1/*- 2 * Copyright (c) 2008 Attilio Rao <attilio@FreeBSD.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice(s), this list of conditions and the following disclaimer as 10 * the first lines of this file unmodified other than the possible 11 * addition of one or more copyright notices. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice(s), this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 19 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 20 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 22 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 23 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 26 * DAMAGE. 27 */ 28 29#include "opt_adaptive_lockmgrs.h" 30#include "opt_ddb.h" 31#include "opt_hwpmc_hooks.h" 32 33#include <sys/cdefs.h> 34__FBSDID("$FreeBSD: stable/11/sys/kern/kern_lock.c 315375 2017-03-16 06:14:33Z mjg $"); 35 36#include <sys/param.h> 37#include <sys/kdb.h> 38#include <sys/ktr.h> 39#include <sys/lock.h> 40#include <sys/lock_profile.h> 41#include <sys/lockmgr.h> 42#include <sys/mutex.h> 43#include <sys/proc.h> 44#include <sys/sleepqueue.h> 45#ifdef DEBUG_LOCKS 46#include <sys/stack.h> 47#endif 48#include <sys/sysctl.h> 49#include <sys/systm.h> 50 51#include <machine/cpu.h> 52 53#ifdef DDB 54#include <ddb/ddb.h> 55#endif 56 57#ifdef HWPMC_HOOKS 58#include <sys/pmckern.h> 59PMC_SOFT_DECLARE( , , lock, failed); 60#endif 61 62CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) == 63 (LK_ADAPTIVE | LK_NOSHARE)); 64CTASSERT(LK_UNLOCKED == (LK_UNLOCKED & 65 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS))); 66 67#define SQ_EXCLUSIVE_QUEUE 0 68#define SQ_SHARED_QUEUE 1 69 70#ifndef INVARIANTS 71#define _lockmgr_assert(lk, what, file, line) 72#endif 73 74#define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 75#define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 76 77#ifndef DEBUG_LOCKS 78#define STACK_PRINT(lk) 79#define STACK_SAVE(lk) 80#define STACK_ZERO(lk) 81#else 82#define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 83#define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 84#define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 85#endif 86 87#define LOCK_LOG2(lk, string, arg1, arg2) \ 88 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 89 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 90#define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 91 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 92 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 93 94#define GIANT_DECLARE \ 95 int _i = 0; \ 96 WITNESS_SAVE_DECL(Giant) 97#define GIANT_RESTORE() do { \ 98 if (_i > 0) { \ 99 while (_i--) \ 100 mtx_lock(&Giant); \ 101 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 102 } \ 103} while (0) 104#define GIANT_SAVE() do { \ 105 if (mtx_owned(&Giant)) { \ 106 WITNESS_SAVE(&Giant.lock_object, Giant); \ 107 while (mtx_owned(&Giant)) { \ 108 _i++; \ 109 mtx_unlock(&Giant); \ 110 } \ 111 } \ 112} while (0) 113 114#define LK_CAN_SHARE(x, flags) \ 115 (((x) & LK_SHARE) && \ 116 (((x) & (LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) == 0 || \ 117 (curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) || \ 118 (curthread->td_pflags & TDP_DEADLKTREAT))) 119#define LK_TRYOP(x) \ 120 ((x) & LK_NOWAIT) 121 122#define LK_CAN_WITNESS(x) \ 123 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 124#define LK_TRYWIT(x) \ 125 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 126 127#define LK_CAN_ADAPT(lk, f) \ 128 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 129 ((f) & LK_SLEEPFAIL) == 0) 130 131#define lockmgr_disowned(lk) \ 132 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 133 134#define lockmgr_xlocked(lk) \ 135 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 136 137static void assert_lockmgr(const struct lock_object *lock, int how); 138#ifdef DDB 139static void db_show_lockmgr(const struct lock_object *lock); 140#endif 141static void lock_lockmgr(struct lock_object *lock, uintptr_t how); 142#ifdef KDTRACE_HOOKS 143static int owner_lockmgr(const struct lock_object *lock, 144 struct thread **owner); 145#endif 146static uintptr_t unlock_lockmgr(struct lock_object *lock); 147 148struct lock_class lock_class_lockmgr = { 149 .lc_name = "lockmgr", 150 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 151 .lc_assert = assert_lockmgr, 152#ifdef DDB 153 .lc_ddb_show = db_show_lockmgr, 154#endif 155 .lc_lock = lock_lockmgr, 156 .lc_unlock = unlock_lockmgr, 157#ifdef KDTRACE_HOOKS 158 .lc_owner = owner_lockmgr, 159#endif 160}; 161 162#ifdef ADAPTIVE_LOCKMGRS 163static u_int alk_retries = 10; 164static u_int alk_loops = 10000; 165static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, 166 "lockmgr debugging"); 167SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, ""); 168SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, ""); 169#endif 170 171static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp, 172 int flags); 173static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t x); 174 175static void 176lockmgr_note_shared_acquire(struct lock *lk, int contested, 177 uint64_t waittime, const char *file, int line, int flags) 178{ 179 180 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime, 181 file, line); 182 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line); 183 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line); 184 TD_LOCKS_INC(curthread); 185 TD_SLOCKS_INC(curthread); 186 STACK_SAVE(lk); 187} 188 189static void 190lockmgr_note_shared_release(struct lock *lk, const char *file, int line) 191{ 192 193 lock_profile_release_lock(&lk->lock_object); 194 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 195 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 196 TD_LOCKS_DEC(curthread); 197 TD_SLOCKS_DEC(curthread); 198} 199 200static void 201lockmgr_note_exclusive_acquire(struct