1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 2008 Isilon Systems, Inc. 5 * Copyright (c) 2008 Ilya Maykov <ivmaykov@gmail.com> 6 * Copyright (c) 1998 Berkeley Software Design, Inc. 7 * All rights reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Berkeley Software Design Inc's name may not be used to endorse or 18 * promote products derived from this software without specific prior 19 * written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $ 34 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $ 35 */ 36 37 /* 38 * Implementation of the `witness' lock verifier. Originally implemented for 39 * mutexes in BSD/OS. Extended to handle generic lock objects and lock 40 * classes in FreeBSD. 41 */ 42 43 /* 44 * Main Entry: witness 45 * Pronunciation: 'wit-n&s 46 * Function: noun 47 * Etymology: Middle English witnesse, from Old English witnes knowledge, 48 * testimony, witness, from 2wit 49 * Date: before 12th century 50 * 1 : attestation of a fact or event : TESTIMONY 51 * 2 : one that gives evidence; specifically : one who testifies in 52 * a cause or before a judicial tribunal 53 * 3 : one asked to be present at a transaction so as to be able to 54 * testify to its having taken place 55 * 4 : one who has personal knowledge of something 56 * 5 a : something serving as evidence or proof : SIGN 57 * b : public affirmation by word or example of usually 58 * religious faith or conviction <the heroic witness to divine 59 * life -- Pilot> 60 * 6 capitalized : a member of the Jehovah's Witnesses 61 */ 62 63 /* 64 * Special rules concerning Giant and lock orders: 65 * 66 * 1) Giant must be acquired before any other mutexes. Stated another way, 67 * no other mutex may be held when Giant is acquired. 68 * 69 * 2) Giant must be released when blocking on a sleepable lock. 70 * 71 * This rule is less obvious, but is a result of Giant providing the same 72 * semantics as spl(). Basically, when a thread sleeps, it must release 73 * Giant. When a thread blocks on a sleepable lock, it sleeps. Hence rule 74 * 2). 75 * 76 * 3) Giant may be acquired before or after sleepable locks. 77 * 78 * This rule is also not quite as obvious. Giant may be acquired after 79 * a sleepable lock because it is a non-sleepable lock and non-sleepable 80 * locks may always be acquired while holding a sleepable lock. The second 81 * case, Giant before a sleepable lock, follows from rule 2) above. Suppose 82 * you have two threads T1 and T2 and a sleepable lock X. Suppose that T1 83 * acquires X and blocks on Giant. Then suppose that T2 acquires Giant and 84 * blocks on X. When T2 blocks on X, T2 will release Giant allowing T1 to 85 * execute. Thus, acquiring Giant both before and after a sleepable lock 86 * will not result in a lock order reversal. 87 */ 88 89 #include <sys/cdefs.h> 90 __FBSDID("$FreeBSD$"); 91 92 #include "opt_ddb.h" 93 #include "opt_hwpmc_hooks.h" 94 #include "opt_stack.h" 95 #include "opt_witness.h" 96 97 #include <sys/param.h> 98 #include <sys/bus.h> 99 #include <sys/kdb.h> 100 #include <sys/kernel.h> 101 #include <sys/ktr.h> 102 #include <sys/lock.h> 103 #include <sys/malloc.h> 104 #include <sys/mutex.h> 105 #include <sys/priv.h> 106 #include <sys/proc.h> 107 #include <sys/sbuf.h> 108 #include <sys/sched.h> 109 #include <sys/stack.h> 110 #include <sys/sysctl.h> 111 #include <sys/syslog.h> 112 #include <sys/systm.h> 113 114 #ifdef DDB 115 #include <ddb/ddb.h> 116 #endif 117 118 #include <machine/stdarg.h> 119 120 #if !defined(DDB) && !defined(STACK) 121 #error "DDB or STACK options are required for WITNESS" 122 #endif 123 124 /* Note that these traces do not work with KTR_ALQ. */ 125 #if 0 126 #define KTR_WITNESS KTR_SUBSYS 127 #else 128 #define KTR_WITNESS 0 129 #endif 130 131 #define LI_RECURSEMASK 0x0000ffff /* Recursion depth of lock instance. */ 132 #define LI_EXCLUSIVE 0x00010000 /* Exclusive lock instance. */ 133 #define LI_NORELEASE 0x00020000 /* Lock not allowed to be released. */ 134 #define LI_SLEEPABLE 0x00040000 /* Lock may be held while sleeping. */ 135 136 #ifndef WITNESS_COUNT 137 #define WITNESS_COUNT 1536 138 #endif 139 #define WITNESS_HASH_SIZE 251 /* Prime, gives load factor < 2 */ 140 #define WITNESS_PENDLIST (512 + (MAXCPU * 4)) 141 142 /* Allocate 256 KB of stack data space */ 143 #define WITNESS_LO_DATA_COUNT 2048 144 145 /* Prime, gives load factor of ~2 at full load */ 146 #define WITNESS_LO_HASH_SIZE 1021 147 148 /* 149 * XXX: This is somewhat bogus, as we assume here that at most 2048 threads 150 * will hold LOCK_NCHILDREN locks. We handle failure ok, and we should 151 * probably be safe for the most part, but it's still a SWAG. 152 */ 153 #define LOCK_NCHILDREN 5 154 #define LOCK_CHILDCOUNT 2048 155 156 #define MAX_W_NAME 64 157 158 #define FULLGRAPH_SBUF_SIZE 512 159 160 /* 161 * These flags go in the witness relationship matrix and describe the 162 * relationship between any two struct witness objects. 163 */ 164 #define WITNESS_UNRELATED 0x00 /* No lock order relation. */ 165 #define WITNESS_PARENT 0x01 /* Parent, aka direct ancestor. */ 166 #define WITNESS_ANCESTOR 0x02 /* Direct or indirect ancestor. */ 167 #define WITNESS_CHILD 0x04 /* Child, aka direct descendant. */ 168 #define WITNESS_DESCENDANT 0x08 /* Direct or indirect descendant. */ 169 #define WITNESS_ANCESTOR_MASK (WITNESS_PARENT | WITNESS_ANCESTOR) 170 #define WITNESS_DESCENDANT_MASK (WITNESS_CHILD | WITNESS_DESCENDANT) 171 #define WITNESS_RELATED_MASK \ 172 (WITNESS_ANCESTOR_MASK | WITNESS_DESCENDANT_MASK) 173 #define WITNESS_REVERSAL 0x10 /* A lock order reversal has been 174 * observed. */ 175 #define WITNESS_RESERVED1 0x20 /* Unused flag, reserved. */ 176 #define WITNESS_RESERVED2 0x40 /* Unused flag, reserved. */ 177 #define WITNESS_LOCK_ORDER_KNOWN 0x80 /* This lock order is known. */ 178 179 /* Descendant to ancestor flags */ 180 #define WITNESS_DTOA(x) (((x) & WITNESS_RELATED_MASK) >> 2) 181 182 /* Ancestor to descendant flags */ 183 #define WITNESS_ATOD(x) (((x) & WITNESS_RELATED_MASK) << 2) 184 185 #define WITNESS_INDEX_ASSERT(i) \ 186 MPASS((i) > 0 && (i) <= w_max_used_index && (i) < witness_count) 187 188 static MALLOC_DEFINE(M_WITNESS, "Witness", "Witness"); 189 190 /* 191 * Lock instances. A lock instance is the data associated with a lock while 192 * it is held by witness. For example, a lock instance will hold the 193 * recursion count of a lock. Lock instances are held in lists. Spin locks 194 * are held in a per-cpu list while sleep locks are held in per-thread list. 195 */ 196 struct lock_instance { 197 struct lock_object *li_lock; 198 const char *li_file; 199 int li_line; 200 u_int li_flags; 201 }; 202 203 /* 204 * A simple list type used to build the list of locks held by a thread 205 * or CPU. We can't simply embed the list in struct lock_object since a 206 * lock may be held by more than one thread if it is a shared lock. Locks 207 * are added to the head of the list, so we fill up each list entry from 208 * "the back" logically. To ease some of the arithmetic, we actually fill 209 * in each list entry the normal way (children[0] then children[1], etc.) but 210 * when we traverse the list we read children[count-1] as the first entry 211 * down to children[0] as the final entry. 212 */ 213 struct lock_list_entry { 214 struct lock_list_entry *ll_next; 215 struct lock_instance ll_children[LOCK_NCHILDREN]; 216 u_int ll_count; 217 }; 218 219 /* 220 * The main witness structure. One of these per named lock type in the system 221 * (for example, "vnode interlock"). 222 */ 223 struct witness { 224 char w_name[MAX_W_NAME]; 225 uint32_t w_index; /* Index in the relationship matrix */ 226 struct lock_class *w_class; 227 STAILQ_ENTRY(witness) w_list; /* List of all witnesses. */ 228 STAILQ_ENTRY(witness) w_typelist; /* Witnesses of a type. */ 229 struct witness *w_hash_next; /* Linked list in hash buckets. */ 230 const char *w_file; /* File where last acquired */ 231 uint32_t w_line; /* Line where last acquired */ 232 uint32_t w_refcount; 233 uint16_t w_num_ancestors; /* direct/indirect 234 * ancestor count */ 235 uint16_t w_num_descendants; /* direct/indirect 236 * descendant count */ 237 int16_t w_ddb_level; 238 unsigned w_displayed:1; 239 unsigned w_reversed:1; 240 }; 241 242 STAILQ_HEAD(witness_list, witness); 243 244 /* 245 * The witness hash table. Keys are witness names (const char *), elements are 246 * witness objects (struct witness *). 247 */ 248 struct witness_hash { 249 struct witness *wh_array[WITNESS_HASH_SIZE]; 250 uint32_t wh_size; 251 uint32_t wh_count; 252 }; 253 254 /* 255 * Key type for the lock order data hash table. 256 */ 257 struct witness_lock_order_key { 258 uint16_t from; 259 uint16_t to; 260 }; 261 262 struct witness_lock_order_data { 263 struct stack wlod_stack; 264 struct witness_lock_order_key wlod_key; 265 struct witness_lock_order_data *wlod_next; 266 }; 267 268 /* 269 * The witness lock order data hash table. Keys are witness index tuples 270 * (struct witness_lock_order_key), elements are lock order data objects 271 * (struct witness_lock_order_data). 272 */ 273 struct witness_lock_order_hash { 274 struct witness_lock_order_data *wloh_array[WITNESS_LO_HASH_SIZE]; 275 u_int wloh_size; 276 u_int wloh_count; 277 }; 278 279 struct witness_blessed { 280 const char *b_lock1; 281 const char *b_lock2; 282 }; 283 284 struct witness_pendhelp { 285 const char *wh_type; 286 struct lock_object *wh_lock; 287 }; 288 289 struct witness_order_list_entry { 290 const char *w_name; 291 struct lock_class *w_class; 292 }; 293 294 /* 295 * Returns 0 if one of the locks is a spin lock and the other is not. 296 * Returns 1 otherwise. 297 */ 298 static __inline int 299 witness_lock_type_equal(struct witness *w1, struct witness *w2) 300 { 301 302 return ((w1->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) == 303 (w2->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK))); 304 } 305 306 static __inline int 307 witness_lock_order_key_equal(const struct witness_lock_order_key *a, 308 const struct witness_lock_order_key *b) 309 { 310 311 return (a->from == b->from && a->to == b->to); 312 } 313 314 static int _isitmyx(struct witness *w1, struct witness *w2, int rmask, 315 const char *fname); 316 static void adopt(struct witness *parent, struct witness *child); 317 static int blessed(struct witness *, struct witness *); 318 static void depart(struct witness *w); 319 static struct witness *enroll(const char *description, 320 struct lock_class *lock_class); 321 static struct lock_instance *find_instance(struct lock_list_entry *list, 322 const struct lock_object *lock); 323 static int isitmychild(struct witness *parent, struct witness *child); 324 static int isitmydescendant(struct witness *parent, struct witness *child); 325 static void itismychild(struct witness *parent, struct witness *child); 326 static int sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS); 327 static int sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS); 328 static int sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS); 329 static int sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS); 330 static void witness_add_fullgraph(struct sbuf *sb, struct witness *parent); 331 #ifdef DDB 332 static void witness_ddb_compute_levels(void); 333 static void witness_ddb_display(int(*)(const char *fmt, ...)); 334 static void witness_ddb_display_descendants(int(*)(const char *fmt, ...), 335 struct witness *, int indent); 336 static void witness_ddb_display_list(int(*prnt)(const char *fmt, ...), 337 struct witness_list *list); 338 static void witness_ddb_level_descendants(struct witness *parent, int l); 339 static void witness_ddb_list(struct thread *td); 340 #endif 341 static void witness_debugger(int cond, const char *msg); 342 static void witness_free(struct witness *m); 343 static struct witness *witness_get(void); 344 static uint32_t witness_hash_djb2(const uint8_t *key, uint32_t size); 345 static struct witness *witness_hash_get(const char *key); 346 static void witness_hash_put(struct witness *w); 347 static void witness_init_hash_tables(void); 348 static void witness_increment_graph_generation(void); 349 static void witness_lock_list_free(struct lock_list_entry *lle); 350 static struct lock_list_entry *witness_lock_list_get(void); 351 static int witness_lock_order_add(struct witness *parent, 352 struct witness *child); 353 static int witness_lock_order_check(struct witness *parent, 354 struct witness *child); 355 static struct witness_lock_order_data *witness_lock_order_get( 356 struct witness *parent, 357 struct witness *child); 358 static void witness_list_lock(struct lock_instance *instance, 359 int (*prnt)(const char *fmt, ...)); 360 static int witness_output(const char *fmt, ...) __printflike(1, 2); 361 static int witness_voutput(const char *fmt, va_list ap) __printflike(1, 0); 362 static void witness_setflag(struct lock_object *lock, int flag, int set); 363 364 FEATURE(witness, "kernel has witness(9) support"); 365 366 static SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 367 "Witness Locking"); 368 369 /* 370 * If set to 0, lock order checking is disabled. If set to -1, 371 * witness is completely disabled. Otherwise witness performs full 372 * lock order checking for all locks. At runtime, lock order checking 373 * may be toggled. However, witness cannot be reenabled once it is 374 * completely disabled. 375 */ 376 static int witness_watch = 1; 377 SYSCTL_PROC(_debug_witness, OID_AUTO, watch, 378 CTLFLAG_RWTUN | CTLTYPE_INT | CTLFLAG_MPSAFE, NULL, 0, 379 sysctl_debug_witness_watch, "I", 380 "witness is watching lock operations"); 381 382 #ifdef KDB 383 /* 384 * When KDB is enabled and witness_kdb is 1, it will cause the system 385 * to drop into kdebug() when: 386 * - a lock hierarchy violation occurs 387 * - locks are held when going to sleep. 388 */ 389 #ifdef WITNESS_KDB 390 int witness_kdb = 1; 391 #else 392 int witness_kdb = 0; 393 #endif 394 SYSCTL_INT(_debug_witness, OID_AUTO, kdb, CTLFLAG_RWTUN, &witness_kdb, 0, ""); 395 #endif /* KDB */ 396 397 #if defined(DDB) || defined(KDB) 398 /* 399 * When DDB or KDB is enabled and witness_trace is 1, it will cause the system 400 * to print a stack trace: 401 * - a lock hierarchy violation occurs 402 * - locks are held when going to sleep. 403 */ 404 int witness_trace = 1; 405 SYSCTL_INT(_debug_witness, OID_AUTO, trace, CTLFLAG_RWTUN, &witness_trace, 0, ""); 406 #endif /* DDB || KDB */ 407 408 #ifdef WITNESS_SKIPSPIN 409 int witness_skipspin = 1; 410 #else 411 int witness_skipspin = 0; 412 #endif 413 SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN, &witness_skipspin, 0, ""); 414 415 int badstack_sbuf_size; 416 417 int witness_count = WITNESS_COUNT; 418 SYSCTL_INT(_debug_witness, OID_AUTO, witness_count, CTLFLAG_RDTUN, 419 &witness_count, 0, ""); 420 421 /* 422 * Output channel for witness messages. By default we print to the console. 423 */ 424 enum witness_channel { 425 WITNESS_CONSOLE, 426 WITNESS_LOG, 427 WITNESS_NONE, 428 }; 429 430 static enum witness_channel witness_channel = WITNESS_CONSOLE; 431 SYSCTL_PROC(_debug_witness, OID_AUTO, output_channel, 432 CTLTYPE_STRING | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, NULL, 0, 433 sysctl_debug_witness_channel, "A", 434 "Output channel for warnings"); 435 436 /* 437 * Call this to print out the relations between locks. 438 */ 439 SYSCTL_PROC(_debug_witness, OID_AUTO, fullgraph, 440 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0, 441 sysctl_debug_witness_fullgraph, "A", 442 "Show locks relation graphs"); 443 444 /* 445 * Call this to print out the witness faulty stacks. 446 */ 447 SYSCTL_PROC(_debug_witness, OID_AUTO, badstacks, 448 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0, 449 sysctl_debug_witness_badstacks, "A", 450 "Show bad witness stacks"); 451 452 static struct mtx w_mtx; 453 454 /* w_list */ 455 static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free); 456 static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all); 457 458 /* w_typelist */ 459 static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin); 460 static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep); 461 462 /* lock list */ 463 static struct lock_list_entry *w_lock_list_free = NULL; 464 static struct witness_pendhelp pending_locks[WITNESS_PENDLIST]; 465 static u_int pending_cnt; 466 467 static int w_free_cnt, w_spin_cnt, w_sleep_cnt; 468 SYSCTL_INT(_debug_witness, OID_AUTO, free_cnt, CTLFLAG_RD, &w_free_cnt, 0, ""); 469 SYSCTL_INT(_debug_witness, OID_AUTO, spin_cnt, CTLFLAG_RD, &w_spin_cnt, 0, ""); 470 SYSCTL_INT(_debug_witness, OID_AUTO, sleep_cnt, CTLFLAG_RD, &w_sleep_cnt, 0, 471 ""); 472 473 static struct witness *w_data; 474 static uint8_t **w_rmatrix; 475 static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT]; 476 static struct witness_hash w_hash; /* The witness hash table. */ 477 478 /* The lock order data hash */ 479 static struct witness_lock_order_data w_lodata[WITNESS_LO_DATA_COUNT]; 480 static struct witness_lock_order_data *w_lofree = NULL; 481 static struct witness_lock_order_hash w_lohash; 482 static int w_max_used_index = 0; 483 static unsigned int w_generation = 0; 484 static const char w_notrunning[] = "Witness not running\n"; 485 static const char w_stillcold[] = "Witness is still cold\n"; 486 #ifdef __i386__ 487 static const char w_notallowed[] = "The sysctl is disabled on the arch\n"; 488 #endif 489 490 static struct witness_order_list_entry order_lists[] = { 491 /* 492 * sx locks 493 */ 494 { "proctree", &lock_class_sx }, 495 { "allproc", &lock_class_sx }, 496 { "allprison", &lock_class_sx }, 497 { NULL, NULL }, 498 /* 499 * Various mutexes 500 */ 501 { "Giant", &lock_class_mtx_sleep }, 502 { "pipe mutex", &lock_class_mtx_sleep }, 503 { "sigio lock", &lock_class_mtx_sleep }, 504 { "process group", &lock_class_mtx_sleep }, 505 #ifdef HWPMC_HOOKS 506 { "pmc-sleep", &lock_class_mtx_sleep }, 507 #endif 508 { "process lock", &lock_class_mtx_sleep }, 509 { "session", &lock_class_mtx_sleep }, 510 { "uidinfo hash", &lock_class_rw }, 511 { "time lock", &lock_class_mtx_sleep }, 512 { NULL, NULL }, 513 /* 514 * umtx 515 */ 516 { "umtx lock", &lock_class_mtx_sleep }, 517 { NULL, NULL }, 518 /* 519 * Sockets 520 */ 521 { "accept", &lock_class_mtx_sleep }, 522 { "so_snd", &lock_class_mtx_sleep }, 523 { "so_rcv", &lock_class_mtx_sleep }, 524 { "sellck", &lock_class_mtx_sleep }, 525 { NULL, NULL }, 526 /* 527 * Routing 528 */ 529 { "so_rcv", &lock_class_mtx_sleep }, 530 { "radix node head", &lock_class_rm }, 531 { "rtentry", &lock_class_mtx_sleep }, 532 { "ifaddr", &lock_class_mtx_sleep }, 533 { NULL, NULL }, 534 /* 535 * IPv4 multicast: 536 * protocol locks before interface locks, after UDP locks. 537 */ 538 { "in_multi_sx", &lock_class_sx }, 539 { "udpinp", &lock_class_rw }, 540 { "in_multi_list_mtx", &lock_class_mtx_sleep }, 541 { "igmp_mtx", &lock_class_mtx_sleep }, 542 { "ifnet_rw", &lock_class_rw }, 543 { "if_addr_lock", &lock_class_mtx_sleep }, 544 { NULL, NULL }, 545 /* 546 * IPv6 multicast: 547 * protocol locks before interface locks, after UDP locks. 548 */ 549 { "in6_multi_sx", &lock_class_sx }, 550 { "udpinp", &lock_class_rw }, 551 { "in6_multi_list_mtx", &lock_class_mtx_sleep }, 552 { "mld_mtx", &lock_class_mtx_sleep }, 553 { "ifnet_rw", &lock_class_rw }, 554 { "if_addr_lock", &lock_class_mtx_sleep }, 555 { NULL, NULL }, 556 /* 557 * UNIX Domain Sockets 558 */ 559 { "unp_link_rwlock", &lock_class_rw }, 560 { "unp_list_lock", &lock_class_mtx_sleep }, 561 { "unp", &lock_class_mtx_sleep }, 562 { "so_snd", &lock_class_mtx_sleep }, 563 { NULL, NULL }, 564 /* 565 * UDP/IP 566 */ 567 { "udp", &lock_class_mtx_sleep }, 568 { "udpinp", &lock_class_rw }, 569 { "so_snd", &lock_class_mtx_sleep }, 570 { NULL, NULL }, 571 /* 572 * TCP/IP 573 */ 574 { "tcp", &lock_class_mtx_sleep }, 575 { "tcpinp", &lock_class_rw }, 576 { "so_snd", &lock_class_mtx_sleep }, 577 { NULL, NULL }, 578 /* 579 * BPF 580 */ 581 { "bpf global lock", &lock_class_sx }, 582 { "bpf cdev lock", &lock_class_mtx_sleep }, 583 { NULL, NULL }, 584 /* 585 * NFS server 586 */ 587 { "nfsd_mtx", &lock_class_mtx_sleep }, 588 { "so_snd", &lock_class_mtx_sleep }, 589 { NULL, NULL }, 590 591 /* 592 * IEEE 802.11 593 */ 594 { "802.11 com lock", &lock_class_mtx_sleep}, 595 { NULL, NULL }, 596 /* 597 * Network drivers 598 */ 599 { "network driver", &lock_class_mtx_sleep}, 600 { NULL, NULL }, 601 602 /* 603 * Netgraph 604 */ 605 { "ng_node", &lock_class_mtx_sleep }, 606 { "ng_worklist", &lock_class_mtx_sleep }, 607 { NULL, NULL }, 608 /* 609 * CDEV 610 */ 611 { "vm map (system)", &lock_class_mtx_sleep }, 612 { "vnode interlock", &lock_class_mtx_sleep }, 613 { "cdev", &lock_class_mtx_sleep }, 614 { "devthrd", &lock_class_mtx_sleep }, 615 { NULL, NULL }, 616 /* 617 * VM 618 */ 619 { "vm map (user)", &lock_class_sx }, 620 { "vm object", &lock_class_rw }, 621 { "vm page", &lock_class_mtx_sleep }, 622 { "pmap pv global", &lock_class_rw }, 623 { "pmap", &lock_class_mtx_sleep }, 624 { "pmap pv list", &lock_class_rw }, 625 { "vm page free queue", &lock_class_mtx_sleep }, 626 { "vm pagequeue", &lock_class_mtx_sleep }, 627 { NULL, NULL }, 628 /* 629 * kqueue/VFS interaction 630 */ 631 { "kqueue", &lock_class_mtx_sleep }, 632 { "struct mount mtx", &lock_class_mtx_sleep }, 633 { "vnode interlock", &lock_class_mtx_sleep }, 634 { NULL, NULL }, 635 /* 636 * VFS namecache 637 */ 638 { "ncvn", &lock_class_mtx_sleep }, 639 { "ncbuc", &lock_class_rw }, 640 { "vnode interlock", &lock_class_mtx_sleep }, 641 { "ncneg", &lock_class_mtx_sleep }, 642 { NULL, NULL }, 643 /* 644 * ZFS locking 645 */ 646 { "dn->dn_mtx", &lock_class_sx }, 647 { "dr->dt.di.dr_mtx", &lock_class_sx }, 648 { "db->db_mtx", &lock_class_sx }, 649 { NULL, NULL }, 650 /* 651 * TCP log locks 652 */ 653 { "TCP ID tree", &lock_class_rw }, 654 { "tcp log id bucket", &lock_class_mtx_sleep }, 655 { "tcpinp", &lock_class_rw }, 656 { "TCP log expireq", &lock_class_mtx_sleep }, 657 { NULL, NULL }, 658 /* 659 * spin locks 660 */ 661 #ifdef SMP 662 { "ap boot", &lock_class_mtx_spin }, 663 #endif 664 { "rm.mutex_mtx", &lock_class_mtx_spin }, 665 { "sio", &lock_class_mtx_spin }, 666 #ifdef __i386__ 667 { "cy", &lock_class_mtx_spin }, 668 #endif 669 { "scc_hwmtx", &lock_class_mtx_spin }, 670 { "uart_hwmtx", &lock_class_mtx_spin }, 671 { "fast_taskqueue", &lock_class_mtx_spin }, 672 { "intr table", &lock_class_mtx_spin }, 673 { "process slock", &lock_class_mtx_spin }, 674 { "syscons video lock", &lock_class_mtx_spin }, 675 { "sleepq chain", &lock_class_mtx_spin }, 676 { "rm_spinlock", &lock_class_mtx_spin }, 677 { "turnstile chain", &lock_class_mtx_spin }, 678 { "turnstile lock", &lock_class_mtx_spin }, 679 { "sched lock", &lock_class_mtx_spin }, 680 { "td_contested", &lock_class_mtx_spin }, 681 { "callout", &lock_class_mtx_spin }, 682 { "entropy harvest mutex", &lock_class_mtx_spin }, 683 #ifdef SMP 684 { "smp rendezvous", &lock_class_mtx_spin }, 685 #endif 686 #ifdef __powerpc__ 687 { "tlb0", &lock_class_mtx_spin }, 688 #endif 689 { NULL, NULL }, 690 { "sched lock", &lock_class_mtx_spin }, 691 #ifdef HWPMC_HOOKS 692 { "pmc-per-proc", &lock_class_mtx_spin }, 693 #endif 694 { NULL, NULL }, 695 /* 696 * leaf locks 697 */ 698 { "intrcnt", &lock_class_mtx_spin }, 699 { "icu", &lock_class_mtx_spin }, 700 #ifdef __i386__ 701 { "allpmaps", &lock_class_mtx_spin }, 702 { "descriptor tables", &lock_class_mtx_spin }, 703 #endif 704 { "clk", &lock_class_mtx_spin }, 705 { "cpuset", &lock_class_mtx_spin }, 706 { "mprof lock", &lock_class_mtx_spin }, 707 { "zombie lock", &lock_class_mtx_spin }, 708 { "ALD Queue", &lock_class_mtx_spin }, 709 #if defined(__i386__) || defined(__amd64__) 710 { "pcicfg", &lock_class_mtx_spin }, 711 { "NDIS thread lock", &lock_class_mtx_spin }, 712 #endif 713 { "tw_osl_io_lock", &lock_class_mtx_spin }, 714 { "tw_osl_q_lock", &lock_class_mtx_spin }, 715 { "tw_cl_io_lock", &lock_class_mtx_spin }, 716 { "tw_cl_intr_lock", &lock_class_mtx_spin }, 717 { "tw_cl_gen_lock", &lock_class_mtx_spin }, 718 #ifdef HWPMC_HOOKS 719 { "pmc-leaf", &lock_class_mtx_spin }, 720 #endif 721 { "blocked lock", &lock_class_mtx_spin }, 722 { NULL, NULL }, 723 { NULL, NULL } 724 }; 725 726 /* 727 * Pairs of locks which have been blessed. Witness does not complain about 728 * order problems with blessed lock pairs. Please do not add an entry to the 729 * table without an explanatory comment. 