1 /*- 2 * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org> 3 * Copyright (c) 2001 Jason Evans <jasone@freebsd.org> 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice(s), this list of conditions and the following disclaimer as 11 * the first lines of this file unmodified other than the possible 12 * addition of one or more copyright notices. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice(s), this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 20 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 23 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 24 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 27 * DAMAGE. 28 */ 29 30 /* 31 * Shared/exclusive locks. This implementation attempts to ensure 32 * deterministic lock granting behavior, so that slocks and xlocks are 33 * interleaved. 34 * 35 * Priority propagation will not generally raise the priority of lock holders, 36 * so should not be relied upon in combination with sx locks. 37 */ 38 39 #include "opt_ddb.h" 40 #include "opt_hwpmc_hooks.h" 41 #include "opt_no_adaptive_sx.h" 42 43 #include <sys/cdefs.h> 44 __FBSDID("$FreeBSD$"); 45 46 #include <sys/param.h> 47 #include <sys/systm.h> 48 #include <sys/kdb.h> 49 #include <sys/kernel.h> 50 #include <sys/ktr.h> 51 #include <sys/lock.h> 52 #include <sys/mutex.h> 53 #include <sys/proc.h> 54 #include <sys/sched.h> 55 #include <sys/sleepqueue.h> 56 #include <sys/sx.h> 57 #include <sys/smp.h> 58 #include <sys/sysctl.h> 59 60 #if defined(SMP) && !defined(NO_ADAPTIVE_SX) 61 #include <machine/cpu.h> 62 #endif 63 64 #ifdef DDB 65 #include <ddb/ddb.h> 66 #endif 67 68 #if defined(SMP) && !defined(NO_ADAPTIVE_SX) 69 #define ADAPTIVE_SX 70 #endif 71 72 CTASSERT((SX_NOADAPTIVE & LO_CLASSFLAGS) == SX_NOADAPTIVE); 73 74 #ifdef HWPMC_HOOKS 75 #include <sys/pmckern.h> 76 PMC_SOFT_DECLARE( , , lock, failed); 77 #endif 78 79 /* Handy macros for sleep queues. */ 80 #define SQ_EXCLUSIVE_QUEUE 0 81 #define SQ_SHARED_QUEUE 1 82 83 /* 84 * Variations on DROP_GIANT()/PICKUP_GIANT() for use in this file. We 85 * drop Giant anytime we have to sleep or if we adaptively spin. 86 */ 87 #define GIANT_DECLARE \ 88 int _giantcnt = 0; \ 89 WITNESS_SAVE_DECL(Giant) \ 90 91 #define GIANT_SAVE() do { \ 92 if (mtx_owned(&Giant)) { \ 93 WITNESS_SAVE(&Giant.lock_object, Giant); \ 94 while (mtx_owned(&Giant)) { \ 95 _giantcnt++; \ 96 mtx_unlock(&Giant); \ 97 } \ 98 } \ 99 } while (0) 100 101 #define GIANT_RESTORE() do { \ 102 if (_giantcnt > 0) { \ 103 mtx_assert(&Giant, MA_NOTOWNED); \ 104 while (_giantcnt--) \ 105 mtx_lock(&Giant); \ 106 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 107 } \ 108 } while (0) 109 110 /* 111 * Returns true if an exclusive lock is recursed. It assumes 112 * curthread currently has an exclusive lock. 113 */ 114 #define sx_recursed(sx) ((sx)->sx_recurse != 0) 115 116 static void assert_sx(const struct lock_object *lock, int what); 117 #ifdef DDB 118 static void db_show_sx(const struct lock_object *lock); 119 #endif 120 static void lock_sx(struct lock_object *lock, uintptr_t how); 121 #ifdef KDTRACE_HOOKS 122 static int owner_sx(const struct lock_object *lock, struct thread **owner); 123 #endif 124 static uintptr_t unlock_sx(struct lock_object *lock); 125 126 struct lock_class lock_class_sx = { 127 .lc_name = "sx", 128 .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE, 129 .lc_assert = assert_sx, 130 #ifdef DDB 131 .lc_ddb_show = db_show_sx, 132 #endif 133 .lc_lock = lock_sx, 134 .lc_unlock = unlock_sx, 135 #ifdef KDTRACE_HOOKS 136 .lc_owner = owner_sx, 137 #endif 138 }; 139 140 #ifndef INVARIANTS 141 #define _sx_assert(sx, what, file, line) 142 #endif 143 144 #ifdef ADAPTIVE_SX 145 static __read_frequently u_int asx_retries = 10; 146 static __read_frequently u_int asx_loops = 10000; 147 static SYSCTL_NODE(_debug, OID_AUTO, sx, CTLFLAG_RD, NULL, "sxlock debugging"); 148 SYSCTL_UINT(_debug_sx, OID_AUTO, retries, CTLFLAG_RW, &asx_retries, 0, ""); 149 SYSCTL_UINT(_debug_sx, OID_AUTO, loops, CTLFLAG_RW, &asx_loops, 0, ""); 150 151 static struct lock_delay_config __read_frequently sx_delay; 152 153 SYSCTL_INT(_debug_sx, OID_AUTO, delay_base, CTLFLAG_RW, &sx_delay.base, 154 0, ""); 155 SYSCTL_INT(_debug_sx, OID_AUTO, delay_max, CTLFLAG_RW, &sx_delay.max, 156 0, ""); 157 158 LOCK_DELAY_SYSINIT_DEFAULT(sx_delay); 159 #endif 160 161 void 162 assert_sx(const struct lock_object *lock, int what) 163 { 164 165 sx_assert((const struct sx *)lock, what); 166 } 167 168 void 169 lock_sx(struct lock_object *lock, uintptr_t how) 170 { 171 struct sx *sx; 172 173 sx = (struct sx *)lock; 174 if (how) 175 sx_slock(sx); 176 else 177 sx_xlock(sx); 178 } 179 180 uintptr_t 181 unlock_sx(struct lock_object *lock) 182 { 183 struct sx *sx; 184 185 sx = (struct sx *)lock; 186 sx_assert(sx, SA_LOCKED | SA_NOTRECURSED); 187 if (sx_xlocked(sx)) { 188 sx_xunlock(sx); 189 return (0); 190 } else { 191 sx_sunlock(sx); 