sys/kern/subr_witness.c

   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         { "udp", &lock_class_mtx_sleep },
 568         { "udpinp", &lock_class_rw },
 569         { "so_snd", &lock_class_mtx_sleep },
 570         { NULL, NULL },
 571         /*
 572          * TCP/IP
 573          */
 574         { "tcp", &lock_class_mtx_sleep },
 575         { "tcpinp", &lock_class_rw },
 576         { "so_snd", &lock_class_mtx_sleep },
 577         { NULL, NULL },
 578         /*
 579          * BPF
 580          */
 581         { "bpf global lock", &lock_class_sx },
 582         { "bpf cdev lock", &lock_class_mtx_sleep },
 583         { NULL, NULL },
 584         /*
 585          * NFS server
 586          */
 587         { "nfsd_mtx", &lock_class_mtx_sleep },
 588         { "so_snd", &lock_class_mtx_sleep },
 589         { NULL, NULL },
 590
 591         /*
 592          * IEEE 802.11
 593          */
 594         { "802.11 com lock", &lock_class_mtx_sleep},
 595         { NULL, NULL },
 596         /*
 597          * Network drivers
 598          */
 599         { "network driver", &lock_class_mtx_sleep},
 600         { NULL, NULL },
 601
 602         /*
 603          * Netgraph
 604          */
 605         { "ng_node", &lock_class_mtx_sleep },
 606         { "ng_worklist", &lock_class_mtx_sleep },
 607         { NULL, NULL },
 608         /*
 609          * CDEV
 610          */
 611         { "vm map (system)", &lock_class_mtx_sleep },
 612         { "vnode interlock", &lock_class_mtx_sleep },
 613         { "cdev", &lock_class_mtx_sleep },
 614         { "devthrd", &lock_class_mtx_sleep },
 615         { NULL, NULL },
 616         /*
 617          * VM
 618          */
 619         { "vm map (user)", &lock_class_sx },
 620         { "vm object", &lock_class_rw },
 621         { "vm page", &lock_class_mtx_sleep },
 622         { "pmap pv global", &lock_class_rw },
 623         { "pmap", &lock_class_mtx_sleep },
 624         { "pmap pv list", &lock_class_rw },
 625         { "vm page free queue", &lock_class_mtx_sleep },
 626         { "vm pagequeue", &lock_class_mtx_sleep },
 627         { NULL, NULL },
 628         /*
 629          * kqueue/VFS interaction
 630          */
 631         { "kqueue", &lock_class_mtx_sleep },
 632         { "struct mount mtx", &lock_class_mtx_sleep },
 633         { "vnode interlock", &lock_class_mtx_sleep },
 634         { NULL, NULL },
 635         /*
 636          * VFS namecache
 637          */
 638         { "ncvn", &lock_class_mtx_sleep },
 639         { "ncbuc", &lock_class_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 /*
 746  * This global is set to 0 once it becomes safe to use the witness code.
 747  */
 748 static int witness_cold = 1;
 749
 750 /*
 751  * This global is set to 1 once the static lock orders have been enrolled
 752  * so that a warning can be issued for any spin locks enrolled later.
 753  */
 754 static int witness_spin_warn = 0;
 755
 756 /* Trim useless garbage from filenames. */
 757 static const char *
 758 fixup_filename(const char *file)
 759 {
 760
 761         if (file == NULL)
 762                 return (NULL);
 763         while (strncmp(file, "../", 3) == 0)
 764                 file += 3;
 765         return (file);
 766 }
 767
 768 /*
 769  * Calculate the size of early witness structures.
 770  */
 771 int
 772 witness_startup_count(void)
 773 {
 774         int sz;
 775
 776         sz = sizeof(struct witness) * witness_count;
 777         sz += sizeof(*w_rmatrix) * (witness_count + 1);
 778         sz += sizeof(*w_rmatrix[0]) * (witness_count + 1) *
 779             (witness_count + 1);
 780
 781         return (sz);
 782 }
 783
 784 /*
 785  * The WITNESS-enabled diagnostic code.  Note that the witness code does
 786  * assume that the early boot is single-threaded at least until after this
 787  * routine is completed.
 788  */
 789 void
 790 witness_startup(void *mem)
 791 {
 792         struct lock_object *lock;
 793         struct witness_order_list_entry *order;
 794         struct witness *w, *w1;
 795         uintptr_t p;
 796         int i;
 797
 798         p = (uintptr_t)mem;
 799         w_data = (void *)p;
 800         p += sizeof(struct witness) * witness_count;
 801
 802         w_rmatrix = (void *)p;
 803         p += sizeof(*w_rmatrix) * (witness_count + 1);
 804
 805         for (i = 0; i < witness_count + 1; i++) {
 806                 w_rmatrix[i] = (void *)p;
 807                 p += sizeof(*w_rmatrix[i]) * (witness_count + 1);
 808         }
 809         badstack_sbuf_size = witness_count * 256;
 810
 811         /*
 812          * We have to release Giant before initializing its witness
 813          * structure so that WITNESS doesn't get confused.
 814          */
 815         mtx_unlock(&Giant);
 816         mtx_assert(&Giant, MA_NOTOWNED);
 817
 818         CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
 819         mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET |
 820             MTX_NOWITNESS | MTX_NOPROFILE);
 821         for (i = witness_count - 1; i >= 0; i--) {
 822                 w = &w_data[i];
 823                 memset(w, 0, sizeof(*w));
 824                 w_data[i].w_index = i;  /* Witness index never changes. */
 825                 witness_free(w);
 826         }
 827         KASSERT(STAILQ_FIRST(&w_free)->w_index == 0,
 828             ("%s: Invalid list of free witness objects", __func__));
 829
 830         /* Witness with index 0 is not used to aid in debugging. */
 831         STAILQ_REMOVE_HEAD(&w_free, w_list);
 832         w_free_cnt--;
 833
 834         for (i = 0; i < witness_count; i++) {
 835                 memset(w_rmatrix[i], 0, sizeof(*w_rmatrix[i]) *
 836                     (witness_count + 1));
 837         }
 838
 839         for (i = 0; i < LOCK_CHILDCOUNT; i++)
 840                 witness_lock_list_free(&w_locklistdata[i]);
 841         witness_init_hash_tables();
 842
 843         /* First add in all the specified order lists. */
 844         for (order = order_lists; order->w_name != NULL; order++) {
 845                 w = enroll(order->w_name, order->w_class);
 846                 if (w == NULL)
 847                         continue;
 848                 w->w_file = "order list";
 849                 for (order++; order->w_name != NULL; order++) {
 850                         w1 = enroll(order->w_name, order->w_class);
 851                         if (w1 == NULL)
 852                                 continue;
 853                         w1->w_file = "order list";
 854                         itismychild(w, w1);
 855                         w = w1;
 856                 }
 857         }
 858         witness_spin_warn = 1;
 859
 860         /* Iterate through all locks and add them to witness. */
 861         for (i = 0; pending_locks[i].wh_lock != NULL; i++) {
 862                 lock = pending_locks[i].wh_lock;
 863                 KASSERT(lock->lo_flags & LO_WITNESS,
 864                     ("%s: lock %s is on pending list but not LO_WITNESS",
 865                     __func__, lock->lo_name));
 866                 lock->lo_witness = enroll(pending_locks[i].wh_type,
 867                     LOCK_CLASS(lock));
 868         }
 869
 870         /* Mark the witness code as being ready for use. */
 871         witness_cold = 0;
 872
 873         mtx_lock(&Giant);
 874 }
 875
 876 void
 877 witness_init(struct lock_object *lock, const char *type)
 878 {
 879         struct lock_class *class;
 880
 881         /* Various sanity checks. */
 882         class = LOCK_CLASS(lock);
 883         if ((lock->lo_flags & LO_RECURSABLE) != 0 &&
 884             (class->lc_flags & LC_RECURSABLE) == 0)
 885                 kassert_panic("%s: lock (%s) %s can not be recursable",
 886                     __func__, class->lc_name, lock->lo_name);
 887         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 888             (class->lc_flags & LC_SLEEPABLE) == 0)
 889                 kassert_panic("%s: lock (%s) %s can not be sleepable",
 890                     __func__, class->lc_name, lock->lo_name);
 891         if ((lock->lo_flags & LO_UPGRADABLE) != 0 &&
 892             (class->lc_flags & LC_UPGRADABLE) == 0)
 893                 kassert_panic("%s: lock (%s) %s can not be upgradable",
 894                     __func__, class->lc_name, lock->lo_name);
 895
 896         /*
 897          * If we shouldn't watch this lock, then just clear lo_witness.
 898          * Otherwise, if witness_cold is set, then it is too early to
 899          * enroll this lock, so defer it to witness_initialize() by adding
 900          * it to the pending_locks list.  If it is not too early, then enroll
 901          * the lock now.
 902          */
 903         if (witness_watch < 1 || KERNEL_PANICKED() ||
 904             (lock->lo_flags & LO_WITNESS) == 0)
 905                 lock->lo_witness = NULL;
 906         else if (witness_cold) {
 907                 pending_locks[pending_cnt].wh_lock = lock;
 908                 pending_locks[pending_cnt++].wh_type = type;
 909                 if (pending_cnt > WITNESS_PENDLIST)
 910                         panic("%s: pending locks list is too small, "
 911                             "increase WITNESS_PENDLIST\n",
 912                             __func__);
 913         } else
 914                 lock->lo_witness = enroll(type, class);
 915 }
 916
 917 void
 918 witness_destroy(struct lock_object *lock)
 919 {
 920         struct lock_class *class;
 921         struct witness *w;
 922
 923         class = LOCK_CLASS(lock);
 924
 925         if (witness_cold)
 926                 panic("lock (%s) %s destroyed while witness_cold",
 927                     class->lc_name, lock->lo_name);
 928
 929         /* XXX: need to verify that no one holds the lock */
 930         if ((lock->lo_flags & LO_WITNESS) == 0 || lock->lo_witness == NULL)
 931                 return;
 932         w = lock->lo_witness;
 933
 934         mtx_lock_spin(&w_mtx);
 935         MPASS(w->w_refcount > 0);
 936         w->w_refcount--;
 937
 938         if (w->w_refcount == 0)
 939                 depart(w);
 940         mtx_unlock_spin(&w_mtx);
 941 }
 942
 943 #ifdef DDB
 944 static void
 945 witness_ddb_compute_levels(void)
 946 {
 947         struct witness *w;
 948
 949         /*
 950          * First clear all levels.
 951          */
 952         STAILQ_FOREACH(w, &w_all, w_list)
 953                 w->w_ddb_level = -1;
 954
 955         /*
 956          * Look for locks with no parents and level all their descendants.
