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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/10.2/sys/kern/kern_lock.c 278694 2015-02-13 19:06:22Z sbruno $"); 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 conjuction 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 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 796 tid)) { 797 #ifdef HWPMC_HOOKS 798 PMC_SOFT_CALL( , , lock, failed); 799 #endif 800 lock_profile_obtain_lock_failed(&lk->lock_object, 801 &contested, &waittime); 802 803 /* 804 * If the lock is expected to not sleep just give up 805 * and return. 806 */ 807 if (LK_TRYOP(flags)) { 808 LOCK_LOG2(lk, "%s: %p fails the try operation", 809 __func__, lk); 810 error = EBUSY; 811 break; 812 } 813 814 #ifdef ADAPTIVE_LOCKMGRS 815 /* 816 * If the owner is running on another CPU, spin until 817 * the owner stops running or the state of the lock 818 * changes. 819 */ 820 x = lk->lk_lock; 821 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 822 LK_HOLDER(x) != LK_KERNPROC) { 823 owner = (struct thread *)LK_HOLDER(x); 824 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 825 CTR3(KTR_LOCK, 826 "%s: spinning on %p held by %p", 827 __func__, lk, owner); 828 KTR_STATE1(KTR_SCHED, "thread", 829 sched_tdname(td), "spinning", 830 "lockname:\"%s\"", lk->lock_object.lo_name); 831 832 /* 833 * If we are holding also an interlock drop it 834 * in order to avoid a deadlock if the lockmgr 835 * owner is adaptively spinning on the 836 * interlock itself. 837 */ 838 if (flags & LK_INTERLOCK) { 839 class->lc_unlock(ilk); 840 flags &= ~LK_INTERLOCK; 841 } 842 GIANT_SAVE(); 843 while (LK_HOLDER(lk->lk_lock) == 844 (uintptr_t)owner && TD_IS_RUNNING(owner)) 845 cpu_spinwait(); 846 KTR_STATE0(KTR_SCHED, "thread", 847 sched_tdname(td), "running"); 848 GIANT_RESTORE(); 849 continue; 850 } else if (LK_CAN_ADAPT(lk, flags) && 851 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 852 spintries < alk_retries) { 853 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 854 !atomic_cmpset_ptr(&lk->lk_lock, x, 855 x | LK_EXCLUSIVE_SPINNERS)) 856 continue; 857 KTR_STATE1(KTR_SCHED, "thread", 858 sched_tdname(td), "spinning", 859 "lockname:\"%s\"", lk->lock_object.lo_name); 860 if (flags & LK_INTERLOCK) { 861 class->lc_unlock(ilk); 862 flags &= ~LK_INTERLOCK; 863 } 864 GIANT_SAVE(); 865 spintries++; 866 for (i = 0; i < alk_loops; i++) { 867 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 868 CTR4(KTR_LOCK, 869 "%s: shared spinning on %p with %u and %u", 870 __func__, lk, spintries, i); 871 if ((lk->lk_lock & 872 LK_EXCLUSIVE_SPINNERS) == 0) 873 break; 874 cpu_spinwait(); 875 } 876 KTR_STATE0(KTR_SCHED, "thread", 877 sched_tdname(td), "running"); 878 GIANT_RESTORE(); 879 if (i != alk_loops) 880 continue; 881 } 882 #endif 883 884 /* 885 * Acquire the sleepqueue chain lock because we 886 * probabilly will need to manipulate waiters flags. 887 */ 888 sleepq_lock(&lk->lock_object); 889 x = lk->lk_lock; 890 891 /* 892 * if the lock has been released while we spun on 893 * the sleepqueue chain lock just try again. 894 */ 895 if (x == LK_UNLOCKED) { 896 sleepq_release(&lk->lock_object); 897 continue; 898 } 899 900 #ifdef ADAPTIVE_LOCKMGRS 901 /* 902 * The current lock owner might have started executing 903 * on another CPU (or the lock could have changed 904 * owner) while we were waiting on the turnstile 905 * chain lock. If so, drop the turnstile lock and try 906 * again. 907 */ 908 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 909 LK_HOLDER(x) != LK_KERNPROC) { 910 owner = (struct thread *)LK_HOLDER(x); 911 if (TD_IS_RUNNING(owner)) { 912 sleepq_release(&lk->lock_object); 913 continue; 914 } 915 } 916 #endif 917 918 /* 919 * The lock can be in the state where there is a 920 * pending queue of waiters, but still no owner. 