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/stdint.h> 53 #include <sys/sysctl.h> 54 #include <sys/vmmeter.h> 55 56 #include <machine/atomic.h> 57 #include <machine/bus.h> 58 #include <machine/clock.h> 59 #include <machine/cpu.h> 60 61 #include <ddb/ddb.h> 62 63 #include <vm/vm.h> 64 #include <vm/vm_extern.h> 65 66 /* 67 * Internal utility macros. 68 */ 69 #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED) 70 71 #define mtx_owner(m) (mtx_unowned((m)) ? NULL \ 72 : (struct thread *)((m)->mtx_lock & MTX_FLAGMASK)) 73 74 /* XXXKSE This test will change. */ 75 #define thread_running(td) \ 76 ((td)->td_kse != NULL && (td)->td_kse->ke_oncpu != NOCPU) 77 78 /* 79 * Lock classes for sleep and spin mutexes. 80 */ 81 struct lock_class lock_class_mtx_sleep = { 82 "sleep mutex", 83 LC_SLEEPLOCK | LC_RECURSABLE 84 }; 85 struct lock_class lock_class_mtx_spin = { 86 "spin mutex", 87 LC_SPINLOCK | LC_RECURSABLE 88 }; 89 90 /* 91 * System-wide mutexes 92 */ 93 struct mtx sched_lock; 94 struct mtx Giant; 95 96 /* 97 * Prototypes for non-exported routines. 98 */ 99 static void propagate_priority(struct thread *); 100 101 static void 102 propagate_priority(struct thread *td) 103 { 104 int pri = td->td_priority; 105 struct mtx *m = td->td_blocked; 106 107 mtx_assert(&sched_lock, MA_OWNED); 108 for (;;) { 109 struct thread *td1; 110 111 td = mtx_owner(m); 112 113 if (td == NULL) { 114 /* 115 * This really isn't quite right. Really 116 * ought to bump priority of thread that 117 * next acquires the mutex. 118 */ 119 MPASS(m->mtx_lock == MTX_CONTESTED); 120 return; 121 } 122 123 MPASS(td->td_proc != NULL); 124 MPASS(td->td_proc->p_magic == P_MAGIC); 125 KASSERT(!TD_IS_SLEEPING(td), ("sleeping thread owns a mutex")); 126 if (td->td_priority <= pri) /* lower is higher priority */ 127 return; 128 129 130 /* 131 * If lock holder is actually running, just bump priority. 132 */ 133 if (TD_IS_RUNNING(td)) { 134 td->td_priority = pri; 135 return; 136 } 137 138 #ifndef SMP 139 /* 140 * For UP, we check to see if td is curthread (this shouldn't 141 * ever happen however as it would mean we are in a deadlock.) 142 */ 143 KASSERT(td != curthread, ("Deadlock detected")); 144 #endif 145 146 /* 147 * If on run queue move to new run queue, and quit. 148 * XXXKSE this gets a lot more complicated under threads 149 * but try anyhow. 150 */ 151 if (TD_ON_RUNQ(td)) { 152 MPASS(td->td_blocked == NULL); 153 sched_prio(td, pri); 154 return; 155 } 156 /* 157 * Adjust for any other cases. 158 */ 159 td->td_priority = pri; 160 161 /* 162 * If we aren't blocked on a mutex, we should be. 163 */ 164 KASSERT(TD_ON_LOCK(td), ( 165 "process %d(%s):%d holds %s but isn't blocked on a mutex\n", 166 td->td_proc->p_pid, td->td_proc->p_comm, td->td_state, 167 m->mtx_object.lo_name)); 168 169 /* 170 * Pick up the mutex that td is blocked on. 171 */ 172 m = td->td_blocked; 173 MPASS(m != NULL); 174 175 /* 176 * Check if the thread needs to be moved up on 177 * the blocked chain 178 */ 179 if (td == TAILQ_FIRST(&m->mtx_blocked)) { 180 continue; 181 } 182 183 td1 = TAILQ_PREV(td, threadqueue, td_lockq); 184 if (td1->td_priority <= pri) { 185 continue; 186 } 187 188 /* 189 * Remove thread from blocked chain and determine where 190 * it should be moved up to. Since we know that td1 has 191 * a lower priority than td, we know that at least one 192 * thread in the chain has a lower priority and that 193 * td1 