 957          */
 958         STAILQ_FOREACH(w, &w_all, w_list) {
 959                 /* If the witness has ancestors (is not a root), skip it. */
 960                 if (w->w_num_ancestors > 0)
 961                         continue;
 962                 witness_ddb_level_descendants(w, 0);
 963         }
 964 }
 965
 966 static void
 967 witness_ddb_level_descendants(struct witness *w, int l)
 968 {
 969         int i;
 970
 971         if (w->w_ddb_level >= l)
 972                 return;
 973
 974         w->w_ddb_level = l;
 975         l++;
 976
 977         for (i = 1; i <= w_max_used_index; i++) {
 978                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
 979                         witness_ddb_level_descendants(&w_data[i], l);
 980         }
 981 }
 982
 983 static void
 984 witness_ddb_display_descendants(int(*prnt)(const char *fmt, ...),
 985     struct witness *w, int indent)
 986 {
 987         int i;
 988
 989         for (i = 0; i < indent; i++)
 990                 prnt(" ");
 991         prnt("%s (type: %s, depth: %d, active refs: %d)",
 992              w->w_name, w->w_class->lc_name,
 993              w->w_ddb_level, w->w_refcount);
 994         if (w->w_displayed) {
 995                 prnt(" -- (already displayed)\n");
 996                 return;
 997         }
 998         w->w_displayed = 1;
 999         if (w->w_file != NULL && w->w_line != 0)
1000                 prnt(" -- last acquired @ %s:%d\n", fixup_filename(w->w_file),
1001                     w->w_line);
1002         else
1003                 prnt(" -- never acquired\n");
1004         indent++;
1005         WITNESS_INDEX_ASSERT(w->w_index);
1006         for (i = 1; i <= w_max_used_index; i++) {
1007                 if (db_pager_quit)
1008                         return;
1009                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
1010                         witness_ddb_display_descendants(prnt, &w_data[i],
1011                             indent);
1012         }
1013 }
1014
1015 static void
1016 witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
1017     struct witness_list *list)
1018 {
1019         struct witness *w;
1020
1021         STAILQ_FOREACH(w, list, w_typelist) {
1022                 if (w->w_file == NULL || w->w_ddb_level > 0)
1023                         continue;
1024
1025                 /* This lock has no anscestors - display its descendants. */
1026                 witness_ddb_display_descendants(prnt, w, 0);
1027                 if (db_pager_quit)
1028                         return;
1029         }
1030 }
1031
1032 static void
1033 witness_ddb_display(int(*prnt)(const char *fmt, ...))
1034 {
1035         struct witness *w;
1036
1037         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
1038         witness_ddb_compute_levels();
1039
1040         /* Clear all the displayed flags. */
1041         STAILQ_FOREACH(w, &w_all, w_list)
1042                 w->w_displayed = 0;
1043
1044         /*
1045          * First, handle sleep locks which have been acquired at least
1046          * once.
1047          */
1048         prnt("Sleep locks:\n");
1049         witness_ddb_display_list(prnt, &w_sleep);
1050         if (db_pager_quit)
1051                 return;
1052
1053         /*
1054          * Now do spin locks which have been acquired at least once.
1055          */
1056         prnt("\nSpin locks:\n");
1057         witness_ddb_display_list(prnt, &w_spin);
1058         if (db_pager_quit)
1059                 return;
1060
1061         /*
1062          * Finally, any locks which have not been acquired yet.
1063          */
1064         prnt("\nLocks which were never acquired:\n");
1065         STAILQ_FOREACH(w, &w_all, w_list) {
1066                 if (w->w_file != NULL || w->w_refcount == 0)
1067                         continue;
1068                 prnt("%s (type: %s, depth: %d)\n", w->w_name,
1069                     w->w_class->lc_name, w->w_ddb_level);
1070                 if (db_pager_quit)
1071                         return;
1072         }
1073 }
1074 #endif /* DDB */
1075
1076 int
1077 witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
1078 {
1079
1080         if (witness_watch == -1 || KERNEL_PANICKED())
1081                 return (0);
1082
1083         /* Require locks that witness knows about. */
1084         if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL ||
1085             lock2->lo_witness == NULL)
1086                 return (EINVAL);
1087
1088         mtx_assert(&w_mtx, MA_NOTOWNED);
1089         mtx_lock_spin(&w_mtx);
1090
1091         /*
1092          * If we already have either an explicit or implied lock order that
1093          * is the other way around, then return an error.
1094          */
1095         if (witness_watch &&
1096             isitmydescendant(lock2->lo_witness, lock1->lo_witness)) {
1097                 mtx_unlock_spin(&w_mtx);
1098                 return (EDOOFUS);
1099         }
1100
1101         /* Try to add the new order. */
1102         CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
1103             lock2->lo_witness->w_name, lock1->lo_witness->w_name);
1104         itismychild(lock1->lo_witness, lock2->lo_witness);
1105         mtx_unlock_spin(&w_mtx);
1106         return (0);
1107 }
1108
1109 void
1110 witness_checkorder(struct lock_object *lock, int flags, const char *file,
1111     int line, struct lock_object *interlock)
1112 {
1113         struct lock_list_entry *lock_list, *lle;
1114         struct lock_instance *lock1, *lock2, *plock;
1115         struct lock_class *class, *iclass;
1116         struct witness *w, *w1;
1117         struct thread *td;
1118         int i, j;
1119
1120         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL ||
1121             KERNEL_PANICKED())
1122                 return;
1123
1124         w = lock->lo_witness;
1125         class = LOCK_CLASS(lock);
1126         td = curthread;
1127
1128         if (class->lc_flags & LC_SLEEPLOCK) {
1129                 /*
1130                  * Since spin locks include a critical section, this check
1131                  * implicitly enforces a lock order of all sleep locks before
1132                  * all spin locks.
1133                  */
1134                 if (td->td_critnest != 0 && !kdb_active)
1135                         kassert_panic("acquiring blockable sleep lock with "
1136                             "spinlock or critical section held (%s) %s @ %s:%d",
1137                             class->lc_name, lock->lo_name,
1138                             fixup_filename(file), line);
1139
1140                 /*
1141                  * If this is the first lock acquired then just return as
1142                  * no order checking is needed.
1143                  */
1144                 lock_list = td->td_sleeplocks;
1145                 if (lock_list == NULL || lock_list->ll_count == 0)
1146                         return;
1147         } else {
1148                 /*
1149                  * If this is the first lock, just return as no order
1150                  * checking is needed.  Avoid problems with thread
1151                  * migration pinning the thread while checking if
1152                  * spinlocks are held.  If at least one spinlock is held
1153                  * the thread is in a safe path and it is allowed to
1154                  * unpin it.
1155                  */
1156                 sched_pin();
1157                 lock_list = PCPU_GET(spinlocks);
1158                 if (lock_list == NULL || lock_list->ll_count == 0) {
1159                         sched_unpin();
1160                         return;
1161                 }
1162                 sched_unpin();
1163         }
1164
1165         /*
1166          * Check to see if we are recursing on a lock we already own.  If
1167          * so, make sure that we don't mismatch exclusive and shared lock
1168          * acquires.
1169          */
1170         lock1 = find_instance(lock_list, lock);
1171         if (lock1 != NULL) {
1172                 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 &&
1173                     (flags & LOP_EXCLUSIVE) == 0) {
1174                         witness_output("shared lock of (%s) %s @ %s:%d\n",
1175                             class->lc_name, lock->lo_name,
1176                             fixup_filename(file), line);
1177                         witness_output("while exclusively locked from %s:%d\n",
1178                             fixup_filename(lock1->li_file), lock1->li_line);
1179                         kassert_panic("excl->share");
1180                 }
1181                 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
1182                     (flags & LOP_EXCLUSIVE) != 0) {
1183                         witness_output("exclusive lock of (%s) %s @ %s:%d\n",
1184                             class->lc_name, lock->lo_name,
1185                             fixup_filename(file), line);
1186                         witness_output("while share locked from %s:%d\n",
1187                             fixup_filename(lock1->li_file), lock1->li_line);
1188                         kassert_panic("share->excl");
1189                 }
1190                 return;
1191         }
1192
1193         /* Warn if the interlock is not locked exactly once. */
1194         if (interlock != NULL) {
1195                 iclass = LOCK_CLASS(interlock);
1196                 lock1 = find_instance(lock_list, interlock);
1197                 if (lock1 == NULL)
1198                         kassert_panic("interlock (%s) %s not locked @ %s:%d",
1199                             iclass->lc_name, interlock->lo_name,
1200                             fixup_filename(file), line);
1201                 else if ((lock1->li_flags & LI_RECURSEMASK) != 0)
1202                         kassert_panic("interlock (%s) %s recursed @ %s:%d",
1203                             iclass->lc_name, interlock->lo_name,
1204                             fixup_filename(file), line);
1205         }
1206
1207         /*
1208          * Find the previously acquired lock, but ignore interlocks.
1209          */
1210         plock = &lock_list->ll_children[lock_list->ll_count - 1];
1211         if (interlock != NULL && plock->li_lock == interlock) {
1212                 if (lock_list->ll_count > 1)
1213                         plock =
1214                             &lock_list->ll_children[lock_list->ll_count - 2];
1215                 else {
1216                         lle = lock_list->ll_next;
1217
1218                         /*
1219                          * The interlock is the only lock we hold, so
1220                          * simply return.
1221                          */
1222                         if (lle == NULL)
1223                                 return;
1224                         plock = &lle->ll_children[lle->ll_count - 1];
1225                 }
1226         }
1227
1228         /*
1229          * Try to perform most checks without a lock.  If this succeeds we
1230          * can skip acquiring the lock and return success.  Otherwise we redo
1231          * the check with the lock held to handle races with concurrent updates.
1232          */
1233         w1 = plock->li_lock->lo_witness;
1234         if (witness_lock_order_check(w1, w))
1235                 return;
1236
1237         mtx_lock_spin(&w_mtx);
1238         if (witness_lock_order_check(w1, w)) {
1239                 mtx_unlock_spin(&w_mtx);
1240                 return;
1241         }
1242         witness_lock_order_add(w1, w);
1243
1244         /*
1245          * Check for duplicate locks of the same type.  Note that we only
1246          * have to check for this on the last lock we just acquired.  Any
1247          * other cases will be caught as lock order violations.
1248          */
1249         if (w1 == w) {
1250                 i = w->w_index;
1251                 if (!(lock->lo_flags & LO_DUPOK) && !(flags & LOP_DUPOK) &&
1252                     !(w_rmatrix[i][i] & WITNESS_REVERSAL)) {
1253                     w_rmatrix[i][i] |= WITNESS_REVERSAL;
1254                         w->w_reversed = 1;
1255                         mtx_unlock_spin(&w_mtx);
1256                         witness_output(
1257                             "acquiring duplicate lock of same type: \"%s\"\n",
1258                             w->w_name);
1259                         witness_output(" 1st %s @ %s:%d\n", plock->li_lock->lo_name,
1260                             fixup_filename(plock->li_file), plock->li_line);
1261                         witness_output(" 2nd %s @ %s:%d\n", lock->lo_name,
1262                             fixup_filename(file), line);
1263                         witness_debugger(1, __func__);
1264                 } else
1265                         mtx_unlock_spin(&w_mtx);
1266                 return;
1267         }
1268         mtx_assert(&w_mtx, MA_OWNED);
1269
1270         /*
1271          * If we know that the lock we are acquiring comes after
1272          * the lock we most recently acquired in the lock order tree,
1273          * then there is no need for any further checks.
1274          */
1275         if (isitmychild(w1, w))
1276                 goto out;
1277
1278         for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) {
1279                 for (i = lle->ll_count - 1; i >= 0; i--, j++) {
1280                         struct stack pstack;
1281                         bool pstackv, trace;
1282
1283                         MPASS(j < LOCK_CHILDCOUNT * LOCK_NCHILDREN);
1284                         lock1 = &lle->ll_children[i];
1285
1286                         /*
1287                          * Ignore the interlock.
