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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 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD: releng/11.0/sys/kern/kern_lock.c 301157 2016-06-01 18:32:20Z mjg $"); 35 36 #include <sys/param.h> 37 #include <sys/kdb.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 #ifndef INVARIANTS 71 #define _lockmgr_assert(lk, what, file, line) 72 #endif 73 74 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 75 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 76 77 #ifndef DEBUG_LOCKS 78 #define STACK_PRINT(lk) 79 #define STACK_SAVE(lk) 80 #define STACK_ZERO(lk) 81 #else 82 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 83 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 84 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 85 #endif 86 87 #define LOCK_LOG2(lk, string, arg1, arg2) \ 88 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 89 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 90 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 91 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 92 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 93 94 #define GIANT_DECLARE \ 95 int _i = 0; \ 96 WITNESS_SAVE_DECL(Giant) 97 #define GIANT_RESTORE() do { \ 98 if (_i > 0) { \ 99 while (_i--) \ 100 mtx_lock(&Giant); \ 101 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 102 } \ 103 } while (0) 104 #define GIANT_SAVE() do { \ 105 if (mtx_owned(&Giant)) { \ 106 WITNESS_SAVE(&Giant.lock_object, Giant); \ 107 while (mtx_owned(&Giant)) { \ 108 _i++; \ 109 mtx_unlock(&Giant); \ 110 } \ 111 } \ 112 } while (0) 113 114 #define LK_CAN_SHARE(x, flags) \ 115 (((x) & LK_SHARE) && \ 116 (((x) & (LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) == 0 || \ 117 (curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) || \ 118 (curthread->td_pflags & TDP_DEADLKTREAT))) 119 #define LK_TRYOP(x) \ 120 ((x) & LK_NOWAIT) 121 122 #define LK_CAN_WITNESS(x) \ 123 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 124 #define LK_TRYWIT(x) \ 125 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 126 127 #define LK_CAN_ADAPT(lk, f) \ 128 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 129 ((f) & LK_SLEEPFAIL) == 0) 130 131 #define lockmgr_disowned(lk) \ 132 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 133 134 #define lockmgr_xlocked(lk) \ 135 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 136 137 static void assert_lockmgr(const struct lock_object *lock, int how); 138 #ifdef DDB 139 static void db_show_lockmgr(const struct lock_object *lock); 140 #endif 141 static void lock_lockmgr(struct lock_object *lock, uintptr_t how); 142 #ifdef KDTRACE_HOOKS 143 static int owner_lockmgr(const struct lock_object *lock, 144 struct thread **owner); 145 #endif 146 static uintptr_t unlock_lockmgr(struct lock_object *lock); 147 148 struct lock_class lock_class_lockmgr = { 149 .lc_name = "lockmgr", 150 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 151 .lc_assert = assert_lockmgr, 152 #ifdef DDB 153 .lc_ddb_show = db_show_lockmgr, 154 #endif 155 .lc_lock = lock_lockmgr, 156 .lc_unlock = unlock_lockmgr, 157 #ifdef KDTRACE_HOOKS 158 .lc_owner = owner_lockmgr, 159 #endif 160 }; 161 162 #ifdef ADAPTIVE_LOCKMGRS 163 static u_int alk_retries = 10; 164 static u_int alk_loops = 10000; 165 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, 166 "lockmgr debugging"); 167 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, ""); 168 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, ""); 169 #endif 170 171 static __inline struct thread * 172 lockmgr_xholder(const struct lock *lk) 173 { 174 uintptr_t x; 175 176 x = lk->lk_lock; 177 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 178 } 179 180 /* 181 * It assumes sleepq_lock held and returns with this one unheld. 182 * It also assumes the generic interlock is sane and previously checked. 183 * If LK_INTERLOCK is specified the interlock is not reacquired after the 184 * sleep. 185 */ 186 static __inline int 187 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 188 const char *wmesg, int pri, int timo, int queue) 189 { 190 GIANT_DECLARE; 191 struct lock_class *class; 192 int catch, error; 193 194 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 195 catch = pri & PCATCH; 196 pri &= PRIMASK; 197 error = 0; 198 199 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 200 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 201 202 if (flags & LK_INTERLOCK) 203 class->lc_unlock(ilk); 204 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 205 lk->lk_exslpfail++; 206 GIANT_SAVE(); 207 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 208 SLEEPQ_INTERRUPTIBLE : 0), queue); 209 if ((flags & LK_TIMELOCK) && timo) 210 sleepq_set_timeout(&lk->lock_object, timo); 211 212 /* 213 * Decisional switch for real sleeping. 