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/9.2/sys/kern/kern_mutex.c 250581 2013-05-12 22:01:22Z hiren $"); 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(m->mtx_lock != MTX_DESTROYED, 203 ("mtx_lock() of destroyed mutex @ %s:%d", file, line)); 204 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 205 ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 206 file, line)); 207 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 208 file, line, NULL); 209 210 __mtx_lock(m, curthread, opts, file, line); 211 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 212 line); 213 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 214 curthread->td_locks++; 215 } 216 217 void 218 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) 219 { 220 221 if (SCHEDULER_STOPPED()) 222 return; 223 KASSERT(m->mtx_lock != MTX_DESTROYED, 224 ("mtx_unlock() of destroyed mutex @ %s:%d", file, line)); 225 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 226 ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 227 file, line)); 228 curthread->td_locks--; 229 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 230 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, 231 line); 232 mtx_assert(m, MA_OWNED); 233 234 if (m->mtx_recurse == 0) 235 LOCKSTAT_PROFILE_RELEASE_LOCK(LS_MTX_UNLOCK_RELEASE, m); 236 __mtx_unlock(m, curthread, opts, file, line); 237 } 238 239 void 240 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) 241 { 242 243 if (SCHEDULER_STOPPED()) 244 return; 245 KASSERT(m->mtx_lock != MTX_DESTROYED, 246 ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line)); 247 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 248 ("mtx_lock_spin() of sleep mutex %s @ %s:%d", 249 m->lock_object.lo_name, file, line)); 250 if (mtx_owned(m)) 251 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0, 252 ("mtx_lock_spin: recursed on non-recursive mutex %s @ %s:%d\n", 253 m->lock_object.lo_name, file, line)); 254 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 255 file, line, NULL); 256 __mtx_lock_spin(m, curthread, opts, file, line); 257 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 258 line); 259 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 260 } 261 262 void 263 _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line) 264 { 265 266 if (SCHEDULER_STOPPED()) 267 return; 268 KASSERT(m->mtx_lock != MTX_DESTROYED, 269 ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line)); 270 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 271 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 272 m->lock_object.lo_name, file, line)); 273 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 274 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, 275 line); 276 mtx_assert(m, MA_OWNED); 277 278 __mtx_unlock_spin(m); 279 } 280 281 /* 282 * The important part of mtx_trylock{,_flags}() 283 * Tries to acquire lock `m.' If this function is called on a mutex that 284 * is already owned, it will recursively acquire the lock. 285 */ 286 int 287 _mtx_trylock(struct mtx *m, int opts, const char *file, int line) 288 { 289 #ifdef LOCK_PROFILING 290 uint64_t waittime = 0; 291 int contested = 0; 292 #endif 293 int rval; 294 295 if (SCHEDULER_STOPPED()) 296 return (1); 297 298 KASSERT(m->mtx_lock != MTX_DESTROYED, 299 ("mtx_trylock() of destroyed mutex @ %s:%d", file, line)); 300 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 301 ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 302 file, line)); 303 304 if (mtx_owned(m) && (m->lock_object.lo_flags & LO_RECURSABLE) != 0) { 305 m->mtx_recurse++; 306 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 307 rval = 1; 308 } else 309 rval = _mtx_obtain_lock(m, (uintptr_t)curthread); 310 311 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line); 312 if (rval) { 313 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 314 file, line); 315 curthread->td_locks++; 316 if (m->mtx_recurse == 0) 317 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE, 318 m, contested, waittime, file, line); 319 320 } 321 322 return (rval); 323 } 324 325 /* 326 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 