&Giant); \
112 } \
113 } \
114 } while (0)
115
116 static bool __always_inline
LK_CAN_SHARE(uintptr_t x,int flags,bool fp)117 LK_CAN_SHARE(uintptr_t x, int flags, bool fp)
118 {
119
120 if ((x & (LK_SHARE | LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) ==
121 LK_SHARE)
122 return (true);
123 if (fp || (!(x & LK_SHARE)))
124 return (false);
125 if ((curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) ||
126 (curthread->td_pflags & TDP_DEADLKTREAT))
127 return (true);
128 return (false);
129 }
130
131 #define LK_TRYOP(x) \
132 ((x) & LK_NOWAIT)
133
134 #define LK_CAN_WITNESS(x) \
135 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
136 #define LK_TRYWIT(x) \
137 (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
138
139 #define LK_CAN_ADAPT(lk, f) \
140 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \
141 ((f) & LK_SLEEPFAIL) == 0)
142
143 #define lockmgr_disowned(lk) \
144 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
145
146 #define lockmgr_xlocked_v(v) \
147 (((v) & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
148
149 #define lockmgr_xlocked(lk) lockmgr_xlocked_v((lk)->lk_lock)
150
151 static void assert_lockmgr(const struct lock_object *lock, int how);
152 #ifdef DDB
153 static void db_show_lockmgr(const struct lock_object *lock);
154 #endif
155 static void lock_lockmgr(struct lock_object *lock, uintptr_t how);
156 #ifdef KDTRACE_HOOKS
157 static int owner_lockmgr(const struct lock_object *lock,
158 struct thread **owner);
159 #endif
160 static uintptr_t unlock_lockmgr(struct lock_object *lock);
161
162 struct lock_class lock_class_lockmgr = {
163 .lc_name = "lockmgr",
164 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
165 .lc_assert = assert_lockmgr,
166 #ifdef DDB
167 .lc_ddb_show = db_show_lockmgr,
168 #endif
169 .lc_lock = lock_lockmgr,
170 .lc_unlock = unlock_lockmgr,
171 #ifdef KDTRACE_HOOKS
172 .lc_owner = owner_lockmgr,
173 #endif
174 };
175
176 struct lockmgr_wait {
177 const char *iwmesg;
178 int ipri;
179 int itimo;
180 };
181
182 static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp,
183 int flags, bool fp);
184 static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp);
185
186 static void
lockmgr_exit(u_int flags,struct lock_object * ilk,int wakeup_swapper)187 lockmgr_exit(u_int flags, struct lock_object *ilk, int wakeup_swapper)
188 {
189 struct lock_class *class;
190
191 if (flags & LK_INTERLOCK) {
192 class = LOCK_CLASS(ilk);
193 class->lc_unlock(ilk);
194 }
195
196 if (__predict_false(wakeup_swapper))
197 kick_proc0();
198 }
199
200 static void
lockmgr_note_shared_acquire(struct lock * lk,int contested,uint64_t waittime,const char * file,int line,int flags)201 lockmgr_note_shared_acquire(struct lock *lk, int contested,
202 uint64_t waittime, const char *file, int line, int flags)
203 {
204
205 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested,
206 waittime, file, line, LOCKSTAT_READER);
207 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line);
208 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line);
209 TD_LOCKS_INC(curthread);
210 TD_SLOCKS_INC(curthread);
211 STACK_SAVE(lk);
212 }
213
214 static void
lockmgr_note_shared_release(struct lock * lk,const char * file,int line)215 lockmgr_note_shared_release(struct lock *lk, const char *file, int line)
216 {
217
218 LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER);
219 WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
220 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
221 TD_LOCKS_DEC(curthread);
222 TD_SLOCKS_DEC(curthread);
223 }
224
225 static void
lockmgr_note_exclusive_acquire(struct lock * lk,int contested,uint64_t waittime,const char * file,int line,int flags)226 lockmgr_note_exclusive_acquire(struct lock *lk, int contested,
227 uint64_t waittime, const char *file, int line, int flags)
228 {
229
230 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested,
231 waittime, file, line, LOCKSTAT_WRITER);
232 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
233 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file,
234 line);
235 TD_LOCKS_INC(curthread);
236 STACK_SAVE(lk);
237 }
238
239 static void
lockmgr_note_exclusive_release(struct lock * lk,const char * file,int line)240 lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line)
241 {
242
243 LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_WRITER);
244 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file,
245 line);
246 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
247 TD_LOCKS_DEC(curthread);
248 }
249
250 static __inline struct thread *
lockmgr_xholder(const struct lock * lk)251 lockmgr_xholder(const struct lock *lk)
252 {
253 uintptr_t x;
254
255 x = lk->lk_lock;
256 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
257 }
258
259 /*
260 * It assumes sleepq_lock held and returns with this one unheld.
261 * It also assumes the generic interlock is sane and previously checked.
262 * If LK_INTERLOCK is specified the interlock is not reacquired after the
263 * sleep.
264 */
265 static __inline int
sleeplk(struct lock * lk,u_int flags,struct lock_object * ilk,const char * wmesg,int pri,int timo,int queue)266 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
267 const char *wmesg, int pri, int timo, int queue)
268 {
269 GIANT_DECLARE;
270 struct lock_class *class;
271 int catch, error;
272
273 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
274 catch = pri & PCATCH;
275 pri &= PRIMASK;
276 error = 0;
277
278 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
279 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
280
281 if (flags & LK_INTERLOCK)
282 class->lc_unlock(ilk);
283 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0)
284 lk->lk_exslpfail++;
285 GIANT_SAVE();
286 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
287 SLEEPQ_INTERRUPTIBLE : 0), queue);
288 if ((flags & LK_TIMELOCK) && timo)
289 sleepq_set_timeout(&lk->lock_object, timo);
290
291 /*
292 * Decisional switch for real sleeping.
293 */
294 if ((flags & LK_TIMELOCK) && timo && catch)
295 error = sleepq_timedwait_sig(&lk->lock_object, pri);
296 else if ((flags & LK_TIMELOCK) && timo)
297 error = sleepq_timedwait(&lk->lock_object, pri);
298 else if (catch)
299 error = sleepq_wait_sig(&lk->lock_object, pri);
300 else
301 sleepq_wait(&lk->lock_object, pri);
302 GIANT_RESTORE();
303 if ((flags & LK_SLEEPFAIL) && error == 0)
304 error = ENOLCK;
305
306 return (error);
307 }
308
309 static __inline int
wakeupshlk(struct lock * lk,const char * file,int line)310 wakeupshlk(struct lock *lk, const char *file, int line)
311 {
312 uintptr_t v, x, orig_x;
313 u_int realexslp;
314 int queue, wakeup_swapper;
315
316 wakeup_swapper = 0;
317 for (;;) {
318 x = lk->lk_lock;
319 if (lockmgr_sunlock_try(lk, &x))
320 break;
321
322 /*
323 * We should have a sharer with waiters, so enter the hard
324 * path in order to handle wakeups correctly.
