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("$FreeBSD$"); 38 39 #include "opt_adaptive_mutexes.h" 40 #include "opt_ddb.h" 41 #include "opt_global.h" 42 #include "opt_hwpmc_hooks.h" 43 #include "opt_kdtrace.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/sysctl.h> 61 #include <sys/turnstile.h> 62 #include <sys/vmmeter.h> 63 #include <sys/lock_profile.h> 64 65 #include <machine/atomic.h> 66 #include <machine/bus.h> 67 #include <machine/cpu.h> 68 69 #include <ddb/ddb.h> 70 71 #include <fs/devfs/devfs_int.h> 72 73 #include <vm/vm.h> 74 #include <vm/vm_extern.h> 75 76 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 77 #define ADAPTIVE_MUTEXES 78 #endif 79 80 #ifdef HWPMC_HOOKS 81 #include <sys/pmckern.h> 82 PMC_SOFT_DEFINE( , , lock, failed); 83 #endif 84 85 /* 86 * Internal utility macros. 87 */ 88 #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED) 89 90 #define mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED) 91 92 #define mtx_owner(m) ((struct thread *)((m)->mtx_lock & ~MTX_FLAGMASK)) 93 94 static void assert_mtx(struct lock_object *lock, int what); 95 #ifdef DDB 96 static void db_show_mtx(struct lock_object *lock); 97 #endif 98 static void lock_mtx(struct lock_object *lock, int how); 99 static void lock_spin(struct lock_object *lock, int how); 100 #ifdef KDTRACE_HOOKS 101 static int owner_mtx(struct lock_object *lock, struct thread **owner); 102 #endif 103 static int unlock_mtx(struct lock_object *lock); 104 static int unlock_spin(struct lock_object *lock); 105 106 /* 107 * Lock classes for sleep and spin mutexes. 108 */ 109 struct lock_class lock_class_mtx_sleep = { 110 .lc_name = "sleep mutex", 111 .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE, 112 .lc_assert = assert_mtx, 113 #ifdef DDB 114 .lc_ddb_show = db_show_mtx, 115 #endif 116 .lc_lock = lock_mtx, 117 .lc_unlock = unlock_mtx, 118 #ifdef KDTRACE_HOOKS 119 .lc_owner = owner_mtx, 120 #endif 121 }; 122 struct lock_class lock_class_mtx_spin = { 123 .lc_name = "spin mutex", 124 .lc_flags = LC_SPINLOCK | LC_RECURSABLE, 125 .lc_assert = assert_mtx, 126 #ifdef DDB 127 .lc_ddb_show = db_show_mtx, 128 #endif 129 .lc_lock = lock_spin, 130 .lc_unlock = unlock_spin, 131 #ifdef KDTRACE_HOOKS 132 .lc_owner = owner_mtx, 133 #endif 134 }; 135 136 /* 137 * System-wide mutexes 138 */ 139 struct mtx blocked_lock; 140 struct mtx Giant; 141 142 void 143 assert_mtx(struct lock_object *lock, int what) 144 { 145 146 mtx_assert((struct mtx *)lock, what); 147 } 148 149 void 150 lock_mtx(struct lock_object *lock, int how) 151 { 152 153 mtx_lock((struct mtx *)lock); 154 } 155 156 void 157 lock_spin(struct lock_object *lock, int how) 158 { 159 160 panic("spin locks can only use msleep_spin"); 161 } 162 163 int 164 unlock_mtx(struct lock_object *lock) 165 { 166 struct mtx *m; 167 168 m = (struct mtx *)lock; 169 mtx_assert(m, MA_OWNED | MA_NOTRECURSED); 170 mtx_unlock(m); 171 return (0); 172 } 173 174 int 175 unlock_spin(struct lock_object *lock) 176 { 177 178 panic("spin locks can only use msleep_spin"); 179 } 180 181 #ifdef KDTRACE_HOOKS 182 int 183 owner_mtx(struct lock_object *lock, struct thread **owner) 184 { 185 struct mtx *m = (struct mtx *)lock; 186 187 *owner = mtx_owner(m); 188 return (mtx_unowned(m) == 0); 189 } 190 #endif 191 192 /* 193 * Function versions of the inlined __mtx_* macros. These are used by 194 * modules and can also be called from assembly language if needed. 