1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Berkeley Software Design Inc's name may not be used to endorse or 15 * promote products derived from this software without specific prior 16 * written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 * 30 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $ 31 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $ 32 */ 33 34 /* 35 * Machine independent bits of mutex implementation. 36 */ 37 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 #include "opt_adaptive_mutexes.h" 42 #include "opt_ddb.h" 43 #include "opt_hwpmc_hooks.h" 44 #include "opt_sched.h" 45 46 #include <sys/param.h> 47 #include <sys/systm.h> 48 #include <sys/bus.h> 49 #include <sys/conf.h> 50 #include <sys/kdb.h> 51 #include <sys/kernel.h> 52 #include <sys/ktr.h> 53 #include <sys/lock.h> 54 #include <sys/malloc.h> 55 #include <sys/mutex.h> 56 #include <sys/proc.h> 57 #include <sys/resourcevar.h> 58 #include <sys/sched.h> 59 #include <sys/sbuf.h> 60 #include <sys/smp.h> 61 #include <sys/sysctl.h> 62 #include <sys/turnstile.h> 63 #include <sys/vmmeter.h> 64 #include <sys/lock_profile.h> 65 66 #include <machine/atomic.h> 67 #include <machine/bus.h> 68 #include <machine/cpu.h> 69 70 #include <ddb/ddb.h> 71 72 #include <fs/devfs/devfs_int.h> 73 74 #include <vm/vm.h> 75 #include <vm/vm_extern.h> 76 77 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 78 #define ADAPTIVE_MUTEXES 79 #endif 80 81 #ifdef HWPMC_HOOKS 82 #include <sys/pmckern.h> 83 PMC_SOFT_DEFINE( , , lock, failed); 84 #endif 85 86 /* 87 * Return the mutex address when the lock cookie address is provided. 88 * This functionality assumes that struct mtx* have a member named mtx_lock. 89 */ 90 #define mtxlock2mtx(c) (__containerof(c, struct mtx, mtx_lock)) 91 92 /* 93 * Internal utility macros. 94 */ 95 #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED) 96 97 #define mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED) 98 99 static void assert_mtx(const struct lock_object *lock, int what); 100 #ifdef DDB 101 static void db_show_mtx(const struct lock_object *lock); 102 #endif 103 static void lock_mtx(struct lock_object *lock, uintptr_t how); 104 static void lock_spin(struct lock_object *lock, uintptr_t how); 105 #ifdef KDTRACE_HOOKS 106 static int owner_mtx(const struct lock_object *lock, 107 struct thread **owner); 108 #endif 109 static uintptr_t unlock_mtx(struct lock_object *lock); 110 static uintptr_t unlock_spin(struct lock_object *lock); 111 112 /* 113 * Lock classes for sleep and spin mutexes. 114 */ 115 struct lock_class lock_class_mtx_sleep = { 116 .lc_name = "sleep mutex", 117 .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE, 118 .lc_assert = assert_mtx, 119 #ifdef DDB 120 .lc_ddb_show = db_show_mtx, 121 #endif 122 .lc_lock = lock_mtx, 123 .lc_unlock = unlock_mtx, 124 #ifdef KDTRACE_HOOKS 125 .lc_owner = owner_mtx, 126 #endif 127 }; 128 struct lock_class lock_class_mtx_spin = { 129 .lc_name = "spin mutex", 130 .lc_flags = LC_SPINLOCK | LC_RECURSABLE, 131 .lc_assert = assert_mtx, 132 #ifdef DDB 133 .lc_ddb_show = db_show_mtx, 134 #endif 135 .lc_lock = lock_spin, 136 .lc_unlock = unlock_spin, 137 #ifdef KDTRACE_HOOKS 138 .lc_owner = owner_mtx, 139 #endif 140 }; 141 142 #ifdef ADAPTIVE_MUTEXES 143 #ifdef MUTEX_CUSTOM_BACKOFF 144 static SYSCTL_NODE(_debug, OID_AUTO, mtx, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 145 "mtx debugging"); 146 147 static struct lock_delay_config __read_frequently mtx_delay; 148 149 SYSCTL_U16(_debug_mtx, OID_AUTO, delay_base, CTLFLAG_RW, &mtx_delay.base, 150 0, ""); 151 SYSCTL_U16(_debug_mtx, OID_AUTO, delay_max, CTLFLAG_RW, &mtx_delay.max, 152 0, ""); 153 154 LOCK_DELAY_SYSINIT_DEFAULT(mtx_delay); 155 #else 156 #define mtx_delay locks_delay 157 #endif 158 #endif 159 160 #ifdef MUTEX_SPIN_CUSTOM_BACKOFF 161 static SYSCTL_NODE(_debug, OID_AUTO, mtx_spin, 162 CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 163 "mtx spin debugging"); 164 165 static struct lock_delay_config __read_frequently mtx_spin_delay; 166 167 SYSCTL_INT(_debug_mtx_spin, OID_AUTO, delay_base, CTLFLAG_RW, 168 &mtx_spin_delay.base, 0, ""); 169 SYSCTL_INT(_debug_mtx_spin, OID_AUTO, delay_max, CTLFLAG_RW, 170 &mtx_spin_delay.max, 0, ""); 171 172 LOCK_DELAY_SYSINIT_DEFAULT(mtx_spin_delay); 173 #else 174 #define mtx_spin_delay locks_delay 175 #endif 176 177 /* 178 * System-wide mutexes 179 */ 180 struct mtx blocked_lock; 181 struct mtx __exclusive_cache_line Giant; 182 183 static void _mtx_lock_indefinite_check(struct mtx *, struct lock_delay_arg *); 184 185 void 186 assert_mtx(const struct lock_object *lock, int what) 187 { 188 189 /* 190 * Treat LA_LOCKED as if LA_XLOCKED was asserted. 