1 /*- 2 * Copyright (c) 2008 Attilio Rao <attilio@FreeBSD.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice(s), this list of conditions and the following disclaimer as 10 * the first lines of this file unmodified other than the possible 11 * addition of one or more copyright notices. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice(s), this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 19 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 20 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 22 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 23 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 26 * DAMAGE. 27 */ 28 29 #include "opt_adaptive_lockmgrs.h" 30 #include "opt_ddb.h" 31 #include "opt_hwpmc_hooks.h" 32 #include "opt_kdtrace.h" 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include <sys/param.h> 38 #include <sys/ktr.h> 39 #include <sys/lock.h> 40 #include <sys/lock_profile.h> 41 #include <sys/lockmgr.h> 42 #include <sys/mutex.h> 43 #include <sys/proc.h> 44 #include <sys/sleepqueue.h> 45 #ifdef DEBUG_LOCKS 46 #include <sys/stack.h> 47 #endif 48 #include <sys/sysctl.h> 49 #include <sys/systm.h> 50 51 #include <machine/cpu.h> 52 53 #ifdef DDB 54 #include <ddb/ddb.h> 55 #endif 56 57 #ifdef HWPMC_HOOKS 58 #include <sys/pmckern.h> 59 PMC_SOFT_DECLARE( , , lock, failed); 60 #endif 61 62 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) == 63 (LK_ADAPTIVE | LK_NOSHARE)); 64 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED & 65 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS))); 66 67 #define SQ_EXCLUSIVE_QUEUE 0 68 #define SQ_SHARED_QUEUE 1 69 70 #ifndef INVARIANTS 71 #define _lockmgr_assert(lk, what, file, line) 72 #define TD_LOCKS_INC(td) 73 #define TD_LOCKS_DEC(td) 74 #else 75 #define TD_LOCKS_INC(td) ((td)->td_locks++) 76 #define TD_LOCKS_DEC(td) ((td)->td_locks--) 77 #endif 78 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 79 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 80 81 #ifndef DEBUG_LOCKS 82 #define STACK_PRINT(lk) 83 #define STACK_SAVE(lk) 84 #define STACK_ZERO(lk) 85 #else 86 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 87 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 88 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 89 #endif 90 91 #define LOCK_LOG2(lk, string, arg1, arg2) \ 92 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 93 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 94 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 95 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 96 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 97 98 #define GIANT_DECLARE \ 99 int _i = 0; \ 100 WITNESS_SAVE_DECL(Giant) 101 #define GIANT_RESTORE() do { \ 102 if (_i > 0) { \ 103 while (_i--) \ 104 mtx_lock(&Giant); \ 105 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 106 } \ 107 } while (0) 108 #define GIANT_SAVE() do { \ 109 if (mtx_owned(&Giant)) { \ 110 WITNESS_SAVE(&Giant.lock_object, Giant); \ 111 while (mtx_owned(&Giant)) { \ 112 _i++; \ 113 mtx_unlock(&Giant); \ 114 } \ 115 } \ 116 } while (0) 117 118 #define LK_CAN_SHARE(x) \ 119 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \ 120 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \ 121 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT))) 122 #define LK_TRYOP(x) \ 123 ((x) & LK_NOWAIT) 124 125 #define LK_CAN_WITNESS(x) \ 126 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 127 #define LK_TRYWIT(x) \ 128 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 129 130 #define LK_CAN_ADAPT(lk, f) \ 131 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 132 ((f) & LK_SLEEPFAIL) == 0) 133 134 #define lockmgr_disowned(lk) \ 135 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 136 137 #define lockmgr_xlocked(lk) \ 138 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 139 140 static void assert_lockmgr(const struct lock_object *lock, int how); 141 #ifdef DDB 142 static void db_show_lockmgr(const struct lock_object *lock); 143 #endif 144 static void lock_lockmgr(struct lock_object *lock, int how); 145 #ifdef KDTRACE_HOOKS 146 static int owner_lockmgr(const struct lock_object *lock, 147 struct thread **owner); 148 #endif 149 static int unlock_lockmgr(struct lock_object *lock); 150 151 struct lock_class lock_class_lockmgr = { 152 .lc_name = "lockmgr", 153 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 154 .lc_assert = assert_lockmgr, 155 #ifdef DDB 156 .lc_ddb_show = db_show_lockmgr, 157 #endif 158 .lc_lock = lock_lockmgr, 159 .lc_unlock = unlock_lockmgr, 160 #ifdef KDTRACE_HOOKS 161 .lc_owner = owner_lockmgr, 162 #endif 163 }; 164 165 #ifdef ADAPTIVE_LOCKMGRS 166 static u_int alk_retries = 10; 167 static u_int alk_loops = 10000; 168 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, 169 "lockmgr debugging"); 170 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, ""); 171 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, ""); 172 #endif 173 174 static __inline struct thread * 175 lockmgr_xholder(const struct lock *lk) 176 { 177 uintptr_t x; 178 179 x = lk->lk_lock; 180 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 181 } 182 183 /* 184 * It assumes sleepq_lock held and returns with this one unheld. 