1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 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 #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 #ifdef HWPMC_HOOKS 73 #include <sys/pmckern.h> 74 PMC_SOFT_DECLARE( , , lock, failed); 75 #endif 76 77 /* Handy macros for sleep queues. */ 78 #define SQ_EXCLUSIVE_QUEUE 0 79 #define SQ_SHARED_QUEUE 1 80 81 /* 82 * Variations on DROP_GIANT()/PICKUP_GIANT() for use in this file. We 83 * drop Giant anytime we have to sleep or if we adaptively spin. 84 */ 85 #define GIANT_DECLARE \ 86 int _giantcnt = 0; \ 87 WITNESS_SAVE_DECL(Giant) \ 88 89 #define GIANT_SAVE(work) do { \ 90 if (__predict_false(mtx_owned(&Giant))) { \ 91 work++; \ 92 WITNESS_SAVE(&Giant.lock_object, Giant); \ 93 while (mtx_owned(&Giant)) { \ 94 _giantcnt++; \ 95 mtx_unlock(&Giant); \ 96 } \ 97 } \ 98 } while (0) 99 100 #define GIANT_RESTORE() do { \ 101 if (_giantcnt > 0) { \ 102 mtx_assert(&Giant, MA_NOTOWNED); \ 103 while (_giantcnt--) \ 104 mtx_lock(&Giant); \ 105 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 106 } \ 107 } while (0) 108 109 /* 110 * Returns true if an exclusive lock is recursed. It assumes 111 * curthread currently has an exclusive lock. 112 */ 113 #define sx_recursed(sx) ((sx)->sx_recurse != 0) 114 115 static void assert_sx(const struct lock_object *lock, int what); 116 #ifdef DDB 117 static void db_show_sx(const struct lock_object *lock); 118 #endif 119 static void lock_sx(struct lock_object *lock, uintptr_t how); 120 #ifdef KDTRACE_HOOKS 121 static int owner_sx(const struct lock_object *lock, struct thread **owner); 122 #endif 123 static uintptr_t unlock_sx(struct lock_object *lock); 124 125 struct lock_class lock_class_sx = { 126 .lc_name = "sx", 127 .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE, 128 .lc_assert = assert_sx, 129 #ifdef DDB 130 .lc_ddb_show = db_show_sx, 131 #endif 132 .lc_lock = lock_sx, 133 .lc_unlock = unlock_sx, 134 #ifdef KDTRACE_HOOKS 135 .lc_owner = owner_sx, 136 #endif 137 }; 138 139 #ifndef INVARIANTS 140 #define _sx_assert(sx, what, file, line) 141 #endif 142 143 #ifdef ADAPTIVE_SX 144 #ifdef SX_CUSTOM_BACKOFF 145 static u_short __read_frequently asx_retries; 146 static u_short __read_frequently asx_loops; 147 static SYSCTL_NODE(_debug, OID_AUTO, sx, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 148 "sxlock debugging"); 149 SYSCTL_U16(_debug_sx, OID_AUTO, retries, CTLFLAG_RW, &asx_retries, 0, ""); 150 SYSCTL_U16(_debug_sx, OID_AUTO, loops, CTLFLAG_RW, &asx_loops, 0, ""); 151 152 static struct lock_delay_config __read_frequently sx_delay; 153 154 SYSCTL_U16(_debug_sx, OID_AUTO, delay_base, CTLFLAG_RW, &sx_delay.base, 155 0, ""); 156 SYSCTL_U16(_debug_sx, OID_AUTO, delay_max, CTLFLAG_RW, &sx_delay.max, 157 0, ""); 158 159 static void 160 sx_lock_delay_init(void *arg __unused) 161 { 162 163 lock_delay_default_init(&sx_delay); 164 asx_retries = 10; 165 asx_loops = max(10000, sx_delay.max); 166 } 167 LOCK_DELAY_SYSINIT(sx_lock_delay_init); 168 #else 169 #define sx_delay locks_delay 170 #define asx_retries locks_delay_retries 171 #define asx_loops locks_delay_loops 172 #endif 173 #endif 174 175 void 176 assert_sx(const struct lock_object *lock, int what) 177 { 178 179 sx_assert((const struct sx *)lock, what); 180 } 181 182 void 183 lock_sx(struct lock_object *lock, uintptr_t how) 184 { 185 struct sx *sx; 186 187 sx = (struct sx *)lock; 188 if (how) 189 sx_slock(sx); 190 else 191 sx_xlock(sx); 192 } 193 194 uintptr_t 195 unlock_sx(struct lock_object *lock) 196 { 197 struct sx *sx; 198 199 sx = (struct sx *)lock; 200 sx_assert(sx, SA_LOCKED | SA_NOTRECURSED); 201 if (sx_xlocked(sx)) { 202 sx_xunlock(sx); 203 return (0); 204 } else { 205 sx_sunlock(sx); 206 return (1); 207 } 208 } 209 210 #ifdef KDTRACE_HOOKS 211 int 212 owner_sx(const struct lock_object *lock, struct thread **owner) 213 { 214 const struct sx *sx; 215 uintptr_t x; 216 217 sx = (const struct sx *)lock; 218 x = sx->sx_lock; 219 *owner = NULL; 220 return ((x & SX_LOCK_SHARED) != 0 ? (SX_SHARERS(x) != 0) : 221 ((*owner = (struct thread *)SX_OWNER(x)) != NULL)); 222 } 223 #endif 224 225 void 226 sx_sysinit(void *arg) 227 { 228 struct sx_args *sargs = arg; 229 230 sx_init_flags(sargs->sa_sx, sargs->sa_desc, sargs->sa_flags); 231 } 232 233 void 234 sx_init_flags(struct sx *sx, const char *description, int opts) 235 { 236 int flags; 237 238 MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK | 239 SX_NOPROFILE | SX_NEW)) == 0); 240 ASSERT_ATOMIC_LOAD_PTR(sx->sx_lock, 241 ("%s: sx_lock not aligned for %s: %p", __func__, description, 242 &sx->sx_lock)); 243 244 flags = LO_SLEEPABLE | LO_UPGRADABLE; 245 if (opts & SX_DUPOK) 246 flags |= LO_DUPOK; 247 if (opts & SX_NOPROFILE) 248 flags |= LO_NOPROFILE; 249 if (!(opts & SX_NOWITNESS)) 250 flags |= LO_WITNESS; 251 if (opts & SX_RECURSE) 252 flags |= LO_RECURSABLE; 253 if (opts & SX_QUIET) 254 flags |= LO_QUIET; 255 if (opts & SX_NEW) 256 flags |= LO_NEW; 257 258 lock_init(&sx->lock_object, &lock_class_sx, description, NULL, flags); 259 sx->sx_lock = SX_LOCK_UNLOCKED; 260 sx->sx_recurse = 0; 261 } 262 263 void 264 sx_destroy(struct sx *sx) 265 { 266 267 KASSERT(sx->sx_lock == SX_LOCK_UNLOCKED, ("sx lock still held")); 268 KASSERT(sx->sx_recurse == 0, ("sx lock still recursed")); 269 sx->sx_lock = SX_LOCK_DESTROYED; 270 lock_destroy(&sx->lock_object); 271 } 272 273 int 274 sx_try_slock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 275 { 276 uintptr_t x; 277 278 if (SCHEDULER_STOPPED()) 279 return (1); 280 281 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 282 ("sx_try_slock() by idle thread %p on sx %s @ %s:%d", 283 curthread, sx->lock_object.lo_name, file, line)); 284 285 x = sx->sx_lock; 286 for (;;) { 287 KASSERT(x != SX_LOCK_DESTROYED, 288 ("sx_try_slock() of destroyed sx @ %s:%d", file, line)); 289 if (!