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_hwpmc_hooks.h"
  89 #include "opt_witness.h"
  90
  91 #include <sys/param.h>
  92 #include <sys/bus.h>
  93 #include <sys/kdb.h>
  94 #include <sys/kernel.h>
  95 #include <sys/ktr.h>
  96 #include <sys/lock.h>
  97 #include <sys/malloc.h>
  98 #include <sys/mutex.h>
  99 #include <sys/priv.h>
 100 #include <sys/proc.h>
 101 #include <sys/sysctl.h>
 102 #include <sys/systm.h>
 103
 104 #include <ddb/ddb.h>
 105
 106 #include <machine/stdarg.h>
 107
 108 /* Note that these traces do not work with KTR_ALQ. */
 109 #if 0
 110 #define KTR_WITNESS     KTR_SUBSYS
 111 #else
 112 #define KTR_WITNESS     0
 113 #endif
 114
 115 /* Easier to stay with the old names. */
 116 #define lo_list         lo_witness_data.lod_list
 117 #define lo_witness      lo_witness_data.lod_witness
 118
 119 /* Define this to check for blessed mutexes */
 120 #undef BLESSING
 121
 122 #define WITNESS_COUNT 1024
 123 #define WITNESS_CHILDCOUNT (WITNESS_COUNT * 4)
 124 /*
 125  * XXX: This is somewhat bogus, as we assume here that at most 1024 threads
 126  * will hold LOCK_NCHILDREN * 2 locks.  We handle failure ok, and we should
 127  * probably be safe for the most part, but it's still a SWAG.
 128  */
 129 #define LOCK_CHILDCOUNT (MAXCPU + 1024) * 2
 130
 131 #define WITNESS_NCHILDREN 6
 132
 133 struct witness_child_list_entry;
 134
 135 struct witness {
 136         const   char *w_name;
 137         struct  lock_class *w_class;
 138         STAILQ_ENTRY(witness) w_list;           /* List of all witnesses. */
 139         STAILQ_ENTRY(witness) w_typelist;       /* Witnesses of a type. */
 140         struct  witness_child_list_entry *w_children;   /* Great evilness... */
 141         const   char *w_file;
 142         int     w_line;
 143         u_int   w_level;
 144         u_int   w_refcount;
 145         u_char  w_Giant_squawked:1;
 146         u_char  w_other_squawked:1;
 147         u_char  w_same_squawked:1;
 148         u_char  w_displayed:1;
 149 };
 150
 151 struct witness_child_list_entry {
 152         struct  witness_child_list_entry *wcl_next;
 153         struct  witness *wcl_children[WITNESS_NCHILDREN];
 154         u_int   wcl_count;
 155 };
 156
 157 STAILQ_HEAD(witness_list, witness);
 158
 159 #ifdef BLESSING
 160 struct witness_blessed {
 161         const   char *b_lock1;
 162         const   char *b_lock2;
 163 };
 164 #endif
 165
 166 struct witness_order_list_entry {
 167         const   char *w_name;
 168         struct  lock_class *w_class;
 169 };
 170
 171 #ifdef BLESSING
 172 static int      blessed(struct witness *, struct witness *);
 173 #endif
 174 static int      depart(struct witness *w);
 175 static struct   witness *enroll(const char *description,
 176                                 struct lock_class *lock_class);
 177 static int      insertchild(struct witness *parent, struct witness *child);
 178 static int      isitmychild(struct witness *parent, struct witness *child);
 179 static int      isitmydescendant(struct witness *parent, struct witness *child);
 180 static int      itismychild(struct witness *parent, struct witness *child);
 181 static void     removechild(struct witness *parent, struct witness *child);
 182 static int      sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS);
 183 static const char *fixup_filename(const char *file);
 184 static struct   witness *witness_get(void);
 185 static void     witness_free(struct witness *m);
 186 static struct   witness_child_list_entry *witness_child_get(void);
 187 static void     witness_child_free(struct witness_child_list_entry *wcl);
 188 static struct   lock_list_entry *witness_lock_list_get(void);
 189 static void     witness_lock_list_free(struct lock_list_entry *lle);
 190 static struct   lock_instance *find_instance(struct lock_list_entry *lock_list,
 191                                              struct lock_object *lock);
 192 static void     witness_list_lock(struct lock_instance *instance);
 193 #ifdef DDB
 194 static void     witness_leveldescendents(struct witness *parent, int level);
 195 static void     witness_levelall(void);
 196 static void     witness_displaydescendants(void(*)(const char *fmt, ...),
 197                                            struct witness *, int indent);
 198 static void     witness_display_list(void(*prnt)(const char *fmt, ...),
 199                                      struct witness_list *list);
 200 static void     witness_display(void(*)(const char *fmt, ...));
 201 static void     witness_list(struct thread *td);
 202 #endif
 203
 204 SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW, 0, "Witness Locking");
 205
 206 /*
 207  * If set to 0, witness is disabled.  If set to a non-zero value, witness
 208  * performs full lock order checking for all locks.  At runtime, this
 209  * value may be set to 0 to turn off witness.  witness is not allowed be
 210  * turned on once it is turned off, however.
 211  */
 212 static int witness_watch = 1;
 213 TUNABLE_INT("debug.witness.watch", &witness_watch);
 214 SYSCTL_PROC(_debug_witness, OID_AUTO, watch, CTLFLAG_RW | CTLTYPE_INT, NULL, 0,
 215     sysctl_debug_witness_watch, "I", "witness is watching lock operations");
 216
 217 #ifdef KDB
 218 /*
 219  * When KDB is enabled and witness_kdb is set to 1, it will cause the system
 220  * to drop into kdebug() when:
 221  *      - a lock hierarchy violation occurs
 222  *      - locks are held when going to sleep.
 223  */
 224 #ifdef WITNESS_KDB
 225 int     witness_kdb = 1;
 226 #else
 227 int     witness_kdb = 0;
 228 #endif
 229 TUNABLE_INT("debug.witness.kdb", &witness_kdb);
 230 SYSCTL_INT(_debug_witness, OID_AUTO, kdb, CTLFLAG_RW, &witness_kdb, 0, "");
 231
 232 /*
 233  * When KDB is enabled and witness_trace is set to 1, it will cause the system
 234  * to print a stack trace:
 235  *      - a lock hierarchy violation occurs
 236  *      - locks are held when going to sleep.
 237  */
 238 int     witness_trace = 1;
 239 TUNABLE_INT("debug.witness.trace", &witness_trace);
 240 SYSCTL_INT(_debug_witness, OID_AUTO, trace, CTLFLAG_RW, &witness_trace, 0, "");
 241 #endif /* KDB */
 242
 243 #ifdef WITNESS_SKIPSPIN
 244 int     witness_skipspin = 1;
 245 #else
 246 int     witness_skipspin = 0;
 247 #endif
 248 TUNABLE_INT("debug.witness.skipspin", &witness_skipspin);
 249 SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN,
 250     &witness_skipspin, 0, "");
 251
 252 static struct mtx w_mtx;
 253 static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free);
 254 static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all);
 255 static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin);
 256 static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep);
 257 static struct witness_child_list_entry *w_child_free = NULL;
 258 static struct lock_list_entry *w_lock_list_free = NULL;
 259
 260 static int w_free_cnt, w_spin_cnt, w_sleep_cnt, w_child_free_cnt, w_child_cnt;
 261 SYSCTL_INT(_debug_witness, OID_AUTO, free_cnt, CTLFLAG_RD, &w_free_cnt, 0, "");
 262 SYSCTL_INT(_debug_witness, OID_AUTO, spin_cnt, CTLFLAG_RD, &w_spin_cnt, 0, "");
 263 SYSCTL_INT(_debug_witness, OID_AUTO, sleep_cnt, CTLFLAG_RD, &w_sleep_cnt, 0,
 264     "");
 265 SYSCTL_INT(_debug_witness, OID_AUTO, child_free_cnt, CTLFLAG_RD,
 266     &w_child_free_cnt, 0, "");
 267 SYSCTL_INT(_debug_witness, OID_AUTO, child_cnt, CTLFLAG_RD, &w_child_cnt, 0,
 268     "");
 269
 270 static struct witness w_data[WITNESS_COUNT];
 271 static struct witness_child_list_entry w_childdata[WITNESS_CHILDCOUNT];
 272 static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT];
 273
 274 static struct witness_order_list_entry order_lists[] = {
 275         /*
 276          * sx locks
 277          */
 278         { "proctree", &lock_class_sx },
 279         { "allproc", &lock_class_sx },
 280         { "allprison", &lock_class_sx },
 281         { NULL, NULL },
 282         /*
 283          * Various mutexes
 284          */
 285         { "Giant", &lock_class_mtx_sleep },
 286         { "pipe mutex", &lock_class_mtx_sleep },
 287         { "sigio lock", &lock_class_mtx_sleep },
 288         { "process group", &lock_class_mtx_sleep },
 289         { "process lock", &lock_class_mtx_sleep },
 290         { "session", &lock_class_mtx_sleep },
 291         { "uidinfo hash", &lock_class_mtx_sleep },
 292         { "uidinfo struct", &lock_class_mtx_sleep },
 293 #ifdef  HWPMC_HOOKS
 294         { "pmc-sleep", &lock_class_mtx_sleep },
 295 #endif
 296         { NULL, NULL },
 297         /*
 298          * Sockets
 299          */
 300         { "accept", &lock_class_mtx_sleep },
 301         { "so_snd", &lock_class_mtx_sleep },
 302         { "so_rcv", &lock_class_mtx_sleep },
 303         { "sellck", &lock_class_mtx_sleep },
 304         { NULL, NULL },
 305         /*
 306          * Routing
 307          */
 308         { "so_rcv", &lock_class_mtx_sleep },
 309         { "radix node head", &lock_class_mtx_sleep },
 310         { "rtentry", &lock_class_mtx_sleep },
 311         { "ifaddr", &lock_class_mtx_sleep },
 312         { NULL, NULL },
 313         /*
 314          * Multicast - protocol locks before interface locks, after UDP locks.