191 * 192 * Some callers of lc_assert uses LA_LOCKED to indicate that either 193 * a shared lock or write lock was held, while other callers uses 194 * the more strict LA_XLOCKED (used as MA_OWNED). 195 * 196 * Mutex is the only lock class that can not be shared, as a result, 197 * we can reasonably consider the caller really intends to assert 198 * LA_XLOCKED when they are asserting LA_LOCKED on a mutex object. 199 */ 200 if (what & LA_LOCKED) { 201 what &= ~LA_LOCKED; 202 what |= LA_XLOCKED; 203 } 204 mtx_assert((const struct mtx *)lock, what); 205 } 206 207 void 208 lock_mtx(struct lock_object *lock, uintptr_t how) 209 { 210 211 mtx_lock((struct mtx *)lock); 212 } 213 214 void 215 lock_spin(struct lock_object *lock, uintptr_t how) 216 { 217 218 panic("spin locks can only use msleep_spin"); 219 } 220 221 uintptr_t 222 unlock_mtx(struct lock_object *lock) 223 { 224 struct mtx *m; 225 226 m = (struct mtx *)lock; 227 mtx_assert(m, MA_OWNED | MA_NOTRECURSED); 228 mtx_unlock(m); 229 return (0); 230 } 231 232 uintptr_t 233 unlock_spin(struct lock_object *lock) 234 { 235 236 panic("spin locks can only use msleep_spin"); 237 } 238 239 #ifdef KDTRACE_HOOKS 240 int 241 owner_mtx(const struct lock_object *lock, struct thread **owner) 242 { 243 const struct mtx *m; 244 uintptr_t x; 245 246 m = (const struct mtx *)lock; 247 x = m->mtx_lock; 248 *owner = (struct thread *)(x & ~MTX_FLAGMASK); 249 return (*owner != NULL); 250 } 251 #endif 252 253 /* 254 * Function versions of the inlined __mtx_* macros. These are used by 255 * modules and can also be called from assembly language if needed. 256 */ 257 void 258 __mtx_lock_flags(volatile uintptr_t *c, int opts, const char *file, int line) 259 { 260 struct mtx *m; 261 uintptr_t tid, v; 262 263 m = mtxlock2mtx(c); 264 265 KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() || 266 !TD_IS_IDLETHREAD(curthread), 267 ("mtx_lock() by idle thread %p on sleep mutex %s @ %s:%d", 268 curthread, m->lock_object.lo_name, file, line)); 269 KASSERT(m->mtx_lock != MTX_DESTROYED, 270 ("mtx_lock() of destroyed mutex @ %s:%d", file, line)); 271 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 272 ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 273 file, line)); 274 WITNESS_CHECKORDER(&m->lock_object, (opts & ~MTX_RECURSE) | 275 LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL); 276 277 tid = (uintptr_t)curthread; 278 v = MTX_UNOWNED; 279 if (!_mtx_obtain_lock_fetch(m, &v, tid)) 280 _mtx_lock_sleep(m, v, opts, file, line); 281 else 282 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, 283 m, 0, 0, file, line); 284 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 285 line); 286 WITNESS_LOCK(&m->lock_object, (opts & ~MTX_RECURSE) | LOP_EXCLUSIVE, 287 file, line); 288 TD_LOCKS_INC(curthread); 289 } 290 291 void 292 __mtx_unlock_flags(volatile uintptr_t *c, int opts, const char *file, int line) 293 { 294 struct mtx *m; 295 296 m = mtxlock2mtx(c); 297 298 KASSERT(m->mtx_lock != MTX_DESTROYED, 299 ("mtx_unlock() of destroyed mutex @ %s:%d", file, line)); 300 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 301 ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 302 file, line)); 303 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 304 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, 305 line); 306 mtx_assert(m, MA_OWNED); 307 308 #ifdef LOCK_PROFILING 309 __mtx_unlock_sleep(c, (uintptr_t)curthread, opts, file, line); 310 #else 311 __mtx_unlock(m, curthread, opts, file, line); 312 #endif 313 TD_LOCKS_DEC(curthread); 314 } 315 316 void 317 __mtx_lock_spin_flags(volatile uintptr_t *c, int opts, const char *file, 318 int line) 319 { 320 struct mtx *m; 321 #ifdef SMP 322 uintptr_t tid, v; 323 #endif 324 325 m = mtxlock2mtx(c); 326 327 KASSERT(m->mtx_lock != MTX_DESTROYED, 328 ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line)); 329 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 330 ("mtx_lock_spin() of sleep mutex %s @ %s:%d", 331 m->lock_object.lo_name, file, line)); 332 if (mtx_owned(m)) 333 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 || 334 (opts & MTX_RECURSE) != 0, 335 ("mtx_lock_spin: recursed on non-recursive mutex %s @ %s:%d\n", 336 m->lock_object.lo_name, file, line)); 337 opts &= ~MTX_RECURSE; 338 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 339 file, line, NULL); 340 #ifdef SMP 341 spinlock_enter(); 342 tid = (uintptr_t)curthread; 343 v = MTX_UNOWNED; 344 if (!