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 #include "opt_kdtrace.h"
33
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD: stable/9/sys/kern/kern_lock.c 256076 2013-10-06 06:05:11Z kib $");
36
37 #include <sys/param.h>
38 #include <sys/kdb.h>
39 #include <sys/ktr.h>
40 #include <sys/lock.h>
41 #include <sys/lock_profile.h>
42 #include <sys/lockmgr.h>
43 #include <sys/mutex.h>
44 #include <sys/proc.h>
45 #include <sys/sleepqueue.h>
46 #ifdef DEBUG_LOCKS
47 #include <sys/stack.h>
48 #endif
49 #include <sys/sysctl.h>
50 #include <sys/systm.h>
51
52 #include <machine/cpu.h>
53
54 #ifdef DDB
55 #include <ddb/ddb.h>
56 #endif
57
58 #ifdef HWPMC_HOOKS
59 #include <sys/pmckern.h>
60 PMC_SOFT_DECLARE( , , lock, failed);
61 #endif
62
63 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
64 (LK_ADAPTIVE | LK_NOSHARE));
65 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
66 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
67
68 #define SQ_EXCLUSIVE_QUEUE 0
69 #define SQ_SHARED_QUEUE 1
70
71 #ifdef ADAPTIVE_LOCKMGRS
72 #define ALK_RETRIES 10
73 #define ALK_LOOPS 10000
74 #endif
75
76 #ifndef INVARIANTS
77 #define _lockmgr_assert(lk, what, file, line)
78 #define TD_LOCKS_INC(td)
79 #define TD_LOCKS_DEC(td)
80 #else
81 #define TD_LOCKS_INC(td) ((td)->td_locks++)
82 #define TD_LOCKS_DEC(td) ((td)->td_locks--)
83 #endif
84 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++)
85 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--)
86
87 #ifndef DEBUG_LOCKS
88 #define STACK_PRINT(lk)
89 #define STACK_SAVE(lk)
90 #define STACK_ZERO(lk)
91 #else
92 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
93 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack)
94 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack)
95 #endif
96
97 #define LOCK_LOG2(lk, string, arg1, arg2) \
98 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
99 CTR2(KTR_LOCK, (string), (arg1), (arg2))
100 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \
101 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
102 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
103
104 #define GIANT_DECLARE \
105 int _i = 0; \
106 WITNESS_SAVE_DECL(Giant)
107 #define GIANT_RESTORE() do { \
108 if (_i > 0) { \
109 while (_i--) \
110 mtx_lock(&Giant); \
111 WITNESS_RESTORE(&Giant.lock_object, Giant); \
112 } \
113 } while (0)
114 #define GIANT_SAVE() do { \
115 if (mtx_owned(&Giant)) { \
116 WITNESS_SAVE(&Giant.lock_object, Giant); \
117 while (mtx_owned(&Giant)) { \
118 _i++; \
119 mtx_unlock(&Giant); \
120 } \
121 } \
122 } while (0)
123
124 #define LK_CAN_SHARE(x) \
125 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \
126 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \
127 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT)))
128 #define LK_TRYOP(x) \
129 ((x) & LK_NOWAIT)
130
131 #define LK_CAN_WITNESS(x) \
132 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
133 #define LK_TRYWIT(x) \
134 (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
135
136 #define LK_CAN_ADAPT(lk, f) \
137 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \
138 ((f) & LK_SLEEPFAIL) == 0)
139
140 #define lockmgr_disowned(lk) \
141 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
142
143 #define lockmgr_xlocked(lk) \
144 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
145
146 static void assert_lockmgr(struct lock_object *lock, int how);
147 #ifdef DDB
148 static void db_show_lockmgr(struct lock_object *lock);
149 #endif
150 static void lock_lockmgr(struct lock_object *lock, int how);
151 #ifdef KDTRACE_HOOKS
152 static int owner_lockmgr(struct lock_object *lock, struct thread **owner);
153 #endif
154 static int unlock_lockmgr(struct lock_object *lock);
155
156 struct lock_class lock_class_lockmgr = {
157 .lc_name = "lockmgr",
158 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
159 .lc_assert = assert_lockmgr,
160 #ifdef DDB
161 .lc_ddb_show = db_show_lockmgr,
162 #endif
163 .lc_lock = lock_lockmgr,
164 .lc_unlock = unlock_lockmgr,
165 #ifdef KDTRACE_HOOKS
166 .lc_owner = owner_lockmgr,
167 #endif
168 };
169
170 static __inline struct thread *
lockmgr_xholder(struct lock * lk)171 lockmgr_xholder(struct lock *lk)
172 {
173 uintptr_t x;
174
175 x = lk->lk_lock;
176 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
177 }
178
179 /*
180 * It assumes sleepq_lock held and returns with this one unheld.
181 * It also assumes the generic interlock is sane and previously checked.
182 * If LK_INTERLOCK is specified the interlock is not reacquired after the
183 * sleep.
184 */
185 static __inline int
sleeplk(struct lock * lk,u_int flags,struct lock_object * ilk,const char * wmesg,int pri,int timo,int queue)186 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
187 const char *wmesg, int pri, int timo, int queue)
188 {
189 GIANT_DECLARE;
190 struct lock_class *class;
191 int catch, error;
192
193 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
194 catch = pri & PCATCH;
195 pri &= PRIMASK;
196 error = 0;
197
198 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
199 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
200
201 if (flags & LK_INTERLOCK)
202 class->lc_unlock(ilk);
203 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0)
204 lk->lk_exslpfail++;
205 GIANT_SAVE();
206 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
207 SLEEPQ_INTERRUPTIBLE : 0), queue);
208 if ((flags & LK_TIMELOCK) && timo)
209 sleepq_set_timeout(&lk->lock_object, timo);
210
211 /*
212 * Decisional switch for real sleeping.
