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 (__predict_false(_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 (__predict_false(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 static bool __always_inline 116 LK_CAN_SHARE(uintptr_t x, int flags, bool fp) 117 { 118 119 if ((x & (LK_SHARE | LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) == 120 LK_SHARE) 121 return (true); 122 if (fp || (!(x & LK_SHARE))) 123 return (false); 124 if ((curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) || 125 (curthread->td_pflags & TDP_DEADLKTREAT)) 126 return (true); 127 return (false); 128 } 129 130 #define LK_TRYOP(x) \ 131 ((x) & LK_NOWAIT) 132 133 #define LK_CAN_WITNESS(x) \ 134 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 135 #define LK_TRYWIT(x) \ 136 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 137 138 #define LK_CAN_ADAPT(lk, f) \ 139 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 140 ((f) & LK_SLEEPFAIL) == 0) 141 142 #define lockmgr_disowned(lk) \ 143 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 144 145 #define lockmgr_xlocked_v(v) \ 146 (((v) & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 147 148 #define lockmgr_xlocked(lk) lockmgr_xlocked_v((lk)->lk_lock) 149 150 static void assert_lockmgr(const struct lock_object *lock, int how); 151 #ifdef DDB 152 static void db_show_lockmgr(const struct lock_object *lock); 153 #endif 154 static void lock_lockmgr(struct lock_object *lock, uintptr_t how); 155 #ifdef KDTRACE_HOOKS 156 static int owner_lockmgr(const struct lock_object *lock, 157 struct thread **owner); 158 #endif 159 static uintptr_t unlock_lockmgr(struct lock_object *lock); 160 161 struct lock_class lock_class_lockmgr = { 162 .lc_name = "lockmgr", 163 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 164 .lc_assert = assert_lockmgr, 165 #ifdef DDB 166 .lc_ddb_show = db_show_lockmgr, 167 #endif 168 .lc_lock = lock_lockmgr, 169 .lc_unlock = unlock_lockmgr, 170 #ifdef KDTRACE_HOOKS 171 .lc_owner = owner_lockmgr, 172 #endif 173 }; 174 175 struct lockmgr_wait { 176 const char *iwmesg; 177 int ipri; 178 int itimo; 179 }; 180 181 static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp, 182 int flags, bool fp); 183 static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp); 184 185 static void 186 lockmgr_exit(u_int flags, struct lock_object *ilk, int wakeup_swapper) 187 { 188 struct lock_class *class; 189 190 if (flags & LK_INTERLOCK) { 191 class = LOCK_CLASS(ilk); 192 class->lc_unlock(ilk); 193 } 194 195 if (__predict_false(wakeup_swapper)) 196 kick_proc0(); 197 } 198 199 static void 200 lockmgr_note_shared_acquire(struct lock *lk, int contested, 201 uint64_t waittime, const char *file, int line, int flags) 202 { 203 204 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime, 205 file, line); 206 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line); 207 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line); 208 TD_LOCKS_INC(curthread); 209 TD_SLOCKS_INC(curthread); 210 STACK_SAVE(lk); 211 } 212 213 static void 214 lockmgr_note_shared_release(struct lock *lk, const char *file, int line) 215 { 216 217 lock_profile_release_lock(&lk->lock_object); 218 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 219 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 220 TD_LOCKS_DEC(curthread); 221 TD_SLOCKS_DEC(curthread); 222 } 223 224 static void 225 lockmgr_note_exclusive_acquire(struct lock *lk, int contested, 226 uint64_t waittime, const char *file, int line, int flags) 227 { 228 229 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime, 230 file, line); 231 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line); 232 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, 233 line); 234 TD_LOCKS_INC(curthread); 235 STACK_SAVE(lk); 236 } 237 238 static void 239 lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line) 240 { 241 242 lock_profile_release_lock(&lk->lock_object); 243 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, 244 line); 245 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 246 TD_LOCKS_DEC(curthread); 247 } 248 249 static __inline struct thread * 250 lockmgr_xholder(const struct lock *lk) 251 { 252 uintptr_t x; 253 254 x = lk->lk_lock; 255 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 256 } 257 258 /* 259 * It assumes sleepq_lock held and returns with this one unheld. 260 * It also assumes the generic interlock is sane and previously checked. 261 * If LK_INTERLOCK is specified the interlock is not reacquired after the 262 * sleep. 