kern_mutex.c revision 136437
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: head/sys/kern/kern_mutex.c 136437 2004-10-12 16:28:18Z ups $"); 38 39#include "opt_adaptive_mutexes.h" 40#include "opt_ddb.h" 41#include "opt_mprof.h" 42#include "opt_mutex_wake_all.h" 43#include "opt_sched.h" 44 45#include <sys/param.h> 46#include <sys/systm.h> 47#include <sys/bus.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/sysctl.h> 59#include <sys/turnstile.h> 60#include <sys/vmmeter.h> 61 62#include <machine/atomic.h> 63#include <machine/bus.h> 64#include <machine/clock.h> 65#include <machine/cpu.h> 66 67#include <ddb/ddb.h> 68 69#include <vm/vm.h> 70#include <vm/vm_extern.h> 71 72/* 73 * Force MUTEX_WAKE_ALL for now. 74 * single thread wakeup needs fixes to avoid race conditions with 75 * priority inheritance. 76 */ 77#ifndef MUTEX_WAKE_ALL 78#define MUTEX_WAKE_ALL 79#endif 80 81/* 82 * Internal utility macros. 83 */ 84#define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED) 85 86#define mtx_owner(m) (mtx_unowned((m)) ? NULL \ 87 : (struct thread *)((m)->mtx_lock & MTX_FLAGMASK)) 88 89/* 90 * Lock classes for sleep and spin mutexes. 91 */ 92struct lock_class lock_class_mtx_sleep = { 93 "sleep mutex", 94 LC_SLEEPLOCK | LC_RECURSABLE 95}; 96struct lock_class lock_class_mtx_spin = { 97 "spin mutex", 98 LC_SPINLOCK | LC_RECURSABLE 99}; 100 101/* 102 * System-wide mutexes 103 */ 104struct mtx sched_lock; 105struct mtx Giant; 106 107#ifdef MUTEX_PROFILING 108SYSCTL_NODE(_debug, OID_AUTO, mutex, CTLFLAG_RD, NULL, "mutex debugging"); 109SYSCTL_NODE(_debug_mutex, OID_AUTO, prof, CTLFLAG_RD, NULL, "mutex profiling"); 110static int mutex_prof_enable = 0; 111SYSCTL_INT(_debug_mutex_prof, OID_AUTO, enable, CTLFLAG_RW, 112 &mutex_prof_enable, 0, "Enable tracing of mutex holdtime"); 113 114struct mutex_prof { 115 const char *name; 116 const char *file; 117 int line; 118 uintmax_t cnt_max; 119 uintmax_t cnt_tot; 120 uintmax_t cnt_cur; 121 uintmax_t cnt_contest_holding; 122 uintmax_t cnt_contest_locking; 123 struct mutex_prof *next; 124}; 125 126/* 127 * mprof_buf is a static pool of profiling records to avoid possible 128 * reentrance of the memory allocation functions. 129 * 130 * Note: NUM_MPROF_BUFFERS must be smaller than MPROF_HASH_SIZE. 131 */ 132#ifdef MPROF_BUFFERS 133#define NUM_MPROF_BUFFERS MPROF_BUFFERS 134#else 135#define NUM_MPROF_BUFFERS 1000 136#endif 137static struct mutex_prof mprof_buf[NUM_MPROF_BUFFERS]; 138static int first_free_mprof_buf; 139#ifndef MPROF_HASH_SIZE 140#define MPROF_HASH_SIZE 1009 141#endif 142#if NUM_MPROF_BUFFERS >= MPROF_HASH_SIZE 143#error MPROF_BUFFERS must be larger than MPROF_HASH_SIZE 144#endif 145static struct mutex_prof *mprof_hash[MPROF_HASH_SIZE]; 146/* SWAG: sbuf size = avg stat. line size * number of locks */ 147#define MPROF_SBUF_SIZE 256 * 400 148 149static int mutex_prof_acquisitions; 150SYSCTL_INT(_debug_mutex_prof, OID_AUTO, acquisitions, CTLFLAG_RD, 151 &mutex_prof_acquisitions, 0, "Number of mutex acquistions recorded"); 152static int mutex_prof_records; 153SYSCTL_INT(_debug_mutex_prof, OID_AUTO, records, CTLFLAG_RD, 154 &mutex_prof_records, 0, "Number of profiling records"); 155static int mutex_prof_maxrecords = NUM_MPROF_BUFFERS; 156SYSCTL_INT(_debug_mutex_prof, OID_AUTO, maxrecords, CTLFLAG_RD, 157 &mutex_prof_maxrecords, 0, "Maximum number of profiling records"); 158static int mutex_prof_rejected; 