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(work) do { \ 92 if (mtx_owned(&Giant)) { \ 93 work++; \ 94 WITNESS_SAVE(&Giant.lock_object, Giant); \ 95 while (mtx_owned(&Giant)) { \ 96 _giantcnt++; \ 97 mtx_unlock(&Giant); \ 98 } \ 99 } \ 100 } while (0) 101 102 #define GIANT_RESTORE() do { \ 103 if (_giantcnt > 0) { \ 104 mtx_assert(&Giant, MA_NOTOWNED); \ 105 while (_giantcnt--) \ 106 mtx_lock(&Giant); \ 107 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 108 } \ 109 } while (0) 110 111 /* 112 * Returns true if an exclusive lock is recursed. It assumes 113 * curthread currently has an exclusive lock. 114 */ 115 #define sx_recursed(sx) ((sx)->sx_recurse != 0) 116 117 static void assert_sx(const struct lock_object *lock, int what); 118 #ifdef DDB 119 static void db_show_sx(const struct lock_object *lock); 120 #endif 121 static void lock_sx(struct lock_object *lock, uintptr_t how); 122 #ifdef KDTRACE_HOOKS 123 static int owner_sx(const struct lock_object *lock, struct thread **owner); 124 #endif 125 static uintptr_t unlock_sx(struct lock_object *lock); 126 127 struct lock_class lock_class_sx = { 128 .lc_name = "sx", 129 .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE, 130 .lc_assert = assert_sx, 131 #ifdef DDB 132 .lc_ddb_show = db_show_sx, 133 #endif 134 .lc_lock = lock_sx, 135 .lc_unlock = unlock_sx, 136 #ifdef KDTRACE_HOOKS 137 .lc_owner = owner_sx, 138 #endif 139 }; 140 141 #ifndef INVARIANTS 142 #define _sx_assert(sx, what, file, line) 143 #endif 144 145 #ifdef ADAPTIVE_SX 146 static __read_frequently u_int asx_retries = 10; 147 static __read_frequently u_int asx_loops = 10000; 148 static SYSCTL_NODE(_debug, OID_AUTO, sx, CTLFLAG_RD, NULL, "sxlock debugging"); 149 SYSCTL_UINT(_debug_sx, OID_AUTO, retries, CTLFLAG_RW, &asx_retries, 0, ""); 150 SYSCTL_UINT(_debug_sx, OID_AUTO, loops, CTLFLAG_RW, &asx_loops, 0, ""); 151 152 static struct lock_delay_config __read_frequently sx_delay; 153 154 SYSCTL_INT(_debug_sx, OID_AUTO, delay_base, CTLFLAG_RW, &sx_delay.base, 155 0, ""); 156 SYSCTL_INT(_debug_sx, OID_AUTO, delay_max, CTLFLAG_RW, &sx_delay.max, 157 0, ""); 158 159 LOCK_DELAY_SYSINIT_DEFAULT(sx_delay); 160 #endif 161 162 void 163 assert_sx(const struct lock_object *lock, int what) 164 { 165 166 sx_assert((const struct sx *)lock, what); 167 } 168 169 void 170 lock_sx(struct lock_object *lock, uintptr_t how) 171 { 172 struct sx *sx; 173 174 sx = (struct sx *)lock; 175 if (how) 176 sx_slock(sx); 177 else 178 sx_xlock(sx); 179 } 180 181 uintptr_t 182 unlock_sx(struct lock_object *lock) 183 { 184 struct sx *sx; 185 186 sx = (struct sx *)lock; 187 sx_assert(sx, SA_LOCKED | SA_NOTRECURSED); 188 if (sx_xlocked(sx)) { 189 sx_xunlock(sx); 190 return (0); 191 } else { 192 sx_sunlock(sx); 193 return (1); 194 } 195 } 196 197 #ifdef KDTRACE_HOOKS 198 int 199 owner_sx(const struct lock_object *lock, struct thread **owner) 200 { 201 const struct sx *sx; 202 uintptr_t x; 203 204 sx = (const struct sx *)lock; 205 x = sx->sx_lock; 206 *owner = NULL; 207 return ((x & SX_LOCK_SHARED) != 0 ? (SX_SHARERS(x) != 0) : 208 ((*owner = (struct thread *)SX_OWNER(x)) != NULL)); 209 } 210 #endif 211 212 void 213 sx_sysinit(void *arg) 214 { 215 struct sx_args *sargs = arg; 216 217 sx_init_flags(sargs->sa_sx, sargs->sa_desc, sargs->sa_flags); 218 } 219 220 void 221 sx_init_flags(struct sx *sx, const char *description, int opts) 222 { 223 int flags; 224 225 MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK | 226 SX_NOPROFILE | SX_NOADAPTIVE | SX_NEW)) == 0); 227 ASSERT_ATOMIC_LOAD_PTR(sx->sx_lock, 228 ("%s: sx_lock not aligned for %s: %p", __func__, description, 229 &sx->sx_lock)); 230 231 flags = LO_SLEEPABLE | LO_UPGRADABLE; 232 if (opts & SX_DUPOK) 233 flags |= LO_DUPOK; 234 if (opts & SX_NOPROFILE) 235 flags |= LO_NOPROFILE; 236 if (!(opts & SX_NOWITNESS)) 237 flags |= LO_WITNESS; 238 if (opts & SX_RECURSE) 239 flags |= LO_RECURSABLE; 240 if (opts & SX_QUIET) 241 flags |= LO_QUIET; 242 if (opts & SX_NEW) 243 flags |= LO_NEW; 244 245 flags |= opts & SX_NOADAPTIVE; 246 lock_init(&sx->lock_object, &lock_class_sx, description, NULL, flags); 247 sx->sx_lock = SX_LOCK_UNLOCKED; 248 sx->sx_recurse = 0; 249 } 250 251 void 252 sx_destroy(struct sx *sx) 253 { 254 255 KASSERT(sx->sx_lock == SX_LOCK_UNLOCKED, ("sx lock still held")); 256 KASSERT(sx->sx_recurse == 0, ("sx lock still recursed")); 257 sx->sx_lock = SX_LOCK_DESTROYED; 258 lock_destroy(&sx->lock_object); 259 } 260 261 int 262 sx_try_slock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 263 { 264 uintptr_t x; 265 266 if (SCHEDULER_STOPPED()) 267 return (1); 268 269 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 270 ("sx_try_slock() by idle thread %p on sx %s @ %s:%d", 271 curthread, sx->lock_object.lo_name, file, line)); 272 273 x = sx->sx_lock; 274 for (;;) { 275 KASSERT(x != SX_LOCK_DESTROYED, 276 ("sx_try_slock() of destroyed sx @ %s:%d", file, line)); 277 if (!