1 /*-
2 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. Berkeley Software Design Inc's name may not be used to endorse or
13 * promote products derived from this software without specific prior
14 * written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
29 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
30 */
31
32 /*
33 * Implementation of turnstiles used to hold queue of threads blocked on
34 * non-sleepable locks. Sleepable locks use condition variables to
35 * implement their queues. Turnstiles differ from a sleep queue in that
36 * turnstile queue's are assigned to a lock held by an owning thread. Thus,
37 * when one thread is enqueued onto a turnstile, it can lend its priority
38 * to the owning thread.
39 *
40 * We wish to avoid bloating locks with an embedded turnstile and we do not
41 * want to use back-pointers in the locks for the same reason. Thus, we
42 * use a similar approach to that of Solaris 7 as described in Solaris
43 * Internals by Jim Mauro and Richard McDougall. Turnstiles are looked up
44 * in a hash table based on the address of the lock. Each entry in the
45 * hash table is a linked-lists of turnstiles and is called a turnstile
46 * chain. Each chain contains a spin mutex that protects all of the
47 * turnstiles in the chain.
48 *
49 * Each time a thread is created, a turnstile is allocated from a UMA zone
50 * and attached to that thread. When a thread blocks on a lock, if it is the
51 * first thread to block, it lends its turnstile to the lock. If the lock
52 * already has a turnstile, then it gives its turnstile to the lock's
53 * turnstile's free list. When a thread is woken up, it takes a turnstile from
54 * the free list if there are any other waiters. If it is the only thread
55 * blocked on the lock, then it reclaims the turnstile associated with the lock
56 * and removes it from the hash table.
57 */
58
59 #include <sys/cdefs.h>
60 __FBSDID("$FreeBSD: releng/10.4/sys/kern/subr_turnstile.c 296728 2016-03-12 17:17:34Z kib $");
61
62 #include "opt_ddb.h"
63 #include "opt_kdtrace.h"
64 #include "opt_turnstile_profiling.h"
65 #include "opt_sched.h"
66
67 #include <sys/param.h>
68 #include <sys/systm.h>
69 #include <sys/kdb.h>
70 #include <sys/kernel.h>
71 #include <sys/ktr.h>
72 #include <sys/lock.h>
73 #include <sys/mutex.h>
74 #include <sys/proc.h>
75 #include <sys/queue.h>
76 #include <sys/sched.h>
77 #include <sys/sdt.h>
78 #include <sys/sysctl.h>
79 #include <sys/turnstile.h>
80
81 #include <vm/uma.h>
82
83 #ifdef DDB
84 #include <ddb/ddb.h>
85 #include <sys/lockmgr.h>
86 #include <sys/sx.h>
87 #endif
88
89 /*
90 * Constants for the hash table of turnstile chains. TC_SHIFT is a magic
91 * number chosen because the sleep queue's use the same value for the
92 * shift. Basically, we ignore the lower 8 bits of the address.
93 * TC_TABLESIZE must be a power of two for TC_MASK to work properly.
94 */
95 #define TC_TABLESIZE 128 /* Must be power of 2. */
96 #define TC_MASK (TC_TABLESIZE - 1)
97 #define TC_SHIFT 8
98 #define TC_HASH(lock) (((uintptr_t)(lock) >> TC_SHIFT) & TC_MASK)
99 #define TC_LOOKUP(lock) &turnstile_chains[TC_HASH(lock)]
100
101 /*
102 * There are three different lists of turnstiles as follows. The list
103 * connected by ts_link entries is a per-thread list of all the turnstiles
104 * attached to locks that we own. This is used to fixup our priority when
105 * a lock is released. The other two lists use the ts_hash entries. The
106 * first of these two is the turnstile chain list that a turnstile is on
107 * when it is attached to a lock. The second list to use ts_hash is the
108 * free list hung off of a turnstile that is attached to a lock.
109 *
110 * Each turnstile contains three lists of threads. The two ts_blocked lists
111 * are linked list of threads blocked on the turnstile's lock. One list is
112 * for exclusive waiters, and the other is for shared waiters. The
113 * ts_pending list is a linked list of threads previously awakened by
114 * turnstile_signal() or turnstile_wait() that are waiting to be put on
115 * the run queue.
116 *
117 * Locking key:
118 * c - turnstile chain lock
119 * q - td_contested lock
120 */
121 struct turnstile {
122 struct mtx ts_lock; /* Spin lock for self. */
123 struct threadqueue ts_blocked[2]; /* (c + q) Blocked threads. */
124 struct threadqueue ts_pending; /* (c) Pending threads. */
125 LIST_ENTRY(turnstile) ts_hash; /* (c) Chain and free list. */
126 LIST_ENTRY(turnstile) ts_link; /* (q) Contested locks. */
127 LIST_HEAD(, turnstile) ts_free; /* (c) Free turnstiles. */
128 struct lock_object *ts_lockobj; /* (c) Lock we reference. */
129 struct thread *ts_owner; /* (c + q) Who owns the lock. */
130 };
131
132 struct turnstile_chain {
133 LIST_HEAD(, turnstile) tc_turnstiles; /* List of turnstiles. */
134 struct mtx tc_lock; /* Spin lock for this chain. */
135 #ifdef TURNSTILE_PROFILING
136 u_int tc_depth; /* Length of tc_queues. */
137 u_int tc_max_depth; /* Max length of tc_queues. */
138 #endif
139 };
140
141 #ifdef TURNSTILE_PROFILING
142 u_int turnstile_max_depth;
143 static SYSCTL_NODE(_debug, OID_AUTO, turnstile, CTLFLAG_RD, 0,
144 "turnstile profiling");
145 static SYSCTL_NODE(_debug_turnstile, OID_AUTO, chains, CTLFLAG_RD, 0,
146 "turnstile chain stats");
147 SYSCTL_UINT(_debug_turnstile, OID_AUTO, max_depth, CTLFLAG_RD,
148 &turnstile_max_depth, 0, "maximum depth achieved of a single chain");
149 #endif
150 static struct mtx td_contested_lock;
151 static struct turnstile_chain turnstile_chains[TC_TABLESIZE];
152 static uma_zone_t turnstile_zone;
153
154 /*
155 * Prototypes for non-exported routines.