 315          */
 316         { "udpinp", &lock_class_rw },
 317         { "in_multi_mtx", &lock_class_mtx_sleep },
 318         { "igmp_mtx", &lock_class_mtx_sleep },
 319         { "if_addr_mtx", &lock_class_mtx_sleep },
 320         { NULL, NULL },
 321         /*
 322          * UNIX Domain Sockets
 323          */
 324         { "unp", &lock_class_mtx_sleep },
 325         { "so_snd", &lock_class_mtx_sleep },
 326         { NULL, NULL },
 327         /*
 328          * UDP/IP
 329          */
 330         { "udp", &lock_class_rw },
 331         { "udpinp", &lock_class_rw },
 332         { "so_snd", &lock_class_mtx_sleep },
 333         { NULL, NULL },
 334         /*
 335          * TCP/IP
 336          */
 337         { "tcp", &lock_class_rw },
 338         { "tcpinp", &lock_class_rw },
 339         { "so_snd", &lock_class_mtx_sleep },
 340         { NULL, NULL },
 341         /*
 342          * SLIP
 343          */
 344         { "slip_mtx", &lock_class_mtx_sleep },
 345         { "slip sc_mtx", &lock_class_mtx_sleep },
 346         { NULL, NULL },
 347         /*
 348          * netatalk
 349          */
 350         { "ddp_list_mtx", &lock_class_mtx_sleep },
 351         { "ddp_mtx", &lock_class_mtx_sleep },
 352         { NULL, NULL },
 353         /*
 354          * BPF
 355          */
 356         { "bpf global lock", &lock_class_mtx_sleep },
 357         { "bpf interface lock", &lock_class_mtx_sleep },
 358         { "bpf cdev lock", &lock_class_mtx_sleep },
 359         { NULL, NULL },
 360         /*
 361          * NFS server
 362          */
 363         { "nfsd_mtx", &lock_class_mtx_sleep },
 364         { "so_snd", &lock_class_mtx_sleep },
 365         { NULL, NULL },
 366
 367         /*
 368          * IEEE 802.11
 369          */
 370         { "802.11 com lock", &lock_class_mtx_sleep},
 371         { NULL, NULL },
 372         /*
 373          * Network drivers
 374          */
 375         { "network driver", &lock_class_mtx_sleep},
 376         { NULL, NULL },
 377
 378         /*
 379          * Netgraph
 380          */
 381         { "ng_node", &lock_class_mtx_sleep },
 382         { "ng_worklist", &lock_class_mtx_sleep },
 383         { NULL, NULL },
 384         /*
 385          * CDEV
 386          */
 387         { "system map", &lock_class_mtx_sleep },
 388         { "vm page queue mutex", &lock_class_mtx_sleep },
 389         { "vnode interlock", &lock_class_mtx_sleep },
 390         { "cdev", &lock_class_mtx_sleep },
 391         { NULL, NULL },
 392         /*
 393          * kqueue/VFS interaction
 394          */
 395         { "kqueue", &lock_class_mtx_sleep },
 396         { "struct mount mtx", &lock_class_mtx_sleep },
 397         { "vnode interlock", &lock_class_mtx_sleep },
 398         { NULL, NULL },
 399         /*
 400          * spin locks
 401          */
 402 #ifdef SMP
 403         { "ap boot", &lock_class_mtx_spin },
 404 #endif
 405         { "rm.mutex_mtx", &lock_class_mtx_spin },
 406         { "sio", &lock_class_mtx_spin },
 407         { "scrlock", &lock_class_mtx_spin },
 408 #ifdef __i386__
 409         { "cy", &lock_class_mtx_spin },
 410 #endif
 411 #ifdef __sparc64__
 412         { "pcib_mtx", &lock_class_mtx_spin },
 413         { "rtc_mtx", &lock_class_mtx_spin },
 414 #endif
 415         { "scc_hwmtx", &lock_class_mtx_spin },
 416         { "uart_hwmtx", &lock_class_mtx_spin },
 417         { "fast_taskqueue", &lock_class_mtx_spin },
 418         { "intr table", &lock_class_mtx_spin },
 419 #ifdef  HWPMC_HOOKS
 420         { "pmc-per-proc", &lock_class_mtx_spin },
 421 #endif
 422         { "process slock", &lock_class_mtx_spin },
 423         { "sleepq chain", &lock_class_mtx_spin },
 424         { "umtx lock", &lock_class_mtx_spin },
 425         { "turnstile chain", &lock_class_mtx_spin },
 426         { "turnstile lock", &lock_class_mtx_spin },
 427         { "sched lock", &lock_class_mtx_spin },
 428         { "td_contested", &lock_class_mtx_spin },
 429         { "callout", &lock_class_mtx_spin },
 430         { "entropy harvest mutex", &lock_class_mtx_spin },
 431         { "syscons video lock", &lock_class_mtx_spin },
 432         { "time lock", &lock_class_mtx_spin },
 433 #ifdef SMP
 434         { "smp rendezvous", &lock_class_mtx_spin },
 435 #endif
 436         /*
 437          * leaf locks
 438          */
 439         { "icu", &lock_class_mtx_spin },
 440 #if defined(SMP) && defined(__sparc64__)
 441         { "ipi", &lock_class_mtx_spin },
 442 #endif
 443 #ifdef __i386__
 444         { "allpmaps", &lock_class_mtx_spin },
 445         { "descriptor tables", &lock_class_mtx_spin },
 446 #endif
 447         { "clk", &lock_class_mtx_spin },
 448         { "mprof lock", &lock_class_mtx_spin },
 449         { "kse lock", &lock_class_mtx_spin },
 450         { "zombie lock", &lock_class_mtx_spin },
 451         { "ALD Queue", &lock_class_mtx_spin },
 452 #ifdef __ia64__
 453         { "MCA spin lock", &lock_class_mtx_spin },
 454 #endif
 455 #if defined(__i386__) || defined(__amd64__)
 456         { "pcicfg", &lock_class_mtx_spin },
 457         { "NDIS thread lock", &lock_class_mtx_spin },
 458 #endif
 459         { "tw_osl_io_lock", &lock_class_mtx_spin },
 460         { "tw_osl_q_lock", &lock_class_mtx_spin },
 461         { "tw_cl_io_lock", &lock_class_mtx_spin },
 462         { "tw_cl_intr_lock", &lock_class_mtx_spin },
 463         { "tw_cl_gen_lock", &lock_class_mtx_spin },
 464 #ifdef  HWPMC_HOOKS
 465         { "pmc-leaf", &lock_class_mtx_spin },
 466 #endif
 467         { "blocked lock", &lock_class_mtx_spin },
 468         { NULL, NULL },
 469         { NULL, NULL }
 470 };
 471
 472 #ifdef BLESSING
 473 /*
 474  * Pairs of locks which have been blessed
 475  * Don't complain about order problems with blessed locks
 476  */
 477 static struct witness_blessed blessed_list[] = {
 478 };
 479 static int blessed_count =
 480         sizeof(blessed_list) / sizeof(struct witness_blessed);
 481 #endif
 482
 483 /*
 484  * List of locks initialized prior to witness being initialized whose
 485  * enrollment is currently deferred.
 486  */
 487 STAILQ_HEAD(, lock_object) pending_locks =
 488     STAILQ_HEAD_INITIALIZER(pending_locks);
 489
 490 /*
 491  * This global is set to 0 once it becomes safe to use the witness code.
 492  */
 493 static int witness_cold = 1;
 494
 495 /*
 496  * This global is set to 1 once the static lock orders have been enrolled
 497  * so that a warning can be issued for any spin locks enrolled later.
 498  */
 499 static int witness_spin_warn = 0;
 500
 501 /*
 502  * The WITNESS-enabled diagnostic code.  Note that the witness code does
 503  * assume that the early boot is single-threaded at least until after this
 504  * routine is completed.
 505  */
 506 static void
 507 witness_initialize(void *dummy __unused)
 508 {
 509         struct lock_object *lock;
 510         struct witness_order_list_entry *order;
 511         struct witness *w, *w1;
 512         int i;
 513
 514         /*
 515          * We have to release Giant before initializing its witness
 516          * structure so that WITNESS doesn't get confused.
