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 we already hold an exclusive lock, then recurse. */ 535 if (__predict_false(lv_sx_owner(x) == (struct thread *)tid)) { 536 KASSERT((sx->lock_object.lo_flags & LO_RECURSABLE) != 0, 537 ("_sx_xlock_hard: recursed on non-recursive sx %s @ %s:%d\n", 538 sx->lock_object.lo_name, file, line)); 539 sx->sx_recurse++; 540 atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 541 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 542 CTR2(KTR_LOCK, "%s: %p recursing", __func__, sx); 543 return (0); 544 } 545 546 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 547 CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, 548 sx->lock_object.lo_name, (void *)sx->sx_lock, file, line); 549 550 #ifdef KDTRACE_HOOKS 551 all_time -= lockstat_nsecs(&sx->lock_object); 552 state = x; 553 #endif 554 for (;;) { 555 if (x == SX_LOCK_UNLOCKED) { 556 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 557 break; 558 continue; 559 } 560 #ifdef KDTRACE_HOOKS 561 lda.spin_cnt++; 562 #endif 563 #ifdef HWPMC_HOOKS 564 PMC_SOFT_CALL( , , lock, failed); 565 #endif 566 lock_profile_obtain_lock_failed(&sx->lock_object, &contested, 567 &waittime); 568 #ifdef ADAPTIVE_SX 569 /* 570 * If the lock is write locked and the owner is 571 * running on another CPU, spin until the owner stops 572 * running or the state of the lock changes. 573 */ 574 if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 575 if ((x & SX_LOCK_SHARED) == 0) { 576 owner = lv_sx_owner(x); 577 if (TD_IS_RUNNING(owner)) { 578 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 579 CTR3(KTR_LOCK, 580 "%s: spinning on %p held by %p", 581 __func__, sx, owner); 582 KTR_STATE1(KTR_SCHED, "thread", 583 sched_tdname(curthread), "spinning", 584 "lockname:\"%s\"", 585 sx->lock_object.lo_name); 586 GIANT_SAVE(); 587 do { 588 lock_delay(&lda); 589 x = SX_READ_VALUE(sx); 590 owner = lv_sx_owner(x); 591 } while (owner != NULL && 592 TD_IS_RUNNING(owner)); 593 KTR_STATE0(KTR_SCHED, "thread", 594 sched_tdname(curthread), "running"); 595 continue; 596 } 597 } else if (SX_SHARERS(x) && spintries < asx_retries) { 598 KTR_STATE1(KTR_SCHED, "thread", 599 sched_tdname(curthread), "spinning", 600 "lockname:\"%s\"", sx->lock_object.lo_name); 601 GIANT_SAVE(); 602 spintries++; 603 for (i = 0; i < asx_loops; i++) { 604 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 605 CTR4(KTR_LOCK, 606 "%s: shared spinning on %p with %u and %u", 607 __func__, sx, spintries, i); 608 x = sx->sx_lock; 609 if ((x & SX_LOCK_SHARED) == 0 || 610 SX_SHARERS(x) == 0) 611 break; 612 cpu_spinwait(); 613 #ifdef KDTRACE_HOOKS 614 lda.spin_cnt++; 615 #endif 616 } 617 KTR_STATE0(KTR_SCHED, "thread", 618 sched_tdname(curthread), "running"); 619 x = SX_READ_VALUE(sx); 620 if (i != asx_loops) 621 continue; 622 } 623 } 624 #endif 625 626 sleepq_lock(&sx->lock_object); 627 x = SX_READ_VALUE(sx); 628 629 /* 630 * If the lock was released while spinning on the 631 * sleep queue chain lock, try again. 632 */ 633 if (x == SX_LOCK_UNLOCKED) { 634 sleepq_release(&sx->lock_object); 635 continue; 636 } 637 638 #ifdef ADAPTIVE_SX 639 /* 640 * The current lock owner might have started executing 641 * on another CPU (or the lock could have changed 642 * owners) while we were waiting on the sleep queue 643 * chain lock. If so, drop the sleep queue lock and try 644 * again. 