1288                          */
1289                         if (interlock == lock1->li_lock)
1290                                 continue;
1291
1292                         /*
1293                          * If this lock doesn't undergo witness checking,
1294                          * then skip it.
1295                          */
1296                         w1 = lock1->li_lock->lo_witness;
1297                         if (w1 == NULL) {
1298                                 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0,
1299                                     ("lock missing witness structure"));
1300                                 continue;
1301                         }
1302
1303                         /*
1304                          * If we are locking Giant and this is a sleepable
1305                          * lock, then skip it.
1306                          */
1307                         if ((lock1->li_flags & LI_SLEEPABLE) != 0 &&
1308                             lock == &Giant.lock_object)
1309                                 continue;
1310
1311                         /*
1312                          * If we are locking a sleepable lock and this lock
1313                          * is Giant, then skip it.
1314                          */
1315                         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
1316                             (flags & LOP_NOSLEEP) == 0 &&
1317                             lock1->li_lock == &Giant.lock_object)
1318                                 continue;
1319
1320                         /*
1321                          * If we are locking a sleepable lock and this lock
1322                          * isn't sleepable, we want to treat it as a lock
1323                          * order violation to enfore a general lock order of
1324                          * sleepable locks before non-sleepable locks.
1325                          */
1326                         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
1327                             (flags & LOP_NOSLEEP) == 0 &&
1328                             (lock1->li_flags & LI_SLEEPABLE) == 0)
1329                                 goto reversal;
1330
1331                         /*
1332                          * If we are locking Giant and this is a non-sleepable
1333                          * lock, then treat it as a reversal.
1334                          */
1335                         if ((lock1->li_flags & LI_SLEEPABLE) == 0 &&
1336                             lock == &Giant.lock_object)
1337                                 goto reversal;
1338
1339                         /*
1340                          * Check the lock order hierarchy for a reveresal.
1341                          */
1342                         if (!isitmydescendant(w, w1))
1343                                 continue;
1344                 reversal:
1345
1346                         /*
1347                          * We have a lock order violation, check to see if it
1348                          * is allowed or has already been yelled about.
1349                          */
1350
1351                         /* Bail if this violation is known */
1352                         if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL)
1353                                 goto out;
1354
1355                         /* Record this as a violation */
1356                         w_rmatrix[w1->w_index][w->w_index] |= WITNESS_REVERSAL;
1357                         w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL;
1358                         w->w_reversed = w1->w_reversed = 1;
1359                         witness_increment_graph_generation();
1360
1361                         /*
1362                          * If the lock order is blessed, bail before logging
1363                          * anything.  We don't look for other lock order
1364                          * violations though, which may be a bug.
1365                          */
1366                         if (blessed(w, w1))
1367                                 goto out;
1368
1369                         trace = atomic_load_int(&witness_trace);
1370                         if (trace) {
1371                                 struct witness_lock_order_data *data;
1372
1373                                 pstackv = false;
1374                                 data = witness_lock_order_get(w, w1);
1375                                 if (data != NULL) {
1376                                         stack_copy(&data->wlod_stack,
1377                                             &pstack);
1378                                         pstackv = true;
1379                                 }
1380                         }
1381                         mtx_unlock_spin(&w_mtx);
1382
1383 #ifdef WITNESS_NO_VNODE
1384                         /*
1385                          * There are known LORs between VNODE locks. They are
1386                          * not an indication of a bug. VNODE locks are flagged
1387                          * as such (LO_IS_VNODE) and we don't yell if the LOR
1388                          * is between 2 VNODE locks.
1389                          */
1390                         if ((lock->lo_flags & LO_IS_VNODE) != 0 &&
1391                             (lock1->li_lock->lo_flags & LO_IS_VNODE) != 0)
1392                                 return;
1393 #endif
1394
1395                         /*
1396                          * Ok, yell about it.
1397                          */
1398                         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
1399                             (flags & LOP_NOSLEEP) == 0 &&
1400                             (lock1->li_flags & LI_SLEEPABLE) == 0)
1401                                 witness_output(
1402                 "lock order reversal: (sleepable after non-sleepable)\n");
1403                         else if ((lock1->li_flags & LI_SLEEPABLE) == 0
1404                             && lock == &Giant.lock_object)
1405                                 witness_output(
1406                 "lock order reversal: (Giant after non-sleepable)\n");
1407                         else
1408                                 witness_output("lock order reversal:\n");
1409
1410                         /*
1411                          * Try to locate an earlier lock with
1412                          * witness w in our list.
1413                          */
1414                         do {
1415                                 lock2 = &lle->ll_children[i];
1416                                 MPASS(lock2->li_lock != NULL);
1417                                 if (lock2->li_lock->lo_witness == w)
1418                                         break;
1419                                 if (i == 0 && lle->ll_next != NULL) {
1420                                         lle = lle->ll_next;
1421                                         i = lle->ll_count - 1;
1422                                         MPASS(i >= 0 && i < LOCK_NCHILDREN);
1423                                 } else
1424                                         i--;
1425                         } while (i >= 0);
1426                         if (i < 0) {
1427                                 witness_output(" 1st %p %s (%s, %s) @ %s:%d\n",
1428                                     lock1->li_lock, lock1->li_lock->lo_name,
1429                                     w1->w_name, w1->w_class->lc_name,
1430                                     fixup_filename(lock1->li_file),
1431                                     lock1->li_line);
1432                                 witness_output(" 2nd %p %s (%s, %s) @ %s:%d\n",
1433                                     lock, lock->lo_name, w->w_name,
1434                                     w->w_class->lc_name, fixup_filename(file),
1435                                     line);
1436                         } else {
1437                                 struct witness *w2 = lock2->li_lock->lo_witness;
1438
1439                                 witness_output(" 1st %p %s (%s, %s) @ %s:%d\n",
1440                                     lock2->li_lock, lock2->li_lock->lo_name,
1441                                     w2->w_name, w2->w_class->lc_name,
1442                                     fixup_filename(lock2->li_file),
1443                                     lock2->li_line);
1444                                 witness_output(" 2nd %p %s (%s, %s) @ %s:%d\n",
1445                                     lock1->li_lock, lock1->li_lock->lo_name,
1446                                     w1->w_name, w1->w_class->lc_name,
1447                                     fixup_filename(lock1->li_file),
1448                                     lock1->li_line);
1449                                 witness_output(" 3rd %p %s (%s, %s) @ %s:%d\n", lock,
1450                                     lock->lo_name, w->w_name,
1451                                     w->w_class->lc_name, fixup_filename(file),
1452                                     line);
1453                         }
1454                         if (trace) {
1455                                 char buf[64];
1456                                 struct sbuf sb;
1457
1458                                 sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN);
1459                                 sbuf_set_drain(&sb, witness_output_drain,
1460                                     NULL);
1461
1462                                 if (pstackv) {
1463                                         sbuf_printf(&sb,
1464                                     "lock order %s -> %s established at:\n",
1465                                             w->w_name, w1->w_name);
1466                                         stack_sbuf_print_flags(&sb, &pstack,
1467                                             M_NOWAIT, STACK_SBUF_FMT_LONG);
1468                                 }
1469
1470                                 sbuf_printf(&sb,
1471                                     "lock order %s -> %s attempted at:\n",
1472                                     w1->w_name, w->w_name);
1473                                 stack_save(&pstack);
1474                                 stack_sbuf_print_flags(&sb, &pstack, M_NOWAIT,
1475                                     STACK_SBUF_FMT_LONG);
1476
1477                                 sbuf_finish(&sb);
1478                                 sbuf_delete(&sb);
1479                         }
1480                         witness_enter_debugger(__func__);
1481                         return;
1482                 }
1483         }
1484
1485         /*
1486          * If requested, build a new lock order.  However, don't build a new
1487          * relationship between a sleepable lock and Giant if it is in the
1488          * wrong direction.  The correct lock order is that sleepable locks
1489          * always come before Giant.