195 */ 196 void 197 _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line) 198 { 199 200 if (SCHEDULER_STOPPED()) 201 return; 202 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 203 ("mtx_lock() by idle thread %p on sleep mutex %s @ %s:%d", 204 curthread, m->lock_object.lo_name, file, line)); 205 KASSERT(m->mtx_lock != MTX_DESTROYED, 206 ("mtx_lock() of destroyed mutex @ %s:%d", file, line)); 207 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 208 ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 209 file, line)); 210 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 211 file, line, NULL); 212 213 __mtx_lock(m, curthread, opts, file, line); 214 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 215 line); 216 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 217 curthread->td_locks++; 218 } 219 220 void 221 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) 222 { 223 224 if (SCHEDULER_STOPPED()) 225 return; 226 KASSERT(m->mtx_lock != MTX_DESTROYED, 227 ("mtx_unlock() of destroyed mutex @ %s:%d", file, line)); 228 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 229 ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 230 file, line)); 231 curthread->td_locks--; 232 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 233 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, 234 line); 235 mtx_assert(m, MA_OWNED); 236 237 if (m->mtx_recurse == 0) 238 LOCKSTAT_PROFILE_RELEASE_LOCK(LS_MTX_UNLOCK_RELEASE, m); 239 __mtx_unlock(m, curthread, opts, file, line); 240 } 241 242 void 243 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) 244 { 245 246 if (SCHEDULER_STOPPED()) 247 return; 248 KASSERT(m->mtx_lock != MTX_DESTROYED, 249 ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line)); 250 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 251 ("mtx_lock_spin() of sleep mutex %s @ %s:%d", 252 m->lock_object.lo_name, file, line)); 253 if (mtx_owned(m)) 254 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0, 255 ("mtx_lock_spin: recursed on non-recursive mutex %s @ %s:%d\n", 256 m->lock_object.lo_name, file, line)); 257 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 258 file, line, NULL); 259 __mtx_lock_spin(m, curthread, opts, file, line); 260 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 261 line); 262 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 263 } 264 265 void 266 _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line) 267 { 268 269 if (SCHEDULER_STOPPED()) 270 return; 271 KASSERT(m->mtx_lock != MTX_DESTROYED, 272 ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line)); 273 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 274 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 275 m->lock_object.lo_name, file, line)); 276 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 277 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, 278 line); 279 mtx_assert(m, MA_OWNED); 280 281 __mtx_unlock_spin(m); 282 } 283 284 /* 285 * The important part of mtx_trylock{,_flags}() 286 * Tries to acquire lock `m.' If this function is called on a mutex that 287 * is already owned, it will recursively acquire the lock. 288 */ 289 int 290 _mtx_trylock(struct mtx *m, int opts, const char *file, int line) 291 { 292 #ifdef LOCK_PROFILING 293 uint64_t waittime = 0; 294 int contested = 0; 295 #endif 296 int rval; 297 298 if (SCHEDULER_STOPPED()) 299 return (1); 300 301 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 302 ("mtx_trylock() by idle thread %p on sleep mutex %s @ %s:%d", 303 curthread, m->lock_object.lo_name, file, line)); 304 KASSERT(m->mtx_lock != MTX_DESTROYED, 305 ("mtx_trylock() of destroyed mutex @ %s:%d", file, line)); 306 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 