Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_witness.c
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1 /*- 2 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 3. Berkeley Software Design Inc's name may not be used to endorse or 13 * promote products derived from this software without specific prior 14 * written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 * 28 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $ 29 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $ 30 * $FreeBSD: releng/5.1/sys/kern/subr_witness.c 115425 2003-05-31 06:42:37Z peter $ 31 */ 32 33 /* 34 * Implementation of the `witness' lock verifier. Originally implemented for 35 * mutexes in BSD/OS. Extended to handle generic lock objects and lock 36 * classes in FreeBSD. 37 */ 38 39 /* 40 * Main Entry: witness 41 * Pronunciation: 'wit-n&s 42 * Function: noun 43 * Etymology: Middle English witnesse, from Old English witnes knowledge, 44 * testimony, witness, from 2wit 45 * Date: before 12th century 46 * 1 : attestation of a fact or event : TESTIMONY 47 * 2 : one that gives evidence; specifically : one who testifies in 48 * a cause or before a judicial tribunal 49 * 3 : one asked to be present at a transaction so as to be able to 50 * testify to its having taken place 51 * 4 : one who has personal knowledge of something 52 * 5 a : something serving as evidence or proof : SIGN 53 * b : public affirmation by word or example of usually 54 * religious faith or conviction <the heroic witness to divine 55 * life -- Pilot> 56 * 6 capitalized : a member of the Jehovah's Witnesses 57 */ 58 59 /* 60 * Special rules concerning Giant and lock orders: 61 * 62 * 1) Giant must be acquired before any other mutexes. Stated another way, 63 * no other mutex may be held when Giant is acquired. 64 * 65 * 2) Giant must be released when blocking on a sleepable lock. 66 * 67 * This rule is less obvious, but is a result of Giant providing the same 68 * semantics as spl(). Basically, when a thread sleeps, it must release 69 * Giant. When a thread blocks on a sleepable lock, it sleeps. Hence rule 70 * 2). 71 * 72 * 3) Giant may be acquired before or after sleepable locks. 73 * 74 * This rule is also not quite as obvious. Giant may be acquired after 75 * a sleepable lock because it is a non-sleepable lock and non-sleepable 76 * locks may always be acquired while holding a sleepable lock. The second 77 * case, Giant before a sleepable lock, follows from rule 2) above. Suppose 78 * you have two threads T1 and T2 and a sleepable lock X. Suppose that T1 79 * acquires X and blocks on Giant. Then suppose that T2 acquires Giant and 80 * blocks on X. When T2 blocks on X, T2 will release Giant allowing T1 to 81 * execute. Thus, acquiring Giant both before and after a sleepable lock 82 * will not result in a lock order reversal. 83 */ 84 85 #include "opt_ddb.h" 86 #include "opt_witness.h" 87 #ifdef __i386__ 88 #include "opt_swtch.h" 89 #endif 90 91 #include <sys/param.h> 92 #include <sys/bus.h> 93 #include <sys/kernel.h> 94 #include <sys/ktr.h> 95 #include <sys/lock.h> 96 #include <sys/malloc.h> 97 #include <sys/mutex.h> 98 #include <sys/proc.h> 99 #include <sys/sysctl.h> 100 #include <sys/systm.h> 101 102 #include <ddb/ddb.h> 103 104 #include <machine/stdarg.h> 105 106 /* Define this to check for blessed mutexes */ 107 #undef BLESSING 108 109 #define WITNESS_COUNT 200 110 #define WITNESS_CHILDCOUNT (WITNESS_COUNT * 4) 111 /* 112 * XXX: This is somewhat bogus, as we assume here that at most 1024 threads 113 * will hold LOCK_NCHILDREN * 2 locks. We handle failure ok, and we should 114 * probably be safe for the most part, but it's still a SWAG. 115 */ 116 #define LOCK_CHILDCOUNT (MAXCPU + 1024) * 2 117 118 #define WITNESS_NCHILDREN 6 119 120 struct witness_child_list_entry; 121 122 struct witness { 123 const char *w_name; 124 struct lock_class *w_class; 125 STAILQ_ENTRY(witness) w_list; /* List of all witnesses. */ 126 STAILQ_ENTRY(witness) w_typelist; /* Witnesses of a type. */ 127 struct witness_child_list_entry *w_children; /* Great evilness... */ 128 const char *w_file; 129 int w_line; 130 u_int w_level; 131 u_int w_refcount; 132 u_char w_Giant_squawked:1; 133 u_char w_other_squawked:1; 134 u_char w_same_squawked:1; 135 u_char w_displayed:1; 136 }; 137 138 struct witness_child_list_entry { 139 struct witness_child_list_entry *wcl_next; 140 struct witness *wcl_children[WITNESS_NCHILDREN]; 141 u_int wcl_count; 142 }; 143 144 STAILQ_HEAD(witness_list, witness); 145 146 #ifdef BLESSING 147 struct witness_blessed { 148 const char *b_lock1; 149 const char *b_lock2; 150 }; 151 #endif 152 153 struct witness_order_list_entry { 154 const char *w_name; 155 struct lock_class *w_class; 156 }; 157 158 #ifdef BLESSING 159 static int blessed(struct witness *, struct witness *); 160 #endif 161 static int depart(struct witness *w); 162 static struct witness *enroll(const char *description, 163 struct lock_class *lock_class); 164 static int insertchild(struct witness *parent, struct witness *child); 165 static int isitmychild(struct witness *parent, struct witness *child); 166 static int isitmydescendant(struct witness *parent, struct witness *child); 167 static int itismychild(struct witness *parent, struct witness *child); 168 static int rebalancetree(struct witness_list *list); 169 static void removechild(struct witness *parent, struct witness *child); 170 static int reparentchildren(struct witness *newparent, 171 struct witness *oldparent); 172 static int sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS); 173 static void witness_displaydescendants(void(*)(const char *fmt, ...), 174 struct witness *, int indent); 175 static const char *fixup_filename(const char *file); 176 static void witness_leveldescendents(struct witness *parent, int level); 177 static void witness_levelall(void); 178 static struct witness *witness_get(void); 179 static void witness_free(struct witness *m); 180 static struct witness_child_list_entry *witness_child_get(void); 181 static void witness_child_free(struct witness_child_list_entry *wcl); 182 static struct lock_list_entry *witness_lock_list_get(void); 183 static void witness_lock_list_free(struct lock_list_entry *lle); 184 static struct lock_instance *find_instance(struct lock_list_entry *lock_list, 185 struct lock_object *lock); 186 static void witness_list_lock(struct lock_instance *instance); 187 #ifdef DDB 188 static void witness_list(struct thread *td); 189 static void witness_display_list(void(*prnt)(const char *fmt, ...), 190 struct witness_list *list); 191 static void witness_display(void(*)(const char *fmt, ...)); 192 #endif 193 194 MALLOC_DEFINE(M_WITNESS, "witness", "witness structure"); 195 196 /* 197 * If set to 0, witness is disabled. If set to 1, witness performs full lock 198 * order checking for all locks. If set to 2 or higher, then witness skips 199 * the full lock order check if the lock being acquired is at a higher level 200 * (i.e. farther down in the tree) than the current lock. This last mode is 201 * somewhat experimental and not considered fully safe. At runtime, this 202 * value may be set to 0 to turn off witness. witness is not allowed be 203 * turned on once it is turned off, however. 