(x & SX_LOCK_SHARED)) 278 break; 279 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, x + SX_ONE_SHARER)) { 280 LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 1, file, line); 281 WITNESS_LOCK(&sx->lock_object, LOP_TRYLOCK, file, line); 282 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, 283 sx, 0, 0, file, line, LOCKSTAT_READER); 284 TD_LOCKS_INC(curthread); 285 return (1); 286 } 287 } 288 289 LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 0, file, line); 290 return (0); 291 } 292 293 int 294 sx_try_slock_(struct sx *sx, const char *file, int line) 295 { 296 297 return (sx_try_slock_int(sx LOCK_FILE_LINE_ARG)); 298 } 299 300 int 301 _sx_xlock(struct sx *sx, int opts, const char *file, int line) 302 { 303 uintptr_t tid, x; 304 int error = 0; 305 306 KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() || 307 !TD_IS_IDLETHREAD(curthread), 308 ("sx_xlock() by idle thread %p on sx %s @ %s:%d", 309 curthread, sx->lock_object.lo_name, file, line)); 310 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 311 ("sx_xlock() of destroyed sx @ %s:%d", file, line)); 312 WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, 313 line, NULL); 314 tid = (uintptr_t)curthread; 315 x = SX_LOCK_UNLOCKED; 316 if (!atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 317 error = _sx_xlock_hard(sx, x, opts LOCK_FILE_LINE_ARG); 318 else 319 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 320 0, 0, file, line, LOCKSTAT_WRITER); 321 if (!error) { 322 LOCK_LOG_LOCK("XLOCK", &sx->lock_object, 0, sx->sx_recurse, 323 file, line); 324 WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); 325 TD_LOCKS_INC(curthread); 326 } 327 328 return (error); 329 } 330 331 int 332 sx_try_xlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 333 { 334 struct thread *td; 335 uintptr_t tid, x; 336 int rval; 337 bool recursed; 338 339 td = curthread; 340 tid = (uintptr_t)td; 341 if (SCHEDULER_STOPPED_TD(td)) 342 return (1); 343 344 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(td), 345 ("sx_try_xlock() by idle thread %p on sx %s @ %s:%d", 346 curthread, sx->lock_object.lo_name, file, line)); 347 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 348 ("sx_try_xlock() of destroyed sx @ %s:%d", file, line)); 349 350 rval = 1; 351 recursed = false; 352 x = SX_LOCK_UNLOCKED; 353 for (;;) { 354 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 355 break; 356 if (x == SX_LOCK_UNLOCKED) 357 continue; 358 if (x == tid && (sx->lock_object.lo_flags & LO_RECURSABLE)) { 359 sx->sx_recurse++; 360 atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 361 break; 362 } 363 rval = 0; 364 break; 365 } 366 367 LOCK_LOG_TRY("XLOCK", &sx->lock_object, 0, rval, file, line); 368 if (rval) { 369 WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 370 file, line); 371 if (!recursed) 372 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, 373 sx, 0, 0, file, line, LOCKSTAT_WRITER); 374 TD_LOCKS_INC(curthread); 375 } 376 377 return (rval); 378 } 379 380 int 381 sx_try_xlock_(struct sx *sx, const char *file, int line) 382 { 383 384 return (sx_try_xlock_int(sx LOCK_FILE_LINE_ARG)); 385 } 386 387 void 388 _sx_xunlock(struct sx *sx, const char *file, int line) 389 { 390 391 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 392 ("sx_xunlock() of destroyed sx @ %s:%d", file, line)); 393 _sx_assert(sx, SA_XLOCKED, file, line); 394 WITNESS_UNLOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); 395 LOCK_LOG_LOCK("XUNLOCK", &sx->lock_object, 0, sx->sx_recurse, file, 396 line); 397 #if LOCK_DEBUG > 0 398 _sx_xunlock_hard(sx, (uintptr_t)curthread, file, line); 399 #else 400 __sx_xunlock(sx, curthread, file, line); 401 #endif 402 TD_LOCKS_DEC(curthread); 403 } 404 405 /* 406 * Try to do a non-blocking upgrade from a shared lock to an exclusive lock. 407 * This will only succeed if this thread holds a single shared lock. 408 * Return 1 if if the upgrade succeed, 0 otherwise. 409 */ 410 int 411 sx_try_upgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 412 { 413 uintptr_t x; 414 int success; 415 416 if (SCHEDULER_STOPPED()) 417 return (1); 418 419 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 420 ("sx_try_upgrade() of destroyed sx @ %s:%d", file, line)); 421 _sx_assert(sx, SA_SLOCKED, file, line); 422 423 /* 424 * Try to switch from one shared lock to an exclusive lock. We need 425 * to maintain the SX_LOCK_EXCLUSIVE_WAITERS flag if set so that 426 * we will wake up the exclusive waiters when we drop the lock. 427 */ 428 x = sx->sx_lock & SX_LOCK_EXCLUSIVE_WAITERS; 429 success = atomic_cmpset_acq_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | x, 430 (uintptr_t)curthread | x); 431 LOCK_LOG_TRY("XUPGRADE", &sx->lock_object, 