will thus not be NULL after the loop. 194 */ 195 TAILQ_REMOVE(&m->mtx_blocked, td, td_lockq); 196 TAILQ_FOREACH(td1, &m->mtx_blocked, td_lockq) { 197 MPASS(td1->td_proc->p_magic == P_MAGIC); 198 if (td1->td_priority > pri) 199 break; 200 } 201 202 MPASS(td1 != NULL); 203 TAILQ_INSERT_BEFORE(td1, td, td_lockq); 204 CTR4(KTR_LOCK, 205 "propagate_priority: p %p moved before %p on [%p] %s", 206 td, td1, m, m->mtx_object.lo_name); 207 } 208 } 209 210 #ifdef MUTEX_PROFILING 211 SYSCTL_NODE(_debug, OID_AUTO, mutex, CTLFLAG_RD, NULL, "mutex debugging"); 212 SYSCTL_NODE(_debug_mutex, OID_AUTO, prof, CTLFLAG_RD, NULL, "mutex profiling"); 213 static int mutex_prof_enable = 0; 214 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, enable, CTLFLAG_RW, 215 &mutex_prof_enable, 0, "Enable tracing of mutex holdtime"); 216 217 struct mutex_prof { 218 const char *name; 219 const char *file; 220 int line; 221 struct { 222 uintmax_t max; 223 uintmax_t tot; 224 uintmax_t cur; 225 } cnt; 226 struct mutex_prof *next; 227 }; 228 229 /* 230 * mprof_buf is a static pool of profiling records to avoid possible 231 * reentrance of the memory allocation functions. 232 * 233 * Note: NUM_MPROF_BUFFERS must be smaller than MPROF_HASH_SIZE. 234 */ 235 #define NUM_MPROF_BUFFERS 1000 236 static struct mutex_prof mprof_buf[NUM_MPROF_BUFFERS]; 237 static int first_free_mprof_buf; 238 #define MPROF_HASH_SIZE 1009 239 static struct mutex_prof *mprof_hash[MPROF_HASH_SIZE]; 240 241 static int mutex_prof_acquisitions; 242 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, acquisitions, CTLFLAG_RD, 243 &mutex_prof_acquisitions, 0, "Number of mutex acquistions recorded"); 244 static int mutex_prof_records; 245 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, records, CTLFLAG_RD, 246 &mutex_prof_records, 0, "Number of profiling records"); 247 static int mutex_prof_maxrecords = NUM_MPROF_BUFFERS; 248 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, maxrecords, CTLFLAG_RD, 249 &mutex_prof_maxrecords, 0, "Maximum number of profiling records"); 250 static int mutex_prof_rejected; 251 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, rejected, CTLFLAG_RD, 252 &mutex_prof_rejected, 0, "Number of rejected profiling records"); 253 static int mutex_prof_hashsize = MPROF_HASH_SIZE; 254 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, hashsize, CTLFLAG_RD, 255 &mutex_prof_hashsize, 0, "Hash size"); 256 static int mutex_prof_collisions = 0; 257 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, collisions, CTLFLAG_RD, 258 &mutex_prof_collisions, 0, "Number of hash collisions"); 259 260 /* 261 * mprof_mtx protects the profiling buffers and the hash. 262 */ 263 static struct mtx mprof_mtx; 264 MTX_SYSINIT(mprof, &mprof_mtx, "mutex profiling lock", MTX_SPIN | MTX_QUIET); 265 266 static u_int64_t 267 nanoseconds(void) 268 { 269 struct timespec tv; 270 271 nanotime(&tv); 272 return (tv.tv_sec * (u_int64_t)1000000000 + tv.tv_nsec); 273 } 274 275 static int 276 dump_mutex_prof_stats(SYSCTL_HANDLER_ARGS) 277 { 278 struct sbuf *sb; 279 int error, i; 280 281 if (first_free_mprof_buf == 0) 282 return (SYSCTL_OUT(req, "No locking recorded", 283 sizeof("No locking recorded"))); 284 285 sb = sbuf_new(NULL, NULL, 1024, SBUF_AUTOEXTEND); 286 sbuf_printf(sb, "%6s %12s %11s %5s %s\n", 287 "max", "total", "count", "avg", "name"); 288 /* 289 * XXX this spinlock seems to be by far the largest perpetrator 290 * of spinlock latency (1.6 msec on an Athlon1600 was recorded 291 * even before I pessimized it further by moving the average 292 * computation here). 