(x & SX_LOCK_SHARED)) 290 break; 291 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, x + SX_ONE_SHARER)) { 292 LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 1, file, line); 293 WITNESS_LOCK(&sx->lock_object, LOP_TRYLOCK, file, line); 294 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, 295 sx, 0, 0, file, line, LOCKSTAT_READER); 296 TD_LOCKS_INC(curthread); 297 curthread->td_sx_slocks++; 298 return (1); 299 } 300 } 301 302 LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 0, file, line); 303 return (0); 304 } 305 306 int 307 sx_try_slock_(struct sx *sx, const char *file, int line) 308 { 309 310 return (sx_try_slock_int(sx LOCK_FILE_LINE_ARG)); 311 } 312 313 int 314 _sx_xlock(struct sx *sx, int opts, const char *file, int line) 315 { 316 uintptr_t tid, x; 317 int error = 0; 318 319 KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() || 320 !TD_IS_IDLETHREAD(curthread), 321 ("sx_xlock() by idle thread %p on sx %s @ %s:%d", 322 curthread, sx->lock_object.lo_name, file, line)); 323 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 324 ("sx_xlock() of destroyed sx @ %s:%d", file, line)); 325 WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, 326 line, NULL); 327 tid = (uintptr_t)curthread; 328 x = SX_LOCK_UNLOCKED; 329 if (!atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 330 error = _sx_xlock_hard(sx, x, opts LOCK_FILE_LINE_ARG); 331 else 332 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 333 0, 0, file, line, LOCKSTAT_WRITER); 334 if (!error) { 335 LOCK_LOG_LOCK("XLOCK", &sx->lock_object, 0, sx->sx_recurse, 336 file, line); 337 WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); 338 TD_LOCKS_INC(curthread); 339 } 340 341 return (error); 342 } 343 344 int 345 sx_try_xlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 346 { 347 struct thread *td; 348 uintptr_t tid, x; 349 int rval; 350 bool recursed; 351 352 td = curthread; 353 tid = (uintptr_t)td; 354 if (SCHEDULER_STOPPED_TD(td)) 355 return (1); 356 357 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(td), 358 ("sx_try_xlock() by idle thread %p on sx %s @ %s:%d", 359 curthread, sx->lock_object.lo_name, file, line)); 360 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 361 ("sx_try_xlock() of destroyed sx @ %s:%d", file, line)); 362 363 rval = 1; 364 recursed = false; 365 x = SX_LOCK_UNLOCKED; 366 for (;;) { 367 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 368 break; 369 if (x == SX_LOCK_UNLOCKED) 370 continue; 371 if (x == tid && (sx->lock_object.lo_flags & LO_RECURSABLE)) { 372 sx->sx_recurse++; 373 atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 374 break; 375 } 376 rval = 0; 377 break; 378 } 379 380 LOCK_LOG_TRY("XLOCK", &sx->lock_object, 0, rval, file, line); 381 if (rval) { 382 WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 383 file, line); 384 if (!recursed) 385 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, 386 sx, 0, 0, file, line, LOCKSTAT_WRITER); 387 TD_LOCKS_INC(curthread); 388 } 389 390 return (rval); 391 } 392 393 int 394 sx_try_xlock_(struct sx *sx, const char *file, int line) 395 { 396 397 return (sx_try_xlock_int(sx LOCK_FILE_LINE_ARG)); 398 } 399 400 void 401 _sx_xunlock(struct sx *sx, const char *file, int line) 402 { 403 404 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 405 ("sx_xunlock() of destroyed sx @ %s:%d", file, line)); 406 _sx_assert(sx, SA_XLOCKED, file, line); 407 WITNESS_UNLOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); 408 LOCK_LOG_LOCK("XUNLOCK", &sx->lock_object, 0, sx->sx_recurse, file, 409 line); 410 #if LOCK_DEBUG > 0 411 _sx_xunlock_hard(sx, (uintptr_t)curthread, file, line); 412 #else 413 __sx_xunlock(sx, curthread, file, line); 414 #endif 415 TD_LOCKS_DEC(curthread); 416 } 417 418 /* 419 * Try to do a non-blocking upgrade from a shared lock to an exclusive lock. 420 * This will only succeed if this thread holds a single shared lock. 421 * Return 1 if if the upgrade succeed, 0 otherwise. 422 */ 423 int 424 sx_try_upgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 425 { 426 uintptr_t x; 427 uintptr_t waiters; 428 int success; 429 430 if (SCHEDULER_STOPPED()) 431 return (1); 432 433 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 434 ("sx_try_upgrade() of destroyed sx @ %s:%d", file, line)); 435 _sx_assert(sx, SA_SLOCKED, file, line); 436 437 /* 438 * Try to switch from one shared lock to an exclusive lock. We need 439 * to maintain the SX_LOCK_EXCLUSIVE_WAITERS flag if set so that 440 * we will wake up the exclusive waiters when we drop the lock. 441 */ 442 success = 0; 443 x = SX_READ_VALUE(sx); 444 for (;;) { 445 if (SX_SHARERS(x) > 1) 446 break; 447 waiters = (x & SX_LOCK_WAITERS); 448 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, 449 (uintptr_t)curthread | waiters)) { 450 success = 1; 451 break; 452 } 453 } 454 LOCK_LOG_TRY("XUPGRADE", &sx->lock_object, 0, success, file, line); 455 if (success) { 456 curthread->td_sx_slocks--; 457 