159SYSCTL_INT(_debug_mutex_prof, OID_AUTO, rejected, CTLFLAG_RD, 160 &mutex_prof_rejected, 0, "Number of rejected profiling records"); 161static int mutex_prof_hashsize = MPROF_HASH_SIZE; 162SYSCTL_INT(_debug_mutex_prof, OID_AUTO, hashsize, CTLFLAG_RD, 163 &mutex_prof_hashsize, 0, "Hash size"); 164static int mutex_prof_collisions = 0; 165SYSCTL_INT(_debug_mutex_prof, OID_AUTO, collisions, CTLFLAG_RD, 166 &mutex_prof_collisions, 0, "Number of hash collisions"); 167 168/* 169 * mprof_mtx protects the profiling buffers and the hash. 170 */ 171static struct mtx mprof_mtx; 172MTX_SYSINIT(mprof, &mprof_mtx, "mutex profiling lock", MTX_SPIN | MTX_QUIET); 173 174static u_int64_t 175nanoseconds(void) 176{ 177 struct timespec tv; 178 179 nanotime(&tv); 180 return (tv.tv_sec * (u_int64_t)1000000000 + tv.tv_nsec); 181} 182 183static int 184dump_mutex_prof_stats(SYSCTL_HANDLER_ARGS) 185{ 186 struct sbuf *sb; 187 int error, i; 188 static int multiplier = 1; 189 190 if (first_free_mprof_buf == 0) 191 return (SYSCTL_OUT(req, "No locking recorded", 192 sizeof("No locking recorded"))); 193 194retry_sbufops: 195 sb = sbuf_new(NULL, NULL, MPROF_SBUF_SIZE * multiplier, SBUF_FIXEDLEN); 196 sbuf_printf(sb, "%6s %12s %11s %5s %12s %12s %s\n", 197 "max", "total", "count", "avg", "cnt_hold", "cnt_lock", "name"); 198 /* 199 * XXX this spinlock seems to be by far the largest perpetrator 200 * of spinlock latency (1.6 msec on an Athlon1600 was recorded 201 * even before I pessimized it further by moving the average 202 * computation here). 203 */ 204 mtx_lock_spin(&mprof_mtx); 205 for (i = 0; i < first_free_mprof_buf; ++i) { 206 sbuf_printf(sb, "%6ju %12ju %11ju %5ju %12ju %12ju %s:%d (%s)\n", 207 mprof_buf[i].cnt_max / 1000, 208 mprof_buf[i].cnt_tot / 1000, 209 mprof_buf[i].cnt_cur, 210 mprof_buf[i].cnt_cur == 0 ? (uintmax_t)0 : 211 mprof_buf[i].cnt_tot / (mprof_buf[i].cnt_cur * 1000), 212 mprof_buf[i].cnt_contest_holding, 213 mprof_buf[i].cnt_contest_locking, 214 mprof_buf[i].file, mprof_buf[i].line, mprof_buf[i].name); 215 if (sbuf_overflowed(sb)) { 216 mtx_unlock_spin(&mprof_mtx); 217 sbuf_delete(sb); 218 multiplier++; 219 goto retry_sbufops; 220 } 221 } 222 mtx_unlock_spin(&mprof_mtx); 223 sbuf_finish(sb); 224 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1); 225 sbuf_delete(sb); 226 return (error); 227} 228SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD, 229 NULL, 0, dump_mutex_prof_stats, "A", "Mutex profiling statistics"); 230 231static int 232reset_mutex_prof_stats(SYSCTL_HANDLER_ARGS) 233{ 234 int error, v; 235 236 if (first_free_mprof_buf == 0) 237 return (0); 238 239 v = 0; 240 error = sysctl_handle_int(oidp, &v, 0, req); 241 if (error) 242 return (error); 243 if (req->newptr == NULL) 244 return (error); 245 if (v == 0) 246 return (0); 247 248 mtx_lock_spin(&mprof_mtx); 249 bzero(mprof_buf, sizeof(*mprof_buf) * first_free_mprof_buf); 250 bzero(mprof_hash, sizeof(struct mtx *) * MPROF_HASH_SIZE); 251 first_free_mprof_buf = 0; 252 mtx_unlock_spin(&mprof_mtx); 253 return (0); 254} 255SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW, 256 NULL, 0, reset_mutex_prof_stats, "I", "Reset mutex profiling statistics"); 257#endif 258 259/* 260 * Function versions of the inlined __mtx_* macros. These are used by 261 * modules and can also be called from assembly language if needed. 