0, success, file, line); 432 if (success) { 433 WITNESS_UPGRADE(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 434 file, line); 435 LOCKSTAT_RECORD0(sx__upgrade, sx); 436 } 437 return (success); 438 } 439 440 int 441 sx_try_upgrade_(struct sx *sx, const char *file, int line) 442 { 443 444 return (sx_try_upgrade_int(sx LOCK_FILE_LINE_ARG)); 445 } 446 447 /* 448 * Downgrade an unrecursed exclusive lock into a single shared lock. 449 */ 450 void 451 sx_downgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 452 { 453 uintptr_t x; 454 int wakeup_swapper; 455 456 if (SCHEDULER_STOPPED()) 457 return; 458 459 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 460 ("sx_downgrade() of destroyed sx @ %s:%d", file, line)); 461 _sx_assert(sx, SA_XLOCKED | SA_NOTRECURSED, file, line); 462 #ifndef INVARIANTS 463 if (sx_recursed(sx)) 464 panic("downgrade of a recursed lock"); 465 #endif 466 467 WITNESS_DOWNGRADE(&sx->lock_object, 0, file, line); 468 469 /* 470 * Try to switch from an exclusive lock with no shared waiters 471 * to one sharer with no shared waiters. If there are 472 * exclusive waiters, we don't need to lock the sleep queue so 473 * long as we preserve the flag. We do one quick try and if 474 * that fails we grab the sleepq lock to keep the flags from 475 * changing and do it the slow way. 476 * 477 * We have to lock the sleep queue if there are shared waiters 478 * so we can wake them up. 479 */ 480 x = sx->sx_lock; 481 if (!(x & SX_LOCK_SHARED_WAITERS) && 482 atomic_cmpset_rel_ptr(&sx->sx_lock, x, SX_SHARERS_LOCK(1) | 483 (x & SX_LOCK_EXCLUSIVE_WAITERS))) 484 goto out; 485 486 /* 487 * Lock the sleep queue so we can read the waiters bits 488 * without any races and wakeup any shared waiters. 489 */ 490 sleepq_lock(&sx->lock_object); 491 492 /* 493 * Preserve SX_LOCK_EXCLUSIVE_WAITERS while downgraded to a single 494 * shared lock. If there are any shared waiters, wake them up. 495 */ 496 wakeup_swapper = 0; 497 x = sx->sx_lock; 498 atomic_store_rel_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | 499 (x & SX_LOCK_EXCLUSIVE_WAITERS)); 500 if (x & SX_LOCK_SHARED_WAITERS) 501 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 502 0, SQ_SHARED_QUEUE); 503 sleepq_release(&sx->lock_object); 504 505 if (wakeup_swapper) 506 kick_proc0(); 507 508 out: 509 LOCK_LOG_LOCK("XDOWNGRADE", &sx->lock_object, 0, 0, file, line); 510 LOCKSTAT_RECORD0(sx__downgrade, sx); 511 } 512 513 void 514 sx_downgrade_(struct sx *sx, const char *file, int line) 515 { 516 517 sx_downgrade_int(sx LOCK_FILE_LINE_ARG); 518 } 519 520 /* 521 * This function represents the so-called 'hard case' for sx_xlock 522 * operation. All 'easy case' failures are redirected to this. Note 523 * that ideally this would be a static function, but it needs to be 524 * accessible from at least sx.h. 525 */ 526 int 527 _sx_xlock_hard(struct sx *sx, uintptr_t x, int opts LOCK_FILE_LINE_ARG_DEF) 528 { 529 GIANT_DECLARE; 530 uintptr_t tid; 531 #ifdef ADAPTIVE_SX 532 volatile struct thread *owner; 533 u_int i, n, spintries = 0; 534 #endif 535 #ifdef LOCK_PROFILING 536 uint64_t waittime = 0; 537 int contested = 0; 538 #endif 539 int error = 0; 540 #if defined(ADAPTIVE_SX) || defined(KDTRACE_HOOKS) 541 struct lock_delay_arg lda; 542 #endif 543 #ifdef KDTRACE_HOOKS 544 u_int sleep_cnt = 0; 545 int64_t sleep_time = 0; 546 int64_t all_time = 0; 547 #endif 548 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 549 uintptr_t state; 550 #endif 551 int extra_work = 0; 552 553 tid = (uintptr_t)curthread; 554 if (SCHEDULER_STOPPED()) 555 return (0); 556 557 #if defined(ADAPTIVE_SX) 558 lock_delay_arg_init(&lda, &sx_delay); 559 #elif defined(KDTRACE_HOOKS) 560 lock_delay_arg_init(&lda, NULL); 561 #endif 562 563 if (__predict_false(x == SX_LOCK_UNLOCKED)) 564 x = SX_READ_VALUE(sx); 565 566 /* If we already hold an exclusive lock, then recurse. */ 567 if (__predict_false(lv_sx_owner(x) == (struct thread *)tid)) { 568 KASSERT((sx->lock_object.lo_flags & LO_RECURSABLE) != 0, 569 ("_sx_xlock_hard: recursed on non-recursive sx %s @ %s:%d\n", 570 sx->lock_object.lo_name, file, line)); 571 sx->sx_recurse++; 572 atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 573 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 574 CTR2(KTR_LOCK, "%s: %p recursing", __func__, sx); 575 return (0); 576 } 577 578 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 579 CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, 580 sx->lock_object.lo_name, (void *)sx->sx_lock, file, line); 581 582 #ifdef HWPMC_HOOKS 583 PMC_SOFT_CALL( , , lock, failed); 584 #endif 585 lock_profile_obtain_lock_failed(&sx->lock_object, &contested, 586 &waittime); 587 588 #ifdef LOCK_PROFILING 589 extra_work = 1; 590 state = x; 591 #elif defined(KDTRACE_HOOKS) 592 extra_work = lockstat_enabled; 593 if (__predict_false(extra_work)) { 594 all_time -= lockstat_nsecs(&sx->lock_object); 595 state = x; 596 } 597 #endif 598 599 for (;;) { 600 if (x == SX_LOCK_UNLOCKED) { 601 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 602 break; 603 continue; 604 } 605 #ifdef KDTRACE_HOOKS 606 lda.spin_cnt++; 607 #endif 608 #ifdef ADAPTIVE_SX 609 /* 610 * If the lock is write locked and the owner is 611 * running on another CPU, spin until the owner stops 612 * running or the state of the lock changes. 