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 * $FreeBSD$ 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 /* XXXKSE This test will change. */ 74 #define thread_running(td) \ 75 ((td)->td_kse != NULL && (td)->td_kse->ke_oncpu != NOCPU) 76 77 /* 78 * Lock classes for sleep and spin mutexes. 79 */ 80 struct lock_class lock_class_mtx_sleep = { 81 "sleep mutex", 82 LC_SLEEPLOCK | LC_RECURSABLE 83 }; 84 struct lock_class lock_class_mtx_spin = { 85 "spin mutex", 86 LC_SPINLOCK | LC_RECURSABLE 87 }; 88 89 /* 90 * System-wide mutexes 91 */ 92 struct mtx sched_lock; 93 struct mtx Giant; 94 95 /* 96 * Prototypes for non-exported routines. 97 */ 98 static void propagate_priority(struct thread *); 99 100 static void 101 propagate_priority(struct thread *td) 102 { 103 int pri = td->td_priority; 104 struct mtx *m = td->td_blocked; 105 106 mtx_assert(&sched_lock, MA_OWNED); 107 for (;;) { 108 struct thread *td1; 109 110 td = mtx_owner(m); 111 112 if (td == NULL) { 113 /* 114 * This really isn't quite right. Really 115 * ought to bump priority of thread that 116 * next acquires the mutex. 117 */ 118 MPASS(m->mtx_lock == MTX_CONTESTED); 119 return; 120 } 121 122 MPASS(td->td_proc != NULL); 123 MPASS(td->td_proc->p_magic == P_MAGIC); 124 KASSERT(!TD_IS_SLEEPING(td), ("sleeping thread owns a mutex")); 125 if (td->td_priority <= pri) /* lower is higher priority */ 126 return; 127 128 129 /* 130 * If lock holder is actually running, just bump priority. 131 */ 132 if (TD_IS_RUNNING(td)) { 133 td->td_priority = pri; 134 return; 135 } 136 137 #ifndef SMP 138 /* 139 * For UP, we check to see if td is curthread (this shouldn't 140 * ever happen however as it would mean we are in a deadlock.) 141 */ 142 KASSERT(td != curthread, ("Deadlock detected")); 143 #endif 144 145 /* 146 * If on run queue move to new run queue, and quit. 147 * XXXKSE this gets a lot more complicated under threads 148 * but try anyhow. 149 */ 150 if (TD_ON_RUNQ(td)) { 151 MPASS(td->td_blocked == NULL); 152 sched_prio(td, pri); 153 return; 154 } 155 /* 156 * Adjust for any other cases. 157 */ 158 td->td_priority = pri; 159 160 /* 161 * If we aren't blocked on a mutex, we should be. 162 */ 163 KASSERT(TD_ON_LOCK(td), ( 164 "process %d(%s):%d holds %s but isn't blocked on a mutex\n", 165 td->td_proc->p_pid, td->td_proc->p_comm, td->td_state, 166 m->mtx_object.lo_name)); 167 168 /* 169 * Pick up the mutex that td is blocked on. 170 */ 171 m = td->td_blocked; 172 MPASS(m != NULL); 173 174 /* 175 * Check if the thread needs to be moved up on 176 * the blocked chain 177 */ 178 if (td == TAILQ_FIRST(&m->mtx_blocked)) { 179 continue; 180 } 181 182 td1 = TAILQ_PREV(td, threadqueue, td_lockq); 183 if (td1->td_priority <= pri) { 184 continue; 185 } 186 187 /* 188 * Remove thread from blocked chain and determine where 189 * it should be moved up to. Since we know that td1 has 190 * a lower priority than td, we know that at least one 191 * thread in the chain has a lower priority and that 192 * td1 will thus not be NULL after the loop. 193 */ 194 TAILQ_REMOVE(&m->mtx_blocked, td, td_lockq); 195 TAILQ_FOREACH(td1, &m->mtx_blocked, td_lockq) { 196 MPASS(td1->td_proc->p_magic == P_MAGIC); 197 if (td1->td_priority > pri) 198 break; 199 } 200 201 MPASS(td1 != NULL); 202 TAILQ_INSERT_BEFORE(td1, td, td_lockq); 203 CTR4(KTR_LOCK, 204 "propagate_priority: p %p moved before %p on [%p] %s", 205 td, td1, m, m->mtx_object.lo_name); 206 } 207 } 208 209 #ifdef MUTEX_PROFILING 210 SYSCTL_NODE(_debug, OID_AUTO, mutex, CTLFLAG_RD, NULL, "mutex debugging"); 211 SYSCTL_NODE(_debug_mutex, OID_AUTO, prof, CTLFLAG_RD, NULL, "mutex profiling"); 212 static int mutex_prof_enable = 0; 213 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, enable, CTLFLAG_RW, 214 &mutex_prof_enable, 0, "Enable tracing of mutex holdtime"); 215 216 struct mutex_prof { 217 const char *name; 218 const char *file; 219 int line; 220 uintmax_t cnt_max; 221 uintmax_t cnt_tot; 222 uintmax_t cnt_cur; 223 struct mutex_prof *next; 224 }; 225 226 /* 227 * mprof_buf is a static pool of profiling records to avoid possible 228 * reentrance of the memory allocation functions. 