Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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sys/kern/kern_mutex.c
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1 /*- 2 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 3. Berkeley Software Design Inc's name may not be used to endorse or 13 * promote products derived from this software without specific prior 14 * written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER 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 26 * SUCH DAMAGE. 27 * 28 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $ 29 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $ 30 */ 31 32 /* 33 * Machine independent bits of mutex implementation. 34 */ 35 36 #include <sys/cdefs.h> 37 __FBSDID("$FreeBSD: releng/11.1/sys/kern/kern_mutex.c 320241 2017-06-22 18:40:34Z markj $"); 38 39 #include "opt_adaptive_mutexes.h" 40 #include "opt_ddb.h" 41 #include "opt_hwpmc_hooks.h" 42 #include "opt_sched.h" 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/bus.h> 47 #include <sys/conf.h> 48 #include <sys/kdb.h> 49 #include <sys/kernel.h> 50 #include <sys/ktr.h> 51 #include <sys/lock.h> 52 #include <sys/malloc.h> 53 #include <sys/mutex.h> 54 #include <sys/proc.h> 55 #include <sys/resourcevar.h> 56 #include <sys/sched.h> 57 #include <sys/sbuf.h> 58 #include <sys/smp.h> 59 #include <sys/sysctl.h> 60 #include <sys/turnstile.h> 61 #include <sys/vmmeter.h> 62 #include <sys/lock_profile.h> 63 64 #include <machine/atomic.h> 65 #include <machine/bus.h> 66 #include <machine/cpu.h> 67 68 #include <ddb/ddb.h> 69 70 #include <fs/devfs/devfs_int.h> 71 72 #include <vm/vm.h> 73 #include <vm/vm_extern.h> 74 75 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 76 #define ADAPTIVE_MUTEXES 77 #endif 78 79 #ifdef HWPMC_HOOKS 80 #include <sys/pmckern.h> 81 PMC_SOFT_DEFINE( , , lock, failed); 82 #endif 83 84 /* 85 * Return the mutex address when the lock cookie address is provided. 86 * This functionality assumes that struct mtx* have a member named mtx_lock. 87 */ 88 #define mtxlock2mtx(c) (__containerof(c, struct mtx, mtx_lock)) 89 90 /* 91 * Internal utility macros. 92 */ 93 #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED) 94 95 #define mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED) 96 97 static void assert_mtx(const struct lock_object *lock, int what); 98 #ifdef DDB 99 static void db_show_mtx(const struct lock_object *lock); 100 #endif 101 static void lock_mtx(struct lock_object *lock, uintptr_t how); 102 static void lock_spin(struct lock_object *lock, uintptr_t how); 103 #ifdef KDTRACE_HOOKS 104 static int owner_mtx(const struct lock_object *lock, 105 struct thread **owner); 106 #endif 107 static uintptr_t unlock_mtx(struct lock_object *lock); 108 static uintptr_t unlock_spin(struct lock_object *lock); 109 110 /* 111 * Lock classes for sleep and spin mutexes. 112 */ 113 struct lock_class lock_class_mtx_sleep = { 114 .lc_name = "sleep mutex", 115 .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE, 116 .lc_assert = assert_mtx, 117 #ifdef DDB 118 .lc_ddb_show = db_show_mtx, 119 #endif 120 .lc_lock = lock_mtx, 121 .lc_unlock = unlock_mtx, 122 #ifdef KDTRACE_HOOKS 123 .lc_owner = owner_mtx, 124 #endif 125 }; 126 struct lock_class lock_class_mtx_spin = { 127 .lc_name = "spin mutex", 128 .lc_flags = LC_SPINLOCK | LC_RECURSABLE, 129 .lc_assert = assert_mtx, 130 #ifdef DDB 131 .lc_ddb_show = db_show_mtx, 132 #endif 133 .lc_lock = lock_spin, 134 .lc_unlock = unlock_spin, 135 #ifdef KDTRACE_HOOKS 136 .lc_owner = owner_mtx, 137 #endif 138 }; 139 140 #ifdef ADAPTIVE_MUTEXES 141 static SYSCTL_NODE(_debug, OID_AUTO, mtx, CTLFLAG_RD, NULL, "mtx debugging"); 142 143 static struct lock_delay_config __read_mostly mtx_delay; 144 145 SYSCTL_INT(_debug_mtx, OID_AUTO, delay_base, CTLFLAG_RW, &mtx_delay.base, 146 0, ""); 147 SYSCTL_INT(_debug_mtx, OID_AUTO, delay_max, CTLFLAG_RW, &mtx_delay.max, 148 0, ""); 149 150 LOCK_DELAY_SYSINIT_DEFAULT(mtx_delay); 151 #endif 152 153 static SYSCTL_NODE(_debug, OID_AUTO, mtx_spin, CTLFLAG_RD, NULL, 154 "mtx spin debugging"); 155 156 