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 */ 31 32 /* 33 * Machine independent bits of mutex implementation. 34 */ 35 36 #include <sys/cdefs.h> 37 __FBSDID("$FreeBSD$"); 38 39 #include "opt_adaptive_mutexes.h" 40 #include "opt_ddb.h" 41 #include "opt_mprof.h" 42 #include "opt_mutex_wake_all.h" 43 #include "opt_sched.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/bus.h> 48 #include <sys/conf.h> 49 #include <sys/kdb.h> 50 #include <sys/kernel.h> 51 #include <sys/ktr.h> 52 #include <sys/lock.h> 53 #include <sys/malloc.h> 54 #include <sys/mutex.h> 55 #include <sys/proc.h> 56 #include <sys/resourcevar.h> 57 #include <sys/sched.h> 58 #include <sys/sbuf.h> 59 #include <sys/sysctl.h> 60 #include <sys/turnstile.h> 61 #include <sys/vmmeter.h> 62 63 #include <machine/atomic.h> 64 #include <machine/bus.h> 65 #include <machine/cpu.h> 66 67 #include <ddb/ddb.h> 68 69 #include <fs/devfs/devfs_int.h> 70 71 #include <vm/vm.h> 72 #include <vm/vm_extern.h> 73 74 /* 75 * Force MUTEX_WAKE_ALL for now. 76 * single thread wakeup needs fixes to avoid race conditions with 77 * priority inheritance. 78 */ 79 #ifndef MUTEX_WAKE_ALL 80 #define MUTEX_WAKE_ALL 81 #endif 82 83 /* 84 * Internal utility macros. 85 */ 86 #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED) 87 88 #define mtx_owner(m) ((struct thread *)((m)->mtx_lock & ~MTX_FLAGMASK)) 89 90 #ifdef DDB 91 static void db_show_mtx(struct lock_object *lock); 92 #endif 93 94 /* 95 * Lock classes for sleep and spin mutexes. 96 */ 97 struct lock_class lock_class_mtx_sleep = { 98 "sleep mutex", 99 LC_SLEEPLOCK | LC_RECURSABLE, 100 #ifdef DDB 101 db_show_mtx 102 #endif 103 }; 104 struct lock_class lock_class_mtx_spin = { 105 "spin mutex", 106 LC_SPINLOCK | LC_RECURSABLE, 107 #ifdef DDB 108 db_show_mtx 109 #endif 110 }; 111 112 /* 113 * System-wide mutexes 114 */ 115 struct mtx sched_lock; 116 struct mtx Giant; 117 118 #ifdef MUTEX_PROFILING 119 SYSCTL_NODE(_debug, OID_AUTO, mutex, CTLFLAG_RD, NULL, "mutex debugging"); 120 SYSCTL_NODE(_debug_mutex, OID_AUTO, prof, CTLFLAG_RD, NULL, "mutex profiling"); 121 static int mutex_prof_enable = 0; 122 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, enable, CTLFLAG_RW, 123 &mutex_prof_enable, 0, "Enable tracing of mutex holdtime"); 124 125 struct mutex_prof { 126 const char *name; 127 const char *file; 128 int line; 129 uintmax_t cnt_max; 130 uintmax_t cnt_tot; 131 uintmax_t cnt_cur; 132 uintmax_t cnt_contest_holding; 133 uintmax_t cnt_contest_locking; 134 struct mutex_prof *next; 135 }; 136 137 /* 138 * mprof_buf is a static pool of profiling records to avoid possible 139 * reentrance of the memory allocation functions. 140 * 141 * Note: NUM_MPROF_BUFFERS must be smaller than MPROF_HASH_SIZE. 142 */ 143 #ifdef MPROF_BUFFERS 144 #define NUM_MPROF_BUFFERS MPROF_BUFFERS 145 #else 146 #define NUM_MPROF_BUFFERS 1000 147 #endif 148 static struct mutex_prof mprof_buf[NUM_MPROF_BUFFERS]; 149 static int first_free_mprof_buf; 150 #ifndef MPROF_HASH_SIZE 151 #define MPROF_HASH_SIZE 1009 152 #endif 153 #if NUM_MPROF_BUFFERS >= MPROF_HASH_SIZE 154 #error MPROF_BUFFERS must be larger than MPROF_HASH_SIZE 155 #endif 156 static struct mutex_prof *mprof_hash[MPROF_HASH_SIZE]; 157 /* SWAG: sbuf size = avg stat. line size * number of locks */ 158 #define MPROF_SBUF_SIZE 256 * 400 159 160 static int mutex_prof_acquisitions; 161 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, acquisitions, CTLFLAG_RD, 162 &mutex_prof_acquisitions, 0, "Number of mutex acquistions recorded"); 163 static int mutex_prof_records; 164 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, records, CTLFLAG_RD, 165 &mutex_prof_records, 0, "Number of profiling records"); 166 static int mutex_prof_maxrecords = NUM_MPROF_BUFFERS; 167 