327 * 328 * We call this if the lock is either contested (i.e. we need to go to 329 * sleep waiting for it), or if we need to recurse on it. 330 */ 331 void 332 _mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file, 333 int line) 334 { 335 struct turnstile *ts; 336 uintptr_t v; 337 #ifdef ADAPTIVE_MUTEXES 338 volatile struct thread *owner; 339 #endif 340 #ifdef KTR 341 int cont_logged = 0; 342 #endif 343 #ifdef LOCK_PROFILING 344 int contested = 0; 345 uint64_t waittime = 0; 346 #endif 347 #ifdef KDTRACE_HOOKS 348 uint64_t spin_cnt = 0; 349 uint64_t sleep_cnt = 0; 350 int64_t sleep_time = 0; 351 #endif 352 353 if (SCHEDULER_STOPPED()) 354 return; 355 356 if (mtx_owned(m)) { 357 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0, 358 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n", 359 m->lock_object.lo_name, file, line)); 360 m->mtx_recurse++; 361 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 362 if (LOCK_LOG_TEST(&m->lock_object, opts)) 363 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 364 return; 365 } 366 367 #ifdef HWPMC_HOOKS 368 PMC_SOFT_CALL( , , lock, failed); 369 #endif 370 lock_profile_obtain_lock_failed(&m->lock_object, 371 &contested, &waittime); 372 if (LOCK_LOG_TEST(&m->lock_object, opts)) 373 CTR4(KTR_LOCK, 374 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 375 m->lock_object.lo_name, (void *)m->mtx_lock, file, line); 376 377 while (!_mtx_obtain_lock(m, tid)) { 378 #ifdef KDTRACE_HOOKS 379 spin_cnt++; 380 #endif 381 #ifdef ADAPTIVE_MUTEXES 382 /* 383 * If the owner is running on another CPU, spin until the 384 * owner stops running or the state of the lock changes. 385 */ 386 v = m->mtx_lock; 387 if (v != MTX_UNOWNED) { 388 owner = (struct thread *)(v & ~MTX_FLAGMASK); 389 if (TD_IS_RUNNING(owner)) { 390 if (LOCK_LOG_TEST(&m->lock_object, 0)) 391 CTR3(KTR_LOCK, 392 "%s: spinning on %p held by %p", 393 __func__, m, owner); 394 while (mtx_owner(m) == owner && 395 TD_IS_RUNNING(owner)) { 396 cpu_spinwait(); 397 #ifdef KDTRACE_HOOKS 398 spin_cnt++; 399 #endif 400 } 401 continue; 402 } 403 } 404 #endif 405 406 ts = turnstile_trywait(&m->lock_object); 407 v = m->mtx_lock; 408 409 /* 410 * Check if the lock has been released while spinning for 411 * the turnstile chain lock. 412 */ 413 if (v == MTX_UNOWNED) { 414 turnstile_cancel(ts); 415 continue; 416 } 417 418 #ifdef ADAPTIVE_MUTEXES 419 /* 420 * The current lock owner might have started executing 421 * on another CPU (or the lock could have changed 422 * owners) while we were waiting on the turnstile 423 * chain lock. If so, drop the turnstile lock and try 424 * again. 425 */ 426 owner = (struct thread *)(v & ~MTX_FLAGMASK); 427 if (TD_IS_RUNNING(owner)) { 428 turnstile_cancel(ts); 429 continue; 430 } 431 #endif 432 433 /* 434 * If the mutex isn't already contested and a failure occurs 435 * setting the contested bit, the mutex was either released 436 * or the state of the MTX_RECURSED bit changed. 437 */ 438 if ((v & MTX_CONTESTED) == 0 && 439 !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) { 440 turnstile_cancel(ts); 441 continue; 442 } 443 444 /* 445 * We definitely must sleep for this lock. 446 */ 447 mtx_assert(m, MA_NOTOWNED); 448 449 #ifdef KTR 450 if (!cont_logged) { 451 CTR6(KTR_CONTENTION, 452 "contention: %p at %s:%d wants %s, taken by %s:%d", 453 (void *)tid, file, line, m->lock_object.lo_name, 454 WITNESS_FILE(&m->lock_object), 455 WITNESS_LINE(&m->lock_object)); 456 cont_logged = 1; 457 } 458 #endif 459 460 /* 461 * Block on the turnstile. 462 */ 463 #ifdef KDTRACE_HOOKS 464 sleep_time -= lockstat_nsecs(); 465 #endif 466 turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE); 467 #ifdef KDTRACE_HOOKS 468 sleep_time += lockstat_nsecs(); 469 sleep_cnt++; 470 #endif 471 } 472 #ifdef KTR 473 if (cont_logged) { 474 CTR4(KTR_CONTENTION, 475 "contention end: %s acquired by %p at %s:%d", 476 m->lock_object.lo_name, (void *)tid, file, line); 477 } 478 #endif 479 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE, m, contested, 480 waittime, file, line); 481 #ifdef KDTRACE_HOOKS 482 if (sleep_time) 483 LOCKSTAT_RECORD1(LS_MTX_LOCK_BLOCK, m, sleep_time); 484 485 /* 486 * Only record the loops spinning and not sleeping. 