1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org> 5 * Copyright (c) 2001 Jason Evans <jasone@freebsd.org> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice(s), this list of conditions and the following disclaimer as 13 * the first lines of this file unmodified other than the possible 14 * addition of one or more copyright notices. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice(s), this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 20 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 21 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 22 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 23 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 24 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 25 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 26 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 29 * DAMAGE. 30 */ 31 32 /* 33 * Shared/exclusive locks. This implementation attempts to ensure 34 * deterministic lock granting behavior, so that slocks and xlocks are 35 * interleaved. 36 * 37 * Priority propagation will not generally raise the priority of lock holders, 38 * so should not be relied upon in combination with sx locks. 39 */ 40 41 #include "opt_ddb.h" 42 #include "opt_hwpmc_hooks.h" 43 #include "opt_no_adaptive_sx.h" 44 45 #include <sys/cdefs.h> 46 __FBSDID("$FreeBSD$"); 47 48 #include <sys/param.h> 49 #include <sys/systm.h> 50 #include <sys/kdb.h> 51 #include <sys/kernel.h> 52 #include <sys/ktr.h> 53 #include <sys/lock.h> 54 #include <sys/mutex.h> 55 #include <sys/proc.h> 56 #include <sys/sched.h> 57 #include <sys/sleepqueue.h> 58 #include <sys/sx.h> 59 #include <sys/smp.h> 60 #include <sys/sysctl.h> 61 62 #if defined(SMP) && !defined(NO_ADAPTIVE_SX) 63 #include <machine/cpu.h> 64 #endif 65 66 #ifdef DDB 67 #include <ddb/ddb.h> 68 #endif 69 70 #if defined(SMP) && !defined(NO_ADAPTIVE_SX) 71 #define ADAPTIVE_SX 72 #endif 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 (__predict_false(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 #ifdef SX_CUSTOM_BACKOFF 147 static u_short __read_frequently asx_retries; 148 static u_short __read_frequently asx_loops; 149 static SYSCTL_NODE(_debug, OID_AUTO, sx, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 150 "sxlock debugging"); 151 SYSCTL_U16(_debug_sx, OID_AUTO, retries, CTLFLAG_RW, &asx_retries, 0, ""); 152 SYSCTL_U16(_debug_sx, OID_AUTO, loops, CTLFLAG_RW, &asx_loops, 0, ""); 153 154 static struct lock_delay_config __read_frequently sx_delay; 155 156 SYSCTL_U16(_debug_sx, OID_AUTO, delay_base, CTLFLAG_RW, &sx_delay.base, 157 0, ""); 158 SYSCTL_U16(_debug_sx, OID_AUTO, delay_max, CTLFLAG_RW, &sx_delay.max, 159 0, ""); 160 161 static void 162 sx_lock_delay_init(void *arg __unused) 163 { 164 165 lock_delay_default_init(&sx_delay); 166 asx_retries = 10; 167 asx_loops = max(10000, sx_delay.max); 168 } 169 LOCK_DELAY_SYSINIT(sx_lock_delay_init); 170 #else 171 #define sx_delay locks_delay 172 #define asx_retries locks_delay_retries 173 #define asx_loops locks_delay_loops 174 #endif 175 #endif 176 177 void 178 assert_sx(const struct lock_object *lock, int what) 179 { 180 181 sx_assert((const struct sx *)lock, what); 182 } 183 184 void 185 lock_sx(struct lock_object *lock, uintptr_t how) 186 { 187 struct sx *sx; 188 189 sx = (struct sx *)lock; 190 if (how) 191 sx_slock(sx); 192 else 193 sx_xlock(sx); 194 } 195 196 uintptr_t 197 unlock_sx(struct lock_object *lock) 198 { 199 struct sx *sx; 200 201 sx = (struct sx *)lock; 202 sx_assert(sx, SA_LOCKED | SA_NOTRECURSED); 203 if (sx_xlocked(sx)) { 204 sx_xunlock(sx); 205 return (0); 206 } else { 207 sx_sunlock(sx); 208 return (1); 209 } 210 } 211 212 #ifdef KDTRACE_HOOKS 213 int 214 owner_sx(const struct lock_object *lock, struct thread **owner) 215 { 216 const struct sx *sx; 217 uintptr_t x; 218 219 sx = (const struct sx *)lock; 220 x = sx->sx_lock; 221 *owner = NULL; 222 return ((x & SX_LOCK_SHARED) != 0 ? (SX_SHARERS(x) != 0) : 223 ((*owner = (struct thread *)SX_OWNER(x)) != NULL)); 224 } 225 #endif 226 227 void 228 sx_sysinit(void *arg) 229 { 230 struct sx_args *sargs = arg; 231 232 sx_init_flags(sargs->sa_sx, sargs->sa_desc, sargs->sa_flags); 233 } 234 235 void 236 sx_init_flags(struct sx *sx, const char *description, int opts) 237 { 238 int flags; 239 240 MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK | 241 SX_NOPROFILE | SX_NEW)) == 0); 242 ASSERT_ATOMIC_LOAD_PTR(sx->sx_lock, 243 ("%s: sx_lock not aligned for %s: %p", __func__, description, 244 &sx->sx_lock)); 245 246 flags = LO_SLEEPABLE | LO_UPGRADABLE; 247 if (opts & SX_DUPOK) 248 flags |= LO_DUPOK; 249 if (opts & SX_NOPROFILE) 250 flags |= LO_NOPROFILE; 251 if (!(opts & SX_NOWITNESS)) 252 flags |= LO_WITNESS; 253 if (opts & SX_RECURSE) 254 flags |= LO_RECURSABLE; 255 if (opts & SX_QUIET) 256 flags |= LO_QUIET; 257 if (opts & SX_NEW) 258 flags |= LO_NEW; 259 260 lock_init(&sx->lock_object, &lock_class_sx, description, NULL, flags); 261 sx->sx_lock = SX_LOCK_UNLOCKED; 262 sx->sx_recurse = 0; 263 } 264 265 void 266 sx_destroy(struct sx *sx) 267 { 268 269 KASSERT(sx->sx_lock == SX_LOCK_UNLOCKED, ("sx lock still held")); 270 KASSERT(sx->sx_recurse == 0, ("sx lock still recursed")); 271 sx->sx_lock = SX_LOCK_DESTROYED; 272 lock_destroy(&sx->lock_object); 273 } 274 275 int 276 sx_try_slock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 277 { 278 uintptr_t x; 279 280 if (SCHEDULER_STOPPED()) 281 return (1); 282 283 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 284 ("sx_try_slock() by idle thread %p on sx %s @ %s:%d", 285 curthread, sx->lock_object.lo_name, file, line)); 286 287 x = sx->sx_lock; 288 for (;;) { 289 KASSERT(x != SX_LOCK_DESTROYED, 290 ("sx_try_slock() of destroyed sx @ %s:%d", file, line)); 291 if (!