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, maxrecords, CTLFLAG_RD, 168 &mutex_prof_maxrecords, 0, "Maximum number of profiling records"); 169 static int mutex_prof_rejected; 170 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, rejected, CTLFLAG_RD, 171 &mutex_prof_rejected, 0, "Number of rejected profiling records"); 172 static int mutex_prof_hashsize = MPROF_HASH_SIZE; 173 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, hashsize, CTLFLAG_RD, 174 &mutex_prof_hashsize, 0, "Hash size"); 175 static int mutex_prof_collisions = 0; 176 SYSCTL_INT(_debug_mutex_prof, OID_AUTO, collisions, CTLFLAG_RD, 177 &mutex_prof_collisions, 0, "Number of hash collisions"); 178 179 /* 180 * mprof_mtx protects the profiling buffers and the hash. 181 */ 182 static struct mtx mprof_mtx; 183 MTX_SYSINIT(mprof, &mprof_mtx, "mutex profiling lock", MTX_SPIN | MTX_QUIET); 184 185 static u_int64_t 186 nanoseconds(void) 187 { 188 struct timespec tv; 189 190 nanotime(&tv); 191 return (tv.tv_sec * (u_int64_t)1000000000 + tv.tv_nsec); 192 } 193 194 static int 195 dump_mutex_prof_stats(SYSCTL_HANDLER_ARGS) 196 { 197 struct sbuf *sb; 198 int error, i; 199 static int multiplier = 1; 200 201 if (first_free_mprof_buf == 0) 202 return (SYSCTL_OUT(req, "No locking recorded", 203 sizeof("No locking recorded"))); 204 205 retry_sbufops: 206 sb = sbuf_new(NULL, NULL, MPROF_SBUF_SIZE * multiplier, SBUF_FIXEDLEN); 207 sbuf_printf(sb, "\n%6s %12s %11s %5s %12s %12s %s\n", 208 "max", "total", "count", "avg", "cnt_hold", "cnt_lock", "name"); 209 /* 210 * XXX this spinlock seems to be by far the largest perpetrator 211 * of spinlock latency (1.6 msec on an Athlon1600 was recorded 212 * even before I pessimized it further by moving the average 213 * computation here). 214 */ 215 mtx_lock_spin(&mprof_mtx); 216 for (i = 0; i < first_free_mprof_buf; ++i) { 217 sbuf_printf(sb, "%6ju %12ju %11ju %5ju %12ju %12ju %s:%d (%s)\n", 218 mprof_buf[i].cnt_max / 1000, 219 mprof_buf[i].cnt_tot / 1000, 220 mprof_buf[i].cnt_cur, 221 mprof_buf[i].cnt_cur == 0 ? (uintmax_t)0 : 222 mprof_buf[i].cnt_tot / (mprof_buf[i].cnt_cur * 1000), 223 mprof_buf[i].cnt_contest_holding, 224 mprof_buf[i].cnt_contest_locking, 225 mprof_buf[i].file, mprof_buf[i].line, mprof_buf[i].name); 226 if (sbuf_overflowed(sb)) { 227 mtx_unlock_spin(&mprof_mtx); 228 sbuf_delete(sb); 229 multiplier++; 230 goto retry_sbufops; 231 } 232 } 233 mtx_unlock_spin(&mprof_mtx); 234 sbuf_finish(sb); 235 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1); 236 sbuf_delete(sb); 237 return (error); 238 } 239 SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD, 240 NULL, 0, dump_mutex_prof_stats, "A", "Mutex profiling statistics"); 241 242 static int 243 reset_mutex_prof_stats(SYSCTL_HANDLER_ARGS) 244 { 245 int error, v; 246 247 if (first_free_mprof_buf == 0) 248 return (0); 249 250 v = 0; 251 error = sysctl_handle_int(oidp, &v, 0, req); 252 if (error) 253 return (error); 254 if (req->newptr == NULL) 255 return (error); 256 if (v == 0) 257 return (0); 258 259 mtx_lock_spin(&mprof_mtx); 260 bzero(mprof_buf, sizeof(*mprof_buf) * first_free_mprof_buf); 261 bzero(mprof_hash, sizeof(struct mtx *) * MPROF_HASH_SIZE); 262 first_free_mprof_buf = 0; 263 mtx_unlock_spin(&mprof_mtx); 264 return (0); 265 } 266 SYSCTL_PROC(_debug_mutex_prof, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW, 267 NULL, 0, reset_mutex_prof_stats, "I", "Reset mutex profiling statistics"); 268 #endif 269 270 /* 271 * Function versions of the inlined __mtx_* macros. These are used by 272 * modules and can also be called from assembly language if needed. 