subr_witness.c revision 122849
1153570Sjhb/*- 2153570Sjhb * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved. 3153570Sjhb * 4153570Sjhb * Redistribution and use in source and binary forms, with or without 5153570Sjhb * modification, are permitted provided that the following conditions 6153570Sjhb * are met: 7153570Sjhb * 1. Redistributions of source code must retain the above copyright 8153570Sjhb * notice, this list of conditions and the following disclaimer. 9153570Sjhb * 2. Redistributions in binary form must reproduce the above copyright 10153570Sjhb * notice, this list of conditions and the following disclaimer in the 11153570Sjhb * documentation and/or other materials provided with the distribution. 12153570Sjhb * 3. Berkeley Software Design Inc's name may not be used to endorse or 13153570Sjhb * promote products derived from this software without specific prior 14153570Sjhb * written permission. 15153570Sjhb * 16153570Sjhb * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND 17153570Sjhb * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18153570Sjhb * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19153570Sjhb * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE 20153570Sjhb * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21153570Sjhb * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22153570Sjhb * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23153570Sjhb * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24153570Sjhb * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25153570Sjhb * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26153570Sjhb * SUCH DAMAGE. 27153570Sjhb * 28153570Sjhb * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $ 29153570Sjhb * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $ 30153570Sjhb */ 31153570Sjhb 32153570Sjhb/* 33153570Sjhb * Implementation of the `witness' lock verifier. Originally implemented for 34153570Sjhb * mutexes in BSD/OS. Extended to handle generic lock objects and lock 35153570Sjhb * classes in FreeBSD. 36153570Sjhb */ 37153570Sjhb 38153570Sjhb/* 39153570Sjhb * Main Entry: witness 40153570Sjhb * Pronunciation: 'wit-n&s 41153570Sjhb * Function: noun 42153570Sjhb * Etymology: Middle English witnesse, from Old English witnes knowledge, 43153570Sjhb * testimony, witness, from 2wit 44153570Sjhb * Date: before 12th century 45153570Sjhb * 1 : attestation of a fact or event : TESTIMONY 46153570Sjhb * 2 : one that gives evidence; specifically : one who testifies in 47153570Sjhb * a cause or before a judicial tribunal 48153570Sjhb * 3 : one asked to be present at a transaction so as to be able to 49153570Sjhb * testify to its having taken place 50153570Sjhb * 4 : one who has personal knowledge of something 51153570Sjhb * 5 a : something serving as evidence or proof : SIGN 52153570Sjhb * b : public affirmation by word or example of usually 53153570Sjhb * religious faith or conviction <the heroic witness to divine 54153570Sjhb * life -- Pilot> 55153570Sjhb * 6 capitalized : a member of the Jehovah's Witnesses 56153570Sjhb */ 57153570Sjhb 58153570Sjhb/* 59153570Sjhb * Special rules concerning Giant and lock orders: 60153570Sjhb * 61153570Sjhb * 1) Giant must be acquired before any other mutexes. Stated another way, 62153570Sjhb * no other mutex may be held when Giant is acquired. 63153570Sjhb * 64153570Sjhb * 2) Giant must be released when blocking on a sleepable lock. 65153570Sjhb * 66153570Sjhb * This rule is less obvious, but is a result of Giant providing the same 67153570Sjhb * semantics as spl(). Basically, when a thread sleeps, it must release 68153570Sjhb * Giant. When a thread blocks on a sleepable lock, it sleeps. Hence rule 69153570Sjhb * 2). 70153570Sjhb * 71153570Sjhb * 3) Giant may be acquired before or after sleepable locks. 72153570Sjhb * 73153570Sjhb * This rule is also not quite as obvious. Giant may be acquired after 74153570Sjhb * a sleepable lock because it is a non-sleepable lock and non-sleepable 75153570Sjhb * locks may always be acquired while holding a sleepable lock. The second 76153570Sjhb * case, Giant before a sleepable lock, follows from rule 2) above. Suppose 77153570Sjhb * you have two threads T1 and T2 and a sleepable lock X. Suppose that T1 78153570Sjhb * acquires X and blocks on Giant. Then suppose that T2 acquires Giant and 79153570Sjhb * blocks on X. When T2 blocks on X, T2 will release Giant allowing T1 to 80153570Sjhb * execute. Thus, acquiring Giant both before and after a sleepable lock 81219902Sjhb * will not result in a lock order reversal. 82153570Sjhb */ 83153570Sjhb 84153570Sjhb#include <sys/cdefs.h> 85153570Sjhb__FBSDID("$FreeBSD: head/sys/kern/subr_witness.c 122849 2003-11-17 08:58:16Z peter $"); 86153570Sjhb 87153570Sjhb#include "opt_ddb.h" 88153570Sjhb#include "opt_witness.h" 89153570Sjhb 90153570Sjhb#include <sys/param.h> 91153570Sjhb#include <sys/bus.h> 92153570Sjhb#include <sys/kernel.h> 93153570Sjhb#include <sys/ktr.h> 94153570Sjhb#include <sys/lock.h> 95153570Sjhb#include <sys/malloc.h> 96153570Sjhb#include <sys/mutex.h> 97153570Sjhb#include <sys/proc.h> 98153570Sjhb#include <sys/sysctl.h> 99153570Sjhb#include <sys/systm.h> 100153570Sjhb 101153570Sjhb#include <ddb/ddb.h> 102153570Sjhb 103153570Sjhb#include <machine/stdarg.h> 104153570Sjhb 105153570Sjhb/* Define this to check for blessed mutexes */ 106153570Sjhb#undef BLESSING 107153570Sjhb 108153570Sjhb#define WITNESS_COUNT 200 109153570Sjhb#define WITNESS_CHILDCOUNT (WITNESS_COUNT * 4) 110153570Sjhb/* 111153570Sjhb * XXX: This is somewhat bogus, as we assume here that at most 1024 threads 112153570Sjhb * will hold LOCK_NCHILDREN * 2 locks. We handle failure ok, and we should 113153570Sjhb * probably be safe for the most part, but it's still a SWAG. 114153570Sjhb */ 115153570Sjhb#define LOCK_CHILDCOUNT (MAXCPU + 1024) * 2 116153570Sjhb 117153570Sjhb#define WITNESS_NCHILDREN 6 118153570Sjhb 119153570Sjhbstruct witness_child_list_entry; 120153570Sjhb 121153570Sjhbstruct witness { 122153570Sjhb const char *w_name; 123153570Sjhb struct lock_class *w_class; 124153570Sjhb STAILQ_ENTRY(witness) w_list; /* List of all witnesses. */ 125153570Sjhb STAILQ_ENTRY(witness) w_typelist; /* Witnesses of a type. */ 126153570Sjhb struct witness_child_list_entry *w_children; /* Great evilness... */ 127153570Sjhb const char *w_file; 128153570Sjhb int w_line; 129153570Sjhb u_int w_level; 130153570Sjhb u_int w_refcount; 131153570Sjhb u_char w_Giant_squawked:1; 132153570Sjhb u_char w_other_squawked:1; 133153570Sjhb u_char w_same_squawked:1; 134153570Sjhb u_char w_displayed:1; 135153570Sjhb}; 136153570Sjhb 137153570Sjhbstruct witness_child_list_entry { 138153570Sjhb struct witness_child_list_entry *wcl_next; 139153570Sjhb struct witness *wcl_children[WITNESS_NCHILDREN]; 140153570Sjhb u_int wcl_count; 141153570Sjhb}; 142153570Sjhb 143153570SjhbSTAILQ_HEAD(witness_list, witness); 144153570Sjhb 145153570Sjhb#ifdef BLESSING 146153570Sjhbstruct witness_blessed { 147153570Sjhb const char *b_lock1; 148153570Sjhb const char *b_lock2; 149153570Sjhb}; 150153570Sjhb#endif 151153570Sjhb 152153570Sjhbstruct