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("$FreeBSD$"); 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> 59 PMC_SOFT_DECLARE( , , lock, failed); 60 #endif 61 62 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) == 63 (LK_ADAPTIVE | LK_NOSHARE)); 64 CTASSERT(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 #define TD_LOCKS_INC(td) 73 #define TD_LOCKS_DEC(td) 74 #else 75 #define TD_LOCKS_INC(td) ((td)->td_locks++) 76 #define TD_LOCKS_DEC(td) ((td)->td_locks--) 77 #endif 78 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 79 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 80 81 #ifndef DEBUG_LOCKS 82 #define STACK_PRINT(lk) 83 #define STACK_SAVE(lk) 84 #define STACK_ZERO(lk) 85 #else 86 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 87 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 88 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 89 #endif 90 91 #define LOCK_LOG2(lk, string, arg1, arg2) \ 92 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 93 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 94 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 95 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 96 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 97 98 #define GIANT_DECLARE \ 99 int _i = 0; \ 100 WITNESS_SAVE_DECL(Giant) 101 #define GIANT_RESTORE() do { \ 102 if (_i > 0) { \ 103 while (_i--) \ 104 mtx_lock(&Giant); \ 105 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 106 } \ 107 } while (0) 108 #define GIANT_SAVE() do { \ 109 if (mtx_owned(&Giant)) { \ 110 WITNESS_SAVE(&Giant.lock_object, Giant); \ 111 while (mtx_owned(&Giant)) { \ 112 _i++; \ 113 mtx_unlock(&Giant); \ 114 } \ 115 } \ 116 } while (0) 117 118 #define LK_CAN_SHARE(x) \ 119 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \ 120 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \ 121 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT))) 122 #define LK_TRYOP(x) \ 123 ((x) & LK_NOWAIT) 124 125 #define LK_CAN_WITNESS(x) \ 126 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 127 #define LK_TRYWIT(x) \ 128 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 129 130 #define LK_CAN_ADAPT(lk, f) \ 131 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 132 ((f) & LK_SLEEPFAIL) == 0) 133 134 #define lockmgr_disowned(lk) \ 135 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 136 137 #define lockmgr_xlocked(lk) \ 138 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 139 140 static void assert_lockmgr(const struct lock_object *lock, int how); 141 #ifdef DDB 142 static void db_show_lockmgr(const struct lock_object *lock); 143 #endif 144 static void lock_lockmgr(struct lock_object *lock, uintptr_t how); 145 #ifdef KDTRACE_HOOKS 146 static int owner_lockmgr(const struct lock_object *lock, 147 struct thread **owner); 148 #endif 149 static uintptr_t unlock_lockmgr(struct lock_object *lock); 150 151 struct lock_class lock_class_lockmgr = { 152 .lc_name = "lockmgr", 153 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 154 .lc_assert = assert_lockmgr, 155 #ifdef DDB 156 .lc_ddb_show = db_show_lockmgr, 157 #endif 158 .lc_lock = lock_lockmgr, 159 .lc_unlock = unlock_lockmgr, 160 #ifdef KDTRACE_HOOKS 161 .lc_owner = owner_lockmgr, 162 #endif 163 }; 164 165 #ifdef ADAPTIVE_LOCKMGRS 166 static u_int alk_retries = 10; 167 static u_int alk_loops = 10000; 168 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, 169 "lockmgr debugging"); 170 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, ""); 171 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, ""); 172 #endif 173 174 static __inline struct thread * 175 lockmgr_xholder(const struct lock *lk) 176 { 177 uintptr_t x; 178 179 x = lk->lk_lock; 180 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 181 } 182 183 /* 184 * It assumes sleepq_lock held and returns with this one unheld. 185 * It also assumes the generic interlock is sane and previously checked. 186 * If LK_INTERLOCK is specified the interlock is not reacquired after the 187 * sleep. 188 */ 189 static __inline int 190 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 191 const char *wmesg, int pri, int timo, int queue) 192 { 193 GIANT_DECLARE; 194 struct lock_class *class; 195 int catch, error; 196 197 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 198 catch = pri & PCATCH; 199 pri &= PRIMASK; 200 error = 0; 201 202 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 203 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 204 205 if (flags & LK_INTERLOCK) 206 class->lc_unlock(ilk); 207 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 208 lk->lk_exslpfail++; 209 GIANT_SAVE(); 210 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 211 SLEEPQ_INTERRUPTIBLE : 0), queue); 212 if ((flags & LK_TIMELOCK) && timo) 213 sleepq_set_timeout(&lk->lock_object, timo); 214 215 /* 216 * Decisional switch for real sleeping. 