1 /*- 2 * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org> 3 * Copyright (c) 2001 Jason Evans <jasone@freebsd.org> 4 * 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(s), this list of conditions and the following disclaimer as 11 * the first lines of this file unmodified other than the possible 12 * addition of one or more copyright notices. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice(s), this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 20 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 23 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 24 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 27 * DAMAGE. 28 */ 29 30 /* 31 * Shared/exclusive locks. This implementation attempts to ensure 32 * deterministic lock granting behavior, so that slocks and xlocks are 33 * interleaved. 34 * 35 * Priority propagation will not generally raise the priority of lock holders, 36 * so should not be relied upon in combination with sx locks. 37 */ 38 39 #include "opt_ddb.h" 40 #include "opt_hwpmc_hooks.h" 41 #include "opt_no_adaptive_sx.h" 42 43 #include <sys/cdefs.h> 44 __FBSDID("$FreeBSD$"); 45 46 #include <sys/param.h> 47 #include <sys/systm.h> 48 #include <sys/kdb.h> 49 #include <sys/kernel.h> 50 #include <sys/ktr.h> 51 #include <sys/lock.h> 52 #include <sys/mutex.h> 53 #include <sys/proc.h> 54 #include <sys/sched.h> 55 #include <sys/sleepqueue.h> 56 #include <sys/sx.h> 57 #include <sys/smp.h> 58 #include <sys/sysctl.h> 59 60 #if defined(SMP) && !defined(NO_ADAPTIVE_SX) 61 #include <machine/cpu.h> 62 #endif 63 64 #ifdef DDB 65 #include <ddb/ddb.h> 66 #endif 67 68 #if defined(SMP) && !defined(NO_ADAPTIVE_SX) 69 #define ADAPTIVE_SX 70 #endif 71 72 CTASSERT((SX_NOADAPTIVE & LO_CLASSFLAGS) == SX_NOADAPTIVE); 73 74 #ifdef HWPMC_HOOKS 75 #include <sys/pmckern.h> 76 PMC_SOFT_DECLARE( , , lock, failed); 77 #endif 78 79 /* Handy macros for sleep queues. */ 80 #define SQ_EXCLUSIVE_QUEUE 0 81 #define SQ_SHARED_QUEUE 1 82 83 /* 84 * Variations on DROP_GIANT()/PICKUP_GIANT() for use in this file. We 85 * drop Giant anytime we have to sleep or if we adaptively spin. 86 */ 87 #define GIANT_DECLARE \ 88 int _giantcnt = 0; \ 89 WITNESS_SAVE_DECL(Giant) \ 90 91 #define GIANT_SAVE() do { \ 92 if (mtx_owned(&Giant)) { \ 93 WITNESS_SAVE(&Giant.lock_object, Giant); \ 94 while (mtx_owned(&Giant)) { \ 95 _giantcnt++; \ 96 mtx_unlock(&Giant); \ 97 } \ 98 } \ 99 } while (0) 100 101 #define GIANT_RESTORE() do { \ 102 if (_giantcnt > 0) { \ 103 mtx_assert(&Giant, MA_NOTOWNED); \ 104 while (_giantcnt--) \ 105 mtx_lock(&Giant); \ 106 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 107 } \ 108 } while (0) 109 110 /* 111 * Returns true if an exclusive lock is recursed. It assumes 112 * curthread currently has an exclusive lock. 113 */ 114 #define sx_recursed(sx) ((sx)->sx_recurse != 0) 115 116 static void assert_sx(const struct lock_object *lock, int what); 117 #ifdef DDB 118 static void db_show_sx(const struct lock_object *lock); 119 #endif 120 static void lock_sx(struct lock_object *lock, uintptr_t how); 121 #ifdef KDTRACE_HOOKS 122 static int owner_sx(const struct lock_object *lock, struct thread **owner); 123 #endif 124 static uintptr_t unlock_sx(struct lock_object *lock); 125 126 struct lock_class lock_class_sx = { 127 .lc_name = "sx", 128 .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE, 129 .lc_assert = assert_sx, 130 #ifdef DDB 131 .lc_ddb_show = db_show_sx, 132 #endif 133 .lc_lock = lock_sx, 134 .lc_unlock = unlock_sx, 135 #ifdef KDTRACE_HOOKS 136 .lc_owner = owner_sx, 137 #endif 138 }; 139 140 #ifndef INVARIANTS 141 #define _sx_assert(sx, what, file, line) 142 #endif 143 144 #ifdef ADAPTIVE_SX 145 static u_int asx_retries = 10; 146 static u_int asx_loops = 10000; 147 static SYSCTL_NODE(_debug, OID_AUTO, sx, CTLFLAG_RD, NULL, "sxlock debugging"); 148 SYSCTL_UINT(_debug_sx, OID_AUTO, retries, CTLFLAG_RW, &asx_retries, 0, ""); 149 SYSCTL_UINT(_debug_sx, OID_AUTO, loops, CTLFLAG_RW, &asx_loops, 0, ""); 150 151 static struct lock_delay_config __read_mostly sx_delay = { 152 .initial = 1000, 153 .step = 500, 154 .min = 100, 155 .max = 5000, 156 }; 157 158 SYSCTL_INT(_debug_sx, OID_AUTO, delay_initial, CTLFLAG_RW, &sx_delay.initial, 159 0, ""); 160 SYSCTL_INT(_debug_sx, OID_AUTO, delay_step, CTLFLAG_RW, &sx_delay.step, 161 0, ""); 162 SYSCTL_INT(_debug_sx, OID_AUTO, delay_min, CTLFLAG_RW, &sx_delay.min, 163 0, ""); 164 SYSCTL_INT(_debug_sx, OID_AUTO, delay_max, CTLFLAG_RW, &sx_delay.max, 165 0, ""); 166 167 static void 168 sx_delay_sysinit(void *dummy) 169 { 170 171 sx_delay.initial = mp_ncpus * 25; 172 sx_delay.step = (mp_ncpus * 25) / 2; 173 sx_delay.min = mp_ncpus * 5; 174 sx_delay.max = mp_ncpus * 25 * 10; 175 } 176 LOCK_DELAY_SYSINIT(sx_delay_sysinit); 177 #endif 178 