214 */ 215 if ((flags & LK_TIMELOCK) && timo && catch) 216 error = sleepq_timedwait_sig(&lk->lock_object, pri); 217 else if ((flags & LK_TIMELOCK) && timo) 218 error = sleepq_timedwait(&lk->lock_object, pri); 219 else if (catch) 220 error = sleepq_wait_sig(&lk->lock_object, pri); 221 else 222 sleepq_wait(&lk->lock_object, pri); 223 GIANT_RESTORE(); 224 if ((flags & LK_SLEEPFAIL) && error == 0) 225 error = ENOLCK; 226 227 return (error); 228 } 229 230 static __inline int 231 wakeupshlk(struct lock *lk, const char *file, int line) 232 { 233 uintptr_t v, x; 234 u_int realexslp; 235 int queue, wakeup_swapper; 236 237 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 conjunction 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 TD_LOCKS_DEC(curthread); 337 TD_SLOCKS_DEC(curthread); 338 return (wakeup_swapper); 339 } 340 341 static void 342 assert_lockmgr(const struct lock_object *lock, int what) 343 { 344 345 panic("lockmgr locks do not support assertions"); 346 } 347 348 static void 349 lock_lockmgr(struct lock_object *lock, uintptr_t how) 350 { 351 352 panic("lockmgr locks do not support sleep interlocking"); 353 } 354 355 static uintptr_t 356 unlock_lockmgr(struct lock_object *lock) 357 { 358 359 panic("lockmgr locks do not support sleep interlocking"); 360 } 361 362 #ifdef KDTRACE_HOOKS 363 static int 364 owner_lockmgr(const struct lock_object *lock, struct thread **owner) 365 { 366 367 panic("lockmgr locks do not support owner inquiring"); 368 } 369 #endif 370 371 void 372 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 373 { 374 int iflags; 375 376 MPASS((flags & ~LK_INIT_MASK) == 0); 377 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 378 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 379 &lk->lk_lock)); 380 381 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 382 if (flags & LK_CANRECURSE) 383 iflags |= LO_RECURSABLE; 384 if ((flags & LK_NODUP) == 0) 385 iflags |= LO_DUPOK; 386 if (flags & LK_NOPROFILE) 387 iflags |= LO_NOPROFILE; 388 if ((flags & LK_NOWITNESS) == 0) 389 iflags |= LO_WITNESS; 390 if (flags & LK_QUIET) 391 iflags |= LO_QUIET; 392 if (flags & LK_IS_VNODE) 393 iflags |= LO_IS_VNODE; 394 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 395 396 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 397 lk->lk_lock = LK_UNLOCKED; 398 lk->lk_recurse = 0; 399 lk->lk_exslpfail = 0; 400 lk->lk_timo = timo; 401 lk->lk_pri = pri; 402 STACK_ZERO(lk); 403 } 404 405 /* 406 * XXX: Gross hacks to manipulate external lock flags after 407 * initialization. Used for certain vnode and buf locks. 408 */ 409 void 410 lockallowshare(struct lock *lk) 411 { 412 413 lockmgr_assert(lk, KA_XLOCKED); 414 lk->lock_object.lo_flags &= ~LK_NOSHARE; 415 } 416 417 void 418 lockdisableshare(struct lock *lk) 419 { 420 421 lockmgr_assert(lk, KA_XLOCKED); 422 lk->lock_object.lo_flags |= LK_NOSHARE; 423 } 424 425 void 426 lockallowrecurse(struct lock *lk) 427 { 428 429 lockmgr_assert(lk, KA_XLOCKED); 430 lk->lock_object.lo_flags |= LO_RECURSABLE; 431 } 432 433 void 434 lockdisablerecurse(struct lock *lk) 435 { 436 437 lockmgr_assert(lk, KA_XLOCKED); 438 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 439 } 440 441 void 442 lockdestroy(struct lock *lk) 443 { 444 445 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 446 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 447 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 448 lock_destroy(&lk->lock_object); 449 } 450 451 int 452 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 453 const char *wmesg, int pri, int timo, const char *file, int line) 454 { 455 GIANT_DECLARE; 456 struct lock_class *class; 457 const char *iwmesg; 458 uintptr_t tid, v, x; 459 u_int op, realexslp; 460 int error, ipri, itimo, queue, wakeup_swapper; 461 #ifdef LOCK_PROFILING 462 uint64_t waittime = 0; 463 int contested = 0; 464 #endif 465 #ifdef ADAPTIVE_LOCKMGRS 466 volatile struct thread *owner; 467 u_int i, spintries = 0; 468 #endif 469 470 error = 0; 471 tid = (uintptr_t)curthread; 472 op = (flags & LK_TYPE_MASK); 473 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 474 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 475 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 476 477 MPASS((flags & ~LK_TOTAL_MASK) == 0); 478 KASSERT((op & (op - 1)) == 0, 479 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 480 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 481 (op != LK_DOWNGRADE && op != LK_RELEASE), 482 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 483 __func__, file, line)); 484 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 485 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 486 __func__, file, line)); 487 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 488 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 489 lk->lock_object.lo_name, file, line)); 490 491 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 492 if (panicstr != NULL) { 493 if (flags & LK_INTERLOCK) 494 class->lc_unlock(ilk); 495 return (0); 496 } 497 498 if (lk->lock_object.lo_flags & LK_NOSHARE) { 