_mtx_obtain_lock_fetch(m, &v, tid)) 345 _mtx_lock_spin(m, v, opts, file, line); 346 else 347 LOCKSTAT_PROFILE_OBTAIN_SPIN_LOCK_SUCCESS(spin__acquire, 348 m, 0, 0, file, line); 349 #else 350 __mtx_lock_spin(m, curthread, opts, file, line); 351 #endif 352 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 353 line); 354 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 355 } 356 357 int 358 __mtx_trylock_spin_flags(volatile uintptr_t *c, int opts, const char *file, 359 int line) 360 { 361 struct mtx *m; 362 363 if (SCHEDULER_STOPPED()) 364 return (1); 365 366 m = mtxlock2mtx(c); 367 368 KASSERT(m->mtx_lock != MTX_DESTROYED, 369 ("mtx_trylock_spin() of destroyed mutex @ %s:%d", file, line)); 370 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 371 ("mtx_trylock_spin() of sleep mutex %s @ %s:%d", 372 m->lock_object.lo_name, file, line)); 373 KASSERT((opts & MTX_RECURSE) == 0, 374 ("mtx_trylock_spin: unsupp. opt MTX_RECURSE on mutex %s @ %s:%d\n", 375 m->lock_object.lo_name, file, line)); 376 if (__mtx_trylock_spin(m, curthread, opts, file, line)) { 377 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 1, file, line); 378 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 379 return (1); 380 } 381 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 0, file, line); 382 return (0); 383 } 384 385 void 386 __mtx_unlock_spin_flags(volatile uintptr_t *c, int opts, const char *file, 387 int line) 388 { 389 struct mtx *m; 390 391 m = mtxlock2mtx(c); 392 393 KASSERT(m->mtx_lock != MTX_DESTROYED, 394 ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line)); 395 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 396 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 397 m->lock_object.lo_name, file, line)); 398 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 399 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, 400 line); 401 mtx_assert(m, MA_OWNED); 402 403 __mtx_unlock_spin(m); 404 } 405 406 /* 407 * The important part of mtx_trylock{,_flags}() 408 * Tries to acquire lock `m.' If this function is called on a mutex that 409 * is already owned, it will recursively acquire the lock. 410 */ 411 int 412 _mtx_trylock_flags_int(struct mtx *m, int opts LOCK_FILE_LINE_ARG_DEF) 413 { 414 struct thread *td; 415 uintptr_t tid, v; 416 #ifdef LOCK_PROFILING 417 uint64_t waittime = 0; 418 int contested = 0; 419 #endif 420 int rval; 421 bool recursed; 422 423 td = curthread; 424 tid = (uintptr_t)td; 425 if (SCHEDULER_STOPPED_TD(td)) 426 return (1); 427 428 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(td), 429 ("mtx_trylock() by idle thread %p on sleep mutex %s @ %s:%d", 430 curthread, m->lock_object.lo_name, file, line)); 431 KASSERT(m->mtx_lock != MTX_DESTROYED, 432 ("mtx_trylock() of destroyed mutex @ %s:%d", file, line)); 433 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 434 ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 435 file, line)); 436 437 rval = 1; 438 recursed = false; 439 v = MTX_UNOWNED; 440 for (;;) { 441 if (_mtx_obtain_lock_fetch(m, &v, tid)) 442 break; 443 if (v == MTX_UNOWNED) 444 continue; 445 if (v == tid && 446 ((m->lock_object.lo_flags & LO_RECURSABLE) != 0 || 447 (opts & MTX_RECURSE) != 0)) { 448 m->mtx_recurse++; 449 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 450 recursed = true; 451 break; 452 } 453 rval = 0; 454 break; 455 } 456 457 opts &= ~MTX_RECURSE; 458 459 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line); 460 if (rval) { 461 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 462 file, line); 463 TD_LOCKS_INC(curthread); 464 if (!recursed) 465 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, 466 m, contested, waittime, file, line); 467 } 468 469 return (rval); 470 } 471 472 int 473 _mtx_trylock_flags_(volatile uintptr_t *c, int opts, const char *file, int line) 474 { 475 struct mtx *m; 476 477 m = mtxlock2mtx(c); 478 return (_mtx_trylock_flags_int(m, opts LOCK_FILE_LINE_ARG)); 479 } 480 481 /* 482 * __mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 483 * 484 * We call this if the lock is either contested (i.e. we need to go to 485 * sleep waiting for it), or if we need to recurse on it. 486 */ 487 #if LOCK_DEBUG > 0 488 void 489 __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v, int opts, const char *file, 490 int line) 491 #else 492 void 493 __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v) 494 #endif 495 { 496 struct thread *td; 497 struct mtx *m; 498 struct turnstile *ts; 499 uintptr_t tid; 500 struct thread *owner; 501 #ifdef LOCK_PROFILING 502 int contested = 0; 503 uint64_t waittime = 0; 504 #endif 505 #if defined(ADAPTIVE_MUTEXES) || defined(KDTRACE_HOOKS) 