 517          */
 518         mtx_unlock(&Giant);
 519         mtx_assert(&Giant, MA_NOTOWNED);
 520
 521         CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
 522         mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET |
 523             MTX_NOWITNESS | MTX_NOPROFILE);
 524         for (i = 0; i < WITNESS_COUNT; i++)
 525                 witness_free(&w_data[i]);
 526         for (i = 0; i < WITNESS_CHILDCOUNT; i++)
 527                 witness_child_free(&w_childdata[i]);
 528         for (i = 0; i < LOCK_CHILDCOUNT; i++)
 529                 witness_lock_list_free(&w_locklistdata[i]);
 530
 531         /* First add in all the specified order lists. */
 532         for (order = order_lists; order->w_name != NULL; order++) {
 533                 w = enroll(order->w_name, order->w_class);
 534                 if (w == NULL)
 535                         continue;
 536                 w->w_file = "order list";
 537                 for (order++; order->w_name != NULL; order++) {
 538                         w1 = enroll(order->w_name, order->w_class);
 539                         if (w1 == NULL)
 540                                 continue;
 541                         w1->w_file = "order list";
 542                         if (!itismychild(w, w1))
 543                                 panic("Not enough memory for static orders!");
 544                         w = w1;
 545                 }
 546         }
 547         witness_spin_warn = 1;
 548
 549         /* Iterate through all locks and add them to witness. */
 550         while (!STAILQ_EMPTY(&pending_locks)) {
 551                 lock = STAILQ_FIRST(&pending_locks);
 552                 STAILQ_REMOVE_HEAD(&pending_locks, lo_list);
 553                 KASSERT(lock->lo_flags & LO_WITNESS,
 554                     ("%s: lock %s is on pending list but not LO_WITNESS",
 555                     __func__, lock->lo_name));
 556                 lock->lo_witness = enroll(lock->lo_type, LOCK_CLASS(lock));
 557         }
 558
 559         /* Mark the witness code as being ready for use. */
 560         witness_cold = 0;
 561
 562         mtx_lock(&Giant);
 563 }
 564 SYSINIT(witness_init, SI_SUB_WITNESS, SI_ORDER_FIRST, witness_initialize,
 565     NULL);
 566
 567 static int
 568 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS)
 569 {
 570         int error, value;
 571
 572         value = witness_watch;
 573         error = sysctl_handle_int(oidp, &value, 0, req);
 574         if (error != 0 || req->newptr == NULL)
 575                 return (error);
 576         if (value == witness_watch)
 577                 return (0);
 578         if (value != 0)
 579                 return (EINVAL);
 580         witness_watch = 0;
 581         return (0);
 582 }
 583
 584 void
 585 witness_init(struct lock_object *lock)
 586 {
 587         struct lock_class *class;
 588
 589         /* Various sanity checks. */
 590         class = LOCK_CLASS(lock);
 591         if ((lock->lo_flags & LO_RECURSABLE) != 0 &&
 592             (class->lc_flags & LC_RECURSABLE) == 0)
 593                 panic("%s: lock (%s) %s can not be recursable", __func__,
 594                     class->lc_name, lock->lo_name);
 595         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 596             (class->lc_flags & LC_SLEEPABLE) == 0)
 597                 panic("%s: lock (%s) %s can not be sleepable", __func__,
 598                     class->lc_name, lock->lo_name);
 599         if ((lock->lo_flags & LO_UPGRADABLE) != 0 &&
 600             (class->lc_flags & LC_UPGRADABLE) == 0)
 601                 panic("%s: lock (%s) %s can not be upgradable", __func__,
 602                     class->lc_name, lock->lo_name);
 603
 604         /*
 605          * If we shouldn't watch this lock, then just clear lo_witness.
 606          * Otherwise, if witness_cold is set, then it is too early to
 607          * enroll this lock, so defer it to witness_initialize() by adding
 608          * it to the pending_locks list.  If it is not too early, then enroll
 609          * the lock now.
 610          */
 611         if (witness_watch == 0 || panicstr != NULL ||
 612             (lock->lo_flags & LO_WITNESS) == 0)
 613                 lock->lo_witness = NULL;
 614         else if (witness_cold) {
 615                 STAILQ_INSERT_TAIL(&pending_locks, lock, lo_list);
 616                 lock->lo_flags |= LO_ENROLLPEND;
 617         } else
 618                 lock->lo_witness = enroll(lock->lo_type, class);
 619 }
 620
 621 void
 622 witness_destroy(struct lock_object *lock)
 623 {
 624         struct lock_class *class;
 625         struct witness *w;
 626
 627         class = LOCK_CLASS(lock);
 628         if (witness_cold)
 629                 panic("lock (%s) %s destroyed while witness_cold",
 630                     class->lc_name, lock->lo_name);
 631
 632         /* XXX: need to verify that no one holds the lock */
 633         if ((lock->lo_flags & (LO_WITNESS | LO_ENROLLPEND)) == LO_WITNESS &&
 634             lock->lo_witness != NULL) {
 635                 w = lock->lo_witness;
 636                 mtx_lock_spin(&w_mtx);
 637                 MPASS(w->w_refcount > 0);
 638                 w->w_refcount--;
 639
 640                 /*
 641                  * Lock is already released if we have an allocation failure
 642                  * and depart() fails.
 643                  */
 644                 if (w->w_refcount != 0 || depart(w))
 645                         mtx_unlock_spin(&w_mtx);
 646         }
 647
 648         /*
 649          * If this lock is destroyed before witness is up and running,
 650          * remove it from the pending list.
 651          */
 652         if (lock->lo_flags & LO_ENROLLPEND) {
 653                 STAILQ_REMOVE(&pending_locks, lock, lock_object, lo_list);
 654                 lock->lo_flags &= ~LO_ENROLLPEND;
 655         }
 656 }
 657
 658 #ifdef DDB
 659 static void
 660 witness_levelall (void)
 661 {
 662         struct witness_list *list;
 663         struct witness *w, *w1;
 664
 665         /*
 666          * First clear all levels.
 667          */
 668         STAILQ_FOREACH(w, &w_all, w_list) {
 669                 w->w_level = 0;
 670         }
 671
 672         /*
 673          * Look for locks with no parent and level all their descendants.
 674          */
 675         STAILQ_FOREACH(w, &w_all, w_list) {
 676                 /*
 677                  * This is just an optimization, technically we could get
 678                  * away just walking the all list each time.
 679                  */
 680                 if (w->w_class->lc_flags & LC_SLEEPLOCK)
 681                         list = &w_sleep;
 682                 else
 683                         list = &w_spin;
 684                 STAILQ_FOREACH(w1, list, w_typelist) {
 685                         if (isitmychild(w1, w))
 686                                 goto skip;
 687                 }
 688                 witness_leveldescendents(w, 0);
 689         skip:
 690                 ;       /* silence GCC 3.x */
 691         }
 692 }
 693
 694 static void
 695 witness_leveldescendents(struct witness *parent, int level)
 696 {
 697         struct witness_child_list_entry *wcl;
 698         int i;
 699
 700         if (parent->w_level < level)
 701                 parent->w_level = level;
 702         level++;
 703         for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next)
 704                 for (i = 0; i < wcl->wcl_count; i++)
 705                         witness_leveldescendents(wcl->wcl_children[i], level);
 706 }
 707
 708 static void
 709 witness_displaydescendants(void(*prnt)(const char *fmt, ...),
 710                            struct witness *parent, int indent)
 711 {
 712         struct witness_child_list_entry *wcl;
 713         int i, level;
 714
 715         level = parent->w_level;
 716         prnt("%-2d", level);
 717         for (i = 0; i < indent; i++)
 718                 prnt(" ");
 719         if (parent->w_refcount > 0)
 720                 prnt("%s", parent->w_name);
 721         else
 722                 prnt("(dead)");
 723         if (parent->w_displayed) {
 724                 prnt(" -- (already displayed)\n");
 725                 return;
 726         }
 727         parent->w_displayed = 1;
 728         if (parent->w_refcount > 0) {
 729                 if (parent->w_file != NULL)
 730                         prnt(" -- last acquired @ %s:%d", parent->w_file,
 731                             parent->w_line);
 732         }
 733         prnt("\n");
 734         for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next)
 735                 for (i = 0; i < wcl->wcl_count; i++)
 736                             witness_displaydescendants(prnt,
 737                                 wcl->wcl_children[i], indent + 1);
 738 }
 739
 740 static void
 741 witness_display_list(void(*prnt)(const char *fmt, ...),
 742                      struct witness_list *list)
 743 {
 744         struct witness *w;
 745
 746         STAILQ_FOREACH(w, list, w_typelist) {
 747                 if (w->w_file == NULL || w->w_level > 0)
 748                         continue;
 749                 /*
 750                  * This lock has no anscestors, display its descendants.
 751                  */
 752                 witness_displaydescendants(prnt, w, 0);
 753         }
 754 }
 755
 756 static void
 757 witness_display(void(*prnt)(const char *fmt, ...))
 758 {
 759         struct witness *w;
 760
 761         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
 762         witness_levelall();
 763
 764         /* Clear all the displayed flags. */
 765         STAILQ_FOREACH(w, &w_all, w_list) {
 766                 w->w_displayed = 0;
 767         }
 768
 769         /*
 770          * First, handle sleep locks which have been acquired at least
 771          * once.