499 switch (op) { 500 case LK_SHARED: 501 op = LK_EXCLUSIVE; 502 break; 503 case LK_UPGRADE: 504 case LK_TRYUPGRADE: 505 case LK_DOWNGRADE: 506 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 507 file, line); 508 if (flags & LK_INTERLOCK) 509 class->lc_unlock(ilk); 510 return (0); 511 } 512 } 513 514 wakeup_swapper = 0; 515 switch (op) { 516 case LK_SHARED: 517 if (LK_CAN_WITNESS(flags)) 518 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 519 file, line, flags & LK_INTERLOCK ? ilk : NULL); 520 for (;;) { 521 x = lk->lk_lock; 522 523 /* 524 * If no other thread has an exclusive lock, or 525 * no exclusive waiter is present, bump the count of 526 * sharers. Since we have to preserve the state of 527 * waiters, if we fail to acquire the shared lock 528 * loop back and retry. 529 */ 530 if (LK_CAN_SHARE(x, flags)) { 531 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 532 x + LK_ONE_SHARER)) 533 break; 534 continue; 535 } 536 #ifdef HWPMC_HOOKS 537 PMC_SOFT_CALL( , , lock, failed); 538 #endif 539 lock_profile_obtain_lock_failed(&lk->lock_object, 540 &contested, &waittime); 541 542 /* 543 * If the lock is already held by curthread in 544 * exclusive way avoid a deadlock. 545 */ 546 if (LK_HOLDER(x) == tid) { 547 LOCK_LOG2(lk, 548 "%s: %p already held in exclusive mode", 549 __func__, lk); 550 error = EDEADLK; 551 break; 552 } 553 554 /* 555 * If the lock is expected to not sleep just give up 556 * and return. 557 */ 558 if (LK_TRYOP(flags)) { 559 LOCK_LOG2(lk, "%s: %p fails the try operation", 560 __func__, lk); 561 error = EBUSY; 562 break; 563 } 564 565 #ifdef ADAPTIVE_LOCKMGRS 566 /* 567 * If the owner is running on another CPU, spin until 568 * the owner stops running or the state of the lock 569 * changes. We need a double-state handle here 570 * because for a failed acquisition the lock can be 571 * either held in exclusive mode or shared mode 572 * (for the writer starvation avoidance technique). 573 */ 574 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 575 LK_HOLDER(x) != LK_KERNPROC) { 576 owner = (struct thread *)LK_HOLDER(x); 577 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 578 CTR3(KTR_LOCK, 579 "%s: spinning on %p held by %p", 580 __func__, lk, owner); 581 KTR_STATE1(KTR_SCHED, "thread", 582 sched_tdname(td), "spinning", 583 "lockname:\"%s\"", lk->lock_object.lo_name); 584 585 /* 586 * If we are holding also an interlock drop it 587 * in order to avoid a deadlock if the lockmgr 588 * owner is adaptively spinning on the 589 * interlock itself. 590 */ 591 if (flags & LK_INTERLOCK) { 592 class->lc_unlock(ilk); 593 flags &= ~LK_INTERLOCK; 594 } 595 GIANT_SAVE(); 596 while (LK_HOLDER(lk->lk_lock) == 597 (uintptr_t)owner && TD_IS_RUNNING(owner)) 598 cpu_spinwait(); 599 KTR_STATE0(KTR_SCHED, "thread", 600 sched_tdname(td), "running"); 601 GIANT_RESTORE(); 602 continue; 603 } else if (LK_CAN_ADAPT(lk, flags) && 604 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 605 spintries < alk_retries) { 606 KTR_STATE1(KTR_SCHED, "thread", 607 sched_tdname(td), "spinning", 608 "lockname:\"%s\"", lk->lock_object.lo_name); 609 if (flags & LK_INTERLOCK) { 610 class->lc_unlock(ilk); 611 flags &= ~LK_INTERLOCK; 612 } 613 GIANT_SAVE(); 614 spintries++; 615 for (i = 0; i < alk_loops; i++) { 616 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 617 CTR4(KTR_LOCK, 618 "%s: shared spinning on %p with %u and %u", 619 __func__, lk, spintries, i); 620 x = lk->lk_lock; 621 if ((x & LK_SHARE) == 0 || 622 LK_CAN_SHARE(x, flags) != 0) 623 break; 624 cpu_spinwait(); 625 } 626 KTR_STATE0(KTR_SCHED, "thread", 627 sched_tdname(td), "running"); 628 GIANT_RESTORE(); 629 if (i != alk_loops) 630 continue; 631 } 632 #endif 633 634 /* 635 * Acquire the sleepqueue chain lock because we 636 * probabilly will need to manipulate waiters flags. 637 */ 638 sleepq_lock(&lk->lock_object); 639 x = lk->lk_lock; 640 641 /* 642 * if the lock can be acquired in shared mode, try 643 * again. 644 */ 645 if (LK_CAN_SHARE(x, flags)) { 646 sleepq_release(&lk->lock_object); 647 continue; 648 } 649 650 #ifdef ADAPTIVE_LOCKMGRS 651 /* 652 * The current lock owner might have started executing 653 * on another CPU (or the lock could have changed 654 * owner) while we were waiting on the turnstile 655 * chain lock. If so, drop the turnstile lock and try 656 * again. 657 */ 658 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 659 LK_HOLDER(x) != LK_KERNPROC) { 660 owner = (struct thread *)LK_HOLDER(x); 661 if (TD_IS_RUNNING(owner)) { 662 sleepq_release(&lk->lock_object); 663 continue; 664 } 665 } 666 #endif 667 668 /* 669 * Try to set the LK_SHARED_WAITERS flag. If we fail, 670 * loop back and retry. 671 */ 672 if ((x & LK_SHARED_WAITERS) == 0) { 673 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 674 x | LK_SHARED_WAITERS)) { 675 sleepq_release(&lk->lock_object); 676 continue; 677 } 678 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 679 __func__, lk); 680 } 681 682 /* 683 * As far as we have been unable to acquire the 684 * shared lock and the shared waiters flag is set, 685 * we will sleep. 