487 */ 488 if (spin_cnt > sleep_cnt) 489 LOCKSTAT_RECORD1(LS_MTX_LOCK_SPIN, m, (spin_cnt - sleep_cnt)); 490 #endif 491 } 492 493 static void 494 _mtx_lock_spin_failed(struct mtx *m) 495 { 496 struct thread *td; 497 498 td = mtx_owner(m); 499 500 /* If the mutex is unlocked, try again. */ 501 if (td == NULL) 502 return; 503 504 printf( "spin lock %p (%s) held by %p (tid %d) too long\n", 505 m, m->lock_object.lo_name, td, td->td_tid); 506 #ifdef WITNESS 507 witness_display_spinlock(&m->lock_object, td, printf); 508 #endif 509 panic("spin lock held too long"); 510 } 511 512 #ifdef SMP 513 /* 514 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. 515 * 516 * This is only called if we need to actually spin for the lock. Recursion 517 * is handled inline. 518 */ 519 void 520 _mtx_lock_spin(struct mtx *m, uintptr_t tid, int opts, const char *file, 521 int line) 522 { 523 int i = 0; 524 #ifdef LOCK_PROFILING 525 int contested = 0; 526 uint64_t waittime = 0; 527 #endif 528 529 if (SCHEDULER_STOPPED()) 530 return; 531 532 if (LOCK_LOG_TEST(&m->lock_object, opts)) 533 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 534 535 #ifdef HWPMC_HOOKS 536 PMC_SOFT_CALL( , , lock, failed); 537 #endif 538 lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime); 539 while (!_mtx_obtain_lock(m, tid)) { 540 541 /* Give interrupts a chance while we spin. */ 542 spinlock_exit(); 543 while (m->mtx_lock != MTX_UNOWNED) { 544 if (i++ < 10000000) { 545 cpu_spinwait(); 546 continue; 547 } 548 if (i < 60000000 || kdb_active || panicstr != NULL) 549 DELAY(1); 550 else 551 _mtx_lock_spin_failed(m); 552 cpu_spinwait(); 553 } 554 spinlock_enter(); 555 } 556 557 if (LOCK_LOG_TEST(&m->lock_object, opts)) 558 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 559 560 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE, m, 561 contested, waittime, (file), (line)); 562 LOCKSTAT_RECORD1(LS_MTX_SPIN_LOCK_SPIN, m, i); 563 } 564 #endif /* SMP */ 565 566 void 567 _thread_lock_flags(struct thread *td, int opts, const char *file, int line) 568 { 569 struct mtx *m; 570 uintptr_t tid; 571 int i; 572 #ifdef LOCK_PROFILING 573 int contested = 0; 574 uint64_t waittime = 0; 575 #endif 576 #ifdef KDTRACE_HOOKS 577 uint64_t spin_cnt = 0; 578 #endif 579 580 i = 0; 581 tid = (uintptr_t)curthread; 582 583 if (SCHEDULER_STOPPED()) 584 return; 585 586 for (;;) { 587 retry: 588 spinlock_enter(); 589 m = td->td_lock; 590 KASSERT(m->mtx_lock != MTX_DESTROYED, 591 ("thread_lock() of destroyed mutex @ %s:%d", file, line)); 592 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 593 ("thread_lock() of sleep mutex %s @ %s:%d", 594 m->lock_object.lo_name, file, line)); 595 if (mtx_owned(m)) 596 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0, 597 ("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n", 598 m->lock_object.lo_name, file, line)); 599 WITNESS_CHECKORDER(&m->lock_object, 600 opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL); 601 while (!_mtx_obtain_lock(m, tid)) { 602 #ifdef KDTRACE_HOOKS 603 spin_cnt++; 604 #endif 605 if (m->mtx_lock == tid) { 606 m->mtx_recurse++; 607 break; 608 } 609 #ifdef HWPMC_HOOKS 610 PMC_SOFT_CALL( , , lock, failed); 611 #endif 612 lock_profile_obtain_lock_failed(&m->lock_object, 613 &contested, &waittime); 614 /* Give interrupts a chance while we spin. */ 615 spinlock_exit(); 616 while (m->mtx_lock != MTX_UNOWNED) { 617 if (i++ < 10000000) 618 cpu_spinwait(); 619 else if (i < 60000000 || 620 kdb_active || panicstr != NULL) 621 DELAY(1); 622 else 623 _mtx_lock_spin_failed(m); 624 cpu_spinwait(); 625 if (m != td->td_lock) 626 goto retry; 627 } 628 spinlock_enter(); 629 } 630 if (m == td->td_lock) 631 break; 632 __mtx_unlock_spin(m); /* does spinlock_exit() */ 633 #ifdef KDTRACE_HOOKS 634 spin_cnt++; 635 #endif 636 } 637 if (m->mtx_recurse == 0) 638 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE, 639 m, contested, waittime, (file), (line)); 640 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 641 line); 642 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 