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/9.1/sys/kern/kern_mutex.c 236238 2012-05-29 14:50:21Z fabient $"); 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 MPASS(curthread != NULL); 203 KASSERT(m->mtx_lock != MTX_DESTROYED, 204 ("mtx_lock() of destroyed mutex @ %s:%d", file, line)); 205 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 206 ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 207 file, line)); 208 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 209 file, line, NULL); 210 211 __mtx_lock(m, curthread, opts, file, line); 212 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 213 line); 214 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 215 curthread->td_locks++; 216 } 217 218 void 219 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) 220 { 221 222 if (SCHEDULER_STOPPED()) 223 return; 224 MPASS(curthread != NULL); 225 KASSERT(m->mtx_lock != MTX_DESTROYED, 226 ("mtx_unlock() of destroyed mutex @ %s:%d", file, line)); 227 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 228 ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 229 file, line)); 230 curthread->td_locks--; 231 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 232 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, 233 line); 234 mtx_assert(m, MA_OWNED); 235 236 if (m->mtx_recurse == 0) 237 LOCKSTAT_PROFILE_RELEASE_LOCK(LS_MTX_UNLOCK_RELEASE, m); 238 __mtx_unlock(m, curthread, opts, file, line); 239 } 240 241 void 242 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) 243 { 244 245 if (SCHEDULER_STOPPED()) 246 return; 247 MPASS(curthread != NULL); 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 MPASS(curthread != NULL); 272 KASSERT(m->mtx_lock != MTX_DESTROYED, 273 ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line)); 274 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 275 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 276 m->lock_object.lo_name, file, line)); 277 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 278 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, 279 line); 280 mtx_assert(m, MA_OWNED); 281 282 __mtx_unlock_spin(m); 283 } 284 285 /* 286 * The important part of mtx_trylock{,_flags}() 287 * Tries to acquire lock `m.' If this function is called on a mutex that 288 * is already owned, it will recursively acquire the lock. 289 */ 290 int 291 _mtx_trylock(struct mtx *m, int opts, const char *file, int line) 292 { 293 #ifdef LOCK_PROFILING 294 uint64_t waittime = 0; 295 int contested = 0; 296 #endif 297 int rval; 298 299 if (SCHEDULER_STOPPED()) 300 return (1); 301 302 MPASS(curthread != NULL); 303 KASSERT(m->mtx_lock != MTX_DESTROYED, 304 ("mtx_trylock() of destroyed mutex @ %s:%d", file, line)); 305 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, 306 ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, 307 file, line)); 308 309 if (mtx_owned(m) && (m->lock_object.lo_flags & LO_RECURSABLE) != 0) { 310 m->mtx_recurse++; 311 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 312 rval = 1; 313 } else 314 rval = _mtx_obtain_lock(m, (uintptr_t)curthread); 315 316 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line); 317 if (rval) { 318 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 319 file, line); 320 curthread->td_locks++; 321 if (m->mtx_recurse == 0) 322 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE, 323 m, contested, waittime, file, line); 324 325 } 326 327 return (rval); 328 } 329 330 /* 331 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 332 * 333 * We call this if the lock is either contested (i.e. we need to go to 334 * sleep waiting for it), or if we need to recurse on it. 335 */ 336 void 337 _mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file, 338 int line) 339 { 340 struct turnstile *ts; 341 uintptr_t v; 342 #ifdef ADAPTIVE_MUTEXES 343 volatile struct thread *owner; 344 #endif 345 #ifdef KTR 346 int cont_logged = 0; 347 #endif 348 #ifdef LOCK_PROFILING 349 int contested = 0; 350 uint64_t waittime = 0; 351 #endif 352 #ifdef KDTRACE_HOOKS 353 uint64_t spin_cnt = 0; 354 uint64_t sleep_cnt = 0; 355 int64_t sleep_time = 0; 356 #endif 357 358 if (SCHEDULER_STOPPED()) 359 return; 360 361 if (mtx_owned(m)) { 362 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0, 363 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n", 364 m->lock_object.lo_name, file, line)); 365 m->mtx_recurse++; 366 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 367 if (LOCK_LOG_TEST(&m->lock_object, opts)) 368 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 369 return; 370 } 371 372 #ifdef HWPMC_HOOKS 373 PMC_SOFT_CALL( , , lock, failed); 374 #endif 375 lock_profile_obtain_lock_failed(&m->lock_object, 376 &contested, &waittime); 377 if (LOCK_LOG_TEST(&m->lock_object, opts)) 378 CTR4(KTR_LOCK, 379 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 380 m->lock_object.lo_name, (void *)m->mtx_lock, file, line); 381 382 while (!_mtx_obtain_lock(m, tid)) { 383 #ifdef KDTRACE_HOOKS 384 spin_cnt++; 385 #endif 386 #ifdef ADAPTIVE_MUTEXES 387 /* 388 * If the owner is running on another CPU, spin until the 389 * owner stops running or the state of the lock changes. 390 */ 391 v = m->mtx_lock; 392 if (v != MTX_UNOWNED) { 393 owner = (struct thread *)(v & ~MTX_FLAGMASK); 394 if (TD_IS_RUNNING(owner)) { 395 if (LOCK_LOG_TEST(&m->lock_object, 0)) 396 CTR3(KTR_LOCK, 397 "%s: spinning on %p held by %p", 398 __func__, m, owner); 399 while (mtx_owner(m) == owner && 400 TD_IS_RUNNING(owner)) { 401 cpu_spinwait(); 402 #ifdef KDTRACE_HOOKS 403 spin_cnt++; 404 #endif 405 } 406 continue; 407 } 408 } 409 #endif 410 411 ts = turnstile_trywait(&m->lock_object); 412 v = m->mtx_lock; 413 414 /* 415 * Check if the lock has been released while spinning for 416 * the turnstile chain lock. 417 */ 418 if (v == MTX_UNOWNED) { 419 turnstile_cancel(ts); 420 continue; 421 } 422 423 #ifdef ADAPTIVE_MUTEXES 424 /* 425 * The current lock owner might have started executing 426 * on another CPU (or the lock could have changed 427 * owners) while we were waiting on the turnstile 428 * chain lock. If so, drop the turnstile lock and try 429 * again. 430 */ 431 owner = (struct thread *)(v & ~MTX_FLAGMASK); 432 if (TD_IS_RUNNING(owner)) { 433 turnstile_cancel(ts); 434 continue; 435 } 436 #endif 437 438 /* 439 * If the mutex isn't already contested and a failure occurs 440 * setting the contested bit, the mutex was either released 441 * or the state of the MTX_RECURSED bit changed. 442 */ 443 if ((v & MTX_CONTESTED) == 0 && 444 !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) { 445 turnstile_cancel(ts); 446 continue; 447 } 448 449 /* 450 * We definitely must sleep for this lock. 451 */ 452 mtx_assert(m, MA_NOTOWNED); 453 454 #ifdef KTR 455 if (!cont_logged) { 456 CTR6(KTR_CONTENTION, 457 "contention: %p at %s:%d wants %s, taken by %s:%d", 458 (void *)tid, file, line, m->lock_object.lo_name, 459 WITNESS_FILE(&m->lock_object), 460 WITNESS_LINE(&m->lock_object)); 461 cont_logged = 1; 462 } 463 #endif 464 465 /* 466 * Block on the turnstile. 467 */ 468 #ifdef KDTRACE_HOOKS 469 sleep_time -= lockstat_nsecs(); 470 #endif 471 turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE); 472 #ifdef KDTRACE_HOOKS 473 sleep_time += lockstat_nsecs(); 474 sleep_cnt++; 475 #endif 476 } 477 #ifdef KTR 478 if (cont_logged) { 479 CTR4(KTR_CONTENTION, 480 "contention end: %s acquired by %p at %s:%d", 481 m->lock_object.lo_name, (void *)tid, file, line); 482 } 483 #endif 484 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE, m, contested, 485 waittime, file, line); 486 #ifdef KDTRACE_HOOKS 487 if (sleep_time) 488 LOCKSTAT_RECORD1(LS_MTX_LOCK_BLOCK, m, sleep_time); 489 490 /* 491 * Only record the loops spinning and not sleeping. 