kern_mutex.c revision 148557
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 148557 2005-07-30 05:54:30Z ps $"); 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/conf.h> 49#include <sys/kdb.h> 50#include <sys/kernel.h> 51#include <sys/ktr.h> 52#include <sys/lock.h> 53#include <sys/malloc.h> 54#include <sys/mutex.h> 55#include <sys/proc.h> 56#include <sys/resourcevar.h> 57#include <sys/sched.h> 58#include <sys/sbuf.h> 59#include <sys/sysctl.h> 60#include <sys/turnstile.h> 61#include <sys/vmmeter.h> 62 63#include <machine/atomic.h> 64#include <machine/bus.h> 65#include <machine/clock.h> 66#include <machine/cpu.h> 67 68#include <ddb/ddb.h> 69 70#include <vm/vm.h> 71#include <vm/vm_extern.h> 72 73/* 74 * Force MUTEX_WAKE_ALL for now. 75 * single thread wakeup needs fixes to avoid race conditions with 76 * priority inheritance. 77 */ 78#ifndef MUTEX_WAKE_ALL 79#define MUTEX_WAKE_ALL 80#endif 81 82/* 83 * Internal utility macros. 84 */ 85#define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED) 86 87#define mtx_owner(m) (mtx_unowned((m)) ? NULL \ 88 : (struct thread *)((m)->mtx_lock & MTX_FLAGMASK)) 89 90/* 91 * Lock classes for sleep and spin mutexes. 92 */ 93struct lock_class lock_class_mtx_sleep = { 94 "sleep mutex", 95 LC_SLEEPLOCK | LC_RECURSABLE 96}; 97struct lock_class lock_class_mtx_spin = { 98 "spin mutex", 99 LC_SPINLOCK | LC_RECURSABLE 100}; 101 102/* 103 * System-wide mutexes 104 */ 105struct mtx sched_lock; 106struct mtx Giant; 107 108#ifdef MUTEX_PROFILING 109SYSCTL_NODE(_debug, OID_AUTO, mutex, CTLFLAG_RD, NULL, "mutex debugging"); 110SYSCTL_NODE(_debug_mutex, OID_AUTO, prof, CTLFLAG_RD, NULL, "mutex profiling"); 111static int mutex_prof_enable = 0; 112SYSCTL_INT(_debug_mutex_prof, OID_AUTO, enable, CTLFLAG_RW, 113 &mutex_prof_enable, 0, "Enable tracing of mutex holdtime"); 114 115struct mutex_prof { 116 const char *name; 117 const char *file; 118 int line; 119 uintmax_t cnt_max; 120 uintmax_t cnt_tot; 121 uintmax_t cnt_cur; 122 uintmax_t cnt_contest_holding; 123 uintmax_t cnt_contest_locking; 124 struct mutex_prof *next; 125}; 126 127/* 128 * mprof_buf is a static pool of profiling records to avoid possible 129 * reentrance of the memory allocation functions. 130 * 131 * Note: NUM_MPROF_BUFFERS must be smaller than MPROF_HASH_SIZE. 132 */ 133#ifdef MPROF_BUFFERS 134#define NUM_MPROF_BUFFERS MPROF_BUFFERS 135#else 136#define NUM_MPROF_BUFFERS 1000 137#endif 138static struct mutex_prof mprof_buf[NUM_MPROF_BUFFERS]; 139static int first_free_mprof_buf; 140#ifndef MPROF_HASH_SIZE 141#define MPROF_HASH_SIZE 1009 142#endif 143#if NUM_MPROF_BUFFERS >= MPROF_HASH_SIZE 144#error MPROF_BUFFERS must be larger than MPROF_HASH_SIZE 145#endif 146static struct mutex_prof *mprof_hash[MPROF_HASH_SIZE]; 147/* SWAG: sbuf size = avg stat. line size * number of locks */ 148#define MPROF_SBUF_SIZE 256 * 400 149 150static int mutex_prof_acquisitions; 151SYSCTL_INT(_debug_mutex_prof, OID_AUTO, acquisitions, CTLFLAG_RD, 152 &mutex_prof_acquisitions, 0, "Number of mutex acquistions recorded"); 153static int mutex_prof_records; 154SYSCTL_INT(_debug_mutex_prof, OID_AUTO, records, CTLFLAG_RD, 155 &mutex_prof_records, 0, "Number of profiling records"); 156static int mutex_prof_maxrecords = NUM_MPROF_BUFFERS; 157SYSCTL_INT(_debug_mutex_prof, OID_AUTO, maxrecords, CTLFLAG_RD, 158 &mutex_prof_maxrecords, 0, "Maximum number of profiling records"); 159static int mutex_prof_rejected; 160SYSCTL_INT(_debug_mutex_prof, OID_AUTO, rejected, CTLFLAG_RD, 