156 */
157 static void init_turnstile0(void *dummy);
158 #ifdef TURNSTILE_PROFILING
159 static void init_turnstile_profiling(void *arg);
160 #endif
161 static void propagate_priority(struct thread *td);
162 static int turnstile_adjust_thread(struct turnstile *ts,
163 struct thread *td);
164 static struct thread *turnstile_first_waiter(struct turnstile *ts);
165 static void turnstile_setowner(struct turnstile *ts, struct thread *owner);
166 #ifdef INVARIANTS
167 static void turnstile_dtor(void *mem, int size, void *arg);
168 #endif
169 static int turnstile_init(void *mem, int size, int flags);
170 static void turnstile_fini(void *mem, int size);
171
172 SDT_PROVIDER_DECLARE(sched);
173 SDT_PROBE_DEFINE(sched, , , sleep);
174 SDT_PROBE_DEFINE2(sched, , , wakeup, "struct thread *",
175 "struct proc *");
176
177 /*
178 * Walks the chain of turnstiles and their owners to propagate the priority
179 * of the thread being blocked to all the threads holding locks that have to
180 * release their locks before this thread can run again.
181 */
182 static void
183 propagate_priority(struct thread *td)
184 {
185 struct turnstile *ts;
186 int pri;
187
188 THREAD_LOCK_ASSERT(td, MA_OWNED);
189 pri = td->td_priority;
190 ts = td->td_blocked;
191 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
192 /*
193 * Grab a recursive lock on this turnstile chain so it stays locked
194 * for the whole operation. The caller expects us to return with
195 * the original lock held. We only ever lock down the chain so
196 * the lock order is constant.
197 */
198 mtx_lock_spin(&ts->ts_lock);
199 for (;;) {
200 td = ts->ts_owner;
201
202 if (td == NULL) {
203 /*
204 * This might be a read lock with no owner. There's
205 * not much we can do, so just bail.
206 */
207 mtx_unlock_spin(&ts->ts_lock);
208 return;
209 }
210
211 thread_lock_flags(td, MTX_DUPOK);
212 mtx_unlock_spin(&ts->ts_lock);
213 MPASS(td->td_proc != NULL);
214 MPASS(td->td_proc->p_magic == P_MAGIC);
215
216 /*
217 * If the thread is asleep, then we are probably about
218 * to deadlock. To make debugging this easier, show
219 * backtrace of misbehaving thread and panic to not
220 * leave the kernel deadlocked.
221 */
222 if (TD_IS_SLEEPING(td)) {
223 printf(
224 "Sleeping thread (tid %d, pid %d) owns a non-sleepable lock\n",
225 td->td_tid, td->td_proc->p_pid);
226 kdb_backtrace_thread(td);
227 panic("sleeping thread");
228 }
229
230 /*
231 * If this thread already has higher priority than the
232 * thread that is being blocked, we are finished.
233 */
234 if (td->td_priority <= pri) {
235 thread_unlock(td);
236 return;
237 }
238
239 /*
240 * Bump this thread's priority.
241 */
242 sched_lend_prio(td, pri);
243
244 /*
245 * If lock holder is actually running or on the run queue
246 * then we are done.
247 */
248 if (TD_IS_RUNNING(td) || TD_ON_RUNQ(td)) {
249 MPASS(td->td_blocked == NULL);
250 thread_unlock(td);
251 return;
252 }
253
254 #ifndef SMP
255 /*
256 * For UP, we check to see if td is curthread (this shouldn't
257 * ever happen however as it would mean we are in a deadlock.)
258 */
259 KASSERT(td != curthread, ("Deadlock detected"));
260 #endif
261
262 /*
263 * If we aren't blocked on a lock, we should be.
264 */
265 KASSERT(TD_ON_LOCK(td), (
266 "thread %d(%s):%d holds %s but isn't blocked on a lock\n",
267 td->td_tid, td->td_name, td->td_state,
268 ts->ts_lockobj->lo_name));
269
270 /*
271 * Pick up the lock that td is blocked on.
272 */
273 ts = td->td_blocked;
274 MPASS(ts != NULL);
275 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
276 /* Resort td on the list if needed. */
277 if (!turnstile_adjust_thread(ts, td)) {
278 mtx_unlock_spin(&ts->ts_lock);
279 return;
280 }
281 /* The thread lock is released as ts lock above. */
282 }
283 }
284
285 /*
286 * Adjust the thread's position on a turnstile after its priority has been
287 * changed.
288 */
289 static int
290 turnstile_adjust_thread(struct turnstile *ts, struct thread *td)
291 {
292 struct thread *td1, *td2;
293 int queue;
294
295 THREAD_LOCK_ASSERT(td, MA_OWNED);
296 MPASS(TD_ON_LOCK(td));
297
298 /*
299 * This thread may not be blocked on this turnstile anymore
300 * but instead might already be woken up on another CPU
301 * that is waiting on the thread lock in turnstile_unpend() to
302 * finish waking this thread up. We can detect this case
303 * by checking to see if this thread has been given a
304 * turnstile by either turnstile_signal() or
305 * turnstile_broadcast(). In this case, treat the thread as
306 * if it was already running.
307 */
308 if (td->td_turnstile != NULL)
309 return (0);
310
311 /*
312 * Check if the thread needs to be moved on the blocked chain.
