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sys/kern/subr_turnstile.c
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1 /*- 2 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 3. Berkeley Software Design Inc's name may not be used to endorse or 13 * promote products derived from this software without specific prior 14 * written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 * 28 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $ 29 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $ 30 */ 31 32 /* 33 * Implementation of turnstiles used to hold queue of threads blocked on 34 * non-sleepable locks. Sleepable locks use condition variables to 35 * implement their queues. Turnstiles differ from a sleep queue in that 36 * turnstile queue's are assigned to a lock held by an owning thread. Thus, 37 * when one thread is enqueued onto a turnstile, it can lend its priority 38 * to the owning thread. 39 * 40 * We wish to avoid bloating locks with an embedded turnstile and we do not 41 * want to use back-pointers in the locks for the same reason. Thus, we 42 * use a similar approach to that of Solaris 7 as described in Solaris 43 * Internals by Jim Mauro and Richard McDougall. Turnstiles are looked up 44 * in a hash table based on the address of the lock. Each entry in the 45 * hash table is a linked-lists of turnstiles and is called a turnstile 46 * chain. Each chain contains a spin mutex that protects all of the 47 * turnstiles in the chain. 48 * 49 * Each time a thread is created, a turnstile is allocated from a UMA zone 50 * and attached to that thread. When a thread blocks on a lock, if it is the 51 * first thread to block, it lends its turnstile to the lock. If the lock 52 * already has a turnstile, then it gives its turnstile to the lock's 53 * turnstile's free list. When a thread is woken up, it takes a turnstile from 54 * the free list if there are any other waiters. If it is the only thread 55 * blocked on the lock, then it reclaims the turnstile associated with the lock 56 * and removes it from the hash table. 57 */ 58 59 #include <sys/cdefs.h> 60 __FBSDID("$FreeBSD: releng/8.2/sys/kern/subr_turnstile.c 202966 2010-01-25 12:05:51Z attilio $"); 61 62 #include "opt_ddb.h" 63 #include "opt_turnstile_profiling.h" 64 #include "opt_sched.h" 65 66 #include <sys/param.h> 67 #include <sys/systm.h> 68 #include <sys/kernel.h> 69 #include <sys/ktr.h> 70 #include <sys/lock.h> 71 #include <sys/mutex.h> 72 #include <sys/proc.h> 73 #include <sys/queue.h> 74 #include <sys/sched.h> 75 #include <sys/sysctl.h> 76 #include <sys/turnstile.h> 77 78 #include <vm/uma.h> 79 80 #ifdef DDB 81 #include <sys/kdb.h> 82 #include <ddb/ddb.h> 83 #include <sys/lockmgr.h> 84 #include <sys/sx.h> 85 #endif 86 87 /* 88 * Constants for the hash table of turnstile chains. TC_SHIFT is a magic 89 * number chosen because the sleep queue's use the same value for the 90 * shift. Basically, we ignore the lower 8 bits of the address. 91 * TC_TABLESIZE must be a power of two for TC_MASK to work properly. 92 */ 93 #define TC_TABLESIZE 128 /* Must be power of 2. */ 94 #define TC_MASK (TC_TABLESIZE - 1) 95 #define TC_SHIFT 8 96 #define TC_HASH(lock) (((uintptr_t)(lock) >> TC_SHIFT) & TC_MASK) 97 #define TC_LOOKUP(lock) &turnstile_chains[TC_HASH(lock)] 98 99 /* 100 * There are three different lists of turnstiles as follows. The list 101 * connected by ts_link entries is a per-thread list of all the turnstiles 102 * attached to locks that we own. This is used to fixup our priority when 103 * a lock is released. The other two lists use the ts_hash entries. The 104 * first of these two is the turnstile chain list that a turnstile is on 105 * when it is attached to a lock. The second list to use ts_hash is the 106 * free list hung off of a turnstile that is attached to a lock. 107 * 108 * Each turnstile contains three lists of threads. The two ts_blocked lists 109 * are linked list of threads blocked on the turnstile's lock. One list is 110 * for exclusive waiters, and the other is for shared waiters. The 111 * ts_pending list is a linked list of threads previously awakened by 112 * turnstile_signal() or turnstile_wait() that are waiting to be put on 113 * the run queue. 