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 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD$"); 35 36 #include <sys/param.h> 37 #include <sys/kdb.h> 38 #include <sys/ktr.h> 39 #include <sys/lock.h> 40 #include <sys/lock_profile.h> 41 #include <sys/lockmgr.h> 42 #include <sys/mutex.h> 43 #include <sys/proc.h> 44 #include <sys/sleepqueue.h> 45 #ifdef DEBUG_LOCKS 46 #include <sys/stack.h> 47 #endif 48 #include <sys/sysctl.h> 49 #include <sys/systm.h> 50 51 #include <machine/cpu.h> 52 53 #ifdef DDB 54 #include <ddb/ddb.h> 55 #endif 56 57 #ifdef HWPMC_HOOKS 58 #include <sys/pmckern.h> 59 PMC_SOFT_DECLARE( , , lock, failed); 60 #endif 61 62 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) == 63 (LK_ADAPTIVE | LK_NOSHARE)); 64 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED & 65 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS))); 66 67 #define SQ_EXCLUSIVE_QUEUE 0 68 #define SQ_SHARED_QUEUE 1 69 70 #ifndef INVARIANTS 71 #define _lockmgr_assert(lk, what, file, line) 72 #define TD_LOCKS_INC(td) 73 #define TD_LOCKS_DEC(td) 74 #else 75 #define TD_LOCKS_INC(td) ((td)->td_locks++) 76 #define TD_LOCKS_DEC(td) ((td)->td_locks--) 77 #endif 78 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) 79 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) 80 81 #ifndef DEBUG_LOCKS 82 #define STACK_PRINT(lk) 83 #define STACK_SAVE(lk) 84 #define STACK_ZERO(lk) 85 #else 86 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) 87 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) 88 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) 89 #endif 90 91 #define LOCK_LOG2(lk, string, arg1, arg2) \ 92 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 93 CTR2(KTR_LOCK, (string), (arg1), (arg2)) 94 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ 95 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ 96 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) 97 98 #define GIANT_DECLARE \ 99 int _i = 0; \ 100 WITNESS_SAVE_DECL(Giant) 101 #define GIANT_RESTORE() do { \ 102 if (_i > 0) { \ 103 while (_i--) \ 104 mtx_lock(&Giant); \ 105 WITNESS_RESTORE(&Giant.lock_object, Giant); \ 106 } \ 107 } while (0) 108 #define GIANT_SAVE() do { \ 109 if (mtx_owned(&Giant)) { \ 110 WITNESS_SAVE(&Giant.lock_object, Giant); \ 111 while (mtx_owned(&Giant)) { \ 112 _i++; \ 113 mtx_unlock(&Giant); \ 114 } \ 115 } \ 116 } while (0) 117 118 #define LK_CAN_SHARE(x, flags) \ 119 (((x) & LK_SHARE) && \ 120 (((x) & (LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) == 0 || \ 121 (curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) || \ 122 (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, uintptr_t how); 146 #ifdef KDTRACE_HOOKS 147 static int owner_lockmgr(const struct lock_object *lock, 148 struct thread **owner); 149 #endif 150 static uintptr_t 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_release(&lk->lock_object); 215 sleepq_set_timeout(&lk->lock_object, timo); 216 sleepq_lock(&lk->lock_object); 217 } 218 /* 219 * Decisional switch for real sleeping. 220 */ 221 if ((flags & LK_TIMELOCK) && timo && catch) 222 error = sleepq_timedwait_sig(&lk->lock_object, pri); 223 else if ((flags & LK_TIMELOCK) && timo) 224 error = sleepq_timedwait(&lk->lock_object, pri); 225 else if (catch) 226 error = sleepq_wait_sig(&lk->lock_object, pri); 227 else 228 sleepq_wait(&lk->lock_object, pri); 229 GIANT_RESTORE(); 230 if ((flags & LK_SLEEPFAIL) && error == 0) 231 error = ENOLCK; 232 233 return (error); 234 } 235 236 static __inline int 237 wakeupshlk(struct lock *lk, const char *file, int line) 238 { 239 uintptr_t v, x; 240 u_int realexslp; 241 int queue, wakeup_swapper; 242 243 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 TD_LOCKS_DEC(curthread); 343 TD_SLOCKS_DEC(curthread); 344 return (wakeup_swapper); 345 } 346 347 static void 348 assert_lockmgr(const struct lock_object *lock, int what) 349 { 350 351 panic("lockmgr locks do not support assertions"); 352 } 353 354 static void 355 lock_lockmgr(struct lock_object *lock, uintptr_t how) 356 { 357 358 panic("lockmgr locks do not support sleep interlocking"); 359 } 360 361 static uintptr_t 362 unlock_lockmgr(struct lock_object *lock) 363 { 364 365 panic("lockmgr locks do not support sleep interlocking"); 366 } 367 368 #ifdef KDTRACE_HOOKS 369 static int 370 owner_lockmgr(const struct lock_object *lock, struct thread **owner) 371 { 372 373 panic("lockmgr locks do not support owner inquiring"); 374 } 375 #endif 376 377 void 378 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) 379 { 380 int iflags; 381 382 MPASS((flags & ~LK_INIT_MASK) == 0); 383 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, 384 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, 