313 * It needs to be moved if either its priority is lower than
314 * the previous thread or higher than the next thread.
315 */
316 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
317 td1 = TAILQ_PREV(td, threadqueue, td_lockq);
318 td2 = TAILQ_NEXT(td, td_lockq);
319 if ((td1 != NULL && td->td_priority < td1->td_priority) ||
320 (td2 != NULL && td->td_priority > td2->td_priority)) {
321
322 /*
323 * Remove thread from blocked chain and determine where
324 * it should be moved to.
325 */
326 queue = td->td_tsqueue;
327 MPASS(queue == TS_EXCLUSIVE_QUEUE || queue == TS_SHARED_QUEUE);
328 mtx_lock_spin(&td_contested_lock);
329 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq);
330 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq) {
331 MPASS(td1->td_proc->p_magic == P_MAGIC);
332 if (td1->td_priority > td->td_priority)
333 break;
334 }
335
336 if (td1 == NULL)
337 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
338 else
339 TAILQ_INSERT_BEFORE(td1, td, td_lockq);
340 mtx_unlock_spin(&td_contested_lock);
341 if (td1 == NULL)
342 CTR3(KTR_LOCK,
343 "turnstile_adjust_thread: td %d put at tail on [%p] %s",
344 td->td_tid, ts->ts_lockobj, ts->ts_lockobj->lo_name);
345 else
346 CTR4(KTR_LOCK,
347 "turnstile_adjust_thread: td %d moved before %d on [%p] %s",
348 td->td_tid, td1->td_tid, ts->ts_lockobj,
349 ts->ts_lockobj->lo_name);
350 }
351 return (1);
352 }
353
354 /*
355 * Early initialization of turnstiles. This is not done via a SYSINIT()
356 * since this needs to be initialized very early when mutexes are first
357 * initialized.
358 */
359 void
360 init_turnstiles(void)
361 {
362 int i;
363
364 for (i = 0; i < TC_TABLESIZE; i++) {
365 LIST_INIT(&turnstile_chains[i].tc_turnstiles);
366 mtx_init(&turnstile_chains[i].tc_lock, "turnstile chain",
367 NULL, MTX_SPIN);
368 }
369 mtx_init(&td_contested_lock, "td_contested", NULL, MTX_SPIN);
370 LIST_INIT(&thread0.td_contested);
371 thread0.td_turnstile = NULL;
372 }
373
374 #ifdef TURNSTILE_PROFILING
375 static void
376 init_turnstile_profiling(void *arg)
377 {
378 struct sysctl_oid *chain_oid;
379 char chain_name[10];
380 int i;
381
382 for (i = 0; i < TC_TABLESIZE; i++) {
383 snprintf(chain_name, sizeof(chain_name), "%d", i);
384 chain_oid = SYSCTL_ADD_NODE(NULL,
385 SYSCTL_STATIC_CHILDREN(_debug_turnstile_chains), OID_AUTO,
386 chain_name, CTLFLAG_RD, NULL, "turnstile chain stats");
387 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
388 "depth", CTLFLAG_RD, &turnstile_chains[i].tc_depth, 0,
389 NULL);
390 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
391 "max_depth", CTLFLAG_RD, &turnstile_chains[i].tc_max_depth,
392 0, NULL);
393 }
394 }
395 SYSINIT(turnstile_profiling, SI_SUB_LOCK, SI_ORDER_ANY,
396 init_turnstile_profiling, NULL);
397 #endif
398
399 static void
400 init_turnstile0(void *dummy)
401 {
402
403 turnstile_zone = uma_zcreate("TURNSTILE", sizeof(struct turnstile),
404 NULL,
405 #ifdef INVARIANTS
406 turnstile_dtor,
407 #else
408 NULL,
409 #endif
410 turnstile_init, turnstile_fini, UMA_ALIGN_CACHE, UMA_ZONE_NOFREE);
411 thread0.td_turnstile = turnstile_alloc();
412 }
413 SYSINIT(turnstile0, SI_SUB_LOCK, SI_ORDER_ANY, init_turnstile0, NULL);
414
415 /*
416 * Update a thread on the turnstile list after it's priority has been changed.
417 * The old priority is passed in as an argument.
418 */
419 void
420 turnstile_adjust(struct thread *td, u_char oldpri)
421 {
422 struct turnstile *ts;
423
424 MPASS(TD_ON_LOCK(td));
425
426 /*
427 * Pick up the lock that td is blocked on.
428 */
429 ts = td->td_blocked;
430 MPASS(ts != NULL);
431 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
432 mtx_assert(&ts->ts_lock, MA_OWNED);
433
434 /* Resort the turnstile on the list. */
435 if (!turnstile_adjust_thread(ts, td))
436 return;
437 /*
438 * If our priority was lowered and we are at the head of the
439 * turnstile, then propagate our new priority up the chain.
440 * Note that we currently don't try to revoke lent priorities
441 * when our priority goes up.
442 */
443 MPASS(td->td_tsqueue == TS_EXCLUSIVE_QUEUE ||
444 td->td_tsqueue == TS_SHARED_QUEUE);
445 if (td == TAILQ_FIRST(&ts->ts_blocked[td->td_tsqueue]) &&
446 td->td_priority < oldpri) {
447 propagate_priority(td);
448 }
449 }
450
451 /*
452 * Set the owner of the lock this turnstile is attached to.
453 */
454 static void
455 turnstile_setowner(struct turnstile *ts, struct thread *owner)
456 {
457
458 mtx_assert(&td_contested_lock, MA_OWNED);
459 MPASS(ts->ts_owner == NULL);
460
461 /* A shared lock might not have an owner. */
462 if (owner == NULL)
463 return;
464
465 MPASS(owner->td_proc->p_magic == P_MAGIC);
466 ts->ts_owner = owner;
467 LIST_INSERT_HEAD(&owner->td_contested, ts, ts_link);
468 }
469
470 #ifdef INVARIANTS
471 /*
472 * UMA zone item deallocator.
