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