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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/9.2/sys/kern/kern_lock.c 245351 2013-01-13 00:32:07Z mjg $"); 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 if (flags & LK_INTERLOCK) 493 class->lc_unlock(ilk); 494 return (0); 495 } 496 } 497 498 wakeup_swapper = 0; 499 switch (op) { 500 case LK_SHARED: 501 if (LK_CAN_WITNESS(flags)) 502 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 503 file, line, ilk); 504 for (;;) { 505 x = lk->lk_lock; 506 507 /* 508 * If no other thread has an exclusive lock, or 509 * no exclusive waiter is present, bump the count of 510 * sharers. Since we have to preserve the state of 511 * waiters, if we fail to acquire the shared lock 512 * loop back and retry. 513 */ 514 if (LK_CAN_SHARE(x)) { 515 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 516 x + LK_ONE_SHARER)) 517 break; 518 continue; 519 } 520 #ifdef HWPMC_HOOKS 521 PMC_SOFT_CALL( , , lock, failed); 522 #endif 523 lock_profile_obtain_lock_failed(&lk->lock_object, 524 &contested, &waittime); 525 526 /* 527 * If the lock is already held by curthread in 528 * exclusive way avoid a deadlock. 529 */ 530 if (LK_HOLDER(x) == tid) { 531 LOCK_LOG2(lk, 532 "%s: %p already held in exclusive mode", 533 __func__, lk); 534 error = EDEADLK; 535 break; 536 } 537 538 /* 539 * If the lock is expected to not sleep just give up 540 * and return. 541 */ 542 if (LK_TRYOP(flags)) { 543 LOCK_LOG2(lk, "%s: %p fails the try operation", 544 __func__, lk); 545 error = EBUSY; 546 break; 547 } 548 549 #ifdef ADAPTIVE_LOCKMGRS 550 /* 551 * If the owner is running on another CPU, spin until 552 * the owner stops running or the state of the lock 553 * changes. We need a double-state handle here 554 * because for a failed acquisition the lock can be 555 * either held in exclusive mode or shared mode 556 * (for the writer starvation avoidance technique). 557 */ 558 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 559 LK_HOLDER(x) != LK_KERNPROC) { 560 owner = (struct thread *)LK_HOLDER(x); 561 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 562 CTR3(KTR_LOCK, 563 "%s: spinning on %p held by %p", 564 __func__, lk, owner); 565 566 /* 567 * If we are holding also an interlock drop it 568 * in order to avoid a deadlock if the lockmgr 569 * owner is adaptively spinning on the 570 * interlock itself. 571 */ 572 if (flags & LK_INTERLOCK) { 573 class->lc_unlock(ilk); 574 flags &= ~LK_INTERLOCK; 575 } 576 GIANT_SAVE(); 577 while (LK_HOLDER(lk->lk_lock) == 578 (uintptr_t)owner && TD_IS_RUNNING(owner)) 579 cpu_spinwait(); 580 GIANT_RESTORE(); 581 continue; 582 } else if (LK_CAN_ADAPT(lk, flags) && 583 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 584 spintries < ALK_RETRIES) { 585 if (flags & LK_INTERLOCK) { 586 class->lc_unlock(ilk); 587 flags &= ~LK_INTERLOCK; 588 } 589 GIANT_SAVE(); 590 spintries++; 591 for (i = 0; i < ALK_LOOPS; i++) { 592 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 593 CTR4(KTR_LOCK, 594 "%s: shared spinning on %p with %u and %u", 595 __func__, lk, spintries, i); 596 x = lk->lk_lock; 597 if ((x & LK_SHARE) == 0 || 598 LK_CAN_SHARE(x) != 0) 599 break; 600 cpu_spinwait(); 601 } 602 GIANT_RESTORE(); 603 if (i != ALK_LOOPS) 604 continue; 605 } 606 #endif 607 608 /* 609 * Acquire the sleepqueue chain lock because we 610 * probabilly will need to manipulate waiters flags. 611 */ 612 sleepq_lock(&lk->lock_object); 613 x = lk->lk_lock; 614 615 /* 616 * if the lock can be acquired in shared mode, try 617 * again. 