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("$FreeBSD$"); 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 #ifdef INVARIANTS 400 NULL, turnstile_dtor, turnstile_init, turnstile_fini, 401 UMA_ALIGN_CACHE, 0); 402 #else 403 NULL, NULL, turnstile_init, turnstile_fini, UMA_ALIGN_CACHE, 0); 404 #endif 405 thread0.td_turnstile = turnstile_alloc(); 406 } 407 SYSINIT(turnstile0, SI_SUB_LOCK, SI_ORDER_ANY, init_turnstile0, NULL); 408 409 /* 410 * Update a thread on the turnstile list after it's priority has been changed. 411 * The old priority is passed in as an argument. 412 */ 413 void 414 turnstile_adjust(struct thread *td, u_char oldpri) 415 { 416 struct turnstile *ts; 417 418 MPASS(TD_ON_LOCK(td)); 419 420 /* 421 * Pick up the lock that td is blocked on. 422 */ 423 ts = td->td_blocked; 424 MPASS(ts != NULL); 425 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 426 mtx_assert(&ts->ts_lock, MA_OWNED); 427 428 /* Resort the turnstile on the list. */ 429 if (!turnstile_adjust_thread(ts, td)) 430 return; 431 /* 432 * If our priority was lowered and we are at the head of the 433 * turnstile, then propagate our new priority up the chain. 434 * Note that we currently don't try to revoke lent priorities 435 * when our priority goes up. 436 */ 437 MPASS(td->td_tsqueue == TS_EXCLUSIVE_QUEUE || 438 td->td_tsqueue == TS_SHARED_QUEUE); 439 if (td == TAILQ_FIRST(&ts->ts_blocked[td->td_tsqueue]) && 440 td->td_priority < oldpri) { 441 propagate_priority(td); 442 } 443 } 444 445 /* 446 * Set the owner of the lock this turnstile is attached to. 447 */ 448 static void 449 turnstile_setowner(struct turnstile *ts, struct thread *owner) 450 { 451 452 mtx_assert(&td_contested_lock, MA_OWNED); 453 MPASS(ts->ts_owner == NULL); 454 455 /* A shared lock might not have an owner. */ 456 if (owner == NULL) 457 return; 458 459 MPASS(owner->td_proc->p_magic == P_MAGIC); 460 ts->ts_owner = owner; 461 LIST_INSERT_HEAD(&owner->td_contested, ts, ts_link); 462 } 463 464 #ifdef INVARIANTS 465 /* 466 * UMA zone item deallocator. 467 */ 468 static void 469 turnstile_dtor(void *mem, int size, void *arg) 470 { 471 struct turnstile *ts; 472 473 ts = mem; 474 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE])); 475 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE])); 476 MPASS(TAILQ_EMPTY(&ts->ts_pending)); 477 } 478 #endif 479 480 /* 481 * UMA zone item initializer. 482 */ 483 static int 484 turnstile_init(void *mem, int size, int flags) 485 { 486 struct turnstile *ts; 487 488 bzero(mem, size); 489 ts = mem; 490 TAILQ_INIT(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]); 491 TAILQ_INIT(&ts->ts_blocked[TS_SHARED_QUEUE]); 492 TAILQ_INIT(&ts->ts_pending); 493 LIST_INIT(&ts->ts_free); 494 mtx_init(&ts->ts_lock, "turnstile lock", NULL, MTX_SPIN | MTX_RECURSE); 495 return (0); 496 } 497 498 static void 499 turnstile_fini(void *mem, int size) 500 { 501 struct turnstile *ts; 502 503 ts = mem; 504 mtx_destroy(&ts->ts_lock); 505 } 506 507 /* 508 * Get a turnstile for a new thread. 509 */ 510 struct turnstile * 511 turnstile_alloc(void) 512 { 513 514 return (uma_zalloc(turnstile_zone, M_WAITOK)); 515 } 516 517 /* 518 * Free a turnstile when a thread is destroyed. 