273 */ 274 void 275 _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line) 276 { 277 278 MPASS(curthread != NULL); 279 KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_sleep, 280 ("mtx_lock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 281 file, line)); 282 WITNESS_CHECKORDER(&m->mtx_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 283 file, line); 284 _get_sleep_lock(m, curthread, opts, file, line); 285 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 286 line); 287 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 288 #ifdef MUTEX_PROFILING 289 /* don't reset the timer when/if recursing */ 290 if (m->mtx_acqtime == 0) { 291 m->mtx_filename = file; 292 m->mtx_lineno = line; 293 m->mtx_acqtime = mutex_prof_enable ? nanoseconds() : 0; 294 ++mutex_prof_acquisitions; 295 } 296 #endif 297 } 298 299 void 300 _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) 301 { 302 303 MPASS(curthread != NULL); 304 KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_sleep, 305 ("mtx_unlock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 306 file, line)); 307 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 308 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 309 line); 310 mtx_assert(m, MA_OWNED); 311 #ifdef MUTEX_PROFILING 312 if (m->mtx_acqtime != 0) { 313 static const char *unknown = "(unknown)"; 314 struct mutex_prof *mpp; 315 u_int64_t acqtime, now; 316 const char *p, *q; 317 volatile u_int hash; 318 319 now = nanoseconds(); 320 acqtime = m->mtx_acqtime; 321 m->mtx_acqtime = 0; 322 if (now <= acqtime) 323 goto out; 324 for (p = m->mtx_filename; 325 p != NULL && strncmp(p, "../", 3) == 0; p += 3) 326 /* nothing */ ; 327 if (p == NULL || *p == '\0') 328 p = unknown; 329 for (hash = m->mtx_lineno, q = p; *q != '\0'; ++q) 330 hash = (hash * 2 + *q) % MPROF_HASH_SIZE; 331 mtx_lock_spin(&mprof_mtx); 332 for (mpp = mprof_hash[hash]; mpp != NULL; mpp = mpp->next) 333 if (mpp->line == m->mtx_lineno && 334 strcmp(mpp->file, p) == 0) 335 break; 336 if (mpp == NULL) { 337 /* Just exit if we cannot get a trace buffer */ 338 if (first_free_mprof_buf >= NUM_MPROF_BUFFERS) { 339 ++mutex_prof_rejected; 340 goto unlock; 341 } 342 mpp = &mprof_buf[first_free_mprof_buf++]; 343 mpp->name = mtx_name(m); 344 mpp->file = p; 345 mpp->line = m->mtx_lineno; 346 mpp->next = mprof_hash[hash]; 347 if (mprof_hash[hash] != NULL) 348 ++mutex_prof_collisions; 349 mprof_hash[hash] = mpp; 350 ++mutex_prof_records; 351 } 352 /* 353 * Record if the mutex has been held longer now than ever 354 * before. 355 */ 356 if (now - acqtime > mpp->cnt_max) 357 mpp->cnt_max = now - acqtime; 358 mpp->cnt_tot += now - acqtime; 359 mpp->cnt_cur++; 360 /* 361 * There's a small race, really we should cmpxchg 362 * 0 with the current value, but that would bill 363 * the contention to the wrong lock instance if 364 * it followed this also. 365 */ 366 mpp->cnt_contest_holding += m->mtx_contest_holding; 367 m->mtx_contest_holding = 0; 368 mpp->cnt_contest_locking += m->mtx_contest_locking; 369 m->mtx_contest_locking = 0; 370 unlock: 371 mtx_unlock_spin(&mprof_mtx); 372 } 373 out: 374 #endif 375 _rel_sleep_lock(m, curthread, opts, file, line); 376 } 377 378 void 379 _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) 380 { 381 382 MPASS(curthread != NULL); 383 KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_spin, 384 ("mtx_lock_spin() of sleep mutex %s @ %s:%d", 385 m->mtx_object.lo_name, file, line)); 386 WITNESS_CHECKORDER(&m->mtx_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, 387 file, line); 388 _get_spin_lock(m, curthread, opts, file, line); 389 LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file, 390 line); 391 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 392 } 393 394 void 395 _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line) 396 { 397 398 MPASS(curthread != NULL); 399 KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_spin, 400 