The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_witness.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 2008 Isilon Systems, Inc.
    5  * Copyright (c) 2008 Ilya Maykov <ivmaykov@gmail.com>
    6  * Copyright (c) 1998 Berkeley Software Design, Inc.
    7  * All rights reserved.
    8  *
    9  * Redistribution and use in source and binary forms, with or without
   10  * modification, are permitted provided that the following conditions
   11  * are met:
   12  * 1. Redistributions of source code must retain the above copyright
   13  *    notice, this list of conditions and the following disclaimer.
   14  * 2. Redistributions in binary form must reproduce the above copyright
   15  *    notice, this list of conditions and the following disclaimer in the
   16  *    documentation and/or other materials provided with the distribution.
   17  * 3. Berkeley Software Design Inc's name may not be used to endorse or
   18  *    promote products derived from this software without specific prior
   19  *    written permission.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  *
   33  *      from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
   34  *      and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
   35  */
   36 
   37 /*
   38  * Implementation of the `witness' lock verifier.  Originally implemented for
   39  * mutexes in BSD/OS.  Extended to handle generic lock objects and lock
   40  * classes in FreeBSD.
   41  */
   42 
   43 /*
   44  *      Main Entry: witness
   45  *      Pronunciation: 'wit-n&s
   46  *      Function: noun
   47  *      Etymology: Middle English witnesse, from Old English witnes knowledge,
   48  *          testimony, witness, from 2wit
   49  *      Date: before 12th century
   50  *      1 : attestation of a fact or event : TESTIMONY
   51  *      2 : one that gives evidence; specifically : one who testifies in
   52  *          a cause or before a judicial tribunal
   53  *      3 : one asked to be present at a transaction so as to be able to
   54  *          testify to its having taken place
   55  *      4 : one who has personal knowledge of something
   56  *      5 a : something serving as evidence or proof : SIGN
   57  *        b : public affirmation by word or example of usually
   58  *            religious faith or conviction <the heroic witness to divine
   59  *            life -- Pilot>
   60  *      6 capitalized : a member of the Jehovah's Witnesses 
   61  */
   62 
   63 /*
   64  * Special rules concerning Giant and lock orders:
   65  *
   66  * 1) Giant must be acquired before any other mutexes.  Stated another way,
   67  *    no other mutex may be held when Giant is acquired.
   68  *
   69  * 2) Giant must be released when blocking on a sleepable lock.
   70  *
   71  * This rule is less obvious, but is a result of Giant providing the same
   72  * semantics as spl().  Basically, when a thread sleeps, it must release
   73  * Giant.  When a thread blocks on a sleepable lock, it sleeps.  Hence rule
   74  * 2).
   75  *
   76  * 3) Giant may be acquired before or after sleepable locks.
   77  *
   78  * This rule is also not quite as obvious.  Giant may be acquired after
   79  * a sleepable lock because it is a non-sleepable lock and non-sleepable
   80  * locks may always be acquired while holding a sleepable lock.  The second
   81  * case, Giant before a sleepable lock, follows from rule 2) above.  Suppose
   82  * you have two threads T1 and T2 and a sleepable lock X.  Suppose that T1
   83  * acquires X and blocks on Giant.  Then suppose that T2 acquires Giant and
   84  * blocks on X.  When T2 blocks on X, T2 will release Giant allowing T1 to
   85  * execute.  Thus, acquiring Giant both before and after a sleepable lock
   86  * will not result in a lock order reversal.
   87  */
   88 
   89 #include <sys/cdefs.h>
   90 __FBSDID("$FreeBSD: releng/12.0/sys/kern/subr_witness.c 335356 2018-06-19 01:54:00Z mmacy $");
   91 
   92 #include "opt_ddb.h"
   93 #include "opt_hwpmc_hooks.h"
   94 #include "opt_stack.h"
   95 #include "opt_witness.h"
   96 
   97 #include <sys/param.h>
   98 #include <sys/bus.h>
   99 #include <sys/kdb.h>
  100 #include <sys/kernel.h>
  101 #include <sys/ktr.h>
  102 #include <sys/lock.h>
  103 #include <sys/malloc.h>
  104 #include <sys/mutex.h>
  105 #include <sys/priv.h>
  106 #include <sys/proc.h>
  107 #include <sys/sbuf.h>
  108 #include <sys/sched.h>
  109 #include <sys/stack.h>
  110 #include <sys/sysctl.h>
  111 #include <sys/syslog.h>
  112 #include <sys/systm.h>
  113 
  114 #ifdef DDB
  115 #include <ddb/ddb.h>
  116 #endif
  117 
  118 #include <machine/stdarg.h>
  119 
  120 #if !defined(DDB) && !defined(STACK)
  121 #error "DDB or STACK options are required for WITNESS"
  122 #endif
  123 
  124 /* Note that these traces do not work with KTR_ALQ. */
  125 #if 0
  126 #define KTR_WITNESS     KTR_SUBSYS
  127 #else
  128 #define KTR_WITNESS     0
  129 #endif
  130 
  131 #define LI_RECURSEMASK  0x0000ffff      /* Recursion depth of lock instance. */
  132 #define LI_EXCLUSIVE    0x00010000      /* Exclusive lock instance. */
  133 #define LI_NORELEASE    0x00020000      /* Lock not allowed to be released. */
  134 
  135 /* Define this to check for blessed mutexes */
  136 #undef BLESSING
  137 
  138 #ifndef WITNESS_COUNT
  139 #define WITNESS_COUNT           1536
  140 #endif
  141 #define WITNESS_HASH_SIZE       251     /* Prime, gives load factor < 2 */
  142 #define WITNESS_PENDLIST        (512 + (MAXCPU * 4))
  143 
  144 /* Allocate 256 KB of stack data space */
  145 #define WITNESS_LO_DATA_COUNT   2048
  146 
  147 /* Prime, gives load factor of ~2 at full load */
  148 #define WITNESS_LO_HASH_SIZE    1021
  149 
  150 /*
  151  * XXX: This is somewhat bogus, as we assume here that at most 2048 threads
  152  * will hold LOCK_NCHILDREN locks.  We handle failure ok, and we should
  153  * probably be safe for the most part, but it's still a SWAG.
  154  */
  155 #define LOCK_NCHILDREN  5
  156 #define LOCK_CHILDCOUNT 2048
  157 
  158 #define MAX_W_NAME      64
  159 
  160 #define FULLGRAPH_SBUF_SIZE     512
  161 
  162 /*
  163  * These flags go in the witness relationship matrix and describe the
  164  * relationship between any two struct witness objects.
  165  */
  166 #define WITNESS_UNRELATED        0x00    /* No lock order relation. */
  167 #define WITNESS_PARENT           0x01    /* Parent, aka direct ancestor. */
  168 #define WITNESS_ANCESTOR         0x02    /* Direct or indirect ancestor. */
  169 #define WITNESS_CHILD            0x04    /* Child, aka direct descendant. */
  170 #define WITNESS_DESCENDANT       0x08    /* Direct or indirect descendant. */
  171 #define WITNESS_ANCESTOR_MASK    (WITNESS_PARENT | WITNESS_ANCESTOR)
  172 #define WITNESS_DESCENDANT_MASK  (WITNESS_CHILD | WITNESS_DESCENDANT)
  173 #define WITNESS_RELATED_MASK                                            \
  174         (WITNESS_ANCESTOR_MASK | WITNESS_DESCENDANT_MASK)
  175 #define WITNESS_REVERSAL         0x10    /* A lock order reversal has been
  176                                           * observed. */
  177 #define WITNESS_RESERVED1        0x20    /* Unused flag, reserved. */
  178 #define WITNESS_RESERVED2        0x40    /* Unused flag, reserved. */
  179 #define WITNESS_LOCK_ORDER_KNOWN 0x80    /* This lock order is known. */
  180 
  181 /* Descendant to ancestor flags */
  182 #define WITNESS_DTOA(x) (((x) & WITNESS_RELATED_MASK) >> 2)
  183 
  184 /* Ancestor to descendant flags */
  185 #define WITNESS_ATOD(x) (((x) & WITNESS_RELATED_MASK) << 2)
  186 
  187 #define WITNESS_INDEX_ASSERT(i)                                         \
  188         MPASS((i) > 0 && (i) <= w_max_used_index && (i) < witness_count)
  189 
  190 static MALLOC_DEFINE(M_WITNESS, "Witness", "Witness");
  191 
  192 /*
  193  * Lock instances.  A lock instance is the data associated with a lock while
  194  * it is held by witness.  For example, a lock instance will hold the
  195  * recursion count of a lock.  Lock instances are held in lists.  Spin locks
  196  * are held in a per-cpu list while sleep locks are held in per-thread list.
  197  */
  198 struct lock_instance {
  199         struct lock_object      *li_lock;
  200         const char              *li_file;
  201         int                     li_line;
  202         u_int                   li_flags;
  203 };
  204 
  205 /*
  206  * A simple list type used to build the list of locks held by a thread
  207  * or CPU.  We can't simply embed the list in struct lock_object since a
  208  * lock may be held by more than one thread if it is a shared lock.  Locks
  209  * are added to the head of the list, so we fill up each list entry from
  210  * "the back" logically.  To ease some of the arithmetic, we actually fill
  211  * in each list entry the normal way (children[0] then children[1], etc.) but
  212  * when we traverse the list we read children[count-1] as the first entry
  213  * down to children[0] as the final entry.
  214  */
  215 struct lock_list_entry {
  216         struct lock_list_entry  *ll_next;
  217         struct lock_instance    ll_children[LOCK_NCHILDREN];
  218         u_int                   ll_count;
  219 };
  220 
  221 /*
  222  * The main witness structure. One of these per named lock type in the system
  223  * (for example, "vnode interlock").
  224  */
  225 struct witness {
  226         char                    w_name[MAX_W_NAME];
  227         uint32_t                w_index;  /* Index in the relationship matrix */
  228         struct lock_class       *w_class;
  229         STAILQ_ENTRY(witness)   w_list;         /* List of all witnesses. */
  230         STAILQ_ENTRY(witness)   w_typelist;     /* Witnesses of a type. */
  231         struct witness          *w_hash_next; /* Linked list in hash buckets. */
  232         const char              *w_file; /* File where last acquired */
  233         uint32_t                w_line; /* Line where last acquired */
  234         uint32_t                w_refcount;
  235         uint16_t                w_num_ancestors; /* direct/indirect
  236                                                   * ancestor count */
  237         uint16_t                w_num_descendants; /* direct/indirect
  238                                                     * descendant count */
  239         int16_t                 w_ddb_level;
  240         unsigned                w_displayed:1;
  241         unsigned                w_reversed:1;
  242 };
  243 
  244 STAILQ_HEAD(witness_list, witness);
  245 
  246 /*
  247  * The witness hash table. Keys are witness names (const char *), elements are
  248  * witness objects (struct witness *).
  249  */
  250 struct witness_hash {
  251         struct witness  *wh_array[WITNESS_HASH_SIZE];
  252         uint32_t        wh_size;
  253         uint32_t        wh_count;
  254 };
  255 
  256 /*
  257  * Key type for the lock order data hash table.
  258  */
  259 struct witness_lock_order_key {
  260         uint16_t        from;
  261         uint16_t        to;
  262 };
  263 
  264 struct witness_lock_order_data {
  265         struct stack                    wlod_stack;
  266         struct witness_lock_order_key   wlod_key;
  267         struct witness_lock_order_data  *wlod_next;
  268 };
  269 
  270 /*
  271  * The witness lock order data hash table. Keys are witness index tuples
  272  * (struct witness_lock_order_key), elements are lock order data objects
  273  * (struct witness_lock_order_data). 
  274  */
  275 struct witness_lock_order_hash {
  276         struct witness_lock_order_data  *wloh_array[WITNESS_LO_HASH_SIZE];
  277         u_int   wloh_size;
  278         u_int   wloh_count;
  279 };
  280 
  281 #ifdef BLESSING
  282 struct witness_blessed {
  283         const char      *b_lock1;
  284         const char      *b_lock2;
  285 };
  286 #endif
  287 
  288 struct witness_pendhelp {
  289         const char              *wh_type;
  290         struct lock_object      *wh_lock;
  291 };
  292 
  293 struct witness_order_list_entry {
  294         const char              *w_name;
  295         struct lock_class       *w_class;
  296 };
  297 
  298 /*
  299  * Returns 0 if one of the locks is a spin lock and the other is not.
  300  * Returns 1 otherwise.
  301  */
  302 static __inline int
  303 witness_lock_type_equal(struct witness *w1, struct witness *w2)
  304 {
  305 
  306         return ((w1->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) ==
  307                 (w2->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)));
  308 }
  309 
  310 static __inline int
  311 witness_lock_order_key_equal(const struct witness_lock_order_key *a,
  312     const struct witness_lock_order_key *b)
  313 {
  314 
  315         return (a->from == b->from && a->to == b->to);
  316 }
  317 
  318 static int      _isitmyx(struct witness *w1, struct witness *w2, int rmask,
  319                     const char *fname);
  320 static void     adopt(struct witness *parent, struct witness *child);
  321 #ifdef BLESSING
  322 static int      blessed(struct witness *, struct witness *);
  323 #endif
  324 static void     depart(struct witness *w);
  325 static struct witness   *enroll(const char *description,
  326                             struct lock_class *lock_class);
  327 static struct lock_instance     *find_instance(struct lock_list_entry *list,
  328                                     const struct lock_object *lock);
  329 static int      isitmychild(struct witness *parent, struct witness *child);
  330 static int      isitmydescendant(struct witness *parent, struct witness *child);
  331 static void     itismychild(struct witness *parent, struct witness *child);
  332 static int      sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS);
  333 static int      sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS);
  334 static int      sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS);
  335 static int      sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS);
  336 static void     witness_add_fullgraph(struct sbuf *sb, struct witness *parent);
  337 #ifdef DDB
  338 static void     witness_ddb_compute_levels(void);
  339 static void     witness_ddb_display(int(*)(const char *fmt, ...));
  340 static void     witness_ddb_display_descendants(int(*)(const char *fmt, ...),
  341                     struct witness *, int indent);
  342 static void     witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
  343                     struct witness_list *list);
  344 static void     witness_ddb_level_descendants(struct witness *parent, int l);
  345 static void     witness_ddb_list(struct thread *td);
  346 #endif
  347 static void     witness_debugger(int cond, const char *msg);
  348 static void     witness_free(struct witness *m);
  349 static struct witness   *witness_get(void);
  350 static uint32_t witness_hash_djb2(const uint8_t *key, uint32_t size);
  351 static struct witness   *witness_hash_get(const char *key);
  352 static void     witness_hash_put(struct witness *w);
  353 static void     witness_init_hash_tables(void);
  354 static void     witness_increment_graph_generation(void);
  355 static void     witness_lock_list_free(struct lock_list_entry *lle);
  356 static struct lock_list_entry   *witness_lock_list_get(void);
  357 static int      witness_lock_order_add(struct witness *parent,
  358                     struct witness *child);
  359 static int      witness_lock_order_check(struct witness *parent,
  360                     struct witness *child);
  361 static struct witness_lock_order_data   *witness_lock_order_get(
  362                                             struct witness *parent,
  363                                             struct witness *child);
  364 static void     witness_list_lock(struct lock_instance *instance,
  365                     int (*prnt)(const char *fmt, ...));
  366 static int      witness_output(const char *fmt, ...) __printflike(1, 2);
  367 static int      witness_voutput(const char *fmt, va_list ap) __printflike(1, 0);
  368 static void     witness_setflag(struct lock_object *lock, int flag, int set);
  369 
  370 static SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW, NULL,
  371     "Witness Locking");
  372 
  373 /*
  374  * If set to 0, lock order checking is disabled.  If set to -1,
  375  * witness is completely disabled.  Otherwise witness performs full
  376  * lock order checking for all locks.  At runtime, lock order checking
  377  * may be toggled.  However, witness cannot be reenabled once it is
  378  * completely disabled.