(x & SX_LOCK_SHARED)) 292 break; 293 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, x + SX_ONE_SHARER)) { 294 LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 1, file, line); 295 WITNESS_LOCK(&sx->lock_object, LOP_TRYLOCK, file, line); 296 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, 297 sx, 0, 0, file, line, LOCKSTAT_READER); 298 TD_LOCKS_INC(curthread); 299 curthread->td_sx_slocks++; 300 return (1); 301 } 302 } 303 304 LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 0, file, line); 305 return (0); 306 } 307 308 int 309 sx_try_slock_(struct sx *sx, const char *file, int line) 310 { 311 312 return (sx_try_slock_int(sx LOCK_FILE_LINE_ARG)); 313 } 314 315 int 316 _sx_xlock(struct sx *sx, int opts, const char *file, int line) 317 { 318 uintptr_t tid, x; 319 int error = 0; 320 321 KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() || 322 !TD_IS_IDLETHREAD(curthread), 323 ("sx_xlock() by idle thread %p on sx %s @ %s:%d", 324 curthread, sx->lock_object.lo_name, file, line)); 325 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 326 ("sx_xlock() of destroyed sx @ %s:%d", file, line)); 327 WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, 328 line, NULL); 329 tid = (uintptr_t)curthread; 330 x = SX_LOCK_UNLOCKED; 331 if (!atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 332 error = _sx_xlock_hard(sx, x, opts LOCK_FILE_LINE_ARG); 333 else 334 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 335 0, 0, file, line, LOCKSTAT_WRITER); 336 if (!error) { 337 LOCK_LOG_LOCK("XLOCK", &sx->lock_object, 0, sx->sx_recurse, 338 file, line); 339 WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); 340 TD_LOCKS_INC(curthread); 341 } 342 343 return (error); 344 } 345 346 int 347 sx_try_xlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 348 { 349 struct thread *td; 350 uintptr_t tid, x; 351 int rval; 352 bool recursed; 353 354 td = curthread; 355 tid = (uintptr_t)td; 356 if (SCHEDULER_STOPPED_TD(td)) 357 return (1); 358 359 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(td), 360 ("sx_try_xlock() by idle thread %p on sx %s @ %s:%d", 361 curthread, sx->lock_object.lo_name, file, line)); 362 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 363 ("sx_try_xlock() of destroyed sx @ %s:%d", file, line)); 364 365 rval = 1; 366 recursed = false; 367 x = SX_LOCK_UNLOCKED; 368 for (;;) { 369 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 370 break; 371 if (x == SX_LOCK_UNLOCKED) 372 continue; 373 if (x == tid && (sx->lock_object.lo_flags & LO_RECURSABLE)) { 374 sx->sx_recurse++; 375 atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 376 break; 377 } 378 rval = 0; 379 break; 380 } 381 382 LOCK_LOG_TRY("XLOCK", &sx->lock_object, 0, rval, file, line); 383 if (rval) { 384 WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 385 file, line); 386 if (!recursed) 387 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, 388 sx, 0, 0, file, line, LOCKSTAT_WRITER); 389 TD_LOCKS_INC(curthread); 390 } 391 392 return (rval); 393 } 394 395 int 396 sx_try_xlock_(struct sx *sx, const char *file, int line) 397 { 398 399 return (sx_try_xlock_int(sx LOCK_FILE_LINE_ARG)); 400 } 401 402 void 403 _sx_xunlock(struct sx *sx, const char *file, int line) 404 { 405 406 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 407 ("sx_xunlock() of destroyed sx @ %s:%d", file, line)); 408 _sx_assert(sx, SA_XLOCKED, file, line); 409 WITNESS_UNLOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); 410 LOCK_LOG_LOCK("XUNLOCK", &sx->lock_object, 0, sx->sx_recurse, file, 411 line); 412 #if LOCK_DEBUG > 0 413 _sx_xunlock_hard(sx, (uintptr_t)curthread, file, line); 414 #else 415 __sx_xunlock(sx, curthread, file, line); 416 #endif 417 TD_LOCKS_DEC(curthread); 418 } 419 420 /* 421 * Try to do a non-blocking upgrade from a shared lock to an exclusive lock. 422 * This will only succeed if this thread holds a single shared lock. 423 * Return 1 if if the upgrade succeed, 0 otherwise. 424 */ 425 int 426 sx_try_upgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 427 { 428 uintptr_t x; 429 uintptr_t waiters; 430 int success; 431 432 if (SCHEDULER_STOPPED()) 433 return (1); 434 435 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 436 ("sx_try_upgrade() of destroyed sx @ %s:%d", file, line)); 437 _sx_assert(sx, SA_SLOCKED, file, line); 438 439 /* 440 * Try to switch from one shared lock to an exclusive lock. We need 441 * to maintain the SX_LOCK_EXCLUSIVE_WAITERS flag if set so that 442 * we will wake up the exclusive waiters when we drop the lock. 443 */ 444 success = 0; 445 x = SX_READ_VALUE(sx); 446 for (;;) { 447 if (SX_SHARERS(x) > 1) 448 break; 449 waiters = (x & SX_LOCK_WAITERS); 450 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, 451 (uintptr_t)curthread | waiters)) { 452 success = 1; 453 break; 454 } 455 } 456 LOCK_LOG_TRY("XUPGRADE", &sx->lock_object, 0, success, file, line); 457 if (success) { 458 curthread->td_sx_slocks--; 459 WITNESS_UPGRADE(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 