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  * Copyright (c) 2008 Isilon Systems, Inc.
    3  * Copyright (c) 2008 Ilya Maykov <ivmaykov@gmail.com>
    4  * Copyright (c) 1998 Berkeley Software Design, Inc.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Berkeley Software Design Inc's name may not be used to endorse or
   16  *    promote products derived from this software without specific prior
   17  *    written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  *
   31  *      from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
   32  *      and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
   33  */
   34 
   35 /*
   36  * Implementation of the `witness' lock verifier.  Originally implemented for
   37  * mutexes in BSD/OS.  Extended to handle generic lock objects and lock
   38  * classes in FreeBSD.
   39  */
   40 
   41 /*
   42  *      Main Entry: witness
   43  *      Pronunciation: 'wit-n&s
   44  *      Function: noun
   45  *      Etymology: Middle English witnesse, from Old English witnes knowledge,
   46  *          testimony, witness, from 2wit
   47  *      Date: before 12th century
   48  *      1 : attestation of a fact or event : TESTIMONY
   49  *      2 : one that gives evidence; specifically : one who testifies in
   50  *          a cause or before a judicial tribunal
   51  *      3 : one asked to be present at a transaction so as to be able to
   52  *          testify to its having taken place
   53  *      4 : one who has personal knowledge of something
   54  *      5 a : something serving as evidence or proof : SIGN
   55  *        b : public affirmation by word or example of usually
   56  *            religious faith or conviction <the heroic witness to divine
   57  *            life -- Pilot>
   58  *      6 capitalized : a member of the Jehovah's Witnesses 
   59  */
   60 
   61 /*
   62  * Special rules concerning Giant and lock orders:
   63  *
   64  * 1) Giant must be acquired before any other mutexes.  Stated another way,
   65  *    no other mutex may be held when Giant is acquired.
   66  *
   67  * 2) Giant must be released when blocking on a sleepable lock.
   68  *
   69  * This rule is less obvious, but is a result of Giant providing the same
   70  * semantics as spl().  Basically, when a thread sleeps, it must release
   71  * Giant.  When a thread blocks on a sleepable lock, it sleeps.  Hence rule
   72  * 2).
   73  *
   74  * 3) Giant may be acquired before or after sleepable locks.
   75  *
   76  * This rule is also not quite as obvious.  Giant may be acquired after
   77  * a sleepable lock because it is a non-sleepable lock and non-sleepable
   78  * locks may always be acquired while holding a sleepable lock.  The second
   79  * case, Giant before a sleepable lock, follows from rule 2) above.  Suppose
   80  * you have two threads T1 and T2 and a sleepable lock X.  Suppose that T1
   81  * acquires X and blocks on Giant.  Then suppose that T2 acquires Giant and
   82  * blocks on X.  When T2 blocks on X, T2 will release Giant allowing T1 to
   83  * execute.  Thus, acquiring Giant both before and after a sleepable lock
   84  * will not result in a lock order reversal.
   85  */
   86 
   87 #include <sys/cdefs.h>
   88 __FBSDID("$FreeBSD: stable/10/sys/kern/subr_witness.c 309871 2016-12-12 02:24:46Z markj $");
   89 
   90 #include "opt_ddb.h"
   91 #include "opt_hwpmc_hooks.h"
   92 #include "opt_stack.h"
   93 #include "opt_witness.h"
   94 
   95 #include <sys/param.h>
   96 #include <sys/bus.h>
   97 #include <sys/kdb.h>
   98 #include <sys/kernel.h>
   99 #include <sys/ktr.h>
  100 #include <sys/lock.h>
  101 #include <sys/malloc.h>
  102 #include <sys/mutex.h>
  103 #include <sys/priv.h>
  104 #include <sys/proc.h>
  105 #include <sys/sbuf.h>
  106 #include <sys/sched.h>
  107 #include <sys/stack.h>
  108 #include <sys/sysctl.h>
  109 #include <sys/systm.h>
  110 
  111 #ifdef DDB
  112 #include <ddb/ddb.h>
  113 #endif
  114 
  115 #include <machine/stdarg.h>
  116 
  117 #if !defined(DDB) && !defined(STACK)
  118 #error "DDB or STACK options are required for WITNESS"
  119 #endif
  120 
  121 /* Note that these traces do not work with KTR_ALQ. */
  122 #if 0
  123 #define KTR_WITNESS     KTR_SUBSYS
  124 #else
  125 #define KTR_WITNESS     0
  126 #endif
  127 
  128 #define LI_RECURSEMASK  0x0000ffff      /* Recursion depth of lock instance. */
  129 #define LI_EXCLUSIVE    0x00010000      /* Exclusive lock instance. */
  130 #define LI_NORELEASE    0x00020000      /* Lock not allowed to be released. */
  131 
  132 /* Define this to check for blessed mutexes */
  133 #undef BLESSING
  134 
  135 #define WITNESS_COUNT           1024
  136 #define WITNESS_CHILDCOUNT      (WITNESS_COUNT * 4)
  137 #define WITNESS_HASH_SIZE       251     /* Prime, gives load factor < 2 */
  138 #define WITNESS_PENDLIST        (1024 + MAXCPU)
  139 
  140 /* Allocate 256 KB of stack data space */
  141 #define WITNESS_LO_DATA_COUNT   2048
  142 
  143 /* Prime, gives load factor of ~2 at full load */
  144 #define WITNESS_LO_HASH_SIZE    1021
  145 
  146 /*
  147  * XXX: This is somewhat bogus, as we assume here that at most 2048 threads
  148  * will hold LOCK_NCHILDREN locks.  We handle failure ok, and we should
  149  * probably be safe for the most part, but it's still a SWAG.
  150  */
  151 #define LOCK_NCHILDREN  5
  152 #define LOCK_CHILDCOUNT 2048
  153 
  154 #define MAX_W_NAME      64
  155 
  156 #define BADSTACK_SBUF_SIZE      (256 * WITNESS_COUNT)
  157 #define FULLGRAPH_SBUF_SIZE     512
  158 
  159 /*
  160  * These flags go in the witness relationship matrix and describe the
  161  * relationship between any two struct witness objects.
  162  */
  163 #define WITNESS_UNRELATED        0x00    /* No lock order relation. */
  164 #define WITNESS_PARENT           0x01    /* Parent, aka direct ancestor. */
  165 #define WITNESS_ANCESTOR         0x02    /* Direct or indirect ancestor. */
  166 #define WITNESS_CHILD            0x04    /* Child, aka direct descendant. */
  167 #define WITNESS_DESCENDANT       0x08    /* Direct or indirect descendant. */
  168 #define WITNESS_ANCESTOR_MASK    (WITNESS_PARENT | WITNESS_ANCESTOR)
  169 #define WITNESS_DESCENDANT_MASK  (WITNESS_CHILD | WITNESS_DESCENDANT)
  170 #define WITNESS_RELATED_MASK                                            \
  171         (WITNESS_ANCESTOR_MASK | WITNESS_DESCENDANT_MASK)
  172 #define WITNESS_REVERSAL         0x10    /* A lock order reversal has been
  173                                           * observed. */
  174 #define WITNESS_RESERVED1        0x20    /* Unused flag, reserved. */
  175 #define WITNESS_RESERVED2        0x40    /* Unused flag, reserved. */
  176 #define WITNESS_LOCK_ORDER_KNOWN 0x80    /* This lock order is known. */
  177 
  178 /* Descendant to ancestor flags */
  179 #define WITNESS_DTOA(x) (((x) & WITNESS_RELATED_MASK) >> 2)
  180 
  181 /* Ancestor to descendant flags */
  182 #define WITNESS_ATOD(x) (((x) & WITNESS_RELATED_MASK) << 2)
  183 
  184 #define WITNESS_INDEX_ASSERT(i)                                         \
  185         MPASS((i) > 0 && (i) <= w_max_used_index && (i) < WITNESS_COUNT)
  186 
  187 static MALLOC_DEFINE(M_WITNESS, "Witness", "Witness");
  188 
  189 /*
  190  * Lock instances.  A lock instance is the data associated with a lock while
  191  * it is held by witness.  For example, a lock instance will hold the
  192  * recursion count of a lock.  Lock instances are held in lists.  Spin locks
  193  * are held in a per-cpu list while sleep locks are held in per-thread list.
  194  */
  195 struct lock_instance {
  196         struct lock_object      *li_lock;
  197         const char              *li_file;
  198         int                     li_line;
  199         u_int                   li_flags;
  200 };
  201 
  202 /*
  203  * A simple list type used to build the list of locks held by a thread
  204  * or CPU.  We can't simply embed the list in struct lock_object since a
  205  * lock may be held by more than one thread if it is a shared lock.  Locks
  206  * are added to the head of the list, so we fill up each list entry from
  207  * "the back" logically.  To ease some of the arithmetic, we actually fill
  208  * in each list entry the normal way (children[0] then children[1], etc.) but
  209  * when we traverse the list we read children[count-1] as the first entry
  210  * down to children[0] as the final entry.
  211  */
  212 struct lock_list_entry {
  213         struct lock_list_entry  *ll_next;
  214         struct lock_instance    ll_children[LOCK_NCHILDREN];
  215         u_int                   ll_count;
  216 };
  217 
  218 /*
  219  * The main witness structure. One of these per named lock type in the system
  220  * (for example, "vnode interlock").
  221  */
  222 struct witness {
  223         char                    w_name[MAX_W_NAME];
  224         uint32_t                w_index;  /* Index in the relationship matrix */
  225         struct lock_class       *w_class;
  226         STAILQ_ENTRY(witness)   w_list;         /* List of all witnesses. */
  227         STAILQ_ENTRY(witness)   w_typelist;     /* Witnesses of a type. */
  228         struct witness          *w_hash_next; /* Linked list in hash buckets. */
  229         const char              *w_file; /* File where last acquired */
  230         uint32_t                w_line; /* Line where last acquired */
  231         uint32_t                w_refcount;
  232         uint16_t                w_num_ancestors; /* direct/indirect
  233                                                   * ancestor count */
  234         uint16_t                w_num_descendants; /* direct/indirect
  235                                                     * descendant count */
  236         int16_t                 w_ddb_level;
  237         unsigned                w_displayed:1;
  238         unsigned                w_reversed:1;
  239 };
  240 
  241 STAILQ_HEAD(witness_list, witness);
  242 
  243 /*
  244  * The witness hash table. Keys are witness names (const char *), elements are
  245  * witness objects (struct witness *).
  246  */
  247 struct witness_hash {
  248         struct witness  *wh_array[WITNESS_HASH_SIZE];
  249         uint32_t        wh_size;
  250         uint32_t        wh_count;
  251 };
  252 
  253 /*
  254  * Key type for the lock order data hash table.
  255  */
  256 struct witness_lock_order_key {
  257         uint16_t        from;
  258         uint16_t        to;
  259 };
  260 
  261 struct witness_lock_order_data {
  262         struct stack                    wlod_stack;
  263         struct witness_lock_order_key   wlod_key;
  264         struct witness_lock_order_data  *wlod_next;
  265 };
  266 
  267 /*
  268  * The witness lock order data hash table. Keys are witness index tuples
  269  * (struct witness_lock_order_key), elements are lock order data objects
  270  * (struct witness_lock_order_data). 
  271  */
  272 struct witness_lock_order_hash {
  273         struct witness_lock_order_data  *wloh_array[WITNESS_LO_HASH_SIZE];
  274         u_int   wloh_size;
  275         u_int   wloh_count;
  276 };
  277 
  278 #ifdef BLESSING
  279 struct witness_blessed {
  280         const char      *b_lock1;
  281         const char      *b_lock2;
  282 };
  283 #endif
  284 
  285 struct witness_pendhelp {
  286         const char              *wh_type;
  287         struct lock_object      *wh_lock;
  288 };
  289 
  290 struct witness_order_list_entry {
  291         const char              *w_name;
  292         struct lock_class       *w_class;
  293 };
  294 
  295 /*
  296  * Returns 0 if one of the locks is a spin lock and the other is not.
  297  * Returns 1 otherwise.
  298  */
  299 static __inline int
  300 witness_lock_type_equal(struct witness *w1, struct witness *w2)
  301 {
  302 
  303         return ((w1->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) ==
  304                 (w2->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)));
  305 }
  306 
  307 static __inline int
  308 witness_lock_order_key_equal(const struct witness_lock_order_key *a,
  309     const struct witness_lock_order_key *b)
  310 {
  311 
  312         return (a->from == b->from && a->to == b->to);
  313 }
  314 
  315 static int      _isitmyx(struct witness *w1, struct witness *w2, int rmask,
  316                     const char *fname);
  317 #ifdef KDB
  318 static void     _witness_debugger(int cond, const char *msg);
  319 #endif
  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 void     witness_add_fullgraph(struct sbuf *sb, struct witness *parent);
  336 #ifdef DDB
  337 static void     witness_ddb_compute_levels(void);
  338 static void     witness_ddb_display(int(*)(const char *fmt, ...));
  339 static void     witness_ddb_display_descendants(int(*)(const char *fmt, ...),
  340                     struct witness *, int indent);
  341 static void     witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
  342                     struct witness_list *list);
  343 static void     witness_ddb_level_descendants(struct witness *parent, int l);
  344 static void     witness_ddb_list(struct thread *td);
  345 #endif
  346 static void     witness_free(struct witness *m);
  347 static struct witness   *witness_get(void);
  348 static uint32_t witness_hash_djb2(const uint8_t *key, uint32_t size);
  349 static struct witness   *witness_hash_get(const char *key);
  350 static void     witness_hash_put(struct witness *w);
  351 static void     witness_init_hash_tables(void);
  352 static void     witness_increment_graph_generation(void);
  353 static void     witness_lock_list_free(struct lock_list_entry *lle);
  354 static struct lock_list_entry   *witness_lock_list_get(void);
  355 static int      witness_lock_order_add(struct witness *parent,
  356                     struct witness *child);
  357 static int      witness_lock_order_check(struct witness *parent,
  358                     struct witness *child);
  359 static struct witness_lock_order_data   *witness_lock_order_get(
  360                                             struct witness *parent,
  361                                             struct witness *child);
  362 static void     witness_list_lock(struct lock_instance *instance,
  363                     int (*prnt)(const char *fmt, ...));
  364 static void     witness_setflag(struct lock_object *lock, int flag, int set);
  365 
  366 #ifdef KDB
  367 #define witness_debugger(c)     _witness_debugger(c, __func__)
  368 #else
  369 #define witness_debugger(c)
  370 #endif
  371 
  372 static SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW, NULL,
  373     "Witness Locking");
  374 
  375 /*
  376  * If set to 0, lock order checking is disabled.  If set to -1,
  377  * witness is completely disabled.  Otherwise witness performs full
  378  * lock order checking for all locks.  At runtime, lock order checking
  379  * may be toggled.  However, witness cannot be reenabled once it is
  380  * completely disabled.