161 &mutex_prof_rejected, 0, "Number of rejected profiling records"); 162static int mutex_prof_hashsize = MPROF_HASH_SIZE; 163SYSCTL_INT(_debug_mutex_prof, OID_AUTO, hashsize, CTLFLAG_RD, 164 &mutex_prof_hashsize, 0, "Hash size"); 165static int mutex_prof_collisions = 0; 166SYSCTL_INT(_debug_mutex_prof, OID_AUTO, collisions, CTLFLAG_RD, 167 &mutex_prof_collisions, 0, "Number of hash collisions"); 168 169/* 170 * mprof_mtx protects the profiling buffers and the hash. 171 */ 172static struct mtx mprof_mtx; 173MTX_SYSINIT(mprof, &mprof_mtx, "mutex profiling lock", MTX_SPIN | MTX_QUIET); 174 175static u_int64_t 176nanoseconds(void) 177{ 178 struct timespec tv; 179 180 nanotime(&tv); 181 return (tv.tv_sec * (u_int64_t)1000000000 + tv.tv_nsec); 182} 183 184static int 185dump_mutex_prof_stats(SYSCTL_HANDLER_ARGS) 186{ 187 struct sbuf *sb; 188 int error, i; 189 static int multiplier = 1; 190 191 if (first_free_mprof_buf == 0) 192 return (SYSCTL_OUT(req, "No locking recorded", 193 sizeof("No locking recorded"))); 194 195retry_sbufops: 196 sb = sbuf_new(NULL, NULL, MPROF_SBUF_SIZE * multiplier, SBUF_FIXEDLEN); 197 sbuf_printf(sb, "\n%6s %12s %11s %5s %12s %12s %s\n", 198 "max", "total", "count", "avg", "cnt_hold", "cnt_lock", "name"); 199 /* 200 * XXX this spinlock seems to be by far the largest perpetrator 201 * of spinlock latency (1.6 msec on an Athlon1600 was recorded 202 * even before I pessimized it further by moving the average 203 * computation here). 204 */ 205 mtx_lock_spin(&mprof_mtx); 206 for (i = 0; i < first_free_mprof_buf; ++i) { 207 sbuf_printf(sb, "%6ju %12ju %11ju %5ju %12ju %12ju %s:%d (%s)\n", 208 mprof_buf[i].cnt_max / 1000, 209 mprof_buf[i].cnt_tot / 1000, 210 mprof_buf[i].cnt_cur, 211 mprof_buf[i].cnt_cur == 0 ? (uintmax_t)0 : 212 mprof_buf[i].cnt_tot / (mprof_buf[i].cnt_cur * 1000), 213 mprof_buf[i].cnt_contest_holding, 214 mprof_buf[i].cnt_contest_locking, 215 mprof_buf[i].file, mprof_buf[i].line, mprof_buf[i].name); 216 if (sbuf_overflowed(sb)) { 217 mtx_unlock_spin(&mprof_mtx); 218 sbuf_delete(sb); 219 multiplier++; 220 goto retry_sbufops; 221 } 222 } 223 mtx_unlock_spin(&mprof_mtx); 224 sbuf_finish(sb); 225 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1); 226 sbuf_delete(sb); 227 return (error); 228} 229SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD, 230 NULL, 0, dump_mutex_prof_stats, "A", "Mutex profiling statistics"); 231 232static int 233reset_mutex_prof_stats(SYSCTL_HANDLER_ARGS) 234{ 235 int error, v; 236 237 if (first_free_mprof_buf == 0) 238 return (0); 239 240 v = 0; 241 error = sysctl_handle_int(oidp, &v, 0, req); 242 if (error) 243 return (error); 244 if (req->newptr == NULL) 245 return (error); 246 if (v == 0) 247 return (0); 248 249 mtx_lock_spin(&mprof_mtx); 250 bzero(mprof_buf, sizeof(*mprof_buf) * first_free_mprof_buf); 251 bzero(mprof_hash, sizeof(struct mtx *) * MPROF_HASH_SIZE); 252 first_free_mprof_buf = 0; 253 mtx_unlock_spin(&mprof_mtx); 254 return (0); 255} 256SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW, 257 NULL, 0, reset_mutex_prof_stats, "I", "Reset mutex profiling statistics"); 258#endif 259 260/* 261 * Function versions of the inlined __mtx_* macros. These are used by 262 * modules and can also be called from assembly language if needed. 