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sys/kern/subr_turnstile.c
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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: releng/12.0/sys/kern/subr_turnstile.c 334546 2018-06-02 22:37:53Z mjg $"); 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 */ 122 struct 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 }; 132 133 struct 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 143 u_int turnstile_max_depth; 144 static SYSCTL_NODE(_debug, OID_AUTO, turnstile, CTLFLAG_RD, 0, 145 "turnstile profiling"); 146 static SYSCTL_NODE(_debug_turnstile, OID_AUTO, chains, CTLFLAG_RD, 0, 147 "turnstile chain stats"); 148 SYSCTL_UINT(_debug_turnstile, OID_AUTO, max_depth, CTLFLAG_RD, 149 &turnstile_max_depth, 0, "maximum depth achieved of a single chain"); 150 #endif 151 static struct mtx td_contested_lock; 152 static struct turnstile_chain turnstile_chains[TC_TABLESIZE]; 153 static uma_zone_t turnstile_zone; 154 155 /* 156 * Prototypes for non-exported routines. 157 */ 158 static void init_turnstile0(void *dummy); 159 #ifdef TURNSTILE_PROFILING 160 static void init_turnstile_profiling(void *arg); 161 #endif 162 static void propagate_priority(struct thread *td); 163 static int turnstile_adjust_thread(struct turnstile *ts, 164 struct thread *td); 165 static struct thread *turnstile_first_waiter(struct turnstile *ts); 166 static void turnstile_setowner(struct turnstile *ts, struct thread *owner); 167 #ifdef INVARIANTS 168 static void turnstile_dtor(void *mem, int size, void *arg); 169 #endif 170 static int turnstile_init(void *mem, int size, int flags); 171 static void turnstile_fini(void *mem, int size); 172 173 SDT_PROVIDER_DECLARE(sched); 174 SDT_PROBE_DEFINE(sched, , , sleep); 175 SDT_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 */ 183 static void 184 propagate_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 */ 290 static int 291 turnstile_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 */ 360 void 361 init_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 376 static void 377 init_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 } 396 SYSINIT(turnstile_profiling, SI_SUB_LOCK, SI_ORDER_ANY, 397 init_turnstile_profiling, NULL); 398 #endif 399 400 static void 401 init_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 } 414 SYSINIT(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 */ 420 void 421 turnstile_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 */ 455 static void 456 turnstile_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 */ 475 static void 476 turnstile_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 */ 490 static int 491 turnstile_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 } 504 505 static void 506 turnstile_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 */ 517 struct turnstile * 518 turnstile_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 */ 527 void 528 turnstile_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 */ 537 void 538 turnstile_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 } 545 546 struct turnstile * 547 turnstile_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 } 568 569 struct thread * 570 turnstile_lock(struct turnstile *ts, struct lock_object **lockp) 571 { 572 struct turnstile_chain *tc; 573 struct lock_object *lock; 574 575 if ((lock = ts->ts_lockobj) == NULL) 576 return (NULL); 577 tc = TC_LOOKUP(lock); 578 mtx_lock_spin(&tc->tc_lock); 