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_v(v) \ 136 (((v) & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 137 138 #define lockmgr_xlocked(lk) lockmgr_xlocked_v((lk)->lk_lock) 139 140 static void assert_lockmgr(const struct lock_object *lock, int how); 141 #ifdef DDB 142 static void db_show_lockmgr(const struct lock_object *lock); 143 #endif 144 static void lock_lockmgr(struct lock_object *lock, uintptr_t how); 145 #ifdef KDTRACE_HOOKS 146 static int owner_lockmgr(const struct lock_object *lock, 147 struct thread **owner); 148 #endif 149 static uintptr_t unlock_lockmgr(struct lock_object *lock); 150 151 struct lock_class lock_class_lockmgr = { 152 .lc_name = "lockmgr", 153 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 154 .lc_assert = assert_lockmgr, 155 #ifdef DDB 156 .lc_ddb_show = db_show_lockmgr, 157 #endif 158 .lc_lock = lock_lockmgr, 159 .lc_unlock = unlock_lockmgr, 160 #ifdef KDTRACE_HOOKS 161 .lc_owner = owner_lockmgr, 162 #endif 163 }; 164 165 struct lockmgr_wait { 166 const char *iwmesg; 167 int ipri; 168 int itimo; 169 }; 170 171 static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp, 172 int flags); 173 static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp); 174 175 static void 176 lockmgr_exit(u_int flags, struct lock_object *ilk, int wakeup_swapper) 177 { 178 struct lock_class *class; 179 180 if (flags & LK_INTERLOCK) { 181 class = LOCK_CLASS(ilk); 182 class->lc_unlock(ilk); 183 } 184 185 if (__predict_false(wakeup_swapper)) 186 kick_proc0(); 187 } 188 189 static void 190 lockmgr_note_shared_acquire(struct lock *lk, int contested, 191 uint64_t waittime, const char *file, int line, int flags) 192 { 193 194 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime, 195 file, line); 196 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line); 197 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line); 198 TD_LOCKS_INC(curthread); 199 TD_SLOCKS_INC(curthread); 200 STACK_SAVE(lk); 201 } 202 203 static void 204 lockmgr_note_shared_release(struct lock *lk, const char *file, int line) 205 { 206 207 lock_profile_release_lock(&lk->lock_object); 208 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 209 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 210 TD_LOCKS_DEC(curthread); 211 TD_SLOCKS_DEC(curthread); 212 } 213 214 static void 215 lockmgr_note_exclusive_acquire(struct lock *lk, int contested, 216 uint64_t waittime, const char *file, int line, int flags) 217 { 218 219 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime, 220 file, line); 221 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line); 222 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, 223 line); 224 TD_LOCKS_INC(curthread); 225 STACK_SAVE(lk); 226 } 227 228 static void 229 lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line) 230 { 231 232 lock_profile_release_lock(&lk->lock_object); 233 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, 234 line); 235 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 236 TD_LOCKS_DEC(curthread); 237 } 238 239 static __inline struct thread * 240 lockmgr_xholder(const struct lock *lk) 241 { 242 uintptr_t x; 243 244 x = lk->lk_lock; 245 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 246 } 247 248 /* 249 * It assumes sleepq_lock held and returns with this one unheld. 250 * It also assumes the generic interlock is sane and previously checked. 251 * If LK_INTERLOCK is specified the interlock is not reacquired after the 252 * sleep. 253 */ 254 static __inline int 255 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 256 const char *wmesg, int pri, int timo, int queue) 257 { 258 GIANT_DECLARE; 259 struct lock_class *class; 260 int catch, error; 261 262 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 263 catch = pri & PCATCH; 264 pri &= PRIMASK; 265 error = 0; 266 267 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 268 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 269 270 if (flags & LK_INTERLOCK) 271 class->lc_unlock(ilk); 272 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 273 lk->lk_exslpfail++; 274 GIANT_SAVE(); 275 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 276 SLEEPQ_INTERRUPTIBLE : 0), queue); 277 if ((flags & LK_TIMELOCK) && timo) 278 sleepq_set_timeout(&lk->lock_object, timo); 279 280 /* 281 * Decisional switch for real sleeping. 282 */ 283 if ((flags & LK_TIMELOCK) && timo && catch) 284 error = sleepq_timedwait_sig(&lk->lock_object, pri); 285 else if ((flags & LK_TIMELOCK) && timo) 286 error = sleepq_timedwait(&lk->lock_object, pri); 287 else if (catch) 288 error = sleepq_wait_sig(&lk->lock_object, pri); 289 else 290 sleepq_wait(&lk->lock_object, pri); 291 GIANT_RESTORE(); 292 if ((flags & LK_SLEEPFAIL) && error == 0) 293 error = ENOLCK; 294 295 return (error); 296 } 297 298 static __inline int 299 wakeupshlk(struct lock *lk, const char *file, int line) 300 { 301 uintptr_t v, x, orig_x; 302 u_int realexslp; 303 int queue, wakeup_swapper; 304 305 wakeup_swapper = 0; 306 for (;;) { 307 x = lk->lk_lock; 308 if (lockmgr_sunlock_try(lk, &x)) 309 break; 310 311 /* 312 * We should have a sharer with waiters, so enter the hard 313 * path in order to handle wakeups correctly. 