519 */ 520 void 521 turnstile_free(struct turnstile *ts) 522 { 523 524 uma_zfree(turnstile_zone, ts); 525 } 526 527 /* 528 * Lock the turnstile chain associated with the specified lock. 529 */ 530 void 531 turnstile_chain_lock(struct lock_object *lock) 532 { 533 struct turnstile_chain *tc; 534 535 tc = TC_LOOKUP(lock); 536 mtx_lock_spin(&tc->tc_lock); 537 } 538 539 struct turnstile * 540 turnstile_trywait(struct lock_object *lock) 541 { 542 struct turnstile_chain *tc; 543 struct turnstile *ts; 544 545 tc = TC_LOOKUP(lock); 546 mtx_lock_spin(&tc->tc_lock); 547 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash) 548 if (ts->ts_lockobj == lock) { 549 mtx_lock_spin(&ts->ts_lock); 550 return (ts); 551 } 552 553 ts = curthread->td_turnstile; 554 MPASS(ts != NULL); 555 mtx_lock_spin(&ts->ts_lock); 556 KASSERT(ts->ts_lockobj == NULL, ("stale ts_lockobj pointer")); 557 ts->ts_lockobj = lock; 558 559 return (ts); 560 } 561 562 void 563 turnstile_cancel(struct turnstile *ts) 564 { 565 struct turnstile_chain *tc; 566 struct lock_object *lock; 567 568 mtx_assert(&ts->ts_lock, MA_OWNED); 569 570 mtx_unlock_spin(&ts->ts_lock); 571 lock = ts->ts_lockobj; 572 if (ts == curthread->td_turnstile) 573 ts->ts_lockobj = NULL; 574 tc = TC_LOOKUP(lock); 575 mtx_unlock_spin(&tc->tc_lock); 576 } 577 578 /* 579 * Look up the turnstile for a lock in the hash table locking the associated 580 * turnstile chain along the way. If no turnstile is found in the hash 581 * table, NULL is returned. 582 */ 583 struct turnstile * 584 turnstile_lookup(struct lock_object *lock) 585 { 586 struct turnstile_chain *tc; 587 struct turnstile *ts; 588 589 tc = TC_LOOKUP(lock); 590 mtx_assert(&tc->tc_lock, MA_OWNED); 591 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash) 592 if (ts->ts_lockobj == lock) { 593 mtx_lock_spin(&ts->ts_lock); 594 return (ts); 595 } 596 return (NULL); 597 } 598 599 /* 600 * Unlock the turnstile chain associated with a given lock. 601 */ 602 void 603 turnstile_chain_unlock(struct lock_object *lock) 604 { 605 struct turnstile_chain *tc; 606 607 tc = TC_LOOKUP(lock); 608 mtx_unlock_spin(&tc->tc_lock); 609 } 610 611 /* 612 * Return a pointer to the thread waiting on this turnstile with the 613 * most important priority or NULL if the turnstile has no waiters. 614 */ 615 static struct thread * 616 turnstile_first_waiter(struct turnstile *ts) 617 { 618 struct thread *std, *xtd; 619 620 std = TAILQ_FIRST(&ts->ts_blocked[TS_SHARED_QUEUE]); 621 xtd = TAILQ_FIRST(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]); 622 if (xtd == NULL || (std != NULL && std->td_priority < xtd->td_priority)) 623 return (std); 624 return (xtd); 625 } 626 627 /* 628 * Take ownership of a turnstile and adjust the priority of the new 629 * owner appropriately. 630 */ 631 void 632 turnstile_claim(struct turnstile *ts) 633 { 634 struct thread *td, *owner; 635 struct turnstile_chain *tc; 636 637 mtx_assert(&ts->ts_lock, MA_OWNED); 638 MPASS(ts != curthread->td_turnstile); 639 640 owner = curthread; 641 mtx_lock_spin(&td_contested_lock); 642 turnstile_setowner(ts, owner); 643 mtx_unlock_spin(&td_contested_lock); 644 645 td = turnstile_first_waiter(ts); 646 MPASS(td != NULL); 647 MPASS(td->td_proc->p_magic == P_MAGIC); 648 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 649 650 /* 651 * Update the priority of the new owner if needed. 