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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/10.4/sys/kern/kern_lock.c 310979 2016-12-31 16:37:47Z mjg $"); 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, flags) \ 120 (((x) & LK_SHARE) && \ 121 (((x) & (LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) == 0 || \ 122 (curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) || \ 123 (curthread->td_pflags & TDP_DEADLKTREAT))) 124 #define LK_TRYOP(x) \ 125 ((x) & LK_NOWAIT) 126 127 #define LK_CAN_WITNESS(x) \ 128 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 129 #define LK_TRYWIT(x) \ 130 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 131 132 #define LK_CAN_ADAPT(lk, f) \ 133 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 134 ((f) & LK_SLEEPFAIL) == 0) 135 136 #define lockmgr_disowned(lk) \ 137 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 138 139 #define lockmgr_xlocked(lk) \ 140 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 141 142 static void assert_lockmgr(const struct lock_object *lock, int how); 143 #ifdef DDB 144 static void db_show_lockmgr(const struct lock_object *lock); 145 #endif 146 static void lock_lockmgr(struct lock_object *lock, uintptr_t how); 147 #ifdef KDTRACE_HOOKS 148 static int owner_lockmgr(const struct lock_object *lock, 149 struct thread **owner); 150 #endif 151 static uintptr_t unlock_lockmgr(struct lock_object *lock); 152 153 struct lock_class lock_class_lockmgr = { 154 .lc_name = "lockmgr", 155 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 156 .lc_assert = assert_lockmgr, 157 #ifdef DDB 158 .lc_ddb_show = db_show_lockmgr, 159 #endif 160 .lc_lock = lock_lockmgr, 161 .lc_unlock = unlock_lockmgr, 162 #ifdef KDTRACE_HOOKS 163 .lc_owner = owner_lockmgr, 164 #endif 165 }; 166 167 #ifdef ADAPTIVE_LOCKMGRS 168 static u_int alk_retries = 10; 169 static u_int alk_loops = 10000; 170 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, 171 "lockmgr debugging"); 172 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, ""); 173 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, ""); 174 #endif 175 176 static __inline struct thread * 177 lockmgr_xholder(const struct lock *lk) 178 { 179 uintptr_t x; 180 181 x = lk->lk_lock; 182 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 183 } 184 185 /* 186 * It assumes sleepq_lock held and returns with this one unheld. 187 * It also assumes the generic interlock is sane and previously checked. 188 * If LK_INTERLOCK is specified the interlock is not reacquired after the 189 * sleep. 190 */ 191 static __inline int 192 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 193 const char *wmesg, int pri, int timo, int queue) 194 { 195 GIANT_DECLARE; 196 struct lock_class *class; 197 int catch, error; 198 199 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 200 catch = pri & PCATCH; 201 pri &= PRIMASK; 202 error = 0; 203 204 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 205 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 206 207 if (flags & LK_INTERLOCK) 208 class->lc_unlock(ilk); 209 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 210 lk->lk_exslpfail++; 211 GIANT_SAVE(); 212 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 213 SLEEPQ_INTERRUPTIBLE : 0), queue); 214 if ((flags & LK_TIMELOCK) && timo) 215 sleepq_set_timeout(&lk->lock_object, timo); 216 217 /* 218 * Decisional switch for real sleeping. 219 */ 220 if ((flags & LK_TIMELOCK) && timo && catch) 221 error = sleepq_timedwait_sig(&lk->lock_object, pri); 222 else if ((flags & LK_TIMELOCK) && timo) 223 error = sleepq_timedwait(&lk->lock_object, pri); 224 else if (catch) 225 error = sleepq_wait_sig(&lk->lock_object, pri); 226 else 227 sleepq_wait(&lk->lock_object, pri); 228 GIANT_RESTORE(); 229 if ((flags & LK_SLEEPFAIL) && error == 0) 230 error = ENOLCK; 231 232 return (error); 233 } 234 235 static __inline int 236 wakeupshlk(struct lock *lk, const char *file, int line) 237 { 238 uintptr_t v, x; 239 u_int realexslp; 240 int queue, wakeup_swapper; 241 242 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 243 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 244 245 wakeup_swapper = 0; 246 for (;;) { 247 x = lk->lk_lock; 248 249 /* 250 * If there is more than one shared lock held, just drop one 251 * and return. 252 */ 253 if (LK_SHARERS(x) > 1) { 254 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, 255 x - LK_ONE_SHARER)) 256 break; 257 continue; 258 } 259 260 /* 261 * If there are not waiters on the exclusive queue, drop the 262 * lock quickly. 263 */ 264 if ((x & LK_ALL_WAITERS) == 0) { 265 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == 266 LK_SHARERS_LOCK(1)); 267 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED)) 268 break; 269 continue; 270 } 271 272 /* 273 * We should have a sharer with waiters, so enter the hard 274 * path in order to handle wakeups correctly. 275 */ 276 sleepq_lock(&lk->lock_object); 277 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 278 v = LK_UNLOCKED; 279 280 /* 281 * If the lock has exclusive waiters, give them preference in 282 * order to avoid deadlock with shared runners up. 283 * If interruptible sleeps left the exclusive queue empty 284 * avoid a starvation for the threads sleeping on the shared 285 * queue by giving them precedence and cleaning up the 286 * exclusive waiters bit anyway. 