314 */ 315 sleepq_lock(&lk->lock_object); 316 orig_x = lk->lk_lock; 317 retry_sleepq: 318 x = orig_x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 319 v = LK_UNLOCKED; 320 321 /* 322 * If the lock has exclusive waiters, give them preference in 323 * order to avoid deadlock with shared runners up. 324 * If interruptible sleeps left the exclusive queue empty 325 * avoid a starvation for the threads sleeping on the shared 326 * queue by giving them precedence and cleaning up the 327 * exclusive waiters bit anyway. 328 * Please note that lk_exslpfail count may be lying about 329 * the real number of waiters with the LK_SLEEPFAIL flag on 330 * because they may be used in conjunction with interruptible 331 * sleeps so lk_exslpfail might be considered an 'upper limit' 332 * bound, including the edge cases. 333 */ 334 realexslp = sleepq_sleepcnt(&lk->lock_object, 335 SQ_EXCLUSIVE_QUEUE); 336 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 337 if (lk->lk_exslpfail < realexslp) { 338 lk->lk_exslpfail = 0; 339 queue = SQ_EXCLUSIVE_QUEUE; 340 v |= (x & LK_SHARED_WAITERS); 341 } else { 342 lk->lk_exslpfail = 0; 343 LOCK_LOG2(lk, 344 "%s: %p has only LK_SLEEPFAIL sleepers", 345 __func__, lk); 346 LOCK_LOG2(lk, 347 "%s: %p waking up threads on the exclusive queue", 348 __func__, lk); 349 wakeup_swapper = 350 sleepq_broadcast(&lk->lock_object, 351 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 352 queue = SQ_SHARED_QUEUE; 353 } 354 355 } else { 356 357 /* 358 * Exclusive waiters sleeping with LK_SLEEPFAIL on 359 * and using interruptible sleeps/timeout may have 360 * left spourious lk_exslpfail counts on, so clean 361 * it up anyway. 362 */ 363 lk->lk_exslpfail = 0; 364 queue = SQ_SHARED_QUEUE; 365 } 366 367 if (lockmgr_sunlock_try(lk, &orig_x)) { 368 sleepq_release(&lk->lock_object); 369 break; 370 } 371 372 x |= LK_SHARERS_LOCK(1); 373 if (!atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, v)) { 374 orig_x = x; 375 goto retry_sleepq; 376 } 377 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 378 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 379 "exclusive"); 380 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 381 0, queue); 382 sleepq_release(&lk->lock_object); 383 break; 384 } 385 386 lockmgr_note_shared_release(lk, file, line); 387 return (wakeup_swapper); 388 } 389 390 static void 391 assert_lockmgr(const struct lock_object *lock, int what) 392 { 393 394 panic("lockmgr locks do not support assertions"); 395 } 396 397 static void 398 lock_lockmgr(struct lock_object *lock, uintptr_t how) 399 { 400 401 panic("lockmgr locks do not support sleep interlocking"); 402 } 403 404 static uintptr_t 405 unlock_lockmgr(struct lock_object *lock) 406 { 407 408 panic("lockmgr locks do not support sleep interlocking"); 409 } 410 411 #ifdef KDTRACE_HOOKS 412 static int 413 owner_lockmgr(const struct lock_object *lock, struct thread **owner) 414 { 415 416 panic("lockmgr locks do not support owner inquiring"); 417 } 418 #endif 419 420 void 421 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 422 { 423 int iflags; 424 425 MPASS((flags & ~LK_INIT_MASK) == 0); 426 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 427 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 428 &lk->lk_lock)); 429 430 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 431 if (flags & LK_CANRECURSE) 432 iflags |= LO_RECURSABLE; 433 if ((flags & LK_NODUP) == 0) 434 iflags |= LO_DUPOK; 435 if (flags & LK_NOPROFILE) 436 iflags |= LO_NOPROFILE; 437 if ((flags & LK_NOWITNESS) == 0) 438 iflags |= LO_WITNESS; 439 if (flags & LK_QUIET) 440 iflags |= LO_QUIET; 441 if (flags & LK_IS_VNODE) 442 iflags |= LO_IS_VNODE; 443 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 444 445 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 446 lk->lk_lock = LK_UNLOCKED; 447 lk->lk_recurse = 0; 448 lk->lk_exslpfail = 0; 449 lk->lk_timo = timo; 450 lk->lk_pri = pri; 451 STACK_ZERO(lk); 452 } 453 454 /* 455 * XXX: Gross hacks to manipulate external lock flags after 456 * initialization. Used for certain vnode and buf locks. 457 */ 458 void 459 lockallowshare(struct lock *lk) 460 { 461 462 lockmgr_assert(lk, KA_XLOCKED); 463 lk->lock_object.lo_flags &= ~LK_NOSHARE; 464 } 465 466 void 467 lockdisableshare(struct lock *lk) 468 { 469 470 lockmgr_assert(lk, KA_XLOCKED); 471 lk->lock_object.lo_flags |= LK_NOSHARE; 472 } 473 474 void 475 lockallowrecurse(struct lock *lk) 476 { 477 478 lockmgr_assert(lk, KA_XLOCKED); 479 lk->lock_object.lo_flags |= LO_RECURSABLE; 480 } 481 482 void 483 lockdisablerecurse(struct lock *lk) 484 { 485 486 lockmgr_assert(lk, KA_XLOCKED); 487 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 488 } 489 490 void 491 lockdestroy(struct lock *lk) 492 { 493 494 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 495 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 496 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 497 lock_destroy(&lk->lock_object); 498 } 499 500 static bool __always_inline 501 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags) 502 { 503 504 /* 505 * If no other thread has an exclusive lock, or 506 * no exclusive waiter is present, bump the count of 507 * sharers. Since we have to preserve the state of 508 * waiters, if we fail to acquire the shared lock 509 * loop back and retry. 