473 */
474 static void
475 turnstile_dtor(void *mem, int size, void *arg)
476 {
477 struct turnstile *ts;
478
479 ts = mem;
480 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]));
481 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]));
482 MPASS(TAILQ_EMPTY(&ts->ts_pending));
483 }
484 #endif
485
486 /*
487 * UMA zone item initializer.
488 */
489 static int
490 turnstile_init(void *mem, int size, int flags)
491 {
492 struct turnstile *ts;
493
494 bzero(mem, size);
495 ts = mem;
496 TAILQ_INIT(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]);
497 TAILQ_INIT(&ts->ts_blocked[TS_SHARED_QUEUE]);
498 TAILQ_INIT(&ts->ts_pending);
499 LIST_INIT(&ts->ts_free);
500 mtx_init(&ts->ts_lock, "turnstile lock", NULL, MTX_SPIN | MTX_RECURSE);
501 return (0);
502 }
503
504 static void
505 turnstile_fini(void *mem, int size)
506 {
507 struct turnstile *ts;
508
509 ts = mem;
510 mtx_destroy(&ts->ts_lock);
511 }
512
513 /*
514 * Get a turnstile for a new thread.
515 */
516 struct turnstile *
517 turnstile_alloc(void)
518 {
519
520 return (uma_zalloc(turnstile_zone, M_WAITOK));
521 }
522
523 /*
524 * Free a turnstile when a thread is destroyed.
525 */
526 void
527 turnstile_free(struct turnstile *ts)
528 {
529
530 uma_zfree(turnstile_zone, ts);
531 }
532
533 /*
534 * Lock the turnstile chain associated with the specified lock.
535 */
536 void
537 turnstile_chain_lock(struct lock_object *lock)
538 {
539 struct turnstile_chain *tc;
540
541 tc = TC_LOOKUP(lock);
542 mtx_lock_spin(&tc->tc_lock);
543 }
544
545 struct turnstile *
546 turnstile_trywait(struct lock_object *lock)
547 {
548 struct turnstile_chain *tc;
549 struct turnstile *ts;
550
551 tc = TC_LOOKUP(lock);
552 mtx_lock_spin(&tc->tc_lock);
553 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
554 if (ts->ts_lockobj == lock) {
555 mtx_lock_spin(&ts->ts_lock);
556 return (ts);
557 }
558
559 ts = curthread->td_turnstile;
560 MPASS(ts != NULL);
561 mtx_lock_spin(&ts->ts_lock);
562 KASSERT(ts->ts_lockobj == NULL, ("stale ts_lockobj pointer"));
563 ts->ts_lockobj = lock;
564
565 return (ts);
566 }
567
568 void
569 turnstile_cancel(struct turnstile *ts)
570 {
571 struct turnstile_chain *tc;
572 struct lock_object *lock;
573
574 mtx_assert(&ts->ts_lock, MA_OWNED);
575
576 mtx_unlock_spin(&ts->ts_lock);
577 lock = ts->ts_lockobj;
578 if (ts == curthread->td_turnstile)
579 ts->ts_lockobj = NULL;
580 tc = TC_LOOKUP(lock);
581 mtx_unlock_spin(&tc->tc_lock);
582 }
583
584 /*
585 * Look up the turnstile for a lock in the hash table locking the associated
586 * turnstile chain along the way. If no turnstile is found in the hash
587 * table, NULL is returned.
588 */
589 struct turnstile *
590 turnstile_lookup(struct lock_object *lock)
591 {
592 struct turnstile_chain *tc;
593 struct turnstile *ts;
594
595 tc = TC_LOOKUP(lock);
596 mtx_assert(&tc->tc_lock, MA_OWNED);
597 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
598 if (ts->ts_lockobj == lock) {
599 mtx_lock_spin(&ts->ts_lock);
600 return (ts);
601 }
602 return (NULL);
603 }
604
605 /*
606 * Unlock the turnstile chain associated with a given lock.
607 */
608 void
609 turnstile_chain_unlock(struct lock_object *lock)
610 {
611 struct turnstile_chain *tc;
612
613 tc = TC_LOOKUP(lock);
614 mtx_unlock_spin(&tc->tc_lock);
615 }
616
617 /*
618 * Return a pointer to the thread waiting on this turnstile with the
619 * most important priority or NULL if the turnstile has no waiters.
620 */
621 static struct thread *
622 turnstile_first_waiter(struct turnstile *ts)
623 {
624 struct thread *std, *xtd;
625
626 std = TAILQ_FIRST(&ts->ts_blocked[TS_SHARED_QUEUE]);
627 xtd = TAILQ_FIRST(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]);
628 if (xtd == NULL || (std != NULL && std->td_priority < xtd->td_priority))
629 return (std);
630 return (xtd);
631 }
632
633 /*
634 * Take ownership of a turnstile and adjust the priority of the new
635 * owner appropriately.
636 */
637 void
638 turnstile_claim(struct turnstile *ts)
639 {
640 struct thread *td, *owner;
641 struct turnstile_chain *tc;
642
643 mtx_assert(&ts->ts_lock, MA_OWNED);
644 MPASS(ts != curthread->td_turnstile);
645
646 owner = curthread;
647 mtx_lock_spin(&td_contested_lock);
648 turnstile_setowner(ts, owner);
649 mtx_unlock_spin(&td_contested_lock);
650
651 td = turnstile_first_waiter(ts);
652 MPASS(td != NULL);
653 MPASS(td->td_proc->p_magic == P_MAGIC);
654 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
655
656 /*
657 * Update the priority of the new owner if needed.