618 */ 619 if (LK_CAN_SHARE(x)) { 620 sleepq_release(&lk->lock_object); 621 continue; 622 } 623 624 #ifdef ADAPTIVE_LOCKMGRS 625 /* 626 * The current lock owner might have started executing 627 * on another CPU (or the lock could have changed 628 * owner) while we were waiting on the turnstile 629 * chain lock. If so, drop the turnstile lock and try 630 * again. 631 */ 632 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 633 LK_HOLDER(x) != LK_KERNPROC) { 634 owner = (struct thread *)LK_HOLDER(x); 635 if (TD_IS_RUNNING(owner)) { 636 sleepq_release(&lk->lock_object); 637 continue; 638 } 639 } 640 #endif 641 642 /* 643 * Try to set the LK_SHARED_WAITERS flag. If we fail, 644 * loop back and retry. 645 */ 646 if ((x & LK_SHARED_WAITERS) == 0) { 647 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 648 x | LK_SHARED_WAITERS)) { 649 sleepq_release(&lk->lock_object); 650 continue; 651 } 652 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 653 __func__, lk); 654 } 655 656 /* 657 * As far as we have been unable to acquire the 658 * shared lock and the shared waiters flag is set, 659 * we will sleep. 660 */ 661 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 662 SQ_SHARED_QUEUE); 663 flags &= ~LK_INTERLOCK; 664 if (error) { 665 LOCK_LOG3(lk, 666 "%s: interrupted sleep for %p with %d", 667 __func__, lk, error); 668 break; 669 } 670 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 671 __func__, lk); 672 } 673 if (error == 0) { 674 lock_profile_obtain_lock_success(&lk->lock_object, 675 contested, waittime, file, line); 676 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 677 line); 678 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 679 line); 680 TD_LOCKS_INC(curthread); 681 TD_SLOCKS_INC(curthread); 682 STACK_SAVE(lk); 683 } 684 break; 685 case LK_UPGRADE: 686 _lockmgr_assert(lk, KA_SLOCKED, file, line); 687 v = lk->lk_lock; 688 x = v & LK_ALL_WAITERS; 689 v &= LK_EXCLUSIVE_SPINNERS; 690 691 /* 692 * Try to switch from one shared lock to an exclusive one. 693 * We need to preserve waiters flags during the operation. 694 */ 695 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 696 tid | x)) { 697 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 698 line); 699 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 700 LK_TRYWIT(flags), file, line); 701 TD_SLOCKS_DEC(curthread); 702 break; 703 } 704 705 /* 706 * We have been unable to succeed in upgrading, so just 707 * give up the shared lock. 708 */ 709 wakeup_swapper |= wakeupshlk(lk, file, line); 710 711 /* FALLTHROUGH */ 712 case LK_EXCLUSIVE: 713 if (LK_CAN_WITNESS(flags)) 714 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 715 LOP_EXCLUSIVE, file, line, ilk); 716 717 /* 718 * If curthread already holds the lock and this one is 719 * allowed to recurse, simply recurse on it. 720 */ 721 if (lockmgr_xlocked(lk)) { 722 if ((flags & LK_CANRECURSE) == 0 && 723 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 724 725 /* 726 * If the lock is expected to not panic just 727 * give up and return. 