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/8.0/sys/kern/subr_turnstile.c 183054 2008-09-15 22:45:14Z sam $");
61
62 #include "opt_ddb.h"
63 #include "opt_turnstile_profiling.h"
64 #include "opt_sched.h"
65
66 #include <sys/param.h>
67 #include <sys/systm.h>
68 #include <sys/kernel.h>
69 #include <sys/ktr.h>
70 #include <sys/lock.h>
71 #include <sys/mutex.h>
72 #include <sys/proc.h>
73 #include <sys/queue.h>
74 #include <sys/sched.h>
75 #include <sys/sysctl.h>
76 #include <sys/turnstile.h>
77
78 #include <vm/uma.h>
79
80 #ifdef DDB
81 #include <sys/kdb.h>
82 #include <ddb/ddb.h>
83 #include <sys/lockmgr.h>
84 #include <sys/sx.h>
85 #endif
86
87 /*
88 * Constants for the hash table of turnstile chains. TC_SHIFT is a magic
89 * number chosen because the sleep queue's use the same value for the
90 * shift. Basically, we ignore the lower 8 bits of the address.
91 * TC_TABLESIZE must be a power of two for TC_MASK to work properly.
92 */
93 #define TC_TABLESIZE 128 /* Must be power of 2. */
94 #define TC_MASK (TC_TABLESIZE - 1)
95 #define TC_SHIFT 8
96 #define TC_HASH(lock) (((uintptr_t)(lock) >> TC_SHIFT) & TC_MASK)
97 #define TC_LOOKUP(lock) &turnstile_chains[TC_HASH(lock)]
98
99 /*
100 * There are three different lists of turnstiles as follows. The list
101 * connected by ts_link entries is a per-thread list of all the turnstiles
102 * attached to locks that we own. This is used to fixup our priority when
103 * a lock is released. The other two lists use the ts_hash entries. The
104 * first of these two is the turnstile chain list that a turnstile is on
105 * when it is attached to a lock. The second list to use ts_hash is the
106 * free list hung off of a turnstile that is attached to a lock.
107 *
108 * Each turnstile contains three lists of threads. The two ts_blocked lists
109 * are linked list of threads blocked on the turnstile's lock. One list is
110 * for exclusive waiters, and the other is for shared waiters. The
111 * ts_pending list is a linked list of threads previously awakened by
112 * turnstile_signal() or turnstile_wait() that are waiting to be put on
113 * the run queue.
114 *
115 * Locking key:
116 * c - turnstile chain lock
117 * q - td_contested lock
118 */
119 struct turnstile {
120 struct mtx ts_lock; /* Spin lock for self. */
121 struct threadqueue ts_blocked[2]; /* (c + q) Blocked threads. */
122 struct threadqueue ts_pending; /* (c) Pending threads. */
123 LIST_ENTRY(turnstile) ts_hash; /* (c) Chain and free list. */
124 LIST_ENTRY(turnstile) ts_link; /* (q) Contested locks. */
125 LIST_HEAD(, turnstile) ts_free; /* (c) Free turnstiles. */
126 struct lock_object *ts_lockobj; /* (c) Lock we reference. */
127 struct thread *ts_owner; /* (c + q) Who owns the lock. */
128 };
129
130 struct turnstile_chain {
131 LIST_HEAD(, turnstile) tc_turnstiles; /* List of turnstiles. */
132 struct mtx tc_lock; /* Spin lock for this chain. */
133 #ifdef TURNSTILE_PROFILING
134 u_int tc_depth; /* Length of tc_queues. */
135 u_int tc_max_depth; /* Max length of tc_queues. */
136 #endif
137 };
138
139 #ifdef TURNSTILE_PROFILING
140 u_int turnstile_max_depth;
141 SYSCTL_NODE(_debug, OID_AUTO, turnstile, CTLFLAG_RD, 0, "turnstile profiling");
142 SYSCTL_NODE(_debug_turnstile, OID_AUTO, chains, CTLFLAG_RD, 0,
143 "turnstile chain stats");
144 SYSCTL_UINT(_debug_turnstile, OID_AUTO, max_depth, CTLFLAG_RD,
145 &turnstile_max_depth, 0, "maxmimum depth achieved of a single chain");
146 #endif
147 static struct mtx td_contested_lock;
148 static struct turnstile_chain turnstile_chains[TC_TABLESIZE];
149 static uma_zone_t turnstile_zone;
150
151 /*
152 * Prototypes for non-exported routines.
153 */
154 static void init_turnstile0(void *dummy);
155 #ifdef TURNSTILE_PROFILING
156 static void init_turnstile_profiling(void *arg);
157 #endif
158 static void propagate_priority(struct thread *td);
159 static int turnstile_adjust_thread(struct turnstile *ts,
160 struct thread *td);
161 static struct thread *turnstile_first_waiter(struct turnstile *ts);
162 static void turnstile_setowner(struct turnstile *ts, struct thread *owner);
163 #ifdef INVARIANTS
164 static void turnstile_dtor(void *mem, int size, void *arg);
165 #endif
166 static int turnstile_init(void *mem, int size, int flags);
167 static void turnstile_fini(void *mem, int size);
168
169 /*
170 * Walks the chain of turnstiles and their owners to propagate the priority
171 * of the thread being blocked to all the threads holding locks that have to
172 * release their locks before this thread can run again.
