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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/10.1/sys/kern/kern_lock.c 271161 2014-09-05 13:22:28Z kib $"); 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 #ifndef INVARIANTS 72 #define _lockmgr_assert(lk, what, file, line) 73 #define TD_LOCKS_INC(td) 74 #define TD_LOCKS_DEC(td) 75 #else 76 #define TD_LOCKS_INC(td) ((td)->td_locks++) 77 #define TD_LOCKS_DEC(td) ((td)->td_locks--) 78 #endif 79 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 80 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 81 82 #ifndef DEBUG_LOCKS 83 #define STACK_PRINT(lk) 84 #define STACK_SAVE(lk) 85 #define STACK_ZERO(lk) 86 #else 87 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 88 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 89 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 90 #endif 91 92 #define LOCK_LOG2(lk, string, arg1, arg2) \ 93 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 94 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 95 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 96 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 97 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 98 99 #define GIANT_DECLARE \ 100 int _i = 0; \ 101 WITNESS_SAVE_DECL(Giant) 102 #define GIANT_RESTORE() do { \ 103 if (_i > 0) { \ 104 while (_i--) \ 105 mtx_lock(&Giant); \ 106 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 107 } \ 108 } while (0) 109 #define GIANT_SAVE() do { \ 110 if (mtx_owned(&Giant)) { \ 111 WITNESS_SAVE(&Giant.lock_object, Giant); \ 112 while (mtx_owned(&Giant)) { \ 113 _i++; \ 114 mtx_unlock(&Giant); \ 115 } \ 116 } \ 117 } while (0) 118 119 #define LK_CAN_SHARE(x) \ 120 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \ 121 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \ 122 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT))) 123 #define LK_TRYOP(x) \ 124 ((x) & LK_NOWAIT) 125 126 #define LK_CAN_WITNESS(x) \ 127 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 128 #define LK_TRYWIT(x) \ 129 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 130 131 #define LK_CAN_ADAPT(lk, f) \ 132 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 133 ((f) & LK_SLEEPFAIL) == 0) 134 135 #define lockmgr_disowned(lk) \ 136 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 137 138 #define lockmgr_xlocked(lk) \ 139 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 140 141 static void assert_lockmgr(const struct lock_object *lock, int how); 142 #ifdef DDB 143 static void db_show_lockmgr(const struct lock_object *lock); 144 #endif 145 static void lock_lockmgr(struct lock_object *lock, uintptr_t how); 146 #ifdef KDTRACE_HOOKS 147 static int owner_lockmgr(const struct lock_object *lock, 148 struct thread **owner); 149 #endif 150 static uintptr_t unlock_lockmgr(struct lock_object *lock); 151 152 struct lock_class lock_class_lockmgr = { 153 .lc_name = "lockmgr", 154 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 155 .lc_assert = assert_lockmgr, 156 #ifdef DDB 157 .lc_ddb_show = db_show_lockmgr, 158 #endif 159 .lc_lock = lock_lockmgr, 160 .lc_unlock = unlock_lockmgr, 161 #ifdef KDTRACE_HOOKS 162 .lc_owner = owner_lockmgr, 163 #endif 164 }; 165 166 #ifdef ADAPTIVE_LOCKMGRS 167 static u_int alk_retries = 10; 168 static u_int alk_loops = 10000; 169 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, 170 "lockmgr debugging"); 171 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, ""); 172 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, ""); 173 #endif 174 175 static __inline struct thread * 176 lockmgr_xholder(const struct lock *lk) 177 { 178 uintptr_t x; 179 180 x = lk->lk_lock; 181 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 182 } 183 184 /* 185 * It assumes sleepq_lock held and returns with this one unheld. 186 * It also assumes the generic interlock is sane and previously checked. 187 * If LK_INTERLOCK is specified the interlock is not reacquired after the 188 * sleep. 189 */ 190 static __inline int 191 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 192 const char *wmesg, int pri, int timo, int queue) 193 { 194 GIANT_DECLARE; 195 struct lock_class *class; 196 int catch, error; 197 198 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 199 catch = pri & PCATCH; 200 pri &= PRIMASK; 201 error = 0; 202 203 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 204 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 205 206 if (flags & LK_INTERLOCK) 207 class->lc_unlock(ilk); 208 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 209 lk->lk_exslpfail++; 210 GIANT_SAVE(); 211 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 212 SLEEPQ_INTERRUPTIBLE : 0), queue); 213 if ((flags & LK_TIMELOCK) && timo) 214 sleepq_set_timeout(&lk->lock_object, timo); 215 216 /* 217 * Decisional switch for real sleeping. 