293 */ 294 mtx_lock_spin(&mprof_mtx); 295 for (i = 0; i < first_free_mprof_buf; ++i) 296 sbuf_printf(sb, "%6ju %12ju %11ju %5ju %s:%d (%s)\n", 297 mprof_buf[i].cnt.max / 1000, 298 mprof_buf[i].cnt.tot / 1000, 299 mprof_buf[i].cnt.cur, 300 mprof_buf[i].cnt.cur == 0 ? (uintmax_t)0 : 301 mprof_buf[i].cnt.tot / (mprof_buf[i].cnt.cur * 1000), 302 mprof_buf[i].file, mprof_buf[i].line, mprof_buf[i].name); 303 mtx_unlock_spin(&mprof_mtx); 304 sbuf_finish(sb); 305 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1); 306 sbuf_delete(sb); 307 return (error); 308 } 309 SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD, 310 NULL, 0, dump_mutex_prof_stats, "A", "Mutex profiling statistics"); 311 #endif 312 313 /* 314 * Function versions of the inlined __mtx_* macros. These are used by 315 * modules and can also be called from assembly language if needed. 316 */ 317 void 318 _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line) 319 { 320 321 MPASS(curthread != NULL); 322 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 323 ("mtx_lock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 324 file, line)); 325 _get_sleep_lock(m, curthread, opts, file, line); 326 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 327 line); 328 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 329 #ifdef MUTEX_PROFILING 330 /* don't reset the timer when/if recursing */ 331 if (m->mtx_acqtime == 0) { 332 m->mtx_filename = file; 333 m->mtx_lineno = line; 334 m->mtx_acqtime = mutex_prof_enable ? nanoseconds() : 0; 335 ++mutex_prof_acquisitions; 336 } 337 #endif 338 } 339 340 void 341 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) 342 { 343 344 MPASS(curthread != NULL); 345 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 346 ("mtx_unlock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 347 file, line)); 348 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 349 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 350 line); 351 mtx_assert(m, MA_OWNED); 352 #ifdef MUTEX_PROFILING 353 if (m->mtx_acqtime != 0) { 354 static const char *unknown = "(unknown)"; 355 struct mutex_prof *mpp; 356 u_int64_t acqtime, now; 357 const char *p, *q; 358 volatile u_int hash; 359 360 now = nanoseconds(); 361 acqtime = m->mtx_acqtime; 362 m->mtx_acqtime = 0; 363 if (now <= acqtime) 364 goto out; 365 for (p = m->mtx_filename; strncmp(p, "../", 3) == 0; p += 3) 366 /* nothing */ ; 367 if (p == NULL || *p == '\0') 368 p = unknown; 369 for (hash = m->mtx_lineno, q = p; *q != '\0'; ++q) 370 hash = (hash * 2 + *q) % MPROF_HASH_SIZE; 371 mtx_lock_spin(&mprof_mtx); 372 for (mpp = mprof_hash[hash]; mpp != NULL; mpp = mpp->next) 373 if (mpp->line == m->mtx_lineno && 374 strcmp(mpp->file, p) == 0) 375 break; 376 if (mpp == NULL) { 377 /* Just exit if we cannot get a trace buffer */ 378 if (first_free_mprof_buf >= NUM_MPROF_BUFFERS) { 379 ++mutex_prof_rejected; 380 goto unlock; 381 } 382 mpp = &mprof_buf[first_free_mprof_buf++]; 383 mpp->name = mtx_name(m); 384 mpp->file = p; 385 mpp->line = m->mtx_lineno; 386 mpp->next = mprof_hash[hash]; 387 if (mprof_hash[hash] != NULL) 388 ++mutex_prof_collisions; 389 mprof_hash[hash] = mpp; 390 ++mutex_prof_records; 391 } 392 /* 393 * Record if the mutex has been held longer now than ever 394 * before. 