213 */
214 if ((flags & LK_TIMELOCK) && timo && catch)
215 error = sleepq_timedwait_sig(&lk->lock_object, pri);
216 else if ((flags & LK_TIMELOCK) && timo)
217 error = sleepq_timedwait(&lk->lock_object, pri);
218 else if (catch)
219 error = sleepq_wait_sig(&lk->lock_object, pri);
220 else
221 sleepq_wait(&lk->lock_object, pri);
222 GIANT_RESTORE();
223 if ((flags & LK_SLEEPFAIL) && error == 0)
224 error = ENOLCK;
225
226 return (error);
227 }
228
229 static __inline int
wakeupshlk(struct lock * lk,const char * file,int line)230 wakeupshlk(struct lock *lk, const char *file, int line)
231 {
232 uintptr_t v, x;
233 u_int realexslp;
234 int queue, wakeup_swapper;
235
236 TD_LOCKS_DEC(curthread);
237 TD_SLOCKS_DEC(curthread);
238 WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
239 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
240
241 wakeup_swapper = 0;
242 for (;;) {
243 x = lk->lk_lock;
244
245 /*
246 * If there is more than one shared lock held, just drop one
247 * and return.
248 */
249 if (LK_SHARERS(x) > 1) {
250 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x,
251 x - LK_ONE_SHARER))
252 break;
253 continue;
254 }
255
256 /*
257 * If there are not waiters on the exclusive queue, drop the
258 * lock quickly.
259 */
260 if ((x & LK_ALL_WAITERS) == 0) {
261 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) ==
262 LK_SHARERS_LOCK(1));
263 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED))
264 break;
265 continue;
266 }
267
268 /*
269 * We should have a sharer with waiters, so enter the hard
270 * path in order to handle wakeups correctly.
271 */
272 sleepq_lock(&lk->lock_object);
273 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
274 v = LK_UNLOCKED;
275
276 /*
277 * If the lock has exclusive waiters, give them preference in
278 * order to avoid deadlock with shared runners up.
279 * If interruptible sleeps left the exclusive queue empty
280 * avoid a starvation for the threads sleeping on the shared
281 * queue by giving them precedence and cleaning up the
282 * exclusive waiters bit anyway.
283 * Please note that lk_exslpfail count may be lying about
284 * the real number of waiters with the LK_SLEEPFAIL flag on
285 * because they may be used in conjuction with interruptible
286 * sleeps so lk_exslpfail might be considered an 'upper limit'
287 * bound, including the edge cases.
288 */
289 realexslp = sleepq_sleepcnt(&lk->lock_object,
290 SQ_EXCLUSIVE_QUEUE);
291 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
292 if (lk->lk_exslpfail < realexslp) {
293 lk->lk_exslpfail = 0;
294 queue = SQ_EXCLUSIVE_QUEUE;
295 v |= (x & LK_SHARED_WAITERS);
296 } else {
297 lk->lk_exslpfail = 0;
298 LOCK_LOG2(lk,
299 "%s: %p has only LK_SLEEPFAIL sleepers",
300 __func__, lk);
301 LOCK_LOG2(lk,
302 "%s: %p waking up threads on the exclusive queue",
303 __func__, lk);
304 wakeup_swapper =
305 sleepq_broadcast(&lk->lock_object,
306 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
307 queue = SQ_SHARED_QUEUE;
308 }
309
310 } else {
311
312 /*
313 * Exclusive waiters sleeping with LK_SLEEPFAIL on
314 * and using interruptible sleeps/timeout may have
315 * left spourious lk_exslpfail counts on, so clean
316 * it up anyway.
317 */
318 lk->lk_exslpfail = 0;
319 queue = SQ_SHARED_QUEUE;
320 }
321
322 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x,
323 v)) {
324 sleepq_release(&lk->lock_object);
325 continue;
326 }
327 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
328 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
329 "exclusive");
330 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
331 0, queue);
332 sleepq_release(&lk->lock_object);
333 break;
334 }
335
336 lock_profile_release_lock(&lk->lock_object);
337 return (wakeup_swapper);
338 }
339
340 static void
assert_lockmgr(struct lock_object * lock,int what)341 assert_lockmgr(struct lock_object *lock, int what)
342 {
343
344 panic("lockmgr locks do not support assertions");
345 }
346
347 static void
lock_lockmgr(struct lock_object * lock,int how)348 lock_lockmgr(struct lock_object *lock, int how)
349 {
350
351 panic("lockmgr locks do not support sleep interlocking");
352 }
353
354 static int
unlock_lockmgr(struct lock_object * lock)355 unlock_lockmgr(struct lock_object *lock)
356 {
357
358 panic("lockmgr locks do not support sleep interlocking");
359 }
360
361 #ifdef KDTRACE_HOOKS
362 static int
owner_lockmgr(struct lock_object * lock,struct thread ** owner)363 owner_lockmgr(struct lock_object *lock, struct thread **owner)
364 {
365
366 panic("lockmgr locks do not support owner inquiring");
367 }
368 #endif
369
370 void
lockinit(struct lock * lk,int pri,const char * wmesg,int timo,int flags)371 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
372 {
373 int iflags;
374
375 MPASS((flags & ~LK_INIT_MASK) == 0);
376 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
377 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
378 &lk->lk_lock));
379
380 iflags = LO_SLEEPABLE | LO_UPGRADABLE;
381 if (flags & LK_CANRECURSE)
382 iflags |= LO_RECURSABLE;
383 if ((flags & LK_NODUP) == 0)
384 iflags |= LO_DUPOK;
385 if (flags & LK_NOPROFILE)
386 iflags |= LO_NOPROFILE;
387 if ((flags & LK_NOWITNESS) == 0)
388 iflags |= LO_WITNESS;
389 if (flags & LK_QUIET)
390 iflags |= LO_QUIET;
391 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
392
393 lk->lk_lock = LK_UNLOCKED;
394 lk->lk_recurse = 0;
395 lk->lk_exslpfail = 0;
396 lk->lk_timo = timo;
397 lk->lk_pri = pri;
398 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
399 STACK_ZERO(lk);
400 }
401
402 /*
403 * XXX: Gross hacks to manipulate external lock flags after
404 * initialization. Used for certain vnode and buf locks.