730 */ 731 static struct witness_blessed blessed_list[] = { 732 /* 733 * See the comment in ufs_dirhash.c. Basically, a vnode lock serializes 734 * both lock orders, so a deadlock cannot happen as a result of this 735 * LOR. 736 */ 737 { "dirhash", "bufwait" }, 738 739 /* 740 * A UFS vnode may be locked in vget() while a buffer belonging to the 741 * parent directory vnode is locked. 742 */ 743 { "ufs", "bufwait" }, 744 }; 745 746 /* 747 * This global is set to 0 once it becomes safe to use the witness code. 748 */ 749 static int witness_cold = 1; 750 751 /* 752 * This global is set to 1 once the static lock orders have been enrolled 753 * so that a warning can be issued for any spin locks enrolled later. 754 */ 755 static int witness_spin_warn = 0; 756 757 /* Trim useless garbage from filenames. */ 758 static const char * 759 fixup_filename(const char *file) 760 { 761 762 if (file == NULL) 763 return (NULL); 764 while (strncmp(file, "../", 3) == 0) 765 file += 3; 766 return (file); 767 } 768 769 /* 770 * Calculate the size of early witness structures. 771 */ 772 int 773 witness_startup_count(void) 774 { 775 int sz; 776 777 sz = sizeof(struct witness) * witness_count; 778 sz += sizeof(*w_rmatrix) * (witness_count + 1); 779 sz += sizeof(*w_rmatrix[0]) * (witness_count + 1) * 780 (witness_count + 1); 781 782 return (sz); 783 } 784 785 /* 786 * The WITNESS-enabled diagnostic code. Note that the witness code does 787 * assume that the early boot is single-threaded at least until after this 788 * routine is completed. 789 */ 790 void 791 witness_startup(void *mem) 792 { 793 struct lock_object *lock; 794 struct witness_order_list_entry *order; 795 struct witness *w, *w1; 796 uintptr_t p; 797 int i; 798 799 p = (uintptr_t)mem; 800 w_data = (void *)p; 801 p += sizeof(struct witness) * witness_count; 802 803 w_rmatrix = (void *)p; 804 p += sizeof(*w_rmatrix) * (witness_count + 1); 805 806 for (i = 0; i < witness_count + 1; i++) { 807 w_rmatrix[i] = (void *)p; 808 p += sizeof(*w_rmatrix[i]) * (witness_count + 1); 809 } 810 badstack_sbuf_size = witness_count * 256; 811 812 /* 813 * We have to release Giant before initializing its witness 814 * structure so that WITNESS doesn't get confused. 815 */ 816 mtx_unlock(&Giant); 817 mtx_assert(&Giant, MA_NOTOWNED); 818 819 CTR1(KTR_WITNESS, "%s: initializing witness", __func__); 820 mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET | 821 MTX_NOWITNESS | MTX_NOPROFILE); 822 for (i = witness_count - 1; i >= 0; i--) { 823 w = &w_data[i]; 824 memset(w, 0, sizeof(*w)); 825 w_data[i].w_index = i; /* Witness index never changes. */ 826 witness_free(w); 827 } 828 KASSERT(STAILQ_FIRST(&w_free)->w_index == 0, 829 ("%s: Invalid list of free witness objects", __func__)); 830 831 /* Witness with index 0 is not used to aid in debugging. */ 832 STAILQ_REMOVE_HEAD(&w_free, w_list); 833 w_free_cnt--; 834 835 for (i = 0; i < witness_count; i++) { 836 memset(w_rmatrix[i], 0, sizeof(*w_rmatrix[i]) * 837 (witness_count + 1)); 838 } 839 840 for (i = 0; i < LOCK_CHILDCOUNT; i++) 841 witness_lock_list_free(&w_locklistdata[i]); 842 witness_init_hash_tables(); 843 844 /* First add in all the specified order lists. */ 845 for (order = order_lists; order->w_name != NULL; order++) { 846 w = enroll(order->w_name, order->w_class); 847 if (w == NULL) 848 continue; 849 w->w_file = "order list"; 850 for (order++; order->w_name != NULL; order++) { 851 w1 = enroll(order->w_name, order->w_class); 852 if (w1 == NULL) 853 continue; 854 w1->w_file = "order list"; 855 itismychild(w, w1); 856 w = w1; 857 } 858 } 859 witness_spin_warn = 1; 860 861 /* Iterate through all locks and add them to witness. */ 862 for (i = 0; pending_locks[i].wh_lock != NULL; i++) { 863 lock = pending_locks[i].wh_lock; 864 KASSERT(lock->lo_flags & LO_WITNESS, 865 ("%s: lock %s is on pending list but not LO_WITNESS", 866 __func__, lock->lo_name)); 867 lock->lo_witness = enroll(pending_locks[i].wh_type, 868 LOCK_CLASS(lock)); 869 } 870 871 /* Mark the witness code as being ready for use. */ 872 witness_cold = 0; 873 874 mtx_lock(&Giant); 875 } 876 877 void 878 witness_init(struct lock_object *lock, const char *type) 879 { 880 struct lock_class *class; 881 882 /* Various sanity checks. */ 883 class = LOCK_CLASS(lock); 884 if ((lock->lo_flags & LO_RECURSABLE) != 0 && 885 (class->lc_flags & LC_RECURSABLE) == 0) 886 kassert_panic("%s: lock (%s) %s can not be recursable", 887 __func__, class->lc_name, lock->lo_name); 888 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 889 (class->lc_flags & LC_SLEEPABLE) == 0) 890 kassert_panic("%s: lock (%s) %s can not be sleepable", 891 __func__, class->lc_name, lock->lo_name); 892 if ((lock->lo_flags & LO_UPGRADABLE) != 0 && 893 (class->lc_flags & LC_UPGRADABLE) == 0) 894 kassert_panic("%s: lock (%s) %s can not be upgradable", 895 __func__, class->lc_name, lock->lo_name); 896 897 /* 898 * If we shouldn't watch this lock, then just clear lo_witness. 899 * Otherwise, if witness_cold is set, then it is too early to 900 * enroll this lock, so defer it to witness_initialize() by adding 901 * it to the pending_locks list. If it is not too early, then enroll 902 * the lock now. 903 */ 904 if (witness_watch < 1 || KERNEL_PANICKED() || 905 (lock->lo_flags & LO_WITNESS) == 0) 906 lock->lo_witness = NULL; 907 else if (witness_cold) { 908 pending_locks[pending_cnt].wh_lock = lock; 909 pending_locks[pending_cnt++].wh_type = type; 910 if (pending_cnt > WITNESS_PENDLIST) 911 panic("%s: pending locks list is too small, " 912 "increase WITNESS_PENDLIST\n", 913 __func__); 914 } else 915 lock->lo_witness = enroll(type, class); 916 } 917 918 void 919 witness_destroy(struct lock_object *lock) 920 { 921 struct lock_class *class; 922 struct witness *w; 923 924 class = LOCK_CLASS(lock); 925 926 if (witness_cold) 927 panic("lock (%s) %s destroyed while witness_cold", 928 class->lc_name, lock->lo_name); 929 930 /* XXX: need to verify that no one holds the lock */ 931 if ((lock->lo_flags & LO_WITNESS) == 0 || lock->lo_witness == NULL) 932 return; 933 w = lock->lo_witness; 934 935 mtx_lock_spin(&w_mtx); 936 MPASS(w->w_refcount > 0); 937 w->w_refcount--; 938 939 if (w->w_refcount == 0) 940 depart(w); 941 mtx_unlock_spin(&w_mtx); 942 } 943 944 #ifdef DDB 945 static void 946 witness_ddb_compute_levels(void) 947 { 948 struct witness *w; 949 950 /* 951 * First clear all levels. 952 */ 953 STAILQ_FOREACH(w, &w_all, w_list) 954 w->w_ddb_level = -1; 955 956 /* 957 * Look for locks with no parents and level all their descendants. 958 */ 959 STAILQ_FOREACH(w, &w_all, w_list) { 960 961 /* If the witness has ancestors (is not a root), skip it. */ 962 if (w->w_num_ancestors > 0) 963 continue; 964 witness_ddb_level_descendants(w, 0); 965 } 966 } 967 968 static void 969 witness_ddb_level_descendants(struct witness *w, int l) 970 { 971 int i; 972 973 if (w->w_ddb_level >= l) 974 return; 975 976 w->w_ddb_level = l; 977 l++; 978 979 for (i = 1; i <= w_max_used_index; i++) { 980 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) 981 witness_ddb_level_descendants(&w_data[i], l); 982 } 983 } 984 985 static void 986 witness_ddb_display_descendants(int(*prnt)(const char *fmt, ...), 987 struct witness *w, int indent) 988 { 989 int i; 990 991 for (i = 0; i < indent; i++) 992 prnt(" "); 993 prnt("%s (type: %s, depth: %d, active refs: %d)", 994 w->w_name, w->w_class->lc_name, 995 w->w_ddb_level, w->w_refcount); 996 if (w->w_displayed) { 997 prnt(" -- (already displayed)\n"); 998 return; 999 } 1000 w->w_displayed = 1; 1001 if (w->w_file != NULL && w->w_line != 0) 1002 prnt(" -- last acquired @ %s:%d\n", fixup_filename(w->w_file), 1003 w->w_line); 1004 else 1005 prnt(" -- never acquired\n"); 1006 indent++; 1007 WITNESS_INDEX_ASSERT(w->w_index); 1008 for (i = 1; i <= w_max_used_index; i++) { 1009 if (db_pager_quit) 1010 return; 1011 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) 1012 witness_ddb_display_descendants(prnt, &w_data[i], 1013 indent); 1014 } 1015 } 1016 1017 static void 1018 witness_ddb_display_list(int(*prnt)(const char *fmt, ...), 1019 struct witness_list *list) 1020 { 1021 struct witness *w; 1022 1023 STAILQ_FOREACH(w, list, w_typelist) { 1024 if (w->w_file == NULL || w->w_ddb_level > 0) 1025 continue; 1026 1027 /* This lock has no anscestors - display its descendants. */ 1028 witness_ddb_display_descendants(prnt, w, 0); 1029 if (db_pager_quit) 1030 return; 1031 } 1032 } 1033 1034 static void 1035 witness_ddb_display(int(*prnt)(const char *fmt, ...)) 1036 { 1037 struct witness *w; 1038 1039 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 1040 witness_ddb_compute_levels(); 1041 1042 /* Clear all the displayed flags. */ 1043 STAILQ_FOREACH(w, &w_all, w_list) 1044 w->w_displayed = 0; 1045 1046 /* 1047 * First, handle sleep locks which have been acquired at least 1048 * once. 1049 */ 1050 prnt("Sleep locks:\n"); 1051 witness_ddb_display_list(prnt, &w_sleep); 1052 if (db_pager_quit) 1053 return; 1054 1055 /* 1056 * Now do spin locks which have been acquired at least once. 1057 */ 1058 prnt("\nSpin locks:\n"); 1059 witness_ddb_display_list(prnt, &w_spin); 1060 if (db_pager_quit) 1061 return; 1062 1063 /* 1064 * Finally, any locks which have not been acquired yet. 1065 */ 1066 prnt("\nLocks which were never acquired:\n"); 1067 STAILQ_FOREACH(w, &w_all, w_list) { 1068 if (w->w_file != NULL || w->w_refcount == 0) 1069 continue; 1070 prnt("%s (type: %s, depth: %d)\n", w->w_name, 1071 w->w_class->lc_name, w->w_ddb_level); 1072 if (db_pager_quit) 1073 return; 1074 } 1075 } 1076 #endif /* DDB */ 1077 1078 int 1079 witness_defineorder(struct lock_object *lock1, struct lock_object *lock2) 1080 { 1081 1082 if (witness_watch == -1 || KERNEL_PANICKED()) 1083 return (0); 1084 1085 /* Require locks that witness knows about. */ 1086 if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL || 1087 lock2->lo_witness == NULL) 1088 return (EINVAL); 1089 1090 mtx_assert(&w_mtx, MA_NOTOWNED); 1091 mtx_lock_spin(&w_mtx); 1092 1093 /* 1094 * If we already have either an explicit or implied lock order that 1095 * is the other way around, then return an error. 