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 if (flags & LK_IS_VNODE) 397 iflags |= LO_IS_VNODE; 398 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 399 400 lk->lk_lock = LK_UNLOCKED; 401 lk->lk_recurse = 0; 402 lk->lk_exslpfail = 0; 403 lk->lk_timo = timo; 404 lk->lk_pri = pri; 405 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 406 STACK_ZERO(lk); 407 } 408 409 /* 410 * XXX: Gross hacks to manipulate external lock flags after 411 * initialization. Used for certain vnode and buf locks. 412 */ 413 void 414 lockallowshare(struct lock *lk) 415 { 416 417 lockmgr_assert(lk, KA_XLOCKED); 418 lk->lock_object.lo_flags &= ~LK_NOSHARE; 419 } 420 421 void 422 lockallowrecurse(struct lock *lk) 423 { 424 425 lockmgr_assert(lk, KA_XLOCKED); 426 lk->lock_object.lo_flags |= LO_RECURSABLE; 427 } 428 429 void 430 lockdisablerecurse(struct lock *lk) 431 { 432 433 lockmgr_assert(lk, KA_XLOCKED); 434 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 435 } 436 437 void 438 lockdestroy(struct lock *lk) 439 { 440 441 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 442 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 443 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 444 lock_destroy(&lk->lock_object); 445 } 446 447 int 448 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 449 const char *wmesg, int pri, int timo, const char *file, int line) 450 { 451 GIANT_DECLARE; 452 struct lock_class *class; 453 const char *iwmesg; 454 uintptr_t tid, v, x; 455 u_int op, realexslp; 456 int error, ipri, itimo, queue, wakeup_swapper; 457 #ifdef LOCK_PROFILING 458 uint64_t waittime = 0; 459 int contested = 0; 460 #endif 461 #ifdef ADAPTIVE_LOCKMGRS 462 volatile struct thread *owner; 463 u_int i, spintries = 0; 464 #endif 465 466 error = 0; 467 tid = (uintptr_t)curthread; 468 op = (flags & LK_TYPE_MASK); 469 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 470 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 471 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 472 473 MPASS((flags & ~LK_TOTAL_MASK) == 0); 474 KASSERT((op & (op - 1)) == 0, 475 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 476 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 477 (op != LK_DOWNGRADE && op != LK_RELEASE), 478 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 479 __func__, file, line)); 480 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 481 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 482 __func__, file, line)); 483 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 484 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 485 lk->lock_object.lo_name, file, line)); 486 487 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 488 if (panicstr != NULL) { 489 if (flags & LK_INTERLOCK) 490 class->lc_unlock(ilk); 491 return (0); 492 } 493 494 if (lk->lock_object.lo_flags & LK_NOSHARE) { 495 switch (op) { 496 case LK_SHARED: 497 op = LK_EXCLUSIVE; 498 break; 499 case LK_UPGRADE: 500 case LK_DOWNGRADE: 501 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 502 file, line); 503 if (flags & LK_INTERLOCK) 504 class->lc_unlock(ilk); 505 return (0); 506 } 507 } 508 509 wakeup_swapper = 0; 510 switch (op) { 511 case LK_SHARED: 512 if (LK_CAN_WITNESS(flags)) 513 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 514 file, line, flags & LK_INTERLOCK ? ilk : NULL); 515 for (;;) { 516 x = lk->lk_lock; 517 518 /* 519 * If no other thread has an exclusive lock, or 520 * no exclusive waiter is present, bump the count of 521 * sharers. Since we have to preserve the state of 522 * waiters, if we fail to acquire the shared lock 523 * loop back and retry. 524 */ 525 if (LK_CAN_SHARE(x)) { 526 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 527 x + LK_ONE_SHARER)) 528 break; 529 continue; 530 } 531 #ifdef HWPMC_HOOKS 532 PMC_SOFT_CALL( , , lock, failed); 533 #endif 534 lock_profile_obtain_lock_failed(&lk->lock_object, 535 &contested, &waittime); 536 537 /* 538 * If the lock is already held by curthread in 539 * exclusive way avoid a deadlock. 