287 * Please note that lk_exslpfail count may be lying about 288 * the real number of waiters with the LK_SLEEPFAIL flag on 289 * because they may be used in conjunction with interruptible 290 * sleeps so lk_exslpfail might be considered an 'upper limit' 291 * bound, including the edge cases. 292 */ 293 realexslp = sleepq_sleepcnt(&lk->lock_object, 294 SQ_EXCLUSIVE_QUEUE); 295 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 296 if (lk->lk_exslpfail < realexslp) { 297 lk->lk_exslpfail = 0; 298 queue = SQ_EXCLUSIVE_QUEUE; 299 v |= (x & LK_SHARED_WAITERS); 300 } else { 301 lk->lk_exslpfail = 0; 302 LOCK_LOG2(lk, 303 "%s: %p has only LK_SLEEPFAIL sleepers", 304 __func__, lk); 305 LOCK_LOG2(lk, 306 "%s: %p waking up threads on the exclusive queue", 307 __func__, lk); 308 wakeup_swapper = 309 sleepq_broadcast(&lk->lock_object, 310 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 311 queue = SQ_SHARED_QUEUE; 312 } 313 314 } else { 315 316 /* 317 * Exclusive waiters sleeping with LK_SLEEPFAIL on 318 * and using interruptible sleeps/timeout may have 319 * left spourious lk_exslpfail counts on, so clean 320 * it up anyway. 321 */ 322 lk->lk_exslpfail = 0; 323 queue = SQ_SHARED_QUEUE; 324 } 325 326 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, 327 v)) { 328 sleepq_release(&lk->lock_object); 329 continue; 330 } 331 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 332 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 333 "exclusive"); 334 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 335 0, queue); 336 sleepq_release(&lk->lock_object); 337 break; 338 } 339 340 lock_profile_release_lock(&lk->lock_object); 341 TD_LOCKS_DEC(curthread); 342 TD_SLOCKS_DEC(curthread); 343 return (wakeup_swapper); 344 } 345 346 static void 347 assert_lockmgr(const struct lock_object *lock, int what) 348 { 349 350 panic("lockmgr locks do not support assertions"); 351 } 352 353 static void 354 lock_lockmgr(struct lock_object *lock, uintptr_t how) 355 { 356 357 panic("lockmgr locks do not support sleep interlocking"); 358 } 359 360 static uintptr_t 361 unlock_lockmgr(struct lock_object *lock) 362 { 363 364 panic("lockmgr locks do not support sleep interlocking"); 365 } 366 367 #ifdef KDTRACE_HOOKS 368 static int 369 owner_lockmgr(const struct lock_object *lock, struct thread **owner) 370 { 371 372 panic("lockmgr locks do not support owner inquiring"); 373 } 374 #endif 375 376 void 377 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 378 { 379 int iflags; 380 381 MPASS((flags & ~LK_INIT_MASK) == 0); 382 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 383 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 384 &lk->lk_lock)); 385 386 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 387 if (flags & LK_CANRECURSE) 388 iflags |= LO_RECURSABLE; 389 if ((flags & LK_NODUP) == 0) 390 iflags |= LO_DUPOK; 391 if (flags & LK_NOPROFILE) 392 iflags |= LO_NOPROFILE; 393 if ((flags & LK_NOWITNESS) == 0) 394 iflags |= LO_WITNESS; 395 if (flags & LK_QUIET) 396 iflags |= LO_QUIET; 397 if (flags & LK_IS_VNODE) 398 iflags |= LO_IS_VNODE; 399 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 400 401 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 402 lk->lk_lock = LK_UNLOCKED; 403 lk->lk_recurse = 0; 404 lk->lk_exslpfail = 0; 405 lk->lk_timo = timo; 406 lk->lk_pri = pri; 407 STACK_ZERO(lk); 408 } 409 410 /* 411 * XXX: Gross hacks to manipulate external lock flags after 412 * initialization. Used for certain vnode and buf locks. 413 */ 414 void 415 lockallowshare(struct lock *lk) 416 { 417 418 lockmgr_assert(lk, KA_XLOCKED); 419 lk->lock_object.lo_flags &= ~LK_NOSHARE; 420 } 421 422 void 423 lockdisableshare(struct lock *lk) 424 { 425 426 lockmgr_assert(lk, KA_XLOCKED); 427 lk->lock_object.lo_flags |= LK_NOSHARE; 428 } 429 430 void 431 lockallowrecurse(struct lock *lk) 432 { 433 434 lockmgr_assert(lk, KA_XLOCKED); 435 lk->lock_object.lo_flags |= LO_RECURSABLE; 436 } 437 438 void 439 lockdisablerecurse(struct lock *lk) 440 { 441 442 lockmgr_assert(lk, KA_XLOCKED); 443 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 444 } 445 446 void 447 lockdestroy(struct lock *lk) 448 { 449 450 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 451 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 452 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 453 lock_destroy(&lk->lock_object); 454 } 455 456 int 457 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 458 const char *wmesg, int pri, int timo, const char *file, int line) 459 { 460 GIANT_DECLARE; 461 struct lock_class *class; 462 const char *iwmesg; 463 uintptr_t tid, v, x; 464 u_int op, realexslp; 465 int error, ipri, itimo, queue, wakeup_swapper; 466 #ifdef LOCK_PROFILING 467 uint64_t waittime = 0; 468 int contested = 0; 469 #endif 470 #ifdef ADAPTIVE_LOCKMGRS 471 volatile struct thread *owner; 472 u_int i, spintries = 0; 473 #endif 474 475 error = 0; 476 