385 &lk->lk_lock)); 386 387 iflags = LO_SLEEPABLE | LO_UPGRADABLE; 388 if (flags & LK_CANRECURSE) 389 iflags |= LO_RECURSABLE; 390 if ((flags & LK_NODUP) == 0) 391 iflags |= LO_DUPOK; 392 if (flags & LK_NOPROFILE) 393 iflags |= LO_NOPROFILE; 394 if ((flags & LK_NOWITNESS) == 0) 395 iflags |= LO_WITNESS; 396 if (flags & LK_QUIET) 397 iflags |= LO_QUIET; 398 if (flags & LK_IS_VNODE) 399 iflags |= LO_IS_VNODE; 400 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); 401 402 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); 403 lk->lk_lock = LK_UNLOCKED; 404 lk->lk_recurse = 0; 405 lk->lk_exslpfail = 0; 406 lk->lk_timo = timo; 407 lk->lk_pri = pri; 408 STACK_ZERO(lk); 409 } 410 411 /* 412 * XXX: Gross hacks to manipulate external lock flags after 413 * initialization. Used for certain vnode and buf locks. 414 */ 415 void 416 lockallowshare(struct lock *lk) 417 { 418 419 lockmgr_assert(lk, KA_XLOCKED); 420 lk->lock_object.lo_flags &= ~LK_NOSHARE; 421 } 422 423 void 424 lockdisableshare(struct lock *lk) 425 { 426 427 lockmgr_assert(lk, KA_XLOCKED); 428 lk->lock_object.lo_flags |= LK_NOSHARE; 429 } 430 431 void 432 lockallowrecurse(struct lock *lk) 433 { 434 435 lockmgr_assert(lk, KA_XLOCKED); 436 lk->lock_object.lo_flags |= LO_RECURSABLE; 437 } 438 439 void 440 lockdisablerecurse(struct lock *lk) 441 { 442 443 lockmgr_assert(lk, KA_XLOCKED); 444 lk->lock_object.lo_flags &= ~LO_RECURSABLE; 445 } 446 447 void 448 lockdestroy(struct lock *lk) 449 { 450 451 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); 452 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); 453 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); 454 lock_destroy(&lk->lock_object); 455 } 456 457 int 458 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, 459 const char *wmesg, int pri, int timo, const char *file, int line) 460 { 461 GIANT_DECLARE; 462 struct lock_class *class; 463 const char *iwmesg; 464 uintptr_t tid, v, x; 465 u_int op, realexslp; 466 int error, ipri, itimo, queue, wakeup_swapper; 467 #ifdef LOCK_PROFILING 468 uint64_t waittime = 0; 469 int contested = 0; 470 #endif 471 #ifdef ADAPTIVE_LOCKMGRS 472 volatile struct thread *owner; 473 u_int i, spintries = 0; 474 #endif 475 476 error = 0; 477 tid = (uintptr_t)curthread; 478 op = (flags & LK_TYPE_MASK); 479 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; 480 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; 481 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; 482 483 MPASS((flags & ~LK_TOTAL_MASK) == 0); 484 KASSERT((op & (op - 1)) == 0, 485 ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); 486 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || 487 (op != LK_DOWNGRADE && op != LK_RELEASE), 488 ("%s: Invalid flags in regard of the operation desired @ %s:%d", 489 __func__, file, line)); 490 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, 491 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", 492 __func__, file, line)); 493 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 494 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, 495 lk->lock_object.lo_name, file, line)); 496 497 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; 498 if (panicstr != NULL) { 499 if (flags & LK_INTERLOCK) 500 class->lc_unlock(ilk); 501 return (0); 502 } 503 504 if (lk->lock_object.lo_flags & LK_NOSHARE) { 505 switch (op) { 506 case LK_SHARED: 507 op = LK_EXCLUSIVE; 508 break; 509 case LK_UPGRADE: 510 case LK_TRYUPGRADE: 511 case LK_DOWNGRADE: 512 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, 513 file, line); 514 if (flags & LK_INTERLOCK) 515 class->lc_unlock(ilk); 516 return (0); 517 } 518 } 519 520 wakeup_swapper = 0; 521 switch (op) { 522 case LK_SHARED: 523 if (LK_CAN_WITNESS(flags)) 524 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, 525 file, line, flags & LK_INTERLOCK ? ilk : NULL); 526 for (;;) { 527 x = lk->lk_lock; 528 529 /* 530 * If no other thread has an exclusive lock, or 531 * no exclusive waiter is present, bump the count of 532 * sharers. Since we have to preserve the state of 533 * waiters, if we fail to acquire the shared lock 534 * loop back and retry. 535 */ 536 if (LK_CAN_SHARE(x, flags)) { 537 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 538 x + LK_ONE_SHARER)) 539 break; 540 continue; 541 } 542 #ifdef HWPMC_HOOKS 543 PMC_SOFT_CALL( , , lock, failed); 544 #endif 545 lock_profile_obtain_lock_failed(&lk->lock_object, 546 &contested, &waittime); 547 548 /* 549 * If the lock is already held by curthread in 550 * exclusive way avoid a deadlock. 551 */ 552 if (LK_HOLDER(x) == tid) { 553 LOCK_LOG2(lk, 554 "%s: %p already held in exclusive mode", 555 __func__, lk); 556 error = EDEADLK; 557 break; 558 } 559 560 /* 561 * If the lock is expected to not sleep just give up 562 * and return. 