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_enter_debugger(const char *msg); 342 static void witness_debugger(int cond, const char *msg); 343 static void witness_free(struct witness *m); 344 static struct witness *witness_get(void); 345 static uint32_t witness_hash_djb2(const uint8_t *key, uint32_t size); 346 static struct witness *witness_hash_get(const char *key); 347 static void witness_hash_put(struct witness *w); 348 static void witness_init_hash_tables(void); 349 static void witness_increment_graph_generation(void); 350 static void witness_lock_list_free(struct lock_list_entry *lle); 351 static struct lock_list_entry *witness_lock_list_get(void); 352 static int witness_lock_order_add(struct witness *parent, 353 struct witness *child); 354 static int witness_lock_order_check(struct witness *parent, 355 struct witness *child); 356 static struct witness_lock_order_data *witness_lock_order_get( 357 struct witness *parent, 358 struct witness *child); 359 static void witness_list_lock(struct lock_instance *instance, 360 int (*prnt)(const char *fmt, ...)); 361 static int witness_output(const char *fmt, ...) __printflike(1, 2); 362 static int witness_output_drain(void *arg __unused, const char *data, 363 int len); 364 static int witness_voutput(const char *fmt, va_list ap) __printflike(1, 0); 365 static void witness_setflag(struct lock_object *lock, int flag, int set); 366 367 FEATURE(witness, "kernel has witness(9) support"); 368 369 static SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 370 "Witness Locking"); 371 372 /* 373 * If set to 0, lock order checking is disabled. If set to -1, 374 * witness is completely disabled. Otherwise witness performs full 375 * lock order checking for all locks. At runtime, lock order checking 376 * may be toggled. However, witness cannot be reenabled once it is 377 * completely disabled. 378 */ 379 static int witness_watch = 1; 380 SYSCTL_PROC(_debug_witness, OID_AUTO, watch, 381 CTLFLAG_RWTUN | CTLTYPE_INT | CTLFLAG_MPSAFE, NULL, 0, 382 sysctl_debug_witness_watch, "I", 383 "witness is watching lock operations"); 384 385 #ifdef KDB 386 /* 387 * When KDB is enabled and witness_kdb is 1, it will cause the system 388 * to drop into kdebug() when: 389 * - a lock hierarchy violation occurs 390 * - locks are held when going to sleep. 391 */ 392 #ifdef WITNESS_KDB 393 int witness_kdb = 1; 394 #else 395 int witness_kdb = 0; 396 #endif 397 SYSCTL_INT(_debug_witness, OID_AUTO, kdb, CTLFLAG_RWTUN, &witness_kdb, 0, ""); 398 #endif /* KDB */ 399 400 #if defined(DDB) || defined(KDB) 401 /* 402 * When DDB or KDB is enabled and witness_trace is 1, it will cause the system 403 * to print a stack trace: 404 * - a lock hierarchy violation occurs 405 * - locks are held when going to sleep. 406 */ 407 int witness_trace = 1; 408 SYSCTL_INT(_debug_witness, OID_AUTO, trace, CTLFLAG_RWTUN, &witness_trace, 0, ""); 409 #endif /* DDB || KDB */ 410 411 #ifdef WITNESS_SKIPSPIN 412 int witness_skipspin = 1; 413 #else 414 int witness_skipspin = 0; 415 #endif 416 SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN, &witness_skipspin, 0, ""); 417 418 int badstack_sbuf_size; 419 420 int witness_count = WITNESS_COUNT; 421 SYSCTL_INT(_debug_witness, OID_AUTO, witness_count, CTLFLAG_RDTUN, 422 &witness_count, 0, ""); 423 424 /* 425 * Output channel for witness messages. By default we print to the console. 426 */ 427 enum witness_channel { 428 WITNESS_CONSOLE, 429 WITNESS_LOG, 430 WITNESS_NONE, 431 }; 432 433 static enum witness_channel witness_channel = WITNESS_CONSOLE; 434 SYSCTL_PROC(_debug_witness, OID_AUTO, output_channel, 435 CTLTYPE_STRING | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, NULL, 0, 436 sysctl_debug_witness_channel, "A", 437 "Output channel for warnings"); 438 439 /* 440 * Call this to print out the relations between locks. 441 */ 442 SYSCTL_PROC(_debug_witness, OID_AUTO, fullgraph, 443 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0, 444 sysctl_debug_witness_fullgraph, "A", 445 "Show locks relation graphs"); 446 447 /* 448 * Call this to print out the witness faulty stacks. 449 */ 450 SYSCTL_PROC(_debug_witness, OID_AUTO, badstacks, 451 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0, 452 sysctl_debug_witness_badstacks, "A", 453 "Show bad witness stacks"); 454 455 static struct mtx w_mtx; 456 457 /* w_list */ 458 static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free); 459 static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all); 460 461 /* w_typelist */ 462 static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin); 463 static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep); 464 465 /* lock list */ 466 static struct lock_list_entry *w_lock_list_free = NULL; 467 static struct witness_pendhelp pending_locks[WITNESS_PENDLIST]; 468 static u_int pending_cnt; 469 470 static int w_free_cnt, w_spin_cnt, w_sleep_cnt; 471 SYSCTL_INT(_debug_witness, OID_AUTO, free_cnt, CTLFLAG_RD, &w_free_cnt, 0, ""); 472 SYSCTL_INT(_debug_witness, OID_AUTO, spin_cnt, CTLFLAG_RD, &w_spin_cnt, 0, ""); 473 SYSCTL_INT(_debug_witness, OID_AUTO, sleep_cnt, CTLFLAG_RD, &w_sleep_cnt, 0, 474 ""); 475 476 static struct witness *w_data; 477 static uint8_t **w_rmatrix; 478 static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT]; 479 static struct witness_hash w_hash; /* The witness hash table. */ 480 481 /* The lock order data hash */ 482 static struct witness_lock_order_data w_lodata[WITNESS_LO_DATA_COUNT]; 483 static struct witness_lock_order_data *w_lofree = NULL; 484 static struct witness_lock_order_hash w_lohash; 485 static int w_max_used_index = 0; 486 static unsigned int w_generation = 0; 487 static const char w_notrunning[] = "Witness not running\n"; 488 static const char w_stillcold[] = "Witness is still cold\n"; 489 #ifdef __i386__ 490 static const char w_notallowed[] = "The sysctl is disabled on the arch\n"; 491 #endif 492 493 static struct witness_order_list_entry order_lists[] = { 494 /* 495 * sx locks 496 */ 497 { "proctree", &lock_class_sx }, 498 { "allproc", &lock_class_sx }, 499 { "allprison", &lock_class_sx }, 500 { NULL, NULL }, 501 /* 502 * Various mutexes 503 */ 504 { "Giant", &lock_class_mtx_sleep }, 505 { "pipe mutex", &lock_class_mtx_sleep }, 506 { "sigio lock", &lock_class_mtx_sleep }, 507 { "process group", &lock_class_mtx_sleep }, 508 #ifdef HWPMC_HOOKS 509 { "pmc-sleep", &lock_class_mtx_sleep }, 510 #endif 511 { "process lock", &lock_class_mtx_sleep }, 512 { "session", &lock_class_mtx_sleep }, 513 { "uidinfo hash", &lock_class_rw }, 514 { "time lock", &lock_class_mtx_sleep }, 515 { NULL, NULL }, 516 /* 517 * umtx 518 */ 519 { "umtx lock", &lock_class_mtx_sleep }, 520 { NULL, NULL }, 521 /* 522 * Sockets 523 */ 524 { "accept", &lock_class_mtx_sleep }, 525 { "so_snd", &lock_class_mtx_sleep }, 526 { "so_rcv", &lock_class_mtx_sleep }, 527 { "sellck", &lock_class_mtx_sleep }, 528 { NULL, NULL }, 529 /* 530 * Routing 531 */ 532 { "so_rcv", &lock_class_mtx_sleep }, 533 { "radix node head", &lock_class_rm }, 534 { "ifaddr", &lock_class_mtx_sleep }, 535 { NULL, NULL }, 536 /* 537 * IPv4 multicast: 538 * protocol locks before interface locks, after UDP locks. 539 */ 540 { "in_multi_sx", &lock_class_sx }, 541 { "udpinp", &lock_class_rw }, 542 { "in_multi_list_mtx", &lock_class_mtx_sleep }, 543 { "igmp_mtx", &lock_class_mtx_sleep }, 544 { "if_addr_lock", &lock_class_mtx_sleep }, 545 { NULL, NULL }, 546 /* 547 * IPv6 multicast: 548 * protocol locks before interface locks, after UDP locks. 549 */ 550 { "in6_multi_sx", &lock_class_sx }, 551 { "udpinp", &lock_class_rw }, 552 { "in6_multi_list_mtx", &lock_class_mtx_sleep }, 553 { "mld_mtx", &lock_class_mtx_sleep }, 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 { "udpinp", &lock_class_rw }, 568 { "udp", &lock_class_mtx_sleep }, 569 { "so_snd", &lock_class_mtx_sleep }, 570 { NULL, NULL }, 571 /* 572 * TCP/IP 573 */ 574 { "tcpinp", &lock_class_rw }, 575 { "tcp", &lock_class_mtx_sleep }, 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_mtx_sleep }, 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 #ifdef __i386__ 666 { "cy", &lock_class_mtx_spin }, 667 #endif 668 { "scc_hwmtx", &lock_class_mtx_spin }, 669 { "uart_hwmtx", &lock_class_mtx_spin }, 670 { "fast_taskqueue", &lock_class_mtx_spin }, 671 { "intr table", &lock_class_mtx_spin }, 672 { "process slock", &lock_class_mtx_spin }, 673 { "syscons video lock", &lock_class_mtx_spin }, 674 { "sleepq chain", &lock_class_mtx_spin }, 675 { "rm_spinlock", &lock_class_mtx_spin }, 676 { "turnstile chain", &lock_class_mtx_spin }, 677 { "turnstile lock", &lock_class_mtx_spin }, 678 { "sched lock", &lock_class_mtx_spin }, 679 { "td_contested", &lock_class_mtx_spin }, 680 { "callout", &lock_class_mtx_spin }, 681 { "entropy harvest mutex", &lock_class_mtx_spin }, 682 #ifdef SMP 683 { "smp rendezvous", &lock_class_mtx_spin }, 684 #endif 685 #ifdef __powerpc__ 686 { "tlb0", &lock_class_mtx_spin }, 687 #endif 688 { NULL, NULL }, 689 { "sched lock", &lock_class_mtx_spin }, 690 #ifdef HWPMC_HOOKS 691 { "pmc-per-proc", &lock_class_mtx_spin }, 692 #endif 693 { NULL, NULL }, 694 /* 695 * leaf locks 696 */ 697 { "intrcnt", &lock_class_mtx_spin }, 698 { "icu", &lock_class_mtx_spin }, 699 #ifdef __i386__ 700 { "allpmaps", &lock_class_mtx_spin }, 701 { "descriptor tables", &lock_class_mtx_spin }, 702 #endif 703 { "clk", &lock_class_mtx_spin }, 704 { "cpuset", &lock_class_mtx_spin }, 705 { "mprof lock", &lock_class_mtx_spin }, 706 { "zombie lock", &lock_class_mtx_spin }, 707 { "ALD Queue", &lock_class_mtx_spin }, 708 #if defined(__i386__) || defined(__amd64__) 709 { "pcicfg", &lock_class_mtx_spin }, 710 { "NDIS thread lock", &lock_class_mtx_spin }, 711 #endif 712 { "tw_osl_io_lock", &lock_class_mtx_spin }, 713 { "tw_osl_q_lock", &lock_class_mtx_spin }, 714 { "tw_cl_io_lock", &lock_class_mtx_spin }, 715 { "tw_cl_intr_lock", &lock_class_mtx_spin }, 716 { "tw_cl_gen_lock", &lock_class_mtx_spin }, 717 #ifdef HWPMC_HOOKS 718 { "pmc-leaf", &lock_class_mtx_spin }, 719 #endif 720 { "blocked lock", &lock_class_mtx_spin }, 721 { NULL, NULL }, 722 { NULL, NULL } 723 }; 724 725 /* 726 * Pairs of locks which have been blessed. Witness does not complain about 727 * order problems with blessed lock pairs. Please do not add an entry to the 728 * table without an explanatory comment. 