114 * 115 * Locking key: 116 * c - turnstile chain lock 117 * q - td_contested lock 118 */ 119 struct turnstile { 120 struct mtx ts_lock; /* Spin lock for self. */ 121 struct threadqueue ts_blocked[2]; /* (c + q) Blocked threads. */ 122 struct threadqueue ts_pending; /* (c) Pending threads. */ 123 LIST_ENTRY(turnstile) ts_hash; /* (c) Chain and free list. */ 124 LIST_ENTRY(turnstile) ts_link; /* (q) Contested locks. */ 125 LIST_HEAD(, turnstile) ts_free; /* (c) Free turnstiles. */ 126 struct lock_object *ts_lockobj; /* (c) Lock we reference. */ 127 struct thread *ts_owner; /* (c + q) Who owns the lock. */ 128 }; 129 130 struct turnstile_chain { 131 LIST_HEAD(, turnstile) tc_turnstiles; /* List of turnstiles. */ 132 struct mtx tc_lock; /* Spin lock for this chain. */ 133 #ifdef TURNSTILE_PROFILING 134 u_int tc_depth; /* Length of tc_queues. */ 135 u_int tc_max_depth; /* Max length of tc_queues. */ 136 #endif 137 }; 138 139 #ifdef TURNSTILE_PROFILING 140 u_int turnstile_max_depth; 141 SYSCTL_NODE(_debug, OID_AUTO, turnstile, CTLFLAG_RD, 0, "turnstile profiling"); 142 SYSCTL_NODE(_debug_turnstile, OID_AUTO, chains, CTLFLAG_RD, 0, 143 "turnstile chain stats"); 144 SYSCTL_UINT(_debug_turnstile, OID_AUTO, max_depth, CTLFLAG_RD, 145 &turnstile_max_depth, 0, "maxmimum depth achieved of a single chain"); 146 #endif 147 static struct mtx td_contested_lock; 148 static struct turnstile_chain turnstile_chains[TC_TABLESIZE]; 149 static uma_zone_t turnstile_zone; 150 151 /* 152 * Prototypes for non-exported routines. 153 */ 154 static void init_turnstile0(void *dummy); 155 #ifdef TURNSTILE_PROFILING 156 static void init_turnstile_profiling(void *arg); 157 #endif 158 static void propagate_priority(struct thread *td); 159 static int turnstile_adjust_thread(struct turnstile *ts, 160 struct thread *td); 161 static struct thread *turnstile_first_waiter(struct turnstile *ts); 162 static void turnstile_setowner(struct turnstile *ts, struct thread *owner); 163 #ifdef INVARIANTS 164 static void turnstile_dtor(void *mem, int size, void *arg); 165 #endif 166 static int turnstile_init(void *mem, int size, int flags); 167 static void turnstile_fini(void *mem, int size); 168 169 /* 170 * Walks the chain of turnstiles and their owners to propagate the priority 171 * of the thread being blocked to all the threads holding locks that have to 172 * release their locks before this thread can run again. 173 */ 174 static void 175 propagate_priority(struct thread *td) 176 { 177 struct turnstile *ts; 178 int pri; 179 180 THREAD_LOCK_ASSERT(td, MA_OWNED); 181 pri = td->td_priority; 182 ts = td->td_blocked; 183 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 184 /* 185 * Grab a recursive lock on this turnstile chain so it stays locked 186 * for the whole operation. The caller expects us to return with 187 * the original lock held. We only ever lock down the chain so 188 * the lock order is constant. 189 */ 190 mtx_lock_spin(&ts->ts_lock); 191 for (;;) { 192 td = ts->ts_owner; 193 194 if (td == NULL) { 195 /* 196 * This might be a read lock with no owner. There's 197 * not much we can do, so just bail. 198 */ 199 mtx_unlock_spin(&ts->ts_lock); 200 return; 201 } 202 203 thread_lock_flags(td, MTX_DUPOK); 204 mtx_unlock_spin(&ts->ts_lock); 205 MPASS(td->td_proc != NULL); 206 MPASS(td->td_proc->p_magic == P_MAGIC); 207 208 /* 209 * If the thread is asleep, then we are probably about 210 * to deadlock. To make debugging this easier, just 211 * panic and tell the user which thread misbehaved so 212 * they can hopefully get a stack trace from the truly 213 * misbehaving thread. 214 */ 215 if (TD_IS_SLEEPING(td)) { 216 printf( 217 "Sleeping thread (tid %d, pid %d) owns a non-sleepable lock\n", 218 td->td_tid, td->td_proc->p_pid); 219 #ifdef DDB 220 db_trace_thread(td, -1); 221 #endif 222 panic("sleeping thread"); 223 } 224 225 /* 226 * If this thread already has higher priority than the 227 * thread that is being blocked, we are finished. 228 */ 229 if (td->td_priority <= pri) { 230 thread_unlock(td); 231 return; 232 } 233 234 /* 235 * Bump this thread's priority. 236 */ 237 sched_lend_prio(td, pri); 238 239 /* 240 * If lock holder is actually running or on the run queue 241 * then we are done. 242 */ 243 if (TD_IS_RUNNING(td) || TD_ON_RUNQ(td)) { 244 MPASS(td->td_blocked == NULL); 245 thread_unlock(td); 246 return; 247 } 248 249 #ifndef SMP 250 /* 251 * For UP, we check to see if td is curthread (this shouldn't 252 * ever happen however as it would mean we are in a deadlock.) 253 */ 254 KASSERT(td != curthread, ("Deadlock detected")); 255 #endif 256 257 /* 258 * If we aren't blocked on a lock, we should be. 259 */ 260 KASSERT(TD_ON_LOCK(td), ( 261 "thread %d(%s):%d holds %s but isn't blocked on a lock\n", 262 td->td_tid, td->td_name, td->td_state, 263 ts->ts_lockobj->lo_name)); 264 265 /* 266 * Pick up the lock that td is blocked on. 267 */ 268 ts = td->td_blocked; 269 MPASS(ts != NULL); 270 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 271 /* Resort td on the list if needed. */ 272 if (!turnstile_adjust_thread(ts, td)) { 273 mtx_unlock_spin(&ts->ts_lock); 274 return; 275 } 276 /* The thread lock is released as ts lock above. */ 277 } 278 } 279 280 /* 281 * Adjust the thread's position on a turnstile after its priority has been 282 * changed. 