1096 */ 1097 if (witness_watch && 1098 isitmydescendant(lock2->lo_witness, lock1->lo_witness)) { 1099 mtx_unlock_spin(&w_mtx); 1100 return (EDOOFUS); 1101 } 1102 1103 /* Try to add the new order. */ 1104 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__, 1105 lock2->lo_witness->w_name, lock1->lo_witness->w_name); 1106 itismychild(lock1->lo_witness, lock2->lo_witness); 1107 mtx_unlock_spin(&w_mtx); 1108 return (0); 1109 } 1110 1111 void 1112 witness_checkorder(struct lock_object *lock, int flags, const char *file, 1113 int line, struct lock_object *interlock) 1114 { 1115 struct lock_list_entry *lock_list, *lle; 1116 struct lock_instance *lock1, *lock2, *plock; 1117 struct lock_class *class, *iclass; 1118 struct witness *w, *w1; 1119 struct thread *td; 1120 int i, j; 1121 1122 if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL || 1123 KERNEL_PANICKED()) 1124 return; 1125 1126 w = lock->lo_witness; 1127 class = LOCK_CLASS(lock); 1128 td = curthread; 1129 1130 if (class->lc_flags & LC_SLEEPLOCK) { 1131 1132 /* 1133 * Since spin locks include a critical section, this check 1134 * implicitly enforces a lock order of all sleep locks before 1135 * all spin locks. 1136 */ 1137 if (td->td_critnest != 0 && !kdb_active) 1138 kassert_panic("acquiring blockable sleep lock with " 1139 "spinlock or critical section held (%s) %s @ %s:%d", 1140 class->lc_name, lock->lo_name, 1141 fixup_filename(file), line); 1142 1143 /* 1144 * If this is the first lock acquired then just return as 1145 * no order checking is needed. 1146 */ 1147 lock_list = td->td_sleeplocks; 1148 if (lock_list == NULL || lock_list->ll_count == 0) 1149 return; 1150 } else { 1151 1152 /* 1153 * If this is the first lock, just return as no order 1154 * checking is needed. Avoid problems with thread 1155 * migration pinning the thread while checking if 1156 * spinlocks are held. If at least one spinlock is held 1157 * the thread is in a safe path and it is allowed to 1158 * unpin it. 1159 */ 1160 sched_pin(); 1161 lock_list = PCPU_GET(spinlocks); 1162 if (lock_list == NULL || lock_list->ll_count == 0) { 1163 sched_unpin(); 1164 return; 1165 } 1166 sched_unpin(); 1167 } 1168 1169 /* 1170 * Check to see if we are recursing on a lock we already own. If 1171 * so, make sure that we don't mismatch exclusive and shared lock 1172 * acquires. 1173 */ 1174 lock1 = find_instance(lock_list, lock); 1175 if (lock1 != NULL) { 1176 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 && 1177 (flags & LOP_EXCLUSIVE) == 0) { 1178 witness_output("shared lock of (%s) %s @ %s:%d\n", 1179 class->lc_name, lock->lo_name, 1180 fixup_filename(file), line); 1181 witness_output("while exclusively locked from %s:%d\n", 1182 fixup_filename(lock1->li_file), lock1->li_line); 1183 kassert_panic("excl->share"); 1184 } 1185 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 && 1186 (flags & LOP_EXCLUSIVE) != 0) { 1187 witness_output("exclusive lock of (%s) %s @ %s:%d\n", 1188 class->lc_name, lock->lo_name, 1189 fixup_filename(file), line); 1190 witness_output("while share locked from %s:%d\n", 1191 fixup_filename(lock1->li_file), lock1->li_line); 1192 kassert_panic("share->excl"); 1193 } 1194 return; 1195 } 1196 1197 /* Warn if the interlock is not locked exactly once. */ 1198 if (interlock != NULL) { 1199 iclass = LOCK_CLASS(interlock); 1200 lock1 = find_instance(lock_list, interlock); 1201 if (lock1 == NULL) 1202 kassert_panic("interlock (%s) %s not locked @ %s:%d", 1203 iclass->lc_name, interlock->lo_name, 1204 fixup_filename(file), line); 1205 else if ((lock1->li_flags & LI_RECURSEMASK) != 0) 1206 kassert_panic("interlock (%s) %s recursed @ %s:%d", 1207 iclass->lc_name, interlock->lo_name, 1208 fixup_filename(file), line); 1209 } 1210 1211 /* 1212 * Find the previously acquired lock, but ignore interlocks. 1213 */ 1214 plock = &lock_list->ll_children[lock_list->ll_count - 1]; 1215 if (interlock != NULL && plock->li_lock == interlock) { 1216 if (lock_list->ll_count > 1) 1217 plock = 1218 &lock_list->ll_children[lock_list->ll_count - 2]; 1219 else { 1220 lle = lock_list->ll_next; 1221 1222 /* 1223 * The interlock is the only lock we hold, so 1224 * simply return. 1225 */ 1226 if (lle == NULL) 1227 return; 1228 plock = &lle->ll_children[lle->ll_count - 1]; 1229 } 1230 } 1231 1232 /* 1233 * Try to perform most checks without a lock. If this succeeds we 1234 * can skip acquiring the lock and return success. Otherwise we redo 1235 * the check with the lock held to handle races with concurrent updates. 1236 */ 1237 w1 = plock->li_lock->lo_witness; 1238 if (witness_lock_order_check(w1, w)) 1239 return; 1240 1241 mtx_lock_spin(&w_mtx); 1242 if (witness_lock_order_check(w1, w)) { 1243 mtx_unlock_spin(&w_mtx); 1244 return; 1245 } 1246 witness_lock_order_add(w1, w); 1247 1248 /* 1249 * Check for duplicate locks of the same type. Note that we only 1250 * have to check for this on the last lock we just acquired. Any 1251 * other cases will be caught as lock order violations. 1252 */ 1253 if (w1 == w) { 1254 i = w->w_index; 1255 if (!(lock->lo_flags & LO_DUPOK) && !(flags & LOP_DUPOK) && 1256 !(w_rmatrix[i][i] & WITNESS_REVERSAL)) { 1257 w_rmatrix[i][i] |= WITNESS_REVERSAL; 1258 w->w_reversed = 1; 1259 mtx_unlock_spin(&w_mtx); 1260 witness_output( 1261 "acquiring duplicate lock of same type: \"%s\"\n", 1262 w->w_name); 1263 witness_output(" 1st %s @ %s:%d\n", plock->li_lock->lo_name, 1264 fixup_filename(plock->li_file), plock->li_line); 1265 witness_output(" 2nd %s @ %s:%d\n", lock->lo_name, 1266 fixup_filename(file), line); 1267 witness_debugger(1, __func__); 1268 } else 1269 mtx_unlock_spin(&w_mtx); 1270 return; 1271 } 1272 mtx_assert(&w_mtx, MA_OWNED); 1273 1274 /* 1275 * If we know that the lock we are acquiring comes after 1276 * the lock we most recently acquired in the lock order tree, 1277 * then there is no need for any further checks. 1278 */ 1279 if (isitmychild(w1, w)) 1280 goto out; 1281 1282 for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) { 1283 for (i = lle->ll_count - 1; i >= 0; i--, j++) { 1284 1285 MPASS(j < LOCK_CHILDCOUNT * LOCK_NCHILDREN); 1286 lock1 = &lle->ll_children[i]; 1287 1288 /* 1289 * Ignore the interlock. 1290 */ 1291 if (interlock == lock1->li_lock) 1292 continue; 1293 1294 /* 1295 * If this lock doesn't undergo witness checking, 1296 * then skip it. 1297 */ 1298 w1 = lock1->li_lock->lo_witness; 1299 if (w1 == NULL) { 1300 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0, 1301 ("lock missing witness structure")); 1302 continue; 1303 } 1304 1305 /* 1306 * If we are locking Giant and this is a sleepable 1307 * lock, then skip it. 1308 */ 1309 if ((lock1->li_flags & LI_SLEEPABLE) != 0 && 1310 lock == &Giant.lock_object) 1311 continue; 1312 1313 /* 1314 * If we are locking a sleepable lock and this lock 1315 * is Giant, then skip it. 1316 */ 1317 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 1318 (flags & LOP_NOSLEEP) == 0 && 1319 lock1->li_lock == &Giant.lock_object) 1320 continue; 1321 1322 /* 1323 * If we are locking a sleepable lock and this lock 1324 * isn't sleepable, we want to treat it as a lock 1325 * order violation to enfore a general lock order of 1326 * sleepable locks before non-sleepable locks. 1327 */ 1328 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 1329 (flags & LOP_NOSLEEP) == 0 && 1330 (lock1->li_flags & LI_SLEEPABLE) == 0) 1331 goto reversal; 1332 1333 /* 1334 * If we are locking Giant and this is a non-sleepable 1335 * lock, then treat it as a reversal. 1336 */ 1337 if ((lock1->li_flags & LI_SLEEPABLE) == 0 && 1338 lock == &Giant.lock_object) 1339 goto reversal; 1340 1341 /* 1342 * Check the lock order hierarchy for a reveresal. 1343 */ 1344 if (!isitmydescendant(w, w1)) 1345 continue; 1346 reversal: 1347 1348 /* 1349 * We have a lock order violation, check to see if it 1350 * is allowed or has already been yelled about. 1351 */ 1352 1353 /* Bail if this violation is known */ 1354 if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL) 1355 goto out; 1356 1357 /* Record this as a violation */ 1358 w_rmatrix[w1->w_index][w->w_index] |= WITNESS_REVERSAL; 1359 w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL; 1360 w->w_reversed = w1->w_reversed = 1; 1361 witness_increment_graph_generation(); 1362 1363 /* 1364 * If the lock order is blessed, bail before logging 1365 * anything. We don't look for other lock order 1366 * violations though, which may be a bug. 1367 */ 1368 if (blessed(w, w1)) 1369 goto out; 1370 mtx_unlock_spin(&w_mtx); 1371 1372 #ifdef WITNESS_NO_VNODE 1373 /* 1374 * There are known LORs between VNODE locks. They are 1375 * not an indication of a bug. VNODE locks are flagged 1376 * as such (LO_IS_VNODE) and we don't yell if the LOR 1377 * is between 2 VNODE locks. 1378 */ 1379 if ((lock->lo_flags & LO_IS_VNODE) != 0 && 1380 (lock1->li_lock->lo_flags & LO_IS_VNODE) != 0) 1381 return; 1382 #endif 1383 1384 /* 1385 * Ok, yell about it. 1386 */ 1387 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 1388 (flags & LOP_NOSLEEP) == 0 && 1389 (lock1->li_flags & LI_SLEEPABLE) == 0) 1390 witness_output( 1391 "lock order reversal: (sleepable after non-sleepable)\n"); 1392 else if ((lock1->li_flags & LI_SLEEPABLE) == 0 1393 && lock == &Giant.lock_object) 1394 witness_output( 1395 "lock order reversal: (Giant after non-sleepable)\n"); 1396 else 1397 witness_output("lock order reversal:\n"); 1398 1399 /* 1400 * Try to locate an earlier lock with 1401 * witness w in our list. 1402 */ 1403 do { 1404 lock2 = &lle->ll_children[i]; 1405 MPASS(lock2->li_lock != NULL); 1406 if (lock2->li_lock->lo_witness == w) 1407 break; 1408 if (i == 0 && lle->ll_next != NULL) { 1409 lle = lle->ll_next; 1410 i = lle->ll_count - 1; 1411 MPASS(i >= 0 && i < LOCK_NCHILDREN); 1412 } else 1413 i--; 1414 } while (i >= 0); 1415 if (i < 0) { 1416 witness_output(" 1st %p %s (%s) @ %s:%d\n", 1417 lock1->li_lock, lock1->li_lock->lo_name, 1418 w1->w_name, fixup_filename(lock1->li_file), 1419 lock1->li_line); 1420 witness_output(" 2nd %p %s (%s) @ %s:%d\n", lock, 1421 lock->lo_name, w->w_name, 1422 fixup_filename(file), line); 1423 } else { 1424 witness_output(" 1st %p %s (%s) @ %s:%d\n", 1425 lock2->li_lock, lock2->li_lock->lo_name, 1426 lock2->li_lock->lo_witness->w_name, 1427 fixup_filename(lock2->li_file), 1428 lock2->li_line); 1429 witness_output(" 2nd %p %s (%s) @ %s:%d\n", 1430 lock1->li_lock, lock1->li_lock->lo_name, 1431 w1->w_name, fixup_filename(lock1->li_file), 1432 lock1->li_line); 1433 witness_output(" 3rd %p %s (%s) @ %s:%d\n", lock, 1434 lock->lo_name, w->w_name, 1435 fixup_filename(file), line); 1436 } 1437 witness_debugger(1, __func__); 1438 return; 1439 } 1440 } 1441 1442 /* 1443 * If requested, build a new lock order. However, don't build a new 1444 * relationship between a sleepable lock and Giant if it is in the 1445 * wrong direction. The correct lock order is that sleepable locks 1446 * always come before Giant. 1447 */ 1448 if (flags & LOP_NEWORDER && 1449 !