sys/kern/subr_witness.c

   1 /*-
   2  * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  * 3. Berkeley Software Design Inc's name may not be used to endorse or
  13  *    promote products derived from this software without specific prior
  14  *    written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
  20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  *
  28  *      from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
  29  *      and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
  30  */
  31
  32 /*
  33  * Implementation of the `witness' lock verifier.  Originally implemented for
  34  * mutexes in BSD/OS.  Extended to handle generic lock objects and lock
  35  * classes in FreeBSD.
  36  */
  37
  38 /*
  39  *      Main Entry: witness
  40  *      Pronunciation: 'wit-n&s
  41  *      Function: noun
  42  *      Etymology: Middle English witnesse, from Old English witnes knowledge,
  43  *          testimony, witness, from 2wit
  44  *      Date: before 12th century
  45  *      1 : attestation of a fact or event : TESTIMONY
  46  *      2 : one that gives evidence; specifically : one who testifies in
  47  *          a cause or before a judicial tribunal
  48  *      3 : one asked to be present at a transaction so as to be able to
  49  *          testify to its having taken place
  50  *      4 : one who has personal knowledge of something
  51  *      5 a : something serving as evidence or proof : SIGN
  52  *        b : public affirmation by word or example of usually
  53  *            religious faith or conviction <the heroic witness to divine
  54  *            life -- Pilot>
  55  *      6 capitalized : a member of the Jehovah's Witnesses
  56  */
  57
  58 /*
  59  * Special rules concerning Giant and lock orders:
  60  *
  61  * 1) Giant must be acquired before any other mutexes.  Stated another way,
  62  *    no other mutex may be held when Giant is acquired.
  63  *
  64  * 2) Giant must be released when blocking on a sleepable lock.
  65  *
  66  * This rule is less obvious, but is a result of Giant providing the same
  67  * semantics as spl().  Basically, when a thread sleeps, it must release
  68  * Giant.  When a thread blocks on a sleepable lock, it sleeps.  Hence rule
  69  * 2).
  70  *
  71  * 3) Giant may be acquired before or after sleepable locks.
  72  *
  73  * This rule is also not quite as obvious.  Giant may be acquired after
  74  * a sleepable lock because it is a non-sleepable lock and non-sleepable
  75  * locks may always be acquired while holding a sleepable lock.  The second
  76  * case, Giant before a sleepable lock, follows from rule 2) above.  Suppose
  77  * you have two threads T1 and T2 and a sleepable lock X.  Suppose that T1
  78  * acquires X and blocks on Giant.  Then suppose that T2 acquires Giant and
  79  * blocks on X.  When T2 blocks on X, T2 will release Giant allowing T1 to
  80  * execute.  Thus, acquiring Giant both before and after a sleepable lock
  81  * will not result in a lock order reversal.
  82  */
  83
  84 #include <sys/cdefs.h>
  85 __FBSDID("$FreeBSD$");
  86
  87 #include "opt_ddb.h"
  88 #include "opt_witness.h"
  89
  90 #include <sys/param.h>
  91 #include <sys/bus.h>
  92 #include <sys/kdb.h>
  93 #include <sys/kernel.h>
  94 #include <sys/ktr.h>
  95 #include <sys/lock.h>
  96 #include <sys/malloc.h>
  97 #include <sys/mutex.h>
  98 #include <sys/priv.h>
  99 #include <sys/proc.h>
 100 #include <sys/sysctl.h>
 101 #include <sys/systm.h>
 102
 103 #include <ddb/ddb.h>
 104
 105 #include <machine/stdarg.h>
 106
 107 /* Note that these traces do not work with KTR_ALQ. */
 108 #if 0
 109 #define KTR_WITNESS     KTR_SUBSYS
 110 #else
 111 #define KTR_WITNESS     0
 112 #endif
 113
 114 /* Easier to stay with the old names. */
 115 #define lo_list         lo_witness_data.lod_list
 116 #define lo_witness      lo_witness_data.lod_witness
 117
 118 /* Define this to check for blessed mutexes */
 119 #undef BLESSING
 120
 121 #define WITNESS_COUNT 1024
 122 #define WITNESS_CHILDCOUNT (WITNESS_COUNT * 4)
 123 /*
 124  * XXX: This is somewhat bogus, as we assume here that at most 1024 threads
 125  * will hold LOCK_NCHILDREN * 2 locks.  We handle failure ok, and we should
 126  * probably be safe for the most part, but it's still a SWAG.
 127  */
 128 #define LOCK_CHILDCOUNT (MAXCPU + 1024) * 2
 129
 130 #define WITNESS_NCHILDREN 6
 131
 132 struct witness_child_list_entry;
 133
 134 struct witness {
 135         const   char *w_name;
 136         struct  lock_class *w_class;
 137         STAILQ_ENTRY(witness) w_list;           /* List of all witnesses. */
 138         STAILQ_ENTRY(witness) w_typelist;       /* Witnesses of a type. */
 139         struct  witness_child_list_entry *w_children;   /* Great evilness... */
 140         const   char *w_file;
 141         int     w_line;
 142         u_int   w_level;
 143         u_int   w_refcount;
 144         u_char  w_Giant_squawked:1;
 145         u_char  w_other_squawked:1;
 146         u_char  w_same_squawked:1;
 147         u_char  w_displayed:1;
 148 };
 149
 150 struct witness_child_list_entry {
 151         struct  witness_child_list_entry *wcl_next;
 152         struct  witness *wcl_children[WITNESS_NCHILDREN];
 153         u_int   wcl_count;
 154 };
 155
 156 STAILQ_HEAD(witness_list, witness);
 157
 158 #ifdef BLESSING
 159 struct witness_blessed {
 160         const   char *b_lock1;
 161         const   char *b_lock2;
 162 };
 163 #endif
 164
 165 struct witness_order_list_entry {
 166         const   char *w_name;
 167         struct  lock_class *w_class;
 168 };
 169
 170 #ifdef BLESSING
 171 static int      blessed(struct witness *, struct witness *);
 172 #endif
 173 static int      depart(struct witness *w);
 174 static struct   witness *enroll(const char *description,
 175                                 struct lock_class *lock_class);
 176 static int      insertchild(struct witness *parent, struct witness *child);
 177 static int      isitmychild(struct witness *parent, struct witness *child);
 178 static int      isitmydescendant(struct witness *parent, struct witness *child);
 179 static int      itismychild(struct witness *parent, struct witness *child);
 180 static void     removechild(struct witness *parent, struct witness *child);
 181 static int      sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS);
 182 static const char *fixup_filename(const char *file);
 183 static struct   witness *witness_get(void);
 184 static void     witness_free(struct witness *m);
 185 static struct   witness_child_list_entry *witness_child_get(void);
 186 static void     witness_child_free(struct witness_child_list_entry *wcl);
 187 static struct   lock_list_entry *witness_lock_list_get(void);
 188 static void     witness_lock_list_free(struct lock_list_entry *lle);
 189 static struct   lock_instance *find_instance(struct lock_list_entry *lock_list,
 190                                              struct lock_object *lock);
 191 static void     witness_list_lock(struct lock_instance *instance);
 192 #ifdef DDB
 193 static void     witness_leveldescendents(struct witness *parent, int level);
 194 static void     witness_levelall(void);
 195 static void     witness_displaydescendants(void(*)(const char *fmt, ...),
 196                                            struct witness *, int indent);
 197 static void     witness_display_list(void(*prnt)(const char *fmt, ...),
 198                                      struct witness_list *list);
 199 static void     witness_display(void(*)(const char *fmt, ...));
 200 static void     witness_list(struct thread *td);
 201 #endif
 202
 203 SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW, 0, "Witness Locking");
 204
 205 /*
 206  * If set to 0, witness is disabled.  If set to a non-zero value, witness
 207  * performs full lock order checking for all locks.  At runtime, this
 208  * value may be set to 0 to turn off witness.  witness is not allowed be
 209  * turned on once it is turned off, however.
 210  */
 211 static int witness_watch = 1;
 212 TUNABLE_INT("debug.witness.watch", &witness_watch);
 213 SYSCTL_PROC(_debug_witness, OID_AUTO, watch, CTLFLAG_RW | CTLTYPE_INT, NULL, 0,
 214     sysctl_debug_witness_watch, "I", "witness is watching lock operations");
 215
 216 #ifdef KDB
 217 /*
 218  * When KDB is enabled and witness_kdb is set to 1, it will cause the system
 219  * to drop into kdebug() when:
 220  *      - a lock hierarchy violation occurs
 221  *      - locks are held when going to sleep.
 222  */
 223 #ifdef WITNESS_KDB
 224 int     witness_kdb = 1;
 225 #else
 226 int     witness_kdb = 0;
 227 #endif
 228 TUNABLE_INT("debug.witness.kdb", &witness_kdb);
 229 SYSCTL_INT(_debug_witness, OID_AUTO, kdb, CTLFLAG_RW, &witness_kdb, 0, "");
 230
 231 /*
 232  * When KDB is enabled and witness_trace is set to 1, it will cause the system
 233  * to print a stack trace:
 234  *      - a lock hierarchy violation occurs
 235  *      - locks are held when going to sleep.
