1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2008 Attilio Rao <attilio@FreeBSD.org> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice(s), this list of conditions and the following disclaimer as 12 * the first lines of this file unmodified other than the possible 13 * addition of one or more copyright notices. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice(s), this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 19 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 21 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 24 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 25 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 28 * DAMAGE. 29 */ 30 31 #include "opt_ddb.h" 32 #include "opt_hwpmc_hooks.h" 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include <sys/param.h> 38 #include <sys/kdb.h> 39 #include <sys/ktr.h> 40 #include <sys/lock.h> 41 #include <sys/lock_profile.h> 42 #include <sys/lockmgr.h> 43 #include <sys/mutex.h> 44 #include <sys/proc.h> 45 #include <sys/sleepqueue.h> 46 #ifdef DEBUG_LOCKS 47 #include <sys/stack.h> 48 #endif 49 #include <sys/sysctl.h> 50 #include <sys/systm.h> 51 52 #include <machine/cpu.h> 53 54 #ifdef DDB 55 #include <ddb/ddb.h> 56 #endif 57 58 #ifdef HWPMC_HOOKS 59 #include <sys/pmckern.h> 60 PMC_SOFT_DECLARE( , , lock, failed); 61 #endif 62 63 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) == 64 (LK_ADAPTIVE | LK_NOSHARE)); 65 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED & 66 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS))); 67 68 #define SQ_EXCLUSIVE_QUEUE 0 69 #define SQ_SHARED_QUEUE 1 70 71 #ifndef INVARIANTS 72 #define _lockmgr_assert(lk, what, file, line) 73 #endif 74 75 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 76 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 77 78 #ifndef DEBUG_LOCKS 79 #define STACK_PRINT(lk) 80 #define STACK_SAVE(lk) 81 #define STACK_ZERO(lk) 82 #else 83 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 84 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 85 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 86 #endif 87 88 #define LOCK_LOG2(lk, string, arg1, arg2) \ 89 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 90 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 91 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 92 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 93 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 94 95 #define GIANT_DECLARE \ 96 int _i = 0; \ 97 WITNESS_SAVE_DECL(Giant) 98 #define GIANT_RESTORE() do { \ 99 if (_i > 0) { \ 100 while (_i--) \ 101 mtx_lock(&Giant); \ 102 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 103 } \ 104 } while (0) 105 #define GIANT_SAVE() do { \ 106 if (mtx_owned(&Giant)) { \ 107 WITNESS_SAVE(&Giant.lock_object, Giant); \ 108 while (mtx_owned(&Giant)) { \ 109 _i++; \ 110 mtx_unlock(&Giant); \ 111 } \ 112 } \ 113 } while (0) 114 115 #define LK_CAN_SHARE(x, flags) \ 116 (((x) & LK_SHARE) && \ 117 (((x) & (LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) == 0 || \ 118 (curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) || \ 119 (curthread->td_pflags & TDP_DEADLKTREAT))) 120 #define LK_TRYOP(x) \ 121 ((x) & LK_NOWAIT) 122 123 #define LK_CAN_WITNESS(x) \ 124 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 125 #define LK_TRYWIT(x) \ 126 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 127 128 #define LK_CAN_ADAPT(lk, f) \ 129 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 130 ((f) & LK_SLEEPFAIL) == 0) 131 132 #define lockmgr_disowned(lk) \ 133 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 134 135 #define lockmgr_xlocked(lk) \ 136 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 137 138 static void assert_lockmgr(const struct lock_object *lock, int how); 139 #ifdef DDB 140 static void db_show_lockmgr(const struct lock_object *lock); 141 #endif 142 static void lock_lockmgr(struct lock_object *lock, uintptr_t how); 143 #ifdef KDTRACE_HOOKS 144 static int owner_lockmgr(const struct lock_object *lock, 145 struct thread **owner); 146 #endif 147 static uintptr_t unlock_lockmgr(struct lock_object *lock); 148 149 struct lock_class lock_class_lockmgr = { 150 .lc_name = "lockmgr", 151 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 152 .lc_assert = assert_lockmgr, 153 #ifdef DDB 154 .lc_ddb_show = db_show_lockmgr, 155 #endif 156 .lc_lock = lock_lockmgr, 157 .lc_unlock = unlock_lockmgr, 158 #ifdef KDTRACE_HOOKS 159 .lc_owner = owner_lockmgr, 160 #endif 161 }; 162 163 static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp, 164 int flags); 165 static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t x); 166 167 static void 168 lockmgr_note_shared_acquire(struct lock *lk, int contested, 169 uint64_t waittime, const char *file, int line, int flags) 170 { 171 172 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime, 173 file, line); 174 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line); 175 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line); 176 TD_LOCKS_INC(curthread); 177 TD_SLOCKS_INC(curthread); 178 STACK_SAVE(lk); 179 } 180 181 static void 182 lockmgr_note_shared_release(struct lock *lk, const char *file, int line) 183 { 184 185 lock_profile_release_lock(&lk->lock_object); 186 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 187 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 