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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("$FreeBSD$"); 36 37 #include <sys/param.h> 38 #include <sys/kdb.h> 39 #include <sys/ktr.h> 40 #include <sys/lock.h> 41 #include <sys/lock_profile.h> 42 #include <sys/lockmgr.h> 43 #include <sys/mutex.h> 44 #include <sys/proc.h> 45 #include <sys/sleepqueue.h> 46 #ifdef DEBUG_LOCKS 47 #include <sys/stack.h> 48 #endif 49 #include <sys/sysctl.h> 50 #include <sys/systm.h> 51 52 #include <machine/cpu.h> 53 54 #ifdef DDB 55 #include <ddb/ddb.h> 56 #endif 57 58 #ifdef HWPMC_HOOKS 59 #include <sys/pmckern.h> 60 PMC_SOFT_DECLARE( , , lock, failed); 61 #endif 62 63 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) == 64 (LK_ADAPTIVE | LK_NOSHARE)); 65 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED & 66 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS))); 67 68 #define SQ_EXCLUSIVE_QUEUE 0 69 #define SQ_SHARED_QUEUE 1 70 71 #ifdef ADAPTIVE_LOCKMGRS 72 #define ALK_RETRIES 10 73 #define ALK_LOOPS 10000 74 #endif 75 76 #ifndef INVARIANTS 77 #define _lockmgr_assert(lk, what, file, line) 78 #define TD_LOCKS_INC(td) 79 #define TD_LOCKS_DEC(td) 80 #else 81 #define TD_LOCKS_INC(td) ((td)->td_locks++) 82 #define TD_LOCKS_DEC(td) ((td)->td_locks--) 83 #endif 84 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 85 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 86 87 #ifndef DEBUG_LOCKS 88 #define STACK_PRINT(lk) 89 #define STACK_SAVE(lk) 90 #define STACK_ZERO(lk) 91 #else 92 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 93 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 94 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 95 #endif 96 97 #define LOCK_LOG2(lk, string, arg1, arg2) \ 98 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 99 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 100 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 101 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 102 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 103 104 #define GIANT_DECLARE \ 105 int _i = 0; \ 106 WITNESS_SAVE_DECL(Giant) 107 #define GIANT_RESTORE() do { \ 108 if (_i > 0) { \ 109 while (_i--) \ 110 mtx_lock(&Giant); \ 111 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 112 } \ 113 } while (0) 114 #define GIANT_SAVE() do { \ 115 if (mtx_owned(&Giant)) { \ 116 WITNESS_SAVE(&Giant.lock_object, Giant); \ 117 while (mtx_owned(&Giant)) { \ 118 _i++; \ 119 mtx_unlock(&Giant); \ 120 } \ 121 } \ 122 } while (0) 123 124 #define LK_CAN_SHARE(x) \ 125 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \ 126 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \ 127 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT))) 128 #define LK_TRYOP(x) \ 129 ((x) & LK_NOWAIT) 130 131 #define LK_CAN_WITNESS(x) \ 132 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 133 #define LK_TRYWIT(x) \ 134 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 135 136 #define LK_CAN_ADAPT(lk, f) \ 137 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 138 ((f) & LK_SLEEPFAIL) == 0) 139 140 #define lockmgr_disowned(lk) \ 141 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 142 143 #define lockmgr_xlocked(lk) \ 144 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 145 146 static void assert_lockmgr(struct lock_object *lock, int how); 147 #ifdef DDB 148 static void db_show_lockmgr(struct lock_object *lock); 149 #endif 150 static void lock_lockmgr(struct lock_object *lock, int how); 151 #ifdef KDTRACE_HOOKS 152 static int owner_lockmgr(struct lock_object *lock, struct thread **owner); 153 #endif 154 static int unlock_lockmgr(struct lock_object *lock); 155 156 struct lock_class lock_class_lockmgr = { 157 .lc_name = "lockmgr", 158 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 159 .lc_assert = assert_lockmgr, 160 #ifdef DDB 161 .lc_ddb_show = db_show_lockmgr, 162 #endif 163 .lc_lock = lock_lockmgr, 164 .lc_unlock = unlock_lockmgr, 165 #ifdef KDTRACE_HOOKS 166 .lc_owner = owner_lockmgr, 167 #endif 168 }; 169 170 static __inline struct thread * 171 lockmgr_xholder(struct lock *lk) 172 { 173 uintptr_t x; 174 175 x = lk->lk_lock; 176 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 177 } 178 179 /* 180 * It assumes sleepq_lock held and returns with this one unheld. 181 * It also assumes the generic interlock is sane and previously checked. 182 * If LK_INTERLOCK is specified the interlock is not reacquired after the 183 * sleep. 184 */ 185 static __inline int 186 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 187 const char *wmesg, int pri, int timo, int queue) 188 { 189 GIANT_DECLARE; 190 struct lock_class *class; 191 int catch, error; 192 193 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 194 catch = pri & PCATCH; 195 pri &= PRIMASK; 196 error = 0; 197 198 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 199 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 200 201 if (flags & LK_INTERLOCK) 202 class->lc_unlock(ilk); 203 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 204 lk->lk_exslpfail++; 205 GIANT_SAVE(); 206 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 207 SLEEPQ_INTERRUPTIBLE : 0), queue); 208 if ((flags & LK_TIMELOCK) && timo) 209 sleepq_set_timeout(&lk->lock_object, timo); 210 211 /* 212 * Decisional switch for real sleeping. 