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 uintmax_t cnt_max; 222 uintmax_t cnt_tot; 223 uintmax_t cnt_cur; 224 struct mutex_prof *next; 225 }; 226 227 /* 228 * mprof_buf is a static pool of profiling records to avoid possible 229 * reentrance of the memory allocation functions. 230 * 231 * Note: NUM_MPROF_BUFFERS must be smaller than MPROF_HASH_SIZE. 232 */ 233 #define NUM_MPROF_BUFFERS 1000 234 static struct mutex_prof mprof_buf[NUM_MPROF_BUFFERS]; 235 static int first_free_mprof_buf; 236 #define MPROF_HASH_SIZE 1009 237 static struct mutex_prof *mprof_hash[MPROF_HASH_SIZE]; 238 /* SWAG: sbuf size = avg stat. line size * number of locks */ 239 #define MPROF_SBUF_SIZE 256 * 400 240 241 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 static int multiplier = 1; 281 282 if (first_free_mprof_buf == 0) 283 return (SYSCTL_OUT(req, "No locking recorded", 284 sizeof("No locking recorded"))); 285 286 retry_sbufops: 287 sb = sbuf_new(NULL, NULL, MPROF_SBUF_SIZE * multiplier, SBUF_FIXEDLEN); 288 sbuf_printf(sb, "%6s %12s %11s %5s %s\n", 289 "max", "total", "count", "avg", "name"); 290 /* 291 * XXX this spinlock seems to be by far the largest perpetrator 292 * of spinlock latency (1.6 msec on an Athlon1600 was recorded 293 * even before I pessimized it further by moving the average 294 * computation here). 295 */ 296 mtx_lock_spin(&mprof_mtx); 297 for (i = 0; i < first_free_mprof_buf; ++i) { 298 sbuf_printf(sb, "%6ju %12ju %11ju %5ju %s:%d (%s)\n", 299 mprof_buf[i].cnt_max / 1000, 300 mprof_buf[i].cnt_tot / 1000, 301 mprof_buf[i].cnt_cur, 302 mprof_buf[i].cnt_cur == 0 ? (uintmax_t)0 : 303 mprof_buf[i].cnt_tot / (mprof_buf[i].cnt_cur * 1000), 304 mprof_buf[i].file, mprof_buf[i].line, mprof_buf[i].name); 305 if (sbuf_overflowed(sb)) { 306 mtx_unlock_spin(&mprof_mtx); 307 sbuf_delete(sb); 308 multiplier++; 309 goto retry_sbufops; 310 } 311 } 312 mtx_unlock_spin(&mprof_mtx); 313 sbuf_finish(sb); 314 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1); 315 sbuf_delete(sb); 316 return (error); 317 } 318 SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD, 319 NULL, 0, dump_mutex_prof_stats, "A", "Mutex profiling statistics"); 320 #endif 321 322 /* 323 * Function versions of the inlined __mtx_* macros. These are used by 324 * modules and can also be called from assembly language if needed. 325 */ 326 void 327 _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line) 328 { 329 330 MPASS(curthread != NULL); 331 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 332 ("mtx_lock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 333 file, line)); 334 _get_sleep_lock(m, curthread, opts, file, line); 335 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 336 line); 337 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 338 #ifdef MUTEX_PROFILING 339 /* don't reset the timer when/if recursing */ 340 if (m->mtx_acqtime == 0) { 341 m->mtx_filename = file; 342 m->mtx_lineno = line; 343 m->mtx_acqtime = mutex_prof_enable ? nanoseconds() : 0; 344 ++mutex_prof_acquisitions; 345 } 346 #endif 347 } 348 349 void 350 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) 351 { 352 353 MPASS(curthread != NULL); 354 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep, 355 ("mtx_unlock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 356 file, line)); 357 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 358 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 359 line); 360 mtx_assert(m, MA_OWNED); 361 #ifdef MUTEX_PROFILING 362 if (m->mtx_acqtime != 0) { 363 static const char *unknown = "(unknown)"; 364 struct mutex_prof *mpp; 365 u_int64_t acqtime, now; 366 const char *p, *q; 367 volatile u_int hash; 368 369 now = nanoseconds(); 370 