  379  */
  380 static int witness_watch = 1;
  381 SYSCTL_PROC(_debug_witness, OID_AUTO, watch, CTLFLAG_RWTUN | CTLTYPE_INT, NULL, 0,
  382     sysctl_debug_witness_watch, "I", "witness is watching lock operations");
  383 
  384 #ifdef KDB
  385 /*
  386  * When KDB is enabled and witness_kdb is 1, it will cause the system
  387  * to drop into kdebug() when:
  388  *      - a lock hierarchy violation occurs
  389  *      - locks are held when going to sleep.
  390  */
  391 #ifdef WITNESS_KDB
  392 int     witness_kdb = 1;
  393 #else
  394 int     witness_kdb = 0;
  395 #endif
  396 SYSCTL_INT(_debug_witness, OID_AUTO, kdb, CTLFLAG_RWTUN, &witness_kdb, 0, "");
  397 #endif /* KDB */
  398 
  399 #if defined(DDB) || defined(KDB)
  400 /*
  401  * When DDB or KDB is enabled and witness_trace is 1, it will cause the system
  402  * to print a stack trace:
  403  *      - a lock hierarchy violation occurs
  404  *      - locks are held when going to sleep.
  405  */
  406 int     witness_trace = 1;
  407 SYSCTL_INT(_debug_witness, OID_AUTO, trace, CTLFLAG_RWTUN, &witness_trace, 0, "");
  408 #endif /* DDB || KDB */
  409 
  410 #ifdef WITNESS_SKIPSPIN
  411 int     witness_skipspin = 1;
  412 #else
  413 int     witness_skipspin = 0;
  414 #endif
  415 SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN, &witness_skipspin, 0, "");
  416 
  417 int badstack_sbuf_size;
  418 
  419 int witness_count = WITNESS_COUNT;
  420 SYSCTL_INT(_debug_witness, OID_AUTO, witness_count, CTLFLAG_RDTUN, 
  421     &witness_count, 0, "");
  422 
  423 /*
  424  * Output channel for witness messages.  By default we print to the console.
  425  */
  426 enum witness_channel {
  427         WITNESS_CONSOLE,
  428         WITNESS_LOG,
  429         WITNESS_NONE,
  430 };
  431 
  432 static enum witness_channel witness_channel = WITNESS_CONSOLE;
  433 SYSCTL_PROC(_debug_witness, OID_AUTO, output_channel, CTLTYPE_STRING |
  434     CTLFLAG_RWTUN, NULL, 0, sysctl_debug_witness_channel, "A",
  435     "Output channel for warnings");
  436 
  437 /*
  438  * Call this to print out the relations between locks.
  439  */
  440 SYSCTL_PROC(_debug_witness, OID_AUTO, fullgraph, CTLTYPE_STRING | CTLFLAG_RD,
  441     NULL, 0, sysctl_debug_witness_fullgraph, "A", "Show locks relation graphs");
  442 
  443 /*
  444  * Call this to print out the witness faulty stacks.
  445  */
  446 SYSCTL_PROC(_debug_witness, OID_AUTO, badstacks, CTLTYPE_STRING | CTLFLAG_RD,
  447     NULL, 0, sysctl_debug_witness_badstacks, "A", "Show bad witness stacks");
  448 
  449 static struct mtx w_mtx;
  450 
  451 /* w_list */
  452 static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free);
  453 static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all);
  454 
  455 /* w_typelist */
  456 static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin);
  457 static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep);
  458 
  459 /* lock list */
  460 static struct lock_list_entry *w_lock_list_free = NULL;
  461 static struct witness_pendhelp pending_locks[WITNESS_PENDLIST];
  462 static u_int pending_cnt;
  463 
  464 static int w_free_cnt, w_spin_cnt, w_sleep_cnt;
  465 SYSCTL_INT(_debug_witness, OID_AUTO, free_cnt, CTLFLAG_RD, &w_free_cnt, 0, "");
  466 SYSCTL_INT(_debug_witness, OID_AUTO, spin_cnt, CTLFLAG_RD, &w_spin_cnt, 0, "");
  467 SYSCTL_INT(_debug_witness, OID_AUTO, sleep_cnt, CTLFLAG_RD, &w_sleep_cnt, 0,
  468     "");
  469 
  470 static struct witness *w_data;
  471 static uint8_t **w_rmatrix;
  472 static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT];
  473 static struct witness_hash w_hash;      /* The witness hash table. */
  474 
  475 /* The lock order data hash */
  476 static struct witness_lock_order_data w_lodata[WITNESS_LO_DATA_COUNT];
  477 static struct witness_lock_order_data *w_lofree = NULL;
  478 static struct witness_lock_order_hash w_lohash;
  479 static int w_max_used_index = 0;
  480 static unsigned int w_generation = 0;
  481 static const char w_notrunning[] = "Witness not running\n";
  482 static const char w_stillcold[] = "Witness is still cold\n";
  483 #ifdef __i386__
  484 static const char w_notallowed[] = "The sysctl is disabled on the arch\n";
  485 #endif
  486 
  487 static struct witness_order_list_entry order_lists[] = {
  488         /*
  489          * sx locks
  490          */
  491         { "proctree", &lock_class_sx },
  492         { "allproc", &lock_class_sx },
  493         { "allprison", &lock_class_sx },
  494         { NULL, NULL },
  495         /*
  496          * Various mutexes
  497          */
  498         { "Giant", &lock_class_mtx_sleep },
  499         { "pipe mutex", &lock_class_mtx_sleep },
  500         { "sigio lock", &lock_class_mtx_sleep },
  501         { "process group", &lock_class_mtx_sleep },
  502 #ifdef  HWPMC_HOOKS
  503         { "pmc-sleep", &lock_class_mtx_sleep },
  504 #endif
  505         { "process lock", &lock_class_mtx_sleep },
  506         { "session", &lock_class_mtx_sleep },
  507         { "uidinfo hash", &lock_class_rw },
  508         { "time lock", &lock_class_mtx_sleep },
  509         { NULL, NULL },
  510         /*
  511          * umtx
  512          */
  513         { "umtx lock", &lock_class_mtx_sleep },
  514         { NULL, NULL },
  515         /*
  516          * Sockets
  517          */
  518         { "accept", &lock_class_mtx_sleep },
  519         { "so_snd", &lock_class_mtx_sleep },
  520         { "so_rcv", &lock_class_mtx_sleep },
  521         { "sellck", &lock_class_mtx_sleep },
  522         { NULL, NULL },
  523         /*
  524          * Routing
  525          */
  526         { "so_rcv", &lock_class_mtx_sleep },
  527         { "radix node head", &lock_class_rm },
  528         { "rtentry", &lock_class_mtx_sleep },
  529         { "ifaddr", &lock_class_mtx_sleep },
  530         { NULL, NULL },
  531         /*
  532          * IPv4 multicast:
  533          * protocol locks before interface locks, after UDP locks.
  534          */
  535         { "in_multi_sx", &lock_class_sx },
  536         { "udpinp", &lock_class_rw },
  537         { "in_multi_list_mtx", &lock_class_mtx_sleep },
  538         { "igmp_mtx", &lock_class_mtx_sleep },
  539         { "ifnet_rw", &lock_class_rw },
  540         { "if_addr_lock", &lock_class_mtx_sleep },
  541         { NULL, NULL },
  542         /*
  543          * IPv6 multicast:
  544          * protocol locks before interface locks, after UDP locks.
  545          */
  546         { "in6_multi_sx", &lock_class_sx },
  547         { "udpinp", &lock_class_rw },
  548         { "in6_multi_list_mtx", &lock_class_mtx_sleep },
  549         { "mld_mtx", &lock_class_mtx_sleep },
  550         { "ifnet_rw", &lock_class_rw },
  551         { "if_addr_lock", &lock_class_mtx_sleep },
  552         { NULL, NULL },
  553         /*
  554          * UNIX Domain Sockets
  555          */
  556         { "unp_link_rwlock", &lock_class_rw },
  557         { "unp_list_lock", &lock_class_mtx_sleep },
  558         { "unp", &lock_class_mtx_sleep },
  559         { "so_snd", &lock_class_mtx_sleep },
  560         { NULL, NULL },
  561         /*
  562          * UDP/IP
  563          */
  564         { "udp", &lock_class_mtx_sleep },
  565         { "udpinp", &lock_class_rw },
  566         { "so_snd", &lock_class_mtx_sleep },
  567         { NULL, NULL },
  568         /*
  569          * TCP/IP
  570          */
  571         { "tcp", &lock_class_mtx_sleep },
  572         { "tcpinp", &lock_class_rw },
  573         { "so_snd", &lock_class_mtx_sleep },
  574         { NULL, NULL },
  575         /*
  576          * BPF
  577          */
  578         { "bpf global lock", &lock_class_sx },
  579         { "bpf interface lock", &lock_class_rw },
  580         { "bpf cdev lock", &lock_class_mtx_sleep },
  581         { NULL, NULL },
  582         /*
  583          * NFS server
  584          */
  585         { "nfsd_mtx", &lock_class_mtx_sleep },
  586         { "so_snd", &lock_class_mtx_sleep },
  587         { NULL, NULL },
  588 
  589         /*
  590          * IEEE 802.11
  591          */
  592         { "802.11 com lock", &lock_class_mtx_sleep},
  593         { NULL, NULL },
  594         /*
  595          * Network drivers
  596          */
  597         { "network driver", &lock_class_mtx_sleep},
  598         { NULL, NULL },
  599 
  600         /*
  601          * Netgraph
  602          */
  603         { "ng_node", &lock_class_mtx_sleep },
  604         { "ng_worklist", &lock_class_mtx_sleep },
  605         { NULL, NULL },
  606         /*
  607          * CDEV
  608          */
  609         { "vm map (system)", &lock_class_mtx_sleep },
  610         { "vnode interlock", &lock_class_mtx_sleep },
  611         { "cdev", &lock_class_mtx_sleep },
  612         { NULL, NULL },
  613         /*
  614          * VM
  615          */
  616         { "vm map (user)", &lock_class_sx },
  617         { "vm object", &lock_class_rw },
  618         { "vm page", &lock_class_mtx_sleep },
  619         { "pmap pv global", &lock_class_rw },
  620         { "pmap", &lock_class_mtx_sleep },
  621         { "pmap pv list", &lock_class_rw },
  622         { "vm page free queue", &lock_class_mtx_sleep },
  623         { "vm pagequeue", &lock_class_mtx_sleep },
  624         { NULL, NULL },
  625         /*
  626          * kqueue/VFS interaction
  627          */
  628         { "kqueue", &lock_class_mtx_sleep },
  629         { "struct mount mtx", &lock_class_mtx_sleep },
  630         { "vnode interlock", &lock_class_mtx_sleep },
  631         { NULL, NULL },
  632         /*
  633          * VFS namecache
  634          */
  635         { "ncvn", &lock_class_mtx_sleep },
  636         { "ncbuc", &lock_class_rw },
  637         { "vnode interlock", &lock_class_mtx_sleep },
  638         { "ncneg", &lock_class_mtx_sleep },
  639         { NULL, NULL },
  640         /*
  641          * ZFS locking
  642          */
  643         { "dn->dn_mtx", &lock_class_sx },
  644         { "dr->dt.di.dr_mtx", &lock_class_sx },
  645         { "db->db_mtx", &lock_class_sx },
  646         { NULL, NULL },
  647         /*
  648          * TCP log locks
  649          */
  650         { "TCP ID tree", &lock_class_rw },
  651         { "tcp log id bucket", &lock_class_mtx_sleep },
  652         { "tcpinp", &lock_class_rw },
  653         { "TCP log expireq", &lock_class_mtx_sleep },
  654         { NULL, NULL },
  655         /*
  656          * spin locks
  657          */
  658 #ifdef SMP
  659         { "ap boot", &lock_class_mtx_spin },
  660 #endif
  661         { "rm.mutex_mtx", &lock_class_mtx_spin },
  662         { "sio", &lock_class_mtx_spin },
  663 #ifdef __i386__
  664         { "cy", &lock_class_mtx_spin },
  665 #endif
  666 #ifdef __sparc64__
  667         { "pcib_mtx", &lock_class_mtx_spin },
  668         { "rtc_mtx", &lock_class_mtx_spin },
  669 #endif
  670         { "scc_hwmtx", &lock_class_mtx_spin },
  671         { "uart_hwmtx", &lock_class_mtx_spin },
  672         { "fast_taskqueue", &lock_class_mtx_spin },
  673         { "intr table", &lock_class_mtx_spin },
  674         { "process slock", &lock_class_mtx_spin },
  675         { "syscons video lock", &lock_class_mtx_spin },
  676         { "sleepq chain", &lock_class_mtx_spin },
  677         { "rm_spinlock", &lock_class_mtx_spin },
  678         { "turnstile chain", &lock_class_mtx_spin },
  679         { "turnstile lock", &lock_class_mtx_spin },
  680         { "sched lock", &lock_class_mtx_spin },
  681         { "td_contested", &lock_class_mtx_spin },
  682         { "callout", &lock_class_mtx_spin },
  683         { "entropy harvest mutex", &lock_class_mtx_spin },
  684 #ifdef SMP
  685         { "smp rendezvous", &lock_class_mtx_spin },
  686 #endif
  687 #ifdef __powerpc__
  688         { "tlb0", &lock_class_mtx_spin },
  689 #endif
  690         { NULL, NULL },
  691         { "sched lock", &lock_class_mtx_spin },
  692 #ifdef  HWPMC_HOOKS
  693         { "pmc-per-proc", &lock_class_mtx_spin },
  694 #endif
  695         { NULL, NULL },
  696         /*
  697          * leaf locks
  698          */
  699         { "intrcnt", &lock_class_mtx_spin },
  700         { "icu", &lock_class_mtx_spin },
  701 #if defined(SMP) && defined(__sparc64__)
  702         { "ipi", &lock_class_mtx_spin },
  703 #endif
  704 #ifdef __i386__
  705         { "allpmaps", &lock_class_mtx_spin },
  706         { "descriptor tables", &lock_class_mtx_spin },
  707 #endif
  708         { "clk", &lock_class_mtx_spin },
  709         { "cpuset", &lock_class_mtx_spin },
  710         { "mprof lock", &lock_class_mtx_spin },
  711         { "zombie lock", &lock_class_mtx_spin },
  712         { "ALD Queue", &lock_class_mtx_spin },
  713 #if defined(__i386__) || defined(__amd64__)
  714         { "pcicfg", &lock_class_mtx_spin },
  715         { "NDIS thread lock", &lock_class_mtx_spin },
  716 #endif
  717         { "tw_osl_io_lock", &lock_class_mtx_spin },
  718         { "tw_osl_q_lock", &lock_class_mtx_spin },
  719         { "tw_cl_io_lock", &lock_class_mtx_spin },
  720         { "tw_cl_intr_lock", &lock_class_mtx_spin },
  721         { "tw_cl_gen_lock", &lock_class_mtx_spin },
  722 #ifdef  HWPMC_HOOKS
  723         { "pmc-leaf", &lock_class_mtx_spin },
  724 #endif
  725         { "blocked lock", &lock_class_mtx_spin },
  726         { NULL, NULL },
  727         { NULL, NULL }
  728 };
  729 
  730 #ifdef BLESSING
  731 /*
  732  * Pairs of locks which have been blessed
  733  * Don't complain about order problems with blessed locks
  734  */
  735 static struct witness_blessed blessed_list[] = {
  736 };
  737 #endif
  738 
  739 /*
  740  * This global is set to 0 once it becomes safe to use the witness code.
