The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_witness.c

Version: -  FREEBSD  -  FREEBSD-13-STABLE  -  FREEBSD-13-0  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  l41  -  OPENBSD  -  linux-2.6  -  MK84  -  PLAN9  -  xnu-8792 
SearchContext: -  none  -  3  -  10 

    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("$FreeBSD$");
   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/syslog.h>
  110 #include <sys/systm.h>
  111 
  112 #ifdef DDB
  113 #include <ddb/ddb.h>
  114 #endif
  115 
  116 #include <machine/stdarg.h>
  117 
  118 #if !defined(DDB) && !defined(STACK)
  119 #error "DDB or STACK options are required for WITNESS"
  120 #endif
  121 
  122 /* Note that these traces do not work with KTR_ALQ. */
  123 #if 0
  124 #define KTR_WITNESS     KTR_SUBSYS
  125 #else
  126 #define KTR_WITNESS     0
  127 #endif
  128 
  129 #define LI_RECURSEMASK  0x0000ffff      /* Recursion depth of lock instance. */
  130 #define LI_EXCLUSIVE    0x00010000      /* Exclusive lock instance. */
  131 #define LI_NORELEASE    0x00020000      /* Lock not allowed to be released. */
  132 
  133 /* Define this to check for blessed mutexes */
  134 #undef BLESSING
  135 
  136 #ifndef WITNESS_COUNT
  137 #define WITNESS_COUNT           1536
  138 #endif
  139 #define WITNESS_HASH_SIZE       251     /* Prime, gives load factor < 2 */
  140 #define WITNESS_PENDLIST        (1024 + MAXCPU)
  141 
  142 /* Allocate 256 KB of stack data space */
  143 #define WITNESS_LO_DATA_COUNT   2048
  144 
  145 /* Prime, gives load factor of ~2 at full load */
  146 #define WITNESS_LO_HASH_SIZE    1021
  147 
  148 /*
  149  * XXX: This is somewhat bogus, as we assume here that at most 2048 threads
  150  * will hold LOCK_NCHILDREN locks.  We handle failure ok, and we should
  151  * probably be safe for the most part, but it's still a SWAG.
  152  */
  153 #define LOCK_NCHILDREN  5
  154 #define LOCK_CHILDCOUNT 2048
  155 
  156 #define MAX_W_NAME      64
  157 
  158 #define FULLGRAPH_SBUF_SIZE     512
  159 
  160 /*
  161  * These flags go in the witness relationship matrix and describe the
  162  * relationship between any two struct witness objects.
  163  */
  164 #define WITNESS_UNRELATED        0x00    /* No lock order relation. */
  165 #define WITNESS_PARENT           0x01    /* Parent, aka direct ancestor. */
  166 #define WITNESS_ANCESTOR         0x02    /* Direct or indirect ancestor. */
  167 #define WITNESS_CHILD            0x04    /* Child, aka direct descendant. */
  168 #define WITNESS_DESCENDANT       0x08    /* Direct or indirect descendant. */
  169 #define WITNESS_ANCESTOR_MASK    (WITNESS_PARENT | WITNESS_ANCESTOR)
  170 #define WITNESS_DESCENDANT_MASK  (WITNESS_CHILD | WITNESS_DESCENDANT)
  171 #define WITNESS_RELATED_MASK                                            \
  172         (WITNESS_ANCESTOR_MASK | WITNESS_DESCENDANT_MASK)
  173 #define WITNESS_REVERSAL         0x10    /* A lock order reversal has been
  174                                           * observed. */
  175 #define WITNESS_RESERVED1        0x20    /* Unused flag, reserved. */
  176 #define WITNESS_RESERVED2        0x40    /* Unused flag, reserved. */
  177 #define WITNESS_LOCK_ORDER_KNOWN 0x80    /* This lock order is known. */
  178 
  179 /* Descendant to ancestor flags */
  180 #define WITNESS_DTOA(x) (((x) & WITNESS_RELATED_MASK) >> 2)
  181 
  182 /* Ancestor to descendant flags */
  183 #define WITNESS_ATOD(x) (((x) & WITNESS_RELATED_MASK) << 2)
  184 
  185 #define WITNESS_INDEX_ASSERT(i)                                         \
  186         MPASS((i) > 0 && (i) <= w_max_used_index && (i) < witness_count)
  187 
  188 static MALLOC_DEFINE(M_WITNESS, "Witness", "Witness");
  189 
  190 /*
  191  * Lock instances.  A lock instance is the data associated with a lock while
  192  * it is held by witness.  For example, a lock instance will hold the
  193  * recursion count of a lock.  Lock instances are held in lists.  Spin locks
  194  * are held in a per-cpu list while sleep locks are held in per-thread list.
  195  */
  196 struct lock_instance {
  197         struct lock_object      *li_lock;
  198         const char              *li_file;
  199         int                     li_line;
  200         u_int                   li_flags;
  201 };
  202 
  203 /*
  204  * A simple list type used to build the list of locks held by a thread
  205  * or CPU.  We can't simply embed the list in struct lock_object since a
  206  * lock may be held by more than one thread if it is a shared lock.  Locks
  207  * are added to the head of the list, so we fill up each list entry from
  208  * "the back" logically.  To ease some of the arithmetic, we actually fill
  209  * in each list entry the normal way (children[0] then children[1], etc.) but
  210  * when we traverse the list we read children[count-1] as the first entry
  211  * down to children[0] as the final entry.
  212  */
  213 struct lock_list_entry {
  214         struct lock_list_entry  *ll_next;
  215         struct lock_instance    ll_children[LOCK_NCHILDREN];
  216         u_int                   ll_count;
  217 };
  218 
  219 /*
  220  * The main witness structure. One of these per named lock type in the system
  221  * (for example, "vnode interlock").
  222  */
  223 struct witness {
  224         char                    w_name[MAX_W_NAME];
  225         uint32_t                w_index;  /* Index in the relationship matrix */
  226         struct lock_class       *w_class;
  227         STAILQ_ENTRY(witness)   w_list;         /* List of all witnesses. */
  228         STAILQ_ENTRY(witness)   w_typelist;     /* Witnesses of a type. */
  229         struct witness          *w_hash_next; /* Linked list in hash buckets. */
  230         const char              *w_file; /* File where last acquired */
  231         uint32_t                w_line; /* Line where last acquired */
  232         uint32_t                w_refcount;
  233         uint16_t                w_num_ancestors; /* direct/indirect
  234                                                   * ancestor count */
  235         uint16_t                w_num_descendants; /* direct/indirect
  236                                                     * descendant count */
  237         int16_t                 w_ddb_level;
  238         unsigned                w_displayed:1;
  239         unsigned                w_reversed:1;
  240 };
  241 
  242 STAILQ_HEAD(witness_list, witness);
  243 
  244 /*
  245  * The witness hash table. Keys are witness names (const char *), elements are
  246  * witness objects (struct witness *).
  247  */
  248 struct witness_hash {
  249         struct witness  *wh_array[WITNESS_HASH_SIZE];
  250         uint32_t        wh_size;
  251         uint32_t        wh_count;
  252 };
  253 
  254 /*
  255  * Key type for the lock order data hash table.
