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/kdb.h> 39 #include <sys/ktr.h> 40 #include <sys/lock.h> 41 #include <sys/lock_profile.h> 42 #include <sys/lockmgr.h> 43 #include <sys/mutex.h> 44 #include <sys/proc.h> 45 #include <sys/sleepqueue.h> 46 #ifdef DEBUG_LOCKS 47 #include <sys/stack.h> 48 #endif 49 #include <sys/sysctl.h> 50 #include <sys/systm.h> 51 52 #include <machine/cpu.h> 53 54 #ifdef DDB 55 #include <ddb/ddb.h> 56 #endif 57 58 #ifdef HWPMC_HOOKS 59 #include <sys/pmckern.h> 60 PMC_SOFT_DECLARE( , , lock, failed); 61 #endif 62 63 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) == 64 (LK_ADAPTIVE | LK_NOSHARE)); 65 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED & 66 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS))); 67 68 #define SQ_EXCLUSIVE_QUEUE 0 69 #define SQ_SHARED_QUEUE 1 70 71 #ifndef INVARIANTS 72 #define _lockmgr_assert(lk, what, file, line) 73 #define TD_LOCKS_INC(td) 74 #define TD_LOCKS_DEC(td) 75 #else 76 #define TD_LOCKS_INC(td) ((td)->td_locks++) 77 #define TD_LOCKS_DEC(td) ((td)->td_locks--) 78 #endif 79 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 80 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 81 82 #ifndef DEBUG_LOCKS 83 #define STACK_PRINT(lk) 84 #define STACK_SAVE(lk) 85 #define STACK_ZERO(lk) 86 #else 87 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 88 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 89 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 90 #endif 91 92 #define LOCK_LOG2(lk, string, arg1, arg2) \ 93 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 94 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 95 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 96 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 97 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 98 99 #define GIANT_DECLARE \ 100 int _i = 0; \ 101 WITNESS_SAVE_DECL(Giant) 102 #define GIANT_RESTORE() do { \ 103 if (_i > 0) { \ 104 while (_i--) \ 105 mtx_lock(&Giant); \ 106 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 107 } \ 108 } while (0) 109 #define GIANT_SAVE() do { \ 110 if (mtx_owned(&Giant)) { \ 111 WITNESS_SAVE(&Giant.lock_object, Giant); \ 112 while (mtx_owned(&Giant)) { \ 113 _i++; \ 114 mtx_unlock(&Giant); \ 115 } \ 116 } \ 117 } while (0) 118 119 #define LK_CAN_SHARE(x) \ 120 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \ 121 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \ 122 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT))) 123 #define LK_TRYOP(x) \ 124 ((x) & LK_NOWAIT) 125 126 #define LK_CAN_WITNESS(x) \ 127 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) 128 #define LK_TRYWIT(x) \ 129 (LK_TRYOP(x) ? LOP_TRYLOCK : 0) 130 131 #define LK_CAN_ADAPT(lk, f) \ 132 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ 133 ((f) & LK_SLEEPFAIL) == 0) 134 135 #define lockmgr_disowned(lk) \ 136 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) 137 138 #define lockmgr_xlocked(lk) \ 139 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) 140 141 static void assert_lockmgr(const struct lock_object *lock, int how); 142 #ifdef DDB 143 static void db_show_lockmgr(const struct lock_object *lock); 144 #endif 145 static void lock_lockmgr(struct lock_object *lock, int how); 146 #ifdef KDTRACE_HOOKS 147 static int owner_lockmgr(const struct lock_object *lock, 148 struct thread **owner); 149 #endif 150 static int unlock_lockmgr(struct lock_object *lock); 151 152 struct lock_class lock_class_lockmgr = { 153 .lc_name = "lockmgr", 154 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, 155 .lc_assert = assert_lockmgr, 156 #ifdef DDB 157 .lc_ddb_show = db_show_lockmgr, 158 #endif 159 .lc_lock = lock_lockmgr, 160 .lc_unlock = unlock_lockmgr, 161 #ifdef KDTRACE_HOOKS 162 .lc_owner = owner_lockmgr, 163 #endif 164 }; 165 166 #ifdef ADAPTIVE_LOCKMGRS 167 static u_int alk_retries = 10; 168 static u_int alk_loops = 10000; 169 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, 170 "lockmgr debugging"); 171 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, ""); 172 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, ""); 173 #endif 174 175 static __inline struct thread * 176 lockmgr_xholder(const struct lock *lk) 177 { 178 uintptr_t x; 179 180 x = lk->lk_lock; 181 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); 182 } 183 184 /* 185 * It assumes sleepq_lock held and returns with this one unheld. 186 * It also assumes the generic interlock is sane and previously checked. 187 * If LK_INTERLOCK is specified the interlock is not reacquired after the 188 * sleep. 189 */ 190 static __inline int 191 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, 192 const char *wmesg, int pri, int timo, int queue) 193 { 194 GIANT_DECLARE; 195 struct lock_class *class; 196 int catch, error; 197 198 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 199 catch = pri & PCATCH; 200 pri &= PRIMASK; 201 error = 0; 202 203 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, 204 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); 205 206 if (flags & LK_INTERLOCK) 207 class->lc_unlock(ilk); 208 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) 209 lk->lk_exslpfail++; 210 GIANT_SAVE(); 211 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? 