395 */ 396 if (now - acqtime > mpp->cnt.max) 397 mpp->cnt.max = now - acqtime; 398 mpp->cnt.tot += now - acqtime; 399 mpp->cnt.cur++; 400 unlock: 401 mtx_unlock_spin(&mprof_mtx); 402 } 403 out: 404 #endif 405 _rel_sleep_lock(m, curthread, opts, file, line); 406 } 407 408 void 409 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) 410 { 411 412 MPASS(curthread != NULL); 413 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 414 ("mtx_lock_spin() of sleep mutex %s @ %s:%d", 415 m->mtx_object.lo_name, file, line)); 416 #if defined(SMP) || LOCK_DEBUG > 0 || 1 417 _get_spin_lock(m, curthread, opts, file, line); 418 #else 419 critical_enter(); 420 #endif 421 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 422 line); 423 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 424 } 425 426 void 427 _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line) 428 { 429 430 MPASS(curthread != NULL); 431 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 432 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 433 m->mtx_object.lo_name, file, line)); 434 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 435 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 436 line); 437 mtx_assert(m, MA_OWNED); 438 #if defined(SMP) || LOCK_DEBUG > 0 || 1 439 _rel_spin_lock(m); 440 #else 441 critical_exit(); 442 #endif 443 } 444 445 /* 446 * The important part of mtx_trylock{,_flags}() 447 * Tries to acquire lock `m.' We do NOT handle recursion here; we assume that 448 * if we're called, it's because we know we don't already own this lock. 449 */ 450 int 451 _mtx_trylock(struct mtx *m, int opts, const char *file, int line) 452 { 453 int rval; 454 455 MPASS(curthread != NULL); 456 457 rval = _obtain_lock(m, curthread); 458 459 LOCK_LOG_TRY("LOCK", &m->mtx_object, opts, rval, file, line); 460 if (rval) { 461 /* 462 * We do not handle recursion in _mtx_trylock; see the 463 * note at the top of the routine. 464 */ 465 KASSERT(!mtx_recursed(m), 466 ("mtx_trylock() called on a recursed mutex")); 467 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 468 file, line); 469 } 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 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 485 struct thread *owner; 486 #endif 487 #ifdef KTR 488 int cont_logged = 0; 489 #endif 490 491 if ((m->mtx_lock & MTX_FLAGMASK) == (uintptr_t)td) { 492 m->mtx_recurse++; 493 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 494 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 495 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 496 return; 497 } 498 499 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 500 CTR4(KTR_LOCK, 501 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 502 m->mtx_object.lo_name, (void *)m->mtx_lock, file, line); 503 504 while (!_obtain_lock(m, td)) { 505 uintptr_t v; 506 struct thread *td1; 507 508 mtx_lock_spin(&sched_lock); 509 /* 510 * Check if the lock has been released while spinning for 511 * the sched_lock. 512 */ 513 if ((v = m->mtx_lock) == MTX_UNOWNED) { 514 mtx_unlock_spin(&sched_lock); 515 #ifdef __i386__ 516 ia32_pause(); 517 #endif 518 continue; 519 } 520 521 /* 522 * The mutex was marked contested on release. This means that 523 * there are threads blocked on it. 524 */ 525 if (v == MTX_CONTESTED) { 526 td1 = TAILQ_FIRST(&m->mtx_blocked); 527 MPASS(td1 != NULL); 528 m->mtx_lock = (uintptr_t)td | MTX_CONTESTED; 529 530 if (td1->td_priority < td->td_priority) 531 td->td_priority = td1->td_priority; 532 mtx_unlock_spin(&sched_lock); 533 return; 534 } 535 536 /* 537 * If the mutex isn't already contested and a failure occurs 538 * setting the contested bit, the mutex was either released 539 * or the state of the MTX_RECURSED bit changed. 