kern_mutex.c revision 97836
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 * $FreeBSD: head/sys/kern/kern_mutex.c 97836 2002-06-04 21:50:02Z jhb $ 31 */ 32 33/* 34 * Machine independent bits of mutex implementation. 35 */ 36 37#include "opt_adaptive_mutexes.h" 38#include "opt_ddb.h" 39 40#include <sys/param.h> 41#include <sys/systm.h> 42#include <sys/bus.h> 43#include <sys/kernel.h> 44#include <sys/ktr.h> 45#include <sys/lock.h> 46#include <sys/malloc.h> 47#include <sys/mutex.h> 48#include <sys/proc.h> 49#include <sys/resourcevar.h> 50#include <sys/sbuf.h> 51#include <sys/stdint.h> 52#include <sys/sysctl.h> 53#include <sys/vmmeter.h> 54 55#include <machine/atomic.h> 56#include <machine/bus.h> 57#include <machine/clock.h> 58#include <machine/cpu.h> 59 60#include <ddb/ddb.h> 61 62#include <vm/vm.h> 63#include <vm/vm_extern.h> 64 65/* 66 * Internal utility macros. 67 */ 68#define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED) 69 70#define mtx_owner(m) (mtx_unowned((m)) ? NULL \ 71 : (struct thread *)((m)->mtx_lock & MTX_FLAGMASK)) 72 73#define thread_runnable(td) \ 74 ((td)->td_kse != NULL && (td)->td_kse->ke_oncpu != NOCPU) 75 76/* 77 * Lock classes for sleep and spin mutexes. 78 */ 79struct lock_class lock_class_mtx_sleep = { 80 "sleep mutex", 81 LC_SLEEPLOCK | LC_RECURSABLE 82}; 83struct lock_class lock_class_mtx_spin = { 84 "spin mutex", 85 LC_SPINLOCK | LC_RECURSABLE 86}; 87 88/* 89 * System-wide mutexes 90 */ 91struct mtx sched_lock; 92struct mtx Giant; 93 94/* 95 * Prototypes for non-exported routines. 96 */ 97static void propagate_priority(struct thread *); 98 99static void 100propagate_priority(struct thread *td) 101{ 102 int pri = td->td_priority; 103 struct mtx *m = td->td_blocked; 104 105 mtx_assert(&sched_lock, MA_OWNED); 106 for (;;) { 107 struct thread *td1; 108 109 td = mtx_owner(m); 110 111 if (td == NULL) { 112 /* 113 * This really isn't quite right. Really 114 * ought to bump priority of thread that 115 * next acquires the mutex. 116 */ 117 MPASS(m->mtx_lock == MTX_CONTESTED); 118 return; 119 } 120 121 MPASS(td->td_proc->p_magic == P_MAGIC); 122 KASSERT(td->td_proc->p_stat != SSLEEP, ("sleeping thread owns a mutex")); 123 if (td->td_priority <= pri) /* lower is higher priority */ 124 return; 125 126 /* 127 * Bump this thread's priority. 128 */ 129 td->td_priority = pri; 130 131 /* 132 * If lock holder is actually running, just bump priority. 133 */ 134 /* XXXKSE this test is not sufficient */ 135 if (thread_runnable(td)) { 136 MPASS(td->td_proc->p_stat == SRUN 137 || td->td_proc->p_stat == SZOMB 138 || td->td_proc->p_stat == SSTOP); 139 return; 140 } 141 142#ifndef SMP 143 /* 144 * For UP, we check to see if td is curthread (this shouldn't 145 * ever happen however as it would mean we are in a deadlock.) 146 */ 147 KASSERT(td != curthread, ("Deadlock detected")); 148#endif 149 150 /* 151 * If on run queue move to new run queue, and quit. 152 * XXXKSE this gets a lot more complicated under threads 153 * but try anyhow. 