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 * $FreeBSD: releng/5.1/sys/kern/kern_mutex.c 113632 2003-04-17 22:28:58Z 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/sched.h> 51 #include <sys/sbuf.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 /* 74 * Lock classes for sleep and spin mutexes. 75 */ 76 struct lock_class lock_class_mtx_sleep = { 77 "sleep mutex", 78 LC_SLEEPLOCK | LC_RECURSABLE 79 }; 80 struct lock_class lock_class_mtx_spin = { 81 "spin mutex", 82 LC_SPINLOCK | LC_RECURSABLE 83 }; 84 85 /* 86 * System-wide mutexes 87 */ 88 struct mtx sched_lock; 89 struct mtx Giant; 90 91 /* 92 * Prototypes for non-exported routines. 93 */ 94 static void propagate_priority(struct thread *); 95 96 static void 97 propagate_priority(struct thread *td) 98 { 99 int pri = td->td_priority; 100 struct mtx *m = td->td_blocked; 101 102 mtx_assert(&sched_lock, MA_OWNED); 103 for (;;) { 104 struct thread *td1; 105 106 td = mtx_owner(m); 107 108 if (td == NULL) { 109 /* 110 * This really isn't quite right. Really 111 * ought to bump priority of thread that 112 * next acquires the mutex. 113 */ 114 MPASS(m->mtx_lock == MTX_CONTESTED); 115 return; 116 } 117 118 MPASS(td->td_proc != NULL); 119 MPASS(td->td_proc->p_magic == P_MAGIC); 120 KASSERT(!TD_IS_SLEEPING(td), ("sleeping thread owns a mutex")); 121 if (td->td_priority <= pri) /* lower is higher priority */ 122 return; 123 124 125 /* 126 * If lock holder is actually running, just bump priority. 127 */ 128 if (TD_IS_RUNNING(td)) { 129 td->td_priority = pri; 130 return; 131 } 132 133 #ifndef SMP 134 /* 135 * For UP, we check to see if td is curthread (this shouldn't 136 * ever happen however as it would mean we are in a deadlock.) 137 */ 138 KASSERT(td != curthread, ("Deadlock detected")); 139 #endif 140 141 /* 142 * If on run queue move to new run queue, and quit. 143 * XXXKSE this gets a lot more complicated under threads 144 * but try anyhow. 145 */ 146 if (TD_ON_RUNQ(td)) { 147 MPASS(td->td_blocked == NULL); 148 sched_prio(td, pri); 149 return; 150 } 151 /* 152 * Adjust for any other cases. 153 */ 154 td->td_priority = pri; 155 156 /* 157 * If we aren't blocked on a mutex, we should be. 158 */ 159 KASSERT(TD_ON_LOCK(td), ( 160 "process %d(%s):%d holds %s but isn't blocked on a mutex\n", 161 td->td_proc->p_pid, td->td_proc->p_comm, td->td_state, 162 m->mtx_object.lo_name)); 163 164 /* 165 * Pick up the mutex that td is blocked on. 166 */ 167 m = td->td_blocked; 168 MPASS(m != NULL); 169 170 /* 171 * Check if the thread needs to be moved up on 172 * the blocked chain 173 */ 174 if (td == TAILQ_FIRST(&m->mtx_blocked)) { 175 continue; 176 } 177 178 td1 = TAILQ_PREV(td, threadqueue, td_lockq); 179 if (td1->td_priority <= pri) { 180 continue; 181 } 182 183 /* 184 * Remove thread from blocked chain and determine where 185 * it should be moved up to. Since we know that td1 has 186 * a lower priority than td, we know that at least one 187 * thread in the chain has a lower priority and that 188 * td1 will thus not be NULL after the loop. 189 */ 190 TAILQ_REMOVE(&m->mtx_blocked, td, td_lockq); 191 TAILQ_FOREACH(td1, &m->mtx_blocked, td_lockq) { 192 MPASS(td1->td_proc->p_magic == P_MAGIC); 193 if (td1->td_priority > pri) 194 break; 195 } 196 197 MPASS(td1 != NULL); 198 TAILQ_INSERT_BEFORE(td1, td, td_lockq); 199 CTR4(KTR_LOCK, 200 "propagate_priority: p %p moved before %p on [%p] %s", 201 td, td1, m, m->mtx_object.lo_name); 202 } 203 } 204 205 #ifdef MUTEX_PROFILING 206 SYSCTL_NODE(_debug, OID_AUTO, mutex, CTLFLAG_RD, NULL, "mutex debugging"); 207 SYSCTL_NODE(_debug_mutex, OID_AUTO, prof, CTLFLAG_RD, NULL, "mutex profiling"); 208 static int mutex_prof_enable = 0; 209 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, enable, CTLFLAG_RW, 210 &mutex_prof_enable, 0, "Enable tracing of mutex holdtime"); 211 212 struct mutex_prof { 213 const char *name; 214 const char *file; 215 int line; 216 uintmax_t cnt_max; 217 uintmax_t cnt_tot; 218 uintmax_t cnt_cur; 219 struct mutex_prof *next; 220 }; 221 222 /* 223 * mprof_buf is a static pool of profiling records to avoid possible 224 * reentrance of the memory allocation functions. 