506 struct lock_delay_arg lda; 507 #endif 508 #ifdef KDTRACE_HOOKS 509 u_int sleep_cnt = 0; 510 int64_t sleep_time = 0; 511 int64_t all_time = 0; 512 #endif 513 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 514 int doing_lockprof = 0; 515 #endif 516 517 td = curthread; 518 tid = (uintptr_t)td; 519 m = mtxlock2mtx(c); 520 521 #ifdef KDTRACE_HOOKS 522 if (LOCKSTAT_PROFILE_ENABLED(adaptive__acquire)) { 523 while (v == MTX_UNOWNED) { 524 if (_mtx_obtain_lock_fetch(m, &v, tid)) 525 goto out_lockstat; 526 } 527 doing_lockprof = 1; 528 all_time -= lockstat_nsecs(&m->lock_object); 529 } 530 #endif 531 #ifdef LOCK_PROFILING 532 doing_lockprof = 1; 533 #endif 534 535 if (SCHEDULER_STOPPED_TD(td)) 536 return; 537 538 if (__predict_false(v == MTX_UNOWNED)) 539 v = MTX_READ_VALUE(m); 540 541 if (__predict_false(lv_mtx_owner(v) == td)) { 542 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 || 543 (opts & MTX_RECURSE) != 0, 544 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n", 545 m->lock_object.lo_name, file, line)); 546 #if LOCK_DEBUG > 0 547 opts &= ~MTX_RECURSE; 548 #endif 549 m->mtx_recurse++; 550 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 551 if (LOCK_LOG_TEST(&m->lock_object, opts)) 552 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 553 return; 554 } 555 #if LOCK_DEBUG > 0 556 opts &= ~MTX_RECURSE; 557 #endif 558 559 #if defined(ADAPTIVE_MUTEXES) 560 lock_delay_arg_init(&lda, &mtx_delay); 561 #elif defined(KDTRACE_HOOKS) 562 lock_delay_arg_init_noadapt(&lda); 563 #endif 564 565 #ifdef HWPMC_HOOKS 566 PMC_SOFT_CALL( , , lock, failed); 567 #endif 568 lock_profile_obtain_lock_failed(&m->lock_object, false, 569 &contested, &waittime); 570 if (LOCK_LOG_TEST(&m->lock_object, opts)) 571 CTR4(KTR_LOCK, 572 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 573 m->lock_object.lo_name, (void *)m->mtx_lock, file, line); 574 575 for (;;) { 576 if (v == MTX_UNOWNED) { 577 if (_mtx_obtain_lock_fetch(m, &v, tid)) 578 break; 579 continue; 580 } 581 #ifdef KDTRACE_HOOKS 582 lda.spin_cnt++; 583 #endif 584 #ifdef ADAPTIVE_MUTEXES 585 /* 586 * If the owner is running on another CPU, spin until the 587 * owner stops running or the state of the lock changes. 588 */ 589 owner = lv_mtx_owner(v); 590 if (TD_IS_RUNNING(owner)) { 591 if (LOCK_LOG_TEST(&m->lock_object, 0)) 592 CTR3(KTR_LOCK, 593 "%s: spinning on %p held by %p", 594 __func__, m, owner); 595 KTR_STATE1(KTR_SCHED, "thread", 596 sched_tdname((struct thread *)tid), 597 "spinning", "lockname:\"%s\"", 598 m->lock_object.lo_name); 599 do { 600 lock_delay(&lda); 601 v = MTX_READ_VALUE(m); 602 owner = lv_mtx_owner(v); 603 } while (v != MTX_UNOWNED && TD_IS_RUNNING(owner)); 604 KTR_STATE0(KTR_SCHED, "thread", 605 sched_tdname((struct thread *)tid), 606 "running"); 607 continue; 608 } 609 #endif 610 611 ts = turnstile_trywait(&m->lock_object); 612 v = MTX_READ_VALUE(m); 613 retry_turnstile: 614 615 /* 616 * Check if the lock has been released while spinning for 617 * the turnstile chain lock. 618 */ 619 if (v == MTX_UNOWNED) { 620 turnstile_cancel(ts); 621 continue; 622 } 623 624 #ifdef ADAPTIVE_MUTEXES 625 /* 626 * The current lock owner might have started executing 627 * on another CPU (or the lock could have changed 628 * owners) while we were waiting on the turnstile 629 * chain lock. If so, drop the turnstile lock and try 630 * again. 631 */ 632 owner = lv_mtx_owner(v); 633 if (TD_IS_RUNNING(owner)) { 634 turnstile_cancel(ts); 635 continue; 636 } 637 #endif 638 639 /* 640 * If the mutex isn't already contested and a failure occurs 641 * setting the contested bit, the mutex was either released 642 * or the state of the MTX_RECURSED bit changed. 643 */ 644 if ((v & MTX_CONTESTED) == 0 && 645 !atomic_fcmpset_ptr(&m->mtx_lock, &v, v | MTX_CONTESTED)) { 646 goto retry_turnstile; 647 } 648 649 /* 650 * We definitely must sleep for this lock. 651 */ 652 mtx_assert(m, MA_NOTOWNED); 653 654 /* 655 * Block on the turnstile. 656 */ 657 #ifdef KDTRACE_HOOKS 658 sleep_time -= lockstat_nsecs(&m->lock_object); 659 #endif 660 #ifndef ADAPTIVE_MUTEXES 661 owner = mtx_owner(m); 662 #endif 663 MPASS(owner == mtx_owner(m)); 664 turnstile_wait(ts, owner, TS_EXCLUSIVE_QUEUE); 665 #ifdef KDTRACE_HOOKS 666 sleep_time += lockstat_nsecs(&m->lock_object); 667 sleep_cnt++; 668 #endif 669 v = MTX_READ_VALUE(m); 670 } 671 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 672 if (__predict_true(!doing_lockprof)) 673 return; 674 #endif 675 #ifdef KDTRACE_HOOKS 676 all_time += lockstat_nsecs(&m->lock_object); 677 if (sleep_time) 678 LOCKSTAT_RECORD1(adaptive__block, m, sleep_time); 679 680 /* 681 * Only record the loops spinning and not sleeping. 