static struct lock_delay_config __read_mostly mtx_spin_delay; 157 158 SYSCTL_INT(_debug_mtx_spin, OID_AUTO, delay_base, CTLFLAG_RW, 159 &mtx_spin_delay.base, 0, ""); 160 SYSCTL_INT(_debug_mtx_spin, OID_AUTO, delay_max, CTLFLAG_RW, 161 &mtx_spin_delay.max, 0, ""); 162 163 LOCK_DELAY_SYSINIT_DEFAULT(mtx_spin_delay); 164 165 /* 166 * System-wide mutexes 167 */ 168 struct mtx blocked_lock; 169 struct mtx Giant; 170 171 void 172 assert_mtx(const struct lock_object *lock, int what) 173 { 174 175 mtx_assert((const struct mtx *)lock, what); 176 } 177 178 void 179 lock_mtx(struct lock_object *lock, uintptr_t how) 180 { 181 182 mtx_lock((struct mtx *)lock); 183 } 184 185 void 186 lock_spin(struct lock_object *lock, uintptr_t how) 187 { 188 189 panic("spin locks can only use msleep_spin"); 190 } 191 192 uintptr_t 193 unlock_mtx(struct lock_object *lock) 194 { 195 struct mtx *m; 196 197 m = (struct mtx *)lock; 198 mtx_assert(m, MA_OWNED | MA_NOTRECURSED); 199 mtx_unlock(m); 200 return (0); 201 } 202 203 uintptr_t 204 unlock_spin(struct lock_object *lock) 205 { 206 207 panic("spin locks can only use msleep_spin"); 208 } 209 210 #ifdef KDTRACE_HOOKS 211 int 212 owner_mtx(const struct lock_object *lock, struct thread **owner) 213 { 214 const struct mtx *m; 215 uintptr_t x; 216 217 m = (const struct mtx *)lock; 218 x = m->mtx_lock; 219 *owner = (struct thread *)(x & ~MTX_FLAGMASK); 220 return (x != MTX_UNOWNED); 221 } 222 #endif 223 224 /* 225 * Function versions of the inlined __mtx_* macros. These are used by 226 * modules and can also be called from assembly language if needed. 227 */ 228 void 229 __mtx_lock_flags(volatile uintptr_t *c, int opts, const char *file, int line) 230 { 231 struct mtx *m; 232 uintptr_t tid, v; 233 234 m = mtxlock2mtx(c); 235 236 KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() || 237 !TD_IS_IDLETHREAD(curthread), 238 ("mtx_lock() by idle thread %p on sleep mutex %s @ %s:%d", 239 curthread, m->lock_object.lo_name, file, line)); 240 KASSERT(m->mtx_lock != MTX_DESTROYED, 241 ("mtx_lock() of destroyed mutex @ %s:%d", file, line)); 242 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 243 ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 244 file, line)); 245 WITNESS_CHECKORDER(&m->lock_object, (opts & ~MTX_RECURSE) | 246 LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL); 247 248 tid = (uintptr_t)curthread; 249 v = MTX_UNOWNED; 250 if (!_mtx_obtain_lock_fetch(m, &v, tid)) 251 _mtx_lock_sleep(m, v, tid, opts, file, line); 252 else 253 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, 254 m, 0, 0, file, line); 255 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 256 line); 257 WITNESS_LOCK(&m->lock_object, (opts & ~MTX_RECURSE) | LOP_EXCLUSIVE, 258 file, line); 259 TD_LOCKS_INC(curthread); 260 } 261 262 void 263 __mtx_unlock_flags(volatile uintptr_t *c, int opts, const char *file, int line) 264 { 265 struct mtx *m; 266 267 m = mtxlock2mtx(c); 268 269 KASSERT(m->mtx_lock != MTX_DESTROYED, 270 ("mtx_unlock() of destroyed mutex @ %s:%d", file, line)); 271 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 272 ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 273 file, line)); 274 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 275 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, 276 line); 277 mtx_assert(m, MA_OWNED); 278 279 #ifdef LOCK_PROFILING 280 __mtx_unlock_sleep(c, opts, file, line); 281 #else 282 __mtx_unlock(m, curthread, opts, file, line); 283 #endif 284 TD_LOCKS_DEC(curthread); 285 } 286 287 void 288 __mtx_lock_spin_flags(volatile uintptr_t *c, int opts, const char *file, 289 int line) 290 { 291 struct mtx *m; 292 293 if (SCHEDULER_STOPPED()) 294 return; 295 296 m = mtxlock2mtx(c); 297 298 KASSERT(m->mtx_lock != MTX_DESTROYED, 299 ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line)); 300 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 301 ("mtx_lock_spin() of sleep mutex %s @ %s:%d", 302 m->lock_object.lo_name, file, line)); 303 if (mtx_owned(m)) 304 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 || 305 (opts & MTX_RECURSE) != 