283 */ 284 static int 285 turnstile_adjust_thread(struct turnstile *ts, struct thread *td) 286 { 287 struct thread *td1, *td2; 288 int queue; 289 290 THREAD_LOCK_ASSERT(td, MA_OWNED); 291 MPASS(TD_ON_LOCK(td)); 292 293 /* 294 * This thread may not be blocked on this turnstile anymore 295 * but instead might already be woken up on another CPU 296 * that is waiting on the thread lock in turnstile_unpend() to 297 * finish waking this thread up. We can detect this case 298 * by checking to see if this thread has been given a 299 * turnstile by either turnstile_signal() or 300 * turnstile_broadcast(). In this case, treat the thread as 301 * if it was already running. 302 */ 303 if (td->td_turnstile != NULL) 304 return (0); 305 306 /* 307 * Check if the thread needs to be moved on the blocked chain. 308 * It needs to be moved if either its priority is lower than 309 * the previous thread or higher than the next thread. 310 */ 311 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 312 td1 = TAILQ_PREV(td, threadqueue, td_lockq); 313 td2 = TAILQ_NEXT(td, td_lockq); 314 if ((td1 != NULL && td->td_priority < td1->td_priority) || 315 (td2 != NULL && td->td_priority > td2->td_priority)) { 316 317 /* 318 * Remove thread from blocked chain and determine where 319 * it should be moved to. 320 */ 321 queue = td->td_tsqueue; 322 MPASS(queue == TS_EXCLUSIVE_QUEUE || queue == TS_SHARED_QUEUE); 323 mtx_lock_spin(&td_contested_lock); 324 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq); 325 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq) { 326 MPASS(td1->td_proc->p_magic == P_MAGIC); 327 if (td1->td_priority > td->td_priority) 328 break; 329 } 330 331 if (td1 == NULL) 332 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq); 333 else 334 TAILQ_INSERT_BEFORE(td1, td, td_lockq); 335 mtx_unlock_spin(&td_contested_lock); 336 if (td1 == NULL) 337 CTR3(KTR_LOCK, 338 "turnstile_adjust_thread: td %d put at tail on [%p] %s", 339 td->td_tid, ts->ts_lockobj, ts->ts_lockobj->lo_name); 340 else 341 CTR4(KTR_LOCK, 342 "turnstile_adjust_thread: td %d moved before %d on [%p] %s", 343 td->td_tid, td1->td_tid, ts->ts_lockobj, 344 ts->ts_lockobj->lo_name); 345 } 346 return (1); 347 } 348 349 /* 350 * Early initialization of turnstiles. This is not done via a SYSINIT() 351 * since this needs to be initialized very early when mutexes are first 352 * initialized. 353 */ 354 void 355 init_turnstiles(void) 356 { 357 int i; 358 359 for (i = 0; i < TC_TABLESIZE; i++) { 360 LIST_INIT(&turnstile_chains[i].tc_turnstiles); 361 mtx_init(&turnstile_chains[i].tc_lock, "turnstile chain", 362 NULL, MTX_SPIN); 363 } 364 mtx_init(&td_contested_lock, "td_contested", NULL, MTX_SPIN); 365 LIST_INIT(&thread0.td_contested); 366 thread0.td_turnstile = NULL; 367 } 368 369 #ifdef TURNSTILE_PROFILING 370 static void 371 init_turnstile_profiling(void *arg) 372 { 373 struct sysctl_oid *chain_oid; 374 char chain_name[10]; 375 int i; 376 377 for (i = 0; i < TC_TABLESIZE; i++) { 378 snprintf(chain_name, sizeof(chain_name), "%d", i); 379 chain_oid = SYSCTL_ADD_NODE(NULL, 380 SYSCTL_STATIC_CHILDREN(_debug_turnstile_chains), OID_AUTO, 381 chain_name, CTLFLAG_RD, NULL, "turnstile chain stats"); 382 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, 383 "depth", CTLFLAG_RD, &turnstile_chains[i].tc_depth, 0, 384 NULL); 385 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, 386 "max_depth", CTLFLAG_RD, &turnstile_chains[i].tc_max_depth, 387 0, NULL); 388 } 389 } 390 SYSINIT(turnstile_profiling, SI_SUB_LOCK, SI_ORDER_ANY, 391 init_turnstile_profiling, NULL); 392 #endif 393 394 static void 395 init_turnstile0(void *dummy) 396 { 397 398 turnstile_zone = uma_zcreate("TURNSTILE", sizeof(struct turnstile), 399 NULL, 400 #ifdef INVARIANTS 401 turnstile_dtor, 402 #else 403 NULL, 404 #endif 405 turnstile_init, turnstile_fini, UMA_ALIGN_CACHE, UMA_ZONE_NOFREE); 406 thread0.td_turnstile = turnstile_alloc(); 407 } 408 SYSINIT(turnstile0, SI_SUB_LOCK, SI_ORDER_ANY, init_turnstile0, NULL); 409 410 /* 411 * Update a thread on the turnstile list after it's priority has been changed. 412 * The old priority is passed in as an argument. 413 */ 414 void 415 turnstile_adjust(struct thread *td, u_char oldpri) 416 { 417 struct turnstile *ts; 418 419 MPASS(TD_ON_LOCK(td)); 420 421 /* 422 * Pick up the lock that td is blocked on. 423 */ 424 ts = td->td_blocked; 425 MPASS(ts != NULL); 426 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 427 mtx_assert(&ts->ts_lock, MA_OWNED); 428 429 /* Resort the turnstile on the list. */ 430 if (!turnstile_adjust_thread(ts, td)) 431 return; 432 /* 433 * If our priority was lowered and we are at the head of the 434 * turnstile, then propagate our new priority up the chain. 