witness_order_list_entry { 153153570Sjhb const char *w_name; 154153570Sjhb struct lock_class *w_class; 155153570Sjhb}; 156153570Sjhb 157153570Sjhb#ifdef BLESSING 158153570Sjhbstatic int blessed(struct witness *, struct witness *); 159153570Sjhb#endif 160153570Sjhbstatic int depart(struct witness *w); 161153570Sjhbstatic struct witness *enroll(const char *description, 162153570Sjhb struct lock_class *lock_class); 163153570Sjhbstatic int insertchild(struct witness *parent, struct witness *child); 164153570Sjhbstatic int isitmychild(struct witness *parent, struct witness *child); 165153570Sjhbstatic int isitmydescendant(struct witness *parent, struct witness *child); 166153570Sjhbstatic int itismychild(struct witness *parent, struct witness *child); 167153570Sjhbstatic int rebalancetree(struct witness_list *list); 168153570Sjhbstatic void removechild(struct witness *parent, struct witness *child); 169153570Sjhbstatic int reparentchildren(struct witness *newparent, 170153570Sjhb struct witness *oldparent); 171153570Sjhbstatic int sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS); 172153570Sjhbstatic void witness_displaydescendants(void(*)(const char *fmt, ...), 173153570Sjhb struct witness *, int indent); 174153570Sjhbstatic const char *fixup_filename(const char *file); 175153570Sjhbstatic void witness_leveldescendents(struct witness *parent, int level); 176153570Sjhbstatic void witness_levelall(void); 177153570Sjhbstatic struct witness *witness_get(void); 178153570Sjhbstatic void witness_free(struct witness *m); 179153570Sjhbstatic struct witness_child_list_entry *witness_child_get(void); 180153570Sjhbstatic void witness_child_free(struct witness_child_list_entry *wcl); 181153570Sjhbstatic struct lock_list_entry *witness_lock_list_get(void); 182153570Sjhbstatic void witness_lock_list_free(struct lock_list_entry *lle); 183153570Sjhbstatic struct lock_instance *find_instance(struct lock_list_entry *lock_list, 184153570Sjhb struct lock_object *lock); 185153570Sjhbstatic void witness_list_lock(struct lock_instance *instance); 186153570Sjhb#ifdef DDB 187153570Sjhbstatic void witness_list(struct thread *td); 188153570Sjhbstatic void witness_display_list(void(*prnt)(const char *fmt, ...), 189153570Sjhb struct witness_list *list); 190153570Sjhbstatic void witness_display(void(*)(const char *fmt, ...)); 191153570Sjhb#endif 192153570Sjhb 193153570SjhbMALLOC_DEFINE(M_WITNESS, "witness", "witness structure"); 194153570Sjhb 195153570Sjhb/* 196153570Sjhb * If set to 0, witness is disabled. If set to 1, witness performs full lock 197153570Sjhb * order checking for all locks. If set to 2 or higher, then witness skips 198153570Sjhb * the full lock order check if the lock being acquired is at a higher level 199153570Sjhb * (i.e. farther down in the tree) than the current lock. This last mode is 200153570Sjhb * somewhat experimental and not considered fully safe. At runtime, this 201153570Sjhb * value may be set to 0 to turn off witness. witness is not allowed be 202153570Sjhb * turned on once it is turned off, however. 203153570Sjhb */ 204153570Sjhbstatic int witness_watch = 1; 205153570SjhbTUNABLE_INT("debug.witness_watch", &witness_watch); 206153570SjhbSYSCTL_PROC(_debug, OID_AUTO, witness_watch, CTLFLAG_RW | CTLTYPE_INT, NULL, 0, 207153570Sjhb sysctl_debug_witness_watch, "I", "witness is watching lock operations"); 208153570Sjhb 209153570Sjhb#ifdef DDB 210153570Sjhb/* 211153570Sjhb * When DDB is enabled and witness_ddb is set to 1, it will cause the system to 212153570Sjhb * drop into kdebug() when: 213153570Sjhb * - a lock heirarchy violation occurs 214153570Sjhb * - locks are held when going to sleep. 215153570Sjhb */ 216153570Sjhb#ifdef WITNESS_DDB 217153570Sjhbint witness_ddb = 1; 218153570Sjhb#else 219153570Sjhbint witness_ddb = 0; 220153570Sjhb#endif 221153570SjhbTUNABLE_INT("debug.witness_ddb", &witness_ddb); 222153570SjhbSYSCTL_INT(_debug, OID_AUTO, witness_ddb, CTLFLAG_RW, &witness_ddb, 0, ""); 223153570Sjhb 224153570Sjhb/* 225153570Sjhb * When DDB is enabled and witness_trace is set to 1, it will cause the system 226153570Sjhb * to print a stack trace: 227153570Sjhb * - a lock heirarchy violation occurs 228153570Sjhb * - locks are held when going to sleep. 229153570Sjhb */ 230153570Sjhbint witness_trace = 1; 231153570SjhbTUNABLE_INT("debug.witness_trace", &witness_trace); 232153570SjhbSYSCTL_INT(_debug, OID_AUTO, witness_trace, CTLFLAG_RW, &witness_trace, 0, ""); 233153570Sjhb#endif /* DDB */ 234153570Sjhb 235153570Sjhb#ifdef WITNESS_SKIPSPIN 236153570Sjhbint witness_skipspin = 1; 237153570Sjhb#else 238153570Sjhbint witness_skipspin = 0; 239153570Sjhb#endif 240153570SjhbTUNABLE_INT("debug.witness_skipspin", &witness_skipspin); 241153570SjhbSYSCTL_INT(_debug, OID_AUTO, witness_skipspin, CTLFLAG_RDTUN, &witness_skipspin, 0, 242153570Sjhb ""); 243153570Sjhb 244153570Sjhbstatic struct mtx w_mtx; 245153570Sjhbstatic struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free); 246153570Sjhbstatic struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all); 247153570Sjhbstatic struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin); 248153570Sjhbstatic struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep); 249153570Sjhbstatic struct witness_child_list_entry *w_child_free = NULL; 250static struct lock_list_entry *w_lock_list_free = NULL; 251 252static struct witness w_data[WITNESS_COUNT]; 253static struct witness_child_list_entry w_childdata[WITNESS_CHILDCOUNT]; 254static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT]; 255 256static struct witness_order_list_entry order_lists[] = { 257 { "proctree", &lock_class_sx }, 258 { "allproc", &lock_class_sx }, 259 { "Giant", &lock_class_mtx_sleep }, 260 { "filedesc structure", &lock_class_mtx_sleep }, 261 { "pipe mutex", &lock_class_mtx_sleep }, 262 { "sigio lock", &lock_class_mtx_sleep }, 263 { "process group", &lock_class_mtx_sleep }, 264 { "process lock", &lock_class_mtx_sleep }, 265 { "session", &lock_class_mtx_sleep }, 266 { "uidinfo hash", &lock_class_mtx_sleep }, 267 { "uidinfo struct", &lock_class_mtx_sleep }, 268 { "allprison", &lock_class_mtx_sleep }, 269 { NULL, NULL }, 270 /* 271 * spin locks 272 */ 273#ifdef SMP 274 { "ap boot", &lock_class_mtx_spin }, 275#endif 276 { "sio", &lock_class_mtx_spin }, 277#ifdef __i386__ 278 { "cy", &lock_class_mtx_spin }, 279#endif 280 { "sabtty", &lock_class_mtx_spin }, 281 { "zstty", &lock_class_mtx_spin }, 282 { "ng_node", &lock_class_mtx_spin }, 283 { "ng_worklist", &lock_class_mtx_spin }, 284 { "taskqueue_fast", &lock_class_mtx_spin }, 285 { "intr table", &lock_class_mtx_spin }, 286 { "ithread table lock", &lock_class_mtx_spin }, 287 { "sched lock", &lock_class_mtx_spin }, 288 { "turnstile chain", &lock_class_mtx_spin }, 289 { "td_contested", &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(__amd64__) 300 { "tlb", &lock_class_mtx_spin }, 301 { "lazypmap", &lock_class_mtx_spin }, 302#endif 303#ifdef __sparc64__ 304 { "ipi", &lock_class_mtx_spin }, 305#endif 306#endif 307 { "clk", &lock_class_mtx_spin }, 308 { "mutex profiling lock", &lock_class_mtx_spin }, 309 { "kse zombie lock", &lock_class_mtx_spin }, 310 { "ALD Queue", &lock_class_mtx_spin }, 311#ifdef __ia64__ 312 { "MCA spin lock", &lock_class_mtx_spin }, 313#endif 314#if defined(__i386__) || defined(__amd64__) 315 { "pcicfg", &lock_class_mtx_spin }, 316#endif 317 { NULL, NULL }, 318 { NULL, NULL } 319}; 320 321#ifdef BLESSING 322/* 323 * Pairs of locks which have been blessed 324 * Don't complain about order problems with blessed locks 325 */ 326static struct witness_blessed blessed_list[] = { 327}; 328static int blessed_count = 329 sizeof(blessed_list) / sizeof(struct witness_blessed); 330#endif 331 332/* 333 * List of all locks in the system. 