263 */ 264 static __inline int 265 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 266 const char *wmesg, int pri, int timo, int queue) 267 { 268 GIANT_DECLARE; 269 struct lock_class *class; 270 int catch, error; 271 272 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 273 catch = pri & PCATCH; 274 pri &= PRIMASK; 275 error = 0; 276 277 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 278 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 279 280 if (flags & LK_INTERLOCK) 281 class->lc_unlock(ilk); 282 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 283 lk->lk_exslpfail++; 284 GIANT_SAVE(); 285 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 286 SLEEPQ_INTERRUPTIBLE : 0), queue); 287 if ((flags & LK_TIMELOCK) && timo) 288 sleepq_set_timeout(&lk->lock_object, timo); 289 290 /* 291 * Decisional switch for real sleeping. 292 */ 293 if ((flags & LK_TIMELOCK) && timo && catch) 294 error = sleepq_timedwait_sig(&lk->lock_object, pri); 295 else if ((flags & LK_TIMELOCK) && timo) 296 error = sleepq_timedwait(&lk->lock_object, pri); 297 else if (catch) 298 error = sleepq_wait_sig(&lk->lock_object, pri); 299 else 300 sleepq_wait(&lk->lock_object, pri); 301 GIANT_RESTORE(); 302 if ((flags & LK_SLEEPFAIL) && error == 0) 303 error = ENOLCK; 304 305 return (error); 306 } 307 308 static __inline int 309 wakeupshlk(struct lock *lk, const char *file, int line) 310 { 311 uintptr_t v, x, orig_x; 312 u_int realexslp; 313 int queue, wakeup_swapper; 314 315 wakeup_swapper = 0; 316 for (;;) { 317 x = lk->lk_lock; 318 if (lockmgr_sunlock_try(lk, &x)) 319 break; 320 321 /* 322 * We should have a sharer with waiters, so enter the hard 323 * path in order to handle wakeups correctly. 324 */ 325 sleepq_lock(&lk->lock_object); 326 orig_x = lk->lk_lock; 327 retry_sleepq: 328 x = orig_x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 329 v = LK_UNLOCKED; 330 331 /* 332 * If the lock has exclusive waiters, give them preference in 333 * order to avoid deadlock with shared runners up. 334 * If interruptible sleeps left the exclusive queue empty 335 * avoid a starvation for the threads sleeping on the shared 336 * queue by giving them precedence and cleaning up the 337 * exclusive waiters bit anyway. 338 * Please note that lk_exslpfail count may be lying about 339 * the real number of waiters with the LK_SLEEPFAIL flag on 340 * because they may be used in conjunction with interruptible 341 * sleeps so lk_exslpfail might be considered an 'upper limit' 342 * bound, including the edge cases. 343 */ 344 realexslp = sleepq_sleepcnt(&lk->lock_object, 345 SQ_EXCLUSIVE_QUEUE); 346 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 347 if (lk->lk_exslpfail < realexslp) { 348 lk->lk_exslpfail = 0; 349 queue = SQ_EXCLUSIVE_QUEUE; 350 v |= (x & LK_SHARED_WAITERS); 351 } else { 352 lk->lk_exslpfail = 0; 353 LOCK_LOG2(lk, 354 "%s: %p has only LK_SLEEPFAIL sleepers", 355 __func__, lk); 356 LOCK_LOG2(lk, 357 "%s: %p waking up threads on the exclusive queue", 358 __func__, lk); 359 wakeup_swapper = 360 sleepq_broadcast(&lk->lock_object, 361 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 362 queue = SQ_SHARED_QUEUE; 363 } 364 365 } else { 366 367 /* 368 * Exclusive waiters sleeping with LK_SLEEPFAIL on 369 * and using interruptible sleeps/timeout may have 370 * left spourious lk_exslpfail counts on, so clean 371 * it up anyway. 372 */ 373 lk->lk_exslpfail = 0; 374 queue = SQ_SHARED_QUEUE; 375 } 376 377 if (lockmgr_sunlock_try(lk, &orig_x)) { 378 sleepq_release(&lk->lock_object); 379 break; 380 } 381 382 x |= LK_SHARERS_LOCK(1); 383 if (!atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, v)) { 384 orig_x = x; 385 goto retry_sleepq; 386 } 387 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 388 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 389 "exclusive"); 390 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 391 0, queue); 392 sleepq_release(&lk->lock_object); 393 break; 394 } 395 396 lockmgr_note_shared_release(lk, file, line); 397 return (wakeup_swapper); 398 } 399 400 static void 401 assert_lockmgr(const struct lock_object *lock, int what) 402 { 403 404 panic("lockmgr locks do not support assertions"); 405 } 406 407 static void 408 lock_lockmgr(struct lock_object *lock, uintptr_t how) 409 { 410 411 panic("lockmgr locks do not support sleep interlocking"); 412 } 413 414 static uintptr_t 415 unlock_lockmgr(struct lock_object *lock) 416 { 417 418 panic("lockmgr locks do not support sleep interlocking"); 419 } 420 421 #ifdef KDTRACE_HOOKS 422 static int 423 owner_lockmgr(const struct lock_object *lock, struct thread **owner) 424 { 425 426 panic("lockmgr locks do not support owner inquiring"); 427 } 428 #endif 429 430 void 431 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 432 { 433 int iflags; 434 435 MPASS((flags & ~LK_INIT_MASK) == 0); 436 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 437 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 438 &lk->lk_lock)); 439 440 