218 */ 219 if ((flags & LK_TIMELOCK) && timo && catch) 220 error = sleepq_timedwait_sig(&lk->lock_object, pri); 221 else if ((flags & LK_TIMELOCK) && timo) 222 error = sleepq_timedwait(&lk->lock_object, pri); 223 else if (catch) 224 error = sleepq_wait_sig(&lk->lock_object, pri); 225 else 226 sleepq_wait(&lk->lock_object, pri); 227 GIANT_RESTORE(); 228 if ((flags & LK_SLEEPFAIL) && error == 0) 229 error = ENOLCK; 230 231 return (error); 232 } 233 234 static __inline int 235 wakeupshlk(struct lock *lk, const char *file, int line) 236 { 237 uintptr_t v, x; 238 u_int realexslp; 239 int queue, wakeup_swapper; 240 241 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 242 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 243 244 wakeup_swapper = 0; 245 for (;;) { 246 x = lk->lk_lock; 247 248 /* 249 * If there is more than one shared lock held, just drop one 250 * and return. 251 */ 252 if (LK_SHARERS(x) > 1) { 253 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, 254 x - LK_ONE_SHARER)) 255 break; 256 continue; 257 } 258 259 /* 260 * If there are not waiters on the exclusive queue, drop the 261 * lock quickly. 262 */ 263 if ((x & LK_ALL_WAITERS) == 0) { 264 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == 265 LK_SHARERS_LOCK(1)); 266 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED)) 267 break; 268 continue; 269 } 270 271 /* 272 * We should have a sharer with waiters, so enter the hard 273 * path in order to handle wakeups correctly. 274 */ 275 sleepq_lock(&lk->lock_object); 276 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 277 v = LK_UNLOCKED; 278 279 /* 280 * If the lock has exclusive waiters, give them preference in 281 * order to avoid deadlock with shared runners up. 282 * If interruptible sleeps left the exclusive queue empty 283 * avoid a starvation for the threads sleeping on the shared 284 * queue by giving them precedence and cleaning up the 285 * exclusive waiters bit anyway. 286 * Please note that lk_exslpfail count may be lying about 287 * the real number of waiters with the LK_SLEEPFAIL flag on 288 * because they may be used in conjuction with interruptible 289 * sleeps so lk_exslpfail might be considered an 'upper limit' 290 * bound, including the edge cases. 291 */ 292 realexslp = sleepq_sleepcnt(&lk->lock_object, 293 SQ_EXCLUSIVE_QUEUE); 294 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 295 if (lk->lk_exslpfail < realexslp) { 296 lk->lk_exslpfail = 0; 297 queue = SQ_EXCLUSIVE_QUEUE; 298 v |= (x & LK_SHARED_WAITERS); 299 } else { 300 lk->lk_exslpfail = 0; 301 LOCK_LOG2(lk, 302 "%s: %p has only LK_SLEEPFAIL sleepers", 303 __func__, lk); 304 LOCK_LOG2(lk, 305 "%s: %p waking up threads on the exclusive queue", 306 __func__, lk); 307 wakeup_swapper = 308 sleepq_broadcast(&lk->lock_object, 309 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 310 queue = SQ_SHARED_QUEUE; 311 } 312 313 } else { 314 315 /* 316 * Exclusive waiters sleeping with LK_SLEEPFAIL on 317 * and using interruptible sleeps/timeout may have 318 * left spourious lk_exslpfail counts on, so clean 319 * it up anyway. 320 */ 321 lk->lk_exslpfail = 0; 322 queue = SQ_SHARED_QUEUE; 323 } 324 325 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, 326 v)) { 327 sleepq_release(&lk->lock_object); 328 continue; 329 } 330 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 331 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 332 "exclusive"); 333 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 334 0, queue); 335 sleepq_release(&lk->lock_object); 336 break; 337 } 338 339 lock_profile_release_lock(&lk->lock_object); 340 TD_LOCKS_DEC(curthread); 341 TD_SLOCKS_DEC(curthread); 342 return (wakeup_swapper); 343 } 344 345 static void 346 assert_lockmgr(const struct lock_object *lock, int what) 347 { 348 349 panic("lockmgr locks do not support assertions"); 350 } 351 352 static void 353 lock_lockmgr(struct lock_object *lock, uintptr_t how) 354 { 355 356 panic("lockmgr locks do not support sleep interlocking"); 357 } 358 359 static uintptr_t 360 unlock_lockmgr(struct lock_object *lock) 361 { 362 363 panic("lockmgr locks do not support sleep interlocking"); 364 } 365 366 #ifdef KDTRACE_HOOKS 367 static int 368 owner_lockmgr(const struct lock_object *lock, struct thread **owner) 369 { 370 371 panic("lockmgr locks do not support owner inquiring"); 372 } 373 #endif 374 375 void 376 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 377 { 378 int iflags; 379 380 MPASS((flags & ~LK_INIT_MASK) == 0); 381 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 382 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 383 &lk->lk_lock)); 384 385 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 386 if (flags & LK_CANRECURSE) 387 iflags |= LO_RECURSABLE; 388 if ((flags & LK_NODUP) == 0) 389 iflags |= LO_DUPOK; 390 if (flags & LK_NOPROFILE) 391 iflags |= LO_NOPROFILE; 392 if ((flags & LK_NOWITNESS) == 0) 393 iflags |= LO_WITNESS; 394 if (flags & LK_QUIET) 395 iflags |= LO_QUIET; 396 if (flags & LK_IS_VNODE) 397 iflags |= LO_IS_VNODE; 398 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 399 400 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 401 lk->lk_lock = LK_UNLOCKED; 402 lk->lk_recurse = 0; 403 lk->lk_exslpfail = 0; 404 lk->lk_timo = timo; 405 lk->lk_pri = pri; 406 STACK_ZERO(lk); 407 } 408 409 /* 410 * XXX: Gross hacks to manipulate external lock flags after 411 * initialization. Used for certain vnode and buf locks. 