921 * This happens when the lock is contested and an 922 * owner is going to claim the lock. 923 * If curthread is the one successfully acquiring it 924 * claim lock ownership and return, preserving waiters 925 * flags. 926 */ 927 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 928 if ((x & ~v) == LK_UNLOCKED) { 929 v &= ~LK_EXCLUSIVE_SPINNERS; 930 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 931 tid | v)) { 932 sleepq_release(&lk->lock_object); 933 LOCK_LOG2(lk, 934 "%s: %p claimed by a new writer", 935 __func__, lk); 936 break; 937 } 938 sleepq_release(&lk->lock_object); 939 continue; 940 } 941 942 /* 943 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 944 * fail, loop back and retry. 945 */ 946 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 947 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 948 x | LK_EXCLUSIVE_WAITERS)) { 949 sleepq_release(&lk->lock_object); 950 continue; 951 } 952 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 953 __func__, lk); 954 } 955 956 /* 957 * As far as we have been unable to acquire the 958 * exclusive lock and the exclusive waiters flag 959 * is set, we will sleep. 960 */ 961 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 962 SQ_EXCLUSIVE_QUEUE); 963 flags &= ~LK_INTERLOCK; 964 if (error) { 965 LOCK_LOG3(lk, 966 "%s: interrupted sleep for %p with %d", 967 __func__, lk, error); 968 break; 969 } 970 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 971 __func__, lk); 972 } 973 if (error == 0) { 974 lock_profile_obtain_lock_success(&lk->lock_object, 975 contested, waittime, file, line); 976 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 977 lk->lk_recurse, file, line); 978 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 979 LK_TRYWIT(flags), file, line); 980 TD_LOCKS_INC(curthread); 981 STACK_SAVE(lk); 982 } 983 break; 984 case LK_DOWNGRADE: 985 _lockmgr_assert(lk, KA_XLOCKED, file, line); 986 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 987 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 988 989 /* 990 * Panic if the lock is recursed. 991 */ 992 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 993 if (flags & LK_INTERLOCK) 994 class->lc_unlock(ilk); 995 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 996 __func__, iwmesg, file, line); 997 } 998 TD_SLOCKS_INC(curthread); 999 1000 /* 1001 * In order to preserve waiters flags, just spin. 1002 */ 1003 for (;;) { 1004 x = lk->lk_lock; 1005 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1006 x &= LK_ALL_WAITERS; 1007 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1008 LK_SHARERS_LOCK(1) | x)) 1009 break; 1010 cpu_spinwait(); 1011 } 1012 break; 1013 case LK_RELEASE: 1014 _lockmgr_assert(lk, KA_LOCKED, file, line); 1015 x = lk->lk_lock; 1016 1017 if ((x & LK_SHARE) == 0) { 1018 1019 /* 1020 * As first option, treact the lock as if it has not 1021 * any waiter. 1022 * Fix-up the tid var if the lock has been disowned. 1023 */ 1024 if (LK_HOLDER(x) == LK_KERNPROC) 1025 tid = LK_KERNPROC; 1026 else { 1027 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 1028 file, line); 1029 TD_LOCKS_DEC(curthread); 1030 } 1031 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 1032 lk->lk_recurse, file, line); 1033 1034 /* 1035 * The lock is held in exclusive mode. 1036 * If the lock is recursed also, then unrecurse it. 1037 */ 1038 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 1039 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 1040 lk); 1041 lk->lk_recurse--; 1042 break; 