192 return (1); 193 } 194 } 195 196 #ifdef KDTRACE_HOOKS 197 int 198 owner_sx(const struct lock_object *lock, struct thread **owner) 199 { 200 const struct sx *sx; 201 uintptr_t x; 202 203 sx = (const struct sx *)lock; 204 x = sx->sx_lock; 205 *owner = NULL; 206 return ((x & SX_LOCK_SHARED) != 0 ? (SX_SHARERS(x) != 0) : 207 ((*owner = (struct thread *)SX_OWNER(x)) != NULL)); 208 } 209 #endif 210 211 void 212 sx_sysinit(void *arg) 213 { 214 struct sx_args *sargs = arg; 215 216 sx_init_flags(sargs->sa_sx, sargs->sa_desc, sargs->sa_flags); 217 } 218 219 void 220 sx_init_flags(struct sx *sx, const char *description, int opts) 221 { 222 int flags; 223 224 MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK | 225 SX_NOPROFILE | SX_NOADAPTIVE | SX_NEW)) == 0); 226 ASSERT_ATOMIC_LOAD_PTR(sx->sx_lock, 227 ("%s: sx_lock not aligned for %s: %p", __func__, description, 228 &sx->sx_lock)); 229 230 flags = LO_SLEEPABLE | LO_UPGRADABLE; 231 if (opts & SX_DUPOK) 232 flags |= LO_DUPOK; 233 if (opts & SX_NOPROFILE) 234 flags |= LO_NOPROFILE; 235 if (!(opts & SX_NOWITNESS)) 236 flags |= LO_WITNESS; 237 if (opts & SX_RECURSE) 238 flags |= LO_RECURSABLE; 239 if (opts & SX_QUIET) 240 flags |= LO_QUIET; 241 if (opts & SX_NEW) 242 flags |= LO_NEW; 243 244 flags |= opts & SX_NOADAPTIVE; 245 lock_init(&sx->lock_object, &lock_class_sx, description, NULL, flags); 246 sx->sx_lock = SX_LOCK_UNLOCKED; 247 sx->sx_recurse = 0; 248 } 249 250 void 251 sx_destroy(struct sx *sx) 252 { 253 254 KASSERT(sx->sx_lock == SX_LOCK_UNLOCKED, ("sx lock still held")); 255 KASSERT(sx->sx_recurse == 0, ("sx lock still recursed")); 256 sx->sx_lock = SX_LOCK_DESTROYED; 257 lock_destroy(&sx->lock_object); 258 } 259 260 int 261 sx_try_slock_(struct sx *sx, const char *file, int line) 262 { 263 uintptr_t x; 264 265 if (SCHEDULER_STOPPED()) 266 return (1); 267 268 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 269 ("sx_try_slock() by idle thread %p on sx %s @ %s:%d", 270 curthread, sx->lock_object.lo_name, file, line)); 271 272 x = sx->sx_lock; 273 for (;;) { 274 KASSERT(x != SX_LOCK_DESTROYED, 275 ("sx_try_slock() of destroyed sx @ %s:%d", file, line)); 276 if (!(x & SX_LOCK_SHARED)) 277 break; 278 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, x + SX_ONE_SHARER)) { 279 LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 1, file, line); 280 WITNESS_LOCK(&sx->lock_object, LOP_TRYLOCK, file, line); 281 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, 282 sx, 0, 0, file, line, LOCKSTAT_READER); 283 TD_LOCKS_INC(curthread); 284 return (1); 285 } 286 } 287 288 LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 0, file, line); 289 return (0); 290 } 291 292 int 293 _sx_xlock(struct sx *sx, int opts, const char *file, int line) 294 { 295 uintptr_t tid, x; 296 int error = 0; 297 298 KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() || 299 !TD_IS_IDLETHREAD(curthread), 300 ("sx_xlock() by idle thread %p on sx %s @ %s:%d", 301 curthread, sx->lock_object.lo_name, file, line)); 302 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 303 ("sx_xlock() of destroyed sx @ %s:%d", file, line)); 304 WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, 305 line, NULL); 306 tid = (uintptr_t)curthread; 307 x = SX_LOCK_UNLOCKED; 308 if (!atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 309 error = _sx_xlock_hard(sx, x, tid, opts, file, line); 310 else 311 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 312 0, 0, file, line, LOCKSTAT_WRITER); 313 if (!error) { 314 LOCK_LOG_LOCK("XLOCK", &sx->lock_object, 0, sx->sx_recurse, 315 file, line); 316 WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); 317 TD_LOCKS_INC(curthread); 318 } 319 320 return (error); 321 } 322 323 int 324 sx_try_xlock_(struct sx *sx, const char *file, int line) 325 { 326 struct thread *td; 327 uintptr_t tid, x; 328 int rval; 329 bool recursed; 330 331 td = curthread; 332 tid = (uintptr_t)td; 333 if (SCHEDULER_STOPPED_TD(td)) 334 return (1); 335 336 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(td), 337 ("sx_try_xlock() by idle thread %p on sx %s @ %s:%d", 338 curthread, sx->lock_object.lo_name, file, line)); 339 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 340 ("sx_try_xlock() of destroyed sx @ %s:%d", file, line)); 341 342 rval = 1; 343 recursed = false; 344 x = SX_LOCK_UNLOCKED; 345 for (;;) { 346 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 347 break; 348 if (x == SX_LOCK_UNLOCKED) 349 continue; 350 if (x == tid && (sx->lock_object.lo_flags & LO_RECURSABLE)) { 351 sx->sx_recurse++; 352 atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 353 break; 354 } 355 rval = 0; 356 break; 357 } 358 359 LOCK_LOG_TRY("XLOCK", &sx->lock_object, 0, rval, file, line); 360 if (rval) { 361 WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 362 file, line); 363 if (!recursed) 364 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, 