tid = (uintptr_t)curthread; 477 op = (flags & LK_TYPE_MASK); 478 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 479 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 480 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 481 482 MPASS((flags & ~LK_TOTAL_MASK) == 0); 483 KASSERT((op & (op - 1)) == 0, 484 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 485 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 486 (op != LK_DOWNGRADE && op != LK_RELEASE), 487 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 488 __func__, file, line)); 489 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 490 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 491 __func__, file, line)); 492 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 493 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 494 lk->lock_object.lo_name, file, line)); 495 496 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 497 if (panicstr != NULL) { 498 if (flags & LK_INTERLOCK) 499 class->lc_unlock(ilk); 500 return (0); 501 } 502 503 if (lk->lock_object.lo_flags & LK_NOSHARE) { 504 switch (op) { 505 case LK_SHARED: 506 op = LK_EXCLUSIVE; 507 break; 508 case LK_UPGRADE: 509 case LK_TRYUPGRADE: 510 case LK_DOWNGRADE: 511 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 512 file, line); 513 if (flags & LK_INTERLOCK) 514 class->lc_unlock(ilk); 515 return (0); 516 } 517 } 518 519 wakeup_swapper = 0; 520 switch (op) { 521 case LK_SHARED: 522 if (LK_CAN_WITNESS(flags)) 523 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 524 file, line, flags & LK_INTERLOCK ? ilk : NULL); 525 for (;;) { 526 x = lk->lk_lock; 527 528 /* 529 * If no other thread has an exclusive lock, or 530 * no exclusive waiter is present, bump the count of 531 * sharers. Since we have to preserve the state of 532 * waiters, if we fail to acquire the shared lock 533 * loop back and retry. 534 */ 535 if (LK_CAN_SHARE(x, flags)) { 536 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 537 x + LK_ONE_SHARER)) 538 break; 539 continue; 540 } 541 #ifdef HWPMC_HOOKS 542 PMC_SOFT_CALL( , , lock, failed); 543 #endif 544 lock_profile_obtain_lock_failed(&lk->lock_object, 545 &contested, &waittime); 546 547 /* 548 * If the lock is already held by curthread in 549 * exclusive way avoid a deadlock. 550 */ 551 if (LK_HOLDER(x) == tid) { 552 LOCK_LOG2(lk, 553 "%s: %p already held in exclusive mode", 554 __func__, lk); 555 error = EDEADLK; 556 break; 557 } 558 559 /* 560 * If the lock is expected to not sleep just give up 561 * and return. 562 */ 563 if (LK_TRYOP(flags)) { 564 LOCK_LOG2(lk, "%s: %p fails the try operation", 565 __func__, lk); 566 error = EBUSY; 567 break; 568 } 569 570 #ifdef ADAPTIVE_LOCKMGRS 571 /* 572 * If the owner is running on another CPU, spin until 573 * the owner stops running or the state of the lock 574 * changes. We need a double-state handle here 575 * because for a failed acquisition the lock can be 576 * either held in exclusive mode or shared mode 577 * (for the writer starvation avoidance technique). 578 */ 579 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 580 LK_HOLDER(x) != LK_KERNPROC) { 581 owner = (struct thread *)LK_HOLDER(x); 582 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 583 CTR3(KTR_LOCK, 584 "%s: spinning on %p held by %p", 585 __func__, lk, owner); 586 KTR_STATE1(KTR_SCHED, "thread", 587 sched_tdname(td), "spinning", 588 "lockname:\"%s\"", lk->lock_object.lo_name); 589 590 /* 591 * If we are holding also an interlock drop it 592 * in order to avoid a deadlock if the lockmgr 593 * owner is adaptively spinning on the 594 * interlock itself. 595 */ 596 if (flags & LK_INTERLOCK) { 597 class->lc_unlock(ilk); 598 flags &= ~LK_INTERLOCK; 599 } 600 GIANT_SAVE(); 601 while (LK_HOLDER(lk->lk_lock) == 602 (uintptr_t)owner && TD_IS_RUNNING(owner)) 603 cpu_spinwait(); 604 KTR_STATE0(KTR_SCHED, "thread", 605 sched_tdname(td), "running"); 606 GIANT_RESTORE(); 607 continue; 608 } else if (LK_CAN_ADAPT(lk, flags) && 609 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 610 spintries < alk_retries) { 611 KTR_STATE1(KTR_SCHED, "thread", 612 sched_tdname(td), "spinning", 613 "lockname:\"%s\"", lk->lock_object.lo_name); 614 if (flags & LK_INTERLOCK) { 615 class->lc_unlock(ilk); 616 flags &= ~LK_INTERLOCK; 617 } 618 GIANT_SAVE(); 619 spintries++; 620 for (i = 0; i < alk_loops; i++) { 621 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 622 CTR4(KTR_LOCK, 623 "%s: shared spinning on %p with %u and %u", 624 __func__, lk, spintries, i); 625 x = lk->lk_lock; 626 if ((x & LK_SHARE) == 0 || 627 LK_CAN_SHARE(x, flags) != 0) 628 break; 629 cpu_spinwait(); 630 } 631 KTR_STATE0(KTR_SCHED, "thread", 632 sched_tdname(td), "running"); 633 GIANT_RESTORE(); 634 if (i != alk_loops) 635 continue; 636 } 637 #endif 638 639 /* 640 * Acquire the sleepqueue chain lock because we 641 * probabilly will need to manipulate waiters flags. 642 */ 643 sleepq_lock(&lk->lock_object); 644 x = lk->lk_lock; 645 646 /* 647 * if the lock can be acquired in shared mode, try 648 * again. 