412 */ 413 void 414 lockallowshare(struct lock *lk) 415 { 416 417 lockmgr_assert(lk, KA_XLOCKED); 418 lk->lock_object.lo_flags &= ~LK_NOSHARE; 419 } 420 421 void 422 lockdisableshare(struct lock *lk) 423 { 424 425 lockmgr_assert(lk, KA_XLOCKED); 426 lk->lock_object.lo_flags |= LK_NOSHARE; 427 } 428 429 void 430 lockallowrecurse(struct lock *lk) 431 { 432 433 lockmgr_assert(lk, KA_XLOCKED); 434 lk->lock_object.lo_flags |= LO_RECURSABLE; 435 } 436 437 void 438 lockdisablerecurse(struct lock *lk) 439 { 440 441 lockmgr_assert(lk, KA_XLOCKED); 442 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 443 } 444 445 void 446 lockdestroy(struct lock *lk) 447 { 448 449 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 450 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 451 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 452 lock_destroy(&lk->lock_object); 453 } 454 455 int 456 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 457 const char *wmesg, int pri, int timo, const char *file, int line) 458 { 459 GIANT_DECLARE; 460 struct lock_class *class; 461 const char *iwmesg; 462 uintptr_t tid, v, x; 463 u_int op, realexslp; 464 int error, ipri, itimo, queue, wakeup_swapper; 465 #ifdef LOCK_PROFILING 466 uint64_t waittime = 0; 467 int contested = 0; 468 #endif 469 #ifdef ADAPTIVE_LOCKMGRS 470 volatile struct thread *owner; 471 u_int i, spintries = 0; 472 #endif 473 474 error = 0; 475 tid = (uintptr_t)curthread; 476 op = (flags & LK_TYPE_MASK); 477 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 478 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 479 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 480 481 MPASS((flags & ~LK_TOTAL_MASK) == 0); 482 KASSERT((op & (op - 1)) == 0, 483 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 484 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 485 (op != LK_DOWNGRADE && op != LK_RELEASE), 486 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 487 __func__, file, line)); 488 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 489 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 490 __func__, file, line)); 491 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 492 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 493 lk->lock_object.lo_name, file, line)); 494 495 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 496 if (panicstr != NULL) { 497 if (flags & LK_INTERLOCK) 498 class->lc_unlock(ilk); 499 return (0); 500 } 501 502 if (lk->lock_object.lo_flags & LK_NOSHARE) { 503 switch (op) { 504 case LK_SHARED: 505 op = LK_EXCLUSIVE; 506 break; 507 case LK_UPGRADE: 508 case LK_TRYUPGRADE: 509 case LK_DOWNGRADE: 510 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 511 file, line); 512 if (flags & LK_INTERLOCK) 513 class->lc_unlock(ilk); 514 return (0); 515 } 516 } 517 518 wakeup_swapper = 0; 519 switch (op) { 520 case LK_SHARED: 521 if (LK_CAN_WITNESS(flags)) 522 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 523 file, line, flags & LK_INTERLOCK ? ilk : NULL); 524 for (;;) { 525 x = lk->lk_lock; 526 527 /* 528 * If no other thread has an exclusive lock, or 529 * no exclusive waiter is present, bump the count of 530 * sharers. Since we have to preserve the state of 531 * waiters, if we fail to acquire the shared lock 532 * loop back and retry. 533 */ 534 if (LK_CAN_SHARE(x)) { 535 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 536 x + LK_ONE_SHARER)) 537 break; 538 continue; 539 } 540 #ifdef HWPMC_HOOKS 541 PMC_SOFT_CALL( , , lock, failed); 542 #endif 543 lock_profile_obtain_lock_failed(&lk->lock_object, 544 &contested, &waittime); 545 546 /* 547 * If the lock is already held by curthread in 548 * exclusive way avoid a deadlock. 549 */ 550 if (LK_HOLDER(x) == tid) { 551 LOCK_LOG2(lk, 552 "%s: %p already held in exclusive mode", 553 __func__, lk); 554 error = EDEADLK; 555 break; 556 } 557 558 /* 559 * If the lock is expected to not sleep just give up 560 * and return. 561 */ 562 if (LK_TRYOP(flags)) { 563 LOCK_LOG2(lk, "%s: %p fails the try operation", 564 __func__, lk); 565 error = EBUSY; 566 break; 567 } 568 569 #ifdef ADAPTIVE_LOCKMGRS 570 /* 571 * If the owner is running on another CPU, spin until 572 * the owner stops running or the state of the lock 573 * changes. We need a double-state handle here 574 * because for a failed acquisition the lock can be 575 * either held in exclusive mode or shared mode 576 * (for the writer starvation avoidance technique). 577 */ 578 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 579 LK_HOLDER(x) != LK_KERNPROC) { 580 owner = (struct thread *)LK_HOLDER(x); 581 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 582 CTR3(KTR_LOCK, 583 "%s: spinning on %p held by %p", 584 __func__, lk, owner); 585 586 /* 587 * If we are holding also an interlock drop it 588 * in order to avoid a deadlock if the lockmgr 589 * owner is adaptively spinning on the 590 * interlock itself. 