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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_hwpmc_hooks.h" 32 #include "opt_kdtrace.h" 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD: releng/9.1/sys/kern/kern_lock.c 236238 2012-05-29 14:50:21Z fabient $"); 36 37 #include <sys/param.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 #ifdef ADAPTIVE_LOCKMGRS 71 #define ALK_RETRIES 10 72 #define ALK_LOOPS 10000 73 #endif 74 75 #ifndef INVARIANTS 76 #define _lockmgr_assert(lk, what, file, line) 77 #define TD_LOCKS_INC(td) 78 #define TD_LOCKS_DEC(td) 79 #else 80 #define TD_LOCKS_INC(td) ((td)->td_locks++) 81 #define TD_LOCKS_DEC(td) ((td)->td_locks--) 82 #endif 83 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 84 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 85 86 #ifndef DEBUG_LOCKS 87 #define STACK_PRINT(lk) 88 #define STACK_SAVE(lk) 89 #define STACK_ZERO(lk) 90 #else 91 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 92 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 93 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 94 #endif 95 96 #define LOCK_LOG2(lk, string, arg1, arg2) \ 97 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 98 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 99 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 100 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 101 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 102 103 #define GIANT_DECLARE \ 104 int _i = 0; \ 105 WITNESS_SAVE_DECL(Giant) 106 #define GIANT_RESTORE() do { \ 107 if (_i > 0) { \ 108 while (_i--) \ 109 mtx_lock(&Giant); \ 110 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 111 } \ 112 } while (0) 113 #define GIANT_SAVE() do { \ 114 if (mtx_owned(&Giant)) { \ 115 WITNESS_SAVE(&Giant.lock_object, Giant); \ 116 while (mtx_owned(&Giant)) { \ 117 _i++; \ 118 mtx_unlock(&Giant); \ 119 } \ 120 } \ 121 } while (0) 122 123 #define LK_CAN_SHARE(x) \ 124 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \ 125 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \ 126 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT))) 127 #define LK_TRYOP(x) \ 128 ((x) & LK_NOWAIT) 129 130 #define LK_CAN_WITNESS(x) \ 131 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 132 #define LK_TRYWIT(x) \ 133 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 134 135 #define LK_CAN_ADAPT(lk, f) \ 136 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 137 ((f) & LK_SLEEPFAIL) == 0) 138 139 #define lockmgr_disowned(lk) \ 140 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 141 142 #define lockmgr_xlocked(lk) \ 143 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 144 145 static void assert_lockmgr(struct lock_object *lock, int how); 146 #ifdef DDB 147 static void db_show_lockmgr(struct lock_object *lock); 148 #endif 149 static void lock_lockmgr(struct lock_object *lock, int how); 150 #ifdef KDTRACE_HOOKS 151 static int owner_lockmgr(struct lock_object *lock, struct thread **owner); 152 #endif 153 static int unlock_lockmgr(struct lock_object *lock); 154 155 struct lock_class lock_class_lockmgr = { 156 .lc_name = "lockmgr", 157 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 158 .lc_assert = assert_lockmgr, 159 #ifdef DDB 160 .lc_ddb_show = db_show_lockmgr, 161 #endif 162 .lc_lock = lock_lockmgr, 163 .lc_unlock = unlock_lockmgr, 164 #ifdef KDTRACE_HOOKS 165 .lc_owner = owner_lockmgr, 166 #endif 167 }; 168 169 static __inline struct thread * 170 lockmgr_xholder(struct lock *lk) 171 { 172 uintptr_t x; 173 174 x = lk->lk_lock; 175 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 176 } 177 178 /* 179 * It assumes sleepq_lock held and returns with this one unheld. 180 * It also assumes the generic interlock is sane and previously checked. 181 * If LK_INTERLOCK is specified the interlock is not reacquired after the 182 * sleep. 183 */ 184 static __inline int 185 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 186 const char *wmesg, int pri, int timo, int queue) 187 { 188 GIANT_DECLARE; 189 struct lock_class *class; 190 int catch, error; 191 192 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 193 catch = pri & PCATCH; 194 pri &= PRIMASK; 195 error = 0; 196 197 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 198 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 199 200 if (flags & LK_INTERLOCK) 201 class->lc_unlock(ilk); 202 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 203 lk->lk_exslpfail++; 204 GIANT_SAVE(); 205 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 206 SLEEPQ_INTERRUPTIBLE : 0), queue); 207 if ((flags & LK_TIMELOCK) && timo) 208 sleepq_set_timeout(&lk->lock_object, timo); 209 210 /* 211 * Decisional switch for real sleeping. 