729 */ 730 static struct witness_blessed blessed_list[] = { 731 /* 732 * See the comment in ufs_dirhash.c. Basically, a vnode lock serializes 733 * both lock orders, so a deadlock cannot happen as a result of this 734 * LOR. 735 */ 736 { "dirhash", "bufwait" }, 737 738 /* 739 * A UFS vnode may be locked in vget() while a buffer belonging to the 740 * parent directory vnode is locked. 741 */ 742 { "ufs", "bufwait" }, 743 744 /* 745 * The tarfs decompression stream vnode may be locked while a 746 * buffer belonging to a tarfs data vnode is locked. 747 */ 748 { "tarfs", "bufwait" }, 749 }; 750 751 /* 752 * This global is set to 0 once it becomes safe to use the witness code. 753 */ 754 static int witness_cold = 1; 755 756 /* 757 * This global is set to 1 once the static lock orders have been enrolled 758 * so that a warning can be issued for any spin locks enrolled later. 759 */ 760 static int witness_spin_warn = 0; 761 762 /* Trim useless garbage from filenames. */ 763 static const char * 764 fixup_filename(const char *file) 765 { 766 767 if (file == NULL) 768 return (NULL); 769 while (strncmp(file, "../", 3) == 0) 770 file += 3; 771 return (file); 772 } 773 774 /* 775 * Calculate the size of early witness structures. 776 */ 777 int 778 witness_startup_count(void) 779 { 780 int sz; 781 782 sz = sizeof(struct witness) * witness_count; 783 sz += sizeof(*w_rmatrix) * (witness_count + 1); 784 sz += sizeof(*w_rmatrix[0]) * (witness_count + 1) * 785 (witness_count + 1); 786 787 return (sz); 788 } 789 790 /* 791 * The WITNESS-enabled diagnostic code. Note that the witness code does 792 * assume that the early boot is single-threaded at least until after this 793 * routine is completed. 794 */ 795 void 796 witness_startup(void *mem) 797 { 798 struct lock_object *lock; 799 struct witness_order_list_entry *order; 800 struct witness *w, *w1; 801 uintptr_t p; 802 int i; 803 804 p = (uintptr_t)mem; 805 w_data = (void *)p; 806 p += sizeof(struct witness) * witness_count; 807 808 w_rmatrix = (void *)p; 809 p += sizeof(*w_rmatrix) * (witness_count + 1); 810 811 for (i = 0; i < witness_count + 1; i++) { 812 w_rmatrix[i] = (void *)p; 813 p += sizeof(*w_rmatrix[i]) * (witness_count + 1); 814 } 815 badstack_sbuf_size = witness_count * 256; 816 817 /* 818 * We have to release Giant before initializing its witness 819 * structure so that WITNESS doesn't get confused. 820 */ 821 mtx_unlock(&Giant); 822 mtx_assert(&Giant, MA_NOTOWNED); 823 824 CTR1(KTR_WITNESS, "%s: initializing witness", __func__); 825 mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET | 826 MTX_NOWITNESS | MTX_NOPROFILE); 827 for (i = witness_count - 1; i >= 0; i--) { 828 w = &w_data[i]; 829 memset(w, 0, sizeof(*w)); 830 w_data[i].w_index = i; /* Witness index never changes. */ 831 witness_free(w); 832 } 833 KASSERT(STAILQ_FIRST(&w_free)->w_index == 0, 834 ("%s: Invalid list of free witness objects", __func__)); 835 836 /* Witness with index 0 is not used to aid in debugging. */ 837 STAILQ_REMOVE_HEAD(&w_free, w_list); 838 w_free_cnt--; 839 840 for (i = 0; i < witness_count; i++) { 841 memset(w_rmatrix[i], 0, sizeof(*w_rmatrix[i]) * 842 (witness_count + 1)); 843 } 844 845 for (i = 0; i < LOCK_CHILDCOUNT; i++) 846 witness_lock_list_free(&w_locklistdata[i]); 847 witness_init_hash_tables(); 848 849 /* First add in all the specified order lists. */ 850 for (order = order_lists; order->w_name != NULL; order++) { 851 w = enroll(order->w_name, order->w_class); 852 if (w == NULL) 853 continue; 854 w->w_file = "order list"; 855 for (order++; order->w_name != NULL; order++) { 856 w1 = enroll(order->w_name, order->w_class); 857 if (w1 == NULL) 858 continue; 859 w1->w_file = "order list"; 860 itismychild(w, w1); 861 w = w1; 862 } 863 } 864 witness_spin_warn = 1; 865 866 /* Iterate through all locks and add them to witness. */ 867 for (i = 0; pending_locks[i].wh_lock != NULL; i++) { 868 lock = pending_locks[i].wh_lock; 869 KASSERT(lock->lo_flags & LO_WITNESS, 870 ("%s: lock %s is on pending list but not LO_WITNESS", 871 __func__, lock->lo_name)); 872 lock->lo_witness = enroll(pending_locks[i].wh_type, 873 LOCK_CLASS(lock)); 874 } 875 876 /* Mark the witness code as being ready for use. */ 877 witness_cold = 0; 878 879 mtx_lock(&Giant); 880 } 881 882 void 883 witness_init(struct lock_object *lock, const char *type) 884 { 885 struct lock_class *class; 886 887 /* Various sanity checks. */ 888 class = LOCK_CLASS(lock); 889 if ((lock->lo_flags & LO_RECURSABLE) != 0 && 890 (class->lc_flags & LC_RECURSABLE) == 0) 891 kassert_panic("%s: lock (%s) %s can not be recursable", 892 __func__, class->lc_name, lock->lo_name); 893 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 894 (class->lc_flags & LC_SLEEPABLE) == 0) 895 kassert_panic("%s: lock (%s) %s can not be sleepable", 896 __func__, class->lc_name, lock->lo_name); 897 if ((lock->lo_flags & LO_UPGRADABLE) != 0 && 898 (class->lc_flags & LC_UPGRADABLE) == 0) 899 kassert_panic("%s: lock (%s) %s can not be upgradable", 900 __func__, class->lc_name, lock->lo_name); 901 902 /* 903 * If we shouldn't watch this lock, then just clear lo_witness. 904 * Otherwise, if witness_cold is set, then it is too early to 905 * enroll this lock, so defer it to witness_initialize() by adding 906 * it to the pending_locks list. If it is not too early, then enroll 907 * the lock now. 908 */ 909 if (witness_watch < 1 || KERNEL_PANICKED() || 910 (lock->lo_flags & LO_WITNESS) == 0) 911 lock->lo_witness = NULL; 912 else if (witness_cold) { 913 pending_locks[pending_cnt].wh_lock = lock; 914 pending_locks[pending_cnt++].wh_type = type; 915 if (pending_cnt > WITNESS_PENDLIST) 916 panic("%s: pending locks list is too small, " 917 "increase WITNESS_PENDLIST\n", 918 __func__); 919 } else 920 lock->lo_witness = enroll(type, class); 921 } 922 923 void 924 witness_destroy(struct lock_object *lock) 925 { 926 struct lock_class *class; 927 struct witness *w; 928 929 class = LOCK_CLASS(lock); 930 931 if (witness_cold) 932 panic("lock (%s) %s destroyed while witness_cold", 933 class->lc_name, lock->lo_name); 934 935 /* XXX: need to verify that no one holds the lock */ 936 if ((lock->lo_flags & LO_WITNESS) == 0 || lock->lo_witness == NULL) 937 return; 938 w = lock->lo_witness; 939 940 mtx_lock_spin(&w_mtx); 941 MPASS(w->w_refcount > 0); 942 w->w_refcount--; 943 944 if (w->w_refcount == 0) 945 depart(w); 946 mtx_unlock_spin(&w_mtx); 947 } 948 949 #ifdef DDB 950 static void 951 witness_ddb_compute_levels(void) 952 { 953 struct witness *w; 954 955 /* 956 * First clear all levels. 957 */ 958 STAILQ_FOREACH(w, &w_all, w_list) 959 w->w_ddb_level = -1; 960 961 /* 962 * Look for locks with no parents and level all their descendants. 963 */ 964 STAILQ_FOREACH(w, &w_all, w_list) { 965 /* If the witness has ancestors (is not a root), skip it. */ 966 if (w->w_num_ancestors > 0) 967 continue; 968 witness_ddb_level_descendants(w, 0); 969 } 970 } 971 972 static void 973 witness_ddb_level_descendants(struct witness *w, int l) 974 { 975 int i; 976 977 if (w->w_ddb_level >= l) 978 return; 979 980 w->w_ddb_level = l; 981 l++; 982 983 for (i = 1; i <= w_max_used_index; i++) { 984 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) 985 witness_ddb_level_descendants(&w_data[i], l); 986 } 987 } 988 989 static void 990 witness_ddb_display_descendants(int(*prnt)(const char *fmt, ...), 991 struct witness *w, int indent) 992 { 993 int i; 994 995 for (i = 0; i < indent; i++) 996 prnt(" "); 997 prnt("%s (type: %s, depth: %d, active refs: %d)", 998 w->w_name, w->w_class->lc_name, 999 w->w_ddb_level, w->w_refcount); 1000 if (w->w_displayed) { 1001 prnt(" -- (already displayed)\n"); 1002 return; 1003 } 1004 w->w_displayed = 1; 1005 if (w->w_file != NULL && w->w_line != 0) 1006 prnt(" -- last acquired @ %s:%d\n", fixup_filename(w->w_file), 1007 w->w_line); 1008 else 1009 prnt(" -- never acquired\n"); 1010 indent++; 1011 WITNESS_INDEX_ASSERT(w->w_index); 1012 for (i = 1; i <= w_max_used_index; i++) { 1013 if (db_pager_quit) 1014 return; 1015 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) 1016 witness_ddb_display_descendants(prnt, &w_data[i], 1017 indent); 1018 } 1019 } 1020 1021 static void 1022 witness_ddb_display_list(int(*prnt)(const char *fmt, ...), 1023 struct witness_list *list) 1024 { 1025 struct witness *w; 1026 1027 STAILQ_FOREACH(w, list, w_typelist) { 1028 if (w->w_file == NULL || w->w_ddb_level > 0) 1029 continue; 1030 1031 /* This lock has no anscestors - display its descendants. */ 1032 witness_ddb_display_descendants(prnt, w, 0); 1033 if (db_pager_quit) 1034 return; 1035 } 1036 } 1037 1038 static void 1039 witness_ddb_display(int(*prnt)(const char *fmt, ...)) 1040 { 1041 struct witness *w; 1042 1043 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 1044 witness_ddb_compute_levels(); 1045 1046 /* Clear all the displayed flags. */ 1047 STAILQ_FOREACH(w, &w_all, w_list) 1048 w->w_displayed = 0; 1049 1050 /* 1051 * First, handle sleep locks which have been acquired at least 1052 * once. 1053 */ 1054 prnt("Sleep locks:\n"); 1055 witness_ddb_display_list(prnt, &w_sleep); 1056 if (db_pager_quit) 1057 return; 1058 1059 /* 1060 * Now do spin locks which have been acquired at least once. 1061 */ 1062 prnt("\nSpin locks:\n"); 1063 witness_ddb_display_list(prnt, &w_spin); 1064 if (db_pager_quit) 1065 return; 1066 1067 /* 1068 * Finally, any locks which have not been acquired yet. 1069 */ 1070 prnt("\nLocks which were never acquired:\n"); 1071 STAILQ_FOREACH(w, &w_all, w_list) { 1072 if (w->w_file != NULL || w->w_refcount == 0) 1073 continue; 1074 prnt("%s (type: %s, depth: %d)\n", w->w_name, 1075 w->w_class->lc_name, w->w_ddb_level); 1076 if (db_pager_quit) 1077 return; 1078 } 1079 } 1080 #endif /* DDB */ 1081 1082 int 1083 witness_defineorder(struct lock_object *lock1, struct lock_object *lock2) 1084 { 1085 1086 if (witness_watch == -1 || KERNEL_PANICKED()) 1087 return (0); 1088 1089 /* Require locks that witness knows about. */ 1090 if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL || 1091 lock2->lo_witness == NULL) 1092 return (EINVAL); 1093 1094 mtx_assert(&w_mtx, MA_NOTOWNED); 1095 mtx_lock_spin(&w_mtx); 1096 1097 /* 1098 * If we already have either an explicit or implied lock order that 1099 * is the other way around, then return an error. 