334 */ 335TAILQ_HEAD(, lock_object) all_locks = TAILQ_HEAD_INITIALIZER(all_locks); 336 337static struct mtx all_mtx = { 338 { &lock_class_mtx_sleep, /* mtx_object.lo_class */ 339 "All locks list", /* mtx_object.lo_name */ 340 "All locks list", /* mtx_object.lo_type */ 341 LO_INITIALIZED, /* mtx_object.lo_flags */ 342 { NULL, NULL }, /* mtx_object.lo_list */ 343 NULL }, /* mtx_object.lo_witness */ 344 MTX_UNOWNED, 0 /* mtx_lock, mtx_recurse */ 345}; 346 347/* 348 * This global is set to 0 once it becomes safe to use the witness code. 349 */ 350static int witness_cold = 1; 351 352/* 353 * Global variables for book keeping. 354 */ 355static int lock_cur_cnt; 356static int lock_max_cnt; 357 358/* 359 * The WITNESS-enabled diagnostic code. 360 */ 361static void 362witness_initialize(void *dummy __unused) 363{ 364 struct lock_object *lock; 365 struct witness_order_list_entry *order; 366 struct witness *w, *w1; 367 int i; 368 369 /* 370 * We have to release Giant before initializing its witness 371 * structure so that WITNESS doesn't get confused. 372 */ 373 mtx_unlock(&Giant); 374 mtx_assert(&Giant, MA_NOTOWNED); 375 376 CTR1(KTR_WITNESS, "%s: initializing witness", __func__); 377 TAILQ_INSERT_HEAD(&all_locks, &all_mtx.mtx_object, lo_list); 378 mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET | 379 MTX_NOWITNESS); 380 for (i = 0; i < WITNESS_COUNT; i++) 381 witness_free(&w_data[i]); 382 for (i = 0; i < WITNESS_CHILDCOUNT; i++) 383 witness_child_free(&w_childdata[i]); 384 for (i = 0; i < LOCK_CHILDCOUNT; i++) 385 witness_lock_list_free(&w_locklistdata[i]); 386 387 /* First add in all the specified order lists. */ 388 for (order = order_lists; order->w_name != NULL; order++) { 389 w = enroll(order->w_name, order->w_class); 390 if (w == NULL) 391 continue; 392 w->w_file = "order list"; 393 for (order++; order->w_name != NULL; order++) { 394 w1 = enroll(order->w_name, order->w_class); 395 if (w1 == NULL) 396 continue; 397 w1->w_file = "order list"; 398 if (!itismychild(w, w1)) 399 panic("Not enough memory for static orders!"); 400 w = w1; 401 } 402 } 403 404 /* Iterate through all locks and add them to witness. */ 405 mtx_lock(&all_mtx); 406 TAILQ_FOREACH(lock, &all_locks, lo_list) { 407 if (lock->lo_flags & LO_WITNESS) 408 lock->lo_witness = enroll(lock->lo_type, 409 lock->lo_class); 410 else 411 lock->lo_witness = NULL; 412 } 413 mtx_unlock(&all_mtx); 414 415 /* Mark the witness code as being ready for use. */ 416 atomic_store_rel_int(&witness_cold, 0); 417 418 mtx_lock(&Giant); 419} 420SYSINIT(witness_init, SI_SUB_WITNESS, SI_ORDER_FIRST, witness_initialize, NULL) 421 422static int 423sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS) 424{ 425 int error, value; 426 427 value = witness_watch; 428 error = sysctl_handle_int(oidp, &value, 0, req); 429 if (error != 0 || req->newptr == NULL) 430 return (error); 431 error = suser(req->td); 432 if (error != 0) 433 return (error); 434 if (value == witness_watch) 435 return (0); 436 if (value != 0) 437 return (EINVAL); 438 witness_watch = 0; 439 return (0); 440} 441 442void 443witness_init(struct lock_object *lock) 444{ 445 struct lock_class *class; 446 447 class = lock->lo_class; 448 if (lock->lo_flags & LO_INITIALIZED) 449 panic("%s: lock (%s) %s is already initialized", __func__, 450 class->lc_name, lock->lo_name); 451 if ((lock->lo_flags & LO_RECURSABLE) != 0 && 452 (class->lc_flags & LC_RECURSABLE) == 0) 453 panic("%s: lock (%s) %s can not be recursable", __func__, 454 class->lc_name, lock->lo_name); 455 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 456 (class->lc_flags & LC_SLEEPABLE) == 0) 457 panic("%s: lock (%s) %s can not be sleepable", __func__, 458 class->lc_name, lock->lo_name); 459 if ((lock->lo_flags & LO_UPGRADABLE) != 0 && 460 (class->lc_flags & LC_UPGRADABLE) == 0) 461 panic("%s: lock (%s) %s can not be upgradable", __func__, 462 class->lc_name, lock->lo_name); 463 464 mtx_lock(&all_mtx); 465 TAILQ_INSERT_TAIL(&all_locks, lock, lo_list); 466 lock->lo_flags |= LO_INITIALIZED; 467 lock_cur_cnt++; 468 if (lock_cur_cnt > lock_max_cnt) 469 lock_max_cnt = lock_cur_cnt; 470 mtx_unlock(&all_mtx); 471 if (!witness_cold && witness_watch != 0 && panicstr == NULL && 472 (lock->lo_flags & LO_WITNESS) != 0) 473 lock->lo_witness = enroll(lock->lo_type, class); 474 else 475 lock->lo_witness = NULL; 476} 477 478void 479witness_destroy(struct lock_object *lock) 480{ 481 struct witness *w; 482 483 if (witness_cold) 484 panic("lock (%s) %s destroyed while witness_cold", 485 lock->lo_class->lc_name, lock->lo_name); 486 if ((lock->lo_flags & LO_INITIALIZED) == 0) 487 panic("%s: lock (%s) %s is not initialized", __func__, 488 lock->lo_class->lc_name, lock->lo_name); 489 490 /* XXX: need to verify that no one holds the lock */ 491 w = lock->lo_witness; 492 if (w != NULL) { 493 mtx_lock_spin(&w_mtx); 494 MPASS(w->w_refcount > 0); 495 w->w_refcount--; 496 497 /* 498 * Lock is already released if we have an allocation failure 499 * and depart() fails. 500 */ 501 if (w->w_refcount != 0 || depart(w)) 502 mtx_unlock_spin(&w_mtx); 503 } 504 505 mtx_lock(&all_mtx); 506 lock_cur_cnt--; 507 TAILQ_REMOVE(&all_locks, lock, lo_list); 508 lock->lo_flags &= ~LO_INITIALIZED; 509 mtx_unlock(&all_mtx); 510} 511 512#ifdef DDB 513static void 514witness_display_list(void(*prnt)(const char *fmt, ...), 515 struct witness_list *list) 516{ 517 struct witness *w; 518 519 STAILQ_FOREACH(w, list, w_typelist) { 520 if (w->w_file == NULL || w->w_level > 0) 521 continue; 522 /* 523 * This lock has no anscestors, display its descendants. 524 */ 525 witness_displaydescendants(prnt, w, 0); 526 } 527} 528 529static void 530witness_display(void(*prnt)(const char *fmt, ...)) 