213 */ 214 if ((flags & LK_TIMELOCK) && timo && catch) 215 error = sleepq_timedwait_sig(&lk->lock_object, pri); 216 else if ((flags & LK_TIMELOCK) && timo) 217 error = sleepq_timedwait(&lk->lock_object, pri); 218 else if (catch) 219 error = sleepq_wait_sig(&lk->lock_object, pri); 220 else 221 sleepq_wait(&lk->lock_object, pri); 222 GIANT_RESTORE(); 223 if ((flags & LK_SLEEPFAIL) && error == 0) 224 error = ENOLCK; 225 226 return (error); 227 } 228 229 static __inline int 230 wakeupshlk(struct lock *lk, const char *file, int line) 231 { 232 uintptr_t v, x; 233 u_int realexslp; 234 int queue, wakeup_swapper; 235 236 TD_LOCKS_DEC(curthread); 237 TD_SLOCKS_DEC(curthread); 238 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 239 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 240 241 wakeup_swapper = 0; 242 for (;;) { 243 x = lk->lk_lock; 244 245 /* 246 * If there is more than one shared lock held, just drop one 247 * and return. 248 */ 249 if (LK_SHARERS(x) > 1) { 250 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, 251 x - LK_ONE_SHARER)) 252 break; 253 continue; 254 } 255 256 /* 257 * If there are not waiters on the exclusive queue, drop the 258 * lock quickly. 259 */ 260 if ((x & LK_ALL_WAITERS) == 0) { 261 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == 262 LK_SHARERS_LOCK(1)); 263 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED)) 264 break; 265 continue; 266 } 267 268 /* 269 * We should have a sharer with waiters, so enter the hard 270 * path in order to handle wakeups correctly. 271 */ 272 sleepq_lock(&lk->lock_object); 273 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 274 v = LK_UNLOCKED; 275 276 /* 277 * If the lock has exclusive waiters, give them preference in 278 * order to avoid deadlock with shared runners up. 279 * If interruptible sleeps left the exclusive queue empty 280 * avoid a starvation for the threads sleeping on the shared 281 * queue by giving them precedence and cleaning up the 282 * exclusive waiters bit anyway. 283 * Please note that lk_exslpfail count may be lying about 284 * the real number of waiters with the LK_SLEEPFAIL flag on 285 * because they may be used in conjuction with interruptible 286 * sleeps so lk_exslpfail might be considered an 'upper limit' 287 * bound, including the edge cases. 288 */ 289 realexslp = sleepq_sleepcnt(&lk->lock_object, 290 SQ_EXCLUSIVE_QUEUE); 291 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 292 if (lk->lk_exslpfail < realexslp) { 293 lk->lk_exslpfail = 0; 294 queue = SQ_EXCLUSIVE_QUEUE; 295 v |= (x & LK_SHARED_WAITERS); 296 } else { 297 lk->lk_exslpfail = 0; 298 LOCK_LOG2(lk, 299 "%s: %p has only LK_SLEEPFAIL sleepers", 300 __func__, lk); 301 LOCK_LOG2(lk, 302 "%s: %p waking up threads on the exclusive queue", 303 __func__, lk); 304 wakeup_swapper = 305 sleepq_broadcast(&lk->lock_object, 306 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 307 queue = SQ_SHARED_QUEUE; 308 } 309 310 } else { 311 312 /* 313 * Exclusive waiters sleeping with LK_SLEEPFAIL on 314 * and using interruptible sleeps/timeout may have 315 * left spourious lk_exslpfail counts on, so clean 316 * it up anyway. 317 */ 318 lk->lk_exslpfail = 0; 319 queue = SQ_SHARED_QUEUE; 320 } 321 322 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, 323 v)) { 324 sleepq_release(&lk->lock_object); 325 continue; 326 } 327 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 328 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 329 "exclusive"); 330 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 331 0, queue); 332 sleepq_release(&lk->lock_object); 333 break; 334 } 335 336 lock_profile_release_lock(&lk->lock_object); 337 return (wakeup_swapper); 338 } 339 340 static void 341 assert_lockmgr(struct lock_object *lock, int what) 342 { 343 344 panic("lockmgr locks do not support assertions"); 345 } 346 347 static void 348 lock_lockmgr(struct lock_object *lock, int how) 349 { 350 351 panic("lockmgr locks do not support sleep interlocking"); 352 } 353 354 static int 355 unlock_lockmgr(struct lock_object *lock) 356 { 357 358 panic("lockmgr locks do not support sleep interlocking"); 359 } 360 361 #ifdef KDTRACE_HOOKS 362 static int 363 owner_lockmgr(struct lock_object *lock, struct thread **owner) 364 { 365 366 panic("lockmgr locks do not support owner inquiring"); 367 } 368 #endif 369 370 void 371 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 372 { 373 int iflags; 374 375 MPASS((flags & ~LK_INIT_MASK) == 0); 376 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 377 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 378 &lk->lk_lock)); 379 380 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 381 if (flags & LK_CANRECURSE) 382 iflags |= LO_RECURSABLE; 383 if ((flags & LK_NODUP) == 0) 384 iflags |= LO_DUPOK; 385 if (flags & LK_NOPROFILE) 386 iflags |= LO_NOPROFILE; 387 if ((flags & LK_NOWITNESS) == 0) 388 iflags |= LO_WITNESS; 389 if (flags & LK_QUIET) 390 iflags |= LO_QUIET; 391 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 392 393 lk->lk_lock = LK_UNLOCKED; 394 lk->lk_recurse = 0; 395 lk->lk_exslpfail = 0; 396 lk->lk_timo = timo; 397 lk->lk_pri = pri; 398 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 399 STACK_ZERO(lk); 400 } 401 402 /* 403 * XXX: Gross hacks to manipulate external lock flags after 404 * initialization. Used for certain vnode and buf locks. 