460 file, line); 461 LOCKSTAT_RECORD0(sx__upgrade, sx); 462 } 463 return (success); 464 } 465 466 int 467 sx_try_upgrade_(struct sx *sx, const char *file, int line) 468 { 469 470 return (sx_try_upgrade_int(sx LOCK_FILE_LINE_ARG)); 471 } 472 473 /* 474 * Downgrade an unrecursed exclusive lock into a single shared lock. 475 */ 476 void 477 sx_downgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 478 { 479 uintptr_t x; 480 int wakeup_swapper; 481 482 if (SCHEDULER_STOPPED()) 483 return; 484 485 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 486 ("sx_downgrade() of destroyed sx @ %s:%d", file, line)); 487 _sx_assert(sx, SA_XLOCKED | SA_NOTRECURSED, file, line); 488 #ifndef INVARIANTS 489 if (sx_recursed(sx)) 490 panic("downgrade of a recursed lock"); 491 #endif 492 493 WITNESS_DOWNGRADE(&sx->lock_object, 0, file, line); 494 495 /* 496 * Try to switch from an exclusive lock with no shared waiters 497 * to one sharer with no shared waiters. If there are 498 * exclusive waiters, we don't need to lock the sleep queue so 499 * long as we preserve the flag. We do one quick try and if 500 * that fails we grab the sleepq lock to keep the flags from 501 * changing and do it the slow way. 502 * 503 * We have to lock the sleep queue if there are shared waiters 504 * so we can wake them up. 505 */ 506 x = sx->sx_lock; 507 if (!(x & SX_LOCK_SHARED_WAITERS) && 508 atomic_cmpset_rel_ptr(&sx->sx_lock, x, SX_SHARERS_LOCK(1) | 509 (x & SX_LOCK_EXCLUSIVE_WAITERS))) 510 goto out; 511 512 /* 513 * Lock the sleep queue so we can read the waiters bits 514 * without any races and wakeup any shared waiters. 515 */ 516 sleepq_lock(&sx->lock_object); 517 518 /* 519 * Preserve SX_LOCK_EXCLUSIVE_WAITERS while downgraded to a single 520 * shared lock. If there are any shared waiters, wake them up. 521 */ 522 wakeup_swapper = 0; 523 x = sx->sx_lock; 524 atomic_store_rel_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | 525 (x & SX_LOCK_EXCLUSIVE_WAITERS)); 526 if (x & SX_LOCK_SHARED_WAITERS) 527 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 528 0, SQ_SHARED_QUEUE); 529 sleepq_release(&sx->lock_object); 530 531 if (wakeup_swapper) 532 kick_proc0(); 533 534 out: 535 curthread->td_sx_slocks++; 536 LOCK_LOG_LOCK("XDOWNGRADE", &sx->lock_object, 0, 0, file, line); 537 LOCKSTAT_RECORD0(sx__downgrade, sx); 538 } 539 540 void 541 sx_downgrade_(struct sx *sx, const char *file, int line) 542 { 543 544 sx_downgrade_int(sx LOCK_FILE_LINE_ARG); 545 } 546 547 #ifdef ADAPTIVE_SX 548 static inline void 549 sx_drop_critical(uintptr_t x, bool *in_critical, int *extra_work) 550 { 551 552 if (x & SX_LOCK_WRITE_SPINNER) 553 return; 554 if (*in_critical) { 555 critical_exit(); 556 *in_critical = false; 557 (*extra_work)--; 558 } 559 } 560 #else 561 #define sx_drop_critical(x, in_critical, extra_work) do { } while (0) 562 #endif 563 564 /* 565 * This function represents the so-called 'hard case' for sx_xlock 566 * operation. All 'easy case' failures are redirected to this. Note 567 * that ideally this would be a static function, but it needs to be 568 * accessible from at least sx.h. 569 */ 570 int 571 _sx_xlock_hard(struct sx *sx, uintptr_t x, int opts LOCK_FILE_LINE_ARG_DEF) 572 { 573 GIANT_DECLARE; 574 uintptr_t tid, setx; 575 #ifdef ADAPTIVE_SX 576 struct thread *owner; 577 u_int i, n, spintries = 0; 578 enum { READERS, WRITER } sleep_reason = READERS; 579 bool in_critical = false; 580 #endif 581 #ifdef LOCK_PROFILING 582 uint64_t waittime = 0; 583 int contested = 0; 584 #endif 585 int error = 0; 586 #if defined(ADAPTIVE_SX) || defined(KDTRACE_HOOKS) 587 struct lock_delay_arg lda; 588 #endif 589 #ifdef KDTRACE_HOOKS 590 u_int sleep_cnt = 0; 591 int64_t sleep_time = 0; 592 int64_t all_time = 0; 593 #endif 594 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 595 uintptr_t state = 0; 596 int doing_lockprof = 0; 597 #endif 598 int extra_work = 0; 599 600 tid = (uintptr_t)curthread; 601 602 #ifdef KDTRACE_HOOKS 603 if (LOCKSTAT_PROFILE_ENABLED(sx__acquire)) { 604 while (x == SX_LOCK_UNLOCKED) { 605 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 606 goto out_lockstat; 607 } 608 extra_work = 1; 609 doing_lockprof = 1; 610 all_time -= lockstat_nsecs(&sx->lock_object); 611 state = x; 612 } 613 #endif 614 #ifdef LOCK_PROFILING 615 extra_work = 1; 616 doing_lockprof = 1; 617 state = x; 618 #endif 619 620 if (SCHEDULER_STOPPED()) 621 return (0); 622 623 if (__predict_false(x == SX_LOCK_UNLOCKED)) 624 x = SX_READ_VALUE(sx); 625 626 /* If we already hold an exclusive lock, then recurse. */ 627 if (__predict_false(lv_sx_owner(x) == (struct thread *)tid)) { 628 KASSERT((sx->lock_object.lo_flags & LO_RECURSABLE) != 0, 629 ("_sx_xlock_hard: recursed on non-recursive sx %s @ %s:%d\n", 630 sx->lock_object.lo_name, file, line)); 631 sx->sx_recurse++; 632 atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 633 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 634 CTR2(KTR_LOCK, "%s: %p recursing", __func__, sx); 635 return (0); 636 } 637 638 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 639 CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, 640 sx->lock_object.lo_name, (void *)sx->sx_lock, file, line); 641 642 #if defined(ADAPTIVE_SX) 643 lock_delay_arg_init(&lda, &sx_delay); 644 #elif defined(KDTRACE_HOOKS) 645 lock_delay_arg_init_noadapt(&lda); 646 #endif 647 648 #ifdef HWPMC_HOOKS 649 PMC_SOFT_CALL( , , lock, failed); 650 #endif 651 lock_profile_obtain_lock_failed(&sx->lock_object, false, &contested, 652 &waittime); 653 654 #ifndef INVARIANTS 655 GIANT_SAVE(extra_work); 656 #endif 657 658 for (;;) { 659 if (x == SX_LOCK_UNLOCKED) { 660 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 661 break; 662 continue; 663 } 664 #ifdef INVARIANTS 665 GIANT_SAVE(extra_work); 666 #endif 667 #ifdef KDTRACE_HOOKS 668 lda.spin_cnt++; 669 #endif 670 #ifdef ADAPTIVE_SX 671 if (x == (SX_LOCK_SHARED | SX_LOCK_WRITE_SPINNER)) { 672 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 673 break; 674 continue; 675 } 676 677 /* 678 * If the lock is write locked and the owner is 679 * running on another CPU, spin until the owner stops 680 * running or the state of the lock changes. 