217 */ 218 if ((flags & LK_TIMELOCK) && timo && catch) 219 error = sleepq_timedwait_sig(&lk->lock_object, pri); 220 else if ((flags & LK_TIMELOCK) && timo) 221 error = sleepq_timedwait(&lk->lock_object, pri); 222 else if (catch) 223 error = sleepq_wait_sig(&lk->lock_object, pri); 224 else 225 sleepq_wait(&lk->lock_object, pri); 226 GIANT_RESTORE(); 227 if ((flags & LK_SLEEPFAIL) && error == 0) 228 error = ENOLCK; 229 230 return (error); 231 } 232 233 static __inline int 234 wakeupshlk(struct lock *lk, const char *file, int line) 235 { 236 uintptr_t v, x; 237 u_int realexslp; 238 int queue, wakeup_swapper; 239 240 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 241 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 242 243 wakeup_swapper = 0; 244 for (;;) { 245 x = lk->lk_lock; 246 247 /* 248 * If there is more than one shared lock held, just drop one 249 * and return. 250 */ 251 if (LK_SHARERS(x) > 1) { 252 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, 253 x - LK_ONE_SHARER)) 254 break; 255 continue; 256 } 257 258 /* 259 * If there are not waiters on the exclusive queue, drop the 260 * lock quickly. 261 */ 262 if ((x & LK_ALL_WAITERS) == 0) { 263 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == 264 LK_SHARERS_LOCK(1)); 265 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED)) 266 break; 267 continue; 268 } 269 270 /* 271 * We should have a sharer with waiters, so enter the hard 272 * path in order to handle wakeups correctly. 273 */ 274 sleepq_lock(&lk->lock_object); 275 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 276 v = LK_UNLOCKED; 277 278 /* 279 * If the lock has exclusive waiters, give them preference in 280 * order to avoid deadlock with shared runners up. 281 * If interruptible sleeps left the exclusive queue empty 282 * avoid a starvation for the threads sleeping on the shared 283 * queue by giving them precedence and cleaning up the 284 * exclusive waiters bit anyway. 285 * Please note that lk_exslpfail count may be lying about 286 * the real number of waiters with the LK_SLEEPFAIL flag on 287 * because they may be used in conjuction with interruptible 288 * sleeps so lk_exslpfail might be considered an 'upper limit' 289 * bound, including the edge cases. 290 */ 291 realexslp = sleepq_sleepcnt(&lk->lock_object, 292 SQ_EXCLUSIVE_QUEUE); 293 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 294 if (lk->lk_exslpfail < realexslp) { 295 lk->lk_exslpfail = 0; 296 queue = SQ_EXCLUSIVE_QUEUE; 297 v |= (x & LK_SHARED_WAITERS); 298 } else { 299 lk->lk_exslpfail = 0; 300 LOCK_LOG2(lk, 301 "%s: %p has only LK_SLEEPFAIL sleepers", 302 __func__, lk); 303 LOCK_LOG2(lk, 304 "%s: %p waking up threads on the exclusive queue", 305 __func__, lk); 306 wakeup_swapper = 307 sleepq_broadcast(&lk->lock_object, 308 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 309 queue = SQ_SHARED_QUEUE; 310 } 311 312 } else { 313 314 /* 315 * Exclusive waiters sleeping with LK_SLEEPFAIL on 316 * and using interruptible sleeps/timeout may have 317 * left spourious lk_exslpfail counts on, so clean 318 * it up anyway. 319 */ 320 lk->lk_exslpfail = 0; 321 queue = SQ_SHARED_QUEUE; 322 } 323 324 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, 325 v)) { 326 sleepq_release(&lk->lock_object); 327 continue; 328 } 329 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 330 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 331 "exclusive"); 332 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 333 0, queue); 334 sleepq_release(&lk->lock_object); 335 break; 336 } 337 338 lock_profile_release_lock(&lk->lock_object); 339 TD_LOCKS_DEC(curthread); 340 TD_SLOCKS_DEC(curthread); 341 return (wakeup_swapper); 342 } 343 344 static void 345 assert_lockmgr(const struct lock_object *lock, int what) 346 { 347 348 panic("lockmgr locks do not support assertions"); 349 } 350 351 static void 352 lock_lockmgr(struct lock_object *lock, uintptr_t how) 353 { 354 355 panic("lockmgr locks do not support sleep interlocking"); 356 } 357 358 static uintptr_t 359 unlock_lockmgr(struct lock_object *lock) 360 { 361 362 panic("lockmgr locks do not support sleep interlocking"); 363 } 364 365 #ifdef KDTRACE_HOOKS 366 static int 367 owner_lockmgr(const struct lock_object *lock, struct thread **owner) 368 { 369 370 panic("lockmgr locks do not support owner inquiring"); 371 } 372 #endif 373 374 void 375 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 376 { 377 int iflags; 378 379 MPASS((flags & ~LK_INIT_MASK) == 0); 380 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 381 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 382 &lk->lk_lock)); 383 384 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 385 if (flags & LK_CANRECURSE) 386 iflags |= LO_RECURSABLE; 387 if ((flags & LK_NODUP) == 0) 388 iflags |= LO_DUPOK; 389 if (flags & LK_NOPROFILE) 390 iflags |= LO_NOPROFILE; 391 if ((flags & LK_NOWITNESS) == 0) 392 iflags |= LO_WITNESS; 393 if (flags & LK_QUIET) 394 iflags |= LO_QUIET; 395 if (flags & LK_IS_VNODE) 396 iflags |= LO_IS_VNODE; 397 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 398 399 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 400 lk->lk_lock = LK_UNLOCKED; 401 lk->lk_recurse = 0; 402 lk->lk_exslpfail = 0; 403 lk->lk_timo = timo; 404 lk->lk_pri = pri; 405 STACK_ZERO(lk); 406 } 407 408 /* 409 * XXX: Gross hacks to manipulate external lock flags after 410 * initialization. Used for certain vnode and buf locks. 