262 */ 263void 264_mtx_lock_flags(struct mtx *m, int opts, const char *file, int line) 265{ 266 267 MPASS(curthread != NULL); 268 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 269 ("mtx_lock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 270 file, line)); 271 WITNESS_CHECKORDER(&m->mtx_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 272 file, line); 273 _get_sleep_lock(m, curthread, opts, file, line); 274 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 275 line); 276 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 277#ifdef MUTEX_PROFILING 278 /* don't reset the timer when/if recursing */ 279 if (m->mtx_acqtime == 0) { 280 m->mtx_filename = file; 281 m->mtx_lineno = line; 282 m->mtx_acqtime = mutex_prof_enable ? nanoseconds() : 0; 283 ++mutex_prof_acquisitions; 284 } 285#endif 286} 287 288void 289_mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) 290{ 291 292 MPASS(curthread != NULL); 293 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 294 ("mtx_unlock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 295 file, line)); 296 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 297 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 298 line); 299 mtx_assert(m, MA_OWNED); 300#ifdef MUTEX_PROFILING 301 if (m->mtx_acqtime != 0) { 302 static const char *unknown = "(unknown)"; 303 struct mutex_prof *mpp; 304 u_int64_t acqtime, now; 305 const char *p, *q; 306 volatile u_int hash; 307 308 now = nanoseconds(); 309 acqtime = m->mtx_acqtime; 310 m->mtx_acqtime = 0; 311 if (now <= acqtime) 312 goto out; 313 for (p = m->mtx_filename; 314 p != NULL && strncmp(p, "../", 3) == 0; p += 3) 315 /* nothing */ ; 316 if (p == NULL || *p == '\0') 317 p = unknown; 318 for (hash = m->mtx_lineno, q = p; *q != '\0'; ++q) 319 hash = (hash * 2 + *q) % MPROF_HASH_SIZE; 320 mtx_lock_spin(&mprof_mtx); 321 for (mpp = mprof_hash[hash]; mpp != NULL; mpp = mpp->next) 322 if (mpp->line == m->mtx_lineno && 323 strcmp(mpp->file, p) == 0) 324 break; 325 if (mpp == NULL) { 326 /* Just exit if we cannot get a trace buffer */ 327 if (first_free_mprof_buf >= NUM_MPROF_BUFFERS) { 328 ++mutex_prof_rejected; 329 goto unlock; 330 } 331 mpp = &mprof_buf[first_free_mprof_buf++]; 332 mpp->name = mtx_name(m); 333 mpp->file = p; 334 mpp->line = m->mtx_lineno; 335 mpp->next = mprof_hash[hash]; 336 if (mprof_hash[hash] != NULL) 337 ++mutex_prof_collisions; 338 mprof_hash[hash] = mpp; 339 ++mutex_prof_records; 340 } 341 /* 342 * Record if the mutex has been held longer now than ever 343 * before. 344 */ 345 if (now - acqtime > mpp->cnt_max) 346 mpp->cnt_max = now - acqtime; 347 mpp->cnt_tot += now - acqtime; 348 mpp->cnt_cur++; 349 /* 350 * There's a small race, really we should cmpxchg 351 * 0 with the current value, but that would bill 352 * the contention to the wrong lock instance if 353 * it followed this also. 354 */ 355 mpp->cnt_contest_holding += m->mtx_contest_holding; 356 m->mtx_contest_holding = 0; 357 mpp->cnt_contest_locking += m->mtx_contest_locking; 358 m->mtx_contest_locking = 0; 359unlock: 360 mtx_unlock_spin(&mprof_mtx); 361 } 362out: 363#endif 364 _rel_sleep_lock(m, curthread, opts, file, line); 365} 366 367void 368_mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) 369{ 370 371 MPASS(curthread != NULL); 372 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 373 ("mtx_lock_spin() of sleep mutex %s @ %s:%d", 374 m->mtx_object.lo_name, file, line)); 375 WITNESS_CHECKORDER(&m->mtx_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 