728 */ 729 if (LK_TRYOP(flags)) { 730 LOCK_LOG2(lk, 731 "%s: %p fails the try operation", 732 __func__, lk); 733 error = EBUSY; 734 break; 735 } 736 if (flags & LK_INTERLOCK) 737 class->lc_unlock(ilk); 738 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 739 __func__, iwmesg, file, line); 740 } 741 lk->lk_recurse++; 742 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 743 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 744 lk->lk_recurse, file, line); 745 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 746 LK_TRYWIT(flags), file, line); 747 TD_LOCKS_INC(curthread); 748 break; 749 } 750 751 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 752 tid)) { 753 #ifdef HWPMC_HOOKS 754 PMC_SOFT_CALL( , , lock, failed); 755 #endif 756 lock_profile_obtain_lock_failed(&lk->lock_object, 757 &contested, &waittime); 758 759 /* 760 * If the lock is expected to not sleep just give up 761 * and return. 762 */ 763 if (LK_TRYOP(flags)) { 764 LOCK_LOG2(lk, "%s: %p fails the try operation", 765 __func__, lk); 766 error = EBUSY; 767 break; 768 } 769 770 #ifdef ADAPTIVE_LOCKMGRS 771 /* 772 * If the owner is running on another CPU, spin until 773 * the owner stops running or the state of the lock 774 * changes. 775 */ 776 x = lk->lk_lock; 777 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 778 LK_HOLDER(x) != LK_KERNPROC) { 779 owner = (struct thread *)LK_HOLDER(x); 780 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 781 CTR3(KTR_LOCK, 782 "%s: spinning on %p held by %p", 783 __func__, lk, owner); 784 785 /* 786 * If we are holding also an interlock drop it 787 * in order to avoid a deadlock if the lockmgr 788 * owner is adaptively spinning on the 789 * interlock itself. 790 */ 791 if (flags & LK_INTERLOCK) { 792 class->lc_unlock(ilk); 793 flags &= ~LK_INTERLOCK; 794 } 795 GIANT_SAVE(); 796 while (LK_HOLDER(lk->lk_lock) == 797 (uintptr_t)owner && TD_IS_RUNNING(owner)) 798 cpu_spinwait(); 799 GIANT_RESTORE(); 800 continue; 801 } else if (LK_CAN_ADAPT(lk, flags) && 802 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 803 spintries < ALK_RETRIES) { 804 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 805 !atomic_cmpset_ptr(&lk->lk_lock, x, 806 x | LK_EXCLUSIVE_SPINNERS)) 807 continue; 808 if (flags & LK_INTERLOCK) { 809 class->lc_unlock(ilk); 810 flags &= ~LK_INTERLOCK; 811 } 812 GIANT_SAVE(); 813 spintries++; 814 for (i = 0; i < ALK_LOOPS; i++) { 815 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 816 CTR4(KTR_LOCK, 817 "%s: shared spinning on %p with %u and %u", 818 __func__, lk, spintries, i); 819 if ((lk->lk_lock & 820 LK_EXCLUSIVE_SPINNERS) == 0) 821 break; 822 cpu_spinwait(); 823 } 824 GIANT_RESTORE(); 825 if (i != ALK_LOOPS) 826 continue; 827 } 828 #endif 829 830 /* 831 * Acquire the sleepqueue chain lock because we 832 * probabilly will need to manipulate waiters flags. 833 */ 834 sleepq_lock(&lk->lock_object); 835 x = lk->lk_lock; 836 837 /* 838 * if the lock has been released while we spun on 839 * the sleepqueue chain lock just try again. 840 */ 841 if (x == LK_UNLOCKED) { 842 sleepq_release(&lk->lock_object); 843 continue; 844 } 845 846 #ifdef ADAPTIVE_LOCKMGRS 847 /* 848 * The current lock owner might have started executing 849 * on another CPU (or the lock could have changed 850 * owner) while we were waiting on the turnstile 851 * chain lock. If so, drop the turnstile lock and try 852 * again. 853 */ 854 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 855 LK_HOLDER(x) != LK_KERNPROC) { 856 owner = (struct thread *)LK_HOLDER(x); 857 if (TD_IS_RUNNING(owner)) { 858 sleepq_release(&lk->lock_object); 859 continue; 860 } 861 } 862 #endif 863 864 /* 865 * The lock can be in the state where there is a 866 * pending queue of waiters, but still no owner. 