(plock->li_lock == &Giant.lock_object && 1450 (lock->lo_flags & LO_SLEEPABLE) != 0 && 1451 (flags & LOP_NOSLEEP) == 0)) { 1452 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__, 1453 w->w_name, plock->li_lock->lo_witness->w_name); 1454 itismychild(plock->li_lock->lo_witness, w); 1455 } 1456 out: 1457 mtx_unlock_spin(&w_mtx); 1458 } 1459 1460 void 1461 witness_lock(struct lock_object *lock, int flags, const char *file, int line) 1462 { 1463 struct lock_list_entry **lock_list, *lle; 1464 struct lock_instance *instance; 1465 struct witness *w; 1466 struct thread *td; 1467 1468 if (witness_cold || witness_watch == -1 || lock->lo_witness == NULL || 1469 KERNEL_PANICKED()) 1470 return; 1471 w = lock->lo_witness; 1472 td = curthread; 1473 1474 /* Determine lock list for this lock. */ 1475 if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK) 1476 lock_list = &td->td_sleeplocks; 1477 else 1478 lock_list = PCPU_PTR(spinlocks); 1479 1480 /* Check to see if we are recursing on a lock we already own. */ 1481 instance = find_instance(*lock_list, lock); 1482 if (instance != NULL) { 1483 instance->li_flags++; 1484 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__, 1485 td->td_proc->p_pid, lock->lo_name, 1486 instance->li_flags & LI_RECURSEMASK); 1487 instance->li_file = file; 1488 instance->li_line = line; 1489 return; 1490 } 1491 1492 /* Update per-witness last file and line acquire. */ 1493 w->w_file = file; 1494 w->w_line = line; 1495 1496 /* Find the next open lock instance in the list and fill it. */ 1497 lle = *lock_list; 1498 if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) { 1499 lle = witness_lock_list_get(); 1500 if (lle == NULL) 1501 return; 1502 lle->ll_next = *lock_list; 1503 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__, 1504 td->td_proc->p_pid, lle); 1505 *lock_list = lle; 1506 } 1507 instance = &lle->ll_children[lle->ll_count++]; 1508 instance->li_lock = lock; 1509 instance->li_line = line; 1510 instance->li_file = file; 1511 instance->li_flags = 0; 1512 if ((flags & LOP_EXCLUSIVE) != 0) 1513 instance->li_flags |= LI_EXCLUSIVE; 1514 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && (flags & LOP_NOSLEEP) == 0) 1515 instance->li_flags |= LI_SLEEPABLE; 1516 CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__, 1517 td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1); 1518 } 1519 1520 void 1521 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line) 1522 { 1523 struct lock_instance *instance; 1524 struct lock_class *class; 1525 1526 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 1527 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED()) 1528 return; 1529 class = LOCK_CLASS(lock); 1530 if (witness_watch) { 1531 if ((lock->lo_flags & LO_UPGRADABLE) == 0) 1532 kassert_panic( 1533 "upgrade of non-upgradable lock (%s) %s @ %s:%d", 1534 class->lc_name, lock->lo_name, 1535 fixup_filename(file), line); 1536 if ((class->lc_flags & LC_SLEEPLOCK) == 0) 1537 kassert_panic( 1538 "upgrade of non-sleep lock (%s) %s @ %s:%d", 1539 class->lc_name, lock->lo_name, 1540 fixup_filename(file), line); 1541 } 1542 instance = find_instance(curthread->td_sleeplocks, lock); 1543 if (instance == NULL) { 1544 kassert_panic("upgrade of unlocked lock (%s) %s @ %s:%d", 1545 class->lc_name, lock->lo_name, 1546 fixup_filename(file), line); 1547 return; 1548 } 1549 if (witness_watch) { 1550 if ((instance->li_flags & LI_EXCLUSIVE) != 0) 1551 kassert_panic( 1552 "upgrade of exclusive lock (%s) %s @ %s:%d", 1553 class->lc_name, lock->lo_name, 1554 fixup_filename(file), line); 1555 if ((instance->li_flags & LI_RECURSEMASK) != 0) 1556 kassert_panic( 1557 "upgrade of recursed lock (%s) %s r=%d @ %s:%d", 1558 class->lc_name, lock->lo_name, 1559 instance->li_flags & LI_RECURSEMASK, 1560 fixup_filename(file), line); 1561 } 1562 instance->li_flags |= LI_EXCLUSIVE; 1563 } 1564 1565 void 1566 witness_downgrade(struct lock_object *lock, int flags, const char *file, 1567 int line) 1568 { 1569 struct lock_instance *instance; 1570 struct lock_class *class; 1571 1572 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 1573 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED()) 1574 return; 1575 class = LOCK_CLASS(lock); 1576 if (witness_watch) { 1577 if ((lock->lo_flags & LO_UPGRADABLE) == 0) 1578 kassert_panic( 1579 "downgrade of non-upgradable lock (%s) %s @ %s:%d", 1580 class->lc_name, lock->lo_name, 1581 fixup_filename(file), line); 1582 if ((class->lc_flags & LC_SLEEPLOCK) == 0) 1583 kassert_panic( 1584 "downgrade of non-sleep lock (%s) %s @ %s:%d", 1585 class->lc_name, lock->lo_name, 1586 fixup_filename(file), line); 1587 } 1588 instance = find_instance(curthread->td_sleeplocks, lock); 1589 if (instance == NULL) { 1590 kassert_panic("downgrade of unlocked lock (%s) %s @ %s:%d", 1591 class->lc_name, lock->lo_name, 1592 fixup_filename(file), line); 1593 return; 1594 } 1595 if (witness_watch) { 1596 if ((instance->li_flags & LI_EXCLUSIVE) == 0) 1597 kassert_panic( 1598 "downgrade of shared lock (%s) %s @ %s:%d", 1599 class->lc_name, lock->lo_name, 1600 fixup_filename(file), line); 1601 if ((instance->li_flags & LI_RECURSEMASK) != 0) 1602 kassert_panic( 1603 "downgrade of recursed lock (%s) %s r=%d @ %s:%d", 1604 class->lc_name, lock->lo_name, 1605 instance->li_flags & LI_RECURSEMASK, 1606 fixup_filename(file), line); 1607 } 1608 instance->li_flags &= ~LI_EXCLUSIVE; 1609 } 1610 1611 void 1612 witness_unlock(struct lock_object *lock, int flags, const char *file, int line) 1613 { 1614 struct lock_list_entry **lock_list, *lle; 1615 struct lock_instance *instance; 1616 struct lock_class *class; 1617 struct thread *td; 1618 register_t s; 1619 int i, j; 1620 1621 if (witness_cold || lock->lo_witness == NULL || KERNEL_PANICKED()) 1622 return; 1623 td = curthread; 1624 class = LOCK_CLASS(lock); 1625 1626 /* Find lock instance associated with this lock. */ 1627 if (class->lc_flags & LC_SLEEPLOCK) 1628 lock_list = &td->td_sleeplocks; 1629 else 1630 lock_list = PCPU_PTR(spinlocks); 1631 lle = *lock_list; 1632 for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next) 1633 for (i = 0; i < (*lock_list)->ll_count; i++) { 1634 instance = &(*lock_list)->ll_children[i]; 1635 if (instance->li_lock == lock) 1636 goto found; 1637 } 1638 1639 /* 1640 * When disabling WITNESS through witness_watch we could end up in 1641 * having registered locks in the td_sleeplocks queue. 1642 * We have to make sure we flush these queues, so just search for 1643 * eventual register locks and remove them. 1644 */ 1645 if (witness_watch > 0) { 1646 kassert_panic("lock (%s) %s not locked @ %s:%d", class->lc_name, 1647 lock->lo_name, fixup_filename(file), line); 1648 return; 1649 } else { 1650 return; 1651 } 1652 found: 1653 1654 /* First, check for shared/exclusive mismatches. */ 1655 if ((instance->li_flags & LI_EXCLUSIVE) != 0 && witness_watch > 0 && 1656 (flags & LOP_EXCLUSIVE) == 0) { 1657 witness_output("shared unlock of (%s) %s @ %s:%d\n", 1658 class->lc_name, lock->lo_name, fixup_filename(file), line); 1659 witness_output("while exclusively locked from %s:%d\n", 1660 fixup_filename(instance->li_file), instance->li_line); 1661 kassert_panic("excl->ushare"); 1662 } 1663 if ((instance->li_flags & LI_EXCLUSIVE) == 0 && witness_watch > 0 && 1664 (flags & LOP_EXCLUSIVE) != 0) { 1665 witness_output("exclusive unlock of (%s) %s @ %s:%d\n", 1666 class->lc_name, lock->lo_name, fixup_filename(file), line); 1667 witness_output("while share locked from %s:%d\n", 1668 fixup_filename(instance->li_file), 1669 instance->li_line); 1670 kassert_panic("share->uexcl"); 1671 } 1672 /* If we are recursed, unrecurse. */ 1673 if ((instance->li_flags & LI_RECURSEMASK) > 0) { 1674 CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__, 1675 td->td_proc->p_pid, instance->li_lock->lo_name, 1676 instance->li_flags); 1677 instance->li_flags--; 1678 return; 1679 } 1680 /* The lock is now being dropped, check for NORELEASE flag */ 1681 if ((instance->li_flags & LI_NORELEASE) != 0 && witness_watch > 0) { 1682 witness_output("forbidden unlock of (%s) %s @ %s:%d\n", 1683 class->lc_name, lock->lo_name, fixup_filename(file), line); 1684 kassert_panic("lock marked norelease"); 1685 } 1686 1687 /* Otherwise, remove this item from the list. */ 1688 s = intr_disable(); 1689 CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__, 1690 td->td_proc->p_pid, instance->li_lock->lo_name, 1691 (*lock_list)->ll_count - 1); 1692 for (j = i; j < (*lock_list)->ll_count - 1; j++) 1693 (*lock_list)->ll_children[j] = 1694 (*lock_list)->ll_children[j + 1]; 1695 (*lock_list)->ll_count--; 1696 intr_restore(s); 1697 1698 /* 1699 * In order to reduce contention on w_mtx, we want to keep always an 1700 * head object into lists so that frequent allocation from the 1701 * free witness pool (and subsequent locking) is avoided. 1702 * In order to maintain the current code simple, when the head 1703 * object is totally unloaded it means also that we do not have 1704 * further objects in the list, so the list ownership needs to be 1705 * hand over to another object if the current head needs to be freed. 1706 */ 1707 if ((*lock_list)->ll_count == 0) { 1708 if (*lock_list == lle) { 1709 if (lle->ll_next == NULL) 1710 return; 1711 } else 1712 lle = *lock_list; 1713 *lock_list = lle->ll_next; 1714 CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__, 1715 td->td_proc->p_pid, lle); 1716 witness_lock_list_free(lle); 1717 } 1718 } 1719 1720 void 1721 witness_thread_exit(struct thread *td) 1722 { 1723 struct lock_list_entry *lle; 1724 int i, n; 1725 1726 lle = td->td_sleeplocks; 1727 if (lle == NULL || KERNEL_PANICKED()) 1728 return; 1729 if (lle->ll_count != 0) { 1730 for (n = 0; lle != NULL; lle = lle->ll_next) 1731 for (i = lle->ll_count - 1; i >= 0; i--) { 1732 if (n == 0) 1733 witness_output( 1734 "Thread %p exiting with the following locks held:\n", td); 1735 n++; 1736 witness_list_lock(&lle->ll_children[i], 1737 witness_output); 1738 1739 } 1740 kassert_panic( 1741 "Thread %p cannot exit while holding sleeplocks\n", td); 1742 } 1743 witness_lock_list_free(lle); 1744 } 1745 1746 /* 1747 * Warn if any locks other than 'lock' are held. Flags can be passed in to 1748 * exempt Giant and sleepable locks from the checks as well. If any 1749 * non-exempt locks are held, then a supplied message is printed to the 1750 * output channel along with a list of the offending locks. If indicated in the 1751 * flags then a failure results in a panic as well. 1752 */ 1753 int 1754 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...) 1755 { 1756 struct lock_list_entry *lock_list, *lle; 1757 struct lock_instance *lock1; 1758 struct thread *td; 1759 va_list ap; 1760 int i, n; 1761 1762 if (witness_cold || witness_watch < 1 || KERNEL_PANICKED()) 1763 return (0); 1764 n = 0; 1765 td = curthread; 1766 for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next) 1767 for (i = lle->ll_count - 1; i >= 0; i--) { 1768 lock1 = &lle->ll_children[i]; 1769 if (lock1->li_lock == lock) 1770 continue; 1771 if (flags & WARN_GIANTOK && 1772 lock1->li_lock == &Giant.lock_object) 1773 continue; 1774 if (flags & WARN_SLEEPOK && 1775 (lock1->li_flags & LI_SLEEPABLE) != 0) 1776 continue; 1777 if (n == 0) { 1778 va_start(ap, fmt); 1779 vprintf(fmt, ap); 1780 va_end(ap); 1781 printf(" with the following %slocks held:\n", 1782 (flags & WARN_SLEEPOK) != 0 ? 1783 "non-sleepable " : ""); 1784 } 1785 n++; 1786 witness_list_lock(lock1, printf); 1787 } 1788 1789 /* 1790 * Pin the thread in order to avoid problems with thread migration. 1791 * Once that all verifies are passed about spinlocks ownership, 1792 * the thread is in a safe path and it can be unpinned. 