 236  */
 237 int     witness_trace = 1;
 238 TUNABLE_INT("debug.witness.trace", &witness_trace);
 239 SYSCTL_INT(_debug_witness, OID_AUTO, trace, CTLFLAG_RW, &witness_trace, 0, "");
 240 #endif /* KDB */
 241
 242 #ifdef WITNESS_SKIPSPIN
 243 int     witness_skipspin = 1;
 244 #else
 245 int     witness_skipspin = 0;
 246 #endif
 247 TUNABLE_INT("debug.witness.skipspin", &witness_skipspin);
 248 SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN,
 249     &witness_skipspin, 0, "");
 250
 251 static struct mtx w_mtx;
 252 static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free);
 253 static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all);
 254 static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin);
 255 static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep);
 256 static struct witness_child_list_entry *w_child_free = NULL;
 257 static struct lock_list_entry *w_lock_list_free = NULL;
 258
 259 static int w_free_cnt, w_spin_cnt, w_sleep_cnt, w_child_free_cnt, w_child_cnt;
 260 SYSCTL_INT(_debug_witness, OID_AUTO, free_cnt, CTLFLAG_RD, &w_free_cnt, 0, "");
 261 SYSCTL_INT(_debug_witness, OID_AUTO, spin_cnt, CTLFLAG_RD, &w_spin_cnt, 0, "");
 262 SYSCTL_INT(_debug_witness, OID_AUTO, sleep_cnt, CTLFLAG_RD, &w_sleep_cnt, 0,
 263     "");
 264 SYSCTL_INT(_debug_witness, OID_AUTO, child_free_cnt, CTLFLAG_RD,
 265     &w_child_free_cnt, 0, "");
 266 SYSCTL_INT(_debug_witness, OID_AUTO, child_cnt, CTLFLAG_RD, &w_child_cnt, 0,
 267     "");
 268
 269 static struct witness w_data[WITNESS_COUNT];
 270 static struct witness_child_list_entry w_childdata[WITNESS_CHILDCOUNT];
 271 static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT];
 272
 273 static struct witness_order_list_entry order_lists[] = {
 274         /*
 275          * sx locks
 276          */
 277         { "proctree", &lock_class_sx },
 278         { "allproc", &lock_class_sx },
 279         { NULL, NULL },
 280         /*
 281          * Various mutexes
 282          */
 283         { "Giant", &lock_class_mtx_sleep },
 284         { "filedesc structure", &lock_class_mtx_sleep },
 285         { "pipe mutex", &lock_class_mtx_sleep },
 286         { "sigio lock", &lock_class_mtx_sleep },
 287         { "process group", &lock_class_mtx_sleep },
 288         { "process lock", &lock_class_mtx_sleep },
 289         { "session", &lock_class_mtx_sleep },
 290         { "uidinfo hash", &lock_class_mtx_sleep },
 291         { "uidinfo struct", &lock_class_mtx_sleep },
 292         { "allprison", &lock_class_mtx_sleep },
 293         { NULL, NULL },
 294         /*
 295          * Sockets
 296          */
 297         { "filedesc structure", &lock_class_mtx_sleep },
 298         { "accept", &lock_class_mtx_sleep },
 299         { "so_snd", &lock_class_mtx_sleep },
 300         { "so_rcv", &lock_class_mtx_sleep },
 301         { "sellck", &lock_class_mtx_sleep },
 302         { NULL, NULL },
 303         /*
 304          * Routing
 305          */
 306         { "so_rcv", &lock_class_mtx_sleep },
 307         { "radix node head", &lock_class_mtx_sleep },
 308         { "rtentry", &lock_class_mtx_sleep },
 309         { "ifaddr", &lock_class_mtx_sleep },
 310         { NULL, NULL },
 311         /*
 312          * Multicast - protocol locks before interface locks, after UDP locks.
 313          */
 314         { "udpinp", &lock_class_mtx_sleep },
 315         { "in_multi_mtx", &lock_class_mtx_sleep },
 316         { "igmp_mtx", &lock_class_mtx_sleep },
 317         { "if_addr_mtx", &lock_class_mtx_sleep },
 318         { NULL, NULL },
 319         /*
 320          * UNIX Domain Sockets
 321          */
 322         { "unp", &lock_class_mtx_sleep },
 323         { "so_snd", &lock_class_mtx_sleep },
 324         { NULL, NULL },
 325         /*
 326          * UDP/IP
 327          */
 328         { "udp", &lock_class_mtx_sleep },
 329         { "udpinp", &lock_class_mtx_sleep },
 330         { "so_snd", &lock_class_mtx_sleep },
 331         { NULL, NULL },
 332         /*
 333          * TCP/IP
 334          */
 335         { "tcp", &lock_class_mtx_sleep },
 336         { "tcpinp", &lock_class_mtx_sleep },
 337         { "so_snd", &lock_class_mtx_sleep },
 338         { NULL, NULL },
 339         /*
 340          * SLIP
 341          */
 342         { "slip_mtx", &lock_class_mtx_sleep },
 343         { "slip sc_mtx", &lock_class_mtx_sleep },
 344         { NULL, NULL },
 345         /*
 346          * netatalk
 347          */
 348         { "ddp_list_mtx", &lock_class_mtx_sleep },
 349         { "ddp_mtx", &lock_class_mtx_sleep },
 350         { NULL, NULL },
 351         /*
 352          * BPF
 353          */
 354         { "bpf global lock", &lock_class_mtx_sleep },
 355         { "bpf interface lock", &lock_class_mtx_sleep },
 356         { "bpf cdev lock", &lock_class_mtx_sleep },
 357         { NULL, NULL },
 358         /*
 359          * NFS server
 360          */
 361         { "nfsd_mtx", &lock_class_mtx_sleep },
 362         { "so_snd", &lock_class_mtx_sleep },
 363         { NULL, NULL },
 364         /*
 365          * CDEV
 366          */
 367         { "system map", &lock_class_mtx_sleep },
 368         { "vm page queue mutex", &lock_class_mtx_sleep },
 369         { "vnode interlock", &lock_class_mtx_sleep },
 370         { "cdev", &lock_class_mtx_sleep },
 371         { NULL, NULL },
 372         /*
 373          * spin locks
 374          */
 375 #ifdef SMP
 376         { "ap boot", &lock_class_mtx_spin },
 377 #endif
 378         { "rm.mutex_mtx", &lock_class_mtx_spin },
 379         { "hptlock", &lock_class_mtx_spin },
 380         { "sio", &lock_class_mtx_spin },
 381 #ifdef __i386__
 382         { "cy", &lock_class_mtx_spin },
 383 #endif
 384         { "scc_hwmtx", &lock_class_mtx_spin },
 385         { "uart_hwmtx", &lock_class_mtx_spin },
 386         { "zstty", &lock_class_mtx_spin },
 387         { "ng_node", &lock_class_mtx_spin },
 388         { "ng_worklist", &lock_class_mtx_spin },
 389         { "fast_taskqueue", &lock_class_mtx_spin },
 390         { "intr table", &lock_class_mtx_spin },
 391         { "sleepq chain", &lock_class_mtx_spin },
 392         { "sched lock", &lock_class_mtx_spin },
 393         { "turnstile chain", &lock_class_mtx_spin },
 394         { "td_contested", &lock_class_mtx_spin },
 395         { "callout", &lock_class_mtx_spin },
 396         { "entropy harvest mutex", &lock_class_mtx_spin },
 397         { "syscons video lock", &lock_class_mtx_spin },
 398         /*
 399          * leaf locks
 400          */
 401         { "allpmaps", &lock_class_mtx_spin },
 402         { "vm page queue free mutex", &lock_class_mtx_spin },
 403         { "icu", &lock_class_mtx_spin },
 404 #ifdef SMP
 405         { "smp rendezvous", &lock_class_mtx_spin },
 406 #if defined(__i386__) || defined(__amd64__)
 407         { "tlb", &lock_class_mtx_spin },
 408 #endif
 409 #ifdef __sparc64__
 410         { "ipi", &lock_class_mtx_spin },
 411         { "rtc_mtx", &lock_class_mtx_spin },
 412 #endif
 413 #endif
 414         { "clk", &lock_class_mtx_spin },
 415         { "mutex profiling lock", &lock_class_mtx_spin },
 416         { "kse zombie lock", &lock_class_mtx_spin },
 417         { "ALD Queue", &lock_class_mtx_spin },
 418 #ifdef __ia64__
 419         { "MCA spin lock", &lock_class_mtx_spin },
 420 #endif
 421 #if defined(__i386__) || defined(__amd64__)
 422         { "pcicfg", &lock_class_mtx_spin },
 423         { "NDIS thread lock", &lock_class_mtx_spin },
 424 #endif
 425         { "tw_osl_io_lock", &lock_class_mtx_spin },
 426         { "tw_osl_q_lock", &lock_class_mtx_spin },
 427         { "tw_cl_io_lock", &lock_class_mtx_spin },
 428         { "tw_cl_intr_lock", &lock_class_mtx_spin },
 429         { "tw_cl_gen_lock", &lock_class_mtx_spin },
 430         { NULL, NULL },
 431         { NULL, NULL }
 432 };
 433
 434 #ifdef BLESSING
 435 /*
 436  * Pairs of locks which have been blessed
 437  * Don't complain about order problems with blessed locks
 438  */
 439 static struct witness_blessed blessed_list[] = {
 440 };
 441 static int blessed_count =
 442         sizeof(blessed_list) / sizeof(struct witness_blessed);
 443 #endif
 444
 445 /*
 446  * List of locks initialized prior to witness being initialized whose
 447  * enrollment is currently deferred.