645 */ 646 if (!(x & SX_LOCK_SHARED) && 647 (sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 648 owner = (struct thread *)SX_OWNER(x); 649 if (TD_IS_RUNNING(owner)) { 650 sleepq_release(&sx->lock_object); 651 continue; 652 } 653 } 654 #endif 655 656 /* 657 * If an exclusive lock was released with both shared 658 * and exclusive waiters and a shared waiter hasn't 659 * woken up and acquired the lock yet, sx_lock will be 660 * set to SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS. 661 * If we see that value, try to acquire it once. Note 662 * that we have to preserve SX_LOCK_EXCLUSIVE_WAITERS 663 * as there are other exclusive waiters still. If we 664 * fail, restart the loop. 665 */ 666 if (x == (SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS)) { 667 if (atomic_cmpset_acq_ptr(&sx->sx_lock, 668 SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS, 669 tid | SX_LOCK_EXCLUSIVE_WAITERS)) { 670 sleepq_release(&sx->lock_object); 671 CTR2(KTR_LOCK, "%s: %p claimed by new writer", 672 __func__, sx); 673 break; 674 } 675 sleepq_release(&sx->lock_object); 676 x = SX_READ_VALUE(sx); 677 continue; 678 } 679 680 /* 681 * Try to set the SX_LOCK_EXCLUSIVE_WAITERS. If we fail, 682 * than loop back and retry. 683 */ 684 if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) { 685 if (!atomic_cmpset_ptr(&sx->sx_lock, x, 686 x | SX_LOCK_EXCLUSIVE_WAITERS)) { 687 sleepq_release(&sx->lock_object); 688 x = SX_READ_VALUE(sx); 689 continue; 690 } 691 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 692 CTR2(KTR_LOCK, "%s: %p set excl waiters flag", 693 __func__, sx); 694 } 695 696 /* 697 * Since we have been unable to acquire the exclusive 698 * lock and the exclusive waiters flag is set, we have 699 * to sleep. 700 */ 701 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 702 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 703 __func__, sx); 704 705 #ifdef KDTRACE_HOOKS 706 sleep_time -= lockstat_nsecs(&sx->lock_object); 707 #endif 708 GIANT_SAVE(); 709 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 710 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 711 SLEEPQ_INTERRUPTIBLE : 0), SQ_EXCLUSIVE_QUEUE); 712 if (!(opts & SX_INTERRUPTIBLE)) 713 sleepq_wait(&sx->lock_object, 0); 714 else 715 error = sleepq_wait_sig(&sx->lock_object, 0); 716 #ifdef KDTRACE_HOOKS 717 sleep_time += lockstat_nsecs(&sx->lock_object); 718 sleep_cnt++; 719 #endif 720 if (error) { 721 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 722 CTR2(KTR_LOCK, 723 "%s: interruptible sleep by %p suspended by signal", 724 __func__, sx); 725 break; 726 } 727 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 728 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 729 __func__, sx); 730 x = SX_READ_VALUE(sx); 731 } 732 #ifdef KDTRACE_HOOKS 733 all_time += lockstat_nsecs(&sx->lock_object); 734 if (sleep_time) 735 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 736 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 737 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 738 if (lda.spin_cnt > sleep_cnt) 739 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 740 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 741 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 