325 */
326 sleepq_lock(&lk->lock_object);
327 orig_x = lk->lk_lock;
328 retry_sleepq:
329 x = orig_x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
330 v = LK_UNLOCKED;
331
332 /*
333 * If the lock has exclusive waiters, give them preference in
334 * order to avoid deadlock with shared runners up.
335 * If interruptible sleeps left the exclusive queue empty
336 * avoid a starvation for the threads sleeping on the shared
337 * queue by giving them precedence and cleaning up the
338 * exclusive waiters bit anyway.
339 * Please note that lk_exslpfail count may be lying about
340 * the real number of waiters with the LK_SLEEPFAIL flag on
341 * because they may be used in conjunction with interruptible
342 * sleeps so lk_exslpfail might be considered an 'upper limit'
343 * bound, including the edge cases.
344 */
345 realexslp = sleepq_sleepcnt(&lk->lock_object,
346 SQ_EXCLUSIVE_QUEUE);
347 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
348 if (lk->lk_exslpfail < realexslp) {
349 lk->lk_exslpfail = 0;
350 queue = SQ_EXCLUSIVE_QUEUE;
351 v |= (x & LK_SHARED_WAITERS);
352 } else {
353 lk->lk_exslpfail = 0;
354 LOCK_LOG2(lk,
355 "%s: %p has only LK_SLEEPFAIL sleepers",
356 __func__, lk);
357 LOCK_LOG2(lk,
358 "%s: %p waking up threads on the exclusive queue",
359 __func__, lk);
360 wakeup_swapper =
361 sleepq_broadcast(&lk->lock_object,
362 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
363 queue = SQ_SHARED_QUEUE;
364 }
365
366 } else {
367
368 /*
369 * Exclusive waiters sleeping with LK_SLEEPFAIL on
370 * and using interruptible sleeps/timeout may have
371 * left spourious lk_exslpfail counts on, so clean
372 * it up anyway.
373 */
374 lk->lk_exslpfail = 0;
375 queue = SQ_SHARED_QUEUE;
376 }
377
378 if (lockmgr_sunlock_try(lk, &orig_x)) {
379 sleepq_release(&lk->lock_object);
380 break;
381 }
382
383 x |= LK_SHARERS_LOCK(1);
384 if (!atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, v)) {
385 orig_x = x;
386 goto retry_sleepq;
387 }
388 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
389 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
390 "exclusive");
391 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
392 0, queue);
393 sleepq_release(&lk->lock_object);
394 break;
395 }
396
397 lockmgr_note_shared_release(lk, file, line);
398 return (wakeup_swapper);
399 }
400
401 static void
assert_lockmgr(const struct lock_object * lock,int what)402 assert_lockmgr(const struct lock_object *lock, int what)
403 {
404
405 panic("lockmgr locks do not support assertions");
406 }
407
408 static void
lock_lockmgr(struct lock_object * lock,uintptr_t how)409 lock_lockmgr(struct lock_object *lock, uintptr_t how)
410 {
411
412 panic("lockmgr locks do not support sleep interlocking");
413 }
414
415 static uintptr_t
unlock_lockmgr(struct lock_object * lock)416 unlock_lockmgr(struct lock_object *lock)
417 {
418
419 panic("lockmgr locks do not support sleep interlocking");
420 }
421
422 #ifdef KDTRACE_HOOKS
423 static int
owner_lockmgr(const struct lock_object * lock,struct thread ** owner)424 owner_lockmgr(const struct lock_object *lock, struct thread **owner)
425 {
426
427 panic("lockmgr locks do not support owner inquiring");
428 }
429 #endif
430
431 void
lockinit(struct lock * lk,int pri,const char * wmesg,int timo,int flags)432 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
433 {
434 int iflags;
435
436 MPASS((flags & ~LK_INIT_MASK) == 0);
437 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
438 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
439 &lk->lk_lock));
440
441 iflags = LO_SLEEPABLE | LO_UPGRADABLE;
442 if (flags & LK_CANRECURSE)
443 iflags |= LO_RECURSABLE;
444 if ((flags & LK_NODUP) == 0)
445 iflags |= LO_DUPOK;
446 if (flags & LK_NOPROFILE)
447 iflags |= LO_NOPROFILE;
448 if ((flags & LK_NOWITNESS) == 0)
449 iflags |= LO_WITNESS;
450 if (flags & LK_QUIET)
451 iflags |= LO_QUIET;
452 if (flags & LK_IS_VNODE)
453 iflags |= LO_IS_VNODE;
454 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
455
456 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
457 lk->lk_lock = LK_UNLOCKED;
458 lk->lk_recurse = 0;
459 lk->lk_exslpfail = 0;
460 lk->lk_timo = timo;
461 lk->lk_pri = pri;
462 STACK_ZERO(lk);
463 }
464
465 /*
466 * XXX: Gross hacks to manipulate external lock flags after
467 * initialization. Used for certain vnode and buf locks.
468 */
469 void
lockallowshare(struct lock * lk)470 lockallowshare(struct lock *lk)
471 {
472
473 lockmgr_assert(lk, KA_XLOCKED);
474 lk->lock_object.lo_flags &= ~LK_NOSHARE;
475 }
476
477 void
lockdisableshare(struct lock * lk)478 lockdisableshare(struct lock *lk)
479 {
480
481 lockmgr_assert(lk, KA_XLOCKED);
482 lk->lock_object.lo_flags |= LK_NOSHARE;
483 }
484
485 void
lockallowrecurse(struct lock * lk)486 lockallowrecurse(struct lock *lk)
487 {
488
489 lockmgr_assert(lk, KA_XLOCKED);
490 lk->lock_object.lo_flags |= LO_RECURSABLE;
491 }
492
493 void
lockdisablerecurse(struct lock * lk)494 lockdisablerecurse(struct lock *lk)
495 {
496
497 lockmgr_assert(lk, KA_XLOCKED);
498 lk->lock_object.lo_flags &= ~LO_RECURSABLE;
499 }
500
501 void
lockdestroy(struct lock * lk)502 lockdestroy(struct lock *lk)
503 {
504
505 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
506 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
507 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
508 lock_destroy(&lk->lock_object);
509 }
510
511 static bool __always_inline
lockmgr_slock_try(struct lock * lk,uintptr_t * xp,int flags,bool fp)512 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags, bool fp)
513 {
514
515 /*
516 * If no other thread has an exclusive lock, or
517 * no exclusive waiter is present, bump the count of
518 * sharers. Since we have to preserve the state of
519 * waiters, if we fail to acquire the shared lock
520 * loop back and retry.