531{ 532 struct witness *w; 533 534 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 535 witness_levelall(); 536 537 /* Clear all the displayed flags. */ 538 STAILQ_FOREACH(w, &w_all, w_list) { 539 w->w_displayed = 0; 540 } 541 542 /* 543 * First, handle sleep locks which have been acquired at least 544 * once. 545 */ 546 prnt("Sleep locks:\n"); 547 witness_display_list(prnt, &w_sleep); 548 549 /* 550 * Now do spin locks which have been acquired at least once. 551 */ 552 prnt("\nSpin locks:\n"); 553 witness_display_list(prnt, &w_spin); 554 555 /* 556 * Finally, any locks which have not been acquired yet. 557 */ 558 prnt("\nLocks which were never acquired:\n"); 559 STAILQ_FOREACH(w, &w_all, w_list) { 560 if (w->w_file != NULL || w->w_refcount == 0) 561 continue; 562 prnt("%s\n", w->w_name); 563 } 564} 565#endif /* DDB */ 566 567/* Trim useless garbage from filenames. */ 568static const char * 569fixup_filename(const char *file) 570{ 571 572 if (file == NULL) 573 return (NULL); 574 while (strncmp(file, "../", 3) == 0) 575 file += 3; 576 return (file); 577} 578 579void 580witness_lock(struct lock_object *lock, int flags, const char *file, int line) 581{ 582 struct lock_list_entry **lock_list, *lle; 583 struct lock_instance *lock1, *lock2; 584 struct lock_class *class; 585 struct witness *w, *w1; 586 struct thread *td; 587 int i, j; 588#ifdef DDB 589 int go_into_ddb = 0; 590#endif 591 592 if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL || 593 panicstr != NULL) 594 return; 595 w = lock->lo_witness; 596 class = lock->lo_class; 597 td = curthread; 598 file = fixup_filename(file); 599 600 if (class->lc_flags & LC_SLEEPLOCK) { 601 /* 602 * Since spin locks include a critical section, this check 603 * impliclty enforces a lock order of all sleep locks before 604 * all spin locks. 605 */ 606 if (td->td_critnest != 0 && (flags & LOP_TRYLOCK) == 0) 607 panic("blockable sleep lock (%s) %s @ %s:%d", 608 class->lc_name, lock->lo_name, file, line); 609 lock_list = &td->td_sleeplocks; 610 } else 611 lock_list = PCPU_PTR(spinlocks); 612 613 /* 614 * Is this the first lock acquired? If so, then no order checking 615 * is needed. 616 */ 617 if (*lock_list == NULL) 618 goto out; 619 620 /* 621 * Check to see if we are recursing on a lock we already own. 622 */ 623 lock1 = find_instance(*lock_list, lock); 624 if (lock1 != NULL) { 625 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 && 626 (flags & LOP_EXCLUSIVE) == 0) { 627 printf("shared lock of (%s) %s @ %s:%d\n", 628 class->lc_name, lock->lo_name, file, line); 629 printf("while exclusively locked from %s:%d\n", 630 lock1->li_file, lock1->li_line); 631 panic("share->excl"); 632 } 633 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 && 634 (flags & LOP_EXCLUSIVE) != 0) { 635 printf("exclusive lock of (%s) %s @ %s:%d\n", 636 class->lc_name, lock->lo_name, file, line); 637 printf("while share locked from %s:%d\n", 638 lock1->li_file, lock1->li_line); 639 panic("excl->share"); 640 } 641 lock1->li_flags++; 642 if ((lock->lo_flags & LO_RECURSABLE) == 0) { 643 printf( 644 "recursed on non-recursive lock (%s) %s @ %s:%d\n", 645 class->lc_name, lock->lo_name, file, line); 646 printf("first acquired @ %s:%d\n", lock1->li_file, 647 lock1->li_line); 648 panic("recurse"); 649 } 650 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__, 651 td->td_proc->p_pid, lock->lo_name, 652 lock1->li_flags & LI_RECURSEMASK); 653 lock1->li_file = file; 654 lock1->li_line = line; 655 return; 656 } 657 658 /* 659 * Try locks do not block if they fail to acquire the lock, thus 660 * there is no danger of deadlocks or of switching while holding a 661 * spin lock if we acquire a lock via a try operation. 662 */ 663 if (flags & LOP_TRYLOCK) 664 goto out; 665 666 /* 667 * Check for duplicate locks of the same type. Note that we only 668 * have to check for this on the last lock we just acquired. Any 669 * other cases will be caught as lock order violations. 670 */ 671 lock1 = &(*lock_list)->ll_children[(*lock_list)->ll_count - 1]; 672 w1 = lock1->li_lock->lo_witness; 673 if (w1 == w) { 674 if (w->w_same_squawked || (lock->lo_flags & LO_DUPOK)) 675 goto out; 676 w->w_same_squawked = 1; 677 printf("acquiring duplicate lock of same type: \"%s\"\n", 678 lock->lo_type); 679 printf(" 1st %s @ %s:%d\n", lock1->li_lock->lo_name, 680 lock1->li_file, lock1->li_line); 681 printf(" 2nd %s @ %s:%d\n", lock->lo_name, file, line); 682#ifdef DDB 683 go_into_ddb = 1; 684#endif 685 goto out; 686 } 687 MPASS(!mtx_owned(&w_mtx)); 688 mtx_lock_spin(&w_mtx); 689 /* 690 * If we have a known higher number just say ok 691 */ 692 if (witness_watch > 1 && w->w_level > w1->w_level) { 693 mtx_unlock_spin(&w_mtx); 694 goto out; 695 } 696 /* 697 * If we know that the the lock we are acquiring comes after 698 * the lock we most recently acquired in the lock order tree, 699 * then there is no need for any further checks. 700 */ 701 if (isitmydescendant(w1, w)) { 702 mtx_unlock_spin(&w_mtx); 703 goto out; 704 } 705 for (j = 0, lle = *lock_list; lle != NULL; lle = lle->ll_next) { 706 for (i = lle->ll_count - 1; i >= 0; i--, j++) { 707 708 MPASS(j < WITNESS_COUNT); 709 lock1 = &lle->ll_children[i]; 710 w1 = lock1->li_lock->lo_witness; 711 712 /* 713 * If this lock doesn't undergo witness checking, 714 * then skip it. 715 */ 716 if (w1 == NULL) { 717 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0, 718 ("lock missing witness structure")); 719 continue; 720 } 721 /* 722 * If we are locking Giant and this is a sleepable 723 * lock, then skip it. 724 */ 725 if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0 && 726 lock == &Giant.mtx_object) 727 continue; 728 /* 729 * If we are locking a sleepable lock and this lock 730 * is Giant, then skip it. 731 */ 732 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 733 lock1->li_lock == &Giant.mtx_object) 734 continue; 735 /* 736 * If we are locking a sleepable lock and this lock 737 * isn't sleepable, we want to treat it as a lock 738 * order violation to enfore a general lock order of 739 * sleepable locks before non-sleepable locks. 740 */ 741 if (!((lock->lo_flags & LO_SLEEPABLE) != 0 && 742 (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0)) 743 /* 744 * Check the lock order hierarchy for a reveresal. 745 */ 746 if (!isitmydescendant(w, w1)) 747 continue; 748 /* 749 * We have a lock order violation, check to see if it 750 * is allowed or has already been yelled about. 751 */ 752 mtx_unlock_spin(&w_mtx); 753#ifdef BLESSING 754 if (blessed(w, w1)) 755 goto out; 756#endif 757 if (lock1->li_lock == &Giant.mtx_object) { 758 if (w1->w_Giant_squawked) 759 goto out; 760 else 761 w1->w_Giant_squawked = 1; 762 } else { 763 if (w1->w_other_squawked) 764 goto out; 765 else 766 w1->w_other_squawked = 1; 767 } 768 /* 769 * Ok, yell about it. 770 */ 771 printf("lock order reversal\n"); 772 /* 773 * Try to locate an earlier lock with 774 * witness w in our list. 775 */ 776 do { 777 lock2 = &lle->ll_children[i]; 778 MPASS(lock2->li_lock != NULL); 779 if (lock2->li_lock->lo_witness == w) 780 break; 781 i--; 782 if (i == 0 && lle->ll_next != NULL) { 783 lle = lle->ll_next; 784 i = lle->ll_count - 1; 785 MPASS(i >= 0 && i < LOCK_NCHILDREN); 786 } 787 } while (i >= 0); 788 if (i < 0) { 789 printf(" 1st %p %s (%s) @ %s:%d\n", 790 lock1->li_lock, lock1->li_lock->lo_name, 791 lock1->li_lock->lo_type, lock1->li_file, 792 lock1->li_line); 793 printf(" 2nd %p %s (%s) @ %s:%d\n", lock, 794 lock->lo_name, lock->lo_type, file, line); 795 } else { 796 printf(" 1st %p %s (%s) @ %s:%d\n", 797 lock2->li_lock, lock2->li_lock->lo_name, 798 lock2->li_lock->lo_type, lock2->li_file, 799 lock2->li_line); 800 printf(" 2nd %p %s (%s) @ %s:%d\n", 801 lock1->li_lock, lock1->li_lock->lo_name, 802 lock1->li_lock->lo_type, lock1->li_file, 803 lock1->li_line); 804 printf(" 3rd %p %s (%s) @ %s:%d\n", lock, 805 lock->lo_name, lock->lo_type, file, line); 806 } 807#ifdef DDB 808 go_into_ddb = 1; 809#endif 810 goto out; 811 } 812 } 813 lock1 = &(*lock_list)->ll_children[(*lock_list)->ll_count - 1]; 814 /* 815 * Don't build a new relationship between a sleepable lock and 816 * Giant if it is the wrong direction. The real lock order is that 817 * sleepable locks come before Giant. 