307 ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 308 file, line)); 309 310 if (mtx_owned(m) && (m->lock_object.lo_flags & LO_RECURSABLE) != 0) { 311 m->mtx_recurse++; 312 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 313 rval = 1; 314 } else 315 rval = _mtx_obtain_lock(m, (uintptr_t)curthread); 316 317 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line); 318 if (rval) { 319 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 320 file, line); 321 curthread->td_locks++; 322 if (m->mtx_recurse == 0) 323 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE, 324 m, contested, waittime, file, line); 325 326 } 327 328 return (rval); 329 } 330 331 /* 332 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 333 * 334 * We call this if the lock is either contested (i.e. we need to go to 335 * sleep waiting for it), or if we need to recurse on it. 336 */ 337 void 338 _mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file, 339 int line) 340 { 341 struct turnstile *ts; 342 uintptr_t v; 343 #ifdef ADAPTIVE_MUTEXES 344 volatile struct thread *owner; 345 #endif 346 #ifdef KTR 347 int cont_logged = 0; 348 #endif 349 #ifdef LOCK_PROFILING 350 int contested = 0; 351 uint64_t waittime = 0; 352 #endif 353 #ifdef KDTRACE_HOOKS 354 uint64_t spin_cnt = 0; 355 uint64_t sleep_cnt = 0; 356 int64_t sleep_time = 0; 357 int64_t all_time = 0; 358 #endif 359 360 if (SCHEDULER_STOPPED()) 361 return; 362 363 if (mtx_owned(m)) { 364 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0, 365 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n", 366 m->lock_object.lo_name, file, line)); 367 m->mtx_recurse++; 368 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 369 if (LOCK_LOG_TEST(&m->lock_object, opts)) 370 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 371 return; 372 } 373 374 #ifdef HWPMC_HOOKS 375 PMC_SOFT_CALL( , , lock, failed); 376 #endif 377 lock_profile_obtain_lock_failed(&m->lock_object, 378 &contested, &waittime); 379 if (LOCK_LOG_TEST(&m->lock_object, opts)) 380 CTR4(KTR_LOCK, 381 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 382 m->lock_object.lo_name, (void *)m->mtx_lock, file, line); 383 #ifdef KDTRACE_HOOKS 384 all_time -= lockstat_nsecs(&m->lock_object); 385 #endif 386 387 while (!_mtx_obtain_lock(m, tid)) { 388 #ifdef KDTRACE_HOOKS 389 spin_cnt++; 390 #endif 391 #ifdef ADAPTIVE_MUTEXES 392 /* 393 * If the owner is running on another CPU, spin until the 394 * owner stops running or the state of the lock changes. 395 */ 396 v = m->mtx_lock; 397 if (v != MTX_UNOWNED) { 398 owner = (struct thread *)(v & ~MTX_FLAGMASK); 399 if (TD_IS_RUNNING(owner)) { 400 if (LOCK_LOG_TEST(&m->lock_object, 0)) 401 CTR3(KTR_LOCK, 402 "%s: spinning on %p held by %p", 403 __func__, m, owner); 404 while (mtx_owner(m) == owner && 405 TD_IS_RUNNING(owner)) { 406 cpu_spinwait(); 407 #ifdef KDTRACE_HOOKS 408 spin_cnt++; 409 #endif 410 } 411 continue; 412 } 413 } 414 #endif 415 416 ts = turnstile_trywait(&m->lock_object); 417 v = m->mtx_lock; 418 419 /* 420 * Check if the lock has been released while spinning for 421 * the turnstile chain lock. 422 */ 423 if (v == MTX_UNOWNED) { 424 turnstile_cancel(ts); 425 continue; 426 } 427 428 #ifdef ADAPTIVE_MUTEXES 429 /* 430 * The current lock owner might have started executing 431 * on another CPU (or the lock could have changed 432 * owners) while we were waiting on the turnstile 433 * chain lock. If so, drop the turnstile lock and try 434 * again. 