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