 448  */
 449 STAILQ_HEAD(, lock_object) pending_locks =
 450     STAILQ_HEAD_INITIALIZER(pending_locks);
 451
 452 /*
 453  * This global is set to 0 once it becomes safe to use the witness code.
 454  */
 455 static int witness_cold = 1;
 456
 457 /*
 458  * This global is set to 1 once the static lock orders have been enrolled
 459  * so that a warning can be issued for any spin locks enrolled later.
 460  */
 461 static int witness_spin_warn = 0;
 462
 463 /*
 464  * The WITNESS-enabled diagnostic code.  Note that the witness code does
 465  * assume that the early boot is single-threaded at least until after this
 466  * routine is completed.
 467  */
 468 static void
 469 witness_initialize(void *dummy __unused)
 470 {
 471         struct lock_object *lock;
 472         struct witness_order_list_entry *order;
 473         struct witness *w, *w1;
 474         int i;
 475
 476         /*
 477          * We have to release Giant before initializing its witness
 478          * structure so that WITNESS doesn't get confused.
 479          */
 480         mtx_unlock(&Giant);
 481         mtx_assert(&Giant, MA_NOTOWNED);
 482
 483         CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
 484         mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET |
 485             MTX_NOWITNESS | MTX_NOPROFILE);
 486         for (i = 0; i < WITNESS_COUNT; i++)
 487                 witness_free(&w_data[i]);
 488         for (i = 0; i < WITNESS_CHILDCOUNT; i++)
 489                 witness_child_free(&w_childdata[i]);
 490         for (i = 0; i < LOCK_CHILDCOUNT; i++)
 491                 witness_lock_list_free(&w_locklistdata[i]);
 492
 493         /* First add in all the specified order lists. */
 494         for (order = order_lists; order->w_name != NULL; order++) {
 495                 w = enroll(order->w_name, order->w_class);
 496                 if (w == NULL)
 497                         continue;
 498                 w->w_file = "order list";
 499                 for (order++; order->w_name != NULL; order++) {
 500                         w1 = enroll(order->w_name, order->w_class);
 501                         if (w1 == NULL)
 502                                 continue;
 503                         w1->w_file = "order list";
 504                         if (!itismychild(w, w1))
 505                                 panic("Not enough memory for static orders!");
 506                         w = w1;
 507                 }
 508         }
 509         witness_spin_warn = 1;
 510
 511         /* Iterate through all locks and add them to witness. */
 512         while (!STAILQ_EMPTY(&pending_locks)) {
 513                 lock = STAILQ_FIRST(&pending_locks);
 514                 STAILQ_REMOVE_HEAD(&pending_locks, lo_list);
 515                 KASSERT(lock->lo_flags & LO_WITNESS,
 516                     ("%s: lock %s is on pending list but not LO_WITNESS",
 517                     __func__, lock->lo_name));
 518                 lock->lo_witness = enroll(lock->lo_type, LOCK_CLASS(lock));
 519         }
 520
 521         /* Mark the witness code as being ready for use. */
 522         witness_cold = 0;
 523
 524         mtx_lock(&Giant);
 525 }
 526 SYSINIT(witness_init, SI_SUB_WITNESS, SI_ORDER_FIRST, witness_initialize, NULL)
 527
 528 static int
 529 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS)
 530 {
 531         int error, value;
 532
 533         value = witness_watch;
 534         error = sysctl_handle_int(oidp, &value, 0, req);
 535         if (error != 0 || req->newptr == NULL)
 536                 return (error);
 537         /*
 538          * XXXRW: Why a priv check here?
 539          */
 540         error = priv_check(req->td, PRIV_WITNESS);
 541         if (error != 0)
 542                 return (error);
 543         if (value == witness_watch)
 544                 return (0);
 545         if (value != 0)
 546                 return (EINVAL);
 547         witness_watch = 0;
 548         return (0);
 549 }
 550
 551 void
 552 witness_init(struct lock_object *lock)
 553 {
 554         struct lock_class *class;
 555
 556         /* Various sanity checks. */
 557         class = LOCK_CLASS(lock);
 558         if ((lock->lo_flags & LO_RECURSABLE) != 0 &&
 559             (class->lc_flags & LC_RECURSABLE) == 0)
 560                 panic("%s: lock (%s) %s can not be recursable", __func__,
 561                     class->lc_name, lock->lo_name);
 562         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 563             (class->lc_flags & LC_SLEEPABLE) == 0)
 564                 panic("%s: lock (%s) %s can not be sleepable", __func__,
 565                     class->lc_name, lock->lo_name);
 566         if ((lock->lo_flags & LO_UPGRADABLE) != 0 &&
 567             (class->lc_flags & LC_UPGRADABLE) == 0)
 568                 panic("%s: lock (%s) %s can not be upgradable", __func__,
 569                     class->lc_name, lock->lo_name);
 570
 571         /*
 572          * If we shouldn't watch this lock, then just clear lo_witness.
 573          * Otherwise, if witness_cold is set, then it is too early to
 574          * enroll this lock, so defer it to witness_initialize() by adding
 575          * it to the pending_locks list.  If it is not too early, then enroll
 576          * the lock now.
 577          */
 578         if (witness_watch == 0 || panicstr != NULL ||
 579             (lock->lo_flags & LO_WITNESS) == 0)
 580                 lock->lo_witness = NULL;
 581         else if (witness_cold) {
 582                 STAILQ_INSERT_TAIL(&pending_locks, lock, lo_list);
 583                 lock->lo_flags |= LO_ENROLLPEND;
 584         } else
 585                 lock->lo_witness = enroll(lock->lo_type, class);
 586 }
 587
 588 void
 589 witness_destroy(struct lock_object *lock)
 590 {
 591         struct lock_class *class;
 592         struct witness *w;
 593
 594         class = LOCK_CLASS(lock);
 595         if (witness_cold)
 596                 panic("lock (%s) %s destroyed while witness_cold",
 597                     class->lc_name, lock->lo_name);
 598
 599         /* XXX: need to verify that no one holds the lock */
 600         if ((lock->lo_flags & (LO_WITNESS | LO_ENROLLPEND)) == LO_WITNESS &&
 601             lock->lo_witness != NULL) {
 602                 w = lock->lo_witness;
 603                 mtx_lock_spin(&w_mtx);
 604                 MPASS(w->w_refcount > 0);
 605                 w->w_refcount--;
 606
 607                 /*
 608                  * Lock is already released if we have an allocation failure
 609                  * and depart() fails.
 610                  */
 611                 if (w->w_refcount != 0 || depart(w))
 612                         mtx_unlock_spin(&w_mtx);
 613         }
 614
 615         /*
 616          * If this lock is destroyed before witness is up and running,
 617          * remove it from the pending list.
 618          */
 619         if (lock->lo_flags & LO_ENROLLPEND) {
 620                 STAILQ_REMOVE(&pending_locks, lock, lock_object, lo_list);
 621                 lock->lo_flags &= ~LO_ENROLLPEND;
 622         }
 623 }
 624
 625 #ifdef DDB
 626 static void
 627 witness_levelall (void)
 628 {
 629         struct witness_list *list;
 630         struct witness *w, *w1;
 631
 632         /*
 633          * First clear all levels.
 634          */
 635         STAILQ_FOREACH(w, &w_all, w_list) {
 636                 w->w_level = 0;
 637         }
 638
 639         /*
 640          * Look for locks with no parent and level all their descendants.
 641          */
 642         STAILQ_FOREACH(w, &w_all, w_list) {
 643                 /*
 644                  * This is just an optimization, technically we could get
 645                  * away just walking the all list each time.
 646                  */
 647                 if (w->w_class->lc_flags & LC_SLEEPLOCK)
 648                         list = &w_sleep;
 649                 else
 650                         list = &w_spin;
 651                 STAILQ_FOREACH(w1, list, w_typelist) {
 652                         if (isitmychild(w1, w))
 653                                 goto skip;
 654                 }
 655                 witness_leveldescendents(w, 0);
 656         skip:
 657                 ;       /* silence GCC 3.x */
 658         }
 659 }
 660
 661 static void
 662 witness_leveldescendents(struct witness *parent, int level)
 663 {
 664         struct witness_child_list_entry *wcl;
 665         int i;
 666
 667         if (parent->w_level < level)
 668                 parent->w_level = level;
 669         level++;
 670         for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next)
 671                 for (i = 0; i < wcl->wcl_count; i++)
 672                         witness_leveldescendents(wcl->wcl_children[i], level);
 673 }
 674
 675 static void
 676 witness_displaydescendants(void(*prnt)(const char *fmt, ...),
 677                            struct witness *parent, int indent)
 678 {
 679         struct witness_child_list_entry *wcl;
 680         int i, level;
 681
 682         level = parent->w_level;
 683         prnt("%-2d", level);
 684         for (i = 0; i < indent; i++)
 685                 prnt(" ");
 686         if (parent->w_refcount > 0)
 687                 prnt("%s", parent->w_name);
 688         else
 689                 prnt("(dead)");
 690         if (parent->w_displayed) {
 691                 prnt(" -- (already displayed)\n");
 692                 return;
 693         }
 694         parent->w_displayed = 1;
 695         if (parent->w_refcount > 0) {
 696                 if (parent->w_file != NULL)
 697                         prnt(" -- last acquired @ %s:%d", parent->w_file,
 698                             parent->w_line);
 699         }
 700         prnt("\n");
 701         for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next)
 702                 for (i = 0; i < wcl->wcl_count; i++)
 703                             witness_displaydescendants(prnt,
 704                                 wcl->wcl_children[i], indent + 1);
 705 }
 706
 707 static void
 708 witness_display_list(void(*prnt)(const char *fmt, ...),
 709                      struct witness_list *list)
 710 {
 711         struct witness *w;
 712
 713         STAILQ_FOREACH(w, list, w_typelist) {
 714                 if (w->w_file == NULL || w->w_level > 0)
 715                         continue;
 716                 /*
 717                  * This lock has no anscestors, display its descendants.