204 */ 205 static int witness_watch = 1; 206 TUNABLE_INT("debug.witness_watch", &witness_watch); 207 SYSCTL_PROC(_debug, OID_AUTO, witness_watch, CTLFLAG_RW | CTLTYPE_INT, NULL, 0, 208 sysctl_debug_witness_watch, "I", "witness is watching lock operations"); 209 210 #ifdef DDB 211 /* 212 * When DDB is enabled and witness_ddb is set to 1, it will cause the system to 213 * drop into kdebug() when: 214 * - a lock heirarchy violation occurs 215 * - locks are held when going to sleep. 216 */ 217 #ifdef WITNESS_DDB 218 int witness_ddb = 1; 219 #else 220 int witness_ddb = 0; 221 #endif 222 TUNABLE_INT("debug.witness_ddb", &witness_ddb); 223 SYSCTL_INT(_debug, OID_AUTO, witness_ddb, CTLFLAG_RW, &witness_ddb, 0, ""); 224 225 /* 226 * When DDB is enabled and witness_trace is set to 1, it will cause the system 227 * to print a stack trace: 228 * - a lock heirarchy violation occurs 229 * - locks are held when going to sleep. 230 */ 231 int witness_trace = 1; 232 TUNABLE_INT("debug.witness_trace", &witness_trace); 233 SYSCTL_INT(_debug, OID_AUTO, witness_trace, CTLFLAG_RW, &witness_trace, 0, ""); 234 #endif /* DDB */ 235 236 #ifdef WITNESS_SKIPSPIN 237 int witness_skipspin = 1; 238 #else 239 int witness_skipspin = 0; 240 #endif 241 TUNABLE_INT("debug.witness_skipspin", &witness_skipspin); 242 SYSCTL_INT(_debug, OID_AUTO, witness_skipspin, CTLFLAG_RD, &witness_skipspin, 0, 243 ""); 244 245 static struct mtx w_mtx; 246 static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free); 247 static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all); 248 static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin); 249 static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep); 250 static struct witness_child_list_entry *w_child_free = NULL; 251 static struct lock_list_entry *w_lock_list_free = NULL; 252 253 static struct witness w_data[WITNESS_COUNT]; 254 static struct witness_child_list_entry w_childdata[WITNESS_CHILDCOUNT]; 255 static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT]; 256 257 static struct witness_order_list_entry order_lists[] = { 258 { "proctree", &lock_class_sx }, 259 { "allproc", &lock_class_sx }, 260 { "Giant", &lock_class_mtx_sleep }, 261 { "filedesc structure", &lock_class_mtx_sleep }, 262 { "pipe mutex", &lock_class_mtx_sleep }, 263 { "sigio lock", &lock_class_mtx_sleep }, 264 { "process group", &lock_class_mtx_sleep }, 265 { "process lock", &lock_class_mtx_sleep }, 266 { "session", &lock_class_mtx_sleep }, 267 { "uidinfo hash", &lock_class_mtx_sleep }, 268 { "uidinfo struct", &lock_class_mtx_sleep }, 269 { "allprison", &lock_class_mtx_sleep }, 270 { NULL, NULL }, 271 /* 272 * spin locks 273 */ 274 #ifdef SMP 275 { "ap boot", &lock_class_mtx_spin }, 276 #ifdef __i386__ 277 { "com", &lock_class_mtx_spin }, 278 #endif 279 #endif 280 { "sio", &lock_class_mtx_spin }, 281 #ifdef __i386__ 282 { "cy", &lock_class_mtx_spin }, 283 #endif 284 { "sabtty", &lock_class_mtx_spin }, 285 { "zstty", &lock_class_mtx_spin }, 286 { "ng_node", &lock_class_mtx_spin }, 287 { "ng_worklist", &lock_class_mtx_spin }, 288 { "ithread table lock", &lock_class_mtx_spin }, 289 { "sched lock", &lock_class_mtx_spin }, 290 { "callout", &lock_class_mtx_spin }, 291 /* 292 * leaf locks 293 */ 294 { "allpmaps", &lock_class_mtx_spin }, 295 { "vm page queue free mutex", &lock_class_mtx_spin }, 296 { "icu", &lock_class_mtx_spin }, 297 #ifdef SMP 298 { "smp rendezvous", &lock_class_mtx_spin }, 299 #if defined(__i386__) && defined(APIC_IO) 300 { "tlb", &lock_class_mtx_spin }, 301 #endif 302 #if defined(__i386__) && defined(LAZY_SWITCH) 303 { "lazypmap", &lock_class_mtx_spin }, 304 #endif 305 #ifdef __sparc64__ 306 { "ipi", &lock_class_mtx_spin }, 307 #endif 308 #endif 309 { "clk", &lock_class_mtx_spin }, 310 { "mutex profiling lock", &lock_class_mtx_spin }, 311 { "kse zombie lock", &lock_class_mtx_spin }, 312 { "ALD Queue", &lock_class_mtx_spin }, 313 #ifdef __ia64__ 314 { "MCA spin lock", &lock_class_mtx_spin }, 315 #endif 316 #if defined(__i386__) || defined(__amd64__) 317 { "pcicfg", &lock_class_mtx_spin }, 318 #endif 319 { NULL, NULL }, 320 { NULL, NULL } 321 }; 322 323 #ifdef BLESSING 324 /* 325 * Pairs of locks which have been blessed 326 * Don't complain about order problems with blessed locks 327 */ 328 static struct witness_blessed blessed_list[] = { 329 }; 330 static int blessed_count = 331 sizeof(blessed_list) / sizeof(struct witness_blessed); 332 #endif 333 334 /* 335 * List of all locks in the system. 336 */ 337 TAILQ_HEAD(, lock_object) all_locks = TAILQ_HEAD_INITIALIZER(all_locks); 338 339 static struct mtx all_mtx = { 340 { &lock_class_mtx_sleep, /* mtx_object.lo_class */ 341 "All locks list", /* mtx_object.lo_name */ 342 "All locks list", /* mtx_object.lo_type */ 343 LO_INITIALIZED, /* mtx_object.lo_flags */ 344 { NULL, NULL }, /* mtx_object.lo_list */ 345 NULL }, /* mtx_object.lo_witness */ 346 MTX_UNOWNED, 0, /* mtx_lock, mtx_recurse */ 347 TAILQ_HEAD_INITIALIZER(all_mtx.mtx_blocked), 348 { NULL, NULL } /* mtx_contested */ 349 }; 350 351 /* 352 * This global is set to 0 once it becomes safe to use the witness code. 353 */ 354 static int witness_cold = 1; 355 356 /* 357 * Global variables for book keeping. 358 */ 359 static int lock_cur_cnt; 360 static int lock_max_cnt; 361 362 /* 363 * The WITNESS-enabled diagnostic code. 364 */ 365 static void 366 witness_initialize(void *dummy __unused) 367 { 368 struct lock_object *lock; 369 struct witness_order_list_entry *order; 370 struct witness *w, *w1; 371 int i; 372 373 /* 374 * We have to release Giant before initializing its witness 375 * structure so that WITNESS doesn't get confused. 