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 441 if (flags & LK_CANRECURSE) 442 iflags |= LO_RECURSABLE; 443 if ((flags & LK_NODUP) == 0) 444 iflags |= LO_DUPOK; 445 if (flags & LK_NOPROFILE) 446 iflags |= LO_NOPROFILE; 447 if ((flags & LK_NOWITNESS) == 0) 448 iflags |= LO_WITNESS; 449 if (flags & LK_QUIET) 450 iflags |= LO_QUIET; 451 if (flags & LK_IS_VNODE) 452 iflags |= LO_IS_VNODE; 453 if (flags & LK_NEW) 454 iflags |= LO_NEW; 455 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 456 457 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 458 lk->lk_lock = LK_UNLOCKED; 459 lk->lk_recurse = 0; 460 lk->lk_exslpfail = 0; 461 lk->lk_timo = timo; 462 lk->lk_pri = pri; 463 STACK_ZERO(lk); 464 } 465 466 /* 467 * XXX: Gross hacks to manipulate external lock flags after 468 * initialization. Used for certain vnode and buf locks. 469 */ 470 void 471 lockallowshare(struct lock *lk) 472 { 473 474 lockmgr_assert(lk, KA_XLOCKED); 475 lk->lock_object.lo_flags &= ~LK_NOSHARE; 476 } 477 478 void 479 lockdisableshare(struct lock *lk) 480 { 481 482 lockmgr_assert(lk, KA_XLOCKED); 483 lk->lock_object.lo_flags |= LK_NOSHARE; 484 } 485 486 void 487 lockallowrecurse(struct lock *lk) 488 { 489 490 lockmgr_assert(lk, KA_XLOCKED); 491 lk->lock_object.lo_flags |= LO_RECURSABLE; 492 } 493 494 void 495 lockdisablerecurse(struct lock *lk) 496 { 497 498 lockmgr_assert(lk, KA_XLOCKED); 499 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 500 } 501 502 void 503 lockdestroy(struct lock *lk) 504 { 505 506 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 507 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 508 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 509 lock_destroy(&lk->lock_object); 510 } 511 512 static bool __always_inline 513 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags, bool fp) 514 { 515 516 /* 517 * If no other thread has an exclusive lock, or 518 * no exclusive waiter is present, bump the count of 519 * sharers. Since we have to preserve the state of 520 * waiters, if we fail to acquire the shared lock 521 * loop back and retry. 522 */ 523 *xp = lk->lk_lock; 524 while (LK_CAN_SHARE(*xp, flags, fp)) { 525 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp, 526 *xp + LK_ONE_SHARER)) { 527 return (true); 528 } 529 } 530 return (false); 531 } 532 533 static bool __always_inline 534 lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp) 535 { 536 537 for (;;) { 538 if (LK_SHARERS(*xp) > 1 || !(*xp & LK_ALL_WAITERS)) { 539 if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp, 540 *xp - LK_ONE_SHARER)) 541 return (true); 542 continue; 543 } 544 break; 545 } 546 return (false); 547 } 548 549 static __noinline int 550 lockmgr_slock_hard(struct lock *lk, u_int flags, struct lock_object *ilk, 551 const char *file, int line, struct lockmgr_wait *lwa) 552 { 553 uintptr_t tid, x; 554 int error = 0; 555 const char *iwmesg; 556 int ipri, itimo; 557 558 #ifdef LOCK_PROFILING 559 uint64_t waittime = 0; 560 int contested = 0; 561 #endif 562 563 if (__predict_false(panicstr != NULL)) 564 goto out; 565 566 tid = (uintptr_t)curthread; 567 568 if (LK_CAN_WITNESS(flags)) 569 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 570 file, line, flags & LK_INTERLOCK ? ilk : NULL); 571 for (;;) { 572 if (lockmgr_slock_try(lk, &x, flags, false)) 573 break; 574 #ifdef HWPMC_HOOKS 575 PMC_SOFT_CALL( , , lock, failed); 576 #endif 577 lock_profile_obtain_lock_failed(&lk->lock_object, 578 &contested, &waittime); 579 580 /* 581 * If the lock is already held by curthread in 582 * exclusive way avoid a deadlock. 583 */ 584 if (LK_HOLDER(x) == tid) { 585 LOCK_LOG2(lk, 586 "%s: %p already held in exclusive mode", 587 __func__, lk); 588 error = EDEADLK; 589 break; 590 } 591 592 /* 593 * If the lock is expected to not sleep just give up 594 * and return. 595 */ 596 if (LK_TRYOP(flags)) { 597 LOCK_LOG2(lk, "%s: %p fails the try operation", 598 __func__, lk); 599 error = EBUSY; 600 break; 601 } 602 603 /* 604 * Acquire the sleepqueue chain lock because we 605 * probabilly will need to manipulate waiters flags. 606 */ 607 sleepq_lock(&lk->lock_object); 608 x = lk->lk_lock; 609 retry_sleepq: 610 611 /* 612 * if the lock can be acquired in shared mode, try 613 * again. 614 */ 615 if (LK_CAN_SHARE(x, flags, false)) { 616 sleepq_release(&lk->lock_object); 617 continue; 618 } 619 620 /* 621 * Try to set the LK_SHARED_WAITERS flag. If we fail, 622 * loop back and retry. 623 */ 624 if ((x & LK_SHARED_WAITERS) == 0) { 625 if (!atomic_fcmpset_acq_ptr(&lk->lk_lock, &x, 626 x | LK_SHARED_WAITERS)) { 627 goto retry_sleepq; 628 } 629 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 630 __func__, lk); 631 } 632 633 if (lwa == NULL) { 634 iwmesg = lk->lock_object.lo_name; 635 ipri = lk->lk_pri; 636 itimo = lk->lk_timo; 637 } else { 638 iwmesg = lwa->iwmesg; 639 ipri = lwa->ipri; 640 itimo = lwa->itimo; 641 } 642 643 /* 644 * As far as we have been unable to acquire the 645 * shared lock and the shared waiters flag is set, 646 * we will sleep. 