649 */ 650 if (LK_CAN_SHARE(x, flags)) { 651 sleepq_release(&lk->lock_object); 652 continue; 653 } 654 655 #ifdef ADAPTIVE_LOCKMGRS 656 /* 657 * The current lock owner might have started executing 658 * on another CPU (or the lock could have changed 659 * owner) while we were waiting on the turnstile 660 * chain lock. If so, drop the turnstile lock and try 661 * again. 662 */ 663 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 664 LK_HOLDER(x) != LK_KERNPROC) { 665 owner = (struct thread *)LK_HOLDER(x); 666 if (TD_IS_RUNNING(owner)) { 667 sleepq_release(&lk->lock_object); 668 continue; 669 } 670 } 671 #endif 672 673 /* 674 * Try to set the LK_SHARED_WAITERS flag. If we fail, 675 * loop back and retry. 676 */ 677 if ((x & LK_SHARED_WAITERS) == 0) { 678 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 679 x | LK_SHARED_WAITERS)) { 680 sleepq_release(&lk->lock_object); 681 continue; 682 } 683 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 684 __func__, lk); 685 } 686 687 /* 688 * As far as we have been unable to acquire the 689 * shared lock and the shared waiters flag is set, 690 * we will sleep. 691 */ 692 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 693 SQ_SHARED_QUEUE); 694 flags &= ~LK_INTERLOCK; 695 if (error) { 696 LOCK_LOG3(lk, 697 "%s: interrupted sleep for %p with %d", 698 __func__, lk, error); 699 break; 700 } 701 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 702 __func__, lk); 703 } 704 if (error == 0) { 705 lock_profile_obtain_lock_success(&lk->lock_object, 706 contested, waittime, file, line); 707 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 708 line); 709 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 710 line); 711 TD_LOCKS_INC(curthread); 712 TD_SLOCKS_INC(curthread); 713 STACK_SAVE(lk); 714 } 715 break; 716 case LK_UPGRADE: 717 case LK_TRYUPGRADE: 718 _lockmgr_assert(lk, KA_SLOCKED, file, line); 719 v = lk->lk_lock; 720 x = v & LK_ALL_WAITERS; 721 v &= LK_EXCLUSIVE_SPINNERS; 722 723 /* 724 * Try to switch from one shared lock to an exclusive one. 725 * We need to preserve waiters flags during the operation. 726 */ 727 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 728 tid | x)) { 729 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 730 line); 731 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 732 LK_TRYWIT(flags), file, line); 733 TD_SLOCKS_DEC(curthread); 734 break; 735 } 736 737 /* 738 * In LK_TRYUPGRADE mode, do not drop the lock, 739 * returning EBUSY instead. 740 */ 741 if (op == LK_TRYUPGRADE) { 742 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", 743 __func__, lk); 744 error = EBUSY; 745 break; 746 } 747 748 /* 749 * We have been unable to succeed in upgrading, so just 750 * give up the shared lock. 751 */ 752 wakeup_swapper |= wakeupshlk(lk, file, line); 753 754 /* FALLTHROUGH */ 755 case LK_EXCLUSIVE: 756 if (LK_CAN_WITNESS(flags)) 757 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 758 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 759 ilk : NULL); 760 761 /* 762 * If curthread already holds the lock and this one is 763 * allowed to recurse, simply recurse on it. 764 */ 765 if (lockmgr_xlocked(lk)) { 766 if ((flags & LK_CANRECURSE) == 0 && 767 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 768 769 /* 770 * If the lock is expected to not panic just 771 * give up and return. 772 */ 773 if (LK_TRYOP(flags)) { 774 LOCK_LOG2(lk, 775 "%s: %p fails the try operation", 776 __func__, lk); 777 error = EBUSY; 778 break; 779 } 780 if (flags & LK_INTERLOCK) 781 class->lc_unlock(ilk); 782 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 783 __func__, iwmesg, file, line); 784 } 785 lk->lk_recurse++; 786 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 787 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 788 lk->lk_recurse, file, line); 789 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 790 LK_TRYWIT(flags), file, line); 791 TD_LOCKS_INC(curthread); 792 break; 793 } 794 795 for (;;) { 796 if (lk->lk_lock == LK_UNLOCKED && 797 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 798 break; 799 #ifdef HWPMC_HOOKS 800 PMC_SOFT_CALL( , , lock, failed); 801 #endif 802 lock_profile_obtain_lock_failed(&lk->lock_object, 803 &contested, &waittime); 804 805 /* 806 * If the lock is expected to not sleep just give up 807 * and return. 808 */ 809 if (LK_TRYOP(flags)) { 810 LOCK_LOG2(lk, "%s: %p fails the try operation", 811 __func__, lk); 812 error = EBUSY; 813 break; 814 } 815 816 #ifdef ADAPTIVE_LOCKMGRS 817 /* 818 * If the owner is running on another CPU, spin until 819 * the owner stops running or the state of the lock 820 * changes. 821 */ 822 x = lk->lk_lock; 823 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 824 LK_HOLDER(x) != LK_KERNPROC) { 825 owner = (struct thread *)LK_HOLDER(x); 826 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 827 CTR3(KTR_LOCK, 828 "%s: spinning on %p held by %p", 829 __func__, lk, owner); 830 KTR_STATE1(KTR_SCHED, "thread", 831 sched_tdname(td), "spinning", 832 "lockname:\"%s\"", lk->lock_object.lo_name); 833 834 /* 835 * If we are holding also an interlock drop it 836 * in order to avoid a deadlock if the lockmgr 837 * owner is adaptively spinning on the 838 * interlock itself. 