376 */ 377 mtx_unlock(&Giant); 378 mtx_assert(&Giant, MA_NOTOWNED); 379 380 CTR1(KTR_WITNESS, "%s: initializing witness", __func__); 381 TAILQ_INSERT_HEAD(&all_locks, &all_mtx.mtx_object, lo_list); 382 mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET | 383 MTX_NOWITNESS); 384 for (i = 0; i < WITNESS_COUNT; i++) 385 witness_free(&w_data[i]); 386 for (i = 0; i < WITNESS_CHILDCOUNT; i++) 387 witness_child_free(&w_childdata[i]); 388 for (i = 0; i < LOCK_CHILDCOUNT; i++) 389 witness_lock_list_free(&w_locklistdata[i]); 390 391 /* First add in all the specified order lists. */ 392 for (order = order_lists; order->w_name != NULL; order++) { 393 w = enroll(order->w_name, order->w_class); 394 if (w == NULL) 395 continue; 396 w->w_file = "order list"; 397 for (order++; order->w_name != NULL; order++) { 398 w1 = enroll(order->w_name, order->w_class); 399 if (w1 == NULL) 400 continue; 401 w1->w_file = "order list"; 402 if (!itismychild(w, w1)) 403 panic("Not enough memory for static orders!"); 404 w = w1; 405 } 406 } 407 408 /* Iterate through all locks and add them to witness. */ 409 mtx_lock(&all_mtx); 410 TAILQ_FOREACH(lock, &all_locks, lo_list) { 411 if (lock->lo_flags & LO_WITNESS) 412 lock->lo_witness = enroll(lock->lo_type, 413 lock->lo_class); 414 else 415 lock->lo_witness = NULL; 416 } 417 mtx_unlock(&all_mtx); 418 419 /* Mark the witness code as being ready for use. */ 420 atomic_store_rel_int(&witness_cold, 0); 421 422 mtx_lock(&Giant); 423 } 424 SYSINIT(witness_init, SI_SUB_WITNESS, SI_ORDER_FIRST, witness_initialize, NULL) 425 426 static int 427 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS) 428 { 429 int error, value; 430 431 value = witness_watch; 432 error = sysctl_handle_int(oidp, &value, 0, req); 433 if (error != 0 || req->newptr == NULL) 434 return (error); 435 error = suser(req->td); 436 if (error != 0) 437 return (error); 438 if (value == witness_watch) 439 return (0); 440 if (value != 0) 441 return (EINVAL); 442 witness_watch = 0; 443 return (0); 444 } 445 446 void 447 witness_init(struct lock_object *lock) 448 { 449 struct lock_class *class; 450 451 class = lock->lo_class; 452 if (lock->lo_flags & LO_INITIALIZED) 453 panic("%s: lock (%s) %s is already initialized", __func__, 454 class->lc_name, lock->lo_name); 455 if ((lock->lo_flags & LO_RECURSABLE) != 0 && 456 (class->lc_flags & LC_RECURSABLE) == 0) 457 panic("%s: lock (%s) %s can not be recursable", __func__, 458 class->lc_name, lock->lo_name); 459 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 460 (class->lc_flags & LC_SLEEPABLE) == 0) 461 panic("%s: lock (%s) %s can not be sleepable", __func__, 462 class->lc_name, lock->lo_name); 463 if ((lock->lo_flags & LO_UPGRADABLE) != 0 && 464 (class->lc_flags & LC_UPGRADABLE) == 0) 465 panic("%s: lock (%s) %s can not be upgradable", __func__, 466 class->lc_name, lock->lo_name); 467 468 mtx_lock(&all_mtx); 469 TAILQ_INSERT_TAIL(&all_locks, lock, lo_list); 470 lock->lo_flags |= LO_INITIALIZED; 471 lock_cur_cnt++; 472 if (lock_cur_cnt > lock_max_cnt) 473 lock_max_cnt = lock_cur_cnt; 474 mtx_unlock(&all_mtx); 475 if (!witness_cold && witness_watch != 0 && panicstr == NULL && 476 (lock->lo_flags & LO_WITNESS) != 0) 477 lock->lo_witness = enroll(lock->lo_type, class); 478 else 479 lock->lo_witness = NULL; 480 } 481 482 void 483 witness_destroy(struct lock_object *lock) 484 { 485 struct witness *w; 486 487 if (witness_cold) 488 panic("lock (%s) %s destroyed while witness_cold", 489 lock->lo_class->lc_name, lock->lo_name); 490 if ((lock->lo_flags & LO_INITIALIZED) == 0) 491 panic("%s: lock (%s) %s is not initialized", __func__, 492 lock->lo_class->lc_name, lock->lo_name); 493 494 /* XXX: need to verify that no one holds the lock */ 495 w = lock->lo_witness; 496 if (w != NULL) { 497 mtx_lock_spin(&w_mtx); 498 MPASS(w->w_refcount > 0); 499 w->w_refcount--; 500 501 /* 502 * Lock is already released if we have an allocation failure 503 * and depart() fails. 504 */ 505 if (w->w_refcount != 0 || depart(w)) 506 mtx_unlock_spin(&w_mtx); 507 } 508 509 mtx_lock(&all_mtx); 510 lock_cur_cnt--; 511 TAILQ_REMOVE(&all_locks, lock, lo_list); 512 lock->lo_flags &= ~LO_INITIALIZED; 513 mtx_unlock(&all_mtx); 514 } 515 516 #ifdef DDB 517 static void 518 witness_display_list(void(*prnt)(const char *fmt, ...), 519 struct witness_list *list) 520 { 521 struct witness *w; 522 523 STAILQ_FOREACH(w, list, w_typelist) { 524 if (w->w_file == NULL || w->w_level > 0) 525 continue; 526 /* 527 * This lock has no anscestors, display its descendants. 528 */ 529 witness_displaydescendants(prnt, w, 0); 530 } 531 } 532 533 static void 534 witness_display(void(*prnt)(const char *fmt, ...)) 535 { 536 struct witness *w; 537 538 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 539 witness_levelall(); 540 541 /* Clear all the displayed flags. */ 542 STAILQ_FOREACH(w, &w_all, w_list) { 543 w->w_displayed = 0; 544 } 545 546 /* 547 * First, handle sleep locks which have been acquired at least 548 * once. 549 */ 550 prnt("Sleep locks:\n"); 551 witness_display_list(prnt, &w_sleep); 552 553 /* 554 * Now do spin locks which have been acquired at least once. 555 */ 556 prnt("\nSpin locks:\n"); 557 witness_display_list(prnt, &w_spin); 558 559 /* 560 * Finally, any locks which have not been acquired yet. 561 */ 562 prnt("\nLocks which were never acquired:\n"); 563 STAILQ_FOREACH(w, &w_all, w_list) { 564 if (w->w_file != NULL || w->w_refcount == 0) 565 continue; 566 prnt("%s\n", w->w_name); 567 } 568 } 569 #endif /* DDB */ 570 571 /* Trim useless garbage from filenames. */ 572 static const char * 573 fixup_filename(const char *file) 574 { 575 576 if (file == NULL) 577 return (NULL); 578 while (strncmp(file, "../", 3) == 0) 579 file += 3; 580 return (file); 581 } 582 583 void 584 witness_lock(struct lock_object *lock, int flags, const char *file, int line) 585 { 586 struct lock_list_entry **lock_list, *lle; 587 struct lock_instance *lock1, *lock2; 588 struct lock_class *class; 589 struct witness *w, *w1; 590 struct thread *td; 591 int i, j; 592 #ifdef DDB 593 int go_into_ddb = 0; 594 #endif 595 596 if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL || 597 panicstr != NULL) 598 return; 599 w = lock->lo_witness; 600 class = lock->lo_class; 601 td = curthread; 602 file = fixup_filename(file); 603 604 if (class->lc_flags & LC_SLEEPLOCK) { 605 /* 606 * Since spin locks include a critical section, this check 607 * impliclty enforces a lock order of all sleep locks before 608 * all spin locks. 609 */ 610 if (td->td_critnest != 0 && (flags & LOP_TRYLOCK) == 0) 611 panic("blockable sleep lock (%s) %s @ %s:%d", 612 class->lc_name, lock->lo_name, file, line); 613 lock_list = &td->td_sleeplocks; 614 } else 615 lock_list = PCPU_PTR(spinlocks); 616 617 /* 618 * Is this the first lock acquired? If so, then no order checking 619 * is needed. 