540 */ 541 if (LK_HOLDER(x) == tid) { 542 LOCK_LOG2(lk, 543 "%s: %p already held in exclusive mode", 544 __func__, lk); 545 error = EDEADLK; 546 break; 547 } 548 549 /* 550 * If the lock is expected to not sleep just give up 551 * and return. 552 */ 553 if (LK_TRYOP(flags)) { 554 LOCK_LOG2(lk, "%s: %p fails the try operation", 555 __func__, lk); 556 error = EBUSY; 557 break; 558 } 559 560 #ifdef ADAPTIVE_LOCKMGRS 561 /* 562 * If the owner is running on another CPU, spin until 563 * the owner stops running or the state of the lock 564 * changes. We need a double-state handle here 565 * because for a failed acquisition the lock can be 566 * either held in exclusive mode or shared mode 567 * (for the writer starvation avoidance technique). 568 */ 569 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 570 LK_HOLDER(x) != LK_KERNPROC) { 571 owner = (struct thread *)LK_HOLDER(x); 572 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 573 CTR3(KTR_LOCK, 574 "%s: spinning on %p held by %p", 575 __func__, lk, owner); 576 577 /* 578 * If we are holding also an interlock drop it 579 * in order to avoid a deadlock if the lockmgr 580 * owner is adaptively spinning on the 581 * interlock itself. 582 */ 583 if (flags & LK_INTERLOCK) { 584 class->lc_unlock(ilk); 585 flags &= ~LK_INTERLOCK; 586 } 587 GIANT_SAVE(); 588 while (LK_HOLDER(lk->lk_lock) == 589 (uintptr_t)owner && TD_IS_RUNNING(owner)) 590 cpu_spinwait(); 591 GIANT_RESTORE(); 592 continue; 593 } else if (LK_CAN_ADAPT(lk, flags) && 594 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 595 spintries < alk_retries) { 596 if (flags & LK_INTERLOCK) { 597 class->lc_unlock(ilk); 598 flags &= ~LK_INTERLOCK; 599 } 600 GIANT_SAVE(); 601 spintries++; 602 for (i = 0; i < alk_loops; i++) { 603 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 604 CTR4(KTR_LOCK, 605 "%s: shared spinning on %p with %u and %u", 606 __func__, lk, spintries, i); 607 x = lk->lk_lock; 608 if ((x & LK_SHARE) == 0 || 609 LK_CAN_SHARE(x) != 0) 610 break; 611 cpu_spinwait(); 612 } 613 GIANT_RESTORE(); 614 if (i != alk_loops) 615 continue; 616 } 617 #endif 618 619 /* 620 * Acquire the sleepqueue chain lock because we 621 * probabilly will need to manipulate waiters flags. 622 */ 623 sleepq_lock(&lk->lock_object); 624 x = lk->lk_lock; 625 626 /* 627 * if the lock can be acquired in shared mode, try 628 * again. 629 */ 630 if (LK_CAN_SHARE(x)) { 631 sleepq_release(&lk->lock_object); 632 continue; 633 } 634 635 #ifdef ADAPTIVE_LOCKMGRS 636 /* 637 * The current lock owner might have started executing 638 * on another CPU (or the lock could have changed 639 * owner) while we were waiting on the turnstile 640 * chain lock. If so, drop the turnstile lock and try 641 * again. 642 */ 643 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 644 LK_HOLDER(x) != LK_KERNPROC) { 645 owner = (struct thread *)LK_HOLDER(x); 646 if (TD_IS_RUNNING(owner)) { 647 sleepq_release(&lk->lock_object); 648 continue; 649 } 650 } 651 #endif 652 653 /* 654 * Try to set the LK_SHARED_WAITERS flag. If we fail, 655 * loop back and retry. 656 */ 657 if ((x & LK_SHARED_WAITERS) == 0) { 658 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 659 x | LK_SHARED_WAITERS)) { 660 sleepq_release(&lk->lock_object); 661 continue; 662 } 663 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 664 __func__, lk); 665 } 666 667 /* 668 * As far as we have been unable to acquire the 669 * shared lock and the shared waiters flag is set, 670 * we will sleep. 