839 */ 840 if (flags & LK_INTERLOCK) { 841 class->lc_unlock(ilk); 842 flags &= ~LK_INTERLOCK; 843 } 844 GIANT_SAVE(); 845 while (LK_HOLDER(lk->lk_lock) == 846 (uintptr_t)owner && TD_IS_RUNNING(owner)) 847 cpu_spinwait(); 848 KTR_STATE0(KTR_SCHED, "thread", 849 sched_tdname(td), "running"); 850 GIANT_RESTORE(); 851 continue; 852 } else if (LK_CAN_ADAPT(lk, flags) && 853 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 854 spintries < alk_retries) { 855 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 856 !atomic_cmpset_ptr(&lk->lk_lock, x, 857 x | LK_EXCLUSIVE_SPINNERS)) 858 continue; 859 KTR_STATE1(KTR_SCHED, "thread", 860 sched_tdname(td), "spinning", 861 "lockname:\"%s\"", lk->lock_object.lo_name); 862 if (flags & LK_INTERLOCK) { 863 class->lc_unlock(ilk); 864 flags &= ~LK_INTERLOCK; 865 } 866 GIANT_SAVE(); 867 spintries++; 868 for (i = 0; i < alk_loops; i++) { 869 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 870 CTR4(KTR_LOCK, 871 "%s: shared spinning on %p with %u and %u", 872 __func__, lk, spintries, i); 873 if ((lk->lk_lock & 874 LK_EXCLUSIVE_SPINNERS) == 0) 875 break; 876 cpu_spinwait(); 877 } 878 KTR_STATE0(KTR_SCHED, "thread", 879 sched_tdname(td), "running"); 880 GIANT_RESTORE(); 881 if (i != alk_loops) 882 continue; 883 } 884 #endif 885 886 /* 887 * Acquire the sleepqueue chain lock because we 888 * probabilly will need to manipulate waiters flags. 889 */ 890 sleepq_lock(&lk->lock_object); 891 x = lk->lk_lock; 892 893 /* 894 * if the lock has been released while we spun on 895 * the sleepqueue chain lock just try again. 896 */ 897 if (x == LK_UNLOCKED) { 898 sleepq_release(&lk->lock_object); 899 continue; 900 } 901 902 #ifdef ADAPTIVE_LOCKMGRS 903 /* 904 * The current lock owner might have started executing 905 * on another CPU (or the lock could have changed 906 * owner) while we were waiting on the turnstile 907 * chain lock. If so, drop the turnstile lock and try 908 * again. 909 */ 910 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 911 LK_HOLDER(x) != LK_KERNPROC) { 912 owner = (struct thread *)LK_HOLDER(x); 913 if (TD_IS_RUNNING(owner)) { 914 sleepq_release(&lk->lock_object); 915 continue; 916 } 917 } 918 #endif 919 920 /* 921 * The lock can be in the state where there is a 922 * pending queue of waiters, but still no owner. 923 * This happens when the lock is contested and an 924 * owner is going to claim the lock. 925 * If curthread is the one successfully acquiring it 926 * claim lock ownership and return, preserving waiters 927 * flags. 928 */ 929 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 930 if ((x & ~v) == LK_UNLOCKED) { 931 v &= ~LK_EXCLUSIVE_SPINNERS; 932 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 933 tid | v)) { 934 sleepq_release(&lk->lock_object); 935 LOCK_LOG2(lk, 936 "%s: %p claimed by a new writer", 937 __func__, lk); 938 break; 939 } 940 sleepq_release(&lk->lock_object); 941 continue; 942 } 943 944 /* 945 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 946 * fail, loop back and retry. 947 */ 948 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 949 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 950 x | LK_EXCLUSIVE_WAITERS)) { 951 sleepq_release(&lk->lock_object); 952 continue; 953 } 954 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 955 __func__, lk); 956 } 957 958 /* 959 * As far as we have been unable to acquire the 960 * exclusive lock and the exclusive waiters flag 961 * is set, we will sleep. 962 */ 963 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 964 SQ_EXCLUSIVE_QUEUE); 965 flags &= ~LK_INTERLOCK; 966 if (error) { 967 LOCK_LOG3(lk, 968 "%s: interrupted sleep for %p with %d", 969 __func__, lk, error); 970 break; 971 } 972 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 973 __func__, lk); 974 } 975 if (error == 0) { 976 lock_profile_obtain_lock_success(&lk->lock_object, 977 contested, waittime, file, line); 978 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 979 lk->lk_recurse, file, line); 980 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 981 LK_TRYWIT(flags), file, line); 982 TD_LOCKS_INC(curthread); 983 STACK_SAVE(lk); 984 } 985 break; 986 case LK_DOWNGRADE: 987 _lockmgr_assert(lk, KA_XLOCKED, file, line); 988 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 989 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 990 991 /* 992 * Panic if the lock is recursed. 993 */ 994 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 995 if (flags & LK_INTERLOCK) 996 class->lc_unlock(ilk); 997 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 998 __func__, iwmesg, file, line); 999 } 1000 TD_SLOCKS_INC(curthread); 1001 1002 /* 1003 * In order to preserve waiters flags, just spin. 1004 */ 1005 for (;;) { 1006 x = lk->lk_lock; 1007 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1008 x &= LK_ALL_WAITERS; 1009 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1010 LK_SHARERS_LOCK(1) | x)) 1011 break; 1012 cpu_spinwait(); 1013 } 1014 break; 1015 case LK_RELEASE: 1016 _lockmgr_assert(lk, KA_LOCKED, file, line); 1017 x = lk->lk_lock; 1018 1019 if ((x & LK_SHARE) == 0) { 1020 1021 /* 1022 * As first option, treact the lock as if it has not 1023 * any waiter. 