  381  */
  382 static int witness_watch = 1;
  383 TUNABLE_INT("debug.witness.watch", &witness_watch);
  384 SYSCTL_PROC(_debug_witness, OID_AUTO, watch, CTLFLAG_RW | CTLTYPE_INT, NULL, 0,
  385     sysctl_debug_witness_watch, "I", "witness is watching lock operations");
  386 
  387 #ifdef KDB
  388 /*
  389  * When KDB is enabled and witness_kdb is 1, it will cause the system
  390  * to drop into kdebug() when:
  391  *      - a lock hierarchy violation occurs
  392  *      - locks are held when going to sleep.
  393  */
  394 #ifdef WITNESS_KDB
  395 int     witness_kdb = 1;
  396 #else
  397 int     witness_kdb = 0;
  398 #endif
  399 TUNABLE_INT("debug.witness.kdb", &witness_kdb);
  400 SYSCTL_INT(_debug_witness, OID_AUTO, kdb, CTLFLAG_RW, &witness_kdb, 0, "");
  401 
  402 /*
  403  * When KDB is enabled and witness_trace is 1, it will cause the system
  404  * to print a stack trace:
  405  *      - a lock hierarchy violation occurs
  406  *      - locks are held when going to sleep.
  407  */
  408 int     witness_trace = 1;
  409 TUNABLE_INT("debug.witness.trace", &witness_trace);
  410 SYSCTL_INT(_debug_witness, OID_AUTO, trace, CTLFLAG_RW, &witness_trace, 0, "");
  411 #endif /* KDB */
  412 
  413 #ifdef WITNESS_SKIPSPIN
  414 int     witness_skipspin = 1;
  415 #else
  416 int     witness_skipspin = 0;
  417 #endif
  418 TUNABLE_INT("debug.witness.skipspin", &witness_skipspin);
  419 SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN, &witness_skipspin,
  420     0, "");
  421 
  422 /*
  423  * Call this to print out the relations between locks.
  424  */
  425 SYSCTL_PROC(_debug_witness, OID_AUTO, fullgraph, CTLTYPE_STRING | CTLFLAG_RD,
  426     NULL, 0, sysctl_debug_witness_fullgraph, "A", "Show locks relation graphs");
  427 
  428 /*
  429  * Call this to print out the witness faulty stacks.
  430  */
  431 SYSCTL_PROC(_debug_witness, OID_AUTO, badstacks, CTLTYPE_STRING | CTLFLAG_RD,
  432     NULL, 0, sysctl_debug_witness_badstacks, "A", "Show bad witness stacks");
  433 
  434 static struct mtx w_mtx;
  435 
  436 /* w_list */
  437 static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free);
  438 static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all);
  439 
  440 /* w_typelist */
  441 static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin);
  442 static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep);
  443 
  444 /* lock list */
  445 static struct lock_list_entry *w_lock_list_free = NULL;
  446 static struct witness_pendhelp pending_locks[WITNESS_PENDLIST];
  447 static u_int pending_cnt;
  448 
  449 static int w_free_cnt, w_spin_cnt, w_sleep_cnt;
  450 SYSCTL_INT(_debug_witness, OID_AUTO, free_cnt, CTLFLAG_RD, &w_free_cnt, 0, "");
  451 SYSCTL_INT(_debug_witness, OID_AUTO, spin_cnt, CTLFLAG_RD, &w_spin_cnt, 0, "");
  452 SYSCTL_INT(_debug_witness, OID_AUTO, sleep_cnt, CTLFLAG_RD, &w_sleep_cnt, 0,
  453     "");
  454 
  455 static struct witness *w_data;
  456 static uint8_t w_rmatrix[WITNESS_COUNT+1][WITNESS_COUNT+1];
  457 static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT];
  458 static struct witness_hash w_hash;      /* The witness hash table. */
  459 
  460 /* The lock order data hash */
  461 static struct witness_lock_order_data w_lodata[WITNESS_LO_DATA_COUNT];
  462 static struct witness_lock_order_data *w_lofree = NULL;
  463 static struct witness_lock_order_hash w_lohash;
  464 static int w_max_used_index = 0;
  465 static unsigned int w_generation = 0;
  466 static const char w_notrunning[] = "Witness not running\n";
  467 static const char w_stillcold[] = "Witness is still cold\n";
  468 
  469 
  470 static struct witness_order_list_entry order_lists[] = {
  471         /*
  472          * sx locks
  473          */
  474         { "proctree", &lock_class_sx },
  475         { "allproc", &lock_class_sx },
  476         { "allprison", &lock_class_sx },
  477         { NULL, NULL },
  478         /*
  479          * Various mutexes
  480          */
  481         { "Giant", &lock_class_mtx_sleep },
  482         { "pipe mutex", &lock_class_mtx_sleep },
  483         { "sigio lock", &lock_class_mtx_sleep },
  484         { "process group", &lock_class_mtx_sleep },
  485         { "process lock", &lock_class_mtx_sleep },
  486         { "session", &lock_class_mtx_sleep },
  487         { "uidinfo hash", &lock_class_rw },
  488 #ifdef  HWPMC_HOOKS
  489         { "pmc-sleep", &lock_class_mtx_sleep },
  490 #endif
  491         { "time lock", &lock_class_mtx_sleep },
  492         { NULL, NULL },
  493         /*
  494          * umtx
  495          */
  496         { "umtx lock", &lock_class_mtx_sleep },
  497         { NULL, NULL },
  498         /*
  499          * Sockets
  500          */
  501         { "accept", &lock_class_mtx_sleep },
  502         { "so_snd", &lock_class_mtx_sleep },
  503         { "so_rcv", &lock_class_mtx_sleep },
  504         { "sellck", &lock_class_mtx_sleep },
  505         { NULL, NULL },
  506         /*
  507          * Routing
  508          */
  509         { "so_rcv", &lock_class_mtx_sleep },
  510         { "radix node head", &lock_class_rw },
  511         { "rtentry", &lock_class_mtx_sleep },
  512         { "ifaddr", &lock_class_mtx_sleep },
  513         { NULL, NULL },
  514         /*
  515          * IPv4 multicast:
  516          * protocol locks before interface locks, after UDP locks.
  517          */
  518         { "udpinp", &lock_class_rw },
  519         { "in_multi_mtx", &lock_class_mtx_sleep },
  520         { "igmp_mtx", &lock_class_mtx_sleep },
  521         { "if_addr_lock", &lock_class_rw },
  522         { NULL, NULL },
  523         /*
  524          * IPv6 multicast:
  525          * protocol locks before interface locks, after UDP locks.
  526          */
  527         { "udpinp", &lock_class_rw },
  528         { "in6_multi_mtx", &lock_class_mtx_sleep },
  529         { "mld_mtx", &lock_class_mtx_sleep },
  530         { "if_addr_lock", &lock_class_rw },
  531         { NULL, NULL },
  532         /*
  533          * UNIX Domain Sockets
  534          */
  535         { "unp_link_rwlock", &lock_class_rw },
  536         { "unp_list_lock", &lock_class_mtx_sleep },
  537         { "unp", &lock_class_mtx_sleep },
  538         { "so_snd", &lock_class_mtx_sleep },
  539         { NULL, NULL },
  540         /*
  541          * UDP/IP
  542          */
  543         { "udp", &lock_class_rw },
  544         { "udpinp", &lock_class_rw },
  545         { "so_snd", &lock_class_mtx_sleep },
  546         { NULL, NULL },
  547         /*
  548          * TCP/IP
  549          */
  550         { "tcp", &lock_class_rw },
  551         { "tcpinp", &lock_class_rw },
  552         { "so_snd", &lock_class_mtx_sleep },
  553         { NULL, NULL },
  554         /*
  555          * netatalk
  556          */
  557         { "ddp_list_mtx", &lock_class_mtx_sleep },
  558         { "ddp_mtx", &lock_class_mtx_sleep },
  559         { NULL, NULL },
  560         /*
  561          * BPF
  562          */
  563         { "bpf global lock", &lock_class_mtx_sleep },
  564         { "bpf interface lock", &lock_class_rw },
  565         { "bpf cdev lock", &lock_class_mtx_sleep },
  566         { NULL, NULL },
  567         /*
  568          * NFS server
  569          */
  570         { "nfsd_mtx", &lock_class_mtx_sleep },
  571         { "so_snd", &lock_class_mtx_sleep },
  572         { NULL, NULL },
  573 
  574         /*
  575          * IEEE 802.11
  576          */
  577         { "802.11 com lock", &lock_class_mtx_sleep},
  578         { NULL, NULL },
  579         /*
  580          * Network drivers
  581          */
  582         { "network driver", &lock_class_mtx_sleep},
  583         { NULL, NULL },
  584 
  585         /*
  586          * Netgraph
  587          */
  588         { "ng_node", &lock_class_mtx_sleep },
  589         { "ng_worklist", &lock_class_mtx_sleep },
  590         { NULL, NULL },
  591         /*
  592          * CDEV
  593          */
  594         { "vm map (system)", &lock_class_mtx_sleep },
  595         { "vm pagequeue", &lock_class_mtx_sleep },
  596         { "vnode interlock", &lock_class_mtx_sleep },
  597         { "cdev", &lock_class_mtx_sleep },
  598         { NULL, NULL },
  599         /*
  600          * VM
  601          */
  602         { "vm map (user)", &lock_class_sx },
  603         { "vm object", &lock_class_rw },
  604         { "vm page", &lock_class_mtx_sleep },
  605         { "vm pagequeue", &lock_class_mtx_sleep },
  606         { "pmap pv global", &lock_class_rw },
  607         { "pmap", &lock_class_mtx_sleep },
  608         { "pmap pv list", &lock_class_rw },
  609         { "vm page free queue", &lock_class_mtx_sleep },
  610         { NULL, NULL },
  611         /*
  612          * kqueue/VFS interaction
  613          */
  614         { "kqueue", &lock_class_mtx_sleep },
  615         { "struct mount mtx", &lock_class_mtx_sleep },
  616         { "vnode interlock", &lock_class_mtx_sleep },
  617         { NULL, NULL },
  618         /*
  619          * ZFS locking
  620          */
  621         { "dn->dn_mtx", &lock_class_sx },
  622         { "dr->dt.di.dr_mtx", &lock_class_sx },
  623         { "db->db_mtx", &lock_class_sx },
  624         { NULL, NULL },
  625         /*
  626          * spin locks
  627          */
  628 #ifdef SMP
  629         { "ap boot", &lock_class_mtx_spin },
  630 #endif
  631         { "rm.mutex_mtx", &lock_class_mtx_spin },
  632         { "sio", &lock_class_mtx_spin },
  633         { "scrlock", &lock_class_mtx_spin },
  634 #ifdef __i386__
  635         { "cy", &lock_class_mtx_spin },
  636 #endif
  637 #ifdef __sparc64__
  638         { "pcib_mtx", &lock_class_mtx_spin },
  639         { "rtc_mtx", &lock_class_mtx_spin },
  640 #endif
  641         { "scc_hwmtx", &lock_class_mtx_spin },
  642         { "uart_hwmtx", &lock_class_mtx_spin },
  643         { "fast_taskqueue", &lock_class_mtx_spin },
  644         { "intr table", &lock_class_mtx_spin },
  645 #ifdef  HWPMC_HOOKS
  646         { "pmc-per-proc", &lock_class_mtx_spin },
  647 #endif
  648         { "process slock", &lock_class_mtx_spin },
  649         { "sleepq chain", &lock_class_mtx_spin },
  650         { "rm_spinlock", &lock_class_mtx_spin },
  651         { "turnstile chain", &lock_class_mtx_spin },
  652         { "turnstile lock", &lock_class_mtx_spin },
  653         { "sched lock", &lock_class_mtx_spin },
  654         { "td_contested", &lock_class_mtx_spin },
  655         { "callout", &lock_class_mtx_spin },
  656         { "entropy harvest mutex", &lock_class_mtx_spin },
  657         { "syscons video lock", &lock_class_mtx_spin },
  658 #ifdef SMP
  659         { "smp rendezvous", &lock_class_mtx_spin },
  660 #endif
  661 #ifdef __powerpc__
  662         { "tlb0", &lock_class_mtx_spin },
  663 #endif
  664         /*
  665          * leaf locks
  666          */
  667         { "intrcnt", &lock_class_mtx_spin },
  668         { "icu", &lock_class_mtx_spin },
  669 #if defined(SMP) && defined(__sparc64__)
  670         { "ipi", &lock_class_mtx_spin },
  671 #endif
  672 #ifdef __i386__
  673         { "allpmaps", &lock_class_mtx_spin },
  674         { "descriptor tables", &lock_class_mtx_spin },
  675 #endif
  676         { "clk", &lock_class_mtx_spin },
  677         { "cpuset", &lock_class_mtx_spin },
  678         { "mprof lock", &lock_class_mtx_spin },
  679         { "zombie lock", &lock_class_mtx_spin },
  680         { "ALD Queue", &lock_class_mtx_spin },
  681 #ifdef __ia64__
  682         { "MCA spin lock", &lock_class_mtx_spin },
  683 #endif
  684 #if defined(__i386__) || defined(__amd64__)
  685         { "pcicfg", &lock_class_mtx_spin },
  686         { "NDIS thread lock", &lock_class_mtx_spin },
  687 #endif
  688         { "tw_osl_io_lock", &lock_class_mtx_spin },
  689         { "tw_osl_q_lock", &lock_class_mtx_spin },
  690         { "tw_cl_io_lock", &lock_class_mtx_spin },
  691         { "tw_cl_intr_lock", &lock_class_mtx_spin },
  692         { "tw_cl_gen_lock", &lock_class_mtx_spin },
  693 #ifdef  HWPMC_HOOKS
  694         { "pmc-leaf", &lock_class_mtx_spin },
  695 #endif
  696         { "blocked lock", &lock_class_mtx_spin },
  697         { NULL, NULL },
  698         { NULL, NULL }
  699 };
  700 
  701 #ifdef BLESSING
  702 /*
  703  * Pairs of locks which have been blessed
  704  * Don't complain about order problems with blessed locks
  705  */
  706 static struct witness_blessed blessed_list[] = {
  707 };
  708 static int blessed_count =
  709         sizeof(blessed_list) / sizeof(struct witness_blessed);
  710 #endif
  711 
  712 /*
  713  * This global is set to 0 once it becomes safe to use the witness code.