376 file, line); 377#if defined(SMP) || LOCK_DEBUG > 0 || 1 378 _get_spin_lock(m, curthread, opts, file, line); 379#else 380 critical_enter(); 381#endif 382 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 383 line); 384 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 385} 386 387void 388_mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line) 389{ 390 391 MPASS(curthread != NULL); 392 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 393 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 394 m->mtx_object.lo_name, file, line)); 395 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 396 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 397 line); 398 mtx_assert(m, MA_OWNED); 399#if defined(SMP) || LOCK_DEBUG > 0 || 1 400 _rel_spin_lock(m); 401#else 402 critical_exit(); 403#endif 404} 405 406/* 407 * The important part of mtx_trylock{,_flags}() 408 * Tries to acquire lock `m.' If this function is called on a mutex that 409 * is already owned, it will recursively acquire the lock. 410 */ 411int 412_mtx_trylock(struct mtx *m, int opts, const char *file, int line) 413{ 414 int rval; 415 416 MPASS(curthread != NULL); 417 418 if (mtx_owned(m) && (m->mtx_object.lo_flags & LO_RECURSABLE) != 0) { 419 m->mtx_recurse++; 420 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 421 rval = 1; 422 } else 423 rval = _obtain_lock(m, curthread); 424 425 LOCK_LOG_TRY("LOCK", &m->mtx_object, opts, rval, file, line); 426 if (rval) 427 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 428 file, line); 429 430 return (rval); 431} 432 433/* 434 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 435 * 436 * We call this if the lock is either contested (i.e. we need to go to 437 * sleep waiting for it), or if we need to recurse on it. 438 */ 439void 440_mtx_lock_sleep(struct mtx *m, struct thread *td, int opts, const char *file, 441 int line) 442{ 443 struct turnstile *ts; 444#if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 445 struct thread *owner; 446#endif 447 uintptr_t v; 448#ifdef KTR 449 int cont_logged = 0; 450#endif 451#ifdef MUTEX_PROFILING 452 int contested; 453#endif 454 455 if (mtx_owned(m)) { 456 KASSERT((m->mtx_object.lo_flags & LO_RECURSABLE) != 0, 457 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n", 458 m->mtx_object.lo_name, file, line)); 459 m->mtx_recurse++; 460 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 461 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 462 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 463 return; 464 } 465 466 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 467 CTR4(KTR_LOCK, 468 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 469 m->mtx_object.lo_name, (void *)m->mtx_lock, file, line); 470 471#ifdef MUTEX_PROFILING 472 contested = 0; 473#endif 474 while (!_obtain_lock(m, td)) { 475#ifdef MUTEX_PROFILING 476 contested = 1; 477 atomic_add_int(&m->mtx_contest_holding, 1); 478#endif 479 ts = turnstile_lookup(&m->mtx_object); 480 v = m->mtx_lock; 481 482 /* 483 * Check if the lock has been released while spinning for 484 * the turnstile chain lock. 485 */ 486 if (v == MTX_UNOWNED) { 487 turnstile_release(&m->mtx_object); 488 cpu_spinwait(); 489 continue; 490 } 491 492#ifdef MUTEX_WAKE_ALL 493 MPASS(v != MTX_CONTESTED); 494#else 495 /* 496 * The mutex was marked contested on release. This means that 497 * there are other threads blocked on it. Grab ownership of 498 * it and propagate its priority to the current thread if 499 * necessary. 