225 * 226 * Note: NUM_MPROF_BUFFERS must be smaller than MPROF_HASH_SIZE. 227 */ 228 #define NUM_MPROF_BUFFERS 1000 229 static struct mutex_prof mprof_buf[NUM_MPROF_BUFFERS]; 230 static int first_free_mprof_buf; 231 #define MPROF_HASH_SIZE 1009 232 static struct mutex_prof *mprof_hash[MPROF_HASH_SIZE]; 233 /* SWAG: sbuf size = avg stat. line size * number of locks */ 234 #define MPROF_SBUF_SIZE 256 * 400 235 236 static int mutex_prof_acquisitions; 237 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, acquisitions, CTLFLAG_RD, 238 &mutex_prof_acquisitions, 0, "Number of mutex acquistions recorded"); 239 static int mutex_prof_records; 240 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, records, CTLFLAG_RD, 241 &mutex_prof_records, 0, "Number of profiling records"); 242 static int mutex_prof_maxrecords = NUM_MPROF_BUFFERS; 243 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, maxrecords, CTLFLAG_RD, 244 &mutex_prof_maxrecords, 0, "Maximum number of profiling records"); 245 static int mutex_prof_rejected; 246 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, rejected, CTLFLAG_RD, 247 &mutex_prof_rejected, 0, "Number of rejected profiling records"); 248 static int mutex_prof_hashsize = MPROF_HASH_SIZE; 249 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, hashsize, CTLFLAG_RD, 250 &mutex_prof_hashsize, 0, "Hash size"); 251 static int mutex_prof_collisions = 0; 252 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, collisions, CTLFLAG_RD, 253 &mutex_prof_collisions, 0, "Number of hash collisions"); 254 255 /* 256 * mprof_mtx protects the profiling buffers and the hash. 257 */ 258 static struct mtx mprof_mtx; 259 MTX_SYSINIT(mprof, &mprof_mtx, "mutex profiling lock", MTX_SPIN | MTX_QUIET); 260 261 static u_int64_t 262 nanoseconds(void) 263 { 264 struct timespec tv; 265 266 nanotime(&tv); 267 return (tv.tv_sec * (u_int64_t)1000000000 + tv.tv_nsec); 268 } 269 270 static int 271 dump_mutex_prof_stats(SYSCTL_HANDLER_ARGS) 272 { 273 struct sbuf *sb; 274 int error, i; 275 static int multiplier = 1; 276 277 if (first_free_mprof_buf == 0) 278 return (SYSCTL_OUT(req, "No locking recorded", 279 sizeof("No locking recorded"))); 280 281 retry_sbufops: 282 sb = sbuf_new(NULL, NULL, MPROF_SBUF_SIZE * multiplier, SBUF_FIXEDLEN); 283 sbuf_printf(sb, "%6s %12s %11s %5s %s\n", 284 "max", "total", "count", "avg", "name"); 285 /* 286 * XXX this spinlock seems to be by far the largest perpetrator 287 * of spinlock latency (1.6 msec on an Athlon1600 was recorded 288 * even before I pessimized it further by moving the average 289 * computation here). 290 */ 291 mtx_lock_spin(&mprof_mtx); 292 for (i = 0; i < first_free_mprof_buf; ++i) { 293 sbuf_printf(sb, "%6ju %12ju %11ju %5ju %s:%d (%s)\n", 294 mprof_buf[i].cnt_max / 1000, 295 mprof_buf[i].cnt_tot / 1000, 296 mprof_buf[i].cnt_cur, 297 mprof_buf[i].cnt_cur == 0 ? (uintmax_t)0 : 298 mprof_buf[i].cnt_tot / (mprof_buf[i].cnt_cur * 1000), 299 mprof_buf[i].file, mprof_buf[i].line, mprof_buf[i].name); 300 if (sbuf_overflowed(sb)) { 301 mtx_unlock_spin(&mprof_mtx); 302 sbuf_delete(sb); 303 multiplier++; 304 goto retry_sbufops; 305 } 306 } 307 mtx_unlock_spin(&mprof_mtx); 308 sbuf_finish(sb); 309 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1); 310 sbuf_delete(sb); 311 return (error); 312 } 313 SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD, 314 NULL, 0, dump_mutex_prof_stats, "A", "Mutex profiling statistics"); 315 #endif 316 317 /* 318 * Function versions of the inlined __mtx_* macros. These are used by 319 * modules and can also be called from assembly language if needed. 