185 * It also assumes the generic interlock is sane and previously checked. 186 * If LK_INTERLOCK is specified the interlock is not reacquired after the 187 * sleep. 188 */ 189 static __inline int 190 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 191 const char *wmesg, int pri, int timo, int queue) 192 { 193 GIANT_DECLARE; 194 struct lock_class *class; 195 int catch, error; 196 197 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 198 catch = pri & PCATCH; 199 pri &= PRIMASK; 200 error = 0; 201 202 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 203 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 204 205 if (flags & LK_INTERLOCK) 206 class->lc_unlock(ilk); 207 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 208 lk->lk_exslpfail++; 209 GIANT_SAVE(); 210 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 211 SLEEPQ_INTERRUPTIBLE : 0), queue); 212 if ((flags & LK_TIMELOCK) && timo) 213 sleepq_set_timeout(&lk->lock_object, timo); 214 215 /* 216 * Decisional switch for real sleeping. 217 */ 218 if ((flags & LK_TIMELOCK) && timo && catch) 219 error = sleepq_timedwait_sig(&lk->lock_object, pri); 220 else if ((flags & LK_TIMELOCK) && timo) 221 error = sleepq_timedwait(&lk->lock_object, pri); 222 else if (catch) 223 error = sleepq_wait_sig(&lk->lock_object, pri); 224 else 225 sleepq_wait(&lk->lock_object, pri); 226 GIANT_RESTORE(); 227 if ((flags & LK_SLEEPFAIL) && error == 0) 228 error = ENOLCK; 229 230 return (error); 231 } 232 233 static __inline int 234 wakeupshlk(struct lock *lk, const char *file, int line) 235 { 236 uintptr_t v, x; 237 u_int realexslp; 238 int queue, wakeup_swapper; 239 240 TD_LOCKS_DEC(curthread); 241 TD_SLOCKS_DEC(curthread); 242 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 243 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 244 245 wakeup_swapper = 0; 246 for (;;) { 247 x = lk->lk_lock; 248 249 /* 250 * If there is more than one shared lock held, just drop one 251 * and return. 252 */ 253 if (LK_SHARERS(x) > 1) { 254 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, 255 x - LK_ONE_SHARER)) 256 break; 257 continue; 258 } 259 260 /* 261 * If there are not waiters on the exclusive queue, drop the 262 * lock quickly. 263 */ 264 if ((x & LK_ALL_WAITERS) == 0) { 265 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == 266 LK_SHARERS_LOCK(1)); 267 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED)) 268 break; 269 continue; 270 } 271 272 /* 273 * We should have a sharer with waiters, so enter the hard 274 * path in order to handle wakeups correctly. 275 */ 276 sleepq_lock(&lk->lock_object); 277 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 278 v = LK_UNLOCKED; 279 280 /* 281 * If the lock has exclusive waiters, give them preference in 282 * order to avoid deadlock with shared runners up. 283 * If interruptible sleeps left the exclusive queue empty 284 * avoid a starvation for the threads sleeping on the shared 285 * queue by giving them precedence and cleaning up the 286 * exclusive waiters bit anyway. 287 * Please note that lk_exslpfail count may be lying about 288 * the real number of waiters with the LK_SLEEPFAIL flag on 289 * because they may be used in conjuction with interruptible 290 * sleeps so lk_exslpfail might be considered an 'upper limit' 291 * bound, including the edge cases. 292 */ 293 realexslp = sleepq_sleepcnt(&lk->lock_object, 294 SQ_EXCLUSIVE_QUEUE); 295 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 296 if (lk->lk_exslpfail < realexslp) { 297 lk->lk_exslpfail = 0; 298 queue = SQ_EXCLUSIVE_QUEUE; 299 v |= (x & LK_SHARED_WAITERS); 300 } else { 301 lk->lk_exslpfail = 0; 302 LOCK_LOG2(lk, 303 "%s: %p has only LK_SLEEPFAIL sleepers", 304 __func__, lk); 305 LOCK_LOG2(lk, 306 "%s: %p waking up threads on the exclusive queue", 307 __func__, lk); 308 wakeup_swapper = 309 sleepq_broadcast(&lk->lock_object, 310 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 311 queue = SQ_SHARED_QUEUE; 312 } 313 314 } else { 315 316 /* 317 * Exclusive waiters sleeping with LK_SLEEPFAIL on 318 * and using interruptible sleeps/timeout may have 319 * left spourious lk_exslpfail counts on, so clean 320 * it up anyway. 321 */ 322 lk->lk_exslpfail = 0; 323 queue = SQ_SHARED_QUEUE; 324 } 325 326 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, 327 v)) { 328 sleepq_release(&lk->lock_object); 329 continue; 330 } 331 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 332 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 333 "exclusive"); 334 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 335 0, queue); 336 sleepq_release(&lk->lock_object); 337 break; 338 } 339 340 lock_profile_release_lock(&lk->lock_object); 341 return (wakeup_swapper); 342 } 343 344 static void 345 assert_lockmgr(const struct lock_object *lock, int what) 346 { 347 348 panic("lockmgr locks do not support assertions"); 349 } 350 351 static void 352 lock_lockmgr(struct lock_object *lock, int how) 353 { 354 355 panic("lockmgr locks do not support sleep interlocking"); 356 } 357 358 static int 359 unlock_lockmgr(struct lock_object *lock) 360 { 361 362 panic("lockmgr locks do not support sleep