591 */ 592 if (flags & LK_INTERLOCK) { 593 class->lc_unlock(ilk); 594 flags &= ~LK_INTERLOCK; 595 } 596 GIANT_SAVE(); 597 while (LK_HOLDER(lk->lk_lock) == 598 (uintptr_t)owner && TD_IS_RUNNING(owner)) 599 cpu_spinwait(); 600 GIANT_RESTORE(); 601 continue; 602 } else if (LK_CAN_ADAPT(lk, flags) && 603 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 604 spintries < alk_retries) { 605 if (flags & LK_INTERLOCK) { 606 class->lc_unlock(ilk); 607 flags &= ~LK_INTERLOCK; 608 } 609 GIANT_SAVE(); 610 spintries++; 611 for (i = 0; i < alk_loops; i++) { 612 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 613 CTR4(KTR_LOCK, 614 "%s: shared spinning on %p with %u and %u", 615 __func__, lk, spintries, i); 616 x = lk->lk_lock; 617 if ((x & LK_SHARE) == 0 || 618 LK_CAN_SHARE(x) != 0) 619 break; 620 cpu_spinwait(); 621 } 622 GIANT_RESTORE(); 623 if (i != alk_loops) 624 continue; 625 } 626 #endif 627 628 /* 629 * Acquire the sleepqueue chain lock because we 630 * probabilly will need to manipulate waiters flags. 631 */ 632 sleepq_lock(&lk->lock_object); 633 x = lk->lk_lock; 634 635 /* 636 * if the lock can be acquired in shared mode, try 637 * again. 638 */ 639 if (LK_CAN_SHARE(x)) { 640 sleepq_release(&lk->lock_object); 641 continue; 642 } 643 644 #ifdef ADAPTIVE_LOCKMGRS 645 /* 646 * The current lock owner might have started executing 647 * on another CPU (or the lock could have changed 648 * owner) while we were waiting on the turnstile 649 * chain lock. If so, drop the turnstile lock and try 650 * again. 651 */ 652 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 653 LK_HOLDER(x) != LK_KERNPROC) { 654 owner = (struct thread *)LK_HOLDER(x); 655 if (TD_IS_RUNNING(owner)) { 656 sleepq_release(&lk->lock_object); 657 continue; 658 } 659 } 660 #endif 661 662 /* 663 * Try to set the LK_SHARED_WAITERS flag. If we fail, 664 * loop back and retry. 665 */ 666 if ((x & LK_SHARED_WAITERS) == 0) { 667 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 668 x | LK_SHARED_WAITERS)) { 669 sleepq_release(&lk->lock_object); 670 continue; 671 } 672 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 673 __func__, lk); 674 } 675 676 /* 677 * As far as we have been unable to acquire the 678 * shared lock and the shared waiters flag is set, 679 * we will sleep. 680 */ 681 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 682 SQ_SHARED_QUEUE); 683 flags &= ~LK_INTERLOCK; 684 if (error) { 685 LOCK_LOG3(lk, 686 "%s: interrupted sleep for %p with %d", 687 __func__, lk, error); 688 break; 689 } 690 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 691 __func__, lk); 692 } 693 if (error == 0) { 694 lock_profile_obtain_lock_success(&lk->lock_object, 695 contested, waittime, file, line); 696 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 697 line); 698 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 699 line); 700 TD_LOCKS_INC(curthread); 701 TD_SLOCKS_INC(curthread); 702 STACK_SAVE(lk); 703 } 704 break; 705 case LK_UPGRADE: 706 case LK_TRYUPGRADE: 707 _lockmgr_assert(lk, KA_SLOCKED, file, line); 708 v = lk->lk_lock; 709 x = v & LK_ALL_WAITERS; 710 v &= LK_EXCLUSIVE_SPINNERS; 711 712 /* 713 * Try to switch from one shared lock to an exclusive one. 714 * We need to preserve waiters flags during the operation. 715 */ 716 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 717 tid | x)) { 718 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 719 line); 720 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 721 LK_TRYWIT(flags), file, line); 722 TD_SLOCKS_DEC(curthread); 723 break; 724 } 725 726 /* 727 * In LK_TRYUPGRADE mode, do not drop the lock, 728 * returning EBUSY instead. 729 */ 730 if (op == LK_TRYUPGRADE) { 731 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", 732 __func__, lk); 733 error = EBUSY; 734 break; 735 } 736 737 /* 738 * We have been unable to succeed in upgrading, so just 739 * give up the shared lock. 740 */ 741 wakeup_swapper |= wakeupshlk(lk, file, line); 742 743 /* FALLTHROUGH */ 744 case LK_EXCLUSIVE: 745 if (LK_CAN_WITNESS(flags)) 746 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 747 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 748 ilk : NULL); 749 750 /* 751 * If curthread already holds the lock and this one is 752 * allowed to recurse, simply recurse on it. 753 */ 754 if (lockmgr_xlocked(lk)) { 755 if ((flags & LK_CANRECURSE) == 0 && 756 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 757 758 /* 759 * If the lock is expected to not panic just 760 * give up and return. 761 */ 762 if (LK_TRYOP(flags)) { 763 LOCK_LOG2(lk, 764 "%s: %p fails the try operation", 765 __func__, lk); 766 error = EBUSY; 767 break; 768 } 769 if (flags & LK_INTERLOCK) 770 class->lc_unlock(ilk); 771 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 772 __func__, iwmesg, file, line); 773 } 774 lk->lk_recurse++; 775 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 776 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 777 lk->lk_recurse, file, line); 778 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 779 LK_TRYWIT(flags), file, line); 780 TD_LOCKS_INC(curthread); 781 break; 782 } 783 784 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 785 tid)) { 786 #ifdef HWPMC_HOOKS 787 PMC_SOFT_CALL( , , lock, failed); 788 #endif 789 lock_profile_obtain_lock_failed(&lk->lock_object, 790 &contested, &waittime); 791 792 /* 793 * If the lock is expected to not sleep just give up 794 * and return. 