lock *lk, int contested, 202 uint64_t waittime, const char *file, int line, int flags) 203{ 204 205 lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime, 206 file, line); 207 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line); 208 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, 209 line); 210 TD_LOCKS_INC(curthread); 211 STACK_SAVE(lk); 212} 213 214static void 215lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line) 216{ 217 218 lock_profile_release_lock(&lk->lock_object); 219 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, 220 line); 221 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 222 TD_LOCKS_DEC(curthread); 223} 224 225static void 226lockmgr_note_exclusive_upgrade(struct lock *lk, const char *file, int line, 227 int flags) 228{ 229 230 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 231 line); 232 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 233 LK_TRYWIT(flags), file, line); 234 TD_SLOCKS_DEC(curthread); 235} 236 237static __inline struct thread * 238lockmgr_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 */ 252static __inline int 253sleeplk(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 296static __inline int 297wakeupshlk(struct lock *lk, const char *file, int line) 298{ 299 uintptr_t v, 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 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 315 v = LK_UNLOCKED; 316 317 /* 318 * If the lock has exclusive waiters, give them preference in 319 * order to avoid deadlock with shared runners up. 320 * If interruptible sleeps left the exclusive queue empty 321 * avoid a starvation for the threads sleeping on the shared 322 * queue by giving them precedence and cleaning up the 323 * exclusive waiters bit anyway. 324 * Please note that lk_exslpfail count may be lying about 325 * the real number of waiters with the LK_SLEEPFAIL flag on 326 * because they may be used in conjunction with interruptible 327 * sleeps so lk_exslpfail might be considered an 'upper limit' 328 * bound, including the edge cases. 329 */ 330 realexslp = sleepq_sleepcnt(&lk->lock_object, 331 SQ_EXCLUSIVE_QUEUE); 332 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 333 if (lk->lk_exslpfail < realexslp) { 334 lk->lk_exslpfail = 0; 335 queue = SQ_EXCLUSIVE_QUEUE; 336 v |= (x & LK_SHARED_WAITERS); 337 } else { 338 lk->lk_exslpfail = 0; 339 LOCK_LOG2(lk, 340 "%s: %p has only LK_SLEEPFAIL sleepers", 341 __func__, lk); 342 LOCK_LOG2(lk, 343 "%s: %p waking up threads on the exclusive queue", 344 __func__, lk); 345 wakeup_swapper = 346 sleepq_broadcast(&lk->lock_object, 347 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 348 queue = SQ_SHARED_QUEUE; 349 } 350 351 } else { 352 353 /* 354 * Exclusive waiters sleeping with LK_SLEEPFAIL on 355 * and using interruptible sleeps/timeout may have 356 * left spourious lk_exslpfail counts on, so clean 357 * it up anyway. 358 */ 359 lk->lk_exslpfail = 0; 360 queue = SQ_SHARED_QUEUE; 361 } 362 363 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, 364 v)) { 365 sleepq_release(&lk->lock_object); 366 continue; 367 } 368 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 369 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 370 "exclusive"); 371 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 372 0, queue); 373 sleepq_release(&lk->lock_object); 374 break; 375 } 376 377 lockmgr_note_shared_release(lk, file, line); 378 return (wakeup_swapper); 379} 380 381static void 382assert_lockmgr(const struct lock_object *lock, int what) 383{ 384 385 panic("lockmgr locks do not support assertions"); 386} 387 388static void 389lock_lockmgr(struct lock_object *lock, uintptr_t how) 390{ 391 392 panic("lockmgr locks do not support sleep interlocking"); 393} 394 395static uintptr_t 396unlock_lockmgr(struct lock_object *lock) 397{ 398 399 panic("lockmgr locks do not support sleep interlocking"); 400} 401 402#ifdef KDTRACE_HOOKS 403static int 404owner_lockmgr(const struct lock_object *lock, struct thread **owner) 405{ 406 407 panic("lockmgr locks do not support owner inquiring"); 408} 409#endif 410 411void 412lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 413{ 414 int iflags; 415 416 MPASS((flags & ~LK_INIT_MASK) == 0); 417 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 418 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 419 &lk->lk_lock)); 420 421 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 422 if (flags & LK_CANRECURSE) 423 iflags |= LO_RECURSABLE; 424 if ((flags & LK_NODUP) == 0) 425 iflags |= LO_DUPOK; 426 if (flags & LK_NOPROFILE) 427 iflags |= LO_NOPROFILE; 428 if ((flags & LK_NOWITNESS) == 0) 429 iflags |= LO_WITNESS; 430 if (flags & LK_QUIET) 431 iflags |= LO_QUIET; 432 if (flags & LK_IS_VNODE) 433 iflags |= LO_IS_VNODE; 434 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 435 436 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 437 lk->lk_lock = LK_UNLOCKED; 438 lk->lk_recurse = 0; 439 lk->lk_exslpfail = 0; 440 lk->lk_timo = timo; 441 lk->lk_pri = pri; 442 STACK_ZERO(lk); 443} 444 445/* 446 * XXX: Gross hacks to manipulate external lock flags after 447 * initialization. Used for certain vnode and buf locks. 448 */ 449void 450lockallowshare(struct lock *lk) 451{ 452 453 lockmgr_assert(lk, KA_XLOCKED); 454 lk->lock_object.lo_flags &= ~LK_NOSHARE; 455} 456 457void 458lockdisableshare(struct lock *lk) 459{ 460 461 lockmgr_assert(lk, KA_XLOCKED); 462 lk->lock_object.lo_flags |= LK_NOSHARE; 463} 464 465void 466lockallowrecurse(struct lock *lk) 467{ 468 469 lockmgr_assert(lk, KA_XLOCKED); 470 lk->lock_object.lo_flags |= LO_RECURSABLE; 471} 472 473void 474lockdisablerecurse(struct lock *lk) 475{ 476 477 lockmgr_assert(lk, KA_XLOCKED); 478 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 479} 480 481void 482lockdestroy(struct lock *lk) 483{ 484 485 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 486 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 487 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 488 lock_destroy(&lk->lock_object); 489} 490 491static bool __always_inline 492lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags) 493{ 494 495 /* 496 * If no other thread has an exclusive lock, or 497 * no exclusive waiter is present, bump the count of 498 * sharers. Since we have to preserve the state of 499 * waiters, if we fail to acquire the shared lock 500 * loop back and retry. 