579 mtx_lock_spin(&ts->ts_lock); 580 if (__predict_false(lock != ts->ts_lockobj)) { 581 mtx_unlock_spin(&tc->tc_lock); 582 mtx_unlock_spin(&ts->ts_lock); 583 return (NULL); 584 } 585 *lockp = lock; 586 return (ts->ts_owner); 587 } 588 589 void 590 turnstile_unlock(struct turnstile *ts, struct lock_object *lock) 591 { 592 struct turnstile_chain *tc; 593 594 mtx_assert(&ts->ts_lock, MA_OWNED); 595 mtx_unlock_spin(&ts->ts_lock); 596 if (ts == curthread->td_turnstile) 597 ts->ts_lockobj = NULL; 598 tc = TC_LOOKUP(lock); 599 mtx_unlock_spin(&tc->tc_lock); 600 } 601 602 void 603 turnstile_assert(struct turnstile *ts) 604 { 605 MPASS(ts->ts_lockobj == NULL); 606 } 607 608 void 609 turnstile_cancel(struct turnstile *ts) 610 { 611 struct turnstile_chain *tc; 612 struct lock_object *lock; 613 614 mtx_assert(&ts->ts_lock, MA_OWNED); 615 616 mtx_unlock_spin(&ts->ts_lock); 617 lock = ts->ts_lockobj; 618 if (ts == curthread->td_turnstile) 619 ts->ts_lockobj = NULL; 620 tc = TC_LOOKUP(lock); 621 mtx_unlock_spin(&tc->tc_lock); 622 } 623 624 /* 625 * Look up the turnstile for a lock in the hash table locking the associated 626 * turnstile chain along the way. If no turnstile is found in the hash 627 * table, NULL is returned. 628 */ 629 struct turnstile * 630 turnstile_lookup(struct lock_object *lock) 631 { 632 struct turnstile_chain *tc; 633 struct turnstile *ts; 634 635 tc = TC_LOOKUP(lock); 636 mtx_assert(&tc->tc_lock, MA_OWNED); 637 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash) 638 if (ts->ts_lockobj == lock) { 639 mtx_lock_spin(&ts->ts_lock); 640 return (ts); 641 } 642 return (NULL); 643 } 644 645 /* 646 * Unlock the turnstile chain associated with a given lock. 647 */ 648 void 649 turnstile_chain_unlock(struct lock_object *lock) 650 { 651 struct turnstile_chain *tc; 652 653 tc = TC_LOOKUP(lock); 654 mtx_unlock_spin(&tc->tc_lock); 655 } 656 657 /* 658 * Return a pointer to the thread waiting on this turnstile with the 659 * most important priority or NULL if the turnstile has no waiters. 660 */ 661 static struct thread * 662 turnstile_first_waiter(struct turnstile *ts) 663 { 664 struct thread *std, *xtd; 665 666 std = TAILQ_FIRST(&ts->ts_blocked[TS_SHARED_QUEUE]); 667 xtd = TAILQ_FIRST(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]); 668 if (xtd == NULL || (std != NULL && std->td_priority < xtd->td_priority)) 669 return (std); 670 return (xtd); 671 } 672 673 /* 674 * Take ownership of a turnstile and adjust the priority of the new 675 * owner appropriately. 676 */ 677 void 678 turnstile_claim(struct turnstile *ts) 679 { 680 struct thread *td, *owner; 681 struct turnstile_chain *tc; 682 683 mtx_assert(&ts->ts_lock, MA_OWNED); 684 MPASS(ts != curthread->td_turnstile); 685 686 owner = curthread; 687 mtx_lock_spin(&td_contested_lock); 688 turnstile_setowner(ts, owner); 689 mtx_unlock_spin(&td_contested_lock); 690 691 td = turnstile_first_waiter(ts); 692 MPASS(td != NULL); 693 MPASS(td->td_proc->p_magic == P_MAGIC); 694 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 695 696 /* 697 * Update the priority of the new owner if needed. 698 */ 699 thread_lock(owner); 700 if (td->td_priority < owner->td_priority) 701 sched_lend_prio(owner, td->td_priority); 702 thread_unlock(owner); 703 tc = TC_LOOKUP(ts->ts_lockobj); 704 mtx_unlock_spin(&ts->ts_lock); 705 mtx_unlock_spin(&tc->tc_lock); 706 } 707 708 /* 709 * Block the current thread on the turnstile assicated with 'lock'. This 710 * function will context switch and not return until this thread has been 711 * woken back up. This function must be called with the appropriate 712 * turnstile chain locked and will return with it unlocked. 