405 */
406 void
lockallowshare(struct lock * lk)407 lockallowshare(struct lock *lk)
408 {
409
410 lockmgr_assert(lk, KA_XLOCKED);
411 lk->lock_object.lo_flags &= ~LK_NOSHARE;
412 }
413
414 void
lockallowrecurse(struct lock * lk)415 lockallowrecurse(struct lock *lk)
416 {
417
418 lockmgr_assert(lk, KA_XLOCKED);
419 lk->lock_object.lo_flags |= LO_RECURSABLE;
420 }
421
422 void
lockdisablerecurse(struct lock * lk)423 lockdisablerecurse(struct lock *lk)
424 {
425
426 lockmgr_assert(lk, KA_XLOCKED);
427 lk->lock_object.lo_flags &= ~LO_RECURSABLE;
428 }
429
430 void
lockdestroy(struct lock * lk)431 lockdestroy(struct lock *lk)
432 {
433
434 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
435 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
436 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
437 lock_destroy(&lk->lock_object);
438 }
439
440 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)441 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
442 const char *wmesg, int pri, int timo, const char *file, int line)
443 {
444 GIANT_DECLARE;
445 struct lock_class *class;
446 const char *iwmesg;
447 uintptr_t tid, v, x;
448 u_int op, realexslp;
449 int error, ipri, itimo, queue, wakeup_swapper;
450 #ifdef LOCK_PROFILING
451 uint64_t waittime = 0;
452 int contested = 0;
453 #endif
454 #ifdef ADAPTIVE_LOCKMGRS
455 volatile struct thread *owner;
456 u_int i, spintries = 0;
457 #endif
458
459 error = 0;
460 tid = (uintptr_t)curthread;
461 op = (flags & LK_TYPE_MASK);
462 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
463 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
464 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
465
466 MPASS((flags & ~LK_TOTAL_MASK) == 0);
467 KASSERT((op & (op - 1)) == 0,
468 ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
469 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
470 (op != LK_DOWNGRADE && op != LK_RELEASE),
471 ("%s: Invalid flags in regard of the operation desired @ %s:%d",
472 __func__, file, line));
473 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
474 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
475 __func__, file, line));
476 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
477 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread,
478 lk->lock_object.lo_name, file, line));
479
480 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
481 if (panicstr != NULL) {
482 if (flags & LK_INTERLOCK)
483 class->lc_unlock(ilk);
484 return (0);
485 }
486
487 if (lk->lock_object.lo_flags & LK_NOSHARE) {
488 switch (op) {
489 case LK_SHARED:
490 op = LK_EXCLUSIVE;
491 break;
492 case LK_UPGRADE:
493 case LK_TRYUPGRADE:
494 case LK_DOWNGRADE:
495 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
496 file, line);
497 if (flags & LK_INTERLOCK)
498 class->lc_unlock(ilk);
499 return (0);
500 }
501 }
502
503 wakeup_swapper = 0;
504 switch (op) {
505 case LK_SHARED:
506 if (LK_CAN_WITNESS(flags))
507 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
508 file, line, ilk);
509 for (;;) {
510 x = lk->lk_lock;
511
512 /*
513 * If no other thread has an exclusive lock, or
514 * no exclusive waiter is present, bump the count of
515 * sharers. Since we have to preserve the state of
516 * waiters, if we fail to acquire the shared lock
517 * loop back and retry.
518 */
519 if (LK_CAN_SHARE(x)) {
520 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
521 x + LK_ONE_SHARER))
522 break;
523 continue;
524 }
525 #ifdef HWPMC_HOOKS
526 PMC_SOFT_CALL( , , lock, failed);
527 #endif
528 lock_profile_obtain_lock_failed(&lk->lock_object,
529 &contested, &waittime);
530
531 /*
532 * If the lock is already held by curthread in
533 * exclusive way avoid a deadlock.
534 */
535 if (LK_HOLDER(x) == tid) {
536 LOCK_LOG2(lk,
537 "%s: %p already held in exclusive mode",
538 __func__, lk);
539 error = EDEADLK;
540 break;
541 }
542
543 /*
544 * If the lock is expected to not sleep just give up
545 * and return.
546 */
547 if (LK_TRYOP(flags)) {
548 LOCK_LOG2(lk, "%s: %p fails the try operation",
549 __func__, lk);
550 error = EBUSY;
551 break;
552 }
553
554 #ifdef ADAPTIVE_LOCKMGRS
555 /*
556 * If the owner is running on another CPU, spin until
557 * the owner stops running or the state of the lock
558 * changes. We need a double-state handle here
559 * because for a failed acquisition the lock can be
560 * either held in exclusive mode or shared mode
561 * (for the writer starvation avoidance technique).
562 */
563 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
564 LK_HOLDER(x) != LK_KERNPROC) {
565 owner = (struct thread *)LK_HOLDER(x);
566 if (LOCK_LOG_TEST(&lk->lock_object, 0))
567 CTR3(KTR_LOCK,
568 "%s: spinning on %p held by %p",
569 __func__, lk, owner);
570
571 /*
572 * If we are holding also an interlock drop it
573 * in order to avoid a deadlock if the lockmgr
574 * owner is adaptively spinning on the
575 * interlock itself.