229 * 230 * Note: NUM_MPROF_BUFFERS must be smaller than MPROF_HASH_SIZE. 231 */ 232 #define NUM_MPROF_BUFFERS 1000 233 static struct mutex_prof mprof_buf[NUM_MPROF_BUFFERS]; 234 static int first_free_mprof_buf; 235 #define MPROF_HASH_SIZE 1009 236 static struct mutex_prof *mprof_hash[MPROF_HASH_SIZE]; 237 /* SWAG: sbuf size = avg stat. line size * number of locks */ 238 #define MPROF_SBUF_SIZE 256 * 400 239 240 static int mutex_prof_acquisitions; 241 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, acquisitions, CTLFLAG_RD, 242 &mutex_prof_acquisitions, 0, "Number of mutex acquistions recorded"); 243 static int mutex_prof_records; 244 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, records, CTLFLAG_RD, 245 &mutex_prof_records, 0, "Number of profiling records"); 246 static int mutex_prof_maxrecords = NUM_MPROF_BUFFERS; 247 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, maxrecords, CTLFLAG_RD, 248 &mutex_prof_maxrecords, 0, "Maximum number of profiling records"); 249 static int mutex_prof_rejected; 250 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, rejected, CTLFLAG_RD, 251 &mutex_prof_rejected, 0, "Number of rejected profiling records"); 252 static int mutex_prof_hashsize = MPROF_HASH_SIZE; 253 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, hashsize, CTLFLAG_RD, 254 &mutex_prof_hashsize, 0, "Hash size"); 255 static int mutex_prof_collisions = 0; 256 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, collisions, CTLFLAG_RD, 257 &mutex_prof_collisions, 0, "Number of hash collisions"); 258 259 /* 260 * mprof_mtx protects the profiling buffers and the hash. 261 */ 262 static struct mtx mprof_mtx; 263 MTX_SYSINIT(mprof, &mprof_mtx, "mutex profiling lock", MTX_SPIN | MTX_QUIET); 264 265 static u_int64_t 266 nanoseconds(void) 267 { 268 struct timespec tv; 269 270 nanotime(&tv); 271 return (tv.tv_sec * (u_int64_t)1000000000 + tv.tv_nsec); 272 } 273 274 static int 275 dump_mutex_prof_stats(SYSCTL_HANDLER_ARGS) 276 { 277 struct sbuf *sb; 278 int error, i; 279 static int multiplier = 1; 280 281 if (first_free_mprof_buf == 0) 282 return (SYSCTL_OUT(req, "No locking recorded", 283 sizeof("No locking recorded"))); 284 285 retry_sbufops: 286 sb = sbuf_new(NULL, NULL, MPROF_SBUF_SIZE * multiplier, SBUF_FIXEDLEN); 287 sbuf_printf(sb, "%6s %12s %11s %5s %s\n", 288 "max", "total", "count", "avg", "name"); 289 /* 290 * XXX this spinlock seems to be by far the largest perpetrator 291 * of spinlock latency (1.6 msec on an Athlon1600 was recorded 292 * even before I pessimized it further by moving the average 293 * computation here). 294 */ 295 mtx_lock_spin(&mprof_mtx); 296 for (i = 0; i < first_free_mprof_buf; ++i) { 297 sbuf_printf(sb, "%6ju %12ju %11ju %5ju %s:%d (%s)\n", 298 mprof_buf[i].cnt_max / 1000, 299 mprof_buf[i].cnt_tot / 1000, 300 mprof_buf[i].cnt_cur, 301 mprof_buf[i].cnt_cur == 0 ? (uintmax_t)0 : 302 mprof_buf[i].cnt_tot / (mprof_buf[i].cnt_cur * 1000), 303 mprof_buf[i].file, mprof_buf[i].line, mprof_buf[i].name); 304 if (sbuf_overflowed(sb)) { 305 mtx_unlock_spin(&mprof_mtx); 306 sbuf_delete(sb); 307 multiplier++; 308 goto retry_sbufops; 309 } 310 } 311 mtx_unlock_spin(&mprof_mtx); 312 sbuf_finish(sb); 313 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1); 314 sbuf_delete(sb); 315 return (error); 316 } 317 SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD, 318 NULL, 0, dump_mutex_prof_stats, "A", "Mutex profiling statistics"); 319 #endif 320 321 /* 322 * Function versions of the inlined __mtx_* macros. These are used by 323 * modules and can also be called from assembly language if needed. 