1100 */ 1101 if (witness_watch && 1102 isitmydescendant(lock2->lo_witness, lock1->lo_witness)) { 1103 mtx_unlock_spin(&w_mtx); 1104 return (EDOOFUS); 1105 } 1106 1107 /* Try to add the new order. */ 1108 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__, 1109 lock2->lo_witness->w_name, lock1->lo_witness->w_name); 1110 itismychild(lock1->lo_witness, lock2->lo_witness); 1111 mtx_unlock_spin(&w_mtx); 1112 return (0); 1113 } 1114 1115 void 1116 witness_checkorder(struct lock_object *lock, int flags, const char *file, 1117 int line, struct lock_object *interlock) 1118 { 1119 struct lock_list_entry *lock_list, *lle; 1120 struct lock_instance *lock1, *lock2, *plock; 1121 struct lock_class *class, *iclass; 1122 struct witness *w, *w1; 1123 struct thread *td; 1124 int i, j; 1125 1126 if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL || 1127 KERNEL_PANICKED()) 1128 return; 1129 1130 w = lock->lo_witness; 1131 class = LOCK_CLASS(lock); 1132 td = curthread; 1133 1134 if (class->lc_flags & LC_SLEEPLOCK) { 1135 /* 1136 * Since spin locks include a critical section, this check 1137 * implicitly enforces a lock order of all sleep locks before 1138 * all spin locks. 1139 */ 1140 if (td->td_critnest != 0 && !kdb_active) 1141 kassert_panic("acquiring blockable sleep lock with " 1142 "spinlock or critical section held (%s) %s @ %s:%d", 1143 class->lc_name, lock->lo_name, 1144 fixup_filename(file), line); 1145 1146 /* 1147 * If this is the first lock acquired then just return as 1148 * no order checking is needed. 1149 */ 1150 lock_list = td->td_sleeplocks; 1151 if (lock_list == NULL || lock_list->ll_count == 0) 1152 return; 1153 } else { 1154 /* 1155 * If this is the first lock, just return as no order 1156 * checking is needed. Avoid problems with thread 1157 * migration pinning the thread while checking if 1158 * spinlocks are held. If at least one spinlock is held 1159 * the thread is in a safe path and it is allowed to 1160 * unpin it. 1161 */ 1162 sched_pin(); 1163 lock_list = PCPU_GET(spinlocks); 1164 if (lock_list == NULL || lock_list->ll_count == 0) { 1165 sched_unpin(); 1166 return; 1167 } 1168 sched_unpin(); 1169 } 1170 1171 /* 1172 * Check to see if we are recursing on a lock we already own. If 1173 * so, make sure that we don't mismatch exclusive and shared lock 1174 * acquires. 1175 */ 1176 lock1 = find_instance(lock_list, lock); 1177 if (lock1 != NULL) { 1178 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 && 1179 (flags & LOP_EXCLUSIVE) == 0) { 1180 witness_output("shared lock of (%s) %s @ %s:%d\n", 1181 class->lc_name, lock->lo_name, 1182 fixup_filename(file), line); 1183 witness_output("while exclusively locked from %s:%d\n", 1184 fixup_filename(lock1->li_file), lock1->li_line); 1185 kassert_panic("excl->share"); 1186 } 1187 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 && 1188 (flags & LOP_EXCLUSIVE) != 0) { 1189 witness_output("exclusive lock of (%s) %s @ %s:%d\n", 1190 class->lc_name, lock->lo_name, 1191 fixup_filename(file), line); 1192 witness_output("while share locked from %s:%d\n", 1193 fixup_filename(lock1->li_file), lock1->li_line); 1194 kassert_panic("share->excl"); 1195 } 1196 return; 1197 } 1198 1199 /* Warn if the interlock is not locked exactly once. */ 1200 if (interlock != NULL) { 1201 iclass = LOCK_CLASS(interlock); 1202 lock1 = find_instance(lock_list, interlock); 1203 if (lock1 == NULL) 1204 kassert_panic("interlock (%s) %s not locked @ %s:%d", 1205 iclass->lc_name, interlock->lo_name, 1206 fixup_filename(file), line); 1207 else if ((lock1->li_flags & LI_RECURSEMASK) != 0) 1208 kassert_panic("interlock (%s) %s recursed @ %s:%d", 1209 iclass->lc_name, interlock->lo_name, 1210 fixup_filename(file), line); 1211 } 1212 1213 /* 1214 * Find the previously acquired lock, but ignore interlocks. 1215 */ 1216 plock = &lock_list->ll_children[lock_list->ll_count - 1]; 1217 if (interlock != NULL && plock->li_lock == interlock) { 1218 if (lock_list->ll_count > 1) 1219 plock = 1220 &lock_list->ll_children[lock_list->ll_count - 2]; 1221 else { 1222 lle = lock_list->ll_next; 1223 1224 /* 1225 * The interlock is the only lock we hold, so 1226 * simply return. 1227 */ 1228 if (lle == NULL) 1229 return; 1230 plock = &lle->ll_children[lle->ll_count - 1]; 1231 } 1232 } 1233 1234 /* 1235 * Try to perform most checks without a lock. If this succeeds we 1236 * can skip acquiring the lock and return success. Otherwise we redo 1237 * the check with the lock held to handle races with concurrent updates. 1238 */ 1239 w1 = plock->li_lock->lo_witness; 1240 if (witness_lock_order_check(w1, w)) 1241 return; 1242 1243 mtx_lock_spin(&w_mtx); 1244 if (witness_lock_order_check(w1, w)) { 1245 mtx_unlock_spin(&w_mtx); 1246 return; 1247 } 1248 witness_lock_order_add(w1, w); 1249 1250 /* 1251 * Check for duplicate locks of the same type. Note that we only 1252 * have to check for this on the last lock we just acquired. Any 1253 * other cases will be caught as lock order violations. 1254 */ 1255 if (w1 == w) { 1256 i = w->w_index; 1257 if (!(lock->lo_flags & LO_DUPOK) && !(flags & LOP_DUPOK) && 1258 !(w_rmatrix[i][i] & WITNESS_REVERSAL)) { 1259 w_rmatrix[i][i] |= WITNESS_REVERSAL; 1260 w->w_reversed = 1; 1261 mtx_unlock_spin(&w_mtx); 1262 witness_output( 1263 "acquiring duplicate lock of same type: \"%s\"\n", 1264 w->w_name); 1265 witness_output(" 1st %s @ %s:%d\n", plock->li_lock->lo_name, 1266 fixup_filename(plock->li_file), plock->li_line); 1267 witness_output(" 2nd %s @ %s:%d\n", lock->lo_name, 1268 fixup_filename(file), line); 1269 witness_debugger(1, __func__); 1270 } else 1271 mtx_unlock_spin(&w_mtx); 1272 return; 1273 } 1274 mtx_assert(&w_mtx, MA_OWNED); 1275 1276 /* 1277 * If we know that the lock we are acquiring comes after 1278 * the lock we most recently acquired in the lock order tree, 1279 * then there is no need for any further checks. 1280 */ 1281 if (isitmychild(w1, w)) 1282 goto out; 1283 1284 for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) { 1285 for (i = lle->ll_count - 1; i >= 0; i--, j++) { 1286 struct stack pstack; 1287 bool pstackv, trace; 1288 1289 MPASS(j < LOCK_CHILDCOUNT * LOCK_NCHILDREN); 1290 lock1 = &lle->ll_children[i]; 1291 1292 /* 1293 * Ignore the interlock. 1294 */ 1295 if (interlock == lock1->li_lock) 1296 continue; 1297 1298 /* 1299 * If this lock doesn't undergo witness checking, 1300 * then skip it. 1301 */ 1302 w1 = lock1->li_lock->lo_witness; 1303 if (w1 == NULL) { 1304 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0, 1305 ("lock missing witness structure")); 1306 continue; 1307 } 1308 1309 /* 1310 * If we are locking Giant and this is a sleepable 1311 * lock, then skip it. 1312 */ 1313 if ((lock1->li_flags & LI_SLEEPABLE) != 0 && 1314 lock == &Giant.lock_object) 1315 continue; 1316 1317 /* 1318 * If we are locking a sleepable lock and this lock 1319 * is Giant, then skip it. 1320 */ 1321 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 1322 (flags & LOP_NOSLEEP) == 0 && 1323 lock1->li_lock == &Giant.lock_object) 1324 continue; 1325 1326 /* 1327 * If we are locking a sleepable lock and this lock 1328 * isn't sleepable, we want to treat it as a lock 1329 * order violation to enfore a general lock order of 1330 * sleepable locks before non-sleepable locks. 1331 */ 1332 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 1333 (flags & LOP_NOSLEEP) == 0 && 1334 (lock1->li_flags & LI_SLEEPABLE) == 0) 1335 goto reversal; 1336 1337 /* 1338 * If we are locking Giant and this is a non-sleepable 1339 * lock, then treat it as a reversal. 1340 */ 1341 if ((lock1->li_flags & LI_SLEEPABLE) == 0 && 1342 lock == &Giant.lock_object) 1343 goto reversal; 1344 1345 /* 1346 * Check the lock order hierarchy for a reveresal. 1347 */ 1348 if (!isitmydescendant(w, w1)) 1349 continue; 1350 reversal: 1351 1352 /* 1353 * We have a lock order violation, check to see if it 1354 * is allowed or has already been yelled about. 1355 */ 1356 1357 /* Bail if this violation is known */ 1358 if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL) 1359 goto out; 1360 1361 /* Record this as a violation */ 1362 w_rmatrix[w1->w_index][w->w_index] |= WITNESS_REVERSAL; 1363 w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL; 1364 w->w_reversed = w1->w_reversed = 1; 1365 witness_increment_graph_generation(); 1366 1367 /* 1368 * If the lock order is blessed, bail before logging 1369 * anything. We don't look for other lock order 1370 * violations though, which may be a bug. 1371 */ 1372 if (blessed(w, w1)) 1373 goto out; 1374 1375 trace = atomic_load_int(&witness_trace); 1376 if (trace) { 1377 struct witness_lock_order_data *data; 1378 1379 pstackv = false; 1380 data = witness_lock_order_get(w, w1); 1381 if (data != NULL) { 1382 stack_copy(&data->wlod_stack, 1383 &pstack); 1384 pstackv = true; 1385 } 1386 } 1387 mtx_unlock_spin(&w_mtx); 1388 1389 #ifdef WITNESS_NO_VNODE 1390 /* 1391 * There are known LORs between VNODE locks. They are 1392 * not an indication of a bug. VNODE locks are flagged 1393 * as such (LO_IS_VNODE) and we don't yell if the LOR 1394 * is between 2 VNODE locks. 