681 */ 682 if ((x & SX_LOCK_SHARED) == 0) { 683 sx_drop_critical(x, &in_critical, &extra_work); 684 sleep_reason = WRITER; 685 owner = lv_sx_owner(x); 686 if (!TD_IS_RUNNING(owner)) 687 goto sleepq; 688 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 689 CTR3(KTR_LOCK, "%s: spinning on %p held by %p", 690 __func__, sx, owner); 691 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread), 692 "spinning", "lockname:\"%s\"", 693 sx->lock_object.lo_name); 694 do { 695 lock_delay(&lda); 696 x = SX_READ_VALUE(sx); 697 owner = lv_sx_owner(x); 698 } while (owner != NULL && TD_IS_RUNNING(owner)); 699 KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread), 700 "running"); 701 continue; 702 } else if (SX_SHARERS(x) > 0) { 703 sleep_reason = READERS; 704 if (spintries == asx_retries) 705 goto sleepq; 706 if (!(x & SX_LOCK_WRITE_SPINNER)) { 707 if (!in_critical) { 708 critical_enter(); 709 in_critical = true; 710 extra_work++; 711 } 712 if (!atomic_fcmpset_ptr(&sx->sx_lock, &x, 713 x | SX_LOCK_WRITE_SPINNER)) { 714 critical_exit(); 715 in_critical = false; 716 extra_work--; 717 continue; 718 } 719 } 720 spintries++; 721 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread), 722 "spinning", "lockname:\"%s\"", 723 sx->lock_object.lo_name); 724 n = SX_SHARERS(x); 725 for (i = 0; i < asx_loops; i += n) { 726 lock_delay_spin(n); 727 x = SX_READ_VALUE(sx); 728 if (!(x & SX_LOCK_WRITE_SPINNER)) 729 break; 730 if (!(x & SX_LOCK_SHARED)) 731 break; 732 n = SX_SHARERS(x); 733 if (n == 0) 734 break; 735 } 736 #ifdef KDTRACE_HOOKS 737 lda.spin_cnt += i; 738 #endif 739 KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread), 740 "running"); 741 if (i < asx_loops) 742 continue; 743 } 744 sleepq: 745 #endif 746 sleepq_lock(&sx->lock_object); 747 x = SX_READ_VALUE(sx); 748 retry_sleepq: 749 750 /* 751 * If the lock was released while spinning on the 752 * sleep queue chain lock, try again. 753 */ 754 if (x == SX_LOCK_UNLOCKED) { 755 sleepq_release(&sx->lock_object); 756 sx_drop_critical(x, &in_critical, &extra_work); 757 continue; 758 } 759 760 #ifdef ADAPTIVE_SX 761 /* 762 * The current lock owner might have started executing 763 * on another CPU (or the lock could have changed 764 * owners) while we were waiting on the sleep queue 765 * chain lock. If so, drop the sleep queue lock and try 766 * again. 767 */ 768 if (!(x & SX_LOCK_SHARED)) { 769 owner = (struct thread *)SX_OWNER(x); 770 if (TD_IS_RUNNING(owner)) { 771 sleepq_release(&sx->lock_object); 772 sx_drop_critical(x, &in_critical, 773 &extra_work); 774 continue; 775 } 776 } else if (SX_SHARERS(x) > 0 && sleep_reason == WRITER) { 777 sleepq_release(&sx->lock_object); 778 sx_drop_critical(x, &in_critical, &extra_work); 779 continue; 780 } 781 #endif 782 783 /* 784 * If an exclusive lock was released with both shared 785 * and exclusive waiters and a shared waiter hasn't 786 * woken up and acquired the lock yet, sx_lock will be 787 * set to SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS. 788 * If we see that value, try to acquire it once. Note 789 * that we have to preserve SX_LOCK_EXCLUSIVE_WAITERS 790 * as there are other exclusive waiters still. If we 791 * fail, restart the loop. 792 */ 793 setx = x & (SX_LOCK_WAITERS | SX_LOCK_WRITE_SPINNER); 794 if ((x & ~setx) == SX_LOCK_SHARED) { 795 setx &= ~SX_LOCK_WRITE_SPINNER; 796 if (!atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid | setx)) 797 goto retry_sleepq; 798 sleepq_release(&sx->lock_object); 799 CTR2(KTR_LOCK, "%s: %p claimed by new writer", 800 __func__, sx); 801 break; 802 } 803 804 #ifdef ADAPTIVE_SX 805 /* 806 * It is possible we set the SX_LOCK_WRITE_SPINNER bit. 807 * It is an invariant that when the bit is set, there is 808 * a writer ready to grab the lock. Thus clear the bit since 809 * we are going to sleep. 810 */ 811 if (in_critical) { 812 if ((x & SX_LOCK_WRITE_SPINNER) || 813 !((x & SX_LOCK_EXCLUSIVE_WAITERS))) { 814 setx = x & ~SX_LOCK_WRITE_SPINNER; 815 setx |= SX_LOCK_EXCLUSIVE_WAITERS; 816 if (!atomic_fcmpset_ptr(&sx->sx_lock, &x, 817 setx)) { 818 goto retry_sleepq; 819 } 820 } 821 critical_exit(); 822 in_critical = false; 823 } else { 824 #endif 825 /* 826 * Try to set the SX_LOCK_EXCLUSIVE_WAITERS. If we fail, 827 * than loop back and retry. 828 */ 829 if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) { 830 if (!atomic_fcmpset_ptr(&sx->sx_lock, &x, 831 x | SX_LOCK_EXCLUSIVE_WAITERS)) { 832 goto retry_sleepq; 833 } 834 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 835 CTR2(KTR_LOCK, "%s: %p set excl waiters flag", 836 __func__, sx); 837 } 838 #ifdef ADAPTIVE_SX 839 } 840 #endif 841 842 /* 843 * Since we have been unable to acquire the exclusive 844 * lock and the exclusive waiters flag is set, we have 845 * to sleep. 