 718                  */
 719                 witness_displaydescendants(prnt, w, 0);
 720         }
 721 }
 722
 723 static void
 724 witness_display(void(*prnt)(const char *fmt, ...))
 725 {
 726         struct witness *w;
 727
 728         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
 729         witness_levelall();
 730
 731         /* Clear all the displayed flags. */
 732         STAILQ_FOREACH(w, &w_all, w_list) {
 733                 w->w_displayed = 0;
 734         }
 735
 736         /*
 737          * First, handle sleep locks which have been acquired at least
 738          * once.
 739          */
 740         prnt("Sleep locks:\n");
 741         witness_display_list(prnt, &w_sleep);
 742
 743         /*
 744          * Now do spin locks which have been acquired at least once.
 745          */
 746         prnt("\nSpin locks:\n");
 747         witness_display_list(prnt, &w_spin);
 748
 749         /*
 750          * Finally, any locks which have not been acquired yet.
 751          */
 752         prnt("\nLocks which were never acquired:\n");
 753         STAILQ_FOREACH(w, &w_all, w_list) {
 754                 if (w->w_file != NULL || w->w_refcount == 0)
 755                         continue;
 756                 prnt("%s\n", w->w_name);
 757         }
 758 }
 759 #endif /* DDB */
 760
 761 /* Trim useless garbage from filenames. */
 762 static const char *
 763 fixup_filename(const char *file)
 764 {
 765
 766         if (file == NULL)
 767                 return (NULL);
 768         while (strncmp(file, "../", 3) == 0)
 769                 file += 3;
 770         return (file);
 771 }
 772
 773 int
 774 witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
 775 {
 776
 777         if (witness_watch == 0 || panicstr != NULL)
 778                 return (0);
 779
 780         /* Require locks that witness knows about. */
 781         if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL ||
 782             lock2->lo_witness == NULL)
 783                 return (EINVAL);
 784
 785         MPASS(!mtx_owned(&w_mtx));
 786         mtx_lock_spin(&w_mtx);
 787
 788         /*
 789          * If we already have either an explicit or implied lock order that
 790          * is the other way around, then return an error.
 791          */
 792         if (isitmydescendant(lock2->lo_witness, lock1->lo_witness)) {
 793                 mtx_unlock_spin(&w_mtx);
 794                 return (EDOOFUS);
 795         }
 796
 797         /* Try to add the new order. */
 798         CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 799             lock2->lo_type, lock1->lo_type);
 800         if (!itismychild(lock1->lo_witness, lock2->lo_witness))
 801                 return (ENOMEM);
 802         mtx_unlock_spin(&w_mtx);
 803         return (0);
 804 }
 805
 806 void
 807 witness_checkorder(struct lock_object *lock, int flags, const char *file,
 808     int line)
 809 {
 810         struct lock_list_entry **lock_list, *lle;
 811         struct lock_instance *lock1, *lock2;
 812         struct lock_class *class;
 813         struct witness *w, *w1;
 814         struct thread *td;
 815         int i, j;
 816
 817         if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL ||
 818             panicstr != NULL)
 819                 return;
 820
 821         /*
 822          * Try locks do not block if they fail to acquire the lock, thus
 823          * there is no danger of deadlocks or of switching while holding a
 824          * spin lock if we acquire a lock via a try operation.  This
 825          * function shouldn't even be called for try locks, so panic if
 826          * that happens.
 827          */
 828         if (flags & LOP_TRYLOCK)
 829                 panic("%s should not be called for try lock operations",
 830                     __func__);
 831
 832         w = lock->lo_witness;
 833         class = LOCK_CLASS(lock);
 834         td = curthread;
 835         file = fixup_filename(file);
 836
 837         if (class->lc_flags & LC_SLEEPLOCK) {
 838                 /*
 839                  * Since spin locks include a critical section, this check
 840                  * implicitly enforces a lock order of all sleep locks before
 841                  * all spin locks.
 842                  */
 843                 if (td->td_critnest != 0 && !kdb_active)
 844                         panic("blockable sleep lock (%s) %s @ %s:%d",
 845                             class->lc_name, lock->lo_name, file, line);
 846
 847                 /*
 848                  * If this is the first lock acquired then just return as
 849                  * no order checking is needed.
 850                  */
 851                 if (td->td_sleeplocks == NULL)
 852                         return;
 853                 lock_list = &td->td_sleeplocks;
 854         } else {
 855                 /*
 856                  * If this is the first lock, just return as no order
 857                  * checking is needed.  We check this in both if clauses
 858                  * here as unifying the check would require us to use a
 859                  * critical section to ensure we don't migrate while doing
 860                  * the check.  Note that if this is not the first lock, we
 861                  * are already in a critical section and are safe for the
 862                  * rest of the check.
 863                  */
 864                 if (PCPU_GET(spinlocks) == NULL)
 865                         return;
 866                 lock_list = PCPU_PTR(spinlocks);
 867         }
 868
 869         /*
 870          * Check to see if we are recursing on a lock we already own.  If
 871          * so, make sure that we don't mismatch exclusive and shared lock
 872          * acquires.
 873          */
 874         lock1 = find_instance(*lock_list, lock);
 875         if (lock1 != NULL) {
 876                 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 &&
 877                     (flags & LOP_EXCLUSIVE) == 0) {
 878                         printf("shared lock of (%s) %s @ %s:%d\n",
 879                             class->lc_name, lock->lo_name, file, line);
 880                         printf("while exclusively locked from %s:%d\n",
 881                             lock1->li_file, lock1->li_line);
 882                         panic("share->excl");
 883                 }
 884                 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
 885                     (flags & LOP_EXCLUSIVE) != 0) {
 886                         printf("exclusive lock of (%s) %s @ %s:%d\n",
 887                             class->lc_name, lock->lo_name, file, line);
 888                         printf("while share locked from %s:%d\n",
 889                             lock1->li_file, lock1->li_line);
 890                         panic("excl->share");
 891                 }
 892                 return;
 893         }
 894
 895         /*
 896          * Try locks do not block if they fail to acquire the lock, thus
 897          * there is no danger of deadlocks or of switching while holding a
 898          * spin lock if we acquire a lock via a try operation.
 899          */
 900         if (flags & LOP_TRYLOCK)
 901                 return;
 902
 903         /*
 904          * Check for duplicate locks of the same type.  Note that we only
 905          * have to check for this on the last lock we just acquired.  Any
 906          * other cases will be caught as lock order violations.
 907          */
 908         lock1 = &(*lock_list)->ll_children[(*lock_list)->ll_count - 1];
 909         w1 = lock1->li_lock->lo_witness;
 910         if (w1 == w) {
 911                 if (w->w_same_squawked || (lock->lo_flags & LO_DUPOK) ||
 912                     (flags & LOP_DUPOK))
 913                         return;
 914                 w->w_same_squawked = 1;
 915                 printf("acquiring duplicate lock of same type: \"%s\"\n",
 916                         lock->lo_type);
 917                 printf(" 1st %s @ %s:%d\n", lock1->li_lock->lo_name,
 918                     lock1->li_file, lock1->li_line);
 919                 printf(" 2nd %s @ %s:%d\n", lock->lo_name, file, line);
 920 #ifdef KDB
 921                 goto debugger;
 922 #else
 923                 return;
 924 #endif
 925         }
 926         MPASS(!mtx_owned(&w_mtx));
 927         mtx_lock_spin(&w_mtx);
 928         /*
 929          * If we know that the the lock we are acquiring comes after
 930          * the lock we most recently acquired in the lock order tree,
 931          * then there is no need for any further checks.
 932          */
 933         if (isitmychild(w1, w)) {
 934                 mtx_unlock_spin(&w_mtx);
 935                 return;
 936         }
 937         for (j = 0, lle = *lock_list; lle != NULL; lle = lle->ll_next) {
 938                 for (i = lle->ll_count - 1; i >= 0; i--, j++) {
 939
 940                         MPASS(j < WITNESS_COUNT);
 941                         lock1 = &lle->ll_children[i];
 942                         w1 = lock1->li_lock->lo_witness;
 943
 944                         /*
 945                          * If this lock doesn't undergo witness checking,
 946                          * then skip it.
 947                          */
 948                         if (w1 == NULL) {
 949                                 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0,
 950                                     ("lock missing witness structure"));
 951                                 continue;
 952                         }
 953                         /*
 954                          * If we are locking Giant and this is a sleepable
 955                          * lock, then skip it.
 956                          */
 957                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0 &&
 958                             lock == &Giant.mtx_object)
 959                                 continue;
 960                         /*
 961                          * If we are locking a sleepable lock and this lock
 962                          * is Giant, then skip it.