411 */ 412 void 413 lockallowshare(struct lock *lk) 414 { 415 416 lockmgr_assert(lk, KA_XLOCKED); 417 lk->lock_object.lo_flags &= ~LK_NOSHARE; 418 } 419 420 void 421 lockallowrecurse(struct lock *lk) 422 { 423 424 lockmgr_assert(lk, KA_XLOCKED); 425 lk->lock_object.lo_flags |= LO_RECURSABLE; 426 } 427 428 void 429 lockdisablerecurse(struct lock *lk) 430 { 431 432 lockmgr_assert(lk, KA_XLOCKED); 433 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 434 } 435 436 void 437 lockdestroy(struct lock *lk) 438 { 439 440 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 441 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 442 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 443 lock_destroy(&lk->lock_object); 444 } 445 446 int 447 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 448 const char *wmesg, int pri, int timo, const char *file, int line) 449 { 450 GIANT_DECLARE; 451 struct lock_class *class; 452 const char *iwmesg; 453 uintptr_t tid, v, x; 454 u_int op, realexslp; 455 int error, ipri, itimo, queue, wakeup_swapper; 456 #ifdef LOCK_PROFILING 457 uint64_t waittime = 0; 458 int contested = 0; 459 #endif 460 #ifdef ADAPTIVE_LOCKMGRS 461 volatile struct thread *owner; 462 u_int i, spintries = 0; 463 #endif 464 465 error = 0; 466 tid = (uintptr_t)curthread; 467 op = (flags & LK_TYPE_MASK); 468 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 469 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 470 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 471 472 MPASS((flags & ~LK_TOTAL_MASK) == 0); 473 KASSERT((op & (op - 1)) == 0, 474 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 475 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 476 (op != LK_DOWNGRADE && op != LK_RELEASE), 477 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 478 __func__, file, line)); 479 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 480 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 481 __func__, file, line)); 482 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 483 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 484 lk->lock_object.lo_name, file, line)); 485 486 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 487 if (panicstr != NULL) { 488 if (flags & LK_INTERLOCK) 489 class->lc_unlock(ilk); 490 return (0); 491 } 492 493 if (lk->lock_object.lo_flags & LK_NOSHARE) { 494 switch (op) { 495 case LK_SHARED: 496 op = LK_EXCLUSIVE; 497 break; 498 case LK_UPGRADE: 499 case LK_TRYUPGRADE: 500 case LK_DOWNGRADE: 501 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 502 file, line); 503 if (flags & LK_INTERLOCK) 504 class->lc_unlock(ilk); 505 return (0); 506 } 507 } 508 509 wakeup_swapper = 0; 510 switch (op) { 511 case LK_SHARED: 512 if (LK_CAN_WITNESS(flags)) 513 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 514 file, line, flags & LK_INTERLOCK ? ilk : NULL); 515 for (;;) { 516 x = lk->lk_lock; 517 518 /* 519 * If no other thread has an exclusive lock, or 520 * no exclusive waiter is present, bump the count of 521 * sharers. Since we have to preserve the state of 522 * waiters, if we fail to acquire the shared lock 523 * loop back and retry. 524 */ 525 if (LK_CAN_SHARE(x)) { 526 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 527 x + LK_ONE_SHARER)) 528 break; 529 continue; 530 } 531 #ifdef HWPMC_HOOKS 532 PMC_SOFT_CALL( , , lock, failed); 533 #endif 534 lock_profile_obtain_lock_failed(&lk->lock_object, 535 &contested, &waittime); 536 537 /* 538 * If the lock is already held by curthread in 539 * exclusive way avoid a deadlock. 540 */ 541 if (LK_HOLDER(x) == tid) { 542 LOCK_LOG2(lk, 543 "%s: %p already held in exclusive mode", 544 __func__, lk); 545 error = EDEADLK; 546 break; 547 } 548 549 /* 550 * If the lock is expected to not sleep just give up 551 * and return. 552 */ 553 if (LK_TRYOP(flags)) { 554 LOCK_LOG2(lk, "%s: %p fails the try operation", 555 __func__, lk); 556 error = EBUSY; 557 break; 558 } 559 560 #ifdef ADAPTIVE_LOCKMGRS 561 /* 562 * If the owner is running on another CPU, spin until 563 * the owner stops running or the state of the lock 564 * changes. We need a double-state handle here 565 * because for a failed acquisition the lock can be 566 * either held in exclusive mode or shared mode 567 * (for the writer starvation avoidance technique). 568 */ 569 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 570 LK_HOLDER(x) != LK_KERNPROC) { 571 owner = (struct thread *)LK_HOLDER(x); 572 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 573 CTR3(KTR_LOCK, 574 "%s: spinning on %p held by %p", 575 __func__, lk, owner); 576 577 /* 578 * If we are holding also an interlock drop it 579 * in order to avoid a deadlock if the lockmgr 580 * owner is adaptively spinning on the 581 * interlock itself. 