435 * Note that we currently don't try to revoke lent priorities 436 * when our priority goes up. 437 */ 438 MPASS(td->td_tsqueue == TS_EXCLUSIVE_QUEUE || 439 td->td_tsqueue == TS_SHARED_QUEUE); 440 if (td == TAILQ_FIRST(&ts->ts_blocked[td->td_tsqueue]) && 441 td->td_priority < oldpri) { 442 propagate_priority(td); 443 } 444 } 445 446 /* 447 * Set the owner of the lock this turnstile is attached to. 448 */ 449 static void 450 turnstile_setowner(struct turnstile *ts, struct thread *owner) 451 { 452 453 mtx_assert(&td_contested_lock, MA_OWNED); 454 MPASS(ts->ts_owner == NULL); 455 456 /* A shared lock might not have an owner. */ 457 if (owner == NULL) 458 return; 459 460 MPASS(owner->td_proc->p_magic == P_MAGIC); 461 ts->ts_owner = owner; 462 LIST_INSERT_HEAD(&owner->td_contested, ts, ts_link); 463 } 464 465 #ifdef INVARIANTS 466 /* 467 * UMA zone item deallocator. 468 */ 469 static void 470 turnstile_dtor(void *mem, int size, void *arg) 471 { 472 struct turnstile *ts; 473 474 ts = mem; 475 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE])); 476 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE])); 477 MPASS(TAILQ_EMPTY(&ts->ts_pending)); 478 } 479 #endif 480 481 /* 482 * UMA zone item initializer. 483 */ 484 static int 485 turnstile_init(void *mem, int size, int flags) 486 { 487 struct turnstile *ts; 488 489 bzero(mem, size); 490 ts = mem; 491 TAILQ_INIT(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]); 492 TAILQ_INIT(&ts->ts_blocked[TS_SHARED_QUEUE]); 493 TAILQ_INIT(&ts->ts_pending); 494 LIST_INIT(&ts->ts_free); 495 mtx_init(&ts->ts_lock, "turnstile lock", NULL, MTX_SPIN | MTX_RECURSE); 496 return (0); 497 } 498 499 static void 500 turnstile_fini(void *mem, int size) 501 { 502 struct turnstile *ts; 503 504 ts = mem; 505 mtx_destroy(&ts->ts_lock); 506 } 507 508 /* 509 * Get a turnstile for a new thread. 510 */ 511 struct turnstile * 512 turnstile_alloc(void) 513 { 514 515 return (uma_zalloc(turnstile_zone, M_WAITOK)); 516 } 517 518 /* 519 * Free a turnstile when a thread is destroyed. 520 */ 521 void 522 turnstile_free(struct turnstile *ts) 523 { 524 525 uma_zfree(turnstile_zone, ts); 526 } 527 528 /* 529 * Lock the turnstile chain associated with the specified lock. 530 */ 531 void 532 turnstile_chain_lock(struct lock_object *lock) 533 { 534 struct turnstile_chain *tc; 535 536 tc = TC_LOOKUP(lock); 537 mtx_lock_spin(&tc->tc_lock); 538 } 539 540 struct turnstile * 541 turnstile_trywait(struct lock_object *lock) 542 { 543 struct turnstile_chain *tc; 544 struct turnstile *ts; 545 546 tc = TC_LOOKUP(lock); 547 mtx_lock_spin(&tc->tc_lock); 548 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash) 549 if (ts->ts_lockobj == lock) { 550 mtx_lock_spin(&ts->ts_lock); 551 return (ts); 552 } 553 554 ts = curthread->td_turnstile; 555 MPASS(ts != NULL); 556 mtx_lock_spin(&ts->ts_lock); 557 KASSERT(ts->ts_lockobj == NULL, ("stale ts_lockobj pointer")); 558 ts->ts_lockobj = lock; 559 560 return (ts); 561 } 562 563 void 564 turnstile_cancel(struct turnstile *ts) 565 { 566 struct turnstile_chain *tc; 567 struct lock_object *lock; 568 569 mtx_assert(&ts->ts_lock, MA_OWNED); 570 571 mtx_unlock_spin(&ts->ts_lock); 572 lock = ts->ts_lockobj; 573 if (ts == curthread->td_turnstile) 574 ts->ts_lockobj = NULL; 575 tc = TC_LOOKUP(lock); 576 mtx_unlock_spin(&tc->tc_lock); 577 } 578 579 /* 580 * Look up the turnstile for a lock in the hash table locking the associated 581 * turnstile chain along the way. If no turnstile is found in the hash 582 * table, NULL is returned. 583 */ 584 struct turnstile * 585 turnstile_lookup(struct lock_object *lock) 586 { 587 struct turnstile_chain *tc; 588 struct turnstile *ts; 589 590 tc = TC_LOOKUP(lock); 591 mtx_assert(&tc->tc_lock, MA_OWNED); 592 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash) 593 if (ts->ts_lockobj == lock) { 594 mtx_lock_spin(&ts->ts_lock); 595 return (ts); 596 } 597 return (NULL); 598 } 599 600 /* 601 * Unlock the turnstile chain associated with a given lock. 602 */ 603 void 604 turnstile_chain_unlock(struct lock_object *lock) 605 { 606 struct turnstile_chain *tc; 607 608 tc = TC_LOOKUP(lock); 609 mtx_unlock_spin(&tc->tc_lock); 610 } 611 612 /* 613 * Return a pointer to the thread waiting on this turnstile with the 614 * most important priority or NULL if the turnstile has no waiters. 615 */ 616 static struct thread * 617 turnstile_first_waiter(struct turnstile *ts) 618 { 619 struct thread *std, *xtd; 620 621 std = TAILQ_FIRST(&ts->ts_blocked[TS_SHARED_QUEUE]); 622 xtd = TAILQ_FIRST(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]); 623 if (xtd == NULL || (std != NULL && std->td_priority < xtd->td_priority)) 624 return (std); 625 return (xtd); 626 } 627 628 /* 629 * Take ownership of a turnstile and adjust the priority of the new 630 * owner appropriately. 