 963                          */
 964                         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 965                             lock1->li_lock == &Giant.mtx_object)
 966                                 continue;
 967                         /*
 968                          * If we are locking a sleepable lock and this lock
 969                          * isn't sleepable, we want to treat it as a lock
 970                          * order violation to enfore a general lock order of
 971                          * sleepable locks before non-sleepable locks.
 972                          */
 973                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 974                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
 975                                 goto reversal;
 976                         /*
 977                          * If we are locking Giant and this is a non-sleepable
 978                          * lock, then treat it as a reversal.
 979                          */
 980                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0 &&
 981                             lock == &Giant.mtx_object)
 982                                 goto reversal;
 983                         /*
 984                          * Check the lock order hierarchy for a reveresal.
 985                          */
 986                         if (!isitmydescendant(w, w1))
 987                                 continue;
 988                 reversal:
 989                         /*
 990                          * We have a lock order violation, check to see if it
 991                          * is allowed or has already been yelled about.
 992                          */
 993                         mtx_unlock_spin(&w_mtx);
 994 #ifdef BLESSING
 995                         /*
 996                          * If the lock order is blessed, just bail.  We don't
 997                          * look for other lock order violations though, which
 998                          * may be a bug.
 999                          */
1000                         if (blessed(w, w1))
1001                                 return;
1002 #endif
1003                         if (lock1->li_lock == &Giant.mtx_object) {
1004                                 if (w1->w_Giant_squawked)
1005                                         return;
1006                                 else
1007                                         w1->w_Giant_squawked = 1;
1008                         } else {
1009                                 if (w1->w_other_squawked)
1010                                         return;
1011                                 else
1012                                         w1->w_other_squawked = 1;
1013                         }
1014                         /*
1015                          * Ok, yell about it.
1016                          */
1017                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
1018                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
1019                                 printf(
1020                 "lock order reversal: (sleepable after non-sleepable)\n");
1021                         else if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0
1022                             && lock == &Giant.mtx_object)
1023                                 printf(
1024                 "lock order reversal: (Giant after non-sleepable)\n");
1025                         else
1026                                 printf("lock order reversal:\n");
1027                         /*
1028                          * Try to locate an earlier lock with
1029                          * witness w in our list.
1030                          */
1031                         do {
1032                                 lock2 = &lle->ll_children[i];
1033                                 MPASS(lock2->li_lock != NULL);
1034                                 if (lock2->li_lock->lo_witness == w)
1035                                         break;
1036                                 if (i == 0 && lle->ll_next != NULL) {
1037                                         lle = lle->ll_next;
1038                                         i = lle->ll_count - 1;
1039                                         MPASS(i >= 0 && i < LOCK_NCHILDREN);
1040                                 } else
1041                                         i--;
1042                         } while (i >= 0);
1043                         if (i < 0) {
1044                                 printf(" 1st %p %s (%s) @ %s:%d\n",
1045                                     lock1->li_lock, lock1->li_lock->lo_name,
1046                                     lock1->li_lock->lo_type, lock1->li_file,
1047                                     lock1->li_line);
1048                                 printf(" 2nd %p %s (%s) @ %s:%d\n", lock,
1049                                     lock->lo_name, lock->lo_type, file, line);
1050                         } else {
1051                                 printf(" 1st %p %s (%s) @ %s:%d\n",
1052                                     lock2->li_lock, lock2->li_lock->lo_name,
1053                                     lock2->li_lock->lo_type, lock2->li_file,
1054                                     lock2->li_line);
1055                                 printf(" 2nd %p %s (%s) @ %s:%d\n",
1056                                     lock1->li_lock, lock1->li_lock->lo_name,
1057                                     lock1->li_lock->lo_type, lock1->li_file,
1058                                     lock1->li_line);
1059                                 printf(" 3rd %p %s (%s) @ %s:%d\n", lock,
1060                                     lock->lo_name, lock->lo_type, file, line);
1061                         }
1062 #ifdef KDB
1063                         goto debugger;
1064 #else
1065                         return;
1066 #endif
1067                 }
1068         }
1069         lock1 = &(*lock_list)->ll_children[(*lock_list)->ll_count - 1];
1070         /*
1071          * If requested, build a new lock order.  However, don't build a new
1072          * relationship between a sleepable lock and Giant if it is in the
1073          * wrong direction.  The correct lock order is that sleepable locks
1074          * always come before Giant.
1075          */
1076         if (flags & LOP_NEWORDER &&
1077             !(lock1->li_lock == &Giant.mtx_object &&
1078             (lock->lo_flags & LO_SLEEPABLE) != 0)) {
1079                 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
1080                     lock->lo_type, lock1->li_lock->lo_type);
1081                 if (!itismychild(lock1->li_lock->lo_witness, w))
1082                         /* Witness is dead. */
1083                         return;
1084         }
1085         mtx_unlock_spin(&w_mtx);
1086         return;
1087
1088 #ifdef KDB
1089 debugger:
1090         if (witness_trace)
1091                 kdb_backtrace();
1092         if (witness_kdb)
1093                 kdb_enter(__func__);
1094 #endif
1095 }
1096
1097 void
1098 witness_lock(struct lock_object *lock, int flags, const char *file, int line)
1099 {
1100         struct lock_list_entry **lock_list, *lle;
1101         struct lock_instance *instance;
1102         struct witness *w;
1103         struct thread *td;
1104
1105         if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL ||
1106             panicstr != NULL)
1107                 return;
1108         w = lock->lo_witness;
1109         td = curthread;
1110         file = fixup_filename(file);
1111
1112         /* Determine lock list for this lock. */
1113         if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK)
1114                 lock_list = &td->td_sleeplocks;
1115         else
1116                 lock_list = PCPU_PTR(spinlocks);
1117
1118         /* Check to see if we are recursing on a lock we already own. */
1119         instance = find_instance(*lock_list, lock);
1120         if (instance != NULL) {
1121                 instance->li_flags++;
1122                 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__,
1123                     td->td_proc->p_pid, lock->lo_name,
1124                     instance->li_flags & LI_RECURSEMASK);
1125                 instance->li_file = file;
1126                 instance->li_line = line;
1127                 return;
1128         }
1129
1130         /* Update per-witness last file and line acquire. */
1131         w->w_file = file;
1132         w->w_line = line;
1133
1134         /* Find the next open lock instance in the list and fill it. */
1135         lle = *lock_list;
1136         if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
1137                 lle = witness_lock_list_get();
1138                 if (lle == NULL)
1139                         return;
1140                 lle->ll_next = *lock_list;
1141                 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__,
1142                     td->td_proc->p_pid, lle);
1143                 *lock_list = lle;
1144         }
1145         instance = &lle->ll_children[lle->ll_count++];
1146         instance->li_lock = lock;
1147         instance->li_line = line;
1148         instance->li_file = file;
1149         if ((flags & LOP_EXCLUSIVE) != 0)
1150                 instance->li_flags = LI_EXCLUSIVE;
1151         else
1152                 instance->li_flags = 0;
1153         CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__,
1154             td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1);
1155 }
1156
1157 void
1158 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line)
1159 {
1160         struct lock_instance *instance;
1161         struct lock_class *class;
1162
1163         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
1164         if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
1165                 return;
1166         class = LOCK_CLASS(lock);
1167         file = fixup_filename(file);
1168         if ((lock->lo_flags & LO_UPGRADABLE) == 0)
1169                 panic("upgrade of non-upgradable lock (%s) %s @ %s:%d",
1170                     class->lc_name, lock->lo_name, file, line);
1171         if ((flags & LOP_TRYLOCK) == 0)
1172                 panic("non-try upgrade of lock (%s) %s @ %s:%d", class->lc_name,
1173                     lock->lo_name, file, line);
1174         if ((class->lc_flags & LC_SLEEPLOCK) == 0)
1175                 panic("upgrade of non-sleep lock (%s) %s @ %s:%d",
1176                     class->lc_name, lock->lo_name, file, line);
1177         instance = find_instance(curthread->td_sleeplocks, lock);
1178         if (instance == NULL)
1179                 panic("upgrade of unlocked lock (%s) %s @ %s:%d",
1180                     class->lc_name, lock->lo_name, file, line);
1181         if ((instance->li_flags & LI_EXCLUSIVE) != 0)
1182                 panic("upgrade of exclusive lock (%s) %s @ %s:%d",
1183                     class->lc_name, lock->lo_name, file, line);
1184         if ((instance->li_flags & LI_RECURSEMASK) != 0)
1185                 panic("upgrade of recursed lock (%s) %s r=%d @ %s:%d",
1186                     class->lc_name, lock->lo_name,
1187                     instance->li_flags & LI_RECURSEMASK, file, line);