613 */ 614 if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 615 if ((x & SX_LOCK_SHARED) == 0) { 616 owner = lv_sx_owner(x); 617 if (TD_IS_RUNNING(owner)) { 618 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 619 CTR3(KTR_LOCK, 620 "%s: spinning on %p held by %p", 621 __func__, sx, owner); 622 KTR_STATE1(KTR_SCHED, "thread", 623 sched_tdname(curthread), "spinning", 624 "lockname:\"%s\"", 625 sx->lock_object.lo_name); 626 GIANT_SAVE(extra_work); 627 do { 628 lock_delay(&lda); 629 x = SX_READ_VALUE(sx); 630 owner = lv_sx_owner(x); 631 } while (owner != NULL && 632 TD_IS_RUNNING(owner)); 633 KTR_STATE0(KTR_SCHED, "thread", 634 sched_tdname(curthread), "running"); 635 continue; 636 } 637 } else if (SX_SHARERS(x) && spintries < asx_retries) { 638 KTR_STATE1(KTR_SCHED, "thread", 639 sched_tdname(curthread), "spinning", 640 "lockname:\"%s\"", sx->lock_object.lo_name); 641 GIANT_SAVE(extra_work); 642 spintries++; 643 for (i = 0; i < asx_loops; i += n) { 644 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 645 CTR4(KTR_LOCK, 646 "%s: shared spinning on %p with %u and %u", 647 __func__, sx, spintries, i); 648 n = SX_SHARERS(x); 649 lock_delay_spin(n); 650 x = SX_READ_VALUE(sx); 651 if ((x & SX_LOCK_SHARED) == 0 || 652 SX_SHARERS(x) == 0) 653 break; 654 } 655 #ifdef KDTRACE_HOOKS 656 lda.spin_cnt += i; 657 #endif 658 KTR_STATE0(KTR_SCHED, "thread", 659 sched_tdname(curthread), "running"); 660 if (i != asx_loops) 661 continue; 662 } 663 } 664 #endif 665 666 sleepq_lock(&sx->lock_object); 667 x = SX_READ_VALUE(sx); 668 retry_sleepq: 669 670 /* 671 * If the lock was released while spinning on the 672 * sleep queue chain lock, try again. 673 */ 674 if (x == SX_LOCK_UNLOCKED) { 675 sleepq_release(&sx->lock_object); 676 continue; 677 } 678 679 #ifdef ADAPTIVE_SX 680 /* 681 * The current lock owner might have started executing 682 * on another CPU (or the lock could have changed 683 * owners) while we were waiting on the sleep queue 684 * chain lock. If so, drop the sleep queue lock and try 685 * again. 686 */ 687 if (!(x & SX_LOCK_SHARED) && 688 (sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 689 owner = (struct thread *)SX_OWNER(x); 690 if (TD_IS_RUNNING(owner)) { 691 sleepq_release(&sx->lock_object); 692 continue; 693 } 694 } 695 #endif 696 697 /* 698 * If an exclusive lock was released with both shared 699 * and exclusive waiters and a shared waiter hasn't 700 * woken up and acquired the lock yet, sx_lock will be 701 * set to SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS. 702 * If we see that value, try to acquire it once. Note 703 * that we have to preserve SX_LOCK_EXCLUSIVE_WAITERS 704 * as there are other exclusive waiters still. If we 705 * fail, restart the loop. 706 */ 707 if (x == (SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS)) { 708 if (!atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, 709 tid | SX_LOCK_EXCLUSIVE_WAITERS)) 710 goto retry_sleepq; 711 sleepq_release(&sx->lock_object); 712 CTR2(KTR_LOCK, "%s: %p claimed by new writer", 713 __func__, sx); 714 break; 715 } 716 717 /* 718 * Try to set the SX_LOCK_EXCLUSIVE_WAITERS. If we fail, 719 * than loop back and retry. 720 */ 721 if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) { 722 if (!atomic_fcmpset_ptr(&sx->sx_lock, &x, 723 x | SX_LOCK_EXCLUSIVE_WAITERS)) { 724 goto retry_sleepq; 725 } 726 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 727 CTR2(KTR_LOCK, "%s: %p set excl waiters flag", 728 __func__, sx); 729 } 730 731 /* 732 * Since we have been unable to acquire the exclusive 733 * lock and the exclusive waiters flag is set, we have 734 * to sleep. 735 */ 736 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 737 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 738 __func__, sx); 739 740 #ifdef KDTRACE_HOOKS 741 sleep_time -= lockstat_nsecs(&sx->lock_object); 742 #endif 743 GIANT_SAVE(extra_work); 744 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 745 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 746 SLEEPQ_INTERRUPTIBLE : 0), SQ_EXCLUSIVE_QUEUE); 747 if (!