154 */ 155 if (td->td_proc->p_stat == SRUN) { 156 MPASS(td->td_blocked == NULL); 157 remrunqueue(td); 158 setrunqueue(td); 159 return; 160 } 161 162 /* 163 * If we aren't blocked on a mutex, we should be. 164 */ 165 KASSERT(td->td_proc->p_stat == SMTX, ( 166 "process %d(%s):%d holds %s but isn't blocked on a mutex\n", 167 td->td_proc->p_pid, td->td_proc->p_comm, td->td_proc->p_stat, 168 m->mtx_object.lo_name)); 169 170 /* 171 * Pick up the mutex that td is blocked on. 172 */ 173 m = td->td_blocked; 174 MPASS(m != NULL); 175 176 /* 177 * Check if the thread needs to be moved up on 178 * the blocked chain 179 */ 180 if (td == TAILQ_FIRST(&m->mtx_blocked)) { 181 continue; 182 } 183 184 td1 = TAILQ_PREV(td, threadqueue, td_blkq); 185 if (td1->td_priority <= pri) { 186 continue; 187 } 188 189 /* 190 * Remove thread from blocked chain and determine where 191 * it should be moved up to. Since we know that td1 has 192 * a lower priority than td, we know that at least one 193 * thread in the chain has a lower priority and that 194 * td1 will thus not be NULL after the loop. 195 */ 196 TAILQ_REMOVE(&m->mtx_blocked, td, td_blkq); 197 TAILQ_FOREACH(td1, &m->mtx_blocked, td_blkq) { 198 MPASS(td1->td_proc->p_magic == P_MAGIC); 199 if (td1->td_priority > pri) 200 break; 201 } 202 203 MPASS(td1 != NULL); 204 TAILQ_INSERT_BEFORE(td1, td, td_blkq); 205 CTR4(KTR_LOCK, 206 "propagate_priority: p %p moved before %p on [%p] %s", 207 td, td1, m, m->mtx_object.lo_name); 208 } 209} 210 211#ifdef MUTEX_PROFILING 212SYSCTL_NODE(_debug, OID_AUTO, mutex, CTLFLAG_RD, NULL, "mutex debugging"); 213SYSCTL_NODE(_debug_mutex, OID_AUTO, prof, CTLFLAG_RD, NULL, "mutex profiling"); 214static int mutex_prof_enable = 0; 215SYSCTL_INT(_debug_mutex_prof, OID_AUTO, enable, CTLFLAG_RW, 216 &mutex_prof_enable, 0, "Enable tracing of mutex holdtime"); 217 218struct mutex_prof { 219 const char *name; 220 const char *file; 221 int line; 222#define MPROF_MAX 0 223#define MPROF_TOT 1 224#define MPROF_CNT 2 225#define MPROF_AVG 3 226 uintmax_t counter[4]; 227 struct mutex_prof *next; 228}; 229 230/* 231 * mprof_buf is a static pool of profiling records to avoid possible 232 * reentrance of the memory allocation functions. 233 * 234 * Note: NUM_MPROF_BUFFERS must be smaller than MPROF_HASH_SIZE. 235 */ 236#define NUM_MPROF_BUFFERS 1000 237static struct mutex_prof mprof_buf[NUM_MPROF_BUFFERS]; 238static int first_free_mprof_buf; 239#define MPROF_HASH_SIZE 1009 240static struct mutex_prof *mprof_hash[MPROF_HASH_SIZE]; 241 242static int mutex_prof_acquisitions; 243SYSCTL_INT(_debug_mutex_prof, OID_AUTO, acquisitions, CTLFLAG_RD, 244 &mutex_prof_acquisitions, 0, "Number of mutex acquistions recorded"); 245static int mutex_prof_records; 246SYSCTL_INT(_debug_mutex_prof, OID_AUTO, records, CTLFLAG_RD, 247 &mutex_prof_records, 0, "Number of profiling records"); 248static int mutex_prof_maxrecords = NUM_MPROF_BUFFERS; 249SYSCTL_INT(_debug_mutex_prof, OID_AUTO, maxrecords, CTLFLAG_RD, 250 &mutex_prof_maxrecords, 0, "Maximum number of profiling records"); 251static int mutex_prof_rejected; 252SYSCTL_INT(_debug_mutex_prof, OID_AUTO, rejected, CTLFLAG_RD, 253 &mutex_prof_rejected, 0, "Number of rejected profiling records"); 254static int mutex_prof_hashsize = MPROF_HASH_SIZE; 255SYSCTL_INT(_debug_mutex_prof, OID_AUTO, hashsize, CTLFLAG_RD, 256 &mutex_prof_hashsize, 0, "Hash size"); 257static int mutex_prof_collisions = 0; 258SYSCTL_INT(_debug_mutex_prof, OID_AUTO, collisions, CTLFLAG_RD, 259 &mutex_prof_collisions, 0, "Number of hash collisions"); 260 261/* 262 * mprof_mtx protects the profiling buffers and the hash. 263 */ 264static struct mtx mprof_mtx; 