742 #endif 743 if (!error) 744 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 745 contested, waittime, file, line, LOCKSTAT_WRITER); 746 GIANT_RESTORE(); 747 return (error); 748 } 749 750 /* 751 * This function represents the so-called 'hard case' for sx_xunlock 752 * operation. All 'easy case' failures are redirected to this. Note 753 * that ideally this would be a static function, but it needs to be 754 * accessible from at least sx.h. 755 */ 756 void 757 _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int line) 758 { 759 uintptr_t x; 760 int queue, wakeup_swapper; 761 762 if (SCHEDULER_STOPPED()) 763 return; 764 765 MPASS(!(sx->sx_lock & SX_LOCK_SHARED)); 766 767 if (!sx_recursed(sx)) { 768 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, 769 LOCKSTAT_WRITER); 770 if (atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED)) 771 return; 772 } else { 773 /* The lock is recursed, unrecurse one level. */ 774 if ((--sx->sx_recurse) == 0) 775 atomic_clear_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 776 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 777 CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, sx); 778 return; 779 } 780 MPASS(sx->sx_lock & (SX_LOCK_SHARED_WAITERS | 781 SX_LOCK_EXCLUSIVE_WAITERS)); 782 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 783 CTR2(KTR_LOCK, "%s: %p contested", __func__, sx); 784 785 sleepq_lock(&sx->lock_object); 786 x = SX_LOCK_UNLOCKED; 787 788 /* 789 * The wake up algorithm here is quite simple and probably not 790 * ideal. It gives precedence to shared waiters if they are 791 * present. For this condition, we have to preserve the 792 * state of the exclusive waiters flag. 793 * If interruptible sleeps left the shared queue empty avoid a 794 * starvation for the threads sleeping on the exclusive queue by giving 795 * them precedence and cleaning up the shared waiters bit anyway. 796 */ 797 if ((sx->sx_lock & SX_LOCK_SHARED_WAITERS) != 0 && 798 sleepq_sleepcnt(&sx->lock_object, SQ_SHARED_QUEUE) != 0) { 799 queue = SQ_SHARED_QUEUE; 800 x |= (sx->sx_lock & SX_LOCK_EXCLUSIVE_WAITERS); 801 } else 802 queue = SQ_EXCLUSIVE_QUEUE; 803 804 /* Wake up all the waiters for the specific queue. */ 805 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 806 CTR3(KTR_LOCK, "%s: %p waking up all threads on %s queue", 807 __func__, sx, queue == SQ_SHARED_QUEUE ? "shared" : 808 "exclusive"); 809 atomic_store_rel_ptr(&sx->sx_lock, x); 810 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 0, 811 queue); 812 sleepq_release(&sx->lock_object); 813 if (wakeup_swapper) 814 kick_proc0(); 815 } 816 817 int 818 _sx_slock(struct sx *sx, int opts, const char *file, int line) 819 { 820 GIANT_DECLARE; 821 #ifdef ADAPTIVE_SX 822 volatile struct thread *owner; 823 #endif 824 #ifdef LOCK_PROFILING 825 uint64_t waittime = 0; 826 int contested = 0; 827 #endif 828 uintptr_t x; 829 int error = 0; 830 #if defined(ADAPTIVE_SX) || defined(KDTRACE_HOOKS) 831 struct lock_delay_arg lda; 832 #endif 833 #ifdef KDTRACE_HOOKS 834 uintptr_t state; 835 u_int sleep_cnt = 0; 836 int64_t sleep_time = 0; 837 int64_t all_time = 0; 838 #endif 839 840 if (SCHEDULER_STOPPED()) 841 return (0); 842 843 #if defined(ADAPTIVE_SX) 844 lock_delay_arg_init(&lda, &sx_delay); 845 #elif defined(KDTRACE_HOOKS) 846 