interlocking"); 363 } 364 365 #ifdef KDTRACE_HOOKS 366 static int 367 owner_lockmgr(const struct lock_object *lock, struct thread **owner) 368 { 369 370 panic("lockmgr locks do not support owner inquiring"); 371 } 372 #endif 373 374 void 375 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 376 { 377 int iflags; 378 379 MPASS((flags & ~LK_INIT_MASK) == 0); 380 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 381 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 382 &lk->lk_lock)); 383 384 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 385 if (flags & LK_CANRECURSE) 386 iflags |= LO_RECURSABLE; 387 if ((flags & LK_NODUP) == 0) 388 iflags |= LO_DUPOK; 389 if (flags & LK_NOPROFILE) 390 iflags |= LO_NOPROFILE; 391 if ((flags & LK_NOWITNESS) == 0) 392 iflags |= LO_WITNESS; 393 if (flags & LK_QUIET) 394 iflags |= LO_QUIET; 395 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 396 397 lk->lk_lock = LK_UNLOCKED; 398 lk->lk_recurse = 0; 399 lk->lk_exslpfail = 0; 400 lk->lk_timo = timo; 401 lk->lk_pri = pri; 402 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 403 STACK_ZERO(lk); 404 } 405 406 /* 407 * XXX: Gross hacks to manipulate external lock flags after 408 * initialization. Used for certain vnode and buf locks. 409 */ 410 void 411 lockallowshare(struct lock *lk) 412 { 413 414 lockmgr_assert(lk, KA_XLOCKED); 415 lk->lock_object.lo_flags &= ~LK_NOSHARE; 416 } 417 418 void 419 lockallowrecurse(struct lock *lk) 420 { 421 422 lockmgr_assert(lk, KA_XLOCKED); 423 lk->lock_object.lo_flags |= LO_RECURSABLE; 424 } 425 426 void 427 lockdisablerecurse(struct lock *lk) 428 { 429 430 lockmgr_assert(lk, KA_XLOCKED); 431 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 432 } 433 434 void 435 lockdestroy(struct lock *lk) 436 { 437 438 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 439 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 440 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 441 lock_destroy(&lk->lock_object); 442 } 443 444 int 445 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 446 const char *wmesg, int pri, int timo, const char *file, int line) 447 { 448 GIANT_DECLARE; 449 struct lock_class *class; 450 const char *iwmesg; 451 uintptr_t tid, v, x; 452 u_int op, realexslp; 453 int error, ipri, itimo, queue, wakeup_swapper; 454 #ifdef LOCK_PROFILING 455 uint64_t waittime = 0; 456 int contested = 0; 457 #endif 458 #ifdef ADAPTIVE_LOCKMGRS 459 volatile struct thread *owner; 460 u_int i, spintries = 0; 461 #endif 462 463 error = 0; 464 tid = (uintptr_t)curthread; 465 op = (flags & LK_TYPE_MASK); 466 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 467 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 468 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 469 470 MPASS((flags & ~LK_TOTAL_MASK) == 0); 471 KASSERT((op & (op - 1)) == 0, 472 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 473 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 474 (op != LK_DOWNGRADE && op != LK_RELEASE), 475 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 476 __func__, file, line)); 477 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 478 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 479 __func__, file, line)); 480 481 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 482 if (panicstr != NULL) { 483 if (flags & LK_INTERLOCK) 484 class->lc_unlock(ilk); 485 return (0); 486 } 487 488 if (lk->lock_object.lo_flags & LK_NOSHARE) { 489 switch (op) { 490 case LK_SHARED: 491 op = LK_EXCLUSIVE; 492 break; 493 case LK_UPGRADE: 494 case LK_DOWNGRADE: 495 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 496 file, line); 497 return (0); 498 } 499 } 500 501 wakeup_swapper = 0; 502 switch (op) { 503 case LK_SHARED: 504 if (LK_CAN_WITNESS(flags)) 505 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 506 file, line, ilk); 507 for (;;) { 508 x = lk->lk_lock; 509 510 /* 511 * If no other thread has an exclusive lock, or 512 * no exclusive waiter is present, bump the count of 513 * sharers. Since we have to preserve the state of 514 * waiters, if we fail to acquire the shared lock 515 * loop back and retry. 516 */ 517 if (LK_CAN_SHARE(x)) { 518 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 519 x + LK_ONE_SHARER)) 520 break; 521 continue; 522 } 523 #ifdef HWPMC_HOOKS 524 PMC_SOFT_CALL( , , lock, failed); 525 #endif 526 lock_profile_obtain_lock_failed(&lk->lock_object, 527 &contested, &waittime); 528 529 /* 530 * If the lock is already held by curthread in 531 * exclusive way avoid a deadlock. 532 */ 533 if (LK_HOLDER(x) == tid) { 534 LOCK_LOG2(lk, 535 "%s: %p already held in exclusive mode", 536 __func__, lk); 537 error = EDEADLK; 538 break; 539 } 540 541 /* 542 * If the lock is expected to not sleep just give up 543 * and return. 544 */ 545 if (LK_TRYOP(flags)) { 546 LOCK_LOG2(lk, "%s: %p fails the try operation", 547 __func__, lk); 548 error = EBUSY; 549 break; 550 } 551 552 #ifdef ADAPTIVE_LOCKMGRS 553 /* 554 * If the owner is running on another CPU, spin until 555 * the owner stops running or the state of the lock 556 * changes. We need a double-state handle here 557 * because for a failed acquisition the lock can be 558 * either held in exclusive mode or shared mode 559 * (for the writer starvation avoidance technique). 