173 */
174 static void
175 propagate_priority(struct thread *td)
176 {
177 struct turnstile *ts;
178 int pri;
179
180 THREAD_LOCK_ASSERT(td, MA_OWNED);
181 pri = td->td_priority;
182 ts = td->td_blocked;
183 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
184 /*
185 * Grab a recursive lock on this turnstile chain so it stays locked
186 * for the whole operation. The caller expects us to return with
187 * the original lock held. We only ever lock down the chain so
188 * the lock order is constant.
189 */
190 mtx_lock_spin(&ts->ts_lock);
191 for (;;) {
192 td = ts->ts_owner;
193
194 if (td == NULL) {
195 /*
196 * This might be a read lock with no owner. There's
197 * not much we can do, so just bail.
198 */
199 mtx_unlock_spin(&ts->ts_lock);
200 return;
201 }
202
203 thread_lock_flags(td, MTX_DUPOK);
204 mtx_unlock_spin(&ts->ts_lock);
205 MPASS(td->td_proc != NULL);
206 MPASS(td->td_proc->p_magic == P_MAGIC);
207
208 /*
209 * If the thread is asleep, then we are probably about
210 * to deadlock. To make debugging this easier, just
211 * panic and tell the user which thread misbehaved so
212 * they can hopefully get a stack trace from the truly
213 * misbehaving thread.
214 */
215 if (TD_IS_SLEEPING(td)) {
216 printf(
217 "Sleeping thread (tid %d, pid %d) owns a non-sleepable lock\n",
218 td->td_tid, td->td_proc->p_pid);
219 #ifdef DDB
220 db_trace_thread(td, -1);
221 #endif
222 panic("sleeping thread");
223 }
224
225 /*
226 * If this thread already has higher priority than the
227 * thread that is being blocked, we are finished.
228 */
229 if (td->td_priority <= pri) {
230 thread_unlock(td);
231 return;
232 }
233
234 /*
235 * Bump this thread's priority.
236 */
237 sched_lend_prio(td, pri);
238
239 /*
240 * If lock holder is actually running or on the run queue
241 * then we are done.
242 */
243 if (TD_IS_RUNNING(td) || TD_ON_RUNQ(td)) {
244 MPASS(td->td_blocked == NULL);
245 thread_unlock(td);
246 return;
247 }
248
249 #ifndef SMP
250 /*
251 * For UP, we check to see if td is curthread (this shouldn't
252 * ever happen however as it would mean we are in a deadlock.)
253 */
254 KASSERT(td != curthread, ("Deadlock detected"));
255 #endif
256
257 /*
258 * If we aren't blocked on a lock, we should be.
259 */
260 KASSERT(TD_ON_LOCK(td), (
261 "thread %d(%s):%d holds %s but isn't blocked on a lock\n",
262 td->td_tid, td->td_name, td->td_state,
263 ts->ts_lockobj->lo_name));
264
265 /*
266 * Pick up the lock that td is blocked on.
267 */
268 ts = td->td_blocked;
269 MPASS(ts != NULL);
270 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
271 /* Resort td on the list if needed. */
272 if (!turnstile_adjust_thread(ts, td)) {
273 mtx_unlock_spin(&ts->ts_lock);
274 return;
275 }
276 /* The thread lock is released as ts lock above. */
277 }
278 }
279
280 /*
281 * Adjust the thread's position on a turnstile after its priority has been
282 * changed.
283 */
284 static int
285 turnstile_adjust_thread(struct turnstile *ts, struct thread *td)
286 {
287 struct thread *td1, *td2;
288 int queue;
289
290 THREAD_LOCK_ASSERT(td, MA_OWNED);
291 MPASS(TD_ON_LOCK(td));
292
293 /*
294 * This thread may not be blocked on this turnstile anymore
295 * but instead might already be woken up on another CPU
296 * that is waiting on the thread lock in turnstile_unpend() to
297 * finish waking this thread up. We can detect this case
298 * by checking to see if this thread has been given a
299 * turnstile by either turnstile_signal() or
300 * turnstile_broadcast(). In this case, treat the thread as
301 * if it was already running.
302 */
303 if (td->td_turnstile != NULL)
304 return (0);
305
306 /*
307 * Check if the thread needs to be moved on the blocked chain.
308 * It needs to be moved if either its priority is lower than
309 * the previous thread or higher than the next thread.
310 */
311 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
312 td1 = TAILQ_PREV(td, threadqueue, td_lockq);
313 td2 = TAILQ_NEXT(td, td_lockq);
314 if ((td1 != NULL && td->td_priority < td1->td_priority) ||
315 (td2 != NULL && td->td_priority > td2->td_priority)) {
316
317 /*
318 * Remove thread from blocked chain and determine where
319 * it should be moved to.
320 */
321 queue = td->td_tsqueue;
322 MPASS(queue == TS_EXCLUSIVE_QUEUE || queue == TS_SHARED_QUEUE);
323 mtx_lock_spin(&td_contested_lock);
324 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq);
325 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq) {
326 MPASS(td1->td_proc->p_magic == P_MAGIC);
327 if (td1->td_priority > td->td_priority)
328 break;
329 }
330
331 if (td1 == NULL)
332 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
333 else
334 TAILQ_INSERT_BEFORE(td1, td, td_lockq);
335 mtx_unlock_spin(&td_contested_lock);
336 if (td1 == NULL)
337 CTR3(KTR_LOCK,
338 "turnstile_adjust_thread: td %d put at tail on [%p] %s",
339 td->td_tid, ts->ts_lockobj, ts->ts_lockobj->lo_name);
340 else
341 CTR4(KTR_LOCK,
342 "turnstile_adjust_thread: td %d moved before %d on [%p] %s",
343 td->td_tid, td1->td_tid, ts->ts_lockobj,
344 ts->ts_lockobj->lo_name);
345 }
346 return (1);
347 }
348
349 /*
350 * Early initialization of turnstiles. This is not done via a SYSINIT()
351 * since this needs to be initialized very early when mutexes are first
352 * initialized.