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", 401 m->mtx_object.lo_name, file, line)); 402 WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line); 403 LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file, 404 line); 405 mtx_assert(m, MA_OWNED); 406 _rel_spin_lock(m); 407 } 408 409 /* 410 * The important part of mtx_trylock{,_flags}() 411 * Tries to acquire lock `m.' If this function is called on a mutex that 412 * is already owned, it will recursively acquire the lock. 413 */ 414 int 415 _mtx_trylock(struct mtx *m, int opts, const char *file, int line) 416 { 417 int rval; 418 419 MPASS(curthread != NULL); 420 KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_sleep, 421 ("mtx_trylock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name, 422 file, line)); 423 424 if (mtx_owned(m) && (m->mtx_object.lo_flags & LO_RECURSABLE) != 0) { 425 m->mtx_recurse++; 426 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 427 rval = 1; 428 } else 429 rval = _obtain_lock(m, (uintptr_t)curthread); 430 431 LOCK_LOG_TRY("LOCK", &m->mtx_object, opts, rval, file, line); 432 if (rval) 433 WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, 434 file, line); 435 436 return (rval); 437 } 438 439 /* 440 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. 441 * 442 * We call this if the lock is either contested (i.e. we need to go to 443 * sleep waiting for it), or if we need to recurse on it. 444 */ 445 void 446 _mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file, 447 int line) 448 { 449 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 450 volatile struct thread *owner; 451 #endif 452 uintptr_t v; 453 #ifdef KTR 454 int cont_logged = 0; 455 #endif 456 #ifdef MUTEX_PROFILING 457 int contested; 458 #endif 459 460 if (mtx_owned(m)) { 461 KASSERT((m->mtx_object.lo_flags & LO_RECURSABLE) != 0, 462 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n", 463 m->mtx_object.lo_name, file, line)); 464 m->mtx_recurse++; 465 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); 466 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 467 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); 468 return; 469 } 470 471 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 472 CTR4(KTR_LOCK, 473 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", 474 m->mtx_object.lo_name, (void *)m->mtx_lock, file, line); 475 476 #ifdef MUTEX_PROFILING 477 contested = 0; 478 #endif 479 while (!_obtain_lock(m, tid)) { 480 #ifdef MUTEX_PROFILING 481 contested = 1; 482 atomic_add_int(&m->mtx_contest_holding, 1); 483 #endif 484 turnstile_lock(&m->mtx_object); 485 v = m->mtx_lock; 486 487 /* 488 * Check if the lock has been released while spinning for 489 * the turnstile chain lock. 490 */ 491 if (v == MTX_UNOWNED) { 492 turnstile_release(&m->mtx_object); 493 cpu_spinwait(); 494 continue; 495 } 496 497 #ifdef MUTEX_WAKE_ALL 498 MPASS(v != MTX_CONTESTED); 499 #else 500 /* 501 * The mutex was marked contested on release. This means that 502 * there are other threads blocked on it. Grab ownership of 503 * it and propagate its priority to the current thread if 504 * necessary. 505 */ 506 if (v == MTX_CONTESTED) { 507 m->mtx_lock = tid | MTX_CONTESTED; 508 turnstile_claim(&m->mtx_object); 509 break; 510 } 511 #endif 512 513 /* 514 * If the mutex isn't already contested and a failure occurs 515 * setting the contested bit, the mutex was either released 516 * or the state of the MTX_RECURSED bit changed. 517 */ 518 if ((v & MTX_CONTESTED) == 0 && 519 !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) { 520 turnstile_release(&m->mtx_object); 521 cpu_spinwait(); 522 continue; 523 } 524 525 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 526 /* 527 * If the current owner of the lock is executing on another 528 * CPU, spin instead of blocking. 