501 */ 502 *xp = lk->lk_lock; 503 while (LK_CAN_SHARE(*xp, flags)) { 504 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp, 505 *xp + LK_ONE_SHARER)) { 506 return (true); 507 } 508 } 509 return (false); 510} 511 512static bool __always_inline 513lockmgr_sunlock_try(struct lock *lk, uintptr_t x) 514{ 515 516 for (;;) { 517 /* 518 * If there is more than one shared lock held, just drop one 519 * and return. 520 */ 521 if (LK_SHARERS(x) > 1) { 522 if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, 523 x - LK_ONE_SHARER)) 524 return (true); 525 continue; 526 } 527 528 /* 529 * If there are not waiters on the exclusive queue, drop the 530 * lock quickly. 531 */ 532 if ((x & LK_ALL_WAITERS) == 0) { 533 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == 534 LK_SHARERS_LOCK(1)); 535 if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, 536 LK_UNLOCKED)) 537 return (true); 538 continue; 539 } 540 break; 541 } 542 return (false); 543} 544 545int 546lockmgr_lock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk, 547 const char *file, int line) 548{ 549 struct lock_class *class; 550 uintptr_t x, v, tid; 551 u_int op; 552 bool locked; 553 554 op = flags & LK_TYPE_MASK; 555 locked = false; 556 switch (op) { 557 case LK_SHARED: 558 if (LK_CAN_WITNESS(flags)) 559 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 560 file, line, flags & LK_INTERLOCK ? ilk : NULL); 561 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE)) 562 break; 563 if (lockmgr_slock_try(lk, &x, flags)) { 564 lockmgr_note_shared_acquire(lk, 0, 0, 565 file, line, flags); 566 locked = true; 567 } 568 break; 569 case LK_EXCLUSIVE: 570 if (LK_CAN_WITNESS(flags)) 571 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 572 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 573 ilk : NULL); 574 tid = (uintptr_t)curthread; 575 if (lk->lk_lock == LK_UNLOCKED && 576 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 577 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line, 578 flags); 579 locked = true; 580 } 581 break; 582 case LK_UPGRADE: 583 case LK_TRYUPGRADE: 584 _lockmgr_assert(lk, KA_SLOCKED, file, line); 585 tid = (uintptr_t)curthread; 586 v = lk->lk_lock; 587 x = v & LK_ALL_WAITERS; 588 v &= LK_EXCLUSIVE_SPINNERS; 589 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 590 tid | x)) { 591 lockmgr_note_exclusive_upgrade(lk, file, line, flags); 592 locked = true; 593 } 594 break; 595 default: 596 break; 597 } 598 if (__predict_true(locked)) { 599 if (__predict_false(flags & LK_INTERLOCK)) { 600 class = LOCK_CLASS(ilk); 601 class->lc_unlock(ilk); 602 } 603 return (0); 604 } else { 605 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT, 606 LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line)); 607 } 608} 609 610int 611lockmgr_unlock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk) 612{ 613 struct lock_class *class; 614 uintptr_t x, tid; 615 bool unlocked; 616 const char *file; 617 int line; 618 619 file = __FILE__; 620 line = __LINE__; 621 622 _lockmgr_assert(lk, KA_LOCKED, file, line); 623 unlocked = false; 624 x = lk->lk_lock; 625 if (__predict_true(x & LK_SHARE) != 0) { 626 if (lockmgr_sunlock_try(lk, x)) { 627 lockmgr_note_shared_release(lk, file, line); 628 unlocked = true; 629 } 630 } else { 631 tid = (uintptr_t)curthread; 632 if (!lockmgr_recursed(lk) && 633 atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) { 634 lockmgr_note_exclusive_release(lk, file, line); 635 unlocked = true; 636 } 637 } 638 if (__predict_true(unlocked)) { 639 if (__predict_false(flags & LK_INTERLOCK)) { 640 class = LOCK_CLASS(ilk); 641 class->lc_unlock(ilk); 642 } 643 return (0); 644 } else { 645 return (__lockmgr_args(lk, flags | LK_RELEASE, ilk, LK_WMESG_DEFAULT, 646 LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, LOCK_FILE, LOCK_LINE)); 647 } 648} 649 650int 651__lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 652 const char *wmesg, int pri, int timo, const char *file, int line) 653{ 654 GIANT_DECLARE; 655 struct lock_class *class; 656 const char *iwmesg; 657 uintptr_t tid, v, x; 658 u_int op, realexslp; 659 int error, ipri, itimo, queue, wakeup_swapper; 660#ifdef LOCK_PROFILING 661 uint64_t waittime = 0; 662 int contested = 0; 663#endif 664#ifdef ADAPTIVE_LOCKMGRS 665 volatile struct thread *owner; 666 u_int i, spintries = 0; 667#endif 668 669 error = 0; 670 tid = (uintptr_t)curthread; 671 op = (flags & LK_TYPE_MASK); 672 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 673 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 674 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 675 676 MPASS((flags & ~LK_TOTAL_MASK) == 0); 677 KASSERT((op & (op - 1)) == 0, 678 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 679 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 680 (op != LK_DOWNGRADE && op != LK_RELEASE), 681 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 682 __func__, file, line)); 683 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 684 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 685 __func__, file, line)); 686 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 687 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 688 lk->lock_object.lo_name, file, line)); 689 690 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 691 if (panicstr != NULL) { 692 if (flags & LK_INTERLOCK) 