405 */ 406 void 407 lockallowshare(struct lock *lk) 408 { 409 410 lockmgr_assert(lk, KA_XLOCKED); 411 lk->lock_object.lo_flags &= ~LK_NOSHARE; 412 } 413 414 void 415 lockallowrecurse(struct lock *lk) 416 { 417 418 lockmgr_assert(lk, KA_XLOCKED); 419 lk->lock_object.lo_flags |= LO_RECURSABLE; 420 } 421 422 void 423 lockdisablerecurse(struct lock *lk) 424 { 425 426 lockmgr_assert(lk, KA_XLOCKED); 427 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 428 } 429 430 void 431 lockdestroy(struct lock *lk) 432 { 433 434 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 435 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 436 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 437 lock_destroy(&lk->lock_object); 438 } 439 440 int 441 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 442 const char *wmesg, int pri, int timo, const char *file, int line) 443 { 444 GIANT_DECLARE; 445 struct lock_class *class; 446 const char *iwmesg; 447 uintptr_t tid, v, x; 448 u_int op, realexslp; 449 int error, ipri, itimo, queue, wakeup_swapper; 450 #ifdef LOCK_PROFILING 451 uint64_t waittime = 0; 452 int contested = 0; 453 #endif 454 #ifdef ADAPTIVE_LOCKMGRS 455 volatile struct thread *owner; 456 u_int i, spintries = 0; 457 #endif 458 459 error = 0; 460 tid = (uintptr_t)curthread; 461 op = (flags & LK_TYPE_MASK); 462 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 463 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 464 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 465 466 MPASS((flags & ~LK_TOTAL_MASK) == 0); 467 KASSERT((op & (op - 1)) == 0, 468 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 469 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 470 (op != LK_DOWNGRADE && op != LK_RELEASE), 471 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 472 __func__, file, line)); 473 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 474 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 475 __func__, file, line)); 476 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 477 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 478 lk->lock_object.lo_name, file, line)); 479 480 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 481 if (panicstr != NULL) { 482 if (flags & LK_INTERLOCK) 483 class->lc_unlock(ilk); 484 return (0); 485 } 486 487 if (lk->lock_object.lo_flags & LK_NOSHARE) { 488 switch (op) { 489 case LK_SHARED: 490 op = LK_EXCLUSIVE; 491 break; 492 case LK_UPGRADE: 493 case LK_TRYUPGRADE: 494 case LK_DOWNGRADE: 495 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 496 file, line); 497 if (flags & LK_INTERLOCK) 498 class->lc_unlock(ilk); 499 return (0); 500 } 501 } 502 503 wakeup_swapper = 0; 504 switch (op) { 505 case LK_SHARED: 506 if (LK_CAN_WITNESS(flags)) 507 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 508 file, line, ilk); 509 for (;;) { 510 x = lk->lk_lock; 511 512 /* 513 * If no other thread has an exclusive lock, or 514 * no exclusive waiter is present, bump the count of 515 * sharers. Since we have to preserve the state of 516 * waiters, if we fail to acquire the shared lock 517 * loop back and retry. 518 */ 519 if (LK_CAN_SHARE(x)) { 520 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 521 x + LK_ONE_SHARER)) 522 break; 523 continue; 524 } 525 #ifdef HWPMC_HOOKS 526 PMC_SOFT_CALL( , , lock, failed); 527 #endif 528 lock_profile_obtain_lock_failed(&lk->lock_object, 529 &contested, &waittime); 530 531 /* 532 * If the lock is already held by curthread in 533 * exclusive way avoid a deadlock. 534 */ 535 if (LK_HOLDER(x) == tid) { 536 LOCK_LOG2(lk, 537 "%s: %p already held in exclusive mode", 538 __func__, lk); 539 error = EDEADLK; 540 break; 541 } 542 543 /* 544 * If the lock is expected to not sleep just give up 545 * and return. 546 */ 547 if (LK_TRYOP(flags)) { 548 LOCK_LOG2(lk, "%s: %p fails the try operation", 549 __func__, lk); 550 error = EBUSY; 551 break; 552 } 553 554 #ifdef ADAPTIVE_LOCKMGRS 555 /* 556 * If the owner is running on another CPU, spin until 557 * the owner stops running or the state of the lock 558 * changes. We need a double-state handle here 559 * because for a failed acquisition the lock can be 560 * either held in exclusive mode or shared mode 561 * (for the writer starvation avoidance technique). 562 */ 563 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 564 LK_HOLDER(x) != LK_KERNPROC) { 565 owner = (struct thread *)LK_HOLDER(x); 566 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 567 CTR3(KTR_LOCK, 568 "%s: spinning on %p held by %p", 569 __func__, lk, owner); 570 571 /* 572 * If we are holding also an interlock drop it 573 * in order to avoid a deadlock if the lockmgr 574 * owner is adaptively spinning on the 575 * interlock itself. 