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