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sys/kern/kern_lock.c
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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_kdtrace.h" 32 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD: releng/9.0/sys/kern/kern_lock.c 226255 2011-10-11 13:45:04Z attilio $"); 35 36 #include <sys/param.h> 37 #include <sys/ktr.h> 38 #include <sys/lock.h> 39 #include <sys/lock_profile.h> 40 #include <sys/lockmgr.h> 41 #include <sys/mutex.h> 42 #include <sys/proc.h> 43 #include <sys/sleepqueue.h> 44 #ifdef DEBUG_LOCKS 45 #include <sys/stack.h> 46 #endif 47 #include <sys/sysctl.h> 48 #include <sys/systm.h> 49 50 #include <machine/cpu.h> 51 52 #ifdef DDB 53 #include <ddb/ddb.h> 54 #endif 55 56 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) == 57 (LK_ADAPTIVE | LK_NOSHARE)); 58 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED & 59 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS))); 60 61 #define SQ_EXCLUSIVE_QUEUE 0 62 #define SQ_SHARED_QUEUE 1 63 64 #ifdef ADAPTIVE_LOCKMGRS 65 #define ALK_RETRIES 10 66 #define ALK_LOOPS 10000 67 #endif 68 69 #ifndef INVARIANTS 70 #define _lockmgr_assert(lk, what, file, line) 71 #define TD_LOCKS_INC(td) 72 #define TD_LOCKS_DEC(td) 73 #else 74 #define TD_LOCKS_INC(td) ((td)->td_locks++) 75 #define TD_LOCKS_DEC(td) ((td)->td_locks--) 76 #endif 77 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 78 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 79 80 #ifndef DEBUG_LOCKS 81 #define STACK_PRINT(lk) 82 #define STACK_SAVE(lk) 83 #define STACK_ZERO(lk) 84 #else 85 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 86 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 87 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 88 #endif 89 90 #define LOCK_LOG2(lk, string, arg1, arg2) \ 91 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 92 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 93 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 94 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 95 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 96 97 #define GIANT_DECLARE \ 98 int _i = 0; \ 99 WITNESS_SAVE_DECL(Giant) 100 #define GIANT_RESTORE() do { \ 101 if (_i > 0) { \ 102 while (_i--) \ 103 mtx_lock(&Giant); \ 104 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 105 } \ 106 } while (0) 107 #define GIANT_SAVE() do { \ 108 if (mtx_owned(&Giant)) { \ 109 WITNESS_SAVE(&Giant.lock_object, Giant); \ 110 while (mtx_owned(&Giant)) { \ 111 _i++; \ 112 mtx_unlock(&Giant); \ 113 } \ 114 } \ 115 } while (0) 116 117 #define LK_CAN_SHARE(x) \ 118 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \ 119 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \ 120 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT))) 121 #define LK_TRYOP(x) \ 122 ((x) & LK_NOWAIT) 123 124 #define LK_CAN_WITNESS(x) \ 125 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 126 #define LK_TRYWIT(x) \ 127 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 128 129 #define LK_CAN_ADAPT(lk, f) \ 130 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 131 ((f) & LK_SLEEPFAIL) == 0) 132 133 #define lockmgr_disowned(lk) \ 134 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 135 136 #define lockmgr_xlocked(lk) \ 137 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 138 139 static void assert_lockmgr(struct lock_object *lock, int how); 140 #ifdef DDB 141 static void db_show_lockmgr(struct lock_object *lock); 142 #endif 143 static void lock_lockmgr(struct lock_object *lock, int how); 144 #ifdef KDTRACE_HOOKS 145 static int owner_lockmgr(struct lock_object *lock, struct thread **owner); 146 #endif 147 static int unlock_lockmgr(struct lock_object *lock); 148 149 struct lock_class lock_class_lockmgr = { 150 .lc_name = "lockmgr", 151 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 152 .lc_assert = assert_lockmgr, 153 #ifdef DDB 154 .lc_ddb_show = db_show_lockmgr, 155 #endif 156 .lc_lock = lock_lockmgr, 157 .lc_unlock = unlock_lockmgr, 158 #ifdef KDTRACE_HOOKS 159 .lc_owner = owner_lockmgr, 160 #endif 161 }; 162 163 static __inline struct thread * 164 lockmgr_xholder(struct lock *lk) 165 { 166 uintptr_t x; 167 168 x = lk->lk_lock; 169 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 170 } 171 172 /* 173 * It assumes sleepq_lock held and returns with this one unheld. 174 * It also assumes the generic interlock is sane and previously checked. 175 * If LK_INTERLOCK is specified the interlock is not reacquired after the 176 * sleep. 177 */ 178 static __inline int 179 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 180 const char *wmesg, int pri, int timo, int queue) 181 { 182 GIANT_DECLARE; 183 struct lock_class *class; 184 int catch, error; 185 186 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 187 catch = pri & PCATCH; 188 pri &= PRIMASK; 189 error = 0; 190 191 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 192 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 193 194 if (flags & LK_INTERLOCK) 195 class->lc_unlock(ilk); 196 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 197 lk->lk_exslpfail++; 198 GIANT_SAVE(); 199 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 200 SLEEPQ_INTERRUPTIBLE : 0), queue); 201 if ((flags & LK_TIMELOCK) && timo) 202 sleepq_set_timeout(&lk->lock_object, timo); 203 204 /* 205 * Decisional switch for real sleeping. 