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_kdtrace.h" 32 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD$"); 35 36 #include <sys/param.h> 37 #include <sys/ktr.h> 38 #include <sys/lock.h> 39 #include <sys/lock_profile.h> 40 #include <sys/lockmgr.h> 41 #include <sys/mutex.h> 42 #include <sys/proc.h> 43 #include <sys/sleepqueue.h> 44 #ifdef DEBUG_LOCKS 45 #include <sys/stack.h> 46 #endif 47 #include <sys/sysctl.h> 48 #include <sys/systm.h> 49 50 #include <machine/cpu.h> 51 52 #ifdef DDB 53 #include <ddb/ddb.h> 54 #endif 55 56 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) == 57 (LK_ADAPTIVE | LK_NOSHARE)); 58 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED & 59 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS))); 60 61 #define SQ_EXCLUSIVE_QUEUE 0 62 #define SQ_SHARED_QUEUE 1 63 64 #ifndef INVARIANTS 65 #define _lockmgr_assert(lk, what, file, line) 66 #define TD_LOCKS_INC(td) 67 #define TD_LOCKS_DEC(td) 68 #else 69 #define TD_LOCKS_INC(td) ((td)->td_locks++) 70 #define TD_LOCKS_DEC(td) ((td)->td_locks--) 71 #endif 72 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 73 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 74 75 #ifndef DEBUG_LOCKS 76 #define STACK_PRINT(lk) 77 #define STACK_SAVE(lk) 78 #define STACK_ZERO(lk) 79 #else 80 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 81 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 82 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 83 #endif 84 85 #define LOCK_LOG2(lk, string, arg1, arg2) \ 86 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 87 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 88 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 89 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 90 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 91 92 #define GIANT_DECLARE \ 93 int _i = 0; \ 94 WITNESS_SAVE_DECL(Giant) 95 #define GIANT_RESTORE() do { \ 96 if (_i > 0) { \ 97 while (_i--) \ 98 mtx_lock(&Giant); \ 99 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 100 } \ 101 } while (0) 102 #define GIANT_SAVE() do { \ 103 if (mtx_owned(&Giant)) { \ 104 WITNESS_SAVE(&Giant.lock_object, Giant); \ 105 while (mtx_owned(&Giant)) { \ 106 _i++; \ 107 mtx_unlock(&Giant); \ 108 } \ 109 } \ 110 } while (0) 111 112 #define LK_CAN_SHARE(x) \ 113 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \ 114 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \ 115 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT))) 116 #define LK_TRYOP(x) \ 117 ((x) & LK_NOWAIT) 118 119 #define LK_CAN_WITNESS(x) \ 120 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 121 #define LK_TRYWIT(x) \ 122 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 123 124 #define LK_CAN_ADAPT(lk, f) \ 125 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 126 ((f) & LK_SLEEPFAIL) == 0) 127 128 #define lockmgr_disowned(lk) \ 129 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 130 131 #define lockmgr_xlocked(lk) \ 132 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 133 134 static void assert_lockmgr(const struct lock_object *lock, int how); 135 #ifdef DDB 136 static void db_show_lockmgr(const struct lock_object *lock); 137 #endif 138 static void lock_lockmgr(struct lock_object *lock, int how); 139 #ifdef KDTRACE_HOOKS 140 static int owner_lockmgr(const struct lock_object *lock, 141 struct thread **owner); 142 #endif 143 static int unlock_lockmgr(struct lock_object *lock); 144 145 struct lock_class lock_class_lockmgr = { 146 .lc_name = "lockmgr", 147 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 148 .lc_assert = assert_lockmgr, 149 #ifdef DDB 150 .lc_ddb_show = db_show_lockmgr, 151 #endif 152 .lc_lock = lock_lockmgr, 153 .lc_unlock = unlock_lockmgr, 154 #ifdef KDTRACE_HOOKS 155 .lc_owner = owner_lockmgr, 156 #endif 157 }; 158 159 #ifdef ADAPTIVE_LOCKMGRS 160 static u_int alk_retries = 10; 161 static u_int alk_loops = 10000; 162 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, 163 "lockmgr debugging"); 164 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, ""); 165 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, ""); 166 #endif 167 168 static __inline struct thread * 169 lockmgr_xholder(const struct lock *lk) 170 { 171 uintptr_t x; 172 173 x = lk->lk_lock; 174 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 175 } 176 177 /* 178 * It assumes sleepq_lock held and returns with this one unheld. 179 * It also assumes the generic interlock is sane and previously checked. 180 * If LK_INTERLOCK is specified the interlock is not reacquired after the 181 * sleep. 182 */ 183 static __inline int 184 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 185 const char *wmesg, int pri, int timo, int queue) 186 { 187 GIANT_DECLARE; 188 struct lock_class *class; 189 int catch, error; 190 191 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 192 catch = pri & PCATCH; 193 pri &= PRIMASK; 194 error = 0; 195 196 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 197 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 198 199 if (flags & LK_INTERLOCK) 200 class->lc_unlock(ilk); 201 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 202 lk->lk_exslpfail++; 203 GIANT_SAVE(); 204 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 205 SLEEPQ_INTERRUPTIBLE : 0), queue); 206 if ((flags & LK_TIMELOCK) && timo) 207 sleepq_set_timeout(&lk->lock_object, timo); 208 209 /* 210 * Decisional switch for real sleeping. 