320 */ 321 void 322 _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line) 323 { 324 325 MPASS(curthread != NULL); 326 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 327 ("mtx_lock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 328 file, line)); 329 _get_sleep_lock(m, curthread, opts, file, line); 330 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 331 line); 332 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 333 #ifdef MUTEX_PROFILING 334 /* don't reset the timer when/if recursing */ 335 if (m->mtx_acqtime == 0) { 336 m->mtx_filename = file; 337 m->mtx_lineno = line; 338 m->mtx_acqtime = mutex_prof_enable ? nanoseconds() : 0; 339 ++mutex_prof_acquisitions; 340 } 341 #endif 342 } 343 344 void 345 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) 346 { 347 348 MPASS(curthread != NULL); 349 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 350 ("mtx_unlock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 351 file, line)); 352 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 353 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 354 line); 355 mtx_assert(m, MA_OWNED); 356 #ifdef MUTEX_PROFILING 357 if (m->mtx_acqtime != 0) { 358 static const char *unknown = "(unknown)"; 359 struct mutex_prof *mpp; 360 u_int64_t acqtime, now; 361 const char *p, *q; 362 volatile u_int hash; 363 364 now = nanoseconds(); 365 acqtime = m->mtx_acqtime; 366 m->mtx_acqtime = 0; 367 if (now <= acqtime) 368 goto out; 369 for (p = m->mtx_filename; 370 p != NULL && strncmp(p, "../", 3) == 0; p += 3) 371 /* nothing */ ; 372 if (p == NULL || *p == '\0') 373 p = unknown; 374 for (hash = m->mtx_lineno, q = p; *q != '\0'; ++q) 375 hash = (hash * 2 + *q) % MPROF_HASH_SIZE; 376 mtx_lock_spin(&mprof_mtx); 377 for (mpp = mprof_hash[hash]; mpp != NULL; mpp = mpp->next) 378 if (mpp->line == m->mtx_lineno && 379 strcmp(mpp->file, p) == 0) 380 break; 381 if (mpp == NULL) { 382 /* Just exit if we cannot get a trace buffer */ 383 if (first_free_mprof_buf >= NUM_MPROF_BUFFERS) { 384 ++mutex_prof_rejected; 385 goto unlock; 386 } 387 mpp = &mprof_buf[first_free_mprof_buf++]; 388 mpp->name = mtx_name(m); 389 mpp->file = p; 390 mpp->line = m->mtx_lineno; 391 mpp->next = mprof_hash[hash]; 392 if (mprof_hash[hash] != NULL) 393 ++mutex_prof_collisions; 394 mprof_hash[hash] = mpp; 395 ++mutex_prof_records; 396 } 397 /* 398 * Record if the mutex has been held longer now than ever 399 * before. 400 */ 401 if (now - acqtime > mpp->cnt_max) 402 mpp->cnt_max = now - acqtime; 403 mpp->cnt_tot += now - acqtime; 404 mpp->cnt_cur++; 405 unlock: 406 mtx_unlock_spin(&mprof_mtx); 407 } 408 out: 409 #endif 410 _rel_sleep_lock(m, curthread, opts, file, line); 411 } 412 413 void 414 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) 415 { 416 417 MPASS(curthread != NULL); 418 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 419 ("mtx_lock_spin() of sleep mutex %s @ %s:%d", 420 m->mtx_object.lo_name, file, line)); 421 #if defined(SMP) || LOCK_DEBUG > 0 || 1 422 _get_spin_lock(m, curthread, opts, file, line); 423 #else 424 critical_enter(); 425 #endif 426 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 427 line); 428 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 429 } 430 431 void 432 _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line) 433 { 434 435 