212 SLEEPQ_INTERRUPTIBLE : 0), queue); 213 if ((flags & LK_TIMELOCK) && timo) 214 sleepq_set_timeout(&lk->lock_object, timo); 215 216 /* 217 * Decisional switch for real sleeping. 218 */ 219 if ((flags & LK_TIMELOCK) && timo && catch) 220 error = sleepq_timedwait_sig(&lk->lock_object, pri); 221 else if ((flags & LK_TIMELOCK) && timo) 222 error = sleepq_timedwait(&lk->lock_object, pri); 223 else if (catch) 224 error = sleepq_wait_sig(&lk->lock_object, pri); 225 else 226 sleepq_wait(&lk->lock_object, pri); 227 GIANT_RESTORE(); 228 if ((flags & LK_SLEEPFAIL) && error == 0) 229 error = ENOLCK; 230 231 return (error); 232 } 233 234 static __inline int 235 wakeupshlk(struct lock *lk, const char *file, int line) 236 { 237 uintptr_t v, x; 238 u_int realexslp; 239 int queue, wakeup_swapper; 240 241 TD_LOCKS_DEC(curthread); 242 TD_SLOCKS_DEC(curthread); 243 WITNESS_UNLOCK(&lk->lock_object, 0, file, line); 244 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); 245 246 wakeup_swapper = 0; 247 for (;;) { 248 x = lk->lk_lock; 249 250 /* 251 * If there is more than one shared lock held, just drop one 252 * and return. 253 */ 254 if (LK_SHARERS(x) > 1) { 255 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, 256 x - LK_ONE_SHARER)) 257 break; 258 continue; 259 } 260 261 /* 262 * If there are not waiters on the exclusive queue, drop the 263 * lock quickly. 264 */ 265 if ((x & LK_ALL_WAITERS) == 0) { 266 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == 267 LK_SHARERS_LOCK(1)); 268 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED)) 269 break; 270 continue; 271 } 272 273 /* 274 * We should have a sharer with waiters, so enter the hard 275 * path in order to handle wakeups correctly. 276 */ 277 sleepq_lock(&lk->lock_object); 278 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 279 v = LK_UNLOCKED; 280 281 /* 282 * If the lock has exclusive waiters, give them preference in 283 * order to avoid deadlock with shared runners up. 284 * If interruptible sleeps left the exclusive queue empty 285 * avoid a starvation for the threads sleeping on the shared 286 * queue by giving them precedence and cleaning up the 287 * exclusive waiters bit anyway. 288 * Please note that lk_exslpfail count may be lying about 289 * the real number of waiters with the LK_SLEEPFAIL flag on 290 * because they may be used in conjuction with interruptible 291 * sleeps so lk_exslpfail might be considered an 'upper limit' 292 * bound, including the edge cases. 293 */ 294 realexslp = sleepq_sleepcnt(&lk->lock_object, 295 SQ_EXCLUSIVE_QUEUE); 296 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 297 if (lk->lk_exslpfail < realexslp) { 298 lk->lk_exslpfail = 0; 299 queue = SQ_EXCLUSIVE_QUEUE; 300 v |= (x & LK_SHARED_WAITERS); 301 } else { 302 lk->lk_exslpfail = 0; 303 LOCK_LOG2(lk, 304 "%s: %p has only LK_SLEEPFAIL sleepers", 305 __func__, lk); 306 LOCK_LOG2(lk, 307 "%s: %p waking up threads on the exclusive queue", 308 __func__, lk); 309 wakeup_swapper = 310 sleepq_broadcast(&lk->lock_object, 311 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 312 queue = SQ_SHARED_QUEUE; 313 } 314 315 } else { 316 317 /* 318 * Exclusive waiters sleeping with LK_SLEEPFAIL on 319 * and using interruptible sleeps/timeout may have 320 * left spourious lk_exslpfail counts on, so clean 321 * it up anyway. 322 */ 323 lk->lk_exslpfail = 0; 324 queue = SQ_SHARED_QUEUE; 325 } 326 327 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, 328 v)) { 329 sleepq_release(&lk->lock_object); 330 continue; 331 } 332 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", 333 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 334 "exclusive"); 335 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 336 0, queue); 337 sleepq_release(&lk->lock_object); 338 break; 339 } 340 341 lock_profile_release_lock(&lk->lock_object); 342 return (wakeup_swapper); 343 } 344 345 static void 346 assert_lockmgr(const struct lock_object *lock, int what) 347 { 348 349 panic("lockmgr locks do not support assertions"); 350 } 351 352 static void 353 lock_lockmgr(struct lock_object *lock, int how) 354 { 355 356 panic("lockmgr locks do not support sleep interlocking"); 357 } 358 359 static int 360 unlock_lockmgr(struct lock_object *lock) 361 { 362 363 panic("lockmgr locks do not support sleep interlocking"); 364 } 365 366 #ifdef KDTRACE_HOOKS 367 static int 368 owner_lockmgr(const struct lock_object *lock, struct thread **owner) 369 { 370 371 panic("lockmgr locks do not support owner inquiring"); 372 } 373 #endif 374 375 void 376 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 377 { 378 int iflags; 379 380 MPASS((flags & ~LK_INIT_MASK) == 0); 381 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 382 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 383 &lk->lk_lock)); 384 385 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 386 if (flags & LK_CANRECURSE) 387 iflags |= LO_RECURSABLE; 388 if ((flags & LK_NODUP) == 0) 389 iflags |= LO_DUPOK; 390 if (flags & LK_NOPROFILE) 391 iflags |= LO_NOPROFILE; 392 if ((flags & LK_NOWITNESS) == 0) 393 iflags |= LO_WITNESS; 394 if (flags & LK_QUIET) 395 iflags |= LO_QUIET; 396 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 397 398 lk->lk_lock = LK_UNLOCKED; 399 lk->lk_recurse = 0; 400 lk->lk_exslpfail = 0; 401 lk->lk_timo = timo; 402 lk->lk_pri = pri; 403 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 404 STACK_ZERO(lk); 405 } 406 407 /* 408 * XXX: Gross hacks to manipulate external lock flags after 409 * initialization. Used for certain vnode and buf locks. 