682 */ 683 if (lda.spin_cnt > sleep_cnt) 684 LOCKSTAT_RECORD1(adaptive__spin, m, all_time - sleep_time); 685 out_lockstat: 686 #endif 687 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, m, contested, 688 waittime, file, line); 689 } 690 691 #ifdef SMP 692 /* 693 * _mtx_lock_spin_cookie: the tougher part of acquiring an MTX_SPIN lock. 694 * 695 * This is only called if we need to actually spin for the lock. Recursion 696 * is handled inline. 697 */ 698 #if LOCK_DEBUG > 0 699 void 700 _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, int opts, 701 const char *file, int line) 702 #else 703 void 704 _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v) 705 #endif 706 { 707 struct mtx *m; 708 struct lock_delay_arg lda; 709 uintptr_t tid; 710 #ifdef LOCK_PROFILING 711 int contested = 0; 712 uint64_t waittime = 0; 713 #endif 714 #ifdef KDTRACE_HOOKS 715 int64_t spin_time = 0; 716 #endif 717 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 718 int doing_lockprof = 0; 719 #endif 720 721 tid = (uintptr_t)curthread; 722 m = mtxlock2mtx(c); 723 724 #ifdef KDTRACE_HOOKS 725 if (LOCKSTAT_PROFILE_ENABLED(adaptive__acquire)) { 726 while (v == MTX_UNOWNED) { 727 if (_mtx_obtain_lock_fetch(m, &v, tid)) 728 goto out_lockstat; 729 } 730 doing_lockprof = 1; 731 spin_time -= lockstat_nsecs(&m->lock_object); 732 } 733 #endif 734 #ifdef LOCK_PROFILING 735 doing_lockprof = 1; 736 #endif 737 738 if (__predict_false(v == MTX_UNOWNED)) 739 v = MTX_READ_VALUE(m); 740 741 if (__predict_false(v == tid)) { 742 m->mtx_recurse++; 743 return; 744 } 745 746 if (SCHEDULER_STOPPED()) 747 return; 748 749 if (LOCK_LOG_TEST(&m->lock_object, opts)) 750 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 751 KTR_STATE1(KTR_SCHED, "thread", sched_tdname((struct thread *)tid), 752 "spinning", "lockname:\"%s\"", m->lock_object.lo_name); 753 754 lock_delay_arg_init(&lda, &mtx_spin_delay); 755 756 #ifdef HWPMC_HOOKS 757 PMC_SOFT_CALL( , , lock, failed); 758 #endif 759 lock_profile_obtain_lock_failed(&m->lock_object, true, &contested, &waittime); 760 761 for (;;) { 762 if (v == MTX_UNOWNED) { 763 if (_mtx_obtain_lock_fetch(m, &v, tid)) 764 break; 765 continue; 766 } 767 /* Give interrupts a chance while we spin. */ 768 spinlock_exit(); 769 do { 770 if (__predict_true(lda.spin_cnt < 10000000)) { 771 lock_delay(&lda); 772 } else { 773 _mtx_lock_indefinite_check(m, &lda); 774 } 775 v = MTX_READ_VALUE(m); 776 } while (v != MTX_UNOWNED); 777 spinlock_enter(); 778 } 779 780 if (LOCK_LOG_TEST(&m->lock_object, opts)) 781 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 782 KTR_STATE0(KTR_SCHED, "thread", sched_tdname((struct thread *)tid), 783 "running"); 784 785 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 786 if (__predict_true(!doing_lockprof)) 787 return; 788 #endif 789 #ifdef KDTRACE_HOOKS 790 spin_time += lockstat_nsecs(&m->lock_object); 791 if (lda.spin_cnt != 0) 792 LOCKSTAT_RECORD1(spin__spin, m, spin_time); 793 out_lockstat: 794 #endif 795 LOCKSTAT_PROFILE_OBTAIN_SPIN_LOCK_SUCCESS(spin__acquire, m, 796 contested, waittime, file, line); 797 } 798 #endif /* SMP */ 799 800 #ifdef INVARIANTS 801 static void 802 thread_lock_validate(struct mtx *m, int opts, const char *file, int line) 803 { 804 805 KASSERT(m->mtx_lock != MTX_DESTROYED, 806 ("thread_lock() of destroyed mutex @ %s:%d", file, line)); 807 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 808 ("thread_lock() of sleep mutex %s @ %s:%d", 809 m->lock_object.lo_name, file, line)); 810 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) == 0, 811 ("thread_lock: got a recursive mutex %s @ %s:%d\n", 812 m->lock_object.lo_name, file, line)); 813 WITNESS_CHECKORDER(&m->lock_object, 814 opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL); 815 } 816 #else 817 #define thread_lock_validate(m, opts, file, line) do { } while (0) 818 #endif 819 820 #ifndef LOCK_PROFILING 821 #if LOCK_DEBUG > 0 822 void 823 _thread_lock(struct thread *td, int opts, const char *file, int line) 824 #else 825 void 826 _thread_lock(struct thread *td) 827 #endif 828 { 829 struct mtx *m; 830 uintptr_t tid; 831 832 tid = (uintptr_t)curthread; 833 834 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(spin__acquire))) 835 goto slowpath_noirq; 836 spinlock_enter(); 837 m = td->td_lock; 838 thread_lock_validate(m, 0, file, line); 839 if (__predict_false(m == &blocked_lock)) 840 goto slowpath_unlocked; 841 if (__predict_false(!