1043 } 1044 if (tid != LK_KERNPROC) 1045 lock_profile_release_lock(&lk->lock_object); 1046 1047 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 1048 LK_UNLOCKED)) 1049 break; 1050 1051 sleepq_lock(&lk->lock_object); 1052 x = lk->lk_lock; 1053 v = LK_UNLOCKED; 1054 1055 /* 1056 * If the lock has exclusive waiters, give them 1057 * preference in order to avoid deadlock with 1058 * shared runners up. 1059 * If interruptible sleeps left the exclusive queue 1060 * empty avoid a starvation for the threads sleeping 1061 * on the shared queue by giving them precedence 1062 * and cleaning up the exclusive waiters bit anyway. 1063 * Please note that lk_exslpfail count may be lying 1064 * about the real number of waiters with the 1065 * LK_SLEEPFAIL flag on because they may be used in 1066 * conjuction with interruptible sleeps so 1067 * lk_exslpfail might be considered an 'upper limit' 1068 * bound, including the edge cases. 1069 */ 1070 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1071 realexslp = sleepq_sleepcnt(&lk->lock_object, 1072 SQ_EXCLUSIVE_QUEUE); 1073 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1074 if (lk->lk_exslpfail < realexslp) { 1075 lk->lk_exslpfail = 0; 1076 queue = SQ_EXCLUSIVE_QUEUE; 1077 v |= (x & LK_SHARED_WAITERS); 1078 } else { 1079 lk->lk_exslpfail = 0; 1080 LOCK_LOG2(lk, 1081 "%s: %p has only LK_SLEEPFAIL sleepers", 1082 __func__, lk); 1083 LOCK_LOG2(lk, 1084 "%s: %p waking up threads on the exclusive queue", 1085 __func__, lk); 1086 wakeup_swapper = 1087 sleepq_broadcast(&lk->lock_object, 1088 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1089 queue = SQ_SHARED_QUEUE; 1090 } 1091 } else { 1092 1093 /* 1094 * Exclusive waiters sleeping with LK_SLEEPFAIL 1095 * on and using interruptible sleeps/timeout 1096 * may have left spourious lk_exslpfail counts 1097 * on, so clean it up anyway. 1098 */ 1099 lk->lk_exslpfail = 0; 1100 queue = SQ_SHARED_QUEUE; 1101 } 1102 1103 LOCK_LOG3(lk, 1104 "%s: %p waking up threads on the %s queue", 1105 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1106 "exclusive"); 1107 atomic_store_rel_ptr(&lk->lk_lock, v); 1108 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1109 SLEEPQ_LK, 0, queue); 1110 sleepq_release(&lk->lock_object); 1111 break; 1112 } else 1113 wakeup_swapper = wakeupshlk(lk, file, line); 1114 break; 1115 case LK_DRAIN: 1116 if (LK_CAN_WITNESS(flags)) 1117 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1118 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 1119 ilk : NULL); 1120 1121 /* 1122 * Trying to drain a lock we already own will result in a 1123 * deadlock. 1124 */ 1125 if (lockmgr_xlocked(lk)) { 1126 if (flags & LK_INTERLOCK) 1127 class->lc_unlock(ilk); 1128 panic("%s: draining %s with the lock held @ %s:%d\n", 1129 __func__, iwmesg, file, line); 1130 } 1131 1132 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1133 #ifdef HWPMC_HOOKS 1134 PMC_SOFT_CALL( , , lock, failed); 1135 #endif 1136 lock_profile_obtain_lock_failed(&lk->lock_object, 1137 &contested, &waittime); 1138 1139 /* 1140 * If the lock is expected to not sleep just give up 1141 * and return. 1142 */ 1143 if (LK_TRYOP(flags)) { 1144 LOCK_LOG2(lk, "%s: %p fails the try operation", 1145 __func__, lk); 1146 error = EBUSY; 1147 break; 1148 } 1149 1150 /* 1151 * Acquire the sleepqueue chain lock because we 1152 * probabilly will need to manipulate waiters flags. 1153 */ 1154 sleepq_lock(&lk->lock_object); 1155 x = lk->lk_lock; 1156 1157 /* 1158 * if the lock has been released while we spun on 1159 * the sleepqueue chain lock just try again. 