647 */ 648 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 649 SQ_SHARED_QUEUE); 650 flags &= ~LK_INTERLOCK; 651 if (error) { 652 LOCK_LOG3(lk, 653 "%s: interrupted sleep for %p with %d", 654 __func__, lk, error); 655 break; 656 } 657 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 658 __func__, lk); 659 } 660 if (error == 0) { 661 #ifdef LOCK_PROFILING 662 lockmgr_note_shared_acquire(lk, contested, waittime, 663 file, line, flags); 664 #else 665 lockmgr_note_shared_acquire(lk, 0, 0, file, line, 666 flags); 667 #endif 668 } 669 670 out: 671 lockmgr_exit(flags, ilk, 0); 672 return (error); 673 } 674 675 static __noinline int 676 lockmgr_xlock_hard(struct lock *lk, u_int flags, struct lock_object *ilk, 677 const char *file, int line, struct lockmgr_wait *lwa) 678 { 679 struct lock_class *class; 680 uintptr_t tid, x, v; 681 int error = 0; 682 const char *iwmesg; 683 int ipri, itimo; 684 685 #ifdef LOCK_PROFILING 686 uint64_t waittime = 0; 687 int contested = 0; 688 #endif 689 690 if (__predict_false(panicstr != NULL)) 691 goto out; 692 693 tid = (uintptr_t)curthread; 694 695 if (LK_CAN_WITNESS(flags)) 696 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 697 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 698 ilk : NULL); 699 700 /* 701 * If curthread already holds the lock and this one is 702 * allowed to recurse, simply recurse on it. 703 */ 704 if (lockmgr_xlocked(lk)) { 705 if ((flags & LK_CANRECURSE) == 0 && 706 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 707 /* 708 * If the lock is expected to not panic just 709 * give up and return. 710 */ 711 if (LK_TRYOP(flags)) { 712 LOCK_LOG2(lk, 713 "%s: %p fails the try operation", 714 __func__, lk); 715 error = EBUSY; 716 goto out; 717 } 718 if (flags & LK_INTERLOCK) { 719 class = LOCK_CLASS(ilk); 720 class->lc_unlock(ilk); 721 } 722 panic("%s: recursing on non recursive lockmgr %p " 723 "@ %s:%d\n", __func__, lk, file, line); 724 } 725 lk->lk_recurse++; 726 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 727 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 728 lk->lk_recurse, file, line); 729 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 730 LK_TRYWIT(flags), file, line); 731 TD_LOCKS_INC(curthread); 732 goto out; 733 } 734 735 for (;;) { 736 if (lk->lk_lock == LK_UNLOCKED && 737 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 738 break; 739 #ifdef HWPMC_HOOKS 740 PMC_SOFT_CALL( , , lock, failed); 741 #endif 742 lock_profile_obtain_lock_failed(&lk->lock_object, 743 &contested, &waittime); 744 745 /* 746 * If the lock is expected to not sleep just give up 747 * and return. 748 */ 749 if (LK_TRYOP(flags)) { 750 LOCK_LOG2(lk, "%s: %p fails the try operation", 751 __func__, lk); 752 error = EBUSY; 753 break; 754 } 755 756 /* 757 * Acquire the sleepqueue chain lock because we 758 * probabilly will need to manipulate waiters flags. 759 */ 760 sleepq_lock(&lk->lock_object); 761 x = lk->lk_lock; 762 retry_sleepq: 763 764 /* 765 * if the lock has been released while we spun on 766 * the sleepqueue chain lock just try again. 767 */ 768 if (x == LK_UNLOCKED) { 769 sleepq_release(&lk->lock_object); 770 continue; 771 } 772 773 /* 774 * The lock can be in the state where there is a 775 * pending queue of waiters, but still no owner. 776 * This happens when the lock is contested and an 777 * owner is going to claim the lock. 778 * If curthread is the one successfully acquiring it 779 * claim lock ownership and return, preserving waiters 780 * flags. 781 */ 782 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 783 if ((x & ~v) == LK_UNLOCKED) { 784 v &= ~LK_EXCLUSIVE_SPINNERS; 785 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x, 786 tid | v)) { 787 sleepq_release(&lk->lock_object); 788 LOCK_LOG2(lk, 789 "%s: %p claimed by a new writer", 790 __func__, lk); 791 break; 792 } 793 goto retry_sleepq; 794 } 795 796 /* 797 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 798 * fail, loop back and retry. 799 */ 800 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 801 if (!atomic_fcmpset_ptr(&lk->lk_lock, &x, 802 x | LK_EXCLUSIVE_WAITERS)) { 803 goto retry_sleepq; 804 } 805 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 806 __func__, lk); 807 } 808 809 if (lwa == NULL) { 810 iwmesg = lk->lock_object.lo_name; 811 ipri = lk->lk_pri; 812 itimo = lk->lk_timo; 813 } else { 814 iwmesg = lwa->iwmesg; 815 ipri = lwa->ipri; 816 itimo = lwa->itimo; 817 } 818 819 /* 820 * As far as we have been unable to acquire the 821 * exclusive lock and the exclusive waiters flag 822 * is set, we will sleep. 