410 */ 411 void 412 lockallowshare(struct lock *lk) 413 { 414 415 lockmgr_assert(lk, KA_XLOCKED); 416 lk->lock_object.lo_flags &= ~LK_NOSHARE; 417 } 418 419 void 420 lockallowrecurse(struct lock *lk) 421 { 422 423 lockmgr_assert(lk, KA_XLOCKED); 424 lk->lock_object.lo_flags |= LO_RECURSABLE; 425 } 426 427 void 428 lockdisablerecurse(struct lock *lk) 429 { 430 431 lockmgr_assert(lk, KA_XLOCKED); 432 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 433 } 434 435 void 436 lockdestroy(struct lock *lk) 437 { 438 439 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 440 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 441 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 442 lock_destroy(&lk->lock_object); 443 } 444 445 int 446 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 447 const char *wmesg, int pri, int timo, const char *file, int line) 448 { 449 GIANT_DECLARE; 450 struct lock_class *class; 451 const char *iwmesg; 452 uintptr_t tid, v, x; 453 u_int op, realexslp; 454 int error, ipri, itimo, queue, wakeup_swapper; 455 #ifdef LOCK_PROFILING 456 uint64_t waittime = 0; 457 int contested = 0; 458 #endif 459 #ifdef ADAPTIVE_LOCKMGRS 460 volatile struct thread *owner; 461 u_int i, spintries = 0; 462 #endif 463 464 error = 0; 465 tid = (uintptr_t)curthread; 466 op = (flags & LK_TYPE_MASK); 467 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 468 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 469 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 470 471 MPASS((flags & ~LK_TOTAL_MASK) == 0); 472 KASSERT((op & (op - 1)) == 0, 473 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 474 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 475 (op != LK_DOWNGRADE && op != LK_RELEASE), 476 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 477 __func__, file, line)); 478 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 479 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 480 __func__, file, line)); 481 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 482 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 483 lk->lock_object.lo_name, file, line)); 484 485 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 486 if (panicstr != NULL) { 487 if (flags & LK_INTERLOCK) 488 class->lc_unlock(ilk); 489 return (0); 490 } 491 492 if (lk->lock_object.lo_flags & LK_NOSHARE) { 493 switch (op) { 494 case LK_SHARED: 495 op = LK_EXCLUSIVE; 496 break; 497 case LK_UPGRADE: 498 case LK_DOWNGRADE: 499 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 500 file, line); 501 return (0); 502 } 503 } 504 505 wakeup_swapper = 0; 506 switch (op) { 507 case LK_SHARED: 508 if (LK_CAN_WITNESS(flags)) 509 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 510 file, line, ilk); 511 for (;;) { 512 x = lk->lk_lock; 513 514 /* 515 * If no other thread has an exclusive lock, or 516 * no exclusive waiter is present, bump the count of 517 * sharers. Since we have to preserve the state of 518 * waiters, if we fail to acquire the shared lock 519 * loop back and retry. 520 */ 521 if (LK_CAN_SHARE(x)) { 522 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 523 x + LK_ONE_SHARER)) 524 break; 525 continue; 526 } 527 #ifdef HWPMC_HOOKS 528 PMC_SOFT_CALL( , , lock, failed); 529 #endif 530 lock_profile_obtain_lock_failed(&lk->lock_object, 531 &contested, &waittime); 532 533 /* 534 * If the lock is already held by curthread in 535 * exclusive way avoid a deadlock. 536 */ 537 if (LK_HOLDER(x) == tid) { 538 LOCK_LOG2(lk, 539 "%s: %p already held in exclusive mode", 540 __func__, lk); 541 error = EDEADLK; 542 break; 543 } 544 545 /* 546 * If the lock is expected to not sleep just give up 547 * and return. 548 */ 549 if (LK_TRYOP(flags)) { 550 LOCK_LOG2(lk, "%s: %p fails the try operation", 551 __func__, lk); 552 error = EBUSY; 553 break; 554 } 555 556 #ifdef ADAPTIVE_LOCKMGRS 557 /* 558 * If the owner is running on another CPU, spin until 559 * the owner stops running or the state of the lock 560 * changes. We need a double-state handle here 561 * because for a failed acquisition the lock can be 562 * either held in exclusive mode or shared mode 563 * (for the writer starvation avoidance technique). 564 */ 565 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 566 LK_HOLDER(x) != LK_KERNPROC) { 567 owner = (struct thread *)LK_HOLDER(x); 568 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 569 CTR3(KTR_LOCK, 570 "%s: spinning on %p held by %p", 571 __func__, lk, owner); 572 573 /* 574 * If we are holding also an interlock drop it 575 * in order to avoid a deadlock if the lockmgr 576 * owner is adaptively spinning on the 577 * interlock itself. 