620 */ 621 if (*lock_list == NULL) 622 goto out; 623 624 /* 625 * Check to see if we are recursing on a lock we already own. 626 */ 627 lock1 = find_instance(*lock_list, lock); 628 if (lock1 != NULL) { 629 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 && 630 (flags & LOP_EXCLUSIVE) == 0) { 631 printf("shared lock of (%s) %s @ %s:%d\n", 632 class->lc_name, lock->lo_name, file, line); 633 printf("while exclusively locked from %s:%d\n", 634 lock1->li_file, lock1->li_line); 635 panic("share->excl"); 636 } 637 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 && 638 (flags & LOP_EXCLUSIVE) != 0) { 639 printf("exclusive lock of (%s) %s @ %s:%d\n", 640 class->lc_name, lock->lo_name, file, line); 641 printf("while share locked from %s:%d\n", 642 lock1->li_file, lock1->li_line); 643 panic("excl->share"); 644 } 645 lock1->li_flags++; 646 if ((lock->lo_flags & LO_RECURSABLE) == 0) { 647 printf( 648 "recursed on non-recursive lock (%s) %s @ %s:%d\n", 649 class->lc_name, lock->lo_name, file, line); 650 printf("first acquired @ %s:%d\n", lock1->li_file, 651 lock1->li_line); 652 panic("recurse"); 653 } 654 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__, 655 td->td_proc->p_pid, lock->lo_name, 656 lock1->li_flags & LI_RECURSEMASK); 657 lock1->li_file = file; 658 lock1->li_line = line; 659 return; 660 } 661 662 /* 663 * Try locks do not block if they fail to acquire the lock, thus 664 * there is no danger of deadlocks or of switching while holding a 665 * spin lock if we acquire a lock via a try operation. 666 */ 667 if (flags & LOP_TRYLOCK) 668 goto out; 669 670 /* 671 * Check for duplicate locks of the same type. Note that we only 672 * have to check for this on the last lock we just acquired. Any 673 * other cases will be caught as lock order violations. 674 */ 675 lock1 = &(*lock_list)->ll_children[(*lock_list)->ll_count - 1]; 676 w1 = lock1->li_lock->lo_witness; 677 if (w1 == w) { 678 if (w->w_same_squawked || (lock->lo_flags & LO_DUPOK)) 679 goto out; 680 w->w_same_squawked = 1; 681 printf("acquiring duplicate lock of same type: \"%s\"\n", 682 lock->lo_type); 683 printf(" 1st %s @ %s:%d\n", lock1->li_lock->lo_name, 684 lock1->li_file, lock1->li_line); 685 printf(" 2nd %s @ %s:%d\n", lock->lo_name, file, line); 686 #ifdef DDB 687 go_into_ddb = 1; 688 #endif 689 goto out; 690 } 691 MPASS(!mtx_owned(&w_mtx)); 692 mtx_lock_spin(&w_mtx); 693 /* 694 * If we have a known higher number just say ok 695 */ 696 if (witness_watch > 1 && w->w_level > w1->w_level) { 697 mtx_unlock_spin(&w_mtx); 698 goto out; 699 } 700 /* 701 * If we know that the the lock we are acquiring comes after 702 * the lock we most recently acquired in the lock order tree, 703 * then there is no need for any further checks. 704 */ 705 if (isitmydescendant(w1, w)) { 706 mtx_unlock_spin(&w_mtx); 707 goto out; 708 } 709 for (j = 0, lle = *lock_list; lle != NULL; lle = lle->ll_next) { 710 for (i = lle->ll_count - 1; i >= 0; i--, j++) { 711 712 MPASS(j < WITNESS_COUNT); 713 lock1 = &lle->ll_children[i]; 714 w1 = lock1->li_lock->lo_witness; 715 716 /* 717 * If this lock doesn't undergo witness checking, 718 * then skip it. 719 */ 720 if (w1 == NULL) { 721 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0, 722 ("lock missing witness structure")); 723 continue; 724 } 725 /* 726 * If we are locking Giant and this is a sleepable 727 * lock, then skip it. 728 */ 729 if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0 && 730 lock == &Giant.mtx_object) 731 continue; 732 /* 733 * If we are locking a sleepable lock and this lock 734 * is Giant, then skip it. 735 */ 736 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 737 lock1->li_lock == &Giant.mtx_object) 738 continue; 739 /* 740 * If we are locking a sleepable lock and this lock 741 * isn't sleepable, we want to treat it as a lock 742 * order violation to enfore a general lock order of 743 * sleepable locks before non-sleepable locks. 744 */ 745 if (!((lock->lo_flags & LO_SLEEPABLE) != 0 && 746 (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0)) 747 /* 748 * Check the lock order hierarchy for a reveresal. 749 */ 750 if (!isitmydescendant(w, w1)) 751 continue; 752 /* 753 * We have a lock order violation, check to see if it 754 * is allowed or has already been yelled about. 755 */ 756 mtx_unlock_spin(&w_mtx); 757 #ifdef BLESSING 758 if (blessed(w, w1)) 759 goto out; 760 #endif 761 if (lock1->li_lock == &Giant.mtx_object) { 762 if (w1->w_Giant_squawked) 763 goto out; 764 else 765 w1->w_Giant_squawked = 1; 766 } else { 767 if (w1->w_other_squawked) 768 goto out; 769 else 770 w1->w_other_squawked = 1; 771 } 772 /* 773 * Ok, yell about it. 774 */ 775 printf("lock order reversal\n"); 776 /* 777 * Try to locate an earlier lock with 778 * witness w in our list. 779 */ 780 do { 781 lock2 = &lle->ll_children[i]; 782 MPASS(lock2->li_lock != NULL); 783 if (lock2->li_lock->lo_witness == w) 784 break; 785 i--; 786 if (i == 0 && lle->ll_next != NULL) { 787 lle = lle->ll_next; 788 i = lle->ll_count - 1; 789 MPASS(i >= 0 && i < LOCK_NCHILDREN); 790 } 791 } while (i >= 0); 792 if (i < 0) { 793 printf(" 1st %p %s (%s) @ %s:%d\n", 794 lock1->li_lock, lock1->li_lock->lo_name, 795 lock1->li_lock->lo_type, lock1->li_file, 796 lock1->li_line); 797 printf(" 2nd %p %s (%s) @ %s:%d\n", lock, 798 lock->lo_name, lock->lo_type, file, line); 799 } else { 800 printf(" 1st %p %s (%s) @ %s:%d\n", 801 lock2->li_lock, lock2->li_lock->lo_name, 802 lock2->li_lock->lo_type, lock2->li_file, 803 lock2->li_line); 804 printf(" 2nd %p %s (%s) @ %s:%d\n", 805 lock1->li_lock, lock1->li_lock->lo_name, 806 lock1->li_lock->lo_type, lock1->li_file, 807 lock1->li_line); 808 printf(" 3rd %p %s (%s) @ %s:%d\n", lock, 809 lock->lo_name, lock->lo_type, file, line); 810 } 811 #ifdef DDB 812 go_into_ddb = 1; 813 #endif 814 goto out; 815 } 816 } 817 lock1 = &(*lock_list)->ll_children[(*lock_list)->ll_count - 1]; 818 /* 819 * Don't build a new relationship between a sleepable lock and 820 * Giant if it is the wrong direction. The real lock order is that 821 * sleepable locks come before Giant. 822 */ 823 if (!