823 */ 824 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 825 SQ_EXCLUSIVE_QUEUE); 826 flags &= ~LK_INTERLOCK; 827 if (error) { 828 LOCK_LOG3(lk, 829 "%s: interrupted sleep for %p with %d", 830 __func__, lk, error); 831 break; 832 } 833 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 834 __func__, lk); 835 } 836 if (error == 0) { 837 #ifdef LOCK_PROFILING 838 lockmgr_note_exclusive_acquire(lk, contested, waittime, 839 file, line, flags); 840 #else 841 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line, 842 flags); 843 #endif 844 } 845 846 out: 847 lockmgr_exit(flags, ilk, 0); 848 return (error); 849 } 850 851 static __noinline int 852 lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk, 853 const char *file, int line, struct lockmgr_wait *lwa) 854 { 855 uintptr_t tid, x, v; 856 int error = 0; 857 int wakeup_swapper = 0; 858 int op; 859 860 if (__predict_false(panicstr != NULL)) 861 goto out; 862 863 tid = (uintptr_t)curthread; 864 865 _lockmgr_assert(lk, KA_SLOCKED, file, line); 866 v = lk->lk_lock; 867 x = v & LK_ALL_WAITERS; 868 v &= LK_EXCLUSIVE_SPINNERS; 869 870 /* 871 * Try to switch from one shared lock to an exclusive one. 872 * We need to preserve waiters flags during the operation. 873 */ 874 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 875 tid | x)) { 876 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 877 line); 878 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 879 LK_TRYWIT(flags), file, line); 880 TD_SLOCKS_DEC(curthread); 881 goto out; 882 } 883 884 op = flags & LK_TYPE_MASK; 885 886 /* 887 * In LK_TRYUPGRADE mode, do not drop the lock, 888 * returning EBUSY instead. 889 */ 890 if (op == LK_TRYUPGRADE) { 891 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", 892 __func__, lk); 893 error = EBUSY; 894 goto out; 895 } 896 897 /* 898 * We have been unable to succeed in upgrading, so just 899 * give up the shared lock. 900 */ 901 wakeup_swapper |= wakeupshlk(lk, file, line); 902 error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa); 903 flags &= ~LK_INTERLOCK; 904 out: 905 lockmgr_exit(flags, ilk, wakeup_swapper); 906 return (error); 907 } 908 909 int 910 lockmgr_lock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk, 911 const char *file, int line) 912 { 913 struct lock_class *class; 914 uintptr_t x, tid; 915 u_int op; 916 bool locked; 917 918 if (__predict_false(panicstr != NULL)) 919 return (0); 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, true)) { 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_v(x) && 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 (x == tid && 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 const char *file; 1100 int line; 1101 1102 if (__predict_false(panicstr != NULL)) 1103 return (0); 1104 1105 file = __FILE__; 1106 line = __LINE__; 1107 1108 _lockmgr_assert(lk, KA_LOCKED, file, line); 1109 x = lk->lk_lock; 1110 if (__predict_true(x & LK_SHARE) != 0) { 1111 if (lockmgr_sunlock_try(lk, &x)) { 1112 lockmgr_note_shared_release(lk, file, line); 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 } else { 1122 return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line)); 1123 } 1124 } 1125 if (__predict_false(flags & LK_INTERLOCK)) { 1126 class = LOCK_CLASS(ilk); 1127 class->lc_unlock(ilk); 1128 } 1129 return (0); 1130 } 1131 1132 int 1133 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 1134 const char *wmesg, int pri, int timo, const char *file, int line) 1135 { 1136 GIANT_DECLARE; 1137 struct lockmgr_wait lwa; 1138 struct lock_class *class; 1139 const char *iwmesg; 1140 uintptr_t tid, v, x; 1141 u_int op, realexslp; 1142 int error, ipri, itimo, queue, wakeup_swapper; 1143 #ifdef LOCK_PROFILING 1144 uint64_t waittime = 0; 1145 int contested = 0; 1146 #endif 1147 1148 if (panicstr != NULL) 1149 return (0); 1150 1151 error = 0; 1152 tid = (uintptr_t)curthread; 1153 op = (flags & LK_TYPE_MASK); 1154 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 1155 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 1156 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 1157 1158 lwa.iwmesg = iwmesg; 1159 lwa.ipri = ipri; 1160 lwa.itimo = itimo; 1161 1162 MPASS((flags & ~LK_TOTAL_MASK) == 0); 1163 KASSERT((op & (op - 1)) == 0, 1164 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 1165 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 1166 (op != LK_DOWNGRADE && op != LK_RELEASE), 1167 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 1168 __func__, file, line)); 1169 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 1170 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 1171 __func__, file, line)); 1172 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 1173 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 1174 