324 */ 325 void 326 _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line) 327 { 328 329 MPASS(curthread != NULL); 330 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 331 ("mtx_lock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 332 file, line)); 333 _get_sleep_lock(m, curthread, opts, file, line); 334 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 335 line); 336 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 337 #ifdef MUTEX_PROFILING 338 /* don't reset the timer when/if recursing */ 339 if (m->mtx_acqtime == 0) { 340 m->mtx_filename = file; 341 m->mtx_lineno = line; 342 m->mtx_acqtime = mutex_prof_enable ? nanoseconds() : 0; 343 ++mutex_prof_acquisitions; 344 } 345 #endif 346 } 347 348 void 349 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) 350 { 351 352 MPASS(curthread != NULL); 353 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 354 ("mtx_unlock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 355 file, line)); 356 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 357 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 358 line); 359 mtx_assert(m, MA_OWNED); 360 #ifdef MUTEX_PROFILING 361 if (m->mtx_acqtime != 0) { 362 static const char *unknown = "(unknown)"; 363 struct mutex_prof *mpp; 364 u_int64_t acqtime, now; 365 const char *p, *q; 366 volatile u_int hash; 367 368 now = nanoseconds(); 369 acqtime = m->mtx_acqtime; 370 m->mtx_acqtime = 0; 371 if (now <= acqtime) 372 goto out; 373 for (p = m->mtx_filename; 374 p != NULL && strncmp(p, "../", 3) == 0; p += 3) 375 /* nothing */ ; 376 if (p == NULL || *p == '\0') 377 p = unknown; 378 for (hash = m->mtx_lineno, q = p; *q != '\0'; ++q) 379 hash = (hash * 2 + *q) % MPROF_HASH_SIZE; 380 mtx_lock_spin(&mprof_mtx); 381 for (mpp = mprof_hash[hash]; mpp != NULL; mpp = mpp->next) 382 if (mpp->line == m->mtx_lineno && 383 strcmp(mpp->file, p) == 0) 384 break; 385 if (mpp == NULL) { 386 /* Just exit if we cannot get a trace buffer */ 387 if (first_free_mprof_buf >= NUM_MPROF_BUFFERS) { 388 ++mutex_prof_rejected; 389 goto unlock; 390 } 391 mpp = &mprof_buf[first_free_mprof_buf++]; 392 mpp->name = mtx_name(m); 393 mpp->file = p; 394 mpp->line = m->mtx_lineno; 395 mpp->next = mprof_hash[hash]; 396 if (mprof_hash[hash] != NULL) 397 ++mutex_prof_collisions; 398 mprof_hash[hash] = mpp; 399 ++mutex_prof_records; 400 } 401 /* 402 * Record if the mutex has been held longer now than ever 403 * before. 404 */ 405 if (now - acqtime > mpp->cnt_max) 406 mpp->cnt_max = now - acqtime; 407 mpp->cnt_tot += now - acqtime; 408 mpp->cnt_cur++; 409 unlock: 410 mtx_unlock_spin(&mprof_mtx); 411 } 412 out: 413 #endif 414 _rel_sleep_lock(m, curthread, opts, file, line); 415 } 416 417 void 418 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) 419 { 420 421 MPASS(curthread != NULL); 422 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 423 ("mtx_lock_spin() of sleep mutex %s @ %s:%d", 424 m->mtx_object.lo_name, file, line)); 425 #if defined(SMP) || LOCK_DEBUG > 0 || 1 426 _get_spin_lock(m, curthread, opts, file, line); 427 #else 428 critical_enter(); 429 #endif 430 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 431 line); 432 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 433 } 434 435 void 436 _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line) 