(lock1->li_lock == &Giant.mtx_object && 824 (lock->lo_flags & LO_SLEEPABLE) != 0)) { 825 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__, 826 lock->lo_type, lock1->li_lock->lo_type); 827 if (!itismychild(lock1->li_lock->lo_witness, w)) 828 /* Witness is dead. */ 829 return; 830 } 831 mtx_unlock_spin(&w_mtx); 832 833 out: 834 #ifdef DDB 835 if (go_into_ddb) { 836 if (witness_trace) 837 backtrace(); 838 if (witness_ddb) 839 Debugger(__func__); 840 } 841 #endif 842 w->w_file = file; 843 w->w_line = line; 844 845 lle = *lock_list; 846 if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) { 847 lle = witness_lock_list_get(); 848 if (lle == NULL) 849 return; 850 lle->ll_next = *lock_list; 851 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__, 852 td->td_proc->p_pid, lle); 853 *lock_list = lle; 854 } 855 lock1 = &lle->ll_children[lle->ll_count++]; 856 lock1->li_lock = lock; 857 lock1->li_line = line; 858 lock1->li_file = file; 859 if ((flags & LOP_EXCLUSIVE) != 0) 860 lock1->li_flags = LI_EXCLUSIVE; 861 else 862 lock1->li_flags = 0; 863 CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__, 864 td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1); 865 } 866 867 void 868 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line) 869 { 870 struct lock_instance *instance; 871 struct lock_class *class; 872 873 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 874 if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) 875 return; 876 class = lock->lo_class; 877 file = fixup_filename(file); 878 if ((lock->lo_flags & LO_UPGRADABLE) == 0) 879 panic("upgrade of non-upgradable lock (%s) %s @ %s:%d", 880 class->lc_name, lock->lo_name, file, line); 881 if ((flags & LOP_TRYLOCK) == 0) 882 panic("non-try upgrade of lock (%s) %s @ %s:%d", class->lc_name, 883 lock->lo_name, file, line); 884 if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0) 885 panic("upgrade of non-sleep lock (%s) %s @ %s:%d", 886 class->lc_name, lock->lo_name, file, line); 887 instance = find_instance(curthread->td_sleeplocks, lock); 888 if (instance == NULL) 889 panic("upgrade of unlocked lock (%s) %s @ %s:%d", 890 class->lc_name, lock->lo_name, file, line); 891 if ((instance->li_flags & LI_EXCLUSIVE) != 0) 892 panic("upgrade of exclusive lock (%s) %s @ %s:%d", 893 class->lc_name, lock->lo_name, file, line); 894 if ((instance->li_flags & LI_RECURSEMASK) != 0) 895 panic("upgrade of recursed lock (%s) %s r=%d @ %s:%d", 896 class->lc_name, lock->lo_name, 897 instance->li_flags & LI_RECURSEMASK, file, line); 898 instance->li_flags |= LI_EXCLUSIVE; 899 } 900 901 void 902 witness_downgrade(struct lock_object *lock, int flags, const char *file, 903 int line) 904 { 905 struct lock_instance *instance; 906 struct lock_class *class; 907 908 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 909 if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) 910 return; 911 class = lock->lo_class; 912 file = fixup_filename(file); 913 if ((lock->lo_flags & LO_UPGRADABLE) == 0) 914 panic("downgrade of non-upgradable lock (%s) %s @ %s:%d", 915 class->lc_name, lock->lo_name, file, line); 916 if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0) 917 panic("downgrade of non-sleep lock (%s) %s @ %s:%d", 918 class->lc_name, lock->lo_name, file, line); 919 instance = find_instance(curthread->td_sleeplocks, lock); 920 if (instance == NULL) 921 panic("downgrade of unlocked lock (%s) %s @ %s:%d", 922 class->lc_name, lock->lo_name, file, line); 923 if ((instance->li_flags & LI_EXCLUSIVE) == 0) 924 panic("downgrade of shared lock (%s) %s @ %s:%d", 925 class->lc_name, lock->lo_name, file, line); 926 if ((instance->li_flags & LI_RECURSEMASK) != 0) 927 panic("downgrade of recursed lock (%s) %s r=%d @ %s:%d", 928 class->lc_name, lock->lo_name, 929 instance->li_flags & LI_RECURSEMASK, file, line); 930 instance->li_flags &= ~LI_EXCLUSIVE; 931 } 932 933 void 934 witness_unlock(struct lock_object *lock, int flags, const char *file, int line) 935 { 936 struct lock_list_entry **lock_list, *lle; 937 struct lock_instance *instance; 938 struct lock_class *class; 939 struct thread *td; 940 register_t s; 941 int i, j; 942 943 if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL || 944 panicstr != NULL) 945 return; 946 td = curthread; 947 class = lock->lo_class; 948 file = fixup_filename(file); 949 if (class->lc_flags & LC_SLEEPLOCK) 950 lock_list = &td->td_sleeplocks; 951 else 952 lock_list = PCPU_PTR(spinlocks); 953 for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next) 954 for (i = 0; i < (*lock_list)->ll_count; i++) { 955 instance = &(*lock_list)->ll_children[i]; 956 if (instance->li_lock == lock) { 957 if ((instance->li_flags & LI_EXCLUSIVE) != 0 && 958 (flags & LOP_EXCLUSIVE) == 0) { 959 printf( 960 "shared unlock of (%s) %s @ %s:%d\n", 961 class->lc_name, lock->lo_name, 962 file, line); 963 printf( 964 "while exclusively locked from %s:%d\n", 965 instance->li_file, 966 instance->li_line); 967 panic("excl->ushare"); 968 } 969 if ((instance->li_flags & LI_EXCLUSIVE) == 0 && 970 (flags & LOP_EXCLUSIVE) != 0) { 971 printf( 972 "exclusive unlock of (%s) %s @ %s:%d\n", 973 class->lc_name, lock->lo_name, 974 file, line); 975 printf( 976 "while share locked from %s:%d\n", 977 instance->li_file, 978 instance->li_line); 979 panic("share->uexcl"); 980 } 981 /* If we are recursed, unrecurse. */ 982 if ((instance->li_flags & LI_RECURSEMASK) > 0) { 983 CTR4(KTR_WITNESS, 984 "%s: pid %d unrecursed on %s r=%d", __func__, 985 td->td_proc->p_pid, 986 instance->li_lock->lo_name, 987 instance->li_flags); 988 instance->li_flags--; 989 return; 990 } 991 s = intr_disable(); 992 CTR4(KTR_WITNESS, 993 "%s: pid %d removed %s from lle[%d]", __func__, 994 td->td_proc->p_pid, 995 instance->li_lock->lo_name, 996 (*lock_list)->ll_count - 1); 997 for (j = i; j < (*lock_list)->ll_count - 1; j++) 998 (*lock_list)->ll_children[j] = 999 (*lock_list)->ll_children[j + 1]; 1000 (*lock_list)->ll_count--; 1001 intr_restore(s); 1002 if ((*lock_list)->ll_count == 0) { 1003 lle = *lock_list; 1004 *lock_list = lle->ll_next; 1005 CTR3(KTR_WITNESS, 1006 "%s: pid %d removed lle %p", __func__, 1007 td->td_proc->p_pid, lle); 1008 witness_lock_list_free(lle); 1009 } 1010 return; 1011 } 1012 } 1013 panic("lock (%s) %s not locked @ %s:%d", class->lc_name, lock->lo_name, 1014 file, line); 1015 } 1016 1017 /* 1018 * Warn if any locks other than 'lock' are held. Flags can be passed in to 1019 * exempt Giant and sleepable locks from the checks as well. If any 1020 * non-exempt locks are held, then a supplied message is printed to the 1021 * console along with a list of the offending locks. If indicated in the 1022 * flags then a failure results in a panic as well. 1023 */ 1024 int 1025 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...) 1026 { 1027 struct lock_list_entry *lle; 1028 struct lock_instance *lock1; 1029 struct thread *td; 1030 va_list ap; 1031 int i, n; 1032 1033 if (witness_cold || witness_watch == 0 || panicstr != NULL) 1034 return (0); 1035 n = 0; 1036 td = curthread; 1037 for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next) 1038 for (i = lle->ll_count - 1; i >= 0; i--) { 1039 lock1 = &lle->ll_children[i]; 1040 if (lock1->li_lock == lock) 1041 continue; 1042 if (flags & WARN_GIANTOK && 1043 lock1->li_lock == &Giant.mtx_object) 1044 continue; 1045 if (flags & WARN_SLEEPOK && 1046 (lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0) 1047 continue; 1048 if (n == 0) { 1049 va_start(ap, fmt); 1050 vprintf(fmt, ap); 1051 va_end(ap); 1052 printf(" with the following"); 1053 if (flags & WARN_SLEEPOK) 1054 printf(" non-sleepable"); 1055 printf("locks held:\n"); 1056 } 1057 n++; 1058 witness_list_lock(lock1); 1059 } 1060 if (PCPU_GET(spinlocks) != NULL) { 1061 /* 1062 * Since we already hold a spinlock preemption is 1063 * already blocked. 