211 */ 212 if ((flags & LK_TIMELOCK) && timo && catch) 213 error = sleepq_timedwait_sig(&lk->lock_object, pri); 214 else if ((flags & LK_TIMELOCK) && timo) 215 error = sleepq_timedwait(&lk->lock_object, pri); 216 else if (catch) 217 error = sleepq_wait_sig(&lk->lock_object, pri); 218 else 219 sleepq_wait(&lk->lock_object, pri); 220 GIANT_RESTORE(); 221 if ((flags & LK_SLEEPFAIL) && error == 0) 222 error = ENOLCK; 223 224 return (error); 225 } 226 227 static __inline int 228 wakeupshlk(struct lock *lk, const char *file, int line) 229 { 230 uintptr_t v, x; 231 u_int realexslp; 232 int queue, wakeup_swapper; 233 234 TD_LOCKS_DEC(curthread); 235 TD_SLOCKS_DEC(curthread); 236 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 237 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 238 239 wakeup_swapper = 0; 240 for (;;) { 241 x = lk->lk_lock; 242 243 /* 244 * If there is more than one shared lock held, just drop one 245 * and return. 246 */ 247 if (LK_SHARERS(x) > 1) { 248 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, 249 x - LK_ONE_SHARER)) 250 break; 251 continue; 252 } 253 254 /* 255 * If there are not waiters on the exclusive queue, drop the 256 * lock quickly. 257 */ 258 if ((x & LK_ALL_WAITERS) == 0) { 259 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == 260 LK_SHARERS_LOCK(1)); 261 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED)) 262 break; 263 continue; 264 } 265 266 /* 267 * We should have a sharer with waiters, so enter the hard 268 * path in order to handle wakeups correctly. 269 */ 270 sleepq_lock(&lk->lock_object); 271 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 272 v = LK_UNLOCKED; 273 274 /* 275 * If the lock has exclusive waiters, give them preference in 276 * order to avoid deadlock with shared runners up. 277 * If interruptible sleeps left the exclusive queue empty 278 * avoid a starvation for the threads sleeping on the shared 279 * queue by giving them precedence and cleaning up the 280 * exclusive waiters bit anyway. 281 * Please note that lk_exslpfail count may be lying about 282 * the real number of waiters with the LK_SLEEPFAIL flag on 283 * because they may be used in conjuction with interruptible 284 * sleeps so lk_exslpfail might be considered an 'upper limit' 285 * bound, including the edge cases. 286 */ 287 realexslp = sleepq_sleepcnt(&lk->lock_object, 288 SQ_EXCLUSIVE_QUEUE); 289 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 290 if (lk->lk_exslpfail < realexslp) { 291 lk->lk_exslpfail = 0; 292 queue = SQ_EXCLUSIVE_QUEUE; 293 v |= (x & LK_SHARED_WAITERS); 294 } else { 295 lk->lk_exslpfail = 0; 296 LOCK_LOG2(lk, 297 "%s: %p has only LK_SLEEPFAIL sleepers", 298 __func__, lk); 299 LOCK_LOG2(lk, 300 "%s: %p waking up threads on the exclusive queue", 301 __func__, lk); 302 wakeup_swapper = 303 sleepq_broadcast(&lk->lock_object, 304 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 305 queue = SQ_SHARED_QUEUE; 306 } 307 308 } else { 309 310 /* 311 * Exclusive waiters sleeping with LK_SLEEPFAIL on 312 * and using interruptible sleeps/timeout may have 313 * left spourious lk_exslpfail counts on, so clean 314 * it up anyway. 315 */ 316 lk->lk_exslpfail = 0; 317 queue = SQ_SHARED_QUEUE; 318 } 319 320 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, 321 v)) { 322 sleepq_release(&lk->lock_object); 323 continue; 324 } 325 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 326 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 327 "exclusive"); 328 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 329 0, queue); 330 sleepq_release(&lk->lock_object); 331 break; 332 } 333 334 lock_profile_release_lock(&lk->lock_object); 335 return (wakeup_swapper); 336 } 337 338 static void 339 assert_lockmgr(const struct lock_object *lock, int what) 340 { 341 342 panic("lockmgr locks do not support assertions"); 343 } 344 345 static void 346 lock_lockmgr(struct lock_object *lock, int how) 347 { 348 349 panic("lockmgr locks do not support sleep interlocking"); 350 } 351 352 static int 353 unlock_lockmgr(struct lock_object *lock) 354 { 355 356 panic("lockmgr locks do not support sleep interlocking"); 357 } 358 359 #ifdef KDTRACE_HOOKS 360 static int 361 owner_lockmgr(const struct lock_object *lock, struct thread **owner) 362 { 363 364 panic("lockmgr locks do not support owner inquiring"); 365 } 366 #endif 367 368 void 369 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 370 { 371 int iflags; 372 373 MPASS((flags & ~LK_INIT_MASK) == 0); 374 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 375 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 376 &lk->lk_lock)); 377 378 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 379 if (flags & LK_CANRECURSE) 380 iflags |= LO_RECURSABLE; 381 if ((flags & LK_NODUP) == 0) 382 iflags |= LO_DUPOK; 383 if (flags & LK_NOPROFILE) 384 iflags |= LO_NOPROFILE; 385 if ((flags & LK_NOWITNESS) == 0) 386 iflags |= LO_WITNESS; 387 if (flags & LK_QUIET) 388 iflags |= LO_QUIET; 389 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 390 391 lk->lk_lock = LK_UNLOCKED; 392 lk->lk_recurse = 0; 393 lk->lk_exslpfail = 0; 394 lk->lk_timo = timo; 395 lk->lk_pri = pri; 396 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 397 STACK_ZERO(lk); 398 } 399 400 /* 401 * XXX: Gross hacks to manipulate external lock flags after 402 * initialization. Used for certain vnode and buf locks. 