1188         instance->li_flags |= LI_EXCLUSIVE;
1189 }
1190
1191 void
1192 witness_downgrade(struct lock_object *lock, int flags, const char *file,
1193     int line)
1194 {
1195         struct lock_instance *instance;
1196         struct lock_class *class;
1197
1198         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
1199         if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
1200                 return;
1201         class = LOCK_CLASS(lock);
1202         file = fixup_filename(file);
1203         if ((lock->lo_flags & LO_UPGRADABLE) == 0)
1204                 panic("downgrade of non-upgradable lock (%s) %s @ %s:%d",
1205                     class->lc_name, lock->lo_name, file, line);
1206         if ((class->lc_flags & LC_SLEEPLOCK) == 0)
1207                 panic("downgrade of non-sleep lock (%s) %s @ %s:%d",
1208                     class->lc_name, lock->lo_name, file, line);
1209         instance = find_instance(curthread->td_sleeplocks, lock);
1210         if (instance == NULL)
1211                 panic("downgrade of unlocked lock (%s) %s @ %s:%d",
1212                     class->lc_name, lock->lo_name, file, line);
1213         if ((instance->li_flags & LI_EXCLUSIVE) == 0)
1214                 panic("downgrade of shared lock (%s) %s @ %s:%d",
1215                     class->lc_name, lock->lo_name, file, line);
1216         if ((instance->li_flags & LI_RECURSEMASK) != 0)
1217                 panic("downgrade of recursed lock (%s) %s r=%d @ %s:%d",
1218                     class->lc_name, lock->lo_name,
1219                     instance->li_flags & LI_RECURSEMASK, file, line);
1220         instance->li_flags &= ~LI_EXCLUSIVE;
1221 }
1222
1223 void
1224 witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
1225 {
1226         struct lock_list_entry **lock_list, *lle;
1227         struct lock_instance *instance;
1228         struct lock_class *class;
1229         struct thread *td;
1230         register_t s;
1231         int i, j;
1232
1233         if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL ||
1234             panicstr != NULL)
1235                 return;
1236         td = curthread;
1237         class = LOCK_CLASS(lock);
1238         file = fixup_filename(file);
1239
1240         /* Find lock instance associated with this lock. */
1241         if (class->lc_flags & LC_SLEEPLOCK)
1242                 lock_list = &td->td_sleeplocks;
1243         else
1244                 lock_list = PCPU_PTR(spinlocks);
1245         for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next)
1246                 for (i = 0; i < (*lock_list)->ll_count; i++) {
1247                         instance = &(*lock_list)->ll_children[i];
1248                         if (instance->li_lock == lock)
1249                                 goto found;
1250                 }
1251         panic("lock (%s) %s not locked @ %s:%d", class->lc_name, lock->lo_name,
1252             file, line);
1253 found:
1254
1255         /* First, check for shared/exclusive mismatches. */
1256         if ((instance->li_flags & LI_EXCLUSIVE) != 0 &&
1257             (flags & LOP_EXCLUSIVE) == 0) {
1258                 printf("shared unlock of (%s) %s @ %s:%d\n", class->lc_name,
1259                     lock->lo_name, file, line);
1260                 printf("while exclusively locked from %s:%d\n",
1261                     instance->li_file, instance->li_line);
1262                 panic("excl->ushare");
1263         }
1264         if ((instance->li_flags & LI_EXCLUSIVE) == 0 &&
1265             (flags & LOP_EXCLUSIVE) != 0) {
1266                 printf("exclusive unlock of (%s) %s @ %s:%d\n", class->lc_name,
1267                     lock->lo_name, file, line);
1268                 printf("while share locked from %s:%d\n", instance->li_file,
1269                     instance->li_line);
1270                 panic("share->uexcl");
1271         }
1272
1273         /* If we are recursed, unrecurse. */
1274         if ((instance->li_flags & LI_RECURSEMASK) > 0) {
1275                 CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__,
1276                     td->td_proc->p_pid, instance->li_lock->lo_name,
1277                     instance->li_flags);
1278                 instance->li_flags--;
1279                 return;
1280         }
1281
1282         /* Otherwise, remove this item from the list. */
1283         s = intr_disable();
1284         CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__,
1285             td->td_proc->p_pid, instance->li_lock->lo_name,
1286             (*lock_list)->ll_count - 1);
1287         for (j = i; j < (*lock_list)->ll_count - 1; j++)
1288                 (*lock_list)->ll_children[j] =
1289                     (*lock_list)->ll_children[j + 1];
1290         (*lock_list)->ll_count--;
1291         intr_restore(s);
1292
1293         /* If this lock list entry is now empty, free it. */
1294         if ((*lock_list)->ll_count == 0) {
1295                 lle = *lock_list;
1296                 *lock_list = lle->ll_next;
1297                 CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__,
1298                     td->td_proc->p_pid, lle);
1299                 witness_lock_list_free(lle);
1300         }
1301 }
1302
1303 /*
1304  * Warn if any locks other than 'lock' are held.  Flags can be passed in to
1305  * exempt Giant and sleepable locks from the checks as well.  If any
1306  * non-exempt locks are held, then a supplied message is printed to the
1307  * console along with a list of the offending locks.  If indicated in the
1308  * flags then a failure results in a panic as well.
1309  */
1310 int
1311 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
1312 {
1313         struct lock_list_entry *lle;
1314         struct lock_instance *lock1;
1315         struct thread *td;
1316         va_list ap;
1317         int i, n;
1318
1319         if (witness_cold || witness_watch == 0 || panicstr != NULL)
1320                 return (0);
1321         n = 0;
1322         td = curthread;
1323         for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next)
1324                 for (i = lle->ll_count - 1; i >= 0; i--) {
1325                         lock1 = &lle->ll_children[i];
1326                         if (lock1->li_lock == lock)
1327                                 continue;
1328                         if (flags & WARN_GIANTOK &&
1329                             lock1->li_lock == &Giant.mtx_object)
1330                                 continue;
1331                         if (flags & WARN_SLEEPOK &&
1332                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0)
1333                                 continue;
1334                         if (n == 0) {
1335                                 va_start(ap, fmt);
1336                                 vprintf(fmt, ap);
1337                                 va_end(ap);
1338                                 printf(" with the following");
1339                                 if (flags & WARN_SLEEPOK)
1340                                         printf(" non-sleepable");
1341                                 printf(" locks held:\n");
1342                         }
1343                         n++;
1344                         witness_list_lock(lock1);
1345                 }
1346         if (PCPU_GET(spinlocks) != NULL) {
1347                 /*
1348                  * Since we already hold a spinlock preemption is
1349                  * already blocked.
1350                  */
1351                 if (n == 0) {
1352                         va_start(ap, fmt);
1353                         vprintf(fmt, ap);
1354                         va_end(ap);
1355                         printf(" with the following");
1356                         if (flags & WARN_SLEEPOK)
1357                                 printf(" non-sleepable");
1358                         printf(" locks held:\n");
1359                 }
1360                 n += witness_list_locks(PCPU_PTR(spinlocks));
1361         }
1362         if (flags & WARN_PANIC && n)
1363                 panic("witness_warn");
1364 #ifdef KDB
1365         else if (witness_kdb && n)
1366                 kdb_enter(__func__);
1367         else if (witness_trace && n)
1368                 kdb_backtrace();
1369 #endif
1370         return (n);
1371 }
1372
1373 const char *
1374 witness_file(struct lock_object *lock)
1375 {
1376         struct witness *w;
1377
1378         if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL)
1379                 return ("?");
1380         w = lock->lo_witness;
1381         return (w->w_file);
1382 }
1383
1384 int
1385 witness_line(struct lock_object *lock)
1386 {
1387         struct witness *w;
1388
1389         if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL)
1390                 return (0);
1391         w = lock->lo_witness;
1392         return (w->w_line);
1393 }
1394
1395 static struct witness *
1396 enroll(const char *description, struct lock_class *lock_class)
1397 {
1398         struct witness *w;
1399
1400         if (witness_watch == 0 || panicstr != NULL)
1401                 return (NULL);
1402         if ((lock_class->lc_flags & LC_SPINLOCK) && witness_skipspin)
1403                 return (NULL);
1404         mtx_lock_spin(&w_mtx);
1405         STAILQ_FOREACH(w, &w_all, w_list) {
1406                 if (w->w_name == description || (w->w_refcount > 0 &&
1407                     strcmp(description, w->w_name) == 0)) {
1408                         w->w_refcount++;
1409                         mtx_unlock_spin(&w_mtx);
1410                         if (lock_class != w->w_class)
1411                                 panic(
1412                                 "lock (%s) %s does not match earlier (%s) lock",
1413                                     description, lock_class->lc_name,
1414                                     w->w_class->lc_name);
1415                         return (w);
1416                 }
1417         }
1418         if ((w = witness_get()) == NULL)
1419                 goto out;
1420         w->w_name = description;
1421         w->w_class = lock_class;
1422         w->w_refcount = 1;
1423         STAILQ_INSERT_HEAD(&w_all, w, w_list);
1424         if (lock_class->lc_flags & LC_SPINLOCK) {
1425                 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist);
1426                 w_spin_cnt++;
1427         } else if (lock_class->lc_flags & LC_SLEEPLOCK) {
1428                 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist);
1429                 w_sleep_cnt++;
1430         } else {
1431                 mtx_unlock_spin(&w_mtx);
1432                 panic("lock class %s is not sleep or spin",
1433                     lock_class->lc_name);
1434         }
1435         mtx_unlock_spin(&w_mtx);
1436 out:
1437         /*
1438          * We issue a warning for any spin locks not defined in the static
1439          * order list as a way to discourage their use (folks should really
1440          * be using non-spin mutexes most of the time).  However, several
1441          * 3rd part device drivers use spin locks because that is all they
1442          * have available on Windows and Linux and they think that normal
1443          * mutexes are insufficient.