540 */ 541 if ((v & MTX_CONTESTED) == 0 && 542 !atomic_cmpset_ptr(&m->mtx_lock, (void *)v, 543 (void *)(v | MTX_CONTESTED))) { 544 mtx_unlock_spin(&sched_lock); 545 #ifdef __i386__ 546 ia32_pause(); 547 #endif 548 continue; 549 } 550 551 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 552 /* 553 * If the current owner of the lock is executing on another 554 * CPU, spin instead of blocking. 555 */ 556 owner = (struct thread *)(v & MTX_FLAGMASK); 557 if (m != &Giant && thread_running(owner)) { 558 mtx_unlock_spin(&sched_lock); 559 while (mtx_owner(m) == owner && thread_running(owner)) { 560 #ifdef __i386__ 561 ia32_pause(); 562 #endif 563 } 564 continue; 565 } 566 #endif /* SMP && ADAPTIVE_MUTEXES */ 567 568 /* 569 * We definitely must sleep for this lock. 570 */ 571 mtx_assert(m, MA_NOTOWNED); 572 573 #ifdef notyet 574 /* 575 * If we're borrowing an interrupted thread's VM context, we 576 * must clean up before going to sleep. 577 */ 578 if (td->td_ithd != NULL) { 579 struct ithd *it = td->td_ithd; 580 581 if (it->it_interrupted) { 582 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 583 CTR2(KTR_LOCK, 584 "_mtx_lock_sleep: %p interrupted %p", 585 it, it->it_interrupted); 586 intr_thd_fixup(it); 587 } 588 } 589 #endif 590 591 /* 592 * Put us on the list of threads blocked on this mutex. 593 */ 594 if (TAILQ_EMPTY(&m->mtx_blocked)) { 595 td1 = mtx_owner(m); 596 LIST_INSERT_HEAD(&td1->td_contested, m, mtx_contested); 597 TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_lockq); 598 } else { 599 TAILQ_FOREACH(td1, &m->mtx_blocked, td_lockq) 600 if (td1->td_priority > td->td_priority) 601 break; 602 if (td1) 603 TAILQ_INSERT_BEFORE(td1, td, td_lockq); 604 else 605 TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_lockq); 606 } 607 #ifdef KTR 608 if (!cont_logged) { 609 CTR6(KTR_CONTENTION, 610 "contention: %p at %s:%d wants %s, taken by %s:%d", 611 td, file, line, m->mtx_object.lo_name, 612 WITNESS_FILE(&m->mtx_object), 613 WITNESS_LINE(&m->mtx_object)); 614 cont_logged = 1; 615 } 616 #endif 617 618 /* 619 * Save who we're blocked on. 620 */ 621 td->td_blocked = m; 622 td->td_lockname = m->mtx_object.lo_name; 623 TD_SET_LOCK(td); 624 propagate_priority(td); 625 626 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 627 CTR3(KTR_LOCK, 628 "_mtx_lock_sleep: p %p blocked on [%p] %s", td, m, 629 m->mtx_object.lo_name); 630 631 td->td_proc->p_stats->p_ru.ru_nvcsw++; 632 mi_switch(); 633 634 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 635 CTR3(KTR_LOCK, 636 "_mtx_lock_sleep: p %p free from blocked on [%p] %s", 637 td, m, m->mtx_object.lo_name); 638 639 mtx_unlock_spin(&sched_lock); 640 } 641 642 #ifdef KTR 643 if (cont_logged) { 644 CTR4(KTR_CONTENTION, 645 "contention end: %s acquired by %p at %s:%d", 646 m->mtx_object.lo_name, td, file, line); 647 } 648 #endif 649 return; 650 } 651 652 /* 653 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. 654 * 655 * This is only called if we need to actually spin for the lock. Recursion 656 * is handled inline. 