403 */ 404 void 405 lockallowshare(struct lock *lk) 406 { 407 408 lockmgr_assert(lk, KA_XLOCKED); 409 lk->lock_object.lo_flags &= ~LK_NOSHARE; 410 } 411 412 void 413 lockallowrecurse(struct lock *lk) 414 { 415 416 lockmgr_assert(lk, KA_XLOCKED); 417 lk->lock_object.lo_flags |= LO_RECURSABLE; 418 } 419 420 void 421 lockdisablerecurse(struct lock *lk) 422 { 423 424 lockmgr_assert(lk, KA_XLOCKED); 425 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 426 } 427 428 void 429 lockdestroy(struct lock *lk) 430 { 431 432 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 433 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 434 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 435 lock_destroy(&lk->lock_object); 436 } 437 438 int 439 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 440 const char *wmesg, int pri, int timo, const char *file, int line) 441 { 442 GIANT_DECLARE; 443 struct lock_class *class; 444 const char *iwmesg; 445 uintptr_t tid, v, x; 446 u_int op, realexslp; 447 int error, ipri, itimo, queue, wakeup_swapper; 448 #ifdef LOCK_PROFILING 449 uint64_t waittime = 0; 450 int contested = 0; 451 #endif 452 #ifdef ADAPTIVE_LOCKMGRS 453 volatile struct thread *owner; 454 u_int i, spintries = 0; 455 #endif 456 457 error = 0; 458 tid = (uintptr_t)curthread; 459 op = (flags & LK_TYPE_MASK); 460 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 461 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 462 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 463 464 MPASS((flags & ~LK_TOTAL_MASK) == 0); 465 KASSERT((op & (op - 1)) == 0, 466 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 467 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 468 (op != LK_DOWNGRADE && op != LK_RELEASE), 469 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 470 __func__, file, line)); 471 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 472 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 473 __func__, file, line)); 474 475 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 476 if (panicstr != NULL) { 477 if (flags & LK_INTERLOCK) 478 class->lc_unlock(ilk); 479 return (0); 480 } 481 482 if (lk->lock_object.lo_flags & LK_NOSHARE) { 483 switch (op) { 484 case LK_SHARED: 485 op = LK_EXCLUSIVE; 486 break; 487 case LK_UPGRADE: 488 case LK_DOWNGRADE: 489 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 490 file, line); 491 return (0); 492 } 493 } 494 495 wakeup_swapper = 0; 496 switch (op) { 497 case LK_SHARED: 498 if (LK_CAN_WITNESS(flags)) 499 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 500 file, line, ilk); 501 for (;;) { 502 x = lk->lk_lock; 503 504 /* 505 * If no other thread has an exclusive lock, or 506 * no exclusive waiter is present, bump the count of 507 * sharers. Since we have to preserve the state of 508 * waiters, if we fail to acquire the shared lock 509 * loop back and retry. 510 */ 511 if (LK_CAN_SHARE(x)) { 512 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 513 x + LK_ONE_SHARER)) 514 break; 515 continue; 516 } 517 lock_profile_obtain_lock_failed(&lk->lock_object, 518 &contested, &waittime); 519 520 /* 521 * If the lock is already held by curthread in 522 * exclusive way avoid a deadlock. 523 */ 524 if (LK_HOLDER(x) == tid) { 525 LOCK_LOG2(lk, 526 "%s: %p already held in exclusive mode", 527 __func__, lk); 528 error = EDEADLK; 529 break; 530 } 531 532 /* 533 * If the lock is expected to not sleep just give up 534 * and return. 535 */ 536 if (LK_TRYOP(flags)) { 537 LOCK_LOG2(lk, "%s: %p fails the try operation", 538 __func__, lk); 539 error = EBUSY; 540 break; 541 } 542 543 #ifdef ADAPTIVE_LOCKMGRS 544 /* 545 * If the owner is running on another CPU, spin until 546 * the owner stops running or the state of the lock 547 * changes. We need a double-state handle here 548 * because for a failed acquisition the lock can be 549 * either held in exclusive mode or shared mode 550 * (for the writer starvation avoidance technique). 551 */ 552 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 553 LK_HOLDER(x) != LK_KERNPROC) { 554 owner = (struct thread *)LK_HOLDER(x); 555 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 556 CTR3(KTR_LOCK, 557 "%s: spinning on %p held by %p", 558 __func__, lk, owner); 559 560 /* 561 * If we are holding also an interlock drop it 562 * in order to avoid a deadlock if the lockmgr 563 * owner is adaptively spinning on the 564 * interlock itself. 