510 */ 511 *xp = lk->lk_lock; 512 while (LK_CAN_SHARE(*xp, flags)) { 513 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp, 514 *xp + LK_ONE_SHARER)) { 515 return (true); 516 } 517 } 518 return (false); 519 } 520 521 static bool __always_inline 522 lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp) 523 { 524 525 for (;;) { 526 /* 527 * If there is more than one shared lock held, just drop one 528 * and return. 529 */ 530 if (LK_SHARERS(*xp) > 1) { 531 if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp, 532 *xp - LK_ONE_SHARER)) 533 return (true); 534 continue; 535 } 536 537 /* 538 * If there are not waiters on the exclusive queue, drop the 539 * lock quickly. 540 */ 541 if ((*xp & LK_ALL_WAITERS) == 0) { 542 MPASS((*xp & ~LK_EXCLUSIVE_SPINNERS) == 543 LK_SHARERS_LOCK(1)); 544 if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp, 545 LK_UNLOCKED)) 546 return (true); 547 continue; 548 } 549 break; 550 } 551 return (false); 552 } 553 554 static __noinline int 555 lockmgr_slock_hard(struct lock *lk, u_int flags, struct lock_object *ilk, 556 const char *file, int line, struct lockmgr_wait *lwa) 557 { 558 uintptr_t tid, x; 559 int error = 0; 560 const char *iwmesg; 561 int ipri, itimo; 562 563 #ifdef LOCK_PROFILING 564 uint64_t waittime = 0; 565 int contested = 0; 566 #endif 567 568 if (__predict_false(panicstr != NULL)) 569 goto out; 570 571 tid = (uintptr_t)curthread; 572 573 if (LK_CAN_WITNESS(flags)) 574 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 575 file, line, flags & LK_INTERLOCK ? ilk : NULL); 576 for (;;) { 577 if (lockmgr_slock_try(lk, &x, flags)) 578 break; 579 #ifdef HWPMC_HOOKS 580 PMC_SOFT_CALL( , , lock, failed); 581 #endif 582 lock_profile_obtain_lock_failed(&lk->lock_object, 583 &contested, &waittime); 584 585 /* 586 * If the lock is already held by curthread in 587 * exclusive way avoid a deadlock. 588 */ 589 if (LK_HOLDER(x) == tid) { 590 LOCK_LOG2(lk, 591 "%s: %p already held in exclusive mode", 592 __func__, lk); 593 error = EDEADLK; 594 break; 595 } 596 597 /* 598 * If the lock is expected to not sleep just give up 599 * and return. 600 */ 601 if (LK_TRYOP(flags)) { 602 LOCK_LOG2(lk, "%s: %p fails the try operation", 603 __func__, lk); 604 error = EBUSY; 605 break; 606 } 607 608 /* 609 * Acquire the sleepqueue chain lock because we 610 * probabilly will need to manipulate waiters flags. 611 */ 612 sleepq_lock(&lk->lock_object); 613 x = lk->lk_lock; 614 retry_sleepq: 615 616 /* 617 * if the lock can be acquired in shared mode, try 618 * again. 619 */ 620 if (LK_CAN_SHARE(x, flags)) { 621 sleepq_release(&lk->lock_object); 622 continue; 623 } 624 625 /* 626 * Try to set the LK_SHARED_WAITERS flag. If we fail, 627 * loop back and retry. 628 */ 629 if ((x & LK_SHARED_WAITERS) == 0) { 630 if (!atomic_fcmpset_acq_ptr(&lk->lk_lock, &x, 631 x | LK_SHARED_WAITERS)) { 632 goto retry_sleepq; 633 } 634 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 635 __func__, lk); 636 } 637 638 if (lwa == NULL) { 639 iwmesg = lk->lock_object.lo_name; 640 ipri = lk->lk_pri; 641 itimo = lk->lk_timo; 642 } else { 643 iwmesg = lwa->iwmesg; 644 ipri = lwa->ipri; 645 itimo = lwa->itimo; 646 } 647 648 /* 649 * As far as we have been unable to acquire the 650 * shared lock and the shared waiters flag is set, 651 * we will sleep. 652 */ 653 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 654 SQ_SHARED_QUEUE); 655 flags &= ~LK_INTERLOCK; 656 if (error) { 657 LOCK_LOG3(lk, 658 "%s: interrupted sleep for %p with %d", 659 __func__, lk, error); 660 break; 661 } 662 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 663 __func__, lk); 664 } 665 if (error == 0) { 666 #ifdef LOCK_PROFILING 667 lockmgr_note_shared_acquire(lk, contested, waittime, 668 file, line, flags); 669 #else 670 lockmgr_note_shared_acquire(lk, 0, 0, file, line, 671 flags); 672 #endif 673 } 674 675 out: 676 lockmgr_exit(flags, ilk, 0); 677 return (error); 678 } 679 680 static __noinline int 681 lockmgr_xlock_hard(struct lock *lk, u_int flags, struct lock_object *ilk, 682 const char *file, int line, struct lockmgr_wait *lwa) 683 { 684 struct lock_class *class; 685 uintptr_t tid, x, v; 686 int error = 0; 687 const char *iwmesg; 688 int ipri, itimo; 689 690 #ifdef LOCK_PROFILING 691 uint64_t waittime = 0; 692 int contested = 0; 693 #endif 694 695 if (__predict_false(panicstr != NULL)) 696 goto out; 697 698 tid = (uintptr_t)curthread; 699 700 if (LK_CAN_WITNESS(flags)) 701 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 702 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 703 ilk : NULL); 704 705 /* 706 * If curthread already holds the lock and this one is 707 * allowed to recurse, simply recurse on it. 708 */ 709 if (lockmgr_xlocked(lk)) { 710 if ((flags & LK_CANRECURSE) == 0 && 711 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 712 /* 713 * If the lock is expected to not panic just 714 * give up and return. 715 */ 716 if (LK_TRYOP(flags)) { 717 LOCK_LOG2(lk, 718 "%s: %p fails the try operation", 719 __func__, lk); 720 error = EBUSY; 721 goto out; 722 } 723 if (flags & LK_INTERLOCK) { 724 class = LOCK_CLASS(ilk); 725 class->lc_unlock(ilk); 726 } 727 panic("%s: recursing on non recursive lockmgr %p " 728 "@ %s:%d\n", __func__, lk, file, line); 729 } 730 lk->lk_recurse++; 731 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 732 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 733 lk->lk_recurse, file, line); 734 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 735 LK_TRYWIT(flags), file, line); 736 TD_LOCKS_INC(curthread); 737 goto out; 738 } 739 740 for (;;) { 741 if (lk->lk_lock == LK_UNLOCKED && 742 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 743 break; 744 #ifdef HWPMC_HOOKS 745 PMC_SOFT_CALL( , , lock, failed); 746 #endif 747 lock_profile_obtain_lock_failed(&lk->lock_object, 748 &contested, &waittime); 749 750 /* 751 * If the lock is expected to not sleep just give up 752 * and return. 