206 */ 207 if ((flags & LK_TIMELOCK) && timo && catch) 208 error = sleepq_timedwait_sig(&lk->lock_object, pri); 209 else if ((flags & LK_TIMELOCK) && timo) 210 error = sleepq_timedwait(&lk->lock_object, pri); 211 else if (catch) 212 error = sleepq_wait_sig(&lk->lock_object, pri); 213 else 214 sleepq_wait(&lk->lock_object, pri); 215 GIANT_RESTORE(); 216 if ((flags & LK_SLEEPFAIL) && error == 0) 217 error = ENOLCK; 218 219 return (error); 220 } 221 222 static __inline int 223 wakeupshlk(struct lock *lk, const char *file, int line) 224 { 225 uintptr_t v, x; 226 u_int realexslp; 227 int queue, wakeup_swapper; 228 229 TD_LOCKS_DEC(curthread); 230 TD_SLOCKS_DEC(curthread); 231 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 232 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 233 234 wakeup_swapper = 0; 235 for (;;) { 236 x = lk->lk_lock; 237 238 /* 239 * If there is more than one shared lock held, just drop one 240 * and return. 241 */ 242 if (LK_SHARERS(x) > 1) { 243 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, 244 x - LK_ONE_SHARER)) 245 break; 246 continue; 247 } 248 249 /* 250 * If there are not waiters on the exclusive queue, drop the 251 * lock quickly. 252 */ 253 if ((x & LK_ALL_WAITERS) == 0) { 254 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == 255 LK_SHARERS_LOCK(1)); 256 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED)) 257 break; 258 continue; 259 } 260 261 /* 262 * We should have a sharer with waiters, so enter the hard 263 * path in order to handle wakeups correctly. 264 */ 265 sleepq_lock(&lk->lock_object); 266 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 267 v = LK_UNLOCKED; 268 269 /* 270 * If the lock has exclusive waiters, give them preference in 271 * order to avoid deadlock with shared runners up. 272 * If interruptible sleeps left the exclusive queue empty 273 * avoid a starvation for the threads sleeping on the shared 274 * queue by giving them precedence and cleaning up the 275 * exclusive waiters bit anyway. 276 * Please note that lk_exslpfail count may be lying about 277 * the real number of waiters with the LK_SLEEPFAIL flag on 278 * because they may be used in conjuction with interruptible 279 * sleeps so lk_exslpfail might be considered an 'upper limit' 280 * bound, including the edge cases. 281 */ 282 realexslp = sleepq_sleepcnt(&lk->lock_object, 283 SQ_EXCLUSIVE_QUEUE); 284 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 285 if (lk->lk_exslpfail < realexslp) { 286 lk->lk_exslpfail = 0; 287 queue = SQ_EXCLUSIVE_QUEUE; 288 v |= (x & LK_SHARED_WAITERS); 289 } else { 290 lk->lk_exslpfail = 0; 291 LOCK_LOG2(lk, 292 "%s: %p has only LK_SLEEPFAIL sleepers", 293 __func__, lk); 294 LOCK_LOG2(lk, 295 "%s: %p waking up threads on the exclusive queue", 296 __func__, lk); 297 wakeup_swapper = 298 sleepq_broadcast(&lk->lock_object, 299 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 300 queue = SQ_SHARED_QUEUE; 301 } 302 303 } else { 304 305 /* 306 * Exclusive waiters sleeping with LK_SLEEPFAIL on 307 * and using interruptible sleeps/timeout may have 308 * left spourious lk_exslpfail counts on, so clean 309 * it up anyway. 310 */ 311 lk->lk_exslpfail = 0; 312 queue = SQ_SHARED_QUEUE; 313 } 314 315 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, 316 v)) { 317 sleepq_release(&lk->lock_object); 318 continue; 319 } 320 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 321 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 322 "exclusive"); 323 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 324 0, queue); 325 sleepq_release(&lk->lock_object); 326 break; 327 } 328 329 lock_profile_release_lock(&lk->lock_object); 330 return (wakeup_swapper); 331 } 332 333 static void 334 assert_lockmgr(struct lock_object *lock, int what) 335 { 336 337 panic("lockmgr locks do not support assertions"); 338 } 339 340 static void 341 lock_lockmgr(struct lock_object *lock, int how) 342 { 343 344 panic("lockmgr locks do not support sleep interlocking"); 345 } 346 347 static int 348 unlock_lockmgr(struct lock_object *lock) 349 { 350 351 panic("lockmgr locks do not support sleep interlocking"); 352 } 353 354 #ifdef KDTRACE_HOOKS 355 static int 356 owner_lockmgr(struct lock_object *lock, struct thread **owner) 357 { 358 359 panic("lockmgr locks do not support owner inquiring"); 360 } 361 #endif 362 363 void 364 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 365 { 366 int iflags; 367 368 MPASS((flags & ~LK_INIT_MASK) == 0); 369 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 370 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 371 &lk->lk_lock)); 372 373 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 374 if (flags & LK_CANRECURSE) 375 iflags |= LO_RECURSABLE; 376 if ((flags & LK_NODUP) == 0) 377 iflags |= LO_DUPOK; 378 if (flags & LK_NOPROFILE) 379 iflags |= LO_NOPROFILE; 380 if ((flags & LK_NOWITNESS) == 0) 381 iflags |= LO_WITNESS; 382 if (flags & LK_QUIET) 383 iflags |= LO_QUIET; 384 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 385 386 lk->lk_lock = LK_UNLOCKED; 387 lk->lk_recurse = 0; 388 lk->lk_exslpfail = 0; 389 lk->lk_timo = timo; 390 lk->lk_pri = pri; 391 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 392 STACK_ZERO(lk); 393 } 394 395 /* 396 * XXX: Gross hacks to manipulate external lock flags after 397 * initialization. Used for certain vnode and buf locks. 