  714  */
  715 static int witness_cold = 1;
  716 
  717 /*
  718  * This global is set to 1 once the static lock orders have been enrolled
  719  * so that a warning can be issued for any spin locks enrolled later.
  720  */
  721 static int witness_spin_warn = 0;
  722 
  723 /* Trim useless garbage from filenames. */
  724 static const char *
  725 fixup_filename(const char *file)
  726 {
  727 
  728         if (file == NULL)
  729                 return (NULL);
  730         while (strncmp(file, "../", 3) == 0)
  731                 file += 3;
  732         return (file);
  733 }
  734 
  735 /*
  736  * The WITNESS-enabled diagnostic code.  Note that the witness code does
  737  * assume that the early boot is single-threaded at least until after this
  738  * routine is completed.
  739  */
  740 static void
  741 witness_initialize(void *dummy __unused)
  742 {
  743         struct lock_object *lock;
  744         struct witness_order_list_entry *order;
  745         struct witness *w, *w1;
  746         int i;
  747 
  748         w_data = malloc(sizeof (struct witness) * WITNESS_COUNT, M_WITNESS,
  749             M_NOWAIT | M_ZERO);
  750 
  751         /*
  752          * We have to release Giant before initializing its witness
  753          * structure so that WITNESS doesn't get confused.
  754          */
  755         mtx_unlock(&Giant);
  756         mtx_assert(&Giant, MA_NOTOWNED);
  757 
  758         CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
  759         mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET |
  760             MTX_NOWITNESS | MTX_NOPROFILE);
  761         for (i = WITNESS_COUNT - 1; i >= 0; i--) {
  762                 w = &w_data[i];
  763                 memset(w, 0, sizeof(*w));
  764                 w_data[i].w_index = i;  /* Witness index never changes. */
  765                 witness_free(w);
  766         }
  767         KASSERT(STAILQ_FIRST(&w_free)->w_index == 0,
  768             ("%s: Invalid list of free witness objects", __func__));
  769 
  770         /* Witness with index 0 is not used to aid in debugging. */
  771         STAILQ_REMOVE_HEAD(&w_free, w_list);
  772         w_free_cnt--;
  773 
  774         memset(w_rmatrix, 0,
  775             (sizeof(**w_rmatrix) * (WITNESS_COUNT+1) * (WITNESS_COUNT+1)));
  776 
  777         for (i = 0; i < LOCK_CHILDCOUNT; i++)
  778                 witness_lock_list_free(&w_locklistdata[i]);
  779         witness_init_hash_tables();
  780 
  781         /* First add in all the specified order lists. */
  782         for (order = order_lists; order->w_name != NULL; order++) {
  783                 w = enroll(order->w_name, order->w_class);
  784                 if (w == NULL)
  785                         continue;
  786                 w->w_file = "order list";
  787                 for (order++; order->w_name != NULL; order++) {
  788                         w1 = enroll(order->w_name, order->w_class);
  789                         if (w1 == NULL)
  790                                 continue;
  791                         w1->w_file = "order list";
  792                         itismychild(w, w1);
  793                         w = w1;
  794                 }
  795         }
  796         witness_spin_warn = 1;
  797 
  798         /* Iterate through all locks and add them to witness. */
  799         for (i = 0; pending_locks[i].wh_lock != NULL; i++) {
  800                 lock = pending_locks[i].wh_lock;
  801                 KASSERT(lock->lo_flags & LO_WITNESS,
  802                     ("%s: lock %s is on pending list but not LO_WITNESS",
  803                     __func__, lock->lo_name));
  804                 lock->lo_witness = enroll(pending_locks[i].wh_type,
  805                     LOCK_CLASS(lock));
  806         }
  807 
  808         /* Mark the witness code as being ready for use. */
  809         witness_cold = 0;
  810 
  811         mtx_lock(&Giant);
  812 }
  813 SYSINIT(witness_init, SI_SUB_WITNESS, SI_ORDER_FIRST, witness_initialize,
  814     NULL);
  815 
  816 void
  817 witness_init(struct lock_object *lock, const char *type)
  818 {
  819         struct lock_class *class;
  820 
  821         /* Various sanity checks. */
  822         class = LOCK_CLASS(lock);
  823         if ((lock->lo_flags & LO_RECURSABLE) != 0 &&
  824             (class->lc_flags & LC_RECURSABLE) == 0)
  825                 kassert_panic("%s: lock (%s) %s can not be recursable",
  826                     __func__, class->lc_name, lock->lo_name);
  827         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
  828             (class->lc_flags & LC_SLEEPABLE) == 0)
  829                 kassert_panic("%s: lock (%s) %s can not be sleepable",
  830                     __func__, class->lc_name, lock->lo_name);
  831         if ((lock->lo_flags & LO_UPGRADABLE) != 0 &&
  832             (class->lc_flags & LC_UPGRADABLE) == 0)
  833                 kassert_panic("%s: lock (%s) %s can not be upgradable",
  834                     __func__, class->lc_name, lock->lo_name);
  835 
  836         /*
  837          * If we shouldn't watch this lock, then just clear lo_witness.
  838          * Otherwise, if witness_cold is set, then it is too early to
  839          * enroll this lock, so defer it to witness_initialize() by adding
  840          * it to the pending_locks list.  If it is not too early, then enroll
  841          * the lock now.
  842          */
  843         if (witness_watch < 1 || panicstr != NULL ||
  844             (lock->lo_flags & LO_WITNESS) == 0)
  845                 lock->lo_witness = NULL;
  846         else if (witness_cold) {
  847                 pending_locks[pending_cnt].wh_lock = lock;
  848                 pending_locks[pending_cnt++].wh_type = type;
  849                 if (pending_cnt > WITNESS_PENDLIST)
  850                         panic("%s: pending locks list is too small, "
  851                             "increase WITNESS_PENDLIST\n",
  852                             __func__);
  853         } else
  854                 lock->lo_witness = enroll(type, class);
  855 }
  856 
  857 void
  858 witness_destroy(struct lock_object *lock)
  859 {
  860         struct lock_class *class;
  861         struct witness *w;
  862 
  863         class = LOCK_CLASS(lock);
  864 
  865         if (witness_cold)
  866                 panic("lock (%s) %s destroyed while witness_cold",
  867                     class->lc_name, lock->lo_name);
  868 
  869         /* XXX: need to verify that no one holds the lock */
  870         if ((lock->lo_flags & LO_WITNESS) == 0 || lock->lo_witness == NULL)
  871                 return;
  872         w = lock->lo_witness;
  873 
  874         mtx_lock_spin(&w_mtx);
  875         MPASS(w->w_refcount > 0);
  876         w->w_refcount--;
  877 
  878         if (w->w_refcount == 0)
  879                 depart(w);
  880         mtx_unlock_spin(&w_mtx);
  881 }
  882 
  883 #ifdef DDB
  884 static void
  885 witness_ddb_compute_levels(void)
  886 {
  887         struct witness *w;
  888 
  889         /*
  890          * First clear all levels.
  891          */
  892         STAILQ_FOREACH(w, &w_all, w_list)
  893                 w->w_ddb_level = -1;
  894 
  895         /*
  896          * Look for locks with no parents and level all their descendants.
  897          */
  898         STAILQ_FOREACH(w, &w_all, w_list) {
  899 
  900                 /* If the witness has ancestors (is not a root), skip it. */
  901                 if (w->w_num_ancestors > 0)
  902                         continue;
  903                 witness_ddb_level_descendants(w, 0);
  904         }
  905 }
  906 
  907 static void
  908 witness_ddb_level_descendants(struct witness *w, int l)
  909 {
  910         int i;
  911 
  912         if (w->w_ddb_level >= l)
  913                 return;
  914 
  915         w->w_ddb_level = l;
  916         l++;
  917 
  918         for (i = 1; i <= w_max_used_index; i++) {
  919                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
  920                         witness_ddb_level_descendants(&w_data[i], l);
  921         }
  922 }
  923 
  924 static void
  925 witness_ddb_display_descendants(int(*prnt)(const char *fmt, ...),
  926     struct witness *w, int indent)
  927 {
  928         int i;
  929 
  930         for (i = 0; i < indent; i++)
  931                 prnt(" ");
  932         prnt("%s (type: %s, depth: %d, active refs: %d)",
  933              w->w_name, w->w_class->lc_name,
  934              w->w_ddb_level, w->w_refcount);
  935         if (w->w_displayed) {
  936                 prnt(" -- (already displayed)\n");
  937                 return;
  938         }
  939         w->w_displayed = 1;
  940         if (w->w_file != NULL && w->w_line != 0)
  941                 prnt(" -- last acquired @ %s:%d\n", fixup_filename(w->w_file),
  942                     w->w_line);
  943         else
  944                 prnt(" -- never acquired\n");
  945         indent++;
  946         WITNESS_INDEX_ASSERT(w->w_index);
  947         for (i = 1; i <= w_max_used_index; i++) {
  948                 if (db_pager_quit)
  949                         return;
  950                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
  951                         witness_ddb_display_descendants(prnt, &w_data[i],
  952                             indent);
  953         }
  954 }
  955 
  956 static void
  957 witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
  958     struct witness_list *list)
  959 {
  960         struct witness *w;
  961 
  962         STAILQ_FOREACH(w, list, w_typelist) {
  963                 if (w->w_file == NULL || w->w_ddb_level > 0)
  964                         continue;
  965 
  966                 /* This lock has no anscestors - display its descendants. */
  967                 witness_ddb_display_descendants(prnt, w, 0);
  968                 if (db_pager_quit)
  969                         return;
  970         }
  971 }
  972         
  973 static void
  974 witness_ddb_display(int(*prnt)(const char *fmt, ...))
  975 {
  976         struct witness *w;
  977 
  978         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
  979         witness_ddb_compute_levels();
  980 
  981         /* Clear all the displayed flags. */
  982         STAILQ_FOREACH(w, &w_all, w_list)
  983                 w->w_displayed = 0;
  984 
  985         /*
  986          * First, handle sleep locks which have been acquired at least
  987          * once.
  988          */
  989         prnt("Sleep locks:\n");
  990         witness_ddb_display_list(prnt, &w_sleep);
  991         if (db_pager_quit)
  992                 return;
  993         
  994         /*
  995          * Now do spin locks which have been acquired at least once.
  996          */
  997         prnt("\nSpin locks:\n");
  998         witness_ddb_display_list(prnt, &w_spin);
  999         if (db_pager_quit)
 1000                 return;
 1001         
 1002         /*
 1003          * Finally, any locks which have not been acquired yet.
 1004          */
 1005         prnt("\nLocks which were never acquired:\n");
 1006         STAILQ_FOREACH(w, &w_all, w_list) {
 1007                 if (w->w_file != NULL || w->w_refcount == 0)
 1008                         continue;
 1009                 prnt("%s (type: %s, depth: %d)\n", w->w_name,
 1010                     w->w_class->lc_name, w->w_ddb_level);
 1011                 if (db_pager_quit)
 1012                         return;
 1013         }
 1014 }
 1015 #endif /* DDB */
 1016 
 1017 int
 1018 witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
 1019 {
 1020 
 1021         if (witness_watch == -1 || panicstr != NULL)
 1022                 return (0);
 1023 
 1024         /* Require locks that witness knows about. */
 1025         if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL ||
 1026             lock2->lo_witness == NULL)
 1027                 return (EINVAL);
 1028 
 1029         mtx_assert(&w_mtx, MA_NOTOWNED);
 1030         mtx_lock_spin(&w_mtx);
 1031 
 1032         /*
 1033          * If we already have either an explicit or implied lock order that
 1034          * is the other way around, then return an error.
 1035          */
 1036         if (witness_watch &&
 1037             isitmydescendant(lock2->lo_witness, lock1->lo_witness)) {
 1038                 mtx_unlock_spin(&w_mtx);
 1039                 return (EDOOFUS);
 1040         }
 1041         
 1042         /* Try to add the new order. */
 1043         CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 1044             lock2->lo_witness->w_name, lock1->lo_witness->w_name);
 1045         itismychild(lock1->lo_witness, lock2->lo_witness);
 1046         mtx_unlock_spin(&w_mtx);
 1047         return (0);
 1048 }
 1049 
 1050 void
 1051 witness_checkorder(struct lock_object *lock, int flags, const char *file,
 1052     int line, struct lock_object *interlock)
 1053 {
 1054         struct lock_list_entry *lock_list, *lle;
 1055         struct lock_instance *lock1, *lock2, *plock;
 1056         struct lock_class *class, *iclass;
 1057         struct witness *w, *w1;
 1058         struct thread *td;
 1059         int i, j;
 1060 
 1061         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL ||
 1062             panicstr != NULL)
 1063                 return;
 1064 
 1065         w = lock->lo_witness;
 1066         class = LOCK_CLASS(lock);
 1067         td = curthread;
 1068 
 1069         if (class->lc_flags & LC_SLEEPLOCK) {
 1070 
 1071                 /*
 1072                  * Since spin locks include a critical section, this check
 1073                  * implicitly enforces a lock order of all sleep locks before
 1074                  * all spin locks.
 1075                  */
 1076                 if (td->td_critnest != 0 && !kdb_active)
 1077                         kassert_panic("acquiring blockable sleep lock with "
 1078                             "spinlock or critical section held (%s) %s @ %s:%d",
 1079                             class->lc_name, lock->lo_name,
 1080                             fixup_filename(file), line);
 1081 
 1082                 /*
 1083                  * If this is the first lock acquired then just return as
 1084                  * no order checking is needed.