1024 * Fix-up the tid var if the lock has been disowned. 1025 */ 1026 if (LK_HOLDER(x) == LK_KERNPROC) 1027 tid = LK_KERNPROC; 1028 else { 1029 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 1030 file, line); 1031 TD_LOCKS_DEC(curthread); 1032 } 1033 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 1034 lk->lk_recurse, file, line); 1035 1036 /* 1037 * The lock is held in exclusive mode. 1038 * If the lock is recursed also, then unrecurse it. 1039 */ 1040 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 1041 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 1042 lk); 1043 lk->lk_recurse--; 1044 break; 1045 } 1046 if (tid != LK_KERNPROC) 1047 lock_profile_release_lock(&lk->lock_object); 1048 1049 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 1050 LK_UNLOCKED)) 1051 break; 1052 1053 sleepq_lock(&lk->lock_object); 1054 x = lk->lk_lock; 1055 v = LK_UNLOCKED; 1056 1057 /* 1058 * If the lock has exclusive waiters, give them 1059 * preference in order to avoid deadlock with 1060 * shared runners up. 1061 * If interruptible sleeps left the exclusive queue 1062 * empty avoid a starvation for the threads sleeping 1063 * on the shared queue by giving them precedence 1064 * and cleaning up the exclusive waiters bit anyway. 1065 * Please note that lk_exslpfail count may be lying 1066 * about the real number of waiters with the 1067 * LK_SLEEPFAIL flag on because they may be used in 1068 * conjunction with interruptible sleeps so 1069 * lk_exslpfail might be considered an 'upper limit' 1070 * bound, including the edge cases. 1071 */ 1072 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1073 realexslp = sleepq_sleepcnt(&lk->lock_object, 1074 SQ_EXCLUSIVE_QUEUE); 1075 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1076 if (lk->lk_exslpfail < realexslp) { 1077 lk->lk_exslpfail = 0; 1078 queue = SQ_EXCLUSIVE_QUEUE; 1079 v |= (x & LK_SHARED_WAITERS); 1080 } else { 1081 lk->lk_exslpfail = 0; 1082 LOCK_LOG2(lk, 1083 "%s: %p has only LK_SLEEPFAIL sleepers", 1084 __func__, lk); 1085 LOCK_LOG2(lk, 1086 "%s: %p waking up threads on the exclusive queue", 1087 __func__, lk); 1088 wakeup_swapper = 1089 sleepq_broadcast(&lk->lock_object, 1090 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1091 queue = SQ_SHARED_QUEUE; 1092 } 1093 } else { 1094 1095 /* 1096 * Exclusive waiters sleeping with LK_SLEEPFAIL 1097 * on and using interruptible sleeps/timeout 1098 * may have left spourious lk_exslpfail counts 1099 * on, so clean it up anyway. 1100 */ 1101 lk->lk_exslpfail = 0; 1102 queue = SQ_SHARED_QUEUE; 1103 } 1104 1105 LOCK_LOG3(lk, 1106 "%s: %p waking up threads on the %s queue", 1107 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1108 "exclusive"); 1109 atomic_store_rel_ptr(&lk->lk_lock, v); 1110 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1111 SLEEPQ_LK, 0, queue); 1112 sleepq_release(&lk->lock_object); 1113 break; 1114 } else 1115 wakeup_swapper = wakeupshlk(lk, file, line); 1116 break; 1117 case LK_DRAIN: 1118 if (LK_CAN_WITNESS(flags)) 1119 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1120 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 1121 ilk : NULL); 1122 1123 /* 1124 * Trying to drain a lock we already own will result in a 1125 * deadlock. 1126 */ 1127 if (lockmgr_xlocked(lk)) { 1128 if (flags & LK_INTERLOCK) 1129 class->lc_unlock(ilk); 1130 panic("%s: draining %s with the lock held @ %s:%d\n", 1131 __func__, iwmesg, file, line); 1132 } 1133 1134 for (;;) { 1135 if (lk->lk_lock == LK_UNLOCKED && 1136 atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) 1137 break; 1138 1139 #ifdef HWPMC_HOOKS 1140 PMC_SOFT_CALL( , , lock, failed); 1141 #endif 1142 lock_profile_obtain_lock_failed(&lk->lock_object, 1143 &contested, &waittime); 1144 1145 /* 1146 * If the lock is expected to not sleep just give up 1147 * and return. 1148 */ 1149 if (LK_TRYOP(flags)) { 1150 LOCK_LOG2(lk, "%s: %p fails the try operation", 1151 __func__, lk); 1152 error = EBUSY; 1153 break; 1154 } 1155 1156 /* 1157 * Acquire the sleepqueue chain lock because we 1158 * probabilly will need to manipulate waiters flags. 1159 */ 1160 sleepq_lock(&lk->lock_object); 1161 x = lk->lk_lock; 1162 1163 /* 1164 * if the lock has been released while we spun on 1165 * the sleepqueue chain lock just try again. 1166 */ 1167 if (x == LK_UNLOCKED) { 1168 sleepq_release(&lk->lock_object); 1169 continue; 1170 } 1171 1172 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1173 if ((x & ~v) == LK_UNLOCKED) { 1174 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1175 1176 /* 1177 * If interruptible sleeps left the exclusive 1178 * queue empty avoid a starvation for the 1179 * threads sleeping on the shared queue by 1180 * giving them precedence and cleaning up the 1181 * exclusive waiters bit anyway. 1182 * Please note that lk_exslpfail count may be 1183 * lying about the real number of waiters with 1184 * the LK_SLEEPFAIL flag on because they may 1185 * be used in conjunction with interruptible 1186 * sleeps so lk_exslpfail might be considered 1187 * an 'upper limit' bound, including the edge 1188 * cases. 