818 */ 819 if (!(lock1->li_lock == &Giant.mtx_object && 820 (lock->lo_flags & LO_SLEEPABLE) != 0)) { 821 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__, 822 lock->lo_type, lock1->li_lock->lo_type); 823 if (!itismychild(lock1->li_lock->lo_witness, w)) 824 /* Witness is dead. */ 825 return; 826 } 827 mtx_unlock_spin(&w_mtx); 828 829out: 830#ifdef DDB 831 if (go_into_ddb) { 832 if (witness_trace) 833 backtrace(); 834 if (witness_ddb) 835 Debugger(__func__); 836 } 837#endif 838 w->w_file = file; 839 w->w_line = line; 840 841 lle = *lock_list; 842 if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) { 843 lle = witness_lock_list_get(); 844 if (lle == NULL) 845 return; 846 lle->ll_next = *lock_list; 847 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__, 848 td->td_proc->p_pid, lle); 849 *lock_list = lle; 850 } 851 lock1 = &lle->ll_children[lle->ll_count++]; 852 lock1->li_lock = lock; 853 lock1->li_line = line; 854 lock1->li_file = file; 855 if ((flags & LOP_EXCLUSIVE) != 0) 856 lock1->li_flags = LI_EXCLUSIVE; 857 else 858 lock1->li_flags = 0; 859 CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__, 860 td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1); 861} 862 863void 864witness_upgrade(struct lock_object *lock, int flags, const char *file, int line) 865{ 866 struct lock_instance *instance; 867 struct lock_class *class; 868 869 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 870 if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) 871 return; 872 class = lock->lo_class; 873 file = fixup_filename(file); 874 if ((lock->lo_flags & LO_UPGRADABLE) == 0) 875 panic("upgrade of non-upgradable lock (%s) %s @ %s:%d", 876 class->lc_name, lock->lo_name, file, line); 877 if ((flags & LOP_TRYLOCK) == 0) 878 panic("non-try upgrade of lock (%s) %s @ %s:%d", class->lc_name, 879 lock->lo_name, file, line); 880 if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0) 881 panic("upgrade of non-sleep lock (%s) %s @ %s:%d", 882 class->lc_name, lock->lo_name, file, line); 883 instance = find_instance(curthread->td_sleeplocks, lock); 884 if (instance == NULL) 885 panic("upgrade of unlocked lock (%s) %s @ %s:%d", 886 class->lc_name, lock->lo_name, file, line); 887 if ((instance->li_flags & LI_EXCLUSIVE) != 0) 888 panic("upgrade of exclusive lock (%s) %s @ %s:%d", 889 class->lc_name, lock->lo_name, file, line); 890 if ((instance->li_flags & LI_RECURSEMASK) != 0) 891 panic("upgrade of recursed lock (%s) %s r=%d @ %s:%d", 892 class->lc_name, lock->lo_name, 893 instance->li_flags & LI_RECURSEMASK, file, line); 894 instance->li_flags |= LI_EXCLUSIVE; 895} 896 897void 898witness_downgrade(struct lock_object *lock, int flags, const char *file, 899 int line) 900{ 901 struct lock_instance *instance; 902 struct lock_class *class; 903 904 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 905 if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) 906 return; 907 class = lock->lo_class; 908 file = fixup_filename(file); 909 if ((lock->lo_flags & LO_UPGRADABLE) == 0) 910 panic("downgrade of non-upgradable lock (%s) %s @ %s:%d", 911 class->lc_name, lock->lo_name, file, line); 912 if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0) 913 panic("downgrade of non-sleep lock (%s) %s @ %s:%d", 914 class->lc_name, lock->lo_name, file, line); 915 instance = find_instance(curthread->td_sleeplocks, lock); 916 if (instance == NULL) 917 panic("downgrade of unlocked lock (%s) %s @ %s:%d", 918 class->lc_name, lock->lo_name, file, line); 919 if ((instance->li_flags & LI_EXCLUSIVE) == 0) 920 panic("downgrade of shared lock (%s) %s @ %s:%d", 921 class->lc_name, lock->lo_name, file, line); 922 if ((instance->li_flags & LI_RECURSEMASK) != 0) 923 panic("downgrade of recursed lock (%s) %s r=%d @ %s:%d", 924 class->lc_name, lock->lo_name, 925 instance->li_flags & LI_RECURSEMASK, file, line); 926 instance->li_flags &= ~LI_EXCLUSIVE; 927} 928 929void 930witness_unlock(struct lock_object *lock, int flags, const char *file, int line) 931{ 932 struct lock_list_entry **lock_list, *lle; 933 struct lock_instance *instance; 934 struct lock_class *class; 935 struct thread *td; 936 register_t s; 937 int i, j; 938 939 if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL || 940 panicstr != NULL) 941 return; 942 td = curthread; 943 class = lock->lo_class; 944 file = fixup_filename(file); 945 if (class->lc_flags & LC_SLEEPLOCK) 946 lock_list = &td->td_sleeplocks; 947 else 948 lock_list = PCPU_PTR(spinlocks); 949 for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next) 950 for (i = 0; i < (*lock_list)->ll_count; i++) { 951 instance = &(*lock_list)->ll_children[i]; 952 if (instance->li_lock == lock) { 953 if ((instance->li_flags & LI_EXCLUSIVE) != 0 && 954 (flags & LOP_EXCLUSIVE) == 0) { 955 printf( 956 "shared unlock of (%s) %s @ %s:%d\n", 957 class->lc_name, lock->lo_name, 958 file, line); 959 printf( 960 "while exclusively locked from %s:%d\n", 961 instance->li_file, 962 instance->li_line); 963 panic("excl->ushare"); 964 } 965 if ((instance->li_flags & LI_EXCLUSIVE) == 0 && 966 (flags & LOP_EXCLUSIVE) != 0) { 967 printf( 968 "exclusive unlock of (%s) %s @ %s:%d\n", 969 class->lc_name, lock->lo_name, 970 file, line); 971 printf( 972 "while share locked from %s:%d\n", 973 instance->li_file, 974 instance->li_line); 975 panic("share->uexcl"); 976 } 977 /* If we are recursed, unrecurse. */ 978 if ((instance->li_flags & LI_RECURSEMASK) > 0) { 979 CTR4(KTR_WITNESS, 980 "%s: pid %d unrecursed on %s r=%d", __func__, 981 td->td_proc->p_pid, 982 instance->li_lock->lo_name, 983 instance->li_flags); 984 instance->li_flags--; 985 return; 986 } 987 s = intr_disable(); 988 CTR4(KTR_WITNESS, 989 "%s: pid %d removed %s from lle[%d]", __func__, 990 td->td_proc->p_pid, 991 instance->li_lock->lo_name, 992 (*lock_list)->ll_count - 1); 993 for (j = i; j < (*lock_list)->ll_count - 1; j++) 994 (*lock_list)->ll_children[j] = 995 (*lock_list)->ll_children[j + 1]; 996 (*lock_list)->ll_count--; 997 intr_restore(s); 998 if ((*lock_list)->ll_count == 0) { 999 lle = *lock_list; 1000 *lock_list = lle->ll_next; 1001 CTR3(KTR_WITNESS, 1002 "%s: pid %d removed lle %p", __func__, 1003 td->td_proc->p_pid, lle); 1004 witness_lock_list_free(lle); 1005 } 1006 return; 1007 } 1008 } 1009 panic("lock (%s) %s not locked @ %s:%d", class->lc_name, lock->lo_name, 1010 file, line); 1011} 1012 1013/* 1014 * Warn if any locks other than 'lock' are held. Flags can be passed in to 1015 * exempt Giant and sleepable locks from the checks as well. If any 1016 * non-exempt locks are held, then a supplied message is printed to the 1017 * console along with a list of the offending locks. If indicated in the 1018 * flags then a failure results in a panic as well. 1019 */ 1020int 1021witness_warn(int flags, struct lock_object *lock, const char *fmt, ...) 