 1085                  */
 1086                 lock_list = td->td_sleeplocks;
 1087                 if (lock_list == NULL || lock_list->ll_count == 0)
 1088                         return;
 1089         } else {
 1090 
 1091                 /*
 1092                  * If this is the first lock, just return as no order
 1093                  * checking is needed.  Avoid problems with thread
 1094                  * migration pinning the thread while checking if
 1095                  * spinlocks are held.  If at least one spinlock is held
 1096                  * the thread is in a safe path and it is allowed to
 1097                  * unpin it.
 1098                  */
 1099                 sched_pin();
 1100                 lock_list = PCPU_GET(spinlocks);
 1101                 if (lock_list == NULL || lock_list->ll_count == 0) {
 1102                         sched_unpin();
 1103                         return;
 1104                 }
 1105                 sched_unpin();
 1106         }
 1107 
 1108         /*
 1109          * Check to see if we are recursing on a lock we already own.  If
 1110          * so, make sure that we don't mismatch exclusive and shared lock
 1111          * acquires.
 1112          */
 1113         lock1 = find_instance(lock_list, lock);
 1114         if (lock1 != NULL) {
 1115                 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 &&
 1116                     (flags & LOP_EXCLUSIVE) == 0) {
 1117                         printf("shared lock of (%s) %s @ %s:%d\n",
 1118                             class->lc_name, lock->lo_name,
 1119                             fixup_filename(file), line);
 1120                         printf("while exclusively locked from %s:%d\n",
 1121                             fixup_filename(lock1->li_file), lock1->li_line);
 1122                         kassert_panic("excl->share");
 1123                 }
 1124                 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
 1125                     (flags & LOP_EXCLUSIVE) != 0) {
 1126                         printf("exclusive lock of (%s) %s @ %s:%d\n",
 1127                             class->lc_name, lock->lo_name,
 1128                             fixup_filename(file), line);
 1129                         printf("while share locked from %s:%d\n",
 1130                             fixup_filename(lock1->li_file), lock1->li_line);
 1131                         kassert_panic("share->excl");
 1132                 }
 1133                 return;
 1134         }
 1135 
 1136         /* Warn if the interlock is not locked exactly once. */
 1137         if (interlock != NULL) {
 1138                 iclass = LOCK_CLASS(interlock);
 1139                 lock1 = find_instance(lock_list, interlock);
 1140                 if (lock1 == NULL)
 1141                         kassert_panic("interlock (%s) %s not locked @ %s:%d",
 1142                             iclass->lc_name, interlock->lo_name,
 1143                             fixup_filename(file), line);
 1144                 else if ((lock1->li_flags & LI_RECURSEMASK) != 0)
 1145                         kassert_panic("interlock (%s) %s recursed @ %s:%d",
 1146                             iclass->lc_name, interlock->lo_name,
 1147                             fixup_filename(file), line);
 1148         }
 1149 
 1150         /*
 1151          * Find the previously acquired lock, but ignore interlocks.
 1152          */
 1153         plock = &lock_list->ll_children[lock_list->ll_count - 1];
 1154         if (interlock != NULL && plock->li_lock == interlock) {
 1155                 if (lock_list->ll_count > 1)
 1156                         plock =
 1157                             &lock_list->ll_children[lock_list->ll_count - 2];
 1158                 else {
 1159                         lle = lock_list->ll_next;
 1160 
 1161                         /*
 1162                          * The interlock is the only lock we hold, so
 1163                          * simply return.
 1164                          */
 1165                         if (lle == NULL)
 1166                                 return;
 1167                         plock = &lle->ll_children[lle->ll_count - 1];
 1168                 }
 1169         }
 1170         
 1171         /*
 1172          * Try to perform most checks without a lock.  If this succeeds we
 1173          * can skip acquiring the lock and return success.  Otherwise we redo
 1174          * the check with the lock held to handle races with concurrent updates.
 1175          */
 1176         w1 = plock->li_lock->lo_witness;
 1177         if (witness_lock_order_check(w1, w))
 1178                 return;
 1179 
 1180         mtx_lock_spin(&w_mtx);
 1181         if (witness_lock_order_check(w1, w)) {
 1182                 mtx_unlock_spin(&w_mtx);
 1183                 return;
 1184         }
 1185         witness_lock_order_add(w1, w);
 1186 
 1187         /*
 1188          * Check for duplicate locks of the same type.  Note that we only
 1189          * have to check for this on the last lock we just acquired.  Any
 1190          * other cases will be caught as lock order violations.
 1191          */
 1192         if (w1 == w) {
 1193                 i = w->w_index;
 1194                 if (!(lock->lo_flags & LO_DUPOK) && !(flags & LOP_DUPOK) &&
 1195                     !(w_rmatrix[i][i] & WITNESS_REVERSAL)) {
 1196                     w_rmatrix[i][i] |= WITNESS_REVERSAL;
 1197                         w->w_reversed = 1;
 1198                         mtx_unlock_spin(&w_mtx);
 1199                         printf(
 1200                             "acquiring duplicate lock of same type: \"%s\"\n", 
 1201                             w->w_name);
 1202                         printf(" 1st %s @ %s:%d\n", plock->li_lock->lo_name,
 1203                             fixup_filename(plock->li_file), plock->li_line);
 1204                         printf(" 2nd %s @ %s:%d\n", lock->lo_name,
 1205                             fixup_filename(file), line);
 1206                         witness_debugger(1);
 1207                 } else
 1208                         mtx_unlock_spin(&w_mtx);
 1209                 return;
 1210         }
 1211         mtx_assert(&w_mtx, MA_OWNED);
 1212 
 1213         /*
 1214          * If we know that the lock we are acquiring comes after
 1215          * the lock we most recently acquired in the lock order tree,
 1216          * then there is no need for any further checks.
 1217          */
 1218         if (isitmychild(w1, w))
 1219                 goto out;
 1220 
 1221         for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) {
 1222                 for (i = lle->ll_count - 1; i >= 0; i--, j++) {
 1223 
 1224                         MPASS(j < LOCK_CHILDCOUNT * LOCK_NCHILDREN);
 1225                         lock1 = &lle->ll_children[i];
 1226 
 1227                         /*
 1228                          * Ignore the interlock.
 1229                          */
 1230                         if (interlock == lock1->li_lock)
 1231                                 continue;
 1232 
 1233                         /*
 1234                          * If this lock doesn't undergo witness checking,
 1235                          * then skip it.
 1236                          */
 1237                         w1 = lock1->li_lock->lo_witness;
 1238                         if (w1 == NULL) {
 1239                                 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0,
 1240                                     ("lock missing witness structure"));
 1241                                 continue;
 1242                         }
 1243 
 1244                         /*
 1245                          * If we are locking Giant and this is a sleepable
 1246                          * lock, then skip it.
 1247                          */
 1248                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1249                             lock == &Giant.lock_object)
 1250                                 continue;
 1251 
 1252                         /*
 1253                          * If we are locking a sleepable lock and this lock
 1254                          * is Giant, then skip it.
 1255                          */
 1256                         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1257                             lock1->li_lock == &Giant.lock_object)
 1258                                 continue;
 1259 
 1260                         /*
 1261                          * If we are locking a sleepable lock and this lock
 1262                          * isn't sleepable, we want to treat it as a lock
 1263                          * order violation to enfore a general lock order of
 1264                          * sleepable locks before non-sleepable locks.
 1265                          */
 1266                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1267                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
 1268                                 goto reversal;
 1269 
 1270                         /*
 1271                          * If we are locking Giant and this is a non-sleepable
 1272                          * lock, then treat it as a reversal.
 1273                          */
 1274                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0 &&
 1275                             lock == &Giant.lock_object)
 1276                                 goto reversal;
 1277 
 1278                         /*
 1279                          * Check the lock order hierarchy for a reveresal.
 1280                          */
 1281                         if (!isitmydescendant(w, w1))
 1282                                 continue;
 1283                 reversal:
 1284 
 1285                         /*
 1286                          * We have a lock order violation, check to see if it
 1287                          * is allowed or has already been yelled about.
 1288                          */
 1289 #ifdef BLESSING
 1290 
 1291                         /*
 1292                          * If the lock order is blessed, just bail.  We don't
 1293                          * look for other lock order violations though, which
 1294                          * may be a bug.
 1295                          */
 1296                         if (blessed(w, w1))
 1297                                 goto out;
 1298 #endif
 1299 
 1300                         /* Bail if this violation is known */
 1301                         if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL)
 1302                                 goto out;
 1303 
 1304                         /* Record this as a violation */
 1305                         w_rmatrix[w1->w_index][w->w_index] |= WITNESS_REVERSAL;
 1306                         w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL;
 1307                         w->w_reversed = w1->w_reversed = 1;
 1308                         witness_increment_graph_generation();
 1309                         mtx_unlock_spin(&w_mtx);
 1310 
 1311 #ifdef WITNESS_NO_VNODE
 1312                         /*
 1313                          * There are known LORs between VNODE locks. They are
 1314                          * not an indication of a bug. VNODE locks are flagged
 1315                          * as such (LO_IS_VNODE) and we don't yell if the LOR
 1316                          * is between 2 VNODE locks.
 1317                          */
 1318                         if ((lock->lo_flags & LO_IS_VNODE) != 0 &&
 1319                             (lock1->li_lock->lo_flags & LO_IS_VNODE) != 0)
 1320                                 return;
 1321 #endif
 1322 
 1323                         /*
 1324                          * Ok, yell about it.
 1325                          */
 1326                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1327                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
 1328                                 printf(
 1329                 "lock order reversal: (sleepable after non-sleepable)\n");
 1330                         else if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0
 1331                             && lock == &Giant.lock_object)
 1332                                 printf(
 1333                 "lock order reversal: (Giant after non-sleepable)\n");
 1334                         else
 1335                                 printf("lock order reversal:\n");
 1336 
 1337                         /*
 1338                          * Try to locate an earlier lock with
 1339                          * witness w in our list.
 1340                          */
 1341                         do {
 1342                                 lock2 = &lle->ll_children[i];
 1343                                 MPASS(lock2->li_lock != NULL);
 1344                                 if (lock2->li_lock->lo_witness == w)
 1345                                         break;
 1346                                 if (i == 0 && lle->ll_next != NULL) {
 1347                                         lle = lle->ll_next;
 1348                                         i = lle->ll_count - 1;
 1349                                         MPASS(i >= 0 && i < LOCK_NCHILDREN);
 1350                                 } else
 1351                                         i--;
 1352                         } while (i >= 0);
 1353                         if (i < 0) {
 1354                                 printf(" 1st %p %s (%s) @ %s:%d\n",
 1355                                     lock1->li_lock, lock1->li_lock->lo_name,
 1356                                     w1->w_name, fixup_filename(lock1->li_file),
 1357                                     lock1->li_line);
 1358                                 printf(" 2nd %p %s (%s) @ %s:%d\n", lock,
 1359                                     lock->lo_name, w->w_name,
 1360                                     fixup_filename(file), line);
 1361                         } else {
 1362                                 printf(" 1st %p %s (%s) @ %s:%d\n",
 1363                                     lock2->li_lock, lock2->li_lock->lo_name,
 1364                                     lock2->li_lock->lo_witness->w_name,
 1365                                     fixup_filename(lock2->li_file),
 1366                                     lock2->li_line);
 1367                                 printf(" 2nd %p %s (%s) @ %s:%d\n",
 1368                                     lock1->li_lock, lock1->li_lock->lo_name,
 1369                                     w1->w_name, fixup_filename(lock1->li_file),
 1370                                     lock1->li_line);
 1371                                 printf(" 3rd %p %s (%s) @ %s:%d\n", lock,
 1372                                     lock->lo_name, w->w_name,
 1373                                     fixup_filename(file), line);
 1374                         }
 1375                         witness_debugger(1);
 1376                         return;
 1377                 }
 1378         }
 1379 
 1380         /*
 1381          * If requested, build a new lock order.  However, don't build a new
 1382          * relationship between a sleepable lock and Giant if it is in the
 1383          * wrong direction.  The correct lock order is that sleepable locks
 1384          * always come before Giant.