353 */
354 void
355 init_turnstiles(void)
356 {
357 int i;
358
359 for (i = 0; i < TC_TABLESIZE; i++) {
360 LIST_INIT(&turnstile_chains[i].tc_turnstiles);
361 mtx_init(&turnstile_chains[i].tc_lock, "turnstile chain",
362 NULL, MTX_SPIN);
363 }
364 mtx_init(&td_contested_lock, "td_contested", NULL, MTX_SPIN);
365 LIST_INIT(&thread0.td_contested);
366 thread0.td_turnstile = NULL;
367 }
368
369 #ifdef TURNSTILE_PROFILING
370 static void
371 init_turnstile_profiling(void *arg)
372 {
373 struct sysctl_oid *chain_oid;
374 char chain_name[10];
375 int i;
376
377 for (i = 0; i < TC_TABLESIZE; i++) {
378 snprintf(chain_name, sizeof(chain_name), "%d", i);
379 chain_oid = SYSCTL_ADD_NODE(NULL,
380 SYSCTL_STATIC_CHILDREN(_debug_turnstile_chains), OID_AUTO,
381 chain_name, CTLFLAG_RD, NULL, "turnstile chain stats");
382 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
383 "depth", CTLFLAG_RD, &turnstile_chains[i].tc_depth, 0,
384 NULL);
385 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
386 "max_depth", CTLFLAG_RD, &turnstile_chains[i].tc_max_depth,
387 0, NULL);
388 }
389 }
390 SYSINIT(turnstile_profiling, SI_SUB_LOCK, SI_ORDER_ANY,
391 init_turnstile_profiling, NULL);
392 #endif
393
394 static void
395 init_turnstile0(void *dummy)
396 {
397
398 turnstile_zone = uma_zcreate("TURNSTILE", sizeof(struct turnstile),
399 NULL,
400 #ifdef INVARIANTS
401 turnstile_dtor,
402 #else
403 NULL,
404 #endif
405 turnstile_init, turnstile_fini, UMA_ALIGN_CACHE, UMA_ZONE_NOFREE);
406 thread0.td_turnstile = turnstile_alloc();
407 }
408 SYSINIT(turnstile0, SI_SUB_LOCK, SI_ORDER_ANY, init_turnstile0, NULL);
409
410 /*
411 * Update a thread on the turnstile list after it's priority has been changed.
412 * The old priority is passed in as an argument.
413 */
414 void
415 turnstile_adjust(struct thread *td, u_char oldpri)
416 {
417 struct turnstile *ts;
418
419 MPASS(TD_ON_LOCK(td));
420
421 /*
422 * Pick up the lock that td is blocked on.
423 */
424 ts = td->td_blocked;
425 MPASS(ts != NULL);
426 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
427 mtx_assert(&ts->ts_lock, MA_OWNED);
428
429 /* Resort the turnstile on the list. */
430 if (!turnstile_adjust_thread(ts, td))
431 return;
432 /*
433 * If our priority was lowered and we are at the head of the
434 * turnstile, then propagate our new priority up the chain.
435 * Note that we currently don't try to revoke lent priorities
436 * when our priority goes up.
437 */
438 MPASS(td->td_tsqueue == TS_EXCLUSIVE_QUEUE ||
439 td->td_tsqueue == TS_SHARED_QUEUE);
440 if (td == TAILQ_FIRST(&ts->ts_blocked[td->td_tsqueue]) &&
441 td->td_priority < oldpri) {
442 propagate_priority(td);
443 }
444 }
445
446 /*
447 * Set the owner of the lock this turnstile is attached to.
448 */
449 static void
450 turnstile_setowner(struct turnstile *ts, struct thread *owner)
451 {
452
453 mtx_assert(&td_contested_lock, MA_OWNED);
454 MPASS(ts->ts_owner == NULL);
455
456 /* A shared lock might not have an owner. */
457 if (owner == NULL)
458 return;
459
460 MPASS(owner->td_proc->p_magic == P_MAGIC);
461 ts->ts_owner = owner;
462 LIST_INSERT_HEAD(&owner->td_contested, ts, ts_link);
463 }
464
465 #ifdef INVARIANTS
466 /*
467 * UMA zone item deallocator.
468 */
469 static void
470 turnstile_dtor(void *mem, int size, void *arg)
471 {
472 struct turnstile *ts;
473
474 ts = mem;
475 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]));
476 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]));
477 MPASS(TAILQ_EMPTY(&ts->ts_pending));
478 }
479 #endif
480
481 /*
482 * UMA zone item initializer.
483 */
484 static int
485 turnstile_init(void *mem, int size, int flags)
486 {
487 struct turnstile *ts;
488
489 bzero(mem, size);
490 ts = mem;
491 TAILQ_INIT(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]);
492 TAILQ_INIT(&ts->ts_blocked[TS_SHARED_QUEUE]);
493 TAILQ_INIT(&ts->ts_pending);
494 LIST_INIT(&ts->ts_free);
495 mtx_init(&ts->ts_lock, "turnstile lock", NULL, MTX_SPIN | MTX_RECURSE);
496 return (0);
497 }
498
499 static void
500 turnstile_fini(void *mem, int size)
501 {
502 struct turnstile *ts;
503
504 ts = mem;
505 mtx_destroy(&ts->ts_lock);
506 }
507
508 /*
509 * Get a turnstile for a new thread.