582 */ 583 if (flags & LK_INTERLOCK) { 584 class->lc_unlock(ilk); 585 flags &= ~LK_INTERLOCK; 586 } 587 GIANT_SAVE(); 588 while (LK_HOLDER(lk->lk_lock) == 589 (uintptr_t)owner && TD_IS_RUNNING(owner)) 590 cpu_spinwait(); 591 GIANT_RESTORE(); 592 continue; 593 } else if (LK_CAN_ADAPT(lk, flags) && 594 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 595 spintries < alk_retries) { 596 if (flags & LK_INTERLOCK) { 597 class->lc_unlock(ilk); 598 flags &= ~LK_INTERLOCK; 599 } 600 GIANT_SAVE(); 601 spintries++; 602 for (i = 0; i < alk_loops; i++) { 603 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 604 CTR4(KTR_LOCK, 605 "%s: shared spinning on %p with %u and %u", 606 __func__, lk, spintries, i); 607 x = lk->lk_lock; 608 if ((x & LK_SHARE) == 0 || 609 LK_CAN_SHARE(x) != 0) 610 break; 611 cpu_spinwait(); 612 } 613 GIANT_RESTORE(); 614 if (i != alk_loops) 615 continue; 616 } 617 #endif 618 619 /* 620 * Acquire the sleepqueue chain lock because we 621 * probabilly will need to manipulate waiters flags. 622 */ 623 sleepq_lock(&lk->lock_object); 624 x = lk->lk_lock; 625 626 /* 627 * if the lock can be acquired in shared mode, try 628 * again. 629 */ 630 if (LK_CAN_SHARE(x)) { 631 sleepq_release(&lk->lock_object); 632 continue; 633 } 634 635 #ifdef ADAPTIVE_LOCKMGRS 636 /* 637 * The current lock owner might have started executing 638 * on another CPU (or the lock could have changed 639 * owner) while we were waiting on the turnstile 640 * chain lock. If so, drop the turnstile lock and try 641 * again. 642 */ 643 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 644 LK_HOLDER(x) != LK_KERNPROC) { 645 owner = (struct thread *)LK_HOLDER(x); 646 if (TD_IS_RUNNING(owner)) { 647 sleepq_release(&lk->lock_object); 648 continue; 649 } 650 } 651 #endif 652 653 /* 654 * Try to set the LK_SHARED_WAITERS flag. If we fail, 655 * loop back and retry. 656 */ 657 if ((x & LK_SHARED_WAITERS) == 0) { 658 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 659 x | LK_SHARED_WAITERS)) { 660 sleepq_release(&lk->lock_object); 661 continue; 662 } 663 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 664 __func__, lk); 665 } 666 667 /* 668 * As far as we have been unable to acquire the 669 * shared lock and the shared waiters flag is set, 670 * we will sleep. 671 */ 672 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 673 SQ_SHARED_QUEUE); 674 flags &= ~LK_INTERLOCK; 675 if (error) { 676 LOCK_LOG3(lk, 677 "%s: interrupted sleep for %p with %d", 678 __func__, lk, error); 679 break; 680 } 681 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 682 __func__, lk); 683 } 684 if (error == 0) { 685 lock_profile_obtain_lock_success(&lk->lock_object, 686 contested, waittime, file, line); 687 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 688 line); 689 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 690 line); 691 TD_LOCKS_INC(curthread); 692 TD_SLOCKS_INC(curthread); 693 STACK_SAVE(lk); 694 } 695 break; 696 case LK_UPGRADE: 697 case LK_TRYUPGRADE: 698 _lockmgr_assert(lk, KA_SLOCKED, file, line); 699 v = lk->lk_lock; 700 x = v & LK_ALL_WAITERS; 701 v &= LK_EXCLUSIVE_SPINNERS; 702 703 /* 704 * Try to switch from one shared lock to an exclusive one. 705 * We need to preserve waiters flags during the operation. 706 */ 707 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 708 tid | x)) { 709 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 710 line); 711 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 712 LK_TRYWIT(flags), file, line); 713 TD_SLOCKS_DEC(curthread); 714 break; 715 } 716 717 /* 718 * In LK_TRYUPGRADE mode, do not drop the lock, 719 * returning EBUSY instead. 720 */ 721 if (op == LK_TRYUPGRADE) { 722 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", 723 __func__, lk); 724 error = EBUSY; 725 break; 726 } 727 728 /* 729 * We have been unable to succeed in upgrading, so just 730 * give up the shared lock. 731 */ 732 wakeup_swapper |= wakeupshlk(lk, file, line); 733 734 /* FALLTHROUGH */ 735 case LK_EXCLUSIVE: 736 if (LK_CAN_WITNESS(flags)) 737 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 738 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 739 ilk : NULL); 740 741 /* 742 * If curthread already holds the lock and this one is 743 * allowed to recurse, simply recurse on it. 744 */ 745 if (lockmgr_xlocked(lk)) { 746 if ((flags & LK_CANRECURSE) == 0 && 747 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 748 749 /* 750 * If the lock is expected to not panic just 751 * give up and return. 752 */ 753 if (LK_TRYOP(flags)) { 754 LOCK_LOG2(lk, 755 "%s: %p fails the try operation", 756 __func__, lk); 757 error = EBUSY; 758 break; 759 } 760 if (flags & LK_INTERLOCK) 761 class->lc_unlock(ilk); 762 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 763 __func__, iwmesg, file, line); 764 } 765 lk->lk_recurse++; 766 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 767 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 768 lk->lk_recurse, file, line); 769 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 770 LK_TRYWIT(flags), file, line); 771 TD_LOCKS_INC(curthread); 772 break; 773 } 774 775 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 776 tid)) { 777 #ifdef HWPMC_HOOKS 778 PMC_SOFT_CALL( , , lock, failed); 779 #endif 780 lock_profile_obtain_lock_failed(&lk->lock_object, 781 &contested, &waittime); 782 783 /* 784 * If the lock is expected to not sleep just give up 785 * and return. 