 772          */
 773         prnt("Sleep locks:\n");
 774         witness_display_list(prnt, &w_sleep);
 775
 776         /*
 777          * Now do spin locks which have been acquired at least once.
 778          */
 779         prnt("\nSpin locks:\n");
 780         witness_display_list(prnt, &w_spin);
 781
 782         /*
 783          * Finally, any locks which have not been acquired yet.
 784          */
 785         prnt("\nLocks which were never acquired:\n");
 786         STAILQ_FOREACH(w, &w_all, w_list) {
 787                 if (w->w_file != NULL || w->w_refcount == 0)
 788                         continue;
 789                 prnt("%s\n", w->w_name);
 790         }
 791 }
 792 #endif /* DDB */
 793
 794 /* Trim useless garbage from filenames. */
 795 static const char *
 796 fixup_filename(const char *file)
 797 {
 798
 799         if (file == NULL)
 800                 return (NULL);
 801         while (strncmp(file, "../", 3) == 0)
 802                 file += 3;
 803         return (file);
 804 }
 805
 806 int
 807 witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
 808 {
 809
 810         if (witness_watch == 0 || panicstr != NULL)
 811                 return (0);
 812
 813         /* Require locks that witness knows about. */
 814         if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL ||
 815             lock2->lo_witness == NULL)
 816                 return (EINVAL);
 817
 818         MPASS(!mtx_owned(&w_mtx));
 819         mtx_lock_spin(&w_mtx);
 820
 821         /*
 822          * If we already have either an explicit or implied lock order that
 823          * is the other way around, then return an error.
 824          */
 825         if (isitmydescendant(lock2->lo_witness, lock1->lo_witness)) {
 826                 mtx_unlock_spin(&w_mtx);
 827                 return (EDOOFUS);
 828         }
 829
 830         /* Try to add the new order. */
 831         CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 832             lock2->lo_type, lock1->lo_type);
 833         if (!itismychild(lock1->lo_witness, lock2->lo_witness))
 834                 return (ENOMEM);
 835         mtx_unlock_spin(&w_mtx);
 836         return (0);
 837 }
 838
 839 void
 840 witness_checkorder(struct lock_object *lock, int flags, const char *file,
 841     int line)
 842 {
 843         struct lock_list_entry **lock_list, *lle;
 844         struct lock_instance *lock1, *lock2;
 845         struct lock_class *class;
 846         struct witness *w, *w1;
 847         struct thread *td;
 848         int i, j;
 849
 850         if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL ||
 851             panicstr != NULL)
 852                 return;
 853
 854         /*
 855          * Try locks do not block if they fail to acquire the lock, thus
 856          * there is no danger of deadlocks or of switching while holding a
 857          * spin lock if we acquire a lock via a try operation.  This
 858          * function shouldn't even be called for try locks, so panic if
 859          * that happens.
 860          */
 861         if (flags & LOP_TRYLOCK)
 862                 panic("%s should not be called for try lock operations",
 863                     __func__);
 864
 865         w = lock->lo_witness;
 866         class = LOCK_CLASS(lock);
 867         td = curthread;
 868         file = fixup_filename(file);
 869
 870         if (class->lc_flags & LC_SLEEPLOCK) {
 871                 /*
 872                  * Since spin locks include a critical section, this check
 873                  * implicitly enforces a lock order of all sleep locks before
 874                  * all spin locks.
 875                  */
 876                 if (td->td_critnest != 0 && !kdb_active)
 877                         panic("blockable sleep lock (%s) %s @ %s:%d",
 878                             class->lc_name, lock->lo_name, file, line);
 879
 880                 /*
 881                  * If this is the first lock acquired then just return as
 882                  * no order checking is needed.
 883                  */
 884                 if (td->td_sleeplocks == NULL)
 885                         return;
 886                 lock_list = &td->td_sleeplocks;
 887         } else {
 888                 /*
 889                  * If this is the first lock, just return as no order
 890                  * checking is needed.  We check this in both if clauses
 891                  * here as unifying the check would require us to use a
 892                  * critical section to ensure we don't migrate while doing
 893                  * the check.  Note that if this is not the first lock, we
 894                  * are already in a critical section and are safe for the
 895                  * rest of the check.
 896                  */
 897                 if (PCPU_GET(spinlocks) == NULL)
 898                         return;
 899                 lock_list = PCPU_PTR(spinlocks);
 900         }
 901
 902         /*
 903          * Check to see if we are recursing on a lock we already own.  If
 904          * so, make sure that we don't mismatch exclusive and shared lock
 905          * acquires.
 906          */
 907         lock1 = find_instance(*lock_list, lock);
 908         if (lock1 != NULL) {
 909                 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 &&
 910                     (flags & LOP_EXCLUSIVE) == 0) {
 911                         printf("shared lock of (%s) %s @ %s:%d\n",
 912                             class->lc_name, lock->lo_name, file, line);
 913                         printf("while exclusively locked from %s:%d\n",
 914                             lock1->li_file, lock1->li_line);
 915                         panic("share->excl");
 916                 }
 917                 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
 918                     (flags & LOP_EXCLUSIVE) != 0) {
 919                         printf("exclusive lock of (%s) %s @ %s:%d\n",
 920                             class->lc_name, lock->lo_name, file, line);
 921                         printf("while share locked from %s:%d\n",
 922                             lock1->li_file, lock1->li_line);
 923                         panic("excl->share");
 924                 }
 925                 return;
 926         }
 927
 928         /*
 929          * Try locks do not block if they fail to acquire the lock, thus
 930          * there is no danger of deadlocks or of switching while holding a
 931          * spin lock if we acquire a lock via a try operation.
 932          */
 933         if (flags & LOP_TRYLOCK)
 934                 return;
 935
 936         /*
 937          * Check for duplicate locks of the same type.  Note that we only
 938          * have to check for this on the last lock we just acquired.  Any
 939          * other cases will be caught as lock order violations.
 940          */
 941         lock1 = &(*lock_list)->ll_children[(*lock_list)->ll_count - 1];
 942         w1 = lock1->li_lock->lo_witness;
 943         if (w1 == w) {
 944                 if (w->w_same_squawked || (lock->lo_flags & LO_DUPOK) ||
 945                     (flags & LOP_DUPOK))
 946                         return;
 947                 w->w_same_squawked = 1;
 948                 printf("acquiring duplicate lock of same type: \"%s\"\n",
 949                         lock->lo_type);
 950                 printf(" 1st %s @ %s:%d\n", lock1->li_lock->lo_name,
 951                     lock1->li_file, lock1->li_line);
 952                 printf(" 2nd %s @ %s:%d\n", lock->lo_name, file, line);
 953 #ifdef KDB
 954                 goto debugger;
 955 #else
 956                 return;
 957 #endif
 958         }
 959         MPASS(!mtx_owned(&w_mtx));
 960         mtx_lock_spin(&w_mtx);
 961         /*
 962          * If we know that the the lock we are acquiring comes after
 963          * the lock we most recently acquired in the lock order tree,
 964          * then there is no need for any further checks.
 965          */
 966         if (isitmychild(w1, w)) {
 967                 mtx_unlock_spin(&w_mtx);
 968                 return;
 969         }
 970         for (j = 0, lle = *lock_list; lle != NULL; lle = lle->ll_next) {
 971                 for (i = lle->ll_count - 1; i >= 0; i--, j++) {
 972
 973                         MPASS(j < WITNESS_COUNT);
 974                         lock1 = &lle->ll_children[i];
 975                         w1 = lock1->li_lock->lo_witness;
 976
 977                         /*
 978                          * If this lock doesn't undergo witness checking,
 979                          * then skip it.
 980                          */
 981                         if (w1 == NULL) {
 982                                 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0,
 983                                     ("lock missing witness structure"));
 984                                 continue;
 985                         }
 986                         /*
 987                          * If we are locking Giant and this is a sleepable
 988                          * lock, then skip it.
 989                          */
 990                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0 &&
 991                             lock == &Giant.lock_object)
 992                                 continue;
 993                         /*
 994                          * If we are locking a sleepable lock and this lock
 995                          * is Giant, then skip it.
 996                          */
 997                         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 998                             lock1->li_lock == &Giant.lock_object)
 999                                 continue;
1000                         /*
1001                          * If we are locking a sleepable lock and this lock
1002                          * isn't sleepable, we want to treat it as a lock
1003                          * order violation to enfore a general lock order of
1004                          * sleepable locks before non-sleepable locks.
1005                          */
1006                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
1007                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
1008                                 goto reversal;
1009                         /*
1010                          * If we are locking Giant and this is a non-sleepable
1011                          * lock, then treat it as a reversal.
1012                          */
1013                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0 &&
1014                             lock == &Giant.lock_object)
1015                                 goto reversal;
1016                         /*
1017                          * Check the lock order hierarchy for a reveresal.
1018                          */
1019                         if (!isitmydescendant(w, w1))
1020                                 continue;
1021                 reversal:
1022                         /*
1023                          * We have a lock order violation, check to see if it
1024                          * is allowed or has already been yelled about.
1025                          */
1026                         mtx_unlock_spin(&w_mtx);
1027 #ifdef BLESSING
1028                         /*
1029                          * If the lock order is blessed, just bail.  We don't
1030                          * look for other lock order violations though, which
1031                          * may be a bug.