1160 */ 1161 if (x == LK_UNLOCKED) { 1162 sleepq_release(&lk->lock_object); 1163 continue; 1164 } 1165 1166 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1167 if ((x & ~v) == LK_UNLOCKED) { 1168 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1169 1170 /* 1171 * If interruptible sleeps left the exclusive 1172 * queue empty avoid a starvation for the 1173 * threads sleeping on the shared queue by 1174 * giving them precedence and cleaning up the 1175 * exclusive waiters bit anyway. 1176 * Please note that lk_exslpfail count may be 1177 * lying about the real number of waiters with 1178 * the LK_SLEEPFAIL flag on because they may 1179 * be used in conjuction with interruptible 1180 * sleeps so lk_exslpfail might be considered 1181 * an 'upper limit' bound, including the edge 1182 * cases. 1183 */ 1184 if (v & LK_EXCLUSIVE_WAITERS) { 1185 queue = SQ_EXCLUSIVE_QUEUE; 1186 v &= ~LK_EXCLUSIVE_WAITERS; 1187 } else { 1188 1189 /* 1190 * Exclusive waiters sleeping with 1191 * LK_SLEEPFAIL on and using 1192 * interruptible sleeps/timeout may 1193 * have left spourious lk_exslpfail 1194 * counts on, so clean it up anyway. 1195 */ 1196 MPASS(v & LK_SHARED_WAITERS); 1197 lk->lk_exslpfail = 0; 1198 queue = SQ_SHARED_QUEUE; 1199 v &= ~LK_SHARED_WAITERS; 1200 } 1201 if (queue == SQ_EXCLUSIVE_QUEUE) { 1202 realexslp = 1203 sleepq_sleepcnt(&lk->lock_object, 1204 SQ_EXCLUSIVE_QUEUE); 1205 if (lk->lk_exslpfail >= realexslp) { 1206 lk->lk_exslpfail = 0; 1207 queue = SQ_SHARED_QUEUE; 1208 v &= ~LK_SHARED_WAITERS; 1209 if (realexslp != 0) { 1210 LOCK_LOG2(lk, 1211 "%s: %p has only LK_SLEEPFAIL sleepers", 1212 __func__, lk); 1213 LOCK_LOG2(lk, 1214 "%s: %p waking up threads on the exclusive queue", 1215 __func__, lk); 1216 wakeup_swapper = 1217 sleepq_broadcast( 1218 &lk->lock_object, 1219 SLEEPQ_LK, 0, 1220 SQ_EXCLUSIVE_QUEUE); 1221 } 1222 } else 1223 lk->lk_exslpfail = 0; 1224 } 1225 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1226 sleepq_release(&lk->lock_object); 1227 continue; 1228 } 1229 LOCK_LOG3(lk, 1230 "%s: %p waking up all threads on the %s queue", 1231 __func__, lk, queue == SQ_SHARED_QUEUE ? 1232 "shared" : "exclusive"); 1233 wakeup_swapper |= sleepq_broadcast( 1234 &lk->lock_object, SLEEPQ_LK, 0, queue); 1235 1236 /* 1237 * If shared waiters have been woken up we need 1238 * to wait for one of them to acquire the lock 1239 * before to set the exclusive waiters in 1240 * order to avoid a deadlock. 1241 */ 1242 if (queue == SQ_SHARED_QUEUE) { 1243 for (v = lk->lk_lock; 1244 (v & LK_SHARE) && !LK_SHARERS(v); 1245 v = lk->lk_lock) 1246 cpu_spinwait(); 1247 } 1248 } 1249 1250 /* 1251 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1252 * fail, loop back and retry. 1253 */ 1254 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1255 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1256 x | LK_EXCLUSIVE_WAITERS)) { 1257 sleepq_release(&lk->lock_object); 1258 continue; 1259 } 1260 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1261 __func__, lk); 1262 } 1263 1264 /* 1265 * As far as we have been unable to acquire the 1266 * exclusive lock and the exclusive waiters flag 1267 * is set, we will sleep. 1268 */ 1269 if (flags & LK_INTERLOCK) { 1270 class->lc_unlock(ilk); 1271 flags &= ~LK_INTERLOCK; 1272 } 1273 GIANT_SAVE(); 1274 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1275 SQ_EXCLUSIVE_QUEUE); 1276 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1277 GIANT_RESTORE(); 1278 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1279 __func__, lk); 1280 } 1281 1282 if (error == 0) { 1283 lock_profile_obtain_lock_success(&lk->lock_object, 1284 contested, waittime, file, line); 1285 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1286 