671 */ 672 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 673 SQ_SHARED_QUEUE); 674 flags &= ~LK_INTERLOCK; 675 if (error) { 676 LOCK_LOG3(lk, 677 "%s: interrupted sleep for %p with %d", 678 __func__, lk, error); 679 break; 680 } 681 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 682 __func__, lk); 683 } 684 if (error == 0) { 685 lock_profile_obtain_lock_success(&lk->lock_object, 686 contested, waittime, file, line); 687 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 688 line); 689 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 690 line); 691 TD_LOCKS_INC(curthread); 692 TD_SLOCKS_INC(curthread); 693 STACK_SAVE(lk); 694 } 695 break; 696 case LK_UPGRADE: 697 _lockmgr_assert(lk, KA_SLOCKED, file, line); 698 v = lk->lk_lock; 699 x = v & LK_ALL_WAITERS; 700 v &= LK_EXCLUSIVE_SPINNERS; 701 702 /* 703 * Try to switch from one shared lock to an exclusive one. 704 * We need to preserve waiters flags during the operation. 705 */ 706 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 707 tid | x)) { 708 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 709 line); 710 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 711 LK_TRYWIT(flags), file, line); 712 TD_SLOCKS_DEC(curthread); 713 break; 714 } 715 716 /* 717 * We have been unable to succeed in upgrading, so just 718 * give up the shared lock. 719 */ 720 wakeup_swapper |= wakeupshlk(lk, file, line); 721 722 /* FALLTHROUGH */ 723 case LK_EXCLUSIVE: 724 if (LK_CAN_WITNESS(flags)) 725 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 726 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 727 ilk : NULL); 728 729 /* 730 * If curthread already holds the lock and this one is 731 * allowed to recurse, simply recurse on it. 732 */ 733 if (lockmgr_xlocked(lk)) { 734 if ((flags & LK_CANRECURSE) == 0 && 735 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 736 737 /* 738 * If the lock is expected to not panic just 739 * give up and return. 740 */ 741 if (LK_TRYOP(flags)) { 742 LOCK_LOG2(lk, 743 "%s: %p fails the try operation", 744 __func__, lk); 745 error = EBUSY; 746 break; 747 } 748 if (flags & LK_INTERLOCK) 749 class->lc_unlock(ilk); 750 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 751 __func__, iwmesg, file, line); 752 } 753 lk->lk_recurse++; 754 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 755 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 756 lk->lk_recurse, file, line); 757 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 758 LK_TRYWIT(flags), file, line); 759 TD_LOCKS_INC(curthread); 760 break; 761 } 762 763 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 764 tid)) { 765 #ifdef HWPMC_HOOKS 766 PMC_SOFT_CALL( , , lock, failed); 767 #endif 768 lock_profile_obtain_lock_failed(&lk->lock_object, 769 &contested, &waittime); 770 771 /* 772 * If the lock is expected to not sleep just give up 773 * and return. 774 */ 775 if (LK_TRYOP(flags)) { 776 LOCK_LOG2(lk, "%s: %p fails the try operation", 777 __func__, lk); 778 error = EBUSY; 779 break; 780 } 781 782 #ifdef ADAPTIVE_LOCKMGRS 783 /* 784 * If the owner is running on another CPU, spin until 785 * the owner stops running or the state of the lock 786 * changes. 787 */ 788 x = lk->lk_lock; 789 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 790 LK_HOLDER(x) != LK_KERNPROC) { 791 owner = (struct thread *)LK_HOLDER(x); 792 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 793 CTR3(KTR_LOCK, 794 "%s: spinning on %p held by %p", 795 __func__, lk, owner); 796 797 /* 798 * If we are holding also an interlock drop it 799 * in order to avoid a deadlock if the lockmgr 800 * owner is adaptively spinning on the 801 * interlock itself. 