1032                          */
1033                         if (blessed(w, w1))
1034                                 return;
1035 #endif
1036                         if (lock1->li_lock == &Giant.lock_object) {
1037                                 if (w1->w_Giant_squawked)
1038                                         return;
1039                                 else
1040                                         w1->w_Giant_squawked = 1;
1041                         } else {
1042                                 if (w1->w_other_squawked)
1043                                         return;
1044                                 else
1045                                         w1->w_other_squawked = 1;
1046                         }
1047                         /*
1048                          * Ok, yell about it.
1049                          */
1050                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
1051                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
1052                                 printf(
1053                 "lock order reversal: (sleepable after non-sleepable)\n");
1054                         else if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0
1055                             && lock == &Giant.lock_object)
1056                                 printf(
1057                 "lock order reversal: (Giant after non-sleepable)\n");
1058                         else
1059                                 printf("lock order reversal:\n");
1060                         /*
1061                          * Try to locate an earlier lock with
1062                          * witness w in our list.
1063                          */
1064                         do {
1065                                 lock2 = &lle->ll_children[i];
1066                                 MPASS(lock2->li_lock != NULL);
1067                                 if (lock2->li_lock->lo_witness == w)
1068                                         break;
1069                                 if (i == 0 && lle->ll_next != NULL) {
1070                                         lle = lle->ll_next;
1071                                         i = lle->ll_count - 1;
1072                                         MPASS(i >= 0 && i < LOCK_NCHILDREN);
1073                                 } else
1074                                         i--;
1075                         } while (i >= 0);
1076                         if (i < 0) {
1077                                 printf(" 1st %p %s (%s) @ %s:%d\n",
1078                                     lock1->li_lock, lock1->li_lock->lo_name,
1079                                     lock1->li_lock->lo_type, lock1->li_file,
1080                                     lock1->li_line);
1081                                 printf(" 2nd %p %s (%s) @ %s:%d\n", lock,
1082                                     lock->lo_name, lock->lo_type, file, line);
1083                         } else {
1084                                 printf(" 1st %p %s (%s) @ %s:%d\n",
1085                                     lock2->li_lock, lock2->li_lock->lo_name,
1086                                     lock2->li_lock->lo_type, lock2->li_file,
1087                                     lock2->li_line);
1088                                 printf(" 2nd %p %s (%s) @ %s:%d\n",
1089                                     lock1->li_lock, lock1->li_lock->lo_name,
1090                                     lock1->li_lock->lo_type, lock1->li_file,
1091                                     lock1->li_line);
1092                                 printf(" 3rd %p %s (%s) @ %s:%d\n", lock,
1093                                     lock->lo_name, lock->lo_type, file, line);
1094                         }
1095 #ifdef KDB
1096                         goto debugger;
1097 #else
1098                         return;
1099 #endif
1100                 }
1101         }
1102         lock1 = &(*lock_list)->ll_children[(*lock_list)->ll_count - 1];
1103         /*
1104          * If requested, build a new lock order.  However, don't build a new
1105          * relationship between a sleepable lock and Giant if it is in the
1106          * wrong direction.  The correct lock order is that sleepable locks
1107          * always come before Giant.
1108          */
1109         if (flags & LOP_NEWORDER &&
1110             !(lock1->li_lock == &Giant.lock_object &&
1111             (lock->lo_flags & LO_SLEEPABLE) != 0)) {
1112                 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
1113                     lock->lo_type, lock1->li_lock->lo_type);
1114                 if (!itismychild(lock1->li_lock->lo_witness, w))
1115                         /* Witness is dead. */
1116                         return;
1117         }
1118         mtx_unlock_spin(&w_mtx);
1119         return;
1120
1121 #ifdef KDB
1122 debugger:
1123         if (witness_trace)
1124                 kdb_backtrace();
1125         if (witness_kdb)
1126                 kdb_enter_why(KDB_WHY_WITNESS, __func__);
1127 #endif
1128 }
1129
1130 void
1131 witness_lock(struct lock_object *lock, int flags, const char *file, int line)
1132 {
1133         struct lock_list_entry **lock_list, *lle;
1134         struct lock_instance *instance;
1135         struct witness *w;
1136         struct thread *td;
1137
1138         if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL ||
1139             panicstr != NULL)
1140                 return;
1141         w = lock->lo_witness;
1142         td = curthread;
1143         file = fixup_filename(file);
1144
1145         /* Determine lock list for this lock. */
1146         if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK)
1147                 lock_list = &td->td_sleeplocks;
1148         else
1149                 lock_list = PCPU_PTR(spinlocks);
1150
1151         /* Check to see if we are recursing on a lock we already own. */
1152         instance = find_instance(*lock_list, lock);
1153         if (instance != NULL) {
1154                 instance->li_flags++;
1155                 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__,
1156                     td->td_proc->p_pid, lock->lo_name,
1157                     instance->li_flags & LI_RECURSEMASK);
1158                 instance->li_file = file;
1159                 instance->li_line = line;
1160                 return;
1161         }
1162
1163         /* Update per-witness last file and line acquire. */
1164         w->w_file = file;
1165         w->w_line = line;
1166
1167         /* Find the next open lock instance in the list and fill it. */
1168         lle = *lock_list;
1169         if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
1170                 lle = witness_lock_list_get();
1171                 if (lle == NULL)
1172                         return;
1173                 lle->ll_next = *lock_list;
1174                 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__,
1175                     td->td_proc->p_pid, lle);
1176                 *lock_list = lle;
1177         }
1178         instance = &lle->ll_children[lle->ll_count++];
1179         instance->li_lock = lock;
1180         instance->li_line = line;
1181         instance->li_file = file;
1182         if ((flags & LOP_EXCLUSIVE) != 0)
1183                 instance->li_flags = LI_EXCLUSIVE;
1184         else
1185                 instance->li_flags = 0;
1186         CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__,
1187             td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1);
1188 }
1189
1190 void
1191 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line)
1192 {
1193         struct lock_instance *instance;
1194         struct lock_class *class;
1195
1196         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
1197         if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
1198                 return;
1199         class = LOCK_CLASS(lock);
1200         file = fixup_filename(file);
1201         if ((lock->lo_flags & LO_UPGRADABLE) == 0)
1202                 panic("upgrade of non-upgradable lock (%s) %s @ %s:%d",
1203                     class->lc_name, lock->lo_name, file, line);
1204         if ((flags & LOP_TRYLOCK) == 0)
1205                 panic("non-try upgrade of lock (%s) %s @ %s:%d", class->lc_name,
1206                     lock->lo_name, file, line);
1207         if ((class->lc_flags & LC_SLEEPLOCK) == 0)
1208                 panic("upgrade of non-sleep lock (%s) %s @ %s:%d",
1209                     class->lc_name, lock->lo_name, file, line);
1210         instance = find_instance(curthread->td_sleeplocks, lock);
1211         if (instance == NULL)
1212                 panic("upgrade of unlocked lock (%s) %s @ %s:%d",
1213                     class->lc_name, lock->lo_name, file, line);
1214         if ((instance->li_flags & LI_EXCLUSIVE) != 0)
1215                 panic("upgrade of exclusive lock (%s) %s @ %s:%d",
1216                     class->lc_name, lock->lo_name, file, line);
1217         if ((instance->li_flags & LI_RECURSEMASK) != 0)
1218                 panic("upgrade of recursed lock (%s) %s r=%d @ %s:%d",
1219                     class->lc_name, lock->lo_name,
1220                     instance->li_flags & LI_RECURSEMASK, file, line);
1221         instance->li_flags |= LI_EXCLUSIVE;
1222 }
1223
1224 void
1225 witness_downgrade(struct lock_object *lock, int flags, const char *file,
1226     int line)
1227 {
1228         struct lock_instance *instance;
1229         struct lock_class *class;
1230
1231         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
1232         if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
1233                 return;
1234         class = LOCK_CLASS(lock);
1235         file = fixup_filename(file);
1236         if ((lock->lo_flags & LO_UPGRADABLE) == 0)
1237                 panic("downgrade of non-upgradable lock (%s) %s @ %s:%d",
1238                     class->lc_name, lock->lo_name, file, line);
1239         if ((class->lc_flags & LC_SLEEPLOCK) == 0)
1240                 panic("downgrade of non-sleep lock (%s) %s @ %s:%d",
1241                     class->lc_name, lock->lo_name, file, line);
1242         instance = find_instance(curthread->td_sleeplocks, lock);
1243         if (instance == NULL)
1244                 panic("downgrade of unlocked lock (%s) %s @ %s:%d",
1245                     class->lc_name, lock->lo_name, file, line);
1246         if ((instance->li_flags & LI_EXCLUSIVE) == 0)
1247                 panic("downgrade of shared lock (%s) %s @ %s:%d",
1248                     class->lc_name, lock->lo_name, file, line);
1249         if ((instance->li_flags & LI_RECURSEMASK) != 0)
1250                 panic("downgrade of recursed lock (%s) %s r=%d @ %s:%d",
1251                     class->lc_name, lock->lo_name,