492 */ 493 if (spin_cnt > sleep_cnt) 494 LOCKSTAT_RECORD1(LS_MTX_LOCK_SPIN, m, (spin_cnt - sleep_cnt)); 495 #endif 496 } 497 498 static void 499 _mtx_lock_spin_failed(struct mtx *m) 500 { 501 struct thread *td; 502 503 td = mtx_owner(m); 504 505 /* If the mutex is unlocked, try again. */ 506 if (td == NULL) 507 return; 508 509 printf( "spin lock %p (%s) held by %p (tid %d) too long\n", 510 m, m->lock_object.lo_name, td, td->td_tid); 511 #ifdef WITNESS 512 witness_display_spinlock(&m->lock_object, td, printf); 513 #endif 514 panic("spin lock held too long"); 515 } 516 517 #ifdef SMP 518 /* 519 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. 520 * 521 * This is only called if we need to actually spin for the lock. Recursion 522 * is handled inline. 523 */ 524 void 525 _mtx_lock_spin(struct mtx *m, uintptr_t tid, int opts, const char *file, 526 int line) 527 { 528 int i = 0; 529 #ifdef LOCK_PROFILING 530 int contested = 0; 531 uint64_t waittime = 0; 532 #endif 533 534 if (SCHEDULER_STOPPED()) 535 return; 536 537 if (LOCK_LOG_TEST(&m->lock_object, opts)) 538 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 539 540 #ifdef HWPMC_HOOKS 541 PMC_SOFT_CALL( , , lock, failed); 542 #endif 543 lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime); 544 while (!_mtx_obtain_lock(m, tid)) { 545 546 /* Give interrupts a chance while we spin. */ 547 spinlock_exit(); 548 while (m->mtx_lock != MTX_UNOWNED) { 549 if (i++ < 10000000) { 550 cpu_spinwait(); 551 continue; 552 } 553 if (i < 60000000 || kdb_active || panicstr != NULL) 554 DELAY(1); 555 else 556 _mtx_lock_spin_failed(m); 557 cpu_spinwait(); 558 } 559 spinlock_enter(); 560 } 561 562 if (LOCK_LOG_TEST(&m->lock_object, opts)) 563 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 564 565 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE, m, 566 contested, waittime, (file), (line)); 567 LOCKSTAT_RECORD1(LS_MTX_SPIN_LOCK_SPIN, m, i); 568 } 569 #endif /* SMP */ 570 571 void 572 _thread_lock_flags(struct thread *td, int opts, const char *file, int line) 573 { 574 struct mtx *m; 575 uintptr_t tid; 576 int i; 577 #ifdef LOCK_PROFILING 578 int contested = 0; 579 uint64_t waittime = 0; 580 #endif 581 #ifdef KDTRACE_HOOKS 582 uint64_t spin_cnt = 0; 583 #endif 584 585 i = 0; 586 tid = (uintptr_t)curthread; 587 588 if (SCHEDULER_STOPPED()) 589 return; 590 591 for (;;) { 592 retry: 593 spinlock_enter(); 594 m = td->td_lock; 595 KASSERT(m->mtx_lock != MTX_DESTROYED, 596 ("thread_lock() of destroyed mutex @ %s:%d", file, line)); 597 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, 598 ("thread_lock() of sleep mutex %s @ %s:%d", 599 m->lock_object.lo_name, file, line)); 600 if (mtx_owned(m)) 601 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0, 602 ("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n", 603 m->lock_object.lo_name, file, line)); 604 WITNESS_CHECKORDER(&m->lock_object, 605 opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL); 606 while (!_mtx_obtain_lock(m, tid)) { 607 #ifdef KDTRACE_HOOKS 608 spin_cnt++; 609 #endif 610 if (m->mtx_lock == tid) { 611 m->mtx_recurse++; 612 break; 613 } 614 #ifdef HWPMC_HOOKS 615 PMC_SOFT_CALL( , , lock, failed); 616 #endif 617 lock_profile_obtain_lock_failed(&m->lock_object, 618 &contested, &waittime); 619 /* Give interrupts a chance while we spin. */ 620 spinlock_exit(); 621 while (m->mtx_lock != MTX_UNOWNED) { 622 if (i++ < 10000000) 623 cpu_spinwait(); 624 else if (i < 60000000 || 625 kdb_active || panicstr != NULL) 626 DELAY(1); 627 else 628 _mtx_lock_spin_failed(m); 629 cpu_spinwait(); 630 if (m != td->td_lock) 631 goto retry; 632 } 633 spinlock_enter(); 634 } 635 if (m == td->td_lock) 636 break; 637 __mtx_unlock_spin(m); /* does spinlock_exit() */ 638 #ifdef KDTRACE_HOOKS 639 spin_cnt++; 640 #endif 641 } 642 if (m->mtx_recurse == 0) 643 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE, 644 m, contested, waittime, (file), (line)); 645 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, 646 line); 647 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); 648 LOCKSTAT_RECORD1(LS_THREAD_LOCK_SPIN, m, spin_cnt); 649 } 650 651 struct mtx * 652 thread_lock_block(struct thread *td) 653 { 654 struct mtx *lock; 655 656 THREAD_LOCK_ASSERT(td, MA_OWNED); 657 lock = td->td_lock; 658 td->td_lock = &blocked_lock; 