576 */
577 if (flags & LK_INTERLOCK) {
578 class->lc_unlock(ilk);
579 flags &= ~LK_INTERLOCK;
580 }
581 GIANT_SAVE();
582 while (LK_HOLDER(lk->lk_lock) ==
583 (uintptr_t)owner && TD_IS_RUNNING(owner))
584 cpu_spinwait();
585 GIANT_RESTORE();
586 continue;
587 } else if (LK_CAN_ADAPT(lk, flags) &&
588 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
589 spintries < ALK_RETRIES) {
590 if (flags & LK_INTERLOCK) {
591 class->lc_unlock(ilk);
592 flags &= ~LK_INTERLOCK;
593 }
594 GIANT_SAVE();
595 spintries++;
596 for (i = 0; i < ALK_LOOPS; i++) {
597 if (LOCK_LOG_TEST(&lk->lock_object, 0))
598 CTR4(KTR_LOCK,
599 "%s: shared spinning on %p with %u and %u",
600 __func__, lk, spintries, i);
601 x = lk->lk_lock;
602 if ((x & LK_SHARE) == 0 ||
603 LK_CAN_SHARE(x) != 0)
604 break;
605 cpu_spinwait();
606 }
607 GIANT_RESTORE();
608 if (i != ALK_LOOPS)
609 continue;
610 }
611 #endif
612
613 /*
614 * Acquire the sleepqueue chain lock because we
615 * probabilly will need to manipulate waiters flags.
616 */
617 sleepq_lock(&lk->lock_object);
618 x = lk->lk_lock;
619
620 /*
621 * if the lock can be acquired in shared mode, try
622 * again.
623 */
624 if (LK_CAN_SHARE(x)) {
625 sleepq_release(&lk->lock_object);
626 continue;
627 }
628
629 #ifdef ADAPTIVE_LOCKMGRS
630 /*
631 * The current lock owner might have started executing
632 * on another CPU (or the lock could have changed
633 * owner) while we were waiting on the turnstile
634 * chain lock. If so, drop the turnstile lock and try
635 * again.
636 */
637 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
638 LK_HOLDER(x) != LK_KERNPROC) {
639 owner = (struct thread *)LK_HOLDER(x);
640 if (TD_IS_RUNNING(owner)) {
641 sleepq_release(&lk->lock_object);
642 continue;
643 }
644 }
645 #endif
646
647 /*
648 * Try to set the LK_SHARED_WAITERS flag. If we fail,
649 * loop back and retry.
650 */
651 if ((x & LK_SHARED_WAITERS) == 0) {
652 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x,
653 x | LK_SHARED_WAITERS)) {
654 sleepq_release(&lk->lock_object);
655 continue;
656 }
657 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
658 __func__, lk);
659 }
660
661 /*
662 * As far as we have been unable to acquire the
663 * shared lock and the shared waiters flag is set,
664 * we will sleep.
665 */
666 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
667 SQ_SHARED_QUEUE);
668 flags &= ~LK_INTERLOCK;
669 if (error) {
670 LOCK_LOG3(lk,
671 "%s: interrupted sleep for %p with %d",
672 __func__, lk, error);
673 break;
674 }
675 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
676 __func__, lk);
677 }
678 if (error == 0) {
679 lock_profile_obtain_lock_success(&lk->lock_object,
680 contested, waittime, file, line);
681 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file,
682 line);
683 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file,
684 line);
685 TD_LOCKS_INC(curthread);
686 TD_SLOCKS_INC(curthread);
687 STACK_SAVE(lk);
688 }
689 break;
690 case LK_UPGRADE:
691 case LK_TRYUPGRADE:
692 _lockmgr_assert(lk, KA_SLOCKED, file, line);
693 v = lk->lk_lock;
694 x = v & LK_ALL_WAITERS;
695 v &= LK_EXCLUSIVE_SPINNERS;
696
697 /*
698 * Try to switch from one shared lock to an exclusive one.
699 * We need to preserve waiters flags during the operation.
700 */
701 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
702 tid | x)) {
703 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
704 line);
705 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
706 LK_TRYWIT(flags), file, line);
707 TD_SLOCKS_DEC(curthread);
708 break;
709 }
710
711 /*
712 * In LK_TRYUPGRADE mode, do not drop the lock,
713 * returning EBUSY instead.
714 */
715 if (op == LK_TRYUPGRADE) {
716 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
717 __func__, lk);
718 error = EBUSY;
719 break;
720 }
721
722 /*
723 * We have been unable to succeed in upgrading, so just
724 * give up the shared lock.
725 */
726 wakeup_swapper |= wakeupshlk(lk, file, line);
727
728 /* FALLTHROUGH */
729 case LK_EXCLUSIVE:
730 if (LK_CAN_WITNESS(flags))
731 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
732 LOP_EXCLUSIVE, file, line, ilk);
733
734 /*
735 * If curthread already holds the lock and this one is
736 * allowed to recurse, simply recurse on it.
737 */
738 if (lockmgr_xlocked(lk)) {
739 if ((flags & LK_CANRECURSE) == 0 &&
740 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
741
742 /*
743 * If the lock is expected to not panic just
744 * give up and return.
745 */
746 if (LK_TRYOP(flags)) {
747 LOCK_LOG2(lk,
748 "%s: %p fails the try operation",
749 __func__, lk);
750 error = EBUSY;
751 break;
752 }
753 if (flags & LK_INTERLOCK)
754 class->lc_unlock(ilk);
755 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n",
756 __func__, iwmesg, file, line);
757 }
758 lk->lk_recurse++;
759 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
760 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
761 lk->lk_recurse, file, line);
762 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
763 LK_TRYWIT(flags), file, line);
764 TD_LOCKS_INC(curthread);
765 break;
766 }
767
768 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED,
769 tid)) {
770 #ifdef HWPMC_HOOKS
771 PMC_SOFT_CALL( , , lock, failed);
772 #endif
773 lock_profile_obtain_lock_failed(&lk->lock_object,
774 &contested, &waittime);
775
776 /*
777 * If the lock is expected to not sleep just give up
778 * and return.
779 */
780 if (LK_TRYOP(flags)) {
781 LOCK_LOG2(lk, "%s: %p fails the try operation",
782 __func__, lk);
783 error = EBUSY;
784 break;
785 }
786
787 #ifdef ADAPTIVE_LOCKMGRS
788 /*
789 * If the owner is running on another CPU, spin until
790 * the owner stops running or the state of the lock
791 * changes.