643 LOCKSTAT_RECORD1(LS_THREAD_LOCK_SPIN, m, spin_cnt); 644 } 645 646 struct mtx * 647 thread_lock_block(struct thread *td) 648 { 649 struct mtx *lock; 650 651 THREAD_LOCK_ASSERT(td, MA_OWNED); 652 lock = td->td_lock; 653 td->td_lock = &blocked_lock; 654 mtx_unlock_spin(lock); 655 656 return (lock); 657 } 658 659 void 660 thread_lock_unblock(struct thread *td, struct mtx *new) 661 { 662 mtx_assert(new, MA_OWNED); 663 MPASS(td->td_lock == &blocked_lock); 664 atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new); 665 } 666 667 void 668 thread_lock_set(struct thread *td, struct mtx *new) 669 { 670 struct mtx *lock; 671 672 mtx_assert(new, MA_OWNED); 673 THREAD_LOCK_ASSERT(td, MA_OWNED); 674 lock = td->td_lock; 675 td->td_lock = new; 676 mtx_unlock_spin(lock); 677 } 678 679 /* 680 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 681 * 682 * We are only called here if the lock is recursed or contested (i.e. we 683 * need to wake up a blocked thread). 684 */ 685 void 686 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) 687 { 688 struct turnstile *ts; 689 690 if (SCHEDULER_STOPPED()) 691 return; 692 693 if (mtx_recursed(m)) { 694 if (--(m->mtx_recurse) == 0) 695 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 696 if (LOCK_LOG_TEST(&m->lock_object, opts)) 697 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 698 return; 699 } 700 701 /* 702 * We have to lock the chain before the turnstile so this turnstile 703 * can be removed from the hash list if it is empty. 704 */ 705 turnstile_chain_lock(&m->lock_object); 706 ts = turnstile_lookup(&m->lock_object); 707 if (LOCK_LOG_TEST(&m->lock_object, opts)) 708 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 709 MPASS(ts != NULL); 710 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE); 711 _mtx_release_lock_quick(m); 712 713 /* 714 * This turnstile is now no longer associated with the mutex. We can 715 * unlock the chain lock so a new turnstile may take it's place. 716 */ 717 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 718 turnstile_chain_unlock(&m->lock_object); 719 } 720 721 /* 722 * All the unlocking of MTX_SPIN locks is done inline. 723 * See the __mtx_unlock_spin() macro for the details. 724 */ 725 726 /* 727 * The backing function for the INVARIANTS-enabled mtx_assert() 728 */ 729 #ifdef INVARIANT_SUPPORT 730 void 731 _mtx_assert(struct mtx *m, int what, const char *file, int line) 732 { 733 734 if (panicstr != NULL || dumping) 735 return; 736 switch (what) { 737 case MA_OWNED: 738 case MA_OWNED | MA_RECURSED: 739 case MA_OWNED | MA_NOTRECURSED: 740 if (!mtx_owned(m)) 741 panic("mutex %s not owned at %s:%d", 742 m->lock_object.lo_name, file, line); 743 if (mtx_recursed(m)) { 744 if ((what & MA_NOTRECURSED) != 0) 745 panic("mutex %s recursed at %s:%d", 746 m->lock_object.lo_name, file, line); 747 } else if ((what & MA_RECURSED) != 0) { 748 panic("mutex %s unrecursed at %s:%d", 749 m->lock_object.lo_name, file, line); 750 } 751 break; 752 case MA_NOTOWNED: 753 if (mtx_owned(m)) 754 panic("mutex %s owned at %s:%d", 755 m->lock_object.lo_name, file, line); 756 break; 757 default: 758 panic("unknown mtx_assert at %s:%d", file, line); 759 } 760 } 761 #endif 762 763 /* 764 * The MUTEX_DEBUG-enabled mtx_validate() 765 * 766 * Most of these checks have been moved off into the LO_INITIALIZED flag 767 * maintained by the witness code. 768 */ 769 #ifdef MUTEX_DEBUG 770 771 void mtx_validate(struct mtx *); 772 773 void 774 mtx_validate(struct mtx *m) 775 { 776 777 /* 778 * XXX: When kernacc() does not require Giant we can reenable this check 779 */ 780 #ifdef notyet 781 /* 782 * Can't call kernacc() from early init386(), especially when 783 * initializing Giant mutex, because some stuff in kernacc() 784 * requires Giant itself. 785 */ 786 if (!cold) 787 if (!kernacc((caddr_t)m, sizeof(m), 788 VM_PROT_READ | VM_PROT_WRITE)) 789 panic("Can't read and write to mutex %p", m); 790 #endif 791 } 792 #endif 793 794 /* 795 * General init routine used by the MTX_SYSINIT() macro. 