1189 */ 1190 if (v & LK_EXCLUSIVE_WAITERS) { 1191 queue = SQ_EXCLUSIVE_QUEUE; 1192 v &= ~LK_EXCLUSIVE_WAITERS; 1193 } else { 1194 1195 /* 1196 * Exclusive waiters sleeping with 1197 * LK_SLEEPFAIL on and using 1198 * interruptible sleeps/timeout may 1199 * have left spourious lk_exslpfail 1200 * counts on, so clean it up anyway. 1201 */ 1202 MPASS(v & LK_SHARED_WAITERS); 1203 lk->lk_exslpfail = 0; 1204 queue = SQ_SHARED_QUEUE; 1205 v &= ~LK_SHARED_WAITERS; 1206 } 1207 if (queue == SQ_EXCLUSIVE_QUEUE) { 1208 realexslp = 1209 sleepq_sleepcnt(&lk->lock_object, 1210 SQ_EXCLUSIVE_QUEUE); 1211 if (lk->lk_exslpfail >= realexslp) { 1212 lk->lk_exslpfail = 0; 1213 queue = SQ_SHARED_QUEUE; 1214 v &= ~LK_SHARED_WAITERS; 1215 if (realexslp != 0) { 1216 LOCK_LOG2(lk, 1217 "%s: %p has only LK_SLEEPFAIL sleepers", 1218 __func__, lk); 1219 LOCK_LOG2(lk, 1220 "%s: %p waking up threads on the exclusive queue", 1221 __func__, lk); 1222 wakeup_swapper = 1223 sleepq_broadcast( 1224 &lk->lock_object, 1225 SLEEPQ_LK, 0, 1226 SQ_EXCLUSIVE_QUEUE); 1227 } 1228 } else 1229 lk->lk_exslpfail = 0; 1230 } 1231 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1232 sleepq_release(&lk->lock_object); 1233 continue; 1234 } 1235 LOCK_LOG3(lk, 1236 "%s: %p waking up all threads on the %s queue", 1237 __func__, lk, queue == SQ_SHARED_QUEUE ? 1238 "shared" : "exclusive"); 1239 wakeup_swapper |= sleepq_broadcast( 1240 &lk->lock_object, SLEEPQ_LK, 0, queue); 1241 1242 /* 1243 * If shared waiters have been woken up we need 1244 * to wait for one of them to acquire the lock 1245 * before to set the exclusive waiters in 1246 * order to avoid a deadlock. 1247 */ 1248 if (queue == SQ_SHARED_QUEUE) { 1249 for (v = lk->lk_lock; 1250 (v & LK_SHARE) && !LK_SHARERS(v); 1251 v = lk->lk_lock) 1252 cpu_spinwait(); 1253 } 1254 } 1255 1256 /* 1257 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1258 * fail, loop back and retry. 1259 */ 1260 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1261 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1262 x | LK_EXCLUSIVE_WAITERS)) { 1263 sleepq_release(&lk->lock_object); 1264 continue; 1265 } 1266 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1267 __func__, lk); 1268 } 1269 1270 /* 1271 * As far as we have been unable to acquire the 1272 * exclusive lock and the exclusive waiters flag 1273 * is set, we will sleep. 1274 */ 1275 if (flags & LK_INTERLOCK) { 1276 class->lc_unlock(ilk); 1277 flags &= ~LK_INTERLOCK; 1278 } 1279 GIANT_SAVE(); 1280 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1281 SQ_EXCLUSIVE_QUEUE); 1282 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1283 GIANT_RESTORE(); 1284 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1285 __func__, lk); 1286 } 1287 1288 if (error == 0) { 1289 lock_profile_obtain_lock_success(&lk->lock_object, 1290 contested, waittime, file, line); 1291 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1292 lk->lk_recurse, file, line); 1293 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1294 LK_TRYWIT(flags), file, line); 1295 TD_LOCKS_INC(curthread); 1296 STACK_SAVE(lk); 1297 } 1298 break; 1299 default: 1300 if (flags & LK_INTERLOCK) 1301 class->lc_unlock(ilk); 1302 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1303 } 1304 1305 if (flags & LK_INTERLOCK) 1306 class->lc_unlock(ilk); 1307 if (wakeup_swapper) 1308 kick_proc0(); 1309 1310 return (error); 1311 } 1312 1313 void 1314 _lockmgr_disown(struct lock *lk, const char *file, int line) 1315 { 1316 uintptr_t tid, x; 1317 1318 if (SCHEDULER_STOPPED()) 1319 return; 1320 1321 tid = (uintptr_t)curthread; 1322 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1323 1324 /* 1325 * Panic if the lock is recursed. 1326 */ 1327 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1328 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1329 __func__, file, line); 1330 1331 /* 1332 * If the owner is already LK_KERNPROC just skip the whole operation. 1333 */ 1334 if (LK_HOLDER(lk->lk_lock) != tid) 1335 return; 1336 lock_profile_release_lock(&lk->lock_object); 1337 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1338 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1339 TD_LOCKS_DEC(curthread); 1340 STACK_SAVE(lk); 1341 1342 /* 1343 * In order to preserve waiters flags, just spin. 1344 */ 1345 for (;;) { 1346 x = lk->lk_lock; 1347 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1348 x &= LK_ALL_WAITERS; 1349 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1350 LK_KERNPROC | x)) 1351 return; 1352 cpu_spinwait(); 1353 } 1354 } 1355 1356 void 1357 lockmgr_printinfo(const struct lock *lk) 1358 { 1359 struct thread *td; 1360 uintptr_t x; 1361 1362 if (lk->lk_lock == LK_UNLOCKED) 1363 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1364 else if (lk->lk_lock & LK_SHARE) 1365 printf("lock type %s: SHARED (count %ju)\n", 1366 lk->lock_object.lo_name, 1367 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1368 else { 1369 td = lockmgr_xholder(lk); 1370 if (td == (struct thread *)LK_KERNPROC) 1371 printf("lock type %s: EXCL by KERNPROC\n", 1372 lk->lock_object.lo_name); 1373 else 1374 