529 */ 530 owner = (struct thread *)(v & ~MTX_FLAGMASK); 531 #ifdef ADAPTIVE_GIANT 532 if (TD_IS_RUNNING(owner)) { 533 #else 534 if (m != &Giant && TD_IS_RUNNING(owner)) { 535 #endif 536 turnstile_release(&m->mtx_object); 537 while (mtx_owner(m) == owner && TD_IS_RUNNING(owner)) { 538 cpu_spinwait(); 539 } 540 continue; 541 } 542 #endif /* SMP && !NO_ADAPTIVE_MUTEXES */ 543 544 /* 545 * We definitely must sleep for this lock. 546 */ 547 mtx_assert(m, MA_NOTOWNED); 548 549 #ifdef KTR 550 if (!cont_logged) { 551 CTR6(KTR_CONTENTION, 552 "contention: %p at %s:%d wants %s, taken by %s:%d", 553 (void *)tid, file, line, m->mtx_object.lo_name, 554 WITNESS_FILE(&m->mtx_object), 555 WITNESS_LINE(&m->mtx_object)); 556 cont_logged = 1; 557 } 558 #endif 559 560 /* 561 * Block on the turnstile. 562 */ 563 turnstile_wait(&m->mtx_object, mtx_owner(m), 564 TS_EXCLUSIVE_QUEUE); 565 } 566 567 #ifdef KTR 568 if (cont_logged) { 569 CTR4(KTR_CONTENTION, 570 "contention end: %s acquired by %p at %s:%d", 571 m->mtx_object.lo_name, (void *)tid, file, line); 572 } 573 #endif 574 #ifdef MUTEX_PROFILING 575 if (contested) 576 m->mtx_contest_locking++; 577 m->mtx_contest_holding = 0; 578 #endif 579 return; 580 } 581 582 #ifdef SMP 583 /* 584 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. 585 * 586 * This is only called if we need to actually spin for the lock. Recursion 587 * is handled inline. 588 */ 589 void 590 _mtx_lock_spin(struct mtx *m, uintptr_t tid, int opts, const char *file, 591 int line) 592 { 593 int i = 0; 594 595 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 596 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); 597 598 while (!_obtain_lock(m, tid)) { 599 600 /* Give interrupts a chance while we spin. */ 601 spinlock_exit(); 602 while (m->mtx_lock != MTX_UNOWNED) { 603 if (i++ < 10000000) { 604 cpu_spinwait(); 605 continue; 606 } 607 if (i < 60000000) 608 DELAY(1); 609 else if (!kdb_active && !panicstr) { 610 printf("spin lock %s held by %p for > 5 seconds\n", 611 m->mtx_object.lo_name, (void *)m->mtx_lock); 612 #ifdef WITNESS 613 witness_display_spinlock(&m->mtx_object, 614 mtx_owner(m)); 615 #endif 616 panic("spin lock held too long"); 617 } 618 cpu_spinwait(); 619 } 620 spinlock_enter(); 621 } 622 623 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 624 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); 625 626 return; 627 } 628 #endif /* SMP */ 629 630 /* 631 * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. 632 * 633 * We are only called here if the lock is recursed or contested (i.e. we 634 * need to wake up a blocked thread). 635 */ 636 void 637 _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) 638 { 639 struct turnstile *ts; 640 #ifndef PREEMPTION 641 struct thread *td, *td1; 642 #endif 643 644 if (mtx_recursed(m)) { 645 if (--(m->mtx_recurse) == 0) 646 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); 647 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 648 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); 649 return; 650 } 651 652 turnstile_lock(&m->mtx_object); 653 ts = turnstile_lookup(&m->mtx_object); 654 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 655 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); 656 657 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) 658 if (ts == NULL) { 659 _release_lock_quick(m); 660 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 661 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p no sleepers", m); 662 turnstile_release(&m->mtx_object); 663 return; 664 } 665 #else 666 MPASS(ts != NULL); 667 #endif 668 #ifndef PREEMPTION 669 /* XXX */ 670 td1 = turnstile_head(ts, TS_EXCLUSIVE_QUEUE); 671 #endif 672 #ifdef MUTEX_WAKE_ALL 673 