(opts & SX_INTERRUPTIBLE)) 748 sleepq_wait(&sx->lock_object, 0); 749 else 750 error = sleepq_wait_sig(&sx->lock_object, 0); 751 #ifdef KDTRACE_HOOKS 752 sleep_time += lockstat_nsecs(&sx->lock_object); 753 sleep_cnt++; 754 #endif 755 if (error) { 756 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 757 CTR2(KTR_LOCK, 758 "%s: interruptible sleep by %p suspended by signal", 759 __func__, sx); 760 break; 761 } 762 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 763 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 764 __func__, sx); 765 x = SX_READ_VALUE(sx); 766 } 767 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 768 if (__predict_true(!extra_work)) 769 return (error); 770 #endif 771 #ifdef KDTRACE_HOOKS 772 all_time += lockstat_nsecs(&sx->lock_object); 773 if (sleep_time) 774 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 775 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 776 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 777 if (lda.spin_cnt > sleep_cnt) 778 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 779 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 780 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 781 #endif 782 if (!error) 783 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 784 contested, waittime, file, line, LOCKSTAT_WRITER); 785 GIANT_RESTORE(); 786 return (error); 787 } 788 789 /* 790 * This function represents the so-called 'hard case' for sx_xunlock 791 * operation. All 'easy case' failures are redirected to this. Note 792 * that ideally this would be a static function, but it needs to be 793 * accessible from at least sx.h. 794 */ 795 void 796 _sx_xunlock_hard(struct sx *sx, uintptr_t x LOCK_FILE_LINE_ARG_DEF) 797 { 798 uintptr_t tid, setx; 799 int queue, wakeup_swapper; 800 801 if (SCHEDULER_STOPPED()) 802 return; 803 804 tid = (uintptr_t)curthread; 805 806 if (__predict_false(x == tid)) 807 x = SX_READ_VALUE(sx); 808 809 MPASS(!(x & SX_LOCK_SHARED)); 810 811 if (__predict_false(x & SX_LOCK_RECURSED)) { 812 /* The lock is recursed, unrecurse one level. */ 813 if ((--sx->sx_recurse) == 0) 814 atomic_clear_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 815 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 816 CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, sx); 817 return; 818 } 819 820 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_WRITER); 821 if (x == tid && 822 atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED)) 823 return; 824 825 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 826 CTR2(KTR_LOCK, "%s: %p contested", __func__, sx); 827 828 sleepq_lock(&sx->lock_object); 829 x = SX_READ_VALUE(sx); 830 MPASS(x & (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)); 831 832 /* 833 * The wake up algorithm here is quite simple and probably not 834 * ideal. It gives precedence to shared waiters if they are 835 * present. For this condition, we have to preserve the 836 * state of the exclusive waiters flag. 837 * If interruptible sleeps left the shared queue empty avoid a 838 * starvation for the threads sleeping on the exclusive queue by giving 839 * them precedence and cleaning up the shared waiters bit anyway. 840 */ 841 setx = SX_LOCK_UNLOCKED; 842 queue = SQ_EXCLUSIVE_QUEUE; 843 if ((x & SX_LOCK_SHARED_WAITERS) != 0 && 844 sleepq_sleepcnt(&sx->lock_object, SQ_SHARED_QUEUE) != 0) { 845 queue = SQ_SHARED_QUEUE; 846 setx |= (x & SX_LOCK_EXCLUSIVE_WAITERS); 847 } 848 atomic_store_rel_ptr(&sx->sx_lock, setx); 849 850 /* Wake up all the waiters for the specific queue. */ 851 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 852 CTR3(KTR_LOCK, "%s: %p waking up all threads on %s queue", 853 __func__, sx, queue == SQ_SHARED_QUEUE ? "shared" : 854 "exclusive"); 855 856 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 0, 857 queue); 858 sleepq_release(&sx->lock_object); 859 if (wakeup_swapper) 860 kick_proc0(); 861 } 862 863 static bool __always_inline 864 __sx_slock_try(struct sx *sx, uintptr_t *xp LOCK_FILE_LINE_ARG_DEF) 865 { 866 867 /* 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 while (*xp & SX_LOCK_SHARED) { 874 MPASS(!(*xp & SX_LOCK_SHARED_WAITERS)); 875 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, xp, 876 *xp + SX_ONE_SHARER)) { 877 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 878 CTR4(KTR_LOCK, "%s: %p succeed %p -> %p", 879 __func__, sx, (void *)*xp, 880 (void *)(*xp + SX_ONE_SHARER)); 881 return (true); 882 } 883 } 884 return (false); 885 } 886 887 static int __noinline 888 _sx_slock_hard(struct sx *sx, int opts, uintptr_t x LOCK_FILE_LINE_ARG_DEF) 889 { 890 GIANT_DECLARE; 891 #ifdef ADAPTIVE_SX 892 volatile struct thread *owner; 893 #endif 894 #ifdef LOCK_PROFILING 895 uint64_t waittime = 0; 896 int contested = 0; 897 #endif 898 int error = 0; 899 #if defined(ADAPTIVE_SX) || defined(KDTRACE_HOOKS) 900 struct lock_delay_arg lda; 901 #endif 902 #ifdef KDTRACE_HOOKS 903 u_int sleep_cnt = 0; 904 int64_t sleep_time = 0; 905 int64_t all_time = 0; 906 #endif 907 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 908 uintptr_t state; 909 #endif 910 