652 */ 653 thread_lock(owner); 654 if (td->td_priority < owner->td_priority) 655 sched_lend_prio(owner, td->td_priority); 656 thread_unlock(owner); 657 tc = TC_LOOKUP(ts->ts_lockobj); 658 mtx_unlock_spin(&ts->ts_lock); 659 mtx_unlock_spin(&tc->tc_lock); 660 } 661 662 /* 663 * Block the current thread on the turnstile assicated with 'lock'. This 664 * function will context switch and not return until this thread has been 665 * woken back up. This function must be called with the appropriate 666 * turnstile chain locked and will return with it unlocked. 667 */ 668 void 669 turnstile_wait(struct turnstile *ts, struct thread *owner, int queue) 670 { 671 struct turnstile_chain *tc; 672 struct thread *td, *td1; 673 struct lock_object *lock; 674 675 td = curthread; 676 mtx_assert(&ts->ts_lock, MA_OWNED); 677 if (owner) 678 MPASS(owner->td_proc->p_magic == P_MAGIC); 679 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 680 681 /* 682 * If the lock does not already have a turnstile, use this thread's 683 * turnstile. Otherwise insert the current thread into the 684 * turnstile already in use by this lock. 685 */ 686 tc = TC_LOOKUP(ts->ts_lockobj); 687 if (ts == td->td_turnstile) { 688 mtx_assert(&tc->tc_lock, MA_OWNED); 689 #ifdef TURNSTILE_PROFILING 690 tc->tc_depth++; 691 if (tc->tc_depth > tc->tc_max_depth) { 692 tc->tc_max_depth = tc->tc_depth; 693 if (tc->tc_max_depth > turnstile_max_depth) 694 turnstile_max_depth = tc->tc_max_depth; 695 } 696 #endif 697 tc = TC_LOOKUP(ts->ts_lockobj); 698 LIST_INSERT_HEAD(&tc->tc_turnstiles, ts, ts_hash); 699 KASSERT(TAILQ_EMPTY(&ts->ts_pending), 700 ("thread's turnstile has pending threads")); 701 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]), 702 ("thread's turnstile has exclusive waiters")); 703 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]), 704 ("thread's turnstile has shared waiters")); 705 KASSERT(LIST_EMPTY(&ts->ts_free), 706 ("thread's turnstile has a non-empty free list")); 707 MPASS(ts->ts_lockobj != NULL); 708 mtx_lock_spin(&td_contested_lock); 709 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq); 710 turnstile_setowner(ts, owner); 711 mtx_unlock_spin(&td_contested_lock); 712 } else { 713 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq) 714 if (td1->td_priority > td->td_priority) 715 break; 716 mtx_lock_spin(&td_contested_lock); 717 if (td1 != NULL) 718 TAILQ_INSERT_BEFORE(td1, td, td_lockq); 719 else 720 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq); 721 MPASS(owner == ts->ts_owner); 722 mtx_unlock_spin(&td_contested_lock); 723 MPASS(td->td_turnstile != NULL); 724 LIST_INSERT_HEAD(&ts->ts_free, td->td_turnstile, ts_hash); 725 } 726 thread_lock(td); 727 thread_lock_set(td, &ts->ts_lock); 728 td->td_turnstile = NULL; 729 730 /* Save who we are blocked on and switch. */ 731 lock = ts->ts_lockobj; 732 td->td_tsqueue = queue; 733 td->td_blocked = ts; 734 td->td_lockname = lock->lo_name; 735 TD_SET_LOCK(td); 736 mtx_unlock_spin(&tc->tc_lock); 737 propagate_priority(td); 738 739 if (LOCK_LOG_TEST(lock, 0)) 740 CTR4(KTR_LOCK, "%s: td %d blocked on [%p] %s", __func__, 741 td->td_tid, lock, lock->lo_name); 742 743 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 744 mi_switch(SW_VOL | SWT_TURNSTILE, NULL); 745 746 if (LOCK_LOG_TEST(lock, 0)) 747 CTR4(KTR_LOCK, "%s: td %d free from blocked on [%p] %s", 748 __func__, td->td_tid, lock, lock->lo_name); 749 thread_unlock(td); 750 } 751 752 /* 753 * Pick the highest priority thread on this turnstile and put it on the 754 * pending list. This must be called with the turnstile chain locked. 755 */ 756 int 757 turnstile_signal(struct turnstile *ts, int queue) 758 { 759 struct turnstile_chain *tc; 760 struct thread *td; 761 int empty; 762 763 MPASS(ts != NULL); 764 mtx_assert(&ts->ts_lock, MA_OWNED); 765 MPASS(curthread->td_proc->p_magic == P_MAGIC); 766 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL); 767 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 768 769 /* 770 * Pick the highest priority thread blocked on this lock and 771 * move it to the pending list. 772 */ 773 td = TAILQ_FIRST(&ts->ts_blocked[queue]); 774 MPASS(td->td_proc->p_magic == P_MAGIC); 775 mtx_lock_spin(&td_contested_lock); 776 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq); 777 mtx_unlock_spin(&td_contested_lock); 778 TAILQ_INSERT_TAIL(&ts->ts_pending, td, td_lockq); 779 780 /* 781 * If the turnstile is now empty, remove it from its chain and 782 * give it to the about-to-be-woken thread. Otherwise take a 783 * turnstile from the free list and give it to the thread. 784 */ 785 empty = TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) && 786 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]); 787 if (empty) { 788 tc = TC_LOOKUP(ts->ts_lockobj); 789 mtx_assert(&tc->tc_lock, MA_OWNED); 790 MPASS(LIST_EMPTY(&ts->ts_free)); 791 #ifdef TURNSTILE_PROFILING 792 tc->tc_depth--; 793 #endif 794 } else 795 ts = LIST_FIRST(&ts->ts_free); 796 MPASS(ts != NULL); 797 LIST_REMOVE(ts, ts_hash); 798 td->td_turnstile = ts; 799 800 return (empty); 801 } 802 803 /* 804 * Put all blocked threads on the pending list. This must be called with 805 * the turnstile chain locked. 806 */ 807 void 808 turnstile_broadcast(struct turnstile *ts, int queue) 809 { 810 struct turnstile_chain *tc; 811 struct turnstile *ts1; 812 struct thread *td; 813 814 MPASS(ts != NULL); 815 mtx_assert(&ts->ts_lock, MA_OWNED); 816 MPASS(curthread->td_proc->p_magic == P_MAGIC); 817 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL); 818 /* 819 * We must have the chain locked so that we can remove the empty 820 * turnstile from the hash queue. 821 */ 822 tc = TC_LOOKUP(ts->ts_lockobj); 823 mtx_assert(&tc->tc_lock, MA_OWNED); 824 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 825 826 /* 827 * Transfer the blocked list to the pending list. 828 */ 829 mtx_lock_spin(&td_contested_lock); 830 TAILQ_CONCAT(&ts->ts_pending, &ts->ts_blocked[queue], td_lockq); 831 mtx_unlock_spin(&td_contested_lock); 832 833 /* 834 * Give a turnstile to each thread. The last thread gets 835 * this turnstile if the turnstile is empty. 