212 */ 213 if ((flags & LK_TIMELOCK) && timo && catch) 214 error = sleepq_timedwait_sig(&lk->lock_object, pri); 215 else if ((flags & LK_TIMELOCK) && timo) 216 error = sleepq_timedwait(&lk->lock_object, pri); 217 else if (catch) 218 error = sleepq_wait_sig(&lk->lock_object, pri); 219 else 220 sleepq_wait(&lk->lock_object, pri); 221 GIANT_RESTORE(); 222 if ((flags & LK_SLEEPFAIL) && error == 0) 223 error = ENOLCK; 224 225 return (error); 226 } 227 228 static __inline int 229 wakeupshlk(struct lock *lk, const char *file, int line) 230 { 231 uintptr_t v, x; 232 u_int realexslp; 233 int queue, wakeup_swapper; 234 235 TD_LOCKS_DEC(curthread); 236 TD_SLOCKS_DEC(curthread); 237 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 238 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 239 240 wakeup_swapper = 0; 241 for (;;) { 242 x = lk->lk_lock; 243 244 /* 245 * If there is more than one shared lock held, just drop one 246 * and return. 247 */ 248 if (LK_SHARERS(x) > 1) { 249 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, 250 x - LK_ONE_SHARER)) 251 break; 252 continue; 253 } 254 255 /* 256 * If there are not waiters on the exclusive queue, drop the 257 * lock quickly. 258 */ 259 if ((x & LK_ALL_WAITERS) == 0) { 260 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == 261 LK_SHARERS_LOCK(1)); 262 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED)) 263 break; 264 continue; 265 } 266 267 /* 268 * We should have a sharer with waiters, so enter the hard 269 * path in order to handle wakeups correctly. 270 */ 271 sleepq_lock(&lk->lock_object); 272 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 273 v = LK_UNLOCKED; 274 275 /* 276 * If the lock has exclusive waiters, give them preference in 277 * order to avoid deadlock with shared runners up. 278 * If interruptible sleeps left the exclusive queue empty 279 * avoid a starvation for the threads sleeping on the shared 280 * queue by giving them precedence and cleaning up the 281 * exclusive waiters bit anyway. 282 * Please note that lk_exslpfail count may be lying about 283 * the real number of waiters with the LK_SLEEPFAIL flag on 284 * because they may be used in conjuction with interruptible 285 * sleeps so lk_exslpfail might be considered an 'upper limit' 286 * bound, including the edge cases. 287 */ 288 realexslp = sleepq_sleepcnt(&lk->lock_object, 289 SQ_EXCLUSIVE_QUEUE); 290 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 291 if (lk->lk_exslpfail < realexslp) { 292 lk->lk_exslpfail = 0; 293 queue = SQ_EXCLUSIVE_QUEUE; 294 v |= (x & LK_SHARED_WAITERS); 295 } else { 296 lk->lk_exslpfail = 0; 297 LOCK_LOG2(lk, 298 "%s: %p has only LK_SLEEPFAIL sleepers", 299 __func__, lk); 300 LOCK_LOG2(lk, 301 "%s: %p waking up threads on the exclusive queue", 302 __func__, lk); 303 wakeup_swapper = 304 sleepq_broadcast(&lk->lock_object, 305 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 306 queue = SQ_SHARED_QUEUE; 307 } 308 309 } else { 310 311 /* 312 * Exclusive waiters sleeping with LK_SLEEPFAIL on 313 * and using interruptible sleeps/timeout may have 314 * left spourious lk_exslpfail counts on, so clean 315 * it up anyway. 316 */ 317 lk->lk_exslpfail = 0; 318 queue = SQ_SHARED_QUEUE; 319 } 320 321 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, 322 v)) { 323 sleepq_release(&lk->lock_object); 324 continue; 325 } 326 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 327 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 328 "exclusive"); 329 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 330 0, queue); 331 sleepq_release(&lk->lock_object); 332 break; 333 } 334 335 lock_profile_release_lock(&lk->lock_object); 336 return (wakeup_swapper); 337 } 338 339 static void 340 assert_lockmgr(struct lock_object *lock, int what) 341 { 342 343 panic("lockmgr locks do not support assertions"); 344 } 345 346 static void 347 lock_lockmgr(struct lock_object *lock, int how) 348 { 349 350 panic("lockmgr locks do not support sleep interlocking"); 351 } 352 353 static int 354 unlock_lockmgr(struct lock_object *lock) 355 { 356 357 panic("lockmgr locks do not support sleep interlocking"); 358 } 359 360 #ifdef KDTRACE_HOOKS 361 static int 362 owner_lockmgr(struct lock_object *lock, struct thread **owner) 363 { 364 365 panic("lockmgr locks do not support owner inquiring"); 366 } 367 #endif 368 369 void 370 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 371 { 372 int iflags; 373 374 MPASS((flags & ~LK_INIT_MASK) == 0); 375 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 376 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 377 &lk->lk_lock)); 378 379 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 380 if (flags & LK_CANRECURSE) 381 iflags |= LO_RECURSABLE; 382 if ((flags & LK_NODUP) == 0) 383 iflags |= LO_DUPOK; 384 if (flags & LK_NOPROFILE) 385 iflags |= LO_NOPROFILE; 386 if ((flags & LK_NOWITNESS) == 0) 387 iflags |= LO_WITNESS; 388 if (flags & LK_QUIET) 389 iflags |= LO_QUIET; 390 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 391 392 lk->lk_lock = LK_UNLOCKED; 393 lk->lk_recurse = 0; 394 lk->lk_exslpfail = 0; 395 lk->lk_timo = timo; 396 lk->lk_pri = pri; 397 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 398 STACK_ZERO(lk); 399 } 400 401 /* 402 * XXX: Gross hacks to manipulate external lock flags after 403 * initialization. Used for certain vnode and buf locks. 