565 */ 566 if (flags & LK_INTERLOCK) { 567 class->lc_unlock(ilk); 568 flags &= ~LK_INTERLOCK; 569 } 570 GIANT_SAVE(); 571 while (LK_HOLDER(lk->lk_lock) == 572 (uintptr_t)owner && TD_IS_RUNNING(owner)) 573 cpu_spinwait(); 574 GIANT_RESTORE(); 575 continue; 576 } else if (LK_CAN_ADAPT(lk, flags) && 577 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 578 spintries < alk_retries) { 579 if (flags & LK_INTERLOCK) { 580 class->lc_unlock(ilk); 581 flags &= ~LK_INTERLOCK; 582 } 583 GIANT_SAVE(); 584 spintries++; 585 for (i = 0; i < alk_loops; i++) { 586 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 587 CTR4(KTR_LOCK, 588 "%s: shared spinning on %p with %u and %u", 589 __func__, lk, spintries, i); 590 x = lk->lk_lock; 591 if ((x & LK_SHARE) == 0 || 592 LK_CAN_SHARE(x) != 0) 593 break; 594 cpu_spinwait(); 595 } 596 GIANT_RESTORE(); 597 if (i != alk_loops) 598 continue; 599 } 600 #endif 601 602 /* 603 * Acquire the sleepqueue chain lock because we 604 * probabilly will need to manipulate waiters flags. 605 */ 606 sleepq_lock(&lk->lock_object); 607 x = lk->lk_lock; 608 609 /* 610 * if the lock can be acquired in shared mode, try 611 * again. 612 */ 613 if (LK_CAN_SHARE(x)) { 614 sleepq_release(&lk->lock_object); 615 continue; 616 } 617 618 #ifdef ADAPTIVE_LOCKMGRS 619 /* 620 * The current lock owner might have started executing 621 * on another CPU (or the lock could have changed 622 * owner) while we were waiting on the turnstile 623 * chain lock. If so, drop the turnstile lock and try 624 * again. 625 */ 626 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 627 LK_HOLDER(x) != LK_KERNPROC) { 628 owner = (struct thread *)LK_HOLDER(x); 629 if (TD_IS_RUNNING(owner)) { 630 sleepq_release(&lk->lock_object); 631 continue; 632 } 633 } 634 #endif 635 636 /* 637 * Try to set the LK_SHARED_WAITERS flag. If we fail, 638 * loop back and retry. 639 */ 640 if ((x & LK_SHARED_WAITERS) == 0) { 641 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 642 x | LK_SHARED_WAITERS)) { 643 sleepq_release(&lk->lock_object); 644 continue; 645 } 646 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 647 __func__, lk); 648 } 649 650 /* 651 * As far as we have been unable to acquire the 652 * shared lock and the shared waiters flag is set, 653 * we will sleep. 654 */ 655 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 656 SQ_SHARED_QUEUE); 657 flags &= ~LK_INTERLOCK; 658 if (error) { 659 LOCK_LOG3(lk, 660 "%s: interrupted sleep for %p with %d", 661 __func__, lk, error); 662 break; 663 } 664 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 665 __func__, lk); 666 } 667 if (error == 0) { 668 lock_profile_obtain_lock_success(&lk->lock_object, 669 contested, waittime, file, line); 670 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 671 line); 672 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 673 line); 674 TD_LOCKS_INC(curthread); 675 TD_SLOCKS_INC(curthread); 676 STACK_SAVE(lk); 677 } 678 break; 679 case LK_UPGRADE: 680 _lockmgr_assert(lk, KA_SLOCKED, file, line); 681 v = lk->lk_lock; 682 x = v & LK_ALL_WAITERS; 683 v &= LK_EXCLUSIVE_SPINNERS; 684 685 /* 686 * Try to switch from one shared lock to an exclusive one. 687 * We need to preserve waiters flags during the operation. 688 */ 689 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 690 tid | x)) { 691 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 692 line); 693 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 694 LK_TRYWIT(flags), file, line); 695 TD_SLOCKS_DEC(curthread); 696 break; 697 } 698 699 /* 700 * We have been unable to succeed in upgrading, so just 701 * give up the shared lock. 702 */ 703 wakeup_swapper |= wakeupshlk(lk, file, line); 704 705 /* FALLTHROUGH */ 706 case LK_EXCLUSIVE: 707 if (LK_CAN_WITNESS(flags)) 708 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 709 LOP_EXCLUSIVE, file, line, ilk); 710 711 /* 712 * If curthread already holds the lock and this one is 713 * allowed to recurse, simply recurse on it. 714 */ 715 if (lockmgr_xlocked(lk)) { 716 if ((flags & LK_CANRECURSE) == 0 && 717 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 718 719 /* 720 * If the lock is expected to not panic just 721 * give up and return. 722 */ 723 if (LK_TRYOP(flags)) { 724 LOCK_LOG2(lk, 725 "%s: %p fails the try operation", 726 __func__, lk); 727 error = EBUSY; 728 break; 729 } 730 if (flags & LK_INTERLOCK) 731 class->lc_unlock(ilk); 732 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 733 __func__, iwmesg, file, line); 734 } 735 lk->lk_recurse++; 736 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 737 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 738 lk->lk_recurse, file, line); 739 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 740 LK_TRYWIT(flags), file, line); 741 TD_LOCKS_INC(curthread); 742 break; 743 } 744 745 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 746 tid)) { 747 lock_profile_obtain_lock_failed(&lk->lock_object, 748 &contested, &waittime); 749 750 /* 751 * If the lock is expected to not sleep just give up 752 * and return. 