753 */ 754 if (LK_TRYOP(flags)) { 755 LOCK_LOG2(lk, "%s: %p fails the try operation", 756 __func__, lk); 757 error = EBUSY; 758 break; 759 } 760 761 /* 762 * Acquire the sleepqueue chain lock because we 763 * probabilly will need to manipulate waiters flags. 764 */ 765 sleepq_lock(&lk->lock_object); 766 x = lk->lk_lock; 767 retry_sleepq: 768 769 /* 770 * if the lock has been released while we spun on 771 * the sleepqueue chain lock just try again. 772 */ 773 if (x == LK_UNLOCKED) { 774 sleepq_release(&lk->lock_object); 775 continue; 776 } 777 778 /* 779 * The lock can be in the state where there is a 780 * pending queue of waiters, but still no owner. 781 * This happens when the lock is contested and an 782 * owner is going to claim the lock. 783 * If curthread is the one successfully acquiring it 784 * claim lock ownership and return, preserving waiters 785 * flags. 786 */ 787 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 788 if ((x & ~v) == LK_UNLOCKED) { 789 v &= ~LK_EXCLUSIVE_SPINNERS; 790 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x, 791 tid | v)) { 792 sleepq_release(&lk->lock_object); 793 LOCK_LOG2(lk, 794 "%s: %p claimed by a new writer", 795 __func__, lk); 796 break; 797 } 798 goto retry_sleepq; 799 } 800 801 /* 802 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 803 * fail, loop back and retry. 804 */ 805 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 806 if (!atomic_fcmpset_ptr(&lk->lk_lock, &x, 807 x | LK_EXCLUSIVE_WAITERS)) { 808 goto retry_sleepq; 809 } 810 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 811 __func__, lk); 812 } 813 814 if (lwa == NULL) { 815 iwmesg = lk->lock_object.lo_name; 816 ipri = lk->lk_pri; 817 itimo = lk->lk_timo; 818 } else { 819 iwmesg = lwa->iwmesg; 820 ipri = lwa->ipri; 821 itimo = lwa->itimo; 822 } 823 824 /* 825 * As far as we have been unable to acquire the 826 * exclusive lock and the exclusive waiters flag 827 * is set, we will sleep. 828 */ 829 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 830 SQ_EXCLUSIVE_QUEUE); 831 flags &= ~LK_INTERLOCK; 832 if (error) { 833 LOCK_LOG3(lk, 834 "%s: interrupted sleep for %p with %d", 835 __func__, lk, error); 836 break; 837 } 838 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 839 __func__, lk); 840 } 841 if (error == 0) { 842 #ifdef LOCK_PROFILING 843 lockmgr_note_exclusive_acquire(lk, contested, waittime, 844 file, line, flags); 845 #else 846 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line, 847 flags); 848 #endif 849 } 850 851 out: 852 lockmgr_exit(flags, ilk, 0); 853 return (error); 854 } 855 856 static __noinline int 857 lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk, 858 const char *file, int line, struct lockmgr_wait *lwa) 859 { 860 uintptr_t tid, x, v; 861 int error = 0; 862 int wakeup_swapper = 0; 863 int op; 864 865 if (__predict_false(panicstr != NULL)) 866 goto out; 867 868 tid = (uintptr_t)curthread; 869 870 _lockmgr_assert(lk, KA_SLOCKED, file, line); 871 v = lk->lk_lock; 872 x = v & LK_ALL_WAITERS; 873 v &= LK_EXCLUSIVE_SPINNERS; 874 875 /* 876 * Try to switch from one shared lock to an exclusive one. 877 * We need to preserve waiters flags during the operation. 878 */ 879 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 880 tid | x)) { 881 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 882 line); 883 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 884 LK_TRYWIT(flags), file, line); 885 TD_SLOCKS_DEC(curthread); 886 goto out; 887 } 888 889 op = flags & LK_TYPE_MASK; 890 891 /* 892 * In LK_TRYUPGRADE mode, do not drop the lock, 893 * returning EBUSY instead. 894 */ 895 if (op == LK_TRYUPGRADE) { 896 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", 897 __func__, lk); 898 error = EBUSY; 899 goto out; 900 } 901 902 /* 903 * We have been unable to succeed in upgrading, so just 904 * give up the shared lock. 905 */ 906 wakeup_swapper |= wakeupshlk(lk, file, line); 907 error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa); 908 flags &= ~LK_INTERLOCK; 909 out: 910 lockmgr_exit(flags, ilk, wakeup_swapper); 911 return (error); 912 } 913 914 int 915 lockmgr_lock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk, 916 const char *file, int line) 917 { 918 struct lock_class *class; 919 uintptr_t x, tid; 920 u_int op; 921 bool locked; 922 923 if (__predict_false(panicstr != NULL)) 924 return (0); 925 926 op = flags & LK_TYPE_MASK; 927 locked = false; 928 switch (op) { 929 case LK_SHARED: 930 if (LK_CAN_WITNESS(flags)) 931 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 932 file, line, flags & LK_INTERLOCK ? ilk : NULL); 933 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE)) 934 break; 935 if (lockmgr_slock_try(lk, &x, flags)) { 936 lockmgr_note_shared_acquire(lk, 0, 0, 937 file, line, flags); 938 locked = true; 939 } else { 940 return (lockmgr_slock_hard(lk, flags, ilk, file, line, 941 NULL)); 942 } 943 break; 944 case LK_EXCLUSIVE: 945 if (LK_CAN_WITNESS(flags)) 