263 */ 264void 265_mtx_lock_flags(struct mtx *m, int opts, const char *file, int line) 266{ 267 268 MPASS(curthread != NULL); 269 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 270 ("mtx_lock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 271 file, line)); 272 WITNESS_CHECKORDER(&m->mtx_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 273 file, line); 274 _get_sleep_lock(m, curthread, opts, file, line); 275 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 276 line); 277 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 278#ifdef MUTEX_PROFILING 279 /* don't reset the timer when/if recursing */ 280 if (m->mtx_acqtime == 0) { 281 m->mtx_filename = file; 282 m->mtx_lineno = line; 283 m->mtx_acqtime = mutex_prof_enable ? nanoseconds() : 0; 284 ++mutex_prof_acquisitions; 285 } 286#endif 287} 288 289void 290_mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) 291{ 292 293 MPASS(curthread != NULL); 294 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 295 ("mtx_unlock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 296 file, line)); 297 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 298 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 299 line); 300 mtx_assert(m, MA_OWNED); 301#ifdef MUTEX_PROFILING 302 if (m->mtx_acqtime != 0) { 303 static const char *unknown = "(unknown)"; 304 struct mutex_prof *mpp; 305 u_int64_t acqtime, now; 306 const char *p, *q; 307 volatile u_int hash; 308 309 now = nanoseconds(); 310 acqtime = m->mtx_acqtime; 311 m->mtx_acqtime = 0; 312 if (now <= acqtime) 313 goto out; 314 for (p = m->mtx_filename; 315 p != NULL && strncmp(p, "../", 3) == 0; p += 3) 316 /* nothing */ ; 317 if (p == NULL || *p == '\0') 318 p = unknown; 319 for (hash = m->mtx_lineno, q = p; *q != '\0'; ++q) 320 hash = (hash * 2 + *q) % MPROF_HASH_SIZE; 321 mtx_lock_spin(&mprof_mtx); 322 for (mpp = mprof_hash[hash]; mpp != NULL; mpp = mpp->next) 323 if (mpp->line == m->mtx_lineno && 324 strcmp(mpp->file, p) == 0) 325 break; 326 if (mpp == NULL) { 327 /* Just exit if we cannot get a trace buffer */ 328 if (first_free_mprof_buf >= NUM_MPROF_BUFFERS) { 329 ++mutex_prof_rejected; 330 goto unlock; 331 } 332 mpp = &mprof_buf[first_free_mprof_buf++]; 333 mpp->name = mtx_name(m); 334 mpp->file = p; 335 mpp->line = m->mtx_lineno; 336 mpp->next = mprof_hash[hash]; 337 if (mprof_hash[hash] != NULL) 338 ++mutex_prof_collisions; 339 mprof_hash[hash] = mpp; 340 ++mutex_prof_records; 341 } 342 /* 343 * Record if the mutex has been held longer now than ever 344 * before. 345 */ 346 if (now - acqtime > mpp->cnt_max) 347 mpp->cnt_max = now - acqtime; 348 mpp->cnt_tot += now - acqtime; 349 mpp->cnt_cur++; 350 /* 351 * There's a small race, really we should cmpxchg 352 * 0 with the current value, but that would bill 353 * the contention to the wrong lock instance if 354 * it followed this also. 355 */ 356 mpp->cnt_contest_holding += m->mtx_contest_holding; 357 m->mtx_contest_holding = 0; 358 mpp->cnt_contest_locking += m->mtx_contest_locking; 359 m->mtx_contest_locking = 0; 360unlock: 361 mtx_unlock_spin(&mprof_mtx); 362 } 363out: 364#endif 365 _rel_sleep_lock(m, curthread, opts, file, line); 366} 367 368void 369_mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) 370{ 371 372 MPASS(curthread != NULL); 373 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 374 ("mtx_lock_spin() of sleep mutex %s @ %s:%d", 375 m->mtx_object.lo_name, file, line)); 376 WITNESS_CHECKORDER(&m->mtx_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 377 file, line); 378 _get_spin_lock(m, curthread, opts, file, line); 379 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 380 line); 381 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 