1490          */
1491         if (flags & LOP_NEWORDER &&
1492             !(plock->li_lock == &Giant.lock_object &&
1493             (lock->lo_flags & LO_SLEEPABLE) != 0 &&
1494             (flags & LOP_NOSLEEP) == 0)) {
1495                 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
1496                     w->w_name, plock->li_lock->lo_witness->w_name);
1497                 itismychild(plock->li_lock->lo_witness, w);
1498         }
1499 out:
1500         mtx_unlock_spin(&w_mtx);
1501 }
1502
1503 void
1504 witness_lock(struct lock_object *lock, int flags, const char *file, int line)
1505 {
1506         struct lock_list_entry **lock_list, *lle;
1507         struct lock_instance *instance;
1508         struct witness *w;
1509         struct thread *td;
1510
1511         if (witness_cold || witness_watch == -1 || lock->lo_witness == NULL ||
1512             KERNEL_PANICKED())
1513                 return;
1514         w = lock->lo_witness;
1515         td = curthread;
1516
1517         /* Determine lock list for this lock. */
1518         if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK)
1519                 lock_list = &td->td_sleeplocks;
1520         else
1521                 lock_list = PCPU_PTR(spinlocks);
1522
1523         /* Check to see if we are recursing on a lock we already own. */
1524         instance = find_instance(*lock_list, lock);
1525         if (instance != NULL) {
1526                 instance->li_flags++;
1527                 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__,
1528                     td->td_proc->p_pid, lock->lo_name,
1529                     instance->li_flags & LI_RECURSEMASK);
1530                 instance->li_file = file;
1531                 instance->li_line = line;
1532                 return;
1533         }
1534
1535         /* Update per-witness last file and line acquire. */
1536         w->w_file = file;
1537         w->w_line = line;
1538
1539         /* Find the next open lock instance in the list and fill it. */
1540         lle = *lock_list;
1541         if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
1542                 lle = witness_lock_list_get();
1543                 if (lle == NULL)
1544                         return;
1545                 lle->ll_next = *lock_list;
1546                 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__,
1547                     td->td_proc->p_pid, lle);
1548                 *lock_list = lle;
1549         }
1550         instance = &lle->ll_children[lle->ll_count++];
1551         instance->li_lock = lock;
1552         instance->li_line = line;
1553         instance->li_file = file;
1554         instance->li_flags = 0;
1555         if ((flags & LOP_EXCLUSIVE) != 0)
1556                 instance->li_flags |= LI_EXCLUSIVE;
1557         if ((lock->lo_flags & LO_SLEEPABLE) != 0 && (flags & LOP_NOSLEEP) == 0)
1558                 instance->li_flags |= LI_SLEEPABLE;
1559         CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__,
1560             td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1);
1561 }
1562
1563 void
1564 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line)
1565 {
1566         struct lock_instance *instance;
1567         struct lock_class *class;
1568
1569         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
1570         if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED())
1571                 return;
1572         class = LOCK_CLASS(lock);
1573         if (witness_watch) {
1574                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
1575                         kassert_panic(
1576                             "upgrade of non-upgradable lock (%s) %s @ %s:%d",
1577                             class->lc_name, lock->lo_name,
1578                             fixup_filename(file), line);
1579                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
1580                         kassert_panic(
1581                             "upgrade of non-sleep lock (%s) %s @ %s:%d",
1582                             class->lc_name, lock->lo_name,
1583                             fixup_filename(file), line);
1584         }
1585         instance = find_instance(curthread->td_sleeplocks, lock);
1586         if (instance == NULL) {
1587                 kassert_panic("upgrade of unlocked lock (%s) %s @ %s:%d",
1588                     class->lc_name, lock->lo_name,
1589                     fixup_filename(file), line);
1590                 return;
1591         }
1592         if (witness_watch) {
1593                 if ((instance->li_flags & LI_EXCLUSIVE) != 0)
1594                         kassert_panic(
1595                             "upgrade of exclusive lock (%s) %s @ %s:%d",
1596                             class->lc_name, lock->lo_name,
1597                             fixup_filename(file), line);
1598                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
1599                         kassert_panic(
1600                             "upgrade of recursed lock (%s) %s r=%d @ %s:%d",
1601                             class->lc_name, lock->lo_name,
1602                             instance->li_flags & LI_RECURSEMASK,
1603                             fixup_filename(file), line);
1604         }
1605         instance->li_flags |= LI_EXCLUSIVE;
1606 }
1607
1608 void
1609 witness_downgrade(struct lock_object *lock, int flags, const char *file,
1610     int line)
1611 {
1612         struct lock_instance *instance;
1613         struct lock_class *class;
1614
1615         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
1616         if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED())
1617                 return;
1618         class = LOCK_CLASS(lock);
1619         if (witness_watch) {
1620                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
1621                         kassert_panic(
1622                             "downgrade of non-upgradable lock (%s) %s @ %s:%d",
1623                             class->lc_name, lock->lo_name,
1624                             fixup_filename(file), line);
1625                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
1626                         kassert_panic(
1627                             "downgrade of non-sleep lock (%s) %s @ %s:%d",
1628                             class->lc_name, lock->lo_name,
1629                             fixup_filename(file), line);
1630         }
1631         instance = find_instance(curthread->td_sleeplocks, lock);
1632         if (instance == NULL) {
1633                 kassert_panic("downgrade of unlocked lock (%s) %s @ %s:%d",
1634                     class->lc_name, lock->lo_name,
1635                     fixup_filename(file), line);
1636                 return;
1637         }
1638         if (witness_watch) {
1639                 if ((instance->li_flags & LI_EXCLUSIVE) == 0)
1640                         kassert_panic(
1641                             "downgrade of shared lock (%s) %s @ %s:%d",
1642                             class->lc_name, lock->lo_name,
1643                             fixup_filename(file), line);
1644                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
1645                         kassert_panic(
1646                             "downgrade of recursed lock (%s) %s r=%d @ %s:%d",
1647                             class->lc_name, lock->lo_name,
1648                             instance->li_flags & LI_RECURSEMASK,
1649                             fixup_filename(file), line);
1650         }
1651         instance->li_flags &= ~LI_EXCLUSIVE;
1652 }
1653
1654 void
1655 witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
1656 {
1657         struct lock_list_entry **lock_list, *lle;
1658         struct lock_instance *instance;
1659         struct lock_class *class;
1660         struct thread *td;
1661         register_t s;
1662         int i, j;
1663
1664         if (witness_cold || lock->lo_witness == NULL || KERNEL_PANICKED())
1665                 return;
1666         td = curthread;
1667         class = LOCK_CLASS(lock);
1668
1669         /* Find lock instance associated with this lock. */
1670         if (class->lc_flags & LC_SLEEPLOCK)
1671                 lock_list = &td->td_sleeplocks;
1672         else
1673                 lock_list = PCPU_PTR(spinlocks);
1674         lle = *lock_list;
1675         for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next)
1676                 for (i = 0; i < (*lock_list)->ll_count; i++) {
1677                         instance = &(*lock_list)->ll_children[i];
1678                         if (instance->li_lock == lock)
1679                                 goto found;
1680                 }
1681
1682         /*
1683          * When disabling WITNESS through witness_watch we could end up in
1684          * having registered locks in the td_sleeplocks queue.
1685          * We have to make sure we flush these queues, so just search for
1686          * eventual register locks and remove them.
1687          */
1688         if (witness_watch > 0) {
1689                 kassert_panic("lock (%s) %s not locked @ %s:%d", class->lc_name,
1690                     lock->lo_name, fixup_filename(file), line);
1691                 return;
1692         } else {
1693                 return;
1694         }
1695 found:
1696
1697         /* First, check for shared/exclusive mismatches. */
1698         if ((instance->li_flags & LI_EXCLUSIVE) != 0 && witness_watch > 0 &&
1699             (flags & LOP_EXCLUSIVE) == 0) {
1700                 witness_output("shared unlock of (%s) %s @ %s:%d\n",
1701                     class->lc_name, lock->lo_name, fixup_filename(file), line);
1702                 witness_output("while exclusively locked from %s:%d\n",
1703                     fixup_filename(instance->li_file), instance->li_line);
1704                 kassert_panic("excl->ushare");
1705         }
1706         if ((instance->li_flags & LI_EXCLUSIVE) == 0 && witness_watch > 0 &&
1707             (flags & LOP_EXCLUSIVE) != 0) {
1708                 witness_output("exclusive unlock of (%s) %s @ %s:%d\n",
1709                     class->lc_name, lock->lo_name, fixup_filename(file), line);
1710                 witness_output("while share locked from %s:%d\n",
1711                     fixup_filename(instance->li_file),
1712                     instance->li_line);
1713                 kassert_panic("share->uexcl");
1714         }
1715         /* If we are recursed, unrecurse. */
1716         if ((instance->li_flags & LI_RECURSEMASK) > 0) {
1717                 CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__,
1718                     td->td_proc->p_pid, instance->li_lock->lo_name,
1719                     instance->li_flags);
1720                 instance->li_flags--;
1721                 return;
1722         }
1723         /* The lock is now being dropped, check for NORELEASE flag */
1724         if ((instance->li_flags & LI_NORELEASE) != 0 && witness_watch > 0) {
1725                 witness_output("forbidden unlock of (%s) %s @ %s:%d\n",
1726                     class->lc_name, lock->lo_name, fixup_filename(file), line);
1727                 kassert_panic("lock marked norelease");
1728         }
1729
1730         /* Otherwise, remove this item from the list. */
1731         s = intr_disable();
1732         CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__,
1733             td->td_proc->p_pid, instance->li_lock->lo_name,
1734             (*lock_list)->ll_count - 1);
1735         for (j = i; j < (*lock_list)->ll_count - 1; j++)
1736                 (*lock_list)->ll_children[j] =
1737                     (*lock_list)->ll_children[j + 1];
1738         (*lock_list)->ll_count--;
1739         intr_restore(s);
1740
1741         /*
1742          * In order to reduce contention on w_mtx, we want to keep always an
1743          * head object into lists so that frequent allocation from the
1744          * free witness pool (and subsequent locking) is avoided.
1745          * In order to maintain the current code simple, when the head
1746          * object is totally unloaded it means also that we do not have
1747          * further objects in the list, so the list ownership needs to be
1748          * hand over to another object if the current head needs to be freed.
1749          */
1750         if ((*lock_list)->ll_count == 0) {
1751                 if (*lock_list == lle) {
1752                         if (lle->ll_next == NULL)
1753                                 return;
1754                 } else
1755                         lle = *lock_list;
1756                 *lock_list = lle->ll_next;
1757                 CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__,
1758                     td->td_proc->p_pid, lle);
1759                 witness_lock_list_free(lle);
1760         }
1761 }
1762
1763 void
1764 witness_thread_exit(struct thread *td)
1765 {
1766         struct lock_list_entry *lle;
1767         int i, n;
1768
1769         lle = td->td_sleeplocks;
1770         if (lle == NULL || KERNEL_PANICKED())
1771                 return;
1772         if (lle->ll_count != 0) {
1773                 for (n = 0; lle != NULL; lle = lle->ll_next)
1774                         for (i = lle->ll_count - 1; i >= 0; i--) {
1775                                 if (n == 0)
1776                                         witness_output(
1777                     "Thread %p exiting with the following locks held:\n", td);
1778                                 n++;
1779                                 witness_list_lock(&lle->ll_children[i],
1780                                     witness_output);
1781
1782                         }
1783                 kassert_panic(
1784                     "Thread %p cannot exit while holding sleeplocks\n", td);
1785         }
1786         witness_lock_list_free(lle);
1787 }
1788
1789 /*
1790  * Warn if any locks other than 'lock' are held.  Flags can be passed in to
1791  * exempt Giant and sleepable locks from the checks as well.  If any
1792  * non-exempt locks are held, then a supplied message is printed to the
1793  * output channel along with a list of the offending locks.  If indicated in the
1794  * flags then a failure results in a panic as well.
1795  */
1796 int
1797 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
1798 {
1799         struct lock_list_entry *lock_list, *lle;
1800         struct lock_instance *lock1;
1801         struct thread *td;
1802         va_list ap;
1803         int i, n;
1804
1805         if (witness_cold || witness_watch < 1 || KERNEL_PANICKED())
1806                 return (0);
1807         n = 0;
1808         td = curthread;
1809         for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next)
1810                 for (i = lle->ll_count - 1; i >= 0; i--) {
1811                         lock1 = &lle->ll_children[i];
1812                         if (lock1->li_lock == lock)
1813                                 continue;
1814                         if (flags & WARN_GIANTOK &&
1815                             lock1->li_lock == &Giant.lock_object)
1816                                 continue;
1817                         if (flags & WARN_SLEEPOK &&
1818                             (lock1->li_flags & LI_SLEEPABLE) != 0)
1819                                 continue;
1820                         if (n == 0) {
1821                                 va_start(ap, fmt);
1822                                 vprintf(fmt, ap);
1823                                 va_end(ap);
1824                                 printf(" with the following %slocks held:\n",
1825                                     (flags & WARN_SLEEPOK) != 0 ?
1826                                     "non-sleepable " : "");
1827                         }
1828                         n++;
1829                         witness_list_lock(lock1, printf);
1830                 }
1831
1832         /*
1833          * Pin the thread in order to avoid problems with thread migration.
1834          * Once that all verifies are passed about spinlocks ownership,
1835          * the thread is in a safe path and it can be unpinned.
1836          */
1837         sched_pin();
1838         lock_list = PCPU_GET(spinlocks);
1839         if (lock_list != NULL && lock_list->ll_count != 0) {
1840                 sched_unpin();
1841
1842                 /*
1843                  * We should only have one spinlock and as long as
1844                  * the flags cannot match for this locks class,
1845                  * check if the first spinlock is the one curthread
1846                  * should hold.