500 */ 501 if (v == MTX_CONTESTED) { 502 MPASS(ts != NULL); 503 m->mtx_lock = (uintptr_t)td | MTX_CONTESTED; 504 turnstile_claim(ts); 505 break; 506 } 507#endif 508 509 /* 510 * If the mutex isn't already contested and a failure occurs 511 * setting the contested bit, the mutex was either released 512 * or the state of the MTX_RECURSED bit changed. 513 */ 514 if ((v & MTX_CONTESTED) == 0 && 515 !atomic_cmpset_ptr(&m->mtx_lock, (void *)v, 516 (void *)(v | MTX_CONTESTED))) { 517 turnstile_release(&m->mtx_object); 518 cpu_spinwait(); 519 continue; 520 } 521 522#if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 523 /* 524 * If the current owner of the lock is executing on another 525 * CPU, spin instead of blocking. 526 */ 527 owner = (struct thread *)(v & MTX_FLAGMASK); 528#ifdef ADAPTIVE_GIANT 529 if (TD_IS_RUNNING(owner)) { 530#else 531 if (m != &Giant && TD_IS_RUNNING(owner)) { 532#endif 533 turnstile_release(&m->mtx_object); 534 while (mtx_owner(m) == owner && TD_IS_RUNNING(owner)) { 535 cpu_spinwait(); 536 } 537 continue; 538 } 539#endif /* SMP && !NO_ADAPTIVE_MUTEXES */ 540 541 /* 542 * We definitely must sleep for this lock. 543 */ 544 mtx_assert(m, MA_NOTOWNED); 545 546#ifdef KTR 547 if (!cont_logged) { 548 CTR6(KTR_CONTENTION, 549 "contention: %p at %s:%d wants %s, taken by %s:%d", 550 td, file, line, m->mtx_object.lo_name, 551 WITNESS_FILE(&m->mtx_object), 552 WITNESS_LINE(&m->mtx_object)); 553 cont_logged = 1; 554 } 555#endif 556 557 /* 558 * Block on the turnstile. 559 */ 560 turnstile_wait(ts, &m->mtx_object, mtx_owner(m)); 561 } 562 563#ifdef KTR 564 if (cont_logged) { 565 CTR4(KTR_CONTENTION, 566 "contention end: %s acquired by %p at %s:%d", 567 m->mtx_object.lo_name, td, file, line); 568 } 569#endif 570#ifdef MUTEX_PROFILING 571 if (contested) 572 m->mtx_contest_locking++; 573 m->mtx_contest_holding = 0; 574#endif 575 return; 576} 577 578/* 579 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. 580 * 581 * This is only called if we need to actually spin for the lock. Recursion 582 * is handled inline. 583 */ 584void 585_mtx_lock_spin(struct mtx *m, struct thread *td, int opts, const char *file, 586 int line) 587{ 588 int i = 0; 589 590 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 591 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 592 593 for (;;) { 594 if (_obtain_lock(m, td)) 595 break; 596 597 /* Give interrupts a chance while we spin. */ 598 critical_exit(); 599 while (m->mtx_lock != MTX_UNOWNED) { 600 if (i++ < 10000000) { 601 cpu_spinwait(); 602 continue; 603 } 604 if (i < 60000000) 605 DELAY(1); 606 else if (!kdb_active) { 607 printf("spin lock %s held by %p for > 5 seconds\n", 608 m->mtx_object.lo_name, (void *)m->mtx_lock); 609#ifdef WITNESS 610 witness_display_spinlock(&m->mtx_object, 611 mtx_owner(m)); 612#endif 613 panic("spin lock held too long"); 614 } 615 cpu_spinwait(); 616 } 617 critical_enter(); 618 } 619 620 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 621 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 622 623 return; 624} 625 626/* 627 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 628 * 629 * We are only called here if the lock is recursed or contested (i.e. we 630 * need to wake up a blocked thread). 