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