382} 383 384void 385_mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line) 386{ 387 388 MPASS(curthread != NULL); 389 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 390 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 391 m->mtx_object.lo_name, file, line)); 392 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 393 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 394 line); 395 mtx_assert(m, MA_OWNED); 396 _rel_spin_lock(m); 397} 398 399/* 400 * The important part of mtx_trylock{,_flags}() 401 * Tries to acquire lock `m.' If this function is called on a mutex that 402 * is already owned, it will recursively acquire the lock. 403 */ 404int 405_mtx_trylock(struct mtx *m, int opts, const char *file, int line) 406{ 407 int rval; 408 409 MPASS(curthread != NULL); 410 411 if (mtx_owned(m) && (m->mtx_object.lo_flags & LO_RECURSABLE) != 0) { 412 m->mtx_recurse++; 413 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 414 rval = 1; 415 } else 416 rval = _obtain_lock(m, (uintptr_t)curthread); 417 418 LOCK_LOG_TRY("LOCK", &m->mtx_object, opts, rval, file, line); 419 if (rval) 420 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 421 file, line); 422 423 return (rval); 424} 425 426/* 427 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 428 * 429 * We call this if the lock is either contested (i.e. we need to go to 430 * sleep waiting for it), or if we need to recurse on it. 431 */ 432void 433_mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file, 434 int line) 435{ 436#if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 437 struct thread *owner; 438#endif 439 uintptr_t v; 440#ifdef KTR 441 int cont_logged = 0; 442#endif 443#ifdef MUTEX_PROFILING 444 int contested; 445#endif 446 447 if (mtx_owned(m)) { 448 KASSERT((m->mtx_object.lo_flags & LO_RECURSABLE) != 0, 449 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n", 450 m->mtx_object.lo_name, file, line)); 451 m->mtx_recurse++; 452 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 453 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 454 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 455 return; 456 } 457 458 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 459 CTR4(KTR_LOCK, 460 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 461 m->mtx_object.lo_name, (void *)m->mtx_lock, file, line); 462 463#ifdef MUTEX_PROFILING 464 contested = 0; 465#endif 466 while (!_obtain_lock(m, tid)) { 467#ifdef MUTEX_PROFILING 468 contested = 1; 469 atomic_add_int(&m->mtx_contest_holding, 1); 470#endif 471 turnstile_lock(&m->mtx_object); 472 v = m->mtx_lock; 473 474 /* 475 * Check if the lock has been released while spinning for 476 * the turnstile chain lock. 477 */ 478 if (v == MTX_UNOWNED) { 479 turnstile_release(&m->mtx_object); 480 cpu_spinwait(); 481 continue; 482 } 483 484#ifdef MUTEX_WAKE_ALL 485 MPASS(v != MTX_CONTESTED); 486#else 487 /* 488 * The mutex was marked contested on release. This means that 489 * there are other threads blocked on it. Grab ownership of 490 * it and propagate its priority to the current thread if 491 * necessary. 492 */ 493 if (v == MTX_CONTESTED) { 494 m->mtx_lock = tid | MTX_CONTESTED; 495 turnstile_claim(&m->mtx_object); 496 break; 497 } 498#endif 499 500 /* 501 * If the mutex isn't already contested and a failure occurs 502 * setting the contested bit, the mutex was either released 503 * or the state of the MTX_RECURSED bit changed. 504 */ 505 if ((v & MTX_CONTESTED) == 0 && 506 !