179 void 180 assert_sx(const struct lock_object *lock, int what) 181 { 182 183 sx_assert((const struct sx *)lock, what); 184 } 185 186 void 187 lock_sx(struct lock_object *lock, uintptr_t how) 188 { 189 struct sx *sx; 190 191 sx = (struct sx *)lock; 192 if (how) 193 sx_slock(sx); 194 else 195 sx_xlock(sx); 196 } 197 198 uintptr_t 199 unlock_sx(struct lock_object *lock) 200 { 201 struct sx *sx; 202 203 sx = (struct sx *)lock; 204 sx_assert(sx, SA_LOCKED | SA_NOTRECURSED); 205 if (sx_xlocked(sx)) { 206 sx_xunlock(sx); 207 return (0); 208 } else { 209 sx_sunlock(sx); 210 return (1); 211 } 212 } 213 214 #ifdef KDTRACE_HOOKS 215 int 216 owner_sx(const struct lock_object *lock, struct thread **owner) 217 { 218 const struct sx *sx; 219 uintptr_t x; 220 221 sx = (const struct sx *)lock; 222 x = sx->sx_lock; 223 *owner = NULL; 224 return ((x & SX_LOCK_SHARED) != 0 ? (SX_SHARERS(x) != 0) : 225 ((*owner = (struct thread *)SX_OWNER(x)) != NULL)); 226 } 227 #endif 228 229 void 230 sx_sysinit(void *arg) 231 { 232 struct sx_args *sargs = arg; 233 234 sx_init_flags(sargs->sa_sx, sargs->sa_desc, sargs->sa_flags); 235 } 236 237 void 238 sx_init_flags(struct sx *sx, const char *description, int opts) 239 { 240 int flags; 241 242 MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK | 243 SX_NOPROFILE | SX_NOADAPTIVE | SX_NEW)) == 0); 244 ASSERT_ATOMIC_LOAD_PTR(sx->sx_lock, 245 ("%s: sx_lock not aligned for %s: %p", __func__, description, 246 &sx->sx_lock)); 247 248 flags = LO_SLEEPABLE | LO_UPGRADABLE; 249 if (opts & SX_DUPOK) 250 flags |= LO_DUPOK; 251 if (opts & SX_NOPROFILE) 252 flags |= LO_NOPROFILE; 253 if (!(opts & SX_NOWITNESS)) 254 flags |= LO_WITNESS; 255 if (opts & SX_RECURSE) 256 flags |= LO_RECURSABLE; 257 if (opts & SX_QUIET) 258 flags |= LO_QUIET; 259 if (opts & SX_NEW) 260 flags |= LO_NEW; 261 262 flags |= opts & SX_NOADAPTIVE; 263 lock_init(&sx->lock_object, &lock_class_sx, description, NULL, flags); 264 sx->sx_lock = SX_LOCK_UNLOCKED; 265 sx->sx_recurse = 0; 266 } 267 268 void 269 sx_destroy(struct sx *sx) 270 { 271 272 KASSERT(sx->sx_lock == SX_LOCK_UNLOCKED, ("sx lock still held")); 273 KASSERT(sx->sx_recurse == 0, ("sx lock still recursed")); 274 sx->sx_lock = SX_LOCK_DESTROYED; 275 lock_destroy(&sx->lock_object); 276 } 277 278 int 279 sx_try_slock_(struct sx *sx, const char *file, int line) 280 { 281 uintptr_t x; 282 283 if (SCHEDULER_STOPPED()) 284 return (1); 285 286 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 287 ("sx_try_slock() by idle thread %p on sx %s @ %s:%d", 288 curthread, sx->lock_object.lo_name, file, line)); 289 290 for (;;) { 291 x = sx->sx_lock; 292 KASSERT(x != SX_LOCK_DESTROYED, 293 ("sx_try_slock() of destroyed sx @ %s:%d", file, line)); 294 if (!(x & SX_LOCK_SHARED)) 295 break; 296 if (atomic_cmpset_acq_ptr(&sx->sx_lock, x, x + SX_ONE_SHARER)) { 297 LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 1, file, line); 298 WITNESS_LOCK(&sx->lock_object, LOP_TRYLOCK, file, line); 299 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, 300 sx, 0, 0, file, line, LOCKSTAT_READER); 301 TD_LOCKS_INC(curthread); 302 return (1); 303 } 304 } 305 306 LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 0, file, line); 307 return (0); 308 } 309 310 int 311 _sx_xlock(struct sx *sx, int opts, const char *file, int line) 312 { 313 uintptr_t tid, x; 314 int error = 0; 315 316 if (SCHEDULER_STOPPED()) 317 return (0); 318 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 319 ("sx_xlock() by idle thread %p on sx %s @ %s:%d", 320 curthread, sx->lock_object.lo_name, file, line)); 321 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 322 ("sx_xlock() of destroyed sx @ %s:%d", file, line)); 323 WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, 324 line, NULL); 325 tid = (uintptr_t)curthread; 326 x = SX_LOCK_UNLOCKED; 327 if (!atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 328 error = _sx_xlock_hard(sx, x, tid, opts, file, line); 329 else 330 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 331 0, 0, file, line, LOCKSTAT_WRITER); 332 if (!error) { 333 LOCK_LOG_LOCK("XLOCK", &sx->lock_object, 0, sx->sx_recurse, 334 file, line); 335 WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); 336 TD_LOCKS_INC(curthread); 337 } 338 339 return (error); 340 } 341 342 int 343 sx_try_xlock_(struct sx *sx, const char *file, int line) 344 { 345 int rval; 346 347 if (SCHEDULER_STOPPED()) 348 return (1); 349 350 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 351 ("sx_try_xlock() by idle thread %p on sx %s @ %s:%d", 352 curthread, sx->lock_object.lo_name, file, line)); 353 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 354 ("sx_try_xlock() of destroyed sx @ %s:%d", file, line)); 355 356 if (sx_xlocked(sx) && 357 (sx->lock_object.lo_flags & LO_RECURSABLE) != 