1847                  */
1848                 lock1 = &lock_list->ll_children[lock_list->ll_count - 1];
1849                 if (lock_list->ll_count == 1 && lock_list->ll_next == NULL &&
1850                     lock1->li_lock == lock && n == 0)
1851                         return (0);
1852
1853                 va_start(ap, fmt);
1854                 vprintf(fmt, ap);
1855                 va_end(ap);
1856                 printf(" with the following %slocks held:\n",
1857                     (flags & WARN_SLEEPOK) != 0 ?  "non-sleepable " : "");
1858                 n += witness_list_locks(&lock_list, printf);
1859         } else
1860                 sched_unpin();
1861         if (flags & WARN_PANIC && n)
1862                 kassert_panic("%s", __func__);
1863         else
1864                 witness_debugger(n, __func__);
1865         return (n);
1866 }
1867
1868 const char *
1869 witness_file(struct lock_object *lock)
1870 {
1871         struct witness *w;
1872
1873         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
1874                 return ("?");
1875         w = lock->lo_witness;
1876         return (w->w_file);
1877 }
1878
1879 int
1880 witness_line(struct lock_object *lock)
1881 {
1882         struct witness *w;
1883
1884         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
1885                 return (0);
1886         w = lock->lo_witness;
1887         return (w->w_line);
1888 }
1889
1890 static struct witness *
1891 enroll(const char *description, struct lock_class *lock_class)
1892 {
1893         struct witness *w;
1894
1895         MPASS(description != NULL);
1896
1897         if (witness_watch == -1 || KERNEL_PANICKED())
1898                 return (NULL);
1899         if ((lock_class->lc_flags & LC_SPINLOCK)) {
1900                 if (witness_skipspin)
1901                         return (NULL);
1902         } else if ((lock_class->lc_flags & LC_SLEEPLOCK) == 0) {
1903                 kassert_panic("lock class %s is not sleep or spin",
1904                     lock_class->lc_name);
1905                 return (NULL);
1906         }
1907
1908         mtx_lock_spin(&w_mtx);
1909         w = witness_hash_get(description);
1910         if (w)
1911                 goto found;
1912         if ((w = witness_get()) == NULL)
1913                 return (NULL);
1914         MPASS(strlen(description) < MAX_W_NAME);
1915         strcpy(w->w_name, description);
1916         w->w_class = lock_class;
1917         w->w_refcount = 1;
1918         STAILQ_INSERT_HEAD(&w_all, w, w_list);
1919         if (lock_class->lc_flags & LC_SPINLOCK) {
1920                 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist);
1921                 w_spin_cnt++;
1922         } else if (lock_class->lc_flags & LC_SLEEPLOCK) {
1923                 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist);
1924                 w_sleep_cnt++;
1925         }
1926
1927         /* Insert new witness into the hash */
1928         witness_hash_put(w);
1929         witness_increment_graph_generation();
1930         mtx_unlock_spin(&w_mtx);
1931         return (w);
1932 found:
1933         w->w_refcount++;
1934         if (w->w_refcount == 1)
1935                 w->w_class = lock_class;
1936         mtx_unlock_spin(&w_mtx);
1937         if (lock_class != w->w_class)
1938                 kassert_panic(
1939                     "lock (%s) %s does not match earlier (%s) lock",
1940                     description, lock_class->lc_name,
1941                     w->w_class->lc_name);
1942         return (w);
1943 }
1944
1945 static void
1946 depart(struct witness *w)
1947 {
1948
1949         MPASS(w->w_refcount == 0);
1950         if (w->w_class->lc_flags & LC_SLEEPLOCK) {
1951                 w_sleep_cnt--;
1952         } else {
1953                 w_spin_cnt--;
1954         }
1955         /*
1956          * Set file to NULL as it may point into a loadable module.
1957          */
1958         w->w_file = NULL;
1959         w->w_line = 0;
1960         witness_increment_graph_generation();
1961 }
1962
1963 static void
1964 adopt(struct witness *parent, struct witness *child)
1965 {
1966         int pi, ci, i, j;
1967
1968         if (witness_cold == 0)
1969                 mtx_assert(&w_mtx, MA_OWNED);
1970
1971         /* If the relationship is already known, there's no work to be done. */
1972         if (isitmychild(parent, child))
1973                 return;
1974
1975         /* When the structure of the graph changes, bump up the generation. */
1976         witness_increment_graph_generation();
1977
1978         /*
1979          * The hard part ... create the direct relationship, then propagate all
1980          * indirect relationships.
1981          */
1982         pi = parent->w_index;
1983         ci = child->w_index;
1984         WITNESS_INDEX_ASSERT(pi);
1985         WITNESS_INDEX_ASSERT(ci);
1986         MPASS(pi != ci);
1987         w_rmatrix[pi][ci] |= WITNESS_PARENT;
1988         w_rmatrix[ci][pi] |= WITNESS_CHILD;
1989
1990         /*
1991          * If parent was not already an ancestor of child,
1992          * then we increment the descendant and ancestor counters.
1993          */
1994         if ((w_rmatrix[pi][ci] & WITNESS_ANCESTOR) == 0) {
1995                 parent->w_num_descendants++;
1996                 child->w_num_ancestors++;
1997         }
1998
1999         /*
2000          * Find each ancestor of 'pi'. Note that 'pi' itself is counted as
2001          * an ancestor of 'pi' during this loop.
2002          */
2003         for (i = 1; i <= w_max_used_index; i++) {
2004                 if ((w_rmatrix[i][pi] & WITNESS_ANCESTOR_MASK) == 0 &&
2005                     (i != pi))
2006                         continue;
2007
2008                 /* Find each descendant of 'i' and mark it as a descendant. */
2009                 for (j = 1; j <= w_max_used_index; j++) {
2010                         /*
2011                          * Skip children that are already marked as
2012                          * descendants of 'i'.
2013                          */
2014                         if (w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK)
2015                                 continue;
2016
2017                         /*
2018                          * We are only interested in descendants of 'ci'. Note
2019                          * that 'ci' itself is counted as a descendant of 'ci'.
2020                          */
2021                         if ((w_rmatrix[ci][j] & WITNESS_ANCESTOR_MASK) == 0 &&
2022                             (j != ci))
2023                                 continue;
2024                         w_rmatrix[i][j] |= WITNESS_ANCESTOR;
2025                         w_rmatrix[j][i] |= WITNESS_DESCENDANT;
2026                         w_data[i].w_num_descendants++;
2027                         w_data[j].w_num_ancestors++;
2028
2029                         /*
2030                          * Make sure we aren't marking a node as both an
2031                          * ancestor and descendant. We should have caught
2032                          * this as a lock order reversal earlier.
2033                          */
2034                         if ((w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) &&
2035                             (w_rmatrix[i][j] & WITNESS_DESCENDANT_MASK)) {
2036                                 printf("witness rmatrix paradox! [%d][%d]=%d "
2037                                     "both ancestor and descendant\n",
2038                                     i, j, w_rmatrix[i][j]);
2039                                 kdb_backtrace();
2040                                 printf("Witness disabled.\n");
2041                                 witness_watch = -1;
2042                         }
2043                         if ((w_rmatrix[j][i] & WITNESS_ANCESTOR_MASK) &&
2044                             (w_rmatrix[j][i] & WITNESS_DESCENDANT_MASK)) {
2045                                 printf("witness rmatrix paradox! [%d][%d]=%d "
2046                                     "both ancestor and descendant\n",
2047                                     j, i, w_rmatrix[j][i]);
2048                                 kdb_backtrace();
2049                                 printf("Witness disabled.\n");
2050                                 witness_watch = -1;
2051                         }
2052                 }
2053         }
2054 }
2055
2056 static void
2057 itismychild(struct witness *parent, struct witness *child)
2058 {
2059         int unlocked;
2060
2061         MPASS(child != NULL && parent != NULL);
2062         if (witness_cold == 0)
2063                 mtx_assert(&w_mtx, MA_OWNED);
2064
2065         if (!witness_lock_type_equal(parent, child)) {
2066                 if (witness_cold == 0) {
2067                         unlocked = 1;
2068                         mtx_unlock_spin(&w_mtx);
2069                 } else {
2070                         unlocked = 0;
2071                 }
2072                 kassert_panic(
2073                     "%s: parent \"%s\" (%s) and child \"%s\" (%s) are not "
2074                     "the same lock type", __func__, parent->w_name,
2075                     parent->w_class->lc_name, child->w_name,
2076                     child->w_class->lc_name);
2077                 if (unlocked)
2078                         mtx_lock_spin(&w_mtx);
2079         }
2080         adopt(parent, child);
2081 }
2082
2083 /*
2084  * Generic code for the isitmy*() functions. The rmask parameter is the
2085  * expected relationship of w1 to w2.
2086  */
2087 static int
2088 _isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname)
2089 {
2090         unsigned char r1, r2;
2091         int i1, i2;
2092
2093         i1 = w1->w_index;
2094         i2 = w2->w_index;
2095         WITNESS_INDEX_ASSERT(i1);
2096         WITNESS_INDEX_ASSERT(i2);
2097         r1 = w_rmatrix[i1][i2] & WITNESS_RELATED_MASK;
2098         r2 = w_rmatrix[i2][i1] & WITNESS_RELATED_MASK;
2099
2100         /* The flags on one better be the inverse of the flags on the other */
2101         if (!((WITNESS_ATOD(r1) == r2 && WITNESS_DTOA(r2) == r1) ||
2102             (WITNESS_DTOA(r1) == r2 && WITNESS_ATOD(r2) == r1))) {
2103                 /* Don't squawk if we're potentially racing with an update. */
2104                 if (!mtx_owned(&w_mtx))
2105                         return (0);
2106                 printf("%s: rmatrix mismatch between %s (index %d) and %s "
2107                     "(index %d): w_rmatrix[%d][%d] == %hhx but "
2108                     "w_rmatrix[%d][%d] == %hhx\n",
2109                     fname, w1->w_name, i1, w2->w_name, i2, i1, i2, r1,
2110                     i2, i1, r2);
2111                 kdb_backtrace();
2112                 printf("Witness disabled.\n");
2113                 witness_watch = -1;
2114         }
2115         return (r1 & rmask);
2116 }
2117
2118 /*
2119  * Checks if @child is a direct child of @parent.
2120  */
2121 static int
2122 isitmychild(struct witness *parent, struct witness *child)
2123 {
2124
2125         return (_isitmyx(parent, child, WITNESS_PARENT, __func__));
2126 }
2127
2128 /*
2129  * Checks if @descendant is a direct or inderect descendant of @ancestor.