1793 */ 1794 sched_pin(); 1795 lock_list = PCPU_GET(spinlocks); 1796 if (lock_list != NULL && lock_list->ll_count != 0) { 1797 sched_unpin(); 1798 1799 /* 1800 * We should only have one spinlock and as long as 1801 * the flags cannot match for this locks class, 1802 * check if the first spinlock is the one curthread 1803 * should hold. 1804 */ 1805 lock1 = &lock_list->ll_children[lock_list->ll_count - 1]; 1806 if (lock_list->ll_count == 1 && lock_list->ll_next == NULL && 1807 lock1->li_lock == lock && n == 0) 1808 return (0); 1809 1810 va_start(ap, fmt); 1811 vprintf(fmt, ap); 1812 va_end(ap); 1813 printf(" with the following %slocks held:\n", 1814 (flags & WARN_SLEEPOK) != 0 ? "non-sleepable " : ""); 1815 n += witness_list_locks(&lock_list, printf); 1816 } else 1817 sched_unpin(); 1818 if (flags & WARN_PANIC && n) 1819 kassert_panic("%s", __func__); 1820 else 1821 witness_debugger(n, __func__); 1822 return (n); 1823 } 1824 1825 const char * 1826 witness_file(struct lock_object *lock) 1827 { 1828 struct witness *w; 1829 1830 if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL) 1831 return ("?"); 1832 w = lock->lo_witness; 1833 return (w->w_file); 1834 } 1835 1836 int 1837 witness_line(struct lock_object *lock) 1838 { 1839 struct witness *w; 1840 1841 if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL) 1842 return (0); 1843 w = lock->lo_witness; 1844 return (w->w_line); 1845 } 1846 1847 static struct witness * 1848 enroll(const char *description, struct lock_class *lock_class) 1849 { 1850 struct witness *w; 1851 1852 MPASS(description != NULL); 1853 1854 if (witness_watch == -1 || KERNEL_PANICKED()) 1855 return (NULL); 1856 if ((lock_class->lc_flags & LC_SPINLOCK)) { 1857 if (witness_skipspin) 1858 return (NULL); 1859 } else if ((lock_class->lc_flags & LC_SLEEPLOCK) == 0) { 1860 kassert_panic("lock class %s is not sleep or spin", 1861 lock_class->lc_name); 1862 return (NULL); 1863 } 1864 1865 mtx_lock_spin(&w_mtx); 1866 w = witness_hash_get(description); 1867 if (w) 1868 goto found; 1869 if ((w = witness_get()) == NULL) 1870 return (NULL); 1871 MPASS(strlen(description) < MAX_W_NAME); 1872 strcpy(w->w_name, description); 1873 w->w_class = lock_class; 1874 w->w_refcount = 1; 1875 STAILQ_INSERT_HEAD(&w_all, w, w_list); 1876 if (lock_class->lc_flags & LC_SPINLOCK) { 1877 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist); 1878 w_spin_cnt++; 1879 } else if (lock_class->lc_flags & LC_SLEEPLOCK) { 1880 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist); 1881 w_sleep_cnt++; 1882 } 1883 1884 /* Insert new witness into the hash */ 1885 witness_hash_put(w); 1886 witness_increment_graph_generation(); 1887 mtx_unlock_spin(&w_mtx); 1888 return (w); 1889 found: 1890 w->w_refcount++; 1891 if (w->w_refcount == 1) 1892 w->w_class = lock_class; 1893 mtx_unlock_spin(&w_mtx); 1894 if (lock_class != w->w_class) 1895 kassert_panic( 1896 "lock (%s) %s does not match earlier (%s) lock", 1897 description, lock_class->lc_name, 1898 w->w_class->lc_name); 1899 return (w); 1900 } 1901 1902 static void 1903 depart(struct witness *w) 1904 { 1905 1906 MPASS(w->w_refcount == 0); 1907 if (w->w_class->lc_flags & LC_SLEEPLOCK) { 1908 w_sleep_cnt--; 1909 } else { 1910 w_spin_cnt--; 1911 } 1912 /* 1913 * Set file to NULL as it may point into a loadable module. 1914 */ 1915 w->w_file = NULL; 1916 w->w_line = 0; 1917 witness_increment_graph_generation(); 1918 } 1919 1920 static void 1921 adopt(struct witness *parent, struct witness *child) 1922 { 1923 int pi, ci, i, j; 1924 1925 if (witness_cold == 0) 1926 mtx_assert(&w_mtx, MA_OWNED); 1927 1928 /* If the relationship is already known, there's no work to be done. */ 1929 if (isitmychild(parent, child)) 1930 return; 1931 1932 /* When the structure of the graph changes, bump up the generation. */ 1933 witness_increment_graph_generation(); 1934 1935 /* 1936 * The hard part ... create the direct relationship, then propagate all 1937 * indirect relationships. 1938 */ 1939 pi = parent->w_index; 1940 ci = child->w_index; 1941 WITNESS_INDEX_ASSERT(pi); 1942 WITNESS_INDEX_ASSERT(ci); 1943 MPASS(pi != ci); 1944 w_rmatrix[pi][ci] |= WITNESS_PARENT; 1945 w_rmatrix[ci][pi] |= WITNESS_CHILD; 1946 1947 /* 1948 * If parent was not already an ancestor of child, 1949 * then we increment the descendant and ancestor counters. 1950 */ 1951 if ((w_rmatrix[pi][ci] & WITNESS_ANCESTOR) == 0) { 1952 parent->w_num_descendants++; 1953 child->w_num_ancestors++; 1954 } 1955 1956 /* 1957 * Find each ancestor of 'pi'. Note that 'pi' itself is counted as 1958 * an ancestor of 'pi' during this loop. 1959 */ 1960 for (i = 1; i <= w_max_used_index; i++) { 1961 if ((w_rmatrix[i][pi] & WITNESS_ANCESTOR_MASK) == 0 && 1962 (i != pi)) 1963 continue; 1964 1965 /* Find each descendant of 'i' and mark it as a descendant. */ 1966 for (j = 1; j <= w_max_used_index; j++) { 1967 1968 /* 1969 * Skip children that are already marked as 1970 * descendants of 'i'. 1971 */ 1972 if (w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) 1973 continue; 1974 1975 /* 1976 * We are only interested in descendants of 'ci'. Note 1977 * that 'ci' itself is counted as a descendant of 'ci'. 1978 */ 1979 if ((w_rmatrix[ci][j] & WITNESS_ANCESTOR_MASK) == 0 && 1980 (j != ci)) 1981 continue; 1982 w_rmatrix[i][j] |= WITNESS_ANCESTOR; 1983 w_rmatrix[j][i] |= WITNESS_DESCENDANT; 1984 w_data[i].w_num_descendants++; 1985 w_data[j].w_num_ancestors++; 1986 1987 /* 1988 * Make sure we aren't marking a node as both an 1989 * ancestor and descendant. We should have caught 1990 * this as a lock order reversal earlier. 1991 */ 1992 if ((w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) && 1993 (w_rmatrix[i][j] & WITNESS_DESCENDANT_MASK)) { 1994 printf("witness rmatrix paradox! [%d][%d]=%d " 1995 "both ancestor and descendant\n", 1996 i, j, w_rmatrix[i][j]); 1997 kdb_backtrace(); 1998 printf("Witness disabled.\n"); 1999 witness_watch = -1; 2000 } 2001 if ((w_rmatrix[j][i] & WITNESS_ANCESTOR_MASK) && 2002 (w_rmatrix[j][i] & WITNESS_DESCENDANT_MASK)) { 2003 printf("witness rmatrix paradox! [%d][%d]=%d " 2004 "both ancestor and descendant\n", 2005 j, i, w_rmatrix[j][i]); 2006 kdb_backtrace(); 2007 printf("Witness disabled.\n"); 2008 witness_watch = -1; 2009 } 2010 } 2011 } 2012 } 2013 2014 static void 2015 itismychild(struct witness *parent, struct witness *child) 2016 { 2017 int unlocked; 2018 2019 MPASS(child != NULL && parent != NULL); 2020 if (witness_cold == 0) 2021 mtx_assert(&w_mtx, MA_OWNED); 2022 2023 if (!witness_lock_type_equal(parent, child)) { 2024 if (witness_cold == 0) { 2025 unlocked = 1; 2026 mtx_unlock_spin(&w_mtx); 2027 } else { 2028 unlocked = 0; 2029 } 2030 kassert_panic( 2031 "%s: parent \"%s\" (%s) and child \"%s\" (%s) are not " 2032 "the same lock type", __func__, parent->w_name, 2033 parent->w_class->lc_name, child->w_name, 2034 child->w_class->lc_name); 2035 if (unlocked) 2036 mtx_lock_spin(&w_mtx); 2037 } 2038 adopt(parent, child); 2039 } 2040 2041 /* 2042 * Generic code for the isitmy*() functions. The rmask parameter is the 2043 * expected relationship of w1 to w2. 2044 */ 2045 static int 2046 _isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname) 2047 { 2048 unsigned char r1, r2; 2049 int i1, i2; 2050 2051 i1 = w1->w_index; 2052 i2 = w2->w_index; 2053 WITNESS_INDEX_ASSERT(i1); 2054 WITNESS_INDEX_ASSERT(i2); 2055 r1 = w_rmatrix[i1][i2] & WITNESS_RELATED_MASK; 2056 r2 = w_rmatrix[i2][i1] & WITNESS_RELATED_MASK; 2057 2058 /* The flags on one better be the inverse of the flags on the other */ 2059 if (!((WITNESS_ATOD(r1) == r2 && WITNESS_DTOA(r2) == r1) || 2060 (WITNESS_DTOA(r1) == r2 && WITNESS_ATOD(r2) == r1))) { 2061 /* Don't squawk if we're potentially racing with an update. */ 2062 if (!mtx_owned(&w_mtx)) 2063 return (0); 2064 printf("%s: rmatrix mismatch between %s (index %d) and %s " 2065 "(index %d): w_rmatrix[%d][%d] == %hhx but " 2066 "w_rmatrix[%d][%d] == %hhx\n", 2067 fname, w1->w_name, i1, w2->w_name, i2, i1, i2, r1, 2068 i2, i1, r2); 2069 kdb_backtrace(); 2070 printf("Witness disabled.\n"); 2071 witness_watch = -1; 2072 } 2073 return (r1 & rmask); 2074 } 2075 2076 /* 2077 * Checks if @child is a direct child of @parent. 2078 */ 2079 static int 2080 isitmychild(struct witness *parent, struct witness *child) 2081 { 2082 2083 return (_isitmyx(parent, child, WITNESS_PARENT, __func__)); 2084 } 2085 2086 /* 2087 * Checks if @descendant is a direct or inderect descendant of @ancestor. 2088 */ 2089 static int 2090 isitmydescendant(struct witness *ancestor, struct witness *descendant) 2091 { 2092 2093 return (_isitmyx(ancestor, descendant, WITNESS_ANCESTOR_MASK, 2094 __func__)); 2095 } 2096 2097 static int 2098 blessed(struct witness *w1, struct witness *w2) 2099 { 2100 int i; 2101 struct witness_blessed *b; 2102 2103 for (i = 0; i < nitems(blessed_list); i++) { 2104 b = &blessed_list[i]; 2105 if (strcmp(w1->w_name, b->b_lock1) == 0) { 2106 if (strcmp(w2->w_name, b->b_lock2) == 0) 2107 return (1); 2108 continue; 2109 } 2110 if (strcmp(w1->w_name, b->b_lock2) == 0) 2111 if (strcmp(w2->w_name, b->b_lock1) == 0) 2112 return (1); 2113 } 2114 return (0); 2115 } 2116 2117 static struct witness * 2118 witness_get(void) 2119 { 2120 struct witness *w; 2121 int index; 2122 2123 if (witness_cold == 0) 2124 mtx_assert(&w_mtx, MA_OWNED); 2125 2126 if (witness_watch == -1) { 2127 mtx_unlock_spin(&w_mtx); 2128 return (NULL); 2129 } 2130 if (STAILQ_EMPTY(&w_free)) { 2131 witness_watch = -1; 2132 mtx_unlock_spin(&w_mtx); 2133 printf("WITNESS: unable to allocate a new witness object\n"); 2134 return (NULL); 2135 } 2136 w = STAILQ_FIRST(&w_free); 2137 STAILQ_REMOVE_HEAD(&w_free, w_list); 2138 w_free_cnt--; 2139 index = w->w_index; 2140 MPASS(index > 0 && index == w_max_used_index+1 && 2141 index < witness_count); 2142 bzero(w, sizeof(*w)); 2143 w->w_index = index; 2144 if (index > w_max_used_index) 2145 w_max_used_index = index; 2146 return (w); 2147 } 2148 2149 static void 2150 witness_free(struct witness *w) 2151 { 2152 2153 STAILQ_INSERT_HEAD(&w_free, w, w_list); 2154 w_free_cnt++; 2155 } 2156 2157 static struct lock_list_entry * 2158 witness_lock_list_get(void) 2159 { 2160 struct lock_list_entry *lle; 2161 2162 if (witness_watch == -1) 2163 return (NULL); 2164 mtx_lock_spin(&w_mtx); 2165 lle = w_lock_list_free; 2166 if (lle == NULL) { 2167 witness_watch = -1; 2168 mtx_unlock_spin(&w_mtx); 2169 printf("%s: witness exhausted\n", __func__); 2170 return (NULL); 2171 } 2172 w_lock_list_free = lle->ll_next; 2173 mtx_unlock_spin(&w_mtx); 2174 bzero(lle, sizeof(*lle)); 2175 return (lle); 2176 } 2177 2178 static void 2179 witness_lock_list_free(struct lock_list_entry *lle) 2180 { 2181 2182 mtx_lock_spin(&w_mtx); 2183 lle->ll_next = w_lock_list_free; 2184 w_lock_list_free = lle; 2185 mtx_unlock_spin(&w_mtx); 2186 } 2187 2188 static struct lock_instance * 2189 find_instance(struct lock_list_entry *list, const struct lock_object *lock) 2190 { 2191 struct lock_list_entry *lle; 2192 struct lock_instance *instance; 2193 int i; 2194 2195 for (lle = list; lle != NULL; lle = lle->ll_next) 2196 for (i = lle->ll_count - 1; i >= 0; i--) { 2197 instance = &lle->ll_children[i]; 2198 if (instance->li_lock == lock) 2199 return (instance); 2200 } 2201 return (NULL); 2202 } 2203 2204 static void 2205 witness_list_lock(struct lock_instance *instance, 2206 int (*prnt)(const char *fmt, ...)) 2207 { 2208 struct lock_object *lock; 2209 2210 lock = instance->li_lock; 2211 prnt("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ? 2212 "exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name); 2213 if (lock->lo_witness->w_name != lock->lo_name) 2214 prnt(" (%s)", lock->lo_witness->w_name); 2215 prnt(" r = %d (%p) locked @ %s:%d\n", 2216 instance->li_flags & LI_RECURSEMASK, lock, 2217 fixup_filename(instance->li_file), instance->li_line); 2218 } 2219 2220 static int 2221 witness_output(const char *fmt, ...) 2222 { 2223 va_list ap; 2224 int ret; 2225 2226 va_start(ap, fmt); 2227 ret = witness_voutput(fmt, ap); 2228 va_end(ap); 2229 return (ret); 2230 } 2231 2232 static int 2233 witness_voutput(const char *fmt, va_list ap) 2234 { 2235 int ret; 2236 2237 ret = 0; 2238 switch (witness_channel) { 2239 case WITNESS_CONSOLE: 2240 ret = vprintf(fmt, ap); 2241 break; 2242 case WITNESS_LOG: 2243 vlog(LOG_NOTICE, fmt, ap); 2244 break; 2245 case WITNESS_NONE: 2246 break; 2247 } 2248 return (ret); 2249 } 2250 2251 #ifdef DDB 2252 static int 2253 witness_thread_has_locks(struct thread *td) 2254 { 2255 2256 if (td->td_sleeplocks == NULL) 2257 return (0); 2258 return (td->td_sleeplocks->ll_count != 0); 2259 } 2260 2261 static int 2262 witness_proc_has_locks(struct proc *p) 2263 { 2264 struct thread *td; 2265 2266 FOREACH_THREAD_IN_PROC(p, td) { 2267 if (witness_thread_has_locks(td)) 2268 return (1); 2269 } 2270 return (0); 2271 } 2272 #endif 2273 2274 int 2275 witness_list_locks(struct lock_list_entry **lock_list, 2276 int (*prnt)(const char *fmt, ...)) 