657 */ 658 void 659 _mtx_lock_spin(struct mtx *m, int opts, const char *file, int line) 660 { 661 int i = 0; 662 663 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 664 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 665 666 for (;;) { 667 if (_obtain_lock(m, curthread)) 668 break; 669 670 /* Give interrupts a chance while we spin. */ 671 critical_exit(); 672 while (m->mtx_lock != MTX_UNOWNED) { 673 if (i++ < 10000000) { 674 #ifdef __i386__ 675 ia32_pause(); 676 #endif 677 continue; 678 } 679 if (i < 60000000) 680 DELAY(1); 681 #ifdef DDB 682 else if (!db_active) 683 #else 684 else 685 #endif 686 panic("spin lock %s held by %p for > 5 seconds", 687 m->mtx_object.lo_name, (void *)m->mtx_lock); 688 #ifdef __i386__ 689 ia32_pause(); 690 #endif 691 } 692 critical_enter(); 693 } 694 695 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 696 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 697 698 return; 699 } 700 701 /* 702 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 703 * 704 * We are only called here if the lock is recursed or contested (i.e. we 705 * need to wake up a blocked thread). 706 */ 707 void 708 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) 709 { 710 struct thread *td, *td1; 711 struct mtx *m1; 712 int pri; 713 714 td = curthread; 715 716 if (mtx_recursed(m)) { 717 if (--(m->mtx_recurse) == 0) 718 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 719 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 720 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 721 return; 722 } 723 724 mtx_lock_spin(&sched_lock); 725 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 726 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 727 728 td1 = TAILQ_FIRST(&m->mtx_blocked); 729 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 730 if (td1 == NULL) { 731 _release_lock_quick(m); 732 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 733 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p no sleepers", m); 734 mtx_unlock_spin(&sched_lock); 735 return; 736 } 737 #endif 738 MPASS(td->td_proc->p_magic == P_MAGIC); 739 MPASS(td1->td_proc->p_magic == P_MAGIC); 740 741 TAILQ_REMOVE(&m->mtx_blocked, td1, td_lockq); 742 743 if (TAILQ_EMPTY(&m->mtx_blocked)) { 744 LIST_REMOVE(m, mtx_contested); 745 _release_lock_quick(m); 746 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 747 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m); 748 } else 749 atomic_store_rel_ptr(&m->mtx_lock, (void *)MTX_CONTESTED); 750 751 pri = PRI_MAX; 752 LIST_FOREACH(m1, &td->td_contested, mtx_contested) { 753 int cp = TAILQ_FIRST(&m1->mtx_blocked)->td_priority; 754 if (cp < pri) 755 pri = cp; 756 } 757 758 if (pri > td->td_base_pri) 759 pri = td->td_base_pri; 760 td->td_priority = pri; 761 762 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 763 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p contested setrunqueue %p", 764 m, td1); 765 766 td1->td_blocked = NULL; 767 TD_CLR_LOCK(td1); 768 if (!TD_CAN_RUN(td1)) { 769 mtx_unlock_spin(&sched_lock); 770 return; 771 } 772 setrunqueue(td1); 773 774 if (td->td_critnest == 1 && td1->td_priority < pri) { 775 #ifdef notyet 776 if (td->td_ithd != NULL) { 777 struct ithd *it = td->td_ithd; 778 779 if (it->it_interrupted) { 780 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 781 CTR2(KTR_LOCK, 782 "_mtx_unlock_sleep: %p interrupted %p", 783 it, it->it_interrupted); 784 intr_thd_fixup(it); 785 } 786 } 787 #endif 788 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 789 CTR2(KTR_LOCK, 790 "_mtx_unlock_sleep: %p switching out lock=%p", m, 791 (void *)m->mtx_lock); 792 793 td->td_proc->p_stats->p_ru.ru_nivcsw++; 794 mi_switch(); 795 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 796 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p", 797 m, (void *)m->mtx_lock); 798 } 799 800 mtx_unlock_spin(&sched_lock); 801 802 return; 803 } 804 805 /* 806 * All the unlocking of MTX_SPIN locks is done inline. 