802 */ 803 if (flags & LK_INTERLOCK) { 804 class->lc_unlock(ilk); 805 flags &= ~LK_INTERLOCK; 806 } 807 GIANT_SAVE(); 808 while (LK_HOLDER(lk->lk_lock) == 809 (uintptr_t)owner && TD_IS_RUNNING(owner)) 810 cpu_spinwait(); 811 GIANT_RESTORE(); 812 continue; 813 } else if (LK_CAN_ADAPT(lk, flags) && 814 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 815 spintries < alk_retries) { 816 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 817 !atomic_cmpset_ptr(&lk->lk_lock, x, 818 x | LK_EXCLUSIVE_SPINNERS)) 819 continue; 820 if (flags & LK_INTERLOCK) { 821 class->lc_unlock(ilk); 822 flags &= ~LK_INTERLOCK; 823 } 824 GIANT_SAVE(); 825 spintries++; 826 for (i = 0; i < alk_loops; i++) { 827 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 828 CTR4(KTR_LOCK, 829 "%s: shared spinning on %p with %u and %u", 830 __func__, lk, spintries, i); 831 if ((lk->lk_lock & 832 LK_EXCLUSIVE_SPINNERS) == 0) 833 break; 834 cpu_spinwait(); 835 } 836 GIANT_RESTORE(); 837 if (i != alk_loops) 838 continue; 839 } 840 #endif 841 842 /* 843 * Acquire the sleepqueue chain lock because we 844 * probabilly will need to manipulate waiters flags. 845 */ 846 sleepq_lock(&lk->lock_object); 847 x = lk->lk_lock; 848 849 /* 850 * if the lock has been released while we spun on 851 * the sleepqueue chain lock just try again. 852 */ 853 if (x == LK_UNLOCKED) { 854 sleepq_release(&lk->lock_object); 855 continue; 856 } 857 858 #ifdef ADAPTIVE_LOCKMGRS 859 /* 860 * The current lock owner might have started executing 861 * on another CPU (or the lock could have changed 862 * owner) while we were waiting on the turnstile 863 * chain lock. If so, drop the turnstile lock and try 864 * again. 865 */ 866 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 867 LK_HOLDER(x) != LK_KERNPROC) { 868 owner = (struct thread *)LK_HOLDER(x); 869 if (TD_IS_RUNNING(owner)) { 870 sleepq_release(&lk->lock_object); 871 continue; 872 } 873 } 874 #endif 875 876 /* 877 * The lock can be in the state where there is a 878 * pending queue of waiters, but still no owner. 879 * This happens when the lock is contested and an 880 * owner is going to claim the lock. 881 * If curthread is the one successfully acquiring it 882 * claim lock ownership and return, preserving waiters 883 * flags. 884 */ 885 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 886 if ((x & ~v) == LK_UNLOCKED) { 887 v &= ~LK_EXCLUSIVE_SPINNERS; 888 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 889 tid | v)) { 890 sleepq_release(&lk->lock_object); 891 LOCK_LOG2(lk, 892 "%s: %p claimed by a new writer", 893 __func__, lk); 894 break; 895 } 896 sleepq_release(&lk->lock_object); 897 continue; 898 } 899 900 /* 901 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 902 * fail, loop back and retry. 903 */ 904 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 905 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 906 x | LK_EXCLUSIVE_WAITERS)) { 907 sleepq_release(&lk->lock_object); 908 continue; 909 } 910 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 911 __func__, lk); 912 } 913 914 /* 915 * As far as we have been unable to acquire the 916 * exclusive lock and the exclusive waiters flag 917 * is set, we will sleep. 918 */ 919 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 920 SQ_EXCLUSIVE_QUEUE); 921 flags &= ~LK_INTERLOCK; 922 if (error) { 923 LOCK_LOG3(lk, 924 "%s: interrupted sleep for %p with %d", 925 __func__, lk, error); 926 break; 927 } 928 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 929 __func__, lk); 930 } 931 if (error == 0) { 932 lock_profile_obtain_lock_success(&lk->lock_object, 933 contested, waittime, file, line); 934 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 935 lk->lk_recurse, file, line); 936 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 937 LK_TRYWIT(flags), file, line); 938 TD_LOCKS_INC(curthread); 939 STACK_SAVE(lk); 940 } 941 break; 942 case LK_DOWNGRADE: 943 _lockmgr_assert(lk, KA_XLOCKED, file, line); 944 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 945 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 946 947 /* 948 * Panic if the lock is recursed. 