658 */
659 thread_lock(owner);
660 if (td->td_priority < owner->td_priority)
661 sched_lend_prio(owner, td->td_priority);
662 thread_unlock(owner);
663 tc = TC_LOOKUP(ts->ts_lockobj);
664 mtx_unlock_spin(&ts->ts_lock);
665 mtx_unlock_spin(&tc->tc_lock);
666 }
667
668 /*
669 * Block the current thread on the turnstile assicated with 'lock'. This
670 * function will context switch and not return until this thread has been
671 * woken back up. This function must be called with the appropriate
672 * turnstile chain locked and will return with it unlocked.
673 */
674 void
675 turnstile_wait(struct turnstile *ts, struct thread *owner, int queue)
676 {
677 struct turnstile_chain *tc;
678 struct thread *td, *td1;
679 struct lock_object *lock;
680
681 td = curthread;
682 mtx_assert(&ts->ts_lock, MA_OWNED);
683 if (owner)
684 MPASS(owner->td_proc->p_magic == P_MAGIC);
685 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
686
687 /*
688 * If the lock does not already have a turnstile, use this thread's
689 * turnstile. Otherwise insert the current thread into the
690 * turnstile already in use by this lock.
691 */
692 tc = TC_LOOKUP(ts->ts_lockobj);
693 mtx_assert(&tc->tc_lock, MA_OWNED);
694 if (ts == td->td_turnstile) {
695 #ifdef TURNSTILE_PROFILING
696 tc->tc_depth++;
697 if (tc->tc_depth > tc->tc_max_depth) {
698 tc->tc_max_depth = tc->tc_depth;
699 if (tc->tc_max_depth > turnstile_max_depth)
700 turnstile_max_depth = tc->tc_max_depth;
701 }
702 #endif
703 LIST_INSERT_HEAD(&tc->tc_turnstiles, ts, ts_hash);
704 KASSERT(TAILQ_EMPTY(&ts->ts_pending),
705 ("thread's turnstile has pending threads"));
706 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]),
707 ("thread's turnstile has exclusive waiters"));
708 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]),
709 ("thread's turnstile has shared waiters"));
710 KASSERT(LIST_EMPTY(&ts->ts_free),
711 ("thread's turnstile has a non-empty free list"));
712 MPASS(ts->ts_lockobj != NULL);
713 mtx_lock_spin(&td_contested_lock);
714 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
715 turnstile_setowner(ts, owner);
716 mtx_unlock_spin(&td_contested_lock);
717 } else {
718 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq)
719 if (td1->td_priority > td->td_priority)
720 break;
721 mtx_lock_spin(&td_contested_lock);
722 if (td1 != NULL)
723 TAILQ_INSERT_BEFORE(td1, td, td_lockq);
724 else
725 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
726 MPASS(owner == ts->ts_owner);
727 mtx_unlock_spin(&td_contested_lock);
728 MPASS(td->td_turnstile != NULL);
729 LIST_INSERT_HEAD(&ts->ts_free, td->td_turnstile, ts_hash);
730 }
731 thread_lock(td);
732 thread_lock_set(td, &ts->ts_lock);
733 td->td_turnstile = NULL;
734
735 /* Save who we are blocked on and switch. */
736 lock = ts->ts_lockobj;
737 td->td_tsqueue = queue;
738 td->td_blocked = ts;
739 td->td_lockname = lock->lo_name;
740 td->td_blktick = ticks;
741 TD_SET_LOCK(td);
742 mtx_unlock_spin(&tc->tc_lock);
743 propagate_priority(td);
744
745 if (LOCK_LOG_TEST(lock, 0))
746 CTR4(KTR_LOCK, "%s: td %d blocked on [%p] %s", __func__,
747 td->td_tid, lock, lock->lo_name);
748
749 SDT_PROBE0(sched, , , sleep);
750
751 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
752 mi_switch(SW_VOL | SWT_TURNSTILE, NULL);
753
754 if (LOCK_LOG_TEST(lock, 0))
755 CTR4(KTR_LOCK, "%s: td %d free from blocked on [%p] %s",
756 __func__, td->td_tid, lock, lock->lo_name);
757 thread_unlock(td);
758 }
759
760 /*
761 * Pick the highest priority thread on this turnstile and put it on the
762 * pending list. This must be called with the turnstile chain locked.
763 */
764 int
765 turnstile_signal(struct turnstile *ts, int queue)
766 {
767 struct turnstile_chain *tc;
768 struct thread *td;
769 int empty;
770
771 MPASS(ts != NULL);
772 mtx_assert(&ts->ts_lock, MA_OWNED);
773 MPASS(curthread->td_proc->p_magic == P_MAGIC);
774 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
775 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
776
777 /*
778 * Pick the highest priority thread blocked on this lock and
779 * move it to the pending list.
780 */
781 td = TAILQ_FIRST(&ts->ts_blocked[queue]);
782 MPASS(td->td_proc->p_magic == P_MAGIC);
783 mtx_lock_spin(&td_contested_lock);
784 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq);
785 mtx_unlock_spin(&td_contested_lock);
786 TAILQ_INSERT_TAIL(&ts->ts_pending, td, td_lockq);
787
788 /*
789 * If the turnstile is now empty, remove it from its chain and
790 * give it to the about-to-be-woken thread. Otherwise take a
791 * turnstile from the free list and give it to the thread.