lk->lock_object.lo_name, file, line)); 1175 1176 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 1177 1178 if (lk->lock_object.lo_flags & LK_NOSHARE) { 1179 switch (op) { 1180 case LK_SHARED: 1181 op = LK_EXCLUSIVE; 1182 break; 1183 case LK_UPGRADE: 1184 case LK_TRYUPGRADE: 1185 case LK_DOWNGRADE: 1186 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 1187 file, line); 1188 if (flags & LK_INTERLOCK) 1189 class->lc_unlock(ilk); 1190 return (0); 1191 } 1192 } 1193 1194 wakeup_swapper = 0; 1195 switch (op) { 1196 case LK_SHARED: 1197 return (lockmgr_slock_hard(lk, flags, ilk, file, line, &lwa)); 1198 break; 1199 case LK_UPGRADE: 1200 case LK_TRYUPGRADE: 1201 return (lockmgr_upgrade(lk, flags, ilk, file, line, &lwa)); 1202 break; 1203 case LK_EXCLUSIVE: 1204 return (lockmgr_xlock_hard(lk, flags, ilk, file, line, &lwa)); 1205 break; 1206 case LK_DOWNGRADE: 1207 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1208 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 1209 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 1210 1211 /* 1212 * Panic if the lock is recursed. 1213 */ 1214 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 1215 if (flags & LK_INTERLOCK) 1216 class->lc_unlock(ilk); 1217 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 1218 __func__, iwmesg, file, line); 1219 } 1220 TD_SLOCKS_INC(curthread); 1221 1222 /* 1223 * In order to preserve waiters flags, just spin. 1224 */ 1225 for (;;) { 1226 x = lk->lk_lock; 1227 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1228 x &= LK_ALL_WAITERS; 1229 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1230 LK_SHARERS_LOCK(1) | x)) 1231 break; 1232 cpu_spinwait(); 1233 } 1234 break; 1235 case LK_RELEASE: 1236 _lockmgr_assert(lk, KA_LOCKED, file, line); 1237 x = lk->lk_lock; 1238 1239 if (__predict_true(x & LK_SHARE) != 0) { 1240 return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line)); 1241 } else { 1242 return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line)); 1243 } 1244 break; 1245 case LK_DRAIN: 1246 if (LK_CAN_WITNESS(flags)) 1247 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1248 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 1249 ilk : NULL); 1250 1251 /* 1252 * Trying to drain a lock we already own will result in a 1253 * deadlock. 1254 */ 1255 if (lockmgr_xlocked(lk)) { 1256 if (flags & LK_INTERLOCK) 1257 class->lc_unlock(ilk); 1258 panic("%s: draining %s with the lock held @ %s:%d\n", 1259 __func__, iwmesg, file, line); 1260 } 1261 1262 for (;;) { 1263 if (lk->lk_lock == LK_UNLOCKED && 1264 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 1265 break; 1266 1267 #ifdef HWPMC_HOOKS 1268 PMC_SOFT_CALL( , , lock, failed); 1269 #endif 1270 lock_profile_obtain_lock_failed(&lk->lock_object, 1271 &contested, &waittime); 1272 1273 /* 1274 * If the lock is expected to not sleep just give up 1275 * and return. 1276 */ 1277 if (LK_TRYOP(flags)) { 1278 LOCK_LOG2(lk, "%s: %p fails the try operation", 1279 __func__, lk); 1280 error = EBUSY; 1281 break; 1282 } 1283 1284 /* 1285 * Acquire the sleepqueue chain lock because we 1286 * probabilly will need to manipulate waiters flags. 1287 */ 1288 sleepq_lock(&lk->lock_object); 1289 x = lk->lk_lock; 1290 1291 /* 1292 * if the lock has been released while we spun on 1293 * the sleepqueue chain lock just try again. 1294 */ 1295 if (x == LK_UNLOCKED) { 1296 sleepq_release(&lk->lock_object); 1297 continue; 1298 } 1299 1300 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1301 if ((x & ~v) == LK_UNLOCKED) { 1302 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1303 1304 /* 1305 * If interruptible sleeps left the exclusive 1306 * queue empty avoid a starvation for the 1307 * threads sleeping on the shared queue by 1308 * giving them precedence and cleaning up the 1309 * exclusive waiters bit anyway. 1310 * Please note that lk_exslpfail count may be 1311 * lying about the real number of waiters with 1312 * the LK_SLEEPFAIL flag on because they may 1313 * be used in conjunction with interruptible 1314 * sleeps so lk_exslpfail might be considered 1315 * an 'upper limit' bound, including the edge 1316 * cases. 1317 */ 1318 if (v & LK_EXCLUSIVE_WAITERS) { 1319 queue = SQ_EXCLUSIVE_QUEUE; 1320 v &= ~LK_EXCLUSIVE_WAITERS; 1321 } else { 1322 1323 /* 1324 * Exclusive waiters sleeping with 1325 * LK_SLEEPFAIL on and using 1326 * interruptible sleeps/timeout may 1327 * have left spourious lk_exslpfail 1328 * counts on, so clean it up anyway. 