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) { 507 turnstile_release(&m->mtx_object); 508 cpu_spinwait(); 509 continue; 510 } 511 512#if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 513 /* 514 * If the current owner of the lock is executing on another 515 * CPU, spin instead of blocking. 516 */ 517 owner = (struct thread *)(v & MTX_FLAGMASK); 518#ifdef ADAPTIVE_GIANT 519 if (TD_IS_RUNNING(owner)) { 520#else 521 if (m != &Giant && TD_IS_RUNNING(owner)) { 522#endif 523 turnstile_release(&m->mtx_object); 524 while (mtx_owner(m) == owner && TD_IS_RUNNING(owner)) { 525 cpu_spinwait(); 526 } 527 continue; 528 } 529#endif /* SMP && !NO_ADAPTIVE_MUTEXES */ 530 531 /* 532 * We definitely must sleep for this lock. 533 */ 534 mtx_assert(m, MA_NOTOWNED); 535 536#ifdef KTR 537 if (!cont_logged) { 538 CTR6(KTR_CONTENTION, 539 "contention: %p at %s:%d wants %s, taken by %s:%d", 540 (void *)tid, file, line, m->mtx_object.lo_name, 541 WITNESS_FILE(&m->mtx_object), 542 WITNESS_LINE(&m->mtx_object)); 543 cont_logged = 1; 544 } 545#endif 546 547 /* 548 * Block on the turnstile. 549 */ 550 turnstile_wait(&m->mtx_object, mtx_owner(m)); 551 } 552 553#ifdef KTR 554 if (cont_logged) { 555 CTR4(KTR_CONTENTION, 556 "contention end: %s acquired by %p at %s:%d", 557 m->mtx_object.lo_name, (void *)tid, file, line); 558 } 559#endif 560#ifdef MUTEX_PROFILING 561 if (contested) 562 m->mtx_contest_locking++; 563 m->mtx_contest_holding = 0; 564#endif 565 return; 566} 567 568#ifdef SMP 569/* 570 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. 571 * 572 * This is only called if we need to actually spin for the lock. Recursion 573 * is handled inline. 574 */ 575void 576_mtx_lock_spin(struct mtx *m, uintptr_t tid, int opts, const char *file, 577 int line) 578{ 579 int i = 0; 580 581 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 582 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 583 584 for (;;) { 585 if (_obtain_lock(m, tid)) 586 break; 587 588 /* Give interrupts a chance while we spin. */ 589 spinlock_exit(); 590 while (m->mtx_lock != MTX_UNOWNED) { 591 if (i++ < 10000000) { 592 cpu_spinwait(); 593 continue; 594 } 595 if (i < 60000000) 596 DELAY(1); 597 else if (!kdb_active) { 598 printf("spin lock %s held by %p for > 5 seconds\n", 599 m->mtx_object.lo_name, (void *)m->mtx_lock); 600#ifdef WITNESS 601 witness_display_spinlock(&m->mtx_object, 602 mtx_owner(m)); 603#endif 604 panic("spin lock held too long"); 605 } 606 cpu_spinwait(); 607 } 608 spinlock_enter(); 609 } 610 611 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 612 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 613 614 return; 615} 616#endif /* SMP */ 617 618/* 619 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 620 * 621 * We are only called here if the lock is recursed or contested (i.e. we 622 * need to wake up a blocked thread). 623 */ 624void 625_mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) 626{ 627 struct turnstile *ts; 628#ifndef PREEMPTION 629 struct thread *td, *td1; 630#endif 631 632 if (mtx_recursed(m)) { 633 if (--(m->mtx_recurse) == 0) 634 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 635 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 636 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 637 return; 638 } 639 640 turnstile_lock(&m->mtx_object); 641 ts = turnstile_lookup(&m->mtx_object); 642 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 643 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 