acqtime = m->mtx_acqtime; 371 m->mtx_acqtime = 0; 372 if (now <= acqtime) 373 goto out; 374 for (p = m->mtx_filename; 375 p != NULL && strncmp(p, "../", 3) == 0; p += 3) 376 /* nothing */ ; 377 if (p == NULL || *p == '\0') 378 p = unknown; 379 for (hash = m->mtx_lineno, q = p; *q != '\0'; ++q) 380 hash = (hash * 2 + *q) % MPROF_HASH_SIZE; 381 mtx_lock_spin(&mprof_mtx); 382 for (mpp = mprof_hash[hash]; mpp != NULL; mpp = mpp->next) 383 if (mpp->line == m->mtx_lineno && 384 strcmp(mpp->file, p) == 0) 385 break; 386 if (mpp == NULL) { 387 /* Just exit if we cannot get a trace buffer */ 388 if (first_free_mprof_buf >= NUM_MPROF_BUFFERS) { 389 ++mutex_prof_rejected; 390 goto unlock; 391 } 392 mpp = &mprof_buf[first_free_mprof_buf++]; 393 mpp->name = mtx_name(m); 394 mpp->file = p; 395 mpp->line = m->mtx_lineno; 396 mpp->next = mprof_hash[hash]; 397 if (mprof_hash[hash] != NULL) 398 ++mutex_prof_collisions; 399 mprof_hash[hash] = mpp; 400 ++mutex_prof_records; 401 } 402 /* 403 * Record if the mutex has been held longer now than ever 404 * before. 405 */ 406 if (now - acqtime > mpp->cnt_max) 407 mpp->cnt_max = now - acqtime; 408 mpp->cnt_tot += now - acqtime; 409 mpp->cnt_cur++; 410 unlock: 411 mtx_unlock_spin(&mprof_mtx); 412 } 413 out: 414 #endif 415 _rel_sleep_lock(m, curthread, opts, file, line); 416 } 417 418 void 419 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) 420 { 421 422 MPASS(curthread != NULL); 423 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 424 ("mtx_lock_spin() of sleep mutex %s @ %s:%d", 425 m->mtx_object.lo_name, file, line)); 426 #if defined(SMP) || LOCK_DEBUG > 0 || 1 427 _get_spin_lock(m, curthread, opts, file, line); 428 #else 429 critical_enter(); 430 #endif 431 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 432 line); 433 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 434 } 435 436 void 437 _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line) 438 { 439 440 MPASS(curthread != NULL); 441 KASSERT(m->mtx_object.lo_class == &lock_class_mtx_spin, 442 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 443 m->mtx_object.lo_name, file, line)); 444 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 445 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 446 line); 447 mtx_assert(m, MA_OWNED); 448 #if defined(SMP) || LOCK_DEBUG > 0 || 1 449 _rel_spin_lock(m); 450 #else 451 critical_exit(); 452 #endif 453 } 454 455 /* 456 * The important part of mtx_trylock{,_flags}() 457 * Tries to acquire lock `m.' We do NOT handle recursion here; we assume that 458 * if we're called, it's because we know we don't already own this lock. 459 */ 460 int 461 _mtx_trylock(struct mtx *m, int opts, const char *file, int line) 462 { 463 int rval; 464 465 MPASS(curthread != NULL); 466 467 rval = _obtain_lock(m, curthread); 468 469 LOCK_LOG_TRY("LOCK", &m->mtx_object, opts, rval, file, line); 470 if (rval) { 471 /* 472 * We do not handle recursion in _mtx_trylock; see the 473 * note at the top of the routine. 474 */ 475 KASSERT(!mtx_recursed(m), 476 ("mtx_trylock() called on a recursed mutex")); 477 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 478 file, line); 479 } 480 481 return (rval); 482 } 483 484 /* 485 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 486 * 487 * We call this if the lock is either contested (i.e. we need to go to 488 * sleep waiting for it), or if we need to recurse on it. 489 */ 490 void 491 _mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line) 492 { 493 struct thread *td = curthread; 494 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 495 struct thread *owner; 496 #endif 497 #ifdef KTR 498 int cont_logged = 0; 499 #endif 500 501 if ((m->mtx_lock & MTX_FLAGMASK) == (uintptr_t)td) { 502 m->mtx_recurse++; 503 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 504 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 505 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 506 return; 507 } 508 509 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 510 CTR4(KTR_LOCK, 511 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 512 m->mtx_object.lo_name, (void *)m->mtx_lock, file, line); 513 514 while (!