686 */ 687 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 688 SQ_SHARED_QUEUE); 689 flags &= ~LK_INTERLOCK; 690 if (error) { 691 LOCK_LOG3(lk, 692 "%s: interrupted sleep for %p with %d", 693 __func__, lk, error); 694 break; 695 } 696 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 697 __func__, lk); 698 } 699 if (error == 0) { 700 lock_profile_obtain_lock_success(&lk->lock_object, 701 contested, waittime, file, line); 702 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 703 line); 704 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 705 line); 706 TD_LOCKS_INC(curthread); 707 TD_SLOCKS_INC(curthread); 708 STACK_SAVE(lk); 709 } 710 break; 711 case LK_UPGRADE: 712 case LK_TRYUPGRADE: 713 _lockmgr_assert(lk, KA_SLOCKED, file, line); 714 v = lk->lk_lock; 715 x = v & LK_ALL_WAITERS; 716 v &= LK_EXCLUSIVE_SPINNERS; 717 718 /* 719 * Try to switch from one shared lock to an exclusive one. 720 * We need to preserve waiters flags during the operation. 721 */ 722 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 723 tid | x)) { 724 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 725 line); 726 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 727 LK_TRYWIT(flags), file, line); 728 TD_SLOCKS_DEC(curthread); 729 break; 730 } 731 732 /* 733 * In LK_TRYUPGRADE mode, do not drop the lock, 734 * returning EBUSY instead. 735 */ 736 if (op == LK_TRYUPGRADE) { 737 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", 738 __func__, lk); 739 error = EBUSY; 740 break; 741 } 742 743 /* 744 * We have been unable to succeed in upgrading, so just 745 * give up the shared lock. 746 */ 747 wakeup_swapper |= wakeupshlk(lk, file, line); 748 749 /* FALLTHROUGH */ 750 case LK_EXCLUSIVE: 751 if (LK_CAN_WITNESS(flags)) 752 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 753 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 754 ilk : NULL); 755 756 /* 757 * If curthread already holds the lock and this one is 758 * allowed to recurse, simply recurse on it. 759 */ 760 if (lockmgr_xlocked(lk)) { 761 if ((flags & LK_CANRECURSE) == 0 && 762 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 763 764 /* 765 * If the lock is expected to not panic just 766 * give up and return. 767 */ 768 if (LK_TRYOP(flags)) { 769 LOCK_LOG2(lk, 770 "%s: %p fails the try operation", 771 __func__, lk); 772 error = EBUSY; 773 break; 774 } 775 if (flags & LK_INTERLOCK) 776 class->lc_unlock(ilk); 777 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 778 __func__, iwmesg, file, line); 779 } 780 lk->lk_recurse++; 781 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 782 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 783 lk->lk_recurse, file, line); 784 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 785 LK_TRYWIT(flags), file, line); 786 TD_LOCKS_INC(curthread); 787 break; 788 } 789 790 for (;;) { 791 if (lk->lk_lock == LK_UNLOCKED && 792 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 793 break; 794 #ifdef HWPMC_HOOKS 795 PMC_SOFT_CALL( , , lock, failed); 796 #endif 797 lock_profile_obtain_lock_failed(&lk->lock_object, 798 &contested, &waittime); 799 800 /* 801 * If the lock is expected to not sleep just give up 802 * and return. 803 */ 804 if (LK_TRYOP(flags)) { 805 LOCK_LOG2(lk, "%s: %p fails the try operation", 806 __func__, lk); 807 error = EBUSY; 808 break; 809 } 810 811 #ifdef ADAPTIVE_LOCKMGRS 812 /* 813 * If the owner is running on another CPU, spin until 814 * the owner stops running or the state of the lock 815 * changes. 816 */ 817 x = lk->lk_lock; 818 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 819 LK_HOLDER(x) != LK_KERNPROC) { 820 owner = (struct thread *)LK_HOLDER(x); 821 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 822 CTR3(KTR_LOCK, 823 "%s: spinning on %p held by %p", 824 __func__, lk, owner); 825 KTR_STATE1(KTR_SCHED, "thread", 826 sched_tdname(td), "spinning", 827 "lockname:\"%s\"", lk->lock_object.lo_name); 828 829 /* 830 * If we are holding also an interlock drop it 831 * in order to avoid a deadlock if the lockmgr 832 * owner is adaptively spinning on the 833 * interlock itself. 834 */ 835 if (flags & LK_INTERLOCK) { 836 class->lc_unlock(ilk); 837 flags &= ~LK_INTERLOCK; 838 } 839 GIANT_SAVE(); 840 while (LK_HOLDER(lk->lk_lock) == 841 (uintptr_t)owner && TD_IS_RUNNING(owner)) 842 cpu_spinwait(); 843 KTR_STATE0(KTR_SCHED, "thread", 844 sched_tdname(td), "running"); 845 GIANT_RESTORE(); 846 continue; 847 } else if (LK_CAN_ADAPT(lk, flags) && 848 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 849 spintries < alk_retries) { 850 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 851 !atomic_cmpset_ptr(&lk->lk_lock, x, 852 x | LK_EXCLUSIVE_SPINNERS)) 853 continue; 854 KTR_STATE1(KTR_SCHED, "thread", 855 sched_tdname(td), "spinning", 856 "lockname:\"%s\"", lk->lock_object.lo_name); 857 if (flags & LK_INTERLOCK) { 858 class->lc_unlock(ilk); 859 flags &= ~LK_INTERLOCK; 860 } 861 GIANT_SAVE(); 862 spintries++; 863 for (i = 0; i < alk_loops; i++) { 864 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 865 CTR4(KTR_LOCK, 866 "%s: shared spinning on %p with %u and %u", 867 __func__, lk, spintries, i); 868 if ((lk->lk_lock & 869 LK_EXCLUSIVE_SPINNERS) == 0) 870 break; 871 cpu_spinwait(); 872 } 873 KTR_STATE0(KTR_SCHED, "thread", 874 sched_tdname(td), "running"); 875 GIANT_RESTORE(); 876 if (i != alk_loops) 877 continue; 878 } 879 #endif 880 881 /* 882 * Acquire the sleepqueue chain lock because we 883 * probabilly will need to manipulate waiters flags. 