int extra_work = 0; 911 912 if (SCHEDULER_STOPPED()) 913 return (0); 914 915 #if defined(ADAPTIVE_SX) 916 lock_delay_arg_init(&lda, &sx_delay); 917 #elif defined(KDTRACE_HOOKS) 918 lock_delay_arg_init(&lda, NULL); 919 #endif 920 921 #ifdef HWPMC_HOOKS 922 PMC_SOFT_CALL( , , lock, failed); 923 #endif 924 lock_profile_obtain_lock_failed(&sx->lock_object, &contested, 925 &waittime); 926 927 #ifdef LOCK_PROFILING 928 extra_work = 1; 929 state = x; 930 #elif defined(KDTRACE_HOOKS) 931 extra_work = lockstat_enabled; 932 if (__predict_false(extra_work)) { 933 all_time -= lockstat_nsecs(&sx->lock_object); 934 state = x; 935 } 936 #endif 937 938 /* 939 * As with rwlocks, we don't make any attempt to try to block 940 * shared locks once there is an exclusive waiter. 941 */ 942 for (;;) { 943 if (__sx_slock_try(sx, &x LOCK_FILE_LINE_ARG)) 944 break; 945 #ifdef KDTRACE_HOOKS 946 lda.spin_cnt++; 947 #endif 948 949 #ifdef ADAPTIVE_SX 950 /* 951 * If the owner is running on another CPU, spin until 952 * the owner stops running or the state of the lock 953 * changes. 954 */ 955 if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 956 owner = lv_sx_owner(x); 957 if (TD_IS_RUNNING(owner)) { 958 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 959 CTR3(KTR_LOCK, 960 "%s: spinning on %p held by %p", 961 __func__, sx, owner); 962 KTR_STATE1(KTR_SCHED, "thread", 963 sched_tdname(curthread), "spinning", 964 "lockname:\"%s\"", sx->lock_object.lo_name); 965 GIANT_SAVE(extra_work); 966 do { 967 lock_delay(&lda); 968 x = SX_READ_VALUE(sx); 969 owner = lv_sx_owner(x); 970 } while (owner != NULL && TD_IS_RUNNING(owner)); 971 KTR_STATE0(KTR_SCHED, "thread", 972 sched_tdname(curthread), "running"); 973 continue; 974 } 975 } 976 #endif 977 978 /* 979 * Some other thread already has an exclusive lock, so 980 * start the process of blocking. 981 */ 982 sleepq_lock(&sx->lock_object); 983 x = SX_READ_VALUE(sx); 984 retry_sleepq: 985 /* 986 * The lock could have been released while we spun. 987 * In this case loop back and retry. 988 */ 989 if (x & SX_LOCK_SHARED) { 990 sleepq_release(&sx->lock_object); 991 continue; 992 } 993 994 #ifdef ADAPTIVE_SX 995 /* 996 * If the owner is running on another CPU, spin until 997 * the owner stops running or the state of the lock 998 * changes. 999 */ 1000 if (!(x & SX_LOCK_SHARED) && 1001 (sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 1002 owner = (struct thread *)SX_OWNER(x); 1003 if (TD_IS_RUNNING(owner)) { 1004 sleepq_release(&sx->lock_object); 1005 x = SX_READ_VALUE(sx); 1006 continue; 1007 } 1008 } 1009 #endif 1010 1011 /* 1012 * Try to set the SX_LOCK_SHARED_WAITERS flag. If we 1013 * fail to set it drop the sleep queue lock and loop 1014 * back. 1015 */ 1016 if (!(x & SX_LOCK_SHARED_WAITERS)) { 1017 if (!atomic_fcmpset_ptr(&sx->sx_lock, &x, 1018 x | SX_LOCK_SHARED_WAITERS)) 1019 goto retry_sleepq; 1020 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1021 CTR2(KTR_LOCK, "%s: %p set shared waiters flag", 1022 __func__, sx); 1023 } 1024 1025 /* 1026 * Since we have been unable to acquire the shared lock, 1027 * we have to sleep. 1028 */ 1029 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1030 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 1031 __func__, sx); 1032 1033 #ifdef KDTRACE_HOOKS 1034 sleep_time -= lockstat_nsecs(&sx->lock_object); 1035 #endif 1036 GIANT_SAVE(extra_work); 1037 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 1038 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 1039 SLEEPQ_INTERRUPTIBLE : 0), SQ_SHARED_QUEUE); 1040 if (!(opts & SX_INTERRUPTIBLE)) 1041 sleepq_wait(&sx->lock_object, 0); 1042 else 1043 error = sleepq_wait_sig(&sx->lock_object, 0); 1044 #ifdef KDTRACE_HOOKS 1045 sleep_time += lockstat_nsecs(&sx->lock_object); 1046 sleep_cnt++; 1047 #endif 1048 if (error) { 1049 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1050 CTR2(KTR_LOCK, 1051 "%s: interruptible sleep by %p suspended by signal", 1052 __func__, sx); 1053 break; 1054 } 1055 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1056 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 1057 __func__, sx); 1058 x = SX_READ_VALUE(sx); 1059 } 1060 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 1061 if (__predict_true(!extra_work)) 1062 return (error); 1063 #endif 1064 #ifdef KDTRACE_HOOKS 1065 all_time += lockstat_nsecs(&sx->lock_object); 1066 if (sleep_time) 1067 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 1068 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1069 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1070 if (lda.spin_cnt > sleep_cnt) 1071 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 1072 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1073 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1074 #endif 1075 if (error == 0) { 1076 