WITNESS_UPGRADE(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 458 file, line); 459 LOCKSTAT_RECORD0(sx__upgrade, sx); 460 } 461 return (success); 462 } 463 464 int 465 sx_try_upgrade_(struct sx *sx, const char *file, int line) 466 { 467 468 return (sx_try_upgrade_int(sx LOCK_FILE_LINE_ARG)); 469 } 470 471 /* 472 * Downgrade an unrecursed exclusive lock into a single shared lock. 473 */ 474 void 475 sx_downgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 476 { 477 uintptr_t x; 478 int wakeup_swapper; 479 480 if (SCHEDULER_STOPPED()) 481 return; 482 483 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 484 ("sx_downgrade() of destroyed sx @ %s:%d", file, line)); 485 _sx_assert(sx, SA_XLOCKED | SA_NOTRECURSED, file, line); 486 #ifndef INVARIANTS 487 if (sx_recursed(sx)) 488 panic("downgrade of a recursed lock"); 489 #endif 490 491 WITNESS_DOWNGRADE(&sx->lock_object, 0, file, line); 492 493 /* 494 * Try to switch from an exclusive lock with no shared waiters 495 * to one sharer with no shared waiters. If there are 496 * exclusive waiters, we don't need to lock the sleep queue so 497 * long as we preserve the flag. We do one quick try and if 498 * that fails we grab the sleepq lock to keep the flags from 499 * changing and do it the slow way. 500 * 501 * We have to lock the sleep queue if there are shared waiters 502 * so we can wake them up. 503 */ 504 x = sx->sx_lock; 505 if (!(x & SX_LOCK_SHARED_WAITERS) && 506 atomic_cmpset_rel_ptr(&sx->sx_lock, x, SX_SHARERS_LOCK(1) | 507 (x & SX_LOCK_EXCLUSIVE_WAITERS))) 508 goto out; 509 510 /* 511 * Lock the sleep queue so we can read the waiters bits 512 * without any races and wakeup any shared waiters. 513 */ 514 sleepq_lock(&sx->lock_object); 515 516 /* 517 * Preserve SX_LOCK_EXCLUSIVE_WAITERS while downgraded to a single 518 * shared lock. If there are any shared waiters, wake them up. 519 */ 520 wakeup_swapper = 0; 521 x = sx->sx_lock; 522 atomic_store_rel_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | 523 (x & SX_LOCK_EXCLUSIVE_WAITERS)); 524 if (x & SX_LOCK_SHARED_WAITERS) 525 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 526 0, SQ_SHARED_QUEUE); 527 sleepq_release(&sx->lock_object); 528 529 if (wakeup_swapper) 530 kick_proc0(); 531 532 out: 533 curthread->td_sx_slocks++; 534 LOCK_LOG_LOCK("XDOWNGRADE", &sx->lock_object, 0, 0, file, line); 535 LOCKSTAT_RECORD0(sx__downgrade, sx); 536 } 537 538 void 539 sx_downgrade_(struct sx *sx, const char *file, int line) 540 { 541 542 sx_downgrade_int(sx LOCK_FILE_LINE_ARG); 543 } 544 545 #ifdef ADAPTIVE_SX 546 static inline void 547 sx_drop_critical(uintptr_t x, bool *in_critical, int *extra_work) 548 { 549 550 if (x & SX_LOCK_WRITE_SPINNER) 551 return; 552 if (*in_critical) { 553 critical_exit(); 554 *in_critical = false; 555 (*extra_work)--; 556 } 557 } 558 #else 559 #define sx_drop_critical(x, in_critical, extra_work) do { } while (0) 560 #endif 561 562 /* 563 * This function represents the so-called 'hard case' for sx_xlock 564 * operation. All 'easy case' failures are redirected to this. Note 565 * that ideally this would be a static function, but it needs to be 566 * accessible from at least sx.h. 567 */ 568 int 569 _sx_xlock_hard(struct sx *sx, uintptr_t x, int opts LOCK_FILE_LINE_ARG_DEF) 570 { 571 GIANT_DECLARE; 572 uintptr_t tid, setx; 573 #ifdef ADAPTIVE_SX 574 struct thread *owner; 575 u_int i, n, spintries = 0; 576 enum { READERS, WRITER } sleep_reason = READERS; 577 bool in_critical = false; 578 #endif 579 #ifdef LOCK_PROFILING 580 uint64_t waittime = 0; 581 int contested = 0; 582 #endif 583 int error = 0; 584 #if defined(ADAPTIVE_SX) || defined(KDTRACE_HOOKS) 585 struct lock_delay_arg lda; 586 #endif 587 #ifdef KDTRACE_HOOKS 588 u_int sleep_cnt = 0; 589 int64_t sleep_time = 0; 590 int64_t all_time = 0; 591 #endif 592 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 593 uintptr_t state = 0; 594 int doing_lockprof = 0; 595 #endif 596 int extra_work = 0; 597 598 tid = (uintptr_t)curthread; 599 600 #ifdef KDTRACE_HOOKS 601 if (LOCKSTAT_PROFILE_ENABLED(sx__acquire)) { 602 while (x == SX_LOCK_UNLOCKED) { 603 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 604 goto out_lockstat; 605 } 606 extra_work = 1; 607 doing_lockprof = 1; 608 all_time -= lockstat_nsecs(&sx->lock_object); 609 state = x; 610 } 611 #endif 612 #ifdef LOCK_PROFILING 613 extra_work = 1; 614 doing_lockprof = 1; 615 state = x; 616 #endif 617 618 if (SCHEDULER_STOPPED()) 619 return (0); 620 621 if (__predict_false(x == SX_LOCK_UNLOCKED)) 622 x = SX_READ_VALUE(sx); 623 624 /* If we already hold an exclusive lock, then recurse. */ 625 if (__predict_false(lv_sx_owner(x) == (struct thread *)tid)) { 626 KASSERT((sx->lock_object.lo_flags & LO_RECURSABLE) != 0, 627 ("_sx_xlock_hard: recursed on non-recursive sx %s @ %s:%d\n", 628 sx->lock_object.lo_name, file, line)); 629 sx->sx_recurse++; 630 atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 631 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 632 CTR2(KTR_LOCK, "%s: %p recursing", __func__, sx); 633 return (0); 634 } 635 636 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 637 CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, 638 sx->lock_object.lo_name, (void *)sx->sx_lock, file, line); 639 640 #if defined(ADAPTIVE_SX) 641 lock_delay_arg_init(&lda, &sx_delay); 642 #elif defined(KDTRACE_HOOKS) 643 lock_delay_arg_init_noadapt(&lda); 644 #endif 645 646 #ifdef HWPMC_HOOKS 647 PMC_SOFT_CALL( , , lock, failed); 648 #endif 649 lock_profile_obtain_lock_failed(&sx->lock_object, false, &contested, 650 &waittime); 651 652 #ifndef INVARIANTS 653 GIANT_SAVE(extra_work); 654 #endif 655 656 for (;;) { 657 if (x == SX_LOCK_UNLOCKED) { 658 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 659 break; 660 continue; 661 } 662 #ifdef INVARIANTS 663 GIANT_SAVE(extra_work); 664 #endif 665 #ifdef KDTRACE_HOOKS 666 lda.spin_cnt++; 667 #endif 668 #ifdef ADAPTIVE_SX 669 if (x == (SX_LOCK_SHARED | SX_LOCK_WRITE_SPINNER)) { 670 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 671 break; 672 continue; 673 } 674 675 /* 676 * If the lock is write locked and the owner is 677 * running on another CPU, spin until the owner stops 678 * running or the state of the lock changes. 679 */ 680 if ((x & SX_LOCK_SHARED) == 0) { 681 sx_drop_critical(x, &in_critical, &extra_work); 682 sleep_reason = WRITER; 683 owner = lv_sx_owner(x); 684 if (!TD_IS_RUNNING(owner)) 685 goto sleepq; 686 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 687 CTR3(KTR_LOCK, "%s: spinning on %p held by %p", 688 __func__, sx, owner); 689 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread), 690 "spinning", "lockname:\"%s\"", 691 sx->lock_object.lo_name); 692 do { 693 lock_delay(&lda); 694 x = SX_READ_VALUE(sx); 695 owner = lv_sx_owner(x); 696 } while (owner != NULL && TD_IS_RUNNING(owner)); 697 KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread), 698 "running"); 699 continue; 700 } else if (SX_SHARERS(x) > 0) { 701 sleep_reason = READERS; 702 if (spintries == asx_retries) 703 goto sleepq; 704 if (!(x & SX_LOCK_WRITE_SPINNER)) { 705 if (!in_critical) { 706 critical_enter(); 707 in_critical = true; 708 extra_work++; 709 } 710 if (!atomic_fcmpset_ptr(&sx->sx_lock, &x, 711 x | SX_LOCK_WRITE_SPINNER)) { 712 critical_exit(); 713 in_critical = false; 714 extra_work--; 715 continue; 716 } 717 } 718 spintries++; 719 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread), 720 "spinning", "lockname:\"%s\"", 721 sx->lock_object.lo_name); 722 n = SX_SHARERS(x); 723 for (i = 0; i < asx_loops; i += n) { 724 lock_delay_spin(n); 725 x = SX_READ_VALUE(sx); 726 if (!(x & SX_LOCK_WRITE_SPINNER)) 727 break; 728 if (!(x & SX_LOCK_SHARED)) 729 break; 730 n = SX_SHARERS(x); 731 if (n == 0) 732 break; 733 } 734 #ifdef KDTRACE_HOOKS 735 lda.spin_cnt += i; 736 #endif 737 KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread), 738 "running"); 739 if (i < asx_loops) 740 continue; 741 } 742 sleepq: 743 #endif 744 sleepq_lock(&sx->lock_object); 745 x = SX_READ_VALUE(sx); 746 retry_sleepq: 747 748 /* 749 * If the lock was released while spinning on the 750 * sleep queue chain lock, try again. 751 */ 752 if (x == SX_LOCK_UNLOCKED) { 753 sleepq_release(&sx->lock_object); 754 sx_drop_critical(x, &in_critical, &extra_work); 755 continue; 756 } 757 758 #ifdef ADAPTIVE_SX 759 /* 760 * The current lock owner might have started executing 761 * on another CPU (or the lock could have changed 762 * owners) while we were waiting on the sleep queue 763 * chain lock. If so, drop the sleep queue lock and try 764 * again. 765 */ 766 if (!(x & SX_LOCK_SHARED)) { 767 owner = (struct thread *)SX_OWNER(x); 768 if (TD_IS_RUNNING(owner)) { 769 sleepq_release(&sx->lock_object); 770 sx_drop_critical(x, &in_critical, 771 &extra_work); 772 continue; 773 } 774 } else if (SX_SHARERS(x) > 0 && sleep_reason == WRITER) { 775 sleepq_release(&sx->lock_object); 776 sx_drop_critical(x, &in_critical, &extra_work); 777 continue; 778 } 779 #endif 780 781 /* 782 * If an exclusive lock was released with both shared 783 * and exclusive waiters and a shared waiter hasn't 784 * woken up and acquired the lock yet, sx_lock will be 785 * set to SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS. 786 * If we see that value, try to acquire it once. Note 787 * that we have to preserve SX_LOCK_EXCLUSIVE_WAITERS 788 * as there are other exclusive waiters still. If we 789 * fail, restart the loop. 790 */ 791 setx = x & (SX_LOCK_WAITERS | SX_LOCK_WRITE_SPINNER); 792 if ((x & ~setx) == SX_LOCK_SHARED) { 793 setx &= ~SX_LOCK_WRITE_SPINNER; 794 if (!atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid | setx)) 795 goto retry_sleepq; 796 sleepq_release(&sx->lock_object); 797 CTR2(KTR_LOCK, "%s: %p claimed by new writer", 798 __func__, sx); 799 break; 800 } 801 802 #ifdef ADAPTIVE_SX 803 /* 804 * It is possible we set the SX_LOCK_WRITE_SPINNER bit. 805 * It is an invariant that when the bit is set, there is 806 * a writer ready to grab the lock. Thus clear the bit since 807 * we are going to sleep. 808 */ 809 if (in_critical) { 810 if ((x & SX_LOCK_WRITE_SPINNER) || 811 !((x & SX_LOCK_EXCLUSIVE_WAITERS))) { 812 setx = x & ~SX_LOCK_WRITE_SPINNER; 813 setx |= SX_LOCK_EXCLUSIVE_WAITERS; 814 if (!atomic_fcmpset_ptr(&sx->sx_lock, &x, 815 setx)) { 816 goto retry_sleepq; 817 } 818 } 819 critical_exit(); 820 in_critical = false; 821 } else { 822 #endif 823 /* 824 * Try to set the SX_LOCK_EXCLUSIVE_WAITERS. If we fail, 825 * than loop back and retry. 826 */ 827 if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) { 828 if (!atomic_fcmpset_ptr(&sx->sx_lock, &x, 829 x | SX_LOCK_EXCLUSIVE_WAITERS)) { 830 goto retry_sleepq; 831 } 832 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 833 CTR2(KTR_LOCK, "%s: %p set excl waiters flag", 834 __func__, sx); 835 } 836 #ifdef ADAPTIVE_SX 837 } 838 #endif 839 840 /* 841 * Since we have been unable to acquire the exclusive 842 * lock and the exclusive waiters flag is set, we have 843 * to sleep. 