printf("lock type %s: EXCL by thread %p " 1375 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, 1376 td, td->td_proc->p_pid, td->td_proc->p_comm, 1377 td->td_tid); 1378 } 1379 1380 x = lk->lk_lock; 1381 if (x & LK_EXCLUSIVE_WAITERS) 1382 printf(" with exclusive waiters pending\n"); 1383 if (x & LK_SHARED_WAITERS) 1384 printf(" with shared waiters pending\n"); 1385 if (x & LK_EXCLUSIVE_SPINNERS) 1386 printf(" with exclusive spinners pending\n"); 1387 1388 STACK_PRINT(lk); 1389 } 1390 1391 int 1392 lockstatus(const struct lock *lk) 1393 { 1394 uintptr_t v, x; 1395 int ret; 1396 1397 ret = LK_SHARED; 1398 x = lk->lk_lock; 1399 v = LK_HOLDER(x); 1400 1401 if ((x & LK_SHARE) == 0) { 1402 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1403 ret = LK_EXCLUSIVE; 1404 else 1405 ret = LK_EXCLOTHER; 1406 } else if (x == LK_UNLOCKED) 1407 ret = 0; 1408 1409 return (ret); 1410 } 1411 1412 #ifdef INVARIANT_SUPPORT 1413 1414 FEATURE(invariant_support, 1415 "Support for modules compiled with INVARIANTS option"); 1416 1417 #ifndef INVARIANTS 1418 #undef _lockmgr_assert 1419 #endif 1420 1421 void 1422 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1423 { 1424 int slocked = 0; 1425 1426 if (panicstr != NULL) 1427 return; 1428 switch (what) { 1429 case KA_SLOCKED: 1430 case KA_SLOCKED | KA_NOTRECURSED: 1431 case KA_SLOCKED | KA_RECURSED: 1432 slocked = 1; 1433 case KA_LOCKED: 1434 case KA_LOCKED | KA_NOTRECURSED: 1435 case KA_LOCKED | KA_RECURSED: 1436 #ifdef WITNESS 1437 1438 /* 1439 * We cannot trust WITNESS if the lock is held in exclusive 1440 * mode and a call to lockmgr_disown() happened. 1441 * Workaround this skipping the check if the lock is held in 1442 * exclusive mode even for the KA_LOCKED case. 1443 */ 1444 if (slocked || (lk->lk_lock & LK_SHARE)) { 1445 witness_assert(&lk->lock_object, what, file, line); 1446 break; 1447 } 1448 #endif 1449 if (lk->lk_lock == LK_UNLOCKED || 1450 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1451 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1452 panic("Lock %s not %slocked @ %s:%d\n", 1453 lk->lock_object.lo_name, slocked ? "share" : "", 1454 file, line); 1455 1456 if ((lk->lk_lock & LK_SHARE) == 0) { 1457 if (lockmgr_recursed(lk)) { 1458 if (what & KA_NOTRECURSED) 1459 panic("Lock %s recursed @ %s:%d\n", 1460 lk->lock_object.lo_name, file, 1461 line); 1462 } else if (what & KA_RECURSED) 1463 panic("Lock %s not recursed @ %s:%d\n", 1464 lk->lock_object.lo_name, file, line); 1465 } 1466 break; 1467 case KA_XLOCKED: 1468 case KA_XLOCKED | KA_NOTRECURSED: 1469 case KA_XLOCKED | KA_RECURSED: 1470 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1471 panic("Lock %s not exclusively locked @ %s:%d\n", 1472 lk->lock_object.lo_name, file, line); 1473 if (lockmgr_recursed(lk)) { 1474 if (what & KA_NOTRECURSED) 1475 panic("Lock %s recursed @ %s:%d\n", 1476 lk->lock_object.lo_name, file, line); 1477 } else if (what & KA_RECURSED) 1478 panic("Lock %s not recursed @ %s:%d\n", 1479 lk->lock_object.lo_name, file, line); 1480 break; 1481 case KA_UNLOCKED: 1482 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1483 panic("Lock %s exclusively locked @ %s:%d\n", 1484 lk->lock_object.lo_name, file, line); 1485 break; 1486 default: 1487 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1488 line); 1489 } 1490 } 1491 #endif 1492 1493 #ifdef DDB 1494 int 1495 lockmgr_chain(struct thread *td, struct thread **ownerp) 1496 { 1497 struct lock *lk; 1498 1499 lk = td->td_wchan; 1500 1501 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1502 return (0); 1503 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1504 if (lk->lk_lock & LK_SHARE) 1505 db_printf("SHARED (count %ju)\n", 1506 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1507 else 1508 db_printf("EXCL\n"); 1509 *ownerp = lockmgr_xholder(lk); 1510 1511 return (1); 1512 } 1513 1514 static void 1515 db_show_lockmgr(const struct lock_object *lock) 1516 { 1517 struct thread *td; 1518 const struct lock *lk; 1519 1520 lk = (const struct lock *)lock; 1521 1522 db_printf(" state: "); 1523 if (lk->lk_lock == LK_UNLOCKED) 1524 db_printf("UNLOCKED\n"); 1525 else if (lk->lk_lock & LK_SHARE) 1526 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1527 else { 1528 td = lockmgr_xholder(lk); 1529 if (td == (struct thread *)LK_KERNPROC) 1530 db_printf("XLOCK: LK_KERNPROC\n"); 1531 else 1532 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1533 td->td_tid, td->td_proc->p_pid, 1534 td->td_proc->p_comm); 1535 if (lockmgr_recursed(lk)) 1536 db_printf(" recursed: %d\n", lk->lk_recurse); 1537 } 1538 db_printf(" waiters: "); 1539 switch (lk->lk_lock & LK_ALL_WAITERS) { 1540 case LK_SHARED_WAITERS: 1541 db_printf("shared\n"); 1542 break; 1543 case LK_EXCLUSIVE_WAITERS: 1544 db_printf("exclusive\n"); 1545 break; 1546 case LK_ALL_WAITERS: 1547 db_printf("shared and exclusive\n"); 1548 break; 1549 default: 1550 db_printf("none\n"); 1551 } 1552 db_printf(" spinners: "); 1553 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1554 db_printf("exclusive\n"); 1555 else 1556 db_printf("none\n"); 1557 } 1558 #endif
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