365 sx, 0, 0, file, line, LOCKSTAT_WRITER); 366 TD_LOCKS_INC(curthread); 367 } 368 369 return (rval); 370 } 371 372 void 373 _sx_xunlock(struct sx *sx, const char *file, int line) 374 { 375 376 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 377 ("sx_xunlock() of destroyed sx @ %s:%d", file, line)); 378 _sx_assert(sx, SA_XLOCKED, file, line); 379 WITNESS_UNLOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); 380 LOCK_LOG_LOCK("XUNLOCK", &sx->lock_object, 0, sx->sx_recurse, file, 381 line); 382 #if LOCK_DEBUG > 0 383 _sx_xunlock_hard(sx, (uintptr_t)curthread, file, line); 384 #else 385 __sx_xunlock(sx, curthread, file, line); 386 #endif 387 TD_LOCKS_DEC(curthread); 388 } 389 390 /* 391 * Try to do a non-blocking upgrade from a shared lock to an exclusive lock. 392 * This will only succeed if this thread holds a single shared lock. 393 * Return 1 if if the upgrade succeed, 0 otherwise. 394 */ 395 int 396 sx_try_upgrade_(struct sx *sx, const char *file, int line) 397 { 398 uintptr_t x; 399 int success; 400 401 if (SCHEDULER_STOPPED()) 402 return (1); 403 404 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 405 ("sx_try_upgrade() of destroyed sx @ %s:%d", file, line)); 406 _sx_assert(sx, SA_SLOCKED, file, line); 407 408 /* 409 * Try to switch from one shared lock to an exclusive lock. We need 410 * to maintain the SX_LOCK_EXCLUSIVE_WAITERS flag if set so that 411 * we will wake up the exclusive waiters when we drop the lock. 412 */ 413 x = sx->sx_lock & SX_LOCK_EXCLUSIVE_WAITERS; 414 success = atomic_cmpset_acq_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | x, 415 (uintptr_t)curthread | x); 416 LOCK_LOG_TRY("XUPGRADE", &sx->lock_object, 0, success, file, line); 417 if (success) { 418 WITNESS_UPGRADE(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 419 file, line); 420 LOCKSTAT_RECORD0(sx__upgrade, sx); 421 } 422 return (success); 423 } 424 425 /* 426 * Downgrade an unrecursed exclusive lock into a single shared lock. 427 */ 428 void 429 sx_downgrade_(struct sx *sx, const char *file, int line) 430 { 431 uintptr_t x; 432 int wakeup_swapper; 433 434 if (SCHEDULER_STOPPED()) 435 return; 436 437 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 438 ("sx_downgrade() of destroyed sx @ %s:%d", file, line)); 439 _sx_assert(sx, SA_XLOCKED | SA_NOTRECURSED, file, line); 440 #ifndef INVARIANTS 441 if (sx_recursed(sx)) 442 panic("downgrade of a recursed lock"); 443 #endif 444 445 WITNESS_DOWNGRADE(&sx->lock_object, 0, file, line); 446 447 /* 448 * Try to switch from an exclusive lock with no shared waiters 449 * to one sharer with no shared waiters. If there are 450 * exclusive waiters, we don't need to lock the sleep queue so 451 * long as we preserve the flag. We do one quick try and if 452 * that fails we grab the sleepq lock to keep the flags from 453 * changing and do it the slow way. 454 * 455 * We have to lock the sleep queue if there are shared waiters 456 * so we can wake them up. 457 */ 458 x = sx->sx_lock; 459 if (!(x & SX_LOCK_SHARED_WAITERS) && 460 atomic_cmpset_rel_ptr(&sx->sx_lock, x, SX_SHARERS_LOCK(1) | 461 (x & SX_LOCK_EXCLUSIVE_WAITERS))) { 462 LOCK_LOG_LOCK("XDOWNGRADE", &sx->lock_object, 0, 0, file, line); 463 return; 464 } 465 466 /* 467 * Lock the sleep queue so we can read the waiters bits 468 * without any races and wakeup any shared waiters. 469 */ 470 sleepq_lock(&sx->lock_object); 471 472 /* 473 * Preserve SX_LOCK_EXCLUSIVE_WAITERS while downgraded to a single 474 * shared lock. If there are any shared waiters, wake them up. 475 */ 476 wakeup_swapper = 0; 477 x = sx->sx_lock; 478 atomic_store_rel_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | 479 (x & SX_LOCK_EXCLUSIVE_WAITERS)); 480 if (x & SX_LOCK_SHARED_WAITERS) 481 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 482 0, SQ_SHARED_QUEUE); 483 sleepq_release(&sx->lock_object); 484 485 LOCK_LOG_LOCK("XDOWNGRADE", &sx->lock_object, 0, 0, file, line); 486 LOCKSTAT_RECORD0(sx__downgrade, sx); 487 488 if (wakeup_swapper) 489 kick_proc0(); 490 } 491 492 /* 493 * This function represents the so-called 'hard case' for sx_xlock 494 * operation. All 'easy case' failures are redirected to this. Note 495 * that ideally this would be a static function, but it needs to be 496 * accessible from at least sx.h. 497 */ 498 int 499 _sx_xlock_hard(struct sx *sx, uintptr_t x, uintptr_t tid, int opts, 500 const char *file, int line) 501 { 502 GIANT_DECLARE; 503 #ifdef ADAPTIVE_SX 504 volatile struct thread *owner; 505 u_int i, n, spintries = 0; 506 #endif 507 #ifdef LOCK_PROFILING 508 uint64_t waittime = 0; 509 int contested = 0; 510 #endif 511 int error = 0; 512 #if defined(ADAPTIVE_SX) || defined(KDTRACE_HOOKS) 513 struct lock_delay_arg lda; 514 #endif 515 #ifdef KDTRACE_HOOKS 516 uintptr_t state; 517 u_int sleep_cnt = 0; 518 int64_t sleep_time = 0; 519 int64_t all_time = 0; 520 #endif 521 522 if (SCHEDULER_STOPPED()) 523 