  741  */
  742 static int witness_cold = 1;
  743 
  744 /*
  745  * This global is set to 1 once the static lock orders have been enrolled
  746  * so that a warning can be issued for any spin locks enrolled later.
  747  */
  748 static int witness_spin_warn = 0;
  749 
  750 /* Trim useless garbage from filenames. */
  751 static const char *
  752 fixup_filename(const char *file)
  753 {
  754 
  755         if (file == NULL)
  756                 return (NULL);
  757         while (strncmp(file, "../", 3) == 0)
  758                 file += 3;
  759         return (file);
  760 }
  761 
  762 /*
  763  * Calculate the size of early witness structures.
  764  */
  765 int
  766 witness_startup_count(void)
  767 {
  768         int sz;
  769 
  770         sz = sizeof(struct witness) * witness_count;
  771         sz += sizeof(*w_rmatrix) * (witness_count + 1);
  772         sz += sizeof(*w_rmatrix[0]) * (witness_count + 1) *
  773             (witness_count + 1);
  774 
  775         return (sz);
  776 }
  777 
  778 /*
  779  * The WITNESS-enabled diagnostic code.  Note that the witness code does
  780  * assume that the early boot is single-threaded at least until after this
  781  * routine is completed.
  782  */
  783 void
  784 witness_startup(void *mem)
  785 {
  786         struct lock_object *lock;
  787         struct witness_order_list_entry *order;
  788         struct witness *w, *w1;
  789         uintptr_t p;
  790         int i;
  791 
  792         p = (uintptr_t)mem;
  793         w_data = (void *)p;
  794         p += sizeof(struct witness) * witness_count;
  795 
  796         w_rmatrix = (void *)p;
  797         p += sizeof(*w_rmatrix) * (witness_count + 1);
  798 
  799         for (i = 0; i < witness_count + 1; i++) {
  800                 w_rmatrix[i] = (void *)p;
  801                 p += sizeof(*w_rmatrix[i]) * (witness_count + 1);
  802         }
  803         badstack_sbuf_size = witness_count * 256;
  804 
  805         /*
  806          * We have to release Giant before initializing its witness
  807          * structure so that WITNESS doesn't get confused.
  808          */
  809         mtx_unlock(&Giant);
  810         mtx_assert(&Giant, MA_NOTOWNED);
  811 
  812         CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
  813         mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET |
  814             MTX_NOWITNESS | MTX_NOPROFILE);
  815         for (i = witness_count - 1; i >= 0; i--) {
  816                 w = &w_data[i];
  817                 memset(w, 0, sizeof(*w));
  818                 w_data[i].w_index = i;  /* Witness index never changes. */
  819                 witness_free(w);
  820         }
  821         KASSERT(STAILQ_FIRST(&w_free)->w_index == 0,
  822             ("%s: Invalid list of free witness objects", __func__));
  823 
  824         /* Witness with index 0 is not used to aid in debugging. */
  825         STAILQ_REMOVE_HEAD(&w_free, w_list);
  826         w_free_cnt--;
  827 
  828         for (i = 0; i < witness_count; i++) {
  829                 memset(w_rmatrix[i], 0, sizeof(*w_rmatrix[i]) * 
  830                     (witness_count + 1));
  831         }
  832 
  833         for (i = 0; i < LOCK_CHILDCOUNT; i++)
  834                 witness_lock_list_free(&w_locklistdata[i]);
  835         witness_init_hash_tables();
  836 
  837         /* First add in all the specified order lists. */
  838         for (order = order_lists; order->w_name != NULL; order++) {
  839                 w = enroll(order->w_name, order->w_class);
  840                 if (w == NULL)
  841                         continue;
  842                 w->w_file = "order list";
  843                 for (order++; order->w_name != NULL; order++) {
  844                         w1 = enroll(order->w_name, order->w_class);
  845                         if (w1 == NULL)
  846                                 continue;
  847                         w1->w_file = "order list";
  848                         itismychild(w, w1);
  849                         w = w1;
  850                 }
  851         }
  852         witness_spin_warn = 1;
  853 
  854         /* Iterate through all locks and add them to witness. */
  855         for (i = 0; pending_locks[i].wh_lock != NULL; i++) {
  856                 lock = pending_locks[i].wh_lock;
  857                 KASSERT(lock->lo_flags & LO_WITNESS,
  858                     ("%s: lock %s is on pending list but not LO_WITNESS",
  859                     __func__, lock->lo_name));
  860                 lock->lo_witness = enroll(pending_locks[i].wh_type,
  861                     LOCK_CLASS(lock));
  862         }
  863 
  864         /* Mark the witness code as being ready for use. */
  865         witness_cold = 0;
  866 
  867         mtx_lock(&Giant);
  868 }
  869 
  870 void
  871 witness_init(struct lock_object *lock, const char *type)
  872 {
  873         struct lock_class *class;
  874 
  875         /* Various sanity checks. */
  876         class = LOCK_CLASS(lock);
  877         if ((lock->lo_flags & LO_RECURSABLE) != 0 &&
  878             (class->lc_flags & LC_RECURSABLE) == 0)
  879                 kassert_panic("%s: lock (%s) %s can not be recursable",
  880                     __func__, class->lc_name, lock->lo_name);
  881         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
  882             (class->lc_flags & LC_SLEEPABLE) == 0)
  883                 kassert_panic("%s: lock (%s) %s can not be sleepable",
  884                     __func__, class->lc_name, lock->lo_name);
  885         if ((lock->lo_flags & LO_UPGRADABLE) != 0 &&
  886             (class->lc_flags & LC_UPGRADABLE) == 0)
  887                 kassert_panic("%s: lock (%s) %s can not be upgradable",
  888                     __func__, class->lc_name, lock->lo_name);
  889 
  890         /*
  891          * If we shouldn't watch this lock, then just clear lo_witness.
  892          * Otherwise, if witness_cold is set, then it is too early to
  893          * enroll this lock, so defer it to witness_initialize() by adding
  894          * it to the pending_locks list.  If it is not too early, then enroll
  895          * the lock now.
  896          */
  897         if (witness_watch < 1 || panicstr != NULL ||
  898             (lock->lo_flags & LO_WITNESS) == 0)
  899                 lock->lo_witness = NULL;
  900         else if (witness_cold) {
  901                 pending_locks[pending_cnt].wh_lock = lock;
  902                 pending_locks[pending_cnt++].wh_type = type;
  903                 if (pending_cnt > WITNESS_PENDLIST)
  904                         panic("%s: pending locks list is too small, "
  905                             "increase WITNESS_PENDLIST\n",
  906                             __func__);
  907         } else
  908                 lock->lo_witness = enroll(type, class);
  909 }
  910 
  911 void
  912 witness_destroy(struct lock_object *lock)
  913 {
  914         struct lock_class *class;
  915         struct witness *w;
  916 
  917         class = LOCK_CLASS(lock);
  918 
  919         if (witness_cold)
  920                 panic("lock (%s) %s destroyed while witness_cold",
  921                     class->lc_name, lock->lo_name);
  922 
  923         /* XXX: need to verify that no one holds the lock */
  924         if ((lock->lo_flags & LO_WITNESS) == 0 || lock->lo_witness == NULL)
  925                 return;
  926         w = lock->lo_witness;
  927 
  928         mtx_lock_spin(&w_mtx);
  929         MPASS(w->w_refcount > 0);
  930         w->w_refcount--;
  931 
  932         if (w->w_refcount == 0)
  933                 depart(w);
  934         mtx_unlock_spin(&w_mtx);
  935 }
  936 
  937 #ifdef DDB
  938 static void
  939 witness_ddb_compute_levels(void)
  940 {
  941         struct witness *w;
  942 
  943         /*
  944          * First clear all levels.
  945          */
  946         STAILQ_FOREACH(w, &w_all, w_list)
  947                 w->w_ddb_level = -1;
  948 
  949         /*
  950          * Look for locks with no parents and level all their descendants.
  951          */
  952         STAILQ_FOREACH(w, &w_all, w_list) {
  953 
  954                 /* If the witness has ancestors (is not a root), skip it. */
  955                 if (w->w_num_ancestors > 0)
  956                         continue;
  957                 witness_ddb_level_descendants(w, 0);
  958         }
  959 }
  960 
  961 static void
  962 witness_ddb_level_descendants(struct witness *w, int l)
  963 {
  964         int i;
  965 
  966         if (w->w_ddb_level >= l)
  967                 return;
  968 
  969         w->w_ddb_level = l;
  970         l++;
  971 
  972         for (i = 1; i <= w_max_used_index; i++) {
  973                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
  974                         witness_ddb_level_descendants(&w_data[i], l);
  975         }
  976 }
  977 
  978 static void
  979 witness_ddb_display_descendants(int(*prnt)(const char *fmt, ...),
  980     struct witness *w, int indent)
  981 {
  982         int i;
  983 
  984         for (i = 0; i < indent; i++)
  985                 prnt(" ");
  986         prnt("%s (type: %s, depth: %d, active refs: %d)",
  987              w->w_name, w->w_class->lc_name,
  988              w->w_ddb_level, w->w_refcount);
  989         if (w->w_displayed) {
  990                 prnt(" -- (already displayed)\n");
  991                 return;
  992         }
  993         w->w_displayed = 1;
  994         if (w->w_file != NULL && w->w_line != 0)
  995                 prnt(" -- last acquired @ %s:%d\n", fixup_filename(w->w_file),
  996                     w->w_line);
  997         else
  998                 prnt(" -- never acquired\n");
  999         indent++;
 1000         WITNESS_INDEX_ASSERT(w->w_index);
 1001         for (i = 1; i <= w_max_used_index; i++) {
 1002                 if (db_pager_quit)
 1003                         return;
 1004                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
 1005                         witness_ddb_display_descendants(prnt, &w_data[i],
 1006                             indent);
 1007         }
 1008 }
 1009 
 1010 static void
 1011 witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
 1012     struct witness_list *list)
 1013 {
 1014         struct witness *w;
 1015 
 1016         STAILQ_FOREACH(w, list, w_typelist) {
 1017                 if (w->w_file == NULL || w->w_ddb_level > 0)
 1018                         continue;
 1019 
 1020                 /* This lock has no anscestors - display its descendants. */
 1021                 witness_ddb_display_descendants(prnt, w, 0);
 1022                 if (db_pager_quit)
 1023                         return;
 1024         }
 1025 }
 1026         
 1027 static void
 1028 witness_ddb_display(int(*prnt)(const char *fmt, ...))
 1029 {
 1030         struct witness *w;
 1031 
 1032         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 1033         witness_ddb_compute_levels();
 1034 
 1035         /* Clear all the displayed flags. */
 1036         STAILQ_FOREACH(w, &w_all, w_list)
 1037                 w->w_displayed = 0;
 1038 
 1039         /*
 1040          * First, handle sleep locks which have been acquired at least
 1041          * once.
 1042          */
 1043         prnt("Sleep locks:\n");
 1044         witness_ddb_display_list(prnt, &w_sleep);
 1045         if (db_pager_quit)
 1046                 return;
 1047         
 1048         /*
 1049          * Now do spin locks which have been acquired at least once.
 1050          */
 1051         prnt("\nSpin locks:\n");
 1052         witness_ddb_display_list(prnt, &w_spin);
 1053         if (db_pager_quit)
 1054                 return;
 1055         
 1056         /*
 1057          * Finally, any locks which have not been acquired yet.
 1058          */
 1059         prnt("\nLocks which were never acquired:\n");
 1060         STAILQ_FOREACH(w, &w_all, w_list) {
 1061                 if (w->w_file != NULL || w->w_refcount == 0)
 1062                         continue;
 1063                 prnt("%s (type: %s, depth: %d)\n", w->w_name,
 1064                     w->w_class->lc_name, w->w_ddb_level);
 1065                 if (db_pager_quit)
 1066                         return;
 1067         }
 1068 }
 1069 #endif /* DDB */
 1070 
 1071 int
 1072 witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
 1073 {
 1074 
 1075         if (witness_watch == -1 || panicstr != NULL)
 1076                 return (0);
 1077 
 1078         /* Require locks that witness knows about. */
 1079         if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL ||
 1080             lock2->lo_witness == NULL)
 1081                 return (EINVAL);
 1082 
 1083         mtx_assert(&w_mtx, MA_NOTOWNED);
 1084         mtx_lock_spin(&w_mtx);
 1085 
 1086         /*
 1087          * If we already have either an explicit or implied lock order that
 1088          * is the other way around, then return an error.
 1089          */
 1090         if (witness_watch &&
 1091             isitmydescendant(lock2->lo_witness, lock1->lo_witness)) {
 1092                 mtx_unlock_spin(&w_mtx);
 1093                 return (EDOOFUS);
 1094         }
 1095         
 1096         /* Try to add the new order. */
 1097         CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 1098             lock2->lo_witness->w_name, lock1->lo_witness->w_name);
 1099         itismychild(lock1->lo_witness, lock2->lo_witness);
 1100         mtx_unlock_spin(&w_mtx);
 1101         return (0);
 1102 }
 1103 
 1104 void
 1105 witness_checkorder(struct lock_object *lock, int flags, const char *file,
 1106     int line, struct lock_object *interlock)
 1107 {
 1108         struct lock_list_entry *lock_list, *lle;
 1109         struct lock_instance *lock1, *lock2, *plock;
 1110         struct lock_class *class, *iclass;
 1111         struct witness *w, *w1;
 1112         struct thread *td;
 1113         int i, j;
 1114 
 1115         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL ||
 1116             panicstr != NULL)
 1117                 return;
 1118 
 1119         w = lock->lo_witness;
 1120         class = LOCK_CLASS(lock);
 1121         td = curthread;
 1122 
 1123         if (class->lc_flags & LC_SLEEPLOCK) {
 1124 
 1125                 /*
 1126                  * Since spin locks include a critical section, this check
 1127                  * implicitly enforces a lock order of all sleep locks before
 1128                  * all spin locks.