2277 { 2278 struct lock_list_entry *lle; 2279 int i, nheld; 2280 2281 nheld = 0; 2282 for (lle = *lock_list; lle != NULL; lle = lle->ll_next) 2283 for (i = lle->ll_count - 1; i >= 0; i--) { 2284 witness_list_lock(&lle->ll_children[i], prnt); 2285 nheld++; 2286 } 2287 return (nheld); 2288 } 2289 2290 /* 2291 * This is a bit risky at best. We call this function when we have timed 2292 * out acquiring a spin lock, and we assume that the other CPU is stuck 2293 * with this lock held. So, we go groveling around in the other CPU's 2294 * per-cpu data to try to find the lock instance for this spin lock to 2295 * see when it was last acquired. 2296 */ 2297 void 2298 witness_display_spinlock(struct lock_object *lock, struct thread *owner, 2299 int (*prnt)(const char *fmt, ...)) 2300 { 2301 struct lock_instance *instance; 2302 struct pcpu *pc; 2303 2304 if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU) 2305 return; 2306 pc = pcpu_find(owner->td_oncpu); 2307 instance = find_instance(pc->pc_spinlocks, lock); 2308 if (instance != NULL) 2309 witness_list_lock(instance, prnt); 2310 } 2311 2312 void 2313 witness_save(struct lock_object *lock, const char **filep, int *linep) 2314 { 2315 struct lock_list_entry *lock_list; 2316 struct lock_instance *instance; 2317 struct lock_class *class; 2318 2319 /* 2320 * This function is used independently in locking code to deal with 2321 * Giant, SCHEDULER_STOPPED() check can be removed here after Giant 2322 * is gone. 2323 */ 2324 if (SCHEDULER_STOPPED()) 2325 return; 2326 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 2327 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED()) 2328 return; 2329 class = LOCK_CLASS(lock); 2330 if (class->lc_flags & LC_SLEEPLOCK) 2331 lock_list = curthread->td_sleeplocks; 2332 else { 2333 if (witness_skipspin) 2334 return; 2335 lock_list = PCPU_GET(spinlocks); 2336 } 2337 instance = find_instance(lock_list, lock); 2338 if (instance == NULL) { 2339 kassert_panic("%s: lock (%s) %s not locked", __func__, 2340 class->lc_name, lock->lo_name); 2341 return; 2342 } 2343 *filep = instance->li_file; 2344 *linep = instance->li_line; 2345 } 2346 2347 void 2348 witness_restore(struct lock_object *lock, const char *file, int line) 2349 { 2350 struct lock_list_entry *lock_list; 2351 struct lock_instance *instance; 2352 struct lock_class *class; 2353 2354 /* 2355 * This function is used independently in locking code to deal with 2356 * Giant, SCHEDULER_STOPPED() check can be removed here after Giant 2357 * is gone. 2358 */ 2359 if (SCHEDULER_STOPPED()) 2360 return; 2361 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 2362 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED()) 2363 return; 2364 class = LOCK_CLASS(lock); 2365 if (class->lc_flags & LC_SLEEPLOCK) 2366 lock_list = curthread->td_sleeplocks; 2367 else { 2368 if (witness_skipspin) 2369 return; 2370 lock_list = PCPU_GET(spinlocks); 2371 } 2372 instance = find_instance(lock_list, lock); 2373 if (instance == NULL) 2374 kassert_panic("%s: lock (%s) %s not locked", __func__, 2375 class->lc_name, lock->lo_name); 2376 lock->lo_witness->w_file = file; 2377 lock->lo_witness->w_line = line; 2378 if (instance == NULL) 2379 return; 2380 instance->li_file = file; 2381 instance->li_line = line; 2382 } 2383 2384 void 2385 witness_assert(const struct lock_object *lock, int flags, const char *file, 2386 int line) 2387 { 2388 #ifdef INVARIANT_SUPPORT 2389 struct lock_instance *instance; 2390 struct lock_class *class; 2391 2392 if (lock->lo_witness == NULL || witness_watch < 1 || KERNEL_PANICKED()) 2393 return; 2394 class = LOCK_CLASS(lock); 2395 if ((class->lc_flags & LC_SLEEPLOCK) != 0) 2396 instance = find_instance(curthread->td_sleeplocks, lock); 2397 else if ((class->lc_flags & LC_SPINLOCK) != 0) 2398 instance = find_instance(PCPU_GET(spinlocks), lock); 2399 else { 2400 kassert_panic("Lock (%s) %s is not sleep or spin!", 2401 class->lc_name, lock->lo_name); 2402 return; 2403 } 2404 switch (flags) { 2405 case LA_UNLOCKED: 2406 if (instance != NULL) 2407 kassert_panic("Lock (%s) %s locked @ %s:%d.", 2408 class->lc_name, lock->lo_name, 2409 fixup_filename(file), line); 2410 break; 2411 case LA_LOCKED: 2412 case LA_LOCKED | LA_RECURSED: 2413 case LA_LOCKED | LA_NOTRECURSED: 2414 case LA_SLOCKED: 2415 case LA_SLOCKED | LA_RECURSED: 2416 case LA_SLOCKED | LA_NOTRECURSED: 2417 case LA_XLOCKED: 2418 case LA_XLOCKED | LA_RECURSED: 2419 case LA_XLOCKED | LA_NOTRECURSED: 2420 if (instance == NULL) { 2421 kassert_panic("Lock (%s) %s not locked @ %s:%d.", 2422 class->lc_name, lock->lo_name, 2423 fixup_filename(file), line); 2424 break; 2425 } 2426 if ((flags & LA_XLOCKED) != 0 && 2427 (instance->li_flags & LI_EXCLUSIVE) == 0) 2428 kassert_panic( 2429 "Lock (%s) %s not exclusively locked @ %s:%d.", 2430 class->lc_name, lock->lo_name, 2431 fixup_filename(file), line); 2432 if ((flags & LA_SLOCKED) != 0 && 2433 (instance->li_flags & LI_EXCLUSIVE) != 0) 2434 kassert_panic( 2435 "Lock (%s) %s exclusively locked @ %s:%d.", 2436 class->lc_name, lock->lo_name, 2437 fixup_filename(file), line); 2438 if ((flags & LA_RECURSED) != 0 && 2439 (instance->li_flags & LI_RECURSEMASK) == 0) 2440 kassert_panic("Lock (%s) %s not recursed @ %s:%d.", 2441 class->lc_name, lock->lo_name, 2442 fixup_filename(file), line); 2443 if ((flags & LA_NOTRECURSED) != 0 && 2444 (instance->li_flags & LI_RECURSEMASK) != 0) 2445 kassert_panic("Lock (%s) %s recursed @ %s:%d.", 2446 class->lc_name, lock->lo_name, 2447 fixup_filename(file), line); 2448 break; 2449 default: 2450 kassert_panic("Invalid lock assertion at %s:%d.", 2451 fixup_filename(file), line); 2452 2453 } 2454 #endif /* INVARIANT_SUPPORT */ 2455 } 2456 2457 static void 2458 witness_setflag(struct lock_object *lock, int flag, int set) 2459 { 2460 struct lock_list_entry *lock_list; 2461 struct lock_instance *instance; 2462 struct lock_class *class; 2463 2464 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED()) 2465 return; 2466 class = LOCK_CLASS(lock); 2467 if (class->lc_flags & LC_SLEEPLOCK) 2468 lock_list = curthread->td_sleeplocks; 2469 else { 2470 if (witness_skipspin) 2471 return; 2472 lock_list = PCPU_GET(spinlocks); 2473 } 2474 instance = find_instance(lock_list, lock); 2475 if (instance == NULL) { 2476 kassert_panic("%s: lock (%s) %s not locked", __func__, 2477 class->lc_name, lock->lo_name); 2478 return; 2479 } 2480 2481 if (set) 2482 instance->li_flags |= flag; 2483 else 2484 instance->li_flags &= ~flag; 2485 } 2486 2487 void 2488 witness_norelease(struct lock_object *lock) 2489 { 2490 2491 witness_setflag(lock, LI_NORELEASE, 1); 2492 } 2493 2494 void 2495 witness_releaseok(struct lock_object *lock) 2496 { 2497 2498 witness_setflag(lock, LI_NORELEASE, 0); 2499 } 2500 2501 #ifdef DDB 2502 static void 2503 witness_ddb_list(struct thread *td) 2504 { 2505 2506 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 2507 KASSERT(kdb_active, ("%s: not in the debugger", __func__)); 2508 2509 if (witness_watch < 1) 2510 return; 2511 2512 witness_list_locks(&td->td_sleeplocks, db_printf); 2513 2514 /* 2515 * We only handle spinlocks if td == curthread. This is somewhat broken 2516 * if td is currently executing on some other CPU and holds spin locks 2517 * as we won't display those locks. If we had a MI way of getting 2518 * the per-cpu data for a given cpu then we could use 2519 * td->td_oncpu to get the list of spinlocks for this thread 2520 * and "fix" this. 2521 * 2522 * That still wouldn't really fix this unless we locked the scheduler 2523 * lock or stopped the other CPU to make sure it wasn't changing the 2524 * list out from under us. It is probably best to just not try to 2525 * handle threads on other CPU's for now. 2526 */ 2527 if (td == curthread && PCPU_GET(spinlocks) != NULL) 2528 witness_list_locks(PCPU_PTR(spinlocks), db_printf); 2529 } 2530 2531 DB_SHOW_COMMAND(locks, db_witness_list) 2532 { 2533 struct thread *td; 2534 2535 if (have_addr) 2536 td = db_lookup_thread(addr, true); 2537 else 2538 td = kdb_thread; 2539 witness_ddb_list(td); 2540 } 2541 2542 DB_SHOW_ALL_COMMAND(locks, db_witness_list_all) 2543 { 2544 struct thread *td; 2545 struct proc *p; 2546 2547 /* 2548 * It would be nice to list only threads and processes that actually 2549 * held sleep locks, but that information is currently not exported 2550 * by WITNESS. 2551 */ 2552 FOREACH_PROC_IN_SYSTEM(p) { 2553 if (!witness_proc_has_locks(p)) 2554 continue; 2555 FOREACH_THREAD_IN_PROC(p, td) { 2556 if (!witness_thread_has_locks(td)) 2557 continue; 2558 db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid, 2559 p->p_comm, td, td->td_tid); 2560 witness_ddb_list(td); 2561 if (db_pager_quit) 2562 return; 2563 } 2564 } 2565 } 2566 DB_SHOW_ALIAS(alllocks, db_witness_list_all) 2567 2568 DB_SHOW_COMMAND(witness, db_witness_display) 2569 { 2570 2571 witness_ddb_display(db_printf); 2572 } 2573 #endif 2574 2575 static void 2576 sbuf_print_witness_badstacks(struct sbuf *sb, size_t *oldidx) 2577 { 2578 struct witness_lock_order_data *data1, *data2, *tmp_data1, *tmp_data2; 2579 struct witness *tmp_w1, *tmp_w2, *w1, *w2; 2580 int generation, i, j; 2581 2582 tmp_data1 = NULL; 2583 tmp_data2 = NULL; 2584 tmp_w1 = NULL; 2585 tmp_w2 = NULL; 2586 2587 /* Allocate and init temporary storage space. */ 2588 tmp_w1 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO); 2589 tmp_w2 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO); 2590 tmp_data1 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 2591 M_WAITOK | M_ZERO); 2592 tmp_data2 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 2593 M_WAITOK | M_ZERO); 2594 stack_zero(&tmp_data1->wlod_stack); 2595 stack_zero(&tmp_data2->wlod_stack); 2596 2597 restart: 2598 mtx_lock_spin(&w_mtx); 2599 generation = w_generation; 2600 mtx_unlock_spin(&w_mtx); 2601 sbuf_printf(sb, "Number of known direct relationships is %d\n", 2602 w_lohash.wloh_count); 2603 for (i = 1; i < w_max_used_index; i++) { 2604 mtx_lock_spin(&w_mtx); 2605 if (generation != w_generation) { 2606 mtx_unlock_spin(&w_mtx); 2607 2608 /* The graph has changed, try again. */ 2609 *oldidx = 0; 2610 sbuf_clear(sb); 2611 goto restart; 2612 } 2613 2614 w1 = &w_data[i]; 2615 if (w1->w_reversed == 0) { 2616 mtx_unlock_spin(&w_mtx); 2617 continue; 2618 } 2619 2620 /* Copy w1 locally so we can release the spin lock. */ 2621 *tmp_w1 = *w1; 2622 mtx_unlock_spin(&w_mtx); 2623 2624 if (tmp_w1->w_reversed == 0) 2625 continue; 2626 for (j = 1; j < w_max_used_index; j++) { 2627 if ((w_rmatrix[i][j] & WITNESS_REVERSAL) == 0 || i > j) 2628 continue; 2629 2630 mtx_lock_spin(&w_mtx); 2631 if (generation != w_generation) { 2632 mtx_unlock_spin(&w_mtx); 2633 2634 /* The graph has changed, try again. */ 2635 *oldidx = 0; 2636 sbuf_clear(sb); 2637 goto restart; 2638 } 2639 2640 w2 = &w_data[j]; 2641 data1 = witness_lock_order_get(w1, w2); 2642 data2 = witness_lock_order_get(w2, w1); 2643 2644 /* 2645 * Copy information locally so we can release the 2646 * spin lock. 2647 */ 2648 *tmp_w2 = *w2; 2649 2650 if (data1) { 2651 stack_zero(&tmp_data1->wlod_stack); 2652 stack_copy(&data1->wlod_stack, 2653 &tmp_data1->wlod_stack); 2654 } 2655 if (data2 && data2 != data1) { 2656 stack_zero(&tmp_data2->wlod_stack); 2657 stack_copy(&data2->wlod_stack, 2658 &tmp_data2->wlod_stack); 2659 } 2660 mtx_unlock_spin(&w_mtx); 2661 2662 if (blessed(tmp_w1, tmp_w2)) 2663 continue; 2664 2665 sbuf_printf(sb, 2666 "\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n", 2667 tmp_w1->w_name, tmp_w1->w_class->lc_name, 2668 tmp_w2->w_name, tmp_w2->w_class->lc_name); 2669 if (data1) { 2670 sbuf_printf(sb, 2671 "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n", 2672 tmp_w1->w_name, tmp_w1->w_class->lc_name, 2673 tmp_w2->w_name, tmp_w2->w_class->lc_name); 2674 stack_sbuf_print(sb, &tmp_data1->wlod_stack); 2675 sbuf_printf(sb, "\n"); 2676 } 2677 if (data2 && data2 != data1) { 2678 sbuf_printf(sb, 2679 "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n", 2680 tmp_w2->w_name, tmp_w2->w_class->lc_name, 2681 tmp_w1->w_name, tmp_w1->w_class->lc_name); 2682 stack_sbuf_print(sb, &tmp_data2->wlod_stack); 2683 sbuf_printf(sb, "\n"); 2684 } 2685 } 2686 } 2687 mtx_lock_spin(&w_mtx); 2688 if (generation != w_generation) { 2689 mtx_unlock_spin(&w_mtx); 2690 2691 /* 2692 * The graph changed while we were printing stack data, 2693 * try again. 