792 */
793 x = lk->lk_lock;
794 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
795 LK_HOLDER(x) != LK_KERNPROC) {
796 owner = (struct thread *)LK_HOLDER(x);
797 if (LOCK_LOG_TEST(&lk->lock_object, 0))
798 CTR3(KTR_LOCK,
799 "%s: spinning on %p held by %p",
800 __func__, lk, owner);
801
802 /*
803 * If we are holding also an interlock drop it
804 * in order to avoid a deadlock if the lockmgr
805 * owner is adaptively spinning on the
806 * interlock itself.
807 */
808 if (flags & LK_INTERLOCK) {
809 class->lc_unlock(ilk);
810 flags &= ~LK_INTERLOCK;
811 }
812 GIANT_SAVE();
813 while (LK_HOLDER(lk->lk_lock) ==
814 (uintptr_t)owner && TD_IS_RUNNING(owner))
815 cpu_spinwait();
816 GIANT_RESTORE();
817 continue;
818 } else if (LK_CAN_ADAPT(lk, flags) &&
819 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
820 spintries < ALK_RETRIES) {
821 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 &&
822 !atomic_cmpset_ptr(&lk->lk_lock, x,
823 x | LK_EXCLUSIVE_SPINNERS))
824 continue;
825 if (flags & LK_INTERLOCK) {
826 class->lc_unlock(ilk);
827 flags &= ~LK_INTERLOCK;
828 }
829 GIANT_SAVE();
830 spintries++;
831 for (i = 0; i < ALK_LOOPS; i++) {
832 if (LOCK_LOG_TEST(&lk->lock_object, 0))
833 CTR4(KTR_LOCK,
834 "%s: shared spinning on %p with %u and %u",
835 __func__, lk, spintries, i);
836 if ((lk->lk_lock &
837 LK_EXCLUSIVE_SPINNERS) == 0)
838 break;
839 cpu_spinwait();
840 }
841 GIANT_RESTORE();
842 if (i != ALK_LOOPS)
843 continue;
844 }
845 #endif
846
847 /*
848 * Acquire the sleepqueue chain lock because we
849 * probabilly will need to manipulate waiters flags.
850 */
851 sleepq_lock(&lk->lock_object);
852 x = lk->lk_lock;
853
854 /*
855 * if the lock has been released while we spun on
856 * the sleepqueue chain lock just try again.
857 */
858 if (x == LK_UNLOCKED) {
859 sleepq_release(&lk->lock_object);
860 continue;
861 }
862
863 #ifdef ADAPTIVE_LOCKMGRS
864 /*
865 * The current lock owner might have started executing
866 * on another CPU (or the lock could have changed
867 * owner) while we were waiting on the turnstile
868 * chain lock. If so, drop the turnstile lock and try
869 * again.
870 */
871 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
872 LK_HOLDER(x) != LK_KERNPROC) {
873 owner = (struct thread *)LK_HOLDER(x);
874 if (TD_IS_RUNNING(owner)) {
875 sleepq_release(&lk->lock_object);
876 continue;
877 }
878 }
879 #endif
880
881 /*
882 * The lock can be in the state where there is a
883 * pending queue of waiters, but still no owner.
884 * This happens when the lock is contested and an
885 * owner is going to claim the lock.
886 * If curthread is the one successfully acquiring it
887 * claim lock ownership and return, preserving waiters
888 * flags.
889 */
890 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
891 if ((x & ~v) == LK_UNLOCKED) {
892 v &= ~LK_EXCLUSIVE_SPINNERS;
893 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
894 tid | v)) {
895 sleepq_release(&lk->lock_object);
896 LOCK_LOG2(lk,
897 "%s: %p claimed by a new writer",
898 __func__, lk);
899 break;
900 }
901 sleepq_release(&lk->lock_object);
902 continue;
903 }
904
905 /*
906 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
907 * fail, loop back and retry.
908 */
909 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
910 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
911 x | LK_EXCLUSIVE_WAITERS)) {
912 sleepq_release(&lk->lock_object);
913 continue;
914 }
915 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
916 __func__, lk);
917 }
918
919 /*
920 * As far as we have been unable to acquire the
921 * exclusive lock and the exclusive waiters flag
922 * is set, we will sleep.
923 */
924 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
925 SQ_EXCLUSIVE_QUEUE);
926 flags &= ~LK_INTERLOCK;
927 if (error) {
928 LOCK_LOG3(lk,
929 "%s: interrupted sleep for %p with %d",
930 __func__, lk, error);
931 break;
932 }
933 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
934 __func__, lk);
935 }
936 if (error == 0) {
937 lock_profile_obtain_lock_success(&lk->lock_object,
938 contested, waittime, file, line);
939 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
940 lk->lk_recurse, file, line);
941 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
942 LK_TRYWIT(flags), file, line);
943 TD_LOCKS_INC(curthread);
944 STACK_SAVE(lk);
945 }
946 break;
947 case LK_DOWNGRADE:
948 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
949 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
950 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
951 TD_SLOCKS_INC(curthread);
952
953 /*
954 * In order to preserve waiters flags, just spin.
955 */
956 for (;;) {
957 x = lk->lk_lock;
958 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
959 x &= LK_ALL_WAITERS;
960 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
961 LK_SHARERS_LOCK(1) | x))
962 break;
963 cpu_spinwait();
964 }
965 break;
966 case LK_RELEASE:
967 _lockmgr_assert(lk, KA_LOCKED, file, line);
968 x = lk->lk_lock;
969
970 if ((x & LK_SHARE) == 0) {
971
972 /*
973 * As first option, treact the lock as if it has not
974 * any waiter.
975 * Fix-up the tid var if the lock has been disowned.
976 */
977 if (LK_HOLDER(x) == LK_KERNPROC)
978 tid = LK_KERNPROC;
979 else {
980 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE,
981 file, line);
982 TD_LOCKS_DEC(curthread);
983 }
984 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0,
985 lk->lk_recurse, file, line);
986
987 /*
988 * The lock is held in exclusive mode.