753 */ 754 if (LK_TRYOP(flags)) { 755 LOCK_LOG2(lk, "%s: %p fails the try operation", 756 __func__, lk); 757 error = EBUSY; 758 break; 759 } 760 761 #ifdef ADAPTIVE_LOCKMGRS 762 /* 763 * If the owner is running on another CPU, spin until 764 * the owner stops running or the state of the lock 765 * changes. 766 */ 767 x = lk->lk_lock; 768 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 769 LK_HOLDER(x) != LK_KERNPROC) { 770 owner = (struct thread *)LK_HOLDER(x); 771 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 772 CTR3(KTR_LOCK, 773 "%s: spinning on %p held by %p", 774 __func__, lk, owner); 775 776 /* 777 * If we are holding also an interlock drop it 778 * in order to avoid a deadlock if the lockmgr 779 * owner is adaptively spinning on the 780 * interlock itself. 781 */ 782 if (flags & LK_INTERLOCK) { 783 class->lc_unlock(ilk); 784 flags &= ~LK_INTERLOCK; 785 } 786 GIANT_SAVE(); 787 while (LK_HOLDER(lk->lk_lock) == 788 (uintptr_t)owner && TD_IS_RUNNING(owner)) 789 cpu_spinwait(); 790 GIANT_RESTORE(); 791 continue; 792 } else if (LK_CAN_ADAPT(lk, flags) && 793 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 794 spintries < alk_retries) { 795 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 796 !atomic_cmpset_ptr(&lk->lk_lock, x, 797 x | LK_EXCLUSIVE_SPINNERS)) 798 continue; 799 if (flags & LK_INTERLOCK) { 800 class->lc_unlock(ilk); 801 flags &= ~LK_INTERLOCK; 802 } 803 GIANT_SAVE(); 804 spintries++; 805 for (i = 0; i < alk_loops; i++) { 806 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 807 CTR4(KTR_LOCK, 808 "%s: shared spinning on %p with %u and %u", 809 __func__, lk, spintries, i); 810 if ((lk->lk_lock & 811 LK_EXCLUSIVE_SPINNERS) == 0) 812 break; 813 cpu_spinwait(); 814 } 815 GIANT_RESTORE(); 816 if (i != alk_loops) 817 continue; 818 } 819 #endif 820 821 /* 822 * Acquire the sleepqueue chain lock because we 823 * probabilly will need to manipulate waiters flags. 824 */ 825 sleepq_lock(&lk->lock_object); 826 x = lk->lk_lock; 827 828 /* 829 * if the lock has been released while we spun on 830 * the sleepqueue chain lock just try again. 831 */ 832 if (x == LK_UNLOCKED) { 833 sleepq_release(&lk->lock_object); 834 continue; 835 } 836 837 #ifdef ADAPTIVE_LOCKMGRS 838 /* 839 * The current lock owner might have started executing 840 * on another CPU (or the lock could have changed 841 * owner) while we were waiting on the turnstile 842 * chain lock. If so, drop the turnstile lock and try 843 * again. 844 */ 845 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 846 LK_HOLDER(x) != LK_KERNPROC) { 847 owner = (struct thread *)LK_HOLDER(x); 848 if (TD_IS_RUNNING(owner)) { 849 sleepq_release(&lk->lock_object); 850 continue; 851 } 852 } 853 #endif 854 855 /* 856 * The lock can be in the state where there is a 857 * pending queue of waiters, but still no owner. 858 * This happens when the lock is contested and an 859 * owner is going to claim the lock. 860 * If curthread is the one successfully acquiring it 861 * claim lock ownership and return, preserving waiters 862 * flags. 863 */ 864 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 865 if ((x & ~v) == LK_UNLOCKED) { 866 v &= ~LK_EXCLUSIVE_SPINNERS; 867 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 868 tid | v)) { 869 sleepq_release(&lk->lock_object); 870 LOCK_LOG2(lk, 871 "%s: %p claimed by a new writer", 872 __func__, lk); 873 break; 874 } 875 sleepq_release(&lk->lock_object); 876 continue; 877 } 878 879 /* 880 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 881 * fail, loop back and retry. 882 */ 883 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 884 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 885 x | LK_EXCLUSIVE_WAITERS)) { 886 sleepq_release(&lk->lock_object); 887 continue; 888 } 889 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 890 __func__, lk); 891 } 892 893 /* 894 * As far as we have been unable to acquire the 895 * exclusive lock and the exclusive waiters flag 896 * is set, we will sleep. 897 */ 898 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 899 SQ_EXCLUSIVE_QUEUE); 900 flags &= ~LK_INTERLOCK; 901 if (error) { 902 LOCK_LOG3(lk, 903 "%s: interrupted sleep for %p with %d", 904 __func__, lk, error); 905 break; 906 } 907 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 908 __func__, lk); 909 } 910 if (error == 0) { 911 lock_profile_obtain_lock_success(&lk->lock_object, 912 contested, waittime, file, line); 913 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 914 lk->lk_recurse, file, line); 915 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 916 LK_TRYWIT(flags), file, line); 917 TD_LOCKS_INC(curthread); 918 STACK_SAVE(lk); 919 } 920 break; 921 case LK_DOWNGRADE: 922 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 923 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 924 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 925 TD_SLOCKS_INC(curthread); 926 927 /* 928 * In order to preserve waiters flags, just spin. 929 */ 930 for (;;) { 931 x = lk->lk_lock; 932 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 933 x &= LK_ALL_WAITERS; 934 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 935 LK_SHARERS_LOCK(1) | x)) 936 break; 937 cpu_spinwait(); 938 } 939 break; 940 case LK_RELEASE: 941 _lockmgr_assert(lk, KA_LOCKED, file, line); 942 x = lk->lk_lock; 943 944 if ((x & LK_SHARE) == 0) { 945 946 /* 947 * As first option, treact the lock as if it has not 948 * any waiter. 