398 */ 399 void 400 lockallowshare(struct lock *lk) 401 { 402 403 lockmgr_assert(lk, KA_XLOCKED); 404 lk->lock_object.lo_flags &= ~LK_NOSHARE; 405 } 406 407 void 408 lockallowrecurse(struct lock *lk) 409 { 410 411 lockmgr_assert(lk, KA_XLOCKED); 412 lk->lock_object.lo_flags |= LO_RECURSABLE; 413 } 414 415 void 416 lockdisablerecurse(struct lock *lk) 417 { 418 419 lockmgr_assert(lk, KA_XLOCKED); 420 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 421 } 422 423 void 424 lockdestroy(struct lock *lk) 425 { 426 427 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 428 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 429 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 430 lock_destroy(&lk->lock_object); 431 } 432 433 int 434 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 435 const char *wmesg, int pri, int timo, const char *file, int line) 436 { 437 GIANT_DECLARE; 438 struct lock_class *class; 439 const char *iwmesg; 440 uintptr_t tid, v, x; 441 u_int op, realexslp; 442 int error, ipri, itimo, queue, wakeup_swapper; 443 #ifdef LOCK_PROFILING 444 uint64_t waittime = 0; 445 int contested = 0; 446 #endif 447 #ifdef ADAPTIVE_LOCKMGRS 448 volatile struct thread *owner; 449 u_int i, spintries = 0; 450 #endif 451 452 error = 0; 453 tid = (uintptr_t)curthread; 454 op = (flags & LK_TYPE_MASK); 455 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 456 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 457 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 458 459 MPASS((flags & ~LK_TOTAL_MASK) == 0); 460 KASSERT((op & (op - 1)) == 0, 461 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 462 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 463 (op != LK_DOWNGRADE && op != LK_RELEASE), 464 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 465 __func__, file, line)); 466 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 467 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 468 __func__, file, line)); 469 470 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 471 if (panicstr != NULL) { 472 if (flags & LK_INTERLOCK) 473 class->lc_unlock(ilk); 474 return (0); 475 } 476 477 if (lk->lock_object.lo_flags & LK_NOSHARE) { 478 switch (op) { 479 case LK_SHARED: 480 op = LK_EXCLUSIVE; 481 break; 482 case LK_UPGRADE: 483 case LK_DOWNGRADE: 484 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 485 file, line); 486 return (0); 487 } 488 } 489 490 wakeup_swapper = 0; 491 switch (op) { 492 case LK_SHARED: 493 if (LK_CAN_WITNESS(flags)) 494 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 495 file, line, ilk); 496 for (;;) { 497 x = lk->lk_lock; 498 499 /* 500 * If no other thread has an exclusive lock, or 501 * no exclusive waiter is present, bump the count of 502 * sharers. Since we have to preserve the state of 503 * waiters, if we fail to acquire the shared lock 504 * loop back and retry. 505 */ 506 if (LK_CAN_SHARE(x)) { 507 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 508 x + LK_ONE_SHARER)) 509 break; 510 continue; 511 } 512 lock_profile_obtain_lock_failed(&lk->lock_object, 513 &contested, &waittime); 514 515 /* 516 * If the lock is already held by curthread in 517 * exclusive way avoid a deadlock. 518 */ 519 if (LK_HOLDER(x) == tid) { 520 LOCK_LOG2(lk, 521 "%s: %p already held in exclusive mode", 522 __func__, lk); 523 error = EDEADLK; 524 break; 525 } 526 527 /* 528 * If the lock is expected to not sleep just give up 529 * and return. 530 */ 531 if (LK_TRYOP(flags)) { 532 LOCK_LOG2(lk, "%s: %p fails the try operation", 533 __func__, lk); 534 error = EBUSY; 535 break; 536 } 537 538 #ifdef ADAPTIVE_LOCKMGRS 539 /* 540 * If the owner is running on another CPU, spin until 541 * the owner stops running or the state of the lock 542 * changes. We need a double-state handle here 543 * because for a failed acquisition the lock can be 544 * either held in exclusive mode or shared mode 545 * (for the writer starvation avoidance technique). 546 */ 547 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 548 LK_HOLDER(x) != LK_KERNPROC) { 549 owner = (struct thread *)LK_HOLDER(x); 550 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 551 CTR3(KTR_LOCK, 552 "%s: spinning on %p held by %p", 553 __func__, lk, owner); 554 555 /* 556 * If we are holding also an interlock drop it 557 * in order to avoid a deadlock if the lockmgr 558 * owner is adaptively spinning on the 559 * interlock itself. 