 1385          */
 1386         if (flags & LOP_NEWORDER &&
 1387             !(plock->li_lock == &Giant.lock_object &&
 1388             (lock->lo_flags & LO_SLEEPABLE) != 0)) {
 1389                 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 1390                     w->w_name, plock->li_lock->lo_witness->w_name);
 1391                 itismychild(plock->li_lock->lo_witness, w);
 1392         }
 1393 out:
 1394         mtx_unlock_spin(&w_mtx);
 1395 }
 1396 
 1397 void
 1398 witness_lock(struct lock_object *lock, int flags, const char *file, int line)
 1399 {
 1400         struct lock_list_entry **lock_list, *lle;
 1401         struct lock_instance *instance;
 1402         struct witness *w;
 1403         struct thread *td;
 1404 
 1405         if (witness_cold || witness_watch == -1 || lock->lo_witness == NULL ||
 1406             panicstr != NULL)
 1407                 return;
 1408         w = lock->lo_witness;
 1409         td = curthread;
 1410 
 1411         /* Determine lock list for this lock. */
 1412         if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK)
 1413                 lock_list = &td->td_sleeplocks;
 1414         else
 1415                 lock_list = PCPU_PTR(spinlocks);
 1416 
 1417         /* Check to see if we are recursing on a lock we already own. */
 1418         instance = find_instance(*lock_list, lock);
 1419         if (instance != NULL) {
 1420                 instance->li_flags++;
 1421                 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__,
 1422                     td->td_proc->p_pid, lock->lo_name,
 1423                     instance->li_flags & LI_RECURSEMASK);
 1424                 instance->li_file = file;
 1425                 instance->li_line = line;
 1426                 return;
 1427         }
 1428 
 1429         /* Update per-witness last file and line acquire. */
 1430         w->w_file = file;
 1431         w->w_line = line;
 1432 
 1433         /* Find the next open lock instance in the list and fill it. */
 1434         lle = *lock_list;
 1435         if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
 1436                 lle = witness_lock_list_get();
 1437                 if (lle == NULL)
 1438                         return;
 1439                 lle->ll_next = *lock_list;
 1440                 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__,
 1441                     td->td_proc->p_pid, lle);
 1442                 *lock_list = lle;
 1443         }
 1444         instance = &lle->ll_children[lle->ll_count++];
 1445         instance->li_lock = lock;
 1446         instance->li_line = line;
 1447         instance->li_file = file;
 1448         if ((flags & LOP_EXCLUSIVE) != 0)
 1449                 instance->li_flags = LI_EXCLUSIVE;
 1450         else
 1451                 instance->li_flags = 0;
 1452         CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__,
 1453             td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1);
 1454 }
 1455 
 1456 void
 1457 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line)
 1458 {
 1459         struct lock_instance *instance;
 1460         struct lock_class *class;
 1461 
 1462         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 1463         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 1464                 return;
 1465         class = LOCK_CLASS(lock);
 1466         if (witness_watch) {
 1467                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
 1468                         kassert_panic(
 1469                             "upgrade of non-upgradable lock (%s) %s @ %s:%d",
 1470                             class->lc_name, lock->lo_name,
 1471                             fixup_filename(file), line);
 1472                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
 1473                         kassert_panic(
 1474                             "upgrade of non-sleep lock (%s) %s @ %s:%d",
 1475                             class->lc_name, lock->lo_name,
 1476                             fixup_filename(file), line);
 1477         }
 1478         instance = find_instance(curthread->td_sleeplocks, lock);
 1479         if (instance == NULL) {
 1480                 kassert_panic("upgrade of unlocked lock (%s) %s @ %s:%d",
 1481                     class->lc_name, lock->lo_name,
 1482                     fixup_filename(file), line);
 1483                 return;
 1484         }
 1485         if (witness_watch) {
 1486                 if ((instance->li_flags & LI_EXCLUSIVE) != 0)
 1487                         kassert_panic(
 1488                             "upgrade of exclusive lock (%s) %s @ %s:%d",
 1489                             class->lc_name, lock->lo_name,
 1490                             fixup_filename(file), line);
 1491                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
 1492                         kassert_panic(
 1493                             "upgrade of recursed lock (%s) %s r=%d @ %s:%d",
 1494                             class->lc_name, lock->lo_name,
 1495                             instance->li_flags & LI_RECURSEMASK,
 1496                             fixup_filename(file), line);
 1497         }
 1498         instance->li_flags |= LI_EXCLUSIVE;
 1499 }
 1500 
 1501 void
 1502 witness_downgrade(struct lock_object *lock, int flags, const char *file,
 1503     int line)
 1504 {
 1505         struct lock_instance *instance;
 1506         struct lock_class *class;
 1507 
 1508         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 1509         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 1510                 return;
 1511         class = LOCK_CLASS(lock);
 1512         if (witness_watch) {
 1513                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
 1514                         kassert_panic(
 1515                             "downgrade of non-upgradable lock (%s) %s @ %s:%d",
 1516                             class->lc_name, lock->lo_name,
 1517                             fixup_filename(file), line);
 1518                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
 1519                         kassert_panic(
 1520                             "downgrade of non-sleep lock (%s) %s @ %s:%d",
 1521                             class->lc_name, lock->lo_name,
 1522                             fixup_filename(file), line);
 1523         }
 1524         instance = find_instance(curthread->td_sleeplocks, lock);
 1525         if (instance == NULL) {
 1526                 kassert_panic("downgrade of unlocked lock (%s) %s @ %s:%d",
 1527                     class->lc_name, lock->lo_name,
 1528                     fixup_filename(file), line);
 1529                 return;
 1530         }
 1531         if (witness_watch) {
 1532                 if ((instance->li_flags & LI_EXCLUSIVE) == 0)
 1533                         kassert_panic(
 1534                             "downgrade of shared lock (%s) %s @ %s:%d",
 1535                             class->lc_name, lock->lo_name,
 1536                             fixup_filename(file), line);
 1537                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
 1538                         kassert_panic(
 1539                             "downgrade of recursed lock (%s) %s r=%d @ %s:%d",
 1540                             class->lc_name, lock->lo_name,
 1541                             instance->li_flags & LI_RECURSEMASK,
 1542                             fixup_filename(file), line);
 1543         }
 1544         instance->li_flags &= ~LI_EXCLUSIVE;
 1545 }
 1546 
 1547 void
 1548 witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
 1549 {
 1550         struct lock_list_entry **lock_list, *lle;
 1551         struct lock_instance *instance;
 1552         struct lock_class *class;
 1553         struct thread *td;
 1554         register_t s;
 1555         int i, j;
 1556 
 1557         if (witness_cold || lock->lo_witness == NULL || panicstr != NULL)
 1558                 return;
 1559         td = curthread;
 1560         class = LOCK_CLASS(lock);
 1561 
 1562         /* Find lock instance associated with this lock. */
 1563         if (class->lc_flags & LC_SLEEPLOCK)
 1564                 lock_list = &td->td_sleeplocks;
 1565         else
 1566                 lock_list = PCPU_PTR(spinlocks);
 1567         lle = *lock_list;
 1568         for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next)
 1569                 for (i = 0; i < (*lock_list)->ll_count; i++) {
 1570                         instance = &(*lock_list)->ll_children[i];
 1571                         if (instance->li_lock == lock)
 1572                                 goto found;
 1573                 }
 1574 
 1575         /*
 1576          * When disabling WITNESS through witness_watch we could end up in
 1577          * having registered locks in the td_sleeplocks queue.
 1578          * We have to make sure we flush these queues, so just search for
 1579          * eventual register locks and remove them.
 1580          */
 1581         if (witness_watch > 0) {
 1582                 kassert_panic("lock (%s) %s not locked @ %s:%d", class->lc_name,
 1583                     lock->lo_name, fixup_filename(file), line);
 1584                 return;
 1585         } else {
 1586                 return;
 1587         }
 1588 found:
 1589 
 1590         /* First, check for shared/exclusive mismatches. */
 1591         if ((instance->li_flags & LI_EXCLUSIVE) != 0 && witness_watch > 0 &&
 1592             (flags & LOP_EXCLUSIVE) == 0) {
 1593                 printf("shared unlock of (%s) %s @ %s:%d\n", class->lc_name,
 1594                     lock->lo_name, fixup_filename(file), line);
 1595                 printf("while exclusively locked from %s:%d\n",
 1596                     fixup_filename(instance->li_file), instance->li_line);
 1597                 kassert_panic("excl->ushare");
 1598         }
 1599         if ((instance->li_flags & LI_EXCLUSIVE) == 0 && witness_watch > 0 &&
 1600             (flags & LOP_EXCLUSIVE) != 0) {
 1601                 printf("exclusive unlock of (%s) %s @ %s:%d\n", class->lc_name,
 1602                     lock->lo_name, fixup_filename(file), line);
 1603                 printf("while share locked from %s:%d\n",
 1604                     fixup_filename(instance->li_file),
 1605                     instance->li_line);
 1606                 kassert_panic("share->uexcl");
 1607         }
 1608         /* If we are recursed, unrecurse. */
 1609         if ((instance->li_flags & LI_RECURSEMASK) > 0) {
 1610                 CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__,
 1611                     td->td_proc->p_pid, instance->li_lock->lo_name,
 1612                     instance->li_flags);
 1613                 instance->li_flags--;
 1614                 return;
 1615         }
 1616         /* The lock is now being dropped, check for NORELEASE flag */
 1617         if ((instance->li_flags & LI_NORELEASE) != 0 && witness_watch > 0) {
 1618                 printf("forbidden unlock of (%s) %s @ %s:%d\n", class->lc_name,
 1619                     lock->lo_name, fixup_filename(file), line);
 1620                 kassert_panic("lock marked norelease");
 1621         }
 1622 
 1623         /* Otherwise, remove this item from the list. */
 1624         s = intr_disable();
 1625         CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__,
 1626             td->td_proc->p_pid, instance->li_lock->lo_name,
 1627             (*lock_list)->ll_count - 1);
 1628         for (j = i; j < (*lock_list)->ll_count - 1; j++)
 1629                 (*lock_list)->ll_children[j] =
 1630                     (*lock_list)->ll_children[j + 1];
 1631         (*lock_list)->ll_count--;
 1632         intr_restore(s);
 1633 
 1634         /*
 1635          * In order to reduce contention on w_mtx, we want to keep always an
 1636          * head object into lists so that frequent allocation from the 
 1637          * free witness pool (and subsequent locking) is avoided.
 1638          * In order to maintain the current code simple, when the head
 1639          * object is totally unloaded it means also that we do not have
 1640          * further objects in the list, so the list ownership needs to be
 1641          * hand over to another object if the current head needs to be freed.
 1642          */
 1643         if ((*lock_list)->ll_count == 0) {
 1644                 if (*lock_list == lle) {
 1645                         if (lle->ll_next == NULL)
 1646                                 return;
 1647                 } else
 1648                         lle = *lock_list;
 1649                 *lock_list = lle->ll_next;
 1650                 CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__,
 1651                     td->td_proc->p_pid, lle);
 1652                 witness_lock_list_free(lle);
 1653         }
 1654 }
 1655 
 1656 void
 1657 witness_thread_exit(struct thread *td)
 1658 {
 1659         struct lock_list_entry *lle;
 1660         int i, n;
 1661 
 1662         lle = td->td_sleeplocks;
 1663         if (lle == NULL || panicstr != NULL)
 1664                 return;
 1665         if (lle->ll_count != 0) {
 1666                 for (n = 0; lle != NULL; lle = lle->ll_next)
 1667                         for (i = lle->ll_count - 1; i >= 0; i--) {
 1668                                 if (n == 0)
 1669                 printf("Thread %p exiting with the following locks held:\n",
 1670                                             td);
 1671                                 n++;
 1672                                 witness_list_lock(&lle->ll_children[i], printf);
 1673                                 
 1674                         }
 1675                 kassert_panic(
 1676                     "Thread %p cannot exit while holding sleeplocks\n", td);
 1677         }
 1678         witness_lock_list_free(lle);
 1679 }
 1680 
 1681 /*
 1682  * Warn if any locks other than 'lock' are held.  Flags can be passed in to
 1683  * exempt Giant and sleepable locks from the checks as well.  If any
 1684  * non-exempt locks are held, then a supplied message is printed to the
 1685  * console along with a list of the offending locks.  If indicated in the
 1686  * flags then a failure results in a panic as well.
 1687  */
 1688 int
 1689 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
 1690 {
 1691         struct lock_list_entry *lock_list, *lle;
 1692         struct lock_instance *lock1;
 1693         struct thread *td;
 1694         va_list ap;
 1695         int i, n;
 1696 
 1697         if (witness_cold || witness_watch < 1 || panicstr != NULL)
 1698                 return (0);
 1699         n = 0;
 1700         td = curthread;
 1701         for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next)
 1702                 for (i = lle->ll_count - 1; i >= 0; i--) {
 1703                         lock1 = &lle->ll_children[i];
 1704                         if (lock1->li_lock == lock)
 1705                                 continue;
 1706                         if (flags & WARN_GIANTOK &&
 1707                             lock1->li_lock == &Giant.lock_object)
 1708                                 continue;
 1709                         if (flags & WARN_SLEEPOK &&
 1710                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0)
 1711                                 continue;
 1712                         if (n == 0) {
 1713                                 va_start(ap, fmt);
 1714                                 vprintf(fmt, ap);
 1715                                 va_end(ap);
 1716                                 printf(" with the following");
 1717                                 if (flags & WARN_SLEEPOK)
 1718                                         printf(" non-sleepable");
 1719                                 printf(" locks held:\n");
 1720                         }
 1721                         n++;
 1722                         witness_list_lock(lock1, printf);
 1723                 }
 1724 
 1725         /*
 1726          * Pin the thread in order to avoid problems with thread migration.
 1727          * Once that all verifies are passed about spinlocks ownership,
 1728          * the thread is in a safe path and it can be unpinned.
 1729          */
 1730         sched_pin();
 1731         lock_list = PCPU_GET(spinlocks);
 1732         if (lock_list != NULL && lock_list->ll_count != 0) {
 1733                 sched_unpin();
 1734 
 1735                 /*
 1736                  * We should only have one spinlock and as long as
 1737                  * the flags cannot match for this locks class,
 1738                  * check if the first spinlock is the one curthread
 1739                  * should hold.
 1740                  */
 1741                 lock1 = &lock_list->ll_children[lock_list->ll_count - 1];
 1742                 if (lock_list->ll_count == 1 && lock_list->ll_next == NULL &&
 1743                     lock1->li_lock == lock && n == 0)
 1744                         return (0);
 1745 
 1746                 va_start(ap, fmt);
 1747                 vprintf(fmt, ap);
 1748                 va_end(ap);
 1749                 printf(" with the following");
 1750                 if (flags & WARN_SLEEPOK)
 1751                         printf(" non-sleepable");
 1752                 printf(" locks held:\n");
 1753                 n += witness_list_locks(&lock_list, printf);
 1754         } else
 1755                 sched_unpin();
 1756         if (flags & WARN_PANIC && n)
 1757                 kassert_panic("%s", __func__);
 1758         else
 1759                 witness_debugger(n);
 1760         return (n);
 1761 }
 1762 
 1763 const char *
 1764 witness_file(struct lock_object *lock)
 1765 {
 1766         struct witness *w;
 1767 
 1768         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
 1769                 return ("?");
 1770         w = lock->lo_witness;
 1771         return (w->w_file);
 1772 }
 1773 
 1774 int
 1775 witness_line(struct lock_object *lock)
 1776 {
 1777         struct witness *w;
 1778 
 1779         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
 1780                 return (0);
 1781         w = lock->lo_witness;
 1782         return (w->w_line);
 1783 }
 1784 
 1785 static struct witness *
 1786 enroll(const char *description, struct lock_class *lock_class)
 1787 {
 1788         struct witness *w;
 1789         struct witness_list *typelist;
 1790 
 1791         MPASS(description != NULL);
 1792 
 1793         if (witness_watch == -1 || panicstr != NULL)
 1794                 return (NULL);
 1795         if ((lock_class->lc_flags & LC_SPINLOCK)) {
 1796                 if (witness_skipspin)
 1797                         return (NULL);
 1798                 else
 1799                         typelist = &w_spin;
 1800         } else if ((lock_class->lc_flags & LC_SLEEPLOCK)) {
 1801                 typelist = &w_sleep;
 1802         } else {
 1803                 kassert_panic("lock class %s is not sleep or spin",
 1804                     lock_class->lc_name);
 1805                 return (NULL);
 1806         }
 1807 
 1808         mtx_lock_spin(&w_mtx);
 1809         w = witness_hash_get(description);
 1810         if (w)
 1811                 goto found;
 1812         if ((w = witness_get()) == NULL)
 1813                 return (NULL);
 1814         MPASS(strlen(description) < MAX_W_NAME);
 1815         strcpy(w->w_name, description);
 1816         w->w_class = lock_class;
 1817         w->w_refcount = 1;
 1818         STAILQ_INSERT_HEAD(&w_all, w, w_list);
 1819         if (lock_class->lc_flags & LC_SPINLOCK) {
 1820                 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist);
 1821                 w_spin_cnt++;
 1822         } else if (lock_class->lc_flags & LC_SLEEPLOCK) {
 1823                 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist);
 1824                 w_sleep_cnt++;
 1825         }
 1826 
 1827         /* Insert new witness into the hash */
 1828         witness_hash_put(w);
 1829         witness_increment_graph_generation();
 1830         mtx_unlock_spin(&w_mtx);
 1831         return (w);
 1832 found:
 1833         w->w_refcount++;
 1834         mtx_unlock_spin(&w_mtx);
 1835         if (lock_class != w->w_class)
 1836                 kassert_panic(
 1837                         "lock (%s) %s does not match earlier (%s) lock",
 1838                         description, lock_class->lc_name,
 1839                         w->w_class->lc_name);
 1840         return (w);
 1841 }
 1842 
 1843 static void
 1844 depart(struct witness *w)
 1845 {
 1846         struct witness_list *list;
 1847 
 1848         MPASS(w->w_refcount == 0);
 1849         if (w->w_class->lc_flags & LC_SLEEPLOCK) {
 1850                 list = &w_sleep;
 1851                 w_sleep_cnt--;
 1852         } else {
 1853                 list = &w_spin;
 1854                 w_spin_cnt--;
 1855         }
 1856         /*
 1857          * Set file to NULL as it may point into a loadable module.