844 */ 845 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 846 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 847 __func__, sx); 848 849 #ifdef KDTRACE_HOOKS 850 sleep_time -= lockstat_nsecs(&sx->lock_object); 851 #endif 852 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 853 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 854 SLEEPQ_INTERRUPTIBLE : 0), SQ_EXCLUSIVE_QUEUE); 855 if (!(opts & SX_INTERRUPTIBLE)) 856 sleepq_wait(&sx->lock_object, 0); 857 else 858 error = sleepq_wait_sig(&sx->lock_object, 0); 859 #ifdef KDTRACE_HOOKS 860 sleep_time += lockstat_nsecs(&sx->lock_object); 861 sleep_cnt++; 862 #endif 863 if (error) { 864 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 865 CTR2(KTR_LOCK, 866 "%s: interruptible sleep by %p suspended by signal", 867 __func__, sx); 868 break; 869 } 870 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 871 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 872 __func__, sx); 873 x = SX_READ_VALUE(sx); 874 } 875 if (__predict_true(!extra_work)) 876 return (error); 877 #ifdef ADAPTIVE_SX 878 if (in_critical) 879 critical_exit(); 880 #endif 881 GIANT_RESTORE(); 882 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 883 if (__predict_true(!doing_lockprof)) 884 return (error); 885 #endif 886 #ifdef KDTRACE_HOOKS 887 all_time += lockstat_nsecs(&sx->lock_object); 888 if (sleep_time) 889 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 890 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 891 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 892 if (lda.spin_cnt > sleep_cnt) 893 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 894 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 895 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 896 out_lockstat: 897 #endif 898 if (!error) 899 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 900 contested, waittime, file, line, LOCKSTAT_WRITER); 901 return (error); 902 } 903 904 /* 905 * This function represents the so-called 'hard case' for sx_xunlock 906 * operation. All 'easy case' failures are redirected to this. Note 907 * that ideally this would be a static function, but it needs to be 908 * accessible from at least sx.h. 909 */ 910 void 911 _sx_xunlock_hard(struct sx *sx, uintptr_t x LOCK_FILE_LINE_ARG_DEF) 912 { 913 uintptr_t tid, setx; 914 int queue, wakeup_swapper; 915 916 if (SCHEDULER_STOPPED()) 917 return; 918 919 tid = (uintptr_t)curthread; 920 921 if (__predict_false(x == tid)) 922 x = SX_READ_VALUE(sx); 923 924 MPASS(!(x & SX_LOCK_SHARED)); 925 926 if (__predict_false(x & SX_LOCK_RECURSED)) { 927 /* The lock is recursed, unrecurse one level. */ 928 if ((--sx->sx_recurse) == 0) 929 atomic_clear_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 930 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 931 CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, sx); 932 return; 933 } 934 935 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_WRITER); 936 if (x == tid && 937 atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED)) 938 return; 939 940 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 941 CTR2(KTR_LOCK, "%s: %p contested", __func__, sx); 942 943 sleepq_lock(&sx->lock_object); 944 x = SX_READ_VALUE(sx); 945 MPASS(x & (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)); 946 947 /* 948 * The wake up algorithm here is quite simple and probably not 949 * ideal. It gives precedence to shared waiters if they are 950 * present. For this condition, we have to preserve the 951 * state of the exclusive waiters flag. 952 * If interruptible sleeps left the shared queue empty avoid a 953 * starvation for the threads sleeping on the exclusive queue by giving 954 * them precedence and cleaning up the shared waiters bit anyway. 955 */ 956 setx = SX_LOCK_UNLOCKED; 957 queue = SQ_SHARED_QUEUE; 958 if ((x & SX_LOCK_EXCLUSIVE_WAITERS) != 0 && 959 sleepq_sleepcnt(&sx->lock_object, SQ_EXCLUSIVE_QUEUE) != 0) { 960 queue = SQ_EXCLUSIVE_QUEUE; 961 setx |= (x & SX_LOCK_SHARED_WAITERS); 962 } 963 atomic_store_rel_ptr(&sx->sx_lock, setx); 964 965 /* Wake up all the waiters for the specific queue. */ 966 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 967 CTR3(KTR_LOCK, "%s: %p waking up all threads on %s queue", 968 __func__, sx, queue == SQ_SHARED_QUEUE ? "shared" : 969 "exclusive"); 970 971 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 0, 972 queue); 973 sleepq_release(&sx->lock_object); 974 if (wakeup_swapper) 975 kick_proc0(); 976 } 977 978 static bool __always_inline 979 __sx_can_read(struct thread *td, uintptr_t x, bool fp) 980 { 981 982 if ((x & (SX_LOCK_SHARED | SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_WRITE_SPINNER)) 983 == SX_LOCK_SHARED) 984 return (true); 985 if (!fp && td->td_sx_slocks && (x & SX_LOCK_SHARED)) 986 return (true); 987 return (false); 988 } 989 990 static bool __always_inline 991 __sx_slock_try(struct sx *sx, struct thread *td, uintptr_t *xp, bool fp 992 LOCK_FILE_LINE_ARG_DEF) 993 { 994 995 /* 996 * If no other thread has an exclusive lock then try to bump up 997 * the count of sharers. Since we have to preserve the state 998 * of SX_LOCK_EXCLUSIVE_WAITERS, if we fail to acquire the 999 * shared lock loop back and retry. 