0, 306 ("mtx_lock_spin: recursed on non-recursive mutex %s @ %s:%d\n", 307 m->lock_object.lo_name, file, line)); 308 opts &= ~MTX_RECURSE; 309 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 310 file, line, NULL); 311 __mtx_lock_spin(m, curthread, opts, file, line); 312 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 313 line); 314 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 315 } 316 317 int 318 __mtx_trylock_spin_flags(volatile uintptr_t *c, int opts, const char *file, 319 int line) 320 { 321 struct mtx *m; 322 323 if (SCHEDULER_STOPPED()) 324 return (1); 325 326 m = mtxlock2mtx(c); 327 328 KASSERT(m->mtx_lock != MTX_DESTROYED, 329 ("mtx_trylock_spin() of destroyed mutex @ %s:%d", file, line)); 330 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 331 ("mtx_trylock_spin() of sleep mutex %s @ %s:%d", 332 m->lock_object.lo_name, file, line)); 333 KASSERT((opts & MTX_RECURSE) == 0, 334 ("mtx_trylock_spin: unsupp. opt MTX_RECURSE on mutex %s @ %s:%d\n", 335 m->lock_object.lo_name, file, line)); 336 if (__mtx_trylock_spin(m, curthread, opts, file, line)) { 337 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 1, file, line); 338 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 339 return (1); 340 } 341 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 0, file, line); 342 return (0); 343 } 344 345 void 346 __mtx_unlock_spin_flags(volatile uintptr_t *c, int opts, const char *file, 347 int line) 348 { 349 struct mtx *m; 350 351 if (SCHEDULER_STOPPED()) 352 return; 353 354 m = mtxlock2mtx(c); 355 356 KASSERT(m->mtx_lock != MTX_DESTROYED, 357 ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line)); 358 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 359 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 360 m->lock_object.lo_name, file, line)); 361 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 362 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, 363 line); 364 mtx_assert(m, MA_OWNED); 365 366 __mtx_unlock_spin(m); 367 } 368 369 /* 370 * The important part of mtx_trylock{,_flags}() 371 * Tries to acquire lock `m.' If this function is called on a mutex that 372 * is already owned, it will recursively acquire the lock. 373 */ 374 int 375 _mtx_trylock_flags_(volatile uintptr_t *c, int opts, const char *file, int line) 376 { 377 struct mtx *m; 378 struct thread *td; 379 uintptr_t tid, v; 380 #ifdef LOCK_PROFILING 381 uint64_t waittime = 0; 382 int contested = 0; 383 #endif 384 int rval; 385 bool recursed; 386 387 td = curthread; 388 tid = (uintptr_t)td; 389 if (SCHEDULER_STOPPED_TD(td)) 390 return (1); 391 392 m = mtxlock2mtx(c); 393 394 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(td), 395 ("mtx_trylock() by idle thread %p on sleep mutex %s @ %s:%d", 396 curthread, m->lock_object.lo_name, file, line)); 397 KASSERT(m->mtx_lock != MTX_DESTROYED, 398 ("mtx_trylock() of destroyed mutex @ %s:%d", file, line)); 399 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 400 ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 401 file, line)); 402 403 rval = 1; 404 recursed = false; 405 v = MTX_UNOWNED; 406 for (;;) { 407 if (_mtx_obtain_lock_fetch(m, &v, tid)) 408 break; 409 if (v == MTX_UNOWNED) 410 continue; 411 if (v == tid && 412 ((m->lock_object.lo_flags & LO_RECURSABLE) != 0 || 413 (opts & MTX_RECURSE) != 0)) { 414 m->mtx_recurse++; 415 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 416 recursed = true; 417 break; 418 } 419 rval = 0; 420 break; 421 } 422 423 opts &= ~MTX_RECURSE; 424 425 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line); 426 if (rval) { 427 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 428 file, line); 429 TD_LOCKS_INC(curthread); 430 if (!recursed) 431 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, 432 m, contested, waittime, file, line); 433 } 434 435 return (rval); 436 } 437 438 /* 439 * __mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 440 * 441 * We call this if the lock is either contested (i.e. we need to go to 442 * sleep waiting for it), or if we need to recurse on it. 443 */ 444 #if LOCK_DEBUG > 0 445 void 446 __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v, uintptr_t tid, int opts, 447 const char *file, int line) 448 #else 449 void 450 __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v, uintptr_t tid) 451 #endif 452 { 453 struct mtx *m; 454 struct turnstile *ts; 455 #ifdef ADAPTIVE_MUTEXES 456 volatile struct thread *owner; 457 #endif 458 #ifdef KTR 459 int cont_logged = 0; 460 #endif 461 #ifdef LOCK_PROFILING 462 int contested = 0; 463 uint64_t waittime = 0; 464 #endif 465 #if defined(ADAPTIVE_MUTEXES) || defined(KDTRACE_HOOKS) 466 struct lock_delay_arg lda; 467 #endif 468 #ifdef KDTRACE_HOOKS 469 u_int sleep_cnt = 0; 470 int64_t sleep_time = 0; 471 int64_t all_time = 0; 472 #endif 473 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 474 int doing_lockprof; 475 #endif 476 477 if (SCHEDULER_STOPPED()) 478 return; 479 480 #if defined(ADAPTIVE_MUTEXES) 481 lock_delay_arg_init(&lda, &mtx_delay); 482 #elif defined(KDTRACE_HOOKS) 483 lock_delay_arg_init(&lda, NULL); 484 #endif 485 m = mtxlock2mtx(c); 486 if (__predict_false(v == MTX_UNOWNED)) 487 v = MTX_READ_VALUE(m); 488 489 if (__predict_false(lv_mtx_owner(v) == (struct thread *)tid)) { 490 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 || 491 (opts & MTX_RECURSE) != 0, 492 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n", 493 m->lock_object.lo_name, file, line)); 494 #if LOCK_DEBUG > 0 495 opts &= ~MTX_RECURSE; 496 #endif 497 m->mtx_recurse++; 498 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 499 if (LOCK_LOG_TEST(&m->lock_object, opts)) 500 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 501 return; 502 } 503 #if LOCK_DEBUG > 0 504 opts &= ~MTX_RECURSE; 505 #endif 506 507 #ifdef HWPMC_HOOKS 508 PMC_SOFT_CALL( , , lock, failed); 509 #endif 510 lock_profile_obtain_lock_failed(&m->lock_object, 511 &contested, &waittime); 512 if (LOCK_LOG_TEST(&m->lock_object, opts)) 513 CTR4(KTR_LOCK, 514 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 515 m->lock_object.lo_name, (void *)m->mtx_lock, file, line); 516 #ifdef LOCK_PROFILING 517 doing_lockprof = 1; 518 #elif defined(KDTRACE_HOOKS) 519 doing_lockprof = lockstat_enabled; 520 if (__predict_false(doing_lockprof)) 521 all_time -= lockstat_nsecs(&m->lock_object); 522 #endif 523 524 for (;;) { 525 if (v == MTX_UNOWNED) { 526 if (_mtx_obtain_lock_fetch(m, &v, tid)) 527 break; 528 continue; 529 } 530 #ifdef KDTRACE_HOOKS 531 lda.spin_cnt++; 532 #endif 533 #ifdef ADAPTIVE_MUTEXES 534 /* 535 * If the owner is running on another CPU, spin until the 536 * owner stops running or the state of the lock changes. 537 */ 538 owner = lv_mtx_owner(v); 539 if (TD_IS_RUNNING(owner)) { 540 if (LOCK_LOG_TEST(&m->lock_object, 0)) 541 CTR3(KTR_LOCK, 542 "%s: spinning on %p held by %p", 543 __func__, m, owner); 544 KTR_STATE1(KTR_SCHED, "thread", 545 sched_tdname((struct thread *)tid), 546 "spinning", "lockname:\"%s\"", 547 m->lock_object.lo_name); 548 do { 549 lock_delay(&lda); 550 v = MTX_READ_VALUE(m); 551 owner = lv_mtx_owner(v); 552 } while (v != MTX_UNOWNED && TD_IS_RUNNING(owner)); 553 KTR_STATE0(KTR_SCHED, "thread", 554 sched_tdname((struct thread *)tid), 555 "running"); 556 continue; 557 } 558 #endif 559 560 ts = turnstile_trywait(&m->lock_object); 561 v = MTX_READ_VALUE(m); 562 563 /* 564 * Check if the lock has been released while spinning for 565 * the turnstile chain lock. 566 */ 567 if (v == MTX_UNOWNED) { 568 turnstile_cancel(ts); 569 continue; 570 } 571 572 #ifdef ADAPTIVE_MUTEXES 573 /* 574 * The current lock owner might have started executing 575 * on another CPU (or the lock could have changed 576 * owners) while we were waiting on the turnstile 577 * chain lock. If so, drop the turnstile lock and try 578 * again. 579 */ 580 owner = lv_mtx_owner(v); 581 if (TD_IS_RUNNING(owner)) { 582 turnstile_cancel(ts); 583 continue; 584 } 585 #endif 586 587 /* 588 * If the mutex isn't already contested and a failure occurs 589 * setting the contested bit, the mutex was either released 590 * or the state of the MTX_RECURSED bit changed. 