867 * This happens when the lock is contested and an 868 * owner is going to claim the lock. 869 * If curthread is the one successfully acquiring it 870 * claim lock ownership and return, preserving waiters 871 * flags. 872 */ 873 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 874 if ((x & ~v) == LK_UNLOCKED) { 875 v &= ~LK_EXCLUSIVE_SPINNERS; 876 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 877 tid | v)) { 878 sleepq_release(&lk->lock_object); 879 LOCK_LOG2(lk, 880 "%s: %p claimed by a new writer", 881 __func__, lk); 882 break; 883 } 884 sleepq_release(&lk->lock_object); 885 continue; 886 } 887 888 /* 889 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 890 * fail, loop back and retry. 891 */ 892 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 893 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 894 x | LK_EXCLUSIVE_WAITERS)) { 895 sleepq_release(&lk->lock_object); 896 continue; 897 } 898 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 899 __func__, lk); 900 } 901 902 /* 903 * As far as we have been unable to acquire the 904 * exclusive lock and the exclusive waiters flag 905 * is set, we will sleep. 906 */ 907 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 908 SQ_EXCLUSIVE_QUEUE); 909 flags &= ~LK_INTERLOCK; 910 if (error) { 911 LOCK_LOG3(lk, 912 "%s: interrupted sleep for %p with %d", 913 __func__, lk, error); 914 break; 915 } 916 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 917 __func__, lk); 918 } 919 if (error == 0) { 920 lock_profile_obtain_lock_success(&lk->lock_object, 921 contested, waittime, file, line); 922 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 923 lk->lk_recurse, file, line); 924 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 925 LK_TRYWIT(flags), file, line); 926 TD_LOCKS_INC(curthread); 927 STACK_SAVE(lk); 928 } 929 break; 930 case LK_DOWNGRADE: 931 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 932 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 933 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 934 TD_SLOCKS_INC(curthread); 935 936 /* 937 * In order to preserve waiters flags, just spin. 938 */ 939 for (;;) { 940 x = lk->lk_lock; 941 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 942 x &= LK_ALL_WAITERS; 943 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 944 LK_SHARERS_LOCK(1) | x)) 945 break; 946 cpu_spinwait(); 947 } 948 break; 949 case LK_RELEASE: 950 _lockmgr_assert(lk, KA_LOCKED, file, line); 951 x = lk->lk_lock; 952 953 if ((x & LK_SHARE) == 0) { 954 955 /* 956 * As first option, treact the lock as if it has not 957 * any waiter. 958 * Fix-up the tid var if the lock has been disowned. 959 */ 960 if (LK_HOLDER(x) == LK_KERNPROC) 961 tid = LK_KERNPROC; 962 else { 963 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 964 file, line); 965 TD_LOCKS_DEC(curthread); 966 } 967 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 968 lk->lk_recurse, file, line); 969 970 /* 971 * The lock is held in exclusive mode. 972 * If the lock is recursed also, then unrecurse it. 973 */ 974 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 975 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 976 lk); 977 lk->lk_recurse--; 978 break; 979 } 980 if (tid != LK_KERNPROC) 981 lock_profile_release_lock(&lk->lock_object); 982 983 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 984 LK_UNLOCKED)) 985 break; 986 987 sleepq_lock(&lk->lock_object); 988 x = lk->lk_lock; 989 v = LK_UNLOCKED; 990 991 /* 992 * If the lock has exclusive waiters, give them 993 * preference in order to avoid deadlock with 994 * shared runners up. 995 * If interruptible sleeps left the exclusive queue 996 * empty avoid a starvation for the threads sleeping 997 * on the shared queue by giving them precedence 998 * and cleaning up the exclusive waiters bit anyway. 