659 mtx_unlock_spin(lock); 660 661 return (lock); 662 } 663 664 void 665 thread_lock_unblock(struct thread *td, struct mtx *new) 666 { 667 mtx_assert(new, MA_OWNED); 668 MPASS(td->td_lock == &blocked_lock); 669 atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new); 670 } 671 672 void 673 thread_lock_set(struct thread *td, struct mtx *new) 674 { 675 struct mtx *lock; 676 677 mtx_assert(new, MA_OWNED); 678 THREAD_LOCK_ASSERT(td, MA_OWNED); 679 lock = td->td_lock; 680 td->td_lock = new; 681 mtx_unlock_spin(lock); 682 } 683 684 /* 685 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 686 * 687 * We are only called here if the lock is recursed or contested (i.e. we 688 * need to wake up a blocked thread). 689 */ 690 void 691 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) 692 { 693 struct turnstile *ts; 694 695 if (SCHEDULER_STOPPED()) 696 return; 697 698 if (mtx_recursed(m)) { 699 if (--(m->mtx_recurse) == 0) 700 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 701 if (LOCK_LOG_TEST(&m->lock_object, opts)) 702 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 703 return; 704 } 705 706 /* 707 * We have to lock the chain before the turnstile so this turnstile 708 * can be removed from the hash list if it is empty. 709 */ 710 turnstile_chain_lock(&m->lock_object); 711 ts = turnstile_lookup(&m->lock_object); 712 if (LOCK_LOG_TEST(&m->lock_object, opts)) 713 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 714 MPASS(ts != NULL); 715 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE); 716 _mtx_release_lock_quick(m); 717 718 /* 719 * This turnstile is now no longer associated with the mutex. We can 720 * unlock the chain lock so a new turnstile may take it's place. 721 */ 722 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 723 turnstile_chain_unlock(&m->lock_object); 724 } 725 726 /* 727 * All the unlocking of MTX_SPIN locks is done inline. 728 * See the __mtx_unlock_spin() macro for the details. 729 */ 730 731 /* 732 * The backing function for the INVARIANTS-enabled mtx_assert() 733 */ 734 #ifdef INVARIANT_SUPPORT 735 void 736 _mtx_assert(struct mtx *m, int what, const char *file, int line) 737 { 738 739 if (panicstr != NULL || dumping) 740 return; 741 switch (what) { 742 case MA_OWNED: 743 case MA_OWNED | MA_RECURSED: 744 case MA_OWNED | MA_NOTRECURSED: 745 if (!mtx_owned(m)) 746 panic("mutex %s not owned at %s:%d", 747 m->lock_object.lo_name, file, line); 748 if (mtx_recursed(m)) { 749 if ((what & MA_NOTRECURSED) != 0) 750 panic("mutex %s recursed at %s:%d", 751 m->lock_object.lo_name, file, line); 752 } else if ((what & MA_RECURSED) != 0) { 753 panic("mutex %s unrecursed at %s:%d", 754 m->lock_object.lo_name, file, line); 755 } 756 break; 757 case MA_NOTOWNED: 758 if (mtx_owned(m)) 759 panic("mutex %s owned at %s:%d", 760 m->lock_object.lo_name, file, line); 761 break; 762 default: 763 panic("unknown mtx_assert at %s:%d", file, line); 764 } 765 } 766 #endif 767 768 /* 769 * The MUTEX_DEBUG-enabled mtx_validate() 770 * 771 * Most of these checks have been moved off into the LO_INITIALIZED flag 772 * maintained by the witness code. 773 */ 774 #ifdef MUTEX_DEBUG 775 776 void mtx_validate(struct mtx *); 777 778 void 779 mtx_validate(struct mtx *m) 780 { 781 782 /* 783 * XXX: When kernacc() does not require Giant we can reenable this check 784 */ 785 #ifdef notyet 786 /* 787 * Can't call kernacc() from early init386(), especially when 788 * initializing Giant mutex, because some stuff in kernacc() 789 * requires Giant itself. 790 */ 791 if (!cold) 792 if (!kernacc((caddr_t)m, sizeof(m), 793 VM_PROT_READ | VM_PROT_WRITE)) 794 panic("Can't read and write to mutex %p", m); 795 #endif 796 } 797 #endif 798 799 /* 800 * General init routine used by the MTX_SYSINIT() macro. 801 */ 802 void 803 mtx_sysinit(void *arg) 804 { 805 struct mtx_args *margs = arg; 806 807 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); 808 } 809 810 /* 811 * Mutex initialization routine; initialize lock `m' of type contained in 812 * `opts' with options contained in `opts' and name `name.' The optional 813 * lock type `type' is used as a general lock category name for use with 814 * witness. 