1444          */
1445         if ((lock_class->lc_flags & LC_SPINLOCK) && witness_spin_warn)
1446                 printf("WITNESS: spin lock %s not in order list\n",
1447                     description);
1448         return (w);
1449 }
1450
1451 /* Don't let the door bang you on the way out... */
1452 static int
1453 depart(struct witness *w)
1454 {
1455         struct witness_child_list_entry *wcl, *nwcl;
1456         struct witness_list *list;
1457         struct witness *parent;
1458
1459         MPASS(w->w_refcount == 0);
1460         if (w->w_class->lc_flags & LC_SLEEPLOCK) {
1461                 list = &w_sleep;
1462                 w_sleep_cnt--;
1463         } else {
1464                 list = &w_spin;
1465                 w_spin_cnt--;
1466         }
1467         /*
1468          * First, we run through the entire tree looking for any
1469          * witnesses that the outgoing witness is a child of.  For
1470          * each parent that we find, we reparent all the direct
1471          * children of the outgoing witness to its parent.
1472          */
1473         STAILQ_FOREACH(parent, list, w_typelist) {
1474                 if (!isitmychild(parent, w))
1475                         continue;
1476                 removechild(parent, w);
1477         }
1478
1479         /*
1480          * Now we go through and free up the child list of the
1481          * outgoing witness.
1482          */
1483         for (wcl = w->w_children; wcl != NULL; wcl = nwcl) {
1484                 nwcl = wcl->wcl_next;
1485                 w_child_cnt--;
1486                 witness_child_free(wcl);
1487         }
1488
1489         /*
1490          * Detach from various lists and free.
1491          */
1492         STAILQ_REMOVE(list, w, witness, w_typelist);
1493         STAILQ_REMOVE(&w_all, w, witness, w_list);
1494         witness_free(w);
1495
1496         return (1);
1497 }
1498
1499 /*
1500  * Add "child" as a direct child of "parent".  Returns false if
1501  * we fail due to out of memory.
1502  */
1503 static int
1504 insertchild(struct witness *parent, struct witness *child)
1505 {
1506         struct witness_child_list_entry **wcl;
1507
1508         MPASS(child != NULL && parent != NULL);
1509
1510         /*
1511          * Insert "child" after "parent"
1512          */
1513         wcl = &parent->w_children;
1514         while (*wcl != NULL && (*wcl)->wcl_count == WITNESS_NCHILDREN)
1515                 wcl = &(*wcl)->wcl_next;
1516         if (*wcl == NULL) {
1517                 *wcl = witness_child_get();
1518                 if (*wcl == NULL)
1519                         return (0);
1520                 w_child_cnt++;
1521         }
1522         (*wcl)->wcl_children[(*wcl)->wcl_count++] = child;
1523
1524         return (1);
1525 }
1526
1527
1528 static int
1529 itismychild(struct witness *parent, struct witness *child)
1530 {
1531         struct witness_list *list;
1532
1533         MPASS(child != NULL && parent != NULL);
1534         if ((parent->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) !=
1535             (child->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)))
1536                 panic(
1537                 "%s: parent (%s) and child (%s) are not the same lock type",
1538                     __func__, parent->w_class->lc_name,
1539                     child->w_class->lc_name);
1540
1541         if (!insertchild(parent, child))
1542                 return (0);
1543
1544         if (parent->w_class->lc_flags & LC_SLEEPLOCK)
1545                 list = &w_sleep;
1546         else
1547                 list = &w_spin;
1548         return (1);
1549 }
1550
1551 static void
1552 removechild(struct witness *parent, struct witness *child)
1553 {
1554         struct witness_child_list_entry **wcl, *wcl1;
1555         int i;
1556
1557         for (wcl = &parent->w_children; *wcl != NULL; wcl = &(*wcl)->wcl_next)
1558                 for (i = 0; i < (*wcl)->wcl_count; i++)
1559                         if ((*wcl)->wcl_children[i] == child)
1560                                 goto found;
1561         return;
1562 found:
1563         (*wcl)->wcl_count--;
1564         if ((*wcl)->wcl_count > i)
1565                 (*wcl)->wcl_children[i] =
1566                     (*wcl)->wcl_children[(*wcl)->wcl_count];
1567         MPASS((*wcl)->wcl_children[i] != NULL);
1568         if ((*wcl)->wcl_count != 0)
1569                 return;
1570         wcl1 = *wcl;
1571         *wcl = wcl1->wcl_next;
1572         w_child_cnt--;
1573         witness_child_free(wcl1);
1574 }
1575
1576 static int
1577 isitmychild(struct witness *parent, struct witness *child)
1578 {
1579         struct witness_child_list_entry *wcl;
1580         int i;
1581
1582         for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) {
1583                 for (i = 0; i < wcl->wcl_count; i++) {
1584                         if (wcl->wcl_children[i] == child)
1585                                 return (1);
1586                 }
1587         }
1588         return (0);
1589 }
1590
1591 static int
1592 isitmydescendant(struct witness *parent, struct witness *child)
1593 {
1594         struct witness_child_list_entry *wcl;
1595         int i, j;
1596
1597         if (isitmychild(parent, child))
1598                 return (1);
1599         j = 0;
1600         for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) {
1601                 MPASS(j < 1000);
1602                 for (i = 0; i < wcl->wcl_count; i++) {
1603                         if (isitmydescendant(wcl->wcl_children[i], child))
1604                                 return (1);
1605                 }
1606                 j++;
1607         }
1608         return (0);
1609 }
1610
1611 #ifdef BLESSING
1612 static int
1613 blessed(struct witness *w1, struct witness *w2)
1614 {
1615         int i;
1616         struct witness_blessed *b;
1617
1618         for (i = 0; i < blessed_count; i++) {
1619                 b = &blessed_list[i];
1620                 if (strcmp(w1->w_name, b->b_lock1) == 0) {
1621                         if (strcmp(w2->w_name, b->b_lock2) == 0)
1622                                 return (1);
1623                         continue;
1624                 }
1625                 if (strcmp(w1->w_name, b->b_lock2) == 0)
1626                         if (strcmp(w2->w_name, b->b_lock1) == 0)
1627                                 return (1);
1628         }
1629         return (0);
1630 }
1631 #endif
1632
1633 static struct witness *
1634 witness_get(void)
1635 {
1636         struct witness *w;
1637
1638         if (witness_watch == 0) {
1639                 mtx_unlock_spin(&w_mtx);
1640                 return (NULL);
1641         }
1642         if (STAILQ_EMPTY(&w_free)) {
1643                 witness_watch = 0;
1644                 mtx_unlock_spin(&w_mtx);
1645                 printf("%s: witness exhausted\n", __func__);
1646                 return (NULL);
1647         }
1648         w = STAILQ_FIRST(&w_free);
1649         STAILQ_REMOVE_HEAD(&w_free, w_list);
1650         w_free_cnt--;
1651         bzero(w, sizeof(*w));
1652         return (w);
1653 }
1654
1655 static void
1656 witness_free(struct witness *w)
1657 {
1658
1659         STAILQ_INSERT_HEAD(&w_free, w, w_list);
1660         w_free_cnt++;
1661 }
1662
1663 static struct witness_child_list_entry *
1664 witness_child_get(void)
1665 {
1666         struct witness_child_list_entry *wcl;
1667
1668         if (witness_watch == 0) {
1669                 mtx_unlock_spin(&w_mtx);
1670                 return (NULL);
1671         }
1672         wcl = w_child_free;
1673         if (wcl == NULL) {
1674                 witness_watch = 0;
1675                 mtx_unlock_spin(&w_mtx);
1676                 printf("%s: witness exhausted\n", __func__);
1677                 return (NULL);
1678         }
1679         w_child_free = wcl->wcl_next;
1680         w_child_free_cnt--;
1681         bzero(wcl, sizeof(*wcl));
1682         return (wcl);
1683 }
1684
1685 static void
1686 witness_child_free(struct witness_child_list_entry *wcl)
1687 {
1688
1689         wcl->wcl_next = w_child_free;
1690         w_child_free = wcl;
1691         w_child_free_cnt++;
1692 }
1693
1694 static struct lock_list_entry *
1695 witness_lock_list_get(void)
1696 {
1697         struct lock_list_entry *lle;
1698
1699         if (witness_watch == 0)
1700                 return (NULL);
1701         mtx_lock_spin(&w_mtx);
1702         lle = w_lock_list_free;
1703         if (lle == NULL) {
1704                 witness_watch = 0;
1705                 mtx_unlock_spin(&w_mtx);
1706                 printf("%s: witness exhausted\n", __func__);
1707                 return (NULL);
1708         }
1709         w_lock_list_free = lle->ll_next;
1710         mtx_unlock_spin(&w_mtx);
1711         bzero(lle, sizeof(*lle));
1712         return (lle);
1713 }
1714
1715 static void
1716 witness_lock_list_free(struct lock_list_entry *lle)
1717 {
1718
1719         mtx_lock_spin(&w_mtx);
1720         lle->ll_next = w_lock_list_free;
1721         w_lock_list_free = lle;
1722         mtx_unlock_spin(&w_mtx);
1723 }
1724
1725 static struct lock_instance *
1726 find_instance(struct lock_list_entry *lock_list, struct lock_object *lock)
1727 {
1728         struct lock_list_entry *lle;
1729         struct lock_instance *instance;
1730         int i;
1731
1732         for (lle = lock_list; lle != NULL; lle = lle->ll_next)
1733                 for (i = lle->ll_count - 1; i >= 0; i--) {
1734                         instance = &lle->ll_children[i];
1735                         if (instance->li_lock == lock)
1736                                 return (instance);
1737                 }
1738         return (NULL);
1739 }
1740
1741 static void
1742 witness_list_lock(struct lock_instance *instance)
1743 {
1744         struct lock_object *lock;
1745
1746         lock = instance->li_lock;
1747         printf("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ?