521 */
522 *xp = lk->lk_lock;
523 while (LK_CAN_SHARE(*xp, flags, fp)) {
524 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp,
525 *xp + LK_ONE_SHARER)) {
526 return (true);
527 }
528 }
529 return (false);
530 }
531
532 static bool __always_inline
lockmgr_sunlock_try(struct lock * lk,uintptr_t * xp)533 lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp)
534 {
535
536 for (;;) {
537 if (LK_SHARERS(*xp) > 1 || !(*xp & LK_ALL_WAITERS)) {
538 if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp,
539 *xp - LK_ONE_SHARER))
540 return (true);
541 continue;
542 }
543 break;
544 }
545 return (false);
546 }
547
548 static __noinline int
lockmgr_slock_hard(struct lock * lk,u_int flags,struct lock_object * ilk,const char * file,int line,struct lockmgr_wait * lwa)549 lockmgr_slock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
550 const char *file, int line, struct lockmgr_wait *lwa)
551 {
552 uintptr_t tid, x;
553 int error = 0;
554 const char *iwmesg;
555 int ipri, itimo;
556
557 #ifdef KDTRACE_HOOKS
558 uint64_t sleep_time = 0;
559 #endif
560 #ifdef LOCK_PROFILING
561 uint64_t waittime = 0;
562 int contested = 0;
563 #endif
564
565 if (__predict_false(panicstr != NULL))
566 goto out;
567
568 tid = (uintptr_t)curthread;
569
570 if (LK_CAN_WITNESS(flags))
571 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
572 file, line, flags & LK_INTERLOCK ? ilk : NULL);
573 for (;;) {
574 if (lockmgr_slock_try(lk, &x, flags, false))
575 break;
576 #ifdef HWPMC_HOOKS
577 PMC_SOFT_CALL( , , lock, failed);
578 #endif
579 lock_profile_obtain_lock_failed(&lk->lock_object,
580 &contested, &waittime);
581
582 /*
583 * If the lock is already held by curthread in
584 * exclusive way avoid a deadlock.
585 */
586 if (LK_HOLDER(x) == tid) {
587 LOCK_LOG2(lk,
588 "%s: %p already held in exclusive mode",
589 __func__, lk);
590 error = EDEADLK;
591 break;
592 }
593
594 /*
595 * If the lock is expected to not sleep just give up
596 * and return.
597 */
598 if (LK_TRYOP(flags)) {
599 LOCK_LOG2(lk, "%s: %p fails the try operation",
600 __func__, lk);
601 error = EBUSY;
602 break;
603 }
604
605 /*
606 * Acquire the sleepqueue chain lock because we
607 * probabilly will need to manipulate waiters flags.
608 */
609 sleepq_lock(&lk->lock_object);
610 x = lk->lk_lock;
611 retry_sleepq:
612
613 /*
614 * if the lock can be acquired in shared mode, try
615 * again.
616 */
617 if (LK_CAN_SHARE(x, flags, false)) {
618 sleepq_release(&lk->lock_object);
619 continue;
620 }
621
622 /*
623 * Try to set the LK_SHARED_WAITERS flag. If we fail,
624 * loop back and retry.
625 */
626 if ((x & LK_SHARED_WAITERS) == 0) {
627 if (!atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
628 x | LK_SHARED_WAITERS)) {
629 goto retry_sleepq;
630 }
631 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
632 __func__, lk);
633 }
634
635 if (lwa == NULL) {
636 iwmesg = lk->lock_object.lo_name;
637 ipri = lk->lk_pri;
638 itimo = lk->lk_timo;
639 } else {
640 iwmesg = lwa->iwmesg;
641 ipri = lwa->ipri;
642 itimo = lwa->itimo;
643 }
644
645 /*
646 * As far as we have been unable to acquire the
647 * shared lock and the shared waiters flag is set,
648 * we will sleep.
649 */
650 #ifdef KDTRACE_HOOKS
651 sleep_time -= lockstat_nsecs(&lk->lock_object);
652 #endif
653 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
654 SQ_SHARED_QUEUE);
655 #ifdef KDTRACE_HOOKS
656 sleep_time += lockstat_nsecs(&lk->lock_object);
657 #endif
658 flags &= ~LK_INTERLOCK;
659 if (error) {
660 LOCK_LOG3(lk,
661 "%s: interrupted sleep for %p with %d",
662 __func__, lk, error);
663 break;
664 }
665 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
666 __func__, lk);
667 }
668 if (error == 0) {
669 #ifdef KDTRACE_HOOKS
670 if (sleep_time != 0)
671 LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
672 LOCKSTAT_READER, (x & LK_SHARE) == 0,
673 (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
674 #endif
675 #ifdef LOCK_PROFILING
676 lockmgr_note_shared_acquire(lk, contested, waittime,
677 file, line, flags);
678 #else
679 lockmgr_note_shared_acquire(lk, 0, 0, file, line,
680 flags);
681 #endif
682 }
683
684 out:
685 lockmgr_exit(flags, ilk, 0);
686 return (error);
687 }
688
689 static __noinline int
lockmgr_xlock_hard(struct lock * lk,u_int flags,struct lock_object * ilk,const char * file,int line,struct lockmgr_wait * lwa)690 lockmgr_xlock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
691 const char *file, int line, struct lockmgr_wait *lwa)
692 {
693 struct lock_class *class;
694 uintptr_t tid, x, v;
695 int error = 0;
696 const char *iwmesg;
697 int ipri, itimo;
698
699 #ifdef KDTRACE_HOOKS
700 uint64_t sleep_time = 0;
701 #endif
702 #ifdef LOCK_PROFILING
703 uint64_t waittime = 0;
704 int contested = 0;
705 #endif
706
707 if (__predict_false(panicstr != NULL))
708 goto out;
709
710 tid = (uintptr_t)curthread;
711
712 if (LK_CAN_WITNESS(flags))
713 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
714 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
715 ilk : NULL);
716
717 /*
718 * If curthread already holds the lock and this one is
719 * allowed to recurse, simply recurse on it.