1252                     instance->li_flags & LI_RECURSEMASK, file, line);
1253         instance->li_flags &= ~LI_EXCLUSIVE;
1254 }
1255
1256 void
1257 witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
1258 {
1259         struct lock_list_entry **lock_list, *lle;
1260         struct lock_instance *instance;
1261         struct lock_class *class;
1262         struct thread *td;
1263         register_t s;
1264         int i, j;
1265
1266         if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL ||
1267             panicstr != NULL)
1268                 return;
1269         td = curthread;
1270         class = LOCK_CLASS(lock);
1271         file = fixup_filename(file);
1272
1273         /* Find lock instance associated with this lock. */
1274         if (class->lc_flags & LC_SLEEPLOCK)
1275                 lock_list = &td->td_sleeplocks;
1276         else
1277                 lock_list = PCPU_PTR(spinlocks);
1278         for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next)
1279                 for (i = 0; i < (*lock_list)->ll_count; i++) {
1280                         instance = &(*lock_list)->ll_children[i];
1281                         if (instance->li_lock == lock)
1282                                 goto found;
1283                 }
1284         panic("lock (%s) %s not locked @ %s:%d", class->lc_name, lock->lo_name,
1285             file, line);
1286 found:
1287
1288         /* First, check for shared/exclusive mismatches. */
1289         if ((instance->li_flags & LI_EXCLUSIVE) != 0 &&
1290             (flags & LOP_EXCLUSIVE) == 0) {
1291                 printf("shared unlock of (%s) %s @ %s:%d\n", class->lc_name,
1292                     lock->lo_name, file, line);
1293                 printf("while exclusively locked from %s:%d\n",
1294                     instance->li_file, instance->li_line);
1295                 panic("excl->ushare");
1296         }
1297         if ((instance->li_flags & LI_EXCLUSIVE) == 0 &&
1298             (flags & LOP_EXCLUSIVE) != 0) {
1299                 printf("exclusive unlock of (%s) %s @ %s:%d\n", class->lc_name,
1300                     lock->lo_name, file, line);
1301                 printf("while share locked from %s:%d\n", instance->li_file,
1302                     instance->li_line);
1303                 panic("share->uexcl");
1304         }
1305
1306         /* If we are recursed, unrecurse. */
1307         if ((instance->li_flags & LI_RECURSEMASK) > 0) {
1308                 CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__,
1309                     td->td_proc->p_pid, instance->li_lock->lo_name,
1310                     instance->li_flags);
1311                 instance->li_flags--;
1312                 return;
1313         }
1314
1315         /* Otherwise, remove this item from the list. */
1316         s = intr_disable();
1317         CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__,
1318             td->td_proc->p_pid, instance->li_lock->lo_name,
1319             (*lock_list)->ll_count - 1);
1320         for (j = i; j < (*lock_list)->ll_count - 1; j++)
1321                 (*lock_list)->ll_children[j] =
1322                     (*lock_list)->ll_children[j + 1];
1323         (*lock_list)->ll_count--;
1324         intr_restore(s);
1325
1326         /* If this lock list entry is now empty, free it. */
1327         if ((*lock_list)->ll_count == 0) {
1328                 lle = *lock_list;
1329                 *lock_list = lle->ll_next;
1330                 CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__,
1331                     td->td_proc->p_pid, lle);
1332                 witness_lock_list_free(lle);
1333         }
1334 }
1335
1336 /*
1337  * Warn if any locks other than 'lock' are held.  Flags can be passed in to
1338  * exempt Giant and sleepable locks from the checks as well.  If any
1339  * non-exempt locks are held, then a supplied message is printed to the
1340  * console along with a list of the offending locks.  If indicated in the
1341  * flags then a failure results in a panic as well.
1342  */
1343 int
1344 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
1345 {
1346         struct lock_list_entry *lle;
1347         struct lock_instance *lock1;
1348         struct thread *td;
1349         va_list ap;
1350         int i, n;
1351
1352         if (witness_cold || witness_watch == 0 || panicstr != NULL)
1353                 return (0);
1354         n = 0;
1355         td = curthread;
1356         for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next)
1357                 for (i = lle->ll_count - 1; i >= 0; i--) {
1358                         lock1 = &lle->ll_children[i];
1359                         if (lock1->li_lock == lock)
1360                                 continue;
1361                         if (flags & WARN_GIANTOK &&
1362                             lock1->li_lock == &Giant.lock_object)
1363                                 continue;
1364                         if (flags & WARN_SLEEPOK &&
1365                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0)
1366                                 continue;
1367                         if (n == 0) {
1368                                 va_start(ap, fmt);
1369                                 vprintf(fmt, ap);
1370                                 va_end(ap);
1371                                 printf(" with the following");
1372                                 if (flags & WARN_SLEEPOK)
1373                                         printf(" non-sleepable");
1374                                 printf(" locks held:\n");
1375                         }
1376                         n++;
1377                         witness_list_lock(lock1);
1378                 }
1379         if (PCPU_GET(spinlocks) != NULL) {
1380                 /*
1381                  * Since we already hold a spinlock preemption is
1382                  * already blocked.
1383                  */
1384                 if (n == 0) {
1385                         va_start(ap, fmt);
1386                         vprintf(fmt, ap);
1387                         va_end(ap);
1388                         printf(" with the following");
1389                         if (flags & WARN_SLEEPOK)
1390                                 printf(" non-sleepable");
1391                         printf(" locks held:\n");
1392                 }
1393                 n += witness_list_locks(PCPU_PTR(spinlocks));
1394         }
1395         if (flags & WARN_PANIC && n)
1396                 panic("witness_warn");
1397 #ifdef KDB
1398         else if (witness_kdb && n)
1399                 kdb_enter_why(KDB_WHY_WITNESS, __func__);
1400         else if (witness_trace && n)
1401                 kdb_backtrace();
1402 #endif
1403         return (n);
1404 }
1405
1406 const char *
1407 witness_file(struct lock_object *lock)
1408 {
1409         struct witness *w;
1410
1411         if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL)
1412                 return ("?");
1413         w = lock->lo_witness;
1414         return (w->w_file);
1415 }
1416
1417 int
1418 witness_line(struct lock_object *lock)
1419 {
1420         struct witness *w;
1421
1422         if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL)
1423                 return (0);
1424         w = lock->lo_witness;
1425         return (w->w_line);
1426 }
1427
1428 static struct witness *
1429 enroll(const char *description, struct lock_class *lock_class)
1430 {
1431         struct witness *w;
1432
1433         if (witness_watch == 0 || panicstr != NULL)
1434                 return (NULL);
1435         if ((lock_class->lc_flags & LC_SPINLOCK) && witness_skipspin)
1436                 return (NULL);
1437         mtx_lock_spin(&w_mtx);
1438         STAILQ_FOREACH(w, &w_all, w_list) {
1439                 if (w->w_name == description || (w->w_refcount > 0 &&
1440                     strcmp(description, w->w_name) == 0)) {
1441                         w->w_refcount++;
1442                         mtx_unlock_spin(&w_mtx);
1443                         if (lock_class != w->w_class)
1444                                 panic(
1445                                 "lock (%s) %s does not match earlier (%s) lock",
1446                                     description, lock_class->lc_name,
1447                                     w->w_class->lc_name);
1448                         return (w);
1449                 }
1450         }
1451         if ((w = witness_get()) == NULL)
1452                 goto out;
1453         w->w_name = description;
1454         w->w_class = lock_class;
1455         w->w_refcount = 1;
1456         STAILQ_INSERT_HEAD(&w_all, w, w_list);
1457         if (lock_class->lc_flags & LC_SPINLOCK) {
1458                 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist);
1459                 w_spin_cnt++;
1460         } else if (lock_class->lc_flags & LC_SLEEPLOCK) {
1461                 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist);
1462                 w_sleep_cnt++;
1463         } else {
1464                 mtx_unlock_spin(&w_mtx);
1465                 panic("lock class %s is not sleep or spin",
1466                     lock_class->lc_name);
1467         }
1468         mtx_unlock_spin(&w_mtx);
1469 out:
1470         /*
1471          * We issue a warning for any spin locks not defined in the static
1472          * order list as a way to discourage their use (folks should really
1473          * be using non-spin mutexes most of the time).  However, several
1474          * 3rd part device drivers use spin locks because that is all they
1475          * have available on Windows and Linux and they think that normal
1476          * mutexes are insufficient.
1477          */
1478         if ((lock_class->lc_flags & LC_SPINLOCK) && witness_spin_warn)
1479                 printf("WITNESS: spin lock %s not in order list\n",
1480                     description);
1481         return (w);
1482 }
1483
1484 /* Don't let the door bang you on the way out... */
1485 static int
1486 depart(struct witness *w)
1487 {
1488         struct witness_child_list_entry *wcl, *nwcl;
1489         struct witness_list *list;
1490         struct witness *parent;
1491
1492         MPASS(w->w_refcount == 0);
1493         if (w->w_class->lc_flags & LC_SLEEPLOCK) {
1494                 list = &w_sleep;
1495                 w_sleep_cnt--;
1496         } else {
1497                 list = &w_spin;
1498                 w_spin_cnt--;
1499         }
1500         /*
1501          * First, we run through the entire tree looking for any
1502          * witnesses that the outgoing witness is a child of.  For
1503          * each parent that we find, we reparent all the direct
1504          * children of the outgoing witness to its parent.