576 */ 577 if (flags & LK_INTERLOCK) { 578 class->lc_unlock(ilk); 579 flags &= ~LK_INTERLOCK; 580 } 581 GIANT_SAVE(); 582 while (LK_HOLDER(lk->lk_lock) == 583 (uintptr_t)owner && TD_IS_RUNNING(owner)) 584 cpu_spinwait(); 585 GIANT_RESTORE(); 586 continue; 587 } else if (LK_CAN_ADAPT(lk, flags) && 588 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 589 spintries < ALK_RETRIES) { 590 if (flags & LK_INTERLOCK) { 591 class->lc_unlock(ilk); 592 flags &= ~LK_INTERLOCK; 593 } 594 GIANT_SAVE(); 595 spintries++; 596 for (i = 0; i < ALK_LOOPS; i++) { 597 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 598 CTR4(KTR_LOCK, 599 "%s: shared spinning on %p with %u and %u", 600 __func__, lk, spintries, i); 601 x = lk->lk_lock; 602 if ((x & LK_SHARE) == 0 || 603 LK_CAN_SHARE(x) != 0) 604 break; 605 cpu_spinwait(); 606 } 607 GIANT_RESTORE(); 608 if (i != ALK_LOOPS) 609 continue; 610 } 611 #endif 612 613 /* 614 * Acquire the sleepqueue chain lock because we 615 * probabilly will need to manipulate waiters flags. 616 */ 617 sleepq_lock(&lk->lock_object); 618 x = lk->lk_lock; 619 620 /* 621 * if the lock can be acquired in shared mode, try 622 * again. 623 */ 624 if (LK_CAN_SHARE(x)) { 625 sleepq_release(&lk->lock_object); 626 continue; 627 } 628 629 #ifdef ADAPTIVE_LOCKMGRS 630 /* 631 * The current lock owner might have started executing 632 * on another CPU (or the lock could have changed 633 * owner) while we were waiting on the turnstile 634 * chain lock. If so, drop the turnstile lock and try 635 * again. 636 */ 637 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 638 LK_HOLDER(x) != LK_KERNPROC) { 639 owner = (struct thread *)LK_HOLDER(x); 640 if (TD_IS_RUNNING(owner)) { 641 sleepq_release(&lk->lock_object); 642 continue; 643 } 644 } 645 #endif 646 647 /* 648 * Try to set the LK_SHARED_WAITERS flag. If we fail, 649 * loop back and retry. 650 */ 651 if ((x & LK_SHARED_WAITERS) == 0) { 652 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 653 x | LK_SHARED_WAITERS)) { 654 sleepq_release(&lk->lock_object); 655 continue; 656 } 657 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 658 __func__, lk); 659 } 660 661 /* 662 * As far as we have been unable to acquire the 663 * shared lock and the shared waiters flag is set, 664 * we will sleep. 665 */ 666 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 667 SQ_SHARED_QUEUE); 668 flags &= ~LK_INTERLOCK; 669 if (error) { 670 LOCK_LOG3(lk, 671 "%s: interrupted sleep for %p with %d", 672 __func__, lk, error); 673 break; 674 } 675 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 676 __func__, lk); 677 } 678 if (error == 0) { 679 lock_profile_obtain_lock_success(&lk->lock_object, 680 contested, waittime, file, line); 681 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 682 line); 683 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 684 line); 685 TD_LOCKS_INC(curthread); 686 TD_SLOCKS_INC(curthread); 687 STACK_SAVE(lk); 688 } 689 break; 690 case LK_UPGRADE: 691 case LK_TRYUPGRADE: 692 _lockmgr_assert(lk, KA_SLOCKED, file, line); 693 v = lk->lk_lock; 694 x = v & LK_ALL_WAITERS; 695 v &= LK_EXCLUSIVE_SPINNERS; 696 697 /* 698 * Try to switch from one shared lock to an exclusive one. 699 * We need to preserve waiters flags during the operation. 700 */ 701 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 702 tid | x)) { 703 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 704 line); 705 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 706 LK_TRYWIT(flags), file, line); 707 TD_SLOCKS_DEC(curthread); 708 break; 709 } 710 711 /* 712 * In LK_TRYUPGRADE mode, do not drop the lock, 713 * returning EBUSY instead. 714 */ 715 if (op == LK_TRYUPGRADE) { 716 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", 717 __func__, lk); 718 error = EBUSY; 719 break; 720 } 721 722 /* 723 * We have been unable to succeed in upgrading, so just 724 * give up the shared lock. 725 */ 726 wakeup_swapper |= wakeupshlk(lk, file, line); 727 728 /* FALLTHROUGH */ 729 case LK_EXCLUSIVE: 730 if (LK_CAN_WITNESS(flags)) 731 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 732 LOP_EXCLUSIVE, file, line, ilk); 733 734 /* 735 * If curthread already holds the lock and this one is 736 * allowed to recurse, simply recurse on it. 737 */ 738 if (lockmgr_xlocked(lk)) { 739 if ((flags & LK_CANRECURSE) == 0 && 740 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 741 742 /* 743 * If the lock is expected to not panic just 744 * give up and return. 745 */ 746 if (LK_TRYOP(flags)) { 747 LOCK_LOG2(lk, 748 "%s: %p fails the try operation", 749 __func__, lk); 750 error = EBUSY; 751 break; 752 } 753 if (flags & LK_INTERLOCK) 754 class->lc_unlock(ilk); 755 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 756 __func__, iwmesg, file, line); 757 } 758 lk->lk_recurse++; 759 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 760 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 761 lk->lk_recurse, file, line); 762 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 763 LK_TRYWIT(flags), file, line); 764 TD_LOCKS_INC(curthread); 765 break; 766 } 767 768 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 769 tid)) { 770 #ifdef HWPMC_HOOKS 771 PMC_SOFT_CALL( , , lock, failed); 772 #endif 773 lock_profile_obtain_lock_failed(&lk->lock_object, 774 &contested, &waittime); 775 776 /* 777 * If the lock is expected to not sleep just give up 778 * and return. 