 1129                  */
 1130                 if (td->td_critnest != 0 && !kdb_active)
 1131                         kassert_panic("acquiring blockable sleep lock with "
 1132                             "spinlock or critical section held (%s) %s @ %s:%d",
 1133                             class->lc_name, lock->lo_name,
 1134                             fixup_filename(file), line);
 1135 
 1136                 /*
 1137                  * If this is the first lock acquired then just return as
 1138                  * no order checking is needed.
 1139                  */
 1140                 lock_list = td->td_sleeplocks;
 1141                 if (lock_list == NULL || lock_list->ll_count == 0)
 1142                         return;
 1143         } else {
 1144 
 1145                 /*
 1146                  * If this is the first lock, just return as no order
 1147                  * checking is needed.  Avoid problems with thread
 1148                  * migration pinning the thread while checking if
 1149                  * spinlocks are held.  If at least one spinlock is held
 1150                  * the thread is in a safe path and it is allowed to
 1151                  * unpin it.
 1152                  */
 1153                 sched_pin();
 1154                 lock_list = PCPU_GET(spinlocks);
 1155                 if (lock_list == NULL || lock_list->ll_count == 0) {
 1156                         sched_unpin();
 1157                         return;
 1158                 }
 1159                 sched_unpin();
 1160         }
 1161 
 1162         /*
 1163          * Check to see if we are recursing on a lock we already own.  If
 1164          * so, make sure that we don't mismatch exclusive and shared lock
 1165          * acquires.
 1166          */
 1167         lock1 = find_instance(lock_list, lock);
 1168         if (lock1 != NULL) {
 1169                 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 &&
 1170                     (flags & LOP_EXCLUSIVE) == 0) {
 1171                         witness_output("shared lock of (%s) %s @ %s:%d\n",
 1172                             class->lc_name, lock->lo_name,
 1173                             fixup_filename(file), line);
 1174                         witness_output("while exclusively locked from %s:%d\n",
 1175                             fixup_filename(lock1->li_file), lock1->li_line);
 1176                         kassert_panic("excl->share");
 1177                 }
 1178                 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
 1179                     (flags & LOP_EXCLUSIVE) != 0) {
 1180                         witness_output("exclusive lock of (%s) %s @ %s:%d\n",
 1181                             class->lc_name, lock->lo_name,
 1182                             fixup_filename(file), line);
 1183                         witness_output("while share locked from %s:%d\n",
 1184                             fixup_filename(lock1->li_file), lock1->li_line);
 1185                         kassert_panic("share->excl");
 1186                 }
 1187                 return;
 1188         }
 1189 
 1190         /* Warn if the interlock is not locked exactly once. */
 1191         if (interlock != NULL) {
 1192                 iclass = LOCK_CLASS(interlock);
 1193                 lock1 = find_instance(lock_list, interlock);
 1194                 if (lock1 == NULL)
 1195                         kassert_panic("interlock (%s) %s not locked @ %s:%d",
 1196                             iclass->lc_name, interlock->lo_name,
 1197                             fixup_filename(file), line);
 1198                 else if ((lock1->li_flags & LI_RECURSEMASK) != 0)
 1199                         kassert_panic("interlock (%s) %s recursed @ %s:%d",
 1200                             iclass->lc_name, interlock->lo_name,
 1201                             fixup_filename(file), line);
 1202         }
 1203 
 1204         /*
 1205          * Find the previously acquired lock, but ignore interlocks.
 1206          */
 1207         plock = &lock_list->ll_children[lock_list->ll_count - 1];
 1208         if (interlock != NULL && plock->li_lock == interlock) {
 1209                 if (lock_list->ll_count > 1)
 1210                         plock =
 1211                             &lock_list->ll_children[lock_list->ll_count - 2];
 1212                 else {
 1213                         lle = lock_list->ll_next;
 1214 
 1215                         /*
 1216                          * The interlock is the only lock we hold, so
 1217                          * simply return.
 1218                          */
 1219                         if (lle == NULL)
 1220                                 return;
 1221                         plock = &lle->ll_children[lle->ll_count - 1];
 1222                 }
 1223         }
 1224         
 1225         /*
 1226          * Try to perform most checks without a lock.  If this succeeds we
 1227          * can skip acquiring the lock and return success.  Otherwise we redo
 1228          * the check with the lock held to handle races with concurrent updates.
 1229          */
 1230         w1 = plock->li_lock->lo_witness;
 1231         if (witness_lock_order_check(w1, w))
 1232                 return;
 1233 
 1234         mtx_lock_spin(&w_mtx);
 1235         if (witness_lock_order_check(w1, w)) {
 1236                 mtx_unlock_spin(&w_mtx);
 1237                 return;
 1238         }
 1239         witness_lock_order_add(w1, w);
 1240 
 1241         /*
 1242          * Check for duplicate locks of the same type.  Note that we only
 1243          * have to check for this on the last lock we just acquired.  Any
 1244          * other cases will be caught as lock order violations.
 1245          */
 1246         if (w1 == w) {
 1247                 i = w->w_index;
 1248                 if (!(lock->lo_flags & LO_DUPOK) && !(flags & LOP_DUPOK) &&
 1249                     !(w_rmatrix[i][i] & WITNESS_REVERSAL)) {
 1250                     w_rmatrix[i][i] |= WITNESS_REVERSAL;
 1251                         w->w_reversed = 1;
 1252                         mtx_unlock_spin(&w_mtx);
 1253                         witness_output(
 1254                             "acquiring duplicate lock of same type: \"%s\"\n", 
 1255                             w->w_name);
 1256                         witness_output(" 1st %s @ %s:%d\n", plock->li_lock->lo_name,
 1257                             fixup_filename(plock->li_file), plock->li_line);
 1258                         witness_output(" 2nd %s @ %s:%d\n", lock->lo_name,
 1259                             fixup_filename(file), line);
 1260                         witness_debugger(1, __func__);
 1261                 } else
 1262                         mtx_unlock_spin(&w_mtx);
 1263                 return;
 1264         }
 1265         mtx_assert(&w_mtx, MA_OWNED);
 1266 
 1267         /*
 1268          * If we know that the lock we are acquiring comes after
 1269          * the lock we most recently acquired in the lock order tree,
 1270          * then there is no need for any further checks.
 1271          */
 1272         if (isitmychild(w1, w))
 1273                 goto out;
 1274 
 1275         for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) {
 1276                 for (i = lle->ll_count - 1; i >= 0; i--, j++) {
 1277 
 1278                         MPASS(j < LOCK_CHILDCOUNT * LOCK_NCHILDREN);
 1279                         lock1 = &lle->ll_children[i];
 1280 
 1281                         /*
 1282                          * Ignore the interlock.
 1283                          */
 1284                         if (interlock == lock1->li_lock)
 1285                                 continue;
 1286 
 1287                         /*
 1288                          * If this lock doesn't undergo witness checking,
 1289                          * then skip it.
 1290                          */
 1291                         w1 = lock1->li_lock->lo_witness;
 1292                         if (w1 == NULL) {
 1293                                 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0,
 1294                                     ("lock missing witness structure"));
 1295                                 continue;
 1296                         }
 1297 
 1298                         /*
 1299                          * If we are locking Giant and this is a sleepable
 1300                          * lock, then skip it.
 1301                          */
 1302                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1303                             lock == &Giant.lock_object)
 1304                                 continue;
 1305 
 1306                         /*
 1307                          * If we are locking a sleepable lock and this lock
 1308                          * is Giant, then skip it.
 1309                          */
 1310                         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1311                             lock1->li_lock == &Giant.lock_object)
 1312                                 continue;
 1313 
 1314                         /*
 1315                          * If we are locking a sleepable lock and this lock
 1316                          * isn't sleepable, we want to treat it as a lock
 1317                          * order violation to enfore a general lock order of
 1318                          * sleepable locks before non-sleepable locks.
 1319                          */
 1320                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1321                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
 1322                                 goto reversal;
 1323 
 1324                         /*
 1325                          * If we are locking Giant and this is a non-sleepable
 1326                          * lock, then treat it as a reversal.
 1327                          */
 1328                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0 &&
 1329                             lock == &Giant.lock_object)
 1330                                 goto reversal;
 1331 
 1332                         /*
 1333                          * Check the lock order hierarchy for a reveresal.
 1334                          */
 1335                         if (!isitmydescendant(w, w1))
 1336                                 continue;
 1337                 reversal:
 1338 
 1339                         /*
 1340                          * We have a lock order violation, check to see if it
 1341                          * is allowed or has already been yelled about.
 1342                          */
 1343 #ifdef BLESSING
 1344 
 1345                         /*
 1346                          * If the lock order is blessed, just bail.  We don't
 1347                          * look for other lock order violations though, which
 1348                          * may be a bug.
 1349                          */
 1350                         if (blessed(w, w1))
 1351                                 goto out;
 1352 #endif
 1353 
 1354                         /* Bail if this violation is known */
 1355                         if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL)
 1356                                 goto out;
 1357 
 1358                         /* Record this as a violation */
 1359                         w_rmatrix[w1->w_index][w->w_index] |= WITNESS_REVERSAL;
 1360                         w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL;
 1361                         w->w_reversed = w1->w_reversed = 1;
 1362                         witness_increment_graph_generation();
 1363                         mtx_unlock_spin(&w_mtx);
 1364 
 1365 #ifdef WITNESS_NO_VNODE
 1366                         /*
 1367                          * There are known LORs between VNODE locks. They are
 1368                          * not an indication of a bug. VNODE locks are flagged
 1369                          * as such (LO_IS_VNODE) and we don't yell if the LOR
 1370                          * is between 2 VNODE locks.
 1371                          */
 1372                         if ((lock->lo_flags & LO_IS_VNODE) != 0 &&
 1373                             (lock1->li_lock->lo_flags & LO_IS_VNODE) != 0)
 1374                                 return;
 1375 #endif
 1376 
 1377                         /*
 1378                          * Ok, yell about it.
 1379                          */
 1380                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1381                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
 1382                                 witness_output(
 1383                 "lock order reversal: (sleepable after non-sleepable)\n");
 1384                         else if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0
 1385                             && lock == &Giant.lock_object)
 1386                                 witness_output(
 1387                 "lock order reversal: (Giant after non-sleepable)\n");
 1388                         else
 1389                                 witness_output("lock order reversal:\n");
 1390 
 1391                         /*
 1392                          * Try to locate an earlier lock with
 1393                          * witness w in our list.
 1394                          */
 1395                         do {
 1396                                 lock2 = &lle->ll_children[i];
 1397                                 MPASS(lock2->li_lock != NULL);
 1398                                 if (lock2->li_lock->lo_witness == w)
 1399                                         break;
 1400                                 if (i == 0 && lle->ll_next != NULL) {
 1401                                         lle = lle->ll_next;
 1402                                         i = lle->ll_count - 1;
 1403                                         MPASS(i >= 0 && i < LOCK_NCHILDREN);
 1404                                 } else
 1405                                         i--;
 1406                         } while (i >= 0);
 1407                         if (i < 0) {
 1408                                 witness_output(" 1st %p %s (%s) @ %s:%d\n",
 1409                                     lock1->li_lock, lock1->li_lock->lo_name,
 1410                                     w1->w_name, fixup_filename(lock1->li_file),
 1411                                     lock1->li_line);
 1412                                 witness_output(" 2nd %p %s (%s) @ %s:%d\n", lock,
 1413                                     lock->lo_name, w->w_name,
 1414                                     fixup_filename(file), line);
 1415                         } else {
 1416                                 witness_output(" 1st %p %s (%s) @ %s:%d\n",
 1417                                     lock2->li_lock, lock2->li_lock->lo_name,
 1418                                     lock2->li_lock->lo_witness->w_name,
 1419                                     fixup_filename(lock2->li_file),
 1420                                     lock2->li_line);
 1421                                 witness_output(" 2nd %p %s (%s) @ %s:%d\n",
 1422                                     lock1->li_lock, lock1->li_lock->lo_name,
 1423                                     w1->w_name, fixup_filename(lock1->li_file),
 1424                                     lock1->li_line);
 1425                                 witness_output(" 3rd %p %s (%s) @ %s:%d\n", lock,
 1426                                     lock->lo_name, w->w_name,
 1427                                     fixup_filename(file), line);
 1428                         }
 1429                         witness_debugger(1, __func__);
 1430                         return;
 1431                 }
 1432         }
 1433 
 1434         /*
 1435          * If requested, build a new lock order.  However, don't build a new
 1436          * relationship between a sleepable lock and Giant if it is in the
 1437          * wrong direction.  The correct lock order is that sleepable locks
 1438          * always come before Giant.