  256  */
  257 struct witness_lock_order_key {
  258         uint16_t        from;
  259         uint16_t        to;
  260 };
  261 
  262 struct witness_lock_order_data {
  263         struct stack                    wlod_stack;
  264         struct witness_lock_order_key   wlod_key;
  265         struct witness_lock_order_data  *wlod_next;
  266 };
  267 
  268 /*
  269  * The witness lock order data hash table. Keys are witness index tuples
  270  * (struct witness_lock_order_key), elements are lock order data objects
  271  * (struct witness_lock_order_data). 
  272  */
  273 struct witness_lock_order_hash {
  274         struct witness_lock_order_data  *wloh_array[WITNESS_LO_HASH_SIZE];
  275         u_int   wloh_size;
  276         u_int   wloh_count;
  277 };
  278 
  279 #ifdef BLESSING
  280 struct witness_blessed {
  281         const char      *b_lock1;
  282         const char      *b_lock2;
  283 };
  284 #endif
  285 
  286 struct witness_pendhelp {
  287         const char              *wh_type;
  288         struct lock_object      *wh_lock;
  289 };
  290 
  291 struct witness_order_list_entry {
  292         const char              *w_name;
  293         struct lock_class       *w_class;
  294 };
  295 
  296 /*
  297  * Returns 0 if one of the locks is a spin lock and the other is not.
  298  * Returns 1 otherwise.
  299  */
  300 static __inline int
  301 witness_lock_type_equal(struct witness *w1, struct witness *w2)
  302 {
  303 
  304         return ((w1->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) ==
  305                 (w2->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)));
  306 }
  307 
  308 static __inline int
  309 witness_lock_order_key_equal(const struct witness_lock_order_key *a,
  310     const struct witness_lock_order_key *b)
  311 {
  312 
  313         return (a->from == b->from && a->to == b->to);
  314 }
  315 
  316 static int      _isitmyx(struct witness *w1, struct witness *w2, int rmask,
  317                     const char *fname);
  318 static void     adopt(struct witness *parent, struct witness *child);
  319 #ifdef BLESSING
  320 static int      blessed(struct witness *, struct witness *);
  321 #endif
  322 static void     depart(struct witness *w);
  323 static struct witness   *enroll(const char *description,
  324                             struct lock_class *lock_class);
  325 static struct lock_instance     *find_instance(struct lock_list_entry *list,
  326                                     const struct lock_object *lock);
  327 static int      isitmychild(struct witness *parent, struct witness *child);
  328 static int      isitmydescendant(struct witness *parent, struct witness *child);
  329 static void     itismychild(struct witness *parent, struct witness *child);
  330 static int      sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS);
  331 static int      sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS);
  332 static int      sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS);
  333 static int      sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS);
  334 static void     witness_add_fullgraph(struct sbuf *sb, struct witness *parent);
  335 #ifdef DDB
  336 static void     witness_ddb_compute_levels(void);
  337 static void     witness_ddb_display(int(*)(const char *fmt, ...));
  338 static void     witness_ddb_display_descendants(int(*)(const char *fmt, ...),
  339                     struct witness *, int indent);
  340 static void     witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
  341                     struct witness_list *list);
  342 static void     witness_ddb_level_descendants(struct witness *parent, int l);
  343 static void     witness_ddb_list(struct thread *td);
  344 #endif
  345 static void     witness_debugger(int cond, const char *msg);
  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 int      witness_output(const char *fmt, ...) __printflike(1, 2);
  365 static int      witness_voutput(const char *fmt, va_list ap) __printflike(1, 0);
  366 static void     witness_setflag(struct lock_object *lock, int flag, int set);
  367 
  368 static SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW, NULL,
  369     "Witness Locking");
  370 
  371 /*
  372  * If set to 0, lock order checking is disabled.  If set to -1,
  373  * witness is completely disabled.  Otherwise witness performs full
  374  * lock order checking for all locks.  At runtime, lock order checking
  375  * may be toggled.  However, witness cannot be reenabled once it is
  376  * completely disabled.
  377  */
  378 static int witness_watch = 1;
  379 SYSCTL_PROC(_debug_witness, OID_AUTO, watch, CTLFLAG_RWTUN | CTLTYPE_INT, NULL, 0,
  380     sysctl_debug_witness_watch, "I", "witness is watching lock operations");
  381 
  382 #ifdef KDB
  383 /*
  384  * When KDB is enabled and witness_kdb is 1, it will cause the system
  385  * to drop into kdebug() when:
  386  *      - a lock hierarchy violation occurs
  387  *      - locks are held when going to sleep.
  388  */
  389 #ifdef WITNESS_KDB
  390 int     witness_kdb = 1;
  391 #else
  392 int     witness_kdb = 0;
  393 #endif
  394 SYSCTL_INT(_debug_witness, OID_AUTO, kdb, CTLFLAG_RWTUN, &witness_kdb, 0, "");
  395 #endif /* KDB */
  396 
  397 #if defined(DDB) || defined(KDB)
  398 /*
  399  * When DDB or KDB is enabled and witness_trace is 1, it will cause the system
  400  * to print a stack trace:
  401  *      - a lock hierarchy violation occurs
  402  *      - locks are held when going to sleep.
  403  */
  404 int     witness_trace = 1;
  405 SYSCTL_INT(_debug_witness, OID_AUTO, trace, CTLFLAG_RWTUN, &witness_trace, 0, "");
  406 #endif /* DDB || KDB */
  407 
  408 #ifdef WITNESS_SKIPSPIN
  409 int     witness_skipspin = 1;
  410 #else
  411 int     witness_skipspin = 0;
  412 #endif
  413 SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN, &witness_skipspin, 0, "");
  414 
  415 int badstack_sbuf_size;
  416 
  417 int witness_count = WITNESS_COUNT;
  418 SYSCTL_INT(_debug_witness, OID_AUTO, witness_count, CTLFLAG_RDTUN, 
  419     &witness_count, 0, "");
  420 
  421 /*
  422  * Output channel for witness messages.  By default we print to the console.
  423  */
  424 enum witness_channel {
  425         WITNESS_CONSOLE,
  426         WITNESS_LOG,
  427         WITNESS_NONE,
  428 };
  429 
  430 static enum witness_channel witness_channel = WITNESS_CONSOLE;
  431 SYSCTL_PROC(_debug_witness, OID_AUTO, output_channel, CTLTYPE_STRING |
  432     CTLFLAG_RWTUN, NULL, 0, sysctl_debug_witness_channel, "A",
  433     "Output channel for warnings");
  434 
  435 /*
  436  * Call this to print out the relations between locks.
  437  */
  438 SYSCTL_PROC(_debug_witness, OID_AUTO, fullgraph, CTLTYPE_STRING | CTLFLAG_RD,
  439     NULL, 0, sysctl_debug_witness_fullgraph, "A", "Show locks relation graphs");
  440 
  441 /*
  442  * Call this to print out the witness faulty stacks.