1329 */ 1330 MPASS(v & LK_SHARED_WAITERS); 1331 lk->lk_exslpfail = 0; 1332 queue = SQ_SHARED_QUEUE; 1333 v &= ~LK_SHARED_WAITERS; 1334 } 1335 if (queue == SQ_EXCLUSIVE_QUEUE) { 1336 realexslp = 1337 sleepq_sleepcnt(&lk->lock_object, 1338 SQ_EXCLUSIVE_QUEUE); 1339 if (lk->lk_exslpfail >= realexslp) { 1340 lk->lk_exslpfail = 0; 1341 queue = SQ_SHARED_QUEUE; 1342 v &= ~LK_SHARED_WAITERS; 1343 if (realexslp != 0) { 1344 LOCK_LOG2(lk, 1345 "%s: %p has only LK_SLEEPFAIL sleepers", 1346 __func__, lk); 1347 LOCK_LOG2(lk, 1348 "%s: %p waking up threads on the exclusive queue", 1349 __func__, lk); 1350 wakeup_swapper = 1351 sleepq_broadcast( 1352 &lk->lock_object, 1353 SLEEPQ_LK, 0, 1354 SQ_EXCLUSIVE_QUEUE); 1355 } 1356 } else 1357 lk->lk_exslpfail = 0; 1358 } 1359 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1360 sleepq_release(&lk->lock_object); 1361 continue; 1362 } 1363 LOCK_LOG3(lk, 1364 "%s: %p waking up all threads on the %s queue", 1365 __func__, lk, queue == SQ_SHARED_QUEUE ? 1366 "shared" : "exclusive"); 1367 wakeup_swapper |= sleepq_broadcast( 1368 &lk->lock_object, SLEEPQ_LK, 0, queue); 1369 1370 /* 1371 * If shared waiters have been woken up we need 1372 * to wait for one of them to acquire the lock 1373 * before to set the exclusive waiters in 1374 * order to avoid a deadlock. 1375 */ 1376 if (queue == SQ_SHARED_QUEUE) { 1377 for (v = lk->lk_lock; 1378 (v & LK_SHARE) && !LK_SHARERS(v); 1379 v = lk->lk_lock) 1380 cpu_spinwait(); 1381 } 1382 } 1383 1384 /* 1385 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1386 * fail, loop back and retry. 1387 */ 1388 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1389 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1390 x | LK_EXCLUSIVE_WAITERS)) { 1391 sleepq_release(&lk->lock_object); 1392 continue; 1393 } 1394 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1395 __func__, lk); 1396 } 1397 1398 /* 1399 * As far as we have been unable to acquire the 1400 * exclusive lock and the exclusive waiters flag 1401 * is set, we will sleep. 1402 */ 1403 if (flags & LK_INTERLOCK) { 1404 class->lc_unlock(ilk); 1405 flags &= ~LK_INTERLOCK; 1406 } 1407 GIANT_SAVE(); 1408 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1409 SQ_EXCLUSIVE_QUEUE); 1410 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1411 GIANT_RESTORE(); 1412 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1413 __func__, lk); 1414 } 1415 1416 if (error == 0) { 1417 lock_profile_obtain_lock_success(&lk->lock_object, 1418 contested, waittime, file, line); 1419 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1420 lk->lk_recurse, file, line); 1421 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1422 LK_TRYWIT(flags), file, line); 1423 TD_LOCKS_INC(curthread); 1424 STACK_SAVE(lk); 1425 } 1426 break; 1427 default: 1428 if (flags & LK_INTERLOCK) 1429 class->lc_unlock(ilk); 1430 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1431 } 1432 1433 if (flags & LK_INTERLOCK) 1434 class->lc_unlock(ilk); 1435 if (wakeup_swapper) 1436 kick_proc0(); 1437 1438 return (error); 1439 } 1440 1441 void 1442 _lockmgr_disown(struct lock *lk, const char *file, int line) 1443 { 1444 uintptr_t tid, x; 1445 1446 if (SCHEDULER_STOPPED()) 1447 return; 1448 1449 tid = (uintptr_t)curthread; 1450 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1451 1452 /* 1453 * Panic if the lock is recursed. 1454 */ 1455 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1456 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1457 __func__, file, line); 1458 1459 /* 1460 * If the owner is already LK_KERNPROC just skip the whole operation. 1461 */ 1462 if (LK_HOLDER(lk->lk_lock) != tid) 1463 return; 1464 lock_profile_release_lock(&lk->lock_object); 1465 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1466 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1467 TD_LOCKS_DEC(curthread); 1468 STACK_SAVE(lk); 1469 1470 /* 1471 * In order to preserve waiters flags, just spin. 1472 */ 1473 for (;;) { 1474 x = lk->lk_lock; 1475 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1476 x &= LK_ALL_WAITERS; 1477 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1478 LK_KERNPROC | x)) 1479 return; 1480 cpu_spinwait(); 1481 } 1482 } 1483 1484 void 1485 lockmgr_printinfo(const struct lock *lk) 1486 { 1487 struct thread *td; 1488 uintptr_t x; 1489 1490 if (lk->lk_lock == LK_UNLOCKED) 1491 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1492 else if (lk->lk_lock & LK_SHARE) 1493 printf("lock type %s: SHARED (count %ju)\n", 1494 lk->lock_object.lo_name, 1495 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1496 else { 1497 td = lockmgr_xholder(lk); 1498 if (td == (struct thread *)LK_KERNPROC) 1499 printf("lock type %s: EXCL by KERNPROC\n", 1500 lk->lock_object.lo_name); 1501 else 1502 printf("lock type %s: EXCL by thread %p " 1503 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, 1504 td, td->td_proc->p_pid, td->td_proc->p_comm, 1505 td->td_tid); 1506 } 1507 1508 x = lk->lk_lock; 1509 if (x & LK_EXCLUSIVE_WAITERS) 1510 printf(" with exclusive waiters pending\n"); 1511 if (x & LK_SHARED_WAITERS) 