0) { 358 sx->sx_recurse++; 359 atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 360 rval = 1; 361 } else 362 rval = atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, 363 (uintptr_t)curthread); 364 LOCK_LOG_TRY("XLOCK", &sx->lock_object, 0, rval, file, line); 365 if (rval) { 366 WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 367 file, line); 368 if (!sx_recursed(sx)) 369 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, 370 sx, 0, 0, file, line, LOCKSTAT_WRITER); 371 TD_LOCKS_INC(curthread); 372 } 373 374 return (rval); 375 } 376 377 void 378 _sx_xunlock(struct sx *sx, const char *file, int line) 379 { 380 381 if (SCHEDULER_STOPPED()) 382 return; 383 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 384 ("sx_xunlock() of destroyed sx @ %s:%d", file, line)); 385 _sx_assert(sx, SA_XLOCKED, file, line); 386 WITNESS_UNLOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); 387 LOCK_LOG_LOCK("XUNLOCK", &sx->lock_object, 0, sx->sx_recurse, file, 388 line); 389 _sx_xunlock_hard(sx, (uintptr_t)curthread, file, line); 390 TD_LOCKS_DEC(curthread); 391 } 392 393 /* 394 * Try to do a non-blocking upgrade from a shared lock to an exclusive lock. 395 * This will only succeed if this thread holds a single shared lock. 396 * Return 1 if if the upgrade succeed, 0 otherwise. 397 */ 398 int 399 sx_try_upgrade_(struct sx *sx, const char *file, int line) 400 { 401 uintptr_t x; 402 int success; 403 404 if (SCHEDULER_STOPPED()) 405 return (1); 406 407 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 408 ("sx_try_upgrade() of destroyed sx @ %s:%d", file, line)); 409 _sx_assert(sx, SA_SLOCKED, file, line); 410 411 /* 412 * Try to switch from one shared lock to an exclusive lock. We need 413 * to maintain the SX_LOCK_EXCLUSIVE_WAITERS flag if set so that 414 * we will wake up the exclusive waiters when we drop the lock. 415 */ 416 x = sx->sx_lock & SX_LOCK_EXCLUSIVE_WAITERS; 417 success = atomic_cmpset_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | x, 418 (uintptr_t)curthread | x); 419 LOCK_LOG_TRY("XUPGRADE", &sx->lock_object, 0, success, file, line); 420 if (success) { 421 WITNESS_UPGRADE(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 422 file, line); 423 LOCKSTAT_RECORD0(sx__upgrade, sx); 424 } 425 return (success); 426 } 427 428 /* 429 * Downgrade an unrecursed exclusive lock into a single shared lock. 430 */ 431 void 432 sx_downgrade_(struct sx *sx, const char *file, int line) 433 { 434 uintptr_t x; 435 int wakeup_swapper; 436 437 if (SCHEDULER_STOPPED()) 438 return; 439 440 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 441 ("sx_downgrade() of destroyed sx @ %s:%d", file, line)); 442 _sx_assert(sx, SA_XLOCKED | SA_NOTRECURSED, file, line); 443 #ifndef INVARIANTS 444 if (sx_recursed(sx)) 445 panic("downgrade of a recursed lock"); 446 #endif 447 448 WITNESS_DOWNGRADE(&sx->lock_object, 0, file, line); 449 450 /* 451 * Try to switch from an exclusive lock with no shared waiters 452 * to one sharer with no shared waiters. If there are 453 * exclusive waiters, we don't need to lock the sleep queue so 454 * long as we preserve the flag. We do one quick try and if 455 * that fails we grab the sleepq lock to keep the flags from 456 * changing and do it the slow way. 457 * 458 * We have to lock the sleep queue if there are shared waiters 459 * so we can wake them up. 460 */ 461 x = sx->sx_lock; 462 if (!(x & SX_LOCK_SHARED_WAITERS) && 463 atomic_cmpset_rel_ptr(&sx->sx_lock, x, SX_SHARERS_LOCK(1) | 464 (x & SX_LOCK_EXCLUSIVE_WAITERS))) { 465 LOCK_LOG_LOCK("XDOWNGRADE", &sx->lock_object, 0, 0, file, line); 466 return; 467 } 468 469 /* 470 * Lock the sleep queue so we can read the waiters bits 471 * without any races and wakeup any shared waiters. 472 */ 473 sleepq_lock(&sx->lock_object); 474 475 /* 476 * Preserve SX_LOCK_EXCLUSIVE_WAITERS while downgraded to a single 477 * shared lock. If there are any shared waiters, wake them up. 478 */ 479 wakeup_swapper = 0; 480 x = sx->sx_lock; 481 atomic_store_rel_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | 482 (x & SX_LOCK_EXCLUSIVE_WAITERS)); 483 if (x & SX_LOCK_SHARED_WAITERS) 484 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 485 0, SQ_SHARED_QUEUE); 486 sleepq_release(&sx->lock_object); 487 488 LOCK_LOG_LOCK("XDOWNGRADE", &sx->lock_object, 0, 0, file, line); 489 LOCKSTAT_RECORD0(sx__downgrade, sx); 490 491 if (wakeup_swapper) 492 kick_proc0(); 493 } 494 495 /* 496 * This function represents the so-called 'hard case' for sx_xlock 497 * operation. All 'easy case' failures are redirected to this. Note 498 * that ideally this would be a static function, but it needs to be 499 * accessible from at least sx.h. 500 */ 501 int 502 _sx_xlock_hard(struct sx *sx, uintptr_t x, uintptr_t tid, int opts, 