 1858          */
 1859         w->w_file = NULL;
 1860         w->w_line = 0;
 1861         witness_increment_graph_generation();
 1862 }
 1863 
 1864 
 1865 static void
 1866 adopt(struct witness *parent, struct witness *child)
 1867 {
 1868         int pi, ci, i, j;
 1869 
 1870         if (witness_cold == 0)
 1871                 mtx_assert(&w_mtx, MA_OWNED);
 1872 
 1873         /* If the relationship is already known, there's no work to be done. */
 1874         if (isitmychild(parent, child))
 1875                 return;
 1876 
 1877         /* When the structure of the graph changes, bump up the generation. */
 1878         witness_increment_graph_generation();
 1879 
 1880         /*
 1881          * The hard part ... create the direct relationship, then propagate all
 1882          * indirect relationships.
 1883          */
 1884         pi = parent->w_index;
 1885         ci = child->w_index;
 1886         WITNESS_INDEX_ASSERT(pi);
 1887         WITNESS_INDEX_ASSERT(ci);
 1888         MPASS(pi != ci);
 1889         w_rmatrix[pi][ci] |= WITNESS_PARENT;
 1890         w_rmatrix[ci][pi] |= WITNESS_CHILD;
 1891 
 1892         /*
 1893          * If parent was not already an ancestor of child,
 1894          * then we increment the descendant and ancestor counters.
 1895          */
 1896         if ((w_rmatrix[pi][ci] & WITNESS_ANCESTOR) == 0) {
 1897                 parent->w_num_descendants++;
 1898                 child->w_num_ancestors++;
 1899         }
 1900 
 1901         /* 
 1902          * Find each ancestor of 'pi'. Note that 'pi' itself is counted as 
 1903          * an ancestor of 'pi' during this loop.
 1904          */
 1905         for (i = 1; i <= w_max_used_index; i++) {
 1906                 if ((w_rmatrix[i][pi] & WITNESS_ANCESTOR_MASK) == 0 && 
 1907                     (i != pi))
 1908                         continue;
 1909 
 1910                 /* Find each descendant of 'i' and mark it as a descendant. */
 1911                 for (j = 1; j <= w_max_used_index; j++) {
 1912 
 1913                         /* 
 1914                          * Skip children that are already marked as
 1915                          * descendants of 'i'.
 1916                          */
 1917                         if (w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK)
 1918                                 continue;
 1919 
 1920                         /*
 1921                          * We are only interested in descendants of 'ci'. Note
 1922                          * that 'ci' itself is counted as a descendant of 'ci'.
 1923                          */
 1924                         if ((w_rmatrix[ci][j] & WITNESS_ANCESTOR_MASK) == 0 && 
 1925                             (j != ci))
 1926                                 continue;
 1927                         w_rmatrix[i][j] |= WITNESS_ANCESTOR;
 1928                         w_rmatrix[j][i] |= WITNESS_DESCENDANT;
 1929                         w_data[i].w_num_descendants++;
 1930                         w_data[j].w_num_ancestors++;
 1931 
 1932                         /* 
 1933                          * Make sure we aren't marking a node as both an
 1934                          * ancestor and descendant. We should have caught 
 1935                          * this as a lock order reversal earlier.
 1936                          */
 1937                         if ((w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) &&
 1938                             (w_rmatrix[i][j] & WITNESS_DESCENDANT_MASK)) {
 1939                                 printf("witness rmatrix paradox! [%d][%d]=%d "
 1940                                     "both ancestor and descendant\n",
 1941                                     i, j, w_rmatrix[i][j]); 
 1942                                 kdb_backtrace();
 1943                                 printf("Witness disabled.\n");
 1944                                 witness_watch = -1;
 1945                         }
 1946                         if ((w_rmatrix[j][i] & WITNESS_ANCESTOR_MASK) &&
 1947                             (w_rmatrix[j][i] & WITNESS_DESCENDANT_MASK)) {
 1948                                 printf("witness rmatrix paradox! [%d][%d]=%d "
 1949                                     "both ancestor and descendant\n",
 1950                                     j, i, w_rmatrix[j][i]); 
 1951                                 kdb_backtrace();
 1952                                 printf("Witness disabled.\n");
 1953                                 witness_watch = -1;
 1954                         }
 1955                 }
 1956         }
 1957 }
 1958 
 1959 static void
 1960 itismychild(struct witness *parent, struct witness *child)
 1961 {
 1962         int unlocked;
 1963 
 1964         MPASS(child != NULL && parent != NULL);
 1965         if (witness_cold == 0)
 1966                 mtx_assert(&w_mtx, MA_OWNED);
 1967 
 1968         if (!witness_lock_type_equal(parent, child)) {
 1969                 if (witness_cold == 0) {
 1970                         unlocked = 1;
 1971                         mtx_unlock_spin(&w_mtx);
 1972                 } else {
 1973                         unlocked = 0;
 1974                 }
 1975                 kassert_panic(
 1976                     "%s: parent \"%s\" (%s) and child \"%s\" (%s) are not "
 1977                     "the same lock type", __func__, parent->w_name,
 1978                     parent->w_class->lc_name, child->w_name,
 1979                     child->w_class->lc_name);
 1980                 if (unlocked)
 1981                         mtx_lock_spin(&w_mtx);
 1982         }
 1983         adopt(parent, child);
 1984 }
 1985 
 1986 /*
 1987  * Generic code for the isitmy*() functions. The rmask parameter is the
 1988  * expected relationship of w1 to w2.
 1989  */
 1990 static int
 1991 _isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname)
 1992 {
 1993         unsigned char r1, r2;
 1994         int i1, i2;
 1995 
 1996         i1 = w1->w_index;
 1997         i2 = w2->w_index;
 1998         WITNESS_INDEX_ASSERT(i1);
 1999         WITNESS_INDEX_ASSERT(i2);
 2000         r1 = w_rmatrix[i1][i2] & WITNESS_RELATED_MASK;
 2001         r2 = w_rmatrix[i2][i1] & WITNESS_RELATED_MASK;
 2002 
 2003         /* The flags on one better be the inverse of the flags on the other */
 2004         if (!((WITNESS_ATOD(r1) == r2 && WITNESS_DTOA(r2) == r1) ||
 2005             (WITNESS_DTOA(r1) == r2 && WITNESS_ATOD(r2) == r1))) {
 2006                 /* Don't squawk if we're potentially racing with an update. */
 2007                 if (!mtx_owned(&w_mtx))
 2008                         return (0);
 2009                 printf("%s: rmatrix mismatch between %s (index %d) and %s "
 2010                     "(index %d): w_rmatrix[%d][%d] == %hhx but "
 2011                     "w_rmatrix[%d][%d] == %hhx\n",
 2012                     fname, w1->w_name, i1, w2->w_name, i2, i1, i2, r1,
 2013                     i2, i1, r2);
 2014                 kdb_backtrace();
 2015                 printf("Witness disabled.\n");
 2016                 witness_watch = -1;
 2017         }
 2018         return (r1 & rmask);
 2019 }
 2020 
 2021 /*
 2022  * Checks if @child is a direct child of @parent.
 2023  */
 2024 static int
 2025 isitmychild(struct witness *parent, struct witness *child)
 2026 {
 2027 
 2028         return (_isitmyx(parent, child, WITNESS_PARENT, __func__));
 2029 }
 2030 
 2031 /*
 2032  * Checks if @descendant is a direct or inderect descendant of @ancestor.
 2033  */
 2034 static int
 2035 isitmydescendant(struct witness *ancestor, struct witness *descendant)
 2036 {
 2037 
 2038         return (_isitmyx(ancestor, descendant, WITNESS_ANCESTOR_MASK,
 2039             __func__));
 2040 }
 2041 
 2042 #ifdef BLESSING
 2043 static int
 2044 blessed(struct witness *w1, struct witness *w2)
 2045 {
 2046         int i;
 2047         struct witness_blessed *b;
 2048 
 2049         for (i = 0; i < blessed_count; i++) {
 2050                 b = &blessed_list[i];
 2051                 if (strcmp(w1->w_name, b->b_lock1) == 0) {
 2052                         if (strcmp(w2->w_name, b->b_lock2) == 0)
 2053                                 return (1);
 2054                         continue;
 2055                 }
 2056                 if (strcmp(w1->w_name, b->b_lock2) == 0)
 2057                         if (strcmp(w2->w_name, b->b_lock1) == 0)
 2058                                 return (1);
 2059         }
 2060         return (0);
 2061 }
 2062 #endif
 2063 
 2064 static struct witness *
 2065 witness_get(void)
 2066 {
 2067         struct witness *w;
 2068         int index;
 2069 
 2070         if (witness_cold == 0)
 2071                 mtx_assert(&w_mtx, MA_OWNED);
 2072 
 2073         if (witness_watch == -1) {
 2074                 mtx_unlock_spin(&w_mtx);
 2075                 return (NULL);
 2076         }
 2077         if (STAILQ_EMPTY(&w_free)) {
 2078                 witness_watch = -1;
 2079                 mtx_unlock_spin(&w_mtx);
 2080                 printf("WITNESS: unable to allocate a new witness object\n");
 2081                 return (NULL);
 2082         }
 2083         w = STAILQ_FIRST(&w_free);
 2084         STAILQ_REMOVE_HEAD(&w_free, w_list);
 2085         w_free_cnt--;
 2086         index = w->w_index;
 2087         MPASS(index > 0 && index == w_max_used_index+1 &&
 2088             index < WITNESS_COUNT);
 2089         bzero(w, sizeof(*w));
 2090         w->w_index = index;
 2091         if (index > w_max_used_index)
 2092                 w_max_used_index = index;
 2093         return (w);
 2094 }
 2095 
 2096 static void
 2097 witness_free(struct witness *w)
 2098 {
 2099 
 2100         STAILQ_INSERT_HEAD(&w_free, w, w_list);
 2101         w_free_cnt++;
 2102 }
 2103 
 2104 static struct lock_list_entry *
 2105 witness_lock_list_get(void)
 2106 {
 2107         struct lock_list_entry *lle;
 2108 
 2109         if (witness_watch == -1)
 2110                 return (NULL);
 2111         mtx_lock_spin(&w_mtx);
 2112         lle = w_lock_list_free;
 2113         if (lle == NULL) {
 2114                 witness_watch = -1;
 2115                 mtx_unlock_spin(&w_mtx);
 2116                 printf("%s: witness exhausted\n", __func__);
 2117                 return (NULL);
 2118         }
 2119         w_lock_list_free = lle->ll_next;
 2120         mtx_unlock_spin(&w_mtx);
 2121         bzero(lle, sizeof(*lle));
 2122         return (lle);
 2123 }
 2124                 
 2125 static void
 2126 witness_lock_list_free(struct lock_list_entry *lle)
 2127 {
 2128 
 2129         mtx_lock_spin(&w_mtx);
 2130         lle->ll_next = w_lock_list_free;
 2131         w_lock_list_free = lle;
 2132         mtx_unlock_spin(&w_mtx);
 2133 }
 2134 
 2135 static struct lock_instance *
 2136 find_instance(struct lock_list_entry *list, const struct lock_object *lock)
 2137 {
 2138         struct lock_list_entry *lle;
 2139         struct lock_instance *instance;
 2140         int i;
 2141 
 2142         for (lle = list; lle != NULL; lle = lle->ll_next)
 2143                 for (i = lle->ll_count - 1; i >= 0; i--) {
 2144                         instance = &lle->ll_children[i];
 2145                         if (instance->li_lock == lock)
 2146                                 return (instance);
 2147                 }
 2148         return (NULL);
 2149 }
 2150 
 2151 static void
 2152 witness_list_lock(struct lock_instance *instance,
 2153     int (*prnt)(const char *fmt, ...))
 2154 {
 2155         struct lock_object *lock;
 2156 
 2157         lock = instance->li_lock;
 2158         prnt("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ?
 2159             "exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name);
 2160         if (lock->lo_witness->w_name != lock->lo_name)
 2161                 prnt(" (%s)", lock->lo_witness->w_name);
 2162         prnt(" r = %d (%p) locked @ %s:%d\n",
 2163             instance->li_flags & LI_RECURSEMASK, lock,
 2164             fixup_filename(instance->li_file), instance->li_line);
 2165 }
 2166 
 2167 #ifdef DDB
 2168 static int
 2169 witness_thread_has_locks(struct thread *td)
 2170 {
 2171 
 2172         if (td->td_sleeplocks == NULL)
 2173                 return (0);
 2174         return (td->td_sleeplocks->ll_count != 0);
 2175 }
 2176 
 2177 static int
 2178 witness_proc_has_locks(struct proc *p)
 2179 {
 2180         struct thread *td;
 2181 
 2182         FOREACH_THREAD_IN_PROC(p, td) {
 2183                 if (witness_thread_has_locks(td))
 2184                         return (1);
 2185         }
 2186         return (0);
 2187 }
 2188 #endif
 2189 
 2190 int
 2191 witness_list_locks(struct lock_list_entry **lock_list,
 2192     int (*prnt)(const char *fmt, ...))