  443  */
  444 SYSCTL_PROC(_debug_witness, OID_AUTO, badstacks, CTLTYPE_STRING | CTLFLAG_RD,
  445     NULL, 0, sysctl_debug_witness_badstacks, "A", "Show bad witness stacks");
  446 
  447 static struct mtx w_mtx;
  448 
  449 /* w_list */
  450 static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free);
  451 static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all);
  452 
  453 /* w_typelist */
  454 static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin);
  455 static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep);
  456 
  457 /* lock list */
  458 static struct lock_list_entry *w_lock_list_free = NULL;
  459 static struct witness_pendhelp pending_locks[WITNESS_PENDLIST];
  460 static u_int pending_cnt;
  461 
  462 static int w_free_cnt, w_spin_cnt, w_sleep_cnt;
  463 SYSCTL_INT(_debug_witness, OID_AUTO, free_cnt, CTLFLAG_RD, &w_free_cnt, 0, "");
  464 SYSCTL_INT(_debug_witness, OID_AUTO, spin_cnt, CTLFLAG_RD, &w_spin_cnt, 0, "");
  465 SYSCTL_INT(_debug_witness, OID_AUTO, sleep_cnt, CTLFLAG_RD, &w_sleep_cnt, 0,
  466     "");
  467 
  468 static struct witness *w_data;
  469 static uint8_t **w_rmatrix;
  470 static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT];
  471 static struct witness_hash w_hash;      /* The witness hash table. */
  472 
  473 /* The lock order data hash */
  474 static struct witness_lock_order_data w_lodata[WITNESS_LO_DATA_COUNT];
  475 static struct witness_lock_order_data *w_lofree = NULL;
  476 static struct witness_lock_order_hash w_lohash;
  477 static int w_max_used_index = 0;
  478 static unsigned int w_generation = 0;
  479 static const char w_notrunning[] = "Witness not running\n";
  480 static const char w_stillcold[] = "Witness is still cold\n";
  481 
  482 
  483 static struct witness_order_list_entry order_lists[] = {
  484         /*
  485          * sx locks
  486          */
  487         { "proctree", &lock_class_sx },
  488         { "allproc", &lock_class_sx },
  489         { "allprison", &lock_class_sx },
  490         { NULL, NULL },
  491         /*
  492          * Various mutexes
  493          */
  494         { "Giant", &lock_class_mtx_sleep },
  495         { "pipe mutex", &lock_class_mtx_sleep },
  496         { "sigio lock", &lock_class_mtx_sleep },
  497         { "process group", &lock_class_mtx_sleep },
  498         { "process lock", &lock_class_mtx_sleep },
  499         { "session", &lock_class_mtx_sleep },
  500         { "uidinfo hash", &lock_class_rw },
  501 #ifdef  HWPMC_HOOKS
  502         { "pmc-sleep", &lock_class_mtx_sleep },
  503 #endif
  504         { "time lock", &lock_class_mtx_sleep },
  505         { NULL, NULL },
  506         /*
  507          * umtx
  508          */
  509         { "umtx lock", &lock_class_mtx_sleep },
  510         { NULL, NULL },
  511         /*
  512          * Sockets
  513          */
  514         { "accept", &lock_class_mtx_sleep },
  515         { "so_snd", &lock_class_mtx_sleep },
  516         { "so_rcv", &lock_class_mtx_sleep },
  517         { "sellck", &lock_class_mtx_sleep },
  518         { NULL, NULL },
  519         /*
  520          * Routing
  521          */
  522         { "so_rcv", &lock_class_mtx_sleep },
  523         { "radix node head", &lock_class_rw },
  524         { "rtentry", &lock_class_mtx_sleep },
  525         { "ifaddr", &lock_class_mtx_sleep },
  526         { NULL, NULL },
  527         /*
  528          * IPv4 multicast:
  529          * protocol locks before interface locks, after UDP locks.
  530          */
  531         { "udpinp", &lock_class_rw },
  532         { "in_multi_mtx", &lock_class_mtx_sleep },
  533         { "igmp_mtx", &lock_class_mtx_sleep },
  534         { "if_addr_lock", &lock_class_rw },
  535         { NULL, NULL },
  536         /*
  537          * IPv6 multicast:
  538          * protocol locks before interface locks, after UDP locks.
  539          */
  540         { "udpinp", &lock_class_rw },
  541         { "in6_multi_mtx", &lock_class_mtx_sleep },
  542         { "mld_mtx", &lock_class_mtx_sleep },
  543         { "if_addr_lock", &lock_class_rw },
  544         { NULL, NULL },
  545         /*
  546          * UNIX Domain Sockets
  547          */
  548         { "unp_link_rwlock", &lock_class_rw },
  549         { "unp_list_lock", &lock_class_mtx_sleep },
  550         { "unp", &lock_class_mtx_sleep },
  551         { "so_snd", &lock_class_mtx_sleep },
  552         { NULL, NULL },
  553         /*
  554          * UDP/IP
  555          */
  556         { "udp", &lock_class_rw },
  557         { "udpinp", &lock_class_rw },
  558         { "so_snd", &lock_class_mtx_sleep },
  559         { NULL, NULL },
  560         /*
  561          * TCP/IP
  562          */
  563         { "tcp", &lock_class_rw },
  564         { "tcpinp", &lock_class_rw },
  565         { "so_snd", &lock_class_mtx_sleep },
  566         { NULL, NULL },
  567         /*
  568          * BPF
  569          */
  570         { "bpf global lock", &lock_class_sx },
  571         { "bpf interface lock", &lock_class_rw },
  572         { "bpf cdev lock", &lock_class_mtx_sleep },
  573         { NULL, NULL },
  574         /*
  575          * NFS server
  576          */
  577         { "nfsd_mtx", &lock_class_mtx_sleep },
  578         { "so_snd", &lock_class_mtx_sleep },
  579         { NULL, NULL },
  580 
  581         /*
  582          * IEEE 802.11
  583          */
  584         { "802.11 com lock", &lock_class_mtx_sleep},
  585         { NULL, NULL },
  586         /*
  587          * Network drivers
  588          */
  589         { "network driver", &lock_class_mtx_sleep},
  590         { NULL, NULL },
  591 
  592         /*
  593          * Netgraph
  594          */
  595         { "ng_node", &lock_class_mtx_sleep },
  596         { "ng_worklist", &lock_class_mtx_sleep },
  597         { NULL, NULL },
  598         /*
  599          * CDEV
  600          */
  601         { "vm map (system)", &lock_class_mtx_sleep },
  602         { "vm pagequeue", &lock_class_mtx_sleep },
  603         { "vnode interlock", &lock_class_mtx_sleep },
  604         { "cdev", &lock_class_mtx_sleep },
  605         { NULL, NULL },
  606         /*
  607          * VM