560 */ 561 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 562 LK_HOLDER(x) != LK_KERNPROC) { 563 owner = (struct thread *)LK_HOLDER(x); 564 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 565 CTR3(KTR_LOCK, 566 "%s: spinning on %p held by %p", 567 __func__, lk, owner); 568 569 /* 570 * If we are holding also an interlock drop it 571 * in order to avoid a deadlock if the lockmgr 572 * owner is adaptively spinning on the 573 * interlock itself. 574 */ 575 if (flags & LK_INTERLOCK) { 576 class->lc_unlock(ilk); 577 flags &= ~LK_INTERLOCK; 578 } 579 GIANT_SAVE(); 580 while (LK_HOLDER(lk->lk_lock) == 581 (uintptr_t)owner && TD_IS_RUNNING(owner)) 582 cpu_spinwait(); 583 GIANT_RESTORE(); 584 continue; 585 } else if (LK_CAN_ADAPT(lk, flags) && 586 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 587 spintries < alk_retries) { 588 if (flags & LK_INTERLOCK) { 589 class->lc_unlock(ilk); 590 flags &= ~LK_INTERLOCK; 591 } 592 GIANT_SAVE(); 593 spintries++; 594 for (i = 0; i < alk_loops; i++) { 595 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 596 CTR4(KTR_LOCK, 597 "%s: shared spinning on %p with %u and %u", 598 __func__, lk, spintries, i); 599 x = lk->lk_lock; 600 if ((x & LK_SHARE) == 0 || 601 LK_CAN_SHARE(x) != 0) 602 break; 603 cpu_spinwait(); 604 } 605 GIANT_RESTORE(); 606 if (i != alk_loops) 607 continue; 608 } 609 #endif 610 611 /* 612 * Acquire the sleepqueue chain lock because we 613 * probabilly will need to manipulate waiters flags. 614 */ 615 sleepq_lock(&lk->lock_object); 616 x = lk->lk_lock; 617 618 /* 619 * if the lock can be acquired in shared mode, try 620 * again. 621 */ 622 if (LK_CAN_SHARE(x)) { 623 sleepq_release(&lk->lock_object); 624 continue; 625 } 626 627 #ifdef ADAPTIVE_LOCKMGRS 628 /* 629 * The current lock owner might have started executing 630 * on another CPU (or the lock could have changed 631 * owner) while we were waiting on the turnstile 632 * chain lock. If so, drop the turnstile lock and try 633 * again. 634 */ 635 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 636 LK_HOLDER(x) != LK_KERNPROC) { 637 owner = (struct thread *)LK_HOLDER(x); 638 if (TD_IS_RUNNING(owner)) { 639 sleepq_release(&lk->lock_object); 640 continue; 641 } 642 } 643 #endif 644 645 /* 646 * Try to set the LK_SHARED_WAITERS flag. If we fail, 647 * loop back and retry. 648 */ 649 if ((x & LK_SHARED_WAITERS) == 0) { 650 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 651 x | LK_SHARED_WAITERS)) { 652 sleepq_release(&lk->lock_object); 653 continue; 654 } 655 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 656 __func__, lk); 657 } 658 659 /* 660 * As far as we have been unable to acquire the 661 * shared lock and the shared waiters flag is set, 662 * we will sleep. 663 */ 664 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 665 SQ_SHARED_QUEUE); 666 flags &= ~LK_INTERLOCK; 667 if (error) { 668 LOCK_LOG3(lk, 669 "%s: interrupted sleep for %p with %d", 670 __func__, lk, error); 671 break; 672 } 673 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 674 __func__, lk); 675 } 676 if (error == 0) { 677 lock_profile_obtain_lock_success(&lk->lock_object, 678 contested, waittime, file, line); 679 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 680 line); 681 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 682 line); 683 TD_LOCKS_INC(curthread); 684 TD_SLOCKS_INC(curthread); 685 STACK_SAVE(lk); 686 } 687 break; 688 case LK_UPGRADE: 689 _lockmgr_assert(lk, KA_SLOCKED, file, line); 690 v = lk->lk_lock; 691 x = v & LK_ALL_WAITERS; 692 v &= LK_EXCLUSIVE_SPINNERS; 693 694 /* 695 * Try to switch from one shared lock to an exclusive one. 696 * We need to preserve waiters flags during the operation. 697 */ 698 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 699 tid | x)) { 700 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 701 line); 702 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 703 LK_TRYWIT(flags), file, line); 704 TD_SLOCKS_DEC(curthread); 705 break; 706 } 707 708 /* 709 * We have been unable to succeed in upgrading, so just 710 * give up the shared lock. 711 */ 712 wakeup_swapper |= wakeupshlk(lk, file, line); 713 714 /* FALLTHROUGH */ 715 case LK_EXCLUSIVE: 716 if (LK_CAN_WITNESS(flags)) 717 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 718 LOP_EXCLUSIVE, file, line, ilk); 719 720 /* 721 * If curthread already holds the lock and this one is 722 * allowed to recurse, simply recurse on it. 723 */ 724 if (lockmgr_xlocked(lk)) { 725 if ((flags & LK_CANRECURSE) == 0 && 726 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 727 728 /* 729 * If the lock is expected to not panic just 730 * give up and return. 