949 * Fix-up the tid var if the lock has been disowned. 950 */ 951 if (LK_HOLDER(x) == LK_KERNPROC) 952 tid = LK_KERNPROC; 953 else { 954 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 955 file, line); 956 TD_LOCKS_DEC(curthread); 957 } 958 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 959 lk->lk_recurse, file, line); 960 961 /* 962 * The lock is held in exclusive mode. 963 * If the lock is recursed also, then unrecurse it. 964 */ 965 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 966 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 967 lk); 968 lk->lk_recurse--; 969 break; 970 } 971 if (tid != LK_KERNPROC) 972 lock_profile_release_lock(&lk->lock_object); 973 974 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 975 LK_UNLOCKED)) 976 break; 977 978 sleepq_lock(&lk->lock_object); 979 x = lk->lk_lock; 980 v = LK_UNLOCKED; 981 982 /* 983 * If the lock has exclusive waiters, give them 984 * preference in order to avoid deadlock with 985 * shared runners up. 986 * If interruptible sleeps left the exclusive queue 987 * empty avoid a starvation for the threads sleeping 988 * on the shared queue by giving them precedence 989 * and cleaning up the exclusive waiters bit anyway. 990 * Please note that lk_exslpfail count may be lying 991 * about the real number of waiters with the 992 * LK_SLEEPFAIL flag on because they may be used in 993 * conjuction with interruptible sleeps so 994 * lk_exslpfail might be considered an 'upper limit' 995 * bound, including the edge cases. 996 */ 997 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 998 realexslp = sleepq_sleepcnt(&lk->lock_object, 999 SQ_EXCLUSIVE_QUEUE); 1000 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1001 if (lk->lk_exslpfail < realexslp) { 1002 lk->lk_exslpfail = 0; 1003 queue = SQ_EXCLUSIVE_QUEUE; 1004 v |= (x & LK_SHARED_WAITERS); 1005 } else { 1006 lk->lk_exslpfail = 0; 1007 LOCK_LOG2(lk, 1008 "%s: %p has only LK_SLEEPFAIL sleepers", 1009 __func__, lk); 1010 LOCK_LOG2(lk, 1011 "%s: %p waking up threads on the exclusive queue", 1012 __func__, lk); 1013 wakeup_swapper = 1014 sleepq_broadcast(&lk->lock_object, 1015 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1016 queue = SQ_SHARED_QUEUE; 1017 } 1018 } else { 1019 1020 /* 1021 * Exclusive waiters sleeping with LK_SLEEPFAIL 1022 * on and using interruptible sleeps/timeout 1023 * may have left spourious lk_exslpfail counts 1024 * on, so clean it up anyway. 1025 */ 1026 lk->lk_exslpfail = 0; 1027 queue = SQ_SHARED_QUEUE; 1028 } 1029 1030 LOCK_LOG3(lk, 1031 "%s: %p waking up threads on the %s queue", 1032 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1033 "exclusive"); 1034 atomic_store_rel_ptr(&lk->lk_lock, v); 1035 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1036 SLEEPQ_LK, 0, queue); 1037 sleepq_release(&lk->lock_object); 1038 break; 1039 } else 1040 wakeup_swapper = wakeupshlk(lk, file, line); 1041 break; 1042 case LK_DRAIN: 1043 if (LK_CAN_WITNESS(flags)) 1044 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1045 LOP_EXCLUSIVE, file, line, ilk); 1046 1047 /* 1048 * Trying to drain a lock we already own will result in a 1049 * deadlock. 1050 */ 1051 if (lockmgr_xlocked(lk)) { 1052 if (flags & LK_INTERLOCK) 1053 class->lc_unlock(ilk); 1054 panic("%s: draining %s with the lock held @ %s:%d\n", 1055 __func__, iwmesg, file, line); 1056 } 1057 1058 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1059 lock_profile_obtain_lock_failed(&lk->lock_object, 1060 &contested, &waittime); 1061 1062 /* 1063 * If the lock is expected to not sleep just give up 1064 * and return. 1065 */ 1066 if (LK_TRYOP(flags)) { 1067 LOCK_LOG2(lk, "%s: %p fails the try operation", 1068 __func__, lk); 1069 error = EBUSY; 1070 break; 1071 } 1072 1073 /* 1074 * Acquire the sleepqueue chain lock because we 1075 * probabilly will need to manipulate waiters flags. 1076 */ 1077 sleepq_lock(&lk->lock_object); 1078 x = lk->lk_lock; 1079 1080 /* 1081 * if the lock has been released while we spun on 1082 * the sleepqueue chain lock just try again. 1083 */ 1084 if (x == LK_UNLOCKED) { 1085 sleepq_release(&lk->lock_object); 1086 continue; 1087 } 1088 1089 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1090 if ((x & ~v) == LK_UNLOCKED) { 1091 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1092 1093 /* 1094 * If interruptible sleeps left the exclusive 1095 * queue empty avoid a starvation for the 1096 * threads sleeping on the shared queue by 1097 * giving them precedence and cleaning up the 1098 * exclusive waiters bit anyway. 