693 class->lc_unlock(ilk); 694 return (0); 695 } 696 697 if (lk->lock_object.lo_flags & LK_NOSHARE) { 698 switch (op) { 699 case LK_SHARED: 700 op = LK_EXCLUSIVE; 701 break; 702 case LK_UPGRADE: 703 case LK_TRYUPGRADE: 704 case LK_DOWNGRADE: 705 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 706 file, line); 707 if (flags & LK_INTERLOCK) 708 class->lc_unlock(ilk); 709 return (0); 710 } 711 } 712 713 wakeup_swapper = 0; 714 switch (op) { 715 case LK_SHARED: 716 if (LK_CAN_WITNESS(flags)) 717 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 718 file, line, flags & LK_INTERLOCK ? ilk : NULL); 719 for (;;) { 720 if (lockmgr_slock_try(lk, &x, flags)) 721 break; 722#ifdef HWPMC_HOOKS 723 PMC_SOFT_CALL( , , lock, failed); 724#endif 725 lock_profile_obtain_lock_failed(&lk->lock_object, 726 &contested, &waittime); 727 728 /* 729 * If the lock is already held by curthread in 730 * exclusive way avoid a deadlock. 731 */ 732 if (LK_HOLDER(x) == tid) { 733 LOCK_LOG2(lk, 734 "%s: %p already held in exclusive mode", 735 __func__, lk); 736 error = EDEADLK; 737 break; 738 } 739 740 /* 741 * If the lock is expected to not sleep just give up 742 * and return. 743 */ 744 if (LK_TRYOP(flags)) { 745 LOCK_LOG2(lk, "%s: %p fails the try operation", 746 __func__, lk); 747 error = EBUSY; 748 break; 749 } 750 751#ifdef ADAPTIVE_LOCKMGRS 752 /* 753 * If the owner is running on another CPU, spin until 754 * the owner stops running or the state of the lock 755 * changes. We need a double-state handle here 756 * because for a failed acquisition the lock can be 757 * either held in exclusive mode or shared mode 758 * (for the writer starvation avoidance technique). 759 */ 760 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 761 LK_HOLDER(x) != LK_KERNPROC) { 762 owner = (struct thread *)LK_HOLDER(x); 763 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 764 CTR3(KTR_LOCK, 765 "%s: spinning on %p held by %p", 766 __func__, lk, owner); 767 KTR_STATE1(KTR_SCHED, "thread", 768 sched_tdname(td), "spinning", 769 "lockname:\"%s\"", lk->lock_object.lo_name); 770 771 /* 772 * If we are holding also an interlock drop it 773 * in order to avoid a deadlock if the lockmgr 774 * owner is adaptively spinning on the 775 * interlock itself. 776 */ 777 if (flags & LK_INTERLOCK) { 778 class->lc_unlock(ilk); 779 flags &= ~LK_INTERLOCK; 780 } 781 GIANT_SAVE(); 782 while (LK_HOLDER(lk->lk_lock) == 783 (uintptr_t)owner && TD_IS_RUNNING(owner)) 784 cpu_spinwait(); 785 KTR_STATE0(KTR_SCHED, "thread", 786 sched_tdname(td), "running"); 787 GIANT_RESTORE(); 788 continue; 789 } else if (LK_CAN_ADAPT(lk, flags) && 790 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 791 spintries < alk_retries) { 792 KTR_STATE1(KTR_SCHED, "thread", 793 sched_tdname(td), "spinning", 794 "lockname:\"%s\"", lk->lock_object.lo_name); 795 if (flags & LK_INTERLOCK) { 796 class->lc_unlock(ilk); 797 flags &= ~LK_INTERLOCK; 798 } 799 GIANT_SAVE(); 800 spintries++; 801 for (i = 0; i < alk_loops; i++) { 802 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 803 CTR4(KTR_LOCK, 804 "%s: shared spinning on %p with %u and %u", 805 __func__, lk, spintries, i); 806 x = lk->lk_lock; 807 if ((x & LK_SHARE) == 0 || 808 LK_CAN_SHARE(x, flags) != 0) 809 break; 810 cpu_spinwait(); 811 } 812 KTR_STATE0(KTR_SCHED, "thread", 813 sched_tdname(td), "running"); 814 GIANT_RESTORE(); 815 if (i != alk_loops) 816 continue; 817 } 818#endif 819 820 /* 821 * Acquire the sleepqueue chain lock because we 822 * probabilly will need to manipulate waiters flags. 823 */ 824 sleepq_lock(&lk->lock_object); 825 x = lk->lk_lock; 826 827 /* 828 * if the lock can be acquired in shared mode, try 829 * again. 830 */ 831 if (LK_CAN_SHARE(x, flags)) { 832 sleepq_release(&lk->lock_object); 833 continue; 834 } 835 836#ifdef ADAPTIVE_LOCKMGRS 837 /* 838 * The current lock owner might have started executing 839 * on another CPU (or the lock could have changed 840 * owner) while we were waiting on the turnstile 841 * chain lock. If so, drop the turnstile lock and try 842 * again. 843 */ 844 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 845 LK_HOLDER(x) != LK_KERNPROC) { 846 owner = (struct thread *)LK_HOLDER(x); 847 if (TD_IS_RUNNING(owner)) { 848 sleepq_release(&lk->lock_object); 849 continue; 850 } 851 } 852#endif 853 854 /* 855 * Try to set the LK_SHARED_WAITERS flag. If we fail, 856 * loop back and retry. 857 */ 858 if ((x & LK_SHARED_WAITERS) == 0) { 859 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 860 x | LK_SHARED_WAITERS)) { 861 sleepq_release(&lk->lock_object); 862 continue; 863 } 864 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 865 __func__, lk); 866 } 867 868 /* 869 * As far as we have been unable to acquire the 870 * shared lock and the shared waiters flag is set, 871 * we will sleep. 872 */ 873 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 874 SQ_SHARED_QUEUE); 875 flags &= ~LK_INTERLOCK; 876 if (error) { 877 LOCK_LOG3(lk, 878 "%s: interrupted sleep for %p with %d", 879 __func__, lk, error); 880 break; 881 } 882 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 883 __func__, lk); 884 } 885 if (error == 0) { 886#ifdef LOCK_PROFILING 887 lockmgr_note_shared_acquire(lk, contested, waittime, 888 file, line, flags); 889#else 890 lockmgr_note_shared_acquire(lk, 0, 0, file, line, 891 flags); 892#endif 893 } 894 break; 895 case LK_UPGRADE: 896 case LK_TRYUPGRADE: 897 _lockmgr_assert(lk, KA_SLOCKED, file, line); 898 v = lk->lk_lock; 899 x = v & LK_ALL_WAITERS; 900 v &= LK_EXCLUSIVE_SPINNERS; 901 902 /* 903 * Try to switch from one shared lock to an exclusive one. 904 * We need to preserve waiters flags during the operation. 905 */ 906 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 907 tid | x)) { 908 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 909 line); 910 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 911 LK_TRYWIT(flags), file, line); 912 TD_SLOCKS_DEC(curthread); 913 break; 914 } 915 916 /* 917 * In LK_TRYUPGRADE mode, do not drop the lock, 918 * returning EBUSY instead. 