731 */ 732 if (LK_TRYOP(flags)) { 733 LOCK_LOG2(lk, 734 "%s: %p fails the try operation", 735 __func__, lk); 736 error = EBUSY; 737 break; 738 } 739 if (flags & LK_INTERLOCK) 740 class->lc_unlock(ilk); 741 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 742 __func__, iwmesg, file, line); 743 } 744 lk->lk_recurse++; 745 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 746 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 747 lk->lk_recurse, file, line); 748 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 749 LK_TRYWIT(flags), file, line); 750 TD_LOCKS_INC(curthread); 751 break; 752 } 753 754 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 755 tid)) { 756 #ifdef HWPMC_HOOKS 757 PMC_SOFT_CALL( , , lock, failed); 758 #endif 759 lock_profile_obtain_lock_failed(&lk->lock_object, 760 &contested, &waittime); 761 762 /* 763 * If the lock is expected to not sleep just give up 764 * and return. 765 */ 766 if (LK_TRYOP(flags)) { 767 LOCK_LOG2(lk, "%s: %p fails the try operation", 768 __func__, lk); 769 error = EBUSY; 770 break; 771 } 772 773 #ifdef ADAPTIVE_LOCKMGRS 774 /* 775 * If the owner is running on another CPU, spin until 776 * the owner stops running or the state of the lock 777 * changes. 778 */ 779 x = lk->lk_lock; 780 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 781 LK_HOLDER(x) != LK_KERNPROC) { 782 owner = (struct thread *)LK_HOLDER(x); 783 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 784 CTR3(KTR_LOCK, 785 "%s: spinning on %p held by %p", 786 __func__, lk, owner); 787 788 /* 789 * If we are holding also an interlock drop it 790 * in order to avoid a deadlock if the lockmgr 791 * owner is adaptively spinning on the 792 * interlock itself. 793 */ 794 if (flags & LK_INTERLOCK) { 795 class->lc_unlock(ilk); 796 flags &= ~LK_INTERLOCK; 797 } 798 GIANT_SAVE(); 799 while (LK_HOLDER(lk->lk_lock) == 800 (uintptr_t)owner && TD_IS_RUNNING(owner)) 801 cpu_spinwait(); 802 GIANT_RESTORE(); 803 continue; 804 } else if (LK_CAN_ADAPT(lk, flags) && 805 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 806 spintries < alk_retries) { 807 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 808 !atomic_cmpset_ptr(&lk->lk_lock, x, 809 x | LK_EXCLUSIVE_SPINNERS)) 810 continue; 811 if (flags & LK_INTERLOCK) { 812 class->lc_unlock(ilk); 813 flags &= ~LK_INTERLOCK; 814 } 815 GIANT_SAVE(); 816 spintries++; 817 for (i = 0; i < alk_loops; i++) { 818 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 819 CTR4(KTR_LOCK, 820 "%s: shared spinning on %p with %u and %u", 821 __func__, lk, spintries, i); 822 if ((lk->lk_lock & 823 LK_EXCLUSIVE_SPINNERS) == 0) 824 break; 825 cpu_spinwait(); 826 } 827 GIANT_RESTORE(); 828 if (i != alk_loops) 829 continue; 830 } 831 #endif 832 833 /* 834 * Acquire the sleepqueue chain lock because we 835 * probabilly will need to manipulate waiters flags. 836 */ 837 sleepq_lock(&lk->lock_object); 838 x = lk->lk_lock; 839 840 /* 841 * if the lock has been released while we spun on 842 * the sleepqueue chain lock just try again. 843 */ 844 if (x == LK_UNLOCKED) { 845 sleepq_release(&lk->lock_object); 846 continue; 847 } 848 849 #ifdef ADAPTIVE_LOCKMGRS 850 /* 851 * The current lock owner might have started executing 852 * on another CPU (or the lock could have changed 853 * owner) while we were waiting on the turnstile 854 * chain lock. If so, drop the turnstile lock and try 855 * again. 856 */ 857 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 858 LK_HOLDER(x) != LK_KERNPROC) { 859 owner = (struct thread *)LK_HOLDER(x); 860 if (TD_IS_RUNNING(owner)) { 861 sleepq_release(&lk->lock_object); 862 continue; 863 } 864 } 865 #endif 866 867 /* 868 * The lock can be in the state where there is a 869 * pending queue of waiters, but still no owner. 870 * This happens when the lock is contested and an 871 * owner is going to claim the lock. 872 * If curthread is the one successfully acquiring it 873 * claim lock ownership and return, preserving waiters 874 * flags. 875 */ 876 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 877 if ((x & ~v) == LK_UNLOCKED) { 878 v &= ~LK_EXCLUSIVE_SPINNERS; 879 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 880 tid | v)) { 881 sleepq_release(&lk->lock_object); 882 LOCK_LOG2(lk, 883 "%s: %p claimed by a new writer", 884 __func__, lk); 885 break; 886 } 887 sleepq_release(&lk->lock_object); 888 continue; 889 } 890 891 /* 892 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 893 * fail, loop back and retry. 894 */ 895 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 896 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 897 x | LK_EXCLUSIVE_WAITERS)) { 898 sleepq_release(&lk->lock_object); 899 continue; 900 } 901 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 902 __func__, lk); 903 } 904 905 /* 906 * As far as we have been unable to acquire the 907 * exclusive lock and the exclusive waiters flag 908 * is set, we will sleep. 