999 * Please note that lk_exslpfail count may be lying 1000 * about the real number of waiters with the 1001 * LK_SLEEPFAIL flag on because they may be used in 1002 * conjuction with interruptible sleeps so 1003 * lk_exslpfail might be considered an 'upper limit' 1004 * bound, including the edge cases. 1005 */ 1006 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1007 realexslp = sleepq_sleepcnt(&lk->lock_object, 1008 SQ_EXCLUSIVE_QUEUE); 1009 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1010 if (lk->lk_exslpfail < realexslp) { 1011 lk->lk_exslpfail = 0; 1012 queue = SQ_EXCLUSIVE_QUEUE; 1013 v |= (x & LK_SHARED_WAITERS); 1014 } else { 1015 lk->lk_exslpfail = 0; 1016 LOCK_LOG2(lk, 1017 "%s: %p has only LK_SLEEPFAIL sleepers", 1018 __func__, lk); 1019 LOCK_LOG2(lk, 1020 "%s: %p waking up threads on the exclusive queue", 1021 __func__, lk); 1022 wakeup_swapper = 1023 sleepq_broadcast(&lk->lock_object, 1024 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1025 queue = SQ_SHARED_QUEUE; 1026 } 1027 } else { 1028 1029 /* 1030 * Exclusive waiters sleeping with LK_SLEEPFAIL 1031 * on and using interruptible sleeps/timeout 1032 * may have left spourious lk_exslpfail counts 1033 * on, so clean it up anyway. 1034 */ 1035 lk->lk_exslpfail = 0; 1036 queue = SQ_SHARED_QUEUE; 1037 } 1038 1039 LOCK_LOG3(lk, 1040 "%s: %p waking up threads on the %s queue", 1041 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1042 "exclusive"); 1043 atomic_store_rel_ptr(&lk->lk_lock, v); 1044 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1045 SLEEPQ_LK, 0, queue); 1046 sleepq_release(&lk->lock_object); 1047 break; 1048 } else 1049 wakeup_swapper = wakeupshlk(lk, file, line); 1050 break; 1051 case LK_DRAIN: 1052 if (LK_CAN_WITNESS(flags)) 1053 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1054 LOP_EXCLUSIVE, file, line, ilk); 1055 1056 /* 1057 * Trying to drain a lock we already own will result in a 1058 * deadlock. 1059 */ 1060 if (lockmgr_xlocked(lk)) { 1061 if (flags & LK_INTERLOCK) 1062 class->lc_unlock(ilk); 1063 panic("%s: draining %s with the lock held @ %s:%d\n", 1064 __func__, iwmesg, file, line); 1065 } 1066 1067 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1068 #ifdef HWPMC_HOOKS 1069 PMC_SOFT_CALL( , , lock, failed); 1070 #endif 1071 lock_profile_obtain_lock_failed(&lk->lock_object, 1072 &contested, &waittime); 1073 1074 /* 1075 * If the lock is expected to not sleep just give up 1076 * and return. 1077 */ 1078 if (LK_TRYOP(flags)) { 1079 LOCK_LOG2(lk, "%s: %p fails the try operation", 1080 __func__, lk); 1081 error = EBUSY; 1082 break; 1083 } 1084 1085 /* 1086 * Acquire the sleepqueue chain lock because we 1087 * probabilly will need to manipulate waiters flags. 1088 */ 1089 sleepq_lock(&lk->lock_object); 1090 x = lk->lk_lock; 1091 1092 /* 1093 * if the lock has been released while we spun on 1094 * the sleepqueue chain lock just try again. 1095 */ 1096 if (x == LK_UNLOCKED) { 1097 sleepq_release(&lk->lock_object); 1098 continue; 1099 } 1100 1101 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1102 if ((x & ~v) == LK_UNLOCKED) { 1103 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1104 1105 /* 1106 * If interruptible sleeps left the exclusive 1107 * queue empty avoid a starvation for the 1108 * threads sleeping on the shared queue by 1109 * giving them precedence and cleaning up the 1110 * exclusive waiters bit anyway. 