807 * See the _rel_spin_lock() macro for the details. 808 */ 809 810 /* 811 * The backing function for the INVARIANTS-enabled mtx_assert() 812 */ 813 #ifdef INVARIANT_SUPPORT 814 void 815 _mtx_assert(struct mtx *m, int what, const char *file, int line) 816 { 817 818 if (panicstr != NULL) 819 return; 820 switch (what) { 821 case MA_OWNED: 822 case MA_OWNED | MA_RECURSED: 823 case MA_OWNED | MA_NOTRECURSED: 824 if (!mtx_owned(m)) 825 panic("mutex %s not owned at %s:%d", 826 m->mtx_object.lo_name, file, line); 827 if (mtx_recursed(m)) { 828 if ((what & MA_NOTRECURSED) != 0) 829 panic("mutex %s recursed at %s:%d", 830 m->mtx_object.lo_name, file, line); 831 } else if ((what & MA_RECURSED) != 0) { 832 panic("mutex %s unrecursed at %s:%d", 833 m->mtx_object.lo_name, file, line); 834 } 835 break; 836 case MA_NOTOWNED: 837 if (mtx_owned(m)) 838 panic("mutex %s owned at %s:%d", 839 m->mtx_object.lo_name, file, line); 840 break; 841 default: 842 panic("unknown mtx_assert at %s:%d", file, line); 843 } 844 } 845 #endif 846 847 /* 848 * The MUTEX_DEBUG-enabled mtx_validate() 849 * 850 * Most of these checks have been moved off into the LO_INITIALIZED flag 851 * maintained by the witness code. 852 */ 853 #ifdef MUTEX_DEBUG 854 855 void mtx_validate(struct mtx *); 856 857 void 858 mtx_validate(struct mtx *m) 859 { 860 861 /* 862 * XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly 863 * we can re-enable the kernacc() checks. 864 */ 865 #ifndef __alpha__ 866 /* 867 * Can't call kernacc() from early init386(), especially when 868 * initializing Giant mutex, because some stuff in kernacc() 869 * requires Giant itself. 870 */ 871 if (!cold) 872 if (!kernacc((caddr_t)m, sizeof(m), 873 VM_PROT_READ | VM_PROT_WRITE)) 874 panic("Can't read and write to mutex %p", m); 875 #endif 876 } 877 #endif 878 879 /* 880 * General init routine used by the MTX_SYSINIT() macro. 881 */ 882 void 883 mtx_sysinit(void *arg) 884 { 885 struct mtx_args *margs = arg; 886 887 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); 888 } 889 890 /* 891 * Mutex initialization routine; initialize lock `m' of type contained in 892 * `opts' with options contained in `opts' and name `name.' The optional 893 * lock type `type' is used as a general lock category name for use with 894 * witness. 895 */ 896 void 897 mtx_init(struct mtx *m, const char *name, const char *type, int opts) 898 { 899 struct lock_object *lock; 900 901 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 902 MTX_SLEEPABLE | MTX_NOWITNESS | MTX_DUPOK)) == 0); 903 904 #ifdef MUTEX_DEBUG 905 /* Diagnostic and error correction */ 906 mtx_validate(m); 907 #endif 908 909 lock = &m->mtx_object; 910 KASSERT((lock->lo_flags & LO_INITIALIZED) == 0, 911 ("mutex %s %p already initialized", name, m)); 912 bzero(m, sizeof(*m)); 913 if (opts & MTX_SPIN) 914 lock->lo_class = &lock_class_mtx_spin; 915 else 916 lock->lo_class = &lock_class_mtx_sleep; 917 lock->lo_name = name; 