909 */ 910 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 911 SQ_EXCLUSIVE_QUEUE); 912 flags &= ~LK_INTERLOCK; 913 if (error) { 914 LOCK_LOG3(lk, 915 "%s: interrupted sleep for %p with %d", 916 __func__, lk, error); 917 break; 918 } 919 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 920 __func__, lk); 921 } 922 if (error == 0) { 923 lock_profile_obtain_lock_success(&lk->lock_object, 924 contested, waittime, file, line); 925 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 926 lk->lk_recurse, file, line); 927 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 928 LK_TRYWIT(flags), file, line); 929 TD_LOCKS_INC(curthread); 930 STACK_SAVE(lk); 931 } 932 break; 933 case LK_DOWNGRADE: 934 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 935 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 936 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 937 TD_SLOCKS_INC(curthread); 938 939 /* 940 * In order to preserve waiters flags, just spin. 941 */ 942 for (;;) { 943 x = lk->lk_lock; 944 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 945 x &= LK_ALL_WAITERS; 946 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 947 LK_SHARERS_LOCK(1) | x)) 948 break; 949 cpu_spinwait(); 950 } 951 break; 952 case LK_RELEASE: 953 _lockmgr_assert(lk, KA_LOCKED, file, line); 954 x = lk->lk_lock; 955 956 if ((x & LK_SHARE) == 0) { 957 958 /* 959 * As first option, treact the lock as if it has not 960 * any waiter. 961 * Fix-up the tid var if the lock has been disowned. 962 */ 963 if (LK_HOLDER(x) == LK_KERNPROC) 964 tid = LK_KERNPROC; 965 else { 966 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 967 file, line); 968 TD_LOCKS_DEC(curthread); 969 } 970 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 971 lk->lk_recurse, file, line); 972 973 /* 974 * The lock is held in exclusive mode. 975 * If the lock is recursed also, then unrecurse it. 976 */ 977 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 978 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 979 lk); 980 lk->lk_recurse--; 981 break; 982 } 983 if (tid != LK_KERNPROC) 984 lock_profile_release_lock(&lk->lock_object); 985 986 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 987 LK_UNLOCKED)) 988 break; 989 990 sleepq_lock(&lk->lock_object); 991 x = lk->lk_lock; 992 v = LK_UNLOCKED; 993 994 /* 995 * If the lock has exclusive waiters, give them 996 * preference in order to avoid deadlock with 997 * shared runners up. 998 * If interruptible sleeps left the exclusive queue 999 * empty avoid a starvation for the threads sleeping 1000 * on the shared queue by giving them precedence 1001 * and cleaning up the exclusive waiters bit anyway. 1002 * Please note that lk_exslpfail count may be lying 1003 * about the real number of waiters with the 1004 * LK_SLEEPFAIL flag on because they may be used in 1005 * conjuction with interruptible sleeps so 1006 * lk_exslpfail might be considered an 'upper limit' 1007 * bound, including the edge cases. 1008 */ 1009 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1010 realexslp = sleepq_sleepcnt(&lk->lock_object, 1011 SQ_EXCLUSIVE_QUEUE); 1012 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1013 if (lk->lk_exslpfail < realexslp) { 1014 lk->lk_exslpfail = 0; 1015 queue = SQ_EXCLUSIVE_QUEUE; 1016 v |= (x & LK_SHARED_WAITERS); 1017 } else { 1018 lk->lk_exslpfail = 0; 1019 LOCK_LOG2(lk, 1020 "%s: %p has only LK_SLEEPFAIL sleepers", 1021 __func__, lk); 1022 LOCK_LOG2(lk, 1023 "%s: %p waking up threads on the exclusive queue", 1024 __func__, lk); 1025 wakeup_swapper = 1026 sleepq_broadcast(&lk->lock_object, 1027 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1028 queue = SQ_SHARED_QUEUE; 1029 } 1030 } else { 1031 1032 /* 1033 * Exclusive waiters sleeping with LK_SLEEPFAIL 1034 * on and using interruptible sleeps/timeout 1035 * may have left spourious lk_exslpfail counts 1036 * on, so clean it up anyway. 1037 */ 1038 lk->lk_exslpfail = 0; 1039 queue = SQ_SHARED_QUEUE; 1040 } 1041 1042 LOCK_LOG3(lk, 1043 "%s: %p waking up threads on the %s queue", 1044 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1045 "exclusive"); 1046 atomic_store_rel_ptr(&lk->lk_lock, v); 1047 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1048 SLEEPQ_LK, 0, queue); 1049 sleepq_release(&lk->lock_object); 1050 break; 1051 } else 1052 wakeup_swapper = wakeupshlk(lk, file, line); 1053 break; 1054 case LK_DRAIN: 1055 if (LK_CAN_WITNESS(flags)) 1056 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1057 LOP_EXCLUSIVE, file, line, ilk); 1058 1059 /* 1060 * Trying to drain a lock we already own will result in a 1061 * deadlock. 1062 */ 1063 if (lockmgr_xlocked(lk)) { 1064 if (flags & LK_INTERLOCK) 1065 class->lc_unlock(ilk); 1066 panic("%s: draining %s with the lock held @ %s:%d\n", 1067 __func__, iwmesg, file, line); 1068 } 1069 1070 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1071 #ifdef HWPMC_HOOKS 1072 PMC_SOFT_CALL( , , lock, failed); 1073 #endif 1074 lock_profile_obtain_lock_failed(&lk->lock_object, 1075 &contested, &waittime); 1076 1077 /* 1078 * If the lock is expected to not sleep just give up 1079 * and return. 1080 */ 1081 if (LK_TRYOP(flags)) { 1082 LOCK_LOG2(lk, "%s: %p fails the try operation", 1083 __func__, lk); 1084 error = EBUSY; 1085 break; 1086 } 1087 1088 /* 1089 * Acquire the sleepqueue chain lock because we 1090 * probabilly will need to manipulate waiters flags. 1091 */ 1092 sleepq_lock(&lk->lock_object); 1093 x = lk->lk_lock; 1094 1095 /* 1096 * if the lock has been released while we spun on 1097 * the sleepqueue chain lock just try again. 1098 */ 1099 if (x == LK_UNLOCKED) { 1100 sleepq_release(&lk->lock_object); 1101 continue; 1102 } 1103 1104 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1105 if ((x & ~v) == LK_UNLOCKED) { 1106 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1107 1108 /* 1109 * If interruptible sleeps left the exclusive 1110 * queue empty avoid a starvation for the 1111 * threads sleeping on the shared queue by 1112 * giving them precedence and cleaning up the 1113 * exclusive waiters bit anyway. 