631 */ 632void 633_mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) 634{ 635 struct turnstile *ts; 636#ifndef PREEMPTION 637 struct thread *td, *td1; 638#endif 639 640 if (mtx_recursed(m)) { 641 if (--(m->mtx_recurse) == 0) 642 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 643 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 644 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 645 return; 646 } 647 648 ts = turnstile_lookup(&m->mtx_object); 649 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 650 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 651 652#if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 653 if (ts == NULL) { 654 _release_lock_quick(m); 655 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 656 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p no sleepers", m); 657 turnstile_release(&m->mtx_object); 658 return; 659 } 660#else 661 MPASS(ts != NULL); 662#endif 663#ifndef PREEMPTION 664 /* XXX */ 665 td1 = turnstile_head(ts); 666#endif 667#ifdef MUTEX_WAKE_ALL 668 turnstile_broadcast(ts); 669 _release_lock_quick(m); 670#else 671 if (turnstile_signal(ts)) { 672 _release_lock_quick(m); 673 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 674 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m); 675 } else { 676 m->mtx_lock = MTX_CONTESTED; 677 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 678 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p still contested", 679 m); 680 } 681#endif 682 turnstile_unpend(ts); 683 684#ifndef PREEMPTION 685 /* 686 * XXX: This is just a hack until preemption is done. However, 687 * once preemption is done we need to either wrap the 688 * turnstile_signal() and release of the actual lock in an 689 * extra critical section or change the preemption code to 690 * always just set a flag and never do instant-preempts. 691 */ 692 td = curthread; 693 if (td->td_critnest > 0 || td1->td_priority >= td->td_priority) 694 return; 695 mtx_lock_spin(&sched_lock); 696 if (!TD_IS_RUNNING(td1)) { 697#ifdef notyet 698 if (td->td_ithd != NULL) { 699 struct ithd *it = td->td_ithd; 700 701 if (it->it_interrupted) { 702 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 703 CTR2(KTR_LOCK, 704 "_mtx_unlock_sleep: %p interrupted %p", 705 it, it->it_interrupted); 706 intr_thd_fixup(it); 707 } 708 } 709#endif 710 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 711 CTR2(KTR_LOCK, 712 "_mtx_unlock_sleep: %p switching out lock=%p", m, 713 (void *)m->mtx_lock); 714 715 mi_switch(SW_INVOL, NULL); 716 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 717 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p", 718 m, (void *)m->mtx_lock); 719 } 720 mtx_unlock_spin(&sched_lock); 721#endif 722 723 return; 724} 725 726/* 727 * All the unlocking of MTX_SPIN locks is done inline. 728 * See the _rel_spin_lock() macro for the details. 729 */ 730 731/* 732 * The backing function for the INVARIANTS-enabled mtx_assert() 733 */ 734#ifdef INVARIANT_SUPPORT 735void 736_mtx_assert(struct mtx *m, int what, const char *file, int line) 737{ 738 739 if (panicstr != NULL) 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->mtx_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->mtx_object.lo_name, file, line); 752 } else if ((what & MA_RECURSED) != 0) { 753 panic("mutex %s unrecursed at %s:%d", 754 m->mtx_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->mtx_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 776void mtx_validate(struct mtx *); 777 778void 779mtx_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 * XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly 788 * we can re-enable the kernacc() checks. 