720 */
721 if (lockmgr_xlocked(lk)) {
722 if ((flags & LK_CANRECURSE) == 0 &&
723 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
724 /*
725 * If the lock is expected to not panic just
726 * give up and return.
727 */
728 if (LK_TRYOP(flags)) {
729 LOCK_LOG2(lk,
730 "%s: %p fails the try operation",
731 __func__, lk);
732 error = EBUSY;
733 goto out;
734 }
735 if (flags & LK_INTERLOCK) {
736 class = LOCK_CLASS(ilk);
737 class->lc_unlock(ilk);
738 }
739 panic("%s: recursing on non recursive lockmgr %p "
740 "@ %s:%d\n", __func__, lk, file, line);
741 }
742 lk->lk_recurse++;
743 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
744 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
745 lk->lk_recurse, file, line);
746 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
747 LK_TRYWIT(flags), file, line);
748 TD_LOCKS_INC(curthread);
749 goto out;
750 }
751
752 for (;;) {
753 if (lk->lk_lock == LK_UNLOCKED &&
754 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
755 break;
756 #ifdef HWPMC_HOOKS
757 PMC_SOFT_CALL( , , lock, failed);
758 #endif
759 lock_profile_obtain_lock_failed(&lk->lock_object,
760 &contested, &waittime);
761
762 /*
763 * If the lock is expected to not sleep just give up
764 * and return.
765 */
766 if (LK_TRYOP(flags)) {
767 LOCK_LOG2(lk, "%s: %p fails the try operation",
768 __func__, lk);
769 error = EBUSY;
770 break;
771 }
772
773 /*
774 * Acquire the sleepqueue chain lock because we
775 * probabilly will need to manipulate waiters flags.
776 */
777 sleepq_lock(&lk->lock_object);
778 x = lk->lk_lock;
779 retry_sleepq:
780
781 /*
782 * if the lock has been released while we spun on
783 * the sleepqueue chain lock just try again.
784 */
785 if (x == LK_UNLOCKED) {
786 sleepq_release(&lk->lock_object);
787 continue;
788 }
789
790 /*
791 * The lock can be in the state where there is a
792 * pending queue of waiters, but still no owner.
793 * This happens when the lock is contested and an
794 * owner is going to claim the lock.
795 * If curthread is the one successfully acquiring it
796 * claim lock ownership and return, preserving waiters
797 * flags.
798 */
799 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
800 if ((x & ~v) == LK_UNLOCKED) {
801 v &= ~LK_EXCLUSIVE_SPINNERS;
802 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
803 tid | v)) {
804 sleepq_release(&lk->lock_object);
805 LOCK_LOG2(lk,
806 "%s: %p claimed by a new writer",
807 __func__, lk);
808 break;
809 }
810 goto retry_sleepq;
811 }
812
813 /*
814 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
815 * fail, loop back and retry.
816 */
817 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
818 if (!atomic_fcmpset_ptr(&lk->lk_lock, &x,
819 x | LK_EXCLUSIVE_WAITERS)) {
820 goto retry_sleepq;
821 }
822 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
823 __func__, lk);
824 }
825
826 if (lwa == NULL) {
827 iwmesg = lk->lock_object.lo_name;
828 ipri = lk->lk_pri;
829 itimo = lk->lk_timo;
830 } else {
831 iwmesg = lwa->iwmesg;
832 ipri = lwa->ipri;
833 itimo = lwa->itimo;
834 }
835
836 /*
837 * As far as we have been unable to acquire the
838 * exclusive lock and the exclusive waiters flag
839 * is set, we will sleep.
840 */
841 #ifdef KDTRACE_HOOKS
842 sleep_time -= lockstat_nsecs(&lk->lock_object);
843 #endif
844 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
845 SQ_EXCLUSIVE_QUEUE);
846 #ifdef KDTRACE_HOOKS
847 sleep_time += lockstat_nsecs(&lk->lock_object);
848 #endif
849 flags &= ~LK_INTERLOCK;
850 if (error) {
851 LOCK_LOG3(lk,
852 "%s: interrupted sleep for %p with %d",
853 __func__, lk, error);
854 break;
855 }
856 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
857 __func__, lk);
858 }
859 if (error == 0) {
860 #ifdef KDTRACE_HOOKS
861 if (sleep_time != 0)
862 LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
863 LOCKSTAT_WRITER, (x & LK_SHARE) == 0,
864 (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
865 #endif
866 #ifdef LOCK_PROFILING
867 lockmgr_note_exclusive_acquire(lk, contested, waittime,
868 file, line, flags);
869 #else
870 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
871 flags);
872 #endif
873 }
874
875 out:
876 lockmgr_exit(flags, ilk, 0);
877 return (error);
878 }
879
880 static __noinline int
lockmgr_upgrade(struct lock * lk,u_int flags,struct lock_object * ilk,const char * file,int line,struct lockmgr_wait * lwa)881 lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk,
882 const char *file, int line, struct lockmgr_wait *lwa)
883 {
884 uintptr_t tid, x, v;
885 int error = 0;
886 int wakeup_swapper = 0;
887 int op;
888
889 if (__predict_false(panicstr != NULL))
890 goto out;
891
892 tid = (uintptr_t)curthread;
893
894 _lockmgr_assert(lk, KA_SLOCKED, file, line);
895 v = lk->lk_lock;
896 x = v & LK_ALL_WAITERS;
897 v &= LK_EXCLUSIVE_SPINNERS;
898
899 /*
900 * Try to switch from one shared lock to an exclusive one.
901 * We need to preserve waiters flags during the operation.