1064 */ 1065 if (n == 0) { 1066 va_start(ap, fmt); 1067 vprintf(fmt, ap); 1068 va_end(ap); 1069 printf(" with the following"); 1070 if (flags & WARN_SLEEPOK) 1071 printf(" non-sleepable"); 1072 printf("locks held:\n"); 1073 } 1074 n += witness_list_locks(PCPU_PTR(spinlocks)); 1075 } 1076 if (flags & WARN_PANIC && n) 1077 panic("witness_warn"); 1078 #ifdef DDB 1079 else if (witness_ddb && n) 1080 Debugger(__func__); 1081 #endif 1082 return (n); 1083 } 1084 1085 const char * 1086 witness_file(struct lock_object *lock) 1087 { 1088 struct witness *w; 1089 1090 if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL) 1091 return ("?"); 1092 w = lock->lo_witness; 1093 return (w->w_file); 1094 } 1095 1096 int 1097 witness_line(struct lock_object *lock) 1098 { 1099 struct witness *w; 1100 1101 if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL) 1102 return (0); 1103 w = lock->lo_witness; 1104 return (w->w_line); 1105 } 1106 1107 static struct witness * 1108 enroll(const char *description, struct lock_class *lock_class) 1109 { 1110 struct witness *w; 1111 1112 if (!witness_watch || witness_watch == 0 || panicstr != NULL) 1113 return (NULL); 1114 if ((lock_class->lc_flags & LC_SPINLOCK) && witness_skipspin) 1115 return (NULL); 1116 mtx_lock_spin(&w_mtx); 1117 STAILQ_FOREACH(w, &w_all, w_list) { 1118 if (w->w_name == description || (w->w_refcount > 0 && 1119 strcmp(description, w->w_name) == 0)) { 1120 w->w_refcount++; 1121 mtx_unlock_spin(&w_mtx); 1122 if (lock_class != w->w_class) 1123 panic( 1124 "lock (%s) %s does not match earlier (%s) lock", 1125 description, lock_class->lc_name, 1126 w->w_class->lc_name); 1127 return (w); 1128 } 1129 } 1130 /* 1131 * This isn't quite right, as witness_cold is still 0 while we 1132 * enroll all the locks initialized before witness_initialize(). 1133 */ 1134 if ((lock_class->lc_flags & LC_SPINLOCK) && !witness_cold) { 1135 mtx_unlock_spin(&w_mtx); 1136 panic("spin lock %s not in order list", description); 1137 } 1138 if ((w = witness_get()) == NULL) 1139 return (NULL); 1140 w->w_name = description; 1141 w->w_class = lock_class; 1142 w->w_refcount = 1; 1143 STAILQ_INSERT_HEAD(&w_all, w, w_list); 1144 if (lock_class->lc_flags & LC_SPINLOCK) 1145 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist); 1146 else if (lock_class->lc_flags & LC_SLEEPLOCK) 1147 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist); 1148 else { 1149 mtx_unlock_spin(&w_mtx); 1150 panic("lock class %s is not sleep or spin", 1151 lock_class->lc_name); 1152 } 1153 mtx_unlock_spin(&w_mtx); 1154 return (w); 1155 } 1156 1157 /* Don't let the door bang you on the way out... */ 1158 static int 1159 depart(struct witness *w) 1160 { 1161 struct witness_child_list_entry *wcl, *nwcl; 1162 struct witness_list *list; 1163 struct witness *parent; 1164 1165 MPASS(w->w_refcount == 0); 1166 if (w->w_class->lc_flags & LC_SLEEPLOCK) 1167 list = &w_sleep; 1168 else 1169 list = &w_spin; 1170 /* 1171 * First, we run through the entire tree looking for any 1172 * witnesses that the outgoing witness is a child of. For 1173 * each parent that we find, we reparent all the direct 1174 * children of the outgoing witness to its parent. 1175 */ 1176 STAILQ_FOREACH(parent, list, w_typelist) { 1177 if (!isitmychild(parent, w)) 1178 continue; 1179 removechild(parent, w); 1180 if (!reparentchildren(parent, w)) 1181 return (0); 1182 } 1183 1184 /* 1185 * Now we go through and free up the child list of the 1186 * outgoing witness. 1187 */ 1188 for (wcl = w->w_children; wcl != NULL; wcl = nwcl) { 1189 nwcl = wcl->wcl_next; 1190 witness_child_free(wcl); 1191 } 1192 1193 /* 1194 * Detach from various lists and free. 1195 */ 1196 STAILQ_REMOVE(list, w, witness, w_typelist); 1197 STAILQ_REMOVE(&w_all, w, witness, w_list); 1198 witness_free(w); 1199 1200 /* Finally, fixup the tree. */ 1201 return (rebalancetree(list)); 1202 } 1203 1204 /* 1205 * Prune an entire lock order tree. We look for cases where a lock 1206 * is now both a descendant and a direct child of a given lock. In 1207 * that case, we want to remove the direct child link from the tree. 1208 * 1209 * Returns false if insertchild() fails. 1210 */ 1211 static int 1212 rebalancetree(struct witness_list *list) 1213 { 1214 struct witness *child, *parent; 1215 1216 STAILQ_FOREACH(child, list, w_typelist) { 1217 STAILQ_FOREACH(parent, list, w_typelist) { 1218 if (!isitmychild(parent, child)) 1219 continue; 1220 removechild(parent, child); 1221 if (isitmydescendant(parent, child)) 1222 continue; 1223 if (!insertchild(parent, child)) 1224 return (0); 1225 } 1226 } 1227 witness_levelall(); 1228 return (1); 1229 } 1230 1231 /* 1232 * Add "child" as a direct child of "parent". Returns false if 1233 * we fail due to out of memory. 1234 */ 1235 static int 1236 insertchild(struct witness *parent, struct witness *child) 1237 { 1238 struct witness_child_list_entry **wcl; 1239 1240 MPASS(child != NULL && parent != NULL); 1241 1242 /* 1243 * Insert "child" after "parent" 1244 */ 1245 wcl = &parent->w_children; 1246 while (*wcl != NULL && (*wcl)->wcl_count == WITNESS_NCHILDREN) 1247 wcl = &(*wcl)->wcl_next; 1248 if (*wcl == NULL) { 1249 *wcl = witness_child_get(); 1250 if (*wcl == NULL) 1251 return (0); 1252 } 1253 (*wcl)->wcl_children[(*wcl)->wcl_count++] = child; 1254 1255 return (1); 1256 } 1257 1258 /* 1259 * Make all the direct descendants of oldparent be direct descendants 1260 * of newparent. 