578 */ 579 if (flags & LK_INTERLOCK) { 580 class->lc_unlock(ilk); 581 flags &= ~LK_INTERLOCK; 582 } 583 GIANT_SAVE(); 584 while (LK_HOLDER(lk->lk_lock) == 585 (uintptr_t)owner && TD_IS_RUNNING(owner)) 586 cpu_spinwait(); 587 GIANT_RESTORE(); 588 continue; 589 } else if (LK_CAN_ADAPT(lk, flags) && 590 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 591 spintries < alk_retries) { 592 if (flags & LK_INTERLOCK) { 593 class->lc_unlock(ilk); 594 flags &= ~LK_INTERLOCK; 595 } 596 GIANT_SAVE(); 597 spintries++; 598 for (i = 0; i < alk_loops; i++) { 599 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 600 CTR4(KTR_LOCK, 601 "%s: shared spinning on %p with %u and %u", 602 __func__, lk, spintries, i); 603 x = lk->lk_lock; 604 if ((x & LK_SHARE) == 0 || 605 LK_CAN_SHARE(x) != 0) 606 break; 607 cpu_spinwait(); 608 } 609 GIANT_RESTORE(); 610 if (i != alk_loops) 611 continue; 612 } 613 #endif 614 615 /* 616 * Acquire the sleepqueue chain lock because we 617 * probabilly will need to manipulate waiters flags. 618 */ 619 sleepq_lock(&lk->lock_object); 620 x = lk->lk_lock; 621 622 /* 623 * if the lock can be acquired in shared mode, try 624 * again. 625 */ 626 if (LK_CAN_SHARE(x)) { 627 sleepq_release(&lk->lock_object); 628 continue; 629 } 630 631 #ifdef ADAPTIVE_LOCKMGRS 632 /* 633 * The current lock owner might have started executing 634 * on another CPU (or the lock could have changed 635 * owner) while we were waiting on the turnstile 636 * chain lock. If so, drop the turnstile lock and try 637 * again. 638 */ 639 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 640 LK_HOLDER(x) != LK_KERNPROC) { 641 owner = (struct thread *)LK_HOLDER(x); 642 if (TD_IS_RUNNING(owner)) { 643 sleepq_release(&lk->lock_object); 644 continue; 645 } 646 } 647 #endif 648 649 /* 650 * Try to set the LK_SHARED_WAITERS flag. If we fail, 651 * loop back and retry. 652 */ 653 if ((x & LK_SHARED_WAITERS) == 0) { 654 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 655 x | LK_SHARED_WAITERS)) { 656 sleepq_release(&lk->lock_object); 657 continue; 658 } 659 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 660 __func__, lk); 661 } 662 663 /* 664 * As far as we have been unable to acquire the 665 * shared lock and the shared waiters flag is set, 666 * we will sleep. 667 */ 668 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 669 SQ_SHARED_QUEUE); 670 flags &= ~LK_INTERLOCK; 671 if (error) { 672 LOCK_LOG3(lk, 673 "%s: interrupted sleep for %p with %d", 674 __func__, lk, error); 675 break; 676 } 677 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 678 __func__, lk); 679 } 680 if (error == 0) { 681 lock_profile_obtain_lock_success(&lk->lock_object, 682 contested, waittime, file, line); 683 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 684 line); 685 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 686 line); 687 TD_LOCKS_INC(curthread); 688 TD_SLOCKS_INC(curthread); 689 STACK_SAVE(lk); 690 } 691 break; 692 case LK_UPGRADE: 693 _lockmgr_assert(lk, KA_SLOCKED, file, line); 694 v = lk->lk_lock; 695 x = v & LK_ALL_WAITERS; 696 v &= LK_EXCLUSIVE_SPINNERS; 697 698 /* 699 * Try to switch from one shared lock to an exclusive one. 700 * We need to preserve waiters flags during the operation. 701 */ 702 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 703 tid | x)) { 704 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 705 line); 706 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 707 LK_TRYWIT(flags), file, line); 708 TD_SLOCKS_DEC(curthread); 709 break; 710 } 711 712 /* 713 * We have been unable to succeed in upgrading, so just 714 * give up the shared lock. 715 */ 716 wakeup_swapper |= wakeupshlk(lk, file, line); 717 718 /* FALLTHROUGH */ 719 case LK_EXCLUSIVE: 720 if (LK_CAN_WITNESS(flags)) 721 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 722 LOP_EXCLUSIVE, file, line, ilk); 723 724 /* 725 * If curthread already holds the lock and this one is 726 * allowed to recurse, simply recurse on it. 727 */ 728 if (lockmgr_xlocked(lk)) { 729 if ((flags & LK_CANRECURSE) == 0 && 730 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 731 732 /* 733 * If the lock is expected to not panic just 734 * give up and return. 735 */ 736 if (LK_TRYOP(flags)) { 737 LOCK_LOG2(lk, 738 "%s: %p fails the try operation", 739 __func__, lk); 740 error = EBUSY; 741 break; 742 } 743 if (flags & LK_INTERLOCK) 744 class->lc_unlock(ilk); 745 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 746 __func__, iwmesg, file, line); 747 } 748 lk->lk_recurse++; 749 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 750 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 751 lk->lk_recurse, file, line); 752 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 753 LK_TRYWIT(flags), file, line); 754 TD_LOCKS_INC(curthread); 755 break; 756 } 757 758 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 759 tid)) { 760 #ifdef HWPMC_HOOKS 761 PMC_SOFT_CALL( , , lock, failed); 762 #endif 763 lock_profile_obtain_lock_failed(&lk->lock_object, 764 &contested, &waittime); 765 766 /* 767 * If the lock is expected to not sleep just give up 768 * and return. 