631 */ 632 void 633 turnstile_claim(struct turnstile *ts) 634 { 635 struct thread *td, *owner; 636 struct turnstile_chain *tc; 637 638 mtx_assert(&ts->ts_lock, MA_OWNED); 639 MPASS(ts != curthread->td_turnstile); 640 641 owner = curthread; 642 mtx_lock_spin(&td_contested_lock); 643 turnstile_setowner(ts, owner); 644 mtx_unlock_spin(&td_contested_lock); 645 646 td = turnstile_first_waiter(ts); 647 MPASS(td != NULL); 648 MPASS(td->td_proc->p_magic == P_MAGIC); 649 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 650 651 /* 652 * Update the priority of the new owner if needed. 653 */ 654 thread_lock(owner); 655 if (td->td_priority < owner->td_priority) 656 sched_lend_prio(owner, td->td_priority); 657 thread_unlock(owner); 658 tc = TC_LOOKUP(ts->ts_lockobj); 659 mtx_unlock_spin(&ts->ts_lock); 660 mtx_unlock_spin(&tc->tc_lock); 661 } 662 663 /* 664 * Block the current thread on the turnstile assicated with 'lock'. This 665 * function will context switch and not return until this thread has been 666 * woken back up. This function must be called with the appropriate 667 * turnstile chain locked and will return with it unlocked. 668 */ 669 void 670 turnstile_wait(struct turnstile *ts, struct thread *owner, int queue) 671 { 672 struct turnstile_chain *tc; 673 struct thread *td, *td1; 674 struct lock_object *lock; 675 676 td = curthread; 677 mtx_assert(&ts->ts_lock, MA_OWNED); 678 if (owner) 679 MPASS(owner->td_proc->p_magic == P_MAGIC); 680 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 681 682 /* 683 * If the lock does not already have a turnstile, use this thread's 684 * turnstile. Otherwise insert the current thread into the 685 * turnstile already in use by this lock. 686 */ 687 tc = TC_LOOKUP(ts->ts_lockobj); 688 if (ts == td->td_turnstile) { 689 mtx_assert(&tc->tc_lock, MA_OWNED); 690 #ifdef TURNSTILE_PROFILING 691 tc->tc_depth++; 692 if (tc->tc_depth > tc->tc_max_depth) { 693 tc->tc_max_depth = tc->tc_depth; 694 if (tc->tc_max_depth > turnstile_max_depth) 695 turnstile_max_depth = tc->tc_max_depth; 696 } 697 #endif 698 tc = TC_LOOKUP(ts->ts_lockobj); 699 LIST_INSERT_HEAD(&tc->tc_turnstiles, ts, ts_hash); 700 KASSERT(TAILQ_EMPTY(&ts->ts_pending), 701 ("thread's turnstile has pending threads")); 702 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]), 703 ("thread's turnstile has exclusive waiters")); 704 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]), 705 ("thread's turnstile has shared waiters")); 706 KASSERT(LIST_EMPTY(&ts->ts_free), 707 ("thread's turnstile has a non-empty free list")); 708 MPASS(ts->ts_lockobj != NULL); 709 mtx_lock_spin(&td_contested_lock); 710 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq); 711 turnstile_setowner(ts, owner); 712 mtx_unlock_spin(&td_contested_lock); 713 } else { 714 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq) 715 if (td1->td_priority > td->td_priority) 716 break; 717 mtx_lock_spin(&td_contested_lock); 718 if (td1 != NULL) 719 TAILQ_INSERT_BEFORE(td1, td, td_lockq); 720 else 721 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq); 722 MPASS(owner == ts->ts_owner); 723 mtx_unlock_spin(&td_contested_lock); 724 MPASS(td->td_turnstile != NULL); 725 LIST_INSERT_HEAD(&ts->ts_free, td->td_turnstile, ts_hash); 726 } 727 thread_lock(td); 728 thread_lock_set(td, &ts->ts_lock); 729 td->td_turnstile = NULL; 730 731 /* Save who we are blocked on and switch. */ 732 lock = ts->ts_lockobj; 733 td->td_tsqueue = queue; 734 td->td_blocked = ts; 735 td->td_lockname = lock->lo_name; 736 td->td_blktick = ticks; 737 TD_SET_LOCK(td); 738 mtx_unlock_spin(&tc->tc_lock); 739 propagate_priority(td); 740 741 if (LOCK_LOG_TEST(lock, 0)) 742 CTR4(KTR_LOCK, "%s: td %d blocked on [%p] %s", __func__, 743 td->td_tid, lock, lock->lo_name); 744 745 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 746 mi_switch(SW_VOL | SWT_TURNSTILE, NULL); 747 748 if (LOCK_LOG_TEST(lock, 0)) 749 CTR4(KTR_LOCK, "%s: td %d free from blocked on [%p] %s", 750 __func__, td->td_tid, lock, lock->lo_name); 751 thread_unlock(td); 752 } 753 754 /* 755 * Pick the highest priority thread on this turnstile and put it on the 756 * pending list. This must be called with the turnstile chain locked. 757 */ 758 int 759 turnstile_signal(struct turnstile *ts, int queue) 760 { 761 struct turnstile_chain *tc; 762 struct thread *td; 763 int empty; 764 765 MPASS(ts != NULL); 766 mtx_assert(&ts->ts_lock, MA_OWNED); 767 MPASS(curthread->td_proc->p_magic == P_MAGIC); 768 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL); 769 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 770 771 /* 772 * Pick the highest priority thread blocked on this lock and 773 * move it to the pending list. 774 */ 775 td = TAILQ_FIRST(&ts->ts_blocked[queue]); 776 MPASS(td->td_proc->p_magic == P_MAGIC); 777 mtx_lock_spin(&td_contested_lock); 778 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq); 779 mtx_unlock_spin(&td_contested_lock); 780 TAILQ_INSERT_TAIL(&ts->ts_pending, td, td_lockq); 781 782 /* 783 * If the turnstile is now empty, remove it from its chain and 784 * give it to the about-to-be-woken thread. Otherwise take a 785 * turnstile from the free list and give it to the thread. 