435 */ 436 owner = (struct thread *)(v & ~MTX_FLAGMASK); 437 if (TD_IS_RUNNING(owner)) { 438 turnstile_cancel(ts); 439 continue; 440 } 441 #endif 442 443 /* 444 * If the mutex isn't already contested and a failure occurs 445 * setting the contested bit, the mutex was either released 446 * or the state of the MTX_RECURSED bit changed. 447 */ 448 if ((v & MTX_CONTESTED) == 0 && 449 !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) { 450 turnstile_cancel(ts); 451 continue; 452 } 453 454 /* 455 * We definitely must sleep for this lock. 456 */ 457 mtx_assert(m, MA_NOTOWNED); 458 459 #ifdef KTR 460 if (!cont_logged) { 461 CTR6(KTR_CONTENTION, 462 "contention: %p at %s:%d wants %s, taken by %s:%d", 463 (void *)tid, file, line, m->lock_object.lo_name, 464 WITNESS_FILE(&m->lock_object), 465 WITNESS_LINE(&m->lock_object)); 466 cont_logged = 1; 467 } 468 #endif 469 470 /* 471 * Block on the turnstile. 472 */ 473 #ifdef KDTRACE_HOOKS 474 sleep_time -= lockstat_nsecs(&m->lock_object); 475 #endif 476 turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE); 477 #ifdef KDTRACE_HOOKS 478 sleep_time += lockstat_nsecs(&m->lock_object); 479 sleep_cnt++; 480 #endif 481 } 482 #ifdef KDTRACE_HOOKS 483 all_time += lockstat_nsecs(&m->lock_object); 484 #endif 485 #ifdef KTR 486 if (cont_logged) { 487 CTR4(KTR_CONTENTION, 488 "contention end: %s acquired by %p at %s:%d", 489 m->lock_object.lo_name, (void *)tid, file, line); 490 } 491 #endif 492 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE, m, contested, 493 waittime, file, line); 494 #ifdef KDTRACE_HOOKS 495 if (sleep_time) 496 LOCKSTAT_RECORD1(LS_MTX_LOCK_BLOCK, m, sleep_time); 497 498 /* 499 * Only record the loops spinning and not sleeping. 500 */ 501 if (spin_cnt > sleep_cnt) 502 LOCKSTAT_RECORD1(LS_MTX_LOCK_SPIN, m, (all_time - sleep_time)); 503 #endif 504 } 505 506 static void 507 _mtx_lock_spin_failed(struct mtx *m) 508 { 509 struct thread *td; 510 511 td = mtx_owner(m); 512 513 /* If the mutex is unlocked, try again. */ 514 if (td == NULL) 515 return; 516 517 printf( "spin lock %p (%s) held by %p (tid %d) too long\n", 518 m, m->lock_object.lo_name, td, td->td_tid); 519 #ifdef WITNESS 520 witness_display_spinlock(&m->lock_object, td, printf); 521 #endif 522 panic("spin lock held too long"); 523 } 524 525 #ifdef SMP 526 /* 527 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. 528 * 529 * This is only called if we need to actually spin for the lock. Recursion 530 * is handled inline. 531 */ 532 void 533 _mtx_lock_spin(struct mtx *m, uintptr_t tid, int opts, const char *file, 534 int line) 535 { 536 int i = 0; 537 #ifdef LOCK_PROFILING 538 int contested = 0; 539 uint64_t waittime = 0; 540 #endif 541 #ifdef KDTRACE_HOOKS 542 int64_t spin_time = 0; 543 #endif 544 545 if (SCHEDULER_STOPPED()) 546 return; 547 548 if (LOCK_LOG_TEST(&m->lock_object, opts)) 549 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 550 551 #ifdef HWPMC_HOOKS 552 PMC_SOFT_CALL( , , lock, failed); 553 #endif 554 lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime); 555 #ifdef KDTRACE_HOOKS 556 spin_time -= lockstat_nsecs(&m->lock_object); 557 #endif 558 while (!_mtx_obtain_lock(m, tid)) { 559 560 /* Give interrupts a chance while we spin. */ 561 spinlock_exit(); 562 while (m->mtx_lock != MTX_UNOWNED) { 563 if (i++ < 10000000) { 564 cpu_spinwait(); 565 continue; 566 } 567 if (i < 60000000 || kdb_active || panicstr != NULL) 568 DELAY(1); 569 else 570 _mtx_lock_spin_failed(m); 571 cpu_spinwait(); 572 } 573 spinlock_enter(); 574 } 575 #ifdef KDTRACE_HOOKS 576 spin_time += lockstat_nsecs(&m->lock_object); 577 #endif 578 579 if (LOCK_LOG_TEST(&m->lock_object, opts)) 580 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 