902 */
903 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
904 tid | x)) {
905 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
906 line);
907 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
908 LK_TRYWIT(flags), file, line);
909 LOCKSTAT_RECORD0(lockmgr__upgrade, lk);
910 TD_SLOCKS_DEC(curthread);
911 goto out;
912 }
913
914 op = flags & LK_TYPE_MASK;
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 goto out;
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 error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa);
933 flags &= ~LK_INTERLOCK;
934 out:
935 lockmgr_exit(flags, ilk, wakeup_swapper);
936 return (error);
937 }
938
939 int
lockmgr_lock_fast_path(struct lock * lk,u_int flags,struct lock_object * ilk,const char * file,int line)940 lockmgr_lock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk,
941 const char *file, int line)
942 {
943 struct lock_class *class;
944 uintptr_t x, tid;
945 u_int op;
946 bool locked;
947
948 if (__predict_false(panicstr != NULL))
949 return (0);
950
951 op = flags & LK_TYPE_MASK;
952 locked = false;
953 switch (op) {
954 case LK_SHARED:
955 if (LK_CAN_WITNESS(flags))
956 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
957 file, line, flags & LK_INTERLOCK ? ilk : NULL);
958 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE))
959 break;
960 if (lockmgr_slock_try(lk, &x, flags, true)) {
961 lockmgr_note_shared_acquire(lk, 0, 0,
962 file, line, flags);
963 locked = true;
964 } else {
965 return (lockmgr_slock_hard(lk, flags, ilk, file, line,
966 NULL));
967 }
968 break;
969 case LK_EXCLUSIVE:
970 if (LK_CAN_WITNESS(flags))
971 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
972 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
973 ilk : NULL);
974 tid = (uintptr_t)curthread;
975 if (lk->lk_lock == LK_UNLOCKED &&
976 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
977 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
978 flags);
979 locked = true;
980 } else {
981 return (lockmgr_xlock_hard(lk, flags, ilk, file, line,
982 NULL));
983 }
984 break;
985 case LK_UPGRADE:
986 case LK_TRYUPGRADE:
987 return (lockmgr_upgrade(lk, flags, ilk, file, line, NULL));
988 default:
989 break;
990 }
991 if (__predict_true(locked)) {
992 if (__predict_false(flags & LK_INTERLOCK)) {
993 class = LOCK_CLASS(ilk);
994 class->lc_unlock(ilk);
995 }
996 return (0);
997 } else {
998 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT,
999 LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line));
1000 }
1001 }
1002
1003 static __noinline int
lockmgr_sunlock_hard(struct lock * lk,uintptr_t x,u_int flags,struct lock_object * ilk,const char * file,int line)1004 lockmgr_sunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
1005 const char *file, int line)
1006
1007 {
1008 int wakeup_swapper = 0;
1009
1010 if (__predict_false(panicstr != NULL))
1011 goto out;
1012
1013 wakeup_swapper = wakeupshlk(lk, file, line);
1014
1015 out:
1016 lockmgr_exit(flags, ilk, wakeup_swapper);
1017 return (0);
1018 }
1019
1020 static __noinline int
lockmgr_xunlock_hard(struct lock * lk,uintptr_t x,u_int flags,struct lock_object * ilk,const char * file,int line)1021 lockmgr_xunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
1022 const char *file, int line)
1023 {
1024 uintptr_t tid, v;
1025 int wakeup_swapper = 0;
1026 u_int realexslp;
1027 int queue;
1028
1029 if (__predict_false(panicstr != NULL))
1030 goto out;
1031
1032 tid = (uintptr_t)curthread;
1033
1034 /*
1035 * As first option, treact the lock as if it has not
1036 * any waiter.
1037 * Fix-up the tid var if the lock has been disowned.
1038 */
1039 if (LK_HOLDER(x) == LK_KERNPROC)
1040 tid = LK_KERNPROC;
1041 else {
1042 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1043 TD_LOCKS_DEC(curthread);
1044 }
1045 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
1046
1047 /*
1048 * The lock is held in exclusive mode.
1049 * If the lock is recursed also, then unrecurse it.
1050 */
1051 if (lockmgr_xlocked_v(x) && lockmgr_recursed(lk)) {
1052 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk);
1053 lk->lk_recurse--;
1054 goto out;
1055 }
1056 if (tid != LK_KERNPROC)
1057 LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk,
1058 LOCKSTAT_WRITER);
1059
1060 if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED))
1061 goto out;
1062
1063 sleepq_lock(&lk->lock_object);
1064 x = lk->lk_lock;
1065 v = LK_UNLOCKED;
1066
1067 /*
1068 * If the lock has exclusive waiters, give them
1069 * preference in order to avoid deadlock with
1070 * shared runners up.
1071 * If interruptible sleeps left the exclusive queue
1072 * empty avoid a starvation for the threads sleeping
1073 * on the shared queue by giving them precedence
1074 * and cleaning up the exclusive waiters bit anyway.
1075 * Please note that lk_exslpfail count may be lying
1076 * about the real number of waiters with the
1077 * LK_SLEEPFAIL flag on because they may be used in
1078 * conjunction with interruptible sleeps so
1079 * lk_exslpfail might be considered an 'upper limit'
1080 * bound, including the edge cases.
1081 */
1082 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1083 realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE);
1084 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
1085 if (lk->lk_exslpfail < realexslp) {
1086 lk->lk_exslpfail = 0;
1087 queue = SQ_EXCLUSIVE_QUEUE;
1088 v |= (x & LK_SHARED_WAITERS);
1089 } else {
1090 lk->lk_exslpfail = 0;
1091 LOCK_LOG2(lk,
1092 "%s: %p has only LK_SLEEPFAIL sleepers",
1093 __func__, lk);
1094 LOCK_LOG2(lk,
1095 "%s: %p waking up threads on the exclusive queue",
1096 __func__, lk);
1097 wakeup_swapper = sleepq_broadcast(&lk->lock_object,
1098 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1099 queue = SQ_SHARED_QUEUE;
1100 }
1101 } else {
1102
1103 /*
1104 * Exclusive waiters sleeping with LK_SLEEPFAIL
1105 * on and using interruptible sleeps/timeout
1106 * may have left spourious lk_exslpfail counts
1107 * on, so clean it up anyway.