1261 */ 1262 static int 1263 reparentchildren(struct witness *newparent, struct witness *oldparent) 1264 { 1265 struct witness_child_list_entry *wcl; 1266 int i; 1267 1268 /* Avoid making a witness a child of itself. */ 1269 MPASS(!isitmychild(oldparent, newparent)); 1270 1271 for (wcl = oldparent->w_children; wcl != NULL; wcl = wcl->wcl_next) 1272 for (i = 0; i < wcl->wcl_count; i++) 1273 if (!insertchild(newparent, wcl->wcl_children[i])) 1274 return (0); 1275 return (1); 1276 } 1277 1278 static int 1279 itismychild(struct witness *parent, struct witness *child) 1280 { 1281 struct witness_list *list; 1282 1283 MPASS(child != NULL && parent != NULL); 1284 if ((parent->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) != 1285 (child->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK))) 1286 panic( 1287 "%s: parent (%s) and child (%s) are not the same lock type", 1288 __func__, parent->w_class->lc_name, 1289 child->w_class->lc_name); 1290 1291 if (!insertchild(parent, child)) 1292 return (0); 1293 1294 if (parent->w_class->lc_flags & LC_SLEEPLOCK) 1295 list = &w_sleep; 1296 else 1297 list = &w_spin; 1298 return (rebalancetree(list)); 1299 } 1300 1301 static void 1302 removechild(struct witness *parent, struct witness *child) 1303 { 1304 struct witness_child_list_entry **wcl, *wcl1; 1305 int i; 1306 1307 for (wcl = &parent->w_children; *wcl != NULL; wcl = &(*wcl)->wcl_next) 1308 for (i = 0; i < (*wcl)->wcl_count; i++) 1309 if ((*wcl)->wcl_children[i] == child) 1310 goto found; 1311 return; 1312 found: 1313 (*wcl)->wcl_count--; 1314 if ((*wcl)->wcl_count > i) 1315 (*wcl)->wcl_children[i] = 1316 (*wcl)->wcl_children[(*wcl)->wcl_count]; 1317 MPASS((*wcl)->wcl_children[i] != NULL); 1318 if ((*wcl)->wcl_count != 0) 1319 return; 1320 wcl1 = *wcl; 1321 *wcl = wcl1->wcl_next; 1322 witness_child_free(wcl1); 1323 } 1324 1325 static int 1326 isitmychild(struct witness *parent, struct witness *child) 1327 { 1328 struct witness_child_list_entry *wcl; 1329 int i; 1330 1331 for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) { 1332 for (i = 0; i < wcl->wcl_count; i++) { 1333 if (wcl->wcl_children[i] == child) 1334 return (1); 1335 } 1336 } 1337 return (0); 1338 } 1339 1340 static int 1341 isitmydescendant(struct witness *parent, struct witness *child) 1342 { 1343 struct witness_child_list_entry *wcl; 1344 int i, j; 1345 1346 if (isitmychild(parent, child)) 1347 return (1); 1348 j = 0; 1349 for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) { 1350 MPASS(j < 1000); 1351 for (i = 0; i < wcl->wcl_count; i++) { 1352 if (isitmydescendant(wcl->wcl_children[i], child)) 1353 return (1); 1354 } 1355 j++; 1356 } 1357 return (0); 1358 } 1359 1360 static void 1361 witness_levelall (void) 1362 { 1363 struct witness_list *list; 1364 struct witness *w, *w1; 1365 1366 /* 1367 * First clear all levels. 1368 */ 1369 STAILQ_FOREACH(w, &w_all, w_list) { 1370 w->w_level = 0; 1371 } 1372 1373 /* 1374 * Look for locks with no parent and level all their descendants. 1375 */ 1376 STAILQ_FOREACH(w, &w_all, w_list) { 1377 /* 1378 * This is just an optimization, technically we could get 1379 * away just walking the all list each time. 1380 */ 1381 if (w->w_class->lc_flags & LC_SLEEPLOCK) 1382 list = &w_sleep; 1383 else 1384 list = &w_spin; 1385 STAILQ_FOREACH(w1, list, w_typelist) { 1386 if (isitmychild(w1, w)) 1387 goto skip; 1388 } 1389 witness_leveldescendents(w, 0); 1390 skip: 1391 ; /* silence GCC 3.x */ 1392 } 1393 } 1394 1395 static void 1396 witness_leveldescendents(struct witness *parent, int level) 1397 { 1398 struct witness_child_list_entry *wcl; 1399 int i; 1400 1401 if (parent->w_level < level) 1402 parent->w_level = level; 1403 level++; 1404 for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) 1405 for (i = 0; i < wcl->wcl_count; i++) 1406 witness_leveldescendents(wcl->wcl_children[i], level); 1407 } 1408 1409 static void 1410 witness_displaydescendants(void(*prnt)(const char *fmt, ...), 1411 struct witness *parent, int indent) 1412 { 1413 struct witness_child_list_entry *wcl; 1414 int i, level; 1415 1416 level = parent->w_level; 1417 prnt("%-2d", level); 1418 for (i = 0; i < indent; i++) 1419 prnt(" "); 1420 if (parent->w_refcount > 0) 1421 prnt("%s", parent->w_name); 1422 else 1423 prnt("(dead)"); 1424 if (parent->w_displayed) { 1425 prnt(" -- (already displayed)\n"); 1426 return; 1427 } 1428 parent->w_displayed = 1; 1429 if (parent->w_refcount > 0) { 1430 if (parent->w_file != NULL) 1431 prnt(" -- last acquired @ %s:%d", parent->w_file, 1432 parent->w_line); 1433 } 1434 prnt("\n"); 1435 for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) 1436 for (i = 0; i < wcl->wcl_count; i++) 1437 witness_displaydescendants(prnt, 1438 wcl->wcl_children[i], indent + 1); 1439 } 1440 1441 #ifdef BLESSING 1442 static int 1443 blessed(struct witness *w1, struct witness *w2) 1444 { 1445 int i; 1446 struct witness_blessed *b; 1447 1448 for (i = 0; i < blessed_count; i++) { 1449 b = &blessed_list[i]; 1450 if (strcmp(w1->w_name, b->b_lock1) == 0) { 1451 if (strcmp(w2->w_name, b->b_lock2) == 0) 1452 return (1); 1453 continue; 1454 } 1455 if (strcmp(w1->w_name, b->b_lock2) == 0) 1456 if (strcmp(w2->w_name, b->b_lock1) == 0) 1457 return (1); 1458 } 1459 return (0); 1460 } 1461 #endif 1462 1463 static struct witness * 1464 witness_get(void) 1465 { 1466 struct witness *w; 1467 1468 if (witness_watch == 0) { 1469 mtx_unlock_spin(&w_mtx); 1470 return (NULL); 1471 } 1472 if (STAILQ_EMPTY(&w_free)) { 1473 witness_watch = 0; 1474 mtx_unlock_spin(&w_mtx); 1475 printf("%s: witness exhausted\n", __func__); 1476 return (NULL); 1477 } 1478 w = STAILQ_FIRST(&w_free); 1479 STAILQ_REMOVE_HEAD(&w_free, w_list); 1480 bzero(w, sizeof(*w)); 1481 return (w); 1482 } 1483 1484 static void 1485 witness_free(struct witness *w) 1486 { 1487 1488 STAILQ_INSERT_HEAD(&w_free, w, w_list); 1489 } 1490 1491 static struct witness_child_list_entry * 1492 witness_child_get(void) 1493 { 1494 struct witness_child_list_entry *wcl; 1495 1496 if (witness_watch == 0) { 1497 mtx_unlock_spin(&w_mtx); 1498 return (NULL); 1499 } 1500 wcl = w_child_free; 1501 if (wcl == NULL) { 1502 witness_watch = 0; 1503 mtx_unlock_spin(&w_mtx); 1504 printf("%s: witness exhausted\n", __func__); 1505 return (NULL); 1506 } 1507 w_child_free = wcl->wcl_next; 1508 bzero(wcl, sizeof(*wcl)); 1509 return (wcl); 1510 } 1511 1512 static void 1513 witness_child_free(struct witness_child_list_entry *wcl) 1514 { 1515 1516 wcl->wcl_next = w_child_free; 1517 w_child_free = wcl; 1518 } 1519 1520 static struct lock_list_entry * 1521 witness_lock_list_get(void) 1522 { 1523 struct lock_list_entry *lle; 1524 1525 if (witness_watch == 0) 1526 return (NULL); 1527 mtx_lock_spin(&w_mtx); 1528 lle = w_lock_list_free; 1529 if (lle == NULL) { 1530 witness_watch = 0; 1531 mtx_unlock_spin(&w_mtx); 1532 printf("%s: witness exhausted\n", __func__); 1533 return (NULL); 1534 } 1535 w_lock_list_free = lle->ll_next; 1536 mtx_unlock_spin(&w_mtx); 1537 bzero(lle, sizeof(*lle)); 1538 return (lle); 1539 } 1540 1541 static void 1542 witness_lock_list_free(struct lock_list_entry *lle) 1543 { 1544 1545 mtx_lock_spin(&w_mtx); 1546 lle->ll_next = w_lock_list_free; 1547 w_lock_list_free = lle; 1548 mtx_unlock_spin(&w_mtx); 1549 } 1550 1551 static struct lock_instance * 1552 find_instance(struct lock_list_entry *lock_list, struct lock_object *lock) 1553 { 1554 struct lock_list_entry *lle; 1555 struct lock_instance *instance; 1556 int i; 1557 1558 for (lle = lock_list; lle != NULL; lle = lle->ll_next) 1559 for (i = lle->ll_count - 1; i >= 0; i--) { 1560 instance = &lle->ll_children[i]; 1561 if (instance->li_lock == lock) 1562 return (instance); 1563 } 1564 return (NULL); 1565 } 1566 1567 static void 1568 witness_list_lock(struct lock_instance *instance) 1569 { 1570 struct lock_object *lock; 1571 1572 lock = instance->li_lock; 1573 printf("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ? 