188 TD_LOCKS_DEC(curthread); 189 TD_SLOCKS_DEC(curthread); 190 } 191 192 static void 193 lockmgr_note_exclusive_acquire(struct lock *lk, int contested, 194 uint64_t waittime, const char *file, int line, int flags) 195 { 196 197 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime, 198 file, line); 199 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line); 200 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, 201 line); 202 TD_LOCKS_INC(curthread); 203 STACK_SAVE(lk); 204 } 205 206 static void 207 lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line) 208 { 209 210 lock_profile_release_lock(&lk->lock_object); 211 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, 212 line); 213 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 214 TD_LOCKS_DEC(curthread); 215 } 216 217 static void 218 lockmgr_note_exclusive_upgrade(struct lock *lk, const char *file, int line, 219 int flags) 220 { 221 222 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 223 line); 224 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 225 LK_TRYWIT(flags), file, line); 226 TD_SLOCKS_DEC(curthread); 227 } 228 229 static __inline struct thread * 230 lockmgr_xholder(const struct lock *lk) 231 { 232 uintptr_t x; 233 234 x = lk->lk_lock; 235 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 236 } 237 238 /* 239 * It assumes sleepq_lock held and returns with this one unheld. 240 * It also assumes the generic interlock is sane and previously checked. 241 * If LK_INTERLOCK is specified the interlock is not reacquired after the 242 * sleep. 243 */ 244 static __inline int 245 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 246 const char *wmesg, int pri, int timo, int queue) 247 { 248 GIANT_DECLARE; 249 struct lock_class *class; 250 int catch, error; 251 252 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 253 catch = pri & PCATCH; 254 pri &= PRIMASK; 255 error = 0; 256 257 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 258 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 259 260 if (flags & LK_INTERLOCK) 261 class->lc_unlock(ilk); 262 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 263 lk->lk_exslpfail++; 264 GIANT_SAVE(); 265 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 266 SLEEPQ_INTERRUPTIBLE : 0), queue); 267 if ((flags & LK_TIMELOCK) && timo) 268 sleepq_set_timeout(&lk->lock_object, timo); 269 270 /* 271 * Decisional switch for real sleeping. 272 */ 273 if ((flags & LK_TIMELOCK) && timo && catch) 274 error = sleepq_timedwait_sig(&lk->lock_object, pri); 275 else if ((flags & LK_TIMELOCK) && timo) 276 error = sleepq_timedwait(&lk->lock_object, pri); 277 else if (catch) 278 error = sleepq_wait_sig(&lk->lock_object, pri); 279 else 280 sleepq_wait(&lk->lock_object, pri); 281 GIANT_RESTORE(); 282 if ((flags & LK_SLEEPFAIL) && error == 0) 283 error = ENOLCK; 284 285 return (error); 286 } 287 288 static __inline int 289 wakeupshlk(struct lock *lk, const char *file, int line) 290 { 291 uintptr_t v, x; 292 u_int realexslp; 293 int queue, wakeup_swapper; 294 295 wakeup_swapper = 0; 296 for (;;) { 297 x = lk->lk_lock; 298 if (lockmgr_sunlock_try(lk, x)) 299 break; 300 301 /* 302 * We should have a sharer with waiters, so enter the hard 303 * path in order to handle wakeups correctly. 304 */ 305 sleepq_lock(&lk->lock_object); 306 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 307 v = LK_UNLOCKED; 308 309 /* 310 * If the lock has exclusive waiters, give them preference in 311 * order to avoid deadlock with shared runners up. 312 * If interruptible sleeps left the exclusive queue empty 313 * avoid a starvation for the threads sleeping on the shared 314 * queue by giving them precedence and cleaning up the 315 * exclusive waiters bit anyway. 316 * Please note that lk_exslpfail count may be lying about 317 * the real number of waiters with the LK_SLEEPFAIL flag on 318 * because they may be used in conjunction with interruptible 319 * sleeps so lk_exslpfail might be considered an 'upper limit' 320 * bound, including the edge cases. 321 */ 322 realexslp = sleepq_sleepcnt(&lk->lock_object, 323 SQ_EXCLUSIVE_QUEUE); 324 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 325 if (lk->lk_exslpfail < realexslp) { 326 lk->lk_exslpfail = 0; 327 queue = SQ_EXCLUSIVE_QUEUE; 328 v |= (x & LK_SHARED_WAITERS); 329 } else { 330 lk->lk_exslpfail = 0; 331 LOCK_LOG2(lk, 332 "%s: %p has only LK_SLEEPFAIL sleepers", 333 __func__, lk); 334 LOCK_LOG2(lk, 335 "%s: %p waking up threads on the exclusive queue", 336 __func__, lk); 337 wakeup_swapper = 338 sleepq_broadcast(&lk->lock_object, 339 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 340 queue = SQ_SHARED_QUEUE; 341 } 342 343 } else { 344 345 /* 346 * Exclusive waiters sleeping with LK_SLEEPFAIL on 347 * and using interruptible sleeps/timeout may have 348 * left spourious lk_exslpfail counts on, so clean 349 * it up anyway. 