795 */ 796 if (LK_TRYOP(flags)) { 797 LOCK_LOG2(lk, "%s: %p fails the try operation", 798 __func__, lk); 799 error = EBUSY; 800 break; 801 } 802 803 #ifdef ADAPTIVE_LOCKMGRS 804 /* 805 * If the owner is running on another CPU, spin until 806 * the owner stops running or the state of the lock 807 * changes. 808 */ 809 x = lk->lk_lock; 810 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 811 LK_HOLDER(x) != LK_KERNPROC) { 812 owner = (struct thread *)LK_HOLDER(x); 813 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 814 CTR3(KTR_LOCK, 815 "%s: spinning on %p held by %p", 816 __func__, lk, owner); 817 818 /* 819 * If we are holding also an interlock drop it 820 * in order to avoid a deadlock if the lockmgr 821 * owner is adaptively spinning on the 822 * interlock itself. 823 */ 824 if (flags & LK_INTERLOCK) { 825 class->lc_unlock(ilk); 826 flags &= ~LK_INTERLOCK; 827 } 828 GIANT_SAVE(); 829 while (LK_HOLDER(lk->lk_lock) == 830 (uintptr_t)owner && TD_IS_RUNNING(owner)) 831 cpu_spinwait(); 832 GIANT_RESTORE(); 833 continue; 834 } else if (LK_CAN_ADAPT(lk, flags) && 835 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 836 spintries < alk_retries) { 837 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 838 !atomic_cmpset_ptr(&lk->lk_lock, x, 839 x | LK_EXCLUSIVE_SPINNERS)) 840 continue; 841 if (flags & LK_INTERLOCK) { 842 class->lc_unlock(ilk); 843 flags &= ~LK_INTERLOCK; 844 } 845 GIANT_SAVE(); 846 spintries++; 847 for (i = 0; i < alk_loops; i++) { 848 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 849 CTR4(KTR_LOCK, 850 "%s: shared spinning on %p with %u and %u", 851 __func__, lk, spintries, i); 852 if ((lk->lk_lock & 853 LK_EXCLUSIVE_SPINNERS) == 0) 854 break; 855 cpu_spinwait(); 856 } 857 GIANT_RESTORE(); 858 if (i != alk_loops) 859 continue; 860 } 861 #endif 862 863 /* 864 * Acquire the sleepqueue chain lock because we 865 * probabilly will need to manipulate waiters flags. 866 */ 867 sleepq_lock(&lk->lock_object); 868 x = lk->lk_lock; 869 870 /* 871 * if the lock has been released while we spun on 872 * the sleepqueue chain lock just try again. 873 */ 874 if (x == LK_UNLOCKED) { 875 sleepq_release(&lk->lock_object); 876 continue; 877 } 878 879 #ifdef ADAPTIVE_LOCKMGRS 880 /* 881 * The current lock owner might have started executing 882 * on another CPU (or the lock could have changed 883 * owner) while we were waiting on the turnstile 884 * chain lock. If so, drop the turnstile lock and try 885 * again. 886 */ 887 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 888 LK_HOLDER(x) != LK_KERNPROC) { 889 owner = (struct thread *)LK_HOLDER(x); 890 if (TD_IS_RUNNING(owner)) { 891 sleepq_release(&lk->lock_object); 892 continue; 893 } 894 } 895 #endif 896 897 /* 898 * The lock can be in the state where there is a 899 * pending queue of waiters, but still no owner. 900 * This happens when the lock is contested and an 901 * owner is going to claim the lock. 902 * If curthread is the one successfully acquiring it 903 * claim lock ownership and return, preserving waiters 904 * flags. 905 */ 906 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 907 if ((x & ~v) == LK_UNLOCKED) { 908 v &= ~LK_EXCLUSIVE_SPINNERS; 909 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 910 tid | v)) { 911 sleepq_release(&lk->lock_object); 912 LOCK_LOG2(lk, 913 "%s: %p claimed by a new writer", 914 __func__, lk); 915 break; 916 } 917 sleepq_release(&lk->lock_object); 918 continue; 919 } 920 921 /* 922 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 923 * fail, loop back and retry. 924 */ 925 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 926 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 927 x | LK_EXCLUSIVE_WAITERS)) { 928 sleepq_release(&lk->lock_object); 929 continue; 930 } 931 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 932 __func__, lk); 933 } 934 935 /* 936 * As far as we have been unable to acquire the 937 * exclusive lock and the exclusive waiters flag 938 * is set, we will sleep. 939 */ 940 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 941 SQ_EXCLUSIVE_QUEUE); 942 flags &= ~LK_INTERLOCK; 943 if (error) { 944 LOCK_LOG3(lk, 945 "%s: interrupted sleep for %p with %d", 946 __func__, lk, error); 947 break; 948 } 949 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 950 __func__, lk); 951 } 952 if (error == 0) { 953 lock_profile_obtain_lock_success(&lk->lock_object, 954 contested, waittime, file, line); 955 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 956 lk->lk_recurse, file, line); 957 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 958 LK_TRYWIT(flags), file, line); 959 TD_LOCKS_INC(curthread); 960 STACK_SAVE(lk); 961 } 962 break; 963 case LK_DOWNGRADE: 964 _lockmgr_assert(lk, KA_XLOCKED, file, line); 965 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 966 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 967 968 /* 969 * Panic if the lock is recursed. 970 */ 971 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 972 if (flags & LK_INTERLOCK) 973 class->lc_unlock(ilk); 974 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 975 __func__, iwmesg, file, line); 976 } 977 TD_SLOCKS_INC(curthread); 978 979 /* 980 * In order to preserve waiters flags, just spin. 981 */ 982 for (;;) { 983 x = lk->lk_lock; 984 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 985 x &= LK_ALL_WAITERS; 986 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 987 LK_SHARERS_LOCK(1) | x)) 988 break; 989 cpu_spinwait(); 990 } 991 break; 992 case LK_RELEASE: 993 _lockmgr_assert(lk, KA_LOCKED, file, line); 994 x = lk->lk_lock; 995 996 if ((x & LK_SHARE) == 0) { 997 998 /* 999 * As first option, treact the lock as if it has not 1000 * any waiter. 