846 */ 847 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 848 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 849 __func__, sx); 850 851 #ifdef KDTRACE_HOOKS 852 sleep_time -= lockstat_nsecs(&sx->lock_object); 853 #endif 854 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 855 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 856 SLEEPQ_INTERRUPTIBLE : 0), SQ_EXCLUSIVE_QUEUE); 857 if (!(opts & SX_INTERRUPTIBLE)) 858 sleepq_wait(&sx->lock_object, 0); 859 else 860 error = sleepq_wait_sig(&sx->lock_object, 0); 861 #ifdef KDTRACE_HOOKS 862 sleep_time += lockstat_nsecs(&sx->lock_object); 863 sleep_cnt++; 864 #endif 865 if (error) { 866 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 867 CTR2(KTR_LOCK, 868 "%s: interruptible sleep by %p suspended by signal", 869 __func__, sx); 870 break; 871 } 872 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 873 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 874 __func__, sx); 875 x = SX_READ_VALUE(sx); 876 } 877 if (__predict_true(!extra_work)) 878 return (error); 879 #ifdef ADAPTIVE_SX 880 if (in_critical) 881 critical_exit(); 882 #endif 883 GIANT_RESTORE(); 884 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 885 if (__predict_true(!doing_lockprof)) 886 return (error); 887 #endif 888 #ifdef KDTRACE_HOOKS 889 all_time += lockstat_nsecs(&sx->lock_object); 890 if (sleep_time) 891 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 892 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 893 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 894 if (lda.spin_cnt > sleep_cnt) 895 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 896 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 897 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 898 out_lockstat: 899 #endif 900 if (!error) 901 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 902 contested, waittime, file, line, LOCKSTAT_WRITER); 903 return (error); 904 } 905 906 /* 907 * This function represents the so-called 'hard case' for sx_xunlock 908 * operation. All 'easy case' failures are redirected to this. Note 909 * that ideally this would be a static function, but it needs to be 910 * accessible from at least sx.h. 911 */ 912 void 913 _sx_xunlock_hard(struct sx *sx, uintptr_t x LOCK_FILE_LINE_ARG_DEF) 914 { 915 uintptr_t tid, setx; 916 int queue, wakeup_swapper; 917 918 if (SCHEDULER_STOPPED()) 919 return; 920 921 tid = (uintptr_t)curthread; 922 923 if (__predict_false(x == tid)) 924 x = SX_READ_VALUE(sx); 925 926 MPASS(!(x & SX_LOCK_SHARED)); 927 928 if (__predict_false(x & SX_LOCK_RECURSED)) { 929 /* The lock is recursed, unrecurse one level. */ 930 if ((--sx->sx_recurse) == 0) 931 atomic_clear_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 932 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 933 CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, sx); 934 return; 935 } 936 937 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_WRITER); 938 if (x == tid && 939 atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED)) 940 return; 941 942 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 943 CTR2(KTR_LOCK, "%s: %p contested", __func__, sx); 944 945 sleepq_lock(&sx->lock_object); 946 x = SX_READ_VALUE(sx); 947 MPASS(x & (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)); 948 949 /* 950 * The wake up algorithm here is quite simple and probably not 951 * ideal. It gives precedence to shared waiters if they are 952 * present. For this condition, we have to preserve the 953 * state of the exclusive waiters flag. 954 * If interruptible sleeps left the shared queue empty avoid a 955 * starvation for the threads sleeping on the exclusive queue by giving 956 * them precedence and cleaning up the shared waiters bit anyway. 957 */ 958 setx = SX_LOCK_UNLOCKED; 959 queue = SQ_SHARED_QUEUE; 960 if ((x & SX_LOCK_EXCLUSIVE_WAITERS) != 0 && 961 sleepq_sleepcnt(&sx->lock_object, SQ_EXCLUSIVE_QUEUE) != 0) { 962 queue = SQ_EXCLUSIVE_QUEUE; 963 setx |= (x & SX_LOCK_SHARED_WAITERS); 964 } 965 atomic_store_rel_ptr(&sx->sx_lock, setx); 966 967 /* Wake up all the waiters for the specific queue. */ 968 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 969 CTR3(KTR_LOCK, "%s: %p waking up all threads on %s queue", 970 __func__, sx, queue == SQ_SHARED_QUEUE ? "shared" : 971 "exclusive"); 972 973 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 0, 974 queue); 975 sleepq_release(&sx->lock_object); 976 if (wakeup_swapper) 977 kick_proc0(); 978 } 979 980 static bool __always_inline 981 __sx_can_read(struct thread *td, uintptr_t x, bool fp) 982 { 983 984 if ((x & (SX_LOCK_SHARED | SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_WRITE_SPINNER)) 985 == SX_LOCK_SHARED) 986 return (true); 987 if (!fp && td->td_sx_slocks && (x & SX_LOCK_SHARED)) 988 return (true); 989 return (false); 990 } 991 992 static bool __always_inline 993 __sx_slock_try(struct sx *sx, struct thread *td, uintptr_t *xp, bool fp 994 LOCK_FILE_LINE_ARG_DEF) 995 { 996 997 /* 998 * If no other thread has an exclusive lock then try to bump up 999 * the count of sharers. Since we have to preserve the state 1000 * of SX_LOCK_EXCLUSIVE_WAITERS, if we fail to acquire the 1001 * shared lock loop back and retry. 