591 */ 592 if ((v & MTX_CONTESTED) == 0 && 593 !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) { 594 turnstile_cancel(ts); 595 v = MTX_READ_VALUE(m); 596 continue; 597 } 598 599 /* 600 * We definitely must sleep for this lock. 601 */ 602 mtx_assert(m, MA_NOTOWNED); 603 604 #ifdef KTR 605 if (!cont_logged) { 606 CTR6(KTR_CONTENTION, 607 "contention: %p at %s:%d wants %s, taken by %s:%d", 608 (void *)tid, file, line, m->lock_object.lo_name, 609 WITNESS_FILE(&m->lock_object), 610 WITNESS_LINE(&m->lock_object)); 611 cont_logged = 1; 612 } 613 #endif 614 615 /* 616 * Block on the turnstile. 617 */ 618 #ifdef KDTRACE_HOOKS 619 sleep_time -= lockstat_nsecs(&m->lock_object); 620 #endif 621 turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE); 622 #ifdef KDTRACE_HOOKS 623 sleep_time += lockstat_nsecs(&m->lock_object); 624 sleep_cnt++; 625 #endif 626 v = MTX_READ_VALUE(m); 627 } 628 #ifdef KTR 629 if (cont_logged) { 630 CTR4(KTR_CONTENTION, 631 "contention end: %s acquired by %p at %s:%d", 632 m->lock_object.lo_name, (void *)tid, file, line); 633 } 634 #endif 635 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 636 if (__predict_true(!doing_lockprof)) 637 return; 638 #endif 639 #ifdef KDTRACE_HOOKS 640 all_time += lockstat_nsecs(&m->lock_object); 641 #endif 642 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, m, contested, 643 waittime, file, line); 644 #ifdef KDTRACE_HOOKS 645 if (sleep_time) 646 LOCKSTAT_RECORD1(adaptive__block, m, sleep_time); 647 648 /* 649 * Only record the loops spinning and not sleeping. 650 */ 651 if (lda.spin_cnt > sleep_cnt) 652 LOCKSTAT_RECORD1(adaptive__spin, m, all_time - sleep_time); 653 #endif 654 } 655 656 static void 657 _mtx_lock_spin_failed(struct mtx *m) 658 { 659 struct thread *td; 660 661 td = mtx_owner(m); 662 663 /* If the mutex is unlocked, try again. */ 664 if (td == NULL) 665 return; 666 667 printf( "spin lock %p (%s) held by %p (tid %d) too long\n", 668 m, m->lock_object.lo_name, td, td->td_tid); 669 #ifdef WITNESS 670 witness_display_spinlock(&m->lock_object, td, printf); 671 #endif 672 panic("spin lock held too long"); 673 } 674 675 #ifdef SMP 676 /* 677 * _mtx_lock_spin_cookie: the tougher part of acquiring an MTX_SPIN lock. 678 * 679 * This is only called if we need to actually spin for the lock. Recursion 680 * is handled inline. 681 */ 682 void 683 _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, uintptr_t tid, 684 int opts, const char *file, int line) 685 { 686 struct mtx *m; 687 struct lock_delay_arg lda; 688 #ifdef LOCK_PROFILING 689 int contested = 0; 690 uint64_t waittime = 0; 691 #endif 692 #ifdef KDTRACE_HOOKS 693 int64_t spin_time = 0; 694 #endif 695 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 696 int doing_lockprof; 697 #endif 698 699 if (SCHEDULER_STOPPED()) 700 return; 701 702 lock_delay_arg_init(&lda, &mtx_spin_delay); 703 m = mtxlock2mtx(c); 704 705 if (__predict_false(v == MTX_UNOWNED)) 706 v = MTX_READ_VALUE(m); 707 708 if (__predict_false(v == tid)) { 709 m->mtx_recurse++; 710 return; 711 } 712 713 if (LOCK_LOG_TEST(&m->lock_object, opts)) 714 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 715 KTR_STATE1(KTR_SCHED, "thread", sched_tdname((struct thread *)tid), 716 "spinning", "lockname:\"%s\"", m->lock_object.lo_name); 717 718 #ifdef HWPMC_HOOKS 719 PMC_SOFT_CALL( , , lock, failed); 720 #endif 721 lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime); 722 #ifdef LOCK_PROFILING 723 doing_lockprof = 1; 724 #elif defined(KDTRACE_HOOKS) 725 doing_lockprof = lockstat_enabled; 726 if (__predict_false(doing_lockprof)) 727 spin_time -= lockstat_nsecs(&m->lock_object); 728 #endif 729 for (;;) { 730 if (v == MTX_UNOWNED) { 731 if (_mtx_obtain_lock_fetch(m, &v, tid)) 732 break; 733 continue; 734 } 735 /* Give interrupts a chance while we spin. */ 736 spinlock_exit(); 737 do { 738 if (lda.spin_cnt < 10000000) { 739 lock_delay(&lda); 740 } else { 741 lda.spin_cnt++; 742 if (lda.spin_cnt < 60000000 || kdb_active || 743 panicstr != NULL) 744 DELAY(1); 745 else 746 _mtx_lock_spin_failed(m); 747 cpu_spinwait(); 748 } 749 v = MTX_READ_VALUE(m); 750 } while (v != MTX_UNOWNED); 751 spinlock_enter(); 752 } 753 754 if (LOCK_LOG_TEST(&m->lock_object, opts)) 755 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 756 KTR_STATE0(KTR_SCHED, "thread", sched_tdname((struct thread *)tid), 757 "running"); 758 759 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 760 if (__predict_true(!doing_lockprof)) 761 return; 762 #endif 763 #ifdef KDTRACE_HOOKS 764 spin_time += lockstat_nsecs(&m->lock_object); 765 #endif 766 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, m, 767 contested, waittime, file, line); 768 #ifdef KDTRACE_HOOKS 769 if (spin_time != 0) 770 LOCKSTAT_RECORD1(spin__spin, m, spin_time); 771 #endif 772 } 773 #endif /* SMP */ 774 775 void 776 thread_lock_flags_(struct thread *td, int opts, const char *file, int line) 777 { 778 struct mtx *m; 779 uintptr_t tid, v; 780 struct lock_delay_arg lda; 781 #ifdef LOCK_PROFILING 782 int contested = 0; 783 uint64_t waittime = 0; 784 #endif 785 #ifdef KDTRACE_HOOKS 786 int64_t spin_time = 0; 787 #endif 788 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 789 int doing_lockprof = 1; 790 #endif 791 792 tid = (uintptr_t)curthread; 793 794 if (SCHEDULER_STOPPED()) { 795 /* 796 * Ensure that spinlock sections are balanced even when the 797 * scheduler is stopped, since we may otherwise inadvertently 798 * re-enable interrupts while dumping core. 799 */ 800 spinlock_enter(); 801 return; 802 } 803 804 lock_delay_arg_init(&lda, &mtx_spin_delay); 805 806 #ifdef LOCK_PROFILING 807 doing_lockprof = 1; 808 #elif defined(KDTRACE_HOOKS) 809 doing_lockprof = lockstat_enabled; 810 if (__predict_false(doing_lockprof)) 811 spin_time -= lockstat_nsecs(&td->td_lock->lock_object); 812 #endif 813 for (;;) { 814 retry: 815 v = MTX_UNOWNED; 816 spinlock_enter(); 817 m = td->td_lock; 818 KASSERT(m->mtx_lock != MTX_DESTROYED, 819 ("thread_lock() of destroyed mutex @ %s:%d", file, line)); 820 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 821 ("thread_lock() of sleep mutex %s @ %s:%d", 822 m->lock_object.lo_name, file, line)); 823 if (mtx_owned(m)) 824 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0, 825 ("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n", 826 m->lock_object.lo_name, file, line)); 827 WITNESS_CHECKORDER(&m->lock_object, 828 opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL); 829 for (;;) { 830 if (_mtx_obtain_lock_fetch(m, &v, tid)) 831 break; 832 if (v == MTX_UNOWNED) 833 continue; 834 if (v == tid) { 835 m->mtx_recurse++; 836 break; 837 } 838 #ifdef HWPMC_HOOKS 839 PMC_SOFT_CALL( , , lock, failed); 840 #endif 841 lock_profile_obtain_lock_failed(&m->lock_object, 842 &contested, &waittime); 843 /* Give interrupts a chance while we spin. */ 844 spinlock_exit(); 845 do { 846 if (lda.spin_cnt < 10000000) { 847 lock_delay(&lda); 848 } else { 849 lda.spin_cnt++; 850 if (lda.spin_cnt < 60000000 || 851 kdb_active || panicstr != NULL) 852 DELAY(1); 853 else 854 _mtx_lock_spin_failed(m); 855 cpu_spinwait(); 856 } 857 if (m != td->td_lock) 858 goto retry; 859 v = MTX_READ_VALUE(m); 860 } while (v != MTX_UNOWNED); 861 spinlock_enter(); 862 } 863 if (m == td->td_lock) 864 break; 865 __mtx_unlock_spin(m); /* does spinlock_exit() */ 866 } 867 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 868 line); 869 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 870 871 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING) 872 if (__predict_true(!doing_lockprof)) 873 return; 874 #endif 875 #ifdef KDTRACE_HOOKS 876 spin_time += lockstat_nsecs(&m->lock_object); 877 #endif 878 if (m->mtx_recurse == 0) 879 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, m, 880 contested, waittime, file, line); 881 #ifdef KDTRACE_HOOKS 882 if (spin_time != 0) 883 LOCKSTAT_RECORD1(thread__spin, m, spin_time); 884 #endif 885 } 886 887 struct mtx * 888 thread_lock_block(struct thread *td) 889 { 890 struct mtx *lock; 891 892 THREAD_LOCK_ASSERT(td, MA_OWNED); 893 lock = td->td_lock; 894 td->td_lock = &blocked_lock; 895 mtx_unlock_spin(lock); 896 897 return (lock); 898 } 899 900 void 901 