1022{ 1023 struct lock_list_entry *lle; 1024 struct lock_instance *lock1; 1025 struct thread *td; 1026 va_list ap; 1027 int i, n; 1028 1029 if (witness_cold || witness_watch == 0 || panicstr != NULL) 1030 return (0); 1031 n = 0; 1032 td = curthread; 1033 for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next) 1034 for (i = lle->ll_count - 1; i >= 0; i--) { 1035 lock1 = &lle->ll_children[i]; 1036 if (lock1->li_lock == lock) 1037 continue; 1038 if (flags & WARN_GIANTOK && 1039 lock1->li_lock == &Giant.mtx_object) 1040 continue; 1041 if (flags & WARN_SLEEPOK && 1042 (lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0) 1043 continue; 1044 if (n == 0) { 1045 va_start(ap, fmt); 1046 vprintf(fmt, ap); 1047 va_end(ap); 1048 printf(" with the following"); 1049 if (flags & WARN_SLEEPOK) 1050 printf(" non-sleepable"); 1051 printf(" locks held:\n"); 1052 } 1053 n++; 1054 witness_list_lock(lock1); 1055 } 1056 if (PCPU_GET(spinlocks) != NULL) { 1057 /* 1058 * Since we already hold a spinlock preemption is 1059 * already blocked. 1060 */ 1061 if (n == 0) { 1062 va_start(ap, fmt); 1063 vprintf(fmt, ap); 1064 va_end(ap); 1065 printf(" with the following"); 1066 if (flags & WARN_SLEEPOK) 1067 printf(" non-sleepable"); 1068 printf(" locks held:\n"); 1069 } 1070 n += witness_list_locks(PCPU_PTR(spinlocks)); 1071 } 1072 if (flags & WARN_PANIC && n) 1073 panic("witness_warn"); 1074#ifdef DDB 1075 else if (witness_ddb && n) 1076 Debugger(__func__); 1077#endif 1078 return (n); 1079} 1080 1081const char * 1082witness_file(struct lock_object *lock) 1083{ 1084 struct witness *w; 1085 1086 if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL) 1087 return ("?"); 1088 w = lock->lo_witness; 1089 return (w->w_file); 1090} 1091 1092int 1093witness_line(struct lock_object *lock) 1094{ 1095 struct witness *w; 1096 1097 if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL) 1098 return (0); 1099 w = lock->lo_witness; 1100 return (w->w_line); 1101} 1102 1103static struct witness * 1104enroll(const char *description, struct lock_class *lock_class) 1105{ 1106 struct witness *w; 1107 1108 if (!witness_watch || witness_watch == 0 || panicstr != NULL) 1109 return (NULL); 1110 if ((lock_class->lc_flags & LC_SPINLOCK) && witness_skipspin) 1111 return (NULL); 1112 mtx_lock_spin(&w_mtx); 1113 STAILQ_FOREACH(w, &w_all, w_list) { 1114 if (w->w_name == description || (w->w_refcount > 0 && 1115 strcmp(description, w->w_name) == 0)) { 1116 w->w_refcount++; 1117 mtx_unlock_spin(&w_mtx); 1118 if (lock_class != w->w_class) 1119 panic( 1120 "lock (%s) %s does not match earlier (%s) lock", 1121 description, lock_class->lc_name, 1122 w->w_class->lc_name); 1123 return (w); 1124 } 1125 } 1126 /* 1127 * This isn't quite right, as witness_cold is still 0 while we 1128 * enroll all the locks initialized before witness_initialize(). 1129 */ 1130 if ((lock_class->lc_flags & LC_SPINLOCK) && !witness_cold) { 1131 mtx_unlock_spin(&w_mtx); 1132 panic("spin lock %s not in order list", description); 1133 } 1134 if ((w = witness_get()) == NULL) 1135 return (NULL); 1136 w->w_name = description; 1137 w->w_class = lock_class; 1138 w->w_refcount = 1; 1139 STAILQ_INSERT_HEAD(&w_all, w, w_list); 1140 if (lock_class->lc_flags & LC_SPINLOCK) 1141 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist); 1142 else if (lock_class->lc_flags & LC_SLEEPLOCK) 1143 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist); 1144 else { 1145 mtx_unlock_spin(&w_mtx); 1146 panic("lock class %s is not sleep or spin", 1147 lock_class->lc_name); 1148 } 1149 mtx_unlock_spin(&w_mtx); 1150 return (w); 1151} 1152 1153/* Don't let the door bang you on the way out... */ 1154static int 1155depart(struct witness *w) 1156{ 1157 struct witness_child_list_entry *wcl, *nwcl; 1158 struct witness_list *list; 1159 struct witness *parent; 1160 1161 MPASS(w->w_refcount == 0); 1162 if (w->w_class->lc_flags & LC_SLEEPLOCK) 1163 list = &w_sleep; 1164 else 1165 list = &w_spin; 1166 /* 1167 * First, we run through the entire tree looking for any 1168 * witnesses that the outgoing witness is a child of. For 1169 * each parent that we find, we reparent all the direct 1170 * children of the outgoing witness to its parent. 1171 */ 1172 STAILQ_FOREACH(parent, list, w_typelist) { 1173 if (!isitmychild(parent, w)) 1174 continue; 1175 removechild(parent, w); 1176 if (!reparentchildren(parent, w)) 1177 return (0); 1178 } 1179 1180 /* 1181 * Now we go through and free up the child list of the 1182 * outgoing witness. 1183 */ 1184 for (wcl = w->w_children; wcl != NULL; wcl = nwcl) { 1185 nwcl = wcl->wcl_next; 1186 witness_child_free(wcl); 1187 } 1188 1189 /* 1190 * Detach from various lists and free. 1191 */ 1192 STAILQ_REMOVE(list, w, witness, w_typelist); 1193 STAILQ_REMOVE(&w_all, w, witness, w_list); 1194 witness_free(w); 1195 1196 /* Finally, fixup the tree. */ 1197 return (rebalancetree(list)); 1198} 1199 1200/* 1201 * Prune an entire lock order tree. We look for cases where a lock 1202 * is now both a descendant and a direct child of a given lock. In 1203 * that case, we want to remove the direct child link from the tree. 1204 * 1205 * Returns false if insertchild() fails. 1206 */ 1207static int 1208rebalancetree(struct witness_list *list) 1209{ 1210 struct witness *child, *parent; 1211 1212 STAILQ_FOREACH(child, list, w_typelist) { 1213 STAILQ_FOREACH(parent, list, w_typelist) { 1214 if (!isitmychild(parent, child)) 1215 continue; 1216 removechild(parent, child); 1217 if (isitmydescendant(parent, child)) 1218 continue; 1219 if (!insertchild(parent, child)) 1220 return (0); 1221 } 1222 } 1223 witness_levelall(); 1224 return (1); 1225} 1226 1227/* 1228 * Add "child" as a direct child of "parent". Returns false if 1229 * we fail due to out of memory. 1230 */ 1231static int 1232insertchild(struct witness *parent, struct witness *child) 1233{ 1234 struct witness_child_list_entry **wcl; 1235 1236 MPASS(child != NULL && parent != NULL); 1237 1238 /* 1239 * Insert "child" after "parent" 1240 */ 1241 wcl = &parent->w_children; 1242 while (*wcl != NULL && (*wcl)->wcl_count == WITNESS_NCHILDREN) 1243 wcl = &(*wcl)->wcl_next; 1244 if (*wcl == NULL) { 1245 *wcl = witness_child_get(); 1246 if (*wcl == NULL) 1247 return (0); 1248 } 1249 (*wcl)->wcl_children[(*wcl)->wcl_count++] = child; 1250 1251 return (1); 1252} 1253 1254/* 1255 * Make all the direct descendants of oldparent be direct descendants 1256 * of newparent. 