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 1077 contested, waittime, file, line, LOCKSTAT_READER); 1078 } 1079 GIANT_RESTORE(); 1080 return (error); 1081 } 1082 1083 int 1084 _sx_slock_int(struct sx *sx, int opts LOCK_FILE_LINE_ARG_DEF) 1085 { 1086 uintptr_t x; 1087 int error; 1088 1089 KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() || 1090 !TD_IS_IDLETHREAD(curthread), 1091 ("sx_slock() by idle thread %p on sx %s @ %s:%d", 1092 curthread, sx->lock_object.lo_name, file, line)); 1093 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 1094 ("sx_slock() of destroyed sx @ %s:%d", file, line)); 1095 WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER, file, line, NULL); 1096 1097 error = 0; 1098 x = SX_READ_VALUE(sx); 1099 if (__predict_false(LOCKSTAT_OOL_PROFILE_ENABLED(sx__acquire) || 1100 !__sx_slock_try(sx, &x LOCK_FILE_LINE_ARG))) 1101 error = _sx_slock_hard(sx, opts, x LOCK_FILE_LINE_ARG); 1102 if (error == 0) { 1103 LOCK_LOG_LOCK("SLOCK", &sx->lock_object, 0, 0, file, line); 1104 WITNESS_LOCK(&sx->lock_object, 0, file, line); 1105 TD_LOCKS_INC(curthread); 1106 } 1107 return (error); 1108 } 1109 1110 int 1111 _sx_slock(struct sx *sx, int opts, const char *file, int line) 1112 { 1113 1114 return (_sx_slock_int(sx, opts LOCK_FILE_LINE_ARG)); 1115 } 1116 1117 static bool __always_inline 1118 _sx_sunlock_try(struct sx *sx, uintptr_t *xp) 1119 { 1120 1121 for (;;) { 1122 /* 1123 * We should never have sharers while at least one thread 1124 * holds a shared lock. 1125 */ 1126 KASSERT(!(*xp & SX_LOCK_SHARED_WAITERS), 1127 ("%s: waiting sharers", __func__)); 1128 1129 /* 1130 * See if there is more than one shared lock held. If 1131 * so, just drop one and return. 1132 */ 1133 if (SX_SHARERS(*xp) > 1) { 1134 if (atomic_fcmpset_rel_ptr(&sx->sx_lock, xp, 1135 *xp - SX_ONE_SHARER)) { 1136 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1137 CTR4(KTR_LOCK, 1138 "%s: %p succeeded %p -> %p", 1139 __func__, sx, (void *)*xp, 1140 (void *)(*xp - SX_ONE_SHARER)); 1141 return (true); 1142 } 1143 continue; 1144 } 1145 1146 /* 1147 * If there aren't any waiters for an exclusive lock, 1148 * then try to drop it quickly. 1149 */ 1150 if (!(*xp & SX_LOCK_EXCLUSIVE_WAITERS)) { 1151 MPASS(*xp == SX_SHARERS_LOCK(1)); 1152 *xp = SX_SHARERS_LOCK(1); 1153 if (atomic_fcmpset_rel_ptr(&sx->sx_lock, 1154 xp, SX_LOCK_UNLOCKED)) { 1155 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1156 CTR2(KTR_LOCK, "%s: %p last succeeded", 1157 __func__, sx); 1158 return (true); 1159 } 1160 continue; 1161 } 1162 break; 1163 } 1164 return (false); 1165 } 1166 1167 static void __noinline 1168 _sx_sunlock_hard(struct sx *sx, uintptr_t x LOCK_FILE_LINE_ARG_DEF) 1169 { 1170 int wakeup_swapper; 1171 uintptr_t setx; 1172 1173 if (SCHEDULER_STOPPED()) 1174 return; 1175 1176 if (_sx_sunlock_try(sx, &x)) 1177 goto out_lockstat; 1178 1179 /* 1180 * At this point, there should just be one sharer with 1181 * exclusive waiters. 1182 */ 1183 MPASS(x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS)); 1184 1185 sleepq_lock(&sx->lock_object); 1186 x = SX_READ_VALUE(sx); 1187 for (;;) { 1188 MPASS(x & SX_LOCK_EXCLUSIVE_WAITERS); 1189 MPASS(!(x & SX_LOCK_SHARED_WAITERS)); 1190 /* 1191 * Wake up semantic here is quite simple: 1192 * Just wake up all the exclusive waiters. 1193 * Note that the state of the lock could have changed, 1194 * so if it fails loop back and retry. 1195 */ 1196 setx = x - SX_ONE_SHARER; 1197 setx &= ~SX_LOCK_EXCLUSIVE_WAITERS; 1198 if (!atomic_fcmpset_rel_ptr(&sx->sx_lock, &x, setx)) 1199 continue; 1200 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1201 CTR2(KTR_LOCK, "%s: %p waking up all thread on" 1202 "exclusive queue", __func__, sx); 1203 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 1204 0, SQ_EXCLUSIVE_QUEUE); 1205 break; 1206 } 1207 sleepq_release(&sx->lock_object); 1208 if (wakeup_swapper) 1209 kick_proc0(); 1210 out_lockstat: 1211 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_READER); 1212 } 1213 1214 void 1215 _sx_sunlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 1216 { 1217 uintptr_t x; 1218 1219 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 1220 ("sx_sunlock() of destroyed sx @ %s:%d", file, line)); 1221 _sx_assert(sx, SA_SLOCKED, file, line); 1222 WITNESS_UNLOCK(&sx->lock_object, 0, file, line); 1223 LOCK_LOG_LOCK("SUNLOCK", &sx->lock_object, 0, 0, file, line); 1224 1225 x = SX_READ_VALUE(sx); 1226 if (__predict_false(LOCKSTAT_OOL_PROFILE_ENABLED(sx__release) || 1227 !_sx_sunlock_try(sx, &x))) 1228 _sx_sunlock_hard(sx, x LOCK_FILE_LINE_ARG); 1229 1230 TD_LOCKS_DEC(curthread); 1231 } 1232 1233 void 1234 _sx_sunlock(struct sx *sx, const char *file, int line) 1235 { 1236 1237 _sx_sunlock_int(sx LOCK_FILE_LINE_ARG); 1238 } 1239 1240 #ifdef INVARIANT_SUPPORT 1241 #ifndef INVARIANTS 1242 #undef _sx_assert 1243 #endif 1244 1245 /* 1246 * In the non-WITNESS case, sx_assert() can only detect that at least 1247 * *some* thread owns an slock, but it cannot guarantee that *this* 1248 * thread owns an slock. 