_mtx_obtain_lock(m, tid))) 842 goto slowpath_unlocked; 843 if (__predict_true(m == td->td_lock)) { 844 WITNESS_LOCK(&m->lock_object, LOP_EXCLUSIVE, file, line); 845 return; 846 } 847 _mtx_release_lock_quick(m); 848 slowpath_unlocked: 849 spinlock_exit(); 850 slowpath_noirq: 851 #if LOCK_DEBUG > 0 852 thread_lock_flags_(td, opts, file, line); 853 #else 854 thread_lock_flags_(td, 0, 0, 0); 855 #endif 856 } 857 #endif 858 859 void 860 thread_lock_flags_(struct thread *td, int opts, const char *file, int line) 861 { 862 struct mtx *m; 863 uintptr_t tid, v; 864 struct lock_delay_arg lda; 865 #ifdef LOCK_PROFILING 866 int contested = 0; 867 uint64_t waittime = 0; 868 #endif 869 #ifdef KDTRACE_HOOKS 870 int64_t spin_time = 0; 871 #endif 872 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 873 int doing_lockprof = 1; 874 #endif 875 876 tid = (uintptr_t)curthread; 877 878 if (SCHEDULER_STOPPED()) { 879 /* 880 * Ensure that spinlock sections are balanced even when the 881 * scheduler is stopped, since we may otherwise inadvertently 882 * re-enable interrupts while dumping core. 883 */ 884 spinlock_enter(); 885 return; 886 } 887 888 lock_delay_arg_init(&lda, &mtx_spin_delay); 889 890 #ifdef HWPMC_HOOKS 891 PMC_SOFT_CALL( , , lock, failed); 892 #endif 893 894 #ifdef LOCK_PROFILING 895 doing_lockprof = 1; 896 #elif defined(KDTRACE_HOOKS) 897 doing_lockprof = lockstat_enabled; 898 if (__predict_false(doing_lockprof)) 899 spin_time -= lockstat_nsecs(&td->td_lock->lock_object); 900 #endif 901 spinlock_enter(); 902 903 for (;;) { 904 retry: 905 m = td->td_lock; 906 thread_lock_validate(m, opts, file, line); 907 v = MTX_READ_VALUE(m); 908 for (;;) { 909 if (v == MTX_UNOWNED) { 910 if (_mtx_obtain_lock_fetch(m, &v, tid)) 911 break; 912 continue; 913 } 914 MPASS(v != tid); 915 lock_profile_obtain_lock_failed(&m->lock_object, true, 916 &contested, &waittime); 917 /* Give interrupts a chance while we spin. */ 918 spinlock_exit(); 919 do { 920 if (__predict_true(lda.spin_cnt < 10000000)) { 921 lock_delay(&lda); 922 } else { 923 _mtx_lock_indefinite_check(m, &lda); 924 } 925 if (m != td->td_lock) { 926 spinlock_enter(); 927 goto retry; 928 } 929 v = MTX_READ_VALUE(m); 930 } while (v != MTX_UNOWNED); 931 spinlock_enter(); 932 } 933 if (m == td->td_lock) 934 break; 935 _mtx_release_lock_quick(m); 936 } 937 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 938 line); 939 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 940 941 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 942 if (__predict_true(!doing_lockprof)) 943 return; 944 #endif 945 #ifdef KDTRACE_HOOKS 946 spin_time += lockstat_nsecs(&m->lock_object); 947 #endif 948 LOCKSTAT_PROFILE_OBTAIN_SPIN_LOCK_SUCCESS(spin__acquire, m, contested, 949 waittime, file, line); 950 #ifdef KDTRACE_HOOKS 951 if (lda.spin_cnt != 0) 952 LOCKSTAT_RECORD1(thread__spin, m, spin_time); 953 #endif 954 } 955 956 struct mtx * 957 thread_lock_block(struct thread *td) 958 { 959 struct mtx *lock; 960 961 lock = td->td_lock; 962 mtx_assert(lock, MA_OWNED); 963 td->td_lock = &blocked_lock; 964 965 return (lock); 966 } 967 968 void 969 thread_lock_unblock(struct thread *td, struct mtx *new) 970 { 971 972 mtx_assert(new, MA_OWNED); 973 KASSERT(td->td_lock == &blocked_lock, 974 ("thread %p lock %p not blocked_lock %p", 975 td, td->td_lock, &blocked_lock)); 976 atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new); 977 } 978 979 void 980 thread_lock_block_wait(struct thread *td) 981 { 982 983 while (td->td_lock == &blocked_lock) 984 cpu_spinwait(); 985 986 /* Acquire fence to be certain that all thread state is visible. */ 987 atomic_thread_fence_acq(); 988 } 989 990 void 991 thread_lock_set(struct thread *td, struct mtx *new) 992 { 993 struct mtx *lock; 994 995 mtx_assert(new, MA_OWNED); 996 lock = td->td_lock; 997 mtx_assert(lock, MA_OWNED); 998 td->td_lock = new; 999 mtx_unlock_spin(lock); 1000 } 1001 1002 /* 1003 * __mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 1004 * 1005 * We are only called here if the lock is recursed, contested (i.e. we 1006 * need to wake up a blocked thread) or lockstat probe is active. 1007 */ 1008 #if LOCK_DEBUG > 0 1009 void 1010 __mtx_unlock_sleep(volatile uintptr_t *c, uintptr_t v, int opts, 1011 const char *file, int line) 1012 #else 1013 void 1014 __mtx_unlock_sleep(volatile uintptr_t *c, uintptr_t v) 1015 #endif 1016 { 1017 struct mtx *m; 1018 struct turnstile *ts; 1019 uintptr_t tid; 1020 1021 if (SCHEDULER_STOPPED()) 1022 return; 1023 1024 tid = (uintptr_t)curthread; 1025 m = mtxlock2mtx(c); 1026 1027 if (__predict_false(v == tid)) 1028 v = MTX_READ_VALUE(m); 1029 1030 if (__predict_false(v & MTX_RECURSED)) { 1031 if (--(m->mtx_recurse) == 0) 1032 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 1033 if (LOCK_LOG_TEST(&m->lock_object, opts)) 1034 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 1035 return; 1036 } 1037 1038 LOCKSTAT_PROFILE_RELEASE_LOCK(adaptive__release, m); 1039 if (v == tid && _mtx_release_lock(m, tid)) 1040 return; 1041 1042 /* 1043 * We have to lock the chain before the turnstile so this turnstile 1044 * can be removed from the hash list if it is empty. 