1257 */ 1258static int 1259reparentchildren(struct witness *newparent, struct witness *oldparent) 1260{ 1261 struct witness_child_list_entry *wcl; 1262 int i; 1263 1264 /* Avoid making a witness a child of itself. */ 1265 MPASS(!isitmychild(oldparent, newparent)); 1266 1267 for (wcl = oldparent->w_children; wcl != NULL; wcl = wcl->wcl_next) 1268 for (i = 0; i < wcl->wcl_count; i++) 1269 if (!insertchild(newparent, wcl->wcl_children[i])) 1270 return (0); 1271 return (1); 1272} 1273 1274static int 1275itismychild(struct witness *parent, struct witness *child) 1276{ 1277 struct witness_list *list; 1278 1279 MPASS(child != NULL && parent != NULL); 1280 if ((parent->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) != 1281 (child->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK))) 1282 panic( 1283 "%s: parent (%s) and child (%s) are not the same lock type", 1284 __func__, parent->w_class->lc_name, 1285 child->w_class->lc_name); 1286 1287 if (!insertchild(parent, child)) 1288 return (0); 1289 1290 if (parent->w_class->lc_flags & LC_SLEEPLOCK) 1291 list = &w_sleep; 1292 else 1293 list = &w_spin; 1294 return (rebalancetree(list)); 1295} 1296 1297static void 1298removechild(struct witness *parent, struct witness *child) 1299{ 1300 struct witness_child_list_entry **wcl, *wcl1; 1301 int i; 1302 1303 for (wcl = &parent->w_children; *wcl != NULL; wcl = &(*wcl)->wcl_next) 1304 for (i = 0; i < (*wcl)->wcl_count; i++) 1305 if ((*wcl)->wcl_children[i] == child) 1306 goto found; 1307 return; 1308found: 1309 (*wcl)->wcl_count--; 1310 if ((*wcl)->wcl_count > i) 1311 (*wcl)->wcl_children[i] = 1312 (*wcl)->wcl_children[(*wcl)->wcl_count]; 1313 MPASS((*wcl)->wcl_children[i] != NULL); 1314 if ((*wcl)->wcl_count != 0) 1315 return; 1316 wcl1 = *wcl; 1317 *wcl = wcl1->wcl_next; 1318 witness_child_free(wcl1); 1319} 1320 1321static int 1322isitmychild(struct witness *parent, struct witness *child) 1323{ 1324 struct witness_child_list_entry *wcl; 1325 int i; 1326 1327 for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) { 1328 for (i = 0; i < wcl->wcl_count; i++) { 1329 if (wcl->wcl_children[i] == child) 1330 return (1); 1331 } 1332 } 1333 return (0); 1334} 1335 1336static int 1337isitmydescendant(struct witness *parent, struct witness *child) 1338{ 1339 struct witness_child_list_entry *wcl; 1340 int i, j; 1341 1342 if (isitmychild(parent, child)) 1343 return (1); 1344 j = 0; 1345 for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) { 1346 MPASS(j < 1000); 1347 for (i = 0; i < wcl->wcl_count; i++) { 1348 if (isitmydescendant(wcl->wcl_children[i], child)) 1349 return (1); 1350 } 1351 j++; 1352 } 1353 return (0); 1354} 1355 1356static void 1357witness_levelall (void) 1358{ 1359 struct witness_list *list; 1360 struct witness *w, *w1; 1361 1362 /* 1363 * First clear all levels. 1364 */ 1365 STAILQ_FOREACH(w, &w_all, w_list) { 1366 w->w_level = 0; 1367 } 1368 1369 /* 1370 * Look for locks with no parent and level all their descendants. 1371 */ 1372 STAILQ_FOREACH(w, &w_all, w_list) { 1373 /* 1374 * This is just an optimization, technically we could get 1375 * away just walking the all list each time. 1376 */ 1377 if (w->w_class->lc_flags & LC_SLEEPLOCK) 1378 list = &w_sleep; 1379 else 1380 list = &w_spin; 1381 STAILQ_FOREACH(w1, list, w_typelist) { 1382 if (isitmychild(w1, w)) 1383 goto skip; 1384 } 1385 witness_leveldescendents(w, 0); 1386 skip: 1387 ; /* silence GCC 3.x */ 1388 } 1389} 1390 1391static void 1392witness_leveldescendents(struct witness *parent, int level) 1393{ 1394 struct witness_child_list_entry *wcl; 1395 int i; 1396 1397 if (parent->w_level < level) 1398 parent->w_level = level; 1399 level++; 1400 for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) 1401 for (i = 0; i < wcl->wcl_count; i++) 1402 witness_leveldescendents(wcl->wcl_children[i], level); 1403} 1404 1405static void 1406witness_displaydescendants(void(*prnt)(const char *fmt, ...), 1407 struct witness *parent, int indent) 1408{ 1409 struct witness_child_list_entry *wcl; 1410 int i, level; 1411 1412 level = parent->w_level; 1413 prnt("%-2d", level); 1414 for (i = 0; i < indent; i++) 1415 prnt(" "); 1416 if (parent->w_refcount > 0) 1417 prnt("%s", parent->w_name); 1418 else 1419 prnt("(dead)"); 1420 if (parent->w_displayed) { 1421 prnt(" -- (already displayed)\n"); 1422 return; 1423 } 1424 parent->w_displayed = 1; 1425 if (parent->w_refcount > 0) { 1426 if (parent->w_file != NULL) 1427 prnt(" -- last acquired @ %s:%d", parent->w_file, 1428 parent->w_line); 1429 } 1430 prnt("\n"); 1431 for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) 1432 for (i = 0; i < wcl->wcl_count; i++) 1433 witness_displaydescendants(prnt, 1434 wcl->wcl_children[i], indent + 1); 1435} 1436 1437#ifdef BLESSING 1438static int 1439blessed(struct witness *w1, struct witness *w2) 1440{ 1441 int i; 1442 struct witness_blessed *b; 1443 1444 for (i = 0; i < blessed_count; i++) { 1445 b = &blessed_list[i]; 1446 if (strcmp(w1->w_name, b->b_lock1) == 0) { 1447 if (strcmp(w2->w_name, b->b_lock2) == 0) 1448 return (1); 1449 continue; 1450 } 1451 if (strcmp(w1->w_name, b->b_lock2) == 0) 1452 if (strcmp(w2->w_name, b->b_lock1) == 0) 1453 return (1); 1454 } 1455 return (0); 1456} 1457#endif 1458 1459static struct witness * 1460witness_get(void) 1461{ 1462 struct witness *w; 1463 1464 if (witness_watch == 0) { 1465 mtx_unlock_spin(&w_mtx); 1466 return (NULL); 1467 } 1468 if (STAILQ_EMPTY(&w_free)) { 1469 witness_watch = 0; 1470 mtx_unlock_spin(&w_mtx); 1471 printf("%s: witness exhausted\n", __func__); 1472 return (NULL); 1473 } 1474 w = STAILQ_FIRST(&w_free); 1475 STAILQ_REMOVE_HEAD(&w_free, w_list); 1476 bzero(w, sizeof(*w)); 1477 return (w); 1478} 1479 1480static void 1481witness_free(struct witness *w) 1482{ 1483 1484 STAILQ_INSERT_HEAD(&w_free, w, w_list); 1485} 1486 1487static struct witness_child_list_entry * 1488witness_child_get(void) 1489{ 1490 struct witness_child_list_entry *wcl; 1491 1492 if (witness_watch == 0) { 1493 mtx_unlock_spin(&w_mtx); 1494 return (NULL); 1495 } 1496 wcl = w_child_free; 1497 if (wcl == NULL) { 1498 witness_watch = 0; 1499 mtx_unlock_spin(&w_mtx); 1500 printf("%s: witness exhausted\n", __func__); 1501 return (NULL); 1502 } 1503 w_child_free = wcl->wcl_next; 1504 bzero(wcl, sizeof(*wcl)); 1505 return (wcl); 1506} 1507 1508static void 1509witness_child_free(struct witness_child_list_entry *wcl) 1510{ 1511 1512 wcl->wcl_next = w_child_free; 1513 w_child_free = wcl; 1514} 1515 1516static struct lock_list_entry * 1517witness_lock_list_get(void) 1518{ 1519 struct lock_list_entry *lle; 1520 1521 if (witness_watch == 0) 1522 return (NULL); 1523 mtx_lock_spin(&w_mtx); 1524 lle = w_lock_list_free; 1525 if (lle == NULL) { 1526 witness_watch = 0; 1527 mtx_unlock_spin(&w_mtx); 1528 printf("%s: witness exhausted\n", __func__); 1529 return (NULL); 1530 } 1531 w_lock_list_free = lle->ll_next; 1532 mtx_unlock_spin(&w_mtx); 1533 bzero(lle, sizeof(*lle)); 1534 return (lle); 1535} 1536 1537static void 1538witness_lock_list_free(struct lock_list_entry *lle) 1539{ 1540 1541 mtx_lock_spin(&w_mtx); 1542 lle->ll_next = w_lock_list_free; 1543 w_lock_list_free = lle; 1544 mtx_unlock_spin(&w_mtx); 1545} 1546 1547static struct lock_instance * 1548find_instance(struct lock_list_entry *lock_list, struct lock_object *lock) 1549{ 1550 struct lock_list_entry *lle; 1551 struct lock_instance *instance; 1552 int i; 1553 1554 for (lle = lock_list; lle != NULL; lle = lle->ll_next) 1555 for (i = lle->ll_count - 1; i >= 0; i--) { 1556 instance = &lle->ll_children[i]; 1557 if (instance->li_lock == lock) 1558 return (instance); 1559 } 1560 return (NULL); 1561} 1562 1563static void 1564witness_list_lock(struct lock_instance *instance) 1565{ 1566 struct lock_object *lock; 1567 1568 lock = instance->li_lock; 1569 printf("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ? 