581 582 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE, m, 583 contested, waittime, (file), (line)); 584 #ifdef KDTRACE_HOOKS 585 if (spin_time != 0) 586 LOCKSTAT_RECORD1(LS_MTX_SPIN_LOCK_SPIN, m, spin_time); 587 #endif 588 } 589 #endif /* SMP */ 590 591 void 592 _thread_lock_flags(struct thread *td, int opts, const char *file, int line) 593 { 594 struct mtx *m; 595 uintptr_t tid; 596 int i; 597 #ifdef LOCK_PROFILING 598 int contested = 0; 599 uint64_t waittime = 0; 600 #endif 601 #ifdef KDTRACE_HOOKS 602 int64_t spin_time = 0; 603 #endif 604 605 i = 0; 606 tid = (uintptr_t)curthread; 607 608 if (SCHEDULER_STOPPED()) 609 return; 610 611 #ifdef KDTRACE_HOOKS 612 spin_time -= lockstat_nsecs(&td->td_lock->lock_object); 613 #endif 614 for (;;) { 615 retry: 616 spinlock_enter(); 617 m = td->td_lock; 618 KASSERT(m->mtx_lock != MTX_DESTROYED, 619 ("thread_lock() of destroyed mutex @ %s:%d", file, line)); 620 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 621 ("thread_lock() of sleep mutex %s @ %s:%d", 622 m->lock_object.lo_name, file, line)); 623 if (mtx_owned(m)) 624 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0, 625 ("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n", 626 m->lock_object.lo_name, file, line)); 627 WITNESS_CHECKORDER(&m->lock_object, 628 opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL); 629 while (!_mtx_obtain_lock(m, tid)) { 630 if (m->mtx_lock == tid) { 631 m->mtx_recurse++; 632 break; 633 } 634 #ifdef HWPMC_HOOKS 635 PMC_SOFT_CALL( , , lock, failed); 636 #endif 637 lock_profile_obtain_lock_failed(&m->lock_object, 638 &contested, &waittime); 639 /* Give interrupts a chance while we spin. */ 640 spinlock_exit(); 641 while (m->mtx_lock != MTX_UNOWNED) { 642 if (i++ < 10000000) 643 cpu_spinwait(); 644 else if (i < 60000000 || 645 kdb_active || panicstr != NULL) 646 DELAY(1); 647 else 648 _mtx_lock_spin_failed(m); 649 cpu_spinwait(); 650 if (m != td->td_lock) 651 goto retry; 652 } 653 spinlock_enter(); 654 } 655 if (m == td->td_lock) 656 break; 657 __mtx_unlock_spin(m); /* does spinlock_exit() */ 658 } 659 #ifdef KDTRACE_HOOKS 660 spin_time += lockstat_nsecs(&m->lock_object); 661 #endif 662 if (m->mtx_recurse == 0) 663 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE, 664 m, contested, waittime, (file), (line)); 665 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 666 line); 667 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 668 LOCKSTAT_RECORD1(LS_THREAD_LOCK_SPIN, m, spin_time); 669 } 670 671 struct mtx * 672 thread_lock_block(struct thread *td) 673 { 674 struct mtx *lock; 675 676 THREAD_LOCK_ASSERT(td, MA_OWNED); 677 lock = td->td_lock; 678 td->td_lock = &blocked_lock; 679 mtx_unlock_spin(lock); 680 681 return (lock); 682 } 683 684 void 685 thread_lock_unblock(struct thread *td, struct mtx *new) 686 { 687 mtx_assert(new, MA_OWNED); 688 MPASS(td->td_lock == &blocked_lock); 689 atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new); 690 } 691 692 void 693 thread_lock_set(struct thread *td, struct mtx *new) 694 { 695 struct mtx *lock; 696 697 mtx_assert(new, MA_OWNED); 698 THREAD_LOCK_ASSERT(td, MA_OWNED); 699 lock = td->td_lock; 700 td->td_lock = new; 701 mtx_unlock_spin(lock); 702 } 703 704 /* 705 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 706 * 707 * We are only called here if the lock is recursed or contested (i.e. we 708 * need to wake up a blocked thread). 