 1439          */
 1440         if (flags & LOP_NEWORDER &&
 1441             !(plock->li_lock == &Giant.lock_object &&
 1442             (lock->lo_flags & LO_SLEEPABLE) != 0)) {
 1443                 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 1444                     w->w_name, plock->li_lock->lo_witness->w_name);
 1445                 itismychild(plock->li_lock->lo_witness, w);
 1446         }
 1447 out:
 1448         mtx_unlock_spin(&w_mtx);
 1449 }
 1450 
 1451 void
 1452 witness_lock(struct lock_object *lock, int flags, const char *file, int line)
 1453 {
 1454         struct lock_list_entry **lock_list, *lle;
 1455         struct lock_instance *instance;
 1456         struct witness *w;
 1457         struct thread *td;
 1458 
 1459         if (witness_cold || witness_watch == -1 || lock->lo_witness == NULL ||
 1460             panicstr != NULL)
 1461                 return;
 1462         w = lock->lo_witness;
 1463         td = curthread;
 1464 
 1465         /* Determine lock list for this lock. */
 1466         if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK)
 1467                 lock_list = &td->td_sleeplocks;
 1468         else
 1469                 lock_list = PCPU_PTR(spinlocks);
 1470 
 1471         /* Check to see if we are recursing on a lock we already own. */
 1472         instance = find_instance(*lock_list, lock);
 1473         if (instance != NULL) {
 1474                 instance->li_flags++;
 1475                 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__,
 1476                     td->td_proc->p_pid, lock->lo_name,
 1477                     instance->li_flags & LI_RECURSEMASK);
 1478                 instance->li_file = file;
 1479                 instance->li_line = line;
 1480                 return;
 1481         }
 1482 
 1483         /* Update per-witness last file and line acquire. */
 1484         w->w_file = file;
 1485         w->w_line = line;
 1486 
 1487         /* Find the next open lock instance in the list and fill it. */
 1488         lle = *lock_list;
 1489         if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
 1490                 lle = witness_lock_list_get();
 1491                 if (lle == NULL)
 1492                         return;
 1493                 lle->ll_next = *lock_list;
 1494                 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__,
 1495                     td->td_proc->p_pid, lle);
 1496                 *lock_list = lle;
 1497         }
 1498         instance = &lle->ll_children[lle->ll_count++];
 1499         instance->li_lock = lock;
 1500         instance->li_line = line;
 1501         instance->li_file = file;
 1502         if ((flags & LOP_EXCLUSIVE) != 0)
 1503                 instance->li_flags = LI_EXCLUSIVE;
 1504         else
 1505                 instance->li_flags = 0;
 1506         CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__,
 1507             td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1);
 1508 }
 1509 
 1510 void
 1511 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line)
 1512 {
 1513         struct lock_instance *instance;
 1514         struct lock_class *class;
 1515 
 1516         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 1517         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 1518                 return;
 1519         class = LOCK_CLASS(lock);
 1520         if (witness_watch) {
 1521                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
 1522                         kassert_panic(
 1523                             "upgrade of non-upgradable lock (%s) %s @ %s:%d",
 1524                             class->lc_name, lock->lo_name,
 1525                             fixup_filename(file), line);
 1526                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
 1527                         kassert_panic(
 1528                             "upgrade of non-sleep lock (%s) %s @ %s:%d",
 1529                             class->lc_name, lock->lo_name,
 1530                             fixup_filename(file), line);
 1531         }
 1532         instance = find_instance(curthread->td_sleeplocks, lock);
 1533         if (instance == NULL) {
 1534                 kassert_panic("upgrade of unlocked lock (%s) %s @ %s:%d",
 1535                     class->lc_name, lock->lo_name,
 1536                     fixup_filename(file), line);
 1537                 return;
 1538         }
 1539         if (witness_watch) {
 1540                 if ((instance->li_flags & LI_EXCLUSIVE) != 0)
 1541                         kassert_panic(
 1542                             "upgrade of exclusive lock (%s) %s @ %s:%d",
 1543                             class->lc_name, lock->lo_name,
 1544                             fixup_filename(file), line);
 1545                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
 1546                         kassert_panic(
 1547                             "upgrade of recursed lock (%s) %s r=%d @ %s:%d",
 1548                             class->lc_name, lock->lo_name,
 1549                             instance->li_flags & LI_RECURSEMASK,
 1550                             fixup_filename(file), line);
 1551         }
 1552         instance->li_flags |= LI_EXCLUSIVE;
 1553 }
 1554 
 1555 void
 1556 witness_downgrade(struct lock_object *lock, int flags, const char *file,
 1557     int line)
 1558 {
 1559         struct lock_instance *instance;
 1560         struct lock_class *class;
 1561 
 1562         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 1563         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 1564                 return;
 1565         class = LOCK_CLASS(lock);
 1566         if (witness_watch) {
 1567                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
 1568                         kassert_panic(
 1569                             "downgrade of non-upgradable lock (%s) %s @ %s:%d",
 1570                             class->lc_name, lock->lo_name,
 1571                             fixup_filename(file), line);
 1572                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
 1573                         kassert_panic(
 1574                             "downgrade of non-sleep lock (%s) %s @ %s:%d",
 1575                             class->lc_name, lock->lo_name,
 1576                             fixup_filename(file), line);
 1577         }
 1578         instance = find_instance(curthread->td_sleeplocks, lock);
 1579         if (instance == NULL) {
 1580                 kassert_panic("downgrade of unlocked lock (%s) %s @ %s:%d",
 1581                     class->lc_name, lock->lo_name,
 1582                     fixup_filename(file), line);
 1583                 return;
 1584         }
 1585         if (witness_watch) {
 1586                 if ((instance->li_flags & LI_EXCLUSIVE) == 0)
 1587                         kassert_panic(
 1588                             "downgrade of shared lock (%s) %s @ %s:%d",
 1589                             class->lc_name, lock->lo_name,
 1590                             fixup_filename(file), line);
 1591                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
 1592                         kassert_panic(
 1593                             "downgrade of recursed lock (%s) %s r=%d @ %s:%d",
 1594                             class->lc_name, lock->lo_name,
 1595                             instance->li_flags & LI_RECURSEMASK,
 1596                             fixup_filename(file), line);
 1597         }
 1598         instance->li_flags &= ~LI_EXCLUSIVE;
 1599 }
 1600 
 1601 void
 1602 witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
 1603 {
 1604         struct lock_list_entry **lock_list, *lle;
 1605         struct lock_instance *instance;
 1606         struct lock_class *class;
 1607         struct thread *td;
 1608         register_t s;
 1609         int i, j;
 1610 
 1611         if (witness_cold || lock->lo_witness == NULL || panicstr != NULL)
 1612                 return;
 1613         td = curthread;
 1614         class = LOCK_CLASS(lock);
 1615 
 1616         /* Find lock instance associated with this lock. */
 1617         if (class->lc_flags & LC_SLEEPLOCK)
 1618                 lock_list = &td->td_sleeplocks;
 1619         else
 1620                 lock_list = PCPU_PTR(spinlocks);
 1621         lle = *lock_list;
 1622         for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next)
 1623                 for (i = 0; i < (*lock_list)->ll_count; i++) {
 1624                         instance = &(*lock_list)->ll_children[i];
 1625                         if (instance->li_lock == lock)
 1626                                 goto found;
 1627                 }
 1628 
 1629         /*
 1630          * When disabling WITNESS through witness_watch we could end up in
 1631          * having registered locks in the td_sleeplocks queue.
 1632          * We have to make sure we flush these queues, so just search for
 1633          * eventual register locks and remove them.
 1634          */
 1635         if (witness_watch > 0) {
 1636                 kassert_panic("lock (%s) %s not locked @ %s:%d", class->lc_name,
 1637                     lock->lo_name, fixup_filename(file), line);
 1638                 return;
 1639         } else {
 1640                 return;
 1641         }
 1642 found:
 1643 
 1644         /* First, check for shared/exclusive mismatches. */
 1645         if ((instance->li_flags & LI_EXCLUSIVE) != 0 && witness_watch > 0 &&
 1646             (flags & LOP_EXCLUSIVE) == 0) {
 1647                 witness_output("shared unlock of (%s) %s @ %s:%d\n",
 1648                     class->lc_name, lock->lo_name, fixup_filename(file), line);
 1649                 witness_output("while exclusively locked from %s:%d\n",
 1650                     fixup_filename(instance->li_file), instance->li_line);
 1651                 kassert_panic("excl->ushare");
 1652         }
 1653         if ((instance->li_flags & LI_EXCLUSIVE) == 0 && witness_watch > 0 &&
 1654             (flags & LOP_EXCLUSIVE) != 0) {
 1655                 witness_output("exclusive unlock of (%s) %s @ %s:%d\n",
 1656                     class->lc_name, lock->lo_name, fixup_filename(file), line);
 1657                 witness_output("while share locked from %s:%d\n",
 1658                     fixup_filename(instance->li_file),
 1659                     instance->li_line);
 1660                 kassert_panic("share->uexcl");
 1661         }
 1662         /* If we are recursed, unrecurse. */
 1663         if ((instance->li_flags & LI_RECURSEMASK) > 0) {
 1664                 CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__,
 1665                     td->td_proc->p_pid, instance->li_lock->lo_name,
 1666                     instance->li_flags);
 1667                 instance->li_flags--;
 1668                 return;
 1669         }
 1670         /* The lock is now being dropped, check for NORELEASE flag */
 1671         if ((instance->li_flags & LI_NORELEASE) != 0 && witness_watch > 0) {
 1672                 witness_output("forbidden unlock of (%s) %s @ %s:%d\n",
 1673                     class->lc_name, lock->lo_name, fixup_filename(file), line);
 1674                 kassert_panic("lock marked norelease");
 1675         }
 1676 
 1677         /* Otherwise, remove this item from the list. */
 1678         s = intr_disable();
 1679         CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__,
 1680             td->td_proc->p_pid, instance->li_lock->lo_name,
 1681             (*lock_list)->ll_count - 1);
 1682         for (j = i; j < (*lock_list)->ll_count - 1; j++)
 1683                 (*lock_list)->ll_children[j] =
 1684                     (*lock_list)->ll_children[j + 1];
 1685         (*lock_list)->ll_count--;
 1686         intr_restore(s);
 1687 
 1688         /*
 1689          * In order to reduce contention on w_mtx, we want to keep always an
 1690          * head object into lists so that frequent allocation from the 
 1691          * free witness pool (and subsequent locking) is avoided.
 1692          * In order to maintain the current code simple, when the head
 1693          * object is totally unloaded it means also that we do not have
 1694          * further objects in the list, so the list ownership needs to be
 1695          * hand over to another object if the current head needs to be freed.
 1696          */
 1697         if ((*lock_list)->ll_count == 0) {
 1698                 if (*lock_list == lle) {
 1699                         if (lle->ll_next == NULL)
 1700                                 return;
 1701                 } else
 1702                         lle = *lock_list;
 1703                 *lock_list = lle->ll_next;
 1704                 CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__,
 1705                     td->td_proc->p_pid, lle);
 1706                 witness_lock_list_free(lle);
 1707         }
 1708 }
 1709 
 1710 void
 1711 witness_thread_exit(struct thread *td)
 1712 {
 1713         struct lock_list_entry *lle;
 1714         int i, n;
 1715 
 1716         lle = td->td_sleeplocks;
 1717         if (lle == NULL || panicstr != NULL)
 1718                 return;
 1719         if (lle->ll_count != 0) {
 1720                 for (n = 0; lle != NULL; lle = lle->ll_next)
 1721                         for (i = lle->ll_count - 1; i >= 0; i--) {
 1722                                 if (n == 0)
 1723                                         witness_output(
 1724                     "Thread %p exiting with the following locks held:\n", td);
 1725                                 n++;
 1726                                 witness_list_lock(&lle->ll_children[i],
 1727                                     witness_output);
 1728                                 
 1729                         }
 1730                 kassert_panic(
 1731                     "Thread %p cannot exit while holding sleeplocks\n", td);
 1732         }
 1733         witness_lock_list_free(lle);
 1734 }
 1735 
 1736 /*
 1737  * Warn if any locks other than 'lock' are held.  Flags can be passed in to
 1738  * exempt Giant and sleepable locks from the checks as well.  If any
 1739  * non-exempt locks are held, then a supplied message is printed to the
 1740  * output channel along with a list of the offending locks.  If indicated in the
 1741  * flags then a failure results in a panic as well.
 1742  */
 1743 int
 1744 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
 1745 {
 1746         struct lock_list_entry *lock_list, *lle;
 1747         struct lock_instance *lock1;
 1748         struct thread *td;
 1749         va_list ap;
 1750         int i, n;
 1751 
 1752         if (witness_cold || witness_watch < 1 || panicstr != NULL)
 1753                 return (0);
 1754         n = 0;
 1755         td = curthread;
 1756         for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next)
 1757                 for (i = lle->ll_count - 1; i >= 0; i--) {
 1758                         lock1 = &lle->ll_children[i];
 1759                         if (lock1->li_lock == lock)
 1760                                 continue;
 1761                         if (flags & WARN_GIANTOK &&
 1762                             lock1->li_lock == &Giant.lock_object)
 1763                                 continue;
 1764                         if (flags & WARN_SLEEPOK &&
 1765                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0)
 1766                                 continue;
 1767                         if (n == 0) {
 1768                                 va_start(ap, fmt);
 1769                                 vprintf(fmt, ap);
 1770                                 va_end(ap);
 1771                                 printf(" with the following %slocks held:\n",
 1772                                     (flags & WARN_SLEEPOK) != 0 ?
 1773                                     "non-sleepable " : "");
 1774                         }
 1775                         n++;
 1776                         witness_list_lock(lock1, printf);
 1777                 }
 1778 
 1779         /*
 1780          * Pin the thread in order to avoid problems with thread migration.
 1781          * Once that all verifies are passed about spinlocks ownership,
 1782          * the thread is in a safe path and it can be unpinned.
 1783          */
 1784         sched_pin();
 1785         lock_list = PCPU_GET(spinlocks);
 1786         if (lock_list != NULL && lock_list->ll_count != 0) {
 1787                 sched_unpin();
 1788 
 1789                 /*
 1790                  * We should only have one spinlock and as long as
 1791                  * the flags cannot match for this locks class,
 1792                  * check if the first spinlock is the one curthread
 1793                  * should hold.
 1794                  */
 1795                 lock1 = &lock_list->ll_children[lock_list->ll_count - 1];
 1796                 if (lock_list->ll_count == 1 && lock_list->ll_next == NULL &&
 1797                     lock1->li_lock == lock && n == 0)
 1798                         return (0);
 1799 
 1800                 va_start(ap, fmt);
 1801                 vprintf(fmt, ap);
 1802                 va_end(ap);
 1803                 printf(" with the following %slocks held:\n",
 1804                     (flags & WARN_SLEEPOK) != 0 ?  "non-sleepable " : "");
 1805                 n += witness_list_locks(&lock_list, printf);
 1806         } else
 1807                 sched_unpin();
 1808         if (flags & WARN_PANIC && n)
 1809                 kassert_panic("%s", __func__);
 1810         else
 1811                 witness_debugger(n, __func__);
 1812         return (n);
 1813 }
 1814 
 1815 const char *
 1816 witness_file(struct lock_object *lock)
 1817 {
 1818         struct witness *w;
 1819 
 1820         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
 1821                 return ("?");
 1822         w = lock->lo_witness;
 1823         return (w->w_file);
 1824 }
 1825 
 1826 int
 1827 witness_line(struct lock_object *lock)
 1828 {
 1829         struct witness *w;
 1830 
 1831         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
 1832                 return (0);
 1833         w = lock->lo_witness;
 1834         return (w->w_line);
 1835 }
 1836 
 1837 static struct witness *
 1838 enroll(const char *description, struct lock_class *lock_class)
 1839 {
 1840         struct witness *w;
 1841 
 1842         MPASS(description != NULL);
 1843 
 1844         if (witness_watch == -1 || panicstr != NULL)
 1845                 return (NULL);
 1846         if ((lock_class->lc_flags & LC_SPINLOCK)) {
 1847                 if (witness_skipspin)
 1848                         return (NULL);
 1849         } else if ((lock_class->lc_flags & LC_SLEEPLOCK) == 0) {
 1850                 kassert_panic("lock class %s is not sleep or spin",
 1851                     lock_class->lc_name);
 1852                 return (NULL);
 1853         }
 1854 
 1855         mtx_lock_spin(&w_mtx);
 1856         w = witness_hash_get(description);
 1857         if (w)
 1858                 goto found;
 1859         if ((w = witness_get()) == NULL)
 1860                 return (NULL);
 1861         MPASS(strlen(description) < MAX_W_NAME);
 1862         strcpy(w->w_name, description);
 1863         w->w_class = lock_class;
 1864         w->w_refcount = 1;
 1865         STAILQ_INSERT_HEAD(&w_all, w, w_list);
 1866         if (lock_class->lc_flags & LC_SPINLOCK) {
 1867                 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist);
 1868                 w_spin_cnt++;
 1869         } else if (lock_class->lc_flags & LC_SLEEPLOCK) {
 1870                 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist);
 1871                 w_sleep_cnt++;
 1872         }
 1873 
 1874         /* Insert new witness into the hash */
 1875         witness_hash_put(w);
 1876         witness_increment_graph_generation();
 1877         mtx_unlock_spin(&w_mtx);
 1878         return (w);
 1879 found:
 1880         w->w_refcount++;
 1881         if (w->w_refcount == 1)
 1882                 w->w_class = lock_class;
 1883         mtx_unlock_spin(&w_mtx);
 1884         if (lock_class != w->w_class)
 1885                 kassert_panic(
 1886                     "lock (%s) %s does not match earlier (%s) lock",
 1887                     description, lock_class->lc_name,
 1888                     w->w_class->lc_name);
 1889         return (w);
 1890 }
 1891 
 1892 static void
 1893 depart(struct witness *w)
 1894 {
 1895 
 1896         MPASS(w->w_refcount == 0);
 1897         if (w->w_class->lc_flags & LC_SLEEPLOCK) {
 1898                 w_sleep_cnt--;
 1899         } else {
 1900                 w_spin_cnt--;
 1901         }
 1902         /*
 1903          * Set file to NULL as it may point into a loadable module.