1574 "exclusive" : "shared", lock->lo_class->lc_name, lock->lo_name); 1575 if (lock->lo_type != lock->lo_name) 1576 printf(" (%s)", lock->lo_type); 1577 printf(" r = %d (%p) locked @ %s:%d\n", 1578 instance->li_flags & LI_RECURSEMASK, lock, instance->li_file, 1579 instance->li_line); 1580 } 1581 1582 int 1583 witness_list_locks(struct lock_list_entry **lock_list) 1584 { 1585 struct lock_list_entry *lle; 1586 int i, nheld; 1587 1588 nheld = 0; 1589 for (lle = *lock_list; lle != NULL; lle = lle->ll_next) 1590 for (i = lle->ll_count - 1; i >= 0; i--) { 1591 witness_list_lock(&lle->ll_children[i]); 1592 nheld++; 1593 } 1594 return (nheld); 1595 } 1596 1597 void 1598 witness_save(struct lock_object *lock, const char **filep, int *linep) 1599 { 1600 struct lock_instance *instance; 1601 1602 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 1603 if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) 1604 return; 1605 if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0) 1606 panic("%s: lock (%s) %s is not a sleep lock", __func__, 1607 lock->lo_class->lc_name, lock->lo_name); 1608 instance = find_instance(curthread->td_sleeplocks, lock); 1609 if (instance == NULL) 1610 panic("%s: lock (%s) %s not locked", __func__, 1611 lock->lo_class->lc_name, lock->lo_name); 1612 *filep = instance->li_file; 1613 *linep = instance->li_line; 1614 } 1615 1616 void 1617 witness_restore(struct lock_object *lock, const char *file, int line) 1618 { 1619 struct lock_instance *instance; 1620 1621 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 1622 if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) 1623 return; 1624 if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0) 1625 panic("%s: lock (%s) %s is not a sleep lock", __func__, 1626 lock->lo_class->lc_name, lock->lo_name); 1627 instance = find_instance(curthread->td_sleeplocks, lock); 1628 if (instance == NULL) 1629 panic("%s: lock (%s) %s not locked", __func__, 1630 lock->lo_class->lc_name, lock->lo_name); 1631 lock->lo_witness->w_file = file; 1632 lock->lo_witness->w_line = line; 1633 instance->li_file = file; 1634 instance->li_line = line; 1635 } 1636 1637 void 1638 witness_assert(struct lock_object *lock, int flags, const char *file, int line) 1639 { 1640 #ifdef INVARIANT_SUPPORT 1641 struct lock_instance *instance; 1642 1643 if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) 1644 return; 1645 if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) != 0) 1646 instance = find_instance(curthread->td_sleeplocks, lock); 1647 else if ((lock->lo_class->lc_flags & LC_SPINLOCK) != 0) 1648 instance = find_instance(PCPU_GET(spinlocks), lock); 1649 else { 1650 panic("Lock (%s) %s is not sleep or spin!", 1651 lock->lo_class->lc_name, lock->lo_name); 1652 return; 1653 } 1654 file = fixup_filename(file); 1655 switch (flags) { 1656 case LA_UNLOCKED: 1657 if (instance != NULL) 1658 panic("Lock (%s) %s locked @ %s:%d.", 1659 lock->lo_class->lc_name, lock->lo_name, file, line); 1660 break; 1661 case LA_LOCKED: 1662 case LA_LOCKED | LA_RECURSED: 1663 case LA_LOCKED | LA_NOTRECURSED: 1664 case LA_SLOCKED: 1665 case LA_SLOCKED | LA_RECURSED: 1666 case LA_SLOCKED | LA_NOTRECURSED: 1667 case LA_XLOCKED: 1668 case LA_XLOCKED | LA_RECURSED: 1669 case LA_XLOCKED | LA_NOTRECURSED: 1670 if (instance == NULL) { 1671 panic("Lock (%s) %s not locked @ %s:%d.", 1672 lock->lo_class->lc_name, lock->lo_name, file, line); 1673 break; 1674 } 1675 if ((flags & LA_XLOCKED) != 0 && 1676 (instance->li_flags & LI_EXCLUSIVE) == 0) 1677 panic("Lock (%s) %s not exclusively locked @ %s:%d.", 1678 lock->lo_class->lc_name, lock->lo_name, file, line); 1679 if ((flags & LA_SLOCKED) != 0 && 1680 (instance->li_flags & LI_EXCLUSIVE) != 0) 1681 panic("Lock (%s) %s exclusively locked @ %s:%d.", 1682 lock->lo_class->lc_name, lock->lo_name, file, line); 1683 if ((flags & LA_RECURSED) != 0 && 1684 (instance->li_flags & LI_RECURSEMASK) == 0) 1685 panic("Lock (%s) %s not recursed @ %s:%d.", 1686 lock->lo_class->lc_name, lock->lo_name, file, line); 1687 if ((flags & LA_NOTRECURSED) != 0 && 1688 (instance->li_flags & LI_RECURSEMASK) != 0) 1689 panic("Lock (%s) %s recursed @ %s:%d.", 1690 lock->lo_class->lc_name, lock->lo_name, file, line); 1691 break; 1692 default: 1693 panic("Invalid lock assertion at %s:%d.", file, line); 1694 1695 } 1696 #endif /* INVARIANT_SUPPORT */ 1697 } 1698 1699 #ifdef DDB 1700 static void 1701 witness_list(struct thread *td) 1702 { 1703 1704 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 1705 KASSERT(db_active, ("%s: not in the debugger", __func__)); 1706 1707 if (witness_watch == 0) 1708 return; 1709 1710 witness_list_locks(&td->td_sleeplocks); 1711 1712 /* 1713 * We only handle spinlocks if td == curthread. This is somewhat broken 1714 * if td is currently executing on some other CPU and holds spin locks 1715 * as we won't display those locks. If we had a MI way of getting 1716 * the per-cpu data for a given cpu then we could use 1717 * td->td_oncpu to get the list of spinlocks for this thread 1718 * and "fix" this. 1719 * 1720 * That still wouldn't really fix this unless we locked sched_lock 1721 * or stopped the other CPU to make sure it wasn't changing the list 1722 * out from under us. It is probably best to just not try to handle 1723 * threads on other CPU's for now. 1724 */ 1725 if (td == curthread && PCPU_GET(spinlocks) != NULL) 1726 witness_list_locks(PCPU_PTR(spinlocks)); 1727 } 1728 1729 DB_SHOW_COMMAND(locks, db_witness_list) 1730 { 1731 struct thread *td; 1732 pid_t pid; 1733 struct proc *p; 1734 1735 if (have_addr) { 1736 pid = (addr % 16) + ((addr >> 4) % 16) * 10 + 1737 ((addr >> 8) % 16) * 100 + ((addr >> 12) % 16) * 1000 + 1738 ((addr >> 16) % 16) * 10000; 1739 /* sx_slock(&allproc_lock); */ 1740 FOREACH_PROC_IN_SYSTEM(p) { 1741 if (p->p_pid == pid) 1742 break; 1743 } 1744 /* sx_sunlock(&allproc_lock); */ 1745 if (p == NULL) { 1746 db_printf("pid %d not found\n", pid); 1747 return; 1748 } 1749 FOREACH_THREAD_IN_PROC(p, td) { 1750 witness_list(td); 1751 } 1752 } else { 1753 td = curthread; 1754 witness_list(td); 1755 } 1756 } 1757 1758 DB_SHOW_COMMAND(witness, db_witness_display) 1759 { 1760 1761 witness_display(db_printf); 1762 } 1763 #endif
Cache object: 3c307df697e0a61a1057bdb64a4725b0
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