1002 */ 1003 while (__sx_can_read(td, *xp, fp)) { 1004 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, xp, 1005 *xp + SX_ONE_SHARER)) { 1006 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1007 CTR4(KTR_LOCK, "%s: %p succeed %p -> %p", 1008 __func__, sx, (void *)*xp, 1009 (void *)(*xp + SX_ONE_SHARER)); 1010 td->td_sx_slocks++; 1011 return (true); 1012 } 1013 } 1014 return (false); 1015 } 1016 1017 static int __noinline 1018 _sx_slock_hard(struct sx *sx, int opts, uintptr_t x LOCK_FILE_LINE_ARG_DEF) 1019 { 1020 GIANT_DECLARE; 1021 struct thread *td; 1022 #ifdef ADAPTIVE_SX 1023 struct thread *owner; 1024 u_int i, n, spintries = 0; 1025 #endif 1026 #ifdef LOCK_PROFILING 1027 uint64_t waittime = 0; 1028 int contested = 0; 1029 #endif 1030 int error = 0; 1031 #if defined(ADAPTIVE_SX) || defined(KDTRACE_HOOKS) 1032 struct lock_delay_arg lda; 1033 #endif 1034 #ifdef KDTRACE_HOOKS 1035 u_int sleep_cnt = 0; 1036 int64_t sleep_time = 0; 1037 int64_t all_time = 0; 1038 #endif 1039 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 1040 uintptr_t state = 0; 1041 #endif 1042 int extra_work = 0; 1043 1044 td = curthread; 1045 1046 #ifdef KDTRACE_HOOKS 1047 if (LOCKSTAT_PROFILE_ENABLED(sx__acquire)) { 1048 if (__sx_slock_try(sx, td, &x, false LOCK_FILE_LINE_ARG)) 1049 goto out_lockstat; 1050 extra_work = 1; 1051 all_time -= lockstat_nsecs(&sx->lock_object); 1052 state = x; 1053 } 1054 #endif 1055 #ifdef LOCK_PROFILING 1056 extra_work = 1; 1057 state = x; 1058 #endif 1059 1060 if (SCHEDULER_STOPPED()) 1061 return (0); 1062 1063 #if defined(ADAPTIVE_SX) 1064 lock_delay_arg_init(&lda, &sx_delay); 1065 #elif defined(KDTRACE_HOOKS) 1066 lock_delay_arg_init_noadapt(&lda); 1067 #endif 1068 1069 #ifdef HWPMC_HOOKS 1070 PMC_SOFT_CALL( , , lock, failed); 1071 #endif 1072 lock_profile_obtain_lock_failed(&sx->lock_object, false, &contested, 1073 &waittime); 1074 1075 #ifndef INVARIANTS 1076 GIANT_SAVE(extra_work); 1077 #endif 1078 1079 /* 1080 * As with rwlocks, we don't make any attempt to try to block 1081 * shared locks once there is an exclusive waiter. 1082 */ 1083 for (;;) { 1084 if (__sx_slock_try(sx, td, &x, false LOCK_FILE_LINE_ARG)) 1085 break; 1086 #ifdef INVARIANTS 1087 GIANT_SAVE(extra_work); 1088 #endif 1089 #ifdef KDTRACE_HOOKS 1090 lda.spin_cnt++; 1091 #endif 1092 1093 #ifdef ADAPTIVE_SX 1094 /* 1095 * If the owner is running on another CPU, spin until 1096 * the owner stops running or the state of the lock 1097 * changes. 1098 */ 1099 if ((x & SX_LOCK_SHARED) == 0) { 1100 owner = lv_sx_owner(x); 1101 if (TD_IS_RUNNING(owner)) { 1102 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1103 CTR3(KTR_LOCK, 1104 "%s: spinning on %p held by %p", 1105 __func__, sx, owner); 1106 KTR_STATE1(KTR_SCHED, "thread", 1107 sched_tdname(curthread), "spinning", 1108 "lockname:\"%s\"", sx->lock_object.lo_name); 1109 do { 1110 lock_delay(&lda); 1111 x = SX_READ_VALUE(sx); 1112 owner = lv_sx_owner(x); 1113 } while (owner != NULL && TD_IS_RUNNING(owner)); 1114 KTR_STATE0(KTR_SCHED, "thread", 1115 sched_tdname(curthread), "running"); 1116 continue; 1117 } 1118 } else { 1119 if ((x & SX_LOCK_WRITE_SPINNER) && SX_SHARERS(x) == 0) { 1120 MPASS(!__sx_can_read(td, x, false)); 1121 lock_delay_spin(2); 1122 x = SX_READ_VALUE(sx); 1123 continue; 1124 } 1125 if (spintries < asx_retries) { 1126 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread), 1127 "spinning", "lockname:\"%s\"", 1128 sx->lock_object.lo_name); 1129 n = SX_SHARERS(x); 1130 for (i = 0; i < asx_loops; i += n) { 1131 lock_delay_spin(n); 1132 x = SX_READ_VALUE(sx); 1133 if (!(x & SX_LOCK_SHARED)) 1134 break; 1135 n = SX_SHARERS(x); 1136 if (n == 0) 1137 break; 1138 if (__sx_can_read(td, x, false)) 1139 break; 1140 } 1141 #ifdef KDTRACE_HOOKS 1142 lda.spin_cnt += i; 1143 #endif 1144 KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread), 1145 "running"); 1146 if (i < asx_loops) 1147 continue; 1148 } 1149 } 1150 #endif 1151 1152 /* 1153 * Some other thread already has an exclusive lock, so 1154 * start the process of blocking. 1155 */ 1156 sleepq_lock(&sx->lock_object); 1157 x = SX_READ_VALUE(sx); 1158 retry_sleepq: 1159 if (((x & SX_LOCK_WRITE_SPINNER) && SX_SHARERS(x) == 0) || 1160 __sx_can_read(td, x, false)) { 1161 sleepq_release(&sx->lock_object); 1162 continue; 1163 } 1164 1165 #ifdef ADAPTIVE_SX 1166 /* 1167 * If the owner is running on another CPU, spin until 1168 * the owner stops running or the state of the lock 1169 * changes. 1170 */ 1171 if (!(x & SX_LOCK_SHARED)) { 1172 owner = (struct thread *)SX_OWNER(x); 1173 if (TD_IS_RUNNING(owner)) { 1174 sleepq_release(&sx->lock_object); 1175 x = SX_READ_VALUE(sx); 1176 continue; 1177 } 1178 } 1179 #endif 1180 1181 /* 1182 * Try to set the SX_LOCK_SHARED_WAITERS flag. If we 1183 * fail to set it drop the sleep queue lock and loop 1184 * back. 1185 */ 1186 if (!(x & SX_LOCK_SHARED_WAITERS)) { 1187 if (!atomic_fcmpset_ptr(&sx->sx_lock, &x, 1188 x | SX_LOCK_SHARED_WAITERS)) 1189 goto retry_sleepq; 1190 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1191 CTR2(KTR_LOCK, "%s: %p set shared waiters flag", 1192 __func__, sx); 1193 } 1194 1195 /* 1196 * Since we have been unable to acquire the shared lock, 1197 * we have to sleep. 