265MTX_SYSINIT(mprof, &mprof_mtx, "mutex profiling lock", MTX_SPIN | MTX_QUIET); 266 267static u_int64_t 268nanoseconds(void) 269{ 270 struct timespec tv; 271 272 nanotime(&tv); 273 return (tv.tv_sec * (u_int64_t)1000000000 + tv.tv_nsec); 274} 275 276static int 277dump_mutex_prof_stats(SYSCTL_HANDLER_ARGS) 278{ 279 struct sbuf *sb; 280 int error, i; 281 282 if (first_free_mprof_buf == 0) 283 return SYSCTL_OUT(req, "No locking recorded", 284 sizeof("No locking recorded")); 285 286 sb = sbuf_new(NULL, NULL, 1024, SBUF_AUTOEXTEND); 287 sbuf_printf(sb, "%12s %12s %12s %12s %s\n", 288 "max", "total", "count", "average", "name"); 289 mtx_lock_spin(&mprof_mtx); 290 for (i = 0; i < first_free_mprof_buf; ++i) 291 sbuf_printf(sb, "%12ju %12ju %12ju %12ju %s:%d (%s)\n", 292 mprof_buf[i].counter[MPROF_MAX] / 1000, 293 mprof_buf[i].counter[MPROF_TOT] / 1000, 294 mprof_buf[i].counter[MPROF_CNT], 295 mprof_buf[i].counter[MPROF_AVG] / 1000, 296 mprof_buf[i].file, mprof_buf[i].line, mprof_buf[i].name); 297 mtx_unlock_spin(&mprof_mtx); 298 sbuf_finish(sb); 299 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1); 300 sbuf_delete(sb); 301 return (error); 302} 303SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, stats, CTLTYPE_STRING|CTLFLAG_RD, 304 NULL, 0, dump_mutex_prof_stats, "A", "Mutex profiling statistics"); 305#endif 306 307/* 308 * Function versions of the inlined __mtx_* macros. These are used by 309 * modules and can also be called from assembly language if needed. 310 */ 311void 312_mtx_lock_flags(struct mtx *m, int opts, const char *file, int line) 313{ 314 315 MPASS(curthread != NULL); 316 _get_sleep_lock(m, curthread, opts, file, line); 317 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 318 line); 319 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 320#ifdef MUTEX_PROFILING 321 /* don't reset the timer when/if recursing */ 322 if (m->acqtime == 0) { 323 m->file = file; 324 m->line = line; 325 m->acqtime = mutex_prof_enable ? nanoseconds() : 0; 326 ++mutex_prof_acquisitions; 327 } 328#endif 329} 330 331void 332_mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) 333{ 334 335 MPASS(curthread != NULL); 336 mtx_assert(m, MA_OWNED); 337#ifdef MUTEX_PROFILING 338 if (m->acqtime != 0) { 339 static const char *unknown = "(unknown)"; 340 struct mutex_prof *mpp; 341 u_int64_t acqtime, now; 342 const char *p, *q; 343 volatile u_int hash; 344 345 now = nanoseconds(); 346 acqtime = m->acqtime; 347 m->acqtime = 0; 348 if (now <= acqtime) 349 goto out; 350 for (p = file; strncmp(p, "../", 3) == 0; p += 3) 351 /* nothing */ ; 352 if (p == NULL || *p == '\0') 353 p = unknown; 354 for (hash = line, q = p; *q != '\0'; ++q) 355 hash = (hash * 2 + *q) % MPROF_HASH_SIZE; 356 mtx_lock_spin(&mprof_mtx); 357 for (mpp = mprof_hash[hash]; mpp != NULL; mpp = mpp->next) 358 if (mpp->line == line && strcmp(mpp->file, p) == 0) 359 break; 360 if (mpp == NULL) { 361 /* Just exit if we cannot get a trace buffer */ 362 if (first_free_mprof_buf >= NUM_MPROF_BUFFERS) { 363 ++mutex_prof_rejected; 364 goto unlock; 365 } 366 mpp = &mprof_buf[first_free_mprof_buf++]; 367 mpp->name = mtx_name(m); 368 mpp->file = p; 369 mpp->line = line; 370 mpp->next = mprof_hash[hash]; 371 if (mprof_hash[hash] != NULL) 372 ++mutex_prof_collisions; 373 mprof_hash[hash] = mpp; 374 ++mutex_prof_records; 375 } 376 /* 377 * Record if the mutex has been held longer now than ever 378 * before 379 */ 380 if ((now - acqtime) > mpp->counter[MPROF_MAX]) 381 mpp->counter[MPROF_MAX] = now - acqtime; 382 mpp->counter[MPROF_TOT] += now - acqtime; 383 mpp->counter[MPROF_CNT] += 1; 384 mpp->counter[MPROF_AVG] = 385 mpp->counter[MPROF_TOT] / mpp->counter[MPROF_CNT]; 386unlock: 387 mtx_unlock_spin(&mprof_mtx); 388 } 389out: 390#endif 391 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 392 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 393 line); 394 _rel_sleep_lock(m, curthread, opts, file, line); 395} 396 397void 398_mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) 399{ 400 401 MPASS(curthread != NULL); 402#if defined(SMP) || LOCK_DEBUG > 0 403 _get_spin_lock(m, curthread, opts, file, line); 404#else 405 critical_enter(); 406#endif 407 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 408 line); 409 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 410} 411 412void 413_mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line) 414{ 415 416 MPASS(curthread != NULL); 417 mtx_assert(m, MA_OWNED); 418 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 419 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 420 line); 421#if defined(SMP) || LOCK_DEBUG > 0 422 _rel_spin_lock(m); 423#else 424 critical_exit(); 425#endif 426} 427 428/* 429 * The important part of mtx_trylock{,_flags}() 430 * Tries to acquire lock `m.' We do NOT handle recursion here; we assume that 431 * if we're called, it's because we know we don't already own this lock. 432 */ 433int 434_mtx_trylock(struct mtx *m, int opts, const char *file, int line) 435{ 436 int rval; 437 438 MPASS(curthread != NULL); 439 440 rval = _obtain_lock(m, curthread); 441 442 LOCK_LOG_TRY("LOCK", &m->mtx_object, opts, rval, file, line); 443 if (rval) { 444 /* 445 * We do not handle recursion in _mtx_trylock; see the 446 * note at the top of the routine. 447 */ 448 KASSERT(!mtx_recursed(m), 449 ("mtx_trylock() called on a recursed mutex")); 450 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 451 file, line); 452 } 453 454 return (rval); 455} 456 457/* 458 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 459 * 460 * We call this if the lock is either contested (i.e. we need to go to 461 * sleep waiting for it), or if we need to recurse on it. 462 */ 463void 464_mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line) 465{ 466 struct thread *td = curthread; 467#if defined(SMP) && defined(ADAPTIVE_MUTEXES) 468 struct thread *owner; 469#endif 470 471 if ((m->mtx_lock & MTX_FLAGMASK) == (uintptr_t)td) { 472 m->mtx_recurse++; 473 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 474 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 475 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 476 return; 477 } 478 479 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 480 CTR4(KTR_LOCK, 481 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 482 m->mtx_object.lo_name, (void *)m->mtx_lock, file, line); 483 484 while (!