437 { 438 439 MPASS(curthread != NULL); 440 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 441 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 442 m->mtx_object.lo_name, file, line)); 443 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 444 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 445 line); 446 mtx_assert(m, MA_OWNED); 447 #if defined(SMP) || LOCK_DEBUG > 0 || 1 448 _rel_spin_lock(m); 449 #else 450 critical_exit(); 451 #endif 452 } 453 454 /* 455 * The important part of mtx_trylock{,_flags}() 456 * Tries to acquire lock `m.' We do NOT handle recursion here. If this 457 * function is called on a recursed mutex, it will return failure and 458 * will not recursively acquire the lock. You are expected to know what 459 * you are doing. 460 */ 461 int 462 _mtx_trylock(struct mtx *m, int opts, const char *file, int line) 463 { 464 int rval; 465 466 MPASS(curthread != NULL); 467 468 rval = _obtain_lock(m, curthread); 469 470 LOCK_LOG_TRY("LOCK", &m->mtx_object, opts, rval, file, line); 471 if (rval) 472 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 473 file, line); 474 475 return (rval); 476 } 477 478 /* 479 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 480 * 481 * We call this if the lock is either contested (i.e. we need to go to 482 * sleep waiting for it), or if we need to recurse on it. 483 */ 484 void 485 _mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line) 486 { 487 struct thread *td = curthread; 488 struct thread *td1; 489 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 490 struct thread *owner; 491 #endif 492 uintptr_t v; 493 #ifdef KTR 494 int cont_logged = 0; 495 #endif 496 497 if (mtx_owned(m)) { 498 m->mtx_recurse++; 499 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 500 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 501 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 502 return; 503 } 504 505 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 506 CTR4(KTR_LOCK, 507 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 508 m->mtx_object.lo_name, (void *)m->mtx_lock, file, line); 509 510 while (!_obtain_lock(m, td)) { 511 512 mtx_lock_spin(&sched_lock); 513 v = m->mtx_lock; 514 515 /* 516 * Check if the lock has been released while spinning for 517 * the sched_lock. 518 */ 519 if (v == MTX_UNOWNED) { 520 mtx_unlock_spin(&sched_lock); 521 #ifdef __i386__ 522 ia32_pause(); 523 #endif 524 continue; 525 } 526 527 /* 528 * The mutex was marked contested on release. This means that 529 * there are threads blocked on it. 530 */ 531 if (v == MTX_CONTESTED) { 532 td1 = TAILQ_FIRST(&m->mtx_blocked); 533 MPASS(td1 != NULL); 534 m->mtx_lock = (uintptr_t)td | MTX_CONTESTED; 535 536 if (td1->td_priority < td->td_priority) 537 td->td_priority = td1->td_priority; 538 mtx_unlock_spin(&sched_lock); 539 return; 540 } 541 542 /* 543 * If the mutex isn't already contested and a failure occurs 544 * setting the contested bit, the mutex was either released 545 * or the state of the MTX_RECURSED bit changed. 546 */ 547 if ((v & MTX_CONTESTED) == 0 && 548 !atomic_cmpset_ptr(&m->mtx_lock, (void *)v, 549 (void *)(v | MTX_CONTESTED))) { 550 mtx_unlock_spin(&sched_lock); 551 #ifdef __i386__ 552 ia32_pause(); 553 #endif 554 continue; 555 } 556 557 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 558 /* 559 * If the current owner of the lock is executing on another 560 * CPU, spin instead of blocking. 