404 */ 405 void 406 lockallowshare(struct lock *lk) 407 { 408 409 lockmgr_assert(lk, KA_XLOCKED); 410 lk->lock_object.lo_flags &= ~LK_NOSHARE; 411 } 412 413 void 414 lockallowrecurse(struct lock *lk) 415 { 416 417 lockmgr_assert(lk, KA_XLOCKED); 418 lk->lock_object.lo_flags |= LO_RECURSABLE; 419 } 420 421 void 422 lockdisablerecurse(struct lock *lk) 423 { 424 425 lockmgr_assert(lk, KA_XLOCKED); 426 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 427 } 428 429 void 430 lockdestroy(struct lock *lk) 431 { 432 433 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 434 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 435 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 436 lock_destroy(&lk->lock_object); 437 } 438 439 int 440 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 441 const char *wmesg, int pri, int timo, const char *file, int line) 442 { 443 GIANT_DECLARE; 444 struct lock_class *class; 445 const char *iwmesg; 446 uintptr_t tid, v, x; 447 u_int op, realexslp; 448 int error, ipri, itimo, queue, wakeup_swapper; 449 #ifdef LOCK_PROFILING 450 uint64_t waittime = 0; 451 int contested = 0; 452 #endif 453 #ifdef ADAPTIVE_LOCKMGRS 454 volatile struct thread *owner; 455 u_int i, spintries = 0; 456 #endif 457 458 error = 0; 459 tid = (uintptr_t)curthread; 460 op = (flags & LK_TYPE_MASK); 461 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 462 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 463 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 464 465 MPASS((flags & ~LK_TOTAL_MASK) == 0); 466 KASSERT((op & (op - 1)) == 0, 467 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 468 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 469 (op != LK_DOWNGRADE && op != LK_RELEASE), 470 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 471 __func__, file, line)); 472 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 473 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 474 __func__, file, line)); 475 476 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 477 if (panicstr != NULL) { 478 if (flags & LK_INTERLOCK) 479 class->lc_unlock(ilk); 480 return (0); 481 } 482 483 if (lk->lock_object.lo_flags & LK_NOSHARE) { 484 switch (op) { 485 case LK_SHARED: 486 op = LK_EXCLUSIVE; 487 break; 488 case LK_UPGRADE: 489 case LK_DOWNGRADE: 490 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 491 file, line); 492 return (0); 493 } 494 } 495 496 wakeup_swapper = 0; 497 switch (op) { 498 case LK_SHARED: 499 if (LK_CAN_WITNESS(flags)) 500 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 501 file, line, ilk); 502 for (;;) { 503 x = lk->lk_lock; 504 505 /* 506 * If no other thread has an exclusive lock, or 507 * no exclusive waiter is present, bump the count of 508 * sharers. Since we have to preserve the state of 509 * waiters, if we fail to acquire the shared lock 510 * loop back and retry. 511 */ 512 if (LK_CAN_SHARE(x)) { 513 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 514 x + LK_ONE_SHARER)) 515 break; 516 continue; 517 } 518 #ifdef HWPMC_HOOKS 519 PMC_SOFT_CALL( , , lock, failed); 520 #endif 521 lock_profile_obtain_lock_failed(&lk->lock_object, 522 &contested, &waittime); 523 524 /* 525 * If the lock is already held by curthread in 526 * exclusive way avoid a deadlock. 527 */ 528 if (LK_HOLDER(x) == tid) { 529 LOCK_LOG2(lk, 530 "%s: %p already held in exclusive mode", 531 __func__, lk); 532 error = EDEADLK; 533 break; 534 } 535 536 /* 537 * If the lock is expected to not sleep just give up 538 * and return. 539 */ 540 if (LK_TRYOP(flags)) { 541 LOCK_LOG2(lk, "%s: %p fails the try operation", 542 __func__, lk); 543 error = EBUSY; 544 break; 545 } 546 547 #ifdef ADAPTIVE_LOCKMGRS 548 /* 549 * If the owner is running on another CPU, spin until 550 * the owner stops running or the state of the lock 551 * changes. We need a double-state handle here 552 * because for a failed acquisition the lock can be 553 * either held in exclusive mode or shared mode 554 * (for the writer starvation avoidance technique). 555 */ 556 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 557 LK_HOLDER(x) != LK_KERNPROC) { 558 owner = (struct thread *)LK_HOLDER(x); 559 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 560 CTR3(KTR_LOCK, 561 "%s: spinning on %p held by %p", 562 __func__, lk, owner); 563 564 /* 565 * If we are holding also an interlock drop it 566 * in order to avoid a deadlock if the lockmgr 567 * owner is adaptively spinning on the 568 * interlock itself. 