1001 * Fix-up the tid var if the lock has been disowned. 1002 */ 1003 if (LK_HOLDER(x) == LK_KERNPROC) 1004 tid = LK_KERNPROC; 1005 else { 1006 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 1007 file, line); 1008 TD_LOCKS_DEC(curthread); 1009 } 1010 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 1011 lk->lk_recurse, file, line); 1012 1013 /* 1014 * The lock is held in exclusive mode. 1015 * If the lock is recursed also, then unrecurse it. 1016 */ 1017 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 1018 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 1019 lk); 1020 lk->lk_recurse--; 1021 break; 1022 } 1023 if (tid != LK_KERNPROC) 1024 lock_profile_release_lock(&lk->lock_object); 1025 1026 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 1027 LK_UNLOCKED)) 1028 break; 1029 1030 sleepq_lock(&lk->lock_object); 1031 x = lk->lk_lock; 1032 v = LK_UNLOCKED; 1033 1034 /* 1035 * If the lock has exclusive waiters, give them 1036 * preference in order to avoid deadlock with 1037 * shared runners up. 1038 * If interruptible sleeps left the exclusive queue 1039 * empty avoid a starvation for the threads sleeping 1040 * on the shared queue by giving them precedence 1041 * and cleaning up the exclusive waiters bit anyway. 1042 * Please note that lk_exslpfail count may be lying 1043 * about the real number of waiters with the 1044 * LK_SLEEPFAIL flag on because they may be used in 1045 * conjuction with interruptible sleeps so 1046 * lk_exslpfail might be considered an 'upper limit' 1047 * bound, including the edge cases. 1048 */ 1049 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1050 realexslp = sleepq_sleepcnt(&lk->lock_object, 1051 SQ_EXCLUSIVE_QUEUE); 1052 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1053 if (lk->lk_exslpfail < realexslp) { 1054 lk->lk_exslpfail = 0; 1055 queue = SQ_EXCLUSIVE_QUEUE; 1056 v |= (x & LK_SHARED_WAITERS); 1057 } else { 1058 lk->lk_exslpfail = 0; 1059 LOCK_LOG2(lk, 1060 "%s: %p has only LK_SLEEPFAIL sleepers", 1061 __func__, lk); 1062 LOCK_LOG2(lk, 1063 "%s: %p waking up threads on the exclusive queue", 1064 __func__, lk); 1065 wakeup_swapper = 1066 sleepq_broadcast(&lk->lock_object, 1067 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1068 queue = SQ_SHARED_QUEUE; 1069 } 1070 } else { 1071 1072 /* 1073 * Exclusive waiters sleeping with LK_SLEEPFAIL 1074 * on and using interruptible sleeps/timeout 1075 * may have left spourious lk_exslpfail counts 1076 * on, so clean it up anyway. 1077 */ 1078 lk->lk_exslpfail = 0; 1079 queue = SQ_SHARED_QUEUE; 1080 } 1081 1082 LOCK_LOG3(lk, 1083 "%s: %p waking up threads on the %s queue", 1084 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1085 "exclusive"); 1086 atomic_store_rel_ptr(&lk->lk_lock, v); 1087 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1088 SLEEPQ_LK, 0, queue); 1089 sleepq_release(&lk->lock_object); 1090 break; 1091 } else 1092 wakeup_swapper = wakeupshlk(lk, file, line); 1093 break; 1094 case LK_DRAIN: 1095 if (LK_CAN_WITNESS(flags)) 1096 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1097 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 1098 ilk : NULL); 1099 1100 /* 1101 * Trying to drain a lock we already own will result in a 1102 * deadlock. 1103 */ 1104 if (lockmgr_xlocked(lk)) { 1105 if (flags & LK_INTERLOCK) 1106 class->lc_unlock(ilk); 1107 panic("%s: draining %s with the lock held @ %s:%d\n", 1108 __func__, iwmesg, file, line); 1109 } 1110 1111 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1112 #ifdef HWPMC_HOOKS 1113 PMC_SOFT_CALL( , , lock, failed); 1114 #endif 1115 lock_profile_obtain_lock_failed(&lk->lock_object, 1116 &contested, &waittime); 1117 1118 /* 1119 * If the lock is expected to not sleep just give up 1120 * and return. 1121 */ 1122 if (LK_TRYOP(flags)) { 1123 LOCK_LOG2(lk, "%s: %p fails the try operation", 1124 __func__, lk); 1125 error = EBUSY; 1126 break; 1127 } 1128 1129 /* 1130 * Acquire the sleepqueue chain lock because we 1131 * probabilly will need to manipulate waiters flags. 1132 */ 1133 sleepq_lock(&lk->lock_object); 1134 x = lk->lk_lock; 1135 1136 /* 1137 * if the lock has been released while we spun on 1138 * the sleepqueue chain lock just try again. 1139 */ 1140 if (x == LK_UNLOCKED) { 1141 sleepq_release(&lk->lock_object); 1142 continue; 1143 } 1144 1145 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1146 if ((x & ~v) == LK_UNLOCKED) { 1147 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1148 1149 /* 1150 * If interruptible sleeps left the exclusive 1151 * queue empty avoid a starvation for the 1152 * threads sleeping on the shared queue by 1153 * giving them precedence and cleaning up the 1154 * exclusive waiters bit anyway. 