561 */ 562 owner = (struct thread *)(v & MTX_FLAGMASK); 563 if (m != &Giant && thread_running(owner)) { 564 mtx_unlock_spin(&sched_lock); 565 while (mtx_owner(m) == owner && thread_running(owner)) { 566 #ifdef __i386__ 567 ia32_pause(); 568 #endif 569 } 570 continue; 571 } 572 #endif /* SMP && ADAPTIVE_MUTEXES */ 573 574 /* 575 * We definitely must sleep for this lock. 576 */ 577 mtx_assert(m, MA_NOTOWNED); 578 579 #ifdef notyet 580 /* 581 * If we're borrowing an interrupted thread's VM context, we 582 * must clean up before going to sleep. 583 */ 584 if (td->td_ithd != NULL) { 585 struct ithd *it = td->td_ithd; 586 587 if (it->it_interrupted) { 588 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 589 CTR2(KTR_LOCK, 590 "_mtx_lock_sleep: %p interrupted %p", 591 it, it->it_interrupted); 592 intr_thd_fixup(it); 593 } 594 } 595 #endif 596 597 /* 598 * Put us on the list of threads blocked on this mutex. 599 */ 600 if (TAILQ_EMPTY(&m->mtx_blocked)) { 601 td1 = mtx_owner(m); 602 LIST_INSERT_HEAD(&td1->td_contested, m, mtx_contested); 603 TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_lockq); 604 } else { 605 TAILQ_FOREACH(td1, &m->mtx_blocked, td_lockq) 606 if (td1->td_priority > td->td_priority) 607 break; 608 if (td1) 609 TAILQ_INSERT_BEFORE(td1, td, td_lockq); 610 else 611 TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_lockq); 612 } 613 #ifdef KTR 614 if (!cont_logged) { 615 CTR6(KTR_CONTENTION, 616 "contention: %p at %s:%d wants %s, taken by %s:%d", 617 td, file, line, m->mtx_object.lo_name, 618 WITNESS_FILE(&m->mtx_object), 619 WITNESS_LINE(&m->mtx_object)); 620 cont_logged = 1; 621 } 622 #endif 623 624 /* 625 * Save who we're blocked on. 626 */ 627 td->td_blocked = m; 628 td->td_lockname = m->mtx_object.lo_name; 629 TD_SET_LOCK(td); 630 propagate_priority(td); 631 632 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 633 CTR3(KTR_LOCK, 634 "_mtx_lock_sleep: p %p blocked on [%p] %s", td, m, 635 m->mtx_object.lo_name); 636 637 td->td_proc->p_stats->p_ru.ru_nvcsw++; 638 mi_switch(); 639 640 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 641 CTR3(KTR_LOCK, 642 "_mtx_lock_sleep: p %p free from blocked on [%p] %s", 643 td, m, m->mtx_object.lo_name); 644 645 mtx_unlock_spin(&sched_lock); 646 } 647 648 #ifdef KTR 649 if (cont_logged) { 650 CTR4(KTR_CONTENTION, 651 "contention end: %s acquired by %p at %s:%d", 652 m->mtx_object.lo_name, td, file, line); 653 } 654 #endif 655 return; 656 } 657 658 /* 659 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. 660 * 661 * This is only called if we need to actually spin for the lock. Recursion 662 * is handled inline. 663 */ 664 void 665 _mtx_lock_spin(struct mtx *m, int opts, const char *file, int line) 666 { 667 int i = 0; 668 669 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 670 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 671 672 for (;;) { 673 if (_obtain_lock(m, curthread)) 674 break; 675 676 /* Give interrupts a chance while we spin. */ 677 critical_exit(); 678 while (m->mtx_lock != MTX_UNOWNED) { 679 if (i++ < 10000000) { 680 #ifdef __i386__ 681 ia32_pause(); 682 #endif 683 continue; 684 } 685 if (i < 60000000) 686 DELAY(1); 687 #ifdef DDB 688 else if (!db_active) 689 #else 690 else 691 #endif 692 panic("spin lock %s held by %p for > 5 seconds", 693 m->mtx_object.lo_name, (void *)m->mtx_lock); 694 #ifdef __i386__ 695 ia32_pause(); 696 #endif 697 } 698 critical_enter(); 699 } 700 701 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 702 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 703 704 return; 705 } 706 707 /* 708 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 709 * 710 * We are only called here if the lock is recursed or contested (i.e. we 711 * need to wake up a blocked thread). 