lock_delay_arg_init(&lda, NULL); 847 #endif 848 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 849 ("sx_slock() by idle thread %p on sx %s @ %s:%d", 850 curthread, sx->lock_object.lo_name, file, line)); 851 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 852 ("sx_slock() of destroyed sx @ %s:%d", file, line)); 853 WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER, file, line, NULL); 854 #ifdef KDTRACE_HOOKS 855 all_time -= lockstat_nsecs(&sx->lock_object); 856 #endif 857 x = SX_READ_VALUE(sx); 858 #ifdef KDTRACE_HOOKS 859 state = x; 860 #endif 861 862 /* 863 * As with rwlocks, we don't make any attempt to try to block 864 * shared locks once there is an exclusive waiter. 865 */ 866 for (;;) { 867 /* 868 * If no other thread has an exclusive lock then try to bump up 869 * the count of sharers. Since we have to preserve the state 870 * of SX_LOCK_EXCLUSIVE_WAITERS, if we fail to acquire the 871 * shared lock loop back and retry. 872 */ 873 if (x & SX_LOCK_SHARED) { 874 MPASS(!(x & SX_LOCK_SHARED_WAITERS)); 875 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, 876 x + SX_ONE_SHARER)) { 877 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 878 CTR4(KTR_LOCK, 879 "%s: %p succeed %p -> %p", __func__, 880 sx, (void *)x, 881 (void *)(x + SX_ONE_SHARER)); 882 break; 883 } 884 continue; 885 } 886 #ifdef KDTRACE_HOOKS 887 lda.spin_cnt++; 888 #endif 889 890 #ifdef HWPMC_HOOKS 891 PMC_SOFT_CALL( , , lock, failed); 892 #endif 893 lock_profile_obtain_lock_failed(&sx->lock_object, &contested, 894 &waittime); 895 896 #ifdef ADAPTIVE_SX 897 /* 898 * If the owner is running on another CPU, spin until 899 * the owner stops running or the state of the lock 900 * changes. 901 */ 902 if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 903 owner = lv_sx_owner(x); 904 if (TD_IS_RUNNING(owner)) { 905 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 906 CTR3(KTR_LOCK, 907 "%s: spinning on %p held by %p", 908 __func__, sx, owner); 909 KTR_STATE1(KTR_SCHED, "thread", 910 sched_tdname(curthread), "spinning", 911 "lockname:\"%s\"", sx->lock_object.lo_name); 912 GIANT_SAVE(); 913 do { 914 lock_delay(&lda); 915 x = SX_READ_VALUE(sx); 916 owner = lv_sx_owner(x); 917 } while (owner != NULL && TD_IS_RUNNING(owner)); 918 KTR_STATE0(KTR_SCHED, "thread", 919 sched_tdname(curthread), "running"); 920 continue; 921 } 922 } 923 #endif 924 925 /* 926 * Some other thread already has an exclusive lock, so 927 * start the process of blocking. 928 */ 929 sleepq_lock(&sx->lock_object); 930 x = SX_READ_VALUE(sx); 931 932 /* 933 * The lock could have been released while we spun. 934 * In this case loop back and retry. 935 */ 936 if (x & SX_LOCK_SHARED) { 937 sleepq_release(&sx->lock_object); 938 continue; 939 } 940 941 #ifdef ADAPTIVE_SX 942 /* 943 * If the owner is running on another CPU, spin until 944 * the owner stops running or the state of the lock 945 * changes. 946 */ 947 if (!(x & SX_LOCK_SHARED) && 948 (sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 949 owner = (struct thread *)SX_OWNER(x); 950 if (TD_IS_RUNNING(owner)) { 951 sleepq_release(&sx->lock_object); 952 x = SX_READ_VALUE(sx); 953 continue; 954 } 955 } 956 #endif 957 958 /* 959 * Try to set the SX_LOCK_SHARED_WAITERS flag. If we 960 * fail to set it drop the sleep queue lock and loop 961 * back. 962 */ 963 if (!