713 */ 714 void 715 turnstile_wait(struct turnstile *ts, struct thread *owner, int queue) 716 { 717 struct turnstile_chain *tc; 718 struct thread *td, *td1; 719 struct lock_object *lock; 720 721 td = curthread; 722 mtx_assert(&ts->ts_lock, MA_OWNED); 723 if (owner) 724 MPASS(owner->td_proc->p_magic == P_MAGIC); 725 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 726 727 /* 728 * If the lock does not already have a turnstile, use this thread's 729 * turnstile. Otherwise insert the current thread into the 730 * turnstile already in use by this lock. 731 */ 732 tc = TC_LOOKUP(ts->ts_lockobj); 733 mtx_assert(&tc->tc_lock, MA_OWNED); 734 if (ts == td->td_turnstile) { 735 #ifdef TURNSTILE_PROFILING 736 tc->tc_depth++; 737 if (tc->tc_depth > tc->tc_max_depth) { 738 tc->tc_max_depth = tc->tc_depth; 739 if (tc->tc_max_depth > turnstile_max_depth) 740 turnstile_max_depth = tc->tc_max_depth; 741 } 742 #endif 743 LIST_INSERT_HEAD(&tc->tc_turnstiles, ts, ts_hash); 744 KASSERT(TAILQ_EMPTY(&ts->ts_pending), 745 ("thread's turnstile has pending threads")); 746 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]), 747 ("thread's turnstile has exclusive waiters")); 748 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]), 749 ("thread's turnstile has shared waiters")); 750 KASSERT(LIST_EMPTY(&ts->ts_free), 751 ("thread's turnstile has a non-empty free list")); 752 MPASS(ts->ts_lockobj != NULL); 753 mtx_lock_spin(&td_contested_lock); 754 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq); 755 turnstile_setowner(ts, owner); 756 mtx_unlock_spin(&td_contested_lock); 757 } else { 758 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq) 759 if (td1->td_priority > td->td_priority) 760 break; 761 mtx_lock_spin(&td_contested_lock); 762 if (td1 != NULL) 763 TAILQ_INSERT_BEFORE(td1, td, td_lockq); 764 else 765 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq); 766 MPASS(owner == ts->ts_owner); 767 mtx_unlock_spin(&td_contested_lock); 768 MPASS(td->td_turnstile != NULL); 769 LIST_INSERT_HEAD(&ts->ts_free, td->td_turnstile, ts_hash); 770 } 771 thread_lock(td); 772 thread_lock_set(td, &ts->ts_lock); 773 td->td_turnstile = NULL; 774 775 /* Save who we are blocked on and switch. */ 776 lock = ts->ts_lockobj; 777 td->td_tsqueue = queue; 778 td->td_blocked = ts; 779 td->td_lockname = lock->lo_name; 780 td->td_blktick = ticks; 781 TD_SET_LOCK(td); 782 mtx_unlock_spin(&tc->tc_lock); 783 propagate_priority(td); 784 785 if (LOCK_LOG_TEST(lock, 0)) 786 CTR4(KTR_LOCK, "%s: td %d blocked on [%p] %s", __func__, 787 td->td_tid, lock, lock->lo_name); 788 789 SDT_PROBE0(sched, , , sleep); 790 791 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 792 mi_switch(SW_VOL | SWT_TURNSTILE, NULL); 793 794 if (LOCK_LOG_TEST(lock, 0)) 795 CTR4(KTR_LOCK, "%s: td %d free from blocked on [%p] %s", 796 __func__, td->td_tid, lock, lock->lo_name); 797 thread_unlock(td); 798 } 799 800 /* 801 * Pick the highest priority thread on this turnstile and put it on the 802 * pending list. This must be called with the turnstile chain locked. 