779 */ 780 if (LK_TRYOP(flags)) { 781 LOCK_LOG2(lk, "%s: %p fails the try operation", 782 __func__, lk); 783 error = EBUSY; 784 break; 785 } 786 787 #ifdef ADAPTIVE_LOCKMGRS 788 /* 789 * If the owner is running on another CPU, spin until 790 * the owner stops running or the state of the lock 791 * changes. 792 */ 793 x = lk->lk_lock; 794 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 795 LK_HOLDER(x) != LK_KERNPROC) { 796 owner = (struct thread *)LK_HOLDER(x); 797 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 798 CTR3(KTR_LOCK, 799 "%s: spinning on %p held by %p", 800 __func__, lk, owner); 801 802 /* 803 * If we are holding also an interlock drop it 804 * in order to avoid a deadlock if the lockmgr 805 * owner is adaptively spinning on the 806 * interlock itself. 807 */ 808 if (flags & LK_INTERLOCK) { 809 class->lc_unlock(ilk); 810 flags &= ~LK_INTERLOCK; 811 } 812 GIANT_SAVE(); 813 while (LK_HOLDER(lk->lk_lock) == 814 (uintptr_t)owner && TD_IS_RUNNING(owner)) 815 cpu_spinwait(); 816 GIANT_RESTORE(); 817 continue; 818 } else if (LK_CAN_ADAPT(lk, flags) && 819 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 820 spintries < ALK_RETRIES) { 821 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 822 !atomic_cmpset_ptr(&lk->lk_lock, x, 823 x | LK_EXCLUSIVE_SPINNERS)) 824 continue; 825 if (flags & LK_INTERLOCK) { 826 class->lc_unlock(ilk); 827 flags &= ~LK_INTERLOCK; 828 } 829 GIANT_SAVE(); 830 spintries++; 831 for (i = 0; i < ALK_LOOPS; i++) { 832 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 833 CTR4(KTR_LOCK, 834 "%s: shared spinning on %p with %u and %u", 835 __func__, lk, spintries, i); 836 if ((lk->lk_lock & 837 LK_EXCLUSIVE_SPINNERS) == 0) 838 break; 839 cpu_spinwait(); 840 } 841 GIANT_RESTORE(); 842 if (i != ALK_LOOPS) 843 continue; 844 } 845 #endif 846 847 /* 848 * Acquire the sleepqueue chain lock because we 849 * probabilly will need to manipulate waiters flags. 850 */ 851 sleepq_lock(&lk->lock_object); 852 x = lk->lk_lock; 853 854 /* 855 * if the lock has been released while we spun on 856 * the sleepqueue chain lock just try again. 857 */ 858 if (x == LK_UNLOCKED) { 859 sleepq_release(&lk->lock_object); 860 continue; 861 } 862 863 #ifdef ADAPTIVE_LOCKMGRS 864 /* 865 * The current lock owner might have started executing 866 * on another CPU (or the lock could have changed 867 * owner) while we were waiting on the turnstile 868 * chain lock. If so, drop the turnstile lock and try 869 * again. 870 */ 871 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 872 LK_HOLDER(x) != LK_KERNPROC) { 873 owner = (struct thread *)LK_HOLDER(x); 874 if (TD_IS_RUNNING(owner)) { 875 sleepq_release(&lk->lock_object); 876 continue; 877 } 878 } 879 #endif 880 881 /* 882 * The lock can be in the state where there is a 883 * pending queue of waiters, but still no owner. 884 * This happens when the lock is contested and an 885 * owner is going to claim the lock. 886 * If curthread is the one successfully acquiring it 887 * claim lock ownership and return, preserving waiters 888 * flags. 889 */ 890 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 891 if ((x & ~v) == LK_UNLOCKED) { 892 v &= ~LK_EXCLUSIVE_SPINNERS; 893 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 894 tid | v)) { 895 sleepq_release(&lk->lock_object); 896 LOCK_LOG2(lk, 897 "%s: %p claimed by a new writer", 898 __func__, lk); 899 break; 900 } 901 sleepq_release(&lk->lock_object); 902 continue; 903 } 904 905 /* 906 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 907 * fail, loop back and retry. 908 */ 909 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 910 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 911 x | LK_EXCLUSIVE_WAITERS)) { 912 sleepq_release(&lk->lock_object); 913 continue; 914 } 915 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 916 __func__, lk); 917 } 918 919 /* 920 * As far as we have been unable to acquire the 921 * exclusive lock and the exclusive waiters flag 922 * is set, we will sleep. 923 */ 924 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 925 SQ_EXCLUSIVE_QUEUE); 926 flags &= ~LK_INTERLOCK; 927 if (error) { 928 LOCK_LOG3(lk, 929 "%s: interrupted sleep for %p with %d", 930 __func__, lk, error); 931 break; 932 } 933 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 934 __func__, lk); 935 } 936 if (error == 0) { 937 lock_profile_obtain_lock_success(&lk->lock_object, 938 contested, waittime, file, line); 939 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 940 lk->lk_recurse, file, line); 941 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 942 LK_TRYWIT(flags), file, line); 943 TD_LOCKS_INC(curthread); 944 STACK_SAVE(lk); 945 } 946 break; 947 case LK_DOWNGRADE: 948 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 949 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 950 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 951 TD_SLOCKS_INC(curthread); 952 953 /* 954 * In order to preserve waiters flags, just spin. 955 */ 956 for (;;) { 957 x = lk->lk_lock; 958 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 959 x &= LK_ALL_WAITERS; 960 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 961 LK_SHARERS_LOCK(1) | x)) 962 break; 963 cpu_spinwait(); 964 } 965 break; 966 case LK_RELEASE: 967 _lockmgr_assert(lk, KA_LOCKED, file, line); 968 x = lk->lk_lock; 969 970 if ((x & LK_SHARE) == 0) { 971 972 /* 973 * As first option, treact the lock as if it has not 974 * any waiter. 