1108 */
1109 lk->lk_exslpfail = 0;
1110 queue = SQ_SHARED_QUEUE;
1111 }
1112
1113 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
1114 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
1115 "exclusive");
1116 atomic_store_rel_ptr(&lk->lk_lock, v);
1117 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue);
1118 sleepq_release(&lk->lock_object);
1119
1120 out:
1121 lockmgr_exit(flags, ilk, wakeup_swapper);
1122 return (0);
1123 }
1124
1125 int
lockmgr_unlock_fast_path(struct lock * lk,u_int flags,struct lock_object * ilk)1126 lockmgr_unlock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk)
1127 {
1128 struct lock_class *class;
1129 uintptr_t x, tid;
1130 const char *file;
1131 int line;
1132
1133 if (__predict_false(panicstr != NULL))
1134 return (0);
1135
1136 file = __FILE__;
1137 line = __LINE__;
1138
1139 _lockmgr_assert(lk, KA_LOCKED, file, line);
1140 x = lk->lk_lock;
1141 if (__predict_true(x & LK_SHARE) != 0) {
1142 if (lockmgr_sunlock_try(lk, &x)) {
1143 lockmgr_note_shared_release(lk, file, line);
1144 } else {
1145 return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line));
1146 }
1147 } else {
1148 tid = (uintptr_t)curthread;
1149 if (!lockmgr_recursed(lk) &&
1150 atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) {
1151 lockmgr_note_exclusive_release(lk, file, line);
1152 } else {
1153 return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line));
1154 }
1155 }
1156 if (__predict_false(flags & LK_INTERLOCK)) {
1157 class = LOCK_CLASS(ilk);
1158 class->lc_unlock(ilk);
1159 }
1160 return (0);
1161 }
1162
1163 int
__lockmgr_args(struct lock * lk,u_int flags,struct lock_object * ilk,const char * wmesg,int pri,int timo,const char * file,int line)1164 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
1165 const char *wmesg, int pri, int timo, const char *file, int line)
1166 {
1167 GIANT_DECLARE;
1168 struct lockmgr_wait lwa;
1169 struct lock_class *class;
1170 const char *iwmesg;
1171 uintptr_t tid, v, x;
1172 u_int op, realexslp;
1173 int error, ipri, itimo, queue, wakeup_swapper;
1174 #ifdef LOCK_PROFILING
1175 uint64_t waittime = 0;
1176 int contested = 0;
1177 #endif
1178
1179 if (panicstr != NULL)
1180 return (0);
1181
1182 error = 0;
1183 tid = (uintptr_t)curthread;
1184 op = (flags & LK_TYPE_MASK);
1185 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
1186 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
1187 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
1188
1189 lwa.iwmesg = iwmesg;
1190 lwa.ipri = ipri;
1191 lwa.itimo = itimo;
1192
1193 MPASS((flags & ~LK_TOTAL_MASK) == 0);
1194 KASSERT((op & (op - 1)) == 0,
1195 ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
1196 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
1197 (op != LK_DOWNGRADE && op != LK_RELEASE),
1198 ("%s: Invalid flags in regard of the operation desired @ %s:%d",
1199 __func__, file, line));
1200 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
1201 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
1202 __func__, file, line));
1203 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
1204 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread,
1205 lk->lock_object.lo_name, file, line));
1206
1207 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
1208
1209 if (lk->lock_object.lo_flags & LK_NOSHARE) {
1210 switch (op) {
1211 case LK_SHARED:
1212 op = LK_EXCLUSIVE;
1213 break;
1214 case LK_UPGRADE:
1215 case LK_TRYUPGRADE:
1216 case LK_DOWNGRADE:
1217 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
1218 file, line);
1219 if (flags & LK_INTERLOCK)
1220 class->lc_unlock(ilk);
1221 return (0);
1222 }
1223 }
1224
1225 wakeup_swapper = 0;
1226 switch (op) {
1227 case LK_SHARED:
1228 return (lockmgr_slock_hard(lk, flags, ilk, file, line, &lwa));
1229 break;
1230 case LK_UPGRADE:
1231 case LK_TRYUPGRADE:
1232 return (lockmgr_upgrade(lk, flags, ilk, file, line, &lwa));
1233 break;
1234 case LK_EXCLUSIVE:
1235 return (lockmgr_xlock_hard(lk, flags, ilk, file, line, &lwa));
1236 break;
1237 case LK_DOWNGRADE:
1238 _lockmgr_assert(lk, KA_XLOCKED, file, line);
1239 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
1240
1241 /*
1242 * Panic if the lock is recursed.
1243 */
1244 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
1245 if (flags & LK_INTERLOCK)
1246 class->lc_unlock(ilk);
1247 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n",
1248 __func__, iwmesg, file, line);
1249 }
1250 TD_SLOCKS_INC(curthread);
1251
1252 /*
1253 * In order to preserve waiters flags, just spin.
1254 */
1255 for (;;) {
1256 x = lk->lk_lock;
1257 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1258 x &= LK_ALL_WAITERS;
1259 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1260 LK_SHARERS_LOCK(1) | x))
1261 break;
1262 cpu_spinwait();
1263 }
1264 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
1265 LOCKSTAT_RECORD0(lockmgr__downgrade, lk);
1266 break;
1267 case LK_RELEASE:
1268 _lockmgr_assert(lk, KA_LOCKED, file, line);
1269 x = lk->lk_lock;
1270
1271 if (__predict_true(x & LK_SHARE) != 0) {
1272 return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line));
1273 } else {
1274 return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line));
1275 }
1276 break;
1277 case LK_DRAIN:
1278 if (LK_CAN_WITNESS(flags))
1279 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1280 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
1281 ilk : NULL);
1282
1283 /*
1284 * Trying to drain a lock we already own will result in a
1285 * deadlock.
1286 */
1287 if (lockmgr_xlocked(lk)) {
1288 if (flags & LK_INTERLOCK)
1289 class->lc_unlock(ilk);
1290 panic("%s: draining %s with the lock held @ %s:%d\n",
1291 __func__, iwmesg, file, line);
1292 }
1293
1294 for (;;) {
1295 if (lk->lk_lock == LK_UNLOCKED &&
1296 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
1297 break;
1298
1299 #ifdef HWPMC_HOOKS
1300 PMC_SOFT_CALL( , , lock, failed);
1301 #endif
1302 lock_profile_obtain_lock_failed(&lk->lock_object,
1303 &contested, &waittime);
1304
1305 /*
1306 * If the lock is expected to not sleep just give up
1307 * and return.
1308 */
1309 if (LK_TRYOP(flags)) {
1310 LOCK_LOG2(lk, "%s: %p fails the try operation",
1311 __func__, lk);
1312 error = EBUSY;
1313 break;
1314 }
1315
1316 /*
1317 * Acquire the sleepqueue chain lock because we
1318 * probabilly will need to manipulate waiters flags.
1319 */
1320 sleepq_lock(&lk->lock_object);
1321 x = lk->lk_lock;
1322
1323 /*
1324 * if the lock has been released while we spun on
1325 * the sleepqueue chain lock just try again.
1326 */
1327 if (x == LK_UNLOCKED) {
1328 sleepq_release(&lk->lock_object);
1329 continue;
1330 }
1331
1332 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1333 if ((x & ~v) == LK_UNLOCKED) {
1334 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1335
1336 /*
1337 * If interruptible sleeps left the exclusive
1338 * queue empty avoid a starvation for the
1339 * threads sleeping on the shared queue by
1340 * giving them precedence and cleaning up the
1341 * exclusive waiters bit anyway.
1342 * Please note that lk_exslpfail count may be
1343 * lying about the real number of waiters with
1344 * the LK_SLEEPFAIL flag on because they may
1345 * be used in conjunction with interruptible
1346 * sleeps so lk_exslpfail might be considered
1347 * an 'upper limit' bound, including the edge
1348 * cases.