1198 */ 1199 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1200 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 1201 __func__, sx); 1202 1203 #ifdef KDTRACE_HOOKS 1204 sleep_time -= lockstat_nsecs(&sx->lock_object); 1205 #endif 1206 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 1207 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 1208 SLEEPQ_INTERRUPTIBLE : 0), SQ_SHARED_QUEUE); 1209 if (!(opts & SX_INTERRUPTIBLE)) 1210 sleepq_wait(&sx->lock_object, 0); 1211 else 1212 error = sleepq_wait_sig(&sx->lock_object, 0); 1213 #ifdef KDTRACE_HOOKS 1214 sleep_time += lockstat_nsecs(&sx->lock_object); 1215 sleep_cnt++; 1216 #endif 1217 if (error) { 1218 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1219 CTR2(KTR_LOCK, 1220 "%s: interruptible sleep by %p suspended by signal", 1221 __func__, sx); 1222 break; 1223 } 1224 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1225 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 1226 __func__, sx); 1227 x = SX_READ_VALUE(sx); 1228 } 1229 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 1230 if (__predict_true(!extra_work)) 1231 return (error); 1232 #endif 1233 #ifdef KDTRACE_HOOKS 1234 all_time += lockstat_nsecs(&sx->lock_object); 1235 if (sleep_time) 1236 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 1237 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1238 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1239 if (lda.spin_cnt > sleep_cnt) 1240 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 1241 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1242 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1243 out_lockstat: 1244 #endif 1245 if (error == 0) { 1246 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 1247 contested, waittime, file, line, LOCKSTAT_READER); 1248 } 1249 GIANT_RESTORE(); 1250 return (error); 1251 } 1252 1253 int 1254 _sx_slock_int(struct sx *sx, int opts LOCK_FILE_LINE_ARG_DEF) 1255 { 1256 struct thread *td; 1257 uintptr_t x; 1258 int error; 1259 1260 KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() || 1261 !TD_IS_IDLETHREAD(curthread), 1262 ("sx_slock() by idle thread %p on sx %s @ %s:%d", 1263 curthread, sx->lock_object.lo_name, file, line)); 1264 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 1265 ("sx_slock() of destroyed sx @ %s:%d", file, line)); 1266 WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER, file, line, NULL); 1267 1268 error = 0; 1269 td = curthread; 1270 x = SX_READ_VALUE(sx); 1271 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__acquire) || 1272 !__sx_slock_try(sx, td, &x, true LOCK_FILE_LINE_ARG))) 1273 error = _sx_slock_hard(sx, opts, x LOCK_FILE_LINE_ARG); 1274 else 1275 lock_profile_obtain_lock_success(&sx->lock_object, false, 0, 0, 1276 file, line); 1277 if (error == 0) { 1278 LOCK_LOG_LOCK("SLOCK", &sx->lock_object, 0, 0, file, line); 1279 WITNESS_LOCK(&sx->lock_object, 0, file, line); 1280 TD_LOCKS_INC(curthread); 1281 } 1282 return (error); 1283 } 1284 1285 int 1286 _sx_slock(struct sx *sx, int opts, const char *file, int line) 1287 { 1288 1289 return (_sx_slock_int(sx, opts LOCK_FILE_LINE_ARG)); 1290 } 1291 1292 static bool __always_inline 1293 _sx_sunlock_try(struct sx *sx, struct thread *td, uintptr_t *xp) 1294 { 1295 1296 for (;;) { 1297 if (SX_SHARERS(*xp) > 1 || !(*xp & SX_LOCK_WAITERS)) { 1298 if (atomic_fcmpset_rel_ptr(&sx->sx_lock, xp, 1299 *xp - SX_ONE_SHARER)) { 1300 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1301 CTR4(KTR_LOCK, 1302 "%s: %p succeeded %p -> %p", 1303 __func__, sx, (void *)*xp, 1304 (void *)(*xp - SX_ONE_SHARER)); 1305 td->td_sx_slocks--; 1306 return (true); 1307 } 1308 continue; 1309 } 1310 break; 1311 } 1312 return (false); 1313 } 1314 1315 static void __noinline 1316 _sx_sunlock_hard(struct sx *sx, struct thread *td, uintptr_t x 1317 LOCK_FILE_LINE_ARG_DEF) 1318 { 1319 int wakeup_swapper = 0; 1320 uintptr_t setx, queue; 1321 1322 if (SCHEDULER_STOPPED()) 1323 return; 1324 1325 if (_sx_sunlock_try(sx, td, &x)) 1326 goto out_lockstat; 1327 1328 sleepq_lock(&sx->lock_object); 1329 x = SX_READ_VALUE(sx); 1330 for (;;) { 1331 if (_sx_sunlock_try(sx, td, &x)) 1332 break; 1333 1334 /* 1335 * Wake up semantic here is quite simple: 1336 * Just wake up all the exclusive waiters. 1337 * Note that the state of the lock could have changed, 1338 * so if it fails loop back and retry. 1339 */ 1340 setx = SX_LOCK_UNLOCKED; 1341 queue = SQ_SHARED_QUEUE; 1342 if (x & SX_LOCK_EXCLUSIVE_WAITERS) { 1343 setx |= (x & SX_LOCK_SHARED_WAITERS); 1344 queue = SQ_EXCLUSIVE_QUEUE; 1345 } 1346 setx |= (x & SX_LOCK_WRITE_SPINNER); 1347 if (!atomic_fcmpset_rel_ptr(&sx->sx_lock, &x, setx)) 1348 continue; 1349 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1350 CTR2(KTR_LOCK, "%s: %p waking up all thread on" 1351 "exclusive queue", __func__, sx); 1352 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 1353 0, queue); 1354 td->td_sx_slocks--; 1355 break; 1356 } 1357 sleepq_release(&sx->lock_object); 1358 if (wakeup_swapper) 1359 kick_proc0(); 1360 out_lockstat: 1361 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_READER); 1362 } 1363 1364 void 1365 _sx_sunlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 1366 { 1367 struct thread *td; 1368 uintptr_t x; 1369 1370 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 1371 ("sx_sunlock() of destroyed sx @ %s:%d", file, line)); 1372 _sx_assert(sx, SA_SLOCKED, file, line); 1373 WITNESS_UNLOCK(&sx->lock_object, 0, file, line); 1374 LOCK_LOG_LOCK("SUNLOCK", &sx->lock_object, 0, 0, file, line); 1375 1376 td = curthread; 1377 x = SX_READ_VALUE(sx); 1378 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__release) || 1379 !