510 */
511 struct turnstile *
512 turnstile_alloc(void)
513 {
514
515 return (uma_zalloc(turnstile_zone, M_WAITOK));
516 }
517
518 /*
519 * Free a turnstile when a thread is destroyed.
520 */
521 void
522 turnstile_free(struct turnstile *ts)
523 {
524
525 uma_zfree(turnstile_zone, ts);
526 }
527
528 /*
529 * Lock the turnstile chain associated with the specified lock.
530 */
531 void
532 turnstile_chain_lock(struct lock_object *lock)
533 {
534 struct turnstile_chain *tc;
535
536 tc = TC_LOOKUP(lock);
537 mtx_lock_spin(&tc->tc_lock);
538 }
539
540 struct turnstile *
541 turnstile_trywait(struct lock_object *lock)
542 {
543 struct turnstile_chain *tc;
544 struct turnstile *ts;
545
546 tc = TC_LOOKUP(lock);
547 mtx_lock_spin(&tc->tc_lock);
548 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
549 if (ts->ts_lockobj == lock) {
550 mtx_lock_spin(&ts->ts_lock);
551 return (ts);
552 }
553
554 ts = curthread->td_turnstile;
555 MPASS(ts != NULL);
556 mtx_lock_spin(&ts->ts_lock);
557 KASSERT(ts->ts_lockobj == NULL, ("stale ts_lockobj pointer"));
558 ts->ts_lockobj = lock;
559
560 return (ts);
561 }
562
563 void
564 turnstile_cancel(struct turnstile *ts)
565 {
566 struct turnstile_chain *tc;
567 struct lock_object *lock;
568
569 mtx_assert(&ts->ts_lock, MA_OWNED);
570
571 mtx_unlock_spin(&ts->ts_lock);
572 lock = ts->ts_lockobj;
573 if (ts == curthread->td_turnstile)
574 ts->ts_lockobj = NULL;
575 tc = TC_LOOKUP(lock);
576 mtx_unlock_spin(&tc->tc_lock);
577 }
578
579 /*
580 * Look up the turnstile for a lock in the hash table locking the associated
581 * turnstile chain along the way. If no turnstile is found in the hash
582 * table, NULL is returned.
583 */
584 struct turnstile *
585 turnstile_lookup(struct lock_object *lock)
586 {
587 struct turnstile_chain *tc;
588 struct turnstile *ts;
589
590 tc = TC_LOOKUP(lock);
591 mtx_assert(&tc->tc_lock, MA_OWNED);
592 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
593 if (ts->ts_lockobj == lock) {
594 mtx_lock_spin(&ts->ts_lock);
595 return (ts);
596 }
597 return (NULL);
598 }
599
600 /*
601 * Unlock the turnstile chain associated with a given lock.
602 */
603 void
604 turnstile_chain_unlock(struct lock_object *lock)
605 {
606 struct turnstile_chain *tc;
607
608 tc = TC_LOOKUP(lock);
609 mtx_unlock_spin(&tc->tc_lock);
610 }
611
612 /*
613 * Return a pointer to the thread waiting on this turnstile with the
614 * most important priority or NULL if the turnstile has no waiters.
615 */
616 static struct thread *
617 turnstile_first_waiter(struct turnstile *ts)
618 {
619 struct thread *std, *xtd;
620
621 std = TAILQ_FIRST(&ts->ts_blocked[TS_SHARED_QUEUE]);
622 xtd = TAILQ_FIRST(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]);
623 if (xtd == NULL || (std != NULL && std->td_priority < xtd->td_priority))
624 return (std);
625 return (xtd);
626 }
627
628 /*
629 * Take ownership of a turnstile and adjust the priority of the new
630 * owner appropriately.
631 */
632 void
633 turnstile_claim(struct turnstile *ts)
634 {
635 struct thread *td, *owner;
636 struct turnstile_chain *tc;
637
638 mtx_assert(&ts->ts_lock, MA_OWNED);
639 MPASS(ts != curthread->td_turnstile);
640
641 owner = curthread;
642 mtx_lock_spin(&td_contested_lock);
643 turnstile_setowner(ts, owner);
644 mtx_unlock_spin(&td_contested_lock);
645
646 td = turnstile_first_waiter(ts);
647 MPASS(td != NULL);
648 MPASS(td->td_proc->p_magic == P_MAGIC);
649 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
650
651 /*
652 * Update the priority of the new owner if needed.
653 */
654 thread_lock(owner);
655 if (td->td_priority < owner->td_priority)
656 sched_lend_prio(owner, td->td_priority);
657 thread_unlock(owner);
658 tc = TC_LOOKUP(ts->ts_lockobj);
659 mtx_unlock_spin(&ts->ts_lock);
660 mtx_unlock_spin(&tc->tc_lock);
661 }
662
663 /*
664 * Block the current thread on the turnstile assicated with 'lock'. This
665 * function will context switch and not return until this thread has been
666 * woken back up. This function must be called with the appropriate
667 * turnstile chain locked and will return with it unlocked.
