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