569 */ 570 if (flags & LK_INTERLOCK) { 571 class->lc_unlock(ilk); 572 flags &= ~LK_INTERLOCK; 573 } 574 GIANT_SAVE(); 575 while (LK_HOLDER(lk->lk_lock) == 576 (uintptr_t)owner && TD_IS_RUNNING(owner)) 577 cpu_spinwait(); 578 GIANT_RESTORE(); 579 continue; 580 } else if (LK_CAN_ADAPT(lk, flags) && 581 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 582 spintries < ALK_RETRIES) { 583 if (flags & LK_INTERLOCK) { 584 class->lc_unlock(ilk); 585 flags &= ~LK_INTERLOCK; 586 } 587 GIANT_SAVE(); 588 spintries++; 589 for (i = 0; i < ALK_LOOPS; i++) { 590 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 591 CTR4(KTR_LOCK, 592 "%s: shared spinning on %p with %u and %u", 593 __func__, lk, spintries, i); 594 x = lk->lk_lock; 595 if ((x & LK_SHARE) == 0 || 596 LK_CAN_SHARE(x) != 0) 597 break; 598 cpu_spinwait(); 599 } 600 GIANT_RESTORE(); 601 if (i != ALK_LOOPS) 602 continue; 603 } 604 #endif 605 606 /* 607 * Acquire the sleepqueue chain lock because we 608 * probabilly will need to manipulate waiters flags. 609 */ 610 sleepq_lock(&lk->lock_object); 611 x = lk->lk_lock; 612 613 /* 614 * if the lock can be acquired in shared mode, try 615 * again. 616 */ 617 if (LK_CAN_SHARE(x)) { 618 sleepq_release(&lk->lock_object); 619 continue; 620 } 621 622 #ifdef ADAPTIVE_LOCKMGRS 623 /* 624 * The current lock owner might have started executing 625 * on another CPU (or the lock could have changed 626 * owner) while we were waiting on the turnstile 627 * chain lock. If so, drop the turnstile lock and try 628 * again. 629 */ 630 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 631 LK_HOLDER(x) != LK_KERNPROC) { 632 owner = (struct thread *)LK_HOLDER(x); 633 if (TD_IS_RUNNING(owner)) { 634 sleepq_release(&lk->lock_object); 635 continue; 636 } 637 } 638 #endif 639 640 /* 641 * Try to set the LK_SHARED_WAITERS flag. If we fail, 642 * loop back and retry. 643 */ 644 if ((x & LK_SHARED_WAITERS) == 0) { 645 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 646 x | LK_SHARED_WAITERS)) { 647 sleepq_release(&lk->lock_object); 648 continue; 649 } 650 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 651 __func__, lk); 652 } 653 654 /* 655 * As far as we have been unable to acquire the 656 * shared lock and the shared waiters flag is set, 657 * we will sleep. 658 */ 659 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 660 SQ_SHARED_QUEUE); 661 flags &= ~LK_INTERLOCK; 662 if (error) { 663 LOCK_LOG3(lk, 664 "%s: interrupted sleep for %p with %d", 665 __func__, lk, error); 666 break; 667 } 668 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 669 __func__, lk); 670 } 671 if (error == 0) { 672 lock_profile_obtain_lock_success(&lk->lock_object, 673 contested, waittime, file, line); 674 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 675 line); 676 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 677 line); 678 TD_LOCKS_INC(curthread); 679 TD_SLOCKS_INC(curthread); 680 STACK_SAVE(lk); 681 } 682 break; 683 case LK_UPGRADE: 684 _lockmgr_assert(lk, KA_SLOCKED, file, line); 685 v = lk->lk_lock; 686 x = v & LK_ALL_WAITERS; 687 v &= LK_EXCLUSIVE_SPINNERS; 688 689 /* 690 * Try to switch from one shared lock to an exclusive one. 691 * We need to preserve waiters flags during the operation. 692 */ 693 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 694 tid | x)) { 695 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 696 line); 697 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 698 LK_TRYWIT(flags), file, line); 699 TD_SLOCKS_DEC(curthread); 700 break; 701 } 702 703 /* 704 * We have been unable to succeed in upgrading, so just 705 * give up the shared lock. 706 */ 707 wakeup_swapper |= wakeupshlk(lk, file, line); 708 709 /* FALLTHROUGH */ 710 case LK_EXCLUSIVE: 711 if (LK_CAN_WITNESS(flags)) 712 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 713 LOP_EXCLUSIVE, file, line, ilk); 714 715 /* 716 * If curthread already holds the lock and this one is 717 * allowed to recurse, simply recurse on it. 718 */ 719 if (lockmgr_xlocked(lk)) { 720 if ((flags & LK_CANRECURSE) == 0 && 721 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 722 723 /* 724 * If the lock is expected to not panic just 725 * give up and return. 726 */ 727 if (LK_TRYOP(flags)) { 728 LOCK_LOG2(lk, 729 "%s: %p fails the try operation", 730 __func__, lk); 731 error = EBUSY; 732 break; 733 } 734 if (flags & LK_INTERLOCK) 735 class->lc_unlock(ilk); 736 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 737 __func__, iwmesg, file, line); 738 } 739 lk->lk_recurse++; 740 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 741 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 742 lk->lk_recurse, file, line); 743 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 744 LK_TRYWIT(flags), file, line); 745 TD_LOCKS_INC(curthread); 746 break; 747 } 748 749 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 750 tid)) { 751 #ifdef HWPMC_HOOKS 752 PMC_SOFT_CALL( , , lock, failed); 753 #endif 754 lock_profile_obtain_lock_failed(&lk->lock_object, 755 &contested, &waittime); 756 757 /* 758 * If the lock is expected to not sleep just give up 759 * and return. 760 */ 761 if (LK_TRYOP(flags)) { 762 LOCK_LOG2(lk, "%s: %p fails the try operation", 763 __func__, lk); 764 error = EBUSY; 765 break; 766 } 767 768 #ifdef ADAPTIVE_LOCKMGRS 769 /* 770 * If the owner is running on another CPU, spin until 771 * the owner stops running or the state of the lock 772 * changes. 