709 */ 710 void 711 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) 712 { 713 struct turnstile *ts; 714 715 if (SCHEDULER_STOPPED()) 716 return; 717 718 if (mtx_recursed(m)) { 719 if (--(m->mtx_recurse) == 0) 720 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 721 if (LOCK_LOG_TEST(&m->lock_object, opts)) 722 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 723 return; 724 } 725 726 /* 727 * We have to lock the chain before the turnstile so this turnstile 728 * can be removed from the hash list if it is empty. 729 */ 730 turnstile_chain_lock(&m->lock_object); 731 ts = turnstile_lookup(&m->lock_object); 732 if (LOCK_LOG_TEST(&m->lock_object, opts)) 733 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 734 MPASS(ts != NULL); 735 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE); 736 _mtx_release_lock_quick(m); 737 738 /* 739 * This turnstile is now no longer associated with the mutex. We can 740 * unlock the chain lock so a new turnstile may take it's place. 741 */ 742 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 743 turnstile_chain_unlock(&m->lock_object); 744 } 745 746 /* 747 * All the unlocking of MTX_SPIN locks is done inline. 748 * See the __mtx_unlock_spin() macro for the details. 749 */ 750 751 /* 752 * The backing function for the INVARIANTS-enabled mtx_assert() 753 */ 754 #ifdef INVARIANT_SUPPORT 755 void 756 _mtx_assert(struct mtx *m, int what, const char *file, int line) 757 { 758 759 if (panicstr != NULL || dumping) 760 return; 761 switch (what) { 762 case MA_OWNED: 763 case MA_OWNED | MA_RECURSED: 764 case MA_OWNED | MA_NOTRECURSED: 765 if (!mtx_owned(m)) 766 panic("mutex %s not owned at %s:%d", 767 m->lock_object.lo_name, file, line); 768 if (mtx_recursed(m)) { 769 if ((what & MA_NOTRECURSED) != 0) 770 panic("mutex %s recursed at %s:%d", 771 m->lock_object.lo_name, file, line); 772 } else if ((what & MA_RECURSED) != 0) { 773 panic("mutex %s unrecursed at %s:%d", 774 m->lock_object.lo_name, file, line); 775 } 776 break; 777 case MA_NOTOWNED: 778 if (mtx_owned(m)) 779 panic("mutex %s owned at %s:%d", 780 m->lock_object.lo_name, file, line); 781 break; 782 default: 783 panic("unknown mtx_assert at %s:%d", file, line); 784 } 785 } 786 #endif 787 788 /* 789 * The MUTEX_DEBUG-enabled mtx_validate() 790 * 791 * Most of these checks have been moved off into the LO_INITIALIZED flag 792 * maintained by the witness code. 793 */ 794 #ifdef MUTEX_DEBUG 795 796 void mtx_validate(struct mtx *); 797 798 void 799 mtx_validate(struct mtx *m) 800 { 801 802 /* 803 * XXX: When kernacc() does not require Giant we can reenable this check 804 */ 805 #ifdef notyet 806 /* 807 * Can't call kernacc() from early init386(), especially when 808 * initializing Giant mutex, because some stuff in kernacc() 809 * requires Giant itself. 810 */ 811 if (!cold) 812 if (!kernacc((caddr_t)m, sizeof(m), 813 VM_PROT_READ | VM_PROT_WRITE)) 814 panic("Can't read and write to mutex %p", m); 815 #endif 816 } 817 #endif 818 819 /* 820 * General init routine used by the MTX_SYSINIT() macro. 821 */ 822 void 823 mtx_sysinit(void *arg) 824 { 825 struct mtx_args *margs = arg; 826 827 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); 828 } 829 830 /* 831 * Mutex initialization routine; initialize lock `m' of type contained in 832 * `opts' with options contained in `opts' and name `name.' The optional 833 * lock type `type' is used as a general lock category name for use with 834 * witness. 