_obtain_lock(m, td)) { 515 uintptr_t v; 516 struct thread *td1; 517 518 mtx_lock_spin(&sched_lock); 519 /* 520 * Check if the lock has been released while spinning for 521 * the sched_lock. 522 */ 523 if ((v = m->mtx_lock) == MTX_UNOWNED) { 524 mtx_unlock_spin(&sched_lock); 525 #ifdef __i386__ 526 ia32_pause(); 527 #endif 528 continue; 529 } 530 531 /* 532 * The mutex was marked contested on release. This means that 533 * there are threads blocked on it. 534 */ 535 if (v == MTX_CONTESTED) { 536 td1 = TAILQ_FIRST(&m->mtx_blocked); 537 MPASS(td1 != NULL); 538 m->mtx_lock = (uintptr_t)td | MTX_CONTESTED; 539 540 if (td1->td_priority < td->td_priority) 541 td->td_priority = td1->td_priority; 542 mtx_unlock_spin(&sched_lock); 543 return; 544 } 545 546 /* 547 * If the mutex isn't already contested and a failure occurs 548 * setting the contested bit, the mutex was either released 549 * or the state of the MTX_RECURSED bit changed. 550 */ 551 if ((v & MTX_CONTESTED) == 0 && 552 !atomic_cmpset_ptr(&m->mtx_lock, (void *)v, 553 (void *)(v | MTX_CONTESTED))) { 554 mtx_unlock_spin(&sched_lock); 555 #ifdef __i386__ 556 ia32_pause(); 557 #endif 558 continue; 559 } 560 561 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 562 /* 563 * If the current owner of the lock is executing on another 564 * CPU, spin instead of blocking. 565 */ 566 owner = (struct thread *)(v & MTX_FLAGMASK); 567 if (m != &Giant && thread_running(owner)) { 568 mtx_unlock_spin(&sched_lock); 569 while (mtx_owner(m) == owner && thread_running(owner)) { 570 #ifdef __i386__ 571 ia32_pause(); 572 #endif 573 } 574 continue; 575 } 576 #endif /* SMP && ADAPTIVE_MUTEXES */ 577 578 /* 579 * We definitely must sleep for this lock. 580 */ 581 mtx_assert(m, MA_NOTOWNED); 582 583 #ifdef notyet 584 /* 585 * If we're borrowing an interrupted thread's VM context, we 586 * must clean up before going to sleep. 587 */ 588 if (td->td_ithd != NULL) { 589 struct ithd *it = td->td_ithd; 590 591 if (it->it_interrupted) { 592 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 593 CTR2(KTR_LOCK, 594 "_mtx_lock_sleep: %p interrupted %p", 595 it, it->it_interrupted); 596 intr_thd_fixup(it); 597 } 598 } 599 #endif 600 601 /* 602 * Put us on the list of threads blocked on this mutex. 603 */ 604 if (TAILQ_EMPTY(&m->mtx_blocked)) { 605 td1 = mtx_owner(m); 606 LIST_INSERT_HEAD(&td1->td_contested, m, mtx_contested); 607 TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_lockq); 608 } else { 609 TAILQ_FOREACH(td1, &m->mtx_blocked, td_lockq) 610 if (td1->td_priority > td->td_priority) 611 break; 612 if (td1) 613 TAILQ_INSERT_BEFORE(td1, td, td_lockq); 614 else 615 TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_lockq); 616 } 617 #ifdef KTR 618 if (!cont_logged) { 619 CTR6(KTR_CONTENTION, 620 "contention: %p at %s:%d wants %s, taken by %s:%d", 621 td, file, line, m->mtx_object.lo_name, 622 WITNESS_FILE(&m->mtx_object), 623 WITNESS_LINE(&m->mtx_object)); 624 cont_logged = 1; 625 } 626 #endif 627 628 /* 629 * Save who we're blocked on. 630 */ 631 td->td_blocked = m; 632 td->td_lockname = m->mtx_object.lo_name; 633 TD_SET_LOCK(td); 634 propagate_priority(td); 635 636 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 637 CTR3(KTR_LOCK, 638 "_mtx_lock_sleep: p %p blocked on [%p] %s", td, m, 639 m->mtx_object.lo_name); 640 641 td->td_proc->p_stats->p_ru.ru_nvcsw++; 642 mi_switch(); 643 644 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 645 CTR3(KTR_LOCK, 646 "_mtx_lock_sleep: p %p free from blocked on [%p] %s", 647 td, m, m->mtx_object.lo_name); 648 649 mtx_unlock_spin(&sched_lock); 650 } 651 652 #ifdef KTR 653 if (cont_logged) { 654 CTR4(KTR_CONTENTION, 655 "contention end: %s acquired by %p at %s:%d", 656 m->mtx_object.lo_name, td, file, line); 657 } 658 #endif 659 return; 660 } 661 662 /* 663 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. 664 * 665 * This is only called if we need to actually spin for the lock. Recursion 666 * is handled inline. 667 */ 668 void 669 _mtx_lock_spin(struct mtx *m, int opts, const char *file, int line) 670 { 671 int i = 0; 672 673 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 674 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 675 676 for (;;) { 677 if (_obtain_lock(m, curthread)) 678 break; 679 680 /* Give interrupts a chance while we spin. */ 681 critical_exit(); 682 while (m->mtx_lock != MTX_UNOWNED) { 683 if (i++ < 10000000) { 684 #ifdef __i386__ 685 ia32_pause(); 686 #endif 687 continue; 688 } 689 if (i < 60000000) 690 DELAY(1); 691 #ifdef DDB 692 else if (!db_active) 693 #else 694 else 695 #endif 696 panic("spin lock %s held by %p for > 5 seconds", 697 m->mtx_object.lo_name, (void *)m->mtx_lock); 698 #ifdef __i386__ 699 ia32_pause(); 700 #endif 701 } 702 critical_enter(); 703 } 704 705 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 706 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 707 708 return; 709 } 710 711 /* 712 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 713 * 714 * We are only called here if the lock is recursed or contested (i.e. we 715 * need to wake up a blocked thread). 716 */ 717 void 718 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) 719 { 720 struct thread *td, *td1; 721 struct mtx *m1; 722 int pri; 723 724 td = curthread; 725 726 if (mtx_recursed(m)) { 727 if (--(m->mtx_recurse) == 0) 728 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 729 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 730 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 731 return; 732 } 733 734 mtx_lock_spin(&sched_lock); 735 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 736 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 737 738 td1 = TAILQ_FIRST(&m->mtx_blocked); 739 #if defined(SMP) && defined(ADAPTIVE_MUTEXES) 740 if (td1 == NULL) { 741 _release_lock_quick(m); 742 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 743 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p no sleepers", m); 744 mtx_unlock_spin(&sched_lock); 745 return; 746 } 747 #endif 748 MPASS(td->td_proc->p_magic == P_MAGIC); 749 MPASS(td1->td_proc->p_magic == P_MAGIC); 750 751 TAILQ_REMOVE(&m->mtx_blocked, td1, td_lockq); 752 753 if (TAILQ_EMPTY(&m->mtx_blocked)) { 754 LIST_REMOVE(m, mtx_contested); 755 _release_lock_quick(m); 756 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 757 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m); 758 } else 759 atomic_store_rel_ptr(&m->mtx_lock, (void *)MTX_CONTESTED); 760 761 pri = PRI_MAX; 762 LIST_FOREACH(m1, &td->td_contested, mtx_contested) { 763 int cp = TAILQ_FIRST(&m1->mtx_blocked)->td_priority; 764 if (cp < pri) 765 pri = cp; 766 } 767 768 if (pri > td->td_base_pri) 769 pri = td->td_base_pri; 770 td->td_priority = pri; 771 772 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 773 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p contested setrunqueue %p", 774 m, td1); 775 776 td1->td_blocked = NULL; 777 TD_CLR_LOCK(td1); 778 if (!TD_CAN_RUN(td1)) { 779 