786 */ 787 if (LK_TRYOP(flags)) { 788 LOCK_LOG2(lk, "%s: %p fails the try operation", 789 __func__, lk); 790 error = EBUSY; 791 break; 792 } 793 794 #ifdef ADAPTIVE_LOCKMGRS 795 /* 796 * If the owner is running on another CPU, spin until 797 * the owner stops running or the state of the lock 798 * changes. 799 */ 800 x = lk->lk_lock; 801 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 802 LK_HOLDER(x) != LK_KERNPROC) { 803 owner = (struct thread *)LK_HOLDER(x); 804 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 805 CTR3(KTR_LOCK, 806 "%s: spinning on %p held by %p", 807 __func__, lk, owner); 808 809 /* 810 * If we are holding also an interlock drop it 811 * in order to avoid a deadlock if the lockmgr 812 * owner is adaptively spinning on the 813 * interlock itself. 814 */ 815 if (flags & LK_INTERLOCK) { 816 class->lc_unlock(ilk); 817 flags &= ~LK_INTERLOCK; 818 } 819 GIANT_SAVE(); 820 while (LK_HOLDER(lk->lk_lock) == 821 (uintptr_t)owner && TD_IS_RUNNING(owner)) 822 cpu_spinwait(); 823 GIANT_RESTORE(); 824 continue; 825 } else if (LK_CAN_ADAPT(lk, flags) && 826 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 827 spintries < alk_retries) { 828 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 829 !atomic_cmpset_ptr(&lk->lk_lock, x, 830 x | LK_EXCLUSIVE_SPINNERS)) 831 continue; 832 if (flags & LK_INTERLOCK) { 833 class->lc_unlock(ilk); 834 flags &= ~LK_INTERLOCK; 835 } 836 GIANT_SAVE(); 837 spintries++; 838 for (i = 0; i < alk_loops; i++) { 839 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 840 CTR4(KTR_LOCK, 841 "%s: shared spinning on %p with %u and %u", 842 __func__, lk, spintries, i); 843 if ((lk->lk_lock & 844 LK_EXCLUSIVE_SPINNERS) == 0) 845 break; 846 cpu_spinwait(); 847 } 848 GIANT_RESTORE(); 849 if (i != alk_loops) 850 continue; 851 } 852 #endif 853 854 /* 855 * Acquire the sleepqueue chain lock because we 856 * probabilly will need to manipulate waiters flags. 857 */ 858 sleepq_lock(&lk->lock_object); 859 x = lk->lk_lock; 860 861 /* 862 * if the lock has been released while we spun on 863 * the sleepqueue chain lock just try again. 864 */ 865 if (x == LK_UNLOCKED) { 866 sleepq_release(&lk->lock_object); 867 continue; 868 } 869 870 #ifdef ADAPTIVE_LOCKMGRS 871 /* 872 * The current lock owner might have started executing 873 * on another CPU (or the lock could have changed 874 * owner) while we were waiting on the turnstile 875 * chain lock. If so, drop the turnstile lock and try 876 * again. 877 */ 878 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 879 LK_HOLDER(x) != LK_KERNPROC) { 880 owner = (struct thread *)LK_HOLDER(x); 881 if (TD_IS_RUNNING(owner)) { 882 sleepq_release(&lk->lock_object); 883 continue; 884 } 885 } 886 #endif 887 888 /* 889 * The lock can be in the state where there is a 890 * pending queue of waiters, but still no owner. 891 * This happens when the lock is contested and an 892 * owner is going to claim the lock. 893 * If curthread is the one successfully acquiring it 894 * claim lock ownership and return, preserving waiters 895 * flags. 896 */ 897 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 898 if ((x & ~v) == LK_UNLOCKED) { 899 v &= ~LK_EXCLUSIVE_SPINNERS; 900 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 901 tid | v)) { 902 sleepq_release(&lk->lock_object); 903 LOCK_LOG2(lk, 904 "%s: %p claimed by a new writer", 905 __func__, lk); 906 break; 907 } 908 sleepq_release(&lk->lock_object); 909 continue; 910 } 911 912 /* 913 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 914 * fail, loop back and retry. 915 */ 916 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 917 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 918 x | LK_EXCLUSIVE_WAITERS)) { 919 sleepq_release(&lk->lock_object); 920 continue; 921 } 922 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 923 __func__, lk); 924 } 925 926 /* 927 * As far as we have been unable to acquire the 928 * exclusive lock and the exclusive waiters flag 929 * is set, we will sleep. 930 */ 931 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 932 SQ_EXCLUSIVE_QUEUE); 933 flags &= ~LK_INTERLOCK; 934 if (error) { 935 LOCK_LOG3(lk, 936 "%s: interrupted sleep for %p with %d", 937 __func__, lk, error); 938 break; 939 } 940 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 941 __func__, lk); 942 } 943 if (error == 0) { 944 lock_profile_obtain_lock_success(&lk->lock_object, 945 contested, waittime, file, line); 946 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 947 lk->lk_recurse, file, line); 948 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 949 LK_TRYWIT(flags), file, line); 950 TD_LOCKS_INC(curthread); 951 STACK_SAVE(lk); 952 } 953 break; 954 case LK_DOWNGRADE: 955 _lockmgr_assert(lk, KA_XLOCKED, file, line); 956 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 957 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 958 959 /* 960 * Panic if the lock is recursed. 