946 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 947 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 948 ilk : NULL); 949 tid = (uintptr_t)curthread; 950 if (lk->lk_lock == LK_UNLOCKED && 951 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 952 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line, 953 flags); 954 locked = true; 955 } else { 956 return (lockmgr_xlock_hard(lk, flags, ilk, file, line, 957 NULL)); 958 } 959 break; 960 case LK_UPGRADE: 961 case LK_TRYUPGRADE: 962 return (lockmgr_upgrade(lk, flags, ilk, file, line, NULL)); 963 default: 964 break; 965 } 966 if (__predict_true(locked)) { 967 if (__predict_false(flags & LK_INTERLOCK)) { 968 class = LOCK_CLASS(ilk); 969 class->lc_unlock(ilk); 970 } 971 return (0); 972 } else { 973 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT, 974 LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line)); 975 } 976 } 977 978 static __noinline int 979 lockmgr_sunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk, 980 const char *file, int line) 981 982 { 983 int wakeup_swapper = 0; 984 985 if (__predict_false(panicstr != NULL)) 986 goto out; 987 988 wakeup_swapper = wakeupshlk(lk, file, line); 989 990 out: 991 lockmgr_exit(flags, ilk, wakeup_swapper); 992 return (0); 993 } 994 995 static __noinline int 996 lockmgr_xunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk, 997 const char *file, int line) 998 { 999 uintptr_t tid, v; 1000 int wakeup_swapper = 0; 1001 u_int realexslp; 1002 int queue; 1003 1004 if (__predict_false(panicstr != NULL)) 1005 goto out; 1006 1007 tid = (uintptr_t)curthread; 1008 1009 /* 1010 * As first option, treact the lock as if it has not 1011 * any waiter. 1012 * Fix-up the tid var if the lock has been disowned. 1013 */ 1014 if (LK_HOLDER(x) == LK_KERNPROC) 1015 tid = LK_KERNPROC; 1016 else { 1017 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1018 TD_LOCKS_DEC(curthread); 1019 } 1020 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line); 1021 1022 /* 1023 * The lock is held in exclusive mode. 1024 * If the lock is recursed also, then unrecurse it. 1025 */ 1026 if (lockmgr_xlocked_v(x) && lockmgr_recursed(lk)) { 1027 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk); 1028 lk->lk_recurse--; 1029 goto out; 1030 } 1031 if (tid != LK_KERNPROC) 1032 lock_profile_release_lock(&lk->lock_object); 1033 1034 if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) 1035 goto out; 1036 1037 sleepq_lock(&lk->lock_object); 1038 x = lk->lk_lock; 1039 v = LK_UNLOCKED; 1040 1041 /* 1042 * If the lock has exclusive waiters, give them 1043 * preference in order to avoid deadlock with 1044 * shared runners up. 1045 * If interruptible sleeps left the exclusive queue 1046 * empty avoid a starvation for the threads sleeping 1047 * on the shared queue by giving them precedence 1048 * and cleaning up the exclusive waiters bit anyway. 1049 * Please note that lk_exslpfail count may be lying 1050 * about the real number of waiters with the 1051 * LK_SLEEPFAIL flag on because they may be used in 1052 * conjunction with interruptible sleeps so 1053 * lk_exslpfail might be considered an 'upper limit' 1054 * bound, including the edge cases. 1055 */ 1056 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1057 realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE); 1058 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1059 if (lk->lk_exslpfail < realexslp) { 1060 lk->lk_exslpfail = 0; 1061 queue = SQ_EXCLUSIVE_QUEUE; 1062 v |= (x & LK_SHARED_WAITERS); 1063 } else { 1064 lk->lk_exslpfail = 0; 1065 LOCK_LOG2(lk, 1066 "%s: %p has only LK_SLEEPFAIL sleepers", 1067 __func__, lk); 1068 LOCK_LOG2(lk, 1069 "%s: %p waking up threads on the exclusive queue", 1070 __func__, lk); 1071 wakeup_swapper = sleepq_broadcast(&lk->lock_object, 1072 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1073 queue = SQ_SHARED_QUEUE; 1074 } 1075 } else { 1076 1077 /* 1078 * Exclusive waiters sleeping with LK_SLEEPFAIL 1079 * on and using interruptible sleeps/timeout 1080 * may have left spourious lk_exslpfail counts 1081 * on, so clean it up anyway. 1082 */ 1083 lk->lk_exslpfail = 0; 1084 queue = SQ_SHARED_QUEUE; 1085 } 1086 1087 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 1088 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1089 "exclusive"); 1090 atomic_store_rel_ptr(&lk->lk_lock, v); 1091 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue); 1092 sleepq_release(&lk->lock_object); 1093 1094 out: 1095 lockmgr_exit(flags, ilk, wakeup_swapper); 1096 return (0); 1097 } 1098 1099 int 1100 lockmgr_unlock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk) 1101 { 1102 struct lock_class *class; 1103 uintptr_t x, tid; 1104 const char *file; 1105 int line; 1106 1107 if (__predict_false(panicstr != NULL)) 1108 return (0); 1109 1110 file = __FILE__; 1111 line = __LINE__; 1112 1113 _lockmgr_assert(lk, KA_LOCKED, file, line); 1114 x = lk->lk_lock; 1115 if (__predict_true(x & LK_SHARE) != 0) { 1116 if (lockmgr_sunlock_try(lk, &x)) { 1117 lockmgr_note_shared_release(lk, file, line); 1118 } else { 1119 return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line)); 1120 } 1121 } else { 1122 tid = (uintptr_t)curthread; 1123 if (!lockmgr_recursed(lk) && 1124 atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) { 1125 lockmgr_note_exclusive_release(lk, file, line); 