1045 */ 1046 turnstile_chain_lock(&m->lock_object); 1047 _mtx_release_lock_quick(m); 1048 ts = turnstile_lookup(&m->lock_object); 1049 MPASS(ts != NULL); 1050 if (LOCK_LOG_TEST(&m->lock_object, opts)) 1051 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 1052 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE); 1053 1054 /* 1055 * This turnstile is now no longer associated with the mutex. We can 1056 * unlock the chain lock so a new turnstile may take it's place. 1057 */ 1058 turnstile_unpend(ts); 1059 turnstile_chain_unlock(&m->lock_object); 1060 } 1061 1062 /* 1063 * All the unlocking of MTX_SPIN locks is done inline. 1064 * See the __mtx_unlock_spin() macro for the details. 1065 */ 1066 1067 /* 1068 * The backing function for the INVARIANTS-enabled mtx_assert() 1069 */ 1070 #ifdef INVARIANT_SUPPORT 1071 void 1072 __mtx_assert(const volatile uintptr_t *c, int what, const char *file, int line) 1073 { 1074 const struct mtx *m; 1075 1076 if (KERNEL_PANICKED() || dumping || SCHEDULER_STOPPED()) 1077 return; 1078 1079 m = mtxlock2mtx(c); 1080 1081 switch (what) { 1082 case MA_OWNED: 1083 case MA_OWNED | MA_RECURSED: 1084 case MA_OWNED | MA_NOTRECURSED: 1085 if (!mtx_owned(m)) 1086 panic("mutex %s not owned at %s:%d", 1087 m->lock_object.lo_name, file, line); 1088 if (mtx_recursed(m)) { 1089 if ((what & MA_NOTRECURSED) != 0) 1090 panic("mutex %s recursed at %s:%d", 1091 m->lock_object.lo_name, file, line); 1092 } else if ((what & MA_RECURSED) != 0) { 1093 panic("mutex %s unrecursed at %s:%d", 1094 m->lock_object.lo_name, file, line); 1095 } 1096 break; 1097 case MA_NOTOWNED: 1098 if (mtx_owned(m)) 1099 panic("mutex %s owned at %s:%d", 1100 m->lock_object.lo_name, file, line); 1101 break; 1102 default: 1103 panic("unknown mtx_assert at %s:%d", file, line); 1104 } 1105 } 1106 #endif 1107 1108 /* 1109 * General init routine used by the MTX_SYSINIT() macro. 1110 */ 1111 void 1112 mtx_sysinit(void *arg) 1113 { 1114 struct mtx_args *margs = arg; 1115 1116 mtx_init((struct mtx *)margs->ma_mtx, margs->ma_desc, NULL, 1117 margs->ma_opts); 1118 } 1119 1120 /* 1121 * Mutex initialization routine; initialize lock `m' of type contained in 1122 * `opts' with options contained in `opts' and name `name.' The optional 1123 * lock type `type' is used as a general lock category name for use with 1124 * witness. 1125 */ 1126 void 1127 _mtx_init(volatile uintptr_t *c, const char *name, const char *type, int opts) 1128 { 1129 struct mtx *m; 1130 struct lock_class *class; 1131 int flags; 1132 1133 m = mtxlock2mtx(c); 1134 1135 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 1136 MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE | MTX_NEW)) == 0); 1137 ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock, 1138 ("%s: mtx_lock not aligned for %s: %p", __func__, name, 1139 &m->mtx_lock)); 1140 1141 /* Determine lock class and lock flags. */ 1142 if (opts & MTX_SPIN) 1143 class = &lock_class_mtx_spin; 1144 else 1145 class = &lock_class_mtx_sleep; 1146 flags = 0; 1147 if (opts & MTX_QUIET) 1148 flags |= LO_QUIET; 1149 if (opts & MTX_RECURSE) 1150 flags |= LO_RECURSABLE; 1151 if ((opts & MTX_NOWITNESS) == 0) 1152 flags |= LO_WITNESS; 1153 if (opts & MTX_DUPOK) 1154 flags |= LO_DUPOK; 1155 if (opts & MTX_NOPROFILE) 1156 flags |= LO_NOPROFILE; 1157 if (opts & MTX_NEW) 1158 flags |= LO_NEW; 1159 1160 /* Initialize mutex. */ 1161 lock_init(&m->lock_object, class, name, type, flags); 1162 1163 m->mtx_lock = MTX_UNOWNED; 1164 m->mtx_recurse = 0; 1165 } 1166 1167 /* 1168 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 1169 * passed in as a flag here because if the corresponding mtx_init() was 1170 * called with MTX_QUIET set, then it will already be set in the mutex's 1171 * flags. 