786 */ 787 empty = TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) && 788 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]); 789 if (empty) { 790 tc = TC_LOOKUP(ts->ts_lockobj); 791 mtx_assert(&tc->tc_lock, MA_OWNED); 792 MPASS(LIST_EMPTY(&ts->ts_free)); 793 #ifdef TURNSTILE_PROFILING 794 tc->tc_depth--; 795 #endif 796 } else 797 ts = LIST_FIRST(&ts->ts_free); 798 MPASS(ts != NULL); 799 LIST_REMOVE(ts, ts_hash); 800 td->td_turnstile = ts; 801 802 return (empty); 803 } 804 805 /* 806 * Put all blocked threads on the pending list. This must be called with 807 * the turnstile chain locked. 808 */ 809 void 810 turnstile_broadcast(struct turnstile *ts, int queue) 811 { 812 struct turnstile_chain *tc; 813 struct turnstile *ts1; 814 struct thread *td; 815 816 MPASS(ts != NULL); 817 mtx_assert(&ts->ts_lock, MA_OWNED); 818 MPASS(curthread->td_proc->p_magic == P_MAGIC); 819 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL); 820 /* 821 * We must have the chain locked so that we can remove the empty 822 * turnstile from the hash queue. 823 */ 824 tc = TC_LOOKUP(ts->ts_lockobj); 825 mtx_assert(&tc->tc_lock, MA_OWNED); 826 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 827 828 /* 829 * Transfer the blocked list to the pending list. 830 */ 831 mtx_lock_spin(&td_contested_lock); 832 TAILQ_CONCAT(&ts->ts_pending, &ts->ts_blocked[queue], td_lockq); 833 mtx_unlock_spin(&td_contested_lock); 834 835 /* 836 * Give a turnstile to each thread. The last thread gets 837 * this turnstile if the turnstile is empty. 838 */ 839 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq) { 840 if (LIST_EMPTY(&ts->ts_free)) { 841 MPASS(TAILQ_NEXT(td, td_lockq) == NULL); 842 ts1 = ts; 843 #ifdef TURNSTILE_PROFILING 844 tc->tc_depth--; 845 #endif 846 } else 847 ts1 = LIST_FIRST(&ts->ts_free); 848 MPASS(ts1 != NULL); 849 LIST_REMOVE(ts1, ts_hash); 850 td->td_turnstile = ts1; 851 } 852 } 853 854 /* 855 * Wakeup all threads on the pending list and adjust the priority of the 856 * current thread appropriately. This must be called with the turnstile 857 * chain locked. 858 */ 859 void 860 turnstile_unpend(struct turnstile *ts, int owner_type) 861 { 862 TAILQ_HEAD( ,thread) pending_threads; 863 struct turnstile *nts; 864 struct thread *td; 865 u_char cp, pri; 866 867 MPASS(ts != NULL); 868 mtx_assert(&ts->ts_lock, MA_OWNED); 869 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL); 870 MPASS(!TAILQ_EMPTY(&ts->ts_pending)); 871 872 /* 873 * Move the list of pending threads out of the turnstile and 874 * into a local variable. 875 */ 876 TAILQ_INIT(&pending_threads); 877 TAILQ_CONCAT(&pending_threads, &ts->ts_pending, td_lockq); 878 #ifdef INVARIANTS 879 if (TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) && 880 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE])) 881 ts->ts_lockobj = NULL; 882 #endif 883 /* 884 * Adjust the priority of curthread based on other contested 885 * locks it owns. Don't lower the priority below the base 886 * priority however. 887 */ 888 td = curthread; 889 pri = PRI_MAX; 890 thread_lock(td); 891 mtx_lock_spin(&td_contested_lock); 892 /* 893 * Remove the turnstile from this thread's list of contested locks 894 * since this thread doesn't own it anymore. New threads will 895 * not be blocking on the turnstile until it is claimed by a new 896 * owner. There might not be a current owner if this is a shared 897 * lock. 898 */ 899 if (ts->ts_owner != NULL) { 900 ts->ts_owner = NULL; 901 LIST_REMOVE(ts, ts_link); 902 } 903 LIST_FOREACH(nts, &td->td_contested, ts_link) { 904 cp = turnstile_first_waiter(nts)->td_priority; 905 if (cp < pri) 906 pri = cp; 907 } 908 mtx_unlock_spin(&td_contested_lock); 909 sched_unlend_prio(td, pri); 910 thread_unlock(td); 911 /* 912 * Wake up all the pending threads. If a thread is not blocked 913 * on a lock, then it is currently executing on another CPU in 914 * turnstile_wait() or sitting on a run queue waiting to resume 915 * in turnstile_wait(). Set a flag to force it to try to acquire 916 * the lock again instead of blocking. 917 */ 918 while (!TAILQ_EMPTY(&pending_threads)) { 919 td = TAILQ_FIRST(&pending_threads); 920 TAILQ_REMOVE(&pending_threads, td, td_lockq); 921 thread_lock(td); 922 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock); 923 MPASS(td->td_proc->p_magic == P_MAGIC); 924 MPASS(TD_ON_LOCK(td)); 925 TD_CLR_LOCK(td); 926 MPASS(TD_CAN_RUN(td)); 927 td->td_blocked = NULL; 928 td->td_lockname = NULL; 929 td->td_blktick = 0; 930 #ifdef INVARIANTS 931 td->td_tsqueue = 0xff; 932 #endif 933 sched_add(td, SRQ_BORING); 934 thread_unlock(td); 935 } 936 mtx_unlock_spin(&ts->ts_lock); 937 } 938 939 /* 940 * Give up ownership of a turnstile. This must be called with the 941 * turnstile chain locked. 