961 */ 962 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 963 if (flags & LK_INTERLOCK) 964 class->lc_unlock(ilk); 965 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 966 __func__, iwmesg, file, line); 967 } 968 TD_SLOCKS_INC(curthread); 969 970 /* 971 * In order to preserve waiters flags, just spin. 972 */ 973 for (;;) { 974 x = lk->lk_lock; 975 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 976 x &= LK_ALL_WAITERS; 977 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 978 LK_SHARERS_LOCK(1) | x)) 979 break; 980 cpu_spinwait(); 981 } 982 break; 983 case LK_RELEASE: 984 _lockmgr_assert(lk, KA_LOCKED, file, line); 985 x = lk->lk_lock; 986 987 if ((x & LK_SHARE) == 0) { 988 989 /* 990 * As first option, treact the lock as if it has not 991 * any waiter. 992 * Fix-up the tid var if the lock has been disowned. 993 */ 994 if (LK_HOLDER(x) == LK_KERNPROC) 995 tid = LK_KERNPROC; 996 else { 997 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 998 file, line); 999 TD_LOCKS_DEC(curthread); 1000 } 1001 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 1002 lk->lk_recurse, file, line); 1003 1004 /* 1005 * The lock is held in exclusive mode. 1006 * If the lock is recursed also, then unrecurse it. 1007 */ 1008 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 1009 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 1010 lk); 1011 lk->lk_recurse--; 1012 break; 1013 } 1014 if (tid != LK_KERNPROC) 1015 lock_profile_release_lock(&lk->lock_object); 1016 1017 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 1018 LK_UNLOCKED)) 1019 break; 1020 1021 sleepq_lock(&lk->lock_object); 1022 x = lk->lk_lock; 1023 v = LK_UNLOCKED; 1024 1025 /* 1026 * If the lock has exclusive waiters, give them 1027 * preference in order to avoid deadlock with 1028 * shared runners up. 1029 * If interruptible sleeps left the exclusive queue 1030 * empty avoid a starvation for the threads sleeping 1031 * on the shared queue by giving them precedence 1032 * and cleaning up the exclusive waiters bit anyway. 1033 * Please note that lk_exslpfail count may be lying 1034 * about the real number of waiters with the 1035 * LK_SLEEPFAIL flag on because they may be used in 1036 * conjuction with interruptible sleeps so 1037 * lk_exslpfail might be considered an 'upper limit' 1038 * bound, including the edge cases. 1039 */ 1040 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1041 realexslp = sleepq_sleepcnt(&lk->lock_object, 1042 SQ_EXCLUSIVE_QUEUE); 1043 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1044 if (lk->lk_exslpfail < realexslp) { 1045 lk->lk_exslpfail = 0; 1046 queue = SQ_EXCLUSIVE_QUEUE; 1047 v |= (x & LK_SHARED_WAITERS); 1048 } else { 1049 lk->lk_exslpfail = 0; 1050 LOCK_LOG2(lk, 1051 "%s: %p has only LK_SLEEPFAIL sleepers", 1052 __func__, lk); 1053 LOCK_LOG2(lk, 1054 "%s: %p waking up threads on the exclusive queue", 1055 __func__, lk); 1056 wakeup_swapper = 1057 sleepq_broadcast(&lk->lock_object, 1058 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1059 queue = SQ_SHARED_QUEUE; 1060 } 1061 } else { 1062 1063 /* 1064 * Exclusive waiters sleeping with LK_SLEEPFAIL 1065 * on and using interruptible sleeps/timeout 1066 * may have left spourious lk_exslpfail counts 1067 * on, so clean it up anyway. 1068 */ 1069 lk->lk_exslpfail = 0; 1070 queue = SQ_SHARED_QUEUE; 1071 } 1072 1073 LOCK_LOG3(lk, 1074 "%s: %p waking up threads on the %s queue", 1075 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1076 "exclusive"); 1077 atomic_store_rel_ptr(&lk->lk_lock, v); 1078 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1079 SLEEPQ_LK, 0, queue); 1080 sleepq_release(&lk->lock_object); 1081 break; 1082 } else 1083 wakeup_swapper = wakeupshlk(lk, file, line); 1084 break; 1085 case LK_DRAIN: 1086 if (LK_CAN_WITNESS(flags)) 1087 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1088 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 1089 ilk : NULL); 1090 1091 /* 1092 * Trying to drain a lock we already own will result in a 1093 * deadlock. 1094 */ 1095 if (lockmgr_xlocked(lk)) { 1096 if (flags & LK_INTERLOCK) 1097 class->lc_unlock(ilk); 1098 panic("%s: draining %s with the lock held @ %s:%d\n", 1099 __func__, iwmesg, file, line); 1100 } 1101 1102 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1103 #ifdef HWPMC_HOOKS 1104 PMC_SOFT_CALL( , , lock, failed); 1105 #endif 1106 lock_profile_obtain_lock_failed(&lk->lock_object, 1107 &contested, &waittime); 1108 1109 /* 1110 * If the lock is expected to not sleep just give up 1111 * and return. 1112 */ 1113 if (LK_TRYOP(flags)) { 1114 LOCK_LOG2(lk, "%s: %p fails the try operation", 1115 __func__, lk); 1116 error = EBUSY; 1117 break; 1118 } 1119 1120 /* 1121 * Acquire the sleepqueue chain lock because we 1122 * probabilly will need to manipulate waiters flags. 1123 */ 1124 sleepq_lock(&lk->lock_object); 1125 x = lk->lk_lock; 1126 1127 /* 1128 * if the lock has been released while we spun on 1129 * the sleepqueue chain lock just try again. 1130 */ 1131 if (x == LK_UNLOCKED) { 1132 sleepq_release(&lk->lock_object); 1133 continue; 1134 } 1135 1136 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1137 if ((x & ~v) == LK_UNLOCKED) { 1138 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1139 1140 /* 1141 * If interruptible sleeps left the exclusive 1142 * queue empty avoid a starvation for the 1143 * threads sleeping on the shared queue by 1144 * giving them precedence and cleaning up the 1145 * exclusive waiters bit anyway. 