return (0); 524 525 #if defined(ADAPTIVE_SX) 526 lock_delay_arg_init(&lda, &sx_delay); 527 #elif defined(KDTRACE_HOOKS) 528 lock_delay_arg_init(&lda, NULL); 529 #endif 530 531 if (__predict_false(x == SX_LOCK_UNLOCKED)) 532 x = SX_READ_VALUE(sx); 533 534 /* If we already hold an exclusive lock, then recurse. */ 535 if (__predict_false(lv_sx_owner(x) == (struct thread *)tid)) { 536 KASSERT((sx->lock_object.lo_flags & LO_RECURSABLE) != 0, 537 ("_sx_xlock_hard: recursed on non-recursive sx %s @ %s:%d\n", 538 sx->lock_object.lo_name, file, line)); 539 sx->sx_recurse++; 540 atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 541 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 542 CTR2(KTR_LOCK, "%s: %p recursing", __func__, sx); 543 return (0); 544 } 545 546 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 547 CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, 548 sx->lock_object.lo_name, (void *)sx->sx_lock, file, line); 549 550 #ifdef KDTRACE_HOOKS 551 all_time -= lockstat_nsecs(&sx->lock_object); 552 state = x; 553 #endif 554 for (;;) { 555 if (x == SX_LOCK_UNLOCKED) { 556 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid)) 557 break; 558 continue; 559 } 560 #ifdef KDTRACE_HOOKS 561 lda.spin_cnt++; 562 #endif 563 #ifdef HWPMC_HOOKS 564 PMC_SOFT_CALL( , , lock, failed); 565 #endif 566 lock_profile_obtain_lock_failed(&sx->lock_object, &contested, 567 &waittime); 568 #ifdef ADAPTIVE_SX 569 /* 570 * If the lock is write locked and the owner is 571 * running on another CPU, spin until the owner stops 572 * running or the state of the lock changes. 573 */ 574 if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 575 if ((x & SX_LOCK_SHARED) == 0) { 576 owner = lv_sx_owner(x); 577 if (TD_IS_RUNNING(owner)) { 578 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 579 CTR3(KTR_LOCK, 580 "%s: spinning on %p held by %p", 581 __func__, sx, owner); 582 KTR_STATE1(KTR_SCHED, "thread", 583 sched_tdname(curthread), "spinning", 584 "lockname:\"%s\"", 585 sx->lock_object.lo_name); 586 GIANT_SAVE(); 587 do { 588 lock_delay(&lda); 589 x = SX_READ_VALUE(sx); 590 owner = lv_sx_owner(x); 591 } while (owner != NULL && 592 TD_IS_RUNNING(owner)); 593 KTR_STATE0(KTR_SCHED, "thread", 594 sched_tdname(curthread), "running"); 595 continue; 596 } 597 } else if (SX_SHARERS(x) && spintries < asx_retries) { 598 KTR_STATE1(KTR_SCHED, "thread", 599 sched_tdname(curthread), "spinning", 600 "lockname:\"%s\"", sx->lock_object.lo_name); 601 GIANT_SAVE(); 602 spintries++; 603 for (i = 0; i < asx_loops; i += n) { 604 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 605 CTR4(KTR_LOCK, 606 "%s: shared spinning on %p with %u and %u", 607 __func__, sx, spintries, i); 608 n = SX_SHARERS(x); 609 lock_delay_spin(n); 610 x = SX_READ_VALUE(sx); 611 if ((x & SX_LOCK_SHARED) == 0 || 612 SX_SHARERS(x) == 0) 613 break; 614 } 615 #ifdef KDTRACE_HOOKS 616 lda.spin_cnt += i; 617 #endif 618 KTR_STATE0(KTR_SCHED, "thread", 619 sched_tdname(curthread), "running"); 620 if (i != asx_loops) 621 continue; 622 } 623 } 624 #endif 625 626 sleepq_lock(&sx->lock_object); 627 x = SX_READ_VALUE(sx); 628 629 /* 630 * If the lock was released while spinning on the 631 * sleep queue chain lock, try again. 632 */ 633 if (x == SX_LOCK_UNLOCKED) { 634 sleepq_release(&sx->lock_object); 635 continue; 636 } 637 638 #ifdef ADAPTIVE_SX 639 /* 640 * The current lock owner might have started executing 641 * on another CPU (or the lock could have changed 642 * owners) while we were waiting on the sleep queue 643 * chain lock. If so, drop the sleep queue lock and try 644 * again. 645 */ 646 if (!(x & SX_LOCK_SHARED) && 647 (sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 648 owner = (struct thread *)SX_OWNER(x); 649 if (TD_IS_RUNNING(owner)) { 650 sleepq_release(&sx->lock_object); 651 continue; 652 } 653 } 654 #endif 655 656 /* 657 * If an exclusive lock was released with both shared 658 * and exclusive waiters and a shared waiter hasn't 659 * woken up and acquired the lock yet, sx_lock will be 660 * set to SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS. 661 * If we see that value, try to acquire it once. Note 662 * that we have to preserve SX_LOCK_EXCLUSIVE_WAITERS 663 * as there are other exclusive waiters still. If we 664 * fail, restart the loop. 665 */ 666 if (x == (SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS)) { 667 if (atomic_cmpset_acq_ptr(&sx->sx_lock, 668 SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS, 669 tid | SX_LOCK_EXCLUSIVE_WAITERS)) { 670 sleepq_release(&sx->lock_object); 671 CTR2(KTR_LOCK, "%s: %p claimed by new writer", 672 __func__, sx); 673 break; 674 } 675 sleepq_release(&sx->lock_object); 676 x = SX_READ_VALUE(sx); 677 continue; 678 } 679 680 /* 681 * Try to set the SX_LOCK_EXCLUSIVE_WAITERS. If we fail, 682 * than loop back and retry. 