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE); 674 _release_lock_quick(m); 675 #else 676 if (turnstile_signal(ts, TS_EXCLUSIVE_QUEUE)) { 677 _release_lock_quick(m); 678 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 679 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m); 680 } else { 681 m->mtx_lock = MTX_CONTESTED; 682 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 683 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p still contested", 684 m); 685 } 686 #endif 687 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 688 689 #ifndef PREEMPTION 690 /* 691 * XXX: This is just a hack until preemption is done. However, 692 * once preemption is done we need to either wrap the 693 * turnstile_signal() and release of the actual lock in an 694 * extra critical section or change the preemption code to 695 * always just set a flag and never do instant-preempts. 696 */ 697 td = curthread; 698 if (td->td_critnest > 0 || td1->td_priority >= td->td_priority) 699 return; 700 mtx_lock_spin(&sched_lock); 701 if (!TD_IS_RUNNING(td1)) { 702 #ifdef notyet 703 if (td->td_ithd != NULL) { 704 struct ithd *it = td->td_ithd; 705 706 if (it->it_interrupted) { 707 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 708 CTR2(KTR_LOCK, 709 "_mtx_unlock_sleep: %p interrupted %p", 710 it, it->it_interrupted); 711 intr_thd_fixup(it); 712 } 713 } 714 #endif 715 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 716 CTR2(KTR_LOCK, 717 "_mtx_unlock_sleep: %p switching out lock=%p", m, 718 (void *)m->mtx_lock); 719 720 mi_switch(SW_INVOL, NULL); 721 if (LOCK_LOG_TEST(&m->mtx_object, opts)) 722 CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p", 723 m, (void *)m->mtx_lock); 724 } 725 mtx_unlock_spin(&sched_lock); 726 #endif 727 728 return; 729 } 730 731 /* 732 * All the unlocking of MTX_SPIN locks is done inline. 733 * See the _rel_spin_lock() macro for the details. 734 */ 735 736 /* 737 * The backing function for the INVARIANTS-enabled mtx_assert() 738 */ 739 #ifdef INVARIANT_SUPPORT 740 void 741 _mtx_assert(struct mtx *m, int what, const char *file, int line) 742 { 743 744 if (panicstr != NULL || dumping) 745 return; 746 switch (what) { 747 case MA_OWNED: 748 case MA_OWNED | MA_RECURSED: 749 case MA_OWNED | MA_NOTRECURSED: 750 if (!mtx_owned(m)) 751 panic("mutex %s not owned at %s:%d", 752 m->mtx_object.lo_name, file, line); 753 if (mtx_recursed(m)) { 754 if ((what & MA_NOTRECURSED) != 0) 755 panic("mutex %s recursed at %s:%d", 756 m->mtx_object.lo_name, file, line); 757 } else if ((what & MA_RECURSED) != 0) { 758 panic("mutex %s unrecursed at %s:%d", 759 m->mtx_object.lo_name, file, line); 760 } 761 break; 762 case MA_NOTOWNED: 763 if (mtx_owned(m)) 764 panic("mutex %s owned at %s:%d", 765 m->mtx_object.lo_name, file, line); 766 break; 767 default: 768 panic("unknown mtx_assert at %s:%d", file, line); 769 } 770 } 771 #endif 772 773 /* 774 * The MUTEX_DEBUG-enabled mtx_validate() 775 * 776 * Most of these checks have been moved off into the LO_INITIALIZED flag 777 * maintained by the witness code. 778 */ 779 #ifdef MUTEX_DEBUG 780 781 void mtx_validate(struct mtx *); 782 783 void 784 mtx_validate(struct mtx *m) 785 { 786 787 /* 788 * XXX: When kernacc() does not require Giant we can reenable this check 789 */ 790 #ifdef notyet 791 /* 792 * Can't call kernacc() from early init386(), especially when 793 * initializing Giant mutex, because some stuff in kernacc() 794 * requires Giant itself. 795 */ 796 if (!cold) 797 if (!kernacc((caddr_t)m, sizeof(m), 798 VM_PROT_READ | VM_PROT_WRITE)) 799 panic("Can't read and write to mutex %p", m); 800 #endif 801 } 802 #endif 803 804 /* 805 * General init routine used by the MTX_SYSINIT() macro. 