350 */ 351 lk->lk_exslpfail = 0; 352 queue = SQ_SHARED_QUEUE; 353 } 354 355 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, 356 v)) { 357 sleepq_release(&lk->lock_object); 358 continue; 359 } 360 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 361 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 362 "exclusive"); 363 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 364 0, queue); 365 sleepq_release(&lk->lock_object); 366 break; 367 } 368 369 lockmgr_note_shared_release(lk, file, line); 370 return (wakeup_swapper); 371 } 372 373 static void 374 assert_lockmgr(const struct lock_object *lock, int what) 375 { 376 377 panic("lockmgr locks do not support assertions"); 378 } 379 380 static void 381 lock_lockmgr(struct lock_object *lock, uintptr_t how) 382 { 383 384 panic("lockmgr locks do not support sleep interlocking"); 385 } 386 387 static uintptr_t 388 unlock_lockmgr(struct lock_object *lock) 389 { 390 391 panic("lockmgr locks do not support sleep interlocking"); 392 } 393 394 #ifdef KDTRACE_HOOKS 395 static int 396 owner_lockmgr(const struct lock_object *lock, struct thread **owner) 397 { 398 399 panic("lockmgr locks do not support owner inquiring"); 400 } 401 #endif 402 403 void 404 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 405 { 406 int iflags; 407 408 MPASS((flags & ~LK_INIT_MASK) == 0); 409 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 410 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 411 &lk->lk_lock)); 412 413 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 414 if (flags & LK_CANRECURSE) 415 iflags |= LO_RECURSABLE; 416 if ((flags & LK_NODUP) == 0) 417 iflags |= LO_DUPOK; 418 if (flags & LK_NOPROFILE) 419 iflags |= LO_NOPROFILE; 420 if ((flags & LK_NOWITNESS) == 0) 421 iflags |= LO_WITNESS; 422 if (flags & LK_QUIET) 423 iflags |= LO_QUIET; 424 if (flags & LK_IS_VNODE) 425 iflags |= LO_IS_VNODE; 426 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 427 428 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 429 lk->lk_lock = LK_UNLOCKED; 430 lk->lk_recurse = 0; 431 lk->lk_exslpfail = 0; 432 lk->lk_timo = timo; 433 lk->lk_pri = pri; 434 STACK_ZERO(lk); 435 } 436 437 /* 438 * XXX: Gross hacks to manipulate external lock flags after 439 * initialization. Used for certain vnode and buf locks. 440 */ 441 void 442 lockallowshare(struct lock *lk) 443 { 444 445 lockmgr_assert(lk, KA_XLOCKED); 446 lk->lock_object.lo_flags &= ~LK_NOSHARE; 447 } 448 449 void 450 lockdisableshare(struct lock *lk) 451 { 452 453 lockmgr_assert(lk, KA_XLOCKED); 454 lk->lock_object.lo_flags |= LK_NOSHARE; 455 } 456 457 void 458 lockallowrecurse(struct lock *lk) 459 { 460 461 lockmgr_assert(lk, KA_XLOCKED); 462 lk->lock_object.lo_flags |= LO_RECURSABLE; 463 } 464 465 void 466 lockdisablerecurse(struct lock *lk) 467 { 468 469 lockmgr_assert(lk, KA_XLOCKED); 470 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 471 } 472 473 void 474 lockdestroy(struct lock *lk) 475 { 476 477 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 478 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 479 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 480 lock_destroy(&lk->lock_object); 481 } 482 483 static bool __always_inline 484 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags) 485 { 486 487 /* 488 * If no other thread has an exclusive lock, or 489 * no exclusive waiter is present, bump the count of 490 * sharers. Since we have to preserve the state of 491 * waiters, if we fail to acquire the shared lock 492 * loop back and retry. 493 */ 494 *xp = lk->lk_lock; 495 while (LK_CAN_SHARE(*xp, flags)) { 496 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp, 497 *xp + LK_ONE_SHARER)) { 498 return (true); 499 } 500 } 501 return (false); 502 } 503 504 static bool __always_inline 505 lockmgr_sunlock_try(struct lock *lk, uintptr_t x) 506 { 507 508 for (;;) { 509 /* 510 * If there is more than one shared lock held, just drop one 511 * and return. 512 */ 513 if (LK_SHARERS(x) > 1) { 514 if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, 515 x - LK_ONE_SHARER)) 516 return (true); 517 continue; 518 } 519 520 /* 521 * If there are not waiters on the exclusive queue, drop the 522 * lock quickly. 523 */ 524 if ((x & LK_ALL_WAITERS) == 0) { 525 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == 526 LK_SHARERS_LOCK(1)); 527 if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, 528 LK_UNLOCKED)) 529 return (true); 530 continue; 531 } 532 break; 533 } 534 return (false); 535 } 536 537 int 538 lockmgr_lock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk, 539 const char *file, int line) 540 { 541 struct lock_class *class; 542 uintptr_t x, v, tid; 543 u_int op; 544 bool locked; 545 546 op = flags & LK_TYPE_MASK; 547 locked = false; 548 switch (op) { 549 case LK_SHARED: 550 if (LK_CAN_WITNESS(flags)) 551 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 552 file, line, flags & LK_INTERLOCK ? ilk : NULL); 553 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE)) 554 break; 555 if (lockmgr_slock_try(lk, &x, flags)) { 556 lockmgr_note_shared_acquire(lk, 0, 0, 557 file, line, flags); 558 locked = true; 559 } 560 break; 561 case LK_EXCLUSIVE: 562 if (LK_CAN_WITNESS(flags)) 563 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 564 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 565 ilk : NULL); 566 tid = (uintptr_t)curthread; 567 if (lk->lk_lock == LK_UNLOCKED && 568 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 569 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line, 570 flags); 571 locked = true; 572 } 573 break; 574 case LK_UPGRADE: 575 case LK_TRYUPGRADE: 576 _lockmgr_assert(lk, KA_SLOCKED, file, line); 577 tid = (uintptr_t)curthread; 578 v = lk->lk_lock; 579 x = v & LK_ALL_WAITERS; 580 v &= LK_EXCLUSIVE_SPINNERS; 581 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 582 tid | x)) { 583 