803 */ 804 int 805 turnstile_signal(struct turnstile *ts, int queue) 806 { 807 struct turnstile_chain *tc __unused; 808 struct thread *td; 809 int empty; 810 811 MPASS(ts != NULL); 812 mtx_assert(&ts->ts_lock, MA_OWNED); 813 MPASS(curthread->td_proc->p_magic == P_MAGIC); 814 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL); 815 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 816 817 /* 818 * Pick the highest priority thread blocked on this lock and 819 * move it to the pending list. 820 */ 821 td = TAILQ_FIRST(&ts->ts_blocked[queue]); 822 MPASS(td->td_proc->p_magic == P_MAGIC); 823 mtx_lock_spin(&td_contested_lock); 824 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq); 825 mtx_unlock_spin(&td_contested_lock); 826 TAILQ_INSERT_TAIL(&ts->ts_pending, td, td_lockq); 827 828 /* 829 * If the turnstile is now empty, remove it from its chain and 830 * give it to the about-to-be-woken thread. Otherwise take a 831 * turnstile from the free list and give it to the thread. 832 */ 833 empty = TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) && 834 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]); 835 if (empty) { 836 tc = TC_LOOKUP(ts->ts_lockobj); 837 mtx_assert(&tc->tc_lock, MA_OWNED); 838 MPASS(LIST_EMPTY(&ts->ts_free)); 839 #ifdef TURNSTILE_PROFILING 840 tc->tc_depth--; 841 #endif 842 } else 843 ts = LIST_FIRST(&ts->ts_free); 844 MPASS(ts != NULL); 845 LIST_REMOVE(ts, ts_hash); 846 td->td_turnstile = ts; 847 848 return (empty); 849 } 850 851 /* 852 * Put all blocked threads on the pending list. This must be called with 853 * the turnstile chain locked. 854 */ 855 void 856 turnstile_broadcast(struct turnstile *ts, int queue) 857 { 858 struct turnstile_chain *tc __unused; 859 struct turnstile *ts1; 860 struct thread *td; 861 862 MPASS(ts != NULL); 863 mtx_assert(&ts->ts_lock, MA_OWNED); 864 MPASS(curthread->td_proc->p_magic == P_MAGIC); 865 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL); 866 /* 867 * We must have the chain locked so that we can remove the empty 868 * turnstile from the hash queue. 869 */ 870 tc = TC_LOOKUP(ts->ts_lockobj); 871 mtx_assert(&tc->tc_lock, MA_OWNED); 872 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 873 874 /* 875 * Transfer the blocked list to the pending list. 876 */ 877 mtx_lock_spin(&td_contested_lock); 878 TAILQ_CONCAT(&ts->ts_pending, &ts->ts_blocked[queue], td_lockq); 879 mtx_unlock_spin(&td_contested_lock); 880 881 /* 882 * Give a turnstile to each thread. The last thread gets 883 * this turnstile if the turnstile is empty. 884 */ 885 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq) { 886 if (LIST_EMPTY(&ts->ts_free)) { 887 MPASS(TAILQ_NEXT(td, td_lockq) == NULL); 888 ts1 = ts; 889 #ifdef TURNSTILE_PROFILING 890 tc->tc_depth--; 891 #endif 892 } else 893 ts1 = LIST_FIRST(&ts->ts_free); 894 MPASS(ts1 != NULL); 895 LIST_REMOVE(ts1, ts_hash); 896 td->td_turnstile = ts1; 897 } 898 } 899 900 /* 901 * Wakeup all threads on the pending list and adjust the priority of the 902 * current thread appropriately. This must be called with the turnstile 903 * chain locked. 904 */ 905 void 906 turnstile_unpend(struct turnstile *ts) 907 { 908 TAILQ_HEAD( ,thread) pending_threads; 909 struct turnstile *nts; 910 struct thread *td; 911 u_char cp, pri; 912 913 MPASS(ts != NULL); 914 mtx_assert(&ts->ts_lock, MA_OWNED); 915 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL); 916 MPASS(!TAILQ_EMPTY(&ts->ts_pending)); 917 918 /* 919 * Move the list of pending threads out of the turnstile and 920 * into a local variable. 