1395 */ 1396 if ((lock->lo_flags & LO_IS_VNODE) != 0 && 1397 (lock1->li_lock->lo_flags & LO_IS_VNODE) != 0) 1398 return; 1399 #endif 1400 1401 /* 1402 * Ok, yell about it. 1403 */ 1404 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && 1405 (flags & LOP_NOSLEEP) == 0 && 1406 (lock1->li_flags & LI_SLEEPABLE) == 0) 1407 witness_output( 1408 "lock order reversal: (sleepable after non-sleepable)\n"); 1409 else if ((lock1->li_flags & LI_SLEEPABLE) == 0 1410 && lock == &Giant.lock_object) 1411 witness_output( 1412 "lock order reversal: (Giant after non-sleepable)\n"); 1413 else 1414 witness_output("lock order reversal:\n"); 1415 1416 /* 1417 * Try to locate an earlier lock with 1418 * witness w in our list. 1419 */ 1420 do { 1421 lock2 = &lle->ll_children[i]; 1422 MPASS(lock2->li_lock != NULL); 1423 if (lock2->li_lock->lo_witness == w) 1424 break; 1425 if (i == 0 && lle->ll_next != NULL) { 1426 lle = lle->ll_next; 1427 i = lle->ll_count - 1; 1428 MPASS(i >= 0 && i < LOCK_NCHILDREN); 1429 } else 1430 i--; 1431 } while (i >= 0); 1432 if (i < 0) { 1433 witness_output(" 1st %p %s (%s, %s) @ %s:%d\n", 1434 lock1->li_lock, lock1->li_lock->lo_name, 1435 w1->w_name, w1->w_class->lc_name, 1436 fixup_filename(lock1->li_file), 1437 lock1->li_line); 1438 witness_output(" 2nd %p %s (%s, %s) @ %s:%d\n", 1439 lock, lock->lo_name, w->w_name, 1440 w->w_class->lc_name, fixup_filename(file), 1441 line); 1442 } else { 1443 struct witness *w2 = lock2->li_lock->lo_witness; 1444 1445 witness_output(" 1st %p %s (%s, %s) @ %s:%d\n", 1446 lock2->li_lock, lock2->li_lock->lo_name, 1447 w2->w_name, w2->w_class->lc_name, 1448 fixup_filename(lock2->li_file), 1449 lock2->li_line); 1450 witness_output(" 2nd %p %s (%s, %s) @ %s:%d\n", 1451 lock1->li_lock, lock1->li_lock->lo_name, 1452 w1->w_name, w1->w_class->lc_name, 1453 fixup_filename(lock1->li_file), 1454 lock1->li_line); 1455 witness_output(" 3rd %p %s (%s, %s) @ %s:%d\n", lock, 1456 lock->lo_name, w->w_name, 1457 w->w_class->lc_name, fixup_filename(file), 1458 line); 1459 } 1460 if (trace) { 1461 char buf[64]; 1462 struct sbuf sb; 1463 1464 sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN); 1465 sbuf_set_drain(&sb, witness_output_drain, 1466 NULL); 1467 1468 if (pstackv) { 1469 sbuf_printf(&sb, 1470 "lock order %s -> %s established at:\n", 1471 w->w_name, w1->w_name); 1472 stack_sbuf_print_flags(&sb, &pstack, 1473 M_NOWAIT, STACK_SBUF_FMT_LONG); 1474 } 1475 1476 sbuf_printf(&sb, 1477 "lock order %s -> %s attempted at:\n", 1478 w1->w_name, w->w_name); 1479 stack_save(&pstack); 1480 stack_sbuf_print_flags(&sb, &pstack, M_NOWAIT, 1481 STACK_SBUF_FMT_LONG); 1482 1483 sbuf_finish(&sb); 1484 sbuf_delete(&sb); 1485 } 1486 witness_enter_debugger(__func__); 1487 return; 1488 } 1489 } 1490 1491 /* 1492 * If requested, build a new lock order. However, don't build a new 1493 * relationship between a sleepable lock and Giant if it is in the 1494 * wrong direction. The correct lock order is that sleepable locks 1495 * always come before Giant. 1496 */ 1497 if (flags & LOP_NEWORDER && 1498 !(plock->li_lock == &Giant.lock_object && 1499 (lock->lo_flags & LO_SLEEPABLE) != 0 && 1500 (flags & LOP_NOSLEEP) == 0)) { 1501 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__, 1502 w->w_name, plock->li_lock->lo_witness->w_name); 1503 itismychild(plock->li_lock->lo_witness, w); 1504 } 1505 out: 1506 mtx_unlock_spin(&w_mtx); 1507 } 1508 1509 void 1510 witness_lock(struct lock_object *lock, int flags, const char *file, int line) 1511 { 1512 struct lock_list_entry **lock_list, *lle; 1513 struct lock_instance *instance; 1514 struct witness *w; 1515 struct thread *td; 1516 1517 if (witness_cold || witness_watch == -1 || lock->lo_witness == NULL || 1518 KERNEL_PANICKED()) 1519 return; 1520 w = lock->lo_witness; 1521 td = curthread; 1522 1523 /* Determine lock list for this lock. */ 1524 if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK) 1525 lock_list = &td->td_sleeplocks; 1526 else 1527 lock_list = PCPU_PTR(spinlocks); 1528 1529 /* Check to see if we are recursing on a lock we already own. */ 1530 instance = find_instance(*lock_list, lock); 1531 if (instance != NULL) { 1532 instance->li_flags++; 1533 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__, 1534 td->td_proc->p_pid, lock->lo_name, 1535 instance->li_flags & LI_RECURSEMASK); 1536 instance->li_file = file; 1537 instance->li_line = line; 1538 return; 1539 } 1540 1541 /* Update per-witness last file and line acquire. */ 1542 w->w_file = file; 1543 w->w_line = line; 1544 1545 /* Find the next open lock instance in the list and fill it. */ 1546 lle = *lock_list; 1547 if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) { 1548 lle = witness_lock_list_get(); 1549 if (lle == NULL) 1550 return; 1551 lle->ll_next = *lock_list; 1552 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__, 1553 td->td_proc->p_pid, lle); 1554 *lock_list = lle; 1555 } 1556 instance = &lle->ll_children[lle->ll_count++]; 1557 instance->li_lock = lock; 1558 instance->li_line = line; 1559 instance->li_file = file; 1560 instance->li_flags = 0; 1561 if ((flags & LOP_EXCLUSIVE) != 0) 1562 instance->li_flags |= LI_EXCLUSIVE; 1563 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && (flags & LOP_NOSLEEP) == 0) 1564 instance->li_flags |= LI_SLEEPABLE; 1565 CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__, 1566 td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1); 1567 } 1568 1569 void 1570 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line) 1571 { 1572 struct lock_instance *instance; 1573 struct lock_class *class; 1574 1575 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 1576 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED()) 1577 return; 1578 class = LOCK_CLASS(lock); 1579 if (witness_watch) { 1580 if ((lock->lo_flags & LO_UPGRADABLE) == 0) 1581 kassert_panic( 1582 "upgrade of non-upgradable lock (%s) %s @ %s:%d", 1583 class->lc_name, lock->lo_name, 1584 fixup_filename(file), line); 1585 if ((class->lc_flags & LC_SLEEPLOCK) == 0) 1586 kassert_panic( 1587 "upgrade of non-sleep lock (%s) %s @ %s:%d", 1588 class->lc_name, lock->lo_name, 1589 fixup_filename(file), line); 1590 } 1591 instance = find_instance(curthread->td_sleeplocks, lock); 1592 if (instance == NULL) { 1593 kassert_panic("upgrade of unlocked lock (%s) %s @ %s:%d", 1594 class->lc_name, lock->lo_name, 1595 fixup_filename(file), line); 1596 return; 1597 } 1598 if (witness_watch) { 1599 if ((instance->li_flags & LI_EXCLUSIVE) != 0) 1600 kassert_panic( 1601 "upgrade of exclusive lock (%s) %s @ %s:%d", 1602 class->lc_name, lock->lo_name, 1603 fixup_filename(file), line); 1604 if ((instance->li_flags & LI_RECURSEMASK) != 0) 1605 kassert_panic( 1606 "upgrade of recursed lock (%s) %s r=%d @ %s:%d", 1607 class->lc_name, lock->lo_name, 1608 instance->li_flags & LI_RECURSEMASK, 1609 fixup_filename(file), line); 1610 } 1611 instance->li_flags |= LI_EXCLUSIVE; 1612 } 1613 1614 void 1615 witness_downgrade(struct lock_object *lock, int flags, const char *file, 1616 int line) 1617 { 1618 struct lock_instance *instance; 1619 struct lock_class *class; 1620 1621 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 1622 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED()) 1623 return; 1624 class = LOCK_CLASS(lock); 1625 if (witness_watch) { 1626 if ((lock->lo_flags & LO_UPGRADABLE) == 0) 1627 kassert_panic( 1628 "downgrade of non-upgradable lock (%s) %s @ %s:%d", 1629 class->lc_name, lock->lo_name, 1630 fixup_filename(file), line); 1631 if ((class->lc_flags & LC_SLEEPLOCK) == 0) 1632 kassert_panic( 1633 "downgrade of non-sleep lock (%s) %s @ %s:%d", 1634 class->lc_name, lock->lo_name, 1635 fixup_filename(file), line); 1636 } 1637 instance = find_instance(curthread->td_sleeplocks, lock); 1638 if (instance == NULL) { 1639 kassert_panic("downgrade of unlocked lock (%s) %s @ %s:%d", 1640 class->lc_name, lock->lo_name, 1641 fixup_filename(file), line); 1642 return; 1643 } 1644 if (witness_watch) { 1645 if ((instance->li_flags & LI_EXCLUSIVE) == 0) 1646 kassert_panic( 1647 "downgrade of shared lock (%s) %s @ %s:%d", 1648 class->lc_name, lock->lo_name, 1649 fixup_filename(file), line); 1650 if ((instance->li_flags & LI_RECURSEMASK) != 0) 1651 kassert_panic( 1652 "downgrade of recursed lock (%s) %s r=%d @ %s:%d", 1653 class->lc_name, lock->lo_name, 1654 instance->li_flags & LI_RECURSEMASK, 1655 fixup_filename(file), line); 1656 } 1657 instance->li_flags &= ~LI_EXCLUSIVE; 1658 } 1659 1660 void 1661 witness_unlock(struct lock_object *lock, int flags, const char *file, int line) 1662 { 1663 struct lock_list_entry **lock_list, *lle; 1664 struct lock_instance *instance; 1665 struct lock_class *class; 1666 struct thread *td; 1667 register_t s; 1668 int i, j; 1669 1670 if (witness_cold || lock->lo_witness == NULL || KERNEL_PANICKED()) 1671 return; 1672 td = curthread; 1673 class = LOCK_CLASS(lock); 1674 1675 /* Find lock instance associated with this lock. */ 1676 if (class->lc_flags & LC_SLEEPLOCK) 1677 lock_list = &td->td_sleeplocks; 1678 else 1679 lock_list = PCPU_PTR(spinlocks); 1680 lle = *lock_list; 1681 for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next) 1682 for (i = 0; i < (*lock_list)->ll_count; i++) { 1683 instance = &(*lock_list)->ll_children[i]; 1684 if (instance->li_lock == lock) 1685 goto found; 1686 } 1687 1688 /* 1689 * When disabling WITNESS through witness_watch we could end up in 1690 * having registered locks in the td_sleeplocks queue. 1691 * We have to make sure we flush these queues, so just search for 1692 * eventual register locks and remove them. 1693 */ 1694 if (witness_watch > 0) { 1695 kassert_panic("lock (%s) %s not locked @ %s:%d", class->lc_name, 1696 lock->lo_name, fixup_filename(file), line); 1697 return; 1698 } else { 1699 return; 1700 } 1701 found: 1702 1703 /* First, check for shared/exclusive mismatches. */ 1704 if ((instance->li_flags & LI_EXCLUSIVE) != 0 && witness_watch > 0 && 1705 (flags & LOP_EXCLUSIVE) == 0) { 1706 witness_output("shared unlock of (%s) %s @ %s:%d\n", 1707 class->lc_name, lock->lo_name, fixup_filename(file), line); 1708 witness_output("while exclusively locked from %s:%d\n", 1709 fixup_filename(instance->li_file), instance->li_line); 1710 kassert_panic("excl->ushare"); 1711 } 1712 if ((instance->li_flags & LI_EXCLUSIVE) == 0 && witness_watch > 0 && 1713 (flags & LOP_EXCLUSIVE) != 0) { 1714 witness_output("exclusive unlock of (%s) %s @ %s:%d\n", 1715 class->lc_name, lock->lo_name, fixup_filename(file), line); 1716 witness_output("while share locked from %s:%d\n", 1717 fixup_filename(instance->li_file), 1718 instance->li_line); 1719 kassert_panic("share->uexcl"); 1720 } 1721 /* If we are recursed, unrecurse. */ 1722 if ((instance->li_flags & LI_RECURSEMASK) > 0) { 1723 CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__, 1724 td->td_proc->p_pid, instance->li_lock->lo_name, 1725 instance->li_flags); 1726 instance->li_flags--; 1727 return; 1728 } 1729 /* The lock is now being dropped, check for NORELEASE flag */ 1730 if ((instance->li_flags & LI_NORELEASE) != 0 && witness_watch > 0) { 1731 witness_output("forbidden unlock of (%s) %s @ %s:%d\n", 1732 class->lc_name, lock->lo_name, fixup_filename(file), line); 1733 kassert_panic("lock marked norelease"); 1734 } 1735 1736 /* Otherwise, remove this item from the list. */ 1737 s = intr_disable(); 1738 CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__, 1739 td->td_proc->p_pid, instance->li_lock->lo_name, 1740 (*lock_list)->ll_count - 1); 1741 for (j = i; j < (*lock_list)->ll_count - 1; j++) 1742 (*lock_list)->ll_children[j] = 1743 (*lock_list)->ll_children[j + 1]; 1744 (*lock_list)->ll_count--; 1745 intr_restore(s); 1746 1747 /* 1748 * In order to reduce contention on w_mtx, we want to keep always an 1749 * head object into lists so that frequent allocation from the 1750 * free witness pool (and subsequent locking) is avoided. 