836 */ 837 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq) { 838 if (LIST_EMPTY(&ts->ts_free)) { 839 MPASS(TAILQ_NEXT(td, td_lockq) == NULL); 840 ts1 = ts; 841 #ifdef TURNSTILE_PROFILING 842 tc->tc_depth--; 843 #endif 844 } else 845 ts1 = LIST_FIRST(&ts->ts_free); 846 MPASS(ts1 != NULL); 847 LIST_REMOVE(ts1, ts_hash); 848 td->td_turnstile = ts1; 849 } 850 } 851 852 /* 853 * Wakeup all threads on the pending list and adjust the priority of the 854 * current thread appropriately. This must be called with the turnstile 855 * chain locked. 856 */ 857 void 858 turnstile_unpend(struct turnstile *ts, int owner_type) 859 { 860 TAILQ_HEAD( ,thread) pending_threads; 861 struct turnstile *nts; 862 struct thread *td; 863 u_char cp, pri; 864 865 MPASS(ts != NULL); 866 mtx_assert(&ts->ts_lock, MA_OWNED); 867 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL); 868 MPASS(!TAILQ_EMPTY(&ts->ts_pending)); 869 870 /* 871 * Move the list of pending threads out of the turnstile and 872 * into a local variable. 873 */ 874 TAILQ_INIT(&pending_threads); 875 TAILQ_CONCAT(&pending_threads, &ts->ts_pending, td_lockq); 876 #ifdef INVARIANTS 877 if (TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) && 878 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE])) 879 ts->ts_lockobj = NULL; 880 #endif 881 /* 882 * Adjust the priority of curthread based on other contested 883 * locks it owns. Don't lower the priority below the base 884 * priority however. 885 */ 886 td = curthread; 887 pri = PRI_MAX; 888 thread_lock(td); 889 mtx_lock_spin(&td_contested_lock); 890 /* 891 * Remove the turnstile from this thread's list of contested locks 892 * since this thread doesn't own it anymore. New threads will 893 * not be blocking on the turnstile until it is claimed by a new 894 * owner. There might not be a current owner if this is a shared 895 * lock. 896 */ 897 if (ts->ts_owner != NULL) { 898 ts->ts_owner = NULL; 899 LIST_REMOVE(ts, ts_link); 900 } 901 LIST_FOREACH(nts, &td->td_contested, ts_link) { 902 cp = turnstile_first_waiter(nts)->td_priority; 903 if (cp < pri) 904 pri = cp; 905 } 906 mtx_unlock_spin(&td_contested_lock); 907 sched_unlend_prio(td, pri); 908 thread_unlock(td); 909 /* 910 * Wake up all the pending threads. If a thread is not blocked 911 * on a lock, then it is currently executing on another CPU in 912 * turnstile_wait() or sitting on a run queue waiting to resume 913 * in turnstile_wait(). Set a flag to force it to try to acquire 914 * the lock again instead of blocking. 915 */ 916 while (!TAILQ_EMPTY(&pending_threads)) { 917 td = TAILQ_FIRST(&pending_threads); 918 TAILQ_REMOVE(&pending_threads, td, td_lockq); 919 thread_lock(td); 920 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 921 MPASS(td->td_proc->p_magic == P_MAGIC); 922 MPASS(TD_ON_LOCK(td)); 923 TD_CLR_LOCK(td); 924 MPASS(TD_CAN_RUN(td)); 925 td->td_blocked = NULL; 926 td->td_lockname = NULL; 927 #ifdef INVARIANTS 928 td->td_tsqueue = 0xff; 929 #endif 930 sched_add(td, SRQ_BORING); 931 thread_unlock(td); 932 } 933 mtx_unlock_spin(&ts->ts_lock); 934 } 935 936 /* 937 * Give up ownership of a turnstile. This must be called with the 938 * turnstile chain locked. 