563 */ 564 if (LK_TRYOP(flags)) { 565 LOCK_LOG2(lk, "%s: %p fails the try operation", 566 __func__, lk); 567 error = EBUSY; 568 break; 569 } 570 571 #ifdef ADAPTIVE_LOCKMGRS 572 /* 573 * If the owner is running on another CPU, spin until 574 * the owner stops running or the state of the lock 575 * changes. We need a double-state handle here 576 * because for a failed acquisition the lock can be 577 * either held in exclusive mode or shared mode 578 * (for the writer starvation avoidance technique). 579 */ 580 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 581 LK_HOLDER(x) != LK_KERNPROC) { 582 owner = (struct thread *)LK_HOLDER(x); 583 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 584 CTR3(KTR_LOCK, 585 "%s: spinning on %p held by %p", 586 __func__, lk, owner); 587 KTR_STATE1(KTR_SCHED, "thread", 588 sched_tdname(td), "spinning", 589 "lockname:\"%s\"", lk->lock_object.lo_name); 590 591 /* 592 * If we are holding also an interlock drop it 593 * in order to avoid a deadlock if the lockmgr 594 * owner is adaptively spinning on the 595 * interlock itself. 596 */ 597 if (flags & LK_INTERLOCK) { 598 class->lc_unlock(ilk); 599 flags &= ~LK_INTERLOCK; 600 } 601 GIANT_SAVE(); 602 while (LK_HOLDER(lk->lk_lock) == 603 (uintptr_t)owner && TD_IS_RUNNING(owner)) 604 cpu_spinwait(); 605 KTR_STATE0(KTR_SCHED, "thread", 606 sched_tdname(td), "running"); 607 GIANT_RESTORE(); 608 continue; 609 } else if (LK_CAN_ADAPT(lk, flags) && 610 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 611 spintries < alk_retries) { 612 KTR_STATE1(KTR_SCHED, "thread", 613 sched_tdname(td), "spinning", 614 "lockname:\"%s\"", lk->lock_object.lo_name); 615 if (flags & LK_INTERLOCK) { 616 class->lc_unlock(ilk); 617 flags &= ~LK_INTERLOCK; 618 } 619 GIANT_SAVE(); 620 spintries++; 621 for (i = 0; i < alk_loops; i++) { 622 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 623 CTR4(KTR_LOCK, 624 "%s: shared spinning on %p with %u and %u", 625 __func__, lk, spintries, i); 626 x = lk->lk_lock; 627 if ((x & LK_SHARE) == 0 || 628 LK_CAN_SHARE(x, flags) != 0) 629 break; 630 cpu_spinwait(); 631 } 632 KTR_STATE0(KTR_SCHED, "thread", 633 sched_tdname(td), "running"); 634 GIANT_RESTORE(); 635 if (i != alk_loops) 636 continue; 637 } 638 #endif 639 640 /* 641 * Acquire the sleepqueue chain lock because we 642 * probabilly will need to manipulate waiters flags. 643 */ 644 sleepq_lock(&lk->lock_object); 645 x = lk->lk_lock; 646 647 /* 648 * if the lock can be acquired in shared mode, try 649 * again. 650 */ 651 if (LK_CAN_SHARE(x, flags)) { 652 sleepq_release(&lk->lock_object); 653 continue; 654 } 655 656 #ifdef ADAPTIVE_LOCKMGRS 657 /* 658 * The current lock owner might have started executing 659 * on another CPU (or the lock could have changed 660 * owner) while we were waiting on the turnstile 661 * chain lock. If so, drop the turnstile lock and try 662 * again. 663 */ 664 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 665 LK_HOLDER(x) != LK_KERNPROC) { 666 owner = (struct thread *)LK_HOLDER(x); 667 if (TD_IS_RUNNING(owner)) { 668 sleepq_release(&lk->lock_object); 669 continue; 670 } 671 } 672 #endif 673 674 /* 675 * Try to set the LK_SHARED_WAITERS flag. If we fail, 676 * loop back and retry. 677 */ 678 if ((x & LK_SHARED_WAITERS) == 0) { 679 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, 680 x | LK_SHARED_WAITERS)) { 681 sleepq_release(&lk->lock_object); 682 continue; 683 } 684 LOCK_LOG2(lk, "%s: %p set shared waiters flag", 685 __func__, lk); 686 } 687 688 /* 689 * As far as we have been unable to acquire the 690 * shared lock and the shared waiters flag is set, 691 * we will sleep. 692 */ 693 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 694 SQ_SHARED_QUEUE); 695 flags &= ~LK_INTERLOCK; 696 if (error) { 697 LOCK_LOG3(lk, 698 "%s: interrupted sleep for %p with %d", 699 __func__, lk, error); 700 break; 701 } 702 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 703 __func__, lk); 704 } 705 if (error == 0) { 706 lock_profile_obtain_lock_success(&lk->lock_object, 707 contested, waittime, file, line); 708 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, 709 line); 710 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, 711 line); 712 TD_LOCKS_INC(curthread); 713 TD_SLOCKS_INC(curthread); 714 STACK_SAVE(lk); 715 } 716 break; 717 case LK_UPGRADE: 718 case LK_TRYUPGRADE: 719 _lockmgr_assert(lk, KA_SLOCKED, file, line); 720 v = lk->lk_lock; 721 x = v & LK_ALL_WAITERS; 722 v &= LK_EXCLUSIVE_SPINNERS; 723 724 /* 725 * Try to switch from one shared lock to an exclusive one. 726 * We need to preserve waiters flags during the operation. 