989 * If the lock is recursed also, then unrecurse it.
990 */
991 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
992 LOCK_LOG2(lk, "%s: %p unrecursing", __func__,
993 lk);
994 lk->lk_recurse--;
995 break;
996 }
997 if (tid != LK_KERNPROC)
998 lock_profile_release_lock(&lk->lock_object);
999
1000 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid,
1001 LK_UNLOCKED))
1002 break;
1003
1004 sleepq_lock(&lk->lock_object);
1005 x = lk->lk_lock;
1006 v = LK_UNLOCKED;
1007
1008 /*
1009 * If the lock has exclusive waiters, give them
1010 * preference in order to avoid deadlock with
1011 * shared runners up.
1012 * If interruptible sleeps left the exclusive queue
1013 * empty avoid a starvation for the threads sleeping
1014 * on the shared queue by giving them precedence
1015 * and cleaning up the exclusive waiters bit anyway.
1016 * Please note that lk_exslpfail count may be lying
1017 * about the real number of waiters with the
1018 * LK_SLEEPFAIL flag on because they may be used in
1019 * conjuction with interruptible sleeps so
1020 * lk_exslpfail might be considered an 'upper limit'
1021 * bound, including the edge cases.
1022 */
1023 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1024 realexslp = sleepq_sleepcnt(&lk->lock_object,
1025 SQ_EXCLUSIVE_QUEUE);
1026 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
1027 if (lk->lk_exslpfail < realexslp) {
1028 lk->lk_exslpfail = 0;
1029 queue = SQ_EXCLUSIVE_QUEUE;
1030 v |= (x & LK_SHARED_WAITERS);
1031 } else {
1032 lk->lk_exslpfail = 0;
1033 LOCK_LOG2(lk,
1034 "%s: %p has only LK_SLEEPFAIL sleepers",
1035 __func__, lk);
1036 LOCK_LOG2(lk,
1037 "%s: %p waking up threads on the exclusive queue",
1038 __func__, lk);
1039 wakeup_swapper =
1040 sleepq_broadcast(&lk->lock_object,
1041 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1042 queue = SQ_SHARED_QUEUE;
1043 }
1044 } else {
1045
1046 /*
1047 * Exclusive waiters sleeping with LK_SLEEPFAIL
1048 * on and using interruptible sleeps/timeout
1049 * may have left spourious lk_exslpfail counts
1050 * on, so clean it up anyway.
1051 */
1052 lk->lk_exslpfail = 0;
1053 queue = SQ_SHARED_QUEUE;
1054 }
1055
1056 LOCK_LOG3(lk,
1057 "%s: %p waking up threads on the %s queue",
1058 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
1059 "exclusive");
1060 atomic_store_rel_ptr(&lk->lk_lock, v);
1061 wakeup_swapper |= sleepq_broadcast(&lk->lock_object,
1062 SLEEPQ_LK, 0, queue);
1063 sleepq_release(&lk->lock_object);
1064 break;
1065 } else
1066 wakeup_swapper = wakeupshlk(lk, file, line);
1067 break;
1068 case LK_DRAIN:
1069 if (LK_CAN_WITNESS(flags))
1070 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1071 LOP_EXCLUSIVE, file, line, ilk);
1072
1073 /*
1074 * Trying to drain a lock we already own will result in a
1075 * deadlock.
1076 */
1077 if (lockmgr_xlocked(lk)) {
1078 if (flags & LK_INTERLOCK)
1079 class->lc_unlock(ilk);
1080 panic("%s: draining %s with the lock held @ %s:%d\n",
1081 __func__, iwmesg, file, line);
1082 }
1083
1084 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
1085 #ifdef HWPMC_HOOKS
1086 PMC_SOFT_CALL( , , lock, failed);
1087 #endif
1088 lock_profile_obtain_lock_failed(&lk->lock_object,
1089 &contested, &waittime);
1090
1091 /*
1092 * If the lock is expected to not sleep just give up
1093 * and return.
1094 */
1095 if (LK_TRYOP(flags)) {
1096 LOCK_LOG2(lk, "%s: %p fails the try operation",
1097 __func__, lk);
1098 error = EBUSY;
1099 break;
1100 }
1101
1102 /*
1103 * Acquire the sleepqueue chain lock because we
1104 * probabilly will need to manipulate waiters flags.
1105 */
1106 sleepq_lock(&lk->lock_object);
1107 x = lk->lk_lock;
1108
1109 /*
1110 * if the lock has been released while we spun on
1111 * the sleepqueue chain lock just try again.
1112 */
1113 if (x == LK_UNLOCKED) {
1114 sleepq_release(&lk->lock_object);
1115 continue;
1116 }
1117
1118 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1119 if ((x & ~v) == LK_UNLOCKED) {
1120 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1121
1122 /*
1123 * If interruptible sleeps left the exclusive
1124 * queue empty avoid a starvation for the
1125 * threads sleeping on the shared queue by
1126 * giving them precedence and cleaning up the
1127 * exclusive waiters bit anyway.
1128 * Please note that lk_exslpfail count may be
1129 * lying about the real number of waiters with
1130 * the LK_SLEEPFAIL flag on because they may
1131 * be used in conjuction with interruptible
1132 * sleeps so lk_exslpfail might be considered
1133 * an 'upper limit' bound, including the edge
1134 * cases.
1135 */
1136 if (v & LK_EXCLUSIVE_WAITERS) {
1137 queue = SQ_EXCLUSIVE_QUEUE;
1138 v &= ~LK_EXCLUSIVE_WAITERS;
1139 } else {
1140
1141 /*
1142 * Exclusive waiters sleeping with
1143 * LK_SLEEPFAIL on and using
1144 * interruptible sleeps/timeout may
1145 * have left spourious lk_exslpfail
1146 * counts on, so clean it up anyway.
