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