  608          */
  609         { "vm map (user)", &lock_class_sx },
  610         { "vm object", &lock_class_rw },
  611         { "vm page", &lock_class_mtx_sleep },
  612         { "vm pagequeue", &lock_class_mtx_sleep },
  613         { "pmap pv global", &lock_class_rw },
  614         { "pmap", &lock_class_mtx_sleep },
  615         { "pmap pv list", &lock_class_rw },
  616         { "vm page free queue", &lock_class_mtx_sleep },
  617         { NULL, NULL },
  618         /*
  619          * kqueue/VFS interaction
  620          */
  621         { "kqueue", &lock_class_mtx_sleep },
  622         { "struct mount mtx", &lock_class_mtx_sleep },
  623         { "vnode interlock", &lock_class_mtx_sleep },
  624         { NULL, NULL },
  625         /*
  626          * VFS namecache
  627          */
  628         { "ncvn", &lock_class_mtx_sleep },
  629         { "ncbuc", &lock_class_rw },
  630         { "vnode interlock", &lock_class_mtx_sleep },
  631         { "ncneg", &lock_class_mtx_sleep },
  632         { NULL, NULL },
  633         /*
  634          * ZFS locking
  635          */
  636         { "dn->dn_mtx", &lock_class_sx },
  637         { "dr->dt.di.dr_mtx", &lock_class_sx },
  638         { "db->db_mtx", &lock_class_sx },
  639         { NULL, NULL },
  640         /*
  641          * spin locks
  642          */
  643 #ifdef SMP
  644         { "ap boot", &lock_class_mtx_spin },
  645 #endif
  646         { "rm.mutex_mtx", &lock_class_mtx_spin },
  647         { "sio", &lock_class_mtx_spin },
  648 #ifdef __i386__
  649         { "cy", &lock_class_mtx_spin },
  650 #endif
  651 #ifdef __sparc64__
  652         { "pcib_mtx", &lock_class_mtx_spin },
  653         { "rtc_mtx", &lock_class_mtx_spin },
  654 #endif
  655         { "scc_hwmtx", &lock_class_mtx_spin },
  656         { "uart_hwmtx", &lock_class_mtx_spin },
  657         { "fast_taskqueue", &lock_class_mtx_spin },
  658         { "intr table", &lock_class_mtx_spin },
  659 #ifdef  HWPMC_HOOKS
  660         { "pmc-per-proc", &lock_class_mtx_spin },
  661 #endif
  662         { "process slock", &lock_class_mtx_spin },
  663         { "syscons video lock", &lock_class_mtx_spin },
  664         { "sleepq chain", &lock_class_mtx_spin },
  665         { "rm_spinlock", &lock_class_mtx_spin },
  666         { "turnstile chain", &lock_class_mtx_spin },
  667         { "turnstile lock", &lock_class_mtx_spin },
  668         { "sched lock", &lock_class_mtx_spin },
  669         { "td_contested", &lock_class_mtx_spin },
  670         { "callout", &lock_class_mtx_spin },
  671         { "entropy harvest mutex", &lock_class_mtx_spin },
  672 #ifdef SMP
  673         { "smp rendezvous", &lock_class_mtx_spin },
  674 #endif
  675 #ifdef __powerpc__
  676         { "tlb0", &lock_class_mtx_spin },
  677 #endif
  678         /*
  679          * leaf locks
  680          */
  681         { "intrcnt", &lock_class_mtx_spin },
  682         { "icu", &lock_class_mtx_spin },
  683 #if defined(SMP) && defined(__sparc64__)
  684         { "ipi", &lock_class_mtx_spin },
  685 #endif
  686 #ifdef __i386__
  687         { "allpmaps", &lock_class_mtx_spin },
  688         { "descriptor tables", &lock_class_mtx_spin },
  689 #endif
  690         { "clk", &lock_class_mtx_spin },
  691         { "cpuset", &lock_class_mtx_spin },
  692         { "mprof lock", &lock_class_mtx_spin },
  693         { "zombie lock", &lock_class_mtx_spin },
  694         { "ALD Queue", &lock_class_mtx_spin },
  695 #if defined(__i386__) || defined(__amd64__)
  696         { "pcicfg", &lock_class_mtx_spin },
  697         { "NDIS thread lock", &lock_class_mtx_spin },
  698 #endif
  699         { "tw_osl_io_lock", &lock_class_mtx_spin },
  700         { "tw_osl_q_lock", &lock_class_mtx_spin },
  701         { "tw_cl_io_lock", &lock_class_mtx_spin },
  702         { "tw_cl_intr_lock", &lock_class_mtx_spin },
  703         { "tw_cl_gen_lock", &lock_class_mtx_spin },
  704 #ifdef  HWPMC_HOOKS
  705         { "pmc-leaf", &lock_class_mtx_spin },
  706 #endif
  707         { "blocked lock", &lock_class_mtx_spin },
  708         { NULL, NULL },
  709         { NULL, NULL }
  710 };
  711 
  712 #ifdef BLESSING
  713 /*
  714  * Pairs of locks which have been blessed
  715  * Don't complain about order problems with blessed locks
  716  */
  717 static struct witness_blessed blessed_list[] = {
  718 };
  719 #endif
  720 
  721 /*
  722  * This global is set to 0 once it becomes safe to use the witness code.
  723  */
  724 static int witness_cold = 1;
  725 
  726 /*
  727  * This global is set to 1 once the static lock orders have been enrolled
  728  * so that a warning can be issued for any spin locks enrolled later.
  729  */
  730 static int witness_spin_warn = 0;
  731 
  732 /* Trim useless garbage from filenames. */
  733 static const char *
  734 fixup_filename(const char *file)
  735 {
  736 
  737         if (file == NULL)
  738                 return (NULL);
  739         while (strncmp(file, "../", 3) == 0)
  740                 file += 3;
  741         return (file);
  742 }
  743 
  744 /*
  745  * The WITNESS-enabled diagnostic code.  Note that the witness code does
  746  * assume that the early boot is single-threaded at least until after this
  747  * routine is completed.
  748  */
  749 static void
  750 witness_initialize(void *dummy __unused)
  751 {
  752         struct lock_object *lock;
  753         struct witness_order_list_entry *order;
  754         struct witness *w, *w1;
  755         int i;
  756 
  757         w_data = malloc(sizeof (struct witness) * witness_count, M_WITNESS,
  758             M_WAITOK | M_ZERO);
  759 
  760         w_rmatrix = malloc(sizeof(*w_rmatrix) * (witness_count + 1),
  761             M_WITNESS, M_WAITOK | M_ZERO);
  762 
  763         for (i = 0; i < witness_count + 1; i++) {
  764                 w_rmatrix[i] = malloc(sizeof(*w_rmatrix[i]) *
  765                     (witness_count + 1), M_WITNESS, M_WAITOK | M_ZERO);
  766         }
  767         badstack_sbuf_size = witness_count * 256;
  768 
  769         /*
  770          * We have to release Giant before initializing its witness
  771          * structure so that WITNESS doesn't get confused.