792 */
793 empty = TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) &&
794 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]);
795 if (empty) {
796 tc = TC_LOOKUP(ts->ts_lockobj);
797 mtx_assert(&tc->tc_lock, MA_OWNED);
798 MPASS(LIST_EMPTY(&ts->ts_free));
799 #ifdef TURNSTILE_PROFILING
800 tc->tc_depth--;
801 #endif
802 } else
803 ts = LIST_FIRST(&ts->ts_free);
804 MPASS(ts != NULL);
805 LIST_REMOVE(ts, ts_hash);
806 td->td_turnstile = ts;
807
808 return (empty);
809 }
810
811 /*
812 * Put all blocked threads on the pending list. This must be called with
813 * the turnstile chain locked.
814 */
815 void
816 turnstile_broadcast(struct turnstile *ts, int queue)
817 {
818 struct turnstile_chain *tc;
819 struct turnstile *ts1;
820 struct thread *td;
821
822 MPASS(ts != NULL);
823 mtx_assert(&ts->ts_lock, MA_OWNED);
824 MPASS(curthread->td_proc->p_magic == P_MAGIC);
825 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
826 /*
827 * We must have the chain locked so that we can remove the empty
828 * turnstile from the hash queue.
829 */
830 tc = TC_LOOKUP(ts->ts_lockobj);
831 mtx_assert(&tc->tc_lock, MA_OWNED);
832 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
833
834 /*
835 * Transfer the blocked list to the pending list.
836 */
837 mtx_lock_spin(&td_contested_lock);
838 TAILQ_CONCAT(&ts->ts_pending, &ts->ts_blocked[queue], td_lockq);
839 mtx_unlock_spin(&td_contested_lock);
840
841 /*
842 * Give a turnstile to each thread. The last thread gets
843 * this turnstile if the turnstile is empty.
844 */
845 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq) {
846 if (LIST_EMPTY(&ts->ts_free)) {
847 MPASS(TAILQ_NEXT(td, td_lockq) == NULL);
848 ts1 = ts;
849 #ifdef TURNSTILE_PROFILING
850 tc->tc_depth--;
851 #endif
852 } else
853 ts1 = LIST_FIRST(&ts->ts_free);
854 MPASS(ts1 != NULL);
855 LIST_REMOVE(ts1, ts_hash);
856 td->td_turnstile = ts1;
857 }
858 }
859
860 /*
861 * Wakeup all threads on the pending list and adjust the priority of the
862 * current thread appropriately. This must be called with the turnstile
863 * chain locked.
864 */
865 void
866 turnstile_unpend(struct turnstile *ts, int owner_type)
867 {
868 TAILQ_HEAD( ,thread) pending_threads;
869 struct turnstile *nts;
870 struct thread *td;
871 u_char cp, pri;
872
873 MPASS(ts != NULL);
874 mtx_assert(&ts->ts_lock, MA_OWNED);
875 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
876 MPASS(!TAILQ_EMPTY(&ts->ts_pending));
877
878 /*
879 * Move the list of pending threads out of the turnstile and
880 * into a local variable.
881 */
882 TAILQ_INIT(&pending_threads);
883 TAILQ_CONCAT(&pending_threads, &ts->ts_pending, td_lockq);
884 #ifdef INVARIANTS
885 if (TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) &&
886 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]))
887 ts->ts_lockobj = NULL;
888 #endif
889 /*
890 * Adjust the priority of curthread based on other contested
891 * locks it owns. Don't lower the priority below the base
892 * priority however.
893 */
894 td = curthread;
895 pri = PRI_MAX;
896 thread_lock(td);
897 mtx_lock_spin(&td_contested_lock);
898 /*
899 * Remove the turnstile from this thread's list of contested locks
900 * since this thread doesn't own it anymore. New threads will
901 * not be blocking on the turnstile until it is claimed by a new
902 * owner. There might not be a current owner if this is a shared
903 * lock.
904 */
905 if (ts->ts_owner != NULL) {
906 ts->ts_owner = NULL;
907 LIST_REMOVE(ts, ts_link);
908 }
909 LIST_FOREACH(nts, &td->td_contested, ts_link) {
910 cp = turnstile_first_waiter(nts)->td_priority;
911 if (cp < pri)
912 pri = cp;
913 }
914 mtx_unlock_spin(&td_contested_lock);
915 sched_unlend_prio(td, pri);
916 thread_unlock(td);
917 /*
918 * Wake up all the pending threads. If a thread is not blocked
919 * on a lock, then it is currently executing on another CPU in
920 * turnstile_wait() or sitting on a run queue waiting to resume
921 * in turnstile_wait(). Set a flag to force it to try to acquire
922 * the lock again instead of blocking.
923 */
924 while (!TAILQ_EMPTY(&pending_threads)) {
925 td = TAILQ_FIRST(&pending_threads);
926 TAILQ_REMOVE(&pending_threads, td, td_lockq);
927 SDT_PROBE2(sched, , , wakeup, td, td->td_proc);
928 thread_lock(td);
929 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
930 MPASS(td->td_proc->p_magic == P_MAGIC);
931 MPASS(TD_ON_LOCK(td));
932 TD_CLR_LOCK(td);
933 MPASS(TD_CAN_RUN(td));
934 td->td_blocked = NULL;
935 td->td_lockname = NULL;
936 td->td_blktick = 0;
937 #ifdef INVARIANTS
938 td->td_tsqueue = 0xff;
939 #endif
940 sched_add(td, SRQ_BORING);
941 thread_unlock(td);
942 }
943 mtx_unlock_spin(&ts->ts_lock);
944 }
945
946 /*
947 * Give up ownership of a turnstile. This must be called with the
948 * turnstile chain locked.
949 */
950 void
951 turnstile_disown(struct turnstile *ts)
952 {
953 struct thread *td;
954 u_char cp, pri;
955
956 MPASS(ts != NULL);
957 mtx_assert(&ts->ts_lock, MA_OWNED);
958 MPASS(ts->ts_owner == curthread);
959 MPASS(TAILQ_EMPTY(&ts->ts_pending));
960 MPASS(!TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) ||
961 !TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]));
962
963 /*
964 * Remove the turnstile from this thread's list of contested locks
965 * since this thread doesn't own it anymore. New threads will
966 * not be blocking on the turnstile until it is claimed by a new
967 * owner.