thread_lock_unblock(struct thread *td, struct mtx *new) 902 { 903 mtx_assert(new, MA_OWNED); 904 MPASS(td->td_lock == &blocked_lock); 905 atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new); 906 } 907 908 void 909 thread_lock_set(struct thread *td, struct mtx *new) 910 { 911 struct mtx *lock; 912 913 mtx_assert(new, MA_OWNED); 914 THREAD_LOCK_ASSERT(td, MA_OWNED); 915 lock = td->td_lock; 916 td->td_lock = new; 917 mtx_unlock_spin(lock); 918 } 919 920 /* 921 * __mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 922 * 923 * We are only called here if the lock is recursed, contested (i.e. we 924 * need to wake up a blocked thread) or lockstat probe is active. 925 */ 926 #if LOCK_DEBUG > 0 927 void 928 __mtx_unlock_sleep(volatile uintptr_t *c, int opts, const char *file, int line) 929 #else 930 void 931 __mtx_unlock_sleep(volatile uintptr_t *c) 932 #endif 933 { 934 struct mtx *m; 935 struct turnstile *ts; 936 uintptr_t tid, v; 937 938 if (SCHEDULER_STOPPED()) 939 return; 940 941 tid = (uintptr_t)curthread; 942 m = mtxlock2mtx(c); 943 v = MTX_READ_VALUE(m); 944 945 if (v & MTX_RECURSED) { 946 if (--(m->mtx_recurse) == 0) 947 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 948 if (LOCK_LOG_TEST(&m->lock_object, opts)) 949 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 950 return; 951 } 952 953 LOCKSTAT_PROFILE_RELEASE_LOCK(adaptive__release, m); 954 if (v == tid && _mtx_release_lock(m, tid)) 955 return; 956 957 /* 958 * We have to lock the chain before the turnstile so this turnstile 959 * can be removed from the hash list if it is empty. 960 */ 961 turnstile_chain_lock(&m->lock_object); 962 ts = turnstile_lookup(&m->lock_object); 963 if (LOCK_LOG_TEST(&m->lock_object, opts)) 964 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 965 MPASS(ts != NULL); 966 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE); 967 _mtx_release_lock_quick(m); 968 969 /* 970 * This turnstile is now no longer associated with the mutex. We can 971 * unlock the chain lock so a new turnstile may take it's place. 972 */ 973 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 974 turnstile_chain_unlock(&m->lock_object); 975 } 976 977 /* 978 * All the unlocking of MTX_SPIN locks is done inline. 979 * See the __mtx_unlock_spin() macro for the details. 980 */ 981 982 /* 983 * The backing function for the INVARIANTS-enabled mtx_assert() 984 */ 985 #ifdef INVARIANT_SUPPORT 986 void 987 __mtx_assert(const volatile uintptr_t *c, int what, const char *file, int line) 988 { 989 const struct mtx *m; 990 991 if (panicstr != NULL || dumping || SCHEDULER_STOPPED()) 992 return; 993 994 m = mtxlock2mtx(c); 995 996 switch (what) { 997 case MA_OWNED: 998 case MA_OWNED | MA_RECURSED: 999 case MA_OWNED | MA_NOTRECURSED: 1000 if (!mtx_owned(m)) 1001 panic("mutex %s not owned at %s:%d", 1002 m->lock_object.lo_name, file, line); 1003 if (mtx_recursed(m)) { 1004 if ((what & MA_NOTRECURSED) != 0) 1005 panic("mutex %s recursed at %s:%d", 1006 m->lock_object.lo_name, file, line); 1007 } else if ((what & MA_RECURSED) != 0) { 1008 panic("mutex %s unrecursed at %s:%d", 1009 m->lock_object.lo_name, file, line); 1010 } 1011 break; 1012 case MA_NOTOWNED: 1013 if (mtx_owned(m)) 1014 panic("mutex %s owned at %s:%d", 1015 m->lock_object.lo_name, file, line); 1016 break; 1017 default: 1018 panic("unknown mtx_assert at %s:%d", file, line); 1019 } 1020 } 1021 #endif 1022 1023 /* 1024 * General init routine used by the MTX_SYSINIT() macro. 1025 */ 1026 void 1027 mtx_sysinit(void *arg) 1028 { 1029 struct mtx_args *margs = arg; 1030 1031 mtx_init((struct mtx *)margs->ma_mtx, margs->ma_desc, NULL, 1032 margs->ma_opts); 1033 } 1034 1035 /* 1036 * Mutex initialization routine; initialize lock `m' of type contained in 1037 * `opts' with options contained in `opts' and name `name.' The optional 1038 * lock type `type' is used as a general lock category name for use with 1039 * witness. 