773 */ 774 x = lk->lk_lock; 775 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 776 LK_HOLDER(x) != LK_KERNPROC) { 777 owner = (struct thread *)LK_HOLDER(x); 778 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 779 CTR3(KTR_LOCK, 780 "%s: spinning on %p held by %p", 781 __func__, lk, owner); 782 783 /* 784 * If we are holding also an interlock drop it 785 * in order to avoid a deadlock if the lockmgr 786 * owner is adaptively spinning on the 787 * interlock itself. 788 */ 789 if (flags & LK_INTERLOCK) { 790 class->lc_unlock(ilk); 791 flags &= ~LK_INTERLOCK; 792 } 793 GIANT_SAVE(); 794 while (LK_HOLDER(lk->lk_lock) == 795 (uintptr_t)owner && TD_IS_RUNNING(owner)) 796 cpu_spinwait(); 797 GIANT_RESTORE(); 798 continue; 799 } else if (LK_CAN_ADAPT(lk, flags) && 800 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 801 spintries < ALK_RETRIES) { 802 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 803 !atomic_cmpset_ptr(&lk->lk_lock, x, 804 x | LK_EXCLUSIVE_SPINNERS)) 805 continue; 806 if (flags & LK_INTERLOCK) { 807 class->lc_unlock(ilk); 808 flags &= ~LK_INTERLOCK; 809 } 810 GIANT_SAVE(); 811 spintries++; 812 for (i = 0; i < ALK_LOOPS; i++) { 813 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 814 CTR4(KTR_LOCK, 815 "%s: shared spinning on %p with %u and %u", 816 __func__, lk, spintries, i); 817 if ((lk->lk_lock & 818 LK_EXCLUSIVE_SPINNERS) == 0) 819 break; 820 cpu_spinwait(); 821 } 822 GIANT_RESTORE(); 823 if (i != ALK_LOOPS) 824 continue; 825 } 826 #endif 827 828 /* 829 * Acquire the sleepqueue chain lock because we 830 * probabilly will need to manipulate waiters flags. 831 */ 832 sleepq_lock(&lk->lock_object); 833 x = lk->lk_lock; 834 835 /* 836 * if the lock has been released while we spun on 837 * the sleepqueue chain lock just try again. 838 */ 839 if (x == LK_UNLOCKED) { 840 sleepq_release(&lk->lock_object); 841 continue; 842 } 843 844 #ifdef ADAPTIVE_LOCKMGRS 845 /* 846 * The current lock owner might have started executing 847 * on another CPU (or the lock could have changed 848 * owner) while we were waiting on the turnstile 849 * chain lock. If so, drop the turnstile lock and try 850 * again. 851 */ 852 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 853 LK_HOLDER(x) != LK_KERNPROC) { 854 owner = (struct thread *)LK_HOLDER(x); 855 if (TD_IS_RUNNING(owner)) { 856 sleepq_release(&lk->lock_object); 857 continue; 858 } 859 } 860 #endif 861 862 /* 863 * The lock can be in the state where there is a 864 * pending queue of waiters, but still no owner. 865 * This happens when the lock is contested and an 866 * owner is going to claim the lock. 867 * If curthread is the one successfully acquiring it 868 * claim lock ownership and return, preserving waiters 869 * flags. 870 */ 871 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 872 if ((x & ~v) == LK_UNLOCKED) { 873 v &= ~LK_EXCLUSIVE_SPINNERS; 874 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 875 tid | v)) { 876 sleepq_release(&lk->lock_object); 877 LOCK_LOG2(lk, 878 "%s: %p claimed by a new writer", 879 __func__, lk); 880 break; 881 } 882 sleepq_release(&lk->lock_object); 883 continue; 884 } 885 886 /* 887 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 888 * fail, loop back and retry. 889 */ 890 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 891 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 892 x | LK_EXCLUSIVE_WAITERS)) { 893 sleepq_release(&lk->lock_object); 894 continue; 895 } 896 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 897 __func__, lk); 898 } 899 900 /* 901 * As far as we have been unable to acquire the 902 * exclusive lock and the exclusive waiters flag 903 * is set, we will sleep. 904 */ 905 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 906 SQ_EXCLUSIVE_QUEUE); 907 flags &= ~LK_INTERLOCK; 908 if (error) { 909 LOCK_LOG3(lk, 910 "%s: interrupted sleep for %p with %d", 911 __func__, lk, error); 912 break; 913 } 914 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 915 __func__, lk); 916 } 917 if (error == 0) { 918 lock_profile_obtain_lock_success(&lk->lock_object, 919 contested, waittime, file, line); 920 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 921 lk->lk_recurse, file, line); 922 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 923 LK_TRYWIT(flags), file, line); 924 TD_LOCKS_INC(curthread); 925 STACK_SAVE(lk); 926 } 927 break; 928 case LK_DOWNGRADE: 929 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 930 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 931 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 932 TD_SLOCKS_INC(curthread); 933 934 /* 935 * In order to preserve waiters flags, just spin. 936 */ 937 for (;;) { 938 x = lk->lk_lock; 939 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 940 x &= LK_ALL_WAITERS; 941 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 942 LK_SHARERS_LOCK(1) | x)) 943 break; 944 cpu_spinwait(); 945 } 946 break; 947 case LK_RELEASE: 948 _lockmgr_assert(lk, KA_LOCKED, file, line); 949 x = lk->lk_lock; 950 951 if ((x & LK_SHARE) == 0) { 952 953 /* 954 * As first option, treact the lock as if it has not 955 * any waiter. 