939 */ 940 void 941 turnstile_disown(struct turnstile *ts) 942 { 943 struct thread *td; 944 u_char cp, pri; 945 946 MPASS(ts != NULL); 947 mtx_assert(&ts->ts_lock, MA_OWNED); 948 MPASS(ts->ts_owner == curthread); 949 MPASS(TAILQ_EMPTY(&ts->ts_pending)); 950 MPASS(!TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) || 951 !TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE])); 952 953 /* 954 * Remove the turnstile from this thread's list of contested locks 955 * since this thread doesn't own it anymore. New threads will 956 * not be blocking on the turnstile until it is claimed by a new 957 * owner. 958 */ 959 mtx_lock_spin(&td_contested_lock); 960 ts->ts_owner = NULL; 961 LIST_REMOVE(ts, ts_link); 962 mtx_unlock_spin(&td_contested_lock); 963 964 /* 965 * Adjust the priority of curthread based on other contested 966 * locks it owns. Don't lower the priority below the base 967 * priority however. 968 */ 969 td = curthread; 970 pri = PRI_MAX; 971 thread_lock(td); 972 mtx_unlock_spin(&ts->ts_lock); 973 mtx_lock_spin(&td_contested_lock); 974 LIST_FOREACH(ts, &td->td_contested, ts_link) { 975 cp = turnstile_first_waiter(ts)->td_priority; 976 if (cp < pri) 977 pri = cp; 978 } 979 mtx_unlock_spin(&td_contested_lock); 980 sched_unlend_prio(td, pri); 981 thread_unlock(td); 982 } 983 984 /* 985 * Return the first thread in a turnstile. 986 */ 987 struct thread * 988 turnstile_head(struct turnstile *ts, int queue) 989 { 990 #ifdef INVARIANTS 991 992 MPASS(ts != NULL); 993 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 994 mtx_assert(&ts->ts_lock, MA_OWNED); 995 #endif 996 return (TAILQ_FIRST(&ts->ts_blocked[queue])); 997 } 998 999 /* 1000 * Returns true if a sub-queue of a turnstile is empty. 1001 */ 1002 int 1003 turnstile_empty(struct turnstile *ts, int queue) 1004 { 1005 #ifdef INVARIANTS 1006 1007 MPASS(ts != NULL); 1008 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 1009 mtx_assert(&ts->ts_lock, MA_OWNED); 1010 #endif 1011 return (TAILQ_EMPTY(&ts->ts_blocked[queue])); 1012 } 1013 1014 #ifdef DDB 1015 static void 1016 print_thread(struct thread *td, const char *prefix) 1017 { 1018 1019 db_printf("%s%p (tid %d, pid %d, \"%s\")\n", prefix, td, td->td_tid, 1020 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name : 1021 td->td_name); 1022 } 1023 1024 static void 1025 print_queue(struct threadqueue *queue, const char *header, const char *prefix) 1026 { 1027 struct thread *td; 1028 1029 db_printf("%s:\n", header); 1030 if (TAILQ_EMPTY(queue)) { 1031 db_printf("%sempty\n", prefix); 1032 return; 1033 } 1034 TAILQ_FOREACH(td, queue, td_lockq) { 1035 print_thread(td, prefix); 1036 } 1037 } 1038 1039 DB_SHOW_COMMAND(turnstile, db_show_turnstile) 1040 { 1041 struct turnstile_chain *tc; 1042 struct turnstile *ts; 1043 struct lock_object *lock; 1044 int i; 1045 1046 if (!have_addr) 1047 return; 1048 1049 /* 1050 * First, see if there is an active turnstile for the lock indicated 1051 * by the address. 