712 */ 713 void 714 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) 715 { 716 struct thread *td, *td1; 717 struct mtx *m1; 718 int pri; 719 720 td = curthread; 721 722 if (mtx_recursed(m)) { 723 if (--(m->mtx_recurse) == 0) 724 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 725 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 726 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 727 return; 728 } 729 730 mtx_lock_spin(&sched_lock); 731 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 732 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 733 734 td1 = TAILQ_FIRST(&m->mtx_blocked); 735 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 736 if (td1 == NULL) { 737 _release_lock_quick(m); 738 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 739 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p no sleepers", m); 740 mtx_unlock_spin(&sched_lock); 741 return; 742 } 743 #endif 744 MPASS(td->td_proc->p_magic == P_MAGIC); 745 MPASS(td1->td_proc->p_magic == P_MAGIC); 746 747 TAILQ_REMOVE(&m->mtx_blocked, td1, td_lockq); 748 749 if (TAILQ_EMPTY(&m->mtx_blocked)) { 750 LIST_REMOVE(m, mtx_contested); 751 _release_lock_quick(m); 752 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 753 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m); 754 } else 755 atomic_store_rel_ptr(&m->mtx_lock, (void *)MTX_CONTESTED); 756 757 pri = PRI_MAX; 758 LIST_FOREACH(m1, &td->td_contested, mtx_contested) { 759 int cp = TAILQ_FIRST(&m1->mtx_blocked)->td_priority; 760 if (cp < pri) 761 pri = cp; 762 } 763 764 if (pri > td->td_base_pri) 765 pri = td->td_base_pri; 766 td->td_priority = pri; 767 768 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 769 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p contested setrunqueue %p", 770 m, td1); 771 772 td1->td_blocked = NULL; 773 TD_CLR_LOCK(td1); 774 if (!TD_CAN_RUN(td1)) { 775 mtx_unlock_spin(&sched_lock); 776 return; 777 } 778 setrunqueue(td1); 779 780 if (td->td_critnest == 1 && td1->td_priority < pri) { 781 #ifdef notyet 782 if (td->td_ithd != NULL) { 783 struct ithd *it = td->td_ithd; 784 785 if (it->it_interrupted) { 786 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 787 CTR2(KTR_LOCK, 788 "_mtx_unlock_sleep: %p interrupted %p", 789 it, it->it_interrupted); 790 intr_thd_fixup(it); 791 } 792 } 793 #endif 794 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 795 CTR2(KTR_LOCK, 796 "_mtx_unlock_sleep: %p switching out lock=%p", m, 797 (void *)m->mtx_lock); 798 799 td->td_proc->p_stats->p_ru.ru_nivcsw++; 800 mi_switch(); 801 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 802 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p", 803 m, (void *)m->mtx_lock); 804 } 805 806 mtx_unlock_spin(&sched_lock); 807 808 return; 809 } 810 811 /* 812 * All the unlocking of MTX_SPIN locks is done inline. 813 * See the _rel_spin_lock() macro for the details. 814 */ 815 816 /* 817 * The backing function for the INVARIANTS-enabled mtx_assert() 818 */ 819 #ifdef INVARIANT_SUPPORT 820 void 821 _mtx_assert(struct mtx *m, int what, const char *file, int line) 822 { 823 824 if (panicstr != NULL) 825 return; 826 switch (what) { 827 case MA_OWNED: 828 case MA_OWNED | MA_RECURSED: 829 case MA_OWNED | MA_NOTRECURSED: 830 if (!mtx_owned(m)) 831 panic("mutex %s not owned at %s:%d", 832 m->mtx_object.lo_name, file, line); 833 if (mtx_recursed(m)) { 834 if ((what & MA_NOTRECURSED) != 0) 835 panic("mutex %s recursed at %s:%d", 836 m->mtx_object.lo_name, file, line); 837 } else if ((what & MA_RECURSED) != 0) { 838 panic("mutex %s unrecursed at %s:%d", 839 m->mtx_object.lo_name, file, line); 840 } 841 break; 842 case MA_NOTOWNED: 843 if (mtx_owned(m)) 844 panic("mutex %s owned at %s:%d", 845 m->mtx_object.lo_name, file, line); 846 break; 847 default: 848 panic("unknown mtx_assert at %s:%d", file, line); 849 } 850 } 851 #endif 852 853 /* 854 * The MUTEX_DEBUG-enabled mtx_validate() 855 * 856 * Most of these checks have been moved off into the LO_INITIALIZED flag 857 * maintained by the witness code. 858 */ 859 #ifdef MUTEX_DEBUG 860 861 void mtx_validate(struct mtx *); 862 863 void 864 mtx_validate(struct mtx *m) 865 { 866 867 /* 868 * XXX: When kernacc() does not require Giant we can reenable this check 869 */ 870 #ifdef notyet 871 /* 872 * XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly 873 * we can re-enable the kernacc() checks. 