1099 * Please note that lk_exslpfail count may be 1100 * lying about the real number of waiters with 1101 * the LK_SLEEPFAIL flag on because they may 1102 * be used in conjuction with interruptible 1103 * sleeps so lk_exslpfail might be considered 1104 * an 'upper limit' bound, including the edge 1105 * cases. 1106 */ 1107 if (v & LK_EXCLUSIVE_WAITERS) { 1108 queue = SQ_EXCLUSIVE_QUEUE; 1109 v &= ~LK_EXCLUSIVE_WAITERS; 1110 } else { 1111 1112 /* 1113 * Exclusive waiters sleeping with 1114 * LK_SLEEPFAIL on and using 1115 * interruptible sleeps/timeout may 1116 * have left spourious lk_exslpfail 1117 * counts on, so clean it up anyway. 1118 */ 1119 MPASS(v & LK_SHARED_WAITERS); 1120 lk->lk_exslpfail = 0; 1121 queue = SQ_SHARED_QUEUE; 1122 v &= ~LK_SHARED_WAITERS; 1123 } 1124 if (queue == SQ_EXCLUSIVE_QUEUE) { 1125 realexslp = 1126 sleepq_sleepcnt(&lk->lock_object, 1127 SQ_EXCLUSIVE_QUEUE); 1128 if (lk->lk_exslpfail >= realexslp) { 1129 lk->lk_exslpfail = 0; 1130 queue = SQ_SHARED_QUEUE; 1131 v &= ~LK_SHARED_WAITERS; 1132 if (realexslp != 0) { 1133 LOCK_LOG2(lk, 1134 "%s: %p has only LK_SLEEPFAIL sleepers", 1135 __func__, lk); 1136 LOCK_LOG2(lk, 1137 "%s: %p waking up threads on the exclusive queue", 1138 __func__, lk); 1139 wakeup_swapper = 1140 sleepq_broadcast( 1141 &lk->lock_object, 1142 SLEEPQ_LK, 0, 1143 SQ_EXCLUSIVE_QUEUE); 1144 } 1145 } else 1146 lk->lk_exslpfail = 0; 1147 } 1148 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1149 sleepq_release(&lk->lock_object); 1150 continue; 1151 } 1152 LOCK_LOG3(lk, 1153 "%s: %p waking up all threads on the %s queue", 1154 __func__, lk, queue == SQ_SHARED_QUEUE ? 1155 "shared" : "exclusive"); 1156 wakeup_swapper |= sleepq_broadcast( 1157 &lk->lock_object, SLEEPQ_LK, 0, queue); 1158 1159 /* 1160 * If shared waiters have been woken up we need 1161 * to wait for one of them to acquire the lock 1162 * before to set the exclusive waiters in 1163 * order to avoid a deadlock. 1164 */ 1165 if (queue == SQ_SHARED_QUEUE) { 1166 for (v = lk->lk_lock; 1167 (v & LK_SHARE) && !LK_SHARERS(v); 1168 v = lk->lk_lock) 1169 cpu_spinwait(); 1170 } 1171 } 1172 1173 /* 1174 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1175 * fail, loop back and retry. 1176 */ 1177 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1178 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1179 x | LK_EXCLUSIVE_WAITERS)) { 1180 sleepq_release(&lk->lock_object); 1181 continue; 1182 } 1183 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1184 __func__, lk); 1185 } 1186 1187 /* 1188 * As far as we have been unable to acquire the 1189 * exclusive lock and the exclusive waiters flag 1190 * is set, we will sleep. 1191 */ 1192 if (flags & LK_INTERLOCK) { 1193 class->lc_unlock(ilk); 1194 flags &= ~LK_INTERLOCK; 1195 } 1196 GIANT_SAVE(); 1197 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1198 SQ_EXCLUSIVE_QUEUE); 1199 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1200 GIANT_RESTORE(); 1201 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1202 __func__, lk); 1203 } 1204 1205 if (error == 0) { 1206 lock_profile_obtain_lock_success(&lk->lock_object, 1207 contested, waittime, file, line); 1208 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1209 lk->lk_recurse, file, line); 1210 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1211 LK_TRYWIT(flags), file, line); 1212 TD_LOCKS_INC(curthread); 1213 STACK_SAVE(lk); 1214 } 1215 break; 1216 default: 1217 if (flags & LK_INTERLOCK) 1218 class->lc_unlock(ilk); 1219 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1220 } 1221 1222 if (flags & LK_INTERLOCK) 1223 class->lc_unlock(ilk); 1224 if (wakeup_swapper) 1225 kick_proc0(); 1226 1227 return (error); 1228 } 1229 1230 void 1231 _lockmgr_disown(struct lock *lk, const char *file, int line) 1232 { 1233 uintptr_t tid, x; 1234 1235 tid = (uintptr_t)curthread; 1236 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 1237 1238 /* 1239 * If the owner is already LK_KERNPROC just skip the whole operation. 1240 */ 1241 if (LK_HOLDER(lk->lk_lock) != tid) 1242 return; 1243 lock_profile_release_lock(&lk->lock_object); 1244 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1245 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1246 TD_LOCKS_DEC(curthread); 1247 STACK_SAVE(lk); 1248 1249 /* 1250 * In order to preserve waiters flags, just spin. 1251 */ 1252 for (;;) { 1253 x = lk->lk_lock; 1254 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1255 x &= LK_ALL_WAITERS; 1256 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1257 LK_KERNPROC | x)) 1258 return; 1259 cpu_spinwait(); 1260 } 1261 } 1262 1263 void 1264 lockmgr_printinfo(const struct lock *lk) 1265 { 1266 struct thread *td; 1267 uintptr_t x; 1268 1269 if (lk->lk_lock == LK_UNLOCKED) 1270 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1271 else if (lk->lk_lock & LK_SHARE) 1272 printf("lock type %s: SHARED (count %ju)\n", 1273 lk->lock_object.lo_name, 1274 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1275 else { 1276 td = lockmgr_xholder(lk); 