 2193 {
 2194         struct lock_list_entry *lle;
 2195         int i, nheld;
 2196 
 2197         nheld = 0;
 2198         for (lle = *lock_list; lle != NULL; lle = lle->ll_next)
 2199                 for (i = lle->ll_count - 1; i >= 0; i--) {
 2200                         witness_list_lock(&lle->ll_children[i], prnt);
 2201                         nheld++;
 2202                 }
 2203         return (nheld);
 2204 }
 2205 
 2206 /*
 2207  * This is a bit risky at best.  We call this function when we have timed
 2208  * out acquiring a spin lock, and we assume that the other CPU is stuck
 2209  * with this lock held.  So, we go groveling around in the other CPU's
 2210  * per-cpu data to try to find the lock instance for this spin lock to
 2211  * see when it was last acquired.
 2212  */
 2213 void
 2214 witness_display_spinlock(struct lock_object *lock, struct thread *owner,
 2215     int (*prnt)(const char *fmt, ...))
 2216 {
 2217         struct lock_instance *instance;
 2218         struct pcpu *pc;
 2219 
 2220         if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU)
 2221                 return;
 2222         pc = pcpu_find(owner->td_oncpu);
 2223         instance = find_instance(pc->pc_spinlocks, lock);
 2224         if (instance != NULL)
 2225                 witness_list_lock(instance, prnt);
 2226 }
 2227 
 2228 void
 2229 witness_save(struct lock_object *lock, const char **filep, int *linep)
 2230 {
 2231         struct lock_list_entry *lock_list;
 2232         struct lock_instance *instance;
 2233         struct lock_class *class;
 2234 
 2235         /*
 2236          * This function is used independently in locking code to deal with
 2237          * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
 2238          * is gone.
 2239          */
 2240         if (SCHEDULER_STOPPED())
 2241                 return;
 2242         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2243         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2244                 return;
 2245         class = LOCK_CLASS(lock);
 2246         if (class->lc_flags & LC_SLEEPLOCK)
 2247                 lock_list = curthread->td_sleeplocks;
 2248         else {
 2249                 if (witness_skipspin)
 2250                         return;
 2251                 lock_list = PCPU_GET(spinlocks);
 2252         }
 2253         instance = find_instance(lock_list, lock);
 2254         if (instance == NULL) {
 2255                 kassert_panic("%s: lock (%s) %s not locked", __func__,
 2256                     class->lc_name, lock->lo_name);
 2257                 return;
 2258         }
 2259         *filep = instance->li_file;
 2260         *linep = instance->li_line;
 2261 }
 2262 
 2263 void
 2264 witness_restore(struct lock_object *lock, const char *file, int line)
 2265 {
 2266         struct lock_list_entry *lock_list;
 2267         struct lock_instance *instance;
 2268         struct lock_class *class;
 2269 
 2270         /*
 2271          * This function is used independently in locking code to deal with
 2272          * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
 2273          * is gone.
 2274          */
 2275         if (SCHEDULER_STOPPED())
 2276                 return;
 2277         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2278         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2279                 return;
 2280         class = LOCK_CLASS(lock);
 2281         if (class->lc_flags & LC_SLEEPLOCK)
 2282                 lock_list = curthread->td_sleeplocks;
 2283         else {
 2284                 if (witness_skipspin)
 2285                         return;
 2286                 lock_list = PCPU_GET(spinlocks);
 2287         }
 2288         instance = find_instance(lock_list, lock);
 2289         if (instance == NULL)
 2290                 kassert_panic("%s: lock (%s) %s not locked", __func__,
 2291                     class->lc_name, lock->lo_name);
 2292         lock->lo_witness->w_file = file;
 2293         lock->lo_witness->w_line = line;
 2294         if (instance == NULL)
 2295                 return;
 2296         instance->li_file = file;
 2297         instance->li_line = line;
 2298 }
 2299 
 2300 void
 2301 witness_assert(const struct lock_object *lock, int flags, const char *file,
 2302     int line)
 2303 {
 2304 #ifdef INVARIANT_SUPPORT
 2305         struct lock_instance *instance;
 2306         struct lock_class *class;
 2307 
 2308         if (lock->lo_witness == NULL || witness_watch < 1 || panicstr != NULL)
 2309                 return;
 2310         class = LOCK_CLASS(lock);
 2311         if ((class->lc_flags & LC_SLEEPLOCK) != 0)
 2312                 instance = find_instance(curthread->td_sleeplocks, lock);
 2313         else if ((class->lc_flags & LC_SPINLOCK) != 0)
 2314                 instance = find_instance(PCPU_GET(spinlocks), lock);
 2315         else {
 2316                 kassert_panic("Lock (%s) %s is not sleep or spin!",
 2317                     class->lc_name, lock->lo_name);
 2318                 return;
 2319         }
 2320         switch (flags) {
 2321         case LA_UNLOCKED:
 2322                 if (instance != NULL)
 2323                         kassert_panic("Lock (%s) %s locked @ %s:%d.",
 2324                             class->lc_name, lock->lo_name,
 2325                             fixup_filename(file), line);
 2326                 break;
 2327         case LA_LOCKED:
 2328         case LA_LOCKED | LA_RECURSED:
 2329         case LA_LOCKED | LA_NOTRECURSED:
 2330         case LA_SLOCKED:
 2331         case LA_SLOCKED | LA_RECURSED:
 2332         case LA_SLOCKED | LA_NOTRECURSED:
 2333         case LA_XLOCKED:
 2334         case LA_XLOCKED | LA_RECURSED:
 2335         case LA_XLOCKED | LA_NOTRECURSED:
 2336                 if (instance == NULL) {
 2337                         kassert_panic("Lock (%s) %s not locked @ %s:%d.",
 2338                             class->lc_name, lock->lo_name,
 2339                             fixup_filename(file), line);
 2340                         break;
 2341                 }
 2342                 if ((flags & LA_XLOCKED) != 0 &&
 2343                     (instance->li_flags & LI_EXCLUSIVE) == 0)
 2344                         kassert_panic(
 2345                             "Lock (%s) %s not exclusively locked @ %s:%d.",
 2346                             class->lc_name, lock->lo_name,
 2347                             fixup_filename(file), line);
 2348                 if ((flags & LA_SLOCKED) != 0 &&
 2349                     (instance->li_flags & LI_EXCLUSIVE) != 0)
 2350                         kassert_panic(
 2351                             "Lock (%s) %s exclusively locked @ %s:%d.",
 2352                             class->lc_name, lock->lo_name,
 2353                             fixup_filename(file), line);
 2354                 if ((flags & LA_RECURSED) != 0 &&
 2355                     (instance->li_flags & LI_RECURSEMASK) == 0)
 2356                         kassert_panic("Lock (%s) %s not recursed @ %s:%d.",
 2357                             class->lc_name, lock->lo_name,
 2358                             fixup_filename(file), line);
 2359                 if ((flags & LA_NOTRECURSED) != 0 &&
 2360                     (instance->li_flags & LI_RECURSEMASK) != 0)
 2361                         kassert_panic("Lock (%s) %s recursed @ %s:%d.",
 2362                             class->lc_name, lock->lo_name,
 2363                             fixup_filename(file), line);
 2364                 break;
 2365         default:
 2366                 kassert_panic("Invalid lock assertion at %s:%d.",
 2367                     fixup_filename(file), line);
 2368 
 2369         }
 2370 #endif  /* INVARIANT_SUPPORT */
 2371 }
 2372 
 2373 static void
 2374 witness_setflag(struct lock_object *lock, int flag, int set)
 2375 {
 2376         struct lock_list_entry *lock_list;
 2377         struct lock_instance *instance;
 2378         struct lock_class *class;
 2379 
 2380         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2381                 return;
 2382         class = LOCK_CLASS(lock);
 2383         if (class->lc_flags & LC_SLEEPLOCK)
 2384                 lock_list = curthread->td_sleeplocks;
 2385         else {
 2386                 if (witness_skipspin)
 2387                         return;
 2388                 lock_list = PCPU_GET(spinlocks);
 2389         }
 2390         instance = find_instance(lock_list, lock);
 2391         if (instance == NULL) {
 2392                 kassert_panic("%s: lock (%s) %s not locked", __func__,
 2393                     class->lc_name, lock->lo_name);
 2394                 return;
 2395         }
 2396 
 2397         if (set)
 2398                 instance->li_flags |= flag;
 2399         else
 2400                 instance->li_flags &= ~flag;
 2401 }
 2402 
 2403 void
 2404 witness_norelease(struct lock_object *lock)
 2405 {
 2406 
 2407         witness_setflag(lock, LI_NORELEASE, 1);
 2408 }
 2409 
 2410 void
 2411 witness_releaseok(struct lock_object *lock)
 2412 {
 2413 
 2414         witness_setflag(lock, LI_NORELEASE, 0);
 2415 }
 2416 
 2417 #ifdef DDB
 2418 static void
 2419 witness_ddb_list(struct thread *td)
 2420 {
 2421 
 2422         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2423         KASSERT(kdb_active, ("%s: not in the debugger", __func__));
 2424 
 2425         if (witness_watch < 1)
 2426                 return;
 2427 
 2428         witness_list_locks(&td->td_sleeplocks, db_printf);
 2429 
 2430         /*
 2431          * We only handle spinlocks if td == curthread.  This is somewhat broken
 2432          * if td is currently executing on some other CPU and holds spin locks
 2433          * as we won't display those locks.  If we had a MI way of getting
 2434          * the per-cpu data for a given cpu then we could use
 2435          * td->td_oncpu to get the list of spinlocks for this thread
 2436          * and "fix" this.
 2437          *
 2438          * That still wouldn't really fix this unless we locked the scheduler
 2439          * lock or stopped the other CPU to make sure it wasn't changing the
 2440          * list out from under us.  It is probably best to just not try to
 2441          * handle threads on other CPU's for now.
 2442          */
 2443         if (td == curthread && PCPU_GET(spinlocks) != NULL)
 2444                 witness_list_locks(PCPU_PTR(spinlocks), db_printf);
 2445 }
 2446 
 2447 DB_SHOW_COMMAND(locks, db_witness_list)
 2448 {
 2449         struct thread *td;
 2450 
 2451         if (have_addr)
 2452                 td = db_lookup_thread(addr, TRUE);
 2453         else
 2454                 td = kdb_thread;
 2455         witness_ddb_list(td);
 2456 }
 2457 
 2458 DB_SHOW_ALL_COMMAND(locks, db_witness_list_all)
 2459 {
 2460         struct thread *td;
 2461         struct proc *p;
 2462 
 2463         /*
 2464          * It would be nice to list only threads and processes that actually
 2465          * held sleep locks, but that information is currently not exported
 2466          * by WITNESS.
 2467          */
 2468         FOREACH_PROC_IN_SYSTEM(p) {
 2469                 if (!witness_proc_has_locks(p))
 2470                         continue;
 2471                 FOREACH_THREAD_IN_PROC(p, td) {
 2472                         if (!witness_thread_has_locks(td))
 2473                                 continue;
 2474                         db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid,
 2475                             p->p_comm, td, td->td_tid);
 2476                         witness_ddb_list(td);
 2477                         if (db_pager_quit)
 2478                                 return;
 2479                 }
 2480         }
 2481 }
 2482 DB_SHOW_ALIAS(alllocks, db_witness_list_all)
 2483 
 2484 DB_SHOW_COMMAND(witness, db_witness_display)
 2485 {
 2486 
 2487         witness_ddb_display(db_printf);
 2488 }
 2489 #endif
 2490 
 2491 static int
 2492 sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS)
 2493 {
 2494         struct witness_lock_order_data *data1, *data2, *tmp_data1, *tmp_data2;
 2495         struct witness *tmp_w1, *tmp_w2, *w1, *w2;
 2496         struct sbuf *sb;
 2497         u_int w_rmatrix1, w_rmatrix2;
 2498         int error, generation, i, j;
 2499 
 2500         tmp_data1 = NULL;
 2501         tmp_data2 = NULL;
 2502         tmp_w1 = NULL;
 2503         tmp_w2 = NULL;
 2504         if (witness_watch < 1) {
 2505                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
 2506                 return (error);
 2507         }
 2508         if (witness_cold) {
 2509                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
 2510                 return (error);
 2511         }
 2512         error = 0;
 2513         sb = sbuf_new(NULL, NULL, BADSTACK_SBUF_SIZE, SBUF_AUTOEXTEND);
 2514         if (sb == NULL)
 2515                 return (ENOMEM);
 2516 
 2517         /* Allocate and init temporary storage space. */
 2518         tmp_w1 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
 2519         tmp_w2 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
 2520         tmp_data1 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 
 2521             M_WAITOK | M_ZERO);
 2522         tmp_data2 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 
 2523             M_WAITOK | M_ZERO);
 2524         stack_zero(&tmp_data1->wlod_stack);
 2525         stack_zero(&tmp_data2->wlod_stack);
 2526 
 2527 restart:
 2528         mtx_lock_spin(&w_mtx);
 2529         generation = w_generation;
 2530         mtx_unlock_spin(&w_mtx);
 2531         sbuf_printf(sb, "Number of known direct relationships is %d\n",
 2532             w_lohash.wloh_count);
 2533         for (i = 1; i < w_max_used_index; i++) {
 2534                 mtx_lock_spin(&w_mtx);
 2535                 if (generation != w_generation) {
 2536                         mtx_unlock_spin(&w_mtx);
 2537 
 2538                         /* The graph has changed, try again. */
 2539                         req->oldidx = 0;
 2540                         sbuf_clear(sb);
 2541                         goto restart;
 2542                 }
 2543 
 2544                 w1 = &w_data[i];
 2545                 if (w1->w_reversed == 0) {
 2546                         mtx_unlock_spin(&w_mtx);
 2547                         continue;
 2548                 }
 2549 
 2550                 /* Copy w1 locally so we can release the spin lock. */
 2551                 *tmp_w1 = *w1;
 2552                 mtx_unlock_spin(&w_mtx);
 2553 
 2554                 if (tmp_w1->w_reversed == 0)
 2555                         continue;
 2556                 for (j = 1; j < w_max_used_index; j++) {
 2557                         if ((w_rmatrix[i][j] & WITNESS_REVERSAL) == 0 || i > j)
 2558                                 continue;
 2559 
 2560                         mtx_lock_spin(&w_mtx);
 2561                         if (generation != w_generation) {
 2562                                 mtx_unlock_spin(&w_mtx);
 2563 
 2564                                 /* The graph has changed, try again. */
 2565                                 req->oldidx = 0;
 2566                                 sbuf_clear(sb);
 2567                                 goto restart;
 2568                         }
 2569 
 2570                         w2 = &w_data[j];
 2571                         data1 = witness_lock_order_get(w1, w2);
 2572                         data2 = witness_lock_order_get(w2, w1);
 2573 
 2574                         /*
 2575                          * Copy information locally so we can release the
 2576                          * spin lock.