1505          */
1506         STAILQ_FOREACH(parent, list, w_typelist) {
1507                 if (!isitmychild(parent, w))
1508                         continue;
1509                 removechild(parent, w);
1510         }
1511
1512         /*
1513          * Now we go through and free up the child list of the
1514          * outgoing witness.
1515          */
1516         for (wcl = w->w_children; wcl != NULL; wcl = nwcl) {
1517                 nwcl = wcl->wcl_next;
1518                 w_child_cnt--;
1519                 witness_child_free(wcl);
1520         }
1521
1522         /*
1523          * Detach from various lists and free.
1524          */
1525         STAILQ_REMOVE(list, w, witness, w_typelist);
1526         STAILQ_REMOVE(&w_all, w, witness, w_list);
1527         witness_free(w);
1528
1529         return (1);
1530 }
1531
1532 /*
1533  * Add "child" as a direct child of "parent".  Returns false if
1534  * we fail due to out of memory.
1535  */
1536 static int
1537 insertchild(struct witness *parent, struct witness *child)
1538 {
1539         struct witness_child_list_entry **wcl;
1540
1541         MPASS(child != NULL && parent != NULL);
1542
1543         /*
1544          * Insert "child" after "parent"
1545          */
1546         wcl = &parent->w_children;
1547         while (*wcl != NULL && (*wcl)->wcl_count == WITNESS_NCHILDREN)
1548                 wcl = &(*wcl)->wcl_next;
1549         if (*wcl == NULL) {
1550                 *wcl = witness_child_get();
1551                 if (*wcl == NULL)
1552                         return (0);
1553                 w_child_cnt++;
1554         }
1555         (*wcl)->wcl_children[(*wcl)->wcl_count++] = child;
1556
1557         return (1);
1558 }
1559
1560
1561 static int
1562 itismychild(struct witness *parent, struct witness *child)
1563 {
1564         struct witness_list *list;
1565
1566         MPASS(child != NULL && parent != NULL);
1567         if ((parent->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) !=
1568             (child->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)))
1569                 panic(
1570                 "%s: parent (%s) and child (%s) are not the same lock type",
1571                     __func__, parent->w_class->lc_name,
1572                     child->w_class->lc_name);
1573
1574         if (!insertchild(parent, child))
1575                 return (0);
1576
1577         if (parent->w_class->lc_flags & LC_SLEEPLOCK)
1578                 list = &w_sleep;
1579         else
1580                 list = &w_spin;
1581         return (1);
1582 }
1583
1584 static void
1585 removechild(struct witness *parent, struct witness *child)
1586 {
1587         struct witness_child_list_entry **wcl, *wcl1;
1588         int i;
1589
1590         for (wcl = &parent->w_children; *wcl != NULL; wcl = &(*wcl)->wcl_next)
1591                 for (i = 0; i < (*wcl)->wcl_count; i++)
1592                         if ((*wcl)->wcl_children[i] == child)
1593                                 goto found;
1594         return;
1595 found:
1596         (*wcl)->wcl_count--;
1597         if ((*wcl)->wcl_count > i)
1598                 (*wcl)->wcl_children[i] =
1599                     (*wcl)->wcl_children[(*wcl)->wcl_count];
1600         MPASS((*wcl)->wcl_children[i] != NULL);
1601         if ((*wcl)->wcl_count != 0)
1602                 return;
1603         wcl1 = *wcl;
1604         *wcl = wcl1->wcl_next;
1605         w_child_cnt--;
1606         witness_child_free(wcl1);
1607 }
1608
1609 static int
1610 isitmychild(struct witness *parent, struct witness *child)
1611 {
1612         struct witness_child_list_entry *wcl;
1613         int i;
1614
1615         for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) {
1616                 for (i = 0; i < wcl->wcl_count; i++) {
1617                         if (wcl->wcl_children[i] == child)
1618                                 return (1);
1619                 }
1620         }
1621         return (0);
1622 }
1623
1624 static int
1625 isitmydescendant(struct witness *parent, struct witness *child)
1626 {
1627         struct witness_child_list_entry *wcl;
1628         int i, j;
1629
1630         if (isitmychild(parent, child))
1631                 return (1);
1632         j = 0;
1633         for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) {
1634                 MPASS(j < 1000);
1635                 for (i = 0; i < wcl->wcl_count; i++) {
1636                         if (isitmydescendant(wcl->wcl_children[i], child))
1637                                 return (1);
1638                 }
1639                 j++;
1640         }
1641         return (0);
1642 }
1643
1644 #ifdef BLESSING
1645 static int
1646 blessed(struct witness *w1, struct witness *w2)
1647 {
1648         int i;
1649         struct witness_blessed *b;
1650
1651         for (i = 0; i < blessed_count; i++) {
1652                 b = &blessed_list[i];
1653                 if (strcmp(w1->w_name, b->b_lock1) == 0) {
1654                         if (strcmp(w2->w_name, b->b_lock2) == 0)
1655                                 return (1);
1656                         continue;
1657                 }
1658                 if (strcmp(w1->w_name, b->b_lock2) == 0)
1659                         if (strcmp(w2->w_name, b->b_lock1) == 0)
1660                                 return (1);
1661         }
1662         return (0);
1663 }
1664 #endif
1665
1666 static struct witness *
1667 witness_get(void)
1668 {
1669         struct witness *w;
1670
1671         if (witness_watch == 0) {
1672                 mtx_unlock_spin(&w_mtx);
1673                 return (NULL);
1674         }
1675         if (STAILQ_EMPTY(&w_free)) {
1676                 witness_watch = 0;
1677                 mtx_unlock_spin(&w_mtx);
1678                 printf("%s: witness exhausted\n", __func__);
1679                 return (NULL);
1680         }
1681         w = STAILQ_FIRST(&w_free);
1682         STAILQ_REMOVE_HEAD(&w_free, w_list);
1683         w_free_cnt--;
1684         bzero(w, sizeof(*w));
1685         return (w);
1686 }
1687
1688 static void
1689 witness_free(struct witness *w)
1690 {
1691
1692         STAILQ_INSERT_HEAD(&w_free, w, w_list);
1693         w_free_cnt++;
1694 }
1695
1696 static struct witness_child_list_entry *
1697 witness_child_get(void)
1698 {
1699         struct witness_child_list_entry *wcl;
1700
1701         if (witness_watch == 0) {
1702                 mtx_unlock_spin(&w_mtx);
1703                 return (NULL);
1704         }
1705         wcl = w_child_free;
1706         if (wcl == NULL) {
1707                 witness_watch = 0;
1708                 mtx_unlock_spin(&w_mtx);
1709                 printf("%s: witness exhausted\n", __func__);
1710                 return (NULL);
1711         }
1712         w_child_free = wcl->wcl_next;
1713         w_child_free_cnt--;
1714         bzero(wcl, sizeof(*wcl));
1715         return (wcl);
1716 }
1717
1718 static void
1719 witness_child_free(struct witness_child_list_entry *wcl)
1720 {
1721
1722         wcl->wcl_next = w_child_free;
1723         w_child_free = wcl;
1724         w_child_free_cnt++;
1725 }
1726
1727 static struct lock_list_entry *
1728 witness_lock_list_get(void)
1729 {
1730         struct lock_list_entry *lle;
1731
1732         if (witness_watch == 0)
1733                 return (NULL);
1734         mtx_lock_spin(&w_mtx);
1735         lle = w_lock_list_free;
1736         if (lle == NULL) {
1737                 witness_watch = 0;
1738                 mtx_unlock_spin(&w_mtx);
1739                 printf("%s: witness exhausted\n", __func__);
1740                 return (NULL);
1741         }
1742         w_lock_list_free = lle->ll_next;
1743         mtx_unlock_spin(&w_mtx);
1744         bzero(lle, sizeof(*lle));
1745         return (lle);
1746 }
1747
1748 static void
1749 witness_lock_list_free(struct lock_list_entry *lle)
1750 {
1751
1752         mtx_lock_spin(&w_mtx);
1753         lle->ll_next = w_lock_list_free;
1754         w_lock_list_free = lle;
1755         mtx_unlock_spin(&w_mtx);
1756 }
1757
1758 static struct lock_instance *
1759 find_instance(struct lock_list_entry *lock_list, struct lock_object *lock)
1760 {
1761         struct lock_list_entry *lle;
1762         struct lock_instance *instance;
1763         int i;
1764
1765         for (lle = lock_list; lle != NULL; lle = lle->ll_next)
1766                 for (i = lle->ll_count - 1; i >= 0; i--) {
1767                         instance = &lle->ll_children[i];
1768                         if (instance->li_lock == lock)
1769                                 return (instance);
1770                 }
1771         return (NULL);
1772 }
1773
1774 static void
1775 witness_list_lock(struct lock_instance *instance)
1776 {
1777         struct lock_object *lock;
1778
1779         lock = instance->li_lock;
1780         printf("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ?