  772          */
  773         mtx_unlock(&Giant);
  774         mtx_assert(&Giant, MA_NOTOWNED);
  775 
  776         CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
  777         mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET |
  778             MTX_NOWITNESS | MTX_NOPROFILE);
  779         for (i = witness_count - 1; i >= 0; i--) {
  780                 w = &w_data[i];
  781                 memset(w, 0, sizeof(*w));
  782                 w_data[i].w_index = i;  /* Witness index never changes. */
  783                 witness_free(w);
  784         }
  785         KASSERT(STAILQ_FIRST(&w_free)->w_index == 0,
  786             ("%s: Invalid list of free witness objects", __func__));
  787 
  788         /* Witness with index 0 is not used to aid in debugging. */
  789         STAILQ_REMOVE_HEAD(&w_free, w_list);
  790         w_free_cnt--;
  791 
  792         for (i = 0; i < witness_count; i++) {
  793                 memset(w_rmatrix[i], 0, sizeof(*w_rmatrix[i]) * 
  794                     (witness_count + 1));
  795         }
  796 
  797         for (i = 0; i < LOCK_CHILDCOUNT; i++)
  798                 witness_lock_list_free(&w_locklistdata[i]);
  799         witness_init_hash_tables();
  800 
  801         /* First add in all the specified order lists. */
  802         for (order = order_lists; order->w_name != NULL; order++) {
  803                 w = enroll(order->w_name, order->w_class);
  804                 if (w == NULL)
  805                         continue;
  806                 w->w_file = "order list";
  807                 for (order++; order->w_name != NULL; order++) {
  808                         w1 = enroll(order->w_name, order->w_class);
  809                         if (w1 == NULL)
  810                                 continue;
  811                         w1->w_file = "order list";
  812                         itismychild(w, w1);
  813                         w = w1;
  814                 }
  815         }
  816         witness_spin_warn = 1;
  817 
  818         /* Iterate through all locks and add them to witness. */
  819         for (i = 0; pending_locks[i].wh_lock != NULL; i++) {
  820                 lock = pending_locks[i].wh_lock;
  821                 KASSERT(lock->lo_flags & LO_WITNESS,
  822                     ("%s: lock %s is on pending list but not LO_WITNESS",
  823                     __func__, lock->lo_name));
  824                 lock->lo_witness = enroll(pending_locks[i].wh_type,
  825                     LOCK_CLASS(lock));
  826         }
  827 
  828         /* Mark the witness code as being ready for use. */
  829         witness_cold = 0;
  830 
  831         mtx_lock(&Giant);
  832 }
  833 SYSINIT(witness_init, SI_SUB_WITNESS, SI_ORDER_FIRST, witness_initialize,
  834     NULL);
  835 
  836 void
  837 witness_init(struct lock_object *lock, const char *type)
  838 {
  839         struct lock_class *class;
  840 
  841         /* Various sanity checks. */
  842         class = LOCK_CLASS(lock);
  843         if ((lock->lo_flags & LO_RECURSABLE) != 0 &&
  844             (class->lc_flags & LC_RECURSABLE) == 0)
  845                 kassert_panic("%s: lock (%s) %s can not be recursable",
  846                     __func__, class->lc_name, lock->lo_name);
  847         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
  848             (class->lc_flags & LC_SLEEPABLE) == 0)
  849                 kassert_panic("%s: lock (%s) %s can not be sleepable",
  850                     __func__, class->lc_name, lock->lo_name);
  851         if ((lock->lo_flags & LO_UPGRADABLE) != 0 &&
  852             (class->lc_flags & LC_UPGRADABLE) == 0)
  853                 kassert_panic("%s: lock (%s) %s can not be upgradable",
  854                     __func__, class->lc_name, lock->lo_name);
  855 
  856         /*
  857          * If we shouldn't watch this lock, then just clear lo_witness.
  858          * Otherwise, if witness_cold is set, then it is too early to
  859          * enroll this lock, so defer it to witness_initialize() by adding
  860          * it to the pending_locks list.  If it is not too early, then enroll
  861          * the lock now.
  862          */
  863         if (witness_watch < 1 || panicstr != NULL ||
  864             (lock->lo_flags & LO_WITNESS) == 0)
  865                 lock->lo_witness = NULL;
  866         else if (witness_cold) {
  867                 pending_locks[pending_cnt].wh_lock = lock;
  868                 pending_locks[pending_cnt++].wh_type = type;
  869                 if (pending_cnt > WITNESS_PENDLIST)
  870                         panic("%s: pending locks list is too small, "
  871                             "increase WITNESS_PENDLIST\n",
  872                             __func__);
  873         } else
  874                 lock->lo_witness = enroll(type, class);
  875 }
  876 
  877 void
  878 witness_destroy(struct lock_object *lock)
  879 {
  880         struct lock_class *class;
  881         struct witness *w;
  882 
  883         class = LOCK_CLASS(lock);
  884 
  885         if (witness_cold)
  886                 panic("lock (%s) %s destroyed while witness_cold",
  887                     class->lc_name, lock->lo_name);
  888 
  889         /* XXX: need to verify that no one holds the lock */
  890         if ((lock->lo_flags & LO_WITNESS) == 0 || lock->lo_witness == NULL)
  891                 return;
  892         w = lock->lo_witness;
  893 
  894         mtx_lock_spin(&w_mtx);
  895         MPASS(w->w_refcount > 0);
  896         w->w_refcount--;
  897 
  898         if (w->w_refcount == 0)
  899                 depart(w);
  900         mtx_unlock_spin(&w_mtx);
  901 }
  902 
  903 #ifdef DDB
  904 static void
  905 witness_ddb_compute_levels(void)
  906 {
  907         struct witness *w;
  908 
  909         /*
  910          * First clear all levels.
  911          */
  912         STAILQ_FOREACH(w, &w_all, w_list)
  913                 w->w_ddb_level = -1;
  914 
  915         /*
  916          * Look for locks with no parents and level all their descendants.
  917          */
  918         STAILQ_FOREACH(w, &w_all, w_list) {
  919 
  920                 /* If the witness has ancestors (is not a root), skip it. */
  921                 if (w->w_num_ancestors > 0)
  922                         continue;
  923                 witness_ddb_level_descendants(w, 0);
  924         }
  925 }
  926 
  927 static void
  928 witness_ddb_level_descendants(struct witness *w, int l)
  929 {
  930         int i;
  931 
  932         if (w->w_ddb_level >= l)
  933                 return;
  934 
  935         w->w_ddb_level = l;
  936         l++;
  937 
  938         for (i = 1; i <= w_max_used_index; i++) {
  939                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
  940                         witness_ddb_level_descendants(&w_data[i], l);
  941         }
  942 }
  943 
  944 static void
  945 witness_ddb_display_descendants(int(*prnt)(const char *fmt, ...),
  946     struct witness *w, int indent)
  947 {
  948         int i;
  949 
  950         for (i = 0; i < indent; i++)
  951                 prnt(" ");
  952         prnt("%s (type: %s, depth: %d, active refs: %d)",
  953              w->w_name, w->w_class->lc_name,
  954              w->w_ddb_level, w->w_refcount);
  955         if (w->w_displayed) {
  956                 prnt(" -- (already displayed)\n");
  957                 return;
  958         }
  959         w->w_displayed = 1;
  960         if (w->w_file != NULL && w->w_line != 0)
  961                 prnt(" -- last acquired @ %s:%d\n", fixup_filename(w->w_file),
  962                     w->w_line);
  963         else
  964                 prnt(" -- never acquired\n");
  965         indent++;
  966         WITNESS_INDEX_ASSERT(w->w_index);
  967         for (i = 1; i <= w_max_used_index; i++) {
  968                 if (db_pager_quit)
  969                         return;
  970                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
  971                         witness_ddb_display_descendants(prnt, &w_data[i],
  972                             indent);
  973         }
  974 }
  975 
  976 static void
  977 witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
  978     struct witness_list *list)
  979 {
  980         struct witness *w;
  981 
  982         STAILQ_FOREACH(w, list, w_typelist) {
  983                 if (w->w_file == NULL || w->w_ddb_level > 0)
  984                         continue;
  985 
  986                 /* This lock has no anscestors - display its descendants. */
  987                 witness_ddb_display_descendants(prnt, w, 0);
  988                 if (db_pager_quit)
  989                         return;
  990         }
  991 }
  992         
  993 static void
  994 witness_ddb_display(int(*prnt)(const char *fmt, ...))
  995 {
  996         struct witness *w;
  997 
  998         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
  999         witness_ddb_compute_levels();
 1000 
 1001         /* Clear all the displayed flags. */
 1002         STAILQ_FOREACH(w, &w_all, w_list)
 1003                 w->w_displayed = 0;
 1004 
 1005         /*
 1006          * First, handle sleep locks which have been acquired at least
 1007          * once.