956 * Fix-up the tid var if the lock has been disowned. 957 */ 958 if (LK_HOLDER(x) == LK_KERNPROC) 959 tid = LK_KERNPROC; 960 else { 961 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 962 file, line); 963 TD_LOCKS_DEC(curthread); 964 } 965 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 966 lk->lk_recurse, file, line); 967 968 /* 969 * The lock is held in exclusive mode. 970 * If the lock is recursed also, then unrecurse it. 971 */ 972 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 973 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 974 lk); 975 lk->lk_recurse--; 976 break; 977 } 978 if (tid != LK_KERNPROC) 979 lock_profile_release_lock(&lk->lock_object); 980 981 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 982 LK_UNLOCKED)) 983 break; 984 985 sleepq_lock(&lk->lock_object); 986 x = lk->lk_lock; 987 v = LK_UNLOCKED; 988 989 /* 990 * If the lock has exclusive waiters, give them 991 * preference in order to avoid deadlock with 992 * shared runners up. 993 * If interruptible sleeps left the exclusive queue 994 * empty avoid a starvation for the threads sleeping 995 * on the shared queue by giving them precedence 996 * and cleaning up the exclusive waiters bit anyway. 997 * Please note that lk_exslpfail count may be lying 998 * about the real number of waiters with the 999 * LK_SLEEPFAIL flag on because they may be used in 1000 * conjuction with interruptible sleeps so 1001 * lk_exslpfail might be considered an 'upper limit' 1002 * bound, including the edge cases. 1003 */ 1004 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1005 realexslp = sleepq_sleepcnt(&lk->lock_object, 1006 SQ_EXCLUSIVE_QUEUE); 1007 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1008 if (lk->lk_exslpfail < realexslp) { 1009 lk->lk_exslpfail = 0; 1010 queue = SQ_EXCLUSIVE_QUEUE; 1011 v |= (x & LK_SHARED_WAITERS); 1012 } else { 1013 lk->lk_exslpfail = 0; 1014 LOCK_LOG2(lk, 1015 "%s: %p has only LK_SLEEPFAIL sleepers", 1016 __func__, lk); 1017 LOCK_LOG2(lk, 1018 "%s: %p waking up threads on the exclusive queue", 1019 __func__, lk); 1020 wakeup_swapper = 1021 sleepq_broadcast(&lk->lock_object, 1022 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1023 queue = SQ_SHARED_QUEUE; 1024 } 1025 } else { 1026 1027 /* 1028 * Exclusive waiters sleeping with LK_SLEEPFAIL 1029 * on and using interruptible sleeps/timeout 1030 * may have left spourious lk_exslpfail counts 1031 * on, so clean it up anyway. 1032 */ 1033 lk->lk_exslpfail = 0; 1034 queue = SQ_SHARED_QUEUE; 1035 } 1036 1037 LOCK_LOG3(lk, 1038 "%s: %p waking up threads on the %s queue", 1039 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1040 "exclusive"); 1041 atomic_store_rel_ptr(&lk->lk_lock, v); 1042 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1043 SLEEPQ_LK, 0, queue); 1044 sleepq_release(&lk->lock_object); 1045 break; 1046 } else 1047 wakeup_swapper = wakeupshlk(lk, file, line); 1048 break; 1049 case LK_DRAIN: 1050 if (LK_CAN_WITNESS(flags)) 1051 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1052 LOP_EXCLUSIVE, file, line, ilk); 1053 1054 /* 1055 * Trying to drain a lock we already own will result in a 1056 * deadlock. 1057 */ 1058 if (lockmgr_xlocked(lk)) { 1059 if (flags & LK_INTERLOCK) 1060 class->lc_unlock(ilk); 1061 panic("%s: draining %s with the lock held @ %s:%d\n", 1062 __func__, iwmesg, file, line); 1063 } 1064 1065 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1066 #ifdef HWPMC_HOOKS 1067 PMC_SOFT_CALL( , , lock, failed); 1068 #endif 1069 lock_profile_obtain_lock_failed(&lk->lock_object, 1070 &contested, &waittime); 1071 1072 /* 1073 * If the lock is expected to not sleep just give up 1074 * and return. 1075 */ 1076 if (LK_TRYOP(flags)) { 1077 LOCK_LOG2(lk, "%s: %p fails the try operation", 1078 __func__, lk); 1079 error = EBUSY; 1080 break; 1081 } 1082 1083 /* 1084 * Acquire the sleepqueue chain lock because we 1085 * probabilly will need to manipulate waiters flags. 1086 */ 1087 sleepq_lock(&lk->lock_object); 1088 x = lk->lk_lock; 1089 1090 /* 1091 * if the lock has been released while we spun on 1092 * the sleepqueue chain lock just try again. 1093 */ 1094 if (x == LK_UNLOCKED) { 1095 sleepq_release(&lk->lock_object); 1096 continue; 1097 } 1098 1099 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1100 if ((x & ~v) == LK_UNLOCKED) { 1101 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1102 1103 /* 1104 * If interruptible sleeps left the exclusive 1105 * queue empty avoid a starvation for the 1106 * threads sleeping on the shared queue by 1107 * giving them precedence and cleaning up the 1108 * exclusive waiters bit anyway. 1109 * Please note that lk_exslpfail count may be 1110 * lying about the real number of waiters with 1111 * the LK_SLEEPFAIL flag on because they may 1112 * be used in conjuction with interruptible 1113 * sleeps so lk_exslpfail might be considered 1114 * an 'upper limit' bound, including the edge 1115 * cases. 