1155 * Please note that lk_exslpfail count may be 1156 * lying about the real number of waiters with 1157 * the LK_SLEEPFAIL flag on because they may 1158 * be used in conjuction with interruptible 1159 * sleeps so lk_exslpfail might be considered 1160 * an 'upper limit' bound, including the edge 1161 * cases. 1162 */ 1163 if (v & LK_EXCLUSIVE_WAITERS) { 1164 queue = SQ_EXCLUSIVE_QUEUE; 1165 v &= ~LK_EXCLUSIVE_WAITERS; 1166 } else { 1167 1168 /* 1169 * Exclusive waiters sleeping with 1170 * LK_SLEEPFAIL on and using 1171 * interruptible sleeps/timeout may 1172 * have left spourious lk_exslpfail 1173 * counts on, so clean it up anyway. 1174 */ 1175 MPASS(v & LK_SHARED_WAITERS); 1176 lk->lk_exslpfail = 0; 1177 queue = SQ_SHARED_QUEUE; 1178 v &= ~LK_SHARED_WAITERS; 1179 } 1180 if (queue == SQ_EXCLUSIVE_QUEUE) { 1181 realexslp = 1182 sleepq_sleepcnt(&lk->lock_object, 1183 SQ_EXCLUSIVE_QUEUE); 1184 if (lk->lk_exslpfail >= realexslp) { 1185 lk->lk_exslpfail = 0; 1186 queue = SQ_SHARED_QUEUE; 1187 v &= ~LK_SHARED_WAITERS; 1188 if (realexslp != 0) { 1189 LOCK_LOG2(lk, 1190 "%s: %p has only LK_SLEEPFAIL sleepers", 1191 __func__, lk); 1192 LOCK_LOG2(lk, 1193 "%s: %p waking up threads on the exclusive queue", 1194 __func__, lk); 1195 wakeup_swapper = 1196 sleepq_broadcast( 1197 &lk->lock_object, 1198 SLEEPQ_LK, 0, 1199 SQ_EXCLUSIVE_QUEUE); 1200 } 1201 } else 1202 lk->lk_exslpfail = 0; 1203 } 1204 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1205 sleepq_release(&lk->lock_object); 1206 continue; 1207 } 1208 LOCK_LOG3(lk, 1209 "%s: %p waking up all threads on the %s queue", 1210 __func__, lk, queue == SQ_SHARED_QUEUE ? 1211 "shared" : "exclusive"); 1212 wakeup_swapper |= sleepq_broadcast( 1213 &lk->lock_object, SLEEPQ_LK, 0, queue); 1214 1215 /* 1216 * If shared waiters have been woken up we need 1217 * to wait for one of them to acquire the lock 1218 * before to set the exclusive waiters in 1219 * order to avoid a deadlock. 1220 */ 1221 if (queue == SQ_SHARED_QUEUE) { 1222 for (v = lk->lk_lock; 1223 (v & LK_SHARE) && !LK_SHARERS(v); 1224 v = lk->lk_lock) 1225 cpu_spinwait(); 1226 } 1227 } 1228 1229 /* 1230 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1231 * fail, loop back and retry. 1232 */ 1233 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1234 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1235 x | LK_EXCLUSIVE_WAITERS)) { 1236 sleepq_release(&lk->lock_object); 1237 continue; 1238 } 1239 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1240 __func__, lk); 1241 } 1242 1243 /* 1244 * As far as we have been unable to acquire the 1245 * exclusive lock and the exclusive waiters flag 1246 * is set, we will sleep. 1247 */ 1248 if (flags & LK_INTERLOCK) { 1249 class->lc_unlock(ilk); 1250 flags &= ~LK_INTERLOCK; 1251 } 1252 GIANT_SAVE(); 1253 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1254 SQ_EXCLUSIVE_QUEUE); 1255 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1256 GIANT_RESTORE(); 1257 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1258 __func__, lk); 1259 } 1260 1261 if (error == 0) { 1262 lock_profile_obtain_lock_success(&lk->lock_object, 1263 contested, waittime, file, line); 1264 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1265 lk->lk_recurse, file, line); 1266 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1267 LK_TRYWIT(flags), file, line); 1268 TD_LOCKS_INC(curthread); 1269 STACK_SAVE(lk); 1270 } 1271 break; 1272 default: 1273 if (flags & LK_INTERLOCK) 1274 class->lc_unlock(ilk); 1275 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1276 } 1277 1278 if (flags & LK_INTERLOCK) 1279 class->lc_unlock(ilk); 1280 if (wakeup_swapper) 1281 kick_proc0(); 1282 1283 return (error); 1284 } 1285 1286 void 1287 _lockmgr_disown(struct lock *lk, const char *file, int line) 1288 { 1289 uintptr_t tid, x; 1290 1291 if (SCHEDULER_STOPPED()) 1292 return; 1293 1294 tid = (uintptr_t)curthread; 1295 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1296 1297 /* 1298 * Panic if the lock is recursed. 1299 */ 1300 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1301 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1302 __func__, file, line); 1303 1304 /* 1305 * If the owner is already LK_KERNPROC just skip the whole operation. 1306 */ 1307 if (LK_HOLDER(lk->lk_lock) != tid) 1308 return; 1309 lock_profile_release_lock(&lk->lock_object); 1310 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1311 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1312 TD_LOCKS_DEC(curthread); 1313 STACK_SAVE(lk); 1314 1315 /* 1316 * In order to preserve waiters flags, just spin. 1317 */ 1318 for (;;) { 1319 x = lk->lk_lock; 1320 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1321 x &= LK_ALL_WAITERS; 1322 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1323 LK_KERNPROC | x)) 1324 return; 1325 cpu_spinwait(); 1326 } 1327 } 1328 1329 void 1330 lockmgr_printinfo(const struct lock *lk) 1331 { 1332 struct thread *td; 1333 uintptr_t x; 1334 1335 if (lk->lk_lock == LK_UNLOCKED) 1336 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1337 else if (lk->lk_lock & LK_SHARE) 1338 printf("lock type %s: SHARED (count %ju)\n", 1339 lk->lock_object.lo_name, 1340 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1341 else { 1342 td = lockmgr_xholder(lk); 