1748             "exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name);
1749         if (lock->lo_type != lock->lo_name)
1750                 printf(" (%s)", lock->lo_type);
1751         printf(" r = %d (%p) locked @ %s:%d\n",
1752             instance->li_flags & LI_RECURSEMASK, lock, instance->li_file,
1753             instance->li_line);
1754 }
1755
1756 #ifdef DDB
1757 static int
1758 witness_thread_has_locks(struct thread *td)
1759 {
1760
1761         return (td->td_sleeplocks != NULL);
1762 }
1763
1764 static int
1765 witness_proc_has_locks(struct proc *p)
1766 {
1767         struct thread *td;
1768
1769         FOREACH_THREAD_IN_PROC(p, td) {
1770                 if (witness_thread_has_locks(td))
1771                         return (1);
1772         }
1773         return (0);
1774 }
1775 #endif
1776
1777 int
1778 witness_list_locks(struct lock_list_entry **lock_list)
1779 {
1780         struct lock_list_entry *lle;
1781         int i, nheld;
1782
1783         nheld = 0;
1784         for (lle = *lock_list; lle != NULL; lle = lle->ll_next)
1785                 for (i = lle->ll_count - 1; i >= 0; i--) {
1786                         witness_list_lock(&lle->ll_children[i]);
1787                         nheld++;
1788                 }
1789         return (nheld);
1790 }
1791
1792 /*
1793  * This is a bit risky at best.  We call this function when we have timed
1794  * out acquiring a spin lock, and we assume that the other CPU is stuck
1795  * with this lock held.  So, we go groveling around in the other CPU's
1796  * per-cpu data to try to find the lock instance for this spin lock to
1797  * see when it was last acquired.
1798  */
1799 void
1800 witness_display_spinlock(struct lock_object *lock, struct thread *owner)
1801 {
1802         struct lock_instance *instance;
1803         struct pcpu *pc;
1804
1805         if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU)
1806                 return;
1807         pc = pcpu_find(owner->td_oncpu);
1808         instance = find_instance(pc->pc_spinlocks, lock);
1809         if (instance != NULL)
1810                 witness_list_lock(instance);
1811 }
1812
1813 void
1814 witness_save(struct lock_object *lock, const char **filep, int *linep)
1815 {
1816         struct lock_list_entry *lock_list;
1817         struct lock_instance *instance;
1818         struct lock_class *class;
1819
1820         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
1821         if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
1822                 return;
1823         class = LOCK_CLASS(lock);
1824         if (class->lc_flags & LC_SLEEPLOCK)
1825                 lock_list = curthread->td_sleeplocks;
1826         else {
1827                 if (witness_skipspin)
1828                         return;
1829                 lock_list = PCPU_GET(spinlocks);
1830         }
1831         instance = find_instance(lock_list, lock);
1832         if (instance == NULL)
1833                 panic("%s: lock (%s) %s not locked", __func__,
1834                     class->lc_name, lock->lo_name);
1835         *filep = instance->li_file;
1836         *linep = instance->li_line;
1837 }
1838
1839 void
1840 witness_restore(struct lock_object *lock, const char *file, int line)
1841 {
1842         struct lock_list_entry *lock_list;
1843         struct lock_instance *instance;
1844         struct lock_class *class;
1845
1846         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
1847         if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
1848                 return;
1849         class = LOCK_CLASS(lock);
1850         if (class->lc_flags & LC_SLEEPLOCK)
1851                 lock_list = curthread->td_sleeplocks;
1852         else {
1853                 if (witness_skipspin)
1854                         return;
1855                 lock_list = PCPU_GET(spinlocks);
1856         }
1857         instance = find_instance(lock_list, lock);
1858         if (instance == NULL)
1859                 panic("%s: lock (%s) %s not locked", __func__,
1860                     class->lc_name, lock->lo_name);
1861         lock->lo_witness->w_file = file;
1862         lock->lo_witness->w_line = line;
1863         instance->li_file = file;
1864         instance->li_line = line;
1865 }
1866
1867 void
1868 witness_assert(struct lock_object *lock, int flags, const char *file, int line)
1869 {
1870 #ifdef INVARIANT_SUPPORT
1871         struct lock_instance *instance;
1872         struct lock_class *class;
1873
1874         if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
1875                 return;
1876         class = LOCK_CLASS(lock);
1877         if ((class->lc_flags & LC_SLEEPLOCK) != 0)
1878                 instance = find_instance(curthread->td_sleeplocks, lock);
1879         else if ((class->lc_flags & LC_SPINLOCK) != 0)
1880                 instance = find_instance(PCPU_GET(spinlocks), lock);
1881         else {
1882                 panic("Lock (%s) %s is not sleep or spin!",
1883                     class->lc_name, lock->lo_name);
1884         }
1885         file = fixup_filename(file);
1886         switch (flags) {
1887         case LA_UNLOCKED:
1888                 if (instance != NULL)
1889                         panic("Lock (%s) %s locked @ %s:%d.",
1890                             class->lc_name, lock->lo_name, file, line);
1891                 break;
1892         case LA_LOCKED:
1893         case LA_LOCKED | LA_RECURSED:
1894         case LA_LOCKED | LA_NOTRECURSED:
1895         case LA_SLOCKED:
1896         case LA_SLOCKED | LA_RECURSED:
1897         case LA_SLOCKED | LA_NOTRECURSED:
1898         case LA_XLOCKED:
1899         case LA_XLOCKED | LA_RECURSED:
1900         case LA_XLOCKED | LA_NOTRECURSED:
1901                 if (instance == NULL) {
1902                         panic("Lock (%s) %s not locked @ %s:%d.",
1903                             class->lc_name, lock->lo_name, file, line);
1904                         break;
1905                 }
1906                 if ((flags & LA_XLOCKED) != 0 &&
1907                     (instance->li_flags & LI_EXCLUSIVE) == 0)
1908                         panic("Lock (%s) %s not exclusively locked @ %s:%d.",
1909                             class->lc_name, lock->lo_name, file, line);
1910                 if ((flags & LA_SLOCKED) != 0 &&
1911                     (instance->li_flags & LI_EXCLUSIVE) != 0)
1912                         panic("Lock (%s) %s exclusively locked @ %s:%d.",
1913                             class->lc_name, lock->lo_name, file, line);
1914                 if ((flags & LA_RECURSED) != 0 &&
1915                     (instance->li_flags & LI_RECURSEMASK) == 0)
1916                         panic("Lock (%s) %s not recursed @ %s:%d.",
1917                             class->lc_name, lock->lo_name, file, line);
1918                 if ((flags & LA_NOTRECURSED) != 0 &&
1919                     (instance->li_flags & LI_RECURSEMASK) != 0)
1920                         panic("Lock (%s) %s recursed @ %s:%d.",
1921                             class->lc_name, lock->lo_name, file, line);
1922                 break;
1923         default:
1924                 panic("Invalid lock assertion at %s:%d.", file, line);
1925
1926         }
1927 #endif  /* INVARIANT_SUPPORT */
1928 }
1929
1930 #ifdef DDB
1931 static void
1932 witness_list(struct thread *td)
1933 {
1934
1935         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
1936         KASSERT(kdb_active, ("%s: not in the debugger", __func__));
1937
1938         if (witness_watch == 0)
1939                 return;
1940
1941         witness_list_locks(&td->td_sleeplocks);
1942
1943         /*
1944          * We only handle spinlocks if td == curthread.  This is somewhat broken
1945          * if td is currently executing on some other CPU and holds spin locks
1946          * as we won't display those locks.  If we had a MI way of getting
1947          * the per-cpu data for a given cpu then we could use
1948          * td->td_oncpu to get the list of spinlocks for this thread
1949          * and "fix" this.
1950          *
1951          * That still wouldn't really fix this unless we locked sched_lock
1952          * or stopped the other CPU to make sure it wasn't changing the list
1953          * out from under us.  It is probably best to just not try to handle
1954          * threads on other CPU's for now.
1955          */
1956         if (td == curthread && PCPU_GET(spinlocks) != NULL)
1957                 witness_list_locks(PCPU_PTR(spinlocks));
1958 }
1959
1960 DB_SHOW_COMMAND(locks, db_witness_list)
1961 {
1962         struct thread *td;
1963
1964         if (have_addr)
1965                 td = db_lookup_thread(addr, TRUE);
1966         else
1967                 td = kdb_thread;
1968         witness_list(td);
1969 }
1970
1971 DB_SHOW_COMMAND(alllocks, db_witness_list_all)
1972 {
1973         struct thread *td;
1974         struct proc *p;
1975
1976         /*
1977          * It would be nice to list only threads and processes that actually
1978          * held sleep locks, but that information is currently not exported
1979          * by WITNESS.
1980          */
1981         FOREACH_PROC_IN_SYSTEM(p) {
1982                 if (!witness_proc_has_locks(p))
1983                         continue;
1984                 FOREACH_THREAD_IN_PROC(p, td) {
1985                         if (!witness_thread_has_locks(td))
1986                                 continue;
1987                         db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid,
1988                             p->p_comm, td, td->td_tid);
1989                         witness_list(td);
1990                 }
1991         }
1992 }
1993
1994 DB_SHOW_COMMAND(witness, db_witness_display)
1995 {
1996
1997         witness_display(db_printf);
1998 }
1999 #endif