 1904          */
 1905         w->w_file = NULL;
 1906         w->w_line = 0;
 1907         witness_increment_graph_generation();
 1908 }
 1909 
 1910 
 1911 static void
 1912 adopt(struct witness *parent, struct witness *child)
 1913 {
 1914         int pi, ci, i, j;
 1915 
 1916         if (witness_cold == 0)
 1917                 mtx_assert(&w_mtx, MA_OWNED);
 1918 
 1919         /* If the relationship is already known, there's no work to be done. */
 1920         if (isitmychild(parent, child))
 1921                 return;
 1922 
 1923         /* When the structure of the graph changes, bump up the generation. */
 1924         witness_increment_graph_generation();
 1925 
 1926         /*
 1927          * The hard part ... create the direct relationship, then propagate all
 1928          * indirect relationships.
 1929          */
 1930         pi = parent->w_index;
 1931         ci = child->w_index;
 1932         WITNESS_INDEX_ASSERT(pi);
 1933         WITNESS_INDEX_ASSERT(ci);
 1934         MPASS(pi != ci);
 1935         w_rmatrix[pi][ci] |= WITNESS_PARENT;
 1936         w_rmatrix[ci][pi] |= WITNESS_CHILD;
 1937 
 1938         /*
 1939          * If parent was not already an ancestor of child,
 1940          * then we increment the descendant and ancestor counters.
 1941          */
 1942         if ((w_rmatrix[pi][ci] & WITNESS_ANCESTOR) == 0) {
 1943                 parent->w_num_descendants++;
 1944                 child->w_num_ancestors++;
 1945         }
 1946 
 1947         /* 
 1948          * Find each ancestor of 'pi'. Note that 'pi' itself is counted as 
 1949          * an ancestor of 'pi' during this loop.
 1950          */
 1951         for (i = 1; i <= w_max_used_index; i++) {
 1952                 if ((w_rmatrix[i][pi] & WITNESS_ANCESTOR_MASK) == 0 && 
 1953                     (i != pi))
 1954                         continue;
 1955 
 1956                 /* Find each descendant of 'i' and mark it as a descendant. */
 1957                 for (j = 1; j <= w_max_used_index; j++) {
 1958 
 1959                         /* 
 1960                          * Skip children that are already marked as
 1961                          * descendants of 'i'.
 1962                          */
 1963                         if (w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK)
 1964                                 continue;
 1965 
 1966                         /*
 1967                          * We are only interested in descendants of 'ci'. Note
 1968                          * that 'ci' itself is counted as a descendant of 'ci'.
 1969                          */
 1970                         if ((w_rmatrix[ci][j] & WITNESS_ANCESTOR_MASK) == 0 && 
 1971                             (j != ci))
 1972                                 continue;
 1973                         w_rmatrix[i][j] |= WITNESS_ANCESTOR;
 1974                         w_rmatrix[j][i] |= WITNESS_DESCENDANT;
 1975                         w_data[i].w_num_descendants++;
 1976                         w_data[j].w_num_ancestors++;
 1977 
 1978                         /* 
 1979                          * Make sure we aren't marking a node as both an
 1980                          * ancestor and descendant. We should have caught 
 1981                          * this as a lock order reversal earlier.
 1982                          */
 1983                         if ((w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) &&
 1984                             (w_rmatrix[i][j] & WITNESS_DESCENDANT_MASK)) {
 1985                                 printf("witness rmatrix paradox! [%d][%d]=%d "
 1986                                     "both ancestor and descendant\n",
 1987                                     i, j, w_rmatrix[i][j]); 
 1988                                 kdb_backtrace();
 1989                                 printf("Witness disabled.\n");
 1990                                 witness_watch = -1;
 1991                         }
 1992                         if ((w_rmatrix[j][i] & WITNESS_ANCESTOR_MASK) &&
 1993                             (w_rmatrix[j][i] & WITNESS_DESCENDANT_MASK)) {
 1994                                 printf("witness rmatrix paradox! [%d][%d]=%d "
 1995                                     "both ancestor and descendant\n",
 1996                                     j, i, w_rmatrix[j][i]); 
 1997                                 kdb_backtrace();
 1998                                 printf("Witness disabled.\n");
 1999                                 witness_watch = -1;
 2000                         }
 2001                 }
 2002         }
 2003 }
 2004 
 2005 static void
 2006 itismychild(struct witness *parent, struct witness *child)
 2007 {
 2008         int unlocked;
 2009 
 2010         MPASS(child != NULL && parent != NULL);
 2011         if (witness_cold == 0)
 2012                 mtx_assert(&w_mtx, MA_OWNED);
 2013 
 2014         if (!witness_lock_type_equal(parent, child)) {
 2015                 if (witness_cold == 0) {
 2016                         unlocked = 1;
 2017                         mtx_unlock_spin(&w_mtx);
 2018                 } else {
 2019                         unlocked = 0;
 2020                 }
 2021                 kassert_panic(
 2022                     "%s: parent \"%s\" (%s) and child \"%s\" (%s) are not "
 2023                     "the same lock type", __func__, parent->w_name,
 2024                     parent->w_class->lc_name, child->w_name,
 2025                     child->w_class->lc_name);
 2026                 if (unlocked)
 2027                         mtx_lock_spin(&w_mtx);
 2028         }
 2029         adopt(parent, child);
 2030 }
 2031 
 2032 /*
 2033  * Generic code for the isitmy*() functions. The rmask parameter is the
 2034  * expected relationship of w1 to w2.
 2035  */
 2036 static int
 2037 _isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname)
 2038 {
 2039         unsigned char r1, r2;
 2040         int i1, i2;
 2041 
 2042         i1 = w1->w_index;
 2043         i2 = w2->w_index;
 2044         WITNESS_INDEX_ASSERT(i1);
 2045         WITNESS_INDEX_ASSERT(i2);
 2046         r1 = w_rmatrix[i1][i2] & WITNESS_RELATED_MASK;
 2047         r2 = w_rmatrix[i2][i1] & WITNESS_RELATED_MASK;
 2048 
 2049         /* The flags on one better be the inverse of the flags on the other */
 2050         if (!((WITNESS_ATOD(r1) == r2 && WITNESS_DTOA(r2) == r1) ||
 2051             (WITNESS_DTOA(r1) == r2 && WITNESS_ATOD(r2) == r1))) {
 2052                 /* Don't squawk if we're potentially racing with an update. */
 2053                 if (!mtx_owned(&w_mtx))
 2054                         return (0);
 2055                 printf("%s: rmatrix mismatch between %s (index %d) and %s "
 2056                     "(index %d): w_rmatrix[%d][%d] == %hhx but "
 2057                     "w_rmatrix[%d][%d] == %hhx\n",
 2058                     fname, w1->w_name, i1, w2->w_name, i2, i1, i2, r1,
 2059                     i2, i1, r2);
 2060                 kdb_backtrace();
 2061                 printf("Witness disabled.\n");
 2062                 witness_watch = -1;
 2063         }
 2064         return (r1 & rmask);
 2065 }
 2066 
 2067 /*
 2068  * Checks if @child is a direct child of @parent.
 2069  */
 2070 static int
 2071 isitmychild(struct witness *parent, struct witness *child)
 2072 {
 2073 
 2074         return (_isitmyx(parent, child, WITNESS_PARENT, __func__));
 2075 }
 2076 
 2077 /*
 2078  * Checks if @descendant is a direct or inderect descendant of @ancestor.
 2079  */
 2080 static int
 2081 isitmydescendant(struct witness *ancestor, struct witness *descendant)
 2082 {
 2083 
 2084         return (_isitmyx(ancestor, descendant, WITNESS_ANCESTOR_MASK,
 2085             __func__));
 2086 }
 2087 
 2088 #ifdef BLESSING
 2089 static int
 2090 blessed(struct witness *w1, struct witness *w2)
 2091 {
 2092         int i;
 2093         struct witness_blessed *b;
 2094 
 2095         for (i = 0; i < nitems(blessed_list); i++) {
 2096                 b = &blessed_list[i];
 2097                 if (strcmp(w1->w_name, b->b_lock1) == 0) {
 2098                         if (strcmp(w2->w_name, b->b_lock2) == 0)
 2099                                 return (1);
 2100                         continue;
 2101                 }
 2102                 if (strcmp(w1->w_name, b->b_lock2) == 0)
 2103                         if (strcmp(w2->w_name, b->b_lock1) == 0)
 2104                                 return (1);
 2105         }
 2106         return (0);
 2107 }
 2108 #endif
 2109 
 2110 static struct witness *
 2111 witness_get(void)
 2112 {
 2113         struct witness *w;
 2114         int index;
 2115 
 2116         if (witness_cold == 0)
 2117                 mtx_assert(&w_mtx, MA_OWNED);
 2118 
 2119         if (witness_watch == -1) {
 2120                 mtx_unlock_spin(&w_mtx);
 2121                 return (NULL);
 2122         }
 2123         if (STAILQ_EMPTY(&w_free)) {
 2124                 witness_watch = -1;
 2125                 mtx_unlock_spin(&w_mtx);
 2126                 printf("WITNESS: unable to allocate a new witness object\n");
 2127                 return (NULL);
 2128         }
 2129         w = STAILQ_FIRST(&w_free);
 2130         STAILQ_REMOVE_HEAD(&w_free, w_list);
 2131         w_free_cnt--;
 2132         index = w->w_index;
 2133         MPASS(index > 0 && index == w_max_used_index+1 &&
 2134             index < witness_count);
 2135         bzero(w, sizeof(*w));
 2136         w->w_index = index;
 2137         if (index > w_max_used_index)
 2138                 w_max_used_index = index;
 2139         return (w);
 2140 }
 2141 
 2142 static void
 2143 witness_free(struct witness *w)
 2144 {
 2145 
 2146         STAILQ_INSERT_HEAD(&w_free, w, w_list);
 2147         w_free_cnt++;
 2148 }
 2149 
 2150 static struct lock_list_entry *
 2151 witness_lock_list_get(void)
 2152 {
 2153         struct lock_list_entry *lle;
 2154 
 2155         if (witness_watch == -1)
 2156                 return (NULL);
 2157         mtx_lock_spin(&w_mtx);
 2158         lle = w_lock_list_free;
 2159         if (lle == NULL) {
 2160                 witness_watch = -1;
 2161                 mtx_unlock_spin(&w_mtx);
 2162                 printf("%s: witness exhausted\n", __func__);
 2163                 return (NULL);
 2164         }
 2165         w_lock_list_free = lle->ll_next;
 2166         mtx_unlock_spin(&w_mtx);
 2167         bzero(lle, sizeof(*lle));
 2168         return (lle);
 2169 }
 2170                 
 2171 static void
 2172 witness_lock_list_free(struct lock_list_entry *lle)
 2173 {
 2174 
 2175         mtx_lock_spin(&w_mtx);
 2176         lle->ll_next = w_lock_list_free;
 2177         w_lock_list_free = lle;
 2178         mtx_unlock_spin(&w_mtx);
 2179 }
 2180 
 2181 static struct lock_instance *
 2182 find_instance(struct lock_list_entry *list, const struct lock_object *lock)
 2183 {
 2184         struct lock_list_entry *lle;
 2185         struct lock_instance *instance;
 2186         int i;
 2187 
 2188         for (lle = list; lle != NULL; lle = lle->ll_next)
 2189                 for (i = lle->ll_count - 1; i >= 0; i--) {
 2190                         instance = &lle->ll_children[i];
 2191                         if (instance->li_lock == lock)
 2192                                 return (instance);
 2193                 }
 2194         return (NULL);
 2195 }
 2196 
 2197 static void
 2198 witness_list_lock(struct lock_instance *instance,
 2199     int (*prnt)(const char *fmt, ...))
 2200 {
 2201         struct lock_object *lock;
 2202 
 2203         lock = instance->li_lock;
 2204         prnt("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ?
 2205             "exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name);
 2206         if (lock->lo_witness->w_name != lock->lo_name)
 2207                 prnt(" (%s)", lock->lo_witness->w_name);
 2208         prnt(" r = %d (%p) locked @ %s:%d\n",
 2209             instance->li_flags & LI_RECURSEMASK, lock,
 2210             fixup_filename(instance->li_file), instance->li_line);
 2211 }
 2212 
 2213 static int
 2214 witness_output(const char *fmt, ...)
 2215 {
 2216         va_list ap;
 2217         int ret;
 2218 
 2219         va_start(ap, fmt);
 2220         ret = witness_voutput(fmt, ap);
 2221         va_end(ap);
 2222         return (ret);
 2223 }
 2224 
 2225 static int
 2226 witness_voutput(const char *fmt, va_list ap)
 2227 {
 2228         int ret;
 2229 
 2230         ret = 0;
 2231         switch (witness_channel) {
 2232         case WITNESS_CONSOLE:
 2233                 ret = vprintf(fmt, ap);
 2234                 break;
 2235         case WITNESS_LOG:
 2236                 vlog(LOG_NOTICE, fmt, ap);
 2237                 break;
 2238         case WITNESS_NONE:
 2239                 break;
 2240         }
 2241         return (ret);
 2242 }
 2243 
 2244 #ifdef DDB
 2245 static int
 2246 witness_thread_has_locks(struct thread *td)
 2247 {
 2248 
 2249         if (td->td_sleeplocks == NULL)
 2250                 return (0);
 2251         return (td->td_sleeplocks->ll_count != 0);
 2252 }
 2253 
 2254 static int
 2255 witness_proc_has_locks(struct proc *p)
 2256 {
 2257         struct thread *td;
 2258 
 2259         FOREACH_THREAD_IN_PROC(p, td) {
 2260                 if (witness_thread_has_locks(td))
 2261                         return (1);
 2262         }
 2263         return (0);
 2264 }
 2265 #endif
 2266 
 2267 int
 2268 witness_list_locks(struct lock_list_entry **lock_list,
 2269     int (*prnt)(const char *fmt, ...))