lockmgr_note_exclusive_upgrade(lk, file, line, flags); 584 locked = true; 585 } 586 break; 587 default: 588 break; 589 } 590 if (__predict_true(locked)) { 591 if (__predict_false(flags & LK_INTERLOCK)) { 592 class = LOCK_CLASS(ilk); 593 class->lc_unlock(ilk); 594 } 595 return (0); 596 } else { 597 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT, 598 LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line)); 599 } 600 } 601 602 int 603 lockmgr_unlock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk) 604 { 605 struct lock_class *class; 606 uintptr_t x, tid; 607 bool unlocked; 608 const char *file; 609 int line; 610 611 file = __FILE__; 612 line = __LINE__; 613 614 _lockmgr_assert(lk, KA_LOCKED, file, line); 615 unlocked = false; 616 x = lk->lk_lock; 617 if (__predict_true(x & LK_SHARE) != 0) { 618 if (lockmgr_sunlock_try(lk, x)) { 619 lockmgr_note_shared_release(lk, file, line); 620 unlocked = true; 621 } 622 } else { 623 tid = (uintptr_t)curthread; 624 if (!lockmgr_recursed(lk) && 625 atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) { 626 lockmgr_note_exclusive_release(lk, file, line); 627 unlocked = true; 628 } 629 } 630 if (__predict_true(unlocked)) { 631 if (__predict_false(flags & LK_INTERLOCK)) { 632 class = LOCK_CLASS(ilk); 633 class->lc_unlock(ilk); 634 } 635 return (0); 636 } else { 637 return (__lockmgr_args(lk, flags | LK_RELEASE, ilk, LK_WMESG_DEFAULT, 638 LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, LOCK_FILE, LOCK_LINE)); 639 } 640 } 641 642 int 643 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 644 const char *wmesg, int pri, int timo, const char *file, int line) 645 { 646 GIANT_DECLARE; 647 struct lock_class *class; 648 const char *iwmesg; 649 uintptr_t tid, v, x; 650 u_int op, realexslp; 651 int error, ipri, itimo, queue, wakeup_swapper; 652 #ifdef LOCK_PROFILING 653 uint64_t waittime = 0; 654 int contested = 0; 655 #endif 656 657 error = 0; 658 tid = (uintptr_t)curthread; 659 op = (flags & LK_TYPE_MASK); 660 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 661 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 662 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 663 664 MPASS((flags & ~LK_TOTAL_MASK) == 0); 665 KASSERT((op & (op - 1)) == 0, 666 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 667 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 668 (op != LK_DOWNGRADE && op != LK_RELEASE), 669 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 670 __func__, file, line)); 671 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 672 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 673 __func__, file, line)); 674 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 675 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 676 lk->lock_object.lo_name, file, line)); 677 678 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 679 if (panicstr != NULL) { 680 if (flags & LK_INTERLOCK) 681 class->lc_unlock(ilk); 682 return (0); 683 } 684 685 if (lk->lock_object.lo_flags & LK_NOSHARE) { 686 switch (op) { 687 case LK_SHARED: 688 op = LK_EXCLUSIVE; 689 break; 690 case LK_UPGRADE: 691 case LK_TRYUPGRADE: 692 case LK_DOWNGRADE: 693 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 694 file, line); 695 if (flags & LK_INTERLOCK) 696 class->lc_unlock(ilk); 697 return (0); 698 } 699 } 700 701 wakeup_swapper = 0; 702 switch (op) { 703 case LK_SHARED: 704 if (LK_CAN_WITNESS(flags)) 705 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 706 file, line, flags & LK_INTERLOCK ? ilk : NULL); 707 for (;;) { 708 if (lockmgr_slock_try(lk, &x, flags)) 709 break; 710 #ifdef HWPMC_HOOKS 711 PMC_SOFT_CALL( , , lock, failed); 712 #endif 713 lock_profile_obtain_lock_failed(&lk->lock_object, 714 &contested, &waittime); 715 716 /* 717 * If the lock is already held by curthread in 718 * exclusive way avoid a deadlock. 719 */ 720 if (LK_HOLDER(x) == tid) { 721 LOCK_LOG2(lk, 722 "%s: %p already held in exclusive mode", 723 __func__, lk); 724 error = EDEADLK; 725 break; 726 } 727 728 /* 729 * If the lock is expected to not sleep just give up 730 * and return. 731 */ 732 if (LK_TRYOP(flags)) { 733 LOCK_LOG2(lk, "%s: %p fails the try operation", 734 __func__, lk); 735 error = EBUSY; 736 break; 737 } 738 739 /* 740 * Acquire the sleepqueue chain lock because we 741 * probabilly will need to manipulate waiters flags. 742 */ 743 sleepq_lock(&lk->lock_object); 744 x = lk->lk_lock; 745 746 /* 747 * if the lock can be acquired in shared mode, try 748 * again. 749 */ 750 if (LK_CAN_SHARE(x, flags)) { 751 sleepq_release(&lk->lock_object); 752 continue; 753 } 754 755 /* 756 * Try to set the LK_SHARED_WAITERS flag. If we fail, 757 * loop back and retry. 758 */ 759 if ((x & LK_SHARED_WAITERS) == 0) { 760 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 761 x | LK_SHARED_WAITERS)) { 762 sleepq_release(&lk->lock_object); 763 continue; 764 } 765 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 766 __func__, lk); 767 } 768 769 /* 770 * As far as we have been unable to acquire the 771 * shared lock and the shared waiters flag is set, 772 * we will sleep. 