968 */
969 mtx_lock_spin(&td_contested_lock);
970 ts->ts_owner = NULL;
971 LIST_REMOVE(ts, ts_link);
972 mtx_unlock_spin(&td_contested_lock);
973
974 /*
975 * Adjust the priority of curthread based on other contested
976 * locks it owns. Don't lower the priority below the base
977 * priority however.
978 */
979 td = curthread;
980 pri = PRI_MAX;
981 thread_lock(td);
982 mtx_unlock_spin(&ts->ts_lock);
983 mtx_lock_spin(&td_contested_lock);
984 LIST_FOREACH(ts, &td->td_contested, ts_link) {
985 cp = turnstile_first_waiter(ts)->td_priority;
986 if (cp < pri)
987 pri = cp;
988 }
989 mtx_unlock_spin(&td_contested_lock);
990 sched_unlend_prio(td, pri);
991 thread_unlock(td);
992 }
993
994 /*
995 * Return the first thread in a turnstile.
996 */
997 struct thread *
998 turnstile_head(struct turnstile *ts, int queue)
999 {
1000 #ifdef INVARIANTS
1001
1002 MPASS(ts != NULL);
1003 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
1004 mtx_assert(&ts->ts_lock, MA_OWNED);
1005 #endif
1006 return (TAILQ_FIRST(&ts->ts_blocked[queue]));
1007 }
1008
1009 /*
1010 * Returns true if a sub-queue of a turnstile is empty.
1011 */
1012 int
1013 turnstile_empty(struct turnstile *ts, int queue)
1014 {
1015 #ifdef INVARIANTS
1016
1017 MPASS(ts != NULL);
1018 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
1019 mtx_assert(&ts->ts_lock, MA_OWNED);
1020 #endif
1021 return (TAILQ_EMPTY(&ts->ts_blocked[queue]));
1022 }
1023
1024 #ifdef DDB
1025 static void
1026 print_thread(struct thread *td, const char *prefix)
1027 {
1028
1029 db_printf("%s%p (tid %d, pid %d, \"%s\")\n", prefix, td, td->td_tid,
1030 td->td_proc->p_pid, td->td_name);
1031 }
1032
1033 static void
1034 print_queue(struct threadqueue *queue, const char *header, const char *prefix)
1035 {
1036 struct thread *td;
1037
1038 db_printf("%s:\n", header);
1039 if (TAILQ_EMPTY(queue)) {
1040 db_printf("%sempty\n", prefix);
1041 return;
1042 }
1043 TAILQ_FOREACH(td, queue, td_lockq) {
1044 print_thread(td, prefix);
1045 }
1046 }
1047
1048 DB_SHOW_COMMAND(turnstile, db_show_turnstile)
1049 {
1050 struct turnstile_chain *tc;
1051 struct turnstile *ts;
1052 struct lock_object *lock;
1053 int i;
1054
1055 if (!have_addr)
1056 return;
1057
1058 /*
1059 * First, see if there is an active turnstile for the lock indicated
1060 * by the address.
1061 */
1062 lock = (struct lock_object *)addr;
1063 tc = TC_LOOKUP(lock);
1064 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
1065 if (ts->ts_lockobj == lock)
1066 goto found;
1067
1068 /*
1069 * Second, see if there is an active turnstile at the address
1070 * indicated.
1071 */
1072 for (i = 0; i < TC_TABLESIZE; i++)
1073 LIST_FOREACH(ts, &turnstile_chains[i].tc_turnstiles, ts_hash) {
1074 if (ts == (struct turnstile *)addr)
1075 goto found;
1076 }
1077
1078 db_printf("Unable to locate a turnstile via %p\n", (void *)addr);
1079 return;
1080 found:
1081 lock = ts->ts_lockobj;
1082 db_printf("Lock: %p - (%s) %s\n", lock, LOCK_CLASS(lock)->lc_name,
1083 lock->lo_name);
1084 if (ts->ts_owner)
1085 print_thread(ts->ts_owner, "Lock Owner: ");
1086 else
1087 db_printf("Lock Owner: none\n");
1088 print_queue(&ts->ts_blocked[TS_SHARED_QUEUE], "Shared Waiters", "\t");
1089 print_queue(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE], "Exclusive Waiters",
1090 "\t");
1091 print_queue(&ts->ts_pending, "Pending Threads", "\t");
1092
1093 }
1094
1095 /*
1096 * Show all the threads a particular thread is waiting on based on
1097 * non-sleepable and non-spin locks.
1098 */
1099 static void
1100 print_lockchain(struct thread *td, const char *prefix)
1101 {
1102 struct lock_object *lock;
1103 struct lock_class *class;
1104 struct turnstile *ts;
1105
1106 /*
1107 * Follow the chain. We keep walking as long as the thread is
1108 * blocked on a turnstile that has an owner.