MPASS(curthread != NULL); 436 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 437 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 438 m->mtx_object.lo_name, file, line)); 439 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 440 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 441 line); 442 mtx_assert(m, MA_OWNED); 443 #if defined(SMP) || LOCK_DEBUG > 0 || 1 444 _rel_spin_lock(m); 445 #else 446 critical_exit(); 447 #endif 448 } 449 450 /* 451 * The important part of mtx_trylock{,_flags}() 452 * Tries to acquire lock `m.' We do NOT handle recursion here. If this 453 * function is called on a recursed mutex, it will return failure and 454 * will not recursively acquire the lock. You are expected to know what 455 * you are doing. 456 */ 457 int 458 _mtx_trylock(struct mtx *m, int opts, const char *file, int line) 459 { 460 int rval; 461 462 MPASS(curthread != NULL); 463 464 rval = _obtain_lock(m, curthread); 465 466 LOCK_LOG_TRY("LOCK", &m->mtx_object, opts, rval, file, line); 467 if (rval) 468 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 469 file, line); 470 471 return (rval); 472 } 473 474 /* 475 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 476 * 477 * We call this if the lock is either contested (i.e. we need to go to 478 * sleep waiting for it), or if we need to recurse on it. 479 */ 480 void 481 _mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line) 482 { 483 struct thread *td = curthread; 484 struct thread *td1; 485 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 486 struct thread *owner; 487 #endif 488 uintptr_t v; 489 #ifdef KTR 490 int cont_logged = 0; 491 #endif 492 493 if (mtx_owned(m)) { 494 m->mtx_recurse++; 495 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 496 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 497 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 498 return; 499 } 500 501 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 502 CTR4(KTR_LOCK, 503 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 504 m->mtx_object.lo_name, (void *)m->mtx_lock, file, line); 505 506 while (!_obtain_lock(m, td)) { 507 508 mtx_lock_spin(&sched_lock); 509 v = m->mtx_lock; 510 511 /* 512 * Check if the lock has been released while spinning for 513 * the sched_lock. 514 */ 515 if (v == MTX_UNOWNED) { 516 mtx_unlock_spin(&sched_lock); 517 #ifdef __i386__ 518 ia32_pause(); 519 #endif 520 continue; 521 } 522 523 /* 524 * The mutex was marked contested on release. This means that 525 * there are threads blocked on it. 526 */ 527 if (v == MTX_CONTESTED) { 528 td1 = TAILQ_FIRST(&m->mtx_blocked); 529 MPASS(td1 != NULL); 530 m->mtx_lock = (uintptr_t)td | MTX_CONTESTED; 531 532 if (td1->td_priority < td->td_priority) 533 td->td_priority = td1->td_priority; 534 mtx_unlock_spin(&sched_lock); 535 return; 536 } 537 538 /* 539 * If the mutex isn't already contested and a failure occurs 540 * setting the contested bit, the mutex was either released 541 * or the state of the MTX_RECURSED bit changed. 542 */ 543 if ((v & MTX_CONTESTED) == 0 && 544 !atomic_cmpset_ptr(&m->mtx_lock, (void *)v, 545 (void *)(v | MTX_CONTESTED))) { 546 mtx_unlock_spin(&sched_lock); 547 #ifdef __i386__ 548 ia32_pause(); 549 #endif 550 continue; 551 } 552 553 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 554 /* 555 * If the current owner of the lock is executing on another 556 * CPU, spin instead of blocking. 557 */ 558 owner = (struct thread *)(v & MTX_FLAGMASK); 559 if (m != &Giant && TD_IS_RUNNING(owner)) { 560 mtx_unlock_spin(&sched_lock); 561 while (mtx_owner(m) == owner && TD_IS_RUNNING(owner)) { 562 #ifdef __i386__ 563 ia32_pause(); 564 #endif 565 } 566 continue; 567 } 568 #endif /* SMP && ADAPTIVE_MUTEXES */ 569 570 /* 571 * We definitely must sleep for this lock. 572 */ 573 mtx_assert(m, MA_NOTOWNED); 574 575 #ifdef notyet 576 /* 577 * If we're borrowing an interrupted thread's VM context, we 578 * must clean up before going to sleep. 