1349 */
1350 if (v & LK_EXCLUSIVE_WAITERS) {
1351 queue = SQ_EXCLUSIVE_QUEUE;
1352 v &= ~LK_EXCLUSIVE_WAITERS;
1353 } else {
1354
1355 /*
1356 * Exclusive waiters sleeping with
1357 * LK_SLEEPFAIL on and using
1358 * interruptible sleeps/timeout may
1359 * have left spourious lk_exslpfail
1360 * counts on, so clean it up anyway.
1361 */
1362 MPASS(v & LK_SHARED_WAITERS);
1363 lk->lk_exslpfail = 0;
1364 queue = SQ_SHARED_QUEUE;
1365 v &= ~LK_SHARED_WAITERS;
1366 }
1367 if (queue == SQ_EXCLUSIVE_QUEUE) {
1368 realexslp =
1369 sleepq_sleepcnt(&lk->lock_object,
1370 SQ_EXCLUSIVE_QUEUE);
1371 if (lk->lk_exslpfail >= realexslp) {
1372 lk->lk_exslpfail = 0;
1373 queue = SQ_SHARED_QUEUE;
1374 v &= ~LK_SHARED_WAITERS;
1375 if (realexslp != 0) {
1376 LOCK_LOG2(lk,
1377 "%s: %p has only LK_SLEEPFAIL sleepers",
1378 __func__, lk);
1379 LOCK_LOG2(lk,
1380 "%s: %p waking up threads on the exclusive queue",
1381 __func__, lk);
1382 wakeup_swapper =
1383 sleepq_broadcast(
1384 &lk->lock_object,
1385 SLEEPQ_LK, 0,
1386 SQ_EXCLUSIVE_QUEUE);
1387 }
1388 } else
1389 lk->lk_exslpfail = 0;
1390 }
1391 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1392 sleepq_release(&lk->lock_object);
1393 continue;
1394 }
1395 LOCK_LOG3(lk,
1396 "%s: %p waking up all threads on the %s queue",
1397 __func__, lk, queue == SQ_SHARED_QUEUE ?
1398 "shared" : "exclusive");
1399 wakeup_swapper |= sleepq_broadcast(
1400 &lk->lock_object, SLEEPQ_LK, 0, queue);
1401
1402 /*
1403 * If shared waiters have been woken up we need
1404 * to wait for one of them to acquire the lock
1405 * before to set the exclusive waiters in
1406 * order to avoid a deadlock.
1407 */
1408 if (queue == SQ_SHARED_QUEUE) {
1409 for (v = lk->lk_lock;
1410 (v & LK_SHARE) && !LK_SHARERS(v);
1411 v = lk->lk_lock)
1412 cpu_spinwait();
1413 }
1414 }
1415
1416 /*
1417 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
1418 * fail, loop back and retry.
1419 */
1420 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1421 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1422 x | LK_EXCLUSIVE_WAITERS)) {
1423 sleepq_release(&lk->lock_object);
1424 continue;
1425 }
1426 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1427 __func__, lk);
1428 }
1429
1430 /*
1431 * As far as we have been unable to acquire the
1432 * exclusive lock and the exclusive waiters flag
1433 * is set, we will sleep.
1434 */
1435 if (flags & LK_INTERLOCK) {
1436 class->lc_unlock(ilk);
1437 flags &= ~LK_INTERLOCK;
1438 }
1439 GIANT_SAVE();
1440 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1441 SQ_EXCLUSIVE_QUEUE);
1442 sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1443 GIANT_RESTORE();
1444 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1445 __func__, lk);
1446 }
1447
1448 if (error == 0) {
1449 lock_profile_obtain_lock_success(&lk->lock_object,
1450 contested, waittime, file, line);
1451 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1452 lk->lk_recurse, file, line);
1453 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1454 LK_TRYWIT(flags), file, line);
1455 TD_LOCKS_INC(curthread);
1456 STACK_SAVE(lk);
1457 }
1458 break;
1459 default:
1460 if (flags & LK_INTERLOCK)
1461 class->lc_unlock(ilk);
1462 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1463 }
1464
1465 if (flags & LK_INTERLOCK)
1466 class->lc_unlock(ilk);
1467 if (wakeup_swapper)
1468 kick_proc0();
1469
1470 return (error);
1471 }
1472
1473 void
_lockmgr_disown(struct lock * lk,const char * file,int line)1474 _lockmgr_disown(struct lock *lk, const char *file, int line)
1475 {
1476 uintptr_t tid, x;
1477
1478 if (SCHEDULER_STOPPED())
1479 return;
1480
1481 tid = (uintptr_t)curthread;
1482 _lockmgr_assert(lk, KA_XLOCKED, file, line);
1483
1484 /*
1485 * Panic if the lock is recursed.
1486 */
1487 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk))
1488 panic("%s: disown a recursed lockmgr @ %s:%d\n",
1489 __func__, file, line);
1490
1491 /*
1492 * If the owner is already LK_KERNPROC just skip the whole operation.
1493 */
1494 if (LK_HOLDER(lk->lk_lock) != tid)
1495 return;
1496 lock_profile_release_lock(&lk->lock_object);
1497 LOCKSTAT_RECORD1(lockmgr__disown, lk, LOCKSTAT_WRITER);
1498 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1499 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1500 TD_LOCKS_DEC(curthread);
1501 STACK_SAVE(lk);
1502
1503 /*
1504 * In order to preserve waiters flags, just spin.