668 */
669 void
670 turnstile_wait(struct turnstile *ts, struct thread *owner, int queue)
671 {
672 struct turnstile_chain *tc;
673 struct thread *td, *td1;
674 struct lock_object *lock;
675
676 td = curthread;
677 mtx_assert(&ts->ts_lock, MA_OWNED);
678 if (owner)
679 MPASS(owner->td_proc->p_magic == P_MAGIC);
680 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
681
682 /*
683 * If the lock does not already have a turnstile, use this thread's
684 * turnstile. Otherwise insert the current thread into the
685 * turnstile already in use by this lock.
686 */
687 tc = TC_LOOKUP(ts->ts_lockobj);
688 if (ts == td->td_turnstile) {
689 mtx_assert(&tc->tc_lock, MA_OWNED);
690 #ifdef TURNSTILE_PROFILING
691 tc->tc_depth++;
692 if (tc->tc_depth > tc->tc_max_depth) {
693 tc->tc_max_depth = tc->tc_depth;
694 if (tc->tc_max_depth > turnstile_max_depth)
695 turnstile_max_depth = tc->tc_max_depth;
696 }
697 #endif
698 tc = TC_LOOKUP(ts->ts_lockobj);
699 LIST_INSERT_HEAD(&tc->tc_turnstiles, ts, ts_hash);
700 KASSERT(TAILQ_EMPTY(&ts->ts_pending),
701 ("thread's turnstile has pending threads"));
702 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]),
703 ("thread's turnstile has exclusive waiters"));
704 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]),
705 ("thread's turnstile has shared waiters"));
706 KASSERT(LIST_EMPTY(&ts->ts_free),
707 ("thread's turnstile has a non-empty free list"));
708 MPASS(ts->ts_lockobj != NULL);
709 mtx_lock_spin(&td_contested_lock);
710 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
711 turnstile_setowner(ts, owner);
712 mtx_unlock_spin(&td_contested_lock);
713 } else {
714 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq)
715 if (td1->td_priority > td->td_priority)
716 break;
717 mtx_lock_spin(&td_contested_lock);
718 if (td1 != NULL)
719 TAILQ_INSERT_BEFORE(td1, td, td_lockq);
720 else
721 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
722 MPASS(owner == ts->ts_owner);
723 mtx_unlock_spin(&td_contested_lock);
724 MPASS(td->td_turnstile != NULL);
725 LIST_INSERT_HEAD(&ts->ts_free, td->td_turnstile, ts_hash);
726 }
727 thread_lock(td);
728 thread_lock_set(td, &ts->ts_lock);
729 td->td_turnstile = NULL;
730
731 /* Save who we are blocked on and switch. */
732 lock = ts->ts_lockobj;
733 td->td_tsqueue = queue;
734 td->td_blocked = ts;
735 td->td_lockname = lock->lo_name;
736 TD_SET_LOCK(td);
737 mtx_unlock_spin(&tc->tc_lock);
738 propagate_priority(td);
739
740 if (LOCK_LOG_TEST(lock, 0))
741 CTR4(KTR_LOCK, "%s: td %d blocked on [%p] %s", __func__,
742 td->td_tid, lock, lock->lo_name);
743
744 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
745 mi_switch(SW_VOL | SWT_TURNSTILE, NULL);
746
747 if (LOCK_LOG_TEST(lock, 0))
748 CTR4(KTR_LOCK, "%s: td %d free from blocked on [%p] %s",
749 __func__, td->td_tid, lock, lock->lo_name);
750 thread_unlock(td);
751 }
752
753 /*
754 * Pick the highest priority thread on this turnstile and put it on the
755 * pending list. This must be called with the turnstile chain locked.
756 */
757 int
758 turnstile_signal(struct turnstile *ts, int queue)
759 {
760 struct turnstile_chain *tc;
761 struct thread *td;
762 int empty;
763
764 MPASS(ts != NULL);
765 mtx_assert(&ts->ts_lock, MA_OWNED);
766 MPASS(curthread->td_proc->p_magic == P_MAGIC);
767 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
768 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
769
770 /*
771 * Pick the highest priority thread blocked on this lock and
772 * move it to the pending list.
773 */
774 td = TAILQ_FIRST(&ts->ts_blocked[queue]);
775 MPASS(td->td_proc->p_magic == P_MAGIC);
776 mtx_lock_spin(&td_contested_lock);
777 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq);
778 mtx_unlock_spin(&td_contested_lock);
779 TAILQ_INSERT_TAIL(&ts->ts_pending, td, td_lockq);
780
781 /*
782 * If the turnstile is now empty, remove it from its chain and
783 * give it to the about-to-be-woken thread. Otherwise take a
784 * turnstile from the free list and give it to the thread.
785 */
786 empty = TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) &&
787 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]);
788 if (empty) {
789 tc = TC_LOOKUP(ts->ts_lockobj);
790 mtx_assert(&tc->tc_lock, MA_OWNED);
791 MPASS(LIST_EMPTY(&ts->ts_free));
792 #ifdef TURNSTILE_PROFILING
793 tc->tc_depth--;
794 #endif
795 } else
796 ts = LIST_FIRST(&ts->ts_free);
797 MPASS(ts != NULL);
798 LIST_REMOVE(ts, ts_hash);
799 td->td_turnstile = ts;
800
801 return (empty);
802 }
803
804 /*
805 * Put all blocked threads on the pending list. This must be called with
806 * the turnstile chain locked.