(x & SX_LOCK_SHARED_WAITERS)) { 964 if (!atomic_cmpset_ptr(&sx->sx_lock, x, 965 x | SX_LOCK_SHARED_WAITERS)) { 966 sleepq_release(&sx->lock_object); 967 x = SX_READ_VALUE(sx); 968 continue; 969 } 970 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 971 CTR2(KTR_LOCK, "%s: %p set shared waiters flag", 972 __func__, sx); 973 } 974 975 /* 976 * Since we have been unable to acquire the shared lock, 977 * we have to sleep. 978 */ 979 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 980 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 981 __func__, sx); 982 983 #ifdef KDTRACE_HOOKS 984 sleep_time -= lockstat_nsecs(&sx->lock_object); 985 #endif 986 GIANT_SAVE(); 987 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 988 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 989 SLEEPQ_INTERRUPTIBLE : 0), SQ_SHARED_QUEUE); 990 if (!(opts & SX_INTERRUPTIBLE)) 991 sleepq_wait(&sx->lock_object, 0); 992 else 993 error = sleepq_wait_sig(&sx->lock_object, 0); 994 #ifdef KDTRACE_HOOKS 995 sleep_time += lockstat_nsecs(&sx->lock_object); 996 sleep_cnt++; 997 #endif 998 if (error) { 999 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1000 CTR2(KTR_LOCK, 1001 "%s: interruptible sleep by %p suspended by signal", 1002 __func__, sx); 1003 break; 1004 } 1005 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1006 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 1007 __func__, sx); 1008 x = SX_READ_VALUE(sx); 1009 } 1010 #ifdef KDTRACE_HOOKS 1011 all_time += lockstat_nsecs(&sx->lock_object); 1012 if (sleep_time) 1013 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 1014 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1015 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1016 if (lda.spin_cnt > sleep_cnt) 1017 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 1018 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1019 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1020 #endif 1021 if (error == 0) { 1022 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 1023 contested, waittime, file, line, LOCKSTAT_READER); 1024 LOCK_LOG_LOCK("SLOCK", &sx->lock_object, 0, 0, file, line); 1025 WITNESS_LOCK(&sx->lock_object, 0, file, line); 1026 TD_LOCKS_INC(curthread); 1027 } 1028 GIANT_RESTORE(); 1029 return (error); 1030 } 1031 1032 void 1033 _sx_sunlock(struct sx *sx, const char *file, int line) 1034 { 1035 uintptr_t x; 1036 int wakeup_swapper; 1037 1038 if (SCHEDULER_STOPPED()) 1039 return; 1040 1041 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 1042 ("sx_sunlock() of destroyed sx @ %s:%d", file, line)); 1043 _sx_assert(sx, SA_SLOCKED, file, line); 1044 WITNESS_UNLOCK(&sx->lock_object, 0, file, line); 1045 LOCK_LOG_LOCK("SUNLOCK", &sx->lock_object, 0, 0, file, line); 1046 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_READER); 1047 x = SX_READ_VALUE(sx); 1048 for (;;) { 1049 /* 1050 * We should never have sharers while at least one thread 1051 * holds a shared lock. 1052 */ 1053 KASSERT(!(x & SX_LOCK_SHARED_WAITERS), 1054 ("%s: waiting sharers", __func__)); 1055 1056 /* 1057 * See if there is more than one shared lock held. If 1058 * so, just drop one and return. 