 1008          */
 1009         prnt("Sleep locks:\n");
 1010         witness_ddb_display_list(prnt, &w_sleep);
 1011         if (db_pager_quit)
 1012                 return;
 1013         
 1014         /*
 1015          * Now do spin locks which have been acquired at least once.
 1016          */
 1017         prnt("\nSpin locks:\n");
 1018         witness_ddb_display_list(prnt, &w_spin);
 1019         if (db_pager_quit)
 1020                 return;
 1021         
 1022         /*
 1023          * Finally, any locks which have not been acquired yet.
 1024          */
 1025         prnt("\nLocks which were never acquired:\n");
 1026         STAILQ_FOREACH(w, &w_all, w_list) {
 1027                 if (w->w_file != NULL || w->w_refcount == 0)
 1028                         continue;
 1029                 prnt("%s (type: %s, depth: %d)\n", w->w_name,
 1030                     w->w_class->lc_name, w->w_ddb_level);
 1031                 if (db_pager_quit)
 1032                         return;
 1033         }
 1034 }
 1035 #endif /* DDB */
 1036 
 1037 int
 1038 witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
 1039 {
 1040 
 1041         if (witness_watch == -1 || panicstr != NULL)
 1042                 return (0);
 1043 
 1044         /* Require locks that witness knows about. */
 1045         if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL ||
 1046             lock2->lo_witness == NULL)
 1047                 return (EINVAL);
 1048 
 1049         mtx_assert(&w_mtx, MA_NOTOWNED);
 1050         mtx_lock_spin(&w_mtx);
 1051 
 1052         /*
 1053          * If we already have either an explicit or implied lock order that
 1054          * is the other way around, then return an error.
 1055          */
 1056         if (witness_watch &&
 1057             isitmydescendant(lock2->lo_witness, lock1->lo_witness)) {
 1058                 mtx_unlock_spin(&w_mtx);
 1059                 return (EDOOFUS);
 1060         }
 1061         
 1062         /* Try to add the new order. */
 1063         CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 1064             lock2->lo_witness->w_name, lock1->lo_witness->w_name);
 1065         itismychild(lock1->lo_witness, lock2->lo_witness);
 1066         mtx_unlock_spin(&w_mtx);
 1067         return (0);
 1068 }
 1069 
 1070 void
 1071 witness_checkorder(struct lock_object *lock, int flags, const char *file,
 1072     int line, struct lock_object *interlock)
 1073 {
 1074         struct lock_list_entry *lock_list, *lle;
 1075         struct lock_instance *lock1, *lock2, *plock;
 1076         struct lock_class *class, *iclass;
 1077         struct witness *w, *w1;
 1078         struct thread *td;
 1079         int i, j;
 1080 
 1081         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL ||
 1082             panicstr != NULL)
 1083                 return;
 1084 
 1085         w = lock->lo_witness;
 1086         class = LOCK_CLASS(lock);
 1087         td = curthread;
 1088 
 1089         if (class->lc_flags & LC_SLEEPLOCK) {
 1090 
 1091                 /*
 1092                  * Since spin locks include a critical section, this check
 1093                  * implicitly enforces a lock order of all sleep locks before
 1094                  * all spin locks.
 1095                  */
 1096                 if (td->td_critnest != 0 && !kdb_active)
 1097                         kassert_panic("acquiring blockable sleep lock with "
 1098                             "spinlock or critical section held (%s) %s @ %s:%d",
 1099                             class->lc_name, lock->lo_name,
 1100                             fixup_filename(file), line);
 1101 
 1102                 /*
 1103                  * If this is the first lock acquired then just return as
 1104                  * no order checking is needed.
 1105                  */
 1106                 lock_list = td->td_sleeplocks;
 1107                 if (lock_list == NULL || lock_list->ll_count == 0)
 1108                         return;
 1109         } else {
 1110 
 1111                 /*
 1112                  * If this is the first lock, just return as no order
 1113                  * checking is needed.  Avoid problems with thread
 1114                  * migration pinning the thread while checking if
 1115                  * spinlocks are held.  If at least one spinlock is held
 1116                  * the thread is in a safe path and it is allowed to
 1117                  * unpin it.
 1118                  */
 1119                 sched_pin();
 1120                 lock_list = PCPU_GET(spinlocks);
 1121                 if (lock_list == NULL || lock_list->ll_count == 0) {
 1122                         sched_unpin();
 1123                         return;
 1124                 }
 1125                 sched_unpin();
 1126         }
 1127 
 1128         /*
 1129          * Check to see if we are recursing on a lock we already own.  If
 1130          * so, make sure that we don't mismatch exclusive and shared lock
 1131          * acquires.
 1132          */
 1133         lock1 = find_instance(lock_list, lock);
 1134         if (lock1 != NULL) {
 1135                 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 &&
 1136                     (flags & LOP_EXCLUSIVE) == 0) {
 1137                         witness_output("shared lock of (%s) %s @ %s:%d\n",
 1138                             class->lc_name, lock->lo_name,
 1139                             fixup_filename(file), line);
 1140                         witness_output("while exclusively locked from %s:%d\n",
 1141                             fixup_filename(lock1->li_file), lock1->li_line);
 1142                         kassert_panic("excl->share");
 1143                 }
 1144                 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
 1145                     (flags & LOP_EXCLUSIVE) != 0) {
 1146                         witness_output("exclusive lock of (%s) %s @ %s:%d\n",
 1147                             class->lc_name, lock->lo_name,
 1148                             fixup_filename(file), line);
 1149                         witness_output("while share locked from %s:%d\n",
 1150                             fixup_filename(lock1->li_file), lock1->li_line);
 1151                         kassert_panic("share->excl");
 1152                 }
 1153                 return;
 1154         }
 1155 
 1156         /* Warn if the interlock is not locked exactly once. */
 1157         if (interlock != NULL) {
 1158                 iclass = LOCK_CLASS(interlock);
 1159                 lock1 = find_instance(lock_list, interlock);
 1160                 if (lock1 == NULL)
 1161                         kassert_panic("interlock (%s) %s not locked @ %s:%d",
 1162                             iclass->lc_name, interlock->lo_name,
 1163                             fixup_filename(file), line);
 1164                 else if ((lock1->li_flags & LI_RECURSEMASK) != 0)
 1165                         kassert_panic("interlock (%s) %s recursed @ %s:%d",
 1166                             iclass->lc_name, interlock->lo_name,
 1167                             fixup_filename(file), line);
 1168         }
 1169 
 1170         /*
 1171          * Find the previously acquired lock, but ignore interlocks.
 1172          */
 1173         plock = &lock_list->ll_children[lock_list->ll_count - 1];
 1174         if (interlock != NULL && plock->li_lock == interlock) {
 1175                 if (lock_list->ll_count > 1)
 1176                         plock =
 1177                             &lock_list->ll_children[lock_list->ll_count - 2];
 1178                 else {
 1179                         lle = lock_list->ll_next;
 1180 
 1181                         /*
 1182                          * The interlock is the only lock we hold, so
 1183                          * simply return.