560 */ 561 if (flags & LK_INTERLOCK) { 562 class->lc_unlock(ilk); 563 flags &= ~LK_INTERLOCK; 564 } 565 GIANT_SAVE(); 566 while (LK_HOLDER(lk->lk_lock) == 567 (uintptr_t)owner && TD_IS_RUNNING(owner)) 568 cpu_spinwait(); 569 GIANT_RESTORE(); 570 continue; 571 } else if (LK_CAN_ADAPT(lk, flags) && 572 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 573 spintries < ALK_RETRIES) { 574 if (flags & LK_INTERLOCK) { 575 class->lc_unlock(ilk); 576 flags &= ~LK_INTERLOCK; 577 } 578 GIANT_SAVE(); 579 spintries++; 580 for (i = 0; i < ALK_LOOPS; i++) { 581 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 582 CTR4(KTR_LOCK, 583 "%s: shared spinning on %p with %u and %u", 584 __func__, lk, spintries, i); 585 x = lk->lk_lock; 586 if ((x & LK_SHARE) == 0 || 587 LK_CAN_SHARE(x) != 0) 588 break; 589 cpu_spinwait(); 590 } 591 GIANT_RESTORE(); 592 if (i != ALK_LOOPS) 593 continue; 594 } 595 #endif 596 597 /* 598 * Acquire the sleepqueue chain lock because we 599 * probabilly will need to manipulate waiters flags. 600 */ 601 sleepq_lock(&lk->lock_object); 602 x = lk->lk_lock; 603 604 /* 605 * if the lock can be acquired in shared mode, try 606 * again. 607 */ 608 if (LK_CAN_SHARE(x)) { 609 sleepq_release(&lk->lock_object); 610 continue; 611 } 612 613 #ifdef ADAPTIVE_LOCKMGRS 614 /* 615 * The current lock owner might have started executing 616 * on another CPU (or the lock could have changed 617 * owner) while we were waiting on the turnstile 618 * chain lock. If so, drop the turnstile lock and try 619 * again. 620 */ 621 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 622 LK_HOLDER(x) != LK_KERNPROC) { 623 owner = (struct thread *)LK_HOLDER(x); 624 if (TD_IS_RUNNING(owner)) { 625 sleepq_release(&lk->lock_object); 626 continue; 627 } 628 } 629 #endif 630 631 /* 632 * Try to set the LK_SHARED_WAITERS flag. If we fail, 633 * loop back and retry. 634 */ 635 if ((x & LK_SHARED_WAITERS) == 0) { 636 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 637 x | LK_SHARED_WAITERS)) { 638 sleepq_release(&lk->lock_object); 639 continue; 640 } 641 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 642 __func__, lk); 643 } 644 645 /* 646 * As far as we have been unable to acquire the 647 * shared lock and the shared waiters flag is set, 648 * we will sleep. 649 */ 650 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 651 SQ_SHARED_QUEUE); 652 flags &= ~LK_INTERLOCK; 653 if (error) { 654 LOCK_LOG3(lk, 655 "%s: interrupted sleep for %p with %d", 656 __func__, lk, error); 657 break; 658 } 659 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 660 __func__, lk); 661 } 662 if (error == 0) { 663 lock_profile_obtain_lock_success(&lk->lock_object, 664 contested, waittime, file, line); 665 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 666 line); 667 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 668 line); 669 TD_LOCKS_INC(curthread); 670 TD_SLOCKS_INC(curthread); 671 STACK_SAVE(lk); 672 } 673 break; 674 case LK_UPGRADE: 675 _lockmgr_assert(lk, KA_SLOCKED, file, line); 676 v = lk->lk_lock; 677 x = v & LK_ALL_WAITERS; 678 v &= LK_EXCLUSIVE_SPINNERS; 679 680 /* 681 * Try to switch from one shared lock to an exclusive one. 682 * We need to preserve waiters flags during the operation. 683 */ 684 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 685 tid | x)) { 686 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 687 line); 688 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 689 LK_TRYWIT(flags), file, line); 690 TD_SLOCKS_DEC(curthread); 691 break; 692 } 693 694 /* 695 * We have been unable to succeed in upgrading, so just 696 * give up the shared lock. 697 */ 698 wakeup_swapper |= wakeupshlk(lk, file, line); 699 700 /* FALLTHROUGH */ 701 case LK_EXCLUSIVE: 702 if (LK_CAN_WITNESS(flags)) 703 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 704 LOP_EXCLUSIVE, file, line, ilk); 705 706 /* 707 * If curthread already holds the lock and this one is 708 * allowed to recurse, simply recurse on it. 709 */ 710 if (lockmgr_xlocked(lk)) { 711 if ((flags & LK_CANRECURSE) == 0 && 712 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 713 714 /* 715 * If the lock is expected to not panic just 716 * give up and return. 717 */ 718 if (LK_TRYOP(flags)) { 719 LOCK_LOG2(lk, 720 "%s: %p fails the try operation", 721 __func__, lk); 722 error = EBUSY; 723 break; 724 } 725 if (flags & LK_INTERLOCK) 726 class->lc_unlock(ilk); 727 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 728 __func__, iwmesg, file, line); 729 } 730 lk->lk_recurse++; 731 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 732 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 733 lk->lk_recurse, file, line); 734 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 735 LK_TRYWIT(flags), file, line); 736 TD_LOCKS_INC(curthread); 737 break; 738 } 739 740 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 741 tid)) { 742 lock_profile_obtain_lock_failed(&lk->lock_object, 743 &contested, &waittime); 744 745 /* 746 * If the lock is expected to not sleep just give up 747 * and return. 