503 const char *file, int line) 504 { 505 GIANT_DECLARE; 506 #ifdef ADAPTIVE_SX 507 volatile struct thread *owner; 508 u_int i, spintries = 0; 509 #endif 510 #ifdef LOCK_PROFILING 511 uint64_t waittime = 0; 512 int contested = 0; 513 #endif 514 int error = 0; 515 #if defined(ADAPTIVE_SX) || defined(KDTRACE_HOOKS) 516 struct lock_delay_arg lda; 517 #endif 518 #ifdef KDTRACE_HOOKS 519 uintptr_t state; 520 u_int sleep_cnt = 0; 521 int64_t sleep_time = 0; 522 int64_t all_time = 0; 523 #endif 524 525 if (SCHEDULER_STOPPED()) 526 return (0); 527 528 #if defined(ADAPTIVE_SX) 529 lock_delay_arg_init(&lda, &sx_delay); 530 #elif defined(KDTRACE_HOOKS) 531 lock_delay_arg_init(&lda, NULL); 532 #endif 533 534 if (__predict_false(x == SX_LOCK_UNLOCKED)) 535 x = SX_READ_VALUE(sx); 536 537 /* If we already hold an exclusive lock, then recurse. */ 538 if (__predict_false(lv_sx_owner(x) == (struct thread *)tid)) { 539 KASSERT((sx->lock_object.lo_flags & LO_RECURSABLE) != 0, 540 ("_sx_xlock_hard: recursed on non-recursive sx %s @ %s:%d\n", 541 sx->lock_object.lo_name, file, line)); 542 sx->sx_recurse++; 543 atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 544 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 545 CTR2(KTR_LOCK, "%s: %p recursing", __func__, sx); 546 return (0); 547 } 548 549 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 550 CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, 551 sx->lock_object.lo_name, (void *)sx->sx_lock, file, line); 552 553 #ifdef KDTRACE_HOOKS 554 all_time -= lockstat_nsecs(&sx->lock_object); 555 state = x; 556 #endif 557 for (;;) { 558 if (x == SX_LOCK_UNLOCKED) { 559 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 560 break; 561 continue; 562 } 563 #ifdef KDTRACE_HOOKS 564 lda.spin_cnt++; 565 #endif 566 #ifdef HWPMC_HOOKS 567 PMC_SOFT_CALL( , , lock, failed); 568 #endif 569 lock_profile_obtain_lock_failed(&sx->lock_object, &contested, 570 &waittime); 571 #ifdef ADAPTIVE_SX 572 /* 573 * If the lock is write locked and the owner is 574 * running on another CPU, spin until the owner stops 575 * running or the state of the lock changes. 576 */ 577 if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 578 if ((x & SX_LOCK_SHARED) == 0) { 579 owner = lv_sx_owner(x); 580 if (TD_IS_RUNNING(owner)) { 581 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 582 CTR3(KTR_LOCK, 583 "%s: spinning on %p held by %p", 584 __func__, sx, owner); 585 KTR_STATE1(KTR_SCHED, "thread", 586 sched_tdname(curthread), "spinning", 587 "lockname:\"%s\"", 588 sx->lock_object.lo_name); 589 GIANT_SAVE(); 590 do { 591 lock_delay(&lda); 592 x = SX_READ_VALUE(sx); 593 owner = lv_sx_owner(x); 594 } while (owner != NULL && 595 TD_IS_RUNNING(owner)); 596 KTR_STATE0(KTR_SCHED, "thread", 597 sched_tdname(curthread), "running"); 598 continue; 599 } 600 } else if (SX_SHARERS(x) && spintries < asx_retries) { 601 KTR_STATE1(KTR_SCHED, "thread", 602 sched_tdname(curthread), "spinning", 603 "lockname:\"%s\"", sx->lock_object.lo_name); 604 GIANT_SAVE(); 605 spintries++; 606 for (i = 0; i < asx_loops; i++) { 607 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 608 CTR4(KTR_LOCK, 609 "%s: shared spinning on %p with %u and %u", 610 __func__, sx, spintries, i); 611 x = sx->sx_lock; 612 if ((x & SX_LOCK_SHARED) == 0 || 613 SX_SHARERS(x) == 0) 614 break; 615 cpu_spinwait(); 616 #ifdef KDTRACE_HOOKS 617 lda.spin_cnt++; 618 #endif 619 } 620 KTR_STATE0(KTR_SCHED, "thread", 621 sched_tdname(curthread), "running"); 622 x = SX_READ_VALUE(sx); 623 if (i != asx_loops) 624 continue; 625 } 626 } 627 #endif 628 629 sleepq_lock(&sx->lock_object); 630 x = SX_READ_VALUE(sx); 631 632 /* 633 * If the lock was released while spinning on the 634 * sleep queue chain lock, try again. 635 */ 636 if (x == SX_LOCK_UNLOCKED) { 637 sleepq_release(&sx->lock_object); 638 continue; 639 } 640 641 #ifdef ADAPTIVE_SX 642 /* 643 * The current lock owner might have started executing 644 * on another CPU (or the lock could have changed 645 * owners) while we were waiting on the sleep queue 646 * chain lock. If so, drop the sleep queue lock and try 647 * again. 648 */ 649 if (!(x & SX_LOCK_SHARED) && 650 (sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 651 owner = (struct thread *)SX_OWNER(x); 652 if (TD_IS_RUNNING(owner)) { 653 sleepq_release(&sx->lock_object); 654 continue; 655 } 656 } 657 #endif 658 659 /* 660 * If an exclusive lock was released with both shared 661 * and exclusive waiters and a shared waiter hasn't 662 * woken up and acquired the lock yet, sx_lock will be 663 * set to SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS. 664 * If we see that value, try to acquire it once. Note 665 * that we have to preserve SX_LOCK_EXCLUSIVE_WAITERS 666 * as there are other exclusive waiters still. If we 667 * fail, restart the loop. 668 */ 669 if (x == (SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS)) { 670 if (atomic_cmpset_acq_ptr(&sx->sx_lock, 671 SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS, 672 tid | SX_LOCK_EXCLUSIVE_WAITERS)) { 673 sleepq_release(&sx->lock_object); 674 CTR2(KTR_LOCK, "%s: %p claimed by new writer", 675 __func__, sx); 676 break; 677 } 678 sleepq_release(&sx->lock_object); 679 x = SX_READ_VALUE(sx); 680 continue; 681 } 682 683 /* 684 * Try to set the SX_LOCK_EXCLUSIVE_WAITERS. If we fail, 685 * than loop back and retry. 