1111 * Please note that lk_exslpfail count may be 1112 * lying about the real number of waiters with 1113 * the LK_SLEEPFAIL flag on because they may 1114 * be used in conjuction with interruptible 1115 * sleeps so lk_exslpfail might be considered 1116 * an 'upper limit' bound, including the edge 1117 * cases. 1118 */ 1119 if (v & LK_EXCLUSIVE_WAITERS) { 1120 queue = SQ_EXCLUSIVE_QUEUE; 1121 v &= ~LK_EXCLUSIVE_WAITERS; 1122 } else { 1123 1124 /* 1125 * Exclusive waiters sleeping with 1126 * LK_SLEEPFAIL on and using 1127 * interruptible sleeps/timeout may 1128 * have left spourious lk_exslpfail 1129 * counts on, so clean it up anyway. 1130 */ 1131 MPASS(v & LK_SHARED_WAITERS); 1132 lk->lk_exslpfail = 0; 1133 queue = SQ_SHARED_QUEUE; 1134 v &= ~LK_SHARED_WAITERS; 1135 } 1136 if (queue == SQ_EXCLUSIVE_QUEUE) { 1137 realexslp = 1138 sleepq_sleepcnt(&lk->lock_object, 1139 SQ_EXCLUSIVE_QUEUE); 1140 if (lk->lk_exslpfail >= realexslp) { 1141 lk->lk_exslpfail = 0; 1142 queue = SQ_SHARED_QUEUE; 1143 v &= ~LK_SHARED_WAITERS; 1144 if (realexslp != 0) { 1145 LOCK_LOG2(lk, 1146 "%s: %p has only LK_SLEEPFAIL sleepers", 1147 __func__, lk); 1148 LOCK_LOG2(lk, 1149 "%s: %p waking up threads on the exclusive queue", 1150 __func__, lk); 1151 wakeup_swapper = 1152 sleepq_broadcast( 1153 &lk->lock_object, 1154 SLEEPQ_LK, 0, 1155 SQ_EXCLUSIVE_QUEUE); 1156 } 1157 } else 1158 lk->lk_exslpfail = 0; 1159 } 1160 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1161 sleepq_release(&lk->lock_object); 1162 continue; 1163 } 1164 LOCK_LOG3(lk, 1165 "%s: %p waking up all threads on the %s queue", 1166 __func__, lk, queue == SQ_SHARED_QUEUE ? 1167 "shared" : "exclusive"); 1168 wakeup_swapper |= sleepq_broadcast( 1169 &lk->lock_object, SLEEPQ_LK, 0, queue); 1170 1171 /* 1172 * If shared waiters have been woken up we need 1173 * to wait for one of them to acquire the lock 1174 * before to set the exclusive waiters in 1175 * order to avoid a deadlock. 1176 */ 1177 if (queue == SQ_SHARED_QUEUE) { 1178 for (v = lk->lk_lock; 1179 (v & LK_SHARE) && !LK_SHARERS(v); 1180 v = lk->lk_lock) 1181 cpu_spinwait(); 1182 } 1183 } 1184 1185 /* 1186 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1187 * fail, loop back and retry. 1188 */ 1189 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1190 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1191 x | LK_EXCLUSIVE_WAITERS)) { 1192 sleepq_release(&lk->lock_object); 1193 continue; 1194 } 1195 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1196 __func__, lk); 1197 } 1198 1199 /* 1200 * As far as we have been unable to acquire the 1201 * exclusive lock and the exclusive waiters flag 1202 * is set, we will sleep. 1203 */ 1204 if (flags & LK_INTERLOCK) { 1205 class->lc_unlock(ilk); 1206 flags &= ~LK_INTERLOCK; 1207 } 1208 GIANT_SAVE(); 1209 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1210 SQ_EXCLUSIVE_QUEUE); 1211 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1212 GIANT_RESTORE(); 1213 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1214 __func__, lk); 1215 } 1216 1217 if (error == 0) { 1218 lock_profile_obtain_lock_success(&lk->lock_object, 1219 contested, waittime, file, line); 1220 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1221 lk->lk_recurse, file, line); 