727 */ 728 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, 729 tid | x)) { 730 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, 731 line); 732 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | 733 LK_TRYWIT(flags), file, line); 734 TD_SLOCKS_DEC(curthread); 735 break; 736 } 737 738 /* 739 * In LK_TRYUPGRADE mode, do not drop the lock, 740 * returning EBUSY instead. 741 */ 742 if (op == LK_TRYUPGRADE) { 743 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", 744 __func__, lk); 745 error = EBUSY; 746 break; 747 } 748 749 /* 750 * We have been unable to succeed in upgrading, so just 751 * give up the shared lock. 752 */ 753 wakeup_swapper |= wakeupshlk(lk, file, line); 754 755 /* FALLTHROUGH */ 756 case LK_EXCLUSIVE: 757 if (LK_CAN_WITNESS(flags)) 758 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 759 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 760 ilk : NULL); 761 762 /* 763 * If curthread already holds the lock and this one is 764 * allowed to recurse, simply recurse on it. 765 */ 766 if (lockmgr_xlocked(lk)) { 767 if ((flags & LK_CANRECURSE) == 0 && 768 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { 769 770 /* 771 * If the lock is expected to not panic just 772 * give up and return. 773 */ 774 if (LK_TRYOP(flags)) { 775 LOCK_LOG2(lk, 776 "%s: %p fails the try operation", 777 __func__, lk); 778 error = EBUSY; 779 break; 780 } 781 if (flags & LK_INTERLOCK) 782 class->lc_unlock(ilk); 783 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", 784 __func__, iwmesg, file, line); 785 } 786 lk->lk_recurse++; 787 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); 788 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 789 lk->lk_recurse, file, line); 790 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 791 LK_TRYWIT(flags), file, line); 792 TD_LOCKS_INC(curthread); 793 break; 794 } 795 796 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, 797 tid)) { 798 #ifdef HWPMC_HOOKS 799 PMC_SOFT_CALL( , , lock, failed); 800 #endif 801 lock_profile_obtain_lock_failed(&lk->lock_object, 802 &contested, &waittime); 803 804 /* 805 * If the lock is expected to not sleep just give up 806 * and return. 807 */ 808 if (LK_TRYOP(flags)) { 809 LOCK_LOG2(lk, "%s: %p fails the try operation", 810 __func__, lk); 811 error = EBUSY; 812 break; 813 } 814 815 #ifdef ADAPTIVE_LOCKMGRS 816 /* 817 * If the owner is running on another CPU, spin until 818 * the owner stops running or the state of the lock 819 * changes. 820 */ 821 x = lk->lk_lock; 822 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 823 LK_HOLDER(x) != LK_KERNPROC) { 824 owner = (struct thread *)LK_HOLDER(x); 825 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 826 CTR3(KTR_LOCK, 827 "%s: spinning on %p held by %p", 828 __func__, lk, owner); 829 KTR_STATE1(KTR_SCHED, "thread", 830 sched_tdname(td), "spinning", 831 "lockname:\"%s\"", lk->lock_object.lo_name); 832 833 /* 834 * If we are holding also an interlock drop it 835 * in order to avoid a deadlock if the lockmgr 836 * owner is adaptively spinning on the 837 * interlock itself. 838 */ 839 if (flags & LK_INTERLOCK) { 840 class->lc_unlock(ilk); 841 flags &= ~LK_INTERLOCK; 842 } 843 GIANT_SAVE(); 844 while (LK_HOLDER(lk->lk_lock) == 845 (uintptr_t)owner && TD_IS_RUNNING(owner)) 846 cpu_spinwait(); 847 KTR_STATE0(KTR_SCHED, "thread", 848 sched_tdname(td), "running"); 849 GIANT_RESTORE(); 850 continue; 851 } else if (LK_CAN_ADAPT(lk, flags) && 852 (x & LK_SHARE) != 0 && LK_SHARERS(x) && 853 spintries < alk_retries) { 854 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && 855 !atomic_cmpset_ptr(&lk->lk_lock, x, 856 x | LK_EXCLUSIVE_SPINNERS)) 857 continue; 858 KTR_STATE1(KTR_SCHED, "thread", 859 sched_tdname(td), "spinning", 860 "lockname:\"%s\"", lk->lock_object.lo_name); 861 if (flags & LK_INTERLOCK) { 862 class->lc_unlock(ilk); 863 flags &= ~LK_INTERLOCK; 864 } 865 GIANT_SAVE(); 866 spintries++; 867 for (i = 0; i < alk_loops; i++) { 868 if (LOCK_LOG_TEST(&lk->lock_object, 0)) 869 CTR4(KTR_LOCK, 870 "%s: shared spinning on %p with %u and %u", 871 __func__, lk, spintries, i); 872 if ((lk->lk_lock & 873 LK_EXCLUSIVE_SPINNERS) == 0) 874 break; 875 cpu_spinwait(); 876 } 877 KTR_STATE0(KTR_SCHED, "thread", 878 sched_tdname(td), "running"); 879 GIANT_RESTORE(); 880 if (i != alk_loops) 881 continue; 882 } 883 #endif 884 885 /* 886 * Acquire the sleepqueue chain lock because we 887 * probabilly will need to manipulate waiters flags. 888 */ 889 sleepq_lock(&lk->lock_object); 890 x = lk->lk_lock; 891 892 /* 893 * if the lock has been released while we spun on 894 * the sleepqueue chain lock just try again. 