1147 */
1148 MPASS(v & LK_SHARED_WAITERS);
1149 lk->lk_exslpfail = 0;
1150 queue = SQ_SHARED_QUEUE;
1151 v &= ~LK_SHARED_WAITERS;
1152 }
1153 if (queue == SQ_EXCLUSIVE_QUEUE) {
1154 realexslp =
1155 sleepq_sleepcnt(&lk->lock_object,
1156 SQ_EXCLUSIVE_QUEUE);
1157 if (lk->lk_exslpfail >= realexslp) {
1158 lk->lk_exslpfail = 0;
1159 queue = SQ_SHARED_QUEUE;
1160 v &= ~LK_SHARED_WAITERS;
1161 if (realexslp != 0) {
1162 LOCK_LOG2(lk,
1163 "%s: %p has only LK_SLEEPFAIL sleepers",
1164 __func__, lk);
1165 LOCK_LOG2(lk,
1166 "%s: %p waking up threads on the exclusive queue",
1167 __func__, lk);
1168 wakeup_swapper =
1169 sleepq_broadcast(
1170 &lk->lock_object,
1171 SLEEPQ_LK, 0,
1172 SQ_EXCLUSIVE_QUEUE);
1173 }
1174 } else
1175 lk->lk_exslpfail = 0;
1176 }
1177 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1178 sleepq_release(&lk->lock_object);
1179 continue;
1180 }
1181 LOCK_LOG3(lk,
1182 "%s: %p waking up all threads on the %s queue",
1183 __func__, lk, queue == SQ_SHARED_QUEUE ?
1184 "shared" : "exclusive");
1185 wakeup_swapper |= sleepq_broadcast(
1186 &lk->lock_object, SLEEPQ_LK, 0, queue);
1187
1188 /*
1189 * If shared waiters have been woken up we need
1190 * to wait for one of them to acquire the lock
1191 * before to set the exclusive waiters in
1192 * order to avoid a deadlock.
1193 */
1194 if (queue == SQ_SHARED_QUEUE) {
1195 for (v = lk->lk_lock;
1196 (v & LK_SHARE) && !LK_SHARERS(v);
1197 v = lk->lk_lock)
1198 cpu_spinwait();
1199 }
1200 }
1201
1202 /*
1203 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
1204 * fail, loop back and retry.
1205 */
1206 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1207 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1208 x | LK_EXCLUSIVE_WAITERS)) {
1209 sleepq_release(&lk->lock_object);
1210 continue;
1211 }
1212 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1213 __func__, lk);
1214 }
1215
1216 /*
1217 * As far as we have been unable to acquire the
1218 * exclusive lock and the exclusive waiters flag
1219 * is set, we will sleep.
1220 */
1221 if (flags & LK_INTERLOCK) {
1222 class->lc_unlock(ilk);
1223 flags &= ~LK_INTERLOCK;
1224 }
1225 GIANT_SAVE();
1226 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1227 SQ_EXCLUSIVE_QUEUE);
1228 sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1229 GIANT_RESTORE();
1230 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1231 __func__, lk);
1232 }
1233
1234 if (error == 0) {
1235 lock_profile_obtain_lock_success(&lk->lock_object,
1236 contested, waittime, file, line);
1237 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1238 lk->lk_recurse, file, line);
1239 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1240 LK_TRYWIT(flags), file, line);
1241 TD_LOCKS_INC(curthread);
1242 STACK_SAVE(lk);
1243 }
1244 break;
1245 default:
1246 if (flags & LK_INTERLOCK)
1247 class->lc_unlock(ilk);
1248 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1249 }
1250
1251 if (flags & LK_INTERLOCK)
1252 class->lc_unlock(ilk);
1253 if (wakeup_swapper)
1254 kick_proc0();
1255
1256 return (error);
1257 }
1258
1259 void
_lockmgr_disown(struct lock * lk,const char * file,int line)1260 _lockmgr_disown(struct lock *lk, const char *file, int line)
1261 {
1262 uintptr_t tid, x;
1263
1264 if (SCHEDULER_STOPPED())
1265 return;
1266
1267 tid = (uintptr_t)curthread;
1268 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
1269
1270 /*
1271 * If the owner is already LK_KERNPROC just skip the whole operation.
1272 */
1273 if (LK_HOLDER(lk->lk_lock) != tid)
1274 return;
1275 lock_profile_release_lock(&lk->lock_object);
1276 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1277 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1278 TD_LOCKS_DEC(curthread);
1279 STACK_SAVE(lk);
1280
1281 /*
1282 * In order to preserve waiters flags, just spin.