773 */ 774 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 775 SQ_SHARED_QUEUE); 776 flags &= ~LK_INTERLOCK; 777 if (error) { 778 LOCK_LOG3(lk, 779 "%s: interrupted sleep for %p with %d", 780 __func__, lk, error); 781 break; 782 } 783 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 784 __func__, lk); 785 } 786 if (error == 0) { 787 #ifdef LOCK_PROFILING 788 lockmgr_note_shared_acquire(lk, contested, waittime, 789 file, line, flags); 790 #else 791 lockmgr_note_shared_acquire(lk, 0, 0, file, line, 792 flags); 793 #endif 794 } 795 break; 796 case LK_UPGRADE: 797 case LK_TRYUPGRADE: 798 _lockmgr_assert(lk, KA_SLOCKED, file, line); 799 v = lk->lk_lock; 800 x = v & LK_ALL_WAITERS; 801 v &= LK_EXCLUSIVE_SPINNERS; 802 803 /* 804 * Try to switch from one shared lock to an exclusive one. 805 * We need to preserve waiters flags during the operation. 806 */ 807 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 808 tid | x)) { 809 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 810 line); 811 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 812 LK_TRYWIT(flags), file, line); 813 TD_SLOCKS_DEC(curthread); 814 break; 815 } 816 817 /* 818 * In LK_TRYUPGRADE mode, do not drop the lock, 819 * returning EBUSY instead. 820 */ 821 if (op == LK_TRYUPGRADE) { 822 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", 823 __func__, lk); 824 error = EBUSY; 825 break; 826 } 827 828 /* 829 * We have been unable to succeed in upgrading, so just 830 * give up the shared lock. 831 */ 832 wakeup_swapper |= wakeupshlk(lk, file, line); 833 834 /* FALLTHROUGH */ 835 case LK_EXCLUSIVE: 836 if (LK_CAN_WITNESS(flags)) 837 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 838 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 839 ilk : NULL); 840 841 /* 842 * If curthread already holds the lock and this one is 843 * allowed to recurse, simply recurse on it. 844 */ 845 if (lockmgr_xlocked(lk)) { 846 if ((flags & LK_CANRECURSE) == 0 && 847 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 848 849 /* 850 * If the lock is expected to not panic just 851 * give up and return. 852 */ 853 if (LK_TRYOP(flags)) { 854 LOCK_LOG2(lk, 855 "%s: %p fails the try operation", 856 __func__, lk); 857 error = EBUSY; 858 break; 859 } 860 if (flags & LK_INTERLOCK) 861 class->lc_unlock(ilk); 862 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 863 __func__, iwmesg, file, line); 864 } 865 lk->lk_recurse++; 866 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 867 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 868 lk->lk_recurse, file, line); 869 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 870 LK_TRYWIT(flags), file, line); 871 TD_LOCKS_INC(curthread); 872 break; 873 } 874 875 for (;;) { 876 if (lk->lk_lock == LK_UNLOCKED && 877 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 878 break; 879 #ifdef HWPMC_HOOKS 880 PMC_SOFT_CALL( , , lock, failed); 881 #endif 882 lock_profile_obtain_lock_failed(&lk->lock_object, 883 &contested, &waittime); 884 885 /* 886 * If the lock is expected to not sleep just give up 887 * and return. 888 */ 889 if (LK_TRYOP(flags)) { 890 LOCK_LOG2(lk, "%s: %p fails the try operation", 891 __func__, lk); 892 error = EBUSY; 893 break; 894 } 895 896 /* 897 * Acquire the sleepqueue chain lock because we 898 * probabilly will need to manipulate waiters flags. 899 */ 900 sleepq_lock(&lk->lock_object); 901 x = lk->lk_lock; 902 903 /* 904 * if the lock has been released while we spun on 905 * the sleepqueue chain lock just try again. 906 */ 907 if (x == LK_UNLOCKED) { 908 sleepq_release(&lk->lock_object); 909 continue; 910 } 911 912 /* 913 * The lock can be in the state where there is a 914 * pending queue of waiters, but still no owner. 915 * This happens when the lock is contested and an 916 * owner is going to claim the lock. 917 * If curthread is the one successfully acquiring it 918 * claim lock ownership and return, preserving waiters 919 * flags. 920 */ 921 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 922 if ((x & ~v) == LK_UNLOCKED) { 923 v &= ~LK_EXCLUSIVE_SPINNERS; 924 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 925 tid | v)) { 926 sleepq_release(&lk->lock_object); 927 LOCK_LOG2(lk, 928 "%s: %p claimed by a new writer", 929 __func__, lk); 930 break; 931 } 932 sleepq_release(&lk->lock_object); 933 continue; 934 } 935 936 /* 937 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 938 * fail, loop back and retry. 939 */ 940 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 941 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 942 x | LK_EXCLUSIVE_WAITERS)) { 943 sleepq_release(&lk->lock_object); 944 continue; 945 } 946 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 947 __func__, lk); 948 } 949 950 /* 951 * As far as we have been unable to acquire the 952 * exclusive lock and the exclusive waiters flag 953 * is set, we will sleep. 954 */ 955 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 956 SQ_EXCLUSIVE_QUEUE); 957 flags &= ~LK_INTERLOCK; 958 if (error) { 959 LOCK_LOG3(lk, 960 "%s: interrupted sleep for %p with %d", 961 __func__, lk, error); 962 break; 963 } 964 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 965 __func__, lk); 966 } 967 if (error == 0) { 968 #ifdef LOCK_PROFILING 969 lockmgr_note_exclusive_acquire(lk, contested, waittime, 970 file, line, flags); 971 #else 972 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line, 973 flags); 974 #endif 975 } 976 break; 977 case LK_DOWNGRADE: 978 _lockmgr_assert(lk, KA_XLOCKED, file, line); 979 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 980 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 981 982 /* 983 * Panic if the lock is recursed. 