769 */ 770 if (LK_TRYOP(flags)) { 771 LOCK_LOG2(lk, "%s: %p fails the try operation", 772 __func__, lk); 773 error = EBUSY; 774 break; 775 } 776 777 #ifdef ADAPTIVE_LOCKMGRS 778 /* 779 * If the owner is running on another CPU, spin until 780 * the owner stops running or the state of the lock 781 * changes. 782 */ 783 x = lk->lk_lock; 784 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 785 LK_HOLDER(x) != LK_KERNPROC) { 786 owner = (struct thread *)LK_HOLDER(x); 787 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 788 CTR3(KTR_LOCK, 789 "%s: spinning on %p held by %p", 790 __func__, lk, owner); 791 792 /* 793 * If we are holding also an interlock drop it 794 * in order to avoid a deadlock if the lockmgr 795 * owner is adaptively spinning on the 796 * interlock itself. 797 */ 798 if (flags & LK_INTERLOCK) { 799 class->lc_unlock(ilk); 800 flags &= ~LK_INTERLOCK; 801 } 802 GIANT_SAVE(); 803 while (LK_HOLDER(lk->lk_lock) == 804 (uintptr_t)owner && TD_IS_RUNNING(owner)) 805 cpu_spinwait(); 806 GIANT_RESTORE(); 807 continue; 808 } else if (LK_CAN_ADAPT(lk, flags) && 809 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 810 spintries < alk_retries) { 811 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 812 !atomic_cmpset_ptr(&lk->lk_lock, x, 813 x | LK_EXCLUSIVE_SPINNERS)) 814 continue; 815 if (flags & LK_INTERLOCK) { 816 class->lc_unlock(ilk); 817 flags &= ~LK_INTERLOCK; 818 } 819 GIANT_SAVE(); 820 spintries++; 821 for (i = 0; i < alk_loops; i++) { 822 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 823 CTR4(KTR_LOCK, 824 "%s: shared spinning on %p with %u and %u", 825 __func__, lk, spintries, i); 826 if ((lk->lk_lock & 827 LK_EXCLUSIVE_SPINNERS) == 0) 828 break; 829 cpu_spinwait(); 830 } 831 GIANT_RESTORE(); 832 if (i != alk_loops) 833 continue; 834 } 835 #endif 836 837 /* 838 * Acquire the sleepqueue chain lock because we 839 * probabilly will need to manipulate waiters flags. 840 */ 841 sleepq_lock(&lk->lock_object); 842 x = lk->lk_lock; 843 844 /* 845 * if the lock has been released while we spun on 846 * the sleepqueue chain lock just try again. 847 */ 848 if (x == LK_UNLOCKED) { 849 sleepq_release(&lk->lock_object); 850 continue; 851 } 852 853 #ifdef ADAPTIVE_LOCKMGRS 854 /* 855 * The current lock owner might have started executing 856 * on another CPU (or the lock could have changed 857 * owner) while we were waiting on the turnstile 858 * chain lock. If so, drop the turnstile lock and try 859 * again. 860 */ 861 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 862 LK_HOLDER(x) != LK_KERNPROC) { 863 owner = (struct thread *)LK_HOLDER(x); 864 if (TD_IS_RUNNING(owner)) { 865 sleepq_release(&lk->lock_object); 866 continue; 867 } 868 } 869 #endif 870 871 /* 872 * The lock can be in the state where there is a 873 * pending queue of waiters, but still no owner. 874 * This happens when the lock is contested and an 875 * owner is going to claim the lock. 876 * If curthread is the one successfully acquiring it 877 * claim lock ownership and return, preserving waiters 878 * flags. 879 */ 880 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 881 if ((x & ~v) == LK_UNLOCKED) { 882 v &= ~LK_EXCLUSIVE_SPINNERS; 883 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 884 tid | v)) { 885 sleepq_release(&lk->lock_object); 886 LOCK_LOG2(lk, 887 "%s: %p claimed by a new writer", 888 __func__, lk); 889 break; 890 } 891 sleepq_release(&lk->lock_object); 892 continue; 893 } 894 895 /* 896 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 897 * fail, loop back and retry. 898 */ 899 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 900 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 901 x | LK_EXCLUSIVE_WAITERS)) { 902 sleepq_release(&lk->lock_object); 903 continue; 904 } 905 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 906 __func__, lk); 907 } 908 909 /* 910 * As far as we have been unable to acquire the 911 * exclusive lock and the exclusive waiters flag 912 * is set, we will sleep. 913 */ 914 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 915 SQ_EXCLUSIVE_QUEUE); 916 flags &= ~LK_INTERLOCK; 917 if (error) { 918 LOCK_LOG3(lk, 919 "%s: interrupted sleep for %p with %d", 920 __func__, lk, error); 921 break; 922 } 923 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 924 __func__, lk); 925 } 926 if (error == 0) { 927 lock_profile_obtain_lock_success(&lk->lock_object, 928 contested, waittime, file, line); 929 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 930 lk->lk_recurse, file, line); 931 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 932 LK_TRYWIT(flags), file, line); 933 TD_LOCKS_INC(curthread); 934 STACK_SAVE(lk); 935 } 936 break; 937 case LK_DOWNGRADE: 938 _lockmgr_assert(lk, KA_XLOCKED, file, line); 939 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 940 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 941 942 /* 943 * Panic if the lock is recursed. 