1040 */ 1041 void 1042 _mtx_init(volatile uintptr_t *c, const char *name, const char *type, int opts) 1043 { 1044 struct mtx *m; 1045 struct lock_class *class; 1046 int flags; 1047 1048 m = mtxlock2mtx(c); 1049 1050 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 1051 MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE | MTX_NEW)) == 0); 1052 ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock, 1053 ("%s: mtx_lock not aligned for %s: %p", __func__, name, 1054 &m->mtx_lock)); 1055 1056 /* Determine lock class and lock flags. */ 1057 if (opts & MTX_SPIN) 1058 class = &lock_class_mtx_spin; 1059 else 1060 class = &lock_class_mtx_sleep; 1061 flags = 0; 1062 if (opts & MTX_QUIET) 1063 flags |= LO_QUIET; 1064 if (opts & MTX_RECURSE) 1065 flags |= LO_RECURSABLE; 1066 if ((opts & MTX_NOWITNESS) == 0) 1067 flags |= LO_WITNESS; 1068 if (opts & MTX_DUPOK) 1069 flags |= LO_DUPOK; 1070 if (opts & MTX_NOPROFILE) 1071 flags |= LO_NOPROFILE; 1072 if (opts & MTX_NEW) 1073 flags |= LO_NEW; 1074 1075 /* Initialize mutex. */ 1076 lock_init(&m->lock_object, class, name, type, flags); 1077 1078 m->mtx_lock = MTX_UNOWNED; 1079 m->mtx_recurse = 0; 1080 } 1081 1082 /* 1083 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 1084 * passed in as a flag here because if the corresponding mtx_init() was 1085 * called with MTX_QUIET set, then it will already be set in the mutex's 1086 * flags. 1087 */ 1088 void 1089 _mtx_destroy(volatile uintptr_t *c) 1090 { 1091 struct mtx *m; 1092 1093 m = mtxlock2mtx(c); 1094 1095 if (!mtx_owned(m)) 1096 MPASS(mtx_unowned(m)); 1097 else { 1098 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 1099 1100 /* Perform the non-mtx related part of mtx_unlock_spin(). */ 1101 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin) 1102 spinlock_exit(); 1103 else 1104 TD_LOCKS_DEC(curthread); 1105 1106 lock_profile_release_lock(&m->lock_object); 1107 /* Tell witness this isn't locked to make it happy. */ 1108 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__, 1109 __LINE__); 1110 } 1111 1112 m->mtx_lock = MTX_DESTROYED; 1113 lock_destroy(&m->lock_object); 1114 } 1115 1116 /* 1117 * Intialize the mutex code and system mutexes. This is called from the MD 1118 * startup code prior to mi_startup(). The per-CPU data space needs to be 1119 * setup before this is called. 1120 */ 1121 void 1122 mutex_init(void) 1123 { 1124 1125 /* Setup turnstiles so that sleep mutexes work. */ 1126 init_turnstiles(); 1127 1128 /* 1129 * Initialize mutexes. 1130 */ 1131 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 1132 mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN); 1133 blocked_lock.mtx_lock = 0xdeadc0de; /* Always blocked. */ 1134 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 1135 mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN); 1136 mtx_init(&proc0.p_statmtx, "pstatl", NULL, MTX_SPIN); 1137 mtx_init(&proc0.p_itimmtx, "pitiml", NULL, MTX_SPIN); 1138 mtx_init(&proc0.p_profmtx, "pprofl", NULL, MTX_SPIN); 1139 mtx_init(&devmtx, "cdev", NULL, MTX_DEF); 1140 mtx_lock(&Giant); 1141 } 1142 1143 #ifdef DDB 1144 void 1145 db_show_mtx(const struct lock_object *lock) 1146 { 1147 struct thread *td; 1148 const struct mtx *m; 1149 1150 m = (const struct mtx *)lock; 1151 1152 db_printf(" flags: {"); 1153 if (LOCK_CLASS(lock) == &lock_class_mtx_spin) 1154 db_printf("SPIN"); 1155 else 1156 db_printf("DEF"); 1157 if (m->lock_object.lo_flags & LO_RECURSABLE) 1158 db_printf(", RECURSE"); 1159 if (m->lock_object.lo_flags & LO_DUPOK) 1160 db_printf(", DUPOK"); 1161 db_printf("}\n"); 1162 db_printf(" state: {"); 1163 if (mtx_unowned(m)) 1164 db_printf("UNOWNED"); 1165 else if (mtx_destroyed(m)) 1166 db_printf("DESTROYED"); 1167 else { 1168 db_printf("OWNED"); 1169 if (m->mtx_lock & MTX_CONTESTED) 1170 db_printf(", CONTESTED"); 1171 if (m->mtx_lock & MTX_RECURSED) 1172 db_printf(", RECURSED"); 1173 } 1174 db_printf("}\n"); 1175 if (!mtx_unowned(m) && !mtx_destroyed(m)) { 1176 td = mtx_owner(m); 1177 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td, 1178 td->td_tid, td->td_proc->p_pid, td->td_name); 1179 if (mtx_recursed(m)) 1180 db_printf(" recursed: %d\n", m->mtx_recurse); 1181 } 1182 } 1183 #endif
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