1512 printf(" with shared waiters pending\n"); 1513 if (x & LK_EXCLUSIVE_SPINNERS) 1514 printf(" with exclusive spinners pending\n"); 1515 1516 STACK_PRINT(lk); 1517 } 1518 1519 int 1520 lockstatus(const struct lock *lk) 1521 { 1522 uintptr_t v, x; 1523 int ret; 1524 1525 ret = LK_SHARED; 1526 x = lk->lk_lock; 1527 v = LK_HOLDER(x); 1528 1529 if ((x & LK_SHARE) == 0) { 1530 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1531 ret = LK_EXCLUSIVE; 1532 else 1533 ret = LK_EXCLOTHER; 1534 } else if (x == LK_UNLOCKED) 1535 ret = 0; 1536 1537 return (ret); 1538 } 1539 1540 #ifdef INVARIANT_SUPPORT 1541 1542 FEATURE(invariant_support, 1543 "Support for modules compiled with INVARIANTS option"); 1544 1545 #ifndef INVARIANTS 1546 #undef _lockmgr_assert 1547 #endif 1548 1549 void 1550 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1551 { 1552 int slocked = 0; 1553 1554 if (panicstr != NULL) 1555 return; 1556 switch (what) { 1557 case KA_SLOCKED: 1558 case KA_SLOCKED | KA_NOTRECURSED: 1559 case KA_SLOCKED | KA_RECURSED: 1560 slocked = 1; 1561 case KA_LOCKED: 1562 case KA_LOCKED | KA_NOTRECURSED: 1563 case KA_LOCKED | KA_RECURSED: 1564 #ifdef WITNESS 1565 1566 /* 1567 * We cannot trust WITNESS if the lock is held in exclusive 1568 * mode and a call to lockmgr_disown() happened. 1569 * Workaround this skipping the check if the lock is held in 1570 * exclusive mode even for the KA_LOCKED case. 1571 */ 1572 if (slocked || (lk->lk_lock & LK_SHARE)) { 1573 witness_assert(&lk->lock_object, what, file, line); 1574 break; 1575 } 1576 #endif 1577 if (lk->lk_lock == LK_UNLOCKED || 1578 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1579 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1580 panic("Lock %s not %slocked @ %s:%d\n", 1581 lk->lock_object.lo_name, slocked ? "share" : "", 1582 file, line); 1583 1584 if ((lk->lk_lock & LK_SHARE) == 0) { 1585 if (lockmgr_recursed(lk)) { 1586 if (what & KA_NOTRECURSED) 1587 panic("Lock %s recursed @ %s:%d\n", 1588 lk->lock_object.lo_name, file, 1589 line); 1590 } else if (what & KA_RECURSED) 1591 panic("Lock %s not recursed @ %s:%d\n", 1592 lk->lock_object.lo_name, file, line); 1593 } 1594 break; 1595 case KA_XLOCKED: 1596 case KA_XLOCKED | KA_NOTRECURSED: 1597 case KA_XLOCKED | KA_RECURSED: 1598 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1599 panic("Lock %s not exclusively locked @ %s:%d\n", 1600 lk->lock_object.lo_name, file, line); 1601 if (lockmgr_recursed(lk)) { 1602 if (what & KA_NOTRECURSED) 1603 panic("Lock %s recursed @ %s:%d\n", 1604 lk->lock_object.lo_name, file, line); 1605 } else if (what & KA_RECURSED) 1606 panic("Lock %s not recursed @ %s:%d\n", 1607 lk->lock_object.lo_name, file, line); 1608 break; 1609 case KA_UNLOCKED: 1610 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1611 panic("Lock %s exclusively locked @ %s:%d\n", 1612 lk->lock_object.lo_name, file, line); 1613 break; 1614 default: 1615 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1616 line); 1617 } 1618 } 1619 #endif 1620 1621 #ifdef DDB 1622 int 1623 lockmgr_chain(struct thread *td, struct thread **ownerp) 1624 { 1625 struct lock *lk; 1626 1627 lk = td->td_wchan; 1628 1629 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1630 return (0); 1631 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1632 if (lk->lk_lock & LK_SHARE) 1633 db_printf("SHARED (count %ju)\n", 1634 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1635 else 1636 db_printf("EXCL\n"); 1637 *ownerp = lockmgr_xholder(lk); 1638 1639 return (1); 1640 } 1641 1642 static void 1643 db_show_lockmgr(const struct lock_object *lock) 1644 { 1645 struct thread *td; 1646 const struct lock *lk; 1647 1648 lk = (const struct lock *)lock; 1649 1650 db_printf(" state: "); 1651 if (lk->lk_lock == LK_UNLOCKED) 1652 db_printf("UNLOCKED\n"); 1653 else if (lk->lk_lock & LK_SHARE) 1654 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1655 else { 1656 td = lockmgr_xholder(lk); 1657 if (td == (struct thread *)LK_KERNPROC) 1658 db_printf("XLOCK: LK_KERNPROC\n"); 1659 else 1660 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1661 td->td_tid, td->td_proc->p_pid, 1662 td->td_proc->p_comm); 1663 if (lockmgr_recursed(lk)) 1664 db_printf(" recursed: %d\n", lk->lk_recurse); 1665 } 1666 db_printf(" waiters: "); 1667 switch (lk->lk_lock & LK_ALL_WAITERS) { 1668 case LK_SHARED_WAITERS: 1669 db_printf("shared\n"); 1670 break; 1671 case LK_EXCLUSIVE_WAITERS: 1672 db_printf("exclusive\n"); 1673 break; 1674 case LK_ALL_WAITERS: 1675 db_printf("shared and exclusive\n"); 1676 break; 1677 default: 1678 db_printf("none\n"); 1679 } 1680 db_printf(" spinners: "); 1681 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1682 db_printf("exclusive\n"); 1683 else 1684 db_printf("none\n"); 1685 } 1686 #endif 1687