944 */ 945 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 946 if (flags & LK_INTERLOCK) 947 class->lc_unlock(ilk); 948 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 949 __func__, iwmesg, file, line); 950 } 951 TD_SLOCKS_INC(curthread); 952 953 /* 954 * In order to preserve waiters flags, just spin. 955 */ 956 for (;;) { 957 x = lk->lk_lock; 958 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 959 x &= LK_ALL_WAITERS; 960 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 961 LK_SHARERS_LOCK(1) | x)) 962 break; 963 cpu_spinwait(); 964 } 965 break; 966 case LK_RELEASE: 967 _lockmgr_assert(lk, KA_LOCKED, file, line); 968 x = lk->lk_lock; 969 970 if ((x & LK_SHARE) == 0) { 971 972 /* 973 * As first option, treact the lock as if it has not 974 * any waiter. 975 * Fix-up the tid var if the lock has been disowned. 976 */ 977 if (LK_HOLDER(x) == LK_KERNPROC) 978 tid = LK_KERNPROC; 979 else { 980 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 981 file, line); 982 TD_LOCKS_DEC(curthread); 983 } 984 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 985 lk->lk_recurse, file, line); 986 987 /* 988 * The lock is held in exclusive mode. 989 * If the lock is recursed also, then unrecurse it. 990 */ 991 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 992 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 993 lk); 994 lk->lk_recurse--; 995 break; 996 } 997 if (tid != LK_KERNPROC) 998 lock_profile_release_lock(&lk->lock_object); 999 1000 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 1001 LK_UNLOCKED)) 1002 break; 1003 1004 sleepq_lock(&lk->lock_object); 1005 x = lk->lk_lock; 1006 v = LK_UNLOCKED; 1007 1008 /* 1009 * If the lock has exclusive waiters, give them 1010 * preference in order to avoid deadlock with 1011 * shared runners up. 1012 * If interruptible sleeps left the exclusive queue 1013 * empty avoid a starvation for the threads sleeping 1014 * on the shared queue by giving them precedence 1015 * and cleaning up the exclusive waiters bit anyway. 1016 * Please note that lk_exslpfail count may be lying 1017 * about the real number of waiters with the 1018 * LK_SLEEPFAIL flag on because they may be used in 1019 * conjuction with interruptible sleeps so 1020 * lk_exslpfail might be considered an 'upper limit' 1021 * bound, including the edge cases. 1022 */ 1023 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1024 realexslp = sleepq_sleepcnt(&lk->lock_object, 1025 SQ_EXCLUSIVE_QUEUE); 1026 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1027 if (lk->lk_exslpfail < realexslp) { 1028 lk->lk_exslpfail = 0; 1029 queue = SQ_EXCLUSIVE_QUEUE; 1030 v |= (x & LK_SHARED_WAITERS); 1031 } else { 1032 lk->lk_exslpfail = 0; 1033 LOCK_LOG2(lk, 1034 "%s: %p has only LK_SLEEPFAIL sleepers", 1035 __func__, lk); 1036 LOCK_LOG2(lk, 1037 "%s: %p waking up threads on the exclusive queue", 1038 __func__, lk); 1039 wakeup_swapper = 1040 sleepq_broadcast(&lk->lock_object, 1041 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1042 queue = SQ_SHARED_QUEUE; 1043 } 1044 } else { 1045 1046 /* 1047 * Exclusive waiters sleeping with LK_SLEEPFAIL 1048 * on and using interruptible sleeps/timeout 1049 * may have left spourious lk_exslpfail counts 1050 * on, so clean it up anyway. 1051 */ 1052 lk->lk_exslpfail = 0; 1053 queue = SQ_SHARED_QUEUE; 1054 } 1055 1056 LOCK_LOG3(lk, 1057 "%s: %p waking up threads on the %s queue", 1058 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1059 "exclusive"); 1060 atomic_store_rel_ptr(&lk->lk_lock, v); 1061 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1062 SLEEPQ_LK, 0, queue); 1063 sleepq_release(&lk->lock_object); 1064 break; 1065 } else 1066 wakeup_swapper = wakeupshlk(lk, file, line); 1067 break; 1068 case LK_DRAIN: 1069 if (LK_CAN_WITNESS(flags)) 1070 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1071 LOP_EXCLUSIVE, file, line, ilk); 1072 1073 /* 1074 * Trying to drain a lock we already own will result in a 1075 * deadlock. 1076 */ 1077 if (lockmgr_xlocked(lk)) { 1078 if (flags & LK_INTERLOCK) 1079 class->lc_unlock(ilk); 1080 panic("%s: draining %s with the lock held @ %s:%d\n", 1081 __func__, iwmesg, file, line); 1082 } 1083 1084 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1085 #ifdef HWPMC_HOOKS 1086 PMC_SOFT_CALL( , , lock, failed); 1087 #endif 1088 lock_profile_obtain_lock_failed(&lk->lock_object, 1089 &contested, &waittime); 1090 1091 /* 1092 * If the lock is expected to not sleep just give up 1093 * and return. 1094 */ 1095 if (LK_TRYOP(flags)) { 1096 LOCK_LOG2(lk, "%s: %p fails the try operation", 1097 __func__, lk); 1098 error = EBUSY; 1099 break; 1100 } 1101 1102 /* 1103 * Acquire the sleepqueue chain lock because we 1104 * probabilly will need to manipulate waiters flags. 1105 */ 1106 sleepq_lock(&lk->lock_object); 1107 x = lk->lk_lock; 1108 1109 /* 1110 * if the lock has been released while we spun on 1111 * the sleepqueue chain lock just try again. 1112 */ 1113 if (x == LK_UNLOCKED) { 1114 sleepq_release(&lk->lock_object); 1115 continue; 1116 } 1117 1118 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1119 if ((x & ~v) == LK_UNLOCKED) { 1120 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1121 1122 /* 1123 * If interruptible sleeps left the exclusive 1124 * queue empty avoid a starvation for the 1125 * threads sleeping on the shared queue by 1126 * giving them precedence and cleaning up the 1127 * exclusive waiters bit anyway. 