748 */ 749 if (LK_TRYOP(flags)) { 750 LOCK_LOG2(lk, "%s: %p fails the try operation", 751 __func__, lk); 752 error = EBUSY; 753 break; 754 } 755 756 #ifdef ADAPTIVE_LOCKMGRS 757 /* 758 * If the owner is running on another CPU, spin until 759 * the owner stops running or the state of the lock 760 * changes. 761 */ 762 x = lk->lk_lock; 763 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 764 LK_HOLDER(x) != LK_KERNPROC) { 765 owner = (struct thread *)LK_HOLDER(x); 766 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 767 CTR3(KTR_LOCK, 768 "%s: spinning on %p held by %p", 769 __func__, lk, owner); 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 GIANT_RESTORE(); 786 continue; 787 } else if (LK_CAN_ADAPT(lk, flags) && 788 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 789 spintries < ALK_RETRIES) { 790 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 791 !atomic_cmpset_ptr(&lk->lk_lock, x, 792 x | LK_EXCLUSIVE_SPINNERS)) 793 continue; 794 if (flags & LK_INTERLOCK) { 795 class->lc_unlock(ilk); 796 flags &= ~LK_INTERLOCK; 797 } 798 GIANT_SAVE(); 799 spintries++; 800 for (i = 0; i < ALK_LOOPS; i++) { 801 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 802 CTR4(KTR_LOCK, 803 "%s: shared spinning on %p with %u and %u", 804 __func__, lk, spintries, i); 805 if ((lk->lk_lock & 806 LK_EXCLUSIVE_SPINNERS) == 0) 807 break; 808 cpu_spinwait(); 809 } 810 GIANT_RESTORE(); 811 if (i != ALK_LOOPS) 812 continue; 813 } 814 #endif 815 816 /* 817 * Acquire the sleepqueue chain lock because we 818 * probabilly will need to manipulate waiters flags. 819 */ 820 sleepq_lock(&lk->lock_object); 821 x = lk->lk_lock; 822 823 /* 824 * if the lock has been released while we spun on 825 * the sleepqueue chain lock just try again. 826 */ 827 if (x == LK_UNLOCKED) { 828 sleepq_release(&lk->lock_object); 829 continue; 830 } 831 832 #ifdef ADAPTIVE_LOCKMGRS 833 /* 834 * The current lock owner might have started executing 835 * on another CPU (or the lock could have changed 836 * owner) while we were waiting on the turnstile 837 * chain lock. If so, drop the turnstile lock and try 838 * again. 839 */ 840 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 841 LK_HOLDER(x) != LK_KERNPROC) { 842 owner = (struct thread *)LK_HOLDER(x); 843 if (TD_IS_RUNNING(owner)) { 844 sleepq_release(&lk->lock_object); 845 continue; 846 } 847 } 848 #endif 849 850 /* 851 * The lock can be in the state where there is a 852 * pending queue of waiters, but still no owner. 853 * This happens when the lock is contested and an 854 * owner is going to claim the lock. 855 * If curthread is the one successfully acquiring it 856 * claim lock ownership and return, preserving waiters 857 * flags. 858 */ 859 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 860 if ((x & ~v) == LK_UNLOCKED) { 861 v &= ~LK_EXCLUSIVE_SPINNERS; 862 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 863 tid | v)) { 864 sleepq_release(&lk->lock_object); 865 LOCK_LOG2(lk, 866 "%s: %p claimed by a new writer", 867 __func__, lk); 868 break; 869 } 870 sleepq_release(&lk->lock_object); 871 continue; 872 } 873 874 /* 875 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 876 * fail, loop back and retry. 877 */ 878 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 879 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 880 x | LK_EXCLUSIVE_WAITERS)) { 881 sleepq_release(&lk->lock_object); 882 continue; 883 } 884 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 885 __func__, lk); 886 } 887 888 /* 889 * As far as we have been unable to acquire the 890 * exclusive lock and the exclusive waiters flag 891 * is set, we will sleep. 892 */ 893 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 894 SQ_EXCLUSIVE_QUEUE); 895 flags &= ~LK_INTERLOCK; 896 if (error) { 897 LOCK_LOG3(lk, 898 "%s: interrupted sleep for %p with %d", 899 __func__, lk, error); 900 break; 901 } 902 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 903 __func__, lk); 904 } 905 if (error == 0) { 906 lock_profile_obtain_lock_success(&lk->lock_object, 907 contested, waittime, file, line); 908 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 909 lk->lk_recurse, file, line); 910 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 911 LK_TRYWIT(flags), file, line); 912 TD_LOCKS_INC(curthread); 913 STACK_SAVE(lk); 914 } 915 break; 916 case LK_DOWNGRADE: 917 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 918 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 919 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 920 TD_SLOCKS_INC(curthread); 921 922 /* 923 * In order to preserve waiters flags, just spin. 924 */ 925 for (;;) { 926 x = lk->lk_lock; 927 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 928 x &= LK_ALL_WAITERS; 929 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 930 LK_SHARERS_LOCK(1) | x)) 931 break; 932 cpu_spinwait(); 933 } 934 break; 935 case LK_RELEASE: 936 _lockmgr_assert(lk, KA_LOCKED, file, line); 937 x = lk->lk_lock; 938 939 if ((x & LK_SHARE) == 0) { 940 941 /* 942 * As first option, treact the lock as if it has not 943 * any waiter. 