807 */
808 void
809 turnstile_broadcast(struct turnstile *ts, int queue)
810 {
811 struct turnstile_chain *tc;
812 struct turnstile *ts1;
813 struct thread *td;
814
815 MPASS(ts != NULL);
816 mtx_assert(&ts->ts_lock, MA_OWNED);
817 MPASS(curthread->td_proc->p_magic == P_MAGIC);
818 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
819 /*
820 * We must have the chain locked so that we can remove the empty
821 * turnstile from the hash queue.
822 */
823 tc = TC_LOOKUP(ts->ts_lockobj);
824 mtx_assert(&tc->tc_lock, MA_OWNED);
825 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
826
827 /*
828 * Transfer the blocked list to the pending list.
829 */
830 mtx_lock_spin(&td_contested_lock);
831 TAILQ_CONCAT(&ts->ts_pending, &ts->ts_blocked[queue], td_lockq);
832 mtx_unlock_spin(&td_contested_lock);
833
834 /*
835 * Give a turnstile to each thread. The last thread gets
836 * this turnstile if the turnstile is empty.
837 */
838 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq) {
839 if (LIST_EMPTY(&ts->ts_free)) {
840 MPASS(TAILQ_NEXT(td, td_lockq) == NULL);
841 ts1 = ts;
842 #ifdef TURNSTILE_PROFILING
843 tc->tc_depth--;
844 #endif
845 } else
846 ts1 = LIST_FIRST(&ts->ts_free);
847 MPASS(ts1 != NULL);
848 LIST_REMOVE(ts1, ts_hash);
849 td->td_turnstile = ts1;
850 }
851 }
852
853 /*
854 * Wakeup all threads on the pending list and adjust the priority of the
855 * current thread appropriately. This must be called with the turnstile
856 * chain locked.
857 */
858 void
859 turnstile_unpend(struct turnstile *ts, int owner_type)
860 {
861 TAILQ_HEAD( ,thread) pending_threads;
862 struct turnstile *nts;
863 struct thread *td;
864 u_char cp, pri;
865
866 MPASS(ts != NULL);
867 mtx_assert(&ts->ts_lock, MA_OWNED);
868 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
869 MPASS(!TAILQ_EMPTY(&ts->ts_pending));
870
871 /*
872 * Move the list of pending threads out of the turnstile and
873 * into a local variable.
874 */
875 TAILQ_INIT(&pending_threads);
876 TAILQ_CONCAT(&pending_threads, &ts->ts_pending, td_lockq);
877 #ifdef INVARIANTS
878 if (TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) &&
879 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]))
880 ts->ts_lockobj = NULL;
881 #endif
882 /*
883 * Adjust the priority of curthread based on other contested
884 * locks it owns. Don't lower the priority below the base
885 * priority however.
886 */
887 td = curthread;
888 pri = PRI_MAX;
889 thread_lock(td);
890 mtx_lock_spin(&td_contested_lock);
891 /*
892 * Remove the turnstile from this thread's list of contested locks
893 * since this thread doesn't own it anymore. New threads will
894 * not be blocking on the turnstile until it is claimed by a new
895 * owner. There might not be a current owner if this is a shared
896 * lock.
897 */
898 if (ts->ts_owner != NULL) {
899 ts->ts_owner = NULL;
900 LIST_REMOVE(ts, ts_link);
901 }
902 LIST_FOREACH(nts, &td->td_contested, ts_link) {
903 cp = turnstile_first_waiter(nts)->td_priority;
904 if (cp < pri)
905 pri = cp;
906 }
907 mtx_unlock_spin(&td_contested_lock);
908 sched_unlend_prio(td, pri);
909 thread_unlock(td);
910 /*
911 * Wake up all the pending threads. If a thread is not blocked
912 * on a lock, then it is currently executing on another CPU in
913 * turnstile_wait() or sitting on a run queue waiting to resume
914 * in turnstile_wait(). Set a flag to force it to try to acquire
915 * the lock again instead of blocking.
916 */
917 while (!TAILQ_EMPTY(&pending_threads)) {
918 td = TAILQ_FIRST(&pending_threads);
919 TAILQ_REMOVE(&pending_threads, td, td_lockq);
920 thread_lock(td);
921 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
922 MPASS(td->td_proc->p_magic == P_MAGIC);
923 MPASS(TD_ON_LOCK(td));
924 TD_CLR_LOCK(td);
925 MPASS(TD_CAN_RUN(td));
926 td->td_blocked = NULL;
927 td->td_lockname = NULL;
928 #ifdef INVARIANTS
929 td->td_tsqueue = 0xff;
930 #endif
931 sched_add(td, SRQ_BORING);
932 thread_unlock(td);
933 }
934 mtx_unlock_spin(&ts->ts_lock);
935 }
936
937 /*
938 * Give up ownership of a turnstile. This must be called with the
939 * turnstile chain locked.
940 */
941 void
942 turnstile_disown(struct turnstile *ts)
943 {
944 struct thread *td;
945 u_char cp, pri;
946
947 MPASS(ts != NULL);
948 mtx_assert(&ts->ts_lock, MA_OWNED);
949 MPASS(ts->ts_owner == curthread);
950 MPASS(TAILQ_EMPTY(&ts->ts_pending));
951 MPASS(!TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) ||
952 !TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]));
953
954 /*
955 * Remove the turnstile from this thread's list of contested locks
956 * since this thread doesn't own it anymore. New threads will
957 * not be blocking on the turnstile until it is claimed by a new
958 * owner.
959 */
960 mtx_lock_spin(&td_contested_lock);
961 ts->ts_owner = NULL;
962 LIST_REMOVE(ts, ts_link);
963 mtx_unlock_spin(&td_contested_lock);
964
965 /*
966 * Adjust the priority of curthread based on other contested
967 * locks it owns. Don't lower the priority below the base
968 * priority however.