1277 printf("lock type %s: EXCL by thread %p (pid %d)\n", 1278 lk->lock_object.lo_name, td, td->td_proc->p_pid); 1279 } 1280 1281 x = lk->lk_lock; 1282 if (x & LK_EXCLUSIVE_WAITERS) 1283 printf(" with exclusive waiters pending\n"); 1284 if (x & LK_SHARED_WAITERS) 1285 printf(" with shared waiters pending\n"); 1286 if (x & LK_EXCLUSIVE_SPINNERS) 1287 printf(" with exclusive spinners pending\n"); 1288 1289 STACK_PRINT(lk); 1290 } 1291 1292 int 1293 lockstatus(const struct lock *lk) 1294 { 1295 uintptr_t v, x; 1296 int ret; 1297 1298 ret = LK_SHARED; 1299 x = lk->lk_lock; 1300 v = LK_HOLDER(x); 1301 1302 if ((x & LK_SHARE) == 0) { 1303 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1304 ret = LK_EXCLUSIVE; 1305 else 1306 ret = LK_EXCLOTHER; 1307 } else if (x == LK_UNLOCKED) 1308 ret = 0; 1309 1310 return (ret); 1311 } 1312 1313 #ifdef INVARIANT_SUPPORT 1314 1315 FEATURE(invariant_support, 1316 "Support for modules compiled with INVARIANTS option"); 1317 1318 #ifndef INVARIANTS 1319 #undef _lockmgr_assert 1320 #endif 1321 1322 void 1323 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1324 { 1325 int slocked = 0; 1326 1327 if (panicstr != NULL) 1328 return; 1329 switch (what) { 1330 case KA_SLOCKED: 1331 case KA_SLOCKED | KA_NOTRECURSED: 1332 case KA_SLOCKED | KA_RECURSED: 1333 slocked = 1; 1334 case KA_LOCKED: 1335 case KA_LOCKED | KA_NOTRECURSED: 1336 case KA_LOCKED | KA_RECURSED: 1337 #ifdef WITNESS 1338 1339 /* 1340 * We cannot trust WITNESS if the lock is held in exclusive 1341 * mode and a call to lockmgr_disown() happened. 1342 * Workaround this skipping the check if the lock is held in 1343 * exclusive mode even for the KA_LOCKED case. 1344 */ 1345 if (slocked || (lk->lk_lock & LK_SHARE)) { 1346 witness_assert(&lk->lock_object, what, file, line); 1347 break; 1348 } 1349 #endif 1350 if (lk->lk_lock == LK_UNLOCKED || 1351 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1352 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1353 panic("Lock %s not %slocked @ %s:%d\n", 1354 lk->lock_object.lo_name, slocked ? "share" : "", 1355 file, line); 1356 1357 if ((lk->lk_lock & LK_SHARE) == 0) { 1358 if (lockmgr_recursed(lk)) { 1359 if (what & KA_NOTRECURSED) 1360 panic("Lock %s recursed @ %s:%d\n", 1361 lk->lock_object.lo_name, file, 1362 line); 1363 } else if (what & KA_RECURSED) 1364 panic("Lock %s not recursed @ %s:%d\n", 1365 lk->lock_object.lo_name, file, line); 1366 } 1367 break; 1368 case KA_XLOCKED: 1369 case KA_XLOCKED | KA_NOTRECURSED: 1370 case KA_XLOCKED | KA_RECURSED: 1371 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1372 panic("Lock %s not exclusively locked @ %s:%d\n", 1373 lk->lock_object.lo_name, file, line); 1374 if (lockmgr_recursed(lk)) { 1375 if (what & KA_NOTRECURSED) 1376 panic("Lock %s recursed @ %s:%d\n", 1377 lk->lock_object.lo_name, file, line); 1378 } else if (what & KA_RECURSED) 1379 panic("Lock %s not recursed @ %s:%d\n", 1380 lk->lock_object.lo_name, file, line); 1381 break; 1382 case KA_UNLOCKED: 1383 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1384 panic("Lock %s exclusively locked @ %s:%d\n", 1385 lk->lock_object.lo_name, file, line); 1386 break; 1387 default: 1388 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1389 line); 1390 } 1391 } 1392 #endif 1393 1394 #ifdef DDB 1395 int 1396 lockmgr_chain(struct thread *td, struct thread **ownerp) 1397 { 1398 struct lock *lk; 1399 1400 lk = td->td_wchan; 1401 1402 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1403 return (0); 1404 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1405 if (lk->lk_lock & LK_SHARE) 1406 db_printf("SHARED (count %ju)\n", 1407 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1408 else 1409 db_printf("EXCL\n"); 1410 *ownerp = lockmgr_xholder(lk); 1411 1412 return (1); 1413 } 1414 1415 static void 1416 db_show_lockmgr(const struct lock_object *lock) 1417 { 1418 struct thread *td; 1419 const struct lock *lk; 1420 1421 lk = (const struct lock *)lock; 1422 1423 db_printf(" state: "); 1424 if (lk->lk_lock == LK_UNLOCKED) 1425 db_printf("UNLOCKED\n"); 1426 else if (lk->lk_lock & LK_SHARE) 1427 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1428 else { 1429 td = lockmgr_xholder(lk); 1430 if (td == (struct thread *)LK_KERNPROC) 1431 db_printf("XLOCK: LK_KERNPROC\n"); 1432 else 1433 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1434 td->td_tid, td->td_proc->p_pid, 1435 td->td_proc->p_comm); 1436 if (lockmgr_recursed(lk)) 1437 db_printf(" recursed: %d\n", lk->lk_recurse); 1438 } 1439 db_printf(" waiters: "); 1440 switch (lk->lk_lock & LK_ALL_WAITERS) { 1441 case LK_SHARED_WAITERS: 1442 db_printf("shared\n"); 1443 break; 1444 case LK_EXCLUSIVE_WAITERS: 1445 db_printf("exclusive\n"); 1446 break; 1447 case LK_ALL_WAITERS: 1448 db_printf("shared and exclusive\n"); 1449 break; 1450 default: 1451 db_printf("none\n"); 1452 } 1453 db_printf(" spinners: "); 1454 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1455 db_printf("exclusive\n"); 1456 else 1457 db_printf("none\n"); 1458 } 1459 #endif 1460