1222 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1223 LK_TRYWIT(flags), file, line); 1224 TD_LOCKS_INC(curthread); 1225 STACK_SAVE(lk); 1226 } 1227 break; 1228 default: 1229 if (flags & LK_INTERLOCK) 1230 class->lc_unlock(ilk); 1231 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1232 } 1233 1234 if (flags & LK_INTERLOCK) 1235 class->lc_unlock(ilk); 1236 if (wakeup_swapper) 1237 kick_proc0(); 1238 1239 return (error); 1240 } 1241 1242 void 1243 _lockmgr_disown(struct lock *lk, const char *file, int line) 1244 { 1245 uintptr_t tid, x; 1246 1247 if (SCHEDULER_STOPPED()) 1248 return; 1249 1250 tid = (uintptr_t)curthread; 1251 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 1252 1253 /* 1254 * If the owner is already LK_KERNPROC just skip the whole operation. 1255 */ 1256 if (LK_HOLDER(lk->lk_lock) != tid) 1257 return; 1258 lock_profile_release_lock(&lk->lock_object); 1259 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1260 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1261 TD_LOCKS_DEC(curthread); 1262 STACK_SAVE(lk); 1263 1264 /* 1265 * In order to preserve waiters flags, just spin. 1266 */ 1267 for (;;) { 1268 x = lk->lk_lock; 1269 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1270 x &= LK_ALL_WAITERS; 1271 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1272 LK_KERNPROC | x)) 1273 return; 1274 cpu_spinwait(); 1275 } 1276 } 1277 1278 void 1279 lockmgr_printinfo(struct lock *lk) 1280 { 1281 struct thread *td; 1282 uintptr_t x; 1283 1284 if (lk->lk_lock == LK_UNLOCKED) 1285 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1286 else if (lk->lk_lock & LK_SHARE) 1287 printf("lock type %s: SHARED (count %ju)\n", 1288 lk->lock_object.lo_name, 1289 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1290 else { 1291 td = lockmgr_xholder(lk); 1292 printf("lock type %s: EXCL by thread %p (pid %d)\n", 1293 lk->lock_object.lo_name, td, td->td_proc->p_pid); 1294 } 1295 1296 x = lk->lk_lock; 1297 if (x & LK_EXCLUSIVE_WAITERS) 1298 printf(" with exclusive waiters pending\n"); 1299 if (x & LK_SHARED_WAITERS) 1300 printf(" with shared waiters pending\n"); 1301 if (x & LK_EXCLUSIVE_SPINNERS) 1302 printf(" with exclusive spinners pending\n"); 1303 1304 STACK_PRINT(lk); 1305 } 1306 1307 int 1308 lockstatus(struct lock *lk) 1309 { 1310 uintptr_t v, x; 1311 int ret; 1312 1313 ret = LK_SHARED; 1314 x = lk->lk_lock; 1315 v = LK_HOLDER(x); 1316 1317 if ((x & LK_SHARE) == 0) { 1318 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1319 ret = LK_EXCLUSIVE; 1320 else 1321 ret = LK_EXCLOTHER; 1322 } else if (x == LK_UNLOCKED) 1323 ret = 0; 1324 1325 return (ret); 1326 } 1327 1328 #ifdef INVARIANT_SUPPORT 1329 1330 FEATURE(invariant_support, 1331 "Support for modules compiled with INVARIANTS option"); 1332 1333 #ifndef INVARIANTS 1334 #undef _lockmgr_assert 1335 #endif 1336 1337 void 1338 _lockmgr_assert(struct lock *lk, int what, const char *file, int line) 1339 { 1340 int slocked = 0; 1341 1342 if (panicstr != NULL) 1343 return; 1344 switch (what) { 1345 case KA_SLOCKED: 1346 case KA_SLOCKED | KA_NOTRECURSED: 1347 case KA_SLOCKED | KA_RECURSED: 1348 slocked = 1; 1349 case KA_LOCKED: 1350 case KA_LOCKED | KA_NOTRECURSED: 1351 case KA_LOCKED | KA_RECURSED: 1352 #ifdef WITNESS 1353 1354 /* 1355 * We cannot trust WITNESS if the lock is held in exclusive 1356 * mode and a call to lockmgr_disown() happened. 