1000 */ 1001 while (__sx_can_read(td, *xp, fp)) { 1002 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, xp, 1003 *xp + SX_ONE_SHARER)) { 1004 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1005 CTR4(KTR_LOCK, "%s: %p succeed %p -> %p", 1006 __func__, sx, (void *)*xp, 1007 (void *)(*xp + SX_ONE_SHARER)); 1008 td->td_sx_slocks++; 1009 return (true); 1010 } 1011 } 1012 return (false); 1013 } 1014 1015 static int __noinline 1016 _sx_slock_hard(struct sx *sx, int opts, uintptr_t x LOCK_FILE_LINE_ARG_DEF) 1017 { 1018 GIANT_DECLARE; 1019 struct thread *td; 1020 #ifdef ADAPTIVE_SX 1021 struct thread *owner; 1022 u_int i, n, spintries = 0; 1023 #endif 1024 #ifdef LOCK_PROFILING 1025 uint64_t waittime = 0; 1026 int contested = 0; 1027 #endif 1028 int error = 0; 1029 #if defined(ADAPTIVE_SX) || defined(KDTRACE_HOOKS) 1030 struct lock_delay_arg lda; 1031 #endif 1032 #ifdef KDTRACE_HOOKS 1033 u_int sleep_cnt = 0; 1034 int64_t sleep_time = 0; 1035 int64_t all_time = 0; 1036 #endif 1037 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 1038 uintptr_t state = 0; 1039 #endif 1040 int extra_work __sdt_used = 0; 1041 1042 td = curthread; 1043 1044 #ifdef KDTRACE_HOOKS 1045 if (LOCKSTAT_PROFILE_ENABLED(sx__acquire)) { 1046 if (__sx_slock_try(sx, td, &x, false LOCK_FILE_LINE_ARG)) 1047 goto out_lockstat; 1048 extra_work = 1; 1049 all_time -= lockstat_nsecs(&sx->lock_object); 1050 state = x; 1051 } 1052 #endif 1053 #ifdef LOCK_PROFILING 1054 extra_work = 1; 1055 state = x; 1056 #endif 1057 1058 if (SCHEDULER_STOPPED()) 1059 return (0); 1060 1061 #if defined(ADAPTIVE_SX) 1062 lock_delay_arg_init(&lda, &sx_delay); 1063 #elif defined(KDTRACE_HOOKS) 1064 lock_delay_arg_init_noadapt(&lda); 1065 #endif 1066 1067 #ifdef HWPMC_HOOKS 1068 PMC_SOFT_CALL( , , lock, failed); 1069 #endif 1070 lock_profile_obtain_lock_failed(&sx->lock_object, false, &contested, 1071 &waittime); 1072 1073 #ifndef INVARIANTS 1074 GIANT_SAVE(extra_work); 1075 #endif 1076 1077 /* 1078 * As with rwlocks, we don't make any attempt to try to block 1079 * shared locks once there is an exclusive waiter. 1080 */ 1081 for (;;) { 1082 if (__sx_slock_try(sx, td, &x, false LOCK_FILE_LINE_ARG)) 1083 break; 1084 #ifdef INVARIANTS 1085 GIANT_SAVE(extra_work); 1086 #endif 1087 #ifdef KDTRACE_HOOKS 1088 lda.spin_cnt++; 1089 #endif 1090 1091 #ifdef ADAPTIVE_SX 1092 /* 1093 * If the owner is running on another CPU, spin until 1094 * the owner stops running or the state of the lock 1095 * changes. 1096 */ 1097 if ((x & SX_LOCK_SHARED) == 0) { 1098 owner = lv_sx_owner(x); 1099 if (TD_IS_RUNNING(owner)) { 1100 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1101 CTR3(KTR_LOCK, 1102 "%s: spinning on %p held by %p", 1103 __func__, sx, owner); 1104 KTR_STATE1(KTR_SCHED, "thread", 1105 sched_tdname(curthread), "spinning", 1106 "lockname:\"%s\"", sx->lock_object.lo_name); 1107 do { 1108 lock_delay(&lda); 1109 x = SX_READ_VALUE(sx); 1110 owner = lv_sx_owner(x); 1111 } while (owner != NULL && TD_IS_RUNNING(owner)); 1112 KTR_STATE0(KTR_SCHED, "thread", 1113 sched_tdname(curthread), "running"); 1114 continue; 1115 } 1116 } else { 1117 if ((x & SX_LOCK_WRITE_SPINNER) && SX_SHARERS(x) == 0) { 1118 MPASS(!__sx_can_read(td, x, false)); 1119 lock_delay_spin(2); 1120 x = SX_READ_VALUE(sx); 1121 continue; 1122 } 1123 if (spintries < asx_retries) { 1124 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread), 1125 "spinning", "lockname:\"%s\"", 1126 sx->lock_object.lo_name); 1127 n = SX_SHARERS(x); 1128 for (i = 0; i < asx_loops; i += n) { 1129 lock_delay_spin(n); 1130 x = SX_READ_VALUE(sx); 1131 if (!(x & SX_LOCK_SHARED)) 1132 break; 1133 n = SX_SHARERS(x); 1134 if (n == 0) 1135 break; 1136 if (__sx_can_read(td, x, false)) 1137 break; 1138 } 1139 #ifdef KDTRACE_HOOKS 1140 lda.spin_cnt += i; 1141 #endif 1142 KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread), 1143 "running"); 1144 if (i < asx_loops) 1145 continue; 1146 } 1147 } 1148 #endif 1149 1150 /* 1151 * Some other thread already has an exclusive lock, so 1152 * start the process of blocking. 1153 */ 1154 sleepq_lock(&sx->lock_object); 1155 x = SX_READ_VALUE(sx); 1156 retry_sleepq: 1157 if (((x & SX_LOCK_WRITE_SPINNER) && SX_SHARERS(x) == 0) || 1158 __sx_can_read(td, x, false)) { 1159 sleepq_release(&sx->lock_object); 1160 continue; 1161 } 1162 1163 #ifdef ADAPTIVE_SX 1164 /* 1165 * If the owner is running on another CPU, spin until 1166 * the owner stops running or the state of the lock 1167 * changes. 1168 */ 1169 if (!(x & SX_LOCK_SHARED)) { 1170 owner = (struct thread *)SX_OWNER(x); 1171 if (TD_IS_RUNNING(owner)) { 1172 sleepq_release(&sx->lock_object); 1173 x = SX_READ_VALUE(sx); 1174 continue; 1175 } 1176 } 1177 #endif 1178 1179 /* 1180 * Try to set the SX_LOCK_SHARED_WAITERS flag. If we 1181 * fail to set it drop the sleep queue lock and loop 1182 * back. 1183 */ 1184 if (!(x & SX_LOCK_SHARED_WAITERS)) { 1185 if (!atomic_fcmpset_ptr(&sx->sx_lock, &x, 1186 x | SX_LOCK_SHARED_WAITERS)) 1187 goto retry_sleepq; 1188 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1189 CTR2(KTR_LOCK, "%s: %p set shared waiters flag", 1190 __func__, sx); 1191 } 1192 1193 /* 1194 * Since we have been unable to acquire the shared lock, 1195 * we have to sleep. 