949 */ 950 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 951 if (flags & LK_INTERLOCK) 952 class->lc_unlock(ilk); 953 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 954 __func__, iwmesg, file, line); 955 } 956 TD_SLOCKS_INC(curthread); 957 958 /* 959 * In order to preserve waiters flags, just spin. 960 */ 961 for (;;) { 962 x = lk->lk_lock; 963 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 964 x &= LK_ALL_WAITERS; 965 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 966 LK_SHARERS_LOCK(1) | x)) 967 break; 968 cpu_spinwait(); 969 } 970 break; 971 case LK_RELEASE: 972 _lockmgr_assert(lk, KA_LOCKED, file, line); 973 x = lk->lk_lock; 974 975 if ((x & LK_SHARE) == 0) { 976 977 /* 978 * As first option, treact the lock as if it has not 979 * any waiter. 980 * Fix-up the tid var if the lock has been disowned. 981 */ 982 if (LK_HOLDER(x) == LK_KERNPROC) 983 tid = LK_KERNPROC; 984 else { 985 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 986 file, line); 987 TD_LOCKS_DEC(curthread); 988 } 989 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 990 lk->lk_recurse, file, line); 991 992 /* 993 * The lock is held in exclusive mode. 994 * If the lock is recursed also, then unrecurse it. 995 */ 996 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 997 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 998 lk); 999 lk->lk_recurse--; 1000 break; 1001 } 1002 if (tid != LK_KERNPROC) 1003 lock_profile_release_lock(&lk->lock_object); 1004 1005 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 1006 LK_UNLOCKED)) 1007 break; 1008 1009 sleepq_lock(&lk->lock_object); 1010 x = lk->lk_lock; 1011 v = LK_UNLOCKED; 1012 1013 /* 1014 * If the lock has exclusive waiters, give them 1015 * preference in order to avoid deadlock with 1016 * shared runners up. 1017 * If interruptible sleeps left the exclusive queue 1018 * empty avoid a starvation for the threads sleeping 1019 * on the shared queue by giving them precedence 1020 * and cleaning up the exclusive waiters bit anyway. 1021 * Please note that lk_exslpfail count may be lying 1022 * about the real number of waiters with the 1023 * LK_SLEEPFAIL flag on because they may be used in 1024 * conjuction with interruptible sleeps so 1025 * lk_exslpfail might be considered an 'upper limit' 1026 * bound, including the edge cases. 1027 */ 1028 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1029 realexslp = sleepq_sleepcnt(&lk->lock_object, 1030 SQ_EXCLUSIVE_QUEUE); 1031 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1032 if (lk->lk_exslpfail < realexslp) { 1033 lk->lk_exslpfail = 0; 1034 queue = SQ_EXCLUSIVE_QUEUE; 1035 v |= (x & LK_SHARED_WAITERS); 1036 } else { 1037 lk->lk_exslpfail = 0; 1038 LOCK_LOG2(lk, 1039 "%s: %p has only LK_SLEEPFAIL sleepers", 1040 __func__, lk); 1041 LOCK_LOG2(lk, 1042 "%s: %p waking up threads on the exclusive queue", 1043 __func__, lk); 1044 wakeup_swapper = 1045 sleepq_broadcast(&lk->lock_object, 1046 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1047 queue = SQ_SHARED_QUEUE; 1048 } 1049 } else { 1050 1051 /* 1052 * Exclusive waiters sleeping with LK_SLEEPFAIL 1053 * on and using interruptible sleeps/timeout 1054 * may have left spourious lk_exslpfail counts 1055 * on, so clean it up anyway. 1056 */ 1057 lk->lk_exslpfail = 0; 1058 queue = SQ_SHARED_QUEUE; 1059 } 1060 1061 LOCK_LOG3(lk, 1062 "%s: %p waking up threads on the %s queue", 1063 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1064 "exclusive"); 1065 atomic_store_rel_ptr(&lk->lk_lock, v); 1066 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1067 SLEEPQ_LK, 0, queue); 1068 sleepq_release(&lk->lock_object); 1069 break; 1070 } else 1071 wakeup_swapper = wakeupshlk(lk, file, line); 1072 break; 1073 case LK_DRAIN: 1074 if (LK_CAN_WITNESS(flags)) 1075 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1076 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 1077 ilk : NULL); 1078 1079 /* 1080 * Trying to drain a lock we already own will result in a 1081 * deadlock. 