1357 * Workaround this skipping the check if the lock is held in 1358 * exclusive mode even for the KA_LOCKED case. 1359 */ 1360 if (slocked || (lk->lk_lock & LK_SHARE)) { 1361 witness_assert(&lk->lock_object, what, file, line); 1362 break; 1363 } 1364 #endif 1365 if (lk->lk_lock == LK_UNLOCKED || 1366 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1367 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1368 panic("Lock %s not %slocked @ %s:%d\n", 1369 lk->lock_object.lo_name, slocked ? "share" : "", 1370 file, line); 1371 1372 if ((lk->lk_lock & LK_SHARE) == 0) { 1373 if (lockmgr_recursed(lk)) { 1374 if (what & KA_NOTRECURSED) 1375 panic("Lock %s recursed @ %s:%d\n", 1376 lk->lock_object.lo_name, file, 1377 line); 1378 } else if (what & KA_RECURSED) 1379 panic("Lock %s not recursed @ %s:%d\n", 1380 lk->lock_object.lo_name, file, line); 1381 } 1382 break; 1383 case KA_XLOCKED: 1384 case KA_XLOCKED | KA_NOTRECURSED: 1385 case KA_XLOCKED | KA_RECURSED: 1386 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1387 panic("Lock %s not exclusively locked @ %s:%d\n", 1388 lk->lock_object.lo_name, file, line); 1389 if (lockmgr_recursed(lk)) { 1390 if (what & KA_NOTRECURSED) 1391 panic("Lock %s recursed @ %s:%d\n", 1392 lk->lock_object.lo_name, file, line); 1393 } else if (what & KA_RECURSED) 1394 panic("Lock %s not recursed @ %s:%d\n", 1395 lk->lock_object.lo_name, file, line); 1396 break; 1397 case KA_UNLOCKED: 1398 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1399 panic("Lock %s exclusively locked @ %s:%d\n", 1400 lk->lock_object.lo_name, file, line); 1401 break; 1402 default: 1403 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1404 line); 1405 } 1406 } 1407 #endif 1408 1409 #ifdef DDB 1410 int 1411 lockmgr_chain(struct thread *td, struct thread **ownerp) 1412 { 1413 struct lock *lk; 1414 1415 lk = td->td_wchan; 1416 1417 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1418 return (0); 1419 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1420 if (lk->lk_lock & LK_SHARE) 1421 db_printf("SHARED (count %ju)\n", 1422 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1423 else 1424 db_printf("EXCL\n"); 1425 *ownerp = lockmgr_xholder(lk); 1426 1427 return (1); 1428 } 1429 1430 static void 1431 db_show_lockmgr(struct lock_object *lock) 1432 { 1433 struct thread *td; 1434 struct lock *lk; 1435 1436 lk = (struct lock *)lock; 1437 1438 db_printf(" state: "); 1439 if (lk->lk_lock == LK_UNLOCKED) 1440 db_printf("UNLOCKED\n"); 1441 else if (lk->lk_lock & LK_SHARE) 1442 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1443 else { 1444 td = lockmgr_xholder(lk); 1445 if (td == (struct thread *)LK_KERNPROC) 1446 db_printf("XLOCK: LK_KERNPROC\n"); 1447 else 1448 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1449 td->td_tid, td->td_proc->p_pid, 1450 td->td_proc->p_comm); 1451 if (lockmgr_recursed(lk)) 1452 db_printf(" recursed: %d\n", lk->lk_recurse); 1453 } 1454 db_printf(" waiters: "); 1455 switch (lk->lk_lock & LK_ALL_WAITERS) { 1456 case LK_SHARED_WAITERS: 1457 db_printf("shared\n"); 1458 break; 1459 case LK_EXCLUSIVE_WAITERS: 1460 db_printf("exclusive\n"); 1461 break; 1462 case LK_ALL_WAITERS: 1463 db_printf("shared and exclusive\n"); 1464 break; 1465 default: 1466 db_printf("none\n"); 1467 } 1468 db_printf(" spinners: "); 1469 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1470 db_printf("exclusive\n"); 1471 else 1472 db_printf("none\n"); 1473 } 1474 #endif
Cache object: 1c123775b4a586cbcf8fdd011705837e
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