686 */ 687 if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) { 688 if (!atomic_cmpset_ptr(&sx->sx_lock, x, 689 x | SX_LOCK_EXCLUSIVE_WAITERS)) { 690 sleepq_release(&sx->lock_object); 691 x = SX_READ_VALUE(sx); 692 continue; 693 } 694 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 695 CTR2(KTR_LOCK, "%s: %p set excl waiters flag", 696 __func__, sx); 697 } 698 699 /* 700 * Since we have been unable to acquire the exclusive 701 * lock and the exclusive waiters flag is set, we have 702 * to sleep. 703 */ 704 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 705 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 706 __func__, sx); 707 708 #ifdef KDTRACE_HOOKS 709 sleep_time -= lockstat_nsecs(&sx->lock_object); 710 #endif 711 GIANT_SAVE(); 712 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 713 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 714 SLEEPQ_INTERRUPTIBLE : 0), SQ_EXCLUSIVE_QUEUE); 715 if (!(opts & SX_INTERRUPTIBLE)) 716 sleepq_wait(&sx->lock_object, 0); 717 else 718 error = sleepq_wait_sig(&sx->lock_object, 0); 719 #ifdef KDTRACE_HOOKS 720 sleep_time += lockstat_nsecs(&sx->lock_object); 721 sleep_cnt++; 722 #endif 723 if (error) { 724 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 725 CTR2(KTR_LOCK, 726 "%s: interruptible sleep by %p suspended by signal", 727 __func__, sx); 728 break; 729 } 730 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 731 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 732 __func__, sx); 733 x = SX_READ_VALUE(sx); 734 } 735 #ifdef KDTRACE_HOOKS 736 all_time += lockstat_nsecs(&sx->lock_object); 737 if (sleep_time) 738 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 739 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 740 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 741 if (lda.spin_cnt > sleep_cnt) 742 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 743 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 744 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 745 #endif 746 if (!error) 747 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 748 contested, waittime, file, line, LOCKSTAT_WRITER); 749 GIANT_RESTORE(); 750 return (error); 751 } 752 753 /* 754 * This function represents the so-called 'hard case' for sx_xunlock 755 * operation. All 'easy case' failures are redirected to this. Note 756 * that ideally this would be a static function, but it needs to be 757 * accessible from at least sx.h. 758 */ 759 void 760 _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int line) 761 { 762 uintptr_t x; 763 int queue, wakeup_swapper; 764 765 if (SCHEDULER_STOPPED()) 766 return; 767 768 MPASS(!(sx->sx_lock & SX_LOCK_SHARED)); 769 770 if (!sx_recursed(sx)) { 771 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, 772 LOCKSTAT_WRITER); 773 if (atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED)) 774 return; 775 } else { 776 /* The lock is recursed, unrecurse one level. */ 777 if ((--sx->sx_recurse) == 0) 778 atomic_clear_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 779 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 780 CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, sx); 781 return; 782 } 783 MPASS(sx->sx_lock & (SX_LOCK_SHARED_WAITERS | 784 SX_LOCK_EXCLUSIVE_WAITERS)); 785 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 786 CTR2(KTR_LOCK, "%s: %p contested", __func__, sx); 787 788 sleepq_lock(&sx->lock_object); 789 x = SX_LOCK_UNLOCKED; 790 791 /* 792 * The wake up algorithm here is quite simple and probably not 793 * ideal. It gives precedence to shared waiters if they are 794 * present. For this condition, we have to preserve the 795 * state of the exclusive waiters flag. 796 * If interruptible sleeps left the shared queue empty avoid a 797 * starvation for the threads sleeping on the exclusive queue by giving 798 * them precedence and cleaning up the shared waiters bit anyway. 