1082 */ 1083 if (lockmgr_xlocked(lk)) { 1084 if (flags & LK_INTERLOCK) 1085 class->lc_unlock(ilk); 1086 panic("%s: draining %s with the lock held @ %s:%d\n", 1087 __func__, iwmesg, file, line); 1088 } 1089 1090 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1091 #ifdef HWPMC_HOOKS 1092 PMC_SOFT_CALL( , , lock, failed); 1093 #endif 1094 lock_profile_obtain_lock_failed(&lk->lock_object, 1095 &contested, &waittime); 1096 1097 /* 1098 * If the lock is expected to not sleep just give up 1099 * and return. 1100 */ 1101 if (LK_TRYOP(flags)) { 1102 LOCK_LOG2(lk, "%s: %p fails the try operation", 1103 __func__, lk); 1104 error = EBUSY; 1105 break; 1106 } 1107 1108 /* 1109 * Acquire the sleepqueue chain lock because we 1110 * probabilly will need to manipulate waiters flags. 1111 */ 1112 sleepq_lock(&lk->lock_object); 1113 x = lk->lk_lock; 1114 1115 /* 1116 * if the lock has been released while we spun on 1117 * the sleepqueue chain lock just try again. 1118 */ 1119 if (x == LK_UNLOCKED) { 1120 sleepq_release(&lk->lock_object); 1121 continue; 1122 } 1123 1124 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1125 if ((x & ~v) == LK_UNLOCKED) { 1126 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1127 1128 /* 1129 * If interruptible sleeps left the exclusive 1130 * queue empty avoid a starvation for the 1131 * threads sleeping on the shared queue by 1132 * giving them precedence and cleaning up the 1133 * exclusive waiters bit anyway. 1134 * Please note that lk_exslpfail count may be 1135 * lying about the real number of waiters with 1136 * the LK_SLEEPFAIL flag on because they may 1137 * be used in conjuction with interruptible 1138 * sleeps so lk_exslpfail might be considered 1139 * an 'upper limit' bound, including the edge 1140 * cases. 1141 */ 1142 if (v & LK_EXCLUSIVE_WAITERS) { 1143 queue = SQ_EXCLUSIVE_QUEUE; 1144 v &= ~LK_EXCLUSIVE_WAITERS; 1145 } else { 1146 1147 /* 1148 * Exclusive waiters sleeping with 1149 * LK_SLEEPFAIL on and using 1150 * interruptible sleeps/timeout may 1151 * have left spourious lk_exslpfail 1152 * counts on, so clean it up anyway. 1153 */ 1154 MPASS(v & LK_SHARED_WAITERS); 1155 lk->lk_exslpfail = 0; 1156 queue = SQ_SHARED_QUEUE; 1157 v &= ~LK_SHARED_WAITERS; 1158 } 1159 if (queue == SQ_EXCLUSIVE_QUEUE) { 1160 realexslp = 1161 sleepq_sleepcnt(&lk->lock_object, 1162 SQ_EXCLUSIVE_QUEUE); 1163 if (lk->lk_exslpfail >= realexslp) { 1164 lk->lk_exslpfail = 0; 1165 queue = SQ_SHARED_QUEUE; 1166 v &= ~LK_SHARED_WAITERS; 1167 if (realexslp != 0) { 1168 LOCK_LOG2(lk, 1169 "%s: %p has only LK_SLEEPFAIL sleepers", 1170 __func__, lk); 1171 LOCK_LOG2(lk, 1172 "%s: %p waking up threads on the exclusive queue", 1173 __func__, lk); 1174 wakeup_swapper = 1175 sleepq_broadcast( 1176 &lk->lock_object, 1177 SLEEPQ_LK, 0, 1178 SQ_EXCLUSIVE_QUEUE); 1179 } 1180 } else 1181 lk->lk_exslpfail = 0; 1182 } 1183 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1184 sleepq_release(&lk->lock_object); 1185 continue; 1186 } 1187 LOCK_LOG3(lk, 1188 "%s: %p waking up all threads on the %s queue", 1189 __func__, lk, queue == SQ_SHARED_QUEUE ? 1190 "shared" : "exclusive"); 1191 wakeup_swapper |= sleepq_broadcast( 1192 &lk->lock_object, SLEEPQ_LK, 0, queue); 1193 1194 /* 1195 * If shared waiters have been woken up we need 1196 * to wait for one of them to acquire the lock 1197 * before to set the exclusive waiters in 1198 * order to avoid a deadlock. 1199 */ 1200 if (queue == SQ_SHARED_QUEUE) { 1201 for (v = lk->lk_lock; 1202 (v & LK_SHARE) && !LK_SHARERS(v); 1203 v = lk->lk_lock) 1204 cpu_spinwait(); 1205 } 1206 } 1207 1208 /* 1209 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1210 * fail, loop back and retry. 1211 */ 1212 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1213 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1214 x | LK_EXCLUSIVE_WAITERS)) { 1215 sleepq_release(&lk->lock_object); 1216 continue; 1217 } 1218 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1219 __func__, lk); 1220 } 1221 1222 /* 1223 * As far as we have been unable to acquire the 1224 * exclusive lock and the exclusive waiters flag 1225 * is set, we will sleep. 