919 */ 920 if (op == LK_TRYUPGRADE) { 921 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", 922 __func__, lk); 923 error = EBUSY; 924 break; 925 } 926 927 /* 928 * We have been unable to succeed in upgrading, so just 929 * give up the shared lock. 930 */ 931 wakeup_swapper |= wakeupshlk(lk, file, line); 932 933 /* FALLTHROUGH */ 934 case LK_EXCLUSIVE: 935 if (LK_CAN_WITNESS(flags)) 936 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 937 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 938 ilk : NULL); 939 940 /* 941 * If curthread already holds the lock and this one is 942 * allowed to recurse, simply recurse on it. 943 */ 944 if (lockmgr_xlocked(lk)) { 945 if ((flags & LK_CANRECURSE) == 0 && 946 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 947 948 /* 949 * If the lock is expected to not panic just 950 * give up and return. 951 */ 952 if (LK_TRYOP(flags)) { 953 LOCK_LOG2(lk, 954 "%s: %p fails the try operation", 955 __func__, lk); 956 error = EBUSY; 957 break; 958 } 959 if (flags & LK_INTERLOCK) 960 class->lc_unlock(ilk); 961 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 962 __func__, iwmesg, file, line); 963 } 964 lk->lk_recurse++; 965 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 966 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 967 lk->lk_recurse, file, line); 968 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 969 LK_TRYWIT(flags), file, line); 970 TD_LOCKS_INC(curthread); 971 break; 972 } 973 974 for (;;) { 975 if (lk->lk_lock == LK_UNLOCKED && 976 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 977 break; 978#ifdef HWPMC_HOOKS 979 PMC_SOFT_CALL( , , lock, failed); 980#endif 981 lock_profile_obtain_lock_failed(&lk->lock_object, 982 &contested, &waittime); 983 984 /* 985 * If the lock is expected to not sleep just give up 986 * and return. 987 */ 988 if (LK_TRYOP(flags)) { 989 LOCK_LOG2(lk, "%s: %p fails the try operation", 990 __func__, lk); 991 error = EBUSY; 992 break; 993 } 994 995#ifdef ADAPTIVE_LOCKMGRS 996 /* 997 * If the owner is running on another CPU, spin until 998 * the owner stops running or the state of the lock 999 * changes. 1000 */ 1001 x = lk->lk_lock; 1002 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 1003 LK_HOLDER(x) != LK_KERNPROC) { 1004 owner = (struct thread *)LK_HOLDER(x); 1005 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 1006 CTR3(KTR_LOCK, 1007 "%s: spinning on %p held by %p", 1008 __func__, lk, owner); 1009 KTR_STATE1(KTR_SCHED, "thread", 1010 sched_tdname(td), "spinning", 1011 "lockname:\"%s\"", lk->lock_object.lo_name); 1012 1013 /* 1014 * If we are holding also an interlock drop it 1015 * in order to avoid a deadlock if the lockmgr 1016 * owner is adaptively spinning on the 1017 * interlock itself. 1018 */ 1019 if (flags & LK_INTERLOCK) { 1020 class->lc_unlock(ilk); 1021 flags &= ~LK_INTERLOCK; 1022 } 1023 GIANT_SAVE(); 1024 while (LK_HOLDER(lk->lk_lock) == 1025 (uintptr_t)owner && TD_IS_RUNNING(owner)) 1026 cpu_spinwait(); 1027 KTR_STATE0(KTR_SCHED, "thread", 1028 sched_tdname(td), "running"); 1029 GIANT_RESTORE(); 1030 continue; 1031 } else if (LK_CAN_ADAPT(lk, flags) && 1032 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 1033 spintries < alk_retries) { 1034 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 1035 !atomic_cmpset_ptr(&lk->lk_lock, x, 1036 x | LK_EXCLUSIVE_SPINNERS)) 1037 continue; 1038 KTR_STATE1(KTR_SCHED, "thread", 1039 sched_tdname(td), "spinning", 1040 "lockname:\"%s\"", lk->lock_object.lo_name); 1041 if (flags & LK_INTERLOCK) { 1042 class->lc_unlock(ilk); 1043 flags &= ~LK_INTERLOCK; 1044 } 1045 GIANT_SAVE(); 1046 spintries++; 1047 for (i = 0; i < alk_loops; i++) { 1048 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 1049 CTR4(KTR_LOCK, 1050 "%s: shared spinning on %p with %u and %u", 1051 __func__, lk, spintries, i); 1052 if ((lk->lk_lock & 1053 LK_EXCLUSIVE_SPINNERS) == 0) 1054 break; 1055 cpu_spinwait(); 1056 } 1057 KTR_STATE0(KTR_SCHED, "thread", 1058 sched_tdname(td), "running"); 1059 GIANT_RESTORE(); 1060 if (i != alk_loops) 1061 continue; 1062 } 1063#endif 1064 1065 /* 1066 * Acquire the sleepqueue chain lock because we 1067 * probabilly will need to manipulate waiters flags. 1068 */ 1069 sleepq_lock(&lk->lock_object); 1070 x = lk->lk_lock; 1071 1072 /* 1073 * if the lock has been released while we spun on 1074 * the sleepqueue chain lock just try again. 1075 */ 1076 if (x == LK_UNLOCKED) { 1077 sleepq_release(&lk->lock_object); 1078 continue; 1079 } 1080 1081#ifdef ADAPTIVE_LOCKMGRS 1082 /* 1083 * The current lock owner might have started executing 1084 * on another CPU (or the lock could have changed 1085 * owner) while we were waiting on the turnstile 1086 * chain lock. If so, drop the turnstile lock and try 1087 * again. 1088 */ 1089 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 1090 LK_HOLDER(x) != LK_KERNPROC) { 1091 owner = (struct thread *)LK_HOLDER(x); 1092 if (TD_IS_RUNNING(owner)) { 1093 sleepq_release(&lk->lock_object); 1094 continue; 1095 } 1096 } 1097#endif 1098 1099 /* 1100 * The lock can be in the state where there is a 1101 * pending queue of waiters, but still no owner. 1102 * This happens when the lock is contested and an 1103 * owner is going to claim the lock. 1104 * If curthread is the one successfully acquiring it 1105 * claim lock ownership and return, preserving waiters 1106 * flags. 1107 */ 1108 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1109 if ((x & ~v) == LK_UNLOCKED) { 1110 v &= ~LK_EXCLUSIVE_SPINNERS; 1111 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 1112 tid | v)) { 1113 sleepq_release(&lk->lock_object); 1114 LOCK_LOG2(lk, 1115 "%s: %p claimed by a new writer", 1116 __func__, lk); 1117 break; 1118 } 1119 sleepq_release(&lk->lock_object); 1120 continue; 1121 } 1122 1123 /* 1124 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1125 * fail, loop back and retry. 