1052 */ 1053 lock = (struct lock_object *)addr; 1054 tc = TC_LOOKUP(lock); 1055 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash) 1056 if (ts->ts_lockobj == lock) 1057 goto found; 1058 1059 /* 1060 * Second, see if there is an active turnstile at the address 1061 * indicated. 1062 */ 1063 for (i = 0; i < TC_TABLESIZE; i++) 1064 LIST_FOREACH(ts, &turnstile_chains[i].tc_turnstiles, ts_hash) { 1065 if (ts == (struct turnstile *)addr) 1066 goto found; 1067 } 1068 1069 db_printf("Unable to locate a turnstile via %p\n", (void *)addr); 1070 return; 1071 found: 1072 lock = ts->ts_lockobj; 1073 db_printf("Lock: %p - (%s) %s\n", lock, LOCK_CLASS(lock)->lc_name, 1074 lock->lo_name); 1075 if (ts->ts_owner) 1076 print_thread(ts->ts_owner, "Lock Owner: "); 1077 else 1078 db_printf("Lock Owner: none\n"); 1079 print_queue(&ts->ts_blocked[TS_SHARED_QUEUE], "Shared Waiters", "\t"); 1080 print_queue(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE], "Exclusive Waiters", 1081 "\t"); 1082 print_queue(&ts->ts_pending, "Pending Threads", "\t"); 1083 1084 } 1085 1086 /* 1087 * Show all the threads a particular thread is waiting on based on 1088 * non-sleepable and non-spin locks. 1089 */ 1090 static void 1091 print_lockchain(struct thread *td, const char *prefix) 1092 { 1093 struct lock_object *lock; 1094 struct lock_class *class; 1095 struct turnstile *ts; 1096 1097 /* 1098 * Follow the chain. We keep walking as long as the thread is 1099 * blocked on a turnstile that has an owner. 1100 */ 1101 while (!db_pager_quit) { 1102 db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid, 1103 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name : 1104 td->td_name); 1105 switch (td->td_state) { 1106 case TDS_INACTIVE: 1107 db_printf("is inactive\n"); 1108 return; 1109 case TDS_CAN_RUN: 1110 db_printf("can run\n"); 1111 return; 1112 case TDS_RUNQ: 1113 db_printf("is on a run queue\n"); 1114 return; 1115 case TDS_RUNNING: 1116 db_printf("running on CPU %d\n", td->td_oncpu); 1117 return; 1118 case TDS_INHIBITED: 1119 if (TD_ON_LOCK(td)) { 1120 ts = td->td_blocked; 1121 lock = ts->ts_lockobj; 1122 class = LOCK_CLASS(lock); 1123 db_printf("blocked on lock %p (%s) \"%s\"\n", 1124 lock, class->lc_name, lock->lo_name); 1125 if (ts->ts_owner == NULL) 1126 return; 1127 td = ts->ts_owner; 1128 break; 1129 } 1130 db_printf("inhibited\n"); 1131 return; 1132 default: 1133 db_printf("??? (%#x)\n", td->td_state); 1134 return; 1135 } 1136 } 1137 } 1138 1139 DB_SHOW_COMMAND(lockchain, db_show_lockchain) 1140 { 1141 struct thread *td; 1142 1143 /* Figure out which thread to start with. */ 1144 if (have_addr) 1145 td = db_lookup_thread(addr, TRUE); 1146 else 1147 td = kdb_thread; 1148 1149 print_lockchain(td, ""); 1150 } 1151 1152 DB_SHOW_COMMAND(allchains, db_show_allchains) 1153 { 1154 struct thread *td; 1155 struct proc *p; 1156 int i; 1157 1158 i = 1; 1159 FOREACH_PROC_IN_SYSTEM(p) { 1160 FOREACH_THREAD_IN_PROC(p, td) { 1161 if (TD_ON_LOCK(td) && LIST_EMPTY(&td->td_contested)) { 1162 db_printf("chain %d:\n", i++); 1163 print_lockchain(td, " "); 1164 } 1165 if (db_pager_quit) 1166 return; 1167 } 1168 } 1169 } 1170 1171 /* 1172 * Show all the threads a particular thread is waiting on based on 1173 * sleepable locks. 