799 */ 800 if ((sx->sx_lock & SX_LOCK_SHARED_WAITERS) != 0 && 801 sleepq_sleepcnt(&sx->lock_object, SQ_SHARED_QUEUE) != 0) { 802 queue = SQ_SHARED_QUEUE; 803 x |= (sx->sx_lock & SX_LOCK_EXCLUSIVE_WAITERS); 804 } else 805 queue = SQ_EXCLUSIVE_QUEUE; 806 807 /* Wake up all the waiters for the specific queue. */ 808 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 809 CTR3(KTR_LOCK, "%s: %p waking up all threads on %s queue", 810 __func__, sx, queue == SQ_SHARED_QUEUE ? "shared" : 811 "exclusive"); 812 atomic_store_rel_ptr(&sx->sx_lock, x); 813 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 0, 814 queue); 815 sleepq_release(&sx->lock_object); 816 if (wakeup_swapper) 817 kick_proc0(); 818 } 819 820 int 821 _sx_slock(struct sx *sx, int opts, const char *file, int line) 822 { 823 GIANT_DECLARE; 824 #ifdef ADAPTIVE_SX 825 volatile struct thread *owner; 826 #endif 827 #ifdef LOCK_PROFILING 828 uint64_t waittime = 0; 829 int contested = 0; 830 #endif 831 uintptr_t x; 832 int error = 0; 833 #if defined(ADAPTIVE_SX) || defined(KDTRACE_HOOKS) 834 struct lock_delay_arg lda; 835 #endif 836 #ifdef KDTRACE_HOOKS 837 uintptr_t state; 838 u_int sleep_cnt = 0; 839 int64_t sleep_time = 0; 840 int64_t all_time = 0; 841 #endif 842 843 if (SCHEDULER_STOPPED()) 844 return (0); 845 846 #if defined(ADAPTIVE_SX) 847 lock_delay_arg_init(&lda, &sx_delay); 848 #elif defined(KDTRACE_HOOKS) 849 lock_delay_arg_init(&lda, NULL); 850 #endif 851 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 852 ("sx_slock() by idle thread %p on sx %s @ %s:%d", 853 curthread, sx->lock_object.lo_name, file, line)); 854 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 855 ("sx_slock() of destroyed sx @ %s:%d", file, line)); 856 WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER, file, line, NULL); 857 #ifdef KDTRACE_HOOKS 858 all_time -= lockstat_nsecs(&sx->lock_object); 859 #endif 860 x = SX_READ_VALUE(sx); 861 #ifdef KDTRACE_HOOKS 862 state = x; 863 #endif 864 865 /* 866 * As with rwlocks, we don't make any attempt to try to block 867 * shared locks once there is an exclusive waiter. 868 */ 869 for (;;) { 870 /* 871 * If no other thread has an exclusive lock then try to bump up 872 * the count of sharers. Since we have to preserve the state 873 * of SX_LOCK_EXCLUSIVE_WAITERS, if we fail to acquire the 874 * shared lock loop back and retry. 875 */ 876 if (x & SX_LOCK_SHARED) { 877 MPASS(!(x & SX_LOCK_SHARED_WAITERS)); 878 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, 879 x + SX_ONE_SHARER)) { 880 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 881 CTR4(KTR_LOCK, 882 "%s: %p succeed %p -> %p", __func__, 883 sx, (void *)x, 884 (void *)(x + SX_ONE_SHARER)); 885 break; 886 } 887 continue; 888 } 889 #ifdef KDTRACE_HOOKS 890 lda.spin_cnt++; 891 #endif 892 893 #ifdef HWPMC_HOOKS 894 PMC_SOFT_CALL( , , lock, failed); 895 #endif 896 lock_profile_obtain_lock_failed(&sx->lock_object, &contested, 897 &waittime); 898 899 #ifdef ADAPTIVE_SX 900 /* 901 * If the owner is running on another CPU, spin until 902 * the owner stops running or the state of the lock 903 * changes. 904 */ 905 if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 906 owner = lv_sx_owner(x); 907 if (TD_IS_RUNNING(owner)) { 908 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 909 CTR3(KTR_LOCK, 910 "%s: spinning on %p held by %p", 911 __func__, sx, owner); 912 KTR_STATE1(KTR_SCHED, "thread", 913 sched_tdname(curthread), "spinning", 914 "lockname:\"%s\"", sx->lock_object.lo_name); 915 GIANT_SAVE(); 916 do { 917 lock_delay(&lda); 918 x = SX_READ_VALUE(sx); 919 owner = lv_sx_owner(x); 920 } while (owner != NULL && TD_IS_RUNNING(owner)); 921 KTR_STATE0(KTR_SCHED, "thread", 922 sched_tdname(curthread), "running"); 923 continue; 924 } 925 } 926 #endif 927 928 /* 929 * Some other thread already has an exclusive lock, so 930 * start the process of blocking. 931 */ 932 sleepq_lock(&sx->lock_object); 933 x = SX_READ_VALUE(sx); 934 935 /* 936 * The lock could have been released while we spun. 937 * In this case loop back and retry. 938 */ 939 if (x & SX_LOCK_SHARED) { 940 sleepq_release(&sx->lock_object); 941 continue; 942 } 943 944 #ifdef ADAPTIVE_SX 945 /* 946 * If the owner is running on another CPU, spin until 947 * the owner stops running or the state of the lock 948 * changes. 949 */ 950 if (!(x & SX_LOCK_SHARED) && 951 (sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 952 owner = (struct thread *)SX_OWNER(x); 953 if (TD_IS_RUNNING(owner)) { 954 sleepq_release(&sx->lock_object); 955 x = SX_READ_VALUE(sx); 956 continue; 957 } 958 } 959 #endif 960 961 /* 962 * Try to set the SX_LOCK_SHARED_WAITERS flag. If we 963 * fail to set it drop the sleep queue lock and loop 964 * back. 965 */ 966 if (!(x & SX_LOCK_SHARED_WAITERS)) { 967 if (!atomic_cmpset_ptr(&sx->sx_lock, x, 968 x | SX_LOCK_SHARED_WAITERS)) { 969 sleepq_release(&sx->lock_object); 970 x = SX_READ_VALUE(sx); 971 continue; 972 } 973 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 974 CTR2(KTR_LOCK, "%s: %p set shared waiters flag", 975 __func__, sx); 976 } 977 978 /* 979 * Since we have been unable to acquire the shared lock, 980 * we have to sleep. 