1505 */
1506 for (;;) {
1507 x = lk->lk_lock;
1508 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1509 x &= LK_ALL_WAITERS;
1510 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1511 LK_KERNPROC | x))
1512 return;
1513 cpu_spinwait();
1514 }
1515 }
1516
1517 void
lockmgr_printinfo(const struct lock * lk)1518 lockmgr_printinfo(const struct lock *lk)
1519 {
1520 struct thread *td;
1521 uintptr_t x;
1522
1523 if (lk->lk_lock == LK_UNLOCKED)
1524 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1525 else if (lk->lk_lock & LK_SHARE)
1526 printf("lock type %s: SHARED (count %ju)\n",
1527 lk->lock_object.lo_name,
1528 (uintmax_t)LK_SHARERS(lk->lk_lock));
1529 else {
1530 td = lockmgr_xholder(lk);
1531 if (td == (struct thread *)LK_KERNPROC)
1532 printf("lock type %s: EXCL by KERNPROC\n",
1533 lk->lock_object.lo_name);
1534 else
1535 printf("lock type %s: EXCL by thread %p "
1536 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name,
1537 td, td->td_proc->p_pid, td->td_proc->p_comm,
1538 td->td_tid);
1539 }
1540
1541 x = lk->lk_lock;
1542 if (x & LK_EXCLUSIVE_WAITERS)
1543 printf(" with exclusive waiters pending\n");
1544 if (x & LK_SHARED_WAITERS)
1545 printf(" with shared waiters pending\n");
1546 if (x & LK_EXCLUSIVE_SPINNERS)
1547 printf(" with exclusive spinners pending\n");
1548
1549 STACK_PRINT(lk);
1550 }
1551
1552 int
lockstatus(const struct lock * lk)1553 lockstatus(const struct lock *lk)
1554 {
1555 uintptr_t v, x;
1556 int ret;
1557
1558 ret = LK_SHARED;
1559 x = lk->lk_lock;
1560 v = LK_HOLDER(x);
1561
1562 if ((x & LK_SHARE) == 0) {
1563 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1564 ret = LK_EXCLUSIVE;
1565 else
1566 ret = LK_EXCLOTHER;
1567 } else if (x == LK_UNLOCKED)
1568 ret = 0;
1569
1570 return (ret);
1571 }
1572
1573 #ifdef INVARIANT_SUPPORT
1574
1575 FEATURE(invariant_support,
1576 "Support for modules compiled with INVARIANTS option");
1577
1578 #ifndef INVARIANTS
1579 #undef _lockmgr_assert
1580 #endif
1581
1582 void
_lockmgr_assert(const struct lock * lk,int what,const char * file,int line)1583 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line)
1584 {
1585 int slocked = 0;
1586
1587 if (panicstr != NULL)
1588 return;
1589 switch (what) {
1590 case KA_SLOCKED:
1591 case KA_SLOCKED | KA_NOTRECURSED:
1592 case KA_SLOCKED | KA_RECURSED:
1593 slocked = 1;
1594 case KA_LOCKED:
1595 case KA_LOCKED | KA_NOTRECURSED:
1596 case KA_LOCKED | KA_RECURSED:
1597 #ifdef WITNESS
1598
1599 /*
1600 * We cannot trust WITNESS if the lock is held in exclusive
1601 * mode and a call to lockmgr_disown() happened.
1602 * Workaround this skipping the check if the lock is held in
1603 * exclusive mode even for the KA_LOCKED case.
1604 */
1605 if (slocked || (lk->lk_lock & LK_SHARE)) {
1606 witness_assert(&lk->lock_object, what, file, line);
1607 break;
1608 }
1609 #endif
1610 if (lk->lk_lock == LK_UNLOCKED ||
1611 ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1612 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1613 panic("Lock %s not %slocked @ %s:%d\n",
1614 lk->lock_object.lo_name, slocked ? "share" : "",
1615 file, line);
1616
1617 if ((lk->lk_lock & LK_SHARE) == 0) {
1618 if (lockmgr_recursed(lk)) {
1619 if (what & KA_NOTRECURSED)
1620 panic("Lock %s recursed @ %s:%d\n",
1621 lk->lock_object.lo_name, file,
1622 line);
1623 } else if (what & KA_RECURSED)
1624 panic("Lock %s not recursed @ %s:%d\n",
1625 lk->lock_object.lo_name, file, line);
1626 }
1627 break;
1628 case KA_XLOCKED:
1629 case KA_XLOCKED | KA_NOTRECURSED:
1630 case KA_XLOCKED | KA_RECURSED:
1631 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1632 panic("Lock %s not exclusively locked @ %s:%d\n",
1633 lk->lock_object.lo_name, file, line);
1634 if (lockmgr_recursed(lk)) {
1635 if (what & KA_NOTRECURSED)
1636 panic("Lock %s recursed @ %s:%d\n",
1637 lk->lock_object.lo_name, file, line);
1638 } else if (what & KA_RECURSED)
1639 panic("Lock %s not recursed @ %s:%d\n",
1640 lk->lock_object.lo_name, file, line);
1641 break;
1642 case KA_UNLOCKED:
1643 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1644 panic("Lock %s exclusively locked @ %s:%d\n",
1645 lk->lock_object.lo_name, file, line);
1646 break;
1647 default:
1648 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1649 line);
1650 }
1651 }
1652 #endif
1653
1654 #ifdef DDB
1655 int
lockmgr_chain(struct thread * td,struct thread ** ownerp)1656 lockmgr_chain(struct thread *td, struct thread **ownerp)
1657 {
1658 struct lock *lk;
1659
1660 lk = td->td_wchan;
1661
1662 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1663 return (0);
1664 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1665 if (lk->lk_lock & LK_SHARE)
1666 db_printf("SHARED (count %ju)\n",
1667 (uintmax_t)LK_SHARERS(lk->lk_lock));
1668 else
1669 db_printf("EXCL\n");
1670 *ownerp = lockmgr_xholder(lk);
1671
1672 return (1);
1673 }
1674
1675 static void
db_show_lockmgr(const struct lock_object * lock)1676 db_show_lockmgr(const struct lock_object *lock)
1677 {
1678 struct thread *td;
1679 const struct lock *lk;
1680
1681 lk = (const struct lock *)lock;
1682
1683 db_printf(" state: ");
1684 if (lk->lk_lock == LK_UNLOCKED)
1685 db_printf("UNLOCKED\n");
1686 else if (lk->lk_lock & LK_SHARE)
1687 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1688 else {
1689 td = lockmgr_xholder(lk);
1690 if (td == (struct thread *)LK_KERNPROC)
1691 db_printf("XLOCK: LK_KERNPROC\n");
1692 else
1693 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1694 td->td_tid, td->td_proc->p_pid,
1695 td->td_proc->p_comm);
1696 if (lockmgr_recursed(lk))
1697 db_printf(" recursed: %d\n", lk->lk_recurse);
1698 }
1699 db_printf(" waiters: ");
1700 switch (lk->lk_lock & LK_ALL_WAITERS) {
1701 case LK_SHARED_WAITERS:
1702 db_printf("shared\n");
1703 break;
1704 case LK_EXCLUSIVE_WAITERS:
1705 db_printf("exclusive\n");
1706 break;
1707 case LK_ALL_WAITERS:
1708 db_printf("shared and exclusive\n");
1709 break;
1710 default:
1711 db_printf("none\n");
1712 }
1713 db_printf(" spinners: ");
1714 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1715 db_printf("exclusive\n");
1716 else
1717 db_printf("none\n");
1718 }
1719 #endif
1720