1128 * Please note that lk_exslpfail count may be 1129 * lying about the real number of waiters with 1130 * the LK_SLEEPFAIL flag on because they may 1131 * be used in conjuction with interruptible 1132 * sleeps so lk_exslpfail might be considered 1133 * an 'upper limit' bound, including the edge 1134 * cases. 1135 */ 1136 if (v & LK_EXCLUSIVE_WAITERS) { 1137 queue = SQ_EXCLUSIVE_QUEUE; 1138 v &= ~LK_EXCLUSIVE_WAITERS; 1139 } else { 1140 1141 /* 1142 * Exclusive waiters sleeping with 1143 * LK_SLEEPFAIL on and using 1144 * interruptible sleeps/timeout may 1145 * have left spourious lk_exslpfail 1146 * counts on, so clean it up anyway. 1147 */ 1148 MPASS(v & LK_SHARED_WAITERS); 1149 lk->lk_exslpfail = 0; 1150 queue = SQ_SHARED_QUEUE; 1151 v &= ~LK_SHARED_WAITERS; 1152 } 1153 if (queue == SQ_EXCLUSIVE_QUEUE) { 1154 realexslp = 1155 sleepq_sleepcnt(&lk->lock_object, 1156 SQ_EXCLUSIVE_QUEUE); 1157 if (lk->lk_exslpfail >= realexslp) { 1158 lk->lk_exslpfail = 0; 1159 queue = SQ_SHARED_QUEUE; 1160 v &= ~LK_SHARED_WAITERS; 1161 if (realexslp != 0) { 1162 LOCK_LOG2(lk, 1163 "%s: %p has only LK_SLEEPFAIL sleepers", 1164 __func__, lk); 1165 LOCK_LOG2(lk, 1166 "%s: %p waking up threads on the exclusive queue", 1167 __func__, lk); 1168 wakeup_swapper = 1169 sleepq_broadcast( 1170 &lk->lock_object, 1171 SLEEPQ_LK, 0, 1172 SQ_EXCLUSIVE_QUEUE); 1173 } 1174 } else 1175 lk->lk_exslpfail = 0; 1176 } 1177 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1178 sleepq_release(&lk->lock_object); 1179 continue; 1180 } 1181 LOCK_LOG3(lk, 1182 "%s: %p waking up all threads on the %s queue", 1183 __func__, lk, queue == SQ_SHARED_QUEUE ? 1184 "shared" : "exclusive"); 1185 wakeup_swapper |= sleepq_broadcast( 1186 &lk->lock_object, SLEEPQ_LK, 0, queue); 1187 1188 /* 1189 * If shared waiters have been woken up we need 1190 * to wait for one of them to acquire the lock 1191 * before to set the exclusive waiters in 1192 * order to avoid a deadlock. 1193 */ 1194 if (queue == SQ_SHARED_QUEUE) { 1195 for (v = lk->lk_lock; 1196 (v & LK_SHARE) && !LK_SHARERS(v); 1197 v = lk->lk_lock) 1198 cpu_spinwait(); 1199 } 1200 } 1201 1202 /* 1203 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1204 * fail, loop back and retry. 1205 */ 1206 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1207 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1208 x | LK_EXCLUSIVE_WAITERS)) { 1209 sleepq_release(&lk->lock_object); 1210 continue; 1211 } 1212 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1213 __func__, lk); 1214 } 1215 1216 /* 1217 * As far as we have been unable to acquire the 1218 * exclusive lock and the exclusive waiters flag 1219 * is set, we will sleep. 1220 */ 1221 if (flags & LK_INTERLOCK) { 1222 class->lc_unlock(ilk); 1223 flags &= ~LK_INTERLOCK; 1224 } 1225 GIANT_SAVE(); 1226 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1227 SQ_EXCLUSIVE_QUEUE); 1228 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1229 GIANT_RESTORE(); 1230 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1231 __func__, lk); 1232 } 1233 1234 if (error == 0) { 1235 lock_profile_obtain_lock_success(&lk->lock_object, 1236 contested, waittime, file, line); 1237 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1238 lk->lk_recurse, file, line); 1239 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1240 LK_TRYWIT(flags), file, line); 1241 TD_LOCKS_INC(curthread); 1242 STACK_SAVE(lk); 1243 } 1244 break; 1245 default: 1246 if (flags & LK_INTERLOCK) 1247 class->lc_unlock(ilk); 1248 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1249 } 1250 1251 if (flags & LK_INTERLOCK) 1252 class->lc_unlock(ilk); 1253 if (wakeup_swapper) 1254 kick_proc0(); 1255 1256 return (error); 1257 } 1258 1259 void 1260 _lockmgr_disown(struct lock *lk, const char *file, int line) 1261 { 1262 uintptr_t tid, x; 1263 1264 if (SCHEDULER_STOPPED()) 1265 return; 1266 1267 tid = (uintptr_t)curthread; 1268 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1269 1270 /* 1271 * Panic if the lock is recursed. 1272 */ 1273 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1274 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1275 __func__, file, line); 1276 1277 /* 1278 * If the owner is already LK_KERNPROC just skip the whole operation. 1279 */ 1280 if (LK_HOLDER(lk->lk_lock) != tid) 1281 return; 1282 lock_profile_release_lock(&lk->lock_object); 1283 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1284 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1285 TD_LOCKS_DEC(curthread); 1286 STACK_SAVE(lk); 1287 1288 /* 1289 * In order to preserve waiters flags, just spin. 1290 */ 1291 for (;;) { 1292 x = lk->lk_lock; 1293 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1294 x &= LK_ALL_WAITERS; 1295 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1296 LK_KERNPROC | x)) 1297 return; 1298 cpu_spinwait(); 1299 } 1300 } 1301 1302 void 1303 lockmgr_printinfo(const struct lock *lk) 1304 { 1305 struct thread *td; 1306 uintptr_t x; 1307 1308 if (lk->lk_lock == LK_UNLOCKED) 1309 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1310 else if (lk->lk_lock & LK_SHARE) 1311 printf("lock type %s: SHARED (count %ju)\n", 1312 lk->lock_object.lo_name, 1313 