1126 } else { 1127 return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line)); 1128 } 1129 } 1130 if (__predict_false(flags & LK_INTERLOCK)) { 1131 class = LOCK_CLASS(ilk); 1132 class->lc_unlock(ilk); 1133 } 1134 return (0); 1135 } 1136 1137 int 1138 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 1139 const char *wmesg, int pri, int timo, const char *file, int line) 1140 { 1141 GIANT_DECLARE; 1142 struct lockmgr_wait lwa; 1143 struct lock_class *class; 1144 const char *iwmesg; 1145 uintptr_t tid, v, x; 1146 u_int op, realexslp; 1147 int error, ipri, itimo, queue, wakeup_swapper; 1148 #ifdef LOCK_PROFILING 1149 uint64_t waittime = 0; 1150 int contested = 0; 1151 #endif 1152 1153 if (panicstr != NULL) 1154 return (0); 1155 1156 error = 0; 1157 tid = (uintptr_t)curthread; 1158 op = (flags & LK_TYPE_MASK); 1159 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 1160 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 1161 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 1162 1163 lwa.iwmesg = iwmesg; 1164 lwa.ipri = ipri; 1165 lwa.itimo = itimo; 1166 1167 MPASS((flags & ~LK_TOTAL_MASK) == 0); 1168 KASSERT((op & (op - 1)) == 0, 1169 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 1170 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 1171 (op != LK_DOWNGRADE && op != LK_RELEASE), 1172 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 1173 __func__, file, line)); 1174 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 1175 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 1176 __func__, file, line)); 1177 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 1178 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 1179 lk->lock_object.lo_name, file, line)); 1180 1181 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 1182 1183 if (lk->lock_object.lo_flags & LK_NOSHARE) { 1184 switch (op) { 1185 case LK_SHARED: 1186 op = LK_EXCLUSIVE; 1187 break; 1188 case LK_UPGRADE: 1189 case LK_TRYUPGRADE: 1190 case LK_DOWNGRADE: 1191 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 1192 file, line); 1193 if (flags & LK_INTERLOCK) 1194 class->lc_unlock(ilk); 1195 return (0); 1196 } 1197 } 1198 1199 wakeup_swapper = 0; 1200 switch (op) { 1201 case LK_SHARED: 1202 return (lockmgr_slock_hard(lk, flags, ilk, file, line, &lwa)); 1203 break; 1204 case LK_UPGRADE: 1205 case LK_TRYUPGRADE: 1206 return (lockmgr_upgrade(lk, flags, ilk, file, line, &lwa)); 1207 break; 1208 case LK_EXCLUSIVE: 1209 return (lockmgr_xlock_hard(lk, flags, ilk, file, line, &lwa)); 1210 break; 1211 case LK_DOWNGRADE: 1212 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1213 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 1214 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 1215 1216 /* 1217 * Panic if the lock is recursed. 1218 */ 1219 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 1220 if (flags & LK_INTERLOCK) 1221 class->lc_unlock(ilk); 1222 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 1223 __func__, iwmesg, file, line); 1224 } 1225 TD_SLOCKS_INC(curthread); 1226 1227 /* 1228 * In order to preserve waiters flags, just spin. 1229 */ 1230 for (;;) { 1231 x = lk->lk_lock; 1232 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1233 x &= LK_ALL_WAITERS; 1234 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1235 LK_SHARERS_LOCK(1) | x)) 1236 break; 1237 cpu_spinwait(); 1238 } 1239 break; 1240 case LK_RELEASE: 1241 _lockmgr_assert(lk, KA_LOCKED, file, line); 1242 x = lk->lk_lock; 1243 1244 if (__predict_true(x & LK_SHARE) != 0) { 1245 return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line)); 1246 } else { 1247 return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line)); 1248 } 1249 break; 1250 case LK_DRAIN: 1251 if (LK_CAN_WITNESS(flags)) 1252 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1253 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 1254 ilk : NULL); 1255 1256 /* 1257 * Trying to drain a lock we already own will result in a 1258 * deadlock. 1259 */ 1260 if (lockmgr_xlocked(lk)) { 1261 if (flags & LK_INTERLOCK) 1262 class->lc_unlock(ilk); 1263 panic("%s: draining %s with the lock held @ %s:%d\n", 1264 __func__, iwmesg, file, line); 1265 } 1266 1267 for (;;) { 1268 if (lk->lk_lock == LK_UNLOCKED && 1269 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 1270 break; 1271 1272 #ifdef HWPMC_HOOKS 1273 PMC_SOFT_CALL( , , lock, failed); 1274 #endif 1275 lock_profile_obtain_lock_failed(&lk->lock_object, 1276 &contested, &waittime); 1277 1278 /* 1279 * If the lock is expected to not sleep just give up 1280 * and return. 1281 */ 1282 if (LK_TRYOP(flags)) { 1283 LOCK_LOG2(lk, "%s: %p fails the try operation", 1284 __func__, lk); 1285 error = EBUSY; 1286 break; 1287 } 1288 1289 /* 1290 * Acquire the sleepqueue chain lock because we 1291 * probabilly will need to manipulate waiters flags. 1292 */ 1293 sleepq_lock(&lk->lock_object); 1294 x = lk->lk_lock; 1295 1296 /* 1297 * if the lock has been released while we spun on 1298 * the sleepqueue chain lock just try again. 1299 */ 1300 if (x == LK_UNLOCKED) { 1301 sleepq_release(&lk->lock_object); 1302 continue; 1303 } 1304 1305 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1306 if ((x & ~v) == LK_UNLOCKED) { 1307 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1308 1309 /* 1310 * If interruptible sleeps left the exclusive 1311 * queue empty avoid a starvation for the 1312 * threads sleeping on the shared queue by 1313 * giving them precedence and cleaning up the 1314 * exclusive waiters bit anyway. 