683 */ 684 if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) { 685 if (!atomic_cmpset_ptr(&sx->sx_lock, x, 686 x | SX_LOCK_EXCLUSIVE_WAITERS)) { 687 sleepq_release(&sx->lock_object); 688 x = SX_READ_VALUE(sx); 689 continue; 690 } 691 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 692 CTR2(KTR_LOCK, "%s: %p set excl waiters flag", 693 __func__, sx); 694 } 695 696 /* 697 * Since we have been unable to acquire the exclusive 698 * lock and the exclusive waiters flag is set, we have 699 * to sleep. 700 */ 701 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 702 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 703 __func__, sx); 704 705 #ifdef KDTRACE_HOOKS 706 sleep_time -= lockstat_nsecs(&sx->lock_object); 707 #endif 708 GIANT_SAVE(); 709 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 710 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 711 SLEEPQ_INTERRUPTIBLE : 0), SQ_EXCLUSIVE_QUEUE); 712 if (!(opts & SX_INTERRUPTIBLE)) 713 sleepq_wait(&sx->lock_object, 0); 714 else 715 error = sleepq_wait_sig(&sx->lock_object, 0); 716 #ifdef KDTRACE_HOOKS 717 sleep_time += lockstat_nsecs(&sx->lock_object); 718 sleep_cnt++; 719 #endif 720 if (error) { 721 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 722 CTR2(KTR_LOCK, 723 "%s: interruptible sleep by %p suspended by signal", 724 __func__, sx); 725 break; 726 } 727 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 728 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 729 __func__, sx); 730 x = SX_READ_VALUE(sx); 731 } 732 #ifdef KDTRACE_HOOKS 733 all_time += lockstat_nsecs(&sx->lock_object); 734 if (sleep_time) 735 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 736 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 737 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 738 if (lda.spin_cnt > sleep_cnt) 739 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 740 LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0, 741 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 742 #endif 743 if (!error) 744 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 745 contested, waittime, file, line, LOCKSTAT_WRITER); 746 GIANT_RESTORE(); 747 return (error); 748 } 749 750 /* 751 * This function represents the so-called 'hard case' for sx_xunlock 752 * operation. All 'easy case' failures are redirected to this. Note 753 * that ideally this would be a static function, but it needs to be 754 * accessible from at least sx.h. 755 */ 756 void 757 _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int line) 758 { 759 uintptr_t x; 760 int queue, wakeup_swapper; 761 762 if (SCHEDULER_STOPPED()) 763 return; 764 765 MPASS(!(sx->sx_lock & SX_LOCK_SHARED)); 766 767 x = SX_READ_VALUE(sx); 768 if (x & SX_LOCK_RECURSED) { 769 /* The lock is recursed, unrecurse one level. */ 770 if ((--sx->sx_recurse) == 0) 771 atomic_clear_ptr(&sx->sx_lock, SX_LOCK_RECURSED); 772 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 773 CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, sx); 774 return; 775 } 776 777 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_WRITER); 778 if (x == tid && 779 atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED)) 780 return; 781 782 MPASS(sx->sx_lock & (SX_LOCK_SHARED_WAITERS | 783 SX_LOCK_EXCLUSIVE_WAITERS)); 784 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 785 CTR2(KTR_LOCK, "%s: %p contested", __func__, sx); 786 787 sleepq_lock(&sx->lock_object); 788 x = SX_LOCK_UNLOCKED; 789 790 /* 791 * The wake up algorithm here is quite simple and probably not 792 * ideal. It gives precedence to shared waiters if they are 793 * present. For this condition, we have to preserve the 794 * state of the exclusive waiters flag. 795 * If interruptible sleeps left the shared queue empty avoid a 796 * starvation for the threads sleeping on the exclusive queue by giving 797 * them precedence and cleaning up the shared waiters bit anyway. 798 */ 799 if ((sx->sx_lock & SX_LOCK_SHARED_WAITERS) != 0 && 800 sleepq_sleepcnt(&sx->lock_object, SQ_SHARED_QUEUE) != 0) { 801 queue = SQ_SHARED_QUEUE; 802 x |= (sx->sx_lock & SX_LOCK_EXCLUSIVE_WAITERS); 803 } else 804 queue = SQ_EXCLUSIVE_QUEUE; 805 806 /* Wake up all the waiters for the specific queue. */ 807 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 808 CTR3(KTR_LOCK, "%s: %p waking up all threads on %s queue", 809 __func__, sx, queue == SQ_SHARED_QUEUE ? "shared" : 810 "exclusive"); 811 atomic_store_rel_ptr(&sx->sx_lock, x); 812 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 0, 813 queue); 814 sleepq_release(&sx->lock_object); 815 if (wakeup_swapper) 816 kick_proc0(); 817 } 818 819 static bool __always_inline 820 __sx_slock_try(struct sx *sx, uintptr_t *xp, const char *file, int line) 821 { 822 823 /* 824 * If no other thread has an exclusive lock then try to bump up 825 * the count of sharers. Since we have to preserve the state 826 * of SX_LOCK_EXCLUSIVE_WAITERS, if we fail to acquire the 827 * shared lock loop back and retry. 