944 * Fix-up the tid var if the lock has been disowned. 945 */ 946 if (LK_HOLDER(x) == LK_KERNPROC) 947 tid = LK_KERNPROC; 948 else { 949 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 950 file, line); 951 TD_LOCKS_DEC(curthread); 952 } 953 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 954 lk->lk_recurse, file, line); 955 956 /* 957 * The lock is held in exclusive mode. 958 * If the lock is recursed also, then unrecurse it. 959 */ 960 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 961 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 962 lk); 963 lk->lk_recurse--; 964 break; 965 } 966 if (tid != LK_KERNPROC) 967 lock_profile_release_lock(&lk->lock_object); 968 969 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 970 LK_UNLOCKED)) 971 break; 972 973 sleepq_lock(&lk->lock_object); 974 x = lk->lk_lock; 975 v = LK_UNLOCKED; 976 977 /* 978 * If the lock has exclusive waiters, give them 979 * preference in order to avoid deadlock with 980 * shared runners up. 981 * If interruptible sleeps left the exclusive queue 982 * empty avoid a starvation for the threads sleeping 983 * on the shared queue by giving them precedence 984 * and cleaning up the exclusive waiters bit anyway. 985 * Please note that lk_exslpfail count may be lying 986 * about the real number of waiters with the 987 * LK_SLEEPFAIL flag on because they may be used in 988 * conjuction with interruptible sleeps so 989 * lk_exslpfail might be considered an 'upper limit' 990 * bound, including the edge cases. 991 */ 992 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 993 realexslp = sleepq_sleepcnt(&lk->lock_object, 994 SQ_EXCLUSIVE_QUEUE); 995 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 996 if (lk->lk_exslpfail < realexslp) { 997 lk->lk_exslpfail = 0; 998 queue = SQ_EXCLUSIVE_QUEUE; 999 v |= (x & LK_SHARED_WAITERS); 1000 } else { 1001 lk->lk_exslpfail = 0; 1002 LOCK_LOG2(lk, 1003 "%s: %p has only LK_SLEEPFAIL sleepers", 1004 __func__, lk); 1005 LOCK_LOG2(lk, 1006 "%s: %p waking up threads on the exclusive queue", 1007 __func__, lk); 1008 wakeup_swapper = 1009 sleepq_broadcast(&lk->lock_object, 1010 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1011 queue = SQ_SHARED_QUEUE; 1012 } 1013 } else { 1014 1015 /* 1016 * Exclusive waiters sleeping with LK_SLEEPFAIL 1017 * on and using interruptible sleeps/timeout 1018 * may have left spourious lk_exslpfail counts 1019 * on, so clean it up anyway. 1020 */ 1021 lk->lk_exslpfail = 0; 1022 queue = SQ_SHARED_QUEUE; 1023 } 1024 1025 LOCK_LOG3(lk, 1026 "%s: %p waking up threads on the %s queue", 1027 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1028 "exclusive"); 1029 atomic_store_rel_ptr(&lk->lk_lock, v); 1030 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1031 SLEEPQ_LK, 0, queue); 1032 sleepq_release(&lk->lock_object); 1033 break; 1034 } else 1035 wakeup_swapper = wakeupshlk(lk, file, line); 1036 break; 1037 case LK_DRAIN: 1038 if (LK_CAN_WITNESS(flags)) 1039 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1040 LOP_EXCLUSIVE, file, line, ilk); 1041 1042 /* 1043 * Trying to drain a lock we already own will result in a 1044 * deadlock. 1045 */ 1046 if (lockmgr_xlocked(lk)) { 1047 if (flags & LK_INTERLOCK) 1048 class->lc_unlock(ilk); 1049 panic("%s: draining %s with the lock held @ %s:%d\n", 1050 __func__, iwmesg, file, line); 1051 } 1052 1053 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1054 lock_profile_obtain_lock_failed(&lk->lock_object, 1055 &contested, &waittime); 1056 1057 /* 1058 * If the lock is expected to not sleep just give up 1059 * and return. 1060 */ 1061 if (LK_TRYOP(flags)) { 1062 LOCK_LOG2(lk, "%s: %p fails the try operation", 1063 __func__, lk); 1064 error = EBUSY; 1065 break; 1066 } 1067 1068 /* 1069 * Acquire the sleepqueue chain lock because we 1070 * probabilly will need to manipulate waiters flags. 1071 */ 1072 sleepq_lock(&lk->lock_object); 1073 x = lk->lk_lock; 1074 1075 /* 1076 * if the lock has been released while we spun on 1077 * the sleepqueue chain lock just try again. 1078 */ 1079 if (x == LK_UNLOCKED) { 1080 sleepq_release(&lk->lock_object); 1081 continue; 1082 } 1083 1084 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1085 if ((x & ~v) == LK_UNLOCKED) { 1086 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1087 1088 /* 1089 * If interruptible sleeps left the exclusive 1090 * queue empty avoid a starvation for the 1091 * threads sleeping on the shared queue by 1092 * giving them precedence and cleaning up the 1093 * exclusive waiters bit anyway. 1094 * Please note that lk_exslpfail count may be 1095 * lying about the real number of waiters with 1096 * the LK_SLEEPFAIL flag on because they may 1097 * be used in conjuction with interruptible 1098 * sleeps so lk_exslpfail might be considered 1099 * an 'upper limit' bound, including the edge 1100 * cases. 