1315 * Please note that lk_exslpfail count may be 1316 * lying about the real number of waiters with 1317 * the LK_SLEEPFAIL flag on because they may 1318 * be used in conjunction with interruptible 1319 * sleeps so lk_exslpfail might be considered 1320 * an 'upper limit' bound, including the edge 1321 * cases. 1322 */ 1323 if (v & LK_EXCLUSIVE_WAITERS) { 1324 queue = SQ_EXCLUSIVE_QUEUE; 1325 v &= ~LK_EXCLUSIVE_WAITERS; 1326 } else { 1327 1328 /* 1329 * Exclusive waiters sleeping with 1330 * LK_SLEEPFAIL on and using 1331 * interruptible sleeps/timeout may 1332 * have left spourious lk_exslpfail 1333 * counts on, so clean it up anyway. 1334 */ 1335 MPASS(v & LK_SHARED_WAITERS); 1336 lk->lk_exslpfail = 0; 1337 queue = SQ_SHARED_QUEUE; 1338 v &= ~LK_SHARED_WAITERS; 1339 } 1340 if (queue == SQ_EXCLUSIVE_QUEUE) { 1341 realexslp = 1342 sleepq_sleepcnt(&lk->lock_object, 1343 SQ_EXCLUSIVE_QUEUE); 1344 if (lk->lk_exslpfail >= realexslp) { 1345 lk->lk_exslpfail = 0; 1346 queue = SQ_SHARED_QUEUE; 1347 v &= ~LK_SHARED_WAITERS; 1348 if (realexslp != 0) { 1349 LOCK_LOG2(lk, 1350 "%s: %p has only LK_SLEEPFAIL sleepers", 1351 __func__, lk); 1352 LOCK_LOG2(lk, 1353 "%s: %p waking up threads on the exclusive queue", 1354 __func__, lk); 1355 wakeup_swapper = 1356 sleepq_broadcast( 1357 &lk->lock_object, 1358 SLEEPQ_LK, 0, 1359 SQ_EXCLUSIVE_QUEUE); 1360 } 1361 } else 1362 lk->lk_exslpfail = 0; 1363 } 1364 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1365 sleepq_release(&lk->lock_object); 1366 continue; 1367 } 1368 LOCK_LOG3(lk, 1369 "%s: %p waking up all threads on the %s queue", 1370 __func__, lk, queue == SQ_SHARED_QUEUE ? 1371 "shared" : "exclusive"); 1372 wakeup_swapper |= sleepq_broadcast( 1373 &lk->lock_object, SLEEPQ_LK, 0, queue); 1374 1375 /* 1376 * If shared waiters have been woken up we need 1377 * to wait for one of them to acquire the lock 1378 * before to set the exclusive waiters in 1379 * order to avoid a deadlock. 1380 */ 1381 if (queue == SQ_SHARED_QUEUE) { 1382 for (v = lk->lk_lock; 1383 (v & LK_SHARE) && !LK_SHARERS(v); 1384 v = lk->lk_lock) 1385 cpu_spinwait(); 1386 } 1387 } 1388 1389 /* 1390 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1391 * fail, loop back and retry. 1392 */ 1393 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1394 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1395 x | LK_EXCLUSIVE_WAITERS)) { 1396 sleepq_release(&lk->lock_object); 1397 continue; 1398 } 1399 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1400 __func__, lk); 1401 } 1402 1403 /* 1404 * As far as we have been unable to acquire the 1405 * exclusive lock and the exclusive waiters flag 1406 * is set, we will sleep. 1407 */ 1408 if (flags & LK_INTERLOCK) { 1409 class->lc_unlock(ilk); 1410 flags &= ~LK_INTERLOCK; 1411 } 1412 GIANT_SAVE(); 1413 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1414 SQ_EXCLUSIVE_QUEUE); 1415 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1416 GIANT_RESTORE(); 1417 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1418 __func__, lk); 1419 } 1420 1421 if (error == 0) { 1422 lock_profile_obtain_lock_success(&lk->lock_object, 1423 contested, waittime, file, line); 1424 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1425 lk->lk_recurse, file, line); 1426 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1427 LK_TRYWIT(flags), file, line); 1428 TD_LOCKS_INC(curthread); 1429 STACK_SAVE(lk); 1430 } 1431 break; 1432 default: 1433 if (flags & LK_INTERLOCK) 1434 class->lc_unlock(ilk); 1435 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1436 } 1437 1438 if (flags & LK_INTERLOCK) 1439 class->lc_unlock(ilk); 1440 if (wakeup_swapper) 1441 kick_proc0(); 1442 1443 return (error); 1444 } 1445 1446 void 1447 _lockmgr_disown(struct lock *lk, const char *file, int line) 1448 { 1449 uintptr_t tid, x; 1450 1451 if (SCHEDULER_STOPPED()) 1452 return; 1453 1454 tid = (uintptr_t)curthread; 1455 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1456 1457 /* 1458 * Panic if the lock is recursed. 1459 */ 1460 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1461 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1462 __func__, file, line); 1463 1464 /* 1465 * If the owner is already LK_KERNPROC just skip the whole operation. 1466 */ 1467 if (LK_HOLDER(lk->lk_lock) != tid) 1468 return; 1469 lock_profile_release_lock(&lk->lock_object); 1470 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1471 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1472 TD_LOCKS_DEC(curthread); 1473 STACK_SAVE(lk); 1474 1475 /* 1476 * In order to preserve waiters flags, just spin. 1477 */ 1478 for (;;) { 1479 x = lk->lk_lock; 1480 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1481 x &= LK_ALL_WAITERS; 1482 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1483 LK_KERNPROC | x)) 1484 return; 1485 cpu_spinwait(); 1486 } 1487 } 1488 1489 void 1490 lockmgr_printinfo(const struct lock *lk) 1491 { 1492 struct thread *td; 1493 uintptr_t x; 1494 1495 if (lk->lk_lock == LK_UNLOCKED) 1496 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1497 else if (lk->lk_lock & LK_SHARE) 1498 printf("lock type %s: SHARED (count %ju)\n", 1499 