2130  */
2131 static int
2132 isitmydescendant(struct witness *ancestor, struct witness *descendant)
2133 {
2134
2135         return (_isitmyx(ancestor, descendant, WITNESS_ANCESTOR_MASK,
2136             __func__));
2137 }
2138
2139 static int
2140 blessed(struct witness *w1, struct witness *w2)
2141 {
2142         int i;
2143         struct witness_blessed *b;
2144
2145         for (i = 0; i < nitems(blessed_list); i++) {
2146                 b = &blessed_list[i];
2147                 if (strcmp(w1->w_name, b->b_lock1) == 0) {
2148                         if (strcmp(w2->w_name, b->b_lock2) == 0)
2149                                 return (1);
2150                         continue;
2151                 }
2152                 if (strcmp(w1->w_name, b->b_lock2) == 0)
2153                         if (strcmp(w2->w_name, b->b_lock1) == 0)
2154                                 return (1);
2155         }
2156         return (0);
2157 }
2158
2159 static struct witness *
2160 witness_get(void)
2161 {
2162         struct witness *w;
2163         int index;
2164
2165         if (witness_cold == 0)
2166                 mtx_assert(&w_mtx, MA_OWNED);
2167
2168         if (witness_watch == -1) {
2169                 mtx_unlock_spin(&w_mtx);
2170                 return (NULL);
2171         }
2172         if (STAILQ_EMPTY(&w_free)) {
2173                 witness_watch = -1;
2174                 mtx_unlock_spin(&w_mtx);
2175                 printf("WITNESS: unable to allocate a new witness object\n");
2176                 return (NULL);
2177         }
2178         w = STAILQ_FIRST(&w_free);
2179         STAILQ_REMOVE_HEAD(&w_free, w_list);
2180         w_free_cnt--;
2181         index = w->w_index;
2182         MPASS(index > 0 && index == w_max_used_index+1 &&
2183             index < witness_count);
2184         bzero(w, sizeof(*w));
2185         w->w_index = index;
2186         if (index > w_max_used_index)
2187                 w_max_used_index = index;
2188         return (w);
2189 }
2190
2191 static void
2192 witness_free(struct witness *w)
2193 {
2194
2195         STAILQ_INSERT_HEAD(&w_free, w, w_list);
2196         w_free_cnt++;
2197 }
2198
2199 static struct lock_list_entry *
2200 witness_lock_list_get(void)
2201 {
2202         struct lock_list_entry *lle;
2203
2204         if (witness_watch == -1)
2205                 return (NULL);
2206         mtx_lock_spin(&w_mtx);
2207         lle = w_lock_list_free;
2208         if (lle == NULL) {
2209                 witness_watch = -1;
2210                 mtx_unlock_spin(&w_mtx);
2211                 printf("%s: witness exhausted\n", __func__);
2212                 return (NULL);
2213         }
2214         w_lock_list_free = lle->ll_next;
2215         mtx_unlock_spin(&w_mtx);
2216         bzero(lle, sizeof(*lle));
2217         return (lle);
2218 }
2219
2220 static void
2221 witness_lock_list_free(struct lock_list_entry *lle)
2222 {
2223
2224         mtx_lock_spin(&w_mtx);
2225         lle->ll_next = w_lock_list_free;
2226         w_lock_list_free = lle;
2227         mtx_unlock_spin(&w_mtx);
2228 }
2229
2230 static struct lock_instance *
2231 find_instance(struct lock_list_entry *list, const struct lock_object *lock)
2232 {
2233         struct lock_list_entry *lle;
2234         struct lock_instance *instance;
2235         int i;
2236
2237         for (lle = list; lle != NULL; lle = lle->ll_next)
2238                 for (i = lle->ll_count - 1; i >= 0; i--) {
2239                         instance = &lle->ll_children[i];
2240                         if (instance->li_lock == lock)
2241                                 return (instance);
2242                 }
2243         return (NULL);
2244 }
2245
2246 static void
2247 witness_list_lock(struct lock_instance *instance,
2248     int (*prnt)(const char *fmt, ...))
2249 {
2250         struct lock_object *lock;
2251
2252         lock = instance->li_lock;
2253         prnt("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ?
2254             "exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name);
2255         if (lock->lo_witness->w_name != lock->lo_name)
2256                 prnt(" (%s)", lock->lo_witness->w_name);
2257         prnt(" r = %d (%p) locked @ %s:%d\n",
2258             instance->li_flags & LI_RECURSEMASK, lock,
2259             fixup_filename(instance->li_file), instance->li_line);
2260 }
2261
2262 static int
2263 witness_output(const char *fmt, ...)
2264 {
2265         va_list ap;
2266         int ret;
2267
2268         va_start(ap, fmt);
2269         ret = witness_voutput(fmt, ap);
2270         va_end(ap);
2271         return (ret);
2272 }
2273
2274 static int
2275 witness_voutput(const char *fmt, va_list ap)
2276 {
2277         int ret;
2278
2279         ret = 0;
2280         switch (witness_channel) {
2281         case WITNESS_CONSOLE:
2282                 ret = vprintf(fmt, ap);
2283                 break;
2284         case WITNESS_LOG:
2285                 vlog(LOG_NOTICE, fmt, ap);
2286                 break;
2287         case WITNESS_NONE:
2288                 break;
2289         }
2290         return (ret);
2291 }
2292
2293 #ifdef DDB
2294 static int
2295 witness_thread_has_locks(struct thread *td)
2296 {
2297
2298         if (td->td_sleeplocks == NULL)
2299                 return (0);
2300         return (td->td_sleeplocks->ll_count != 0);
2301 }
2302
2303 static int
2304 witness_proc_has_locks(struct proc *p)
2305 {
2306         struct thread *td;
2307
2308         FOREACH_THREAD_IN_PROC(p, td) {
2309                 if (witness_thread_has_locks(td))
2310                         return (1);
2311         }
2312         return (0);
2313 }
2314 #endif
2315
2316 int
2317 witness_list_locks(struct lock_list_entry **lock_list,
2318     int (*prnt)(const char *fmt, ...))
2319 {
2320         struct lock_list_entry *lle;
2321         int i, nheld;
2322
2323         nheld = 0;
2324         for (lle = *lock_list; lle != NULL; lle = lle->ll_next)
2325                 for (i = lle->ll_count - 1; i >= 0; i--) {
2326                         witness_list_lock(&lle->ll_children[i], prnt);
2327                         nheld++;
2328                 }
2329         return (nheld);
2330 }
2331
2332 /*
2333  * This is a bit risky at best.  We call this function when we have timed
2334  * out acquiring a spin lock, and we assume that the other CPU is stuck
2335  * with this lock held.  So, we go groveling around in the other CPU's
2336  * per-cpu data to try to find the lock instance for this spin lock to
2337  * see when it was last acquired.
2338  */
2339 void
2340 witness_display_spinlock(struct lock_object *lock, struct thread *owner,
2341     int (*prnt)(const char *fmt, ...))
2342 {
2343         struct lock_instance *instance;
2344         struct pcpu *pc;
2345
2346         if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU)
2347                 return;
2348         pc = pcpu_find(owner->td_oncpu);
2349         instance = find_instance(pc->pc_spinlocks, lock);
2350         if (instance != NULL)
2351                 witness_list_lock(instance, prnt);
2352 }
2353
2354 void
2355 witness_save(struct lock_object *lock, const char **filep, int *linep)
2356 {
2357         struct lock_list_entry *lock_list;
2358         struct lock_instance *instance;
2359         struct lock_class *class;
2360
2361         /*
2362          * This function is used independently in locking code to deal with
2363          * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
2364          * is gone.
2365          */
2366         if (SCHEDULER_STOPPED())
2367                 return;
2368         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
2369         if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED())
2370                 return;
2371         class = LOCK_CLASS(lock);
2372         if (class->lc_flags & LC_SLEEPLOCK)
2373                 lock_list = curthread->td_sleeplocks;
2374         else {
2375                 if (witness_skipspin)
2376                         return;
2377                 lock_list = PCPU_GET(spinlocks);
2378         }
2379         instance = find_instance(lock_list, lock);
2380         if (instance == NULL) {
2381                 kassert_panic("%s: lock (%s) %s not locked", __func__,
2382                     class->lc_name, lock->lo_name);
2383                 return;
2384         }
2385         *filep = instance->li_file;
2386         *linep = instance->li_line;
2387 }
2388
2389 void
2390 witness_restore(struct lock_object *lock, const char *file, int line)
2391 {
2392         struct lock_list_entry *lock_list;
2393         struct lock_instance *instance;
2394         struct lock_class *class;
2395
2396         /*
2397          * This function is used independently in locking code to deal with
2398          * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
2399          * is gone.
2400          */
2401         if (SCHEDULER_STOPPED())
2402                 return;
2403         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
2404         if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED())
2405                 return;
2406         class = LOCK_CLASS(lock);
2407         if (class->lc_flags & LC_SLEEPLOCK)
2408                 lock_list = curthread->td_sleeplocks;
2409         else {
2410                 if (witness_skipspin)
2411                         return;
2412                 lock_list = PCPU_GET(spinlocks);
2413         }
2414         instance = find_instance(lock_list, lock);
2415         if (instance == NULL)
2416                 kassert_panic("%s: lock (%s) %s not locked", __func__,
2417                     class->lc_name, lock->lo_name);
2418         lock->lo_witness->w_file = file;
2419         lock->lo_witness->w_line = line;
2420         if (instance == NULL)
2421                 return;
2422         instance->li_file = file;
2423         instance->li_line = line;
2424 }
2425
2426 void
2427 witness_assert(const struct lock_object *lock, int flags, const char *file,
2428     int line)
2429 {
2430 #ifdef INVARIANT_SUPPORT
2431         struct lock_instance *instance;
2432         struct lock_class *class;
2433
2434         if (lock->lo_witness == NULL || witness_watch < 1 || KERNEL_PANICKED())
2435                 return;
2436         class = LOCK_CLASS(lock);
2437         if ((class->lc_flags & LC_SLEEPLOCK) != 0)
2438                 instance = find_instance(curthread->td_sleeplocks, lock);
2439         else if ((class->lc_flags & LC_SPINLOCK) != 0)
2440                 instance = find_instance(PCPU_GET(spinlocks), lock);
2441         else {
2442                 kassert_panic("Lock (%s) %s is not sleep or spin!",
2443                     class->lc_name, lock->lo_name);
2444                 return;
2445         }
2446         switch (flags) {
2447         case LA_UNLOCKED:
2448                 if (instance != NULL)
2449                         kassert_panic("Lock (%s) %s locked @ %s:%d.",
2450                             class->lc_name, lock->lo_name,
2451                             fixup_filename(file), line);
2452                 break;
2453         case LA_LOCKED:
2454         case LA_LOCKED | LA_RECURSED:
2455         case LA_LOCKED | LA_NOTRECURSED:
2456         case LA_SLOCKED:
2457         case LA_SLOCKED | LA_RECURSED:
2458         case LA_SLOCKED | LA_NOTRECURSED:
2459         case LA_XLOCKED:
2460         case LA_XLOCKED | LA_RECURSED:
2461         case LA_XLOCKED | LA_NOTRECURSED:
2462                 if (instance == NULL) {
2463                         kassert_panic("Lock (%s) %s not locked @ %s:%d.",
2464                             class->lc_name, lock->lo_name,
2465                             fixup_filename(file), line);
2466                         break;
2467                 }
2468                 if ((flags & LA_XLOCKED) != 0 &&
2469                     (instance->li_flags & LI_EXCLUSIVE) == 0)
2470                         kassert_panic(
2471                             "Lock (%s) %s not exclusively locked @ %s:%d.",
2472                             class->lc_name, lock->lo_name,
2473                             fixup_filename(file), line);
2474                 if ((flags & LA_SLOCKED) != 0 &&
2475                     (instance->li_flags & LI_EXCLUSIVE) != 0)
2476                         kassert_panic(
2477                             "Lock (%s) %s exclusively locked @ %s:%d.",
2478                             class->lc_name, lock->lo_name,
2479                             fixup_filename(file), line);
2480                 if ((flags & LA_RECURSED) != 0 &&
2481                     (instance->li_flags & LI_RECURSEMASK) == 0)
2482                         kassert_panic("Lock (%s) %s not recursed @ %s:%d.",
2483                             class->lc_name, lock->lo_name,
2484                             fixup_filename(file), line);
2485                 if ((flags & LA_NOTRECURSED) != 0 &&
2486                     (instance->li_flags & LI_RECURSEMASK) != 0)
2487                         kassert_panic("Lock (%s) %s recursed @ %s:%d.",
2488                             class->lc_name, lock->lo_name,
2489                             fixup_filename(file), line);
2490                 break;
2491         default:
2492                 kassert_panic("Invalid lock assertion at %s:%d.",
2493                     fixup_filename(file), line);
2494         }
2495 #endif  /* INVARIANT_SUPPORT */
2496 }
2497
2498 static void
2499 witness_setflag(struct lock_object *lock, int flag, int set)
2500 {
2501         struct lock_list_entry *lock_list;
2502         struct lock_instance *instance;
2503         struct lock_class *class;
2504
2505         if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED())
2506                 return;
2507         class = LOCK_CLASS(lock);
2508         if (class->lc_flags & LC_SLEEPLOCK)
2509                 lock_list = curthread->td_sleeplocks;
2510         else {
2511                 if (witness_skipspin)
2512                         return;
2513                 lock_list = PCPU_GET(spinlocks);
2514         }
2515         instance = find_instance(lock_list, lock);
2516         if (instance == NULL) {
2517                 kassert_panic("%s: lock (%s) %s not locked", __func__,
2518                     class->lc_name, lock->lo_name);
2519                 return;
2520         }
2521
2522         if (set)
2523                 instance->li_flags |= flag;
2524         else
2525                 instance->li_flags &= ~flag;
2526 }
2527
2528 void
2529 witness_norelease(struct lock_object *lock)
2530 {
2531
2532         witness_setflag(lock, LI_NORELEASE, 1);
2533 }
2534
2535 void
2536 witness_releaseok(struct lock_object *lock)
2537 {
2538
2539         witness_setflag(lock, LI_NORELEASE, 0);
2540 }
2541
2542 #ifdef DDB
2543 static void
2544 witness_ddb_list(struct thread *td)
2545 {
2546
2547         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
2548         KASSERT(kdb_active, ("%s: not in the debugger", __func__));
2549
2550         if (witness_watch < 1)
2551                 return;
2552
2553         witness_list_locks(&td->td_sleeplocks, db_printf);
2554
2555         /*
2556          * We only handle spinlocks if td == curthread.  This is somewhat broken
2557          * if td is currently executing on some other CPU and holds spin locks
2558          * as we won't display those locks.  If we had a MI way of getting
2559          * the per-cpu data for a given cpu then we could use
2560          * td->td_oncpu to get the list of spinlocks for this thread
2561          * and "fix" this.