_obtain_lock(m, td)) { 485 uintptr_t v; 486 struct thread *td1; 487 488 mtx_lock_spin(&sched_lock); 489 /* 490 * Check if the lock has been released while spinning for 491 * the sched_lock. 492 */ 493 if ((v = m->mtx_lock) == MTX_UNOWNED) { 494 mtx_unlock_spin(&sched_lock); 495#ifdef __i386__ 496 ia32_pause(); 497#endif 498 continue; 499 } 500 501 /* 502 * The mutex was marked contested on release. This means that 503 * there are threads blocked on it. 504 */ 505 if (v == MTX_CONTESTED) { 506 td1 = TAILQ_FIRST(&m->mtx_blocked); 507 MPASS(td1 != NULL); 508 m->mtx_lock = (uintptr_t)td | MTX_CONTESTED; 509 510 if (td1->td_priority < td->td_priority) 511 td->td_priority = td1->td_priority; 512 mtx_unlock_spin(&sched_lock); 513 return; 514 } 515 516 /* 517 * If the mutex isn't already contested and a failure occurs 518 * setting the contested bit, the mutex was either released 519 * or the state of the MTX_RECURSED bit changed. 520 */ 521 if ((v & MTX_CONTESTED) == 0 && 522 !atomic_cmpset_ptr(&m->mtx_lock, (void *)v, 523 (void *)(v | MTX_CONTESTED))) { 524 mtx_unlock_spin(&sched_lock); 525#ifdef __i386__ 526 ia32_pause(); 527#endif 528 continue; 529 } 530 531#if defined(SMP) && defined(ADAPTIVE_MUTEXES) 532 /* 533 * If the current owner of the lock is executing on another 534 * CPU, spin instead of blocking. 535 */ 536 owner = (struct thread *)(v & MTX_FLAGMASK); 537 if (m != &Giant && thread_runnable(owner)) { 538 mtx_unlock_spin(&sched_lock); 539#ifdef __i386__ 540 ia32_pause(); 541#endif 542 continue; 543 } 544#endif /* SMP && ADAPTIVE_MUTEXES */ 545 546 /* 547 * We definitely must sleep for this lock. 548 */ 549 mtx_assert(m, MA_NOTOWNED); 550 551#ifdef notyet 552 /* 553 * If we're borrowing an interrupted thread's VM context, we 554 * must clean up before going to sleep. 555 */ 556 if (td->td_ithd != NULL) { 557 struct ithd *it = td->td_ithd; 558 559 if (it->it_interrupted) { 560 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 561 CTR2(KTR_LOCK, 562 "_mtx_lock_sleep: %p interrupted %p", 563 it, it->it_interrupted); 564 intr_thd_fixup(it); 565 } 566 } 567#endif 568 569 /* 570 * Put us on the list of threads blocked on this mutex. 571 */ 572 if (TAILQ_EMPTY(&m->mtx_blocked)) { 573 td1 = mtx_owner(m); 574 LIST_INSERT_HEAD(&td1->td_contested, m, mtx_contested); 575 TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_blkq); 576 } else { 577 TAILQ_FOREACH(td1, &m->mtx_blocked, td_blkq) 578 if (td1->td_priority > td->td_priority) 579 break; 580 if (td1) 581 TAILQ_INSERT_BEFORE(td1, td, td_blkq); 582 else 583 TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_blkq); 584 } 585 586 /* 587 * Save who we're blocked on. 588 */ 589 td->td_blocked = m; 590 td->td_mtxname = m->mtx_object.lo_name; 591 td->td_proc->p_stat = SMTX; 592 propagate_priority(td); 593 594 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 595 CTR3(KTR_LOCK, 596 "_mtx_lock_sleep: p %p blocked on [%p] %s", td, m, 597 m->mtx_object.lo_name); 598 599 td->td_proc->p_stats->p_ru.ru_nvcsw++; 600 mi_switch(); 601 602 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 603 CTR3(KTR_LOCK, 604 "_mtx_lock_sleep: p %p free from blocked on [%p] %s", 605 td, m, m->mtx_object.lo_name); 606 607 mtx_unlock_spin(&sched_lock); 608 } 609 610 return; 611} 612 613/* 614 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. 615 * 616 * This is only called if we need to actually spin for the lock. Recursion 617 * is handled inline. 