1146 * Please note that lk_exslpfail count may be 1147 * lying about the real number of waiters with 1148 * the LK_SLEEPFAIL flag on because they may 1149 * be used in conjuction with interruptible 1150 * sleeps so lk_exslpfail might be considered 1151 * an 'upper limit' bound, including the edge 1152 * cases. 1153 */ 1154 if (v & LK_EXCLUSIVE_WAITERS) { 1155 queue = SQ_EXCLUSIVE_QUEUE; 1156 v &= ~LK_EXCLUSIVE_WAITERS; 1157 } else { 1158 1159 /* 1160 * Exclusive waiters sleeping with 1161 * LK_SLEEPFAIL on and using 1162 * interruptible sleeps/timeout may 1163 * have left spourious lk_exslpfail 1164 * counts on, so clean it up anyway. 1165 */ 1166 MPASS(v & LK_SHARED_WAITERS); 1167 lk->lk_exslpfail = 0; 1168 queue = SQ_SHARED_QUEUE; 1169 v &= ~LK_SHARED_WAITERS; 1170 } 1171 if (queue == SQ_EXCLUSIVE_QUEUE) { 1172 realexslp = 1173 sleepq_sleepcnt(&lk->lock_object, 1174 SQ_EXCLUSIVE_QUEUE); 1175 if (lk->lk_exslpfail >= realexslp) { 1176 lk->lk_exslpfail = 0; 1177 queue = SQ_SHARED_QUEUE; 1178 v &= ~LK_SHARED_WAITERS; 1179 if (realexslp != 0) { 1180 LOCK_LOG2(lk, 1181 "%s: %p has only LK_SLEEPFAIL sleepers", 1182 __func__, lk); 1183 LOCK_LOG2(lk, 1184 "%s: %p waking up threads on the exclusive queue", 1185 __func__, lk); 1186 wakeup_swapper = 1187 sleepq_broadcast( 1188 &lk->lock_object, 1189 SLEEPQ_LK, 0, 1190 SQ_EXCLUSIVE_QUEUE); 1191 } 1192 } else 1193 lk->lk_exslpfail = 0; 1194 } 1195 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1196 sleepq_release(&lk->lock_object); 1197 continue; 1198 } 1199 LOCK_LOG3(lk, 1200 "%s: %p waking up all threads on the %s queue", 1201 __func__, lk, queue == SQ_SHARED_QUEUE ? 1202 "shared" : "exclusive"); 1203 wakeup_swapper |= sleepq_broadcast( 1204 &lk->lock_object, SLEEPQ_LK, 0, queue); 1205 1206 /* 1207 * If shared waiters have been woken up we need 1208 * to wait for one of them to acquire the lock 1209 * before to set the exclusive waiters in 1210 * order to avoid a deadlock. 1211 */ 1212 if (queue == SQ_SHARED_QUEUE) { 1213 for (v = lk->lk_lock; 1214 (v & LK_SHARE) && !LK_SHARERS(v); 1215 v = lk->lk_lock) 1216 cpu_spinwait(); 1217 } 1218 } 1219 1220 /* 1221 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1222 * fail, loop back and retry. 1223 */ 1224 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1225 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1226 x | LK_EXCLUSIVE_WAITERS)) { 1227 sleepq_release(&lk->lock_object); 1228 continue; 1229 } 1230 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1231 __func__, lk); 1232 } 1233 1234 /* 1235 * As far as we have been unable to acquire the 1236 * exclusive lock and the exclusive waiters flag 1237 * is set, we will sleep. 1238 */ 1239 if (flags & LK_INTERLOCK) { 1240 class->lc_unlock(ilk); 1241 flags &= ~LK_INTERLOCK; 1242 } 1243 GIANT_SAVE(); 1244 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1245 SQ_EXCLUSIVE_QUEUE); 1246 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1247 GIANT_RESTORE(); 1248 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1249 __func__, lk); 1250 } 1251 1252 if (error == 0) { 1253 lock_profile_obtain_lock_success(&lk->lock_object, 1254 contested, waittime, file, line); 1255 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1256 lk->lk_recurse, file, line); 1257 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1258 LK_TRYWIT(flags), file, line); 1259 TD_LOCKS_INC(curthread); 1260 STACK_SAVE(lk); 1261 } 1262 break; 1263 default: 1264 if (flags & LK_INTERLOCK) 1265 class->lc_unlock(ilk); 1266 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1267 } 1268 1269 if (flags & LK_INTERLOCK) 1270 class->lc_unlock(ilk); 1271 if (wakeup_swapper) 1272 kick_proc0(); 1273 1274 return (error); 1275 } 1276 1277 void 1278 _lockmgr_disown(struct lock *lk, const char *file, int line) 1279 { 1280 uintptr_t tid, x; 1281 1282 if (SCHEDULER_STOPPED()) 1283 return; 1284 1285 tid = (uintptr_t)curthread; 1286 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1287 1288 /* 1289 * Panic if the lock is recursed. 1290 */ 1291 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1292 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1293 __func__, file, line); 1294 1295 /* 1296 * If the owner is already LK_KERNPROC just skip the whole operation. 1297 */ 1298 if (LK_HOLDER(lk->lk_lock) != tid) 1299 return; 1300 lock_profile_release_lock(&lk->lock_object); 1301 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1302 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1303 TD_LOCKS_DEC(curthread); 1304 STACK_SAVE(lk); 1305 1306 /* 1307 * In order to preserve waiters flags, just spin. 1308 */ 1309 for (;;) { 1310 x = lk->lk_lock; 1311 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1312 x &= LK_ALL_WAITERS; 1313 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1314 LK_KERNPROC | x)) 1315 return; 1316 cpu_spinwait(); 1317 } 1318 } 1319 1320 void 1321 lockmgr_printinfo(const struct lock *lk) 1322 { 1323 struct thread *td; 1324 uintptr_t x; 1325 1326 if (lk->lk_lock == LK_UNLOCKED) 1327 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1328 else if (lk->lk_lock & LK_SHARE) 1329 printf("lock type %s: SHARED (count %ju)\n", 1330 lk->lock_object.lo_name, 1331 