1114 * Please note that lk_exslpfail count may be 1115 * lying about the real number of waiters with 1116 * the LK_SLEEPFAIL flag on because they may 1117 * be used in conjuction with interruptible 1118 * sleeps so lk_exslpfail might be considered 1119 * an 'upper limit' bound, including the edge 1120 * cases. 1121 */ 1122 if (v & LK_EXCLUSIVE_WAITERS) { 1123 queue = SQ_EXCLUSIVE_QUEUE; 1124 v &= ~LK_EXCLUSIVE_WAITERS; 1125 } else { 1126 1127 /* 1128 * Exclusive waiters sleeping with 1129 * LK_SLEEPFAIL on and using 1130 * interruptible sleeps/timeout may 1131 * have left spourious lk_exslpfail 1132 * counts on, so clean it up anyway. 1133 */ 1134 MPASS(v & LK_SHARED_WAITERS); 1135 lk->lk_exslpfail = 0; 1136 queue = SQ_SHARED_QUEUE; 1137 v &= ~LK_SHARED_WAITERS; 1138 } 1139 if (queue == SQ_EXCLUSIVE_QUEUE) { 1140 realexslp = 1141 sleepq_sleepcnt(&lk->lock_object, 1142 SQ_EXCLUSIVE_QUEUE); 1143 if (lk->lk_exslpfail >= realexslp) { 1144 lk->lk_exslpfail = 0; 1145 queue = SQ_SHARED_QUEUE; 1146 v &= ~LK_SHARED_WAITERS; 1147 if (realexslp != 0) { 1148 LOCK_LOG2(lk, 1149 "%s: %p has only LK_SLEEPFAIL sleepers", 1150 __func__, lk); 1151 LOCK_LOG2(lk, 1152 "%s: %p waking up threads on the exclusive queue", 1153 __func__, lk); 1154 wakeup_swapper = 1155 sleepq_broadcast( 1156 &lk->lock_object, 1157 SLEEPQ_LK, 0, 1158 SQ_EXCLUSIVE_QUEUE); 1159 } 1160 } else 1161 lk->lk_exslpfail = 0; 1162 } 1163 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1164 sleepq_release(&lk->lock_object); 1165 continue; 1166 } 1167 LOCK_LOG3(lk, 1168 "%s: %p waking up all threads on the %s queue", 1169 __func__, lk, queue == SQ_SHARED_QUEUE ? 1170 "shared" : "exclusive"); 1171 wakeup_swapper |= sleepq_broadcast( 1172 &lk->lock_object, SLEEPQ_LK, 0, queue); 1173 1174 /* 1175 * If shared waiters have been woken up we need 1176 * to wait for one of them to acquire the lock 1177 * before to set the exclusive waiters in 1178 * order to avoid a deadlock. 1179 */ 1180 if (queue == SQ_SHARED_QUEUE) { 1181 for (v = lk->lk_lock; 1182 (v & LK_SHARE) && !LK_SHARERS(v); 1183 v = lk->lk_lock) 1184 cpu_spinwait(); 1185 } 1186 } 1187 1188 /* 1189 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1190 * fail, loop back and retry. 1191 */ 1192 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1193 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1194 x | LK_EXCLUSIVE_WAITERS)) { 1195 sleepq_release(&lk->lock_object); 1196 continue; 1197 } 1198 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1199 __func__, lk); 1200 } 1201 1202 /* 1203 * As far as we have been unable to acquire the 1204 * exclusive lock and the exclusive waiters flag 1205 * is set, we will sleep. 1206 */ 1207 if (flags & LK_INTERLOCK) { 1208 class->lc_unlock(ilk); 1209 flags &= ~LK_INTERLOCK; 1210 } 1211 GIANT_SAVE(); 1212 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1213 SQ_EXCLUSIVE_QUEUE); 1214 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1215 GIANT_RESTORE(); 1216 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1217 __func__, lk); 1218 } 1219 1220 if (error == 0) { 1221 lock_profile_obtain_lock_success(&lk->lock_object, 1222 contested, waittime, file, line); 1223 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1224 lk->lk_recurse, file, line); 1225 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1226 LK_TRYWIT(flags), file, line); 1227 TD_LOCKS_INC(curthread); 1228 STACK_SAVE(lk); 1229 } 1230 break; 1231 default: 1232 if (flags & LK_INTERLOCK) 1233 class->lc_unlock(ilk); 1234 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1235 } 1236 1237 if (flags & LK_INTERLOCK) 1238 class->lc_unlock(ilk); 1239 if (wakeup_swapper) 1240 kick_proc0(); 1241 1242 return (error); 1243 } 1244 1245 void 1246 _lockmgr_disown(struct lock *lk, const char *file, int line) 1247 { 1248 uintptr_t tid, x; 1249 1250 if (SCHEDULER_STOPPED()) 1251 return; 1252 1253 tid = (uintptr_t)curthread; 1254 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); 1255 1256 /* 1257 * If the owner is already LK_KERNPROC just skip the whole operation. 1258 */ 1259 if (LK_HOLDER(lk->lk_lock) != tid) 1260 return; 1261 lock_profile_release_lock(&lk->lock_object); 1262 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1263 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1264 TD_LOCKS_DEC(curthread); 1265 STACK_SAVE(lk); 1266 1267 /* 1268 * In order to preserve waiters flags, just spin. 1269 */ 1270 for (;;) { 1271 x = lk->lk_lock; 1272 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1273 x &= LK_ALL_WAITERS; 1274 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1275 LK_KERNPROC | x)) 1276 return; 1277 cpu_spinwait(); 1278 } 1279 } 1280 1281 void 1282 lockmgr_printinfo(const struct lock *lk) 1283 { 1284 struct thread *td; 1285 uintptr_t x; 1286 1287 if (lk->lk_lock == LK_UNLOCKED) 1288 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1289 else if (lk->lk_lock & LK_SHARE) 1290 printf("lock type %s: SHARED (count %ju)\n", 1291 lk->lock_object.lo_name, 1292 