835 */ 836 void 837 mtx_init(struct mtx *m, const char *name, const char *type, int opts) 838 { 839 struct lock_class *class; 840 int flags; 841 842 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 843 MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0); 844 ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock, 845 ("%s: mtx_lock not aligned for %s: %p", __func__, name, 846 &m->mtx_lock)); 847 848 #ifdef MUTEX_DEBUG 849 /* Diagnostic and error correction */ 850 mtx_validate(m); 851 #endif 852 853 /* Determine lock class and lock flags. */ 854 if (opts & MTX_SPIN) 855 class = &lock_class_mtx_spin; 856 else 857 class = &lock_class_mtx_sleep; 858 flags = 0; 859 if (opts & MTX_QUIET) 860 flags |= LO_QUIET; 861 if (opts & MTX_RECURSE) 862 flags |= LO_RECURSABLE; 863 if ((opts & MTX_NOWITNESS) == 0) 864 flags |= LO_WITNESS; 865 if (opts & MTX_DUPOK) 866 flags |= LO_DUPOK; 867 if (opts & MTX_NOPROFILE) 868 flags |= LO_NOPROFILE; 869 870 /* Initialize mutex. */ 871 m->mtx_lock = MTX_UNOWNED; 872 m->mtx_recurse = 0; 873 874 lock_init(&m->lock_object, class, name, type, flags); 875 } 876 877 /* 878 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 879 * passed in as a flag here because if the corresponding mtx_init() was 880 * called with MTX_QUIET set, then it will already be set in the mutex's 881 * flags. 882 */ 883 void 884 mtx_destroy(struct mtx *m) 885 { 886 887 if (!mtx_owned(m)) 888 MPASS(mtx_unowned(m)); 889 else { 890 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 891 892 /* Perform the non-mtx related part of mtx_unlock_spin(). */ 893 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin) 894 spinlock_exit(); 895 else 896 curthread->td_locks--; 897 898 lock_profile_release_lock(&m->lock_object); 899 /* Tell witness this isn't locked to make it happy. */ 900 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__, 901 __LINE__); 902 } 903 904 m->mtx_lock = MTX_DESTROYED; 905 lock_destroy(&m->lock_object); 906 } 907 908 /* 909 * Intialize the mutex code and system mutexes. This is called from the MD 910 * startup code prior to mi_startup(). The per-CPU data space needs to be 911 * setup before this is called. 912 */ 913 void 914 mutex_init(void) 915 { 916 917 /* Setup turnstiles so that sleep mutexes work. */ 918 init_turnstiles(); 919 920 /* 921 * Initialize mutexes. 922 */ 923 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 924 mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN); 925 blocked_lock.mtx_lock = 0xdeadc0de; /* Always blocked. */ 926 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 927 mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN | MTX_RECURSE); 928 mtx_init(&devmtx, "cdev", NULL, MTX_DEF); 929 mtx_lock(&Giant); 930 } 931 932 #ifdef DDB 933 void 934 db_show_mtx(struct lock_object *lock) 935 { 936 struct thread *td; 937 struct mtx *m; 938 939 m = (struct mtx *)lock; 940 941 db_printf(" flags: {"); 942 if (LOCK_CLASS(lock) == &lock_class_mtx_spin) 943 db_printf("SPIN"); 944 else 945 db_printf("DEF"); 946 if (m->lock_object.lo_flags & LO_RECURSABLE) 947 db_printf(", RECURSE"); 948 if (m->lock_object.lo_flags & LO_DUPOK) 949 db_printf(", DUPOK"); 950 db_printf("}\n"); 951 db_printf(" state: {"); 952 if (mtx_unowned(m)) 953 db_printf("UNOWNED"); 954 else if (mtx_destroyed(m)) 955 db_printf("DESTROYED"); 956 else { 957 db_printf("OWNED"); 958 if (m->mtx_lock & MTX_CONTESTED) 959 db_printf(", CONTESTED"); 960 if (m->mtx_lock & MTX_RECURSED) 961 db_printf(", RECURSED"); 962 } 963 db_printf("}\n"); 964 if (!mtx_unowned(m) && !mtx_destroyed(m)) { 965 td = mtx_owner(m); 966 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td, 967 td->td_tid, td->td_proc->p_pid, td->td_name); 968 if (mtx_recursed(m)) 969 db_printf(" recursed: %d\n", m->mtx_recurse); 970 } 971 } 972 #endif
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