1283 */
1284 for (;;) {
1285 x = lk->lk_lock;
1286 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1287 x &= LK_ALL_WAITERS;
1288 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1289 LK_KERNPROC | x))
1290 return;
1291 cpu_spinwait();
1292 }
1293 }
1294
1295 void
lockmgr_printinfo(struct lock * lk)1296 lockmgr_printinfo(struct lock *lk)
1297 {
1298 struct thread *td;
1299 uintptr_t x;
1300
1301 if (lk->lk_lock == LK_UNLOCKED)
1302 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1303 else if (lk->lk_lock & LK_SHARE)
1304 printf("lock type %s: SHARED (count %ju)\n",
1305 lk->lock_object.lo_name,
1306 (uintmax_t)LK_SHARERS(lk->lk_lock));
1307 else {
1308 td = lockmgr_xholder(lk);
1309 printf("lock type %s: EXCL by thread %p (pid %d)\n",
1310 lk->lock_object.lo_name, td, td->td_proc->p_pid);
1311 }
1312
1313 x = lk->lk_lock;
1314 if (x & LK_EXCLUSIVE_WAITERS)
1315 printf(" with exclusive waiters pending\n");
1316 if (x & LK_SHARED_WAITERS)
1317 printf(" with shared waiters pending\n");
1318 if (x & LK_EXCLUSIVE_SPINNERS)
1319 printf(" with exclusive spinners pending\n");
1320
1321 STACK_PRINT(lk);
1322 }
1323
1324 int
lockstatus(struct lock * lk)1325 lockstatus(struct lock *lk)
1326 {
1327 uintptr_t v, x;
1328 int ret;
1329
1330 ret = LK_SHARED;
1331 x = lk->lk_lock;
1332 v = LK_HOLDER(x);
1333
1334 if ((x & LK_SHARE) == 0) {
1335 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1336 ret = LK_EXCLUSIVE;
1337 else
1338 ret = LK_EXCLOTHER;
1339 } else if (x == LK_UNLOCKED)
1340 ret = 0;
1341
1342 return (ret);
1343 }
1344
1345 #ifdef INVARIANT_SUPPORT
1346
1347 FEATURE(invariant_support,
1348 "Support for modules compiled with INVARIANTS option");
1349
1350 #ifndef INVARIANTS
1351 #undef _lockmgr_assert
1352 #endif
1353
1354 void
_lockmgr_assert(struct lock * lk,int what,const char * file,int line)1355 _lockmgr_assert(struct lock *lk, int what, const char *file, int line)
1356 {
1357 int slocked = 0;
1358
1359 if (panicstr != NULL)
1360 return;
1361 switch (what) {
1362 case KA_SLOCKED:
1363 case KA_SLOCKED | KA_NOTRECURSED:
1364 case KA_SLOCKED | KA_RECURSED:
1365 slocked = 1;
1366 case KA_LOCKED:
1367 case KA_LOCKED | KA_NOTRECURSED:
1368 case KA_LOCKED | KA_RECURSED:
1369 #ifdef WITNESS
1370
1371 /*
1372 * We cannot trust WITNESS if the lock is held in exclusive
1373 * mode and a call to lockmgr_disown() happened.
1374 * Workaround this skipping the check if the lock is held in
1375 * exclusive mode even for the KA_LOCKED case.
1376 */
1377 if (slocked || (lk->lk_lock & LK_SHARE)) {
1378 witness_assert(&lk->lock_object, what, file, line);
1379 break;
1380 }
1381 #endif
1382 if (lk->lk_lock == LK_UNLOCKED ||
1383 ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1384 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1385 panic("Lock %s not %slocked @ %s:%d\n",
1386 lk->lock_object.lo_name, slocked ? "share" : "",
1387 file, line);
1388
1389 if ((lk->lk_lock & LK_SHARE) == 0) {
1390 if (lockmgr_recursed(lk)) {
1391 if (what & KA_NOTRECURSED)
1392 panic("Lock %s recursed @ %s:%d\n",
1393 lk->lock_object.lo_name, file,
1394 line);
1395 } else if (what & KA_RECURSED)
1396 panic("Lock %s not recursed @ %s:%d\n",
1397 lk->lock_object.lo_name, file, line);
1398 }
1399 break;
1400 case KA_XLOCKED:
1401 case KA_XLOCKED | KA_NOTRECURSED:
1402 case KA_XLOCKED | KA_RECURSED:
1403 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1404 panic("Lock %s not exclusively locked @ %s:%d\n",
1405 lk->lock_object.lo_name, file, line);
1406 if (lockmgr_recursed(lk)) {
1407 if (what & KA_NOTRECURSED)
1408 panic("Lock %s recursed @ %s:%d\n",
1409 lk->lock_object.lo_name, file, line);
1410 } else if (what & KA_RECURSED)
1411 panic("Lock %s not recursed @ %s:%d\n",
1412 lk->lock_object.lo_name, file, line);
1413 break;
1414 case KA_UNLOCKED:
1415 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1416 panic("Lock %s exclusively locked @ %s:%d\n",
1417 lk->lock_object.lo_name, file, line);
1418 break;
1419 default:
1420 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1421 line);
1422 }
1423 }
1424 #endif
1425
1426 #ifdef DDB
1427 int
lockmgr_chain(struct thread * td,struct thread ** ownerp)1428 lockmgr_chain(struct thread *td, struct thread **ownerp)
1429 {
1430 struct lock *lk;
1431
1432 lk = td->td_wchan;
1433
1434 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1435 return (0);
1436 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1437 if (lk->lk_lock & LK_SHARE)
1438 db_printf("SHARED (count %ju)\n",
1439 (uintmax_t)LK_SHARERS(lk->lk_lock));
1440 else
1441 db_printf("EXCL\n");
1442 *ownerp = lockmgr_xholder(lk);
1443
1444 return (1);
1445 }
1446
1447 static void
db_show_lockmgr(struct lock_object * lock)1448 db_show_lockmgr(struct lock_object *lock)
1449 {
1450 struct thread *td;
1451 struct lock *lk;
1452
1453 lk = (struct lock *)lock;
1454
1455 db_printf(" state: ");
1456 if (lk->lk_lock == LK_UNLOCKED)
1457 db_printf("UNLOCKED\n");
1458 else if (lk->lk_lock & LK_SHARE)
1459 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1460 else {
1461 td = lockmgr_xholder(lk);
1462 if (td == (struct thread *)LK_KERNPROC)
1463 db_printf("XLOCK: LK_KERNPROC\n");
1464 else
1465 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1466 td->td_tid, td->td_proc->p_pid,
1467 td->td_proc->p_comm);
1468 if (lockmgr_recursed(lk))
1469 db_printf(" recursed: %d\n", lk->lk_recurse);
1470 }
1471 db_printf(" waiters: ");
1472 switch (lk->lk_lock & LK_ALL_WAITERS) {
1473 case LK_SHARED_WAITERS:
1474 db_printf("shared\n");
1475 break;
1476 case LK_EXCLUSIVE_WAITERS:
1477 db_printf("exclusive\n");
1478 break;
1479 case LK_ALL_WAITERS:
1480 db_printf("shared and exclusive\n");
1481 break;
1482 default:
1483 db_printf("none\n");
1484 }
1485 db_printf(" spinners: ");
1486 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1487 db_printf("exclusive\n");
1488 else
1489 db_printf("none\n");
1490 }
1491 #endif
1492