 2270 {
 2271         struct lock_list_entry *lle;
 2272         int i, nheld;
 2273 
 2274         nheld = 0;
 2275         for (lle = *lock_list; lle != NULL; lle = lle->ll_next)
 2276                 for (i = lle->ll_count - 1; i >= 0; i--) {
 2277                         witness_list_lock(&lle->ll_children[i], prnt);
 2278                         nheld++;
 2279                 }
 2280         return (nheld);
 2281 }
 2282 
 2283 /*
 2284  * This is a bit risky at best.  We call this function when we have timed
 2285  * out acquiring a spin lock, and we assume that the other CPU is stuck
 2286  * with this lock held.  So, we go groveling around in the other CPU's
 2287  * per-cpu data to try to find the lock instance for this spin lock to
 2288  * see when it was last acquired.
 2289  */
 2290 void
 2291 witness_display_spinlock(struct lock_object *lock, struct thread *owner,
 2292     int (*prnt)(const char *fmt, ...))
 2293 {
 2294         struct lock_instance *instance;
 2295         struct pcpu *pc;
 2296 
 2297         if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU)
 2298                 return;
 2299         pc = pcpu_find(owner->td_oncpu);
 2300         instance = find_instance(pc->pc_spinlocks, lock);
 2301         if (instance != NULL)
 2302                 witness_list_lock(instance, prnt);
 2303 }
 2304 
 2305 void
 2306 witness_save(struct lock_object *lock, const char **filep, int *linep)
 2307 {
 2308         struct lock_list_entry *lock_list;
 2309         struct lock_instance *instance;
 2310         struct lock_class *class;
 2311 
 2312         /*
 2313          * This function is used independently in locking code to deal with
 2314          * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
 2315          * is gone.
 2316          */
 2317         if (SCHEDULER_STOPPED())
 2318                 return;
 2319         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2320         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2321                 return;
 2322         class = LOCK_CLASS(lock);
 2323         if (class->lc_flags & LC_SLEEPLOCK)
 2324                 lock_list = curthread->td_sleeplocks;
 2325         else {
 2326                 if (witness_skipspin)
 2327                         return;
 2328                 lock_list = PCPU_GET(spinlocks);
 2329         }
 2330         instance = find_instance(lock_list, lock);
 2331         if (instance == NULL) {
 2332                 kassert_panic("%s: lock (%s) %s not locked", __func__,
 2333                     class->lc_name, lock->lo_name);
 2334                 return;
 2335         }
 2336         *filep = instance->li_file;
 2337         *linep = instance->li_line;
 2338 }
 2339 
 2340 void
 2341 witness_restore(struct lock_object *lock, const char *file, int line)
 2342 {
 2343         struct lock_list_entry *lock_list;
 2344         struct lock_instance *instance;
 2345         struct lock_class *class;
 2346 
 2347         /*
 2348          * This function is used independently in locking code to deal with
 2349          * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
 2350          * is gone.
 2351          */
 2352         if (SCHEDULER_STOPPED())
 2353                 return;
 2354         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2355         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2356                 return;
 2357         class = LOCK_CLASS(lock);
 2358         if (class->lc_flags & LC_SLEEPLOCK)
 2359                 lock_list = curthread->td_sleeplocks;
 2360         else {
 2361                 if (witness_skipspin)
 2362                         return;
 2363                 lock_list = PCPU_GET(spinlocks);
 2364         }
 2365         instance = find_instance(lock_list, lock);
 2366         if (instance == NULL)
 2367                 kassert_panic("%s: lock (%s) %s not locked", __func__,
 2368                     class->lc_name, lock->lo_name);
 2369         lock->lo_witness->w_file = file;
 2370         lock->lo_witness->w_line = line;
 2371         if (instance == NULL)
 2372                 return;
 2373         instance->li_file = file;
 2374         instance->li_line = line;
 2375 }
 2376 
 2377 void
 2378 witness_assert(const struct lock_object *lock, int flags, const char *file,
 2379     int line)
 2380 {
 2381 #ifdef INVARIANT_SUPPORT
 2382         struct lock_instance *instance;
 2383         struct lock_class *class;
 2384 
 2385         if (lock->lo_witness == NULL || witness_watch < 1 || panicstr != NULL)
 2386                 return;
 2387         class = LOCK_CLASS(lock);
 2388         if ((class->lc_flags & LC_SLEEPLOCK) != 0)
 2389                 instance = find_instance(curthread->td_sleeplocks, lock);
 2390         else if ((class->lc_flags & LC_SPINLOCK) != 0)
 2391                 instance = find_instance(PCPU_GET(spinlocks), lock);
 2392         else {
 2393                 kassert_panic("Lock (%s) %s is not sleep or spin!",
 2394                     class->lc_name, lock->lo_name);
 2395                 return;
 2396         }
 2397         switch (flags) {
 2398         case LA_UNLOCKED:
 2399                 if (instance != NULL)
 2400                         kassert_panic("Lock (%s) %s locked @ %s:%d.",
 2401                             class->lc_name, lock->lo_name,
 2402                             fixup_filename(file), line);
 2403                 break;
 2404         case LA_LOCKED:
 2405         case LA_LOCKED | LA_RECURSED:
 2406         case LA_LOCKED | LA_NOTRECURSED:
 2407         case LA_SLOCKED:
 2408         case LA_SLOCKED | LA_RECURSED:
 2409         case LA_SLOCKED | LA_NOTRECURSED:
 2410         case LA_XLOCKED:
 2411         case LA_XLOCKED | LA_RECURSED:
 2412         case LA_XLOCKED | LA_NOTRECURSED:
 2413                 if (instance == NULL) {
 2414                         kassert_panic("Lock (%s) %s not locked @ %s:%d.",
 2415                             class->lc_name, lock->lo_name,
 2416                             fixup_filename(file), line);
 2417                         break;
 2418                 }
 2419                 if ((flags & LA_XLOCKED) != 0 &&
 2420                     (instance->li_flags & LI_EXCLUSIVE) == 0)
 2421                         kassert_panic(
 2422                             "Lock (%s) %s not exclusively locked @ %s:%d.",
 2423                             class->lc_name, lock->lo_name,
 2424                             fixup_filename(file), line);
 2425                 if ((flags & LA_SLOCKED) != 0 &&
 2426                     (instance->li_flags & LI_EXCLUSIVE) != 0)
 2427                         kassert_panic(
 2428                             "Lock (%s) %s exclusively locked @ %s:%d.",
 2429                             class->lc_name, lock->lo_name,
 2430                             fixup_filename(file), line);
 2431                 if ((flags & LA_RECURSED) != 0 &&
 2432                     (instance->li_flags & LI_RECURSEMASK) == 0)
 2433                         kassert_panic("Lock (%s) %s not recursed @ %s:%d.",
 2434                             class->lc_name, lock->lo_name,
 2435                             fixup_filename(file), line);
 2436                 if ((flags & LA_NOTRECURSED) != 0 &&
 2437                     (instance->li_flags & LI_RECURSEMASK) != 0)
 2438                         kassert_panic("Lock (%s) %s recursed @ %s:%d.",
 2439                             class->lc_name, lock->lo_name,
 2440                             fixup_filename(file), line);
 2441                 break;
 2442         default:
 2443                 kassert_panic("Invalid lock assertion at %s:%d.",
 2444                     fixup_filename(file), line);
 2445 
 2446         }
 2447 #endif  /* INVARIANT_SUPPORT */
 2448 }
 2449 
 2450 static void
 2451 witness_setflag(struct lock_object *lock, int flag, int set)
 2452 {
 2453         struct lock_list_entry *lock_list;
 2454         struct lock_instance *instance;
 2455         struct lock_class *class;
 2456 
 2457         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2458                 return;
 2459         class = LOCK_CLASS(lock);
 2460         if (class->lc_flags & LC_SLEEPLOCK)
 2461                 lock_list = curthread->td_sleeplocks;
 2462         else {
 2463                 if (witness_skipspin)
 2464                         return;
 2465                 lock_list = PCPU_GET(spinlocks);
 2466         }
 2467         instance = find_instance(lock_list, lock);
 2468         if (instance == NULL) {
 2469                 kassert_panic("%s: lock (%s) %s not locked", __func__,
 2470                     class->lc_name, lock->lo_name);
 2471                 return;
 2472         }
 2473 
 2474         if (set)
 2475                 instance->li_flags |= flag;
 2476         else
 2477                 instance->li_flags &= ~flag;
 2478 }
 2479 
 2480 void
 2481 witness_norelease(struct lock_object *lock)
 2482 {
 2483 
 2484         witness_setflag(lock, LI_NORELEASE, 1);
 2485 }
 2486 
 2487 void
 2488 witness_releaseok(struct lock_object *lock)
 2489 {
 2490 
 2491         witness_setflag(lock, LI_NORELEASE, 0);
 2492 }
 2493 
 2494 #ifdef DDB
 2495 static void
 2496 witness_ddb_list(struct thread *td)
 2497 {
 2498 
 2499         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2500         KASSERT(kdb_active, ("%s: not in the debugger", __func__));
 2501 
 2502         if (witness_watch < 1)
 2503                 return;
 2504 
 2505         witness_list_locks(&td->td_sleeplocks, db_printf);
 2506 
 2507         /*
 2508          * We only handle spinlocks if td == curthread.  This is somewhat broken
 2509          * if td is currently executing on some other CPU and holds spin locks
 2510          * as we won't display those locks.  If we had a MI way of getting
 2511          * the per-cpu data for a given cpu then we could use
 2512          * td->td_oncpu to get the list of spinlocks for this thread
 2513          * and "fix" this.
 2514          *
 2515          * That still wouldn't really fix this unless we locked the scheduler
 2516          * lock or stopped the other CPU to make sure it wasn't changing the
 2517          * list out from under us.  It is probably best to just not try to
 2518          * handle threads on other CPU's for now.
 2519          */
 2520         if (td == curthread && PCPU_GET(spinlocks) != NULL)
 2521                 witness_list_locks(PCPU_PTR(spinlocks), db_printf);
 2522 }
 2523 
 2524 DB_SHOW_COMMAND(locks, db_witness_list)
 2525 {
 2526         struct thread *td;
 2527 
 2528         if (have_addr)
 2529                 td = db_lookup_thread(addr, true);
 2530         else
 2531                 td = kdb_thread;
 2532         witness_ddb_list(td);
 2533 }
 2534 
 2535 DB_SHOW_ALL_COMMAND(locks, db_witness_list_all)
 2536 {
 2537         struct thread *td;
 2538         struct proc *p;
 2539 
 2540         /*
 2541          * It would be nice to list only threads and processes that actually
 2542          * held sleep locks, but that information is currently not exported
 2543          * by WITNESS.
 2544          */
 2545         FOREACH_PROC_IN_SYSTEM(p) {
 2546                 if (!witness_proc_has_locks(p))
 2547                         continue;
 2548                 FOREACH_THREAD_IN_PROC(p, td) {
 2549                         if (!witness_thread_has_locks(td))
 2550                                 continue;
 2551                         db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid,
 2552                             p->p_comm, td, td->td_tid);
 2553                         witness_ddb_list(td);
 2554                         if (db_pager_quit)
 2555                                 return;
 2556                 }
 2557         }
 2558 }
 2559 DB_SHOW_ALIAS(alllocks, db_witness_list_all)
 2560 
 2561 DB_SHOW_COMMAND(witness, db_witness_display)
 2562 {
 2563 
 2564         witness_ddb_display(db_printf);
 2565 }
 2566 #endif
 2567 
 2568 static void
 2569 sbuf_print_witness_badstacks(struct sbuf *sb, size_t *oldidx)
 2570 {
 2571         struct witness_lock_order_data *data1, *data2, *tmp_data1, *tmp_data2;
 2572         struct witness *tmp_w1, *tmp_w2, *w1, *w2;
 2573         int generation, i, j;
 2574 
 2575         tmp_data1 = NULL;
 2576         tmp_data2 = NULL;
 2577         tmp_w1 = NULL;
 2578         tmp_w2 = NULL;
 2579 
 2580         /* Allocate and init temporary storage space. */
 2581         tmp_w1 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
 2582         tmp_w2 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
 2583         tmp_data1 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 
 2584             M_WAITOK | M_ZERO);
 2585         tmp_data2 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 
 2586             M_WAITOK | M_ZERO);
 2587         stack_zero(&tmp_data1->wlod_stack);
 2588         stack_zero(&tmp_data2->wlod_stack);
 2589 
 2590 restart:
 2591         mtx_lock_spin(&w_mtx);
 2592         generation = w_generation;
 2593         mtx_unlock_spin(&w_mtx);
 2594         sbuf_printf(sb, "Number of known direct relationships is %d\n",
 2595             w_lohash.wloh_count);
 2596         for (i = 1; i < w_max_used_index; i++) {
 2597                 mtx_lock_spin(&w_mtx);
 2598                 if (generation != w_generation) {
 2599                         mtx_unlock_spin(&w_mtx);
 2600 
 2601                         /* The graph has changed, try again. */
 2602                         *oldidx = 0;
 2603                         sbuf_clear(sb);
 2604                         goto restart;
 2605                 }
 2606 
 2607                 w1 = &w_data[i];
 2608                 if (w1->w_reversed == 0) {
 2609                         mtx_unlock_spin(&w_mtx);
 2610                         continue;
 2611                 }
 2612 
 2613                 /* Copy w1 locally so we can release the spin lock. */
 2614                 *tmp_w1 = *w1;
 2615                 mtx_unlock_spin(&w_mtx);
 2616 
 2617                 if (tmp_w1->w_reversed == 0)
 2618                         continue;
 2619                 for (j = 1; j < w_max_used_index; j++) {
 2620                         if ((w_rmatrix[i][j] & WITNESS_REVERSAL) == 0 || i > j)
 2621                                 continue;
 2622 
 2623                         mtx_lock_spin(&w_mtx);
 2624                         if (generation != w_generation) {
 2625                                 mtx_unlock_spin(&w_mtx);
 2626 
 2627                                 /* The graph has changed, try again. */
 2628                                 *oldidx = 0;
 2629                                 sbuf_clear(sb);
 2630                                 goto restart;
 2631                         }
 2632 
 2633                         w2 = &w_data[j];
 2634                         data1 = witness_lock_order_get(w1, w2);
 2635                         data2 = witness_lock_order_get(w2, w1);
 2636 
 2637                         /*
 2638                          * Copy information locally so we can release the
 2639                          * spin lock.
 2640                          */
 2641                         *tmp_w2 = *w2;
 2642 
 2643                         if (data1) {
 2644                                 stack_zero(&tmp_data1->wlod_stack);
 2645                                 stack_copy(&data1->wlod_stack,
 2646                                     &tmp_data1->wlod_stack);
 2647                         }
 2648                         if (data2 && data2 != data1) {
 2649                                 stack_zero(&tmp_data2->wlod_stack);
 2650                                 stack_copy(&data2->wlod_stack,
 2651                                     &tmp_data2->wlod_stack);
 2652                         }
 2653                         mtx_unlock_spin(&w_mtx);
 2654 
 2655                         sbuf_printf(sb,
 2656             "\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n",
 2657                             tmp_w1->w_name, tmp_w1->w_class->lc_name, 
 2658                             tmp_w2->w_name, tmp_w2->w_class->lc_name);
 2659                         if (data1) {
 2660                                 sbuf_printf(sb,
 2661                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
 2662                                     tmp_w1->w_name, tmp_w1->w_class->lc_name, 
 2663                                     tmp_w2->w_name, tmp_w2->w_class->lc_name);
 2664                                 stack_sbuf_print(sb, &tmp_data1->wlod_stack);
 2665                                 sbuf_printf(sb, "\n");
 2666                         }
 2667                         if (data2 && data2 != data1) {
 2668                                 sbuf_printf(sb,
 2669                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
 2670                                     tmp_w2->w_name, tmp_w2->w_class->lc_name, 
 2671                                     tmp_w1->w_name, tmp_w1->w_class->lc_name);
 2672                                 stack_sbuf_print(sb, &tmp_data2->wlod_stack);
 2673                                 sbuf_printf(sb, "\n");
 2674                         }
 2675                 }
 2676         }
 2677         mtx_lock_spin(&w_mtx);
 2678         if (generation != w_generation) {
 2679                 mtx_unlock_spin(&w_mtx);
 2680 
 2681                 /*
 2682                  * The graph changed while we were printing stack data,
 2683                  * try again.