796 */ 797 void 798 mtx_sysinit(void *arg) 799 { 800 struct mtx_args *margs = arg; 801 802 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); 803 } 804 805 /* 806 * Mutex initialization routine; initialize lock `m' of type contained in 807 * `opts' with options contained in `opts' and name `name.' The optional 808 * lock type `type' is used as a general lock category name for use with 809 * witness. 810 */ 811 void 812 mtx_init(struct mtx *m, const char *name, const char *type, int opts) 813 { 814 struct lock_class *class; 815 int flags; 816 817 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 818 MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0); 819 ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock, 820 ("%s: mtx_lock not aligned for %s: %p", __func__, name, 821 &m->mtx_lock)); 822 823 #ifdef MUTEX_DEBUG 824 /* Diagnostic and error correction */ 825 mtx_validate(m); 826 #endif 827 828 /* Determine lock class and lock flags. */ 829 if (opts & MTX_SPIN) 830 class = &lock_class_mtx_spin; 831 else 832 class = &lock_class_mtx_sleep; 833 flags = 0; 834 if (opts & MTX_QUIET) 835 flags |= LO_QUIET; 836 if (opts & MTX_RECURSE) 837 flags |= LO_RECURSABLE; 838 if ((opts & MTX_NOWITNESS) == 0) 839 flags |= LO_WITNESS; 840 if (opts & MTX_DUPOK) 841 flags |= LO_DUPOK; 842 if (opts & MTX_NOPROFILE) 843 flags |= LO_NOPROFILE; 844 845 /* Initialize mutex. */ 846 m->mtx_lock = MTX_UNOWNED; 847 m->mtx_recurse = 0; 848 849 lock_init(&m->lock_object, class, name, type, flags); 850 } 851 852 /* 853 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 854 * passed in as a flag here because if the corresponding mtx_init() was 855 * called with MTX_QUIET set, then it will already be set in the mutex's 856 * flags. 857 */ 858 void 859 mtx_destroy(struct mtx *m) 860 { 861 862 if (!mtx_owned(m)) 863 MPASS(mtx_unowned(m)); 864 else { 865 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 866 867 /* Perform the non-mtx related part of mtx_unlock_spin(). */ 868 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin) 869 spinlock_exit(); 870 else 871 curthread->td_locks--; 872 873 lock_profile_release_lock(&m->lock_object); 874 /* Tell witness this isn't locked to make it happy. */ 875 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__, 876 __LINE__); 877 } 878 879 m->mtx_lock = MTX_DESTROYED; 880 lock_destroy(&m->lock_object); 881 } 882 883 /* 884 * Intialize the mutex code and system mutexes. This is called from the MD 885 * startup code prior to mi_startup(). The per-CPU data space needs to be 886 * setup before this is called. 887 */ 888 void 889 mutex_init(void) 890 { 891 892 /* Setup turnstiles so that sleep mutexes work. */ 893 init_turnstiles(); 894 895 /* 896 * Initialize mutexes. 897 */ 898 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 899 mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN); 900 blocked_lock.mtx_lock = 0xdeadc0de; /* Always blocked. */ 901 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 902 mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN | MTX_RECURSE); 903 mtx_init(&devmtx, "cdev", NULL, MTX_DEF); 904 mtx_lock(&Giant); 905 } 906 907 #ifdef DDB 908 void 909 db_show_mtx(struct lock_object *lock) 910 { 911 struct thread *td; 912 struct mtx *m; 913 914 m = (struct mtx *)lock; 915 916 db_printf(" flags: {"); 917 if (LOCK_CLASS(lock) == &lock_class_mtx_spin) 918 db_printf("SPIN"); 919 else 920 db_printf("DEF"); 921 if (m->lock_object.lo_flags & LO_RECURSABLE) 922 db_printf(", RECURSE"); 923 if (m->lock_object.lo_flags & LO_DUPOK) 924 db_printf(", DUPOK"); 925 db_printf("}\n"); 926 db_printf(" state: {"); 927 if (mtx_unowned(m)) 928 db_printf("UNOWNED"); 929 else if (mtx_destroyed(m)) 930 db_printf("DESTROYED"); 931 else { 932 db_printf("OWNED"); 933 if (m->mtx_lock & MTX_CONTESTED) 934 db_printf(", CONTESTED"); 935 if (m->mtx_lock & MTX_RECURSED) 936 db_printf(", RECURSED"); 937 } 938 db_printf("}\n"); 939 if (!mtx_unowned(m) && !mtx_destroyed(m)) { 940 td = mtx_owner(m); 941 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td, 942 td->td_tid, td->td_proc->p_pid, td->td_name); 943 if (mtx_recursed(m)) 944 db_printf(" recursed: %d\n", m->mtx_recurse); 945 } 946 } 947 #endif
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