1126 */ 1127 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1128 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1129 x | LK_EXCLUSIVE_WAITERS)) { 1130 sleepq_release(&lk->lock_object); 1131 continue; 1132 } 1133 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 1134 __func__, lk); 1135 } 1136 1137 /* 1138 * As far as we have been unable to acquire the 1139 * exclusive lock and the exclusive waiters flag 1140 * is set, we will sleep. 1141 */ 1142 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 1143 SQ_EXCLUSIVE_QUEUE); 1144 flags &= ~LK_INTERLOCK; 1145 if (error) { 1146 LOCK_LOG3(lk, 1147 "%s: interrupted sleep for %p with %d", 1148 __func__, lk, error); 1149 break; 1150 } 1151 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1152 __func__, lk); 1153 } 1154 if (error == 0) { 1155#ifdef LOCK_PROFILING 1156 lockmgr_note_exclusive_acquire(lk, contested, waittime, 1157 file, line, flags); 1158#else 1159 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line, 1160 flags); 1161#endif 1162 } 1163 break; 1164 case LK_DOWNGRADE: 1165 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1166 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 1167 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 1168 1169 /* 1170 * Panic if the lock is recursed. 1171 */ 1172 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 1173 if (flags & LK_INTERLOCK) 1174 class->lc_unlock(ilk); 1175 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 1176 __func__, iwmesg, file, line); 1177 } 1178 TD_SLOCKS_INC(curthread); 1179 1180 /* 1181 * In order to preserve waiters flags, just spin. 1182 */ 1183 for (;;) { 1184 x = lk->lk_lock; 1185 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1186 x &= LK_ALL_WAITERS; 1187 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1188 LK_SHARERS_LOCK(1) | x)) 1189 break; 1190 cpu_spinwait(); 1191 } 1192 break; 1193 case LK_RELEASE: 1194 _lockmgr_assert(lk, KA_LOCKED, file, line); 1195 x = lk->lk_lock; 1196 1197 if ((x & LK_SHARE) == 0) { 1198 1199 /* 1200 * As first option, treact the lock as if it has not 1201 * any waiter. 1202 * Fix-up the tid var if the lock has been disowned. 1203 */ 1204 if (LK_HOLDER(x) == LK_KERNPROC) 1205 tid = LK_KERNPROC; 1206 else { 1207 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 1208 file, line); 1209 TD_LOCKS_DEC(curthread); 1210 } 1211 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 1212 lk->lk_recurse, file, line); 1213 1214 /* 1215 * The lock is held in exclusive mode. 1216 * If the lock is recursed also, then unrecurse it. 1217 */ 1218 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 1219 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 1220 lk); 1221 lk->lk_recurse--; 1222 break; 1223 } 1224 if (tid != LK_KERNPROC) 1225 lock_profile_release_lock(&lk->lock_object); 1226 1227 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 1228 LK_UNLOCKED)) 1229 break; 1230 1231 sleepq_lock(&lk->lock_object); 1232 x = lk->lk_lock; 1233 v = LK_UNLOCKED; 1234 1235 /* 1236 * If the lock has exclusive waiters, give them 1237 * preference in order to avoid deadlock with 1238 * shared runners up. 1239 * If interruptible sleeps left the exclusive queue 1240 * empty avoid a starvation for the threads sleeping 1241 * on the shared queue by giving them precedence 1242 * and cleaning up the exclusive waiters bit anyway. 1243 * Please note that lk_exslpfail count may be lying 1244 * about the real number of waiters with the 1245 * LK_SLEEPFAIL flag on because they may be used in 1246 * conjunction with interruptible sleeps so 1247 * lk_exslpfail might be considered an 'upper limit' 1248 * bound, including the edge cases. 1249 */ 1250 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1251 realexslp = sleepq_sleepcnt(&lk->lock_object, 1252 SQ_EXCLUSIVE_QUEUE); 1253 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1254 if (lk->lk_exslpfail < realexslp) { 1255 lk->lk_exslpfail = 0; 1256 queue = SQ_EXCLUSIVE_QUEUE; 1257 v |= (x & LK_SHARED_WAITERS); 1258 } else { 1259 lk->lk_exslpfail = 0; 1260 LOCK_LOG2(lk, 1261 "%s: %p has only LK_SLEEPFAIL sleepers", 1262 __func__, lk); 1263 LOCK_LOG2(lk, 1264 "%s: %p waking up threads on the exclusive queue", 1265 __func__, lk); 1266 wakeup_swapper = 1267 sleepq_broadcast(&lk->lock_object, 1268 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1269 queue = SQ_SHARED_QUEUE; 1270 } 1271 } else { 1272 1273 /* 1274 * Exclusive waiters sleeping with LK_SLEEPFAIL 1275 * on and using interruptible sleeps/timeout 1276 * may have left spourious lk_exslpfail counts 1277 * on, so clean it up anyway. 1278 */ 1279 lk->lk_exslpfail = 0; 1280 queue = SQ_SHARED_QUEUE; 1281 } 1282 1283 LOCK_LOG3(lk, 1284 "%s: %p waking up threads on the %s queue", 1285 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1286 "exclusive"); 1287 atomic_store_rel_ptr(&lk->lk_lock, v); 1288 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1289 SLEEPQ_LK, 0, queue); 1290 sleepq_release(&lk->lock_object); 1291 break; 1292 } else 1293 wakeup_swapper = wakeupshlk(lk, file, line); 1294 break; 1295 case LK_DRAIN: 1296 if (LK_CAN_WITNESS(flags)) 1297 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1298 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 1299 ilk : NULL); 1300 1301 /* 1302 * Trying to drain a lock we already own will result in a 1303 * deadlock. 1304 */ 1305 if (lockmgr_xlocked(lk)) { 1306 if (flags & LK_INTERLOCK) 1307 class->lc_unlock(ilk); 1308 panic("%s: draining %s with the lock held @ %s:%d\n", 1309 __func__, iwmesg, file, line); 1310 } 1311 1312 for (;;) { 1313 if (lk->lk_lock == LK_UNLOCKED && 1314 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 1315 break; 1316 1317#ifdef HWPMC_HOOKS 1318 PMC_SOFT_CALL( , , lock, failed); 1319#endif 1320 lock_profile_obtain_lock_failed(&lk->lock_object, 1321 &contested, &waittime); 1322 1323 /* 1324 * If the lock is expected to not sleep just give up 1325 * and return. 