2694 */ 2695 *oldidx = 0; 2696 sbuf_clear(sb); 2697 goto restart; 2698 } 2699 mtx_unlock_spin(&w_mtx); 2700 2701 /* Free temporary storage space. */ 2702 free(tmp_data1, M_TEMP); 2703 free(tmp_data2, M_TEMP); 2704 free(tmp_w1, M_TEMP); 2705 free(tmp_w2, M_TEMP); 2706 } 2707 2708 static int 2709 sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS) 2710 { 2711 struct sbuf *sb; 2712 int error; 2713 2714 if (witness_watch < 1) { 2715 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning)); 2716 return (error); 2717 } 2718 if (witness_cold) { 2719 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold)); 2720 return (error); 2721 } 2722 error = 0; 2723 sb = sbuf_new(NULL, NULL, badstack_sbuf_size, SBUF_AUTOEXTEND); 2724 if (sb == NULL) 2725 return (ENOMEM); 2726 2727 sbuf_print_witness_badstacks(sb, &req->oldidx); 2728 2729 sbuf_finish(sb); 2730 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1); 2731 sbuf_delete(sb); 2732 2733 return (error); 2734 } 2735 2736 #ifdef DDB 2737 static int 2738 sbuf_db_printf_drain(void *arg __unused, const char *data, int len) 2739 { 2740 2741 return (db_printf("%.*s", len, data)); 2742 } 2743 2744 DB_SHOW_COMMAND(badstacks, db_witness_badstacks) 2745 { 2746 struct sbuf sb; 2747 char buffer[128]; 2748 size_t dummy; 2749 2750 sbuf_new(&sb, buffer, sizeof(buffer), SBUF_FIXEDLEN); 2751 sbuf_set_drain(&sb, sbuf_db_printf_drain, NULL); 2752 sbuf_print_witness_badstacks(&sb, &dummy); 2753 sbuf_finish(&sb); 2754 } 2755 #endif 2756 2757 static int 2758 sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS) 2759 { 2760 static const struct { 2761 enum witness_channel channel; 2762 const char *name; 2763 } channels[] = { 2764 { WITNESS_CONSOLE, "console" }, 2765 { WITNESS_LOG, "log" }, 2766 { WITNESS_NONE, "none" }, 2767 }; 2768 char buf[16]; 2769 u_int i; 2770 int error; 2771 2772 buf[0] = '\0'; 2773 for (i = 0; i < nitems(channels); i++) 2774 if (witness_channel == channels[i].channel) { 2775 snprintf(buf, sizeof(buf), "%s", channels[i].name); 2776 break; 2777 } 2778 2779 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 2780 if (error != 0 || req->newptr == NULL) 2781 return (error); 2782 2783 error = EINVAL; 2784 for (i = 0; i < nitems(channels); i++) 2785 if (strcmp(channels[i].name, buf) == 0) { 2786 witness_channel = channels[i].channel; 2787 error = 0; 2788 break; 2789 } 2790 return (error); 2791 } 2792 2793 static int 2794 sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS) 2795 { 2796 struct witness *w; 2797 struct sbuf *sb; 2798 int error; 2799 2800 #ifdef __i386__ 2801 error = SYSCTL_OUT(req, w_notallowed, sizeof(w_notallowed)); 2802 return (error); 2803 #endif 2804 2805 if (witness_watch < 1) { 2806 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning)); 2807 return (error); 2808 } 2809 if (witness_cold) { 2810 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold)); 2811 return (error); 2812 } 2813 error = 0; 2814 2815 error = sysctl_wire_old_buffer(req, 0); 2816 if (error != 0) 2817 return (error); 2818 sb = sbuf_new_for_sysctl(NULL, NULL, FULLGRAPH_SBUF_SIZE, req); 2819 if (sb == NULL) 2820 return (ENOMEM); 2821 sbuf_printf(sb, "\n"); 2822 2823 mtx_lock_spin(&w_mtx); 2824 STAILQ_FOREACH(w, &w_all, w_list) 2825 w->w_displayed = 0; 2826 STAILQ_FOREACH(w, &w_all, w_list) 2827 witness_add_fullgraph(sb, w); 2828 mtx_unlock_spin(&w_mtx); 2829 2830 /* 2831 * Close the sbuf and return to userland. 2832 */ 2833 error = sbuf_finish(sb); 2834 sbuf_delete(sb); 2835 2836 return (error); 2837 } 2838 2839 static int 2840 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS) 2841 { 2842 int error, value; 2843 2844 value = witness_watch; 2845 error = sysctl_handle_int(oidp, &value, 0, req); 2846 if (error != 0 || req->newptr == NULL) 2847 return (error); 2848 if (value > 1 || value < -1 || 2849 (witness_watch == -1 && value != witness_watch)) 2850 return (EINVAL); 2851 witness_watch = value; 2852 return (0); 2853 } 2854 2855 static void 2856 witness_add_fullgraph(struct sbuf *sb, struct witness *w) 2857 { 2858 int i; 2859 2860 if (w->w_displayed != 0 || (w->w_file == NULL && w->w_line == 0)) 2861 return; 2862 w->w_displayed = 1; 2863 2864 WITNESS_INDEX_ASSERT(w->w_index); 2865 for (i = 1; i <= w_max_used_index; i++) { 2866 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) { 2867 sbuf_printf(sb, "\"%s\",\"%s\"\n", w->w_name, 2868 w_data[i].w_name); 2869 witness_add_fullgraph(sb, &w_data[i]); 2870 } 2871 } 2872 } 2873 2874 /* 2875 * A simple hash function. Takes a key pointer and a key size. If size == 0, 2876 * interprets the key as a string and reads until the null 2877 * terminator. Otherwise, reads the first size bytes. Returns an unsigned 32-bit 2878 * hash value computed from the key. 2879 */ 2880 static uint32_t 2881 witness_hash_djb2(const uint8_t *key, uint32_t size) 2882 { 2883 unsigned int hash = 5381; 2884 int i; 2885 2886 /* hash = hash * 33 + key[i] */ 2887 if (size) 2888 for (i = 0; i < size; i++) 2889 hash = ((hash << 5) + hash) + (unsigned int)key[i]; 2890 else 2891 for (i = 0; key[i] != 0; i++) 2892 hash = ((hash << 5) + hash) + (unsigned int)key[i]; 2893 2894 return (hash); 2895 } 2896 2897 /* 2898 * Initializes the two witness hash tables. Called exactly once from 2899 * witness_initialize(). 2900 */ 2901 static void 2902 witness_init_hash_tables(void) 2903 { 2904 int i; 2905 2906 MPASS(witness_cold); 2907 2908 /* Initialize the hash tables. */ 2909 for (i = 0; i < WITNESS_HASH_SIZE; i++) 2910 w_hash.wh_array[i] = NULL; 2911 2912 w_hash.wh_size = WITNESS_HASH_SIZE; 2913 w_hash.wh_count = 0; 2914 2915 /* Initialize the lock order data hash. */ 2916 w_lofree = NULL; 2917 for (i = 0; i < WITNESS_LO_DATA_COUNT; i++) { 2918 memset(&w_lodata[i], 0, sizeof(w_lodata[i])); 2919 w_lodata[i].wlod_next = w_lofree; 2920 w_lofree = &w_lodata[i]; 2921 } 2922 w_lohash.wloh_size = WITNESS_LO_HASH_SIZE; 2923 w_lohash.wloh_count = 0; 2924 for (i = 0; i < WITNESS_LO_HASH_SIZE; i++) 2925 w_lohash.wloh_array[i] = NULL; 2926 } 2927 2928 static struct witness * 2929 witness_hash_get(const char *key) 2930 { 2931 struct witness *w; 2932 uint32_t hash; 2933 2934 MPASS(key != NULL); 2935 if (witness_cold == 0) 2936 mtx_assert(&w_mtx, MA_OWNED); 2937 hash = witness_hash_djb2(key, 0) % w_hash.wh_size; 2938 w = w_hash.wh_array[hash]; 2939 while (w != NULL) { 2940 if (strcmp(w->w_name, key) == 0) 2941 goto out; 2942 w = w->w_hash_next; 2943 } 2944 2945 out: 2946 return (w); 2947 } 2948 2949 static void 2950 witness_hash_put(struct witness *w) 2951 { 2952 uint32_t hash; 2953 2954 MPASS(w != NULL); 2955 MPASS(w->w_name != NULL); 2956 if (witness_cold == 0) 2957 mtx_assert(&w_mtx, MA_OWNED); 2958 KASSERT(witness_hash_get(w->w_name) == NULL, 2959 ("%s: trying to add a hash entry that already exists!", __func__)); 2960 KASSERT(w->w_hash_next == NULL, 2961 ("%s: w->w_hash_next != NULL", __func__)); 2962 2963 hash = witness_hash_djb2(w->w_name, 0) % w_hash.wh_size; 2964 w->w_hash_next = w_hash.wh_array[hash]; 2965 w_hash.wh_array[hash] = w; 2966 w_hash.wh_count++; 2967 } 2968 2969 static struct witness_lock_order_data * 2970 witness_lock_order_get(struct witness *parent, struct witness *child) 2971 { 2972 struct witness_lock_order_data *data = NULL; 2973 struct witness_lock_order_key key; 2974 unsigned int hash; 2975 2976 MPASS(parent != NULL && child != NULL); 2977 key.from = parent->w_index; 2978 key.to = child->w_index; 2979 WITNESS_INDEX_ASSERT(key.from); 2980 WITNESS_INDEX_ASSERT(key.to); 2981 if ((w_rmatrix[parent->w_index][child->w_index] 2982 & WITNESS_LOCK_ORDER_KNOWN) == 0) 2983 goto out; 2984 2985 hash = witness_hash_djb2((const char*)&key, 2986 sizeof(key)) % w_lohash.wloh_size; 2987 data = w_lohash.wloh_array[hash]; 2988 while (data != NULL) { 2989 if (witness_lock_order_key_equal(&data->wlod_key, &key)) 2990 break; 2991 data = data->wlod_next; 2992 } 2993 2994 out: 2995 return (data); 2996 } 2997 2998 /* 2999 * Verify that parent and child have a known relationship, are not the same, 3000 * and child is actually a child of parent. This is done without w_mtx 3001 * to avoid contention in the common case. 3002 */ 3003 static int 3004 witness_lock_order_check(struct witness *parent, struct witness *child) 3005 { 3006 3007 if (parent != child && 3008 w_rmatrix[parent->w_index][child->w_index] 3009 & WITNESS_LOCK_ORDER_KNOWN && 3010 isitmychild(parent, child)) 3011 return (1); 3012 3013 return (0); 3014 } 3015 3016 static int 3017 witness_lock_order_add(struct witness *parent, struct witness *child) 3018 { 3019 struct witness_lock_order_data *data = NULL; 3020 struct witness_lock_order_key key; 3021 unsigned int hash; 3022 3023 MPASS(parent != NULL && child != NULL); 3024 key.from = parent->w_index; 3025 key.to = child->w_index; 3026 WITNESS_INDEX_ASSERT(key.from); 3027 WITNESS_INDEX_ASSERT(key.to); 3028 if (w_rmatrix[parent->w_index][child->w_index] 3029 & WITNESS_LOCK_ORDER_KNOWN) 3030 return (1); 3031 3032 hash = witness_hash_djb2((const char*)&key, 3033 sizeof(key)) % w_lohash.wloh_size; 3034 w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN; 3035 data = w_lofree; 3036 if (data == NULL) 3037 return (0); 3038 w_lofree = data->wlod_next; 3039 data->wlod_next = w_lohash.wloh_array[hash]; 3040 data->wlod_key = key; 3041 w_lohash.wloh_array[hash] = data; 3042 w_lohash.wloh_count++; 3043 stack_zero(&data->wlod_stack); 3044 stack_save(&data->wlod_stack); 3045 return (1); 3046 } 3047 3048 /* Call this whenever the structure of the witness graph changes. */ 3049 static void 3050 witness_increment_graph_generation(void) 3051 { 3052 3053 if (witness_cold == 0) 3054 mtx_assert(&w_mtx, MA_OWNED); 3055 w_generation++; 3056 } 3057 3058 static int 3059 witness_output_drain(void *arg __unused, const char *data, int len) 3060 { 3061 3062 witness_output("%.*s", len, data); 3063 return (len); 3064 } 3065 3066 static void 3067 witness_debugger(int cond, const char *msg) 3068 { 3069 char buf[32]; 3070 struct sbuf sb; 3071 struct stack st; 3072 3073 if (!cond) 3074 return; 3075 3076 if (witness_trace) { 3077 sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN); 3078 sbuf_set_drain(&sb, witness_output_drain, NULL); 3079 3080 stack_zero(&st); 3081 stack_save(&st); 3082 witness_output("stack backtrace:\n"); 3083 stack_sbuf_print_ddb(&sb, &st); 3084 3085 sbuf_finish(&sb); 3086 } 3087 3088 #ifdef KDB 3089 if (witness_kdb) 3090 kdb_enter(KDB_WHY_WITNESS, msg); 3091 #endif 3092 } 3093