975 * Fix-up the tid var if the lock has been disowned. 976 */ 977 if (LK_HOLDER(x) == LK_KERNPROC) 978 tid = LK_KERNPROC; 979 else { 980 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 981 file, line); 982 TD_LOCKS_DEC(curthread); 983 } 984 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 985 lk->lk_recurse, file, line); 986 987 /* 988 * The lock is held in exclusive mode. 989 * If the lock is recursed also, then unrecurse it. 990 */ 991 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 992 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 993 lk); 994 lk->lk_recurse--; 995 break; 996 } 997 if (tid != LK_KERNPROC) 998 lock_profile_release_lock(&lk->lock_object); 999 1000 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 1001 LK_UNLOCKED)) 1002 break; 1003 1004 sleepq_lock(&lk->lock_object); 1005 x = lk->lk_lock; 1006 v = LK_UNLOCKED; 1007 1008 /* 1009 * If the lock has exclusive waiters, give them 1010 * preference in order to avoid deadlock with 1011 * shared runners up. 1012 * If interruptible sleeps left the exclusive queue 1013 * empty avoid a starvation for the threads sleeping 1014 * on the shared queue by giving them precedence 1015 * and cleaning up the exclusive waiters bit anyway. 1016 * Please note that lk_exslpfail count may be lying 1017 * about the real number of waiters with the 1018 * LK_SLEEPFAIL flag on because they may be used in 1019 * conjuction with interruptible sleeps so 1020 * lk_exslpfail might be considered an 'upper limit' 1021 * bound, including the edge cases. 1022 */ 1023 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1024 realexslp = sleepq_sleepcnt(&lk->lock_object, 1025 SQ_EXCLUSIVE_QUEUE); 1026 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1027 if (lk->lk_exslpfail < realexslp) { 1028 lk->lk_exslpfail = 0; 1029 queue = SQ_EXCLUSIVE_QUEUE; 1030 v |= (x & LK_SHARED_WAITERS); 1031 } else { 1032 lk->lk_exslpfail = 0; 1033 LOCK_LOG2(lk, 1034 "%s: %p has only LK_SLEEPFAIL sleepers", 1035 __func__, lk); 1036 LOCK_LOG2(lk, 1037 "%s: %p waking up threads on the exclusive queue", 1038 __func__, lk); 1039 wakeup_swapper = 1040 sleepq_broadcast(&lk->lock_object, 1041 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1042 queue = SQ_SHARED_QUEUE; 1043 } 1044 } else { 1045 1046 /* 1047 * Exclusive waiters sleeping with LK_SLEEPFAIL 1048 * on and using interruptible sleeps/timeout 1049 * may have left spourious lk_exslpfail counts 1050 * on, so clean it up anyway. 1051 */ 1052 lk->lk_exslpfail = 0; 1053 queue = SQ_SHARED_QUEUE; 1054 } 1055 1056 LOCK_LOG3(lk, 1057 "%s: %p waking up threads on the %s queue", 1058 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1059 "exclusive"); 1060 atomic_store_rel_ptr(&lk->lk_lock, v); 1061 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1062 SLEEPQ_LK, 0, queue); 1063 sleepq_release(&lk->lock_object); 1064 break; 1065 } else 1066 wakeup_swapper = wakeupshlk(lk, file, line); 1067 break; 1068 case LK_DRAIN: 1069 if (LK_CAN_WITNESS(flags)) 1070 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1071 LOP_EXCLUSIVE, file, line, ilk); 1072 1073 /* 1074 * Trying to drain a lock we already own will result in a 1075 * deadlock. 1076 */ 1077 if (lockmgr_xlocked(lk)) { 1078 if (flags & LK_INTERLOCK) 1079 class->lc_unlock(ilk); 1080 panic("%s: draining %s with the lock held @ %s:%d\n", 1081 __func__, iwmesg, file, line); 1082 } 1083 1084 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1085 #ifdef HWPMC_HOOKS 1086 PMC_SOFT_CALL( , , lock, failed); 1087 #endif 1088 lock_profile_obtain_lock_failed(&lk->lock_object, 1089 &contested, &waittime); 1090 1091 /* 1092 * If the lock is expected to not sleep just give up 1093 * and return. 1094 */ 1095 if (LK_TRYOP(flags)) { 1096 LOCK_LOG2(lk, "%s: %p fails the try operation", 1097 __func__, lk); 1098 error = EBUSY; 1099 break; 1100 } 1101 1102 /* 1103 * Acquire the sleepqueue chain lock because we 1104 * probabilly will need to manipulate waiters flags. 1105 */ 1106 sleepq_lock(&lk->lock_object); 1107 x = lk->lk_lock; 1108 1109 /* 1110 * if the lock has been released while we spun on 1111 * the sleepqueue chain lock just try again. 1112 */ 1113 if (x == LK_UNLOCKED) { 1114 sleepq_release(&lk->lock_object); 1115 continue; 1116 } 1117 1118 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1119 if ((x & ~v) == LK_UNLOCKED) { 1120 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1121 1122 /* 1123 * If interruptible sleeps left the exclusive 1124 * queue empty avoid a starvation for the 1125 * threads sleeping on the shared queue by 1126 * giving them precedence and cleaning up the 1127 * exclusive waiters bit anyway. 