789 */ 790#ifndef __alpha__ 791 /* 792 * Can't call kernacc() from early init386(), especially when 793 * initializing Giant mutex, because some stuff in kernacc() 794 * requires Giant itself. 795 */ 796 if (!cold) 797 if (!kernacc((caddr_t)m, sizeof(m), 798 VM_PROT_READ | VM_PROT_WRITE)) 799 panic("Can't read and write to mutex %p", m); 800#endif 801#endif 802} 803#endif 804 805/* 806 * General init routine used by the MTX_SYSINIT() macro. 807 */ 808void 809mtx_sysinit(void *arg) 810{ 811 struct mtx_args *margs = arg; 812 813 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); 814} 815 816/* 817 * Mutex initialization routine; initialize lock `m' of type contained in 818 * `opts' with options contained in `opts' and name `name.' The optional 819 * lock type `type' is used as a general lock category name for use with 820 * witness. 821 */ 822void 823mtx_init(struct mtx *m, const char *name, const char *type, int opts) 824{ 825 struct lock_object *lock; 826 827 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 828 MTX_NOWITNESS | MTX_DUPOK)) == 0); 829 830#ifdef MUTEX_DEBUG 831 /* Diagnostic and error correction */ 832 mtx_validate(m); 833#endif 834 835 lock = &m->mtx_object; 836 KASSERT((lock->lo_flags & LO_INITIALIZED) == 0, 837 ("mutex \"%s\" %p already initialized", name, m)); 838 bzero(m, sizeof(*m)); 839 if (opts & MTX_SPIN) 840 lock->lo_class = &lock_class_mtx_spin; 841 else 842 lock->lo_class = &lock_class_mtx_sleep; 843 lock->lo_name = name; 844 lock->lo_type = type != NULL ? type : name; 845 if (opts & MTX_QUIET) 846 lock->lo_flags = LO_QUIET; 847 if (opts & MTX_RECURSE) 848 lock->lo_flags |= LO_RECURSABLE; 849 if ((opts & MTX_NOWITNESS) == 0) 850 lock->lo_flags |= LO_WITNESS; 851 if (opts & MTX_DUPOK) 852 lock->lo_flags |= LO_DUPOK; 853 854 m->mtx_lock = MTX_UNOWNED; 855 856 LOCK_LOG_INIT(lock, opts); 857 858 WITNESS_INIT(lock); 859} 860 861/* 862 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 863 * passed in as a flag here because if the corresponding mtx_init() was 864 * called with MTX_QUIET set, then it will already be set in the mutex's 865 * flags. 866 */ 867void 868mtx_destroy(struct mtx *m) 869{ 870 871 LOCK_LOG_DESTROY(&m->mtx_object, 0); 872 873 if (!mtx_owned(m)) 874 MPASS(mtx_unowned(m)); 875 else { 876 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 877 878 /* Tell witness this isn't locked to make it happy. */ 879 WITNESS_UNLOCK(&m->mtx_object, LOP_EXCLUSIVE, __FILE__, 880 __LINE__); 881 } 882 883 WITNESS_DESTROY(&m->mtx_object); 884} 885 886/* 887 * Intialize the mutex code and system mutexes. This is called from the MD 888 * startup code prior to mi_startup(). The per-CPU data space needs to be 889 * setup before this is called. 890 */ 891void 892mutex_init(void) 893{ 894 895 /* Setup thread0 so that mutexes work. */ 896 LIST_INIT(&thread0.td_contested); 897 898 /* Setup turnstiles so that sleep mutexes work. */ 899 init_turnstiles(); 900 901 /* 902 * Initialize mutexes. 903 */ 904 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 905 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE); 906 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 907 mtx_lock(&Giant); 908} 909