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1314 else { 1315 td = lockmgr_xholder(lk); 1316 printf("lock type %s: EXCL by thread %p " 1317 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, td, 1318 td->td_proc->p_pid, td->td_proc->p_comm, td->td_tid); 1319 } 1320 1321 x = lk->lk_lock; 1322 if (x & LK_EXCLUSIVE_WAITERS) 1323 printf(" with exclusive waiters pending\n"); 1324 if (x & LK_SHARED_WAITERS) 1325 printf(" with shared waiters pending\n"); 1326 if (x & LK_EXCLUSIVE_SPINNERS) 1327 printf(" with exclusive spinners pending\n"); 1328 1329 STACK_PRINT(lk); 1330 } 1331 1332 int 1333 lockstatus(const struct lock *lk) 1334 { 1335 uintptr_t v, x; 1336 int ret; 1337 1338 ret = LK_SHARED; 1339 x = lk->lk_lock; 1340 v = LK_HOLDER(x); 1341 1342 if ((x & LK_SHARE) == 0) { 1343 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1344 ret = LK_EXCLUSIVE; 1345 else 1346 ret = LK_EXCLOTHER; 1347 } else if (x == LK_UNLOCKED) 1348 ret = 0; 1349 1350 return (ret); 1351 } 1352 1353 #ifdef INVARIANT_SUPPORT 1354 1355 FEATURE(invariant_support, 1356 "Support for modules compiled with INVARIANTS option"); 1357 1358 #ifndef INVARIANTS 1359 #undef _lockmgr_assert 1360 #endif 1361 1362 void 1363 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1364 { 1365 int slocked = 0; 1366 1367 if (panicstr != NULL) 1368 return; 1369 switch (what) { 1370 case KA_SLOCKED: 1371 case KA_SLOCKED | KA_NOTRECURSED: 1372 case KA_SLOCKED | KA_RECURSED: 1373 slocked = 1; 1374 case KA_LOCKED: 1375 case KA_LOCKED | KA_NOTRECURSED: 1376 case KA_LOCKED | KA_RECURSED: 1377 #ifdef WITNESS 1378 1379 /* 1380 * We cannot trust WITNESS if the lock is held in exclusive 1381 * mode and a call to lockmgr_disown() happened. 1382 * Workaround this skipping the check if the lock is held in 1383 * exclusive mode even for the KA_LOCKED case. 1384 */ 1385 if (slocked || (lk->lk_lock & LK_SHARE)) { 1386 witness_assert(&lk->lock_object, what, file, line); 1387 break; 1388 } 1389 #endif 1390 if (lk->lk_lock == LK_UNLOCKED || 1391 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1392 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1393 panic("Lock %s not %slocked @ %s:%d\n", 1394 lk->lock_object.lo_name, slocked ? "share" : "", 1395 file, line); 1396 1397 if ((lk->lk_lock & LK_SHARE) == 0) { 1398 if (lockmgr_recursed(lk)) { 1399 if (what & KA_NOTRECURSED) 1400 panic("Lock %s recursed @ %s:%d\n", 1401 lk->lock_object.lo_name, file, 1402 line); 1403 } else if (what & KA_RECURSED) 1404 panic("Lock %s not recursed @ %s:%d\n", 1405 lk->lock_object.lo_name, file, line); 1406 } 1407 break; 1408 case KA_XLOCKED: 1409 case KA_XLOCKED | KA_NOTRECURSED: 1410 case KA_XLOCKED | KA_RECURSED: 1411 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1412 panic("Lock %s not exclusively locked @ %s:%d\n", 1413 lk->lock_object.lo_name, file, line); 1414 if (lockmgr_recursed(lk)) { 1415 if (what & KA_NOTRECURSED) 1416 panic("Lock %s recursed @ %s:%d\n", 1417 lk->lock_object.lo_name, file, line); 1418 } else if (what & KA_RECURSED) 1419 panic("Lock %s not recursed @ %s:%d\n", 1420 lk->lock_object.lo_name, file, line); 1421 break; 1422 case KA_UNLOCKED: 1423 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1424 panic("Lock %s exclusively locked @ %s:%d\n", 1425 lk->lock_object.lo_name, file, line); 1426 break; 1427 default: 1428 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1429 line); 1430 } 1431 } 1432 #endif 1433 1434 #ifdef DDB 1435 int 1436 lockmgr_chain(struct thread *td, struct thread **ownerp) 1437 { 1438 struct lock *lk; 1439 1440 lk = td->td_wchan; 1441 1442 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1443 return (0); 1444 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1445 if (lk->lk_lock & LK_SHARE) 1446 db_printf("SHARED (count %ju)\n", 1447 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1448 else 1449 db_printf("EXCL\n"); 1450 *ownerp = lockmgr_xholder(lk); 1451 1452 return (1); 1453 } 1454 1455 static void 1456 db_show_lockmgr(const struct lock_object *lock) 1457 { 1458 struct thread *td; 1459 const struct lock *lk; 1460 1461 lk = (const struct lock *)lock; 1462 1463 db_printf(" state: "); 1464 if (lk->lk_lock == LK_UNLOCKED) 1465 db_printf("UNLOCKED\n"); 1466 else if (lk->lk_lock & LK_SHARE) 1467 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1468 else { 1469 td = lockmgr_xholder(lk); 1470 if (td == (struct thread *)LK_KERNPROC) 1471 db_printf("XLOCK: LK_KERNPROC\n"); 1472 else 1473 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1474 td->td_tid, td->td_proc->p_pid, 1475 td->td_proc->p_comm); 1476 if (lockmgr_recursed(lk)) 1477 db_printf(" recursed: %d\n", lk->lk_recurse); 1478 } 1479 db_printf(" waiters: "); 1480 switch (lk->lk_lock & LK_ALL_WAITERS) { 1481 case LK_SHARED_WAITERS: 1482 db_printf("shared\n"); 1483 break; 1484 case LK_EXCLUSIVE_WAITERS: 1485 db_printf("exclusive\n"); 1486 break; 1487 case LK_ALL_WAITERS: 1488 db_printf("shared and exclusive\n"); 1489 break; 1490 default: 1491 db_printf("none\n"); 1492 } 1493 db_printf(" spinners: "); 1494 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1495 db_printf("exclusive\n"); 1496 else 1497 db_printf("none\n"); 1498 } 1499 #endif 1500