 1184                          */
 1185                         if (lle == NULL)
 1186                                 return;
 1187                         plock = &lle->ll_children[lle->ll_count - 1];
 1188                 }
 1189         }
 1190         
 1191         /*
 1192          * Try to perform most checks without a lock.  If this succeeds we
 1193          * can skip acquiring the lock and return success.  Otherwise we redo
 1194          * the check with the lock held to handle races with concurrent updates.
 1195          */
 1196         w1 = plock->li_lock->lo_witness;
 1197         if (witness_lock_order_check(w1, w))
 1198                 return;
 1199 
 1200         mtx_lock_spin(&w_mtx);
 1201         if (witness_lock_order_check(w1, w)) {
 1202                 mtx_unlock_spin(&w_mtx);
 1203                 return;
 1204         }
 1205         witness_lock_order_add(w1, w);
 1206 
 1207         /*
 1208          * Check for duplicate locks of the same type.  Note that we only
 1209          * have to check for this on the last lock we just acquired.  Any
 1210          * other cases will be caught as lock order violations.
 1211          */
 1212         if (w1 == w) {
 1213                 i = w->w_index;
 1214                 if (!(lock->lo_flags & LO_DUPOK) && !(flags & LOP_DUPOK) &&
 1215                     !(w_rmatrix[i][i] & WITNESS_REVERSAL)) {
 1216                     w_rmatrix[i][i] |= WITNESS_REVERSAL;
 1217                         w->w_reversed = 1;
 1218                         mtx_unlock_spin(&w_mtx);
 1219                         witness_output(
 1220                             "acquiring duplicate lock of same type: \"%s\"\n", 
 1221                             w->w_name);
 1222                         witness_output(" 1st %s @ %s:%d\n", plock->li_lock->lo_name,
 1223                             fixup_filename(plock->li_file), plock->li_line);
 1224                         witness_output(" 2nd %s @ %s:%d\n", lock->lo_name,
 1225                             fixup_filename(file), line);
 1226                         witness_debugger(1, __func__);
 1227                 } else
 1228                         mtx_unlock_spin(&w_mtx);
 1229                 return;
 1230         }
 1231         mtx_assert(&w_mtx, MA_OWNED);
 1232 
 1233         /*
 1234          * If we know that the lock we are acquiring comes after
 1235          * the lock we most recently acquired in the lock order tree,
 1236          * then there is no need for any further checks.
 1237          */
 1238         if (isitmychild(w1, w))
 1239                 goto out;
 1240 
 1241         for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) {
 1242                 for (i = lle->ll_count - 1; i >= 0; i--, j++) {
 1243 
 1244                         MPASS(j < LOCK_CHILDCOUNT * LOCK_NCHILDREN);
 1245                         lock1 = &lle->ll_children[i];
 1246 
 1247                         /*
 1248                          * Ignore the interlock.
 1249                          */
 1250                         if (interlock == lock1->li_lock)
 1251                                 continue;
 1252 
 1253                         /*
 1254                          * If this lock doesn't undergo witness checking,
 1255                          * then skip it.
 1256                          */
 1257                         w1 = lock1->li_lock->lo_witness;
 1258                         if (w1 == NULL) {
 1259                                 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0,
 1260                                     ("lock missing witness structure"));
 1261                                 continue;
 1262                         }
 1263 
 1264                         /*
 1265                          * If we are locking Giant and this is a sleepable
 1266                          * lock, then skip it.
 1267                          */
 1268                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1269                             lock == &Giant.lock_object)
 1270                                 continue;
 1271 
 1272                         /*
 1273                          * If we are locking a sleepable lock and this lock
 1274                          * is Giant, then skip it.
 1275                          */
 1276                         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1277                             lock1->li_lock == &Giant.lock_object)
 1278                                 continue;
 1279 
 1280                         /*
 1281                          * If we are locking a sleepable lock and this lock
 1282                          * isn't sleepable, we want to treat it as a lock
 1283                          * order violation to enfore a general lock order of
 1284                          * sleepable locks before non-sleepable locks.
 1285                          */
 1286                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1287                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
 1288                                 goto reversal;
 1289 
 1290                         /*
 1291                          * If we are locking Giant and this is a non-sleepable
 1292                          * lock, then treat it as a reversal.
 1293                          */
 1294                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0 &&
 1295                             lock == &Giant.lock_object)
 1296                                 goto reversal;
 1297 
 1298                         /*
 1299                          * Check the lock order hierarchy for a reveresal.
 1300                          */
 1301                         if (!isitmydescendant(w, w1))
 1302                                 continue;
 1303                 reversal:
 1304 
 1305                         /*
 1306                          * We have a lock order violation, check to see if it
 1307                          * is allowed or has already been yelled about.
 1308                          */
 1309 #ifdef BLESSING
 1310 
 1311                         /*
 1312                          * If the lock order is blessed, just bail.  We don't
 1313                          * look for other lock order violations though, which
 1314                          * may be a bug.
 1315                          */
 1316                         if (blessed(w, w1))
 1317                                 goto out;
 1318 #endif
 1319 
 1320                         /* Bail if this violation is known */
 1321                         if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL)
 1322                                 goto out;
 1323 
 1324                         /* Record this as a violation */
 1325                         w_rmatrix[w1->w_index][w->w_index] |= WITNESS_REVERSAL;
 1326                         w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL;
 1327                         w->w_reversed = w1->w_reversed = 1;
 1328                         witness_increment_graph_generation();
 1329                         mtx_unlock_spin(&w_mtx);
 1330 
 1331 #ifdef WITNESS_NO_VNODE
 1332                         /*
 1333                          * There are known LORs between VNODE locks. They are
 1334                          * not an indication of a bug. VNODE locks are flagged
 1335                          * as such (LO_IS_VNODE) and we don't yell if the LOR
 1336                          * is between 2 VNODE locks.
 1337                          */
 1338                         if ((lock->lo_flags & LO_IS_VNODE) != 0 &&
 1339                             (lock1->li_lock->lo_flags & LO_IS_VNODE) != 0)
 1340                                 return;
 1341 #endif
 1342 
 1343                         /*
 1344                          * Ok, yell about it.
 1345                          */
 1346                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1347                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
 1348                                 witness_output(
 1349                 "lock order reversal: (sleepable after non-sleepable)\n");
 1350                         else if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0
 1351                             && lock == &Giant.lock_object)
 1352                                 witness_output(
 1353                 "lock order reversal: (Giant after non-sleepable)\n");
 1354                         else
 1355                                 witness_output("lock order reversal:\n");
 1356 
 1357                         /*
 1358                          * Try to locate an earlier lock with
 1359                          * witness w in our list.