969 */
970 td = curthread;
971 pri = PRI_MAX;
972 thread_lock(td);
973 mtx_unlock_spin(&ts->ts_lock);
974 mtx_lock_spin(&td_contested_lock);
975 LIST_FOREACH(ts, &td->td_contested, ts_link) {
976 cp = turnstile_first_waiter(ts)->td_priority;
977 if (cp < pri)
978 pri = cp;
979 }
980 mtx_unlock_spin(&td_contested_lock);
981 sched_unlend_prio(td, pri);
982 thread_unlock(td);
983 }
984
985 /*
986 * Return the first thread in a turnstile.
987 */
988 struct thread *
989 turnstile_head(struct turnstile *ts, int queue)
990 {
991 #ifdef INVARIANTS
992
993 MPASS(ts != NULL);
994 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
995 mtx_assert(&ts->ts_lock, MA_OWNED);
996 #endif
997 return (TAILQ_FIRST(&ts->ts_blocked[queue]));
998 }
999
1000 /*
1001 * Returns true if a sub-queue of a turnstile is empty.
1002 */
1003 int
1004 turnstile_empty(struct turnstile *ts, int queue)
1005 {
1006 #ifdef INVARIANTS
1007
1008 MPASS(ts != NULL);
1009 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
1010 mtx_assert(&ts->ts_lock, MA_OWNED);
1011 #endif
1012 return (TAILQ_EMPTY(&ts->ts_blocked[queue]));
1013 }
1014
1015 #ifdef DDB
1016 static void
1017 print_thread(struct thread *td, const char *prefix)
1018 {
1019
1020 db_printf("%s%p (tid %d, pid %d, \"%s\")\n", prefix, td, td->td_tid,
1021 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name :
1022 td->td_name);
1023 }
1024
1025 static void
1026 print_queue(struct threadqueue *queue, const char *header, const char *prefix)
1027 {
1028 struct thread *td;
1029
1030 db_printf("%s:\n", header);
1031 if (TAILQ_EMPTY(queue)) {
1032 db_printf("%sempty\n", prefix);
1033 return;
1034 }
1035 TAILQ_FOREACH(td, queue, td_lockq) {
1036 print_thread(td, prefix);
1037 }
1038 }
1039
1040 DB_SHOW_COMMAND(turnstile, db_show_turnstile)
1041 {
1042 struct turnstile_chain *tc;
1043 struct turnstile *ts;
1044 struct lock_object *lock;
1045 int i;
1046
1047 if (!have_addr)
1048 return;
1049
1050 /*
1051 * First, see if there is an active turnstile for the lock indicated
1052 * by the address.
1053 */
1054 lock = (struct lock_object *)addr;
1055 tc = TC_LOOKUP(lock);
1056 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
1057 if (ts->ts_lockobj == lock)
1058 goto found;
1059
1060 /*
1061 * Second, see if there is an active turnstile at the address
1062 * indicated.
1063 */
1064 for (i = 0; i < TC_TABLESIZE; i++)
1065 LIST_FOREACH(ts, &turnstile_chains[i].tc_turnstiles, ts_hash) {
1066 if (ts == (struct turnstile *)addr)
1067 goto found;
1068 }
1069
1070 db_printf("Unable to locate a turnstile via %p\n", (void *)addr);
1071 return;
1072 found:
1073 lock = ts->ts_lockobj;
1074 db_printf("Lock: %p - (%s) %s\n", lock, LOCK_CLASS(lock)->lc_name,
1075 lock->lo_name);
1076 if (ts->ts_owner)
1077 print_thread(ts->ts_owner, "Lock Owner: ");
1078 else
1079 db_printf("Lock Owner: none\n");
1080 print_queue(&ts->ts_blocked[TS_SHARED_QUEUE], "Shared Waiters", "\t");
1081 print_queue(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE], "Exclusive Waiters",
1082 "\t");
1083 print_queue(&ts->ts_pending, "Pending Threads", "\t");
1084
1085 }
1086
1087 /*
1088 * Show all the threads a particular thread is waiting on based on
1089 * non-sleepable and non-spin locks.
1090 */
1091 static void
1092 print_lockchain(struct thread *td, const char *prefix)
1093 {
1094 struct lock_object *lock;
1095 struct lock_class *class;
1096 struct turnstile *ts;
1097
1098 /*
1099 * Follow the chain. We keep walking as long as the thread is
1100 * blocked on a turnstile that has an owner.