1570 "exclusive" : "shared", lock->lo_class->lc_name, lock->lo_name); 1571 if (lock->lo_type != lock->lo_name) 1572 printf(" (%s)", lock->lo_type); 1573 printf(" r = %d (%p) locked @ %s:%d\n", 1574 instance->li_flags & LI_RECURSEMASK, lock, instance->li_file, 1575 instance->li_line); 1576} 1577 1578int 1579witness_list_locks(struct lock_list_entry **lock_list) 1580{ 1581 struct lock_list_entry *lle; 1582 int i, nheld; 1583 1584 nheld = 0; 1585 for (lle = *lock_list; lle != NULL; lle = lle->ll_next) 1586 for (i = lle->ll_count - 1; i >= 0; i--) { 1587 witness_list_lock(&lle->ll_children[i]); 1588 nheld++; 1589 } 1590 return (nheld); 1591} 1592 1593/* 1594 * This is a bit risky at best. We call this function when we have timed 1595 * out acquiring a spin lock, and we assume that the other CPU is stuck 1596 * with this lock held. So, we go groveling around in the other CPU's 1597 * per-cpu data to try to find the lock instance for this spin lock to 1598 * see when it was last acquired. 1599 */ 1600void 1601witness_display_spinlock(struct lock_object *lock, struct thread *owner) 1602{ 1603 struct lock_instance *instance; 1604 struct pcpu *pc; 1605 1606 if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU) 1607 return; 1608 pc = pcpu_find(owner->td_oncpu); 1609 instance = find_instance(pc->pc_spinlocks, lock); 1610 if (instance != NULL) 1611 witness_list_lock(instance); 1612} 1613 1614void 1615witness_save(struct lock_object *lock, const char **filep, int *linep) 1616{ 1617 struct lock_instance *instance; 1618 1619 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 1620 if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) 1621 return; 1622 if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0) 1623 panic("%s: lock (%s) %s is not a sleep lock", __func__, 1624 lock->lo_class->lc_name, lock->lo_name); 1625 instance = find_instance(curthread->td_sleeplocks, lock); 1626 if (instance == NULL) 1627 panic("%s: lock (%s) %s not locked", __func__, 1628 lock->lo_class->lc_name, lock->lo_name); 1629 *filep = instance->li_file; 1630 *linep = instance->li_line; 1631} 1632 1633void 1634witness_restore(struct lock_object *lock, const char *file, int line) 1635{ 1636 struct lock_instance *instance; 1637 1638 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 1639 if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) 1640 return; 1641 if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0) 1642 panic("%s: lock (%s) %s is not a sleep lock", __func__, 1643 lock->lo_class->lc_name, lock->lo_name); 1644 instance = find_instance(curthread->td_sleeplocks, lock); 1645 if (instance == NULL) 1646 panic("%s: lock (%s) %s not locked", __func__, 1647 lock->lo_class->lc_name, lock->lo_name); 1648 lock->lo_witness->w_file = file; 1649 lock->lo_witness->w_line = line; 1650 instance->li_file = file; 1651 instance->li_line = line; 1652} 1653 1654void 1655witness_assert(struct lock_object *lock, int flags, const char *file, int line) 1656{ 1657#ifdef INVARIANT_SUPPORT 1658 struct lock_instance *instance; 1659 1660 if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) 1661 return; 1662 if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) != 0) 1663 instance = find_instance(curthread->td_sleeplocks, lock); 1664 else if ((lock->lo_class->lc_flags & LC_SPINLOCK) != 0) 1665 instance = find_instance(PCPU_GET(spinlocks), lock); 1666 else { 1667 panic("Lock (%s) %s is not sleep or spin!", 1668 lock->lo_class->lc_name, lock->lo_name); 1669 } 1670 file = fixup_filename(file); 1671 switch (flags) { 1672 case LA_UNLOCKED: 1673 if (instance != NULL) 1674 panic("Lock (%s) %s locked @ %s:%d.", 1675 lock->lo_class->lc_name, lock->lo_name, file, line); 1676 break; 1677 case LA_LOCKED: 1678 case LA_LOCKED | LA_RECURSED: 1679 case LA_LOCKED | LA_NOTRECURSED: 1680 case LA_SLOCKED: 1681 case LA_SLOCKED | LA_RECURSED: 1682 case LA_SLOCKED | LA_NOTRECURSED: 1683 case LA_XLOCKED: 1684 case LA_XLOCKED | LA_RECURSED: 1685 case LA_XLOCKED | LA_NOTRECURSED: 1686 if (instance == NULL) { 1687 panic("Lock (%s) %s not locked @ %s:%d.", 1688 lock->lo_class->lc_name, lock->lo_name, file, line); 1689 break; 1690 } 1691 if ((flags & LA_XLOCKED) != 0 && 1692 (instance->li_flags & LI_EXCLUSIVE) == 0) 1693 panic("Lock (%s) %s not exclusively locked @ %s:%d.", 1694 lock->lo_class->lc_name, lock->lo_name, file, line); 1695 if ((flags & LA_SLOCKED) != 0 && 1696 (instance->li_flags & LI_EXCLUSIVE) != 0) 1697 panic("Lock (%s) %s exclusively locked @ %s:%d.", 1698 lock->lo_class->lc_name, lock->lo_name, file, line); 1699 if ((flags & LA_RECURSED) != 0 && 1700 (instance->li_flags & LI_RECURSEMASK) == 0) 1701 panic("Lock (%s) %s not recursed @ %s:%d.", 1702 lock->lo_class->lc_name, lock->lo_name, file, line); 1703 if ((flags & LA_NOTRECURSED) != 0 && 1704 (instance->li_flags & LI_RECURSEMASK) != 0) 1705 panic("Lock (%s) %s recursed @ %s:%d.", 1706 lock->lo_class->lc_name, lock->lo_name, file, line); 1707 break; 1708 default: 1709 panic("Invalid lock assertion at %s:%d.", file, line); 1710 1711 } 1712#endif /* INVARIANT_SUPPORT */ 1713} 1714 1715#ifdef DDB 1716static void 1717witness_list(struct thread *td) 1718{ 1719 1720 KASSERT(!witness_cold, ("%s: witness_cold", __func__)); 1721 KASSERT(db_active, ("%s: not in the debugger", __func__)); 1722 1723 if (witness_watch == 0) 1724 return; 1725 1726 witness_list_locks(&td->td_sleeplocks); 1727 1728 /* 1729 * We only handle spinlocks if td == curthread. This is somewhat broken 1730 * if td is currently executing on some other CPU and holds spin locks 1731 * as we won't display those locks. If we had a MI way of getting 1732 * the per-cpu data for a given cpu then we could use 1733 * td->td_oncpu to get the list of spinlocks for this thread 1734 * and "fix" this. 1735 * 1736 * That still wouldn't really fix this unless we locked sched_lock 1737 * or stopped the other CPU to make sure it wasn't changing the list 1738 * out from under us. It is probably best to just not try to handle 1739 * threads on other CPU's for now. 1740 */ 1741 if (td == curthread && PCPU_GET(spinlocks) != NULL) 1742 witness_list_locks(PCPU_PTR(spinlocks)); 1743} 1744 1745DB_SHOW_COMMAND(locks, db_witness_list) 1746{ 1747 struct thread *td; 1748 pid_t pid; 1749 struct proc *p; 1750 1751 if (have_addr) { 1752 pid = (addr % 16) + ((addr >> 4) % 16) * 10 + 1753 ((addr >> 8) % 16) * 100 + ((addr >> 12) % 16) * 1000 + 1754 ((addr >> 16) % 16) * 10000; 1755 /* sx_slock(&allproc_lock); */ 1756 FOREACH_PROC_IN_SYSTEM(p) { 1757 if (p->p_pid == pid) 1758 break; 1759 } 1760 /* sx_sunlock(&allproc_lock); */ 1761 if (p == NULL) { 1762 db_printf("pid %d not found\n", pid); 1763 return; 1764 } 1765 FOREACH_THREAD_IN_PROC(p, td) { 1766 witness_list(td); 1767 } 1768 } else { 1769 td = curthread; 1770 witness_list(td); 1771 } 1772} 1773 1774DB_SHOW_COMMAND(witness, db_witness_display) 1775{ 1776 1777 witness_display(db_printf); 1778} 1779#endif 1780