921 */ 922 TAILQ_INIT(&pending_threads); 923 TAILQ_CONCAT(&pending_threads, &ts->ts_pending, td_lockq); 924 #ifdef INVARIANTS 925 if (TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) && 926 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE])) 927 ts->ts_lockobj = NULL; 928 #endif 929 /* 930 * Adjust the priority of curthread based on other contested 931 * locks it owns. Don't lower the priority below the base 932 * priority however. 933 */ 934 td = curthread; 935 pri = PRI_MAX; 936 thread_lock(td); 937 mtx_lock_spin(&td_contested_lock); 938 /* 939 * Remove the turnstile from this thread's list of contested locks 940 * since this thread doesn't own it anymore. New threads will 941 * not be blocking on the turnstile until it is claimed by a new 942 * owner. There might not be a current owner if this is a shared 943 * lock. 944 */ 945 if (ts->ts_owner != NULL) { 946 ts->ts_owner = NULL; 947 LIST_REMOVE(ts, ts_link); 948 } 949 LIST_FOREACH(nts, &td->td_contested, ts_link) { 950 cp = turnstile_first_waiter(nts)->td_priority; 951 if (cp < pri) 952 pri = cp; 953 } 954 mtx_unlock_spin(&td_contested_lock); 955 sched_unlend_prio(td, pri); 956 thread_unlock(td); 957 /* 958 * Wake up all the pending threads. If a thread is not blocked 959 * on a lock, then it is currently executing on another CPU in 960 * turnstile_wait() or sitting on a run queue waiting to resume 961 * in turnstile_wait(). Set a flag to force it to try to acquire 962 * the lock again instead of blocking. 963 */ 964 while (!TAILQ_EMPTY(&pending_threads)) { 965 td = TAILQ_FIRST(&pending_threads); 966 TAILQ_REMOVE(&pending_threads, td, td_lockq); 967 SDT_PROBE2(sched, , , wakeup, td, td->td_proc); 968 thread_lock(td); 969 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 970 MPASS(td->td_proc->p_magic == P_MAGIC); 971 MPASS(TD_ON_LOCK(td)); 972 TD_CLR_LOCK(td); 973 MPASS(TD_CAN_RUN(td)); 974 td->td_blocked = NULL; 975 td->td_lockname = NULL; 976 td->td_blktick = 0; 977 #ifdef INVARIANTS 978 td->td_tsqueue = 0xff; 979 #endif 980 sched_add(td, SRQ_BORING); 981 thread_unlock(td); 982 } 983 mtx_unlock_spin(&ts->ts_lock); 984 } 985 986 /* 987 * Give up ownership of a turnstile. This must be called with the 988 * turnstile chain locked. 989 */ 990 void 991 turnstile_disown(struct turnstile *ts) 992 { 993 struct thread *td; 994 u_char cp, pri; 995 996 MPASS(ts != NULL); 997 mtx_assert(&ts->ts_lock, MA_OWNED); 998 MPASS(ts->ts_owner == curthread); 999 MPASS(TAILQ_EMPTY(&ts->ts_pending)); 1000 MPASS(!TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) || 1001 !TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE])); 1002 1003 /* 1004 * Remove the turnstile from this thread's list of contested locks 1005 * since this thread doesn't own it anymore. New threads will 1006 * not be blocking on the turnstile until it is claimed by a new 1007 * owner. 1008 */ 1009 mtx_lock_spin(&td_contested_lock); 1010 ts->ts_owner = NULL; 1011 LIST_REMOVE(ts, ts_link); 1012 mtx_unlock_spin(&td_contested_lock); 1013 1014 /* 1015 * Adjust the priority of curthread based on other contested 1016 * locks it owns. Don't lower the priority below the base 1017 * priority however. 1018 */ 1019 td = curthread; 1020 pri = PRI_MAX; 1021 thread_lock(td); 1022 mtx_unlock_spin(&ts->ts_lock); 1023 mtx_lock_spin(&td_contested_lock); 1024 LIST_FOREACH(ts, &td->td_contested, ts_link) { 1025 cp = turnstile_first_waiter(ts)->td_priority; 1026 if (cp < pri) 1027 pri = cp; 1028 } 1029 mtx_unlock_spin(&td_contested_lock); 1030 sched_unlend_prio(td, pri); 1031 thread_unlock(td); 1032 } 1033 1034 /* 1035 * Return the first thread in a turnstile. 