1751 * In order to maintain the current code simple, when the head 1752 * object is totally unloaded it means also that we do not have 1753 * further objects in the list, so the list ownership needs to be 1754 * hand over to another object if the current head needs to be freed. 1755 */ 1756 if ((*lock_list)->ll_count == 0) { 1757 if (*lock_list == lle) { 1758 if (lle->ll_next == NULL) 1759 return; 1760 } else 1761 lle = *lock_list; 1762 *lock_list = lle->ll_next; 1763 CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__, 1764 td->td_proc->p_pid, lle); 1765 witness_lock_list_free(lle); 1766 } 1767 } 1768 1769 void 1770 witness_thread_exit(struct thread *td) 1771 { 1772 struct lock_list_entry *lle; 1773 int i, n; 1774 1775 lle = td->td_sleeplocks; 1776 if (lle == NULL || KERNEL_PANICKED()) 1777 return; 1778 if (lle->ll_count != 0) { 1779 for (n = 0; lle != NULL; lle = lle->ll_next) 1780 for (i = lle->ll_count - 1; i >= 0; i--) { 1781 if (n == 0) 1782 witness_output( 1783 "Thread %p exiting with the following locks held:\n", td); 1784 n++; 1785 witness_list_lock(&lle->ll_children[i], 1786 witness_output); 1787 1788 } 1789 kassert_panic( 1790 "Thread %p cannot exit while holding sleeplocks\n", td); 1791 } 1792 witness_lock_list_free(lle); 1793 } 1794 1795 /* 1796 * Warn if any locks other than 'lock' are held. Flags can be passed in to 1797 * exempt Giant and sleepable locks from the checks as well. If any 1798 * non-exempt locks are held, then a supplied message is printed to the 1799 * output channel along with a list of the offending locks. If indicated in the 1800 * flags then a failure results in a panic as well. 1801 */ 1802 int 1803 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...) 1804 { 1805 struct lock_list_entry *lock_list, *lle; 1806 struct lock_instance *lock1; 1807 struct thread *td; 1808 va_list ap; 1809 int i, n; 1810 1811 if (witness_cold || witness_watch < 1 || KERNEL_PANICKED()) 1812 return (0); 1813 n = 0; 1814 td = curthread; 1815 for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next) 1816 for (i = lle->ll_count - 1; i >= 0; i--) { 1817 lock1 = &lle->ll_children[i]; 1818 if (lock1->li_lock == lock) 1819 continue; 1820 if (flags & WARN_GIANTOK && 1821 lock1->li_lock == &Giant.lock_object) 1822 continue; 1823 if (flags & WARN_SLEEPOK && 1824 (lock1->li_flags & LI_SLEEPABLE) != 0) 1825 continue; 1826 if (n == 0) { 1827 va_start(ap, fmt); 1828 vprintf(fmt, ap); 1829 va_end(ap); 1830 printf(" with the following %slocks held:\n", 1831 (flags & WARN_SLEEPOK) != 0 ? 1832 "non-sleepable " : ""); 1833 } 1834 n++; 1835 witness_list_lock(lock1, printf); 1836 } 1837 1838 /* 1839 * Pin the thread in order to avoid problems with thread migration. 1840 * Once that all verifies are passed about spinlocks ownership, 1841 * the thread is in a safe path and it can be unpinned. 1842 */ 1843 sched_pin(); 1844 lock_list = PCPU_GET(spinlocks); 1845 if (lock_list != NULL && lock_list->ll_count != 0) { 1846 sched_unpin(); 1847 1848 /* 1849 * We should only have one spinlock and as long as 1850 * the flags cannot match for this locks class, 1851 * check if the first spinlock is the one curthread 1852 * should hold. 1853 */ 1854 lock1 = &lock_list->ll_children[lock_list->ll_count - 1]; 1855 if (lock_list->ll_count == 1 && lock_list->ll_next == NULL && 1856 lock1->li_lock == lock && n == 0) 1857 return (0); 1858 1859 va_start(ap, fmt); 1860 vprintf(fmt, ap); 1861 va_end(ap); 1862 printf(" with the following %slocks held:\n", 1863 (flags & WARN_SLEEPOK) != 0 ? "non-sleepable " : ""); 1864 n += witness_list_locks(&lock_list, printf); 1865 } else 1866 sched_unpin(); 1867 if (flags & WARN_PANIC && n) 1868 kassert_panic("%s", __func__); 1869 else 1870 witness_debugger(n, __func__); 1871 return (n); 1872 } 1873 1874 const char * 1875 witness_file(struct lock_object *lock) 1876 { 1877 struct witness *w; 1878 1879 if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL) 1880 return ("?"); 1881 w = lock->lo_witness; 1882 return (w->w_file); 1883 } 1884 1885 int 1886 witness_line(struct lock_object *lock) 1887 { 1888 struct witness *w; 1889 1890 if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL) 1891 return (0); 1892 w = lock->lo_witness; 1893 return (w->w_line); 1894 } 1895 1896 static struct witness * 1897 enroll(const char *description, struct lock_class *lock_class) 1898 { 1899 struct witness *w; 1900 1901 MPASS(description != NULL); 1902 1903 if (witness_watch == -1 || KERNEL_PANICKED()) 1904 return (NULL); 1905 if ((lock_class->lc_flags & LC_SPINLOCK)) { 1906 if (witness_skipspin) 1907 return (NULL); 1908 } else if ((lock_class->lc_flags & LC_SLEEPLOCK) == 0) { 1909 kassert_panic("lock class %s is not sleep or spin", 1910 lock_class->lc_name); 1911 return (NULL); 1912 } 1913 1914 mtx_lock_spin(&w_mtx); 1915 w = witness_hash_get(description); 1916 if (w) 1917 goto found; 1918 if ((w = witness_get()) == NULL) 1919 return (NULL); 1920 MPASS(strlen(description) < MAX_W_NAME); 1921 strcpy(w->w_name, description); 1922 w->w_class = lock_class; 1923 w->w_refcount = 1; 1924 STAILQ_INSERT_HEAD(&w_all, w, w_list); 1925 if (lock_class->lc_flags & LC_SPINLOCK) { 1926 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist); 1927 w_spin_cnt++; 1928 } else if (lock_class->lc_flags & LC_SLEEPLOCK) { 1929 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist); 1930 w_sleep_cnt++; 1931 } 1932 1933 /* Insert new witness into the hash */ 1934 witness_hash_put(w); 1935 witness_increment_graph_generation(); 1936 mtx_unlock_spin(&w_mtx); 1937 return (w); 1938 found: 1939 w->w_refcount++; 1940 if (w->w_refcount == 1) 1941 w->w_class = lock_class; 1942 mtx_unlock_spin(&w_mtx); 1943 if (lock_class != w->w_class) 1944 kassert_panic( 1945 "lock (%s) %s does not match earlier (%s) lock", 1946 description, lock_class->lc_name, 1947 w->w_class->lc_name); 1948 return (w); 1949 } 1950 1951 static void 1952 depart(struct witness *w) 1953 { 1954 1955 MPASS(w->w_refcount == 0); 1956 if (w->w_class->lc_flags & LC_SLEEPLOCK) { 1957 w_sleep_cnt--; 1958 } else { 1959 w_spin_cnt--; 1960 } 1961 /* 1962 * Set file to NULL as it may point into a loadable module. 1963 */ 1964 w->w_file = NULL; 1965 w->w_line = 0; 1966 witness_increment_graph_generation(); 1967 } 1968 1969 static void 1970 adopt(struct witness *parent, struct witness *child) 1971 { 1972 int pi, ci, i, j; 1973 1974 if (witness_cold == 0) 1975 mtx_assert(&w_mtx, MA_OWNED); 1976 1977 /* If the relationship is already known, there's no work to be done. */ 1978 if (isitmychild(parent, child)) 1979 return; 1980 1981 /* When the structure of the graph changes, bump up the generation. */ 1982 witness_increment_graph_generation(); 1983 1984 /* 1985 * The hard part ... create the direct relationship, then propagate all 1986 * indirect relationships. 1987 */ 1988 pi = parent->w_index; 1989 ci = child->w_index; 1990 WITNESS_INDEX_ASSERT(pi); 1991 WITNESS_INDEX_ASSERT(ci); 1992 MPASS(pi != ci); 1993 w_rmatrix[pi][ci] |= WITNESS_PARENT; 1994 w_rmatrix[ci][pi] |= WITNESS_CHILD; 1995 1996 /* 1997 * If parent was not already an ancestor of child, 1998 * then we increment the descendant and ancestor counters. 1999 */ 2000 if ((w_rmatrix[pi][ci] & WITNESS_ANCESTOR) == 0) { 2001 parent->w_num_descendants++; 2002 child->w_num_ancestors++; 2003 } 2004 2005 /* 2006 * Find each ancestor of 'pi'. Note that 'pi' itself is counted as 2007 * an ancestor of 'pi' during this loop. 2008 */ 2009 for (i = 1; i <= w_max_used_index; i++) { 2010 if ((w_rmatrix[i][pi] & WITNESS_ANCESTOR_MASK) == 0 && 2011 (i != pi)) 2012 continue; 2013 2014 /* Find each descendant of 'i' and mark it as a descendant. */ 2015 for (j = 1; j <= w_max_used_index; j++) { 2016 /* 2017 * Skip children that are already marked as 2018 * descendants of 'i'. 2019 */ 2020 if (w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) 2021 continue; 2022 2023 /* 2024 * We are only interested in descendants of 'ci'. Note 2025 * that 'ci' itself is counted as a descendant of 'ci'. 2026 */ 2027 if ((w_rmatrix[ci][j] & WITNESS_ANCESTOR_MASK) == 0 && 2028 (j != ci)) 2029 continue; 2030 w_rmatrix[i][j] |= WITNESS_ANCESTOR; 2031 w_rmatrix[j][i] |= WITNESS_DESCENDANT; 2032 w_data[i].w_num_descendants++; 2033 w_data[j].w_num_ancestors++; 2034 2035 /* 2036 * Make sure we aren't marking a node as both an 2037 * ancestor and descendant. We should have caught 2038 * this as a lock order reversal earlier. 2039 */ 2040 if ((w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) && 2041 (w_rmatrix[i][j] & WITNESS_DESCENDANT_MASK)) { 2042 printf("witness rmatrix paradox! [%d][%d]=%d " 2043 "both ancestor and descendant\n", 2044 i, j, w_rmatrix[i][j]); 2045 kdb_backtrace(); 2046 printf("Witness disabled.\n"); 2047 witness_watch = -1; 2048 } 2049 if ((w_rmatrix[j][i] & WITNESS_ANCESTOR_MASK) && 2050 (w_rmatrix[j][i] & WITNESS_DESCENDANT_MASK)) { 2051 printf("witness rmatrix paradox! [%d][%d]=%d " 2052 "both ancestor and descendant\n", 2053 j, i, w_rmatrix[j][i]); 2054 kdb_backtrace(); 2055 printf("Witness disabled.