1226 */ 1227 if (flags & LK_INTERLOCK) { 1228 class->lc_unlock(ilk); 1229 flags &= ~LK_INTERLOCK; 1230 } 1231 GIANT_SAVE(); 1232 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1233 SQ_EXCLUSIVE_QUEUE); 1234 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1235 GIANT_RESTORE(); 1236 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1237 __func__, lk); 1238 } 1239 1240 if (error == 0) { 1241 lock_profile_obtain_lock_success(&lk->lock_object, 1242 contested, waittime, file, line); 1243 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1244 lk->lk_recurse, file, line); 1245 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1246 LK_TRYWIT(flags), file, line); 1247 TD_LOCKS_INC(curthread); 1248 STACK_SAVE(lk); 1249 } 1250 break; 1251 default: 1252 if (flags & LK_INTERLOCK) 1253 class->lc_unlock(ilk); 1254 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1255 } 1256 1257 if (flags & LK_INTERLOCK) 1258 class->lc_unlock(ilk); 1259 if (wakeup_swapper) 1260 kick_proc0(); 1261 1262 return (error); 1263 } 1264 1265 void 1266 _lockmgr_disown(struct lock *lk, const char *file, int line) 1267 { 1268 uintptr_t tid, x; 1269 1270 if (SCHEDULER_STOPPED()) 1271 return; 1272 1273 tid = (uintptr_t)curthread; 1274 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1275 1276 /* 1277 * Panic if the lock is recursed. 1278 */ 1279 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1280 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1281 __func__, file, line); 1282 1283 /* 1284 * If the owner is already LK_KERNPROC just skip the whole operation. 1285 */ 1286 if (LK_HOLDER(lk->lk_lock) != tid) 1287 return; 1288 lock_profile_release_lock(&lk->lock_object); 1289 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1290 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1291 TD_LOCKS_DEC(curthread); 1292 STACK_SAVE(lk); 1293 1294 /* 1295 * In order to preserve waiters flags, just spin. 1296 */ 1297 for (;;) { 1298 x = lk->lk_lock; 1299 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1300 x &= LK_ALL_WAITERS; 1301 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1302 LK_KERNPROC | x)) 1303 return; 1304 cpu_spinwait(); 1305 } 1306 } 1307 1308 void 1309 lockmgr_printinfo(const struct lock *lk) 1310 { 1311 struct thread *td; 1312 uintptr_t x; 1313 1314 if (lk->lk_lock == LK_UNLOCKED) 1315 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1316 else if (lk->lk_lock & LK_SHARE) 1317 printf("lock type %s: SHARED (count %ju)\n", 1318 lk->lock_object.lo_name, 1319 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1320 else { 1321 td = lockmgr_xholder(lk); 1322 printf("lock type %s: EXCL by thread %p " 1323 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, td, 1324 td->td_proc->p_pid, td->td_proc->p_comm, td->td_tid); 1325 } 1326 1327 x = lk->lk_lock; 1328 if (x & LK_EXCLUSIVE_WAITERS) 1329 printf(" with exclusive waiters pending\n"); 1330 if (x & LK_SHARED_WAITERS) 1331 printf(" with shared waiters pending\n"); 1332 if (x & LK_EXCLUSIVE_SPINNERS) 1333 printf(" with exclusive spinners pending\n"); 1334 1335 STACK_PRINT(lk); 1336 } 1337 1338 int 1339 lockstatus(const struct lock *lk) 1340 { 1341 uintptr_t v, x; 1342 int ret; 1343 1344 ret = LK_SHARED; 1345 x = lk->lk_lock; 1346 v = LK_HOLDER(x); 1347 1348 if ((x & LK_SHARE) == 0) { 1349 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1350 ret = LK_EXCLUSIVE; 1351 else 1352 ret = LK_EXCLOTHER; 1353 } else if (x == LK_UNLOCKED) 1354 ret = 0; 1355 1356 return (ret); 1357 } 1358 1359 #ifdef INVARIANT_SUPPORT 1360 1361 FEATURE(invariant_support, 1362 "Support for modules compiled with INVARIANTS option"); 1363 1364 #ifndef INVARIANTS 1365 #undef _lockmgr_assert 1366 #endif 1367 1368 void 1369 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1370 { 1371 int slocked = 0; 1372 1373 if (panicstr != NULL) 1374 return; 1375 switch (what) { 1376 case KA_SLOCKED: 1377 case KA_SLOCKED | KA_NOTRECURSED: 1378 case KA_SLOCKED | KA_RECURSED: 1379 slocked = 1; 1380 case KA_LOCKED: 1381 case KA_LOCKED | KA_NOTRECURSED: 1382 case KA_LOCKED | KA_RECURSED: 1383 #ifdef WITNESS 1384 1385 /* 1386 * We cannot trust WITNESS if the lock is held in exclusive 1387 * mode and a call to lockmgr_disown() happened. 