1174 */ 1175 static void 1176 print_sleepchain(struct thread *td, const char *prefix) 1177 { 1178 struct thread *owner; 1179 1180 /* 1181 * Follow the chain. We keep walking as long as the thread is 1182 * blocked on a sleep lock that has an owner. 1183 */ 1184 while (!db_pager_quit) { 1185 db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid, 1186 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name : 1187 td->td_name); 1188 switch (td->td_state) { 1189 case TDS_INACTIVE: 1190 db_printf("is inactive\n"); 1191 return; 1192 case TDS_CAN_RUN: 1193 db_printf("can run\n"); 1194 return; 1195 case TDS_RUNQ: 1196 db_printf("is on a run queue\n"); 1197 return; 1198 case TDS_RUNNING: 1199 db_printf("running on CPU %d\n", td->td_oncpu); 1200 return; 1201 case TDS_INHIBITED: 1202 if (TD_ON_SLEEPQ(td)) { 1203 if (lockmgr_chain(td, &owner) || 1204 sx_chain(td, &owner)) { 1205 if (owner == NULL) 1206 return; 1207 td = owner; 1208 break; 1209 } 1210 db_printf("sleeping on %p \"%s\"\n", 1211 td->td_wchan, td->td_wmesg); 1212 return; 1213 } 1214 db_printf("inhibited\n"); 1215 return; 1216 default: 1217 db_printf("??? (%#x)\n", td->td_state); 1218 return; 1219 } 1220 } 1221 } 1222 1223 DB_SHOW_COMMAND(sleepchain, db_show_sleepchain) 1224 { 1225 struct thread *td; 1226 1227 /* Figure out which thread to start with. */ 1228 if (have_addr) 1229 td = db_lookup_thread(addr, TRUE); 1230 else 1231 td = kdb_thread; 1232 1233 print_sleepchain(td, ""); 1234 } 1235 1236 static void print_waiters(struct turnstile *ts, int indent); 1237 1238 static void 1239 print_waiter(struct thread *td, int indent) 1240 { 1241 struct turnstile *ts; 1242 int i; 1243 1244 if (db_pager_quit) 1245 return; 1246 for (i = 0; i < indent; i++) 1247 db_printf(" "); 1248 print_thread(td, "thread "); 1249 LIST_FOREACH(ts, &td->td_contested, ts_link) 1250 print_waiters(ts, indent + 1); 1251 } 1252 1253 static void 1254 print_waiters(struct turnstile *ts, int indent) 1255 { 1256 struct lock_object *lock; 1257 struct lock_class *class; 1258 struct thread *td; 1259 int i; 1260 1261 if (db_pager_quit) 1262 return; 1263 lock = ts->ts_lockobj; 1264 class = LOCK_CLASS(lock); 1265 for (i = 0; i < indent; i++) 1266 db_printf(" "); 1267 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name, lock->lo_name); 1268 TAILQ_FOREACH(td, &ts->ts_blocked[TS_EXCLUSIVE_QUEUE], td_lockq) 1269 print_waiter(td, indent + 1); 1270 TAILQ_FOREACH(td, &ts->ts_blocked[TS_SHARED_QUEUE], td_lockq) 1271 print_waiter(td, indent + 1); 1272 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq) 1273 print_waiter(td, indent + 1); 1274 } 1275 1276 DB_SHOW_COMMAND(locktree, db_show_locktree) 1277 { 1278 struct lock_object *lock; 1279 struct lock_class *class; 1280 struct turnstile_chain *tc; 1281 struct turnstile *ts; 1282 1283 if (!have_addr) 1284 return; 1285 lock = (struct lock_object *)addr; 1286 tc = TC_LOOKUP(lock); 1287 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash) 1288 if (ts->ts_lockobj == lock) 1289 break; 1290 if (ts == NULL) { 1291 class = LOCK_CLASS(lock); 1292 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name, 1293 lock->lo_name); 1294 } else 1295 print_waiters(ts, 0); 1296 } 1297 #endif 1298