644 645#if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 646 if (ts == NULL) { 647 _release_lock_quick(m); 648 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 649 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p no sleepers", m); 650 turnstile_release(&m->mtx_object); 651 return; 652 } 653#else 654 MPASS(ts != NULL); 655#endif 656#ifndef PREEMPTION 657 /* XXX */ 658 td1 = turnstile_head(ts); 659#endif 660#ifdef MUTEX_WAKE_ALL 661 turnstile_broadcast(ts); 662 _release_lock_quick(m); 663#else 664 if (turnstile_signal(ts)) { 665 _release_lock_quick(m); 666 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 667 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m); 668 } else { 669 m->mtx_lock = MTX_CONTESTED; 670 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 671 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p still contested", 672 m); 673 } 674#endif 675 turnstile_unpend(ts); 676 677#ifndef PREEMPTION 678 /* 679 * XXX: This is just a hack until preemption is done. However, 680 * once preemption is done we need to either wrap the 681 * turnstile_signal() and release of the actual lock in an 682 * extra critical section or change the preemption code to 683 * always just set a flag and never do instant-preempts. 684 */ 685 td = curthread; 686 if (td->td_critnest > 0 || td1->td_priority >= td->td_priority) 687 return; 688 mtx_lock_spin(&sched_lock); 689 if (!TD_IS_RUNNING(td1)) { 690#ifdef notyet 691 if (td->td_ithd != NULL) { 692 struct ithd *it = td->td_ithd; 693 694 if (it->it_interrupted) { 695 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 696 CTR2(KTR_LOCK, 697 "_mtx_unlock_sleep: %p interrupted %p", 698 it, it->it_interrupted); 699 intr_thd_fixup(it); 700 } 701 } 702#endif 703 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 704 CTR2(KTR_LOCK, 705 "_mtx_unlock_sleep: %p switching out lock=%p", m, 706 (void *)m->mtx_lock); 707 708 mi_switch(SW_INVOL, NULL); 709 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 710 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p", 711 m, (void *)m->mtx_lock); 712 } 713 mtx_unlock_spin(&sched_lock); 714#endif 715 716 return; 717} 718 719/* 720 * All the unlocking of MTX_SPIN locks is done inline. 721 * See the _rel_spin_lock() macro for the details. 722 */ 723 724/* 725 * The backing function for the INVARIANTS-enabled mtx_assert() 726 */ 727#ifdef INVARIANT_SUPPORT 728void 729_mtx_assert(struct mtx *m, int what, const char *file, int line) 730{ 731 732 if (panicstr != NULL || dumping) 733 return; 734 switch (what) { 735 case MA_OWNED: 736 case MA_OWNED | MA_RECURSED: 737 case MA_OWNED | MA_NOTRECURSED: 738 if (!mtx_owned(m)) 739 panic("mutex %s not owned at %s:%d", 740 m->mtx_object.lo_name, file, line); 741 if (mtx_recursed(m)) { 742 if ((what & MA_NOTRECURSED) != 0) 743 panic("mutex %s recursed at %s:%d", 744 m->mtx_object.lo_name, file, line); 745 } else if ((what & MA_RECURSED) != 0) { 746 panic("mutex %s unrecursed at %s:%d", 747 m->mtx_object.lo_name, file, line); 748 } 749 break; 750 case MA_NOTOWNED: 751 if (mtx_owned(m)) 752 panic("mutex %s owned at %s:%d", 753 m->mtx_object.lo_name, file, line); 754 break; 755 default: 756 panic("unknown mtx_assert at %s:%d", file, line); 757 } 758} 759#endif 760 761/* 762 * The MUTEX_DEBUG-enabled mtx_validate() 763 * 764 * Most of these checks have been moved off into the LO_INITIALIZED flag 765 * maintained by the witness code. 766 */ 767#ifdef MUTEX_DEBUG 768 769void mtx_validate(struct mtx *); 770 771void 772mtx_validate(struct mtx *m) 773{ 774 775/* 776 * XXX: When kernacc() does not require Giant we can reenable this check 777 */ 778#ifdef notyet 779/* 780 * XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly 781 * we can re-enable the kernacc() checks. 