1781             "exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name);
1782         if (lock->lo_type != lock->lo_name)
1783                 printf(" (%s)", lock->lo_type);
1784         printf(" r = %d (%p) locked @ %s:%d\n",
1785             instance->li_flags & LI_RECURSEMASK, lock, instance->li_file,
1786             instance->li_line);
1787 }
1788
1789 #ifdef DDB
1790 static int
1791 witness_thread_has_locks(struct thread *td)
1792 {
1793
1794         return (td->td_sleeplocks != NULL);
1795 }
1796
1797 static int
1798 witness_proc_has_locks(struct proc *p)
1799 {
1800         struct thread *td;
1801
1802         FOREACH_THREAD_IN_PROC(p, td) {
1803                 if (witness_thread_has_locks(td))
1804                         return (1);
1805         }
1806         return (0);
1807 }
1808 #endif
1809
1810 int
1811 witness_list_locks(struct lock_list_entry **lock_list)
1812 {
1813         struct lock_list_entry *lle;
1814         int i, nheld;
1815
1816         nheld = 0;
1817         for (lle = *lock_list; lle != NULL; lle = lle->ll_next)
1818                 for (i = lle->ll_count - 1; i >= 0; i--) {
1819                         witness_list_lock(&lle->ll_children[i]);
1820                         nheld++;
1821                 }
1822         return (nheld);
1823 }
1824
1825 /*
1826  * This is a bit risky at best.  We call this function when we have timed
1827  * out acquiring a spin lock, and we assume that the other CPU is stuck
1828  * with this lock held.  So, we go groveling around in the other CPU's
1829  * per-cpu data to try to find the lock instance for this spin lock to
1830  * see when it was last acquired.
1831  */
1832 void
1833 witness_display_spinlock(struct lock_object *lock, struct thread *owner)
1834 {
1835         struct lock_instance *instance;
1836         struct pcpu *pc;
1837
1838         if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU)
1839                 return;
1840         pc = pcpu_find(owner->td_oncpu);
1841         instance = find_instance(pc->pc_spinlocks, lock);
1842         if (instance != NULL)
1843                 witness_list_lock(instance);
1844 }
1845
1846 void
1847 witness_save(struct lock_object *lock, const char **filep, int *linep)
1848 {
1849         struct lock_list_entry *lock_list;
1850         struct lock_instance *instance;
1851         struct lock_class *class;
1852
1853         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
1854         if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
1855                 return;
1856         class = LOCK_CLASS(lock);
1857         if (class->lc_flags & LC_SLEEPLOCK)
1858                 lock_list = curthread->td_sleeplocks;
1859         else {
1860                 if (witness_skipspin)
1861                         return;
1862                 lock_list = PCPU_GET(spinlocks);
1863         }
1864         instance = find_instance(lock_list, lock);
1865         if (instance == NULL)
1866                 panic("%s: lock (%s) %s not locked", __func__,
1867                     class->lc_name, lock->lo_name);
1868         *filep = instance->li_file;
1869         *linep = instance->li_line;
1870 }
1871
1872 void
1873 witness_restore(struct lock_object *lock, const char *file, int line)
1874 {
1875         struct lock_list_entry *lock_list;
1876         struct lock_instance *instance;
1877         struct lock_class *class;
1878
1879         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
1880         if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
1881                 return;
1882         class = LOCK_CLASS(lock);
1883         if (class->lc_flags & LC_SLEEPLOCK)
1884                 lock_list = curthread->td_sleeplocks;
1885         else {
1886                 if (witness_skipspin)
1887                         return;
1888                 lock_list = PCPU_GET(spinlocks);
1889         }
1890         instance = find_instance(lock_list, lock);
1891         if (instance == NULL)
1892                 panic("%s: lock (%s) %s not locked", __func__,
1893                     class->lc_name, lock->lo_name);
1894         lock->lo_witness->w_file = file;
1895         lock->lo_witness->w_line = line;
1896         instance->li_file = file;
1897         instance->li_line = line;
1898 }
1899
1900 void
1901 witness_assert(struct lock_object *lock, int flags, const char *file, int line)
1902 {
1903 #ifdef INVARIANT_SUPPORT
1904         struct lock_instance *instance;
1905         struct lock_class *class;
1906
1907         if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
1908                 return;
1909         class = LOCK_CLASS(lock);
1910         if ((class->lc_flags & LC_SLEEPLOCK) != 0)
1911                 instance = find_instance(curthread->td_sleeplocks, lock);
1912         else if ((class->lc_flags & LC_SPINLOCK) != 0)
1913                 instance = find_instance(PCPU_GET(spinlocks), lock);
1914         else {
1915                 panic("Lock (%s) %s is not sleep or spin!",
1916                     class->lc_name, lock->lo_name);
1917         }
1918         file = fixup_filename(file);
1919         switch (flags) {
1920         case LA_UNLOCKED:
1921                 if (instance != NULL)
1922                         panic("Lock (%s) %s locked @ %s:%d.",
1923                             class->lc_name, lock->lo_name, file, line);
1924                 break;
1925         case LA_LOCKED:
1926         case LA_LOCKED | LA_RECURSED:
1927         case LA_LOCKED | LA_NOTRECURSED:
1928         case LA_SLOCKED:
1929         case LA_SLOCKED | LA_RECURSED:
1930         case LA_SLOCKED | LA_NOTRECURSED:
1931         case LA_XLOCKED:
1932         case LA_XLOCKED | LA_RECURSED:
1933         case LA_XLOCKED | LA_NOTRECURSED:
1934                 if (instance == NULL) {
1935                         panic("Lock (%s) %s not locked @ %s:%d.",
1936                             class->lc_name, lock->lo_name, file, line);
1937                         break;
1938                 }
1939                 if ((flags & LA_XLOCKED) != 0 &&
1940                     (instance->li_flags & LI_EXCLUSIVE) == 0)
1941                         panic("Lock (%s) %s not exclusively locked @ %s:%d.",
1942                             class->lc_name, lock->lo_name, file, line);
1943                 if ((flags & LA_SLOCKED) != 0 &&
1944                     (instance->li_flags & LI_EXCLUSIVE) != 0)
1945                         panic("Lock (%s) %s exclusively locked @ %s:%d.",
1946                             class->lc_name, lock->lo_name, file, line);
1947                 if ((flags & LA_RECURSED) != 0 &&
1948                     (instance->li_flags & LI_RECURSEMASK) == 0)
1949                         panic("Lock (%s) %s not recursed @ %s:%d.",
1950                             class->lc_name, lock->lo_name, file, line);
1951                 if ((flags & LA_NOTRECURSED) != 0 &&
1952                     (instance->li_flags & LI_RECURSEMASK) != 0)
1953                         panic("Lock (%s) %s recursed @ %s:%d.",
1954                             class->lc_name, lock->lo_name, file, line);
1955                 break;
1956         default:
1957                 panic("Invalid lock assertion at %s:%d.", file, line);
1958
1959         }
1960 #endif  /* INVARIANT_SUPPORT */
1961 }
1962
1963 #ifdef DDB
1964 static void
1965 witness_list(struct thread *td)
1966 {
1967
1968         KASSERT(!witness_cold, ("%s: witness_cold", __func__));
1969         KASSERT(kdb_active, ("%s: not in the debugger", __func__));
1970
1971         if (witness_watch == 0)
1972                 return;
1973
1974         witness_list_locks(&td->td_sleeplocks);
1975
1976         /*
1977          * We only handle spinlocks if td == curthread.  This is somewhat broken
1978          * if td is currently executing on some other CPU and holds spin locks
1979          * as we won't display those locks.  If we had a MI way of getting
1980          * the per-cpu data for a given cpu then we could use
1981          * td->td_oncpu to get the list of spinlocks for this thread
1982          * and "fix" this.
1983          *
1984          * That still wouldn't really fix this unless we locked the scheduler
1985          * lock or stopped the other CPU to make sure it wasn't changing the
1986          * list out from under us.  It is probably best to just not try to
1987          * handle threads on other CPU's for now.
1988          */
1989         if (td == curthread && PCPU_GET(spinlocks) != NULL)
1990                 witness_list_locks(PCPU_PTR(spinlocks));
1991 }
1992
1993 DB_SHOW_COMMAND(locks, db_witness_list)
1994 {
1995         struct thread *td;
1996
1997         if (have_addr)
1998                 td = db_lookup_thread(addr, TRUE);
1999         else
2000                 td = kdb_thread;
2001         witness_list(td);
2002 }
2003
2004 DB_SHOW_COMMAND(alllocks, db_witness_list_all)
2005 {
2006         struct thread *td;
2007         struct proc *p;
2008
2009         /*
2010          * It would be nice to list only threads and processes that actually
2011          * held sleep locks, but that information is currently not exported
2012          * by WITNESS.
2013          */
2014         FOREACH_PROC_IN_SYSTEM(p) {
2015                 if (!witness_proc_has_locks(p))
2016                         continue;
2017                 FOREACH_THREAD_IN_PROC(p, td) {
2018                         if (!witness_thread_has_locks(td))
2019                                 continue;
2020                         db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid,
2021                             p->p_comm, td, td->td_tid);
2022                         witness_list(td);
2023                 }
2024         }
2025 }
2026
2027 DB_SHOW_COMMAND(witness, db_witness_display)
2028 {
2029
2030         witness_display(db_printf);
2031 }
2032 #endif