2562          *
2563          * That still wouldn't really fix this unless we locked the scheduler
2564          * lock or stopped the other CPU to make sure it wasn't changing the
2565          * list out from under us.  It is probably best to just not try to
2566          * handle threads on other CPU's for now.
2567          */
2568         if (td == curthread && PCPU_GET(spinlocks) != NULL)
2569                 witness_list_locks(PCPU_PTR(spinlocks), db_printf);
2570 }
2571
2572 DB_SHOW_COMMAND(locks, db_witness_list)
2573 {
2574         struct thread *td;
2575
2576         if (have_addr)
2577                 td = db_lookup_thread(addr, true);
2578         else
2579                 td = kdb_thread;
2580         witness_ddb_list(td);
2581 }
2582
2583 DB_SHOW_ALL_COMMAND(locks, db_witness_list_all)
2584 {
2585         struct thread *td;
2586         struct proc *p;
2587
2588         /*
2589          * It would be nice to list only threads and processes that actually
2590          * held sleep locks, but that information is currently not exported
2591          * by WITNESS.
2592          */
2593         FOREACH_PROC_IN_SYSTEM(p) {
2594                 if (!witness_proc_has_locks(p))
2595                         continue;
2596                 FOREACH_THREAD_IN_PROC(p, td) {
2597                         if (!witness_thread_has_locks(td))
2598                                 continue;
2599                         db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid,
2600                             p->p_comm, td, td->td_tid);
2601                         witness_ddb_list(td);
2602                         if (db_pager_quit)
2603                                 return;
2604                 }
2605         }
2606 }
2607 DB_SHOW_ALIAS(alllocks, db_witness_list_all)
2608
2609 DB_SHOW_COMMAND(witness, db_witness_display)
2610 {
2611
2612         witness_ddb_display(db_printf);
2613 }
2614 #endif
2615
2616 static void
2617 sbuf_print_witness_badstacks(struct sbuf *sb, size_t *oldidx)
2618 {
2619         struct witness_lock_order_data *data1, *data2, *tmp_data1, *tmp_data2;
2620         struct witness *tmp_w1, *tmp_w2, *w1, *w2;
2621         int generation, i, j;
2622
2623         tmp_data1 = NULL;
2624         tmp_data2 = NULL;
2625         tmp_w1 = NULL;
2626         tmp_w2 = NULL;
2627
2628         /* Allocate and init temporary storage space. */
2629         tmp_w1 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
2630         tmp_w2 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
2631         tmp_data1 = malloc(sizeof(struct witness_lock_order_data), M_TEMP,
2632             M_WAITOK | M_ZERO);
2633         tmp_data2 = malloc(sizeof(struct witness_lock_order_data), M_TEMP,
2634             M_WAITOK | M_ZERO);
2635         stack_zero(&tmp_data1->wlod_stack);
2636         stack_zero(&tmp_data2->wlod_stack);
2637
2638 restart:
2639         mtx_lock_spin(&w_mtx);
2640         generation = w_generation;
2641         mtx_unlock_spin(&w_mtx);
2642         sbuf_printf(sb, "Number of known direct relationships is %d\n",
2643             w_lohash.wloh_count);
2644         for (i = 1; i < w_max_used_index; i++) {
2645                 mtx_lock_spin(&w_mtx);
2646                 if (generation != w_generation) {
2647                         mtx_unlock_spin(&w_mtx);
2648
2649                         /* The graph has changed, try again. */
2650                         *oldidx = 0;
2651                         sbuf_clear(sb);
2652                         goto restart;
2653                 }
2654
2655                 w1 = &w_data[i];
2656                 if (w1->w_reversed == 0) {
2657                         mtx_unlock_spin(&w_mtx);
2658                         continue;
2659                 }
2660
2661                 /* Copy w1 locally so we can release the spin lock. */
2662                 *tmp_w1 = *w1;
2663                 mtx_unlock_spin(&w_mtx);
2664
2665                 if (tmp_w1->w_reversed == 0)
2666                         continue;
2667                 for (j = 1; j < w_max_used_index; j++) {
2668                         if ((w_rmatrix[i][j] & WITNESS_REVERSAL) == 0 || i > j)
2669                                 continue;
2670
2671                         mtx_lock_spin(&w_mtx);
2672                         if (generation != w_generation) {
2673                                 mtx_unlock_spin(&w_mtx);
2674
2675                                 /* The graph has changed, try again. */
2676                                 *oldidx = 0;
2677                                 sbuf_clear(sb);
2678                                 goto restart;
2679                         }
2680
2681                         w2 = &w_data[j];
2682                         data1 = witness_lock_order_get(w1, w2);
2683                         data2 = witness_lock_order_get(w2, w1);
2684
2685                         /*
2686                          * Copy information locally so we can release the
2687                          * spin lock.
2688                          */
2689                         *tmp_w2 = *w2;
2690
2691                         if (data1) {
2692                                 stack_zero(&tmp_data1->wlod_stack);
2693                                 stack_copy(&data1->wlod_stack,
2694                                     &tmp_data1->wlod_stack);
2695                         }
2696                         if (data2 && data2 != data1) {
2697                                 stack_zero(&tmp_data2->wlod_stack);
2698                                 stack_copy(&data2->wlod_stack,
2699                                     &tmp_data2->wlod_stack);
2700                         }
2701                         mtx_unlock_spin(&w_mtx);
2702
2703                         if (blessed(tmp_w1, tmp_w2))
2704                                 continue;
2705
2706                         sbuf_printf(sb,
2707             "\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n",
2708                             tmp_w1->w_name, tmp_w1->w_class->lc_name,
2709                             tmp_w2->w_name, tmp_w2->w_class->lc_name);
2710                         if (data1) {
2711                                 sbuf_printf(sb,
2712                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
2713                                     tmp_w1->w_name, tmp_w1->w_class->lc_name,
2714                                     tmp_w2->w_name, tmp_w2->w_class->lc_name);
2715                                 stack_sbuf_print(sb, &tmp_data1->wlod_stack);
2716                                 sbuf_printf(sb, "\n");
2717                         }
2718                         if (data2 && data2 != data1) {
2719                                 sbuf_printf(sb,
2720                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
2721                                     tmp_w2->w_name, tmp_w2->w_class->lc_name,
2722                                     tmp_w1->w_name, tmp_w1->w_class->lc_name);
2723                                 stack_sbuf_print(sb, &tmp_data2->wlod_stack);
2724                                 sbuf_printf(sb, "\n");
2725                         }
2726                 }
2727         }
2728         mtx_lock_spin(&w_mtx);
2729         if (generation != w_generation) {
2730                 mtx_unlock_spin(&w_mtx);
2731
2732                 /*
2733                  * The graph changed while we were printing stack data,
2734                  * try again.