_sx_sunlock_try(sx, td, &x))) 1380 _sx_sunlock_hard(sx, td, x LOCK_FILE_LINE_ARG); 1381 else 1382 lock_profile_release_lock(&sx->lock_object, false); 1383 1384 TD_LOCKS_DEC(curthread); 1385 } 1386 1387 void 1388 _sx_sunlock(struct sx *sx, const char *file, int line) 1389 { 1390 1391 _sx_sunlock_int(sx LOCK_FILE_LINE_ARG); 1392 } 1393 1394 #ifdef INVARIANT_SUPPORT 1395 #ifndef INVARIANTS 1396 #undef _sx_assert 1397 #endif 1398 1399 /* 1400 * In the non-WITNESS case, sx_assert() can only detect that at least 1401 * *some* thread owns an slock, but it cannot guarantee that *this* 1402 * thread owns an slock. 1403 */ 1404 void 1405 _sx_assert(const struct sx *sx, int what, const char *file, int line) 1406 { 1407 #ifndef WITNESS 1408 int slocked = 0; 1409 #endif 1410 1411 if (SCHEDULER_STOPPED()) 1412 return; 1413 switch (what) { 1414 case SA_SLOCKED: 1415 case SA_SLOCKED | SA_NOTRECURSED: 1416 case SA_SLOCKED | SA_RECURSED: 1417 #ifndef WITNESS 1418 slocked = 1; 1419 /* FALLTHROUGH */ 1420 #endif 1421 case SA_LOCKED: 1422 case SA_LOCKED | SA_NOTRECURSED: 1423 case SA_LOCKED | SA_RECURSED: 1424 #ifdef WITNESS 1425 witness_assert(&sx->lock_object, what, file, line); 1426 #else 1427 /* 1428 * If some other thread has an exclusive lock or we 1429 * have one and are asserting a shared lock, fail. 1430 * Also, if no one has a lock at all, fail. 1431 */ 1432 if (sx->sx_lock == SX_LOCK_UNLOCKED || 1433 (!(sx->sx_lock & SX_LOCK_SHARED) && (slocked || 1434 sx_xholder(sx) != curthread))) 1435 panic("Lock %s not %slocked @ %s:%d\n", 1436 sx->lock_object.lo_name, slocked ? "share " : "", 1437 file, line); 1438 1439 if (!(sx->sx_lock & SX_LOCK_SHARED)) { 1440 if (sx_recursed(sx)) { 1441 if (what & SA_NOTRECURSED) 1442 panic("Lock %s recursed @ %s:%d\n", 1443 sx->lock_object.lo_name, file, 1444 line); 1445 } else if (what & SA_RECURSED) 1446 panic("Lock %s not recursed @ %s:%d\n", 1447 sx->lock_object.lo_name, file, line); 1448 } 1449 #endif 1450 break; 1451 case SA_XLOCKED: 1452 case SA_XLOCKED | SA_NOTRECURSED: 1453 case SA_XLOCKED | SA_RECURSED: 1454 if (sx_xholder(sx) != curthread) 1455 panic("Lock %s not exclusively locked @ %s:%d\n", 1456 sx->lock_object.lo_name, file, line); 1457 if (sx_recursed(sx)) { 1458 if (what & SA_NOTRECURSED) 1459 panic("Lock %s recursed @ %s:%d\n", 1460 sx->lock_object.lo_name, file, line); 1461 } else if (what & SA_RECURSED) 1462 panic("Lock %s not recursed @ %s:%d\n", 1463 sx->lock_object.lo_name, file, line); 1464 break; 1465 case SA_UNLOCKED: 1466 #ifdef WITNESS 1467 witness_assert(&sx->lock_object, what, file, line); 1468 #else 1469 /* 1470 * If we hold an exclusve lock fail. We can't 1471 * reliably check to see if we hold a shared lock or 1472 * not. 1473 */ 1474 if (sx_xholder(sx) == curthread) 1475 panic("Lock %s exclusively locked @ %s:%d\n", 1476 sx->lock_object.lo_name, file, line); 1477 #endif 1478 break; 1479 default: 1480 panic("Unknown sx lock assertion: %d @ %s:%d", what, file, 1481 line); 1482 } 1483 } 1484 #endif /* INVARIANT_SUPPORT */ 1485 1486 #ifdef DDB 1487 static void 1488 db_show_sx(const struct lock_object *lock) 1489 { 1490 struct thread *td; 1491 const struct sx *sx; 1492 1493 sx = (const struct sx *)lock; 1494 1495 db_printf(" state: "); 1496 if (sx->sx_lock == SX_LOCK_UNLOCKED) 1497 db_printf("UNLOCKED\n"); 1498 else if (sx->sx_lock == SX_LOCK_DESTROYED) { 1499 db_printf("DESTROYED\n"); 1500 return; 1501 } else if (sx->sx_lock & SX_LOCK_SHARED) 1502 db_printf("SLOCK: %ju\n", (uintmax_t)SX_SHARERS(sx->sx_lock)); 1503 else { 1504 td = sx_xholder(sx); 1505 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1506 td->td_tid, td->td_proc->p_pid, td->td_name); 1507 if (sx_recursed(sx)) 1508 db_printf(" recursed: %d\n", sx->sx_recurse); 1509 } 1510 1511 db_printf(" waiters: "); 1512 switch(sx->sx_lock & 1513 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)) { 1514 case SX_LOCK_SHARED_WAITERS: 1515 db_printf("shared\n"); 1516 break; 1517 case SX_LOCK_EXCLUSIVE_WAITERS: 1518 db_printf("exclusive\n"); 1519 break; 1520 case SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS: 1521 db_printf("exclusive and shared\n"); 1522 break; 1523 default: 1524 db_printf("none\n"); 1525 } 1526 } 1527 1528 /* 1529 * Check to see if a thread that is blocked on a sleep queue is actually 1530 * blocked on an sx lock. If so, output some details and return true. 1531 * If the lock has an exclusive owner, return that in *ownerp. 1532 */ 1533 int 1534 sx_chain(struct thread *td, struct thread **ownerp) 1535 { 1536 const struct sx *sx; 1537 1538 /* 1539 * Check to see if this thread is blocked on an sx lock. 1540 * First, we check the lock class. If that is ok, then we 1541 * compare the lock name against the wait message. 1542 */ 1543 sx = td->td_wchan; 1544 if (LOCK_CLASS(&sx->lock_object) != &lock_class_sx || 1545 sx->lock_object.lo_name != td->td_wmesg) 1546 return (0); 1547 1548 /* We think we have an sx lock, so output some details. */ 1549 db_printf("blocked on sx \"%s\" ", td->td_wmesg); 1550 *ownerp = sx_xholder(sx); 1551 if (sx->sx_lock & SX_LOCK_SHARED) 1552 db_printf("SLOCK (count %ju)\n", 1553 (uintmax_t)SX_SHARERS(sx->sx_lock)); 1554 else 1555 db_printf("XLOCK\n"); 1556 return (1); 1557 } 1558 #endif 1559