579 */ 580 if (td->td_ithd != NULL) { 581 struct ithd *it = td->td_ithd; 582 583 if (it->it_interrupted) { 584 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 585 CTR2(KTR_LOCK, 586 "_mtx_lock_sleep: %p interrupted %p", 587 it, it->it_interrupted); 588 intr_thd_fixup(it); 589 } 590 } 591 #endif 592 593 /* 594 * Put us on the list of threads blocked on this mutex. 595 */ 596 if (TAILQ_EMPTY(&m->mtx_blocked)) { 597 td1 = mtx_owner(m); 598 LIST_INSERT_HEAD(&td1->td_contested, m, mtx_contested); 599 TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_lockq); 600 } else { 601 TAILQ_FOREACH(td1, &m->mtx_blocked, td_lockq) 602 if (td1->td_priority > td->td_priority) 603 break; 604 if (td1) 605 TAILQ_INSERT_BEFORE(td1, td, td_lockq); 606 else 607 TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_lockq); 608 } 609 #ifdef KTR 610 if (!cont_logged) { 611 CTR6(KTR_CONTENTION, 612 "contention: %p at %s:%d wants %s, taken by %s:%d", 613 td, file, line, m->mtx_object.lo_name, 614 WITNESS_FILE(&m->mtx_object), 615 WITNESS_LINE(&m->mtx_object)); 616 cont_logged = 1; 617 } 618 #endif 619 620 /* 621 * Save who we're blocked on. 622 */ 623 td->td_blocked = m; 624 td->td_lockname = m->mtx_object.lo_name; 625 TD_SET_LOCK(td); 626 propagate_priority(td); 627 628 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 629 CTR3(KTR_LOCK, 630 "_mtx_lock_sleep: p %p blocked on [%p] %s", td, m, 631 m->mtx_object.lo_name); 632 633 td->td_proc->p_stats->p_ru.ru_nvcsw++; 634 mi_switch(); 635 636 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 637 CTR3(KTR_LOCK, 638 "_mtx_lock_sleep: p %p free from blocked on [%p] %s", 639 td, m, m->mtx_object.lo_name); 640 641 mtx_unlock_spin(&sched_lock); 642 } 643 644 #ifdef KTR 645 if (cont_logged) { 646 CTR4(KTR_CONTENTION, 647 "contention end: %s acquired by %p at %s:%d", 648 m->mtx_object.lo_name, td, file, line); 649 } 650 #endif 651 return; 652 } 653 654 /* 655 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. 656 * 657 * This is only called if we need to actually spin for the lock. Recursion 658 * is handled inline. 659 */ 660 void 661 _mtx_lock_spin(struct mtx *m, int opts, const char *file, int line) 662 { 663 int i = 0; 664 665 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 666 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 667 668 for (;;) { 669 if (_obtain_lock(m, curthread)) 670 break; 671 672 /* Give interrupts a chance while we spin. */ 673 critical_exit(); 674 while (m->mtx_lock != MTX_UNOWNED) { 675 if (i++ < 10000000) { 676 #ifdef __i386__ 677 ia32_pause(); 678 #endif 679 continue; 680 } 681 if (i < 60000000) 682 DELAY(1); 683 #ifdef DDB 684 else if (!db_active) 685 #else 686 else 687 #endif 688 panic("spin lock %s held by %p for > 5 seconds", 689 m->mtx_object.lo_name, (void *)m->mtx_lock); 690 #ifdef __i386__ 691 ia32_pause(); 692 #endif 693 } 694 critical_enter(); 695 } 696 697 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 698 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 699 700 return; 701 } 702 703 /* 704 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 705 * 706 * We are only called here if the lock is recursed or contested (i.e. we 707 * need to wake up a blocked thread). 