618 */ 619void 620_mtx_lock_spin(struct mtx *m, int opts, const char *file, int line) 621{ 622 int i = 0; 623 624 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 625 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 626 627 for (;;) { 628 if (_obtain_lock(m, curthread)) 629 break; 630 631 /* Give interrupts a chance while we spin. */ 632 critical_exit(); 633 while (m->mtx_lock != MTX_UNOWNED) { 634 if (i++ < 10000000) { 635#ifdef __i386__ 636 ia32_pause(); 637#endif 638 continue; 639 } 640 if (i < 60000000) 641 DELAY(1); 642#ifdef DDB 643 else if (!db_active) 644#else 645 else 646#endif 647 panic("spin lock %s held by %p for > 5 seconds", 648 m->mtx_object.lo_name, (void *)m->mtx_lock); 649#ifdef __i386__ 650 ia32_pause(); 651#endif 652 } 653 critical_enter(); 654 } 655 656 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 657 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 658 659 return; 660} 661 662/* 663 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 664 * 665 * We are only called here if the lock is recursed or contested (i.e. we 666 * need to wake up a blocked thread). 667 */ 668void 669_mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) 670{ 671 struct thread *td, *td1; 672 struct mtx *m1; 673 int pri; 674 675 td = curthread; 676 677 if (mtx_recursed(m)) { 678 if (--(m->mtx_recurse) == 0) 679 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 680 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 681 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 682 return; 683 } 684 685 mtx_lock_spin(&sched_lock); 686 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 687 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 688 689 td1 = TAILQ_FIRST(&m->mtx_blocked); 690#if defined(SMP) && defined(ADAPTIVE_MUTEXES) 691 if (td1 == NULL) { 692 _release_lock_quick(m); 693 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 694 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p no sleepers", m); 695 mtx_unlock_spin(&sched_lock); 696 return; 697 } 698#endif 699 MPASS(td->td_proc->p_magic == P_MAGIC); 700 MPASS(td1->td_proc->p_magic == P_MAGIC); 701 702 TAILQ_REMOVE(&m->mtx_blocked, td1, td_blkq); 703 704 if (TAILQ_EMPTY(&m->mtx_blocked)) { 705 LIST_REMOVE(m, mtx_contested); 706 _release_lock_quick(m); 707 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 708 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m); 709 } else 710 atomic_store_rel_ptr(&m->mtx_lock, (void *)MTX_CONTESTED); 711 712 pri = PRI_MAX; 713 LIST_FOREACH(m1, &td->td_contested, mtx_contested) { 714 int cp = TAILQ_FIRST(&m1->mtx_blocked)->td_priority; 715 if (cp < pri) 716 pri = cp; 717 } 718 719 if (pri > td->td_base_pri) 720 pri = td->td_base_pri; 721 td->td_priority = pri; 722 723 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 724 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p contested setrunqueue %p", 725 m, td1); 726 727 td1->td_blocked = NULL; 728 td1->td_proc->p_stat = SRUN; 729 setrunqueue(td1); 730 731 if (td->td_critnest == 1 && td1->td_priority < pri) { 732#ifdef notyet 733 if (td->td_ithd != NULL) { 734 struct ithd *it = td->td_ithd; 735 736 if (it->it_interrupted) { 737 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 738 CTR2(KTR_LOCK, 739 "_mtx_unlock_sleep: %p interrupted %p", 740 it, it->it_interrupted); 741 intr_thd_fixup(it); 742 } 743 } 744#endif 745 setrunqueue(td); 746 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 747 CTR2(KTR_LOCK, 748 "_mtx_unlock_sleep: %p switching out lock=%p", m, 749 (void *)m->mtx_lock); 750 751 td->td_proc->p_stats->p_ru.ru_nivcsw++; 752 mi_switch(); 753 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 754 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p", 755 m, (void *)m->mtx_lock); 756 } 757 758 mtx_unlock_spin(&sched_lock); 759 760 return; 761} 762 763/* 764 * All the unlocking of MTX_SPIN locks is done inline. 