1128 * Please note that lk_exslpfail count may be 1129 * lying about the real number of waiters with 1130 * the LK_SLEEPFAIL flag on because they may 1131 * be used in conjuction with interruptible 1132 * sleeps so lk_exslpfail might be considered 1133 * an 'upper limit' bound, including the edge 1134 * cases. 1135 */ 1136 if (v & LK_EXCLUSIVE_WAITERS) { 1137 queue = SQ_EXCLUSIVE_QUEUE; 1138 v &= ~LK_EXCLUSIVE_WAITERS; 1139 } else { 1140 1141 /* 1142 * Exclusive waiters sleeping with 1143 * LK_SLEEPFAIL on and using 1144 * interruptible sleeps/timeout may 1145 * have left spourious lk_exslpfail 1146 * counts on, so clean it up anyway. 1147 */ 1148 MPASS(v & LK_SHARED_WAITERS); 1149 lk->lk_exslpfail = 0; 1150 queue = SQ_SHARED_QUEUE; 1151 v &= ~LK_SHARED_WAITERS; 1152 } 1153 if (queue == SQ_EXCLUSIVE_QUEUE) { 1154 realexslp = 1155 sleepq_sleepcnt(&lk->lock_object, 1156 SQ_EXCLUSIVE_QUEUE); 1157 if (lk->lk_exslpfail >= realexslp) { 1158 lk->lk_exslpfail = 0; 1159 queue = SQ_SHARED_QUEUE; 1160 v &= ~LK_SHARED_WAITERS; 1161 if (realexslp != 0) { 1162 LOCK_LOG2(lk, 1163 "%s: %p has only LK_SLEEPFAIL sleepers", 1164 __func__, lk); 1165 LOCK_LOG2(lk, 1166 "%s: %p waking up threads on the exclusive queue", 1167 __func__, lk); 1168 wakeup_swapper = 1169 sleepq_broadcast( 1170 &lk->lock_object, 1171 SLEEPQ_LK, 0, 1172 SQ_EXCLUSIVE_QUEUE); 1173 } 1174 } else 1175 lk->lk_exslpfail = 0; 1176 } 1177 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1178 sleepq_release(&lk->lock_object); 1179 continue; 1180 } 1181 LOCK_LOG3(lk, 1182 "%s: %p waking up all threads on the %s queue", 1183 __func__, lk, queue == SQ_SHARED_QUEUE ? 1184 "shared" : "exclusive"); 1185 wakeup_swapper |= sleepq_broadcast( 1186 &lk->lock_object, SLEEPQ_LK, 0, queue); 1187 1188 /* 1189 * If shared waiters have been woken up we need 1190 * to wait for one of them to acquire the lock 1191 * before to set the exclusive waiters in 1192 * order to avoid a deadlock. 1193 */ 1194 if (queue == SQ_SHARED_QUEUE) { 1195 for (v = lk->lk_lock; 1196 (v & LK_SHARE) && !LK_SHARERS(v); 1197 v = lk->lk_lock) 1198 cpu_spinwait(); 1199 } 1200 } 1201 1202 /* 1203 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1204 * fail, loop back and retry. 1205 */ 1206 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1207 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1208 x | LK_EXCLUSIVE_WAITERS)) { 1209 sleepq_release(&lk->lock_object); 1210 continue; 1211 } 1212 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1213 __func__, lk); 1214 } 1215 1216 /* 1217 * As far as we have been unable to acquire the 1218 * exclusive lock and the exclusive waiters flag 1219 * is set, we will sleep. 1220 */ 1221 if (flags & LK_INTERLOCK) { 1222 class->lc_unlock(ilk); 1223 flags &= ~LK_INTERLOCK; 1224 } 1225 GIANT_SAVE(); 1226 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1227 SQ_EXCLUSIVE_QUEUE); 1228 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1229 GIANT_RESTORE(); 1230 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1231 __func__, lk); 1232 } 1233 1234 if (error == 0) { 1235 lock_profile_obtain_lock_success(&lk->lock_object, 1236 contested, waittime, file, line); 1237 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1238 lk->lk_recurse, file, line); 1239 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1240 LK_TRYWIT(flags), file, line); 1241 TD_LOCKS_INC(curthread); 1242 STACK_SAVE(lk); 1243 } 1244 break; 1245 default: 1246 if (flags & LK_INTERLOCK) 1247 class->lc_unlock(ilk); 1248 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1249 } 1250 1251 if (flags & LK_INTERLOCK) 1252 class->lc_unlock(ilk); 1253 if (wakeup_swapper) 1254 kick_proc0(); 1255 1256 return (error); 1257 } 1258 1259 void 1260 _lockmgr_disown(struct lock *lk, const char *file, int line) 1261 { 1262 uintptr_t tid, x; 1263 1264 if (SCHEDULER_STOPPED()) 1265 return; 1266 1267 tid = (uintptr_t)curthread; 1268 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 1269 1270 /* 1271 * If the owner is already LK_KERNPROC just skip the whole operation. 1272 */ 1273 if (LK_HOLDER(lk->lk_lock) != tid) 1274 return; 1275 lock_profile_release_lock(&lk->lock_object); 1276 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1277 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1278 TD_LOCKS_DEC(curthread); 1279 STACK_SAVE(lk); 1280 1281 /* 1282 * In order to preserve waiters flags, just spin. 1283 */ 1284 for (;;) { 1285 x = lk->lk_lock; 1286 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1287 x &= LK_ALL_WAITERS; 1288 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1289 LK_KERNPROC | x)) 1290 return; 1291 cpu_spinwait(); 1292 } 1293 } 1294 1295 void 1296 lockmgr_printinfo(struct lock *lk) 1297 { 1298 struct thread *td; 1299 uintptr_t x; 1300 1301 if (lk->lk_lock == LK_UNLOCKED) 1302 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1303 else if (lk->lk_lock & LK_SHARE) 1304 printf("lock type %s: SHARED (count %ju)\n", 1305 lk->lock_object.lo_name, 1306 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1307 else { 1308 td = lockmgr_xholder(lk); 