884 */ 885 sleepq_lock(&lk->lock_object); 886 x = lk->lk_lock; 887 888 /* 889 * if the lock has been released while we spun on 890 * the sleepqueue chain lock just try again. 891 */ 892 if (x == LK_UNLOCKED) { 893 sleepq_release(&lk->lock_object); 894 continue; 895 } 896 897 #ifdef ADAPTIVE_LOCKMGRS 898 /* 899 * The current lock owner might have started executing 900 * on another CPU (or the lock could have changed 901 * owner) while we were waiting on the turnstile 902 * chain lock. If so, drop the turnstile lock and try 903 * again. 904 */ 905 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 906 LK_HOLDER(x) != LK_KERNPROC) { 907 owner = (struct thread *)LK_HOLDER(x); 908 if (TD_IS_RUNNING(owner)) { 909 sleepq_release(&lk->lock_object); 910 continue; 911 } 912 } 913 #endif 914 915 /* 916 * The lock can be in the state where there is a 917 * pending queue of waiters, but still no owner. 918 * This happens when the lock is contested and an 919 * owner is going to claim the lock. 920 * If curthread is the one successfully acquiring it 921 * claim lock ownership and return, preserving waiters 922 * flags. 923 */ 924 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 925 if ((x & ~v) == LK_UNLOCKED) { 926 v &= ~LK_EXCLUSIVE_SPINNERS; 927 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 928 tid | v)) { 929 sleepq_release(&lk->lock_object); 930 LOCK_LOG2(lk, 931 "%s: %p claimed by a new writer", 932 __func__, lk); 933 break; 934 } 935 sleepq_release(&lk->lock_object); 936 continue; 937 } 938 939 /* 940 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 941 * fail, loop back and retry. 942 */ 943 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 944 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 945 x | LK_EXCLUSIVE_WAITERS)) { 946 sleepq_release(&lk->lock_object); 947 continue; 948 } 949 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 950 __func__, lk); 951 } 952 953 /* 954 * As far as we have been unable to acquire the 955 * exclusive lock and the exclusive waiters flag 956 * is set, we will sleep. 957 */ 958 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 959 SQ_EXCLUSIVE_QUEUE); 960 flags &= ~LK_INTERLOCK; 961 if (error) { 962 LOCK_LOG3(lk, 963 "%s: interrupted sleep for %p with %d", 964 __func__, lk, error); 965 break; 966 } 967 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 968 __func__, lk); 969 } 970 if (error == 0) { 971 lock_profile_obtain_lock_success(&lk->lock_object, 972 contested, waittime, file, line); 973 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 974 lk->lk_recurse, file, line); 975 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 976 LK_TRYWIT(flags), file, line); 977 TD_LOCKS_INC(curthread); 978 STACK_SAVE(lk); 979 } 980 break; 981 case LK_DOWNGRADE: 982 _lockmgr_assert(lk, KA_XLOCKED, file, line); 983 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 984 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 985 986 /* 987 * Panic if the lock is recursed. 988 */ 989 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 990 if (flags & LK_INTERLOCK) 991 class->lc_unlock(ilk); 992 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 993 __func__, iwmesg, file, line); 994 } 995 TD_SLOCKS_INC(curthread); 996 997 /* 998 * In order to preserve waiters flags, just spin. 999 */ 1000 for (;;) { 1001 x = lk->lk_lock; 1002 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1003 x &= LK_ALL_WAITERS; 1004 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1005 LK_SHARERS_LOCK(1) | x)) 1006 break; 1007 cpu_spinwait(); 1008 } 1009 break; 1010 case LK_RELEASE: 1011 _lockmgr_assert(lk, KA_LOCKED, file, line); 1012 x = lk->lk_lock; 1013 1014 if ((x & LK_SHARE) == 0) { 1015 1016 /* 1017 * As first option, treact the lock as if it has not 1018 * any waiter. 1019 * Fix-up the tid var if the lock has been disowned. 