mtx_unlock_spin(&sched_lock); 780 return; 781 } 782 setrunqueue(td1); 783 784 if (td->td_critnest == 1 && td1->td_priority < pri) { 785 #ifdef notyet 786 if (td->td_ithd != NULL) { 787 struct ithd *it = td->td_ithd; 788 789 if (it->it_interrupted) { 790 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 791 CTR2(KTR_LOCK, 792 "_mtx_unlock_sleep: %p interrupted %p", 793 it, it->it_interrupted); 794 intr_thd_fixup(it); 795 } 796 } 797 #endif 798 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 799 CTR2(KTR_LOCK, 800 "_mtx_unlock_sleep: %p switching out lock=%p", m, 801 (void *)m->mtx_lock); 802 803 td->td_proc->p_stats->p_ru.ru_nivcsw++; 804 mi_switch(); 805 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 806 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p", 807 m, (void *)m->mtx_lock); 808 } 809 810 mtx_unlock_spin(&sched_lock); 811 812 return; 813 } 814 815 /* 816 * All the unlocking of MTX_SPIN locks is done inline. 817 * See the _rel_spin_lock() macro for the details. 818 */ 819 820 /* 821 * The backing function for the INVARIANTS-enabled mtx_assert() 822 */ 823 #ifdef INVARIANT_SUPPORT 824 void 825 _mtx_assert(struct mtx *m, int what, const char *file, int line) 826 { 827 828 if (panicstr != NULL) 829 return; 830 switch (what) { 831 case MA_OWNED: 832 case MA_OWNED | MA_RECURSED: 833 case MA_OWNED | MA_NOTRECURSED: 834 if (!mtx_owned(m)) 835 panic("mutex %s not owned at %s:%d", 836 m->mtx_object.lo_name, file, line); 837 if (mtx_recursed(m)) { 838 if ((what & MA_NOTRECURSED) != 0) 839 panic("mutex %s recursed at %s:%d", 840 m->mtx_object.lo_name, file, line); 841 } else if ((what & MA_RECURSED) != 0) { 842 panic("mutex %s unrecursed at %s:%d", 843 m->mtx_object.lo_name, file, line); 844 } 845 break; 846 case MA_NOTOWNED: 847 if (mtx_owned(m)) 848 panic("mutex %s owned at %s:%d", 849 m->mtx_object.lo_name, file, line); 850 break; 851 default: 852 panic("unknown mtx_assert at %s:%d", file, line); 853 } 854 } 855 #endif 856 857 /* 858 * The MUTEX_DEBUG-enabled mtx_validate() 859 * 860 * Most of these checks have been moved off into the LO_INITIALIZED flag 861 * maintained by the witness code. 862 */ 863 #ifdef MUTEX_DEBUG 864 865 void mtx_validate(struct mtx *); 866 867 void 868 mtx_validate(struct mtx *m) 869 { 870 871 /* 872 * XXX: When kernacc() does not require Giant we can reenable this check 873 */ 874 #ifdef notyet 875 /* 876 * XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly 877 * we can re-enable the kernacc() checks. 878 */ 879 #ifndef __alpha__ 880 /* 881 * Can't call kernacc() from early init386(), especially when 882 * initializing Giant mutex, because some stuff in kernacc() 883 * requires Giant itself. 884 */ 885 if (!cold) 886 if (!kernacc((caddr_t)m, sizeof(m), 887 VM_PROT_READ | VM_PROT_WRITE)) 888 panic("Can't read and write to mutex %p", m); 889 #endif 890 #endif 891 } 892 #endif 893 894 /* 895 * General init routine used by the MTX_SYSINIT() macro. 896 */ 897 void 898 mtx_sysinit(void *arg) 899 { 900 struct mtx_args *margs = arg; 901 902 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); 903 } 904 905 /* 906 * Mutex initialization routine; initialize lock `m' of type contained in 907 * `opts' with options contained in `opts' and name `name.' The optional 908 * lock type `type' is used as a general lock category name for use with 909 * witness. 