lk->lk_recurse, file, line); 1287 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1288 LK_TRYWIT(flags), file, line); 1289 TD_LOCKS_INC(curthread); 1290 STACK_SAVE(lk); 1291 } 1292 break; 1293 default: 1294 if (flags & LK_INTERLOCK) 1295 class->lc_unlock(ilk); 1296 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1297 } 1298 1299 if (flags & LK_INTERLOCK) 1300 class->lc_unlock(ilk); 1301 if (wakeup_swapper) 1302 kick_proc0(); 1303 1304 return (error); 1305 } 1306 1307 void 1308 _lockmgr_disown(struct lock *lk, const char *file, int line) 1309 { 1310 uintptr_t tid, x; 1311 1312 if (SCHEDULER_STOPPED()) 1313 return; 1314 1315 tid = (uintptr_t)curthread; 1316 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1317 1318 /* 1319 * Panic if the lock is recursed. 1320 */ 1321 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1322 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1323 __func__, file, line); 1324 1325 /* 1326 * If the owner is already LK_KERNPROC just skip the whole operation. 1327 */ 1328 if (LK_HOLDER(lk->lk_lock) != tid) 1329 return; 1330 lock_profile_release_lock(&lk->lock_object); 1331 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1332 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1333 TD_LOCKS_DEC(curthread); 1334 STACK_SAVE(lk); 1335 1336 /* 1337 * In order to preserve waiters flags, just spin. 1338 */ 1339 for (;;) { 1340 x = lk->lk_lock; 1341 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1342 x &= LK_ALL_WAITERS; 1343 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1344 LK_KERNPROC | x)) 1345 return; 1346 cpu_spinwait(); 1347 } 1348 } 1349 1350 void 1351 lockmgr_printinfo(const struct lock *lk) 1352 { 1353 struct thread *td; 1354 uintptr_t x; 1355 1356 if (lk->lk_lock == LK_UNLOCKED) 1357 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1358 else if (lk->lk_lock & LK_SHARE) 1359 printf("lock type %s: SHARED (count %ju)\n", 1360 lk->lock_object.lo_name, 1361 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1362 else { 1363 td = lockmgr_xholder(lk); 1364 if (td == (struct thread *)LK_KERNPROC) 1365 printf("lock type %s: EXCL by KERNPROC\n", 1366 lk->lock_object.lo_name); 1367 else 1368 printf("lock type %s: EXCL by thread %p " 1369 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, 1370 td, td->td_proc->p_pid, td->td_proc->p_comm, 1371 td->td_tid); 1372 } 1373 1374 x = lk->lk_lock; 1375 if (x & LK_EXCLUSIVE_WAITERS) 1376 printf(" with exclusive waiters pending\n"); 1377 if (x & LK_SHARED_WAITERS) 1378 printf(" with shared waiters pending\n"); 1379 if (x & LK_EXCLUSIVE_SPINNERS) 1380 printf(" with exclusive spinners pending\n"); 1381 1382 STACK_PRINT(lk); 1383 } 1384 1385 int 1386 lockstatus(const struct lock *lk) 1387 { 1388 uintptr_t v, x; 1389 int ret; 1390 1391 ret = LK_SHARED; 1392 x = lk->lk_lock; 1393 v = LK_HOLDER(x); 1394 1395 if ((x & LK_SHARE) == 0) { 1396 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1397 ret = LK_EXCLUSIVE; 1398 else 1399 ret = LK_EXCLOTHER; 1400 } else if (x == LK_UNLOCKED) 1401 ret = 0; 1402 1403 return (ret); 1404 } 1405 1406 #ifdef INVARIANT_SUPPORT 1407 1408 FEATURE(invariant_support, 1409 "Support for modules compiled with INVARIANTS option"); 1410 1411 #ifndef INVARIANTS 1412 #undef _lockmgr_assert 1413 #endif 1414 1415 void 1416 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1417 { 1418 int slocked = 0; 1419 1420 if (panicstr != NULL) 1421 return; 1422 switch (what) { 1423 case KA_SLOCKED: 1424 case KA_SLOCKED | KA_NOTRECURSED: 1425 case KA_SLOCKED | KA_RECURSED: 1426 slocked = 1; 1427 case KA_LOCKED: 1428 case KA_LOCKED | KA_NOTRECURSED: 1429 case KA_LOCKED | KA_RECURSED: 1430 #ifdef WITNESS 1431 1432 /* 1433 * We cannot trust WITNESS if the lock is held in exclusive 1434 * mode and a call to lockmgr_disown() happened. 