1343 printf("lock type %s: EXCL by thread %p " 1344 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, td, 1345 td->td_proc->p_pid, td->td_proc->p_comm, td->td_tid); 1346 } 1347 1348 x = lk->lk_lock; 1349 if (x & LK_EXCLUSIVE_WAITERS) 1350 printf(" with exclusive waiters pending\n"); 1351 if (x & LK_SHARED_WAITERS) 1352 printf(" with shared waiters pending\n"); 1353 if (x & LK_EXCLUSIVE_SPINNERS) 1354 printf(" with exclusive spinners pending\n"); 1355 1356 STACK_PRINT(lk); 1357 } 1358 1359 int 1360 lockstatus(const struct lock *lk) 1361 { 1362 uintptr_t v, x; 1363 int ret; 1364 1365 ret = LK_SHARED; 1366 x = lk->lk_lock; 1367 v = LK_HOLDER(x); 1368 1369 if ((x & LK_SHARE) == 0) { 1370 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1371 ret = LK_EXCLUSIVE; 1372 else 1373 ret = LK_EXCLOTHER; 1374 } else if (x == LK_UNLOCKED) 1375 ret = 0; 1376 1377 return (ret); 1378 } 1379 1380 #ifdef INVARIANT_SUPPORT 1381 1382 FEATURE(invariant_support, 1383 "Support for modules compiled with INVARIANTS option"); 1384 1385 #ifndef INVARIANTS 1386 #undef _lockmgr_assert 1387 #endif 1388 1389 void 1390 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1391 { 1392 int slocked = 0; 1393 1394 if (panicstr != NULL) 1395 return; 1396 switch (what) { 1397 case KA_SLOCKED: 1398 case KA_SLOCKED | KA_NOTRECURSED: 1399 case KA_SLOCKED | KA_RECURSED: 1400 slocked = 1; 1401 case KA_LOCKED: 1402 case KA_LOCKED | KA_NOTRECURSED: 1403 case KA_LOCKED | KA_RECURSED: 1404 #ifdef WITNESS 1405 1406 /* 1407 * We cannot trust WITNESS if the lock is held in exclusive 1408 * mode and a call to lockmgr_disown() happened. 1409 * Workaround this skipping the check if the lock is held in 1410 * exclusive mode even for the KA_LOCKED case. 1411 */ 1412 if (slocked || (lk->lk_lock & LK_SHARE)) { 1413 witness_assert(&lk->lock_object, what, file, line); 1414 break; 1415 } 1416 #endif 1417 if (lk->lk_lock == LK_UNLOCKED || 1418 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1419 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1420 panic("Lock %s not %slocked @ %s:%d\n", 1421 lk->lock_object.lo_name, slocked ? "share" : "", 1422 file, line); 1423 1424 if ((lk->lk_lock & LK_SHARE) == 0) { 1425 if (lockmgr_recursed(lk)) { 1426 if (what & KA_NOTRECURSED) 1427 panic("Lock %s recursed @ %s:%d\n", 1428 lk->lock_object.lo_name, file, 1429 line); 1430 } else if (what & KA_RECURSED) 1431 panic("Lock %s not recursed @ %s:%d\n", 1432 lk->lock_object.lo_name, file, line); 1433 } 1434 break; 1435 case KA_XLOCKED: 1436 case KA_XLOCKED | KA_NOTRECURSED: 1437 case KA_XLOCKED | KA_RECURSED: 1438 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1439 panic("Lock %s not exclusively locked @ %s:%d\n", 1440 lk->lock_object.lo_name, file, line); 1441 if (lockmgr_recursed(lk)) { 1442 if (what & KA_NOTRECURSED) 1443 panic("Lock %s recursed @ %s:%d\n", 1444 lk->lock_object.lo_name, file, line); 1445 } else if (what & KA_RECURSED) 1446 panic("Lock %s not recursed @ %s:%d\n", 1447 lk->lock_object.lo_name, file, line); 1448 break; 1449 case KA_UNLOCKED: 1450 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1451 panic("Lock %s exclusively locked @ %s:%d\n", 1452 lk->lock_object.lo_name, file, line); 1453 break; 1454 default: 1455 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1456 line); 1457 } 1458 } 1459 #endif 1460 1461 #ifdef DDB 1462 int 1463 lockmgr_chain(struct thread *td, struct thread **ownerp) 1464 { 1465 struct lock *lk; 1466 1467 lk = td->td_wchan; 1468 1469 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1470 return (0); 1471 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1472 if (lk->lk_lock & LK_SHARE) 1473 db_printf("SHARED (count %ju)\n", 1474 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1475 else 1476 db_printf("EXCL\n"); 1477 *ownerp = lockmgr_xholder(lk); 1478 1479 return (1); 1480 } 1481 1482 static void 1483 db_show_lockmgr(const struct lock_object *lock) 1484 { 1485 struct thread *td; 1486 const struct lock *lk; 1487 1488 lk = (const struct lock *)lock; 1489 1490 db_printf(" state: "); 1491 if (lk->lk_lock == LK_UNLOCKED) 1492 db_printf("UNLOCKED\n"); 1493 else if (lk->lk_lock & LK_SHARE) 1494 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1495 else { 1496 td = lockmgr_xholder(lk); 1497 if (td == (struct thread *)LK_KERNPROC) 1498 db_printf("XLOCK: LK_KERNPROC\n"); 1499 else 1500 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1501 td->td_tid, td->td_proc->p_pid, 1502 td->td_proc->p_comm); 1503 if (lockmgr_recursed(lk)) 1504 db_printf(" recursed: %d\n", lk->lk_recurse); 1505 } 1506 db_printf(" waiters: "); 1507 switch (lk->lk_lock & LK_ALL_WAITERS) { 1508 case LK_SHARED_WAITERS: 1509 db_printf("shared\n"); 1510 break; 1511 case LK_EXCLUSIVE_WAITERS: 1512 db_printf("exclusive\n"); 1513 break; 1514 case LK_ALL_WAITERS: 1515 db_printf("shared and exclusive\n"); 1516 break; 1517 default: 1518 db_printf("none\n"); 1519 } 1520 db_printf(" spinners: "); 1521 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1522 db_printf("exclusive\n"); 1523 else 1524 db_printf("none\n"); 1525 } 1526 #endif
Cache object: c3ac5db9b2df2b31e4e5122154de16a8
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