1020 */ 1021 if (LK_HOLDER(x) == LK_KERNPROC) 1022 tid = LK_KERNPROC; 1023 else { 1024 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 1025 file, line); 1026 TD_LOCKS_DEC(curthread); 1027 } 1028 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 1029 lk->lk_recurse, file, line); 1030 1031 /* 1032 * The lock is held in exclusive mode. 1033 * If the lock is recursed also, then unrecurse it. 1034 */ 1035 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 1036 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 1037 lk); 1038 lk->lk_recurse--; 1039 break; 1040 } 1041 if (tid != LK_KERNPROC) 1042 lock_profile_release_lock(&lk->lock_object); 1043 1044 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 1045 LK_UNLOCKED)) 1046 break; 1047 1048 sleepq_lock(&lk->lock_object); 1049 x = lk->lk_lock; 1050 v = LK_UNLOCKED; 1051 1052 /* 1053 * If the lock has exclusive waiters, give them 1054 * preference in order to avoid deadlock with 1055 * shared runners up. 1056 * If interruptible sleeps left the exclusive queue 1057 * empty avoid a starvation for the threads sleeping 1058 * on the shared queue by giving them precedence 1059 * and cleaning up the exclusive waiters bit anyway. 1060 * Please note that lk_exslpfail count may be lying 1061 * about the real number of waiters with the 1062 * LK_SLEEPFAIL flag on because they may be used in 1063 * conjunction with interruptible sleeps so 1064 * lk_exslpfail might be considered an 'upper limit' 1065 * bound, including the edge cases. 1066 */ 1067 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1068 realexslp = sleepq_sleepcnt(&lk->lock_object, 1069 SQ_EXCLUSIVE_QUEUE); 1070 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1071 if (lk->lk_exslpfail < realexslp) { 1072 lk->lk_exslpfail = 0; 1073 queue = SQ_EXCLUSIVE_QUEUE; 1074 v |= (x & LK_SHARED_WAITERS); 1075 } else { 1076 lk->lk_exslpfail = 0; 1077 LOCK_LOG2(lk, 1078 "%s: %p has only LK_SLEEPFAIL sleepers", 1079 __func__, lk); 1080 LOCK_LOG2(lk, 1081 "%s: %p waking up threads on the exclusive queue", 1082 __func__, lk); 1083 wakeup_swapper = 1084 sleepq_broadcast(&lk->lock_object, 1085 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1086 queue = SQ_SHARED_QUEUE; 1087 } 1088 } else { 1089 1090 /* 1091 * Exclusive waiters sleeping with LK_SLEEPFAIL 1092 * on and using interruptible sleeps/timeout 1093 * may have left spourious lk_exslpfail counts 1094 * on, so clean it up anyway. 1095 */ 1096 lk->lk_exslpfail = 0; 1097 queue = SQ_SHARED_QUEUE; 1098 } 1099 1100 LOCK_LOG3(lk, 1101 "%s: %p waking up threads on the %s queue", 1102 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1103 "exclusive"); 1104 atomic_store_rel_ptr(&lk->lk_lock, v); 1105 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1106 SLEEPQ_LK, 0, queue); 1107 sleepq_release(&lk->lock_object); 1108 break; 1109 } else 1110 wakeup_swapper = wakeupshlk(lk, file, line); 1111 break; 1112 case LK_DRAIN: 1113 if (LK_CAN_WITNESS(flags)) 1114 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1115 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 1116 ilk : NULL); 1117 1118 /* 1119 * Trying to drain a lock we already own will result in a 1120 * deadlock. 1121 */ 1122 if (lockmgr_xlocked(lk)) { 1123 if (flags & LK_INTERLOCK) 1124 class->lc_unlock(ilk); 1125 panic("%s: draining %s with the lock held @ %s:%d\n", 1126 __func__, iwmesg, file, line); 1127 } 1128 1129 for (;;) { 1130 if (lk->lk_lock == LK_UNLOCKED && 1131 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 1132 break; 1133 1134 #ifdef HWPMC_HOOKS 1135 PMC_SOFT_CALL( , , lock, failed); 1136 #endif 1137 lock_profile_obtain_lock_failed(&lk->lock_object, 1138 &contested, &waittime); 1139 1140 /* 1141 * If the lock is expected to not sleep just give up 1142 * and return. 1143 */ 1144 if (LK_TRYOP(flags)) { 1145 LOCK_LOG2(lk, "%s: %p fails the try operation", 1146 __func__, lk); 1147 error = EBUSY; 1148 break; 1149 } 1150 1151 /* 1152 * Acquire the sleepqueue chain lock because we 1153 * probabilly will need to manipulate waiters flags. 1154 */ 1155 sleepq_lock(&lk->lock_object); 1156 x = lk->lk_lock; 1157 1158 /* 1159 * if the lock has been released while we spun on 1160 * the sleepqueue chain lock just try again. 1161 */ 1162 if (x == LK_UNLOCKED) { 1163 sleepq_release(&lk->lock_object); 1164 continue; 1165 } 1166 1167 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1168 if ((x & ~v) == LK_UNLOCKED) { 1169 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1170 1171 /* 1172 * If interruptible sleeps left the exclusive 1173 * queue empty avoid a starvation for the 1174 * threads sleeping on the shared queue by 1175 * giving them precedence and cleaning up the 1176 * exclusive waiters bit anyway. 1177 * Please note that lk_exslpfail count may be 1178 * lying about the real number of waiters with 1179 * the LK_SLEEPFAIL flag on because they may 1180 * be used in conjunction with interruptible 1181 * sleeps so lk_exslpfail might be considered 1182 * an 'upper limit' bound, including the edge 1183 * cases. 1184 */ 1185 if (v & LK_EXCLUSIVE_WAITERS) { 1186 queue = SQ_EXCLUSIVE_QUEUE; 1187 v &= ~LK_EXCLUSIVE_WAITERS; 1188 } else { 1189 1190 /* 1191 * Exclusive waiters sleeping with 1192 * LK_SLEEPFAIL on and using 1193 * interruptible sleeps/timeout may 1194 * have left spourious lk_exslpfail 1195 * counts on, so clean it up anyway. 