806 */ 807 void 808 mtx_sysinit(void *arg) 809 { 810 struct mtx_args *margs = arg; 811 812 mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); 813 } 814 815 /* 816 * Mutex initialization routine; initialize lock `m' of type contained in 817 * `opts' with options contained in `opts' and name `name.' The optional 818 * lock type `type' is used as a general lock category name for use with 819 * witness. 820 */ 821 void 822 mtx_init(struct mtx *m, const char *name, const char *type, int opts) 823 { 824 struct lock_class *class; 825 int flags; 826 827 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | 828 MTX_NOWITNESS | MTX_DUPOK)) == 0); 829 830 #ifdef MUTEX_DEBUG 831 /* Diagnostic and error correction */ 832 mtx_validate(m); 833 #endif 834 835 /* Determine lock class and lock flags. */ 836 if (opts & MTX_SPIN) 837 class = &lock_class_mtx_spin; 838 else 839 class = &lock_class_mtx_sleep; 840 flags = 0; 841 if (opts & MTX_QUIET) 842 flags |= LO_QUIET; 843 if (opts & MTX_RECURSE) 844 flags |= LO_RECURSABLE; 845 if ((opts & MTX_NOWITNESS) == 0) 846 flags |= LO_WITNESS; 847 if (opts & MTX_DUPOK) 848 flags |= LO_DUPOK; 849 850 /* Initialize mutex. */ 851 m->mtx_lock = MTX_UNOWNED; 852 m->mtx_recurse = 0; 853 #ifdef MUTEX_PROFILING 854 m->mtx_acqtime = 0; 855 m->mtx_filename = NULL; 856 m->mtx_lineno = 0; 857 m->mtx_contest_holding = 0; 858 m->mtx_contest_locking = 0; 859 #endif 860 861 lock_init(&m->mtx_object, class, name, type, flags); 862 } 863 864 /* 865 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be 866 * passed in as a flag here because if the corresponding mtx_init() was 867 * called with MTX_QUIET set, then it will already be set in the mutex's 868 * flags. 869 */ 870 void 871 mtx_destroy(struct mtx *m) 872 { 873 874 if (!mtx_owned(m)) 875 MPASS(mtx_unowned(m)); 876 else { 877 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); 878 879 /* Perform the non-mtx related part of mtx_unlock_spin(). */ 880 if (LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_spin) 881 spinlock_exit(); 882 883 /* Tell witness this isn't locked to make it happy. */ 884 WITNESS_UNLOCK(&m->mtx_object, LOP_EXCLUSIVE, __FILE__, 885 __LINE__); 886 } 887 888 lock_destroy(&m->mtx_object); 889 } 890 891 /* 892 * Intialize the mutex code and system mutexes. This is called from the MD 893 * startup code prior to mi_startup(). The per-CPU data space needs to be 894 * setup before this is called. 895 */ 896 void 897 mutex_init(void) 898 { 899 900 /* Setup turnstiles so that sleep mutexes work. */ 901 init_turnstiles(); 902 903 /* 904 * Initialize mutexes. 905 */ 906 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); 907 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE); 908 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 909 mtx_init(&devmtx, "cdev", NULL, MTX_DEF); 910 mtx_lock(&Giant); 911 } 912 913 #ifdef DDB 914 void 915 db_show_mtx(struct lock_object *lock) 916 { 917 struct thread *td; 918 struct mtx *m; 919 920 m = (struct mtx *)lock; 921 922 db_printf(" flags: {"); 923 if (LOCK_CLASS(lock) == &lock_class_mtx_spin) 924 db_printf("SPIN"); 925 else 926 db_printf("DEF"); 927 if (m->mtx_object.lo_flags & LO_RECURSABLE) 928 db_printf(", RECURSE"); 929 if (m->mtx_object.lo_flags & LO_DUPOK) 930 db_printf(", DUPOK"); 931 db_printf("}\n"); 932 db_printf(" state: {"); 933 if (mtx_unowned(m)) 934 db_printf("UNOWNED"); 935 else { 936 db_printf("OWNED"); 937 if (m->mtx_lock & MTX_CONTESTED) 938 db_printf(", CONTESTED"); 939 if (m->mtx_lock & MTX_RECURSED) 940 db_printf(", RECURSED"); 941 } 942 db_printf("}\n"); 943 if (!mtx_unowned(m)) { 944 td = mtx_owner(m); 945 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td, 946 td->td_tid, td->td_proc->p_pid, td->td_proc->p_comm); 947 if (mtx_recursed(m)) 948 db_printf(" recursed: %d\n", m->mtx_recurse); 949 } 950 } 951 #endif 952