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1293 else { 1294 td = lockmgr_xholder(lk); 1295 printf("lock type %s: EXCL by thread %p " 1296 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, td, 1297 td->td_proc->p_pid, td->td_proc->p_comm, td->td_tid); 1298 } 1299 1300 x = lk->lk_lock; 1301 if (x & LK_EXCLUSIVE_WAITERS) 1302 printf(" with exclusive waiters pending\n"); 1303 if (x & LK_SHARED_WAITERS) 1304 printf(" with shared waiters pending\n"); 1305 if (x & LK_EXCLUSIVE_SPINNERS) 1306 printf(" with exclusive spinners pending\n"); 1307 1308 STACK_PRINT(lk); 1309 } 1310 1311 int 1312 lockstatus(const struct lock *lk) 1313 { 1314 uintptr_t v, x; 1315 int ret; 1316 1317 ret = LK_SHARED; 1318 x = lk->lk_lock; 1319 v = LK_HOLDER(x); 1320 1321 if ((x & LK_SHARE) == 0) { 1322 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1323 ret = LK_EXCLUSIVE; 1324 else 1325 ret = LK_EXCLOTHER; 1326 } else if (x == LK_UNLOCKED) 1327 ret = 0; 1328 1329 return (ret); 1330 } 1331 1332 #ifdef INVARIANT_SUPPORT 1333 1334 FEATURE(invariant_support, 1335 "Support for modules compiled with INVARIANTS option"); 1336 1337 #ifndef INVARIANTS 1338 #undef _lockmgr_assert 1339 #endif 1340 1341 void 1342 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1343 { 1344 int slocked = 0; 1345 1346 if (panicstr != NULL) 1347 return; 1348 switch (what) { 1349 case KA_SLOCKED: 1350 case KA_SLOCKED | KA_NOTRECURSED: 1351 case KA_SLOCKED | KA_RECURSED: 1352 slocked = 1; 1353 case KA_LOCKED: 1354 case KA_LOCKED | KA_NOTRECURSED: 1355 case KA_LOCKED | KA_RECURSED: 1356 #ifdef WITNESS 1357 1358 /* 1359 * We cannot trust WITNESS if the lock is held in exclusive 1360 * mode and a call to lockmgr_disown() happened. 1361 * Workaround this skipping the check if the lock is held in 1362 * exclusive mode even for the KA_LOCKED case. 1363 */ 1364 if (slocked || (lk->lk_lock & LK_SHARE)) { 1365 witness_assert(&lk->lock_object, what, file, line); 1366 break; 1367 } 1368 #endif 1369 if (lk->lk_lock == LK_UNLOCKED || 1370 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1371 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1372 panic("Lock %s not %slocked @ %s:%d\n", 1373 lk->lock_object.lo_name, slocked ? "share" : "", 1374 file, line); 1375 1376 if ((lk->lk_lock & LK_SHARE) == 0) { 1377 if (lockmgr_recursed(lk)) { 1378 if (what & KA_NOTRECURSED) 1379 panic("Lock %s recursed @ %s:%d\n", 1380 lk->lock_object.lo_name, file, 1381 line); 1382 } else if (what & KA_RECURSED) 1383 panic("Lock %s not recursed @ %s:%d\n", 1384 lk->lock_object.lo_name, file, line); 1385 } 1386 break; 1387 case KA_XLOCKED: 1388 case KA_XLOCKED | KA_NOTRECURSED: 1389 case KA_XLOCKED | KA_RECURSED: 1390 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1391 panic("Lock %s not exclusively locked @ %s:%d\n", 1392 lk->lock_object.lo_name, file, line); 1393 if (lockmgr_recursed(lk)) { 1394 if (what & KA_NOTRECURSED) 1395 panic("Lock %s recursed @ %s:%d\n", 1396 lk->lock_object.lo_name, file, line); 1397 } else if (what & KA_RECURSED) 1398 panic("Lock %s not recursed @ %s:%d\n", 1399 lk->lock_object.lo_name, file, line); 1400 break; 1401 case KA_UNLOCKED: 1402 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1403 panic("Lock %s exclusively locked @ %s:%d\n", 1404 lk->lock_object.lo_name, file, line); 1405 break; 1406 default: 1407 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1408 line); 1409 } 1410 } 1411 #endif 1412 1413 #ifdef DDB 1414 int 1415 lockmgr_chain(struct thread *td, struct thread **ownerp) 1416 { 1417 struct lock *lk; 1418 1419 lk = td->td_wchan; 1420 1421 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1422 return (0); 1423 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1424 if (lk->lk_lock & LK_SHARE) 1425 db_printf("SHARED (count %ju)\n", 1426 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1427 else 1428 db_printf("EXCL\n"); 1429 *ownerp = lockmgr_xholder(lk); 1430 1431 return (1); 1432 } 1433 1434 static void 1435 db_show_lockmgr(const struct lock_object *lock) 1436 { 1437 struct thread *td; 1438 const struct lock *lk; 1439 1440 lk = (const struct lock *)lock; 1441 1442 db_printf(" state: "); 1443 if (lk->lk_lock == LK_UNLOCKED) 1444 db_printf("UNLOCKED\n"); 1445 else if (lk->lk_lock & LK_SHARE) 1446 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1447 else { 1448 td = lockmgr_xholder(lk); 1449 if (td == (struct thread *)LK_KERNPROC) 1450 db_printf("XLOCK: LK_KERNPROC\n"); 1451 else 1452 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1453 td->td_tid, td->td_proc->p_pid, 1454 td->td_proc->p_comm); 1455 if (lockmgr_recursed(lk)) 1456 db_printf(" recursed: %d\n", lk->lk_recurse); 1457 } 1458 db_printf(" waiters: "); 1459 switch (lk->lk_lock & LK_ALL_WAITERS) { 1460 case LK_SHARED_WAITERS: 1461 db_printf("shared\n"); 1462 break; 1463 case LK_EXCLUSIVE_WAITERS: 1464 db_printf("exclusive\n"); 1465 break; 1466 case LK_ALL_WAITERS: 1467 db_printf("shared and exclusive\n"); 1468 break; 1469 default: 1470 db_printf("none\n"); 1471 } 1472 db_printf(" spinners: "); 1473 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1474 db_printf("exclusive\n"); 1475 else 1476 db_printf("none\n"); 1477 } 1478 #endif 1479