1309 printf("lock type %s: EXCL by thread %p (pid %d)\n", 1310 lk->lock_object.lo_name, td, td->td_proc->p_pid); 1311 } 1312 1313 x = lk->lk_lock; 1314 if (x & LK_EXCLUSIVE_WAITERS) 1315 printf(" with exclusive waiters pending\n"); 1316 if (x & LK_SHARED_WAITERS) 1317 printf(" with shared waiters pending\n"); 1318 if (x & LK_EXCLUSIVE_SPINNERS) 1319 printf(" with exclusive spinners pending\n"); 1320 1321 STACK_PRINT(lk); 1322 } 1323 1324 int 1325 lockstatus(struct lock *lk) 1326 { 1327 uintptr_t v, x; 1328 int ret; 1329 1330 ret = LK_SHARED; 1331 x = lk->lk_lock; 1332 v = LK_HOLDER(x); 1333 1334 if ((x & LK_SHARE) == 0) { 1335 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1336 ret = LK_EXCLUSIVE; 1337 else 1338 ret = LK_EXCLOTHER; 1339 } else if (x == LK_UNLOCKED) 1340 ret = 0; 1341 1342 return (ret); 1343 } 1344 1345 #ifdef INVARIANT_SUPPORT 1346 1347 FEATURE(invariant_support, 1348 "Support for modules compiled with INVARIANTS option"); 1349 1350 #ifndef INVARIANTS 1351 #undef _lockmgr_assert 1352 #endif 1353 1354 void 1355 _lockmgr_assert(struct lock *lk, int what, const char *file, int line) 1356 { 1357 int slocked = 0; 1358 1359 if (panicstr != NULL) 1360 return; 1361 switch (what) { 1362 case KA_SLOCKED: 1363 case KA_SLOCKED | KA_NOTRECURSED: 1364 case KA_SLOCKED | KA_RECURSED: 1365 slocked = 1; 1366 case KA_LOCKED: 1367 case KA_LOCKED | KA_NOTRECURSED: 1368 case KA_LOCKED | KA_RECURSED: 1369 #ifdef WITNESS 1370 1371 /* 1372 * We cannot trust WITNESS if the lock is held in exclusive 1373 * mode and a call to lockmgr_disown() happened. 1374 * Workaround this skipping the check if the lock is held in 1375 * exclusive mode even for the KA_LOCKED case. 1376 */ 1377 if (slocked || (lk->lk_lock & LK_SHARE)) { 1378 witness_assert(&lk->lock_object, what, file, line); 1379 break; 1380 } 1381 #endif 1382 if (lk->lk_lock == LK_UNLOCKED || 1383 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1384 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1385 panic("Lock %s not %slocked @ %s:%d\n", 1386 lk->lock_object.lo_name, slocked ? "share" : "", 1387 file, line); 1388 1389 if ((lk->lk_lock & LK_SHARE) == 0) { 1390 if (lockmgr_recursed(lk)) { 1391 if (what & KA_NOTRECURSED) 1392 panic("Lock %s recursed @ %s:%d\n", 1393 lk->lock_object.lo_name, file, 1394 line); 1395 } else if (what & KA_RECURSED) 1396 panic("Lock %s not recursed @ %s:%d\n", 1397 lk->lock_object.lo_name, file, line); 1398 } 1399 break; 1400 case KA_XLOCKED: 1401 case KA_XLOCKED | KA_NOTRECURSED: 1402 case KA_XLOCKED | KA_RECURSED: 1403 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1404 panic("Lock %s not exclusively locked @ %s:%d\n", 1405 lk->lock_object.lo_name, file, line); 1406 if (lockmgr_recursed(lk)) { 1407 if (what & KA_NOTRECURSED) 1408 panic("Lock %s recursed @ %s:%d\n", 1409 lk->lock_object.lo_name, file, line); 1410 } else if (what & KA_RECURSED) 1411 panic("Lock %s not recursed @ %s:%d\n", 1412 lk->lock_object.lo_name, file, line); 1413 break; 1414 case KA_UNLOCKED: 1415 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1416 panic("Lock %s exclusively locked @ %s:%d\n", 1417 lk->lock_object.lo_name, file, line); 1418 break; 1419 default: 1420 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1421 line); 1422 } 1423 } 1424 #endif 1425 1426 #ifdef DDB 1427 int 1428 lockmgr_chain(struct thread *td, struct thread **ownerp) 1429 { 1430 struct lock *lk; 1431 1432 lk = td->td_wchan; 1433 1434 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1435 return (0); 1436 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1437 if (lk->lk_lock & LK_SHARE) 1438 db_printf("SHARED (count %ju)\n", 1439 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1440 else 1441 db_printf("EXCL\n"); 1442 *ownerp = lockmgr_xholder(lk); 1443 1444 return (1); 1445 } 1446 1447 static void 1448 db_show_lockmgr(struct lock_object *lock) 1449 { 1450 struct thread *td; 1451 struct lock *lk; 1452 1453 lk = (struct lock *)lock; 1454 1455 db_printf(" state: "); 1456 if (lk->lk_lock == LK_UNLOCKED) 1457 db_printf("UNLOCKED\n"); 1458 else if (lk->lk_lock & LK_SHARE) 1459 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1460 else { 1461 td = lockmgr_xholder(lk); 1462 if (td == (struct thread *)LK_KERNPROC) 1463 db_printf("XLOCK: LK_KERNPROC\n"); 1464 else 1465 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1466 td->td_tid, td->td_proc->p_pid, 1467 td->td_proc->p_comm); 1468 if (lockmgr_recursed(lk)) 1469 db_printf(" recursed: %d\n", lk->lk_recurse); 1470 } 1471 db_printf(" waiters: "); 1472 switch (lk->lk_lock & LK_ALL_WAITERS) { 1473 case LK_SHARED_WAITERS: 1474 db_printf("shared\n"); 1475 break; 1476 case LK_EXCLUSIVE_WAITERS: 1477 db_printf("exclusive\n"); 1478 break; 1479 case LK_ALL_WAITERS: 1480 db_printf("shared and exclusive\n"); 1481 break; 1482 default: 1483 db_printf("none\n"); 1484 } 1485 db_printf(" spinners: "); 1486 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1487 db_printf("exclusive\n"); 1488 else 1489 db_printf("none\n"); 1490 } 1491 #endif
Cache object: 823c68e8d283744601d53cc0768a8856
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