981 */ 982 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 983 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 984 __func__, sx); 985 986 #ifdef KDTRACE_HOOKS 987 sleep_time -= lockstat_nsecs(&sx->lock_object); 988 #endif 989 GIANT_SAVE(); 990 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 991 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 992 SLEEPQ_INTERRUPTIBLE : 0), SQ_SHARED_QUEUE); 993 if (!(opts & SX_INTERRUPTIBLE)) 994 sleepq_wait(&sx->lock_object, 0); 995 else 996 error = sleepq_wait_sig(&sx->lock_object, 0); 997 #ifdef KDTRACE_HOOKS 998 sleep_time += lockstat_nsecs(&sx->lock_object); 999 sleep_cnt++; 1000 #endif 1001 if (error) { 1002 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1003 CTR2(KTR_LOCK, 1004 "%s: interruptible sleep by %p suspended by signal", 1005 __func__, sx); 1006 break; 1007 } 1008 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1009 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 1010 __func__, sx); 1011 x = SX_READ_VALUE(sx); 1012 } 1013 #ifdef KDTRACE_HOOKS 1014 all_time += lockstat_nsecs(&sx->lock_object); 1015 if (sleep_time) 1016 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 1017 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1018 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1019 if (lda.spin_cnt > sleep_cnt) 1020 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 1021 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1022 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1023 #endif 1024 if (error == 0) { 1025 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 1026 contested, waittime, file, line, LOCKSTAT_READER); 1027 LOCK_LOG_LOCK("SLOCK", &sx->lock_object, 0, 0, file, line); 1028 WITNESS_LOCK(&sx->lock_object, 0, file, line); 1029 TD_LOCKS_INC(curthread); 1030 } 1031 GIANT_RESTORE(); 1032 return (error); 1033 } 1034 1035 void 1036 _sx_sunlock(struct sx *sx, const char *file, int line) 1037 { 1038 uintptr_t x; 1039 int wakeup_swapper; 1040 1041 if (SCHEDULER_STOPPED()) 1042 return; 1043 1044 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 1045 ("sx_sunlock() of destroyed sx @ %s:%d", file, line)); 1046 _sx_assert(sx, SA_SLOCKED, file, line); 1047 WITNESS_UNLOCK(&sx->lock_object, 0, file, line); 1048 LOCK_LOG_LOCK("SUNLOCK", &sx->lock_object, 0, 0, file, line); 1049 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_READER); 1050 x = SX_READ_VALUE(sx); 1051 for (;;) { 1052 /* 1053 * We should never have sharers while at least one thread 1054 * holds a shared lock. 1055 */ 1056 KASSERT(!(x & SX_LOCK_SHARED_WAITERS), 1057 ("%s: waiting sharers", __func__)); 1058 1059 /* 1060 * See if there is more than one shared lock held. If 1061 * so, just drop one and return. 1062 */ 1063 if (SX_SHARERS(x) > 1) { 1064 if (atomic_fcmpset_rel_ptr(&sx->sx_lock, &x, 1065 x - SX_ONE_SHARER)) { 1066 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1067 CTR4(KTR_LOCK, 1068 "%s: %p succeeded %p -> %p", 1069 __func__, sx, (void *)x, 1070 (void *)(x - SX_ONE_SHARER)); 1071 break; 1072 } 1073 continue; 1074 } 1075 1076 /* 1077 * If there aren't any waiters for an exclusive lock, 1078 * then try to drop it quickly. 1079 */ 1080 if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) { 1081 MPASS(x == SX_SHARERS_LOCK(1)); 1082 x = SX_SHARERS_LOCK(1); 1083 if (atomic_fcmpset_rel_ptr(&sx->sx_lock, 1084 &x, SX_LOCK_UNLOCKED)) { 1085 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1086 CTR2(KTR_LOCK, "%s: %p last succeeded", 1087 __func__, sx); 1088 break; 1089 } 1090 continue; 1091 } 1092 1093 /* 1094 * At this point, there should just be one sharer with 1095 * exclusive waiters. 1096 */ 1097 MPASS(x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS)); 1098 1099 sleepq_lock(&sx->lock_object); 1100 1101 /* 1102 * Wake up semantic here is quite simple: 1103 * Just wake up all the exclusive waiters. 1104 * Note that the state of the lock could have changed, 1105 * so if it fails loop back and retry. 1106 */ 1107 if (!atomic_cmpset_rel_ptr(&sx->sx_lock, 1108 SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS, 1109 SX_LOCK_UNLOCKED)) { 1110 sleepq_release(&sx->lock_object); 1111 x = SX_READ_VALUE(sx); 1112 continue; 1113 } 1114 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1115 CTR2(KTR_LOCK, "%s: %p waking up all thread on" 1116 "exclusive queue", __func__, sx); 1117 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 1118 0, SQ_EXCLUSIVE_QUEUE); 1119 sleepq_release(&sx->lock_object); 1120 if (wakeup_swapper) 1121 kick_proc0(); 1122 break; 1123 } 1124 TD_LOCKS_DEC(curthread); 1125 } 1126 1127 #ifdef INVARIANT_SUPPORT 1128 #ifndef INVARIANTS 1129 #undef _sx_assert 1130 #endif 1131 1132 /* 1133 * In the non-WITNESS case, sx_assert() can only detect that at least 1134 * *some* thread owns an slock, but it cannot guarantee that *this* 1135 * thread owns an slock. 