782 */ 783#ifndef __alpha__ 784 /* 785 * Can't call kernacc() from early init386(), especially when 786 * initializing Giant mutex, because some stuff in kernacc() 787 * requires Giant itself. 788 */ 789 if (!cold) 790 if (!kernacc((caddr_t)m, sizeof(m), 791 VM_PROT_READ | VM_PROT_WRITE)) 792 panic("Can't read and write to mutex %p", m); 793#endif 794#endif 795} 796#endif 797 798/* 799 * General init routine used by the MTX_SYSINIT() macro. 800 */ 801void 802mtx_sysinit(void *arg) 803{ 804 struct mtx_args *margs = arg; 805 806 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); 807} 808 809/* 810 * Mutex initialization routine; initialize lock `m' of type contained in 811 * `opts' with options contained in `opts' and name `name.' The optional 812 * lock type `type' is used as a general lock category name for use with 813 * witness. 814 */ 815void 816mtx_init(struct mtx *m, const char *name, const char *type, int opts) 817{ 818 struct lock_object *lock; 819 820 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 821 MTX_NOWITNESS | MTX_DUPOK)) == 0); 822 823#ifdef MUTEX_DEBUG 824 /* Diagnostic and error correction */ 825 mtx_validate(m); 826#endif 827 828 lock = &m->mtx_object; 829 KASSERT((lock->lo_flags & LO_INITIALIZED) == 0, 830 ("mutex \"%s\" %p already initialized", name, m)); 831 bzero(m, sizeof(*m)); 832 if (opts & MTX_SPIN) 833 lock->lo_class = &lock_class_mtx_spin; 834 else 835 lock->lo_class = &lock_class_mtx_sleep; 836 lock->lo_name = name; 837 lock->lo_type = type != NULL ? type : name; 838 if (opts & MTX_QUIET) 839 lock->lo_flags = LO_QUIET; 840 if (opts & MTX_RECURSE) 841 lock->lo_flags |= LO_RECURSABLE; 842 if ((opts & MTX_NOWITNESS) == 0) 843 lock->lo_flags |= LO_WITNESS; 844 if (opts & MTX_DUPOK) 845 lock->lo_flags |= LO_DUPOK; 846 847 m->mtx_lock = MTX_UNOWNED; 848 849 LOCK_LOG_INIT(lock, opts); 850 851 WITNESS_INIT(lock); 852} 853 854/* 855 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 856 * passed in as a flag here because if the corresponding mtx_init() was 857 * called with MTX_QUIET set, then it will already be set in the mutex's 858 * flags. 859 */ 860void 861mtx_destroy(struct mtx *m) 862{ 863 864 LOCK_LOG_DESTROY(&m->mtx_object, 0); 865 866 if (!mtx_owned(m)) 867 MPASS(mtx_unowned(m)); 868 else { 869 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 870 871 /* Tell witness this isn't locked to make it happy. */ 872 WITNESS_UNLOCK(&m->mtx_object, LOP_EXCLUSIVE, __FILE__, 873 __LINE__); 874 } 875 876 WITNESS_DESTROY(&m->mtx_object); 877} 878 879/* 880 * Intialize the mutex code and system mutexes. This is called from the MD 881 * startup code prior to mi_startup(). The per-CPU data space needs to be 882 * setup before this is called. 883 */ 884void 885mutex_init(void) 886{ 887 888 /* Setup thread0 so that mutexes work. */ 889 LIST_INIT(&thread0.td_contested); 890 891 /* Setup turnstiles so that sleep mutexes work. */ 892 init_turnstiles(); 893 894 /* 895 * Initialize mutexes. 896 */ 897 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 898 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE); 899 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 900 mtx_lock(&Giant); 901} 902