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