1101 */ 1102 if (v & LK_EXCLUSIVE_WAITERS) { 1103 queue = SQ_EXCLUSIVE_QUEUE; 1104 v &= ~LK_EXCLUSIVE_WAITERS; 1105 } else { 1106 1107 /* 1108 * Exclusive waiters sleeping with 1109 * LK_SLEEPFAIL on and using 1110 * interruptible sleeps/timeout may 1111 * have left spourious lk_exslpfail 1112 * counts on, so clean it up anyway. 1113 */ 1114 MPASS(v & LK_SHARED_WAITERS); 1115 lk->lk_exslpfail = 0; 1116 queue = SQ_SHARED_QUEUE; 1117 v &= ~LK_SHARED_WAITERS; 1118 } 1119 if (queue == SQ_EXCLUSIVE_QUEUE) { 1120 realexslp = 1121 sleepq_sleepcnt(&lk->lock_object, 1122 SQ_EXCLUSIVE_QUEUE); 1123 if (lk->lk_exslpfail >= realexslp) { 1124 lk->lk_exslpfail = 0; 1125 queue = SQ_SHARED_QUEUE; 1126 v &= ~LK_SHARED_WAITERS; 1127 if (realexslp != 0) { 1128 LOCK_LOG2(lk, 1129 "%s: %p has only LK_SLEEPFAIL sleepers", 1130 __func__, lk); 1131 LOCK_LOG2(lk, 1132 "%s: %p waking up threads on the exclusive queue", 1133 __func__, lk); 1134 wakeup_swapper = 1135 sleepq_broadcast( 1136 &lk->lock_object, 1137 SLEEPQ_LK, 0, 1138 SQ_EXCLUSIVE_QUEUE); 1139 } 1140 } else 1141 lk->lk_exslpfail = 0; 1142 } 1143 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1144 sleepq_release(&lk->lock_object); 1145 continue; 1146 } 1147 LOCK_LOG3(lk, 1148 "%s: %p waking up all threads on the %s queue", 1149 __func__, lk, queue == SQ_SHARED_QUEUE ? 1150 "shared" : "exclusive"); 1151 wakeup_swapper |= sleepq_broadcast( 1152 &lk->lock_object, SLEEPQ_LK, 0, queue); 1153 1154 /* 1155 * If shared waiters have been woken up we need 1156 * to wait for one of them to acquire the lock 1157 * before to set the exclusive waiters in 1158 * order to avoid a deadlock. 1159 */ 1160 if (queue == SQ_SHARED_QUEUE) { 1161 for (v = lk->lk_lock; 1162 (v & LK_SHARE) && !LK_SHARERS(v); 1163 v = lk->lk_lock) 1164 cpu_spinwait(); 1165 } 1166 } 1167 1168 /* 1169 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1170 * fail, loop back and retry. 1171 */ 1172 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1173 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1174 x | LK_EXCLUSIVE_WAITERS)) { 1175 sleepq_release(&lk->lock_object); 1176 continue; 1177 } 1178 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1179 __func__, lk); 1180 } 1181 1182 /* 1183 * As far as we have been unable to acquire the 1184 * exclusive lock and the exclusive waiters flag 1185 * is set, we will sleep. 1186 */ 1187 if (flags & LK_INTERLOCK) { 1188 class->lc_unlock(ilk); 1189 flags &= ~LK_INTERLOCK; 1190 } 1191 GIANT_SAVE(); 1192 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1193 SQ_EXCLUSIVE_QUEUE); 1194 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1195 GIANT_RESTORE(); 1196 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1197 __func__, lk); 1198 } 1199 1200 if (error == 0) { 1201 lock_profile_obtain_lock_success(&lk->lock_object, 1202 contested, waittime, file, line); 1203 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1204 lk->lk_recurse, file, line); 1205 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1206 LK_TRYWIT(flags), file, line); 1207 TD_LOCKS_INC(curthread); 1208 STACK_SAVE(lk); 1209 } 1210 break; 1211 default: 1212 if (flags & LK_INTERLOCK) 1213 class->lc_unlock(ilk); 1214 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1215 } 1216 1217 if (flags & LK_INTERLOCK) 1218 class->lc_unlock(ilk); 1219 if (wakeup_swapper) 1220 kick_proc0(); 1221 1222 return (error); 1223 } 1224 1225 void 1226 _lockmgr_disown(struct lock *lk, const char *file, int line) 1227 { 1228 uintptr_t tid, x; 1229 1230 tid = (uintptr_t)curthread; 1231 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 1232 1233 /* 1234 * If the owner is already LK_KERNPROC just skip the whole operation. 1235 */ 1236 if (LK_HOLDER(lk->lk_lock) != tid) 1237 return; 1238 lock_profile_release_lock(&lk->lock_object); 1239 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1240 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1241 TD_LOCKS_DEC(curthread); 1242 STACK_SAVE(lk); 1243 1244 /* 1245 * In order to preserve waiters flags, just spin. 1246 */ 1247 for (;;) { 1248 x = lk->lk_lock; 1249 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1250 x &= LK_ALL_WAITERS; 1251 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1252 LK_KERNPROC | x)) 1253 return; 1254 cpu_spinwait(); 1255 } 1256 } 1257 1258 void 1259 lockmgr_printinfo(struct lock *lk) 1260 { 1261 struct thread *td; 1262 uintptr_t x; 1263 1264 if (lk->lk_lock == LK_UNLOCKED) 1265 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1266 else if (lk->lk_lock & LK_SHARE) 1267 printf("lock type %s: SHARED (count %ju)\n", 1268 lk->lock_object.lo_name, 1269 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1270 else { 1271 td = lockmgr_xholder(lk); 1272 printf("lock type %s: EXCL by thread %p (pid %d)\n", 1273 lk->lock_object.lo_name, td, td->td_proc->p_pid); 1274 } 1275 