895 */ 896 if (x == LK_UNLOCKED) { 897 sleepq_release(&lk->lock_object); 898 continue; 899 } 900 901 #ifdef ADAPTIVE_LOCKMGRS 902 /* 903 * The current lock owner might have started executing 904 * on another CPU (or the lock could have changed 905 * owner) while we were waiting on the turnstile 906 * chain lock. If so, drop the turnstile lock and try 907 * again. 908 */ 909 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && 910 LK_HOLDER(x) != LK_KERNPROC) { 911 owner = (struct thread *)LK_HOLDER(x); 912 if (TD_IS_RUNNING(owner)) { 913 sleepq_release(&lk->lock_object); 914 continue; 915 } 916 } 917 #endif 918 919 /* 920 * The lock can be in the state where there is a 921 * pending queue of waiters, but still no owner. 922 * This happens when the lock is contested and an 923 * owner is going to claim the lock. 924 * If curthread is the one successfully acquiring it 925 * claim lock ownership and return, preserving waiters 926 * flags. 927 */ 928 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 929 if ((x & ~v) == LK_UNLOCKED) { 930 v &= ~LK_EXCLUSIVE_SPINNERS; 931 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, 932 tid | v)) { 933 sleepq_release(&lk->lock_object); 934 LOCK_LOG2(lk, 935 "%s: %p claimed by a new writer", 936 __func__, lk); 937 break; 938 } 939 sleepq_release(&lk->lock_object); 940 continue; 941 } 942 943 /* 944 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 945 * fail, loop back and retry. 946 */ 947 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 948 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 949 x | LK_EXCLUSIVE_WAITERS)) { 950 sleepq_release(&lk->lock_object); 951 continue; 952 } 953 LOCK_LOG2(lk, "%s: %p set excl waiters flag", 954 __func__, lk); 955 } 956 957 /* 958 * As far as we have been unable to acquire the 959 * exclusive lock and the exclusive waiters flag 960 * is set, we will sleep. 961 */ 962 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, 963 SQ_EXCLUSIVE_QUEUE); 964 flags &= ~LK_INTERLOCK; 965 if (error) { 966 LOCK_LOG3(lk, 967 "%s: interrupted sleep for %p with %d", 968 __func__, lk, error); 969 break; 970 } 971 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 972 __func__, lk); 973 } 974 if (error == 0) { 975 lock_profile_obtain_lock_success(&lk->lock_object, 976 contested, waittime, file, line); 977 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, 978 lk->lk_recurse, file, line); 979 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 980 LK_TRYWIT(flags), file, line); 981 TD_LOCKS_INC(curthread); 982 STACK_SAVE(lk); 983 } 984 break; 985 case LK_DOWNGRADE: 986 _lockmgr_assert(lk, KA_XLOCKED, file, line); 987 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); 988 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); 989 990 /* 991 * Panic if the lock is recursed. 992 */ 993 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 994 if (flags & LK_INTERLOCK) 995 class->lc_unlock(ilk); 996 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", 997 __func__, iwmesg, file, line); 998 } 999 TD_SLOCKS_INC(curthread); 1000 1001 /* 1002 * In order to preserve waiters flags, just spin. 1003 */ 1004 for (;;) { 1005 x = lk->lk_lock; 1006 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1007 x &= LK_ALL_WAITERS; 1008 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1009 LK_SHARERS_LOCK(1) | x)) 1010 break; 1011 cpu_spinwait(); 1012 } 1013 break; 1014 case LK_RELEASE: 1015 _lockmgr_assert(lk, KA_LOCKED, file, line); 1016 x = lk->lk_lock; 1017 1018 if ((x & LK_SHARE) == 0) { 1019 1020 /* 1021 * As first option, treact the lock as if it has not 1022 * any waiter. 1023 * Fix-up the tid var if the lock has been disowned. 1024 */ 1025 if (LK_HOLDER(x) == LK_KERNPROC) 1026 tid = LK_KERNPROC; 1027 else { 1028 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, 1029 file, line); 1030 TD_LOCKS_DEC(curthread); 1031 } 1032 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, 1033 lk->lk_recurse, file, line); 1034 1035 /* 1036 * The lock is held in exclusive mode. 1037 * If the lock is recursed also, then unrecurse it. 1038 */ 1039 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { 1040 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, 1041 lk); 1042 lk->lk_recurse--; 1043 break; 1044 } 1045 if (tid != LK_KERNPROC) 1046 lock_profile_release_lock(&lk->lock_object); 1047 1048 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, 1049 LK_UNLOCKED)) 1050 break; 1051 1052 sleepq_lock(&lk->lock_object); 1053 x = lk->lk_lock; 1054 v = LK_UNLOCKED; 1055 1056 /* 1057 * If the lock has exclusive waiters, give them 1058 * preference in order to avoid deadlock with 1059 * shared runners up. 1060 * If interruptible sleeps left the exclusive queue 1061 * empty avoid a starvation for the threads sleeping 1062 * on the shared queue by giving them precedence 1063 * and cleaning up the exclusive waiters bit anyway. 