 2684                  */
 2685                 *oldidx = 0;
 2686                 sbuf_clear(sb);
 2687                 goto restart;
 2688         }
 2689         mtx_unlock_spin(&w_mtx);
 2690 
 2691         /* Free temporary storage space. */
 2692         free(tmp_data1, M_TEMP);
 2693         free(tmp_data2, M_TEMP);
 2694         free(tmp_w1, M_TEMP);
 2695         free(tmp_w2, M_TEMP);
 2696 }
 2697 
 2698 static int
 2699 sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS)
 2700 {
 2701         struct sbuf *sb;
 2702         int error;
 2703 
 2704         if (witness_watch < 1) {
 2705                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
 2706                 return (error);
 2707         }
 2708         if (witness_cold) {
 2709                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
 2710                 return (error);
 2711         }
 2712         error = 0;
 2713         sb = sbuf_new(NULL, NULL, badstack_sbuf_size, SBUF_AUTOEXTEND);
 2714         if (sb == NULL)
 2715                 return (ENOMEM);
 2716 
 2717         sbuf_print_witness_badstacks(sb, &req->oldidx);
 2718 
 2719         sbuf_finish(sb);
 2720         error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
 2721         sbuf_delete(sb);
 2722 
 2723         return (error);
 2724 }
 2725 
 2726 #ifdef DDB
 2727 static int
 2728 sbuf_db_printf_drain(void *arg __unused, const char *data, int len)
 2729 {
 2730 
 2731         return (db_printf("%.*s", len, data));
 2732 }
 2733 
 2734 DB_SHOW_COMMAND(badstacks, db_witness_badstacks)
 2735 {
 2736         struct sbuf sb;
 2737         char buffer[128];
 2738         size_t dummy;
 2739 
 2740         sbuf_new(&sb, buffer, sizeof(buffer), SBUF_FIXEDLEN);
 2741         sbuf_set_drain(&sb, sbuf_db_printf_drain, NULL);
 2742         sbuf_print_witness_badstacks(&sb, &dummy);
 2743         sbuf_finish(&sb);
 2744 }
 2745 #endif
 2746 
 2747 static int
 2748 sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS)
 2749 {
 2750         static const struct {
 2751                 enum witness_channel channel;
 2752                 const char *name;
 2753         } channels[] = {
 2754                 { WITNESS_CONSOLE, "console" },
 2755                 { WITNESS_LOG, "log" },
 2756                 { WITNESS_NONE, "none" },
 2757         };
 2758         char buf[16];
 2759         u_int i;
 2760         int error;
 2761 
 2762         buf[0] = '\0';
 2763         for (i = 0; i < nitems(channels); i++)
 2764                 if (witness_channel == channels[i].channel) {
 2765                         snprintf(buf, sizeof(buf), "%s", channels[i].name);
 2766                         break;
 2767                 }
 2768 
 2769         error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
 2770         if (error != 0 || req->newptr == NULL)
 2771                 return (error);
 2772 
 2773         error = EINVAL;
 2774         for (i = 0; i < nitems(channels); i++)
 2775                 if (strcmp(channels[i].name, buf) == 0) {
 2776                         witness_channel = channels[i].channel;
 2777                         error = 0;
 2778                         break;
 2779                 }
 2780         return (error);
 2781 }
 2782 
 2783 static int
 2784 sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS)
 2785 {
 2786         struct witness *w;
 2787         struct sbuf *sb;
 2788         int error;
 2789 
 2790 #ifdef __i386__
 2791         error = SYSCTL_OUT(req, w_notallowed, sizeof(w_notallowed));
 2792         return (error);
 2793 #endif
 2794 
 2795         if (witness_watch < 1) {
 2796                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
 2797                 return (error);
 2798         }
 2799         if (witness_cold) {
 2800                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
 2801                 return (error);
 2802         }
 2803         error = 0;
 2804 
 2805         error = sysctl_wire_old_buffer(req, 0);
 2806         if (error != 0)
 2807                 return (error);
 2808         sb = sbuf_new_for_sysctl(NULL, NULL, FULLGRAPH_SBUF_SIZE, req);
 2809         if (sb == NULL)
 2810                 return (ENOMEM);
 2811         sbuf_printf(sb, "\n");
 2812 
 2813         mtx_lock_spin(&w_mtx);
 2814         STAILQ_FOREACH(w, &w_all, w_list)
 2815                 w->w_displayed = 0;
 2816         STAILQ_FOREACH(w, &w_all, w_list)
 2817                 witness_add_fullgraph(sb, w);
 2818         mtx_unlock_spin(&w_mtx);
 2819 
 2820         /*
 2821          * Close the sbuf and return to userland.
 2822          */
 2823         error = sbuf_finish(sb);
 2824         sbuf_delete(sb);
 2825 
 2826         return (error);
 2827 }
 2828 
 2829 static int
 2830 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS)
 2831 {
 2832         int error, value;
 2833 
 2834         value = witness_watch;
 2835         error = sysctl_handle_int(oidp, &value, 0, req);
 2836         if (error != 0 || req->newptr == NULL)
 2837                 return (error);
 2838         if (value > 1 || value < -1 ||
 2839             (witness_watch == -1 && value != witness_watch))
 2840                 return (EINVAL);
 2841         witness_watch = value;
 2842         return (0);
 2843 }
 2844 
 2845 static void
 2846 witness_add_fullgraph(struct sbuf *sb, struct witness *w)
 2847 {
 2848         int i;
 2849 
 2850         if (w->w_displayed != 0 || (w->w_file == NULL && w->w_line == 0))
 2851                 return;
 2852         w->w_displayed = 1;
 2853 
 2854         WITNESS_INDEX_ASSERT(w->w_index);
 2855         for (i = 1; i <= w_max_used_index; i++) {
 2856                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) {
 2857                         sbuf_printf(sb, "\"%s\",\"%s\"\n", w->w_name,
 2858                             w_data[i].w_name);
 2859                         witness_add_fullgraph(sb, &w_data[i]);
 2860                 }
 2861         }
 2862 }
 2863 
 2864 /*
 2865  * A simple hash function. Takes a key pointer and a key size. If size == 0,
 2866  * interprets the key as a string and reads until the null
 2867  * terminator. Otherwise, reads the first size bytes. Returns an unsigned 32-bit
 2868  * hash value computed from the key.
 2869  */
 2870 static uint32_t
 2871 witness_hash_djb2(const uint8_t *key, uint32_t size)
 2872 {
 2873         unsigned int hash = 5381;
 2874         int i;
 2875 
 2876         /* hash = hash * 33 + key[i] */
 2877         if (size)
 2878                 for (i = 0; i < size; i++)
 2879                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
 2880         else
 2881                 for (i = 0; key[i] != 0; i++)
 2882                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
 2883 
 2884         return (hash);
 2885 }
 2886 
 2887 
 2888 /*
 2889  * Initializes the two witness hash tables. Called exactly once from
 2890  * witness_initialize().
 2891  */
 2892 static void
 2893 witness_init_hash_tables(void)
 2894 {
 2895         int i;
 2896 
 2897         MPASS(witness_cold);
 2898 
 2899         /* Initialize the hash tables. */
 2900         for (i = 0; i < WITNESS_HASH_SIZE; i++)
 2901                 w_hash.wh_array[i] = NULL;
 2902 
 2903         w_hash.wh_size = WITNESS_HASH_SIZE;
 2904         w_hash.wh_count = 0;
 2905 
 2906         /* Initialize the lock order data hash. */
 2907         w_lofree = NULL;
 2908         for (i = 0; i < WITNESS_LO_DATA_COUNT; i++) {
 2909                 memset(&w_lodata[i], 0, sizeof(w_lodata[i]));
 2910                 w_lodata[i].wlod_next = w_lofree;
 2911                 w_lofree = &w_lodata[i];
 2912         }
 2913         w_lohash.wloh_size = WITNESS_LO_HASH_SIZE;
 2914         w_lohash.wloh_count = 0;
 2915         for (i = 0; i < WITNESS_LO_HASH_SIZE; i++)
 2916                 w_lohash.wloh_array[i] = NULL;
 2917 }
 2918 
 2919 static struct witness *
 2920 witness_hash_get(const char *key)
 2921 {
 2922         struct witness *w;
 2923         uint32_t hash;
 2924         
 2925         MPASS(key != NULL);
 2926         if (witness_cold == 0)
 2927                 mtx_assert(&w_mtx, MA_OWNED);
 2928         hash = witness_hash_djb2(key, 0) % w_hash.wh_size;
 2929         w = w_hash.wh_array[hash];
 2930         while (w != NULL) {
 2931                 if (strcmp(w->w_name, key) == 0)
 2932                         goto out;
 2933                 w = w->w_hash_next;
 2934         }
 2935 
 2936 out:
 2937         return (w);
 2938 }
 2939 
 2940 static void
 2941 witness_hash_put(struct witness *w)
 2942 {
 2943         uint32_t hash;
 2944 
 2945         MPASS(w != NULL);
 2946         MPASS(w->w_name != NULL);
 2947         if (witness_cold == 0)
 2948                 mtx_assert(&w_mtx, MA_OWNED);
 2949         KASSERT(witness_hash_get(w->w_name) == NULL,
 2950             ("%s: trying to add a hash entry that already exists!", __func__));
 2951         KASSERT(w->w_hash_next == NULL,
 2952             ("%s: w->w_hash_next != NULL", __func__));
 2953 
 2954         hash = witness_hash_djb2(w->w_name, 0) % w_hash.wh_size;
 2955         w->w_hash_next = w_hash.wh_array[hash];
 2956         w_hash.wh_array[hash] = w;
 2957         w_hash.wh_count++;
 2958 }
 2959 
 2960 
 2961 static struct witness_lock_order_data *
 2962 witness_lock_order_get(struct witness *parent, struct witness *child)
 2963 {
 2964         struct witness_lock_order_data *data = NULL;
 2965         struct witness_lock_order_key key;
 2966         unsigned int hash;
 2967 
 2968         MPASS(parent != NULL && child != NULL);
 2969         key.from = parent->w_index;
 2970         key.to = child->w_index;
 2971         WITNESS_INDEX_ASSERT(key.from);
 2972         WITNESS_INDEX_ASSERT(key.to);
 2973         if ((w_rmatrix[parent->w_index][child->w_index]
 2974             & WITNESS_LOCK_ORDER_KNOWN) == 0)
 2975                 goto out;
 2976 
 2977         hash = witness_hash_djb2((const char*)&key,
 2978             sizeof(key)) % w_lohash.wloh_size;
 2979         data = w_lohash.wloh_array[hash];
 2980         while (data != NULL) {
 2981                 if (witness_lock_order_key_equal(&data->wlod_key, &key))
 2982                         break;
 2983                 data = data->wlod_next;
 2984         }
 2985 
 2986 out:
 2987         return (data);
 2988 }
 2989 
 2990 /*
 2991  * Verify that parent and child have a known relationship, are not the same,
 2992  * and child is actually a child of parent.  This is done without w_mtx
 2993  * to avoid contention in the common case.
 2994  */
 2995 static int
 2996 witness_lock_order_check(struct witness *parent, struct witness *child)
 2997 {
 2998 
 2999         if (parent != child &&
 3000             w_rmatrix[parent->w_index][child->w_index]
 3001             & WITNESS_LOCK_ORDER_KNOWN &&
 3002             isitmychild(parent, child))
 3003                 return (1);
 3004 
 3005         return (0);
 3006 }
 3007 
 3008 static int
 3009 witness_lock_order_add(struct witness *parent, struct witness *child)
 3010 {
 3011         struct witness_lock_order_data *data = NULL;
 3012         struct witness_lock_order_key key;
 3013         unsigned int hash;
 3014         
 3015         MPASS(parent != NULL && child != NULL);
 3016         key.from = parent->w_index;
 3017         key.to = child->w_index;
 3018         WITNESS_INDEX_ASSERT(key.from);
 3019         WITNESS_INDEX_ASSERT(key.to);
 3020         if (w_rmatrix[parent->w_index][child->w_index]
 3021             & WITNESS_LOCK_ORDER_KNOWN)
 3022                 return (1);
 3023 
 3024         hash = witness_hash_djb2((const char*)&key,
 3025             sizeof(key)) % w_lohash.wloh_size;
 3026         w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN;
 3027         data = w_lofree;
 3028         if (data == NULL)
 3029                 return (0);
 3030         w_lofree = data->wlod_next;
 3031         data->wlod_next = w_lohash.wloh_array[hash];
 3032         data->wlod_key = key;
 3033         w_lohash.wloh_array[hash] = data;
 3034         w_lohash.wloh_count++;
 3035         stack_zero(&data->wlod_stack);
 3036         stack_save(&data->wlod_stack);
 3037         return (1);
 3038 }
 3039 
 3040 /* Call this whenever the structure of the witness graph changes. */
 3041 static void
 3042 witness_increment_graph_generation(void)
 3043 {
 3044 
 3045         if (witness_cold == 0)
 3046                 mtx_assert(&w_mtx, MA_OWNED);
 3047         w_generation++;
 3048 }
 3049 
 3050 static int
 3051 witness_output_drain(void *arg __unused, const char *data, int len)
 3052 {
 3053 
 3054         witness_output("%.*s", len, data);
 3055         return (len);
 3056 }
 3057 
 3058 static void
 3059 witness_debugger(int cond, const char *msg)
 3060 {
 3061         char buf[32];
 3062         struct sbuf sb;
 3063         struct stack st;
 3064 
 3065         if (!cond)
 3066                 return;
 3067 
 3068         if (witness_trace) {
 3069                 sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN);
 3070                 sbuf_set_drain(&sb, witness_output_drain, NULL);
 3071 
 3072                 stack_zero(&st);
 3073                 stack_save(&st);
 3074                 witness_output("stack backtrace:\n");
 3075                 stack_sbuf_print_ddb(&sb, &st);
 3076 
 3077                 sbuf_finish(&sb);
 3078         }
 3079 
 3080 #ifdef KDB
 3081         if (witness_kdb)
 3082                 kdb_enter(KDB_WHY_WITNESS, msg);
 3083 #endif
 3084 }

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