1276 x = lk->lk_lock; 1277 if (x & LK_EXCLUSIVE_WAITERS) 1278 printf(" with exclusive waiters pending\n"); 1279 if (x & LK_SHARED_WAITERS) 1280 printf(" with shared waiters pending\n"); 1281 if (x & LK_EXCLUSIVE_SPINNERS) 1282 printf(" with exclusive spinners pending\n"); 1283 1284 STACK_PRINT(lk); 1285 } 1286 1287 int 1288 lockstatus(struct lock *lk) 1289 { 1290 uintptr_t v, x; 1291 int ret; 1292 1293 ret = LK_SHARED; 1294 x = lk->lk_lock; 1295 v = LK_HOLDER(x); 1296 1297 if ((x & LK_SHARE) == 0) { 1298 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1299 ret = LK_EXCLUSIVE; 1300 else 1301 ret = LK_EXCLOTHER; 1302 } else if (x == LK_UNLOCKED) 1303 ret = 0; 1304 1305 return (ret); 1306 } 1307 1308 #ifdef INVARIANT_SUPPORT 1309 1310 FEATURE(invariant_support, 1311 "Support for modules compiled with INVARIANTS option"); 1312 1313 #ifndef INVARIANTS 1314 #undef _lockmgr_assert 1315 #endif 1316 1317 void 1318 _lockmgr_assert(struct lock *lk, int what, const char *file, int line) 1319 { 1320 int slocked = 0; 1321 1322 if (panicstr != NULL) 1323 return; 1324 switch (what) { 1325 case KA_SLOCKED: 1326 case KA_SLOCKED | KA_NOTRECURSED: 1327 case KA_SLOCKED | KA_RECURSED: 1328 slocked = 1; 1329 case KA_LOCKED: 1330 case KA_LOCKED | KA_NOTRECURSED: 1331 case KA_LOCKED | KA_RECURSED: 1332 #ifdef WITNESS 1333 1334 /* 1335 * We cannot trust WITNESS if the lock is held in exclusive 1336 * mode and a call to lockmgr_disown() happened. 1337 * Workaround this skipping the check if the lock is held in 1338 * exclusive mode even for the KA_LOCKED case. 1339 */ 1340 if (slocked || (lk->lk_lock & LK_SHARE)) { 1341 witness_assert(&lk->lock_object, what, file, line); 1342 break; 1343 } 1344 #endif 1345 if (lk->lk_lock == LK_UNLOCKED || 1346 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1347 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1348 panic("Lock %s not %slocked @ %s:%d\n", 1349 lk->lock_object.lo_name, slocked ? "share" : "", 1350 file, line); 1351 1352 if ((lk->lk_lock & LK_SHARE) == 0) { 1353 if (lockmgr_recursed(lk)) { 1354 if (what & KA_NOTRECURSED) 1355 panic("Lock %s recursed @ %s:%d\n", 1356 lk->lock_object.lo_name, file, 1357 line); 1358 } else if (what & KA_RECURSED) 1359 panic("Lock %s not recursed @ %s:%d\n", 1360 lk->lock_object.lo_name, file, line); 1361 } 1362 break; 1363 case KA_XLOCKED: 1364 case KA_XLOCKED | KA_NOTRECURSED: 1365 case KA_XLOCKED | KA_RECURSED: 1366 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1367 panic("Lock %s not exclusively locked @ %s:%d\n", 1368 lk->lock_object.lo_name, file, line); 1369 if (lockmgr_recursed(lk)) { 1370 if (what & KA_NOTRECURSED) 1371 panic("Lock %s recursed @ %s:%d\n", 1372 lk->lock_object.lo_name, file, line); 1373 } else if (what & KA_RECURSED) 1374 panic("Lock %s not recursed @ %s:%d\n", 1375 lk->lock_object.lo_name, file, line); 1376 break; 1377 case KA_UNLOCKED: 1378 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1379 panic("Lock %s exclusively locked @ %s:%d\n", 1380 lk->lock_object.lo_name, file, line); 1381 break; 1382 default: 1383 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1384 line); 1385 } 1386 } 1387 #endif 1388 1389 #ifdef DDB 1390 int 1391 lockmgr_chain(struct thread *td, struct thread **ownerp) 1392 { 1393 struct lock *lk; 1394 1395 lk = td->td_wchan; 1396 1397 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1398 return (0); 1399 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1400 if (lk->lk_lock & LK_SHARE) 1401 db_printf("SHARED (count %ju)\n", 1402 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1403 else 1404 db_printf("EXCL\n"); 1405 *ownerp = lockmgr_xholder(lk); 1406 1407 return (1); 1408 } 1409 1410 static void 1411 db_show_lockmgr(struct lock_object *lock) 1412 { 1413 struct thread *td; 1414 struct lock *lk; 1415 1416 lk = (struct lock *)lock; 1417 1418 db_printf(" state: "); 1419 if (lk->lk_lock == LK_UNLOCKED) 1420 db_printf("UNLOCKED\n"); 1421 else if (lk->lk_lock & LK_SHARE) 1422 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1423 else { 1424 td = lockmgr_xholder(lk); 1425 if (td == (struct thread *)LK_KERNPROC) 1426 db_printf("XLOCK: LK_KERNPROC\n"); 1427 else 1428 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1429 td->td_tid, td->td_proc->p_pid, 1430 td->td_proc->p_comm); 1431 if (lockmgr_recursed(lk)) 1432 db_printf(" recursed: %d\n", lk->lk_recurse); 1433 } 1434 db_printf(" waiters: "); 1435 switch (lk->lk_lock & LK_ALL_WAITERS) { 1436 case LK_SHARED_WAITERS: 1437 db_printf("shared\n"); 1438 break; 1439 case LK_EXCLUSIVE_WAITERS: 1440 db_printf("exclusive\n"); 1441 break; 1442 case LK_ALL_WAITERS: 1443 db_printf("shared and exclusive\n"); 1444 break; 1445 default: 1446 db_printf("none\n"); 1447 } 1448 db_printf(" spinners: "); 1449 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1450 db_printf("exclusive\n"); 1451 else 1452 db_printf("none\n"); 1453 } 1454 #endif
Cache object: 1fadbd7d18a05cb972f79de24406425c
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