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1332 else { 1333 td = lockmgr_xholder(lk); 1334 printf("lock type %s: EXCL by thread %p " 1335 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, td, 1336 td->td_proc->p_pid, td->td_proc->p_comm, td->td_tid); 1337 } 1338 1339 x = lk->lk_lock; 1340 if (x & LK_EXCLUSIVE_WAITERS) 1341 printf(" with exclusive waiters pending\n"); 1342 if (x & LK_SHARED_WAITERS) 1343 printf(" with shared waiters pending\n"); 1344 if (x & LK_EXCLUSIVE_SPINNERS) 1345 printf(" with exclusive spinners pending\n"); 1346 1347 STACK_PRINT(lk); 1348 } 1349 1350 int 1351 lockstatus(const struct lock *lk) 1352 { 1353 uintptr_t v, x; 1354 int ret; 1355 1356 ret = LK_SHARED; 1357 x = lk->lk_lock; 1358 v = LK_HOLDER(x); 1359 1360 if ((x & LK_SHARE) == 0) { 1361 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1362 ret = LK_EXCLUSIVE; 1363 else 1364 ret = LK_EXCLOTHER; 1365 } else if (x == LK_UNLOCKED) 1366 ret = 0; 1367 1368 return (ret); 1369 } 1370 1371 #ifdef INVARIANT_SUPPORT 1372 1373 FEATURE(invariant_support, 1374 "Support for modules compiled with INVARIANTS option"); 1375 1376 #ifndef INVARIANTS 1377 #undef _lockmgr_assert 1378 #endif 1379 1380 void 1381 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1382 { 1383 int slocked = 0; 1384 1385 if (panicstr != NULL) 1386 return; 1387 switch (what) { 1388 case KA_SLOCKED: 1389 case KA_SLOCKED | KA_NOTRECURSED: 1390 case KA_SLOCKED | KA_RECURSED: 1391 slocked = 1; 1392 case KA_LOCKED: 1393 case KA_LOCKED | KA_NOTRECURSED: 1394 case KA_LOCKED | KA_RECURSED: 1395 #ifdef WITNESS 1396 1397 /* 1398 * We cannot trust WITNESS if the lock is held in exclusive 1399 * mode and a call to lockmgr_disown() happened. 1400 * Workaround this skipping the check if the lock is held in 1401 * exclusive mode even for the KA_LOCKED case. 1402 */ 1403 if (slocked || (lk->lk_lock & LK_SHARE)) { 1404 witness_assert(&lk->lock_object, what, file, line); 1405 break; 1406 } 1407 #endif 1408 if (lk->lk_lock == LK_UNLOCKED || 1409 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1410 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1411 panic("Lock %s not %slocked @ %s:%d\n", 1412 lk->lock_object.lo_name, slocked ? "share" : "", 1413 file, line); 1414 1415 if ((lk->lk_lock & LK_SHARE) == 0) { 1416 if (lockmgr_recursed(lk)) { 1417 if (what & KA_NOTRECURSED) 1418 panic("Lock %s recursed @ %s:%d\n", 1419 lk->lock_object.lo_name, file, 1420 line); 1421 } else if (what & KA_RECURSED) 1422 panic("Lock %s not recursed @ %s:%d\n", 1423 lk->lock_object.lo_name, file, line); 1424 } 1425 break; 1426 case KA_XLOCKED: 1427 case KA_XLOCKED | KA_NOTRECURSED: 1428 case KA_XLOCKED | KA_RECURSED: 1429 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1430 panic("Lock %s not exclusively locked @ %s:%d\n", 1431 lk->lock_object.lo_name, file, line); 1432 if (lockmgr_recursed(lk)) { 1433 if (what & KA_NOTRECURSED) 1434 panic("Lock %s recursed @ %s:%d\n", 1435 lk->lock_object.lo_name, file, line); 1436 } else if (what & KA_RECURSED) 1437 panic("Lock %s not recursed @ %s:%d\n", 1438 lk->lock_object.lo_name, file, line); 1439 break; 1440 case KA_UNLOCKED: 1441 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1442 panic("Lock %s exclusively locked @ %s:%d\n", 1443 lk->lock_object.lo_name, file, line); 1444 break; 1445 default: 1446 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1447 line); 1448 } 1449 } 1450 #endif 1451 1452 #ifdef DDB 1453 int 1454 lockmgr_chain(struct thread *td, struct thread **ownerp) 1455 { 1456 struct lock *lk; 1457 1458 lk = td->td_wchan; 1459 1460 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1461 return (0); 1462 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1463 if (lk->lk_lock & LK_SHARE) 1464 db_printf("SHARED (count %ju)\n", 1465 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1466 else 1467 db_printf("EXCL\n"); 1468 *ownerp = lockmgr_xholder(lk); 1469 1470 return (1); 1471 } 1472 1473 static void 1474 db_show_lockmgr(const struct lock_object *lock) 1475 { 1476 struct thread *td; 1477 const struct lock *lk; 1478 1479 lk = (const struct lock *)lock; 1480 1481 db_printf(" state: "); 1482 if (lk->lk_lock == LK_UNLOCKED) 1483 db_printf("UNLOCKED\n"); 1484 else if (lk->lk_lock & LK_SHARE) 1485 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1486 else { 1487 td = lockmgr_xholder(lk); 1488 if (td == (struct thread *)LK_KERNPROC) 1489 db_printf("XLOCK: LK_KERNPROC\n"); 1490 else 1491 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1492 td->td_tid, td->td_proc->p_pid, 1493 td->td_proc->p_comm); 1494 if (lockmgr_recursed(lk)) 1495 db_printf(" recursed: %d\n", lk->lk_recurse); 1496 } 1497 db_printf(" waiters: "); 1498 switch (lk->lk_lock & LK_ALL_WAITERS) { 1499 case LK_SHARED_WAITERS: 1500 db_printf("shared\n"); 1501 break; 1502 case LK_EXCLUSIVE_WAITERS: 1503 db_printf("exclusive\n"); 1504 break; 1505 case LK_ALL_WAITERS: 1506 db_printf("shared and exclusive\n"); 1507 break; 1508 default: 1509 db_printf("none\n"); 1510 } 1511 db_printf(" spinners: "); 1512 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1513 db_printf("exclusive\n"); 1514 else 1515 db_printf("none\n"); 1516 } 1517 #endif 1518