984 */ 985 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 986 if (flags & LK_INTERLOCK) 987 class->lc_unlock(ilk); 988 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 989 __func__, iwmesg, file, line); 990 } 991 TD_SLOCKS_INC(curthread); 992 993 /* 994 * In order to preserve waiters flags, just spin. 995 */ 996 for (;;) { 997 x = lk->lk_lock; 998 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 999 x &= LK_ALL_WAITERS; 1000 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1001 LK_SHARERS_LOCK(1) | x)) 1002 break; 1003 cpu_spinwait(); 1004 } 1005 break; 1006 case LK_RELEASE: 1007 _lockmgr_assert(lk, KA_LOCKED, file, line); 1008 x = lk->lk_lock; 1009 1010 if ((x & LK_SHARE) == 0) { 1011 1012 /* 1013 * As first option, treact the lock as if it has not 1014 * any waiter. 1015 * Fix-up the tid var if the lock has been disowned. 1016 */ 1017 if (LK_HOLDER(x) == LK_KERNPROC) 1018 tid = LK_KERNPROC; 1019 else { 1020 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 1021 file, line); 1022 TD_LOCKS_DEC(curthread); 1023 } 1024 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 1025 lk->lk_recurse, file, line); 1026 1027 /* 1028 * The lock is held in exclusive mode. 1029 * If the lock is recursed also, then unrecurse it. 1030 */ 1031 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 1032 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 1033 lk); 1034 lk->lk_recurse--; 1035 break; 1036 } 1037 if (tid != LK_KERNPROC) 1038 lock_profile_release_lock(&lk->lock_object); 1039 1040 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 1041 LK_UNLOCKED)) 1042 break; 1043 1044 sleepq_lock(&lk->lock_object); 1045 x = lk->lk_lock; 1046 v = LK_UNLOCKED; 1047 1048 /* 1049 * If the lock has exclusive waiters, give them 1050 * preference in order to avoid deadlock with 1051 * shared runners up. 1052 * If interruptible sleeps left the exclusive queue 1053 * empty avoid a starvation for the threads sleeping 1054 * on the shared queue by giving them precedence 1055 * and cleaning up the exclusive waiters bit anyway. 1056 * Please note that lk_exslpfail count may be lying 1057 * about the real number of waiters with the 1058 * LK_SLEEPFAIL flag on because they may be used in 1059 * conjunction with interruptible sleeps so 1060 * lk_exslpfail might be considered an 'upper limit' 1061 * bound, including the edge cases. 1062 */ 1063 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1064 realexslp = sleepq_sleepcnt(&lk->lock_object, 1065 SQ_EXCLUSIVE_QUEUE); 1066 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1067 if (lk->lk_exslpfail < realexslp) { 1068 lk->lk_exslpfail = 0; 1069 queue = SQ_EXCLUSIVE_QUEUE; 1070 v |= (x & LK_SHARED_WAITERS); 1071 } else { 1072 lk->lk_exslpfail = 0; 1073 LOCK_LOG2(lk, 1074 "%s: %p has only LK_SLEEPFAIL sleepers", 1075 __func__, lk); 1076 LOCK_LOG2(lk, 1077 "%s: %p waking up threads on the exclusive queue", 1078 __func__, lk); 1079 wakeup_swapper = 1080 sleepq_broadcast(&lk->lock_object, 1081 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1082 queue = SQ_SHARED_QUEUE; 1083 } 1084 } else { 1085 1086 /* 1087 * Exclusive waiters sleeping with LK_SLEEPFAIL 1088 * on and using interruptible sleeps/timeout 1089 * may have left spourious lk_exslpfail counts 1090 * on, so clean it up anyway. 1091 */ 1092 lk->lk_exslpfail = 0; 1093 queue = SQ_SHARED_QUEUE; 1094 } 1095 1096 LOCK_LOG3(lk, 1097 "%s: %p waking up threads on the %s queue", 1098 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1099 "exclusive"); 1100 atomic_store_rel_ptr(&lk->lk_lock, v); 1101 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1102 SLEEPQ_LK, 0, queue); 1103 sleepq_release(&lk->lock_object); 1104 break; 1105 } else 1106 wakeup_swapper = wakeupshlk(lk, file, line); 1107 break; 1108 case LK_DRAIN: 1109 if (LK_CAN_WITNESS(flags)) 1110 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1111 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 1112 ilk : NULL); 1113 1114 /* 1115 * Trying to drain a lock we already own will result in a 1116 * deadlock. 1117 */ 1118 if (lockmgr_xlocked(lk)) { 1119 if (flags & LK_INTERLOCK) 1120 class->lc_unlock(ilk); 1121 panic("%s: draining %s with the lock held @ %s:%d\n", 1122 __func__, iwmesg, file, line); 1123 } 1124 1125 for (;;) { 1126 if (lk->lk_lock == LK_UNLOCKED && 1127 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 1128 break; 1129 1130 #ifdef HWPMC_HOOKS 1131 PMC_SOFT_CALL( , , lock, failed); 1132 #endif 1133 lock_profile_obtain_lock_failed(&lk->lock_object, 1134 &contested, &waittime); 1135 1136 /* 1137 * If the lock is expected to not sleep just give up 1138 * and return. 1139 */ 1140 if (LK_TRYOP(flags)) { 1141 LOCK_LOG2(lk, "%s: %p fails the try operation", 1142 __func__, lk); 1143 error = EBUSY; 1144 break; 1145 } 1146 1147 /* 1148 * Acquire the sleepqueue chain lock because we 1149 * probabilly will need to manipulate waiters flags. 1150 */ 1151 sleepq_lock(&lk->lock_object); 1152 x = lk->lk_lock; 1153 1154 /* 1155 * if the lock has been released while we spun on 1156 * the sleepqueue chain lock just try again. 1157 */ 1158 if (x == LK_UNLOCKED) { 1159 sleepq_release(&lk->lock_object); 1160 continue; 1161 } 1162 1163 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1164 if ((x & ~v) == LK_UNLOCKED) { 1165 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1166 1167 /* 1168 * If interruptible sleeps left the exclusive 1169 * queue empty avoid a starvation for the 1170 * threads sleeping on the shared queue by 1171 * giving them precedence and cleaning up the 1172 * exclusive waiters bit anyway. 