708 */ 709 void 710 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) 711 { 712 struct thread *td, *td1; 713 struct mtx *m1; 714 int pri; 715 716 td = curthread; 717 718 if (mtx_recursed(m)) { 719 if (--(m->mtx_recurse) == 0) 720 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 721 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 722 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 723 return; 724 } 725 726 mtx_lock_spin(&sched_lock); 727 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 728 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 729 730 td1 = TAILQ_FIRST(&m->mtx_blocked); 731 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 732 if (td1 == NULL) { 733 _release_lock_quick(m); 734 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 735 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p no sleepers", m); 736 mtx_unlock_spin(&sched_lock); 737 return; 738 } 739 #endif 740 MPASS(td->td_proc->p_magic == P_MAGIC); 741 MPASS(td1->td_proc->p_magic == P_MAGIC); 742 743 TAILQ_REMOVE(&m->mtx_blocked, td1, td_lockq); 744 745 if (TAILQ_EMPTY(&m->mtx_blocked)) { 746 LIST_REMOVE(m, mtx_contested); 747 _release_lock_quick(m); 748 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 749 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m); 750 } else 751 atomic_store_rel_ptr(&m->mtx_lock, (void *)MTX_CONTESTED); 752 753 pri = PRI_MAX; 754 LIST_FOREACH(m1, &td->td_contested, mtx_contested) { 755 int cp = TAILQ_FIRST(&m1->mtx_blocked)->td_priority; 756 if (cp < pri) 757 pri = cp; 758 } 759 760 if (pri > td->td_base_pri) 761 pri = td->td_base_pri; 762 td->td_priority = pri; 763 764 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 765 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p contested setrunqueue %p", 766 m, td1); 767 768 td1->td_blocked = NULL; 769 TD_CLR_LOCK(td1); 770 if (!TD_CAN_RUN(td1)) { 771 mtx_unlock_spin(&sched_lock); 772 return; 773 } 774 setrunqueue(td1); 775 776 if (td->td_critnest == 1 && td1->td_priority < pri) { 777 #ifdef notyet 778 if (td->td_ithd != NULL) { 779 struct ithd *it = td->td_ithd; 780 781 if (it->it_interrupted) { 782 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 783 CTR2(KTR_LOCK, 784 "_mtx_unlock_sleep: %p interrupted %p", 785 it, it->it_interrupted); 786 intr_thd_fixup(it); 787 } 788 } 789 #endif 790 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 791 CTR2(KTR_LOCK, 792 "_mtx_unlock_sleep: %p switching out lock=%p", m, 793 (void *)m->mtx_lock); 794 795 td->td_proc->p_stats->p_ru.ru_nivcsw++; 796 mi_switch(); 797 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 798 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p", 799 m, (void *)m->mtx_lock); 800 } 801 802 mtx_unlock_spin(&sched_lock); 803 804 return; 805 } 806 807 /* 808 * All the unlocking of MTX_SPIN locks is done inline. 809 * See the _rel_spin_lock() macro for the details. 810 */ 811 812 /* 813 * The backing function for the INVARIANTS-enabled mtx_assert() 814 */ 815 #ifdef INVARIANT_SUPPORT 816 void 817 _mtx_assert(struct mtx *m, int what, const char *file, int line) 818 { 819 820 if (panicstr != NULL) 821 return; 822 switch (what) { 823 case MA_OWNED: 824 case MA_OWNED | MA_RECURSED: 825 case MA_OWNED | MA_NOTRECURSED: 826 if (!mtx_owned(m)) 827 panic("mutex %s not owned at %s:%d", 828 m->mtx_object.lo_name, file, line); 829 if (mtx_recursed(m)) { 830 if ((what & MA_NOTRECURSED) != 0) 831 panic("mutex %s recursed at %s:%d", 832 m->mtx_object.lo_name, file, line); 833 } else if ((what & MA_RECURSED) != 0) { 834 panic("mutex %s unrecursed at %s:%d", 835 m->mtx_object.lo_name, file, line); 836 } 837 break; 838 case MA_NOTOWNED: 839 if (mtx_owned(m)) 840 panic("mutex %s owned at %s:%d", 841 m->mtx_object.lo_name, file, line); 842 break; 843 default: 844 panic("unknown mtx_assert at %s:%d", file, line); 845 } 846 } 847 #endif 848 849 /* 850 * The MUTEX_DEBUG-enabled mtx_validate() 851 * 852 * Most of these checks have been moved off into the LO_INITIALIZED flag 853 * maintained by the witness code. 854 */ 855 #ifdef MUTEX_DEBUG 856 857 void mtx_validate(struct mtx *); 858 859 void 860 mtx_validate(struct mtx *m) 861 { 862 863 /* 864 * XXX: When kernacc() does not require Giant we can reenable this check 865 */ 866 #ifdef notyet 867 /* 868 * XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly 869 * we can re-enable the kernacc() checks. 