1172 */ 1173 void 1174 _mtx_destroy(volatile uintptr_t *c) 1175 { 1176 struct mtx *m; 1177 1178 m = mtxlock2mtx(c); 1179 1180 if (!mtx_owned(m)) 1181 MPASS(mtx_unowned(m)); 1182 else { 1183 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 1184 1185 /* Perform the non-mtx related part of mtx_unlock_spin(). */ 1186 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin) { 1187 lock_profile_release_lock(&m->lock_object, true); 1188 spinlock_exit(); 1189 } else { 1190 TD_LOCKS_DEC(curthread); 1191 lock_profile_release_lock(&m->lock_object, false); 1192 } 1193 1194 /* Tell witness this isn't locked to make it happy. */ 1195 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__, 1196 __LINE__); 1197 } 1198 1199 m->mtx_lock = MTX_DESTROYED; 1200 lock_destroy(&m->lock_object); 1201 } 1202 1203 /* 1204 * Intialize the mutex code and system mutexes. This is called from the MD 1205 * startup code prior to mi_startup(). The per-CPU data space needs to be 1206 * setup before this is called. 1207 */ 1208 void 1209 mutex_init(void) 1210 { 1211 1212 /* Setup turnstiles so that sleep mutexes work. */ 1213 init_turnstiles(); 1214 1215 /* 1216 * Initialize mutexes. 1217 */ 1218 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 1219 mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN); 1220 blocked_lock.mtx_lock = 0xdeadc0de; /* Always blocked. */ 1221 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 1222 mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN); 1223 mtx_init(&proc0.p_statmtx, "pstatl", NULL, MTX_SPIN); 1224 mtx_init(&proc0.p_itimmtx, "pitiml", NULL, MTX_SPIN); 1225 mtx_init(&proc0.p_profmtx, "pprofl", NULL, MTX_SPIN); 1226 mtx_init(&devmtx, "cdev", NULL, MTX_DEF); 1227 mtx_lock(&Giant); 1228 } 1229 1230 static void __noinline 1231 _mtx_lock_indefinite_check(struct mtx *m, struct lock_delay_arg *ldap) 1232 { 1233 struct thread *td; 1234 1235 ldap->spin_cnt++; 1236 if (ldap->spin_cnt < 60000000 || kdb_active || KERNEL_PANICKED()) 1237 cpu_lock_delay(); 1238 else { 1239 td = mtx_owner(m); 1240 1241 /* If the mutex is unlocked, try again. */ 1242 if (td == NULL) 1243 return; 1244 1245 printf( "spin lock %p (%s) held by %p (tid %d) too long\n", 1246 m, m->lock_object.lo_name, td, td->td_tid); 1247 #ifdef WITNESS 1248 witness_display_spinlock(&m->lock_object, td, printf); 1249 #endif 1250 panic("spin lock held too long"); 1251 } 1252 cpu_spinwait(); 1253 } 1254 1255 void 1256 mtx_spin_wait_unlocked(struct mtx *m) 1257 { 1258 struct lock_delay_arg lda; 1259 1260 KASSERT(m->mtx_lock != MTX_DESTROYED, 1261 ("%s() of destroyed mutex %p", __func__, m)); 1262 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 1263 ("%s() of sleep mutex %p (%s)", __func__, m, 1264 m->lock_object.lo_name)); 1265 KASSERT(!mtx_owned(m), ("%s() waiting on myself on lock %p (%s)", __func__, m, 1266 m->lock_object.lo_name)); 1267 1268 lda.spin_cnt = 0; 1269 1270 while (atomic_load_acq_ptr(&m->mtx_lock) != MTX_UNOWNED) { 1271 if (__predict_true(lda.spin_cnt < 10000000)) { 1272 cpu_spinwait(); 1273 lda.spin_cnt++; 1274 } else { 1275 _mtx_lock_indefinite_check(m, &lda); 1276 } 1277 } 1278 } 1279 1280 void 1281 mtx_wait_unlocked(struct mtx *m) 1282 { 1283 struct thread *owner; 1284 uintptr_t v; 1285 1286 KASSERT(m->mtx_lock != MTX_DESTROYED, 1287 ("%s() of destroyed mutex %p", __func__, m)); 1288 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 1289 ("%s() not a sleep mutex %p (%s)", __func__, m, 1290 m->lock_object.lo_name)); 1291 KASSERT(!mtx_owned(m), ("%s() waiting on myself on lock %p (%s)", __func__, m, 1292 m->lock_object.lo_name)); 1293 1294 for (;;) { 1295 v = atomic_load_acq_ptr(&m->mtx_lock); 1296 if (v == MTX_UNOWNED) { 1297 break; 1298 } 1299 owner = lv_mtx_owner(v); 1300 if (!TD_IS_RUNNING(owner)) { 1301 mtx_lock(m); 1302 mtx_unlock(m); 1303 break; 1304 } 1305 cpu_spinwait(); 1306 } 1307 } 1308 1309 #ifdef DDB 1310 void 1311 db_show_mtx(const struct lock_object *lock) 1312 { 1313 struct thread *td; 1314 const struct mtx *m; 1315 1316 m = (const struct mtx *)lock; 1317 1318 db_printf(" flags: {"); 1319 if (LOCK_CLASS(lock) == &lock_class_mtx_spin) 1320 db_printf("SPIN"); 1321 else 1322 db_printf("DEF"); 1323 if (m->lock_object.lo_flags & LO_RECURSABLE) 1324 db_printf(", RECURSE"); 1325 if (m->lock_object.lo_flags & LO_DUPOK) 1326 db_printf(", DUPOK"); 1327 db_printf("}\n"); 1328 db_printf(" state: {"); 1329 if (mtx_unowned(m)) 1330 db_printf("UNOWNED"); 1331 else if (mtx_destroyed(m)) 1332 db_printf("DESTROYED"); 1333 else { 1334 db_printf("OWNED"); 1335 if (m->mtx_lock & MTX_CONTESTED) 1336 db_printf(", CONTESTED"); 1337 if (m->mtx_lock & MTX_RECURSED) 1338 db_printf(", RECURSED"); 1339 } 1340 db_printf("}\n"); 1341 if (!mtx_unowned(m) && !mtx_destroyed(m)) { 1342 td = mtx_owner(m); 1343 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td, 1344 td->td_tid, td->td_proc->p_pid, td->td_name); 1345 if (mtx_recursed(m)) 1346 db_printf(" recursed: %d\n", m->mtx_recurse); 1347 } 1348 } 1349 #endif 1350