\n"); 2056 witness_watch = -1; 2057 } 2058 } 2059 } 2060 } 2061 2062 static void 2063 itismychild(struct witness *parent, struct witness *child) 2064 { 2065 int unlocked; 2066 2067 MPASS(child != NULL && parent != NULL); 2068 if (witness_cold == 0) 2069 mtx_assert(&w_mtx, MA_OWNED); 2070 2071 if (!witness_lock_type_equal(parent, child)) { 2072 if (witness_cold == 0) { 2073 unlocked = 1; 2074 mtx_unlock_spin(&w_mtx); 2075 } else { 2076 unlocked = 0; 2077 } 2078 kassert_panic( 2079 "%s: parent \"%s\" (%s) and child \"%s\" (%s) are not " 2080 "the same lock type", __func__, parent->w_name, 2081 parent->w_class->lc_name, child->w_name, 2082 child->w_class->lc_name); 2083 if (unlocked) 2084 mtx_lock_spin(&w_mtx); 2085 } 2086 adopt(parent, child); 2087 } 2088 2089 /* 2090 * Generic code for the isitmy*() functions. The rmask parameter is the 2091 * expected relationship of w1 to w2. 2092 */ 2093 static int 2094 _isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname) 2095 { 2096 unsigned char r1, r2; 2097 int i1, i2; 2098 2099 i1 = w1->w_index; 2100 i2 = w2->w_index; 2101 WITNESS_INDEX_ASSERT(i1); 2102 WITNESS_INDEX_ASSERT(i2); 2103 r1 = w_rmatrix[i1][i2] & WITNESS_RELATED_MASK; 2104 r2 = w_rmatrix[i2][i1] & WITNESS_RELATED_MASK; 2105 2106 /* The flags on one better be the inverse of the flags on the other */ 2107 if (!((WITNESS_ATOD(r1) == r2 && WITNESS_DTOA(r2) == r1) || 2108 (WITNESS_DTOA(r1) == r2 && WITNESS_ATOD(r2) == r1))) { 2109 /* Don't squawk if we're potentially racing with an update. */ 2110 if (!mtx_owned(&w_mtx)) 2111 return (0); 2112 printf("%s: rmatrix mismatch between %s (index %d) and %s " 2113 "(index %d): w_rmatrix[%d][%d] == %hhx but " 2114 "w_rmatrix[%d][%d] == %hhx\n", 2115 fname, w1->w_name, i1, w2->w_name, i2, i1, i2, r1, 2116 i2, i1, r2); 2117 kdb_backtrace(); 2118 printf("Witness disabled.\n"); 2119 witness_watch = -1; 2120 } 2121 return (r1 & rmask); 2122 } 2123 2124 /* 2125 * Checks if @child is a direct child of @parent. 2126 */ 2127 static int 2128 isitmychild(struct witness *parent, struct witness *child) 2129 { 2130 2131 return (_isitmyx(parent, child, WITNESS_PARENT, __func__)); 2132 } 2133 2134 /* 2135 * Checks if @descendant is a direct or inderect descendant of @ancestor. 2136 */ 2137 static int 2138 isitmydescendant(struct witness *ancestor, struct witness *descendant) 2139 { 2140 2141 return (_isitmyx(ancestor, descendant, WITNESS_ANCESTOR_MASK, 2142 __func__)); 2143 } 2144 2145 static int 2146 blessed(struct witness *w1, struct witness *w2) 2147 { 2148 int i; 2149 struct witness_blessed *b; 2150 2151 for (i = 0; i < nitems(blessed_list); i++) { 2152 b = &blessed_list[i]; 2153 if (strcmp(w1->w_name, b->b_lock1) == 0) { 2154 if (strcmp(w2->w_name, b->b_lock2) == 0) 2155 return (1); 2156 continue; 2157 } 2158 if (strcmp(w1->w_name, b->b_lock2) == 0) 2159 if (strcmp(w2->w_name, b->b_lock1) == 0) 2160 return (1); 2161 } 2162 return (0); 2163 } 2164 2165 static struct witness * 2166 witness_get(void) 2167 { 2168 struct witness *w; 2169 int index; 2170 2171 if (witness_cold == 0) 2172 mtx_assert(&w_mtx, MA_OWNED); 2173 2174 if (witness_watch == -1) { 2175 mtx_unlock_spin(&w_mtx); 2176 return (NULL); 2177 } 2178 if (STAILQ_EMPTY(&w_free)) { 2179 witness_watch = -1; 2180 mtx_unlock_spin(&w_mtx); 2181 printf("WITNESS: unable to allocate a new witness object\n"); 2182 return (NULL); 2183 } 2184 w = STAILQ_FIRST(&w_free); 2185 STAILQ_REMOVE_HEAD(&w_free, w_list); 2186 w_free_cnt--; 2187 index = w->w_index; 2188 MPASS(index > 0 && index == w_max_used_index+1 && 2189 index < witness_count); 2190 bzero(w, sizeof(*w)); 2191 w->w_index = index; 2192 if (index > w_max_used_index) 2193 w_max_used_index = index; 2194 return (w); 2195 } 2196 2197 static void 2198 witness_free(struct witness *w) 2199 { 2200 2201 STAILQ_INSERT_HEAD(&w_free, w, w_list); 2202 w_free_cnt++; 2203 } 2204 2205 static struct lock_list_entry * 2206 witness_lock_list_get(void) 2207 { 2208 struct lock_list_entry *lle; 2209 2210 if (witness_watch == -1) 2211 return (NULL); 2212 mtx_lock_spin(&w_mtx); 2213 lle = w_lock_list_free; 2214 if (lle == NULL) { 2215 witness_watch = -1; 2216 mtx_unlock_spin(&w_mtx); 2217 printf("%s: witness exhausted\n", __func__); 2218 return (NULL); 2219 } 2220 w_lock_list_free = lle->ll_next; 2221 mtx_unlock_spin(&w_mtx); 2222 bzero(lle, sizeof(*lle)); 2223 return (lle); 2224 } 2225 2226 static void 2227 witness_lock_list_free(struct lock_list_entry *lle) 2228 { 2229 2230 mtx_lock_spin(&w_mtx); 2231 lle->ll_next = w_lock_list_free; 2232 w_lock_list_free = lle; 2233 mtx_unlock_spin(&w_mtx); 2234 } 2235 2236 static struct lock_instance * 2237 find_instance(struct lock_list_entry *list, const struct lock_object *lock) 2238 { 2239 struct lock_list_entry *lle; 2240 struct lock_instance *instance; 2241 int i; 2242 2243 for (lle = list; lle != NULL; lle = lle->ll_next) 2244 for (i = lle->ll_count - 1; i >= 0; i--) { 2245 instance = &lle->ll_children[i]; 2246 if (instance->li_lock == lock) 2247 return (instance); 2248 } 2249 return (NULL); 2250 } 2251 2252 static void 2253 witness_list_lock(struct lock_instance *instance, 2254 int (*prnt)(const char *fmt, ...)) 2255 { 2256 struct lock_object *lock; 2257 2258 lock = instance->li_lock; 2259 prnt("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ? 2260 "exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name); 2261 if (lock->lo_witness->w_name != lock->lo_name) 2262 prnt(" (%s)", lock->lo_witness->w_name); 2263 prnt(" r = %d (%p) locked @ %s:%d\n", 2264 instance->li_flags & LI_RECURSEMASK, lock, 2265 fixup_filename(instance->li_file), instance->li_line); 2266 } 2267 2268 static int 2269 witness_output(const char *fmt, ...) 2270 { 2271 va_list ap; 2272 int ret; 2273 2274 va_start(ap, fmt); 2275 ret = witness_voutput(fmt, ap); 2276 va_end(ap); 2277 return (ret); 2278 } 2279 2280 static int 2281 witness_voutput(const char *fmt, va_list ap) 2282 { 2283 int ret; 2284 2285 ret = 0; 2286 switch (witness_channel) { 2287 case WITNESS_CONSOLE: 2288 ret = vprintf(fmt, ap); 2289 break; 2290 case WITNESS_LOG: 2291 vlog(LOG_NOTICE, fmt, ap); 2292 break; 2293 case WITNESS_NONE: 2294 break; 2295 } 2296 return (ret); 2297 } 2298 2299 #ifdef DDB 2300 static int 2301 witness_thread_has_locks(struct thread *td) 2302 { 2303 2304 if (td->td_sleeplocks == NULL) 2305 return (0); 2306 return (td->td_sleeplocks->ll_count != 0); 2307 } 2308 2309 static int 2310 witness_proc_has_locks(struct proc *p) 2311 { 2312 struct thread *td; 2313 2314 FOREACH_THREAD_IN_PROC(p, td) { 2315 if (witness_thread_has_locks(td)) 2316 return (1); 2317 } 2318 return (0); 2319 } 2320 #endif 2321 2322 int 2323 witness_list_locks(struct lock_list_entry **lock_list, 2324 int (*prnt)(const char *fmt, ...)) 2325 { 2326 struct lock_list_entry *lle; 2327 int i, nheld; 2328 2329 nheld = 0; 2330 for (lle = *lock_list; lle != NULL; lle = lle->ll_next) 2331 for (i = lle->ll_count - 1; i >= 0; i--) { 2332 witness_list_lock(&lle->ll_children[i], prnt); 2333 nheld++; 2334 } 2335 return (nheld); 2336 } 2337 2338 /* 2339 * This is a bit risky at best. We call this function when we have timed 2340 * out acquiring a spin lock, and we assume that the other CPU is stuck 2341 * with this lock held. So, we go groveling around in the other CPU's 2342 * per-cpu data to try to find the lock instance for this spin lock to 2343 * see when it was last acquired. 2344 */ 2345 void 2346 witness_display_spinlock(struct lock_object *lock, struct thread *owner, 2347 int (*prnt)(const char *fmt, ...)) 2348 { 2349 struct lock_instance *instance; 2350 struct pcpu *pc; 2351 2352 if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU) 2353 return; 2354 pc = pcpu_find(owner->td_oncpu); 2355 instance = find_instance(pc->pc_spinlocks, lock); 2356 if (instance != NULL) 2357 witness_list_lock(instance, prnt); 2358 } 2359 2360 void 2361 witness_save(struct lock_object *lock, const char **filep, int *linep) 2362 { 2363 struct lock_list_entry *lock_list; 2364 struct lock_instance *instance; 2365 struct lock_class *class; 2366 2367 /* 2368 * This function is used independently in locking code to deal with 2369 * Giant, SCHEDULER_STOPPED() check can be removed here after Giant 2370 * is gone. 2371 */ 2372 if (SCHEDULER_STOPPED()) 2373 return; 2374 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 2375 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED()) 2376 return; 2377 class = LOCK_CLASS(lock); 2378 if (class->lc_flags & LC_SLEEPLOCK) 2379 lock_list = curthread->td_sleeplocks; 2380 else { 2381 if (witness_skipspin) 2382 return; 2383 lock_list = PCPU_GET(spinlocks); 2384 } 2385 instance = find_instance(lock_list, lock); 2386 if (instance == NULL) { 2387 kassert_panic("%s: lock (%s) %s not locked", __func__, 2388 class->lc_name, lock->lo_name); 2389 return; 2390 } 2391 *filep = instance->li_file; 2392 *linep = instance->li_line; 2393 } 2394 2395 void 2396 witness_restore(struct lock_object *lock, const char *file, int line) 2397 { 2398 struct lock_list_entry *lock_list; 2399 struct lock_instance *instance; 2400 struct lock_class *class; 2401 2402 /* 2403 * This function is used independently in locking code to deal with 2404 * Giant, SCHEDULER_STOPPED() check can be removed here after Giant 2405 * is gone. 2406 */ 2407 if (SCHEDULER_STOPPED()) 2408 return; 2409 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 2410 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED()) 2411 return; 2412 class = LOCK_CLASS(lock); 2413 if (class->lc_flags & LC_SLEEPLOCK) 2414 lock_list = curthread->td_sleeplocks; 2415 else { 2416 if (witness_skipspin) 2417 return; 2418 lock_list = PCPU_GET(spinlocks); 2419 } 2420 instance = find_instance(lock_list, lock); 2421 if (instance == NULL) 2422 kassert_panic("%s: lock (%s) %s not locked", __func__, 2423 class->lc_name, lock->lo_name); 2424 lock->lo_witness->w_file = file; 2425 lock->lo_witness->w_line = line; 2426 if (instance == NULL) 2427 return; 2428 instance->li_file = file; 2429 instance->li_line = line; 2430 } 2431 2432 static bool 2433 witness_find_instance(const struct lock_object *lock, 2434 struct lock_instance **instance) 2435 { 2436 #ifdef INVARIANT_SUPPORT 2437 struct lock_class *class; 2438 2439 if (lock->lo_witness == NULL || witness_watch < 1 || KERNEL_PANICKED()) 2440 return (false); 2441 class = LOCK_CLASS(lock); 2442 if ((class->lc_flags & LC_SLEEPLOCK) != 0) { 2443 *instance = find_instance(curthread->td_sleeplocks, lock); 2444 return (true); 2445 } else if ((class->lc_flags & LC_SPINLOCK) != 0) { 2446 *instance = find_instance(PCPU_GET(spinlocks), lock); 2447 return (true); 2448 } else { 2449 kassert_panic("Lock (%s) %s is not sleep or spin!", 2450 class->lc_name, lock->lo_name); 2451 return (false); 2452 } 2453 #else 2454 return (false); 2455 #endif 2456 } 2457 2458 void 2459 witness_assert(const struct lock_object *lock, int flags, const char *file, 2460 int line) 2461 { 2462 #ifdef INVARIANT_SUPPORT 2463 struct lock_instance *instance; 2464 struct lock_class *class; 2465 2466 if (!witness_find_instance(lock, &instance)) 2467 return; 2468 class = LOCK_CLASS(lock); 2469 switch (flags) { 2470 case LA_UNLOCKED: 2471 if (instance != NULL) 2472 kassert_panic("Lock (%s) %s locked @ %s:%d.", 2473 class->lc_name, lock->lo_name, 2474 fixup_filename(file), line); 2475 break; 2476 case LA_LOCKED: 2477 case LA_LOCKED | LA_RECURSED: 2478 case LA_LOCKED | LA_NOTRECURSED: 2479 case LA_SLOCKED: 2480 case LA_SLOCKED | LA_RECURSED: 2481 case LA_SLOCKED | LA_NOTRECURSED: 2482 case LA_XLOCKED: 2483 case LA_XLOCKED | LA_RECURSED: 2484 case LA_XLOCKED | LA_NOTRECURSED: 2485 if (instance == NULL) { 2486 kassert_panic("Lock (%s) %s not locked @ %s:%d.", 2487 class->lc_name, lock->lo_name, 2488 fixup_filename(file), line); 2489 break; 2490 } 2491 if ((flags & LA_XLOCKED) != 0 && 2492 (instance->li_flags & LI_EXCLUSIVE) == 0) 2493 kassert_panic( 2494 "Lock (%s) %s not exclusively locked @ %s:%d.", 2495 class->lc_name, lock->lo_name, 2496 fixup_filename(file), line); 2497 if ((flags & LA_SLOCKED) != 0 && 2498 (instance->li_flags & LI_EXCLUSIVE) != 0) 2499 kassert_panic( 2500 "Lock (%s) %s exclusively locked @ %s:%d.", 2501 class->lc_name, lock->lo_name, 2502 fixup_filename(file), line); 2503 if ((flags & LA_RECURSED) != 0 && 2504 (instance->li_flags & LI_RECURSEMASK) == 0) 2505 kassert_panic("Lock (%s) %s not recursed @ %s:%d.", 2506 class->lc_name, lock->lo_name, 2507 fixup_filename(file), line); 2508 if ((flags & LA_NOTRECURSED) != 0 && 2509 (instance->li_flags & LI_RECURSEMASK) != 0) 2510 kassert_panic("Lock (%s) %s recursed @ %s:%d.", 2511 class->lc_name, lock->lo_name, 2512 fixup_filename(file), line); 2513 break; 2514 default: 2515 kassert_panic("Invalid lock assertion at %s:%d.", 2516 fixup_filename(file), line); 2517 } 2518 #endif /* INVARIANT_SUPPORT */ 2519 } 2520 2521 /* 2522 * Checks the ownership of the lock by curthread, consulting the witness list. 2523 * Returns: 2524 * 0 if witness is disabled or did not work 2525 * -1 if not owned 2526 * 1 if owned 2527 */ 2528 int 2529 witness_is_owned(const struct lock_object *lock) 2530 { 2531 #ifdef INVARIANT_SUPPORT 2532 struct lock_instance *instance; 2533 2534 if (!witness_find_instance(lock, &instance)) 2535 return (0); 2536 return (instance == NULL ? -1 : 1); 2537 #else 2538 return (0); 2539 #endif 2540 } 2541 2542 static void 2543 witness_setflag(struct lock_object *lock, int flag, int set) 2544 { 2545 struct lock_list_entry *lock_list; 2546 struct lock_instance *instance; 2547 struct lock_class *class; 2548 2549 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED()) 2550 return; 2551 class = LOCK_CLASS(lock); 2552 if (class->lc_flags & LC_SLEEPLOCK) 2553 lock_list = curthread->td_sleeplocks; 2554 else { 2555 if (witness_skipspin) 2556 return; 2557 lock_list = PCPU_GET(spinlocks); 2558 } 2559 instance = find_instance(lock_list, lock); 2560 if (instance == NULL) { 2561 kassert_panic("%s: lock (%s) %s not locked", __func__, 2562 class->lc_name, lock->lo_name); 2563 return; 2564 } 2565 2566 if (set) 2567 instance->li_flags |= flag; 2568 else 2569 instance->li_flags &= ~flag; 2570 } 2571 2572 void 2573 witness_norelease(struct lock_object *lock) 2574 { 2575 2576 witness_setflag(lock, LI_NORELEASE, 1); 2577 } 2578 2579 void 2580 witness_releaseok(struct lock_object *lock) 2581 { 2582 2583 witness_setflag(lock, LI_NORELEASE, 0); 2584 } 2585 2586 #ifdef DDB 2587 static void 2588 witness_ddb_list(struct thread *td) 2589 { 2590 2591 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__)); 2592 KASSERT(kdb_active, ("%s: not in the debugger", __func__)); 2593 2594 if (witness_watch < 1) 2595 return; 2596 2597 witness_list_locks(&td->td_sleeplocks, db_printf); 2598 2599 /* 2600 * We only handle spinlocks if td == curthread. This is somewhat broken 2601 * if td is currently executing on some other CPU and holds spin locks 2602 * as we won't display those locks. If we had a MI way of getting 2603 * the per-cpu data for a given cpu then we could use 2604 * td->td_oncpu to get the list of spinlocks for this thread 2605 * and "fix" this. 2606 * 2607 * That still wouldn't really fix this unless we locked the scheduler 2608 * lock or stopped the other CPU to make sure it wasn't changing the 2609 * list out from under us. It is probably best to just not try to 2610 * handle threads on other CPU's for now. 2611 */ 2612 if (td == curthread && PCPU_GET(spinlocks) != NULL) 2613 witness_list_locks(PCPU_PTR(spinlocks), db_printf); 2614 } 2615 2616 DB_SHOW_COMMAND(locks, db_witness_list) 2617 { 2618 struct thread *td; 2619 2620 if (have_addr) 2621 td = db_lookup_thread(addr, true); 2622 else 2623 td = kdb_thread; 2624 witness_ddb_list(td); 2625 } 2626 2627 DB_SHOW_ALL_COMMAND(locks, db_witness_list_all) 2628 { 2629 struct thread *td; 2630 struct proc *p; 2631 2632 /* 2633 * It would be nice to list only threads and processes that actually 2634 * held sleep locks, but that information is currently not exported 2635 * by WITNESS. 2636 */ 2637 FOREACH_PROC_IN_SYSTEM(p) { 2638 if (!witness_proc_has_locks(p)) 2639 continue; 2640 FOREACH_THREAD_IN_PROC(p, td) { 2641 if (!witness_thread_has_locks(td)) 2642 continue; 2643 db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid, 2644 p->p_comm, td, td->td_tid); 2645 witness_ddb_list(td); 2646 if (db_pager_quit) 2647 return; 2648 } 2649 } 2650 } 2651 DB_SHOW_ALIAS_FLAGS(alllocks, db_witness_list_all, DB_CMD_MEMSAFE); 2652 2653 DB_SHOW_COMMAND_FLAGS(witness, db_witness_display, DB_CMD_MEMSAFE) 2654 { 2655 2656 witness_ddb_display(db_printf); 2657 } 2658 #endif 2659 2660 static void 2661 sbuf_print_witness_badstacks(struct sbuf *sb, size_t *oldidx) 2662 { 2663 struct witness_lock_order_data *data1, *data2, *tmp_data1, *tmp_data2; 2664 struct witness *tmp_w1, *tmp_w2, *w1, *w2; 2665 int generation, i, j; 2666 2667 tmp_data1 = NULL; 2668 tmp_data2 = NULL; 2669 tmp_w1 = NULL; 2670 tmp_w2 = NULL; 2671 2672 /* Allocate and init temporary storage space. */ 2673 tmp_w1 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO); 2674 tmp_w2 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO); 2675 tmp_data1 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 2676 M_WAITOK | M_ZERO); 2677 tmp_data2 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 2678 M_WAITOK | M_ZERO); 2679 stack_zero(&tmp_data1->wlod_stack); 2680 stack_zero(&tmp_data2->wlod_stack); 2681 2682 restart: 2683 mtx_lock_spin(&w_mtx); 2684 generation = w_generation; 2685 mtx_unlock_spin(&w_mtx); 2686 sbuf_printf(sb, "Number of known direct relationships is %d\n", 2687 w_lohash.wloh_count); 2688 for (i = 1; i < w_max_used_index; i++) { 2689 mtx_lock_spin(&w_mtx); 2690 if (generation != w_generation) { 2691 mtx_unlock_spin(&w_mtx); 2692 2693 /* The graph has changed, try again. */ 2694 *oldidx = 0; 2695 sbuf_clear(sb); 2696 goto restart; 2697 } 2698 2699 w1 = &w_data[i]; 2700 if (w1->w_reversed == 0) { 2701 mtx_unlock_spin(&w_mtx); 2702 continue; 2703 } 2704 2705 /* Copy w1 locally so we can release the spin lock. */ 2706 *tmp_w1 = *w1; 2707 mtx_unlock_spin(&w_mtx); 2708 2709 if (tmp_w1->w_reversed == 0) 2710 continue; 2711 for (j = 1; j < w_max_used_index; j++) { 2712 if ((w_rmatrix[i][j] & WITNESS_REVERSAL) == 0 || i > j) 2713 continue; 2714 2715 mtx_lock_spin(&w_mtx); 2716 if (generation != w_generation) { 2717 mtx_unlock_spin(&w_mtx); 2718 2719 /* The graph has changed, try again. */ 2720 *oldidx = 0; 2721 sbuf_clear(sb); 2722 goto restart; 2723 } 2724 2725 w2 = &w_data[j]; 2726 data1 = witness_lock_order_get(w1, w2); 2727 data2 = witness_lock_order_get(w2, w1); 2728 2729 /* 2730 * Copy information locally so we can release the 2731 * spin lock. 2732 */ 2733 *tmp_w2 = *w2; 2734 2735 if (data1) { 2736 stack_zero(&tmp_data1->wlod_stack); 2737 stack_copy(&data1->wlod_stack, 2738 &tmp_data1->wlod_stack); 2739 } 2740 if (data2 && data2 != data1) { 2741 stack_zero(&tmp_data2->wlod_stack); 2742 stack_copy(&data2->wlod_stack, 2743 &tmp_data2->wlod_stack); 2744 } 2745 mtx_unlock_spin(&w_mtx); 2746 2747 if (blessed(tmp_w1, tmp_w2)) 2748 continue; 2749 2750 sbuf_printf(sb, 2751 "\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n", 2752 tmp_w1->w_name, tmp_w1->w_class->lc_name, 2753 tmp_w2->w_name, tmp_w2->w_class->lc_name); 2754 if (data1) { 2755 sbuf_printf(sb, 2756 "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n", 2757 tmp_w1->w_name, tmp_w1->w_class->lc_name, 2758 tmp_w2->w_name, tmp_w2->w_class->lc_name); 2759 stack_sbuf_print(sb, &tmp_data1->wlod_stack); 2760 sbuf_printf(sb, "\n"); 2761 } 2762 if (data2 && data2 != data1) { 2763 sbuf_printf(sb, 2764 "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n", 2765 tmp_w2->w_name, tmp_w2->w_class->lc_name, 2766 tmp_w1->w_name, tmp_w1->w_class->lc_name); 2767 stack_sbuf_print(sb, &tmp_data2->wlod_stack); 2768 sbuf_printf(sb, "\n"); 2769 } 2770 } 2771 } 2772 mtx_lock_spin(&w_mtx); 2773 if (generation != w_generation) { 2774 mtx_unlock_spin(&w_mtx); 2775 2776 /* 2777 * The graph changed while we were printing stack data, 2778 * try again. 