815 */ 816 void 817 mtx_init(struct mtx *m, const char *name, const char *type, int opts) 818 { 819 struct lock_class *class; 820 int flags; 821 822 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 823 MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0); 824 ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock, 825 ("%s: mtx_lock not aligned for %s: %p", __func__, name, 826 &m->mtx_lock)); 827 828 #ifdef MUTEX_DEBUG 829 /* Diagnostic and error correction */ 830 mtx_validate(m); 831 #endif 832 833 /* Determine lock class and lock flags. */ 834 if (opts & MTX_SPIN) 835 class = &lock_class_mtx_spin; 836 else 837 class = &lock_class_mtx_sleep; 838 flags = 0; 839 if (opts & MTX_QUIET) 840 flags |= LO_QUIET; 841 if (opts & MTX_RECURSE) 842 flags |= LO_RECURSABLE; 843 if ((opts & MTX_NOWITNESS) == 0) 844 flags |= LO_WITNESS; 845 if (opts & MTX_DUPOK) 846 flags |= LO_DUPOK; 847 if (opts & MTX_NOPROFILE) 848 flags |= LO_NOPROFILE; 849 850 /* Initialize mutex. */ 851 m->mtx_lock = MTX_UNOWNED; 852 m->mtx_recurse = 0; 853 854 lock_init(&m->lock_object, class, name, type, flags); 855 } 856 857 /* 858 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 859 * passed in as a flag here because if the corresponding mtx_init() was 860 * called with MTX_QUIET set, then it will already be set in the mutex's 861 * flags. 862 */ 863 void 864 mtx_destroy(struct mtx *m) 865 { 866 867 if (!mtx_owned(m)) 868 MPASS(mtx_unowned(m)); 869 else { 870 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 871 872 /* Perform the non-mtx related part of mtx_unlock_spin(). */ 873 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin) 874 spinlock_exit(); 875 else 876 curthread->td_locks--; 877 878 lock_profile_release_lock(&m->lock_object); 879 /* Tell witness this isn't locked to make it happy. */ 880 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__, 881 __LINE__); 882 } 883 884 m->mtx_lock = MTX_DESTROYED; 885 lock_destroy(&m->lock_object); 886 } 887 888 /* 889 * Intialize the mutex code and system mutexes. This is called from the MD 890 * startup code prior to mi_startup(). The per-CPU data space needs to be 891 * setup before this is called. 892 */ 893 void 894 mutex_init(void) 895 { 896 897 /* Setup turnstiles so that sleep mutexes work. */ 898 init_turnstiles(); 899 900 /* 901 * Initialize mutexes. 902 */ 903 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 904 mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN); 905 blocked_lock.mtx_lock = 0xdeadc0de; /* Always blocked. */ 906 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 907 mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN | MTX_RECURSE); 908 mtx_init(&devmtx, "cdev", NULL, MTX_DEF); 909 mtx_lock(&Giant); 910 } 911 912 #ifdef DDB 913 void 914 db_show_mtx(struct lock_object *lock) 915 { 916 struct thread *td; 917 struct mtx *m; 918 919 m = (struct mtx *)lock; 920 921 db_printf(" flags: {"); 922 if (LOCK_CLASS(lock) == &lock_class_mtx_spin) 923 db_printf("SPIN"); 924 else 925 db_printf("DEF"); 926 if (m->lock_object.lo_flags & LO_RECURSABLE) 927 db_printf(", RECURSE"); 928 if (m->lock_object.lo_flags & LO_DUPOK) 929 db_printf(", DUPOK"); 930 db_printf("}\n"); 931 db_printf(" state: {"); 932 if (mtx_unowned(m)) 933 db_printf("UNOWNED"); 934 else if (mtx_destroyed(m)) 935 db_printf("DESTROYED"); 936 else { 937 db_printf("OWNED"); 938 if (m->mtx_lock & MTX_CONTESTED) 939 db_printf(", CONTESTED"); 940 if (m->mtx_lock & MTX_RECURSED) 941 db_printf(", RECURSED"); 942 } 943 db_printf("}\n"); 944 if (!mtx_unowned(m) && !mtx_destroyed(m)) { 945 td = mtx_owner(m); 946 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td, 947 td->td_tid, td->td_proc->p_pid, td->td_name); 948 if (mtx_recursed(m)) 949 db_printf(" recursed: %d\n", m->mtx_recurse); 950 } 951 } 952 #endif
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