lk->lock_object.lo_name, 1500 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1501 else { 1502 td = lockmgr_xholder(lk); 1503 if (td == (struct thread *)LK_KERNPROC) 1504 printf("lock type %s: EXCL by KERNPROC\n", 1505 lk->lock_object.lo_name); 1506 else 1507 printf("lock type %s: EXCL by thread %p " 1508 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, 1509 td, td->td_proc->p_pid, td->td_proc->p_comm, 1510 td->td_tid); 1511 } 1512 1513 x = lk->lk_lock; 1514 if (x & LK_EXCLUSIVE_WAITERS) 1515 printf(" with exclusive waiters pending\n"); 1516 if (x & LK_SHARED_WAITERS) 1517 printf(" with shared waiters pending\n"); 1518 if (x & LK_EXCLUSIVE_SPINNERS) 1519 printf(" with exclusive spinners pending\n"); 1520 1521 STACK_PRINT(lk); 1522 } 1523 1524 int 1525 lockstatus(const struct lock *lk) 1526 { 1527 uintptr_t v, x; 1528 int ret; 1529 1530 ret = LK_SHARED; 1531 x = lk->lk_lock; 1532 v = LK_HOLDER(x); 1533 1534 if ((x & LK_SHARE) == 0) { 1535 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1536 ret = LK_EXCLUSIVE; 1537 else 1538 ret = LK_EXCLOTHER; 1539 } else if (x == LK_UNLOCKED) 1540 ret = 0; 1541 1542 return (ret); 1543 } 1544 1545 #ifdef INVARIANT_SUPPORT 1546 1547 FEATURE(invariant_support, 1548 "Support for modules compiled with INVARIANTS option"); 1549 1550 #ifndef INVARIANTS 1551 #undef _lockmgr_assert 1552 #endif 1553 1554 void 1555 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1556 { 1557 int slocked = 0; 1558 1559 if (panicstr != NULL) 1560 return; 1561 switch (what) { 1562 case KA_SLOCKED: 1563 case KA_SLOCKED | KA_NOTRECURSED: 1564 case KA_SLOCKED | KA_RECURSED: 1565 slocked = 1; 1566 case KA_LOCKED: 1567 case KA_LOCKED | KA_NOTRECURSED: 1568 case KA_LOCKED | KA_RECURSED: 1569 #ifdef WITNESS 1570 1571 /* 1572 * We cannot trust WITNESS if the lock is held in exclusive 1573 * mode and a call to lockmgr_disown() happened. 1574 * Workaround this skipping the check if the lock is held in 1575 * exclusive mode even for the KA_LOCKED case. 1576 */ 1577 if (slocked || (lk->lk_lock & LK_SHARE)) { 1578 witness_assert(&lk->lock_object, what, file, line); 1579 break; 1580 } 1581 #endif 1582 if (lk->lk_lock == LK_UNLOCKED || 1583 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1584 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1585 panic("Lock %s not %slocked @ %s:%d\n", 1586 lk->lock_object.lo_name, slocked ? "share" : "", 1587 file, line); 1588 1589 if ((lk->lk_lock & LK_SHARE) == 0) { 1590 if (lockmgr_recursed(lk)) { 1591 if (what & KA_NOTRECURSED) 1592 panic("Lock %s recursed @ %s:%d\n", 1593 lk->lock_object.lo_name, file, 1594 line); 1595 } else if (what & KA_RECURSED) 1596 panic("Lock %s not recursed @ %s:%d\n", 1597 lk->lock_object.lo_name, file, line); 1598 } 1599 break; 1600 case KA_XLOCKED: 1601 case KA_XLOCKED | KA_NOTRECURSED: 1602 case KA_XLOCKED | KA_RECURSED: 1603 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1604 panic("Lock %s not exclusively locked @ %s:%d\n", 1605 lk->lock_object.lo_name, file, line); 1606 if (lockmgr_recursed(lk)) { 1607 if (what & KA_NOTRECURSED) 1608 panic("Lock %s recursed @ %s:%d\n", 1609 lk->lock_object.lo_name, file, line); 1610 } else if (what & KA_RECURSED) 1611 panic("Lock %s not recursed @ %s:%d\n", 1612 lk->lock_object.lo_name, file, line); 1613 break; 1614 case KA_UNLOCKED: 1615 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1616 panic("Lock %s exclusively locked @ %s:%d\n", 1617 lk->lock_object.lo_name, file, line); 1618 break; 1619 default: 1620 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1621 line); 1622 } 1623 } 1624 #endif 1625 1626 #ifdef DDB 1627 int 1628 lockmgr_chain(struct thread *td, struct thread **ownerp) 1629 { 1630 struct lock *lk; 1631 1632 lk = td->td_wchan; 1633 1634 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1635 return (0); 1636 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1637 if (lk->lk_lock & LK_SHARE) 1638 db_printf("SHARED (count %ju)\n", 1639 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1640 else 1641 db_printf("EXCL\n"); 1642 *ownerp = lockmgr_xholder(lk); 1643 1644 return (1); 1645 } 1646 1647 static void 1648 db_show_lockmgr(const struct lock_object *lock) 1649 { 1650 struct thread *td; 1651 const struct lock *lk; 1652 1653 lk = (const struct lock *)lock; 1654 1655 db_printf(" state: "); 1656 if (lk->lk_lock == LK_UNLOCKED) 1657 db_printf("UNLOCKED\n"); 1658 else if (lk->lk_lock & LK_SHARE) 1659 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1660 else { 1661 td = lockmgr_xholder(lk); 1662 if (td == (struct thread *)LK_KERNPROC) 1663 db_printf("XLOCK: LK_KERNPROC\n"); 1664 else 1665 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1666 td->td_tid, td->td_proc->p_pid, 1667 td->td_proc->p_comm); 1668 if (lockmgr_recursed(lk)) 1669 db_printf(" recursed: %d\n", lk->lk_recurse); 1670 } 1671 db_printf(" waiters: "); 1672 switch (lk->lk_lock & LK_ALL_WAITERS) { 1673 case LK_SHARED_WAITERS: 1674 db_printf("shared\n"); 1675 break; 1676 case LK_EXCLUSIVE_WAITERS: 1677 db_printf("exclusive\n"); 1678 break; 1679 case LK_ALL_WAITERS: 1680 db_printf("shared and exclusive\n"); 1681 break; 1682 default: 1683 db_printf("none\n"); 1684 } 1685 db_printf(" spinners: "); 1686 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1687 db_printf("exclusive\n"); 1688 else 1689 db_printf("none\n"); 1690 } 1691 #endif 1692