1059 */ 1060 if (SX_SHARERS(x) > 1) { 1061 if (atomic_fcmpset_rel_ptr(&sx->sx_lock, &x, 1062 x - SX_ONE_SHARER)) { 1063 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1064 CTR4(KTR_LOCK, 1065 "%s: %p succeeded %p -> %p", 1066 __func__, sx, (void *)x, 1067 (void *)(x - SX_ONE_SHARER)); 1068 break; 1069 } 1070 continue; 1071 } 1072 1073 /* 1074 * If there aren't any waiters for an exclusive lock, 1075 * then try to drop it quickly. 1076 */ 1077 if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) { 1078 MPASS(x == SX_SHARERS_LOCK(1)); 1079 x = SX_SHARERS_LOCK(1); 1080 if (atomic_fcmpset_rel_ptr(&sx->sx_lock, 1081 &x, SX_LOCK_UNLOCKED)) { 1082 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1083 CTR2(KTR_LOCK, "%s: %p last succeeded", 1084 __func__, sx); 1085 break; 1086 } 1087 continue; 1088 } 1089 1090 /* 1091 * At this point, there should just be one sharer with 1092 * exclusive waiters. 1093 */ 1094 MPASS(x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS)); 1095 1096 sleepq_lock(&sx->lock_object); 1097 1098 /* 1099 * Wake up semantic here is quite simple: 1100 * Just wake up all the exclusive waiters. 1101 * Note that the state of the lock could have changed, 1102 * so if it fails loop back and retry. 1103 */ 1104 if (!atomic_cmpset_rel_ptr(&sx->sx_lock, 1105 SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS, 1106 SX_LOCK_UNLOCKED)) { 1107 sleepq_release(&sx->lock_object); 1108 x = SX_READ_VALUE(sx); 1109 continue; 1110 } 1111 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1112 CTR2(KTR_LOCK, "%s: %p waking up all thread on" 1113 "exclusive queue", __func__, sx); 1114 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 1115 0, SQ_EXCLUSIVE_QUEUE); 1116 sleepq_release(&sx->lock_object); 1117 if (wakeup_swapper) 1118 kick_proc0(); 1119 break; 1120 } 1121 TD_LOCKS_DEC(curthread); 1122 } 1123 1124 #ifdef INVARIANT_SUPPORT 1125 #ifndef INVARIANTS 1126 #undef _sx_assert 1127 #endif 1128 1129 /* 1130 * In the non-WITNESS case, sx_assert() can only detect that at least 1131 * *some* thread owns an slock, but it cannot guarantee that *this* 1132 * thread owns an slock. 1133 */ 1134 void 1135 _sx_assert(const struct sx *sx, int what, const char *file, int line) 1136 { 1137 #ifndef WITNESS 1138 int slocked = 0; 1139 #endif 1140 1141 if (panicstr != NULL) 1142 return; 1143 switch (what) { 1144 case SA_SLOCKED: 1145 case SA_SLOCKED | SA_NOTRECURSED: 1146 case SA_SLOCKED | SA_RECURSED: 1147 #ifndef WITNESS 1148 slocked = 1; 1149 /* FALLTHROUGH */ 1150 #endif 1151 case SA_LOCKED: 1152 case SA_LOCKED | SA_NOTRECURSED: 1153 case SA_LOCKED | SA_RECURSED: 1154 #ifdef WITNESS 1155 witness_assert(&sx->lock_object, what, file, line); 1156 #else 1157 /* 1158 * If some other thread has an exclusive lock or we 1159 * have one and are asserting a shared lock, fail. 1160 * Also, if no one has a lock at all, fail. 1161 */ 1162 if (sx->sx_lock == SX_LOCK_UNLOCKED || 1163 (!(sx->sx_lock & SX_LOCK_SHARED) && (slocked || 1164 sx_xholder(sx) != curthread))) 1165 panic("Lock %s not %slocked @ %s:%d\n", 1166 sx->lock_object.lo_name, slocked ? "share " : "", 1167 file, line); 1168 1169 if (!