1173 * Please note that lk_exslpfail count may be 1174 * lying about the real number of waiters with 1175 * the LK_SLEEPFAIL flag on because they may 1176 * be used in conjunction with interruptible 1177 * sleeps so lk_exslpfail might be considered 1178 * an 'upper limit' bound, including the edge 1179 * cases. 1180 */ 1181 if (v & LK_EXCLUSIVE_WAITERS) { 1182 queue = SQ_EXCLUSIVE_QUEUE; 1183 v &= ~LK_EXCLUSIVE_WAITERS; 1184 } else { 1185 1186 /* 1187 * Exclusive waiters sleeping with 1188 * LK_SLEEPFAIL on and using 1189 * interruptible sleeps/timeout may 1190 * have left spourious lk_exslpfail 1191 * counts on, so clean it up anyway. 1192 */ 1193 MPASS(v & LK_SHARED_WAITERS); 1194 lk->lk_exslpfail = 0; 1195 queue = SQ_SHARED_QUEUE; 1196 v &= ~LK_SHARED_WAITERS; 1197 } 1198 if (queue == SQ_EXCLUSIVE_QUEUE) { 1199 realexslp = 1200 sleepq_sleepcnt(&lk->lock_object, 1201 SQ_EXCLUSIVE_QUEUE); 1202 if (lk->lk_exslpfail >= realexslp) { 1203 lk->lk_exslpfail = 0; 1204 queue = SQ_SHARED_QUEUE; 1205 v &= ~LK_SHARED_WAITERS; 1206 if (realexslp != 0) { 1207 LOCK_LOG2(lk, 1208 "%s: %p has only LK_SLEEPFAIL sleepers", 1209 __func__, lk); 1210 LOCK_LOG2(lk, 1211 "%s: %p waking up threads on the exclusive queue", 1212 __func__, lk); 1213 wakeup_swapper = 1214 sleepq_broadcast( 1215 &lk->lock_object, 1216 SLEEPQ_LK, 0, 1217 SQ_EXCLUSIVE_QUEUE); 1218 } 1219 } else 1220 lk->lk_exslpfail = 0; 1221 } 1222 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1223 sleepq_release(&lk->lock_object); 1224 continue; 1225 } 1226 LOCK_LOG3(lk, 1227 "%s: %p waking up all threads on the %s queue", 1228 __func__, lk, queue == SQ_SHARED_QUEUE ? 1229 "shared" : "exclusive"); 1230 wakeup_swapper |= sleepq_broadcast( 1231 &lk->lock_object, SLEEPQ_LK, 0, queue); 1232 1233 /* 1234 * If shared waiters have been woken up we need 1235 * to wait for one of them to acquire the lock 1236 * before to set the exclusive waiters in 1237 * order to avoid a deadlock. 1238 */ 1239 if (queue == SQ_SHARED_QUEUE) { 1240 for (v = lk->lk_lock; 1241 (v & LK_SHARE) && !LK_SHARERS(v); 1242 v = lk->lk_lock) 1243 cpu_spinwait(); 1244 } 1245 } 1246 1247 /* 1248 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1249 * fail, loop back and retry. 1250 */ 1251 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1252 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1253 x | LK_EXCLUSIVE_WAITERS)) { 1254 sleepq_release(&lk->lock_object); 1255 continue; 1256 } 1257 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1258 __func__, lk); 1259 } 1260 1261 /* 1262 * As far as we have been unable to acquire the 1263 * exclusive lock and the exclusive waiters flag 1264 * is set, we will sleep. 1265 */ 1266 if (flags & LK_INTERLOCK) { 1267 class->lc_unlock(ilk); 1268 flags &= ~LK_INTERLOCK; 1269 } 1270 GIANT_SAVE(); 1271 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1272 SQ_EXCLUSIVE_QUEUE); 1273 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1274 GIANT_RESTORE(); 1275 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1276 __func__, lk); 1277 } 1278 1279 if (error == 0) { 1280 lock_profile_obtain_lock_success(&lk->lock_object, 1281 contested, waittime, file, line); 1282 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1283 lk->lk_recurse, file, line); 1284 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1285 LK_TRYWIT(flags), file, line); 1286 TD_LOCKS_INC(curthread); 1287 STACK_SAVE(lk); 1288 } 1289 break; 1290 default: 1291 if (flags & LK_INTERLOCK) 1292 class->lc_unlock(ilk); 1293 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1294 } 1295 1296 if (flags & LK_INTERLOCK) 1297 class->lc_unlock(ilk); 1298 if (wakeup_swapper) 1299 kick_proc0(); 1300 1301 return (error); 1302 } 1303 1304 void 1305 _lockmgr_disown(struct lock *lk, const char *file, int line) 1306 { 1307 uintptr_t tid, x; 1308 1309 if (SCHEDULER_STOPPED()) 1310 return; 1311 1312 tid = (uintptr_t)curthread; 1313 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1314 1315 /* 1316 * Panic if the lock is recursed. 1317 */ 1318 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1319 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1320 __func__, file, line); 1321 1322 /* 1323 * If the owner is already LK_KERNPROC just skip the whole operation. 1324 */ 1325 if (LK_HOLDER(lk->lk_lock) != tid) 1326 return; 1327 lock_profile_release_lock(&lk->lock_object); 1328 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1329 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1330 TD_LOCKS_DEC(curthread); 1331 STACK_SAVE(lk); 1332 1333 /* 1334 * In order to preserve waiters flags, just spin. 1335 */ 1336 for (;;) { 1337 x = lk->lk_lock; 1338 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1339 x &= LK_ALL_WAITERS; 1340 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1341 LK_KERNPROC | x)) 1342 return; 1343 cpu_spinwait(); 1344 } 1345 } 1346 1347 void 1348 lockmgr_printinfo(const struct lock *lk) 1349 { 1350 struct thread *td; 1351 uintptr_t x; 1352 1353 if (lk->lk_lock == LK_UNLOCKED) 1354 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1355 else if (lk->lk_lock & LK_SHARE) 1356 printf("lock type %s: SHARED (count %ju)\n", 1357 lk->lock_object.lo_name, 1358 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1359 else { 1360 td = lockmgr_xholder(lk); 1361 if (td == (struct thread *)LK_KERNPROC) 1362 printf("lock type %s: EXCL by KERNPROC\n", 1363 lk->lock_object.lo_name); 1364 else 1365 printf("lock type %s: EXCL by thread %p " 1366 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, 1367 td, td->td_proc->p_pid, td->td_proc->p_comm, 1368 td->td_tid); 1369 } 1370 1371 x = lk->lk_lock; 1372 if (x & LK_EXCLUSIVE_WAITERS) 1373 printf(" with exclusive waiters pending\n"); 1374 if (x & LK_SHARED_WAITERS) 1375 printf(" with shared waiters pending\n"); 1376 if (x & LK_EXCLUSIVE_SPINNERS) 1377 printf(" with exclusive spinners pending\n"); 1378 1379 STACK_PRINT(lk); 1380 } 1381 1382 int 1383 lockstatus(const struct lock *lk) 1384 { 1385 uintptr_t v, x; 1386 int ret; 1387 1388 ret = LK_SHARED; 1389 x = lk->lk_lock; 1390 v = LK_HOLDER(x); 1391 1392 if ((x & LK_SHARE) == 0) { 1393 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1394 ret = LK_EXCLUSIVE; 1395 else 1396 ret = LK_EXCLOTHER; 1397 } else if (x == LK_UNLOCKED) 1398 ret = 0; 1399 1400 return (ret); 1401 } 1402 1403 #ifdef INVARIANT_SUPPORT 1404 1405 FEATURE(invariant_support, 1406 "Support for modules compiled with INVARIANTS option"); 1407 1408 #ifndef INVARIANTS 1409 #undef _lockmgr_assert 1410 #endif 1411 1412 void 1413 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1414 { 1415 int slocked = 0; 1416 1417 if (panicstr != NULL) 1418 return; 1419 switch (what) { 1420 case KA_SLOCKED: 1421 case KA_SLOCKED | KA_NOTRECURSED: 1422 case KA_SLOCKED | KA_RECURSED: 1423 slocked = 1; 1424 case KA_LOCKED: 1425 case KA_LOCKED | KA_NOTRECURSED: 1426 case KA_LOCKED | KA_RECURSED: 1427 #ifdef WITNESS 1428 1429 /* 1430 * We cannot trust WITNESS if the lock is held in exclusive 1431 * mode and a call to lockmgr_disown() happened. 1432 * Workaround this skipping the check if the lock is held in 1433 * exclusive mode even for the KA_LOCKED case. 1434 */ 1435 if (slocked || (lk->lk_lock & LK_SHARE)) { 1436 witness_assert(&lk->lock_object, what, file, line); 1437 break; 1438 } 1439 #endif 1440 if (lk->lk_lock == LK_UNLOCKED || 1441 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1442 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1443 panic("Lock %s not %slocked @ %s:%d\n", 1444 lk->lock_object.lo_name, slocked ? "share" : "", 1445 file, line); 1446 1447 if ((lk->lk_lock & LK_SHARE) == 0) { 1448 if (lockmgr_recursed(lk)) { 1449 if (what & KA_NOTRECURSED) 1450 panic("Lock %s recursed @ %s:%d\n", 1451 lk->lock_object.lo_name, file, 1452 line); 1453 } else if (what & KA_RECURSED) 1454 panic("Lock %s not recursed @ %s:%d\n", 1455 lk->lock_object.lo_name, file, line); 1456 } 1457 break; 1458 case KA_XLOCKED: 1459 case KA_XLOCKED | KA_NOTRECURSED: 1460 case KA_XLOCKED | KA_RECURSED: 1461 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1462 panic("Lock %s not exclusively locked @ %s:%d\n", 1463 lk->lock_object.lo_name, file, line); 1464 if (lockmgr_recursed(lk)) { 1465 if (what & KA_NOTRECURSED) 1466 panic("Lock %s recursed @ %s:%d\n", 1467 lk->lock_object.lo_name, file, line); 1468 } else if (what & KA_RECURSED) 1469 panic("Lock %s not recursed @ %s:%d\n", 1470 lk->lock_object.lo_name, file, line); 1471 break; 1472 case KA_UNLOCKED: 1473 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1474 panic("Lock %s exclusively locked @ %s:%d\n", 1475 lk->lock_object.lo_name, file, line); 1476 break; 1477 default: 1478 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1479 line); 1480 } 1481 } 1482 #endif 1483 1484 #ifdef DDB 1485 int 1486 lockmgr_chain(struct thread *td, struct thread **ownerp) 1487 { 1488 struct lock *lk; 1489 1490 lk = td->td_wchan; 1491 1492 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1493 return (0); 1494 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1495 if (lk->lk_lock & LK_SHARE) 1496 db_printf("SHARED (count %ju)\n", 1497 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1498 else 1499 db_printf("EXCL\n"); 1500 *ownerp = lockmgr_xholder(lk); 1501 1502 return (1); 1503 } 1504 1505 static void 1506 db_show_lockmgr(const struct lock_object *lock) 1507 { 1508 struct thread *td; 1509 const struct lock *lk; 1510 1511 lk = (const struct lock *)lock; 1512 1513 db_printf(" state: "); 1514 if (lk->lk_lock == LK_UNLOCKED) 1515 db_printf("UNLOCKED\n"); 1516 else if (lk->lk_lock & LK_SHARE) 1517 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1518 else { 1519 td = lockmgr_xholder(lk); 1520 if (td == (struct thread *)LK_KERNPROC) 1521 db_printf("XLOCK: LK_KERNPROC\n"); 1522 else 1523 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1524 td->td_tid, td->td_proc->p_pid, 1525 td->td_proc->p_comm); 1526 if (lockmgr_recursed(lk)) 1527 db_printf(" recursed: %d\n", lk->lk_recurse); 1528 } 1529 db_printf(" waiters: "); 1530 switch (lk->lk_lock & LK_ALL_WAITERS) { 1531 case LK_SHARED_WAITERS: 1532 db_printf("shared\n"); 1533 break; 1534 case LK_EXCLUSIVE_WAITERS: 1535 db_printf("exclusive\n"); 1536 break; 1537 case LK_ALL_WAITERS: 1538 db_printf("shared and exclusive\n"); 1539 break; 1540 default: 1541 db_printf("none\n"); 1542 } 1543 db_printf(" spinners: "); 1544 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1545 db_printf("exclusive\n"); 1546 else 1547 db_printf("none\n"); 1548 } 1549 #endif 1550