870 */ 871 #ifndef __alpha__ 872 /* 873 * Can't call kernacc() from early init386(), especially when 874 * initializing Giant mutex, because some stuff in kernacc() 875 * requires Giant itself. 876 */ 877 if (!cold) 878 if (!kernacc((caddr_t)m, sizeof(m), 879 VM_PROT_READ | VM_PROT_WRITE)) 880 panic("Can't read and write to mutex %p", m); 881 #endif 882 #endif 883 } 884 #endif 885 886 /* 887 * General init routine used by the MTX_SYSINIT() macro. 888 */ 889 void 890 mtx_sysinit(void *arg) 891 { 892 struct mtx_args *margs = arg; 893 894 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); 895 } 896 897 /* 898 * Mutex initialization routine; initialize lock `m' of type contained in 899 * `opts' with options contained in `opts' and name `name.' The optional 900 * lock type `type' is used as a general lock category name for use with 901 * witness. 902 */ 903 void 904 mtx_init(struct mtx *m, const char *name, const char *type, int opts) 905 { 906 struct lock_object *lock; 907 908 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 909 MTX_NOWITNESS | MTX_DUPOK)) == 0); 910 911 #ifdef MUTEX_DEBUG 912 /* Diagnostic and error correction */ 913 mtx_validate(m); 914 #endif 915 916 lock = &m->mtx_object; 917 KASSERT((lock->lo_flags & LO_INITIALIZED) == 0, 918 ("mutex %s %p already initialized", name, m)); 919 bzero(m, sizeof(*m)); 920 if (opts & MTX_SPIN) 921 lock->lo_class = &lock_class_mtx_spin; 922 else 923 lock->lo_class = &lock_class_mtx_sleep; 924 lock->lo_name = name; 925 lock->lo_type = type != NULL ? type : name; 926 if (opts & MTX_QUIET) 927 lock->lo_flags = LO_QUIET; 928 if (opts & MTX_RECURSE) 929 lock->lo_flags |= LO_RECURSABLE; 930 if ((opts & MTX_NOWITNESS) == 0) 931 lock->lo_flags |= LO_WITNESS; 932 if (opts & MTX_DUPOK) 933 lock->lo_flags |= LO_DUPOK; 934 935 m->mtx_lock = MTX_UNOWNED; 936 TAILQ_INIT(&m->mtx_blocked); 937 938 LOCK_LOG_INIT(lock, opts); 939 940 WITNESS_INIT(lock); 941 } 942 943 /* 944 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 945 * passed in as a flag here because if the corresponding mtx_init() was 946 * called with MTX_QUIET set, then it will already be set in the mutex's 947 * flags. 948 */ 949 void 950 mtx_destroy(struct mtx *m) 951 { 952 953 LOCK_LOG_DESTROY(&m->mtx_object, 0); 954 955 if (!mtx_owned(m)) 956 MPASS(mtx_unowned(m)); 957 else { 958 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 959 960 /* Tell witness this isn't locked to make it happy. */ 961 WITNESS_UNLOCK(&m->mtx_object, LOP_EXCLUSIVE, __FILE__, 962 __LINE__); 963 } 964 965 WITNESS_DESTROY(&m->mtx_object); 966 } 967 968 /* 969 * Intialize the mutex code and system mutexes. This is called from the MD 970 * startup code prior to mi_startup(). The per-CPU data space needs to be 971 * setup before this is called. 972 */ 973 void 974 mutex_init(void) 975 { 976 977 /* Setup thread0 so that mutexes work. */ 978 LIST_INIT(&thread0.td_contested); 979 980 /* 981 * Initialize mutexes. 982 */ 983 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 984 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE); 985 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 986 mtx_lock(&Giant); 987 }
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