(sx->sx_lock & SX_LOCK_SHARED)) { 1170 if (sx_recursed(sx)) { 1171 if (what & SA_NOTRECURSED) 1172 panic("Lock %s recursed @ %s:%d\n", 1173 sx->lock_object.lo_name, file, 1174 line); 1175 } else if (what & SA_RECURSED) 1176 panic("Lock %s not recursed @ %s:%d\n", 1177 sx->lock_object.lo_name, file, line); 1178 } 1179 #endif 1180 break; 1181 case SA_XLOCKED: 1182 case SA_XLOCKED | SA_NOTRECURSED: 1183 case SA_XLOCKED | SA_RECURSED: 1184 if (sx_xholder(sx) != curthread) 1185 panic("Lock %s not exclusively locked @ %s:%d\n", 1186 sx->lock_object.lo_name, file, line); 1187 if (sx_recursed(sx)) { 1188 if (what & SA_NOTRECURSED) 1189 panic("Lock %s recursed @ %s:%d\n", 1190 sx->lock_object.lo_name, file, line); 1191 } else if (what & SA_RECURSED) 1192 panic("Lock %s not recursed @ %s:%d\n", 1193 sx->lock_object.lo_name, file, line); 1194 break; 1195 case SA_UNLOCKED: 1196 #ifdef WITNESS 1197 witness_assert(&sx->lock_object, what, file, line); 1198 #else 1199 /* 1200 * If we hold an exclusve lock fail. We can't 1201 * reliably check to see if we hold a shared lock or 1202 * not. 1203 */ 1204 if (sx_xholder(sx) == curthread) 1205 panic("Lock %s exclusively locked @ %s:%d\n", 1206 sx->lock_object.lo_name, file, line); 1207 #endif 1208 break; 1209 default: 1210 panic("Unknown sx lock assertion: %d @ %s:%d", what, file, 1211 line); 1212 } 1213 } 1214 #endif /* INVARIANT_SUPPORT */ 1215 1216 #ifdef DDB 1217 static void 1218 db_show_sx(const struct lock_object *lock) 1219 { 1220 struct thread *td; 1221 const struct sx *sx; 1222 1223 sx = (const struct sx *)lock; 1224 1225 db_printf(" state: "); 1226 if (sx->sx_lock == SX_LOCK_UNLOCKED) 1227 db_printf("UNLOCKED\n"); 1228 else if (sx->sx_lock == SX_LOCK_DESTROYED) { 1229 db_printf("DESTROYED\n"); 1230 return; 1231 } else if (sx->sx_lock & SX_LOCK_SHARED) 1232 db_printf("SLOCK: %ju\n", (uintmax_t)SX_SHARERS(sx->sx_lock)); 1233 else { 1234 td = sx_xholder(sx); 1235 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1236 td->td_tid, td->td_proc->p_pid, td->td_name); 1237 if (sx_recursed(sx)) 1238 db_printf(" recursed: %d\n", sx->sx_recurse); 1239 } 1240 1241 db_printf(" waiters: "); 1242 switch(sx->sx_lock & 1243 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)) { 1244 case SX_LOCK_SHARED_WAITERS: 1245 db_printf("shared\n"); 1246 break; 1247 case SX_LOCK_EXCLUSIVE_WAITERS: 1248 db_printf("exclusive\n"); 1249 break; 1250 case SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS: 1251 db_printf("exclusive and shared\n"); 1252 break; 1253 default: 1254 db_printf("none\n"); 1255 } 1256 } 1257 1258 /* 1259 * Check to see if a thread that is blocked on a sleep queue is actually 1260 * blocked on an sx lock. If so, output some details and return true. 1261 * If the lock has an exclusive owner, return that in *ownerp. 1262 */ 1263 int 1264 sx_chain(struct thread *td, struct thread **ownerp) 1265 { 1266 struct sx *sx; 1267 1268 /* 1269 * Check to see if this thread is blocked on an sx lock. 1270 * First, we check the lock class. If that is ok, then we 1271 * compare the lock name against the wait message. 1272 */ 1273 sx = td->td_wchan; 1274 if (LOCK_CLASS(&sx->lock_object) != &lock_class_sx || 1275 sx->lock_object.lo_name != td->td_wmesg) 1276 return (0); 1277 1278 /* We think we have an sx lock, so output some details. */ 1279 db_printf("blocked on sx \"%s\" ", td->td_wmesg); 1280 *ownerp = sx_xholder(sx); 1281 if (sx->sx_lock & SX_LOCK_SHARED) 1282 db_printf("SLOCK (count %ju)\n", 1283 (uintmax_t)SX_SHARERS(sx->sx_lock)); 1284 else 1285 db_printf("XLOCK\n"); 1286 return (1); 1287 } 1288 #endif 1289