874 */ 875 #ifndef __alpha__ 876 /* 877 * Can't call kernacc() from early init386(), especially when 878 * initializing Giant mutex, because some stuff in kernacc() 879 * requires Giant itself. 880 */ 881 if (!cold) 882 if (!kernacc((caddr_t)m, sizeof(m), 883 VM_PROT_READ | VM_PROT_WRITE)) 884 panic("Can't read and write to mutex %p", m); 885 #endif 886 #endif 887 } 888 #endif 889 890 /* 891 * General init routine used by the MTX_SYSINIT() macro. 892 */ 893 void 894 mtx_sysinit(void *arg) 895 { 896 struct mtx_args *margs = arg; 897 898 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); 899 } 900 901 /* 902 * Mutex initialization routine; initialize lock `m' of type contained in 903 * `opts' with options contained in `opts' and name `name.' The optional 904 * lock type `type' is used as a general lock category name for use with 905 * witness. 906 */ 907 void 908 mtx_init(struct mtx *m, const char *name, const char *type, int opts) 909 { 910 struct lock_object *lock; 911 912 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 913 MTX_NOWITNESS | MTX_DUPOK)) == 0); 914 915 #ifdef MUTEX_DEBUG 916 /* Diagnostic and error correction */ 917 mtx_validate(m); 918 #endif 919 920 lock = &m->mtx_object; 921 KASSERT((lock->lo_flags & LO_INITIALIZED) == 0, 922 ("mutex %s %p already initialized", name, m)); 923 bzero(m, sizeof(*m)); 924 if (opts & MTX_SPIN) 925 lock->lo_class = &lock_class_mtx_spin; 926 else 927 lock->lo_class = &lock_class_mtx_sleep; 928 lock->lo_name = name; 929 lock->lo_type = type != NULL ? type : name; 930 if (opts & MTX_QUIET) 931 lock->lo_flags = LO_QUIET; 932 if (opts & MTX_RECURSE) 933 lock->lo_flags |= LO_RECURSABLE; 934 if ((opts & MTX_NOWITNESS) == 0) 935 lock->lo_flags |= LO_WITNESS; 936 if (opts & MTX_DUPOK) 937 lock->lo_flags |= LO_DUPOK; 938 939 m->mtx_lock = MTX_UNOWNED; 940 TAILQ_INIT(&m->mtx_blocked); 941 942 LOCK_LOG_INIT(lock, opts); 943 944 WITNESS_INIT(lock); 945 } 946 947 /* 948 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 949 * passed in as a flag here because if the corresponding mtx_init() was 950 * called with MTX_QUIET set, then it will already be set in the mutex's 951 * flags. 952 */ 953 void 954 mtx_destroy(struct mtx *m) 955 { 956 957 LOCK_LOG_DESTROY(&m->mtx_object, 0); 958 959 if (!mtx_owned(m)) 960 MPASS(mtx_unowned(m)); 961 else { 962 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 963 964 /* Tell witness this isn't locked to make it happy. */ 965 WITNESS_UNLOCK(&m->mtx_object, LOP_EXCLUSIVE, __FILE__, 966 __LINE__); 967 } 968 969 WITNESS_DESTROY(&m->mtx_object); 970 } 971 972 /* 973 * Intialize the mutex code and system mutexes. This is called from the MD 974 * startup code prior to mi_startup(). The per-CPU data space needs to be 975 * setup before this is called. 976 */ 977 void 978 mutex_init(void) 979 { 980 981 /* Setup thread0 so that mutexes work. */ 982 LIST_INIT(&thread0.td_contested); 983 984 /* 985 * Initialize mutexes. 986 */ 987 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 988 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE); 989 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 990 mtx_lock(&Giant); 991 } 992