1116 */ 1117 if (v & LK_EXCLUSIVE_WAITERS) { 1118 queue = SQ_EXCLUSIVE_QUEUE; 1119 v &= ~LK_EXCLUSIVE_WAITERS; 1120 } else { 1121 1122 /* 1123 * Exclusive waiters sleeping with 1124 * LK_SLEEPFAIL on and using 1125 * interruptible sleeps/timeout may 1126 * have left spourious lk_exslpfail 1127 * counts on, so clean it up anyway. 1128 */ 1129 MPASS(v & LK_SHARED_WAITERS); 1130 lk->lk_exslpfail = 0; 1131 queue = SQ_SHARED_QUEUE; 1132 v &= ~LK_SHARED_WAITERS; 1133 } 1134 if (queue == SQ_EXCLUSIVE_QUEUE) { 1135 realexslp = 1136 sleepq_sleepcnt(&lk->lock_object, 1137 SQ_EXCLUSIVE_QUEUE); 1138 if (lk->lk_exslpfail >= realexslp) { 1139 lk->lk_exslpfail = 0; 1140 queue = SQ_SHARED_QUEUE; 1141 v &= ~LK_SHARED_WAITERS; 1142 if (realexslp != 0) { 1143 LOCK_LOG2(lk, 1144 "%s: %p has only LK_SLEEPFAIL sleepers", 1145 __func__, lk); 1146 LOCK_LOG2(lk, 1147 "%s: %p waking up threads on the exclusive queue", 1148 __func__, lk); 1149 wakeup_swapper = 1150 sleepq_broadcast( 1151 &lk->lock_object, 1152 SLEEPQ_LK, 0, 1153 SQ_EXCLUSIVE_QUEUE); 1154 } 1155 } else 1156 lk->lk_exslpfail = 0; 1157 } 1158 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1159 sleepq_release(&lk->lock_object); 1160 continue; 1161 } 1162 LOCK_LOG3(lk, 1163 "%s: %p waking up all threads on the %s queue", 1164 __func__, lk, queue == SQ_SHARED_QUEUE ? 1165 "shared" : "exclusive"); 1166 wakeup_swapper |= sleepq_broadcast( 1167 &lk->lock_object, SLEEPQ_LK, 0, queue); 1168 1169 /* 1170 * If shared waiters have been woken up we need 1171 * to wait for one of them to acquire the lock 1172 * before to set the exclusive waiters in 1173 * order to avoid a deadlock. 1174 */ 1175 if (queue == SQ_SHARED_QUEUE) { 1176 for (v = lk->lk_lock; 1177 (v & LK_SHARE) && !LK_SHARERS(v); 1178 v = lk->lk_lock) 1179 cpu_spinwait(); 1180 } 1181 } 1182 1183 /* 1184 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1185 * fail, loop back and retry. 1186 */ 1187 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1188 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1189 x | LK_EXCLUSIVE_WAITERS)) { 1190 sleepq_release(&lk->lock_object); 1191 continue; 1192 } 1193 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1194 __func__, lk); 1195 } 1196 1197 /* 1198 * As far as we have been unable to acquire the 1199 * exclusive lock and the exclusive waiters flag 1200 * is set, we will sleep. 1201 */ 1202 if (flags & LK_INTERLOCK) { 1203 class->lc_unlock(ilk); 1204 flags &= ~LK_INTERLOCK; 1205 } 1206 GIANT_SAVE(); 1207 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1208 SQ_EXCLUSIVE_QUEUE); 1209 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1210 GIANT_RESTORE(); 1211 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1212 __func__, lk); 1213 } 1214 1215 if (error == 0) { 1216 lock_profile_obtain_lock_success(&lk->lock_object, 1217 contested, waittime, file, line); 1218 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1219 lk->lk_recurse, file, line); 1220 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1221 LK_TRYWIT(flags), file, line); 1222 TD_LOCKS_INC(curthread); 1223 STACK_SAVE(lk); 1224 } 1225 break; 1226 default: 1227 if (flags & LK_INTERLOCK) 1228 class->lc_unlock(ilk); 1229 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1230 } 1231 1232 if (flags & LK_INTERLOCK) 1233 class->lc_unlock(ilk); 1234 if (wakeup_swapper) 1235 kick_proc0(); 1236 1237 return (error); 1238 } 1239 1240 void 1241 _lockmgr_disown(struct lock *lk, const char *file, int line) 1242 { 1243 uintptr_t tid, x; 1244 1245 if (SCHEDULER_STOPPED()) 1246 return; 1247 1248 tid = (uintptr_t)curthread; 1249 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 1250 1251 /* 1252 * If the owner is already LK_KERNPROC just skip the whole operation. 1253 */ 1254 if (LK_HOLDER(lk->lk_lock) != tid) 1255 return; 1256 lock_profile_release_lock(&lk->lock_object); 1257 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1258 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1259 TD_LOCKS_DEC(curthread); 1260 STACK_SAVE(lk); 1261 1262 /* 1263 * In order to preserve waiters flags, just spin. 1264 */ 1265 for (;;) { 1266 x = lk->lk_lock; 1267 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1268 x &= LK_ALL_WAITERS; 1269 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1270 LK_KERNPROC | x)) 1271 return; 1272 cpu_spinwait(); 1273 } 1274 } 1275 1276 void 1277 lockmgr_printinfo(struct lock *lk) 1278 { 1279 struct thread *td; 1280 uintptr_t x; 1281 1282 if (lk->lk_lock == LK_UNLOCKED) 1283 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1284 else if (lk->lk_lock & LK_SHARE) 1285 printf("lock type %s: SHARED (count %ju)\n", 1286 lk->lock_object.lo_name, 1287 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1288 else { 1289 td = lockmgr_xholder(lk); 1290 printf("lock type %s: EXCL by thread %p (pid %d)\n", 1291 lk->lock_object.lo_name, td, td->td_proc->p_pid); 1292 } 1293 1294 x = lk->lk_lock; 1295 if (x & LK_EXCLUSIVE_WAITERS) 1296 printf(" with exclusive waiters pending\n"); 1297 if (x & LK_SHARED_WAITERS) 1298 printf(" with shared waiters pending\n"); 1299 if (x & LK_EXCLUSIVE_SPINNERS) 1300 printf(" with exclusive spinners pending\n"); 1301 1302 STACK_PRINT(lk); 1303 } 1304 1305 int 1306 lockstatus(struct lock *lk) 1307 { 1308 uintptr_t v, x; 1309 int ret; 1310 1311 ret = LK_SHARED; 1312 x = lk->lk_lock; 1313 v = LK_HOLDER(x); 1314 1315 if ((x & LK_SHARE) == 0) { 1316 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1317 ret = LK_EXCLUSIVE; 1318 else 1319 ret = LK_EXCLOTHER; 1320 } else if (x == LK_UNLOCKED) 1321 ret = 0; 1322 1323 return (ret); 1324 } 1325 1326 #ifdef INVARIANT_SUPPORT 1327 1328 FEATURE(invariant_support, 1329 "Support for modules compiled with INVARIANTS option"); 1330 1331 #ifndef INVARIANTS 1332 #undef _lockmgr_assert 1333 #endif 1334 1335 void 1336 _lockmgr_assert(struct lock *lk, int what, const char *file, int line) 1337 { 1338 int slocked = 0; 1339 1340 if (panicstr != NULL) 1341 return; 1342 switch (what) { 1343 case KA_SLOCKED: 1344 case KA_SLOCKED | KA_NOTRECURSED: 1345 case KA_SLOCKED | KA_RECURSED: 1346 slocked = 1; 1347 case KA_LOCKED: 1348 case KA_LOCKED | KA_NOTRECURSED: 1349 case KA_LOCKED | KA_RECURSED: 1350 #ifdef WITNESS 1351 1352 /* 1353 * We cannot trust WITNESS if the lock is held in exclusive 1354 * mode and a call to lockmgr_disown() happened. 1355 * Workaround this skipping the check if the lock is held in 1356 * exclusive mode even for the KA_LOCKED case. 1357 */ 1358 if (slocked || (lk->lk_lock & LK_SHARE)) { 1359 witness_assert(&lk->lock_object, what, file, line); 1360 break; 1361 } 1362 #endif 1363 if (lk->lk_lock == LK_UNLOCKED || 1364 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1365 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1366 panic("Lock %s not %slocked @ %s:%d\n", 1367 lk->lock_object.lo_name, slocked ? "share" : "", 1368 file, line); 1369 1370 if ((lk->lk_lock & LK_SHARE) == 0) { 1371 if (lockmgr_recursed(lk)) { 1372 if (what & KA_NOTRECURSED) 1373 panic("Lock %s recursed @ %s:%d\n", 1374 lk->lock_object.lo_name, file, 1375 line); 1376 } else if (what & KA_RECURSED) 1377 panic("Lock %s not recursed @ %s:%d\n", 1378 lk->lock_object.lo_name, file, line); 1379 } 1380 break; 1381 case KA_XLOCKED: 1382 case KA_XLOCKED | KA_NOTRECURSED: 1383 case KA_XLOCKED | KA_RECURSED: 1384 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1385 panic("Lock %s not exclusively locked @ %s:%d\n", 1386 lk->lock_object.lo_name, file, line); 1387 if (lockmgr_recursed(lk)) { 1388 if (what & KA_NOTRECURSED) 1389 panic("Lock %s recursed @ %s:%d\n", 1390 lk->lock_object.lo_name, file, line); 1391 } else if (what & KA_RECURSED) 1392 panic("Lock %s not recursed @ %s:%d\n", 1393 lk->lock_object.lo_name, file, line); 1394 break; 1395 case KA_UNLOCKED: 1396 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1397 panic("Lock %s exclusively locked @ %s:%d\n", 1398 lk->lock_object.lo_name, file, line); 1399 break; 1400 default: 1401 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1402 line); 1403 } 1404 } 1405 #endif 1406 1407 #ifdef DDB 1408 int 1409 lockmgr_chain(struct thread *td, struct thread **ownerp) 1410 { 1411 struct lock *lk; 1412 1413 lk = td->td_wchan; 1414 1415 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1416 return (0); 1417 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1418 if (lk->lk_lock & LK_SHARE) 1419 db_printf("SHARED (count %ju)\n", 1420 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1421 else 1422 db_printf("EXCL\n"); 1423 *ownerp = lockmgr_xholder(lk); 1424 1425 return (1); 1426 } 1427 1428 static void 1429 db_show_lockmgr(struct lock_object *lock) 1430 { 1431 struct thread *td; 1432 struct lock *lk; 1433 1434 lk = (struct lock *)lock; 1435 1436 db_printf(" state: "); 1437 if (lk->lk_lock == LK_UNLOCKED) 1438 db_printf("UNLOCKED\n"); 1439 else if (lk->lk_lock & LK_SHARE) 1440 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1441 else { 1442 td = lockmgr_xholder(lk); 1443 if (td == (struct thread *)LK_KERNPROC) 1444 db_printf("XLOCK: LK_KERNPROC\n"); 1445 else 1446 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1447 td->td_tid, td->td_proc->p_pid, 1448 td->td_proc->p_comm); 1449 if (lockmgr_recursed(lk)) 1450 db_printf(" recursed: %d\n", lk->lk_recurse); 1451 } 1452 db_printf(" waiters: "); 1453 switch (lk->lk_lock & LK_ALL_WAITERS) { 1454 case LK_SHARED_WAITERS: 1455 db_printf("shared\n"); 1456 break; 1457 case LK_EXCLUSIVE_WAITERS: 1458 db_printf("exclusive\n"); 1459 break; 1460 case LK_ALL_WAITERS: 1461 db_printf("shared and exclusive\n"); 1462 break; 1463 default: 1464 db_printf("none\n"); 1465 } 1466 db_printf(" spinners: "); 1467 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1468 db_printf("exclusive\n"); 1469 else 1470 db_printf("none\n"); 1471 } 1472 #endif
Cache object: 7ec3f373c2f2b9c9ab2beaeea15c9d23
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