942 */ 943 void 944 turnstile_disown(struct turnstile *ts) 945 { 946 struct thread *td; 947 u_char cp, pri; 948 949 MPASS(ts != NULL); 950 mtx_assert(&ts->ts_lock, MA_OWNED); 951 MPASS(ts->ts_owner == curthread); 952 MPASS(TAILQ_EMPTY(&ts->ts_pending)); 953 MPASS(!TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) || 954 !TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE])); 955 956 /* 957 * Remove the turnstile from this thread's list of contested locks 958 * since this thread doesn't own it anymore. New threads will 959 * not be blocking on the turnstile until it is claimed by a new 960 * owner. 961 */ 962 mtx_lock_spin(&td_contested_lock); 963 ts->ts_owner = NULL; 964 LIST_REMOVE(ts, ts_link); 965 mtx_unlock_spin(&td_contested_lock); 966 967 /* 968 * Adjust the priority of curthread based on other contested 969 * locks it owns. Don't lower the priority below the base 970 * priority however. 971 */ 972 td = curthread; 973 pri = PRI_MAX; 974 thread_lock(td); 975 mtx_unlock_spin(&ts->ts_lock); 976 mtx_lock_spin(&td_contested_lock); 977 LIST_FOREACH(ts, &td->td_contested, ts_link) { 978 cp = turnstile_first_waiter(ts)->td_priority; 979 if (cp < pri) 980 pri = cp; 981 } 982 mtx_unlock_spin(&td_contested_lock); 983 sched_unlend_prio(td, pri); 984 thread_unlock(td); 985 } 986 987 /* 988 * Return the first thread in a turnstile. 989 */ 990 struct thread * 991 turnstile_head(struct turnstile *ts, int queue) 992 { 993 #ifdef INVARIANTS 994 995 MPASS(ts != NULL); 996 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 997 mtx_assert(&ts->ts_lock, MA_OWNED); 998 #endif 999 return (TAILQ_FIRST(&ts->ts_blocked[queue])); 1000 } 1001 1002 /* 1003 * Returns true if a sub-queue of a turnstile is empty. 1004 */ 1005 int 1006 turnstile_empty(struct turnstile *ts, int queue) 1007 { 1008 #ifdef INVARIANTS 1009 1010 MPASS(ts != NULL); 1011 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE); 1012 mtx_assert(&ts->ts_lock, MA_OWNED); 1013 #endif 1014 return (TAILQ_EMPTY(&ts->ts_blocked[queue])); 1015 } 1016 1017 #ifdef DDB 1018 static void 1019 print_thread(struct thread *td, const char *prefix) 1020 { 1021 1022 db_printf("%s%p (tid %d, pid %d, \"%s\")\n", prefix, td, td->td_tid, 1023 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name : 1024 td->td_name); 1025 } 1026 1027 static void 1028 print_queue(struct threadqueue *queue, const char *header, const char *prefix) 1029 { 1030 struct thread *td; 1031 1032 db_printf("%s:\n", header); 1033 if (TAILQ_EMPTY(queue)) { 1034 db_printf("%sempty\n", prefix); 1035 return; 1036 } 1037 TAILQ_FOREACH(td, queue, td_lockq) { 1038 print_thread(td, prefix); 1039 } 1040 } 1041 1042 DB_SHOW_COMMAND(turnstile, db_show_turnstile) 1043 { 1044 struct turnstile_chain *tc; 1045 struct turnstile *ts; 1046 struct lock_object *lock; 1047 int i; 1048 1049 if (!have_addr) 1050 return; 1051 1052 /* 1053 * First, see if there is an active turnstile for the lock indicated 1054 * by the address. 1055 */ 1056 lock = (struct lock_object *)addr; 1057 tc = TC_LOOKUP(lock); 1058 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash) 1059 if (ts->ts_lockobj == lock) 1060 goto found; 1061 1062 /* 1063 * Second, see if there is an active turnstile at the address 1064 * indicated. 1065 */ 1066 for (i = 0; i < TC_TABLESIZE; i++) 1067 LIST_FOREACH(ts, &turnstile_chains[i].tc_turnstiles, ts_hash) { 1068 if (ts == (struct turnstile *)addr) 1069 goto found; 1070 } 1071 1072 db_printf("Unable to locate a turnstile via %p\n", (void *)addr); 1073 return; 1074 found: 1075 lock = ts->ts_lockobj; 1076 db_printf("Lock: %p - (%s) %s\n", lock, LOCK_CLASS(lock)->lc_name, 1077 lock->lo_name); 1078 if (ts->ts_owner) 1079 print_thread(ts->ts_owner, "Lock Owner: "); 1080 else 1081 db_printf("Lock Owner: none\n"); 1082 print_queue(&ts->ts_blocked[TS_SHARED_QUEUE], "Shared Waiters", "\t"); 1083 print_queue(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE], "Exclusive Waiters", 1084 "\t"); 1085 print_queue(&ts->ts_pending, "Pending Threads", "\t"); 1086 1087 } 1088 1089 /* 1090 * Show all the threads a particular thread is waiting on based on 1091 * non-sleepable and non-spin locks. 1092 */ 1093 static void 1094 print_lockchain(struct thread *td, const char *prefix) 1095 { 1096 struct lock_object *lock; 1097 struct lock_class *class; 1098 struct turnstile *ts; 1099 1100 /* 1101 * Follow the chain. We keep walking as long as the thread is 1102 * blocked on a turnstile that has an owner. 