828 */ 829 while (*xp & SX_LOCK_SHARED) { 830 MPASS(!(*xp & SX_LOCK_SHARED_WAITERS)); 831 if (atomic_fcmpset_acq_ptr(&sx->sx_lock, xp, 832 *xp + SX_ONE_SHARER)) { 833 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 834 CTR4(KTR_LOCK, "%s: %p succeed %p -> %p", 835 __func__, sx, (void *)*xp, 836 (void *)(*xp + SX_ONE_SHARER)); 837 return (true); 838 } 839 } 840 return (false); 841 } 842 843 static int __noinline 844 _sx_slock_hard(struct sx *sx, int opts, const char *file, int line, uintptr_t x) 845 { 846 GIANT_DECLARE; 847 #ifdef ADAPTIVE_SX 848 volatile struct thread *owner; 849 #endif 850 #ifdef LOCK_PROFILING 851 uint64_t waittime = 0; 852 int contested = 0; 853 #endif 854 int error = 0; 855 #if defined(ADAPTIVE_SX) || defined(KDTRACE_HOOKS) 856 struct lock_delay_arg lda; 857 #endif 858 #ifdef KDTRACE_HOOKS 859 uintptr_t state; 860 u_int sleep_cnt = 0; 861 int64_t sleep_time = 0; 862 int64_t all_time = 0; 863 #endif 864 865 if (SCHEDULER_STOPPED()) 866 return (0); 867 868 #if defined(ADAPTIVE_SX) 869 lock_delay_arg_init(&lda, &sx_delay); 870 #elif defined(KDTRACE_HOOKS) 871 lock_delay_arg_init(&lda, NULL); 872 #endif 873 #ifdef KDTRACE_HOOKS 874 all_time -= lockstat_nsecs(&sx->lock_object); 875 state = x; 876 #endif 877 878 /* 879 * As with rwlocks, we don't make any attempt to try to block 880 * shared locks once there is an exclusive waiter. 881 */ 882 for (;;) { 883 if (__sx_slock_try(sx, &x, file, line)) 884 break; 885 #ifdef KDTRACE_HOOKS 886 lda.spin_cnt++; 887 #endif 888 889 #ifdef HWPMC_HOOKS 890 PMC_SOFT_CALL( , , lock, failed); 891 #endif 892 lock_profile_obtain_lock_failed(&sx->lock_object, &contested, 893 &waittime); 894 895 #ifdef ADAPTIVE_SX 896 /* 897 * If the owner is running on another CPU, spin until 898 * the owner stops running or the state of the lock 899 * changes. 900 */ 901 if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 902 owner = lv_sx_owner(x); 903 if (TD_IS_RUNNING(owner)) { 904 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 905 CTR3(KTR_LOCK, 906 "%s: spinning on %p held by %p", 907 __func__, sx, owner); 908 KTR_STATE1(KTR_SCHED, "thread", 909 sched_tdname(curthread), "spinning", 910 "lockname:\"%s\"", sx->lock_object.lo_name); 911 GIANT_SAVE(); 912 do { 913 lock_delay(&lda); 914 x = SX_READ_VALUE(sx); 915 owner = lv_sx_owner(x); 916 } while (owner != NULL && TD_IS_RUNNING(owner)); 917 KTR_STATE0(KTR_SCHED, "thread", 918 sched_tdname(curthread), "running"); 919 continue; 920 } 921 } 922 #endif 923 924 /* 925 * Some other thread already has an exclusive lock, so 926 * start the process of blocking. 927 */ 928 sleepq_lock(&sx->lock_object); 929 x = SX_READ_VALUE(sx); 930 931 /* 932 * The lock could have been released while we spun. 933 * In this case loop back and retry. 934 */ 935 if (x & SX_LOCK_SHARED) { 936 sleepq_release(&sx->lock_object); 937 continue; 938 } 939 940 #ifdef ADAPTIVE_SX 941 /* 942 * If the owner is running on another CPU, spin until 943 * the owner stops running or the state of the lock 944 * changes. 945 */ 946 if (!(x & SX_LOCK_SHARED) && 947 (sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { 948 owner = (struct thread *)SX_OWNER(x); 949 if (TD_IS_RUNNING(owner)) { 950 sleepq_release(&sx->lock_object); 951 x = SX_READ_VALUE(sx); 952 continue; 953 } 954 } 955 #endif 956 957 /* 958 * Try to set the SX_LOCK_SHARED_WAITERS flag. If we 959 * fail to set it drop the sleep queue lock and loop 960 * back. 961 */ 962 if (!(x & SX_LOCK_SHARED_WAITERS)) { 963 if (!atomic_cmpset_ptr(&sx->sx_lock, x, 964 x | SX_LOCK_SHARED_WAITERS)) { 965 sleepq_release(&sx->lock_object); 966 x = SX_READ_VALUE(sx); 967 continue; 968 } 969 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 970 CTR2(KTR_LOCK, "%s: %p set shared waiters flag", 971 __func__, sx); 972 } 973 974 /* 975 * Since we have been unable to acquire the shared lock, 976 * we have to sleep. 977 */ 978 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 979 CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", 980 __func__, sx); 981 982 #ifdef KDTRACE_HOOKS 983 sleep_time -= lockstat_nsecs(&sx->lock_object); 984 #endif 985 GIANT_SAVE(); 986 sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, 987 SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? 988 SLEEPQ_INTERRUPTIBLE : 0), SQ_SHARED_QUEUE); 989 if (!