1136 */ 1137 void 1138 _sx_assert(const struct sx *sx, int what, const char *file, int line) 1139 { 1140 #ifndef WITNESS 1141 int slocked = 0; 1142 #endif 1143 1144 if (panicstr != NULL) 1145 return; 1146 switch (what) { 1147 case SA_SLOCKED: 1148 case SA_SLOCKED | SA_NOTRECURSED: 1149 case SA_SLOCKED | SA_RECURSED: 1150 #ifndef WITNESS 1151 slocked = 1; 1152 /* FALLTHROUGH */ 1153 #endif 1154 case SA_LOCKED: 1155 case SA_LOCKED | SA_NOTRECURSED: 1156 case SA_LOCKED | SA_RECURSED: 1157 #ifdef WITNESS 1158 witness_assert(&sx->lock_object, what, file, line); 1159 #else 1160 /* 1161 * If some other thread has an exclusive lock or we 1162 * have one and are asserting a shared lock, fail. 1163 * Also, if no one has a lock at all, fail. 1164 */ 1165 if (sx->sx_lock == SX_LOCK_UNLOCKED || 1166 (!(sx->sx_lock & SX_LOCK_SHARED) && (slocked || 1167 sx_xholder(sx) != curthread))) 1168 panic("Lock %s not %slocked @ %s:%d\n", 1169 sx->lock_object.lo_name, slocked ? "share " : "", 1170 file, line); 1171 1172 if (!(sx->sx_lock & SX_LOCK_SHARED)) { 1173 if (sx_recursed(sx)) { 1174 if (what & SA_NOTRECURSED) 1175 panic("Lock %s recursed @ %s:%d\n", 1176 sx->lock_object.lo_name, file, 1177 line); 1178 } else if (what & SA_RECURSED) 1179 panic("Lock %s not recursed @ %s:%d\n", 1180 sx->lock_object.lo_name, file, line); 1181 } 1182 #endif 1183 break; 1184 case SA_XLOCKED: 1185 case SA_XLOCKED | SA_NOTRECURSED: 1186 case SA_XLOCKED | SA_RECURSED: 1187 if (sx_xholder(sx) != curthread) 1188 panic("Lock %s not exclusively locked @ %s:%d\n", 1189 sx->lock_object.lo_name, file, line); 1190 if (sx_recursed(sx)) { 1191 if (what & SA_NOTRECURSED) 1192 panic("Lock %s recursed @ %s:%d\n", 1193 sx->lock_object.lo_name, file, line); 1194 } else if (what & SA_RECURSED) 1195 panic("Lock %s not recursed @ %s:%d\n", 1196 sx->lock_object.lo_name, file, line); 1197 break; 1198 case SA_UNLOCKED: 1199 #ifdef WITNESS 1200 witness_assert(&sx->lock_object, what, file, line); 1201 #else 1202 /* 1203 * If we hold an exclusve lock fail. We can't 1204 * reliably check to see if we hold a shared lock or 1205 * not. 1206 */ 1207 if (sx_xholder(sx) == curthread) 1208 panic("Lock %s exclusively locked @ %s:%d\n", 1209 sx->lock_object.lo_name, file, line); 1210 #endif 1211 break; 1212 default: 1213 panic("Unknown sx lock assertion: %d @ %s:%d", what, file, 1214 line); 1215 } 1216 } 1217 #endif /* INVARIANT_SUPPORT */ 1218 1219 #ifdef DDB 1220 static void 1221 db_show_sx(const struct lock_object *lock) 1222 { 1223 struct thread *td; 1224 const struct sx *sx; 1225 1226 sx = (const struct sx *)lock; 1227 1228 db_printf(" state: "); 1229 if (sx->sx_lock == SX_LOCK_UNLOCKED) 1230 db_printf("UNLOCKED\n"); 1231 else if (sx->sx_lock == SX_LOCK_DESTROYED) { 1232 db_printf("DESTROYED\n"); 1233 return; 1234 } else if (sx->sx_lock & SX_LOCK_SHARED) 1235 db_printf("SLOCK: %ju\n", (uintmax_t)SX_SHARERS(sx->sx_lock)); 1236 else { 1237 td = sx_xholder(sx); 1238 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1239 td->td_tid, td->td_proc->p_pid, td->td_name); 1240 if (sx_recursed(sx)) 1241 db_printf(" recursed: %d\n", sx->sx_recurse); 1242 } 1243 1244 db_printf(" waiters: "); 1245 switch(sx->sx_lock & 1246 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)) { 1247 case SX_LOCK_SHARED_WAITERS: 1248 db_printf("shared\n"); 1249 break; 1250 case SX_LOCK_EXCLUSIVE_WAITERS: 1251 db_printf("exclusive\n"); 1252 break; 1253 case SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS: 1254 db_printf("exclusive and shared\n"); 1255 break; 1256 default: 1257 db_printf("none\n"); 1258 } 1259 } 1260 1261 /* 1262 * Check to see if a thread that is blocked on a sleep queue is actually 1263 * blocked on an sx lock. If so, output some details and return true. 1264 * If the lock has an exclusive owner, return that in *ownerp. 1265 */ 1266 int 1267 sx_chain(struct thread *td, struct thread **ownerp) 1268 { 1269 struct sx *sx; 1270 1271 /* 1272 * Check to see if this thread is blocked on an sx lock. 1273 * First, we check the lock class. If that is ok, then we 1274 * compare the lock name against the wait message. 1275 */ 1276 sx = td->td_wchan; 1277 if (LOCK_CLASS(&sx->lock_object) != &lock_class_sx || 1278 sx->lock_object.lo_name != td->td_wmesg) 1279 return (0); 1280 1281 /* We think we have an sx lock, so output some details. */ 1282 db_printf("blocked on sx \"%s\" ", td->td_wmesg); 1283 *ownerp = sx_xholder(sx); 1284 if (sx->sx_lock & SX_LOCK_SHARED) 1285 db_printf("SLOCK (count %ju)\n", 1286 (uintmax_t)SX_SHARERS(sx->sx_lock)); 1287 else 1288 db_printf("XLOCK\n"); 1289 return (1); 1290 } 1291 #endif 1292