1103 */ 1104 while (!db_pager_quit) { 1105 db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid, 1106 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name : 1107 td->td_name); 1108 switch (td->td_state) { 1109 case TDS_INACTIVE: 1110 db_printf("is inactive\n"); 1111 return; 1112 case TDS_CAN_RUN: 1113 db_printf("can run\n"); 1114 return; 1115 case TDS_RUNQ: 1116 db_printf("is on a run queue\n"); 1117 return; 1118 case TDS_RUNNING: 1119 db_printf("running on CPU %d\n", td->td_oncpu); 1120 return; 1121 case TDS_INHIBITED: 1122 if (TD_ON_LOCK(td)) { 1123 ts = td->td_blocked; 1124 lock = ts->ts_lockobj; 1125 class = LOCK_CLASS(lock); 1126 db_printf("blocked on lock %p (%s) \"%s\"\n", 1127 lock, class->lc_name, lock->lo_name); 1128 if (ts->ts_owner == NULL) 1129 return; 1130 td = ts->ts_owner; 1131 break; 1132 } 1133 db_printf("inhibited\n"); 1134 return; 1135 default: 1136 db_printf("??? (%#x)\n", td->td_state); 1137 return; 1138 } 1139 } 1140 } 1141 1142 DB_SHOW_COMMAND(lockchain, db_show_lockchain) 1143 { 1144 struct thread *td; 1145 1146 /* Figure out which thread to start with. */ 1147 if (have_addr) 1148 td = db_lookup_thread(addr, TRUE); 1149 else 1150 td = kdb_thread; 1151 1152 print_lockchain(td, ""); 1153 } 1154 1155 DB_SHOW_ALL_COMMAND(chains, db_show_allchains) 1156 { 1157 struct thread *td; 1158 struct proc *p; 1159 int i; 1160 1161 i = 1; 1162 FOREACH_PROC_IN_SYSTEM(p) { 1163 FOREACH_THREAD_IN_PROC(p, td) { 1164 if (TD_ON_LOCK(td) && LIST_EMPTY(&td->td_contested)) { 1165 db_printf("chain %d:\n", i++); 1166 print_lockchain(td, " "); 1167 } 1168 if (db_pager_quit) 1169 return; 1170 } 1171 } 1172 } 1173 DB_SHOW_ALIAS(allchains, db_show_allchains) 1174 1175 /* 1176 * Show all the threads a particular thread is waiting on based on 1177 * sleepable locks. 1178 */ 1179 static void 1180 print_sleepchain(struct thread *td, const char *prefix) 1181 { 1182 struct thread *owner; 1183 1184 /* 1185 * Follow the chain. We keep walking as long as the thread is 1186 * blocked on a sleep lock that has an owner. 1187 */ 1188 while (!db_pager_quit) { 1189 db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid, 1190 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name : 1191 td->td_name); 1192 switch (td->td_state) { 1193 case TDS_INACTIVE: 1194 db_printf("is inactive\n"); 1195 return; 1196 case TDS_CAN_RUN: 1197 db_printf("can run\n"); 1198 return; 1199 case TDS_RUNQ: 1200 db_printf("is on a run queue\n"); 1201 return; 1202 case TDS_RUNNING: 1203 db_printf("running on CPU %d\n", td->td_oncpu); 1204 return; 1205 case TDS_INHIBITED: 1206 if (TD_ON_SLEEPQ(td)) { 1207 if (lockmgr_chain(td, &owner) || 1208 sx_chain(td, &owner)) { 1209 if (owner == NULL) 1210 return; 1211 td = owner; 1212 break; 1213 } 1214 db_printf("sleeping on %p \"%s\"\n", 1215 td->td_wchan, td->td_wmesg); 1216 return; 1217 } 1218 db_printf("inhibited\n"); 1219 return; 1220 default: 1221 db_printf("??? (%#x)\n", td->td_state); 1222 return; 1223 } 1224 } 1225 } 1226 1227 DB_SHOW_COMMAND(sleepchain, db_show_sleepchain) 1228 { 1229 struct thread *td; 1230 1231 /* Figure out which thread to start with. */ 1232 if (have_addr) 1233 td = db_lookup_thread(addr, TRUE); 1234 else 1235 td = kdb_thread; 1236 1237 print_sleepchain(td, ""); 1238 } 1239 1240 static void print_waiters(struct turnstile *ts, int indent); 1241 1242 static void 1243 print_waiter(struct thread *td, int indent) 1244 { 1245 struct turnstile *ts; 1246 int i; 1247 1248 if (db_pager_quit) 1249 return; 1250 for (i = 0; i < indent; i++) 1251 db_printf(" "); 1252 print_thread(td, "thread "); 1253 LIST_FOREACH(ts, &td->td_contested, ts_link) 1254 print_waiters(ts, indent + 1); 1255 } 1256 1257 static void 1258 print_waiters(struct turnstile *ts, int indent) 1259 { 1260 struct lock_object *lock; 1261 struct lock_class *class; 1262 struct thread *td; 1263 int i; 1264 1265 if (db_pager_quit) 1266 return; 1267 lock = ts->ts_lockobj; 1268 class = LOCK_CLASS(lock); 1269 for (i = 0; i < indent; i++) 1270 db_printf(" "); 1271 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name, lock->lo_name); 1272 TAILQ_FOREACH(td, &ts->ts_blocked[TS_EXCLUSIVE_QUEUE], td_lockq) 1273 print_waiter(td, indent + 1); 1274 TAILQ_FOREACH(td, &ts->ts_blocked[TS_SHARED_QUEUE], td_lockq) 1275 print_waiter(td, indent + 1); 1276 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq) 1277 print_waiter(td, indent + 1); 1278 } 1279 1280 DB_SHOW_COMMAND(locktree, db_show_locktree) 1281 { 1282 struct lock_object *lock; 1283 struct lock_class *class; 1284 struct turnstile_chain *tc; 1285 struct turnstile *ts; 1286 1287 if (!have_addr) 1288 return; 1289 lock = (struct lock_object *)addr; 1290 tc = TC_LOOKUP(lock); 1291 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash) 1292 if (ts->ts_lockobj == lock) 1293 break; 1294 if (ts == NULL) { 1295 class = LOCK_CLASS(lock); 1296 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name, 1297 lock->lo_name); 1298 } else 1299 print_waiters(ts, 0); 1300 } 1301 #endif
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