918 lock->lo_type = type != NULL ? type : name; 919 if (opts & MTX_QUIET) 920 lock->lo_flags = LO_QUIET; 921 if (opts & MTX_RECURSE) 922 lock->lo_flags |= LO_RECURSABLE; 923 if (opts & MTX_SLEEPABLE) 924 lock->lo_flags |= LO_SLEEPABLE; 925 if ((opts & MTX_NOWITNESS) == 0) 926 lock->lo_flags |= LO_WITNESS; 927 if (opts & MTX_DUPOK) 928 lock->lo_flags |= LO_DUPOK; 929 930 m->mtx_lock = MTX_UNOWNED; 931 TAILQ_INIT(&m->mtx_blocked); 932 933 LOCK_LOG_INIT(lock, opts); 934 935 WITNESS_INIT(lock); 936 } 937 938 /* 939 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 940 * passed in as a flag here because if the corresponding mtx_init() was 941 * called with MTX_QUIET set, then it will already be set in the mutex's 942 * flags. 943 */ 944 void 945 mtx_destroy(struct mtx *m) 946 { 947 948 LOCK_LOG_DESTROY(&m->mtx_object, 0); 949 950 if (!mtx_owned(m)) 951 MPASS(mtx_unowned(m)); 952 else { 953 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 954 955 /* Tell witness this isn't locked to make it happy. */ 956 WITNESS_UNLOCK(&m->mtx_object, LOP_EXCLUSIVE, __FILE__, 957 __LINE__); 958 } 959 960 WITNESS_DESTROY(&m->mtx_object); 961 } 962 963 /* 964 * Intialize the mutex code and system mutexes. This is called from the MD 965 * startup code prior to mi_startup(). The per-CPU data space needs to be 966 * setup before this is called. 967 */ 968 void 969 mutex_init(void) 970 { 971 972 /* Setup thread0 so that mutexes work. */ 973 LIST_INIT(&thread0.td_contested); 974 975 /* 976 * Initialize mutexes. 977 */ 978 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 979 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE); 980 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 981 mtx_lock(&Giant); 982 } 983 984 /* 985 * Encapsulated Giant mutex routines. These routines provide encapsulation 986 * control for the Giant mutex, allowing sysctls to be used to turn on and 987 * off Giant around certain subsystems. The default value for the sysctls 988 * are set to what developers believe is stable and working in regards to 989 * the Giant pushdown. Developers should not turn off Giant via these 990 * sysctls unless they know what they are doing. 991 * 992 * Callers of mtx_lock_giant() are expected to pass the return value to an 993 * accompanying mtx_unlock_giant() later on. If multiple subsystems are 994 * effected by a Giant wrap, all related sysctl variables must be zero for 995 * the subsystem call to operate without Giant (as determined by the caller). 996 */ 997 998 SYSCTL_NODE(_kern, OID_AUTO, giant, CTLFLAG_RD, NULL, "Giant mutex manipulation"); 999 1000 static int kern_giant_all = 0; 1001 SYSCTL_INT(_kern_giant, OID_AUTO, all, CTLFLAG_RW, &kern_giant_all, 0, ""); 1002 1003 int kern_giant_proc = 1; /* Giant around PROC locks */ 1004 int kern_giant_file = 1; /* Giant around struct file & filedesc */ 1005 int kern_giant_ucred = 1; /* Giant around ucred */ 1006 SYSCTL_INT(_kern_giant, OID_AUTO, proc, CTLFLAG_RW, &kern_giant_proc, 0, ""); 1007 SYSCTL_INT(_kern_giant, OID_AUTO, file, CTLFLAG_RW, &kern_giant_file, 0, ""); 1008 SYSCTL_INT(_kern_giant, OID_AUTO, ucred, CTLFLAG_RW, &kern_giant_ucred, 0, ""); 1009 1010 int 1011 mtx_lock_giant(int sysctlvar) 1012 { 1013 if (sysctlvar || kern_giant_all) { 1014 mtx_lock(&Giant); 1015 return(1); 1016 } 1017 return(0); 1018 } 1019 1020 void 1021 mtx_unlock_giant(int s) 1022 { 1023 if (s) 1024 mtx_unlock(&Giant); 1025 } 1026