(opts & SX_INTERRUPTIBLE)) 990 sleepq_wait(&sx->lock_object, 0); 991 else 992 error = sleepq_wait_sig(&sx->lock_object, 0); 993 #ifdef KDTRACE_HOOKS 994 sleep_time += lockstat_nsecs(&sx->lock_object); 995 sleep_cnt++; 996 #endif 997 if (error) { 998 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 999 CTR2(KTR_LOCK, 1000 "%s: interruptible sleep by %p suspended by signal", 1001 __func__, sx); 1002 break; 1003 } 1004 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1005 CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", 1006 __func__, sx); 1007 x = SX_READ_VALUE(sx); 1008 } 1009 #ifdef KDTRACE_HOOKS 1010 all_time += lockstat_nsecs(&sx->lock_object); 1011 if (sleep_time) 1012 LOCKSTAT_RECORD4(sx__block, sx, sleep_time, 1013 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1014 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1015 if (lda.spin_cnt > sleep_cnt) 1016 LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time, 1017 LOCKSTAT_READER, (state & SX_LOCK_SHARED) == 0, 1018 (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state)); 1019 #endif 1020 if (error == 0) { 1021 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, 1022 contested, waittime, file, line, LOCKSTAT_READER); 1023 } 1024 GIANT_RESTORE(); 1025 return (error); 1026 } 1027 1028 int 1029 _sx_slock(struct sx *sx, int opts, const char *file, int line) 1030 { 1031 uintptr_t x; 1032 int error; 1033 1034 KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() || 1035 !TD_IS_IDLETHREAD(curthread), 1036 ("sx_slock() by idle thread %p on sx %s @ %s:%d", 1037 curthread, sx->lock_object.lo_name, file, line)); 1038 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 1039 ("sx_slock() of destroyed sx @ %s:%d", file, line)); 1040 WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER, file, line, NULL); 1041 1042 error = 0; 1043 x = SX_READ_VALUE(sx); 1044 if (__predict_false(LOCKSTAT_OOL_PROFILE_ENABLED(sx__acquire) || 1045 !__sx_slock_try(sx, &x, file, line))) 1046 error = _sx_slock_hard(sx, opts, file, line, x); 1047 if (error == 0) { 1048 LOCK_LOG_LOCK("SLOCK", &sx->lock_object, 0, 0, file, line); 1049 WITNESS_LOCK(&sx->lock_object, 0, file, line); 1050 TD_LOCKS_INC(curthread); 1051 } 1052 return (error); 1053 } 1054 1055 static bool __always_inline 1056 _sx_sunlock_try(struct sx *sx, uintptr_t *xp) 1057 { 1058 1059 for (;;) { 1060 /* 1061 * We should never have sharers while at least one thread 1062 * holds a shared lock. 1063 */ 1064 KASSERT(!(*xp & SX_LOCK_SHARED_WAITERS), 1065 ("%s: waiting sharers", __func__)); 1066 1067 /* 1068 * See if there is more than one shared lock held. If 1069 * so, just drop one and return. 1070 */ 1071 if (SX_SHARERS(*xp) > 1) { 1072 if (atomic_fcmpset_rel_ptr(&sx->sx_lock, xp, 1073 *xp - SX_ONE_SHARER)) { 1074 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1075 CTR4(KTR_LOCK, 1076 "%s: %p succeeded %p -> %p", 1077 __func__, sx, (void *)*xp, 1078 (void *)(*xp - SX_ONE_SHARER)); 1079 return (true); 1080 } 1081 continue; 1082 } 1083 1084 /* 1085 * If there aren't any waiters for an exclusive lock, 1086 * then try to drop it quickly. 1087 */ 1088 if (!(*xp & SX_LOCK_EXCLUSIVE_WAITERS)) { 1089 MPASS(*xp == SX_SHARERS_LOCK(1)); 1090 *xp = SX_SHARERS_LOCK(1); 1091 if (atomic_fcmpset_rel_ptr(&sx->sx_lock, 1092 xp, SX_LOCK_UNLOCKED)) { 1093 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1094 CTR2(KTR_LOCK, "%s: %p last succeeded", 1095 __func__, sx); 1096 return (true); 1097 } 1098 continue; 1099 } 1100 break; 1101 } 1102 return (false); 1103 } 1104 1105 static void __noinline 1106 _sx_sunlock_hard(struct sx *sx, uintptr_t x, const char *file, int line) 1107 { 1108 int wakeup_swapper; 1109 1110 if (SCHEDULER_STOPPED()) 1111 return; 1112 1113 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_READER); 1114 1115 for (;;) { 1116 if (_sx_sunlock_try(sx, &x)) 1117 break; 1118 1119 /* 1120 * At this point, there should just be one sharer with 1121 * exclusive waiters. 1122 */ 1123 MPASS(x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS)); 1124 1125 sleepq_lock(&sx->lock_object); 1126 1127 /* 1128 * Wake up semantic here is quite simple: 1129 * Just wake up all the exclusive waiters. 1130 * Note that the state of the lock could have changed, 1131 * so if it fails loop back and retry. 1132 */ 1133 if (!atomic_cmpset_rel_ptr(&sx->sx_lock, 1134 SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS, 1135 SX_LOCK_UNLOCKED)) { 1136 sleepq_release(&sx->lock_object); 1137 x = SX_READ_VALUE(sx); 1138 continue; 1139 } 1140 if (LOCK_LOG_TEST(&sx->lock_object, 0)) 1141 CTR2(KTR_LOCK, "%s: %p waking up all thread on" 1142 "exclusive queue", __func__, sx); 1143 wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 1144 0, SQ_EXCLUSIVE_QUEUE); 1145 sleepq_release(&sx->lock_object); 1146 if (wakeup_swapper) 1147 kick_proc0(); 1148 break; 1149 } 1150 } 1151 1152 void 1153 _sx_sunlock(struct sx *sx, const char *file, int line) 1154 { 1155 uintptr_t x; 1156 1157 KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, 1158 ("sx_sunlock() of destroyed sx @ %s:%d", file, line)); 1159 _sx_assert(sx, SA_SLOCKED, file, line); 1160 WITNESS_UNLOCK(&sx->lock_object, 0, file, line); 1161 LOCK_LOG_LOCK("SUNLOCK", &sx->lock_object, 0, 0, file, line); 1162 1163 x = SX_READ_VALUE(sx); 1164 if (__predict_false(LOCKSTAT_OOL_PROFILE_ENABLED(sx__release) || 1165 !