765 * See the _rel_spin_lock() macro for the details. 766 */ 767 768/* 769 * The backing function for the INVARIANTS-enabled mtx_assert() 770 */ 771#ifdef INVARIANT_SUPPORT 772void 773_mtx_assert(struct mtx *m, int what, const char *file, int line) 774{ 775 776 if (panicstr != NULL) 777 return; 778 switch (what) { 779 case MA_OWNED: 780 case MA_OWNED | MA_RECURSED: 781 case MA_OWNED | MA_NOTRECURSED: 782 if (!mtx_owned(m)) 783 panic("mutex %s not owned at %s:%d", 784 m->mtx_object.lo_name, file, line); 785 if (mtx_recursed(m)) { 786 if ((what & MA_NOTRECURSED) != 0) 787 panic("mutex %s recursed at %s:%d", 788 m->mtx_object.lo_name, file, line); 789 } else if ((what & MA_RECURSED) != 0) { 790 panic("mutex %s unrecursed at %s:%d", 791 m->mtx_object.lo_name, file, line); 792 } 793 break; 794 case MA_NOTOWNED: 795 if (mtx_owned(m)) 796 panic("mutex %s owned at %s:%d", 797 m->mtx_object.lo_name, file, line); 798 break; 799 default: 800 panic("unknown mtx_assert at %s:%d", file, line); 801 } 802} 803#endif 804 805/* 806 * The MUTEX_DEBUG-enabled mtx_validate() 807 * 808 * Most of these checks have been moved off into the LO_INITIALIZED flag 809 * maintained by the witness code. 810 */ 811#ifdef MUTEX_DEBUG 812 813void mtx_validate(struct mtx *); 814 815void 816mtx_validate(struct mtx *m) 817{ 818 819/* 820 * XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly 821 * we can re-enable the kernacc() checks. 822 */ 823#ifndef __alpha__ 824 /* 825 * Can't call kernacc() from early init386(), especially when 826 * initializing Giant mutex, because some stuff in kernacc() 827 * requires Giant itself. 828 */ 829 if (!cold) 830 if (!kernacc((caddr_t)m, sizeof(m), 831 VM_PROT_READ | VM_PROT_WRITE)) 832 panic("Can't read and write to mutex %p", m); 833#endif 834} 835#endif 836 837/* 838 * General init routine used by the MTX_SYSINIT() macro. 839 */ 840void 841mtx_sysinit(void *arg) 842{ 843 struct mtx_args *margs = arg; 844 845 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); 846} 847 848/* 849 * Mutex initialization routine; initialize lock `m' of type contained in 850 * `opts' with options contained in `opts' and name `name.' The optional 851 * lock type `type' is used as a general lock category name for use with 852 * witness. 853 */ 854void 855mtx_init(struct mtx *m, const char *name, const char *type, int opts) 856{ 857 struct lock_object *lock; 858 859 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 860 MTX_SLEEPABLE | MTX_NOWITNESS | MTX_DUPOK)) == 0); 861 862#ifdef MUTEX_DEBUG 863 /* Diagnostic and error correction */ 864 mtx_validate(m); 865#endif 866 867 lock = &m->mtx_object; 868 KASSERT((lock->lo_flags & LO_INITIALIZED) == 0, 869 ("mutex %s %p already initialized", name, m)); 870 bzero(m, sizeof(*m)); 871 if (opts & MTX_SPIN) 872 lock->lo_class = &lock_class_mtx_spin; 873 else 874 lock->lo_class = &lock_class_mtx_sleep; 875 lock->lo_name = name; 876 lock->lo_type = type != NULL ? type : name; 877 if (opts & MTX_QUIET) 878 lock->lo_flags = LO_QUIET; 879 if (opts & MTX_RECURSE) 880 lock->lo_flags |= LO_RECURSABLE; 881 if (opts & MTX_SLEEPABLE) 882 lock->lo_flags |= LO_SLEEPABLE; 883 if ((opts & MTX_NOWITNESS) == 0) 884 lock->lo_flags |= LO_WITNESS; 885 if (opts & MTX_DUPOK) 886 lock->lo_flags |= LO_DUPOK; 887 888 m->mtx_lock = MTX_UNOWNED; 889 TAILQ_INIT(&m->mtx_blocked); 890 891 LOCK_LOG_INIT(lock, opts); 892 893 WITNESS_INIT(lock); 894} 895 896/* 897 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 898 * passed in as a flag here because if the corresponding mtx_init() was 899 * called with MTX_QUIET set, then it will already be set in the mutex's 900 * flags. 901 */ 902void 903mtx_destroy(struct mtx *m) 904{ 905 906 LOCK_LOG_DESTROY(&m->mtx_object, 0); 907 908 if (!mtx_owned(m)) 909 MPASS(mtx_unowned(m)); 910 else { 911 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 912 913 /* Tell witness this isn't locked to make it happy. */ 914 WITNESS_UNLOCK(&m->mtx_object, LOP_EXCLUSIVE, __FILE__, 915 __LINE__); 916 } 917 918 WITNESS_DESTROY(&m->mtx_object); 919} 920 921/* 922 * Intialize the mutex code and system mutexes. This is called from the MD 923 * startup code prior to mi_startup(). The per-CPU data space needs to be 924 * setup before this is called. 925 */ 926void 927mutex_init(void) 928{ 929 930 /* Setup thread0 so that mutexes work. */ 931 LIST_INIT(&thread0.td_contested); 932 933 /* 934 * Initialize mutexes. 935 */ 936 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 937 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE); 938 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 939 mtx_lock(&Giant); 940} 941 942/* 943 * Encapsulated Giant mutex routines. These routines provide encapsulation 944 * control for the Giant mutex, allowing sysctls to be used to turn on and 945 * off Giant around certain subsystems. The default value for the sysctls 946 * are set to what developers believe is stable and working in regards to 947 * the Giant pushdown. Developers should not turn off Giant via these 948 * sysctls unless they know what they are doing. 949 * 950 * Callers of mtx_lock_giant() are expected to pass the return value to an 951 * accompanying mtx_unlock_giant() later on. If multiple subsystems are 952 * effected by a Giant wrap, all related sysctl variables must be zero for 953 * the subsystem call to operate without Giant (as determined by the caller). 954 */ 955 956SYSCTL_NODE(_kern, OID_AUTO, giant, CTLFLAG_RD, NULL, "Giant mutex manipulation"); 957 958static int kern_giant_all = 0; 959SYSCTL_INT(_kern_giant, OID_AUTO, all, CTLFLAG_RW, &kern_giant_all, 0, ""); 960 961int kern_giant_proc = 1; /* Giant around PROC locks */ 962int kern_giant_file = 1; /* Giant around struct file & filedesc */ 963int kern_giant_ucred = 1; /* Giant around ucred */ 964SYSCTL_INT(_kern_giant, OID_AUTO, proc, CTLFLAG_RW, &kern_giant_proc, 0, ""); 965SYSCTL_INT(_kern_giant, OID_AUTO, file, CTLFLAG_RW, &kern_giant_file, 0, ""); 966SYSCTL_INT(_kern_giant, OID_AUTO, ucred, CTLFLAG_RW, &kern_giant_ucred, 0, ""); 967 968int 969mtx_lock_giant(int sysctlvar) 970{ 971 if (sysctlvar || kern_giant_all) { 972 mtx_lock(&Giant); 973 return(1); 974 } 975 return(0); 976} 977 978void 979mtx_unlock_giant(int s) 980{ 981 if (s) 982 mtx_unlock(&Giant); 983} 984 985