2779 */ 2780 *oldidx = 0; 2781 sbuf_clear(sb); 2782 goto restart; 2783 } 2784 mtx_unlock_spin(&w_mtx); 2785 2786 /* Free temporary storage space. */ 2787 free(tmp_data1, M_TEMP); 2788 free(tmp_data2, M_TEMP); 2789 free(tmp_w1, M_TEMP); 2790 free(tmp_w2, M_TEMP); 2791 } 2792 2793 static int 2794 sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS) 2795 { 2796 struct sbuf *sb; 2797 int error; 2798 2799 if (witness_watch < 1) { 2800 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning)); 2801 return (error); 2802 } 2803 if (witness_cold) { 2804 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold)); 2805 return (error); 2806 } 2807 error = 0; 2808 sb = sbuf_new(NULL, NULL, badstack_sbuf_size, SBUF_AUTOEXTEND); 2809 if (sb == NULL) 2810 return (ENOMEM); 2811 2812 sbuf_print_witness_badstacks(sb, &req->oldidx); 2813 2814 sbuf_finish(sb); 2815 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1); 2816 sbuf_delete(sb); 2817 2818 return (error); 2819 } 2820 2821 #ifdef DDB 2822 static int 2823 sbuf_db_printf_drain(void *arg __unused, const char *data, int len) 2824 { 2825 2826 return (db_printf("%.*s", len, data)); 2827 } 2828 2829 DB_SHOW_COMMAND_FLAGS(badstacks, db_witness_badstacks, DB_CMD_MEMSAFE) 2830 { 2831 struct sbuf sb; 2832 char buffer[128]; 2833 size_t dummy; 2834 2835 sbuf_new(&sb, buffer, sizeof(buffer), SBUF_FIXEDLEN); 2836 sbuf_set_drain(&sb, sbuf_db_printf_drain, NULL); 2837 sbuf_print_witness_badstacks(&sb, &dummy); 2838 sbuf_finish(&sb); 2839 } 2840 #endif 2841 2842 static int 2843 sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS) 2844 { 2845 static const struct { 2846 enum witness_channel channel; 2847 const char *name; 2848 } channels[] = { 2849 { WITNESS_CONSOLE, "console" }, 2850 { WITNESS_LOG, "log" }, 2851 { WITNESS_NONE, "none" }, 2852 }; 2853 char buf[16]; 2854 u_int i; 2855 int error; 2856 2857 buf[0] = '\0'; 2858 for (i = 0; i < nitems(channels); i++) 2859 if (witness_channel == channels[i].channel) { 2860 snprintf(buf, sizeof(buf), "%s", channels[i].name); 2861 break; 2862 } 2863 2864 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 2865 if (error != 0 || req->newptr == NULL) 2866 return (error); 2867 2868 error = EINVAL; 2869 for (i = 0; i < nitems(channels); i++) 2870 if (strcmp(channels[i].name, buf) == 0) { 2871 witness_channel = channels[i].channel; 2872 error = 0; 2873 break; 2874 } 2875 return (error); 2876 } 2877 2878 static int 2879 sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS) 2880 { 2881 struct witness *w; 2882 struct sbuf *sb; 2883 int error; 2884 2885 #ifdef __i386__ 2886 error = SYSCTL_OUT(req, w_notallowed, sizeof(w_notallowed)); 2887 return (error); 2888 #endif 2889 2890 if (witness_watch < 1) { 2891 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning)); 2892 return (error); 2893 } 2894 if (witness_cold) { 2895 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold)); 2896 return (error); 2897 } 2898 error = 0; 2899 2900 error = sysctl_wire_old_buffer(req, 0); 2901 if (error != 0) 2902 return (error); 2903 sb = sbuf_new_for_sysctl(NULL, NULL, FULLGRAPH_SBUF_SIZE, req); 2904 if (sb == NULL) 2905 return (ENOMEM); 2906 sbuf_printf(sb, "\n"); 2907 2908 mtx_lock_spin(&w_mtx); 2909 STAILQ_FOREACH(w, &w_all, w_list) 2910 w->w_displayed = 0; 2911 STAILQ_FOREACH(w, &w_all, w_list) 2912 witness_add_fullgraph(sb, w); 2913 mtx_unlock_spin(&w_mtx); 2914 2915 /* 2916 * Close the sbuf and return to userland. 2917 */ 2918 error = sbuf_finish(sb); 2919 sbuf_delete(sb); 2920 2921 return (error); 2922 } 2923 2924 static int 2925 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS) 2926 { 2927 int error, value; 2928 2929 value = witness_watch; 2930 error = sysctl_handle_int(oidp, &value, 0, req); 2931 if (error != 0 || req->newptr == NULL) 2932 return (error); 2933 if (value > 1 || value < -1 || 2934 (witness_watch == -1 && value != witness_watch)) 2935 return (EINVAL); 2936 witness_watch = value; 2937 return (0); 2938 } 2939 2940 static void 2941 witness_add_fullgraph(struct sbuf *sb, struct witness *w) 2942 { 2943 int i; 2944 2945 if (w->w_displayed != 0 || (w->w_file == NULL && w->w_line == 0)) 2946 return; 2947 w->w_displayed = 1; 2948 2949 WITNESS_INDEX_ASSERT(w->w_index); 2950 for (i = 1; i <= w_max_used_index; i++) { 2951 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) { 2952 sbuf_printf(sb, "\"%s\",\"%s\"\n", w->w_name, 2953 w_data[i].w_name); 2954 witness_add_fullgraph(sb, &w_data[i]); 2955 } 2956 } 2957 } 2958 2959 /* 2960 * A simple hash function. Takes a key pointer and a key size. If size == 0, 2961 * interprets the key as a string and reads until the null 2962 * terminator. Otherwise, reads the first size bytes. Returns an unsigned 32-bit 2963 * hash value computed from the key. 2964 */ 2965 static uint32_t 2966 witness_hash_djb2(const uint8_t *key, uint32_t size) 2967 { 2968 unsigned int hash = 5381; 2969 int i; 2970 2971 /* hash = hash * 33 + key[i] */ 2972 if (size) 2973 for (i = 0; i < size; i++) 2974 hash = ((hash << 5) + hash) + (unsigned int)key[i]; 2975 else 2976 for (i = 0; key[i] != 0; i++) 2977 hash = ((hash << 5) + hash) + (unsigned int)key[i]; 2978 2979 return (hash); 2980 } 2981 2982 /* 2983 * Initializes the two witness hash tables. Called exactly once from 2984 * witness_initialize(). 2985 */ 2986 static void 2987 witness_init_hash_tables(void) 2988 { 2989 int i; 2990 2991 MPASS(witness_cold); 2992 2993 /* Initialize the hash tables. */ 2994 for (i = 0; i < WITNESS_HASH_SIZE; i++) 2995 w_hash.wh_array[i] = NULL; 2996 2997 w_hash.wh_size = WITNESS_HASH_SIZE; 2998 w_hash.wh_count = 0; 2999 3000 /* Initialize the lock order data hash. */ 3001 w_lofree = NULL; 3002 for (i = 0; i < WITNESS_LO_DATA_COUNT; i++) { 3003 memset(&w_lodata[i], 0, sizeof(w_lodata[i])); 3004 w_lodata[i].wlod_next = w_lofree; 3005 w_lofree = &w_lodata[i]; 3006 } 3007 w_lohash.wloh_size = WITNESS_LO_HASH_SIZE; 3008 w_lohash.wloh_count = 0; 3009 for (i = 0; i < WITNESS_LO_HASH_SIZE; i++) 3010 w_lohash.wloh_array[i] = NULL; 3011 } 3012 3013 static struct witness * 3014 witness_hash_get(const char *key) 3015 { 3016 struct witness *w; 3017 uint32_t hash; 3018 3019 MPASS(key != NULL); 3020 if (witness_cold == 0) 3021 mtx_assert(&w_mtx, MA_OWNED); 3022 hash = witness_hash_djb2(key, 0) % w_hash.wh_size; 3023 w = w_hash.wh_array[hash]; 3024 while (w != NULL) { 3025 if (strcmp(w->w_name, key) == 0) 3026 goto out; 3027 w = w->w_hash_next; 3028 } 3029 3030 out: 3031 return (w); 3032 } 3033 3034 static void 3035 witness_hash_put(struct witness *w) 3036 { 3037 uint32_t hash; 3038 3039 MPASS(w != NULL); 3040 MPASS(w->w_name != NULL); 3041 if (witness_cold == 0) 3042 mtx_assert(&w_mtx, MA_OWNED); 3043 KASSERT(witness_hash_get(w->w_name) == NULL, 3044 ("%s: trying to add a hash entry that already exists!", __func__)); 3045 KASSERT(w->w_hash_next == NULL, 3046 ("%s: w->w_hash_next != NULL", __func__)); 3047 3048 hash = witness_hash_djb2(w->w_name, 0) % w_hash.wh_size; 3049 w->w_hash_next = w_hash.wh_array[hash]; 3050 w_hash.wh_array[hash] = w; 3051 w_hash.wh_count++; 3052 } 3053 3054 static struct witness_lock_order_data * 3055 witness_lock_order_get(struct witness *parent, struct witness *child) 3056 { 3057 struct witness_lock_order_data *data = NULL; 3058 struct witness_lock_order_key key; 3059 unsigned int hash; 3060 3061 MPASS(parent != NULL && child != NULL); 3062 key.from = parent->w_index; 3063 key.to = child->w_index; 3064 WITNESS_INDEX_ASSERT(key.from); 3065 WITNESS_INDEX_ASSERT(key.to); 3066 if ((w_rmatrix[parent->w_index][child->w_index] 3067 & WITNESS_LOCK_ORDER_KNOWN) == 0) 3068 goto out; 3069 3070 hash = witness_hash_djb2((const char*)&key, 3071 sizeof(key)) % w_lohash.wloh_size; 3072 data = w_lohash.wloh_array[hash]; 3073 while (data != NULL) { 3074 if (witness_lock_order_key_equal(&data->wlod_key, &key)) 3075 break; 3076 data = data->wlod_next; 3077 } 3078 3079 out: 3080 return (data); 3081 } 3082 3083 /* 3084 * Verify that parent and child have a known relationship, are not the same, 3085 * and child is actually a child of parent. This is done without w_mtx 3086 * to avoid contention in the common case. 3087 */ 3088 static int 3089 witness_lock_order_check(struct witness *parent, struct witness *child) 3090 { 3091 3092 if (parent != child && 3093 w_rmatrix[parent->w_index][child->w_index] 3094 & WITNESS_LOCK_ORDER_KNOWN && 3095 isitmychild(parent, child)) 3096 return (1); 3097 3098 return (0); 3099 } 3100 3101 static int 3102 witness_lock_order_add(struct witness *parent, struct witness *child) 3103 { 3104 struct witness_lock_order_data *data = NULL; 3105 struct witness_lock_order_key key; 3106 unsigned int hash; 3107 3108 MPASS(parent != NULL && child != NULL); 3109 key.from = parent->w_index; 3110 key.to = child->w_index; 3111 WITNESS_INDEX_ASSERT(key.from); 3112 WITNESS_INDEX_ASSERT(key.to); 3113 if (w_rmatrix[parent->w_index][child->w_index] 3114 & WITNESS_LOCK_ORDER_KNOWN) 3115 return (1); 3116 3117 hash = witness_hash_djb2((const char*)&key, 3118 sizeof(key)) % w_lohash.wloh_size; 3119 w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN; 3120 data = w_lofree; 3121 if (data == NULL) 3122 return (0); 3123 w_lofree = data->wlod_next; 3124 data->wlod_next = w_lohash.wloh_array[hash]; 3125 data->wlod_key = key; 3126 w_lohash.wloh_array[hash] = data; 3127 w_lohash.wloh_count++; 3128 stack_save(&data->wlod_stack); 3129 return (1); 3130 } 3131 3132 /* Call this whenever the structure of the witness graph changes. */ 3133 static void 3134 witness_increment_graph_generation(void) 3135 { 3136 3137 if (witness_cold == 0) 3138 mtx_assert(&w_mtx, MA_OWNED); 3139 w_generation++; 3140 } 3141 3142 static int 3143 witness_output_drain(void *arg __unused, const char *data, int len) 3144 { 3145 3146 witness_output("%.*s", len, data); 3147 return (len); 3148 } 3149 3150 static void 3151 witness_debugger(int cond, const char *msg) 3152 { 3153 char buf[32]; 3154 struct sbuf sb; 3155 struct stack st; 3156 3157 if (!cond) 3158 return; 3159 3160 if (witness_trace) { 3161 sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN); 3162 sbuf_set_drain(&sb, witness_output_drain, NULL); 3163 3164 stack_save(&st); 3165 witness_output("stack backtrace:\n"); 3166 stack_sbuf_print_ddb(&sb, &st); 3167 3168 sbuf_finish(&sb); 3169 } 3170 3171 witness_enter_debugger(msg); 3172 } 3173 3174 static void 3175 witness_enter_debugger(const char *msg) 3176 { 3177 #ifdef KDB 3178 if (witness_kdb) 3179 kdb_enter(KDB_WHY_WITNESS, msg); 3180 #endif 3181 } 3182