1109 */
1110 while (!db_pager_quit) {
1111 db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid,
1112 td->td_proc->p_pid, td->td_name);
1113 switch (td->td_state) {
1114 case TDS_INACTIVE:
1115 db_printf("is inactive\n");
1116 return;
1117 case TDS_CAN_RUN:
1118 db_printf("can run\n");
1119 return;
1120 case TDS_RUNQ:
1121 db_printf("is on a run queue\n");
1122 return;
1123 case TDS_RUNNING:
1124 db_printf("running on CPU %d\n", td->td_oncpu);
1125 return;
1126 case TDS_INHIBITED:
1127 if (TD_ON_LOCK(td)) {
1128 ts = td->td_blocked;
1129 lock = ts->ts_lockobj;
1130 class = LOCK_CLASS(lock);
1131 db_printf("blocked on lock %p (%s) \"%s\"\n",
1132 lock, class->lc_name, lock->lo_name);
1133 if (ts->ts_owner == NULL)
1134 return;
1135 td = ts->ts_owner;
1136 break;
1137 }
1138 db_printf("inhibited\n");
1139 return;
1140 default:
1141 db_printf("??? (%#x)\n", td->td_state);
1142 return;
1143 }
1144 }
1145 }
1146
1147 DB_SHOW_COMMAND(lockchain, db_show_lockchain)
1148 {
1149 struct thread *td;
1150
1151 /* Figure out which thread to start with. */
1152 if (have_addr)
1153 td = db_lookup_thread(addr, TRUE);
1154 else
1155 td = kdb_thread;
1156
1157 print_lockchain(td, "");
1158 }
1159
1160 DB_SHOW_ALL_COMMAND(chains, db_show_allchains)
1161 {
1162 struct thread *td;
1163 struct proc *p;
1164 int i;
1165
1166 i = 1;
1167 FOREACH_PROC_IN_SYSTEM(p) {
1168 FOREACH_THREAD_IN_PROC(p, td) {
1169 if (TD_ON_LOCK(td) && LIST_EMPTY(&td->td_contested)) {
1170 db_printf("chain %d:\n", i++);
1171 print_lockchain(td, " ");
1172 }
1173 if (db_pager_quit)
1174 return;
1175 }
1176 }
1177 }
1178 DB_SHOW_ALIAS(allchains, db_show_allchains)
1179
1180 /*
1181 * Show all the threads a particular thread is waiting on based on
1182 * sleepable locks.
1183 */
1184 static void
1185 print_sleepchain(struct thread *td, const char *prefix)
1186 {
1187 struct thread *owner;
1188
1189 /*
1190 * Follow the chain. We keep walking as long as the thread is
1191 * blocked on a sleep lock that has an owner.
1192 */
1193 while (!db_pager_quit) {
1194 db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid,
1195 td->td_proc->p_pid, td->td_name);
1196 switch (td->td_state) {
1197 case TDS_INACTIVE:
1198 db_printf("is inactive\n");
1199 return;
1200 case TDS_CAN_RUN:
1201 db_printf("can run\n");
1202 return;
1203 case TDS_RUNQ:
1204 db_printf("is on a run queue\n");
1205 return;
1206 case TDS_RUNNING:
1207 db_printf("running on CPU %d\n", td->td_oncpu);
1208 return;
1209 case TDS_INHIBITED:
1210 if (TD_ON_SLEEPQ(td)) {
1211 if (lockmgr_chain(td, &owner) ||
1212 sx_chain(td, &owner)) {
1213 if (owner == NULL)
1214 return;
1215 td = owner;
1216 break;
1217 }
1218 db_printf("sleeping on %p \"%s\"\n",
1219 td->td_wchan, td->td_wmesg);
1220 return;
1221 }
1222 db_printf("inhibited\n");
1223 return;
1224 default:
1225 db_printf("??? (%#x)\n", td->td_state);
1226 return;
1227 }
1228 }
1229 }
1230
1231 DB_SHOW_COMMAND(sleepchain, db_show_sleepchain)
1232 {
1233 struct thread *td;
1234
1235 /* Figure out which thread to start with. */
1236 if (have_addr)
1237 td = db_lookup_thread(addr, TRUE);
1238 else
1239 td = kdb_thread;
1240
1241 print_sleepchain(td, "");
1242 }
1243
1244 static void print_waiters(struct turnstile *ts, int indent);
1245
1246 static void
1247 print_waiter(struct thread *td, int indent)
1248 {
1249 struct turnstile *ts;
1250 int i;
1251
1252 if (db_pager_quit)
1253 return;
1254 for (i = 0; i < indent; i++)
1255 db_printf(" ");
1256 print_thread(td, "thread ");
1257 LIST_FOREACH(ts, &td->td_contested, ts_link)
1258 print_waiters(ts, indent + 1);
1259 }
1260
1261 static void
1262 print_waiters(struct turnstile *ts, int indent)
1263 {
1264 struct lock_object *lock;
1265 struct lock_class *class;
1266 struct thread *td;
1267 int i;
1268
1269 if (db_pager_quit)
1270 return;
1271 lock = ts->ts_lockobj;
1272 class = LOCK_CLASS(lock);
1273 for (i = 0; i < indent; i++)
1274 db_printf(" ");
1275 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name, lock->lo_name);
1276 TAILQ_FOREACH(td, &ts->ts_blocked[TS_EXCLUSIVE_QUEUE], td_lockq)
1277 print_waiter(td, indent + 1);
1278 TAILQ_FOREACH(td, &ts->ts_blocked[TS_SHARED_QUEUE], td_lockq)
1279 print_waiter(td, indent + 1);
1280 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq)
1281 print_waiter(td, indent + 1);
1282 }
1283
1284 DB_SHOW_COMMAND(locktree, db_show_locktree)
1285 {
1286 struct lock_object *lock;
1287 struct lock_class *class;
1288 struct turnstile_chain *tc;
1289 struct turnstile *ts;
1290
1291 if (!have_addr)
1292 return;
1293 lock = (struct lock_object *)addr;
1294 tc = TC_LOOKUP(lock);
1295 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
1296 if (ts->ts_lockobj == lock)
1297 break;
1298 if (ts == NULL) {
1299 class = LOCK_CLASS(lock);
1300 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name,
1301 lock->lo_name);
1302 } else
1303 print_waiters(ts, 0);
1304 }
1305 #endif
Cache object: e96db879bc3fa7b7191a5586001ff80f
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