1064 * Please note that lk_exslpfail count may be lying 1065 * about the real number of waiters with the 1066 * LK_SLEEPFAIL flag on because they may be used in 1067 * conjuction with interruptible sleeps so 1068 * lk_exslpfail might be considered an 'upper limit' 1069 * bound, including the edge cases. 1070 */ 1071 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1072 realexslp = sleepq_sleepcnt(&lk->lock_object, 1073 SQ_EXCLUSIVE_QUEUE); 1074 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { 1075 if (lk->lk_exslpfail < realexslp) { 1076 lk->lk_exslpfail = 0; 1077 queue = SQ_EXCLUSIVE_QUEUE; 1078 v |= (x & LK_SHARED_WAITERS); 1079 } else { 1080 lk->lk_exslpfail = 0; 1081 LOCK_LOG2(lk, 1082 "%s: %p has only LK_SLEEPFAIL sleepers", 1083 __func__, lk); 1084 LOCK_LOG2(lk, 1085 "%s: %p waking up threads on the exclusive queue", 1086 __func__, lk); 1087 wakeup_swapper = 1088 sleepq_broadcast(&lk->lock_object, 1089 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); 1090 queue = SQ_SHARED_QUEUE; 1091 } 1092 } else { 1093 1094 /* 1095 * Exclusive waiters sleeping with LK_SLEEPFAIL 1096 * on and using interruptible sleeps/timeout 1097 * may have left spourious lk_exslpfail counts 1098 * on, so clean it up anyway. 1099 */ 1100 lk->lk_exslpfail = 0; 1101 queue = SQ_SHARED_QUEUE; 1102 } 1103 1104 LOCK_LOG3(lk, 1105 "%s: %p waking up threads on the %s queue", 1106 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : 1107 "exclusive"); 1108 atomic_store_rel_ptr(&lk->lk_lock, v); 1109 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, 1110 SLEEPQ_LK, 0, queue); 1111 sleepq_release(&lk->lock_object); 1112 break; 1113 } else 1114 wakeup_swapper = wakeupshlk(lk, file, line); 1115 break; 1116 case LK_DRAIN: 1117 if (LK_CAN_WITNESS(flags)) 1118 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | 1119 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? 1120 ilk : NULL); 1121 1122 /* 1123 * Trying to drain a lock we already own will result in a 1124 * deadlock. 1125 */ 1126 if (lockmgr_xlocked(lk)) { 1127 if (flags & LK_INTERLOCK) 1128 class->lc_unlock(ilk); 1129 panic("%s: draining %s with the lock held @ %s:%d\n", 1130 __func__, iwmesg, file, line); 1131 } 1132 1133 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { 1134 #ifdef HWPMC_HOOKS 1135 PMC_SOFT_CALL( , , lock, failed); 1136 #endif 1137 lock_profile_obtain_lock_failed(&lk->lock_object, 1138 &contested, &waittime); 1139 1140 /* 1141 * If the lock is expected to not sleep just give up 1142 * and return. 1143 */ 1144 if (LK_TRYOP(flags)) { 1145 LOCK_LOG2(lk, "%s: %p fails the try operation", 1146 __func__, lk); 1147 error = EBUSY; 1148 break; 1149 } 1150 1151 /* 1152 * Acquire the sleepqueue chain lock because we 1153 * probabilly will need to manipulate waiters flags. 1154 */ 1155 sleepq_lock(&lk->lock_object); 1156 x = lk->lk_lock; 1157 1158 /* 1159 * if the lock has been released while we spun on 1160 * the sleepqueue chain lock just try again. 1161 */ 1162 if (x == LK_UNLOCKED) { 1163 sleepq_release(&lk->lock_object); 1164 continue; 1165 } 1166 1167 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); 1168 if ((x & ~v) == LK_UNLOCKED) { 1169 v = (x & ~LK_EXCLUSIVE_SPINNERS); 1170 1171 /* 1172 * If interruptible sleeps left the exclusive 1173 * queue empty avoid a starvation for the 1174 * threads sleeping on the shared queue by 1175 * giving them precedence and cleaning up the 1176 * exclusive waiters bit anyway. 1177 * Please note that lk_exslpfail count may be 1178 * lying about the real number of waiters with 1179 * the LK_SLEEPFAIL flag on because they may 1180 * be used in conjuction with interruptible 1181 * sleeps so lk_exslpfail might be considered 1182 * an 'upper limit' bound, including the edge 1183 * cases. 1184 */ 1185 if (v & LK_EXCLUSIVE_WAITERS) { 1186 queue = SQ_EXCLUSIVE_QUEUE; 1187 v &= ~LK_EXCLUSIVE_WAITERS; 1188 } else { 1189 1190 /* 1191 * Exclusive waiters sleeping with 1192 * LK_SLEEPFAIL on and using 1193 * interruptible sleeps/timeout may 1194 * have left spourious lk_exslpfail 1195 * counts on, so clean it up anyway. 