1388 * Workaround this skipping the check if the lock is held in 1389 * exclusive mode even for the KA_LOCKED case. 1390 */ 1391 if (slocked || (lk->lk_lock & LK_SHARE)) { 1392 witness_assert(&lk->lock_object, what, file, line); 1393 break; 1394 } 1395 #endif 1396 if (lk->lk_lock == LK_UNLOCKED || 1397 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1398 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1399 panic("Lock %s not %slocked @ %s:%d\n", 1400 lk->lock_object.lo_name, slocked ? "share" : "", 1401 file, line); 1402 1403 if ((lk->lk_lock & LK_SHARE) == 0) { 1404 if (lockmgr_recursed(lk)) { 1405 if (what & KA_NOTRECURSED) 1406 panic("Lock %s recursed @ %s:%d\n", 1407 lk->lock_object.lo_name, file, 1408 line); 1409 } else if (what & KA_RECURSED) 1410 panic("Lock %s not recursed @ %s:%d\n", 1411 lk->lock_object.lo_name, file, line); 1412 } 1413 break; 1414 case KA_XLOCKED: 1415 case KA_XLOCKED | KA_NOTRECURSED: 1416 case KA_XLOCKED | KA_RECURSED: 1417 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1418 panic("Lock %s not exclusively locked @ %s:%d\n", 1419 lk->lock_object.lo_name, file, line); 1420 if (lockmgr_recursed(lk)) { 1421 if (what & KA_NOTRECURSED) 1422 panic("Lock %s recursed @ %s:%d\n", 1423 lk->lock_object.lo_name, file, line); 1424 } else if (what & KA_RECURSED) 1425 panic("Lock %s not recursed @ %s:%d\n", 1426 lk->lock_object.lo_name, file, line); 1427 break; 1428 case KA_UNLOCKED: 1429 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1430 panic("Lock %s exclusively locked @ %s:%d\n", 1431 lk->lock_object.lo_name, file, line); 1432 break; 1433 default: 1434 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1435 line); 1436 } 1437 } 1438 #endif 1439 1440 #ifdef DDB 1441 int 1442 lockmgr_chain(struct thread *td, struct thread **ownerp) 1443 { 1444 struct lock *lk; 1445 1446 lk = td->td_wchan; 1447 1448 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1449 return (0); 1450 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1451 if (lk->lk_lock & LK_SHARE) 1452 db_printf("SHARED (count %ju)\n", 1453 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1454 else 1455 db_printf("EXCL\n"); 1456 *ownerp = lockmgr_xholder(lk); 1457 1458 return (1); 1459 } 1460 1461 static void 1462 db_show_lockmgr(const struct lock_object *lock) 1463 { 1464 struct thread *td; 1465 const struct lock *lk; 1466 1467 lk = (const struct lock *)lock; 1468 1469 db_printf(" state: "); 1470 if (lk->lk_lock == LK_UNLOCKED) 1471 db_printf("UNLOCKED\n"); 1472 else if (lk->lk_lock & LK_SHARE) 1473 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1474 else { 1475 td = lockmgr_xholder(lk); 1476 if (td == (struct thread *)LK_KERNPROC) 1477 db_printf("XLOCK: LK_KERNPROC\n"); 1478 else 1479 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1480 td->td_tid, td->td_proc->p_pid, 1481 td->td_proc->p_comm); 1482 if (lockmgr_recursed(lk)) 1483 db_printf(" recursed: %d\n", lk->lk_recurse); 1484 } 1485 db_printf(" waiters: "); 1486 switch (lk->lk_lock & LK_ALL_WAITERS) { 1487 case LK_SHARED_WAITERS: 1488 db_printf("shared\n"); 1489 break; 1490 case LK_EXCLUSIVE_WAITERS: 1491 db_printf("exclusive\n"); 1492 break; 1493 case LK_ALL_WAITERS: 1494 db_printf("shared and exclusive\n"); 1495 break; 1496 default: 1497 db_printf("none\n"); 1498 } 1499 db_printf(" spinners: "); 1500 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1501 db_printf("exclusive\n"); 1502 else 1503 db_printf("none\n"); 1504 } 1505 #endif 1506