2735                  */
2736                 *oldidx = 0;
2737                 sbuf_clear(sb);
2738                 goto restart;
2739         }
2740         mtx_unlock_spin(&w_mtx);
2741
2742         /* Free temporary storage space. */
2743         free(tmp_data1, M_TEMP);
2744         free(tmp_data2, M_TEMP);
2745         free(tmp_w1, M_TEMP);
2746         free(tmp_w2, M_TEMP);
2747 }
2748
2749 static int
2750 sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS)
2751 {
2752         struct sbuf *sb;
2753         int error;
2754
2755         if (witness_watch < 1) {
2756                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
2757                 return (error);
2758         }
2759         if (witness_cold) {
2760                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
2761                 return (error);
2762         }
2763         error = 0;
2764         sb = sbuf_new(NULL, NULL, badstack_sbuf_size, SBUF_AUTOEXTEND);
2765         if (sb == NULL)
2766                 return (ENOMEM);
2767
2768         sbuf_print_witness_badstacks(sb, &req->oldidx);
2769
2770         sbuf_finish(sb);
2771         error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
2772         sbuf_delete(sb);
2773
2774         return (error);
2775 }
2776
2777 #ifdef DDB
2778 static int
2779 sbuf_db_printf_drain(void *arg __unused, const char *data, int len)
2780 {
2781
2782         return (db_printf("%.*s", len, data));
2783 }
2784
2785 DB_SHOW_COMMAND(badstacks, db_witness_badstacks)
2786 {
2787         struct sbuf sb;
2788         char buffer[128];
2789         size_t dummy;
2790
2791         sbuf_new(&sb, buffer, sizeof(buffer), SBUF_FIXEDLEN);
2792         sbuf_set_drain(&sb, sbuf_db_printf_drain, NULL);
2793         sbuf_print_witness_badstacks(&sb, &dummy);
2794         sbuf_finish(&sb);
2795 }
2796 #endif
2797
2798 static int
2799 sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS)
2800 {
2801         static const struct {
2802                 enum witness_channel channel;
2803                 const char *name;
2804         } channels[] = {
2805                 { WITNESS_CONSOLE, "console" },
2806                 { WITNESS_LOG, "log" },
2807                 { WITNESS_NONE, "none" },
2808         };
2809         char buf[16];
2810         u_int i;
2811         int error;
2812
2813         buf[0] = '\0';
2814         for (i = 0; i < nitems(channels); i++)
2815                 if (witness_channel == channels[i].channel) {
2816                         snprintf(buf, sizeof(buf), "%s", channels[i].name);
2817                         break;
2818                 }
2819
2820         error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
2821         if (error != 0 || req->newptr == NULL)
2822                 return (error);
2823
2824         error = EINVAL;
2825         for (i = 0; i < nitems(channels); i++)
2826                 if (strcmp(channels[i].name, buf) == 0) {
2827                         witness_channel = channels[i].channel;
2828                         error = 0;
2829                         break;
2830                 }
2831         return (error);
2832 }
2833
2834 static int
2835 sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS)
2836 {
2837         struct witness *w;
2838         struct sbuf *sb;
2839         int error;
2840
2841 #ifdef __i386__
2842         error = SYSCTL_OUT(req, w_notallowed, sizeof(w_notallowed));
2843         return (error);
2844 #endif
2845
2846         if (witness_watch < 1) {
2847                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
2848                 return (error);
2849         }
2850         if (witness_cold) {
2851                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
2852                 return (error);
2853         }
2854         error = 0;
2855
2856         error = sysctl_wire_old_buffer(req, 0);
2857         if (error != 0)
2858                 return (error);
2859         sb = sbuf_new_for_sysctl(NULL, NULL, FULLGRAPH_SBUF_SIZE, req);
2860         if (sb == NULL)
2861                 return (ENOMEM);
2862         sbuf_printf(sb, "\n");
2863
2864         mtx_lock_spin(&w_mtx);
2865         STAILQ_FOREACH(w, &w_all, w_list)
2866                 w->w_displayed = 0;
2867         STAILQ_FOREACH(w, &w_all, w_list)
2868                 witness_add_fullgraph(sb, w);
2869         mtx_unlock_spin(&w_mtx);
2870
2871         /*
2872          * Close the sbuf and return to userland.
2873          */
2874         error = sbuf_finish(sb);
2875         sbuf_delete(sb);
2876
2877         return (error);
2878 }
2879
2880 static int
2881 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS)
2882 {
2883         int error, value;
2884
2885         value = witness_watch;
2886         error = sysctl_handle_int(oidp, &value, 0, req);
2887         if (error != 0 || req->newptr == NULL)
2888                 return (error);
2889         if (value > 1 || value < -1 ||
2890             (witness_watch == -1 && value != witness_watch))
2891                 return (EINVAL);
2892         witness_watch = value;
2893         return (0);
2894 }
2895
2896 static void
2897 witness_add_fullgraph(struct sbuf *sb, struct witness *w)
2898 {
2899         int i;
2900
2901         if (w->w_displayed != 0 || (w->w_file == NULL && w->w_line == 0))
2902                 return;
2903         w->w_displayed = 1;
2904
2905         WITNESS_INDEX_ASSERT(w->w_index);
2906         for (i = 1; i <= w_max_used_index; i++) {
2907                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) {
2908                         sbuf_printf(sb, "\"%s\",\"%s\"\n", w->w_name,
2909                             w_data[i].w_name);
2910                         witness_add_fullgraph(sb, &w_data[i]);
2911                 }
2912         }
2913 }
2914
2915 /*
2916  * A simple hash function. Takes a key pointer and a key size. If size == 0,
2917  * interprets the key as a string and reads until the null
2918  * terminator. Otherwise, reads the first size bytes. Returns an unsigned 32-bit
2919  * hash value computed from the key.
2920  */
2921 static uint32_t
2922 witness_hash_djb2(const uint8_t *key, uint32_t size)
2923 {
2924         unsigned int hash = 5381;
2925         int i;
2926
2927         /* hash = hash * 33 + key[i] */
2928         if (size)
2929                 for (i = 0; i < size; i++)
2930                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
2931         else
2932                 for (i = 0; key[i] != 0; i++)
2933                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
2934
2935         return (hash);
2936 }
2937
2938 /*
2939  * Initializes the two witness hash tables. Called exactly once from
2940  * witness_initialize().
2941  */
2942 static void
2943 witness_init_hash_tables(void)
2944 {
2945         int i;
2946
2947         MPASS(witness_cold);
2948
2949         /* Initialize the hash tables. */
2950         for (i = 0; i < WITNESS_HASH_SIZE; i++)
2951                 w_hash.wh_array[i] = NULL;
2952
2953         w_hash.wh_size = WITNESS_HASH_SIZE;
2954         w_hash.wh_count = 0;
2955
2956         /* Initialize the lock order data hash. */
2957         w_lofree = NULL;
2958         for (i = 0; i < WITNESS_LO_DATA_COUNT; i++) {
2959                 memset(&w_lodata[i], 0, sizeof(w_lodata[i]));
2960                 w_lodata[i].wlod_next = w_lofree;
2961                 w_lofree = &w_lodata[i];
2962         }
2963         w_lohash.wloh_size = WITNESS_LO_HASH_SIZE;
2964         w_lohash.wloh_count = 0;
2965         for (i = 0; i < WITNESS_LO_HASH_SIZE; i++)
2966                 w_lohash.wloh_array[i] = NULL;
2967 }
2968
2969 static struct witness *
2970 witness_hash_get(const char *key)
2971 {
2972         struct witness *w;
2973         uint32_t hash;
2974
2975         MPASS(key != NULL);
2976         if (witness_cold == 0)
2977                 mtx_assert(&w_mtx, MA_OWNED);
2978         hash = witness_hash_djb2(key, 0) % w_hash.wh_size;
2979         w = w_hash.wh_array[hash];
2980         while (w != NULL) {
2981                 if (strcmp(w->w_name, key) == 0)
2982                         goto out;
2983                 w = w->w_hash_next;
2984         }
2985
2986 out:
2987         return (w);
2988 }
2989
2990 static void
2991 witness_hash_put(struct witness *w)
2992 {
2993         uint32_t hash;
2994
2995         MPASS(w != NULL);
2996         MPASS(w->w_name != NULL);
2997         if (witness_cold == 0)
2998                 mtx_assert(&w_mtx, MA_OWNED);
2999         KASSERT(witness_hash_get(w->w_name) == NULL,
3000             ("%s: trying to add a hash entry that already exists!", __func__));
3001         KASSERT(w->w_hash_next == NULL,
3002             ("%s: w->w_hash_next != NULL", __func__));
3003
3004         hash = witness_hash_djb2(w->w_name, 0) % w_hash.wh_size;
3005         w->w_hash_next = w_hash.wh_array[hash];
3006         w_hash.wh_array[hash] = w;
3007         w_hash.wh_count++;
3008 }
3009
3010 static struct witness_lock_order_data *
3011 witness_lock_order_get(struct witness *parent, struct witness *child)
3012 {
3013         struct witness_lock_order_data *data = NULL;
3014         struct witness_lock_order_key key;
3015         unsigned int hash;
3016
3017         MPASS(parent != NULL && child != NULL);
3018         key.from = parent->w_index;
3019         key.to = child->w_index;
3020         WITNESS_INDEX_ASSERT(key.from);
3021         WITNESS_INDEX_ASSERT(key.to);
3022         if ((w_rmatrix[parent->w_index][child->w_index]
3023             & WITNESS_LOCK_ORDER_KNOWN) == 0)
3024                 goto out;
3025
3026         hash = witness_hash_djb2((const char*)&key,
3027             sizeof(key)) % w_lohash.wloh_size;
3028         data = w_lohash.wloh_array[hash];
3029         while (data != NULL) {
3030                 if (witness_lock_order_key_equal(&data->wlod_key, &key))
3031                         break;
3032                 data = data->wlod_next;
3033         }
3034
3035 out:
3036         return (data);
3037 }
3038
3039 /*
3040  * Verify that parent and child have a known relationship, are not the same,
3041  * and child is actually a child of parent.  This is done without w_mtx
3042  * to avoid contention in the common case.
3043  */
3044 static int
3045 witness_lock_order_check(struct witness *parent, struct witness *child)
3046 {
3047
3048         if (parent != child &&
3049             w_rmatrix[parent->w_index][child->w_index]
3050             & WITNESS_LOCK_ORDER_KNOWN &&
3051             isitmychild(parent, child))
3052                 return (1);
3053
3054         return (0);
3055 }
3056
3057 static int
3058 witness_lock_order_add(struct witness *parent, struct witness *child)
3059 {
3060         struct witness_lock_order_data *data = NULL;
3061         struct witness_lock_order_key key;
3062         unsigned int hash;
3063
3064         MPASS(parent != NULL && child != NULL);
3065         key.from = parent->w_index;
3066         key.to = child->w_index;
3067         WITNESS_INDEX_ASSERT(key.from);
3068         WITNESS_INDEX_ASSERT(key.to);
3069         if (w_rmatrix[parent->w_index][child->w_index]
3070             & WITNESS_LOCK_ORDER_KNOWN)
3071                 return (1);
3072
3073         hash = witness_hash_djb2((const char*)&key,
3074             sizeof(key)) % w_lohash.wloh_size;
3075         w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN;
3076         data = w_lofree;
3077         if (data == NULL)
3078                 return (0);
3079         w_lofree = data->wlod_next;
3080         data->wlod_next = w_lohash.wloh_array[hash];
3081         data->wlod_key = key;
3082         w_lohash.wloh_array[hash] = data;
3083         w_lohash.wloh_count++;
3084         stack_zero(&data->wlod_stack);
3085         stack_save(&data->wlod_stack);
3086         return (1);
3087 }
3088
3089 /* Call this whenever the structure of the witness graph changes. */
3090 static void
3091 witness_increment_graph_generation(void)
3092 {
3093
3094         if (witness_cold == 0)
3095                 mtx_assert(&w_mtx, MA_OWNED);
3096         w_generation++;
3097 }
3098
3099 static int
3100 witness_output_drain(void *arg __unused, const char *data, int len)
3101 {
3102
3103         witness_output("%.*s", len, data);
3104         return (len);
3105 }
3106
3107 static void
3108 witness_debugger(int cond, const char *msg)
3109 {
3110         char buf[32];
3111         struct sbuf sb;
3112         struct stack st;
3113
3114         if (!cond)
3115                 return;
3116
3117         if (witness_trace) {
3118                 sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN);
3119                 sbuf_set_drain(&sb, witness_output_drain, NULL);
3120
3121                 stack_zero(&st);
3122                 stack_save(&st);
3123                 witness_output("stack backtrace:\n");
3124                 stack_sbuf_print_ddb(&sb, &st);
3125
3126                 sbuf_finish(&sb);
3127         }
3128
3129         witness_enter_debugger(msg);
3130 }
3131
3132 static void
3133 witness_enter_debugger(const char *msg)
3134 {
3135 #ifdef KDB
3136         if (witness_kdb)
3137                 kdb_enter(KDB_WHY_WITNESS, msg);
3138 #endif
3139 }