1249 */ 1250 void 1251 _sx_assert(const struct sx *sx, int what, const char *file, int line) 1252 { 1253 #ifndef WITNESS 1254 int slocked = 0; 1255 #endif 1256 1257 if (panicstr != NULL) 1258 return; 1259 switch (what) { 1260 case SA_SLOCKED: 1261 case SA_SLOCKED | SA_NOTRECURSED: 1262 case SA_SLOCKED | SA_RECURSED: 1263 #ifndef WITNESS 1264 slocked = 1; 1265 /* FALLTHROUGH */ 1266 #endif 1267 case SA_LOCKED: 1268 case SA_LOCKED | SA_NOTRECURSED: 1269 case SA_LOCKED | SA_RECURSED: 1270 #ifdef WITNESS 1271 witness_assert(&sx->lock_object, what, file, line); 1272 #else 1273 /* 1274 * If some other thread has an exclusive lock or we 1275 * have one and are asserting a shared lock, fail. 1276 * Also, if no one has a lock at all, fail. 1277 */ 1278 if (sx->sx_lock == SX_LOCK_UNLOCKED || 1279 (!(sx->sx_lock & SX_LOCK_SHARED) && (slocked || 1280 sx_xholder(sx) != curthread))) 1281 panic("Lock %s not %slocked @ %s:%d\n", 1282 sx->lock_object.lo_name, slocked ? "share " : "", 1283 file, line); 1284 1285 if (!(sx->sx_lock & SX_LOCK_SHARED)) { 1286 if (sx_recursed(sx)) { 1287 if (what & SA_NOTRECURSED) 1288 panic("Lock %s recursed @ %s:%d\n", 1289 sx->lock_object.lo_name, file, 1290 line); 1291 } else if (what & SA_RECURSED) 1292 panic("Lock %s not recursed @ %s:%d\n", 1293 sx->lock_object.lo_name, file, line); 1294 } 1295 #endif 1296 break; 1297 case SA_XLOCKED: 1298 case SA_XLOCKED | SA_NOTRECURSED: 1299 case SA_XLOCKED | SA_RECURSED: 1300 if (sx_xholder(sx) != curthread) 1301 panic("Lock %s not exclusively locked @ %s:%d\n", 1302 sx->lock_object.lo_name, file, line); 1303 if (sx_recursed(sx)) { 1304 if (what & SA_NOTRECURSED) 1305 panic("Lock %s recursed @ %s:%d\n", 1306 sx->lock_object.lo_name, file, line); 1307 } else if (what & SA_RECURSED) 1308 panic("Lock %s not recursed @ %s:%d\n", 1309 sx->lock_object.lo_name, file, line); 1310 break; 1311 case SA_UNLOCKED: 1312 #ifdef WITNESS 1313 witness_assert(&sx->lock_object, what, file, line); 1314 #else 1315 /* 1316 * If we hold an exclusve lock fail. We can't 1317 * reliably check to see if we hold a shared lock or 1318 * not. 1319 */ 1320 if (sx_xholder(sx) == curthread) 1321 panic("Lock %s exclusively locked @ %s:%d\n", 1322 sx->lock_object.lo_name, file, line); 1323 #endif 1324 break; 1325 default: 1326 panic("Unknown sx lock assertion: %d @ %s:%d", what, file, 1327 line); 1328 } 1329 } 1330 #endif /* INVARIANT_SUPPORT */ 1331 1332 #ifdef DDB 1333 static void 1334 db_show_sx(const struct lock_object *lock) 1335 { 1336 struct thread *td; 1337 const struct sx *sx; 1338 1339 sx = (const struct sx *)lock; 1340 1341 db_printf(" state: "); 1342 if (sx->sx_lock == SX_LOCK_UNLOCKED) 1343 db_printf("UNLOCKED\n"); 1344 else if (sx->sx_lock == SX_LOCK_DESTROYED) { 1345 db_printf("DESTROYED\n"); 1346 return; 1347 } else if (sx->sx_lock & SX_LOCK_SHARED) 1348 db_printf("SLOCK: %ju\n", (uintmax_t)SX_SHARERS(sx->sx_lock)); 1349 else { 1350 td = sx_xholder(sx); 1351 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1352 td->td_tid, td->td_proc->p_pid, td->td_name); 1353 if (sx_recursed(sx)) 1354 db_printf(" recursed: %d\n", sx->sx_recurse); 1355 } 1356 1357 db_printf(" waiters: "); 1358 switch(sx->sx_lock & 1359 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)) { 1360 case SX_LOCK_SHARED_WAITERS: 1361 db_printf("shared\n"); 1362 break; 1363 case SX_LOCK_EXCLUSIVE_WAITERS: 1364 db_printf("exclusive\n"); 1365 break; 1366 case SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS: 1367 db_printf("exclusive and shared\n"); 1368 break; 1369 default: 1370 db_printf("none\n"); 1371 } 1372 } 1373 1374 /* 1375 * Check to see if a thread that is blocked on a sleep queue is actually 1376 * blocked on an sx lock. If so, output some details and return true. 1377 * If the lock has an exclusive owner, return that in *ownerp. 1378 */ 1379 int 1380 sx_chain(struct thread *td, struct thread **ownerp) 1381 { 1382 struct sx *sx; 1383 1384 /* 1385 * Check to see if this thread is blocked on an sx lock. 1386 * First, we check the lock class. If that is ok, then we 1387 * compare the lock name against the wait message. 1388 */ 1389 sx = td->td_wchan; 1390 if (LOCK_CLASS(&sx->lock_object) != &lock_class_sx || 1391 sx->lock_object.lo_name != td->td_wmesg) 1392 return (0); 1393 1394 /* We think we have an sx lock, so output some details. */ 1395 db_printf("blocked on sx \"%s\" ", td->td_wmesg); 1396 *ownerp = sx_xholder(sx); 1397 if (sx->sx_lock & SX_LOCK_SHARED) 1398 db_printf("SLOCK (count %ju)\n", 1399 (uintmax_t)SX_SHARERS(sx->sx_lock)); 1400 else 1401 db_printf("XLOCK\n"); 1402 return (1); 1403 } 1404 #endif 1405