1326 */ 1327 if (LK_TRYOP(flags)) { 1328 LOCK_LOG2(lk, "%s: %p fails the try operation", 1329 __func__, lk); 1330 error = EBUSY; 1331 break; 1332 } 1333 1334 /* 1335 * Acquire the sleepqueue chain lock because we 1336 * probabilly will need to manipulate waiters flags. 1337 */ 1338 sleepq_lock(&lk->lock_object); 1339 x = lk->lk_lock; 1340 1341 /* 1342 * if the lock has been released while we spun on 1343 * the sleepqueue chain lock just try again. 1344 */ 1345 if (x == LK_UNLOCKED) { 1346 sleepq_release(&lk->lock_object); 1347 continue; 1348 } 1349 1350 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1351 if ((x & ~v) == LK_UNLOCKED) { 1352 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1353 1354 /* 1355 * If interruptible sleeps left the exclusive 1356 * queue empty avoid a starvation for the 1357 * threads sleeping on the shared queue by 1358 * giving them precedence and cleaning up the 1359 * exclusive waiters bit anyway. 1360 * Please note that lk_exslpfail count may be 1361 * lying about the real number of waiters with 1362 * the LK_SLEEPFAIL flag on because they may 1363 * be used in conjunction with interruptible 1364 * sleeps so lk_exslpfail might be considered 1365 * an 'upper limit' bound, including the edge 1366 * cases. 1367 */ 1368 if (v & LK_EXCLUSIVE_WAITERS) { 1369 queue = SQ_EXCLUSIVE_QUEUE; 1370 v &= ~LK_EXCLUSIVE_WAITERS; 1371 } else { 1372 1373 /* 1374 * Exclusive waiters sleeping with 1375 * LK_SLEEPFAIL on and using 1376 * interruptible sleeps/timeout may 1377 * have left spourious lk_exslpfail 1378 * counts on, so clean it up anyway. 1379 */ 1380 MPASS(v & LK_SHARED_WAITERS); 1381 lk->lk_exslpfail = 0; 1382 queue = SQ_SHARED_QUEUE; 1383 v &= ~LK_SHARED_WAITERS; 1384 } 1385 if (queue == SQ_EXCLUSIVE_QUEUE) { 1386 realexslp = 1387 sleepq_sleepcnt(&lk->lock_object, 1388 SQ_EXCLUSIVE_QUEUE); 1389 if (lk->lk_exslpfail >= realexslp) { 1390 lk->lk_exslpfail = 0; 1391 queue = SQ_SHARED_QUEUE; 1392 v &= ~LK_SHARED_WAITERS; 1393 if (realexslp != 0) { 1394 LOCK_LOG2(lk, 1395 "%s: %p has only LK_SLEEPFAIL sleepers", 1396 __func__, lk); 1397 LOCK_LOG2(lk, 1398 "%s: %p waking up threads on the exclusive queue", 1399 __func__, lk); 1400 wakeup_swapper = 1401 sleepq_broadcast( 1402 &lk->lock_object, 1403 SLEEPQ_LK, 0, 1404 SQ_EXCLUSIVE_QUEUE); 1405 } 1406 } else 1407 lk->lk_exslpfail = 0; 1408 } 1409 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1410 sleepq_release(&lk->lock_object); 1411 continue; 1412 } 1413 LOCK_LOG3(lk, 1414 "%s: %p waking up all threads on the %s queue", 1415 __func__, lk, queue == SQ_SHARED_QUEUE ? 1416 "shared" : "exclusive"); 1417 wakeup_swapper |= sleepq_broadcast( 1418 &lk->lock_object, SLEEPQ_LK, 0, queue); 1419 1420 /* 1421 * If shared waiters have been woken up we need 1422 * to wait for one of them to acquire the lock 1423 * before to set the exclusive waiters in 1424 * order to avoid a deadlock. 1425 */ 1426 if (queue == SQ_SHARED_QUEUE) { 1427 for (v = lk->lk_lock; 1428 (v & LK_SHARE) && !LK_SHARERS(v); 1429 v = lk->lk_lock) 1430 cpu_spinwait(); 1431 } 1432 } 1433 1434 /* 1435 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1436 * fail, loop back and retry. 1437 */ 1438 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1439 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1440 x | LK_EXCLUSIVE_WAITERS)) { 1441 sleepq_release(&lk->lock_object); 1442 continue; 1443 } 1444 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1445 __func__, lk); 1446 } 1447 1448 /* 1449 * As far as we have been unable to acquire the 1450 * exclusive lock and the exclusive waiters flag 1451 * is set, we will sleep. 1452 */ 1453 if (flags & LK_INTERLOCK) { 1454 class->lc_unlock(ilk); 1455 flags &= ~LK_INTERLOCK; 1456 } 1457 GIANT_SAVE(); 1458 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1459 SQ_EXCLUSIVE_QUEUE); 1460 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1461 GIANT_RESTORE(); 1462 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1463 __func__, lk); 1464 } 1465 1466 if (error == 0) { 1467 lock_profile_obtain_lock_success(&lk->lock_object, 1468 contested, waittime, file, line); 1469 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1470 lk->lk_recurse, file, line); 1471 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1472 LK_TRYWIT(flags), file, line); 1473 TD_LOCKS_INC(curthread); 1474 STACK_SAVE(lk); 1475 } 1476 break; 1477 default: 1478 if (flags & LK_INTERLOCK) 1479 class->lc_unlock(ilk); 1480 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1481 } 1482 1483 if (flags & LK_INTERLOCK) 1484 class->lc_unlock(ilk); 1485 if (wakeup_swapper) 1486 kick_proc0(); 1487 1488 return (error); 1489} 1490 1491void 1492_lockmgr_disown(struct lock *lk, const char *file, int line) 1493{ 1494 uintptr_t tid, x; 1495 1496 if (SCHEDULER_STOPPED()) 1497 return; 1498 1499 tid = (uintptr_t)curthread; 1500 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1501 1502 /* 1503 * Panic if the lock is recursed. 1504 */ 1505 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1506 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1507 __func__, file, line); 1508 1509 /* 1510 * If the owner is already LK_KERNPROC just skip the whole operation. 