 2577                          */
 2578                         *tmp_w2 = *w2;
 2579                         w_rmatrix1 = (unsigned int)w_rmatrix[i][j];
 2580                         w_rmatrix2 = (unsigned int)w_rmatrix[j][i];
 2581 
 2582                         if (data1) {
 2583                                 stack_zero(&tmp_data1->wlod_stack);
 2584                                 stack_copy(&data1->wlod_stack,
 2585                                     &tmp_data1->wlod_stack);
 2586                         }
 2587                         if (data2 && data2 != data1) {
 2588                                 stack_zero(&tmp_data2->wlod_stack);
 2589                                 stack_copy(&data2->wlod_stack,
 2590                                     &tmp_data2->wlod_stack);
 2591                         }
 2592                         mtx_unlock_spin(&w_mtx);
 2593 
 2594                         sbuf_printf(sb,
 2595             "\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n",
 2596                             tmp_w1->w_name, tmp_w1->w_class->lc_name, 
 2597                             tmp_w2->w_name, tmp_w2->w_class->lc_name);
 2598 #if 0
 2599                         sbuf_printf(sb,
 2600                         "w_rmatrix[%s][%s] == %x, w_rmatrix[%s][%s] == %x\n",
 2601                             tmp_w1->name, tmp_w2->w_name, w_rmatrix1,
 2602                             tmp_w2->name, tmp_w1->w_name, w_rmatrix2);
 2603 #endif
 2604                         if (data1) {
 2605                                 sbuf_printf(sb,
 2606                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
 2607                                     tmp_w1->w_name, tmp_w1->w_class->lc_name, 
 2608                                     tmp_w2->w_name, tmp_w2->w_class->lc_name);
 2609                                 stack_sbuf_print(sb, &tmp_data1->wlod_stack);
 2610                                 sbuf_printf(sb, "\n");
 2611                         }
 2612                         if (data2 && data2 != data1) {
 2613                                 sbuf_printf(sb,
 2614                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
 2615                                     tmp_w2->w_name, tmp_w2->w_class->lc_name, 
 2616                                     tmp_w1->w_name, tmp_w1->w_class->lc_name);
 2617                                 stack_sbuf_print(sb, &tmp_data2->wlod_stack);
 2618                                 sbuf_printf(sb, "\n");
 2619                         }
 2620                 }
 2621         }
 2622         mtx_lock_spin(&w_mtx);
 2623         if (generation != w_generation) {
 2624                 mtx_unlock_spin(&w_mtx);
 2625 
 2626                 /*
 2627                  * The graph changed while we were printing stack data,
 2628                  * try again.
 2629                  */
 2630                 req->oldidx = 0;
 2631                 sbuf_clear(sb);
 2632                 goto restart;
 2633         }
 2634         mtx_unlock_spin(&w_mtx);
 2635 
 2636         /* Free temporary storage space. */
 2637         free(tmp_data1, M_TEMP);
 2638         free(tmp_data2, M_TEMP);
 2639         free(tmp_w1, M_TEMP);
 2640         free(tmp_w2, M_TEMP);
 2641 
 2642         sbuf_finish(sb);
 2643         error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
 2644         sbuf_delete(sb);
 2645 
 2646         return (error);
 2647 }
 2648 
 2649 static int
 2650 sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS)
 2651 {
 2652         struct witness *w;
 2653         struct sbuf *sb;
 2654         int error;
 2655 
 2656         if (witness_watch < 1) {
 2657                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
 2658                 return (error);
 2659         }
 2660         if (witness_cold) {
 2661                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
 2662                 return (error);
 2663         }
 2664         error = 0;
 2665 
 2666         error = sysctl_wire_old_buffer(req, 0);
 2667         if (error != 0)
 2668                 return (error);
 2669         sb = sbuf_new_for_sysctl(NULL, NULL, FULLGRAPH_SBUF_SIZE, req);
 2670         if (sb == NULL)
 2671                 return (ENOMEM);
 2672         sbuf_printf(sb, "\n");
 2673 
 2674         mtx_lock_spin(&w_mtx);
 2675         STAILQ_FOREACH(w, &w_all, w_list)
 2676                 w->w_displayed = 0;
 2677         STAILQ_FOREACH(w, &w_all, w_list)
 2678                 witness_add_fullgraph(sb, w);
 2679         mtx_unlock_spin(&w_mtx);
 2680 
 2681         /*
 2682          * Close the sbuf and return to userland.
 2683          */
 2684         error = sbuf_finish(sb);
 2685         sbuf_delete(sb);
 2686 
 2687         return (error);
 2688 }
 2689 
 2690 static int
 2691 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS)
 2692 {
 2693         int error, value;
 2694 
 2695         value = witness_watch;
 2696         error = sysctl_handle_int(oidp, &value, 0, req);
 2697         if (error != 0 || req->newptr == NULL)
 2698                 return (error);
 2699         if (value > 1 || value < -1 ||
 2700             (witness_watch == -1 && value != witness_watch))
 2701                 return (EINVAL);
 2702         witness_watch = value;
 2703         return (0);
 2704 }
 2705 
 2706 static void
 2707 witness_add_fullgraph(struct sbuf *sb, struct witness *w)
 2708 {
 2709         int i;
 2710 
 2711         if (w->w_displayed != 0 || (w->w_file == NULL && w->w_line == 0))
 2712                 return;
 2713         w->w_displayed = 1;
 2714 
 2715         WITNESS_INDEX_ASSERT(w->w_index);
 2716         for (i = 1; i <= w_max_used_index; i++) {
 2717                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) {
 2718                         sbuf_printf(sb, "\"%s\",\"%s\"\n", w->w_name,
 2719                             w_data[i].w_name);
 2720                         witness_add_fullgraph(sb, &w_data[i]);
 2721                 }
 2722         }
 2723 }
 2724 
 2725 /*
 2726  * A simple hash function. Takes a key pointer and a key size. If size == 0,
 2727  * interprets the key as a string and reads until the null
 2728  * terminator. Otherwise, reads the first size bytes. Returns an unsigned 32-bit
 2729  * hash value computed from the key.
 2730  */
 2731 static uint32_t
 2732 witness_hash_djb2(const uint8_t *key, uint32_t size)
 2733 {
 2734         unsigned int hash = 5381;
 2735         int i;
 2736 
 2737         /* hash = hash * 33 + key[i] */
 2738         if (size)
 2739                 for (i = 0; i < size; i++)
 2740                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
 2741         else
 2742                 for (i = 0; key[i] != 0; i++)
 2743                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
 2744 
 2745         return (hash);
 2746 }
 2747 
 2748 
 2749 /*
 2750  * Initializes the two witness hash tables. Called exactly once from
 2751  * witness_initialize().
 2752  */
 2753 static void
 2754 witness_init_hash_tables(void)
 2755 {
 2756         int i;
 2757 
 2758         MPASS(witness_cold);
 2759 
 2760         /* Initialize the hash tables. */
 2761         for (i = 0; i < WITNESS_HASH_SIZE; i++)
 2762                 w_hash.wh_array[i] = NULL;
 2763 
 2764         w_hash.wh_size = WITNESS_HASH_SIZE;
 2765         w_hash.wh_count = 0;
 2766 
 2767         /* Initialize the lock order data hash. */
 2768         w_lofree = NULL;
 2769         for (i = 0; i < WITNESS_LO_DATA_COUNT; i++) {
 2770                 memset(&w_lodata[i], 0, sizeof(w_lodata[i]));
 2771                 w_lodata[i].wlod_next = w_lofree;
 2772                 w_lofree = &w_lodata[i];
 2773         }
 2774         w_lohash.wloh_size = WITNESS_LO_HASH_SIZE;
 2775         w_lohash.wloh_count = 0;
 2776         for (i = 0; i < WITNESS_LO_HASH_SIZE; i++)
 2777                 w_lohash.wloh_array[i] = NULL;
 2778 }
 2779 
 2780 static struct witness *
 2781 witness_hash_get(const char *key)
 2782 {
 2783         struct witness *w;
 2784         uint32_t hash;
 2785         
 2786         MPASS(key != NULL);
 2787         if (witness_cold == 0)
 2788                 mtx_assert(&w_mtx, MA_OWNED);
 2789         hash = witness_hash_djb2(key, 0) % w_hash.wh_size;
 2790         w = w_hash.wh_array[hash];
 2791         while (w != NULL) {
 2792                 if (strcmp(w->w_name, key) == 0)
 2793                         goto out;
 2794                 w = w->w_hash_next;
 2795         }
 2796 
 2797 out:
 2798         return (w);
 2799 }
 2800 
 2801 static void
 2802 witness_hash_put(struct witness *w)
 2803 {
 2804         uint32_t hash;
 2805 
 2806         MPASS(w != NULL);
 2807         MPASS(w->w_name != NULL);
 2808         if (witness_cold == 0)
 2809                 mtx_assert(&w_mtx, MA_OWNED);
 2810         KASSERT(witness_hash_get(w->w_name) == NULL,
 2811             ("%s: trying to add a hash entry that already exists!", __func__));
 2812         KASSERT(w->w_hash_next == NULL,
 2813             ("%s: w->w_hash_next != NULL", __func__));
 2814 
 2815         hash = witness_hash_djb2(w->w_name, 0) % w_hash.wh_size;
 2816         w->w_hash_next = w_hash.wh_array[hash];
 2817         w_hash.wh_array[hash] = w;
 2818         w_hash.wh_count++;
 2819 }
 2820 
 2821 
 2822 static struct witness_lock_order_data *
 2823 witness_lock_order_get(struct witness *parent, struct witness *child)
 2824 {
 2825         struct witness_lock_order_data *data = NULL;
 2826         struct witness_lock_order_key key;
 2827         unsigned int hash;
 2828 
 2829         MPASS(parent != NULL && child != NULL);
 2830         key.from = parent->w_index;
 2831         key.to = child->w_index;
 2832         WITNESS_INDEX_ASSERT(key.from);
 2833         WITNESS_INDEX_ASSERT(key.to);
 2834         if ((w_rmatrix[parent->w_index][child->w_index]
 2835             & WITNESS_LOCK_ORDER_KNOWN) == 0)
 2836                 goto out;
 2837 
 2838         hash = witness_hash_djb2((const char*)&key,
 2839             sizeof(key)) % w_lohash.wloh_size;
 2840         data = w_lohash.wloh_array[hash];
 2841         while (data != NULL) {
 2842                 if (witness_lock_order_key_equal(&data->wlod_key, &key))
 2843                         break;
 2844                 data = data->wlod_next;
 2845         }
 2846 
 2847 out:
 2848         return (data);
 2849 }
 2850 
 2851 /*
 2852  * Verify that parent and child have a known relationship, are not the same,
 2853  * and child is actually a child of parent.  This is done without w_mtx
 2854  * to avoid contention in the common case.
 2855  */
 2856 static int
 2857 witness_lock_order_check(struct witness *parent, struct witness *child)
 2858 {
 2859 
 2860         if (parent != child &&
 2861             w_rmatrix[parent->w_index][child->w_index]
 2862             & WITNESS_LOCK_ORDER_KNOWN &&
 2863             isitmychild(parent, child))
 2864                 return (1);
 2865 
 2866         return (0);
 2867 }
 2868 
 2869 static int
 2870 witness_lock_order_add(struct witness *parent, struct witness *child)
 2871 {
 2872         struct witness_lock_order_data *data = NULL;
 2873         struct witness_lock_order_key key;
 2874         unsigned int hash;
 2875         
 2876         MPASS(parent != NULL && child != NULL);
 2877         key.from = parent->w_index;
 2878         key.to = child->w_index;
 2879         WITNESS_INDEX_ASSERT(key.from);
 2880         WITNESS_INDEX_ASSERT(key.to);
 2881         if (w_rmatrix[parent->w_index][child->w_index]
 2882             & WITNESS_LOCK_ORDER_KNOWN)
 2883                 return (1);
 2884 
 2885         hash = witness_hash_djb2((const char*)&key,
 2886             sizeof(key)) % w_lohash.wloh_size;
 2887         w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN;
 2888         data = w_lofree;
 2889         if (data == NULL)
 2890                 return (0);
 2891         w_lofree = data->wlod_next;
 2892         data->wlod_next = w_lohash.wloh_array[hash];
 2893         data->wlod_key = key;
 2894         w_lohash.wloh_array[hash] = data;
 2895         w_lohash.wloh_count++;
 2896         stack_zero(&data->wlod_stack);
 2897         stack_save(&data->wlod_stack);
 2898         return (1);
 2899 }
 2900 
 2901 /* Call this whenever the structure of the witness graph changes. */
 2902 static void
 2903 witness_increment_graph_generation(void)
 2904 {
 2905 
 2906         if (witness_cold == 0)
 2907                 mtx_assert(&w_mtx, MA_OWNED);
 2908         w_generation++;
 2909 }
 2910 
 2911 #ifdef KDB
 2912 static void
 2913 _witness_debugger(int cond, const char *msg)
 2914 {
 2915 
 2916         if (witness_trace && cond)
 2917                 kdb_backtrace();
 2918         if (witness_kdb && cond)
 2919                 kdb_enter(KDB_WHY_WITNESS, msg);
 2920 }
 2921 #endif

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