1196 */ 1197 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1198 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 1199 __func__, sx); 1200 1201 #ifdef KDTRACE_HOOKS 1202 sleep_time -= lockstat_nsecs(&sx->lock_object); 1203 #endif 1204 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 1205 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 1206 SLEEPQ_INTERRUPTIBLE : 0), SQ_SHARED_QUEUE); 1207 if (!(opts & SX_INTERRUPTIBLE)) 1208 sleepq_wait(&sx->lock_object, 0); 1209 else 1210 error = sleepq_wait_sig(&sx->lock_object, 0); 1211 #ifdef KDTRACE_HOOKS 1212 sleep_time += lockstat_nsecs(&sx->lock_object); 1213 sleep_cnt++; 1214 #endif 1215 if (error) { 1216 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1217 CTR2(KTR_LOCK, 1218 "%s: interruptible sleep by %p suspended by signal", 1219 __func__, sx); 1220 break; 1221 } 1222 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1223 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 1224 __func__, sx); 1225 x = SX_READ_VALUE(sx); 1226 } 1227 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 1228 if (__predict_true(!extra_work)) 1229 return (error); 1230 #endif 1231 #ifdef KDTRACE_HOOKS 1232 all_time += lockstat_nsecs(&sx->lock_object); 1233 if (sleep_time) 1234 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 1235 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1236 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1237 if (lda.spin_cnt > sleep_cnt) 1238 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 1239 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1240 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1241 out_lockstat: 1242 #endif 1243 if (error == 0) { 1244 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 1245 contested, waittime, file, line, LOCKSTAT_READER); 1246 } 1247 GIANT_RESTORE(); 1248 return (error); 1249 } 1250 1251 int 1252 _sx_slock_int(struct sx *sx, int opts LOCK_FILE_LINE_ARG_DEF) 1253 { 1254 struct thread *td; 1255 uintptr_t x; 1256 int error; 1257 1258 KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() || 1259 !TD_IS_IDLETHREAD(curthread), 1260 ("sx_slock() by idle thread %p on sx %s @ %s:%d", 1261 curthread, sx->lock_object.lo_name, file, line)); 1262 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 1263 ("sx_slock() of destroyed sx @ %s:%d", file, line)); 1264 WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER, file, line, NULL); 1265 1266 error = 0; 1267 td = curthread; 1268 x = SX_READ_VALUE(sx); 1269 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__acquire) || 1270 !__sx_slock_try(sx, td, &x, true LOCK_FILE_LINE_ARG))) 1271 error = _sx_slock_hard(sx, opts, x LOCK_FILE_LINE_ARG); 1272 else 1273 lock_profile_obtain_lock_success(&sx->lock_object, false, 0, 0, 1274 file, line); 1275 if (error == 0) { 1276 LOCK_LOG_LOCK("SLOCK", &sx->lock_object, 0, 0, file, line); 1277 WITNESS_LOCK(&sx->lock_object, 0, file, line); 1278 TD_LOCKS_INC(curthread); 1279 } 1280 return (error); 1281 } 1282 1283 int 1284 _sx_slock(struct sx *sx, int opts, const char *file, int line) 1285 { 1286 1287 return (_sx_slock_int(sx, opts LOCK_FILE_LINE_ARG)); 1288 } 1289 1290 static bool __always_inline 1291 _sx_sunlock_try(struct sx *sx, struct thread *td, uintptr_t *xp) 1292 { 1293 1294 for (;;) { 1295 if (SX_SHARERS(*xp) > 1 || !(*xp & SX_LOCK_WAITERS)) { 1296 if (atomic_fcmpset_rel_ptr(&sx->sx_lock, xp, 1297 *xp - SX_ONE_SHARER)) { 1298 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1299 CTR4(KTR_LOCK, 1300 "%s: %p succeeded %p -> %p", 1301 __func__, sx, (void *)*xp, 1302 (void *)(*xp - SX_ONE_SHARER)); 1303 td->td_sx_slocks--; 1304 return (true); 1305 } 1306 continue; 1307 } 1308 break; 1309 } 1310 return (false); 1311 } 1312 1313 static void __noinline 1314 _sx_sunlock_hard(struct sx *sx, struct thread *td, uintptr_t x 1315 LOCK_FILE_LINE_ARG_DEF) 1316 { 1317 int wakeup_swapper = 0; 1318 uintptr_t setx, queue; 1319 1320 if (SCHEDULER_STOPPED()) 1321 return; 1322 1323 if (_sx_sunlock_try(sx, td, &x)) 1324 goto out_lockstat; 1325 1326 sleepq_lock(&sx->lock_object); 1327 x = SX_READ_VALUE(sx); 1328 for (;;) { 1329 if (_sx_sunlock_try(sx, td, &x)) 1330 break; 1331 1332 /* 1333 * Wake up semantic here is quite simple: 1334 * Just wake up all the exclusive waiters. 1335 * Note that the state of the lock could have changed, 1336 * so if it fails loop back and retry. 1337 */ 1338 setx = SX_LOCK_UNLOCKED; 1339 queue = SQ_SHARED_QUEUE; 1340 if (x & SX_LOCK_EXCLUSIVE_WAITERS) { 1341 setx |= (x & SX_LOCK_SHARED_WAITERS); 1342 queue = SQ_EXCLUSIVE_QUEUE; 1343 } 1344 setx |= (x & SX_LOCK_WRITE_SPINNER); 1345 if (!atomic_fcmpset_rel_ptr(&sx->sx_lock, &x, setx)) 1346 continue; 1347 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1348 CTR2(KTR_LOCK, "%s: %p waking up all thread on" 1349 "exclusive queue", __func__, sx); 1350 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 1351 0, queue); 1352 td->td_sx_slocks--; 1353 break; 1354 } 1355 sleepq_release(&sx->lock_object); 1356 if (wakeup_swapper) 1357 kick_proc0(); 1358 out_lockstat: 1359 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_READER); 1360 } 1361 1362 void 1363 _sx_sunlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF) 1364 { 1365 struct thread *td; 1366 uintptr_t x; 1367 1368 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 1369 ("sx_sunlock() of destroyed sx @ %s:%d", file, line)); 1370 _sx_assert(sx, SA_SLOCKED, file, line); 1371 WITNESS_UNLOCK(&sx->lock_object, 0, file, line); 1372 LOCK_LOG_LOCK("SUNLOCK", &sx->lock_object, 0, 0, file, line); 1373 1374 td = curthread; 1375 x = SX_READ_VALUE(sx); 1376 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__release) || 1377 !