1435 * Workaround this skipping the check if the lock is held in 1436 * exclusive mode even for the KA_LOCKED case. 1437 */ 1438 if (slocked || (lk->lk_lock & LK_SHARE)) { 1439 witness_assert(&lk->lock_object, what, file, line); 1440 break; 1441 } 1442 #endif 1443 if (lk->lk_lock == LK_UNLOCKED || 1444 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1445 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1446 panic("Lock %s not %slocked @ %s:%d\n", 1447 lk->lock_object.lo_name, slocked ? "share" : "", 1448 file, line); 1449 1450 if ((lk->lk_lock & LK_SHARE) == 0) { 1451 if (lockmgr_recursed(lk)) { 1452 if (what & KA_NOTRECURSED) 1453 panic("Lock %s recursed @ %s:%d\n", 1454 lk->lock_object.lo_name, file, 1455 line); 1456 } else if (what & KA_RECURSED) 1457 panic("Lock %s not recursed @ %s:%d\n", 1458 lk->lock_object.lo_name, file, line); 1459 } 1460 break; 1461 case KA_XLOCKED: 1462 case KA_XLOCKED | KA_NOTRECURSED: 1463 case KA_XLOCKED | KA_RECURSED: 1464 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1465 panic("Lock %s not exclusively locked @ %s:%d\n", 1466 lk->lock_object.lo_name, file, line); 1467 if (lockmgr_recursed(lk)) { 1468 if (what & KA_NOTRECURSED) 1469 panic("Lock %s recursed @ %s:%d\n", 1470 lk->lock_object.lo_name, file, line); 1471 } else if (what & KA_RECURSED) 1472 panic("Lock %s not recursed @ %s:%d\n", 1473 lk->lock_object.lo_name, file, line); 1474 break; 1475 case KA_UNLOCKED: 1476 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1477 panic("Lock %s exclusively locked @ %s:%d\n", 1478 lk->lock_object.lo_name, file, line); 1479 break; 1480 default: 1481 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1482 line); 1483 } 1484 } 1485 #endif 1486 1487 #ifdef DDB 1488 int 1489 lockmgr_chain(struct thread *td, struct thread **ownerp) 1490 { 1491 struct lock *lk; 1492 1493 lk = td->td_wchan; 1494 1495 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1496 return (0); 1497 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1498 if (lk->lk_lock & LK_SHARE) 1499 db_printf("SHARED (count %ju)\n", 1500 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1501 else 1502 db_printf("EXCL\n"); 1503 *ownerp = lockmgr_xholder(lk); 1504 1505 return (1); 1506 } 1507 1508 static void 1509 db_show_lockmgr(const struct lock_object *lock) 1510 { 1511 struct thread *td; 1512 const struct lock *lk; 1513 1514 lk = (const struct lock *)lock; 1515 1516 db_printf(" state: "); 1517 if (lk->lk_lock == LK_UNLOCKED) 1518 db_printf("UNLOCKED\n"); 1519 else if (lk->lk_lock & LK_SHARE) 1520 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1521 else { 1522 td = lockmgr_xholder(lk); 1523 if (td == (struct thread *)LK_KERNPROC) 1524 db_printf("XLOCK: LK_KERNPROC\n"); 1525 else 1526 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1527 td->td_tid, td->td_proc->p_pid, 1528 td->td_proc->p_comm); 1529 if (lockmgr_recursed(lk)) 1530 db_printf(" recursed: %d\n", lk->lk_recurse); 1531 } 1532 db_printf(" waiters: "); 1533 switch (lk->lk_lock & LK_ALL_WAITERS) { 1534 case LK_SHARED_WAITERS: 1535 db_printf("shared\n"); 1536 break; 1537 case LK_EXCLUSIVE_WAITERS: 1538 db_printf("exclusive\n"); 1539 break; 1540 case LK_ALL_WAITERS: 1541 db_printf("shared and exclusive\n"); 1542 break; 1543 default: 1544 db_printf("none\n"); 1545 } 1546 db_printf(" spinners: "); 1547 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1548 db_printf("exclusive\n"); 1549 else 1550 db_printf("none\n"); 1551 } 1552 #endif
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