1196 */ 1197 MPASS(v & LK_SHARED_WAITERS); 1198 lk->lk_exslpfail = 0; 1199 queue = SQ_SHARED_QUEUE; 1200 v &= ~LK_SHARED_WAITERS; 1201 } 1202 if (queue == SQ_EXCLUSIVE_QUEUE) { 1203 realexslp = 1204 sleepq_sleepcnt(&lk->lock_object, 1205 SQ_EXCLUSIVE_QUEUE); 1206 if (lk->lk_exslpfail >= realexslp) { 1207 lk->lk_exslpfail = 0; 1208 queue = SQ_SHARED_QUEUE; 1209 v &= ~LK_SHARED_WAITERS; 1210 if (realexslp != 0) { 1211 LOCK_LOG2(lk, 1212 "%s: %p has only LK_SLEEPFAIL sleepers", 1213 __func__, lk); 1214 LOCK_LOG2(lk, 1215 "%s: %p waking up threads on the exclusive queue", 1216 __func__, lk); 1217 wakeup_swapper = 1218 sleepq_broadcast( 1219 &lk->lock_object, 1220 SLEEPQ_LK, 0, 1221 SQ_EXCLUSIVE_QUEUE); 1222 } 1223 } else 1224 lk->lk_exslpfail = 0; 1225 } 1226 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { 1227 sleepq_release(&lk->lock_object); 1228 continue; 1229 } 1230 LOCK_LOG3(lk, 1231 "%s: %p waking up all threads on the %s queue", 1232 __func__, lk, queue == SQ_SHARED_QUEUE ? 1233 "shared" : "exclusive"); 1234 wakeup_swapper |= sleepq_broadcast( 1235 &lk->lock_object, SLEEPQ_LK, 0, queue); 1236 1237 /* 1238 * If shared waiters have been woken up we need 1239 * to wait for one of them to acquire the lock 1240 * before to set the exclusive waiters in 1241 * order to avoid a deadlock. 1242 */ 1243 if (queue == SQ_SHARED_QUEUE) { 1244 for (v = lk->lk_lock; 1245 (v & LK_SHARE) && !LK_SHARERS(v); 1246 v = lk->lk_lock) 1247 cpu_spinwait(); 1248 } 1249 } 1250 1251 /* 1252 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we 1253 * fail, loop back and retry. 1254 */ 1255 if ((x & LK_EXCLUSIVE_WAITERS) == 0) { 1256 if (!atomic_cmpset_ptr(&lk->lk_lock, x, 1257 x | LK_EXCLUSIVE_WAITERS)) { 1258 sleepq_release(&lk->lock_object); 1259 continue; 1260 } 1261 LOCK_LOG2(lk, "%s: %p set drain waiters flag", 1262 __func__, lk); 1263 } 1264 1265 /* 1266 * As far as we have been unable to acquire the 1267 * exclusive lock and the exclusive waiters flag 1268 * is set, we will sleep. 1269 */ 1270 if (flags & LK_INTERLOCK) { 1271 class->lc_unlock(ilk); 1272 flags &= ~LK_INTERLOCK; 1273 } 1274 GIANT_SAVE(); 1275 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, 1276 SQ_EXCLUSIVE_QUEUE); 1277 sleepq_wait(&lk->lock_object, ipri & PRIMASK); 1278 GIANT_RESTORE(); 1279 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", 1280 __func__, lk); 1281 } 1282 1283 if (error == 0) { 1284 lock_profile_obtain_lock_success(&lk->lock_object, 1285 contested, waittime, file, line); 1286 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, 1287 lk->lk_recurse, file, line); 1288 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | 1289 LK_TRYWIT(flags), file, line); 1290 TD_LOCKS_INC(curthread); 1291 STACK_SAVE(lk); 1292 } 1293 break; 1294 default: 1295 if (flags & LK_INTERLOCK) 1296 class->lc_unlock(ilk); 1297 panic("%s: unknown lockmgr request 0x%x\n", __func__, op); 1298 } 1299 1300 if (flags & LK_INTERLOCK) 1301 class->lc_unlock(ilk); 1302 if (wakeup_swapper) 1303 kick_proc0(); 1304 1305 return (error); 1306 } 1307 1308 void 1309 _lockmgr_disown(struct lock *lk, const char *file, int line) 1310 { 1311 uintptr_t tid, x; 1312 1313 if (SCHEDULER_STOPPED()) 1314 return; 1315 1316 tid = (uintptr_t)curthread; 1317 _lockmgr_assert(lk, KA_XLOCKED, file, line); 1318 1319 /* 1320 * Panic if the lock is recursed. 1321 */ 1322 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) 1323 panic("%s: disown a recursed lockmgr @ %s:%d\n", 1324 __func__, file, line); 1325 1326 /* 1327 * If the owner is already LK_KERNPROC just skip the whole operation. 1328 */ 1329 if (LK_HOLDER(lk->lk_lock) != tid) 1330 return; 1331 lock_profile_release_lock(&lk->lock_object); 1332 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); 1333 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); 1334 TD_LOCKS_DEC(curthread); 1335 STACK_SAVE(lk); 1336 1337 /* 1338 * In order to preserve waiters flags, just spin. 1339 */ 1340 for (;;) { 1341 x = lk->lk_lock; 1342 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); 1343 x &= LK_ALL_WAITERS; 1344 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, 1345 LK_KERNPROC | x)) 1346 return; 1347 cpu_spinwait(); 1348 } 1349 } 1350 1351 void 1352 lockmgr_printinfo(const struct lock *lk) 1353 { 1354 struct thread *td; 1355 uintptr_t x; 1356 1357 if (lk->lk_lock == LK_UNLOCKED) 1358 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); 1359 else if (lk->lk_lock & LK_SHARE) 1360 printf("lock type %s: SHARED (count %ju)\n", 1361 lk->lock_object.lo_name, 1362 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1363 else { 1364 td = lockmgr_xholder(lk); 1365 if (td == (struct thread *)LK_KERNPROC) 1366 printf("lock type %s: EXCL by KERNPROC\n", 1367 lk->lock_object.lo_name); 1368 else 1369 printf("lock type %s: EXCL by thread %p " 1370 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, 1371 td, td->td_proc->p_pid, td->td_proc->p_comm, 1372 td->td_tid); 1373 } 1374 1375 x = lk->lk_lock; 1376 if (x & LK_EXCLUSIVE_WAITERS) 1377 printf(" with exclusive waiters pending\n"); 1378 if (x & LK_SHARED_WAITERS) 1379 printf(" with shared waiters pending\n"); 1380 if (x & LK_EXCLUSIVE_SPINNERS) 1381 printf(" with exclusive spinners pending\n"); 1382 1383 STACK_PRINT(lk); 1384 } 1385 1386 int 1387 lockstatus(const struct lock *lk) 1388 { 1389 uintptr_t v, x; 1390 int ret; 1391 1392 ret = LK_SHARED; 1393 x = lk->lk_lock; 1394 v = LK_HOLDER(x); 1395 1396 if ((x & LK_SHARE) == 0) { 1397 if (v == (uintptr_t)curthread || v == LK_KERNPROC) 1398 ret = LK_EXCLUSIVE; 1399 else 1400 ret = LK_EXCLOTHER; 1401 } else if (x == LK_UNLOCKED) 1402 ret = 0; 1403 1404 return (ret); 1405 } 1406 1407 #ifdef INVARIANT_SUPPORT 1408 1409 FEATURE(invariant_support, 1410 "Support for modules compiled with INVARIANTS option"); 1411 1412 #ifndef INVARIANTS 1413 #undef _lockmgr_assert 1414 #endif 1415 1416 void 1417 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) 1418 { 1419 int slocked = 0; 1420 1421 if (panicstr != NULL) 1422 return; 1423 switch (what) { 1424 case KA_SLOCKED: 1425 case KA_SLOCKED | KA_NOTRECURSED: 1426 case KA_SLOCKED | KA_RECURSED: 1427 slocked = 1; 1428 case KA_LOCKED: 1429 case KA_LOCKED | KA_NOTRECURSED: 1430 case KA_LOCKED | KA_RECURSED: 1431 #ifdef WITNESS 1432 1433 /* 1434 * We cannot trust WITNESS if the lock is held in exclusive 1435 * mode and a call to lockmgr_disown() happened. 1436 * Workaround this skipping the check if the lock is held in 1437 * exclusive mode even for the KA_LOCKED case. 1438 */ 1439 if (slocked || (lk->lk_lock & LK_SHARE)) { 1440 witness_assert(&lk->lock_object, what, file, line); 1441 break; 1442 } 1443 #endif 1444 if (lk->lk_lock == LK_UNLOCKED || 1445 ((lk->lk_lock & LK_SHARE) == 0 && (slocked || 1446 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) 1447 panic("Lock %s not %slocked @ %s:%d\n", 1448 lk->lock_object.lo_name, slocked ? "share" : "", 1449 file, line); 1450 1451 if ((lk->lk_lock & LK_SHARE) == 0) { 1452 if (lockmgr_recursed(lk)) { 1453 if (what & KA_NOTRECURSED) 1454 panic("Lock %s recursed @ %s:%d\n", 1455 lk->lock_object.lo_name, file, 1456 line); 1457 } else if (what & KA_RECURSED) 1458 panic("Lock %s not recursed @ %s:%d\n", 1459 lk->lock_object.lo_name, file, line); 1460 } 1461 break; 1462 case KA_XLOCKED: 1463 case KA_XLOCKED | KA_NOTRECURSED: 1464 case KA_XLOCKED | KA_RECURSED: 1465 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) 1466 panic("Lock %s not exclusively locked @ %s:%d\n", 1467 lk->lock_object.lo_name, file, line); 1468 if (lockmgr_recursed(lk)) { 1469 if (what & KA_NOTRECURSED) 1470 panic("Lock %s recursed @ %s:%d\n", 1471 lk->lock_object.lo_name, file, line); 1472 } else if (what & KA_RECURSED) 1473 panic("Lock %s not recursed @ %s:%d\n", 1474 lk->lock_object.lo_name, file, line); 1475 break; 1476 case KA_UNLOCKED: 1477 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) 1478 panic("Lock %s exclusively locked @ %s:%d\n", 1479 lk->lock_object.lo_name, file, line); 1480 break; 1481 default: 1482 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, 1483 line); 1484 } 1485 } 1486 #endif 1487 1488 #ifdef DDB 1489 int 1490 lockmgr_chain(struct thread *td, struct thread **ownerp) 1491 { 1492 struct lock *lk; 1493 1494 lk = td->td_wchan; 1495 1496 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) 1497 return (0); 1498 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); 1499 if (lk->lk_lock & LK_SHARE) 1500 db_printf("SHARED (count %ju)\n", 1501 (uintmax_t)LK_SHARERS(lk->lk_lock)); 1502 else 1503 db_printf("EXCL\n"); 1504 *ownerp = lockmgr_xholder(lk); 1505 1506 return (1); 1507 } 1508 1509 static void 1510 db_show_lockmgr(const struct lock_object *lock) 1511 { 1512 struct thread *td; 1513 const struct lock *lk; 1514 1515 lk = (const struct lock *)lock; 1516 1517 db_printf(" state: "); 1518 if (lk->lk_lock == LK_UNLOCKED) 1519 db_printf("UNLOCKED\n"); 1520 else if (lk->lk_lock & LK_SHARE) 1521 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); 1522 else { 1523 td = lockmgr_xholder(lk); 1524 if (td == (struct thread *)LK_KERNPROC) 1525 db_printf("XLOCK: LK_KERNPROC\n"); 1526 else 1527 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1528 td->td_tid, td->td_proc->p_pid, 1529 td->td_proc->p_comm); 1530 if (lockmgr_recursed(lk)) 1531 db_printf(" recursed: %d\n", lk->lk_recurse); 1532 } 1533 db_printf(" waiters: "); 1534 switch (lk->lk_lock & LK_ALL_WAITERS) { 1535 case LK_SHARED_WAITERS: 1536 db_printf("shared\n"); 1537 break; 1538 case LK_EXCLUSIVE_WAITERS: 1539 db_printf("exclusive\n"); 1540 break; 1541 case LK_ALL_WAITERS: 1542 db_printf("shared and exclusive\n"); 1543 break; 1544 default: 1545 db_printf("none\n"); 1546 } 1547 db_printf(" spinners: "); 1548 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) 1549 db_printf("exclusive\n"); 1550 else 1551 db_printf("none\n"); 1552 } 1553 #endif 1554