1196 */ 1197 MPASS(v & LK_SHARED_WAITERS); 1198 lk->lk_exslpfail = 0; 1199 queue = SQ_SHARED_QUEUE; 1200 v &= ~LK_SHARED_WAITERS; 1201 } 1202 if (queue == SQ_EXCLUSIVE_QUEUE) { 1203 realexslp = 1204 sleepq_sleepcnt(&lk->lock_object, 1205 SQ_EXCLUSIVE_QUEUE); 1206 if (lk->lk_exslpfail >= realexslp) { 1207 lk->lk_exslpfail = 0; 1208 queue = SQ_SHARED_QUEUE; 1209 v &= ~LK_SHARED_WAITERS; 1210 if (realexslp != 0) { 1211 LOCK_LOG2(lk, 1212 "%s: %p has only LK_SLEEPFAIL sleepers", 1213 __func__, lk); 1214 LOCK_LOG2(lk, 1215 "%s: %p waking up threads on the exclusive queue", 1216 __func__, lk); 1217 wakeup_swapper = 1218 sleepq_broadcast( 1219 &lk->lock_object, 1220 SLEEPQ_LK, 0, 1221 SQ_EXCLUSIVE_QUEUE); 1222 } 1223 } else 1224 lk->lk_exslpfail = 0; 1225 } 1226 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1227 sleepq_release(&lk->lock_object); 1228 continue; 1229 } 1230 LOCK_LOG3(lk, 1231 "%s: %p waking up all threads on the %s queue", 1232 __func__, lk, queue == SQ_SHARED_QUEUE ? 1233 "shared" : "exclusive"); 1234 wakeup_swapper |= sleepq_broadcast( 1235 &lk->lock_object, SLEEPQ_LK, 0, queue); 1236 1237 /* 1238 * If shared waiters have been woken up we need 1239 * to wait for one of them to acquire the lock 1240 * before to set the exclusive waiters in 1241 * order to avoid a deadlock. 1242 */ 1243 if (queue == SQ_SHARED_QUEUE) { 1244 for (v = lk->lk_lock; 1245 (v & LK_SHARE) && !LK_SHARERS(v); 1246 v = lk->lk_lock) 1247 cpu_spinwait(); 1248 } 1249 } 1250 1251 /* 1252 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1253 * fail, loop back and retry. 1254 */ 1255 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1256 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1257 x | LK_EXCLUSIVE_WAITERS)) { 1258 sleepq_release(&lk->lock_object); 1259 continue; 1260 } 1261 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1262 __func__, lk); 1263 } 1264 1265 /* 1266 * As far as we have been unable to acquire the 1267 * exclusive lock and the exclusive waiters flag 1268 * is set, we will sleep. 1269 */ 1270 if (flags & LK_INTERLOCK) { 1271 class->lc_unlock(ilk); 1272 flags &= ~LK_INTERLOCK; 1273 } 1274 GIANT_SAVE(); 1275 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1276 SQ_EXCLUSIVE_QUEUE); 1277 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1278 GIANT_RESTORE(); 1279 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1280 __func__, lk); 1281 } 1282 1283 if (error == 0) { 1284 lock_profile_obtain_lock_success(&lk->lock_object, 1285 contested, waittime, file, line); 1286 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1287 lk->lk_recurse, file, line); 1288 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1289 LK_TRYWIT(flags), file, line); 1290 TD_LOCKS_INC(curthread); 1291 STACK_SAVE(lk); 1292 } 1293 break; 1294 default: 1295 if (flags & LK_INTERLOCK) 1296 class->lc_unlock(ilk); 1297 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1298 } 1299 1300 if (flags & LK_INTERLOCK) 1301 class->lc_unlock(ilk); 1302 if (wakeup_swapper) 1303 kick_proc0(); 1304 1305 return (error); 1306 } 1307 1308 void 1309 _lockmgr_disown(struct lock *lk, const char *file, int line) 1310 { 1311 uintptr_t tid, x; 1312 1313 if (SCHEDULER_STOPPED()) 1314 return; 1315 1316 tid = (uintptr_t)curthread; 1317 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1318 1319 /* 1320 * Panic if the lock is recursed. 1321 */ 1322 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1323 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1324 __func__, file, line); 1325 1326 /* 1327 * If the owner is already LK_KERNPROC just skip the whole operation. 1328 */ 1329 if (LK_HOLDER(lk->lk_lock) != tid) 1330 return; 1331 lock_profile_release_lock(&lk->lock_object); 1332 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1333 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1334 TD_LOCKS_DEC(curthread); 1335 STACK_SAVE(lk); 1336 1337 /* 1338 * In order to preserve waiters flags, just spin. 1339 */ 1340 for (;;) { 1341 x = lk->lk_lock; 1342 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1343 x &= LK_ALL_WAITERS; 1344 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1345 LK_KERNPROC | x)) 1346 return; 1347 cpu_spinwait(); 1348 } 1349 } 1350 1351 void 1352 lockmgr_printinfo(const struct lock *lk) 1353 { 1354 struct thread *td; 1355 uintptr_t x; 1356 1357 if (lk->lk_lock == LK_UNLOCKED) 1358 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1359 else if (lk->lk_lock & LK_SHARE) 1360 printf("lock type %s: SHARED (count %ju)\n", 1361 lk->lock_object.lo_name, 1362 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1363 else { 1364 td = lockmgr_xholder(lk); 1365 if (td == (struct thread *)LK_KERNPROC) 1366 printf("lock type %s: EXCL by KERNPROC\n", 1367 lk->lock_object.lo_name); 1368 else 1369 printf("lock type %s: EXCL by thread %p " 1370 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, 1371 td, td->td_proc->p_pid, td->td_proc->p_comm, 1372 td->td_tid); 1373 } 1374 1375 x = lk->lk_lock; 1376 if (x & LK_EXCLUSIVE_WAITERS) 1377 printf(" with exclusive waiters pending\n"); 1378 if (x & LK_SHARED_WAITERS) 1379 printf(" with shared waiters pending\n"); 1380 if (x & LK_EXCLUSIVE_SPINNERS) 1381 printf(" with exclusive spinners pending\n"); 1382 1383 STACK_PRINT(lk); 1384 } 1385 1386 int 1387 lockstatus(const struct lock *lk) 1388 { 1389 uintptr_t v, x; 1390 int ret; 1391 1392 ret = LK_SHARED; 1393 x = lk->lk_lock; 1394 v = LK_HOLDER(x); 1395 1396 if ((x & LK_SHARE) == 0) { 1397 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1398 ret = LK_EXCLUSIVE; 1399 else 1400 ret = LK_EXCLOTHER; 1401 } else if (x == LK_UNLOCKED) 1402 ret = 0; 1403 1404 return (ret); 1405 } 1406 1407 #ifdef INVARIANT_SUPPORT 1408 1409 FEATURE(invariant_support, 1410 "Support for modules compiled with INVARIANTS option"); 1411 1412 #ifndef INVARIANTS 1413 #undef _lockmgr_assert 1414 #endif 1415 1416 void 1417 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1418 { 1419 int slocked = 0; 1420 1421 if (panicstr != NULL) 1422 return; 1423 switch (what) { 1424 case KA_SLOCKED: 1425 case KA_SLOCKED | KA_NOTRECURSED: 1426 case KA_SLOCKED | KA_RECURSED: 1427 slocked = 1; 1428 case KA_LOCKED: 1429 case KA_LOCKED | KA_NOTRECURSED: 1430 case KA_LOCKED | KA_RECURSED: 1431 #ifdef WITNESS 1432 1433 /* 1434 * We cannot trust WITNESS if the lock is held in exclusive 1435 * mode and a call to lockmgr_disown() happened. 1436 * Workaround this skipping the check if the lock is held in 1437 * exclusive mode even for the KA_LOCKED case. 1438 */ 1439 if (slocked || (lk->lk_lock & LK_SHARE)) { 1440 witness_assert(&lk->lock_object, what, file, line); 1441 break; 1442 } 1443 #endif 1444 if (lk->lk_lock == LK_UNLOCKED || 1445 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1446 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1447 panic("Lock %s not %slocked @ %s:%d\n", 1448 lk->lock_object.lo_name, slocked ? "share" : "", 1449 file, line); 1450 1451 if ((lk->lk_lock & LK_SHARE) == 0) { 1452 if (lockmgr_recursed(lk)) { 1453 if (what & KA_NOTRECURSED) 1454 panic("Lock %s recursed @ %s:%d\n", 1455 lk->lock_object.lo_name, file, 1456 line); 1457 } else if (what & KA_RECURSED) 1458 panic("Lock %s not recursed @ %s:%d\n", 1459 lk->lock_object.lo_name, file, line); 1460 } 1461 break; 1462 case KA_XLOCKED: 1463 case KA_XLOCKED | KA_NOTRECURSED: 1464 case KA_XLOCKED | KA_RECURSED: 1465 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1466 panic("Lock %s not exclusively locked @ %s:%d\n", 1467 lk->lock_object.lo_name, file, line); 1468 if (lockmgr_recursed(lk)) { 1469 if (what & KA_NOTRECURSED) 1470 panic("Lock %s recursed @ %s:%d\n", 1471 lk->lock_object.lo_name, file, line); 1472 } else if (what & KA_RECURSED) 1473 panic("Lock %s not recursed @ %s:%d\n", 1474 lk->lock_object.lo_name, file, line); 1475 break; 1476 case KA_UNLOCKED: 1477 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1478 panic("Lock %s exclusively locked @ %s:%d\n", 1479 lk->lock_object.lo_name, file, line); 1480 break; 1481 default: 1482 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1483 line); 1484 } 1485 } 1486 #endif 1487 1488 #ifdef DDB 1489 int 1490 lockmgr_chain(struct thread *td, struct thread **ownerp) 1491 { 1492 struct lock *lk; 1493 1494 lk = td->td_wchan; 1495 1496 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1497 return (0); 1498 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1499 if (lk->lk_lock & LK_SHARE) 1500 db_printf("SHARED (count %ju)\n", 1501 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1502 else 1503 db_printf("EXCL\n"); 1504 *ownerp = lockmgr_xholder(lk); 1505 1506 return (1); 1507 } 1508 1509 static void 1510 db_show_lockmgr(const struct lock_object *lock) 1511 { 1512 struct thread *td; 1513 const struct lock *lk; 1514 1515 lk = (const struct lock *)lock; 1516 1517 db_printf(" state: "); 1518 if (lk->lk_lock == LK_UNLOCKED) 1519 db_printf("UNLOCKED\n"); 1520 else if (lk->lk_lock & LK_SHARE) 1521 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1522 else { 1523 td = lockmgr_xholder(lk); 1524 if (td == (struct thread *)LK_KERNPROC) 1525 db_printf("XLOCK: LK_KERNPROC\n"); 1526 else 1527 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1528 td->td_tid, td->td_proc->p_pid, 1529 td->td_proc->p_comm); 1530 if (lockmgr_recursed(lk)) 1531 db_printf(" recursed: %d\n", lk->lk_recurse); 1532 } 1533 db_printf(" waiters: "); 1534 switch (lk->lk_lock & LK_ALL_WAITERS) { 1535 case LK_SHARED_WAITERS: 1536 db_printf("shared\n"); 1537 break; 1538 case LK_EXCLUSIVE_WAITERS: 1539 db_printf("exclusive\n"); 1540 break; 1541 case LK_ALL_WAITERS: 1542 db_printf("shared and exclusive\n"); 1543 break; 1544 default: 1545 db_printf("none\n"); 1546 } 1547 db_printf(" spinners: "); 1548 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1549 db_printf("exclusive\n"); 1550 else 1551 db_printf("none\n"); 1552 } 1553 #endif
Cache object: c69303937d2ef307f96532e3ce0b636c
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