910 */ 911 void 912 mtx_init(struct mtx *m, const char *name, const char *type, int opts) 913 { 914 struct lock_object *lock; 915 916 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 917 MTX_SLEEPABLE | MTX_NOWITNESS | MTX_DUPOK)) == 0); 918 919 #ifdef MUTEX_DEBUG 920 /* Diagnostic and error correction */ 921 mtx_validate(m); 922 #endif 923 924 lock = &m->mtx_object; 925 KASSERT((lock->lo_flags & LO_INITIALIZED) == 0, 926 ("mutex %s %p already initialized", name, m)); 927 bzero(m, sizeof(*m)); 928 if (opts & MTX_SPIN) 929 lock->lo_class = &lock_class_mtx_spin; 930 else 931 lock->lo_class = &lock_class_mtx_sleep; 932 lock->lo_name = name; 933 lock->lo_type = type != NULL ? type : name; 934 if (opts & MTX_QUIET) 935 lock->lo_flags = LO_QUIET; 936 if (opts & MTX_RECURSE) 937 lock->lo_flags |= LO_RECURSABLE; 938 if (opts & MTX_SLEEPABLE) 939 lock->lo_flags |= LO_SLEEPABLE; 940 if ((opts & MTX_NOWITNESS) == 0) 941 lock->lo_flags |= LO_WITNESS; 942 if (opts & MTX_DUPOK) 943 lock->lo_flags |= LO_DUPOK; 944 945 m->mtx_lock = MTX_UNOWNED; 946 TAILQ_INIT(&m->mtx_blocked); 947 948 LOCK_LOG_INIT(lock, opts); 949 950 WITNESS_INIT(lock); 951 } 952 953 /* 954 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 955 * passed in as a flag here because if the corresponding mtx_init() was 956 * called with MTX_QUIET set, then it will already be set in the mutex's 957 * flags. 958 */ 959 void 960 mtx_destroy(struct mtx *m) 961 { 962 963 LOCK_LOG_DESTROY(&m->mtx_object, 0); 964 965 if (!mtx_owned(m)) 966 MPASS(mtx_unowned(m)); 967 else { 968 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 969 970 /* Tell witness this isn't locked to make it happy. */ 971 WITNESS_UNLOCK(&m->mtx_object, LOP_EXCLUSIVE, __FILE__, 972 __LINE__); 973 } 974 975 WITNESS_DESTROY(&m->mtx_object); 976 } 977 978 /* 979 * Intialize the mutex code and system mutexes. This is called from the MD 980 * startup code prior to mi_startup(). The per-CPU data space needs to be 981 * setup before this is called. 982 */ 983 void 984 mutex_init(void) 985 { 986 987 /* Setup thread0 so that mutexes work. */ 988 LIST_INIT(&thread0.td_contested); 989 990 /* 991 * Initialize mutexes. 992 */ 993 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 994 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE); 995 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 996 mtx_lock(&Giant); 997 } 998 999 /* 1000 * Encapsulated Giant mutex routines. These routines provide encapsulation 1001 * control for the Giant mutex, allowing sysctls to be used to turn on and 1002 * off Giant around certain subsystems. The default value for the sysctls 1003 * are set to what developers believe is stable and working in regards to 1004 * the Giant pushdown. Developers should not turn off Giant via these 1005 * sysctls unless they know what they are doing. 1006 * 1007 * Callers of mtx_lock_giant() are expected to pass the return value to an 1008 * accompanying mtx_unlock_giant() later on. If multiple subsystems are 1009 * effected by a Giant wrap, all related sysctl variables must be zero for 1010 * the subsystem call to operate without Giant (as determined by the caller). 1011 */ 1012 1013 SYSCTL_NODE(_kern, OID_AUTO, giant, CTLFLAG_RD, NULL, "Giant mutex manipulation"); 1014 1015 static int kern_giant_all = 0; 1016 SYSCTL_INT(_kern_giant, OID_AUTO, all, CTLFLAG_RW, &kern_giant_all, 0, ""); 1017 1018 int kern_giant_proc = 1; /* Giant around PROC locks */ 1019 int kern_giant_file = 1; /* Giant around struct file & filedesc */ 1020 int kern_giant_ucred = 1; /* Giant around ucred */ 1021 SYSCTL_INT(_kern_giant, OID_AUTO, proc, CTLFLAG_RW, &kern_giant_proc, 0, ""); 1022 SYSCTL_INT(_kern_giant, OID_AUTO, file, CTLFLAG_RW, &kern_giant_file, 0, ""); 1023 SYSCTL_INT(_kern_giant, OID_AUTO, ucred, CTLFLAG_RW, &kern_giant_ucred, 0, ""); 1024 1025 int 1026 mtx_lock_giant(int sysctlvar) 1027 { 1028 if (sysctlvar || kern_giant_all) { 1029 mtx_lock(&Giant); 1030 return(1); 1031 } 1032 return(0); 1033 } 1034 1035 void 1036 mtx_unlock_giant(int s) 1037 { 1038 if (s) 1039 mtx_unlock(&Giant); 1040 } 1041