_sx_sunlock_try(sx, td, &x))) 1378 _sx_sunlock_hard(sx, td, x LOCK_FILE_LINE_ARG); 1379 else 1380 lock_profile_release_lock(&sx->lock_object, false); 1381 1382 TD_LOCKS_DEC(curthread); 1383 } 1384 1385 void 1386 _sx_sunlock(struct sx *sx, const char *file, int line) 1387 { 1388 1389 _sx_sunlock_int(sx LOCK_FILE_LINE_ARG); 1390 } 1391 1392 #ifdef INVARIANT_SUPPORT 1393 #ifndef INVARIANTS 1394 #undef _sx_assert 1395 #endif 1396 1397 /* 1398 * In the non-WITNESS case, sx_assert() can only detect that at least 1399 * *some* thread owns an slock, but it cannot guarantee that *this* 1400 * thread owns an slock. 1401 */ 1402 void 1403 _sx_assert(const struct sx *sx, int what, const char *file, int line) 1404 { 1405 #ifndef WITNESS 1406 int slocked = 0; 1407 #endif 1408 1409 if (SCHEDULER_STOPPED()) 1410 return; 1411 switch (what) { 1412 case SA_SLOCKED: 1413 case SA_SLOCKED | SA_NOTRECURSED: 1414 case SA_SLOCKED | SA_RECURSED: 1415 #ifndef WITNESS 1416 slocked = 1; 1417 /* FALLTHROUGH */ 1418 #endif 1419 case SA_LOCKED: 1420 case SA_LOCKED | SA_NOTRECURSED: 1421 case SA_LOCKED | SA_RECURSED: 1422 #ifdef WITNESS 1423 witness_assert(&sx->lock_object, what, file, line); 1424 #else 1425 /* 1426 * If some other thread has an exclusive lock or we 1427 * have one and are asserting a shared lock, fail. 1428 * Also, if no one has a lock at all, fail. 1429 */ 1430 if (sx->sx_lock == SX_LOCK_UNLOCKED || 1431 (!(sx->sx_lock & SX_LOCK_SHARED) && (slocked || 1432 sx_xholder(sx) != curthread))) 1433 panic("Lock %s not %slocked @ %s:%d\n", 1434 sx->lock_object.lo_name, slocked ? "share " : "", 1435 file, line); 1436 1437 if (!(sx->sx_lock & SX_LOCK_SHARED)) { 1438 if (sx_recursed(sx)) { 1439 if (what & SA_NOTRECURSED) 1440 panic("Lock %s recursed @ %s:%d\n", 1441 sx->lock_object.lo_name, file, 1442 line); 1443 } else if (what & SA_RECURSED) 1444 panic("Lock %s not recursed @ %s:%d\n", 1445 sx->lock_object.lo_name, file, line); 1446 } 1447 #endif 1448 break; 1449 case SA_XLOCKED: 1450 case SA_XLOCKED | SA_NOTRECURSED: 1451 case SA_XLOCKED | SA_RECURSED: 1452 if (sx_xholder(sx) != curthread) 1453 panic("Lock %s not exclusively locked @ %s:%d\n", 1454 sx->lock_object.lo_name, file, line); 1455 if (sx_recursed(sx)) { 1456 if (what & SA_NOTRECURSED) 1457 panic("Lock %s recursed @ %s:%d\n", 1458 sx->lock_object.lo_name, file, line); 1459 } else if (what & SA_RECURSED) 1460 panic("Lock %s not recursed @ %s:%d\n", 1461 sx->lock_object.lo_name, file, line); 1462 break; 1463 case SA_UNLOCKED: 1464 #ifdef WITNESS 1465 witness_assert(&sx->lock_object, what, file, line); 1466 #else 1467 /* 1468 * If we hold an exclusve lock fail. We can't 1469 * reliably check to see if we hold a shared lock or 1470 * not. 1471 */ 1472 if (sx_xholder(sx) == curthread) 1473 panic("Lock %s exclusively locked @ %s:%d\n", 1474 sx->lock_object.lo_name, file, line); 1475 #endif 1476 break; 1477 default: 1478 panic("Unknown sx lock assertion: %d @ %s:%d", what, file, 1479 line); 1480 } 1481 } 1482 #endif /* INVARIANT_SUPPORT */ 1483 1484 #ifdef DDB 1485 static void 1486 db_show_sx(const struct lock_object *lock) 1487 { 1488 struct thread *td; 1489 const struct sx *sx; 1490 1491 sx = (const struct sx *)lock; 1492 1493 db_printf(" state: "); 1494 if (sx->sx_lock == SX_LOCK_UNLOCKED) 1495 db_printf("UNLOCKED\n"); 1496 else if (sx->sx_lock == SX_LOCK_DESTROYED) { 1497 db_printf("DESTROYED\n"); 1498 return; 1499 } else if (sx->sx_lock & SX_LOCK_SHARED) 1500 db_printf("SLOCK: %ju\n", (uintmax_t)SX_SHARERS(sx->sx_lock)); 1501 else { 1502 td = sx_xholder(sx); 1503 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1504 td->td_tid, td->td_proc->p_pid, td->td_name); 1505 if (sx_recursed(sx)) 1506 db_printf(" recursed: %d\n", sx->sx_recurse); 1507 } 1508 1509 db_printf(" waiters: "); 1510 switch(sx->sx_lock & 1511 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)) { 1512 case SX_LOCK_SHARED_WAITERS: 1513 db_printf("shared\n"); 1514 break; 1515 case SX_LOCK_EXCLUSIVE_WAITERS: 1516 db_printf("exclusive\n"); 1517 break; 1518 case SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS: 1519 db_printf("exclusive and shared\n"); 1520 break; 1521 default: 1522 db_printf("none\n"); 1523 } 1524 } 1525 1526 /* 1527 * Check to see if a thread that is blocked on a sleep queue is actually 1528 * blocked on an sx lock. If so, output some details and return true. 1529 * If the lock has an exclusive owner, return that in *ownerp. 1530 */ 1531 int 1532 sx_chain(struct thread *td, struct thread **ownerp) 1533 { 1534 const struct sx *sx; 1535 1536 /* 1537 * Check to see if this thread is blocked on an sx lock. 1538 * First, we check the lock class. If that is ok, then we 1539 * compare the lock name against the wait message. 1540 */ 1541 sx = td->td_wchan; 1542 if (LOCK_CLASS(&sx->lock_object) != &lock_class_sx || 1543 sx->lock_object.lo_name != td->td_wmesg) 1544 return (0); 1545 1546 /* We think we have an sx lock, so output some details. */ 1547 db_printf("blocked on sx \"%s\" ", td->td_wmesg); 1548 *ownerp = sx_xholder(sx); 1549 if (sx->sx_lock & SX_LOCK_SHARED) 1550 db_printf("SLOCK (count %ju)\n", 1551 (uintmax_t)SX_SHARERS(sx->sx_lock)); 1552 else 1553 db_printf("XLOCK\n"); 1554 return (1); 1555 } 1556 #endif 1557