1036 */ 1037 struct thread * 1038 turnstile_head(struct turnstile *ts, int queue) 1039 { 1040 #ifdef INVARIANTS 1041 1042 MPASS(ts != NULL); 1043 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 1044 mtx_assert(&ts->ts_lock, MA_OWNED); 1045 #endif 1046 return (TAILQ_FIRST(&ts->ts_blocked[queue])); 1047 } 1048 1049 /* 1050 * Returns true if a sub-queue of a turnstile is empty. 1051 */ 1052 int 1053 turnstile_empty(struct turnstile *ts, int queue) 1054 { 1055 #ifdef INVARIANTS 1056 1057 MPASS(ts != NULL); 1058 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 1059 mtx_assert(&ts->ts_lock, MA_OWNED); 1060 #endif 1061 return (TAILQ_EMPTY(&ts->ts_blocked[queue])); 1062 } 1063 1064 #ifdef DDB 1065 static void 1066 print_thread(struct thread *td, const char *prefix) 1067 { 1068 1069 db_printf("%s%p (tid %d, pid %d, \"%s\")\n", prefix, td, td->td_tid, 1070 td->td_proc->p_pid, td->td_name); 1071 } 1072 1073 static void 1074 print_queue(struct threadqueue *queue, const char *header, const char *prefix) 1075 { 1076 struct thread *td; 1077 1078 db_printf("%s:\n", header); 1079 if (TAILQ_EMPTY(queue)) { 1080 db_printf("%sempty\n", prefix); 1081 return; 1082 } 1083 TAILQ_FOREACH(td, queue, td_lockq) { 1084 print_thread(td, prefix); 1085 } 1086 } 1087 1088 DB_SHOW_COMMAND(turnstile, db_show_turnstile) 1089 { 1090 struct turnstile_chain *tc; 1091 struct turnstile *ts; 1092 struct lock_object *lock; 1093 int i; 1094 1095 if (!have_addr) 1096 return; 1097 1098 /* 1099 * First, see if there is an active turnstile for the lock indicated 1100 * by the address. 1101 */ 1102 lock = (struct lock_object *)addr; 1103 tc = TC_LOOKUP(lock); 1104 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash) 1105 if (ts->ts_lockobj == lock) 1106 goto found; 1107 1108 /* 1109 * Second, see if there is an active turnstile at the address 1110 * indicated. 1111 */ 1112 for (i = 0; i < TC_TABLESIZE; i++) 1113 LIST_FOREACH(ts, &turnstile_chains[i].tc_turnstiles, ts_hash) { 1114 if (ts == (struct turnstile *)addr) 1115 goto found; 1116 } 1117 1118 db_printf("Unable to locate a turnstile via %p\n", (void *)addr); 1119 return; 1120 found: 1121 lock = ts->ts_lockobj; 1122 db_printf("Lock: %p - (%s) %s\n", lock, LOCK_CLASS(lock)->lc_name, 1123 lock->lo_name); 1124 if (ts->ts_owner) 1125 print_thread(ts->ts_owner, "Lock Owner: "); 1126 else 1127 db_printf("Lock Owner: none\n"); 1128 print_queue(&ts->ts_blocked[TS_SHARED_QUEUE], "Shared Waiters", "\t"); 1129 print_queue(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE], "Exclusive Waiters", 1130 "\t"); 1131 print_queue(&ts->ts_pending, "Pending Threads", "\t"); 1132 1133 } 1134 1135 /* 1136 * Show all the threads a particular thread is waiting on based on 1137 * non-spin locks. 1138 */ 1139 static void 1140 print_lockchain(struct thread *td, const char *prefix) 1141 { 1142 struct lock_object *lock; 1143 struct lock_class *class; 1144 struct turnstile *ts; 1145 struct thread *owner; 1146 1147 /* 1148 * Follow the chain. We keep walking as long as the thread is 1149 * blocked on a lock that has an owner. 