1511 */ 1512 if (LK_HOLDER(lk->lk_lock) != tid) 1513 return; 1514 lock_profile_release_lock(&lk->lock_object); 1515 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1516 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1517 TD_LOCKS_DEC(curthread); 1518 STACK_SAVE(lk); 1519 1520 /* 1521 * In order to preserve waiters flags, just spin. 1522 */ 1523 for (;;) { 1524 x = lk->lk_lock; 1525 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1526 x &= LK_ALL_WAITERS; 1527 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1528 LK_KERNPROC | x)) 1529 return; 1530 cpu_spinwait(); 1531 } 1532} 1533 1534void 1535lockmgr_printinfo(const struct lock *lk) 1536{ 1537 struct thread *td; 1538 uintptr_t x; 1539 1540 if (lk->lk_lock == LK_UNLOCKED) 1541 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1542 else if (lk->lk_lock & LK_SHARE) 1543 printf("lock type %s: SHARED (count %ju)\n", 1544 lk->lock_object.lo_name, 1545 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1546 else { 1547 td = lockmgr_xholder(lk); 1548 if (td == (struct thread *)LK_KERNPROC) 1549 printf("lock type %s: EXCL by KERNPROC\n", 1550 lk->lock_object.lo_name); 1551 else 1552 printf("lock type %s: EXCL by thread %p " 1553 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, 1554 td, td->td_proc->p_pid, td->td_proc->p_comm, 1555 td->td_tid); 1556 } 1557 1558 x = lk->lk_lock; 1559 if (x & LK_EXCLUSIVE_WAITERS) 1560 printf(" with exclusive waiters pending\n"); 1561 if (x & LK_SHARED_WAITERS) 1562 printf(" with shared waiters pending\n"); 1563 if (x & LK_EXCLUSIVE_SPINNERS) 1564 printf(" with exclusive spinners pending\n"); 1565 1566 STACK_PRINT(lk); 1567} 1568 1569int 1570lockstatus(const struct lock *lk) 1571{ 1572 uintptr_t v, x; 1573 int ret; 1574 1575 ret = LK_SHARED; 1576 x = lk->lk_lock; 1577 v = LK_HOLDER(x); 1578 1579 if ((x & LK_SHARE) == 0) { 1580 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1581 ret = LK_EXCLUSIVE; 1582 else 1583 ret = LK_EXCLOTHER; 1584 } else if (x == LK_UNLOCKED) 1585 ret = 0; 1586 1587 return (ret); 1588} 1589 1590#ifdef INVARIANT_SUPPORT 1591 1592FEATURE(invariant_support, 1593 "Support for modules compiled with INVARIANTS option"); 1594 1595#ifndef INVARIANTS 1596#undef _lockmgr_assert 1597#endif 1598 1599void 1600_lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1601{ 1602 int slocked = 0; 1603 1604 if (panicstr != NULL) 1605 return; 1606 switch (what) { 1607 case KA_SLOCKED: 1608 case KA_SLOCKED | KA_NOTRECURSED: 1609 case KA_SLOCKED | KA_RECURSED: 1610 slocked = 1; 1611 case KA_LOCKED: 1612 case KA_LOCKED | KA_NOTRECURSED: 1613 case KA_LOCKED | KA_RECURSED: 1614#ifdef WITNESS 1615 1616 /* 1617 * We cannot trust WITNESS if the lock is held in exclusive 1618 * mode and a call to lockmgr_disown() happened. 1619 * Workaround this skipping the check if the lock is held in 1620 * exclusive mode even for the KA_LOCKED case. 1621 */ 1622 if (slocked || (lk->lk_lock & LK_SHARE)) { 1623 witness_assert(&lk->lock_object, what, file, line); 1624 break; 1625 } 1626#endif 1627 if (lk->lk_lock == LK_UNLOCKED || 1628 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1629 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1630 panic("Lock %s not %slocked @ %s:%d\n", 1631 lk->lock_object.lo_name, slocked ? "share" : "", 1632 file, line); 1633 1634 if ((lk->lk_lock & LK_SHARE) == 0) { 1635 if (lockmgr_recursed(lk)) { 1636 if (what & KA_NOTRECURSED) 1637 panic("Lock %s recursed @ %s:%d\n", 1638 lk->lock_object.lo_name, file, 1639 line); 1640 } else if (what & KA_RECURSED) 1641 panic("Lock %s not recursed @ %s:%d\n", 1642 lk->lock_object.lo_name, file, line); 1643 } 1644 break; 1645 case KA_XLOCKED: 1646 case KA_XLOCKED | KA_NOTRECURSED: 1647 case KA_XLOCKED | KA_RECURSED: 1648 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1649 panic("Lock %s not exclusively locked @ %s:%d\n", 1650 lk->lock_object.lo_name, file, line); 1651 if (lockmgr_recursed(lk)) { 1652 if (what & KA_NOTRECURSED) 1653 panic("Lock %s recursed @ %s:%d\n", 1654 lk->lock_object.lo_name, file, line); 1655 } else if (what & KA_RECURSED) 1656 panic("Lock %s not recursed @ %s:%d\n", 1657 lk->lock_object.lo_name, file, line); 1658 break; 1659 case KA_UNLOCKED: 1660 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1661 panic("Lock %s exclusively locked @ %s:%d\n", 1662 lk->lock_object.lo_name, file, line); 1663 break; 1664 default: 1665 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1666 line); 1667 } 1668} 1669#endif 1670 1671#ifdef DDB 1672int 1673lockmgr_chain(struct thread *td, struct thread **ownerp) 1674{ 1675 struct lock *lk; 1676 1677 lk = td->td_wchan; 1678 1679 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1680 return (0); 1681 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1682 if (lk->lk_lock & LK_SHARE) 1683 db_printf("SHARED (count %ju)\n", 1684 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1685 else 1686 db_printf("EXCL\n"); 1687 *ownerp = lockmgr_xholder(lk); 1688 1689 return (1); 1690} 1691 1692static void 1693db_show_lockmgr(const struct lock_object *lock) 1694{ 1695 struct thread *td; 1696 const struct lock *lk; 1697 1698 lk = (const struct lock *)lock; 1699 1700 db_printf(" state: "); 1701 if (lk->lk_lock == LK_UNLOCKED) 1702 db_printf("UNLOCKED\n"); 1703 else if (lk->lk_lock & LK_SHARE) 1704 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1705 else { 1706 td = lockmgr_xholder(lk); 1707 if (td == (struct thread *)LK_KERNPROC) 1708 db_printf("XLOCK: LK_KERNPROC\n"); 1709 else 1710 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1711 td->td_tid, td->td_proc->p_pid, 1712 td->td_proc->p_comm); 1713 if (lockmgr_recursed(lk)) 1714 db_printf(" recursed: %d\n", lk->lk_recurse); 1715 } 1716 db_printf(" waiters: "); 1717 switch (lk->lk_lock & LK_ALL_WAITERS) { 1718 case LK_SHARED_WAITERS: 1719 db_printf("shared\n"); 1720 break; 1721 case LK_EXCLUSIVE_WAITERS: 1722 db_printf("exclusive\n"); 1723 break; 1724 case LK_ALL_WAITERS: 1725 db_printf("shared and exclusive\n"); 1726 break; 1727 default: 1728 db_printf("none\n"); 1729 } 1730 db_printf(" spinners: "); 1731 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1732 db_printf("exclusive\n"); 1733 else 1734 db_printf("none\n"); 1735} 1736#endif 1737