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