1101 */
1102 while (!db_pager_quit) {
1103 db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid,
1104 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name :
1105 td->td_name);
1106 switch (td->td_state) {
1107 case TDS_INACTIVE:
1108 db_printf("is inactive\n");
1109 return;
1110 case TDS_CAN_RUN:
1111 db_printf("can run\n");
1112 return;
1113 case TDS_RUNQ:
1114 db_printf("is on a run queue\n");
1115 return;
1116 case TDS_RUNNING:
1117 db_printf("running on CPU %d\n", td->td_oncpu);
1118 return;
1119 case TDS_INHIBITED:
1120 if (TD_ON_LOCK(td)) {
1121 ts = td->td_blocked;
1122 lock = ts->ts_lockobj;
1123 class = LOCK_CLASS(lock);
1124 db_printf("blocked on lock %p (%s) \"%s\"\n",
1125 lock, class->lc_name, lock->lo_name);
1126 if (ts->ts_owner == NULL)
1127 return;
1128 td = ts->ts_owner;
1129 break;
1130 }
1131 db_printf("inhibited\n");
1132 return;
1133 default:
1134 db_printf("??? (%#x)\n", td->td_state);
1135 return;
1136 }
1137 }
1138 }
1139
1140 DB_SHOW_COMMAND(lockchain, db_show_lockchain)
1141 {
1142 struct thread *td;
1143
1144 /* Figure out which thread to start with. */
1145 if (have_addr)
1146 td = db_lookup_thread(addr, TRUE);
1147 else
1148 td = kdb_thread;
1149
1150 print_lockchain(td, "");
1151 }
1152
1153 DB_SHOW_ALL_COMMAND(chains, db_show_allchains)
1154 {
1155 struct thread *td;
1156 struct proc *p;
1157 int i;
1158
1159 i = 1;
1160 FOREACH_PROC_IN_SYSTEM(p) {
1161 FOREACH_THREAD_IN_PROC(p, td) {
1162 if (TD_ON_LOCK(td) && LIST_EMPTY(&td->td_contested)) {
1163 db_printf("chain %d:\n", i++);
1164 print_lockchain(td, " ");
1165 }
1166 if (db_pager_quit)
1167 return;
1168 }
1169 }
1170 }
1171 DB_SHOW_ALIAS(allchains, db_show_allchains)
1172
1173 /*
1174 * Show all the threads a particular thread is waiting on based on
1175 * sleepable locks.
1176 */
1177 static void
1178 print_sleepchain(struct thread *td, const char *prefix)
1179 {
1180 struct thread *owner;
1181
1182 /*
1183 * Follow the chain. We keep walking as long as the thread is
1184 * blocked on a sleep lock that has an owner.
1185 */
1186 while (!db_pager_quit) {
1187 db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid,
1188 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name :
1189 td->td_name);
1190 switch (td->td_state) {
1191 case TDS_INACTIVE:
1192 db_printf("is inactive\n");
1193 return;
1194 case TDS_CAN_RUN:
1195 db_printf("can run\n");
1196 return;
1197 case TDS_RUNQ:
1198 db_printf("is on a run queue\n");
1199 return;
1200 case TDS_RUNNING:
1201 db_printf("running on CPU %d\n", td->td_oncpu);
1202 return;
1203 case TDS_INHIBITED:
1204 if (TD_ON_SLEEPQ(td)) {
1205 if (lockmgr_chain(td, &owner) ||
1206 sx_chain(td, &owner)) {
1207 if (owner == NULL)
1208 return;
1209 td = owner;
1210 break;
1211 }
1212 db_printf("sleeping on %p \"%s\"\n",
1213 td->td_wchan, td->td_wmesg);
1214 return;
1215 }
1216 db_printf("inhibited\n");
1217 return;
1218 default:
1219 db_printf("??? (%#x)\n", td->td_state);
1220 return;
1221 }
1222 }
1223 }
1224
1225 DB_SHOW_COMMAND(sleepchain, db_show_sleepchain)
1226 {
1227 struct thread *td;
1228
1229 /* Figure out which thread to start with. */
1230 if (have_addr)
1231 td = db_lookup_thread(addr, TRUE);
1232 else
1233 td = kdb_thread;
1234
1235 print_sleepchain(td, "");
1236 }
1237
1238 static void print_waiters(struct turnstile *ts, int indent);
1239
1240 static void
1241 print_waiter(struct thread *td, int indent)
1242 {
1243 struct turnstile *ts;
1244 int i;
1245
1246 if (db_pager_quit)
1247 return;
1248 for (i = 0; i < indent; i++)
1249 db_printf(" ");
1250 print_thread(td, "thread ");
1251 LIST_FOREACH(ts, &td->td_contested, ts_link)
1252 print_waiters(ts, indent + 1);
1253 }
1254
1255 static void
1256 print_waiters(struct turnstile *ts, int indent)
1257 {
1258 struct lock_object *lock;
1259 struct lock_class *class;
1260 struct thread *td;
1261 int i;
1262
1263 if (db_pager_quit)
1264 return;
1265 lock = ts->ts_lockobj;
1266 class = LOCK_CLASS(lock);
1267 for (i = 0; i < indent; i++)
1268 db_printf(" ");
1269 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name, lock->lo_name);
1270 TAILQ_FOREACH(td, &ts->ts_blocked[TS_EXCLUSIVE_QUEUE], td_lockq)
1271 print_waiter(td, indent + 1);
1272 TAILQ_FOREACH(td, &ts->ts_blocked[TS_SHARED_QUEUE], td_lockq)
1273 print_waiter(td, indent + 1);
1274 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq)
1275 print_waiter(td, indent + 1);
1276 }
1277
1278 DB_SHOW_COMMAND(locktree, db_show_locktree)
1279 {
1280 struct lock_object *lock;
1281 struct lock_class *class;
1282 struct turnstile_chain *tc;
1283 struct turnstile *ts;
1284
1285 if (!have_addr)
1286 return;
1287 lock = (struct lock_object *)addr;
1288 tc = TC_LOOKUP(lock);
1289 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
1290 if (ts->ts_lockobj == lock)
1291 break;
1292 if (ts == NULL) {
1293 class = LOCK_CLASS(lock);
1294 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name,
1295 lock->lo_name);
1296 } else
1297 print_waiters(ts, 0);
1298 }
1299 #endif
Cache object: 0c511b509d99d0dbcd7832a34bc5494d
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