1150 */ 1151 while (!db_pager_quit) { 1152 db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid, 1153 td->td_proc->p_pid, td->td_name); 1154 switch (td->td_state) { 1155 case TDS_INACTIVE: 1156 db_printf("is inactive\n"); 1157 return; 1158 case TDS_CAN_RUN: 1159 db_printf("can run\n"); 1160 return; 1161 case TDS_RUNQ: 1162 db_printf("is on a run queue\n"); 1163 return; 1164 case TDS_RUNNING: 1165 db_printf("running on CPU %d\n", td->td_oncpu); 1166 return; 1167 case TDS_INHIBITED: 1168 if (TD_ON_LOCK(td)) { 1169 ts = td->td_blocked; 1170 lock = ts->ts_lockobj; 1171 class = LOCK_CLASS(lock); 1172 db_printf("blocked on lock %p (%s) \"%s\"\n", 1173 lock, class->lc_name, lock->lo_name); 1174 if (ts->ts_owner == NULL) 1175 return; 1176 td = ts->ts_owner; 1177 break; 1178 } else if (TD_ON_SLEEPQ(td)) { 1179 if (!lockmgr_chain(td, &owner) && 1180 !sx_chain(td, &owner)) { 1181 db_printf("sleeping on %p \"%s\"\n", 1182 td->td_wchan, td->td_wmesg); 1183 return; 1184 } 1185 if (owner == NULL) 1186 return; 1187 td = owner; 1188 break; 1189 } 1190 db_printf("inhibited\n"); 1191 return; 1192 default: 1193 db_printf("??? (%#x)\n", td->td_state); 1194 return; 1195 } 1196 } 1197 } 1198 1199 DB_SHOW_COMMAND(lockchain, db_show_lockchain) 1200 { 1201 struct thread *td; 1202 1203 /* Figure out which thread to start with. */ 1204 if (have_addr) 1205 td = db_lookup_thread(addr, true); 1206 else 1207 td = kdb_thread; 1208 1209 print_lockchain(td, ""); 1210 } 1211 DB_SHOW_ALIAS(sleepchain, db_show_lockchain); 1212 1213 DB_SHOW_ALL_COMMAND(chains, db_show_allchains) 1214 { 1215 struct thread *td; 1216 struct proc *p; 1217 int i; 1218 1219 i = 1; 1220 FOREACH_PROC_IN_SYSTEM(p) { 1221 FOREACH_THREAD_IN_PROC(p, td) { 1222 if ((TD_ON_LOCK(td) && LIST_EMPTY(&td->td_contested)) 1223 || (TD_IS_INHIBITED(td) && TD_ON_SLEEPQ(td))) { 1224 db_printf("chain %d:\n", i++); 1225 print_lockchain(td, " "); 1226 } 1227 if (db_pager_quit) 1228 return; 1229 } 1230 } 1231 } 1232 DB_SHOW_ALIAS(allchains, db_show_allchains) 1233 1234 static void print_waiters(struct turnstile *ts, int indent); 1235 1236 static void 1237 print_waiter(struct thread *td, int indent) 1238 { 1239 struct turnstile *ts; 1240 int i; 1241 1242 if (db_pager_quit) 1243 return; 1244 for (i = 0; i < indent; i++) 1245 db_printf(" "); 1246 print_thread(td, "thread "); 1247 LIST_FOREACH(ts, &td->td_contested, ts_link) 1248 print_waiters(ts, indent + 1); 1249 } 1250 1251 static void 1252 print_waiters(struct turnstile *ts, int indent) 1253 { 1254 struct lock_object *lock; 1255 struct lock_class *class; 1256 struct thread *td; 1257 int i; 1258 1259 if (db_pager_quit) 1260 return; 1261 lock = ts->ts_lockobj; 1262 class = LOCK_CLASS(lock); 1263 for (i = 0; i < indent; i++) 1264 db_printf(" "); 1265 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name, lock->lo_name); 1266 TAILQ_FOREACH(td, &ts->ts_blocked[TS_EXCLUSIVE_QUEUE], td_lockq) 1267 print_waiter(td, indent + 1); 1268 TAILQ_FOREACH(td, &ts->ts_blocked[TS_SHARED_QUEUE], td_lockq) 1269 print_waiter(td, indent + 1); 1270 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq) 1271 print_waiter(td, indent + 1); 1272 } 1273 1274 DB_SHOW_COMMAND(locktree, db_show_locktree) 1275 { 1276 struct lock_object *lock; 1277 struct lock_class *class; 1278 struct turnstile_chain *tc; 1279 struct turnstile *ts; 1280 1281 if (!have_addr) 1282 return; 1283 lock = (struct lock_object *)addr; 1284 tc = TC_LOOKUP(lock); 1285 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash) 1286 if (ts->ts_lockobj == lock) 1287 break; 1288 if (ts == NULL) { 1289 class = LOCK_CLASS(lock); 1290 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name, 1291 lock->lo_name); 1292 } else 1293 print_waiters(ts, 0); 1294 } 1295 #endif
Cache object: 61d469c6b578686a36241462ebb5a5cc
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