_sx_sunlock_try(sx, &x))) 1166 _sx_sunlock_hard(sx, x, file, line); 1167 1168 TD_LOCKS_DEC(curthread); 1169 } 1170 1171 #ifdef INVARIANT_SUPPORT 1172 #ifndef INVARIANTS 1173 #undef _sx_assert 1174 #endif 1175 1176 /* 1177 * In the non-WITNESS case, sx_assert() can only detect that at least 1178 * *some* thread owns an slock, but it cannot guarantee that *this* 1179 * thread owns an slock. 1180 */ 1181 void 1182 _sx_assert(const struct sx *sx, int what, const char *file, int line) 1183 { 1184 #ifndef WITNESS 1185 int slocked = 0; 1186 #endif 1187 1188 if (panicstr != NULL) 1189 return; 1190 switch (what) { 1191 case SA_SLOCKED: 1192 case SA_SLOCKED | SA_NOTRECURSED: 1193 case SA_SLOCKED | SA_RECURSED: 1194 #ifndef WITNESS 1195 slocked = 1; 1196 /* FALLTHROUGH */ 1197 #endif 1198 case SA_LOCKED: 1199 case SA_LOCKED | SA_NOTRECURSED: 1200 case SA_LOCKED | SA_RECURSED: 1201 #ifdef WITNESS 1202 witness_assert(&sx->lock_object, what, file, line); 1203 #else 1204 /* 1205 * If some other thread has an exclusive lock or we 1206 * have one and are asserting a shared lock, fail. 1207 * Also, if no one has a lock at all, fail. 1208 */ 1209 if (sx->sx_lock == SX_LOCK_UNLOCKED || 1210 (!(sx->sx_lock & SX_LOCK_SHARED) && (slocked || 1211 sx_xholder(sx) != curthread))) 1212 panic("Lock %s not %slocked @ %s:%d\n", 1213 sx->lock_object.lo_name, slocked ? "share " : "", 1214 file, line); 1215 1216 if (!(sx->sx_lock & SX_LOCK_SHARED)) { 1217 if (sx_recursed(sx)) { 1218 if (what & SA_NOTRECURSED) 1219 panic("Lock %s recursed @ %s:%d\n", 1220 sx->lock_object.lo_name, file, 1221 line); 1222 } else if (what & SA_RECURSED) 1223 panic("Lock %s not recursed @ %s:%d\n", 1224 sx->lock_object.lo_name, file, line); 1225 } 1226 #endif 1227 break; 1228 case SA_XLOCKED: 1229 case SA_XLOCKED | SA_NOTRECURSED: 1230 case SA_XLOCKED | SA_RECURSED: 1231 if (sx_xholder(sx) != curthread) 1232 panic("Lock %s not exclusively locked @ %s:%d\n", 1233 sx->lock_object.lo_name, file, line); 1234 if (sx_recursed(sx)) { 1235 if (what & SA_NOTRECURSED) 1236 panic("Lock %s recursed @ %s:%d\n", 1237 sx->lock_object.lo_name, file, line); 1238 } else if (what & SA_RECURSED) 1239 panic("Lock %s not recursed @ %s:%d\n", 1240 sx->lock_object.lo_name, file, line); 1241 break; 1242 case SA_UNLOCKED: 1243 #ifdef WITNESS 1244 witness_assert(&sx->lock_object, what, file, line); 1245 #else 1246 /* 1247 * If we hold an exclusve lock fail. We can't 1248 * reliably check to see if we hold a shared lock or 1249 * not. 1250 */ 1251 if (sx_xholder(sx) == curthread) 1252 panic("Lock %s exclusively locked @ %s:%d\n", 1253 sx->lock_object.lo_name, file, line); 1254 #endif 1255 break; 1256 default: 1257 panic("Unknown sx lock assertion: %d @ %s:%d", what, file, 1258 line); 1259 } 1260 } 1261 #endif /* INVARIANT_SUPPORT */ 1262 1263 #ifdef DDB 1264 static void 1265 db_show_sx(const struct lock_object *lock) 1266 { 1267 struct thread *td; 1268 const struct sx *sx; 1269 1270 sx = (const struct sx *)lock; 1271 1272 db_printf(" state: "); 1273 if (sx->sx_lock == SX_LOCK_UNLOCKED) 1274 db_printf("UNLOCKED\n"); 1275 else if (sx->sx_lock == SX_LOCK_DESTROYED) { 1276 db_printf("DESTROYED\n"); 1277 return; 1278 } else if (sx->sx_lock & SX_LOCK_SHARED) 1279 db_printf("SLOCK: %ju\n", (uintmax_t)SX_SHARERS(sx->sx_lock)); 1280 else { 1281 td = sx_xholder(sx); 1282 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1283 td->td_tid, td->td_proc->p_pid, td->td_name); 1284 if (sx_recursed(sx)) 1285 db_printf(" recursed: %d\n", sx->sx_recurse); 1286 } 1287 1288 db_printf(" waiters: "); 1289 switch(sx->sx_lock & 1290 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)) { 1291 case SX_LOCK_SHARED_WAITERS: 1292 db_printf("shared\n"); 1293 break; 1294 case SX_LOCK_EXCLUSIVE_WAITERS: 1295 db_printf("exclusive\n"); 1296 break; 1297 case SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS: 1298 db_printf("exclusive and shared\n"); 1299 break; 1300 default: 1301 db_printf("none\n"); 1302 } 1303 } 1304 1305 /* 1306 * Check to see if a thread that is blocked on a sleep queue is actually 1307 * blocked on an sx lock. If so, output some details and return true. 1308 * If the lock has an exclusive owner, return that in *ownerp. 1309 */ 1310 int 1311 sx_chain(struct thread *td, struct thread **ownerp) 1312 { 1313 struct sx *sx; 1314 1315 /* 1316 * Check to see if this thread is blocked on an sx lock. 1317 * First, we check the lock class. If that is ok, then we 1318 * compare the lock name against the wait message. 1319 */ 1320 sx = td->td_wchan; 1321 if (LOCK_CLASS(&sx->lock_object) != &lock_class_sx || 1322 sx->lock_object.lo_name != td->td_wmesg) 1323 return (0); 1324 1325 /* We think we have an sx lock, so output some details. */ 1326 db_printf("blocked on sx \"%s\" ", td->td_wmesg); 1327 *ownerp = sx_xholder(sx); 1328 if (sx->sx_lock & SX_LOCK_SHARED) 1329 db_printf("SLOCK (count %ju)\n", 1330 (uintmax_t)SX_SHARERS(sx->sx_lock)); 1331 else 1332 db_printf("XLOCK\n"); 1333 return (1); 1334 } 1335 #endif 1336