 1360                          */
 1361                         do {
 1362                                 lock2 = &lle->ll_children[i];
 1363                                 MPASS(lock2->li_lock != NULL);
 1364                                 if (lock2->li_lock->lo_witness == w)
 1365                                         break;
 1366                                 if (i == 0 && lle->ll_next != NULL) {
 1367                                         lle = lle->ll_next;
 1368                                         i = lle->ll_count - 1;
 1369                                         MPASS(i >= 0 && i < LOCK_NCHILDREN);
 1370                                 } else
 1371                                         i--;
 1372                         } while (i >= 0);
 1373                         if (i < 0) {
 1374                                 witness_output(" 1st %p %s (%s) @ %s:%d\n",
 1375                                     lock1->li_lock, lock1->li_lock->lo_name,
 1376                                     w1->w_name, fixup_filename(lock1->li_file),
 1377                                     lock1->li_line);
 1378                                 witness_output(" 2nd %p %s (%s) @ %s:%d\n", lock,
 1379                                     lock->lo_name, w->w_name,
 1380                                     fixup_filename(file), line);
 1381                         } else {
 1382                                 witness_output(" 1st %p %s (%s) @ %s:%d\n",
 1383                                     lock2->li_lock, lock2->li_lock->lo_name,
 1384                                     lock2->li_lock->lo_witness->w_name,
 1385                                     fixup_filename(lock2->li_file),
 1386                                     lock2->li_line);
 1387                                 witness_output(" 2nd %p %s (%s) @ %s:%d\n",
 1388                                     lock1->li_lock, lock1->li_lock->lo_name,
 1389                                     w1->w_name, fixup_filename(lock1->li_file),
 1390                                     lock1->li_line);
 1391                                 witness_output(" 3rd %p %s (%s) @ %s:%d\n", lock,
 1392                                     lock->lo_name, w->w_name,
 1393                                     fixup_filename(file), line);
 1394                         }
 1395                         witness_debugger(1, __func__);
 1396                         return;
 1397                 }
 1398         }
 1399 
 1400         /*
 1401          * If requested, build a new lock order.  However, don't build a new
 1402          * relationship between a sleepable lock and Giant if it is in the
 1403          * wrong direction.  The correct lock order is that sleepable locks
 1404          * always come before Giant.
 1405          */
 1406         if (flags & LOP_NEWORDER &&
 1407             !(plock->li_lock == &Giant.lock_object &&
 1408             (lock->lo_flags & LO_SLEEPABLE) != 0)) {
 1409                 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 1410                     w->w_name, plock->li_lock->lo_witness->w_name);
 1411                 itismychild(plock->li_lock->lo_witness, w);
 1412         }
 1413 out:
 1414         mtx_unlock_spin(&w_mtx);
 1415 }
 1416 
 1417 void
 1418 witness_lock(struct lock_object *lock, int flags, const char *file, int line)
 1419 {
 1420         struct lock_list_entry **lock_list, *lle;
 1421         struct lock_instance *instance;
 1422         struct witness *w;
 1423         struct thread *td;
 1424 
 1425         if (witness_cold || witness_watch == -1 || lock->lo_witness == NULL ||
 1426             panicstr != NULL)
 1427                 return;
 1428         w = lock->lo_witness;
 1429         td = curthread;
 1430 
 1431         /* Determine lock list for this lock. */
 1432         if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK)
 1433                 lock_list = &td->td_sleeplocks;
 1434         else
 1435                 lock_list = PCPU_PTR(spinlocks);
 1436 
 1437         /* Check to see if we are recursing on a lock we already own. */
 1438         instance = find_instance(*lock_list, lock);
 1439         if (instance != NULL) {
 1440                 instance->li_flags++;
 1441                 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__,
 1442                     td->td_proc->p_pid, lock->lo_name,
 1443                     instance->li_flags & LI_RECURSEMASK);
 1444                 instance->li_file = file;
 1445                 instance->li_line = line;
 1446                 return;
 1447         }
 1448 
 1449         /* Update per-witness last file and line acquire. */
 1450         w->w_file = file;
 1451         w->w_line = line;
 1452 
 1453         /* Find the next open lock instance in the list and fill it. */
 1454         lle = *lock_list;
 1455         if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
 1456                 lle = witness_lock_list_get();
 1457                 if (lle == NULL)
 1458                         return;
 1459                 lle->ll_next = *lock_list;
 1460                 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__,
 1461                     td->td_proc->p_pid, lle);
 1462                 *lock_list = lle;
 1463         }
 1464         instance = &lle->ll_children[lle->ll_count++];
 1465         instance->li_lock = lock;
 1466         instance->li_line = line;
 1467         instance->li_file = file;
 1468         if ((flags & LOP_EXCLUSIVE) != 0)
 1469                 instance->li_flags = LI_EXCLUSIVE;
 1470         else
 1471                 instance->li_flags = 0;
 1472         CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__,
 1473             td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1);
 1474 }
 1475 
 1476 void
 1477 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line)
 1478 {
 1479         struct lock_instance *instance;
 1480         struct lock_class *class;
 1481 
 1482         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 1483         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 1484                 return;
 1485         class = LOCK_CLASS(lock);
 1486         if (witness_watch) {
 1487                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
 1488                         kassert_panic(
 1489                             "upgrade of non-upgradable lock (%s) %s @ %s:%d",
 1490                             class->lc_name, lock->lo_name,
 1491                             fixup_filename(file), line);
 1492                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
 1493                         kassert_panic(
 1494                             "upgrade of non-sleep lock (%s) %s @ %s:%d",
 1495                             class->lc_name, lock->lo_name,
 1496                             fixup_filename(file), line);
 1497         }
 1498         instance = find_instance(curthread->td_sleeplocks, lock);
 1499         if (instance == NULL) {
 1500                 kassert_panic("upgrade of unlocked lock (%s) %s @ %s:%d",
 1501                     class->lc_name, lock->lo_name,
 1502                     fixup_filename(file), line);
 1503                 return;
 1504         }
 1505         if (witness_watch) {
 1506                 if ((instance->li_flags & LI_EXCLUSIVE) != 0)
 1507                         kassert_panic(
 1508                             "upgrade of exclusive lock (%s) %s @ %s:%d",
 1509                             class->lc_name, lock->lo_name,
 1510                             fixup_filename(file), line);
 1511                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
 1512                         kassert_panic(
 1513                             "upgrade of recursed lock (%s) %s r=%d @ %s:%d",
 1514                             class->lc_name, lock->lo_name,
 1515                             instance->li_flags & LI_RECURSEMASK,
 1516                             fixup_filename(file), line);
 1517         }
 1518         instance->li_flags |= LI_EXCLUSIVE;
 1519 }
 1520 
 1521 void
 1522 witness_downgrade(struct lock_object *lock, int flags, const char *file,
 1523     int line)
 1524 {
 1525         struct lock_instance *instance;
 1526         struct lock_class *class;
 1527 
 1528         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 1529         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 1530                 return;
 1531         class = LOCK_CLASS(lock);
 1532         if (witness_watch) {
 1533                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
 1534                         kassert_panic(
 1535                             "downgrade of non-upgradable lock (%s) %s @ %s:%d",
 1536                             class->lc_name, lock->lo_name,
 1537                             fixup_filename(file), line);
 1538                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
 1539                         kassert_panic(
 1540                             "downgrade of non-sleep lock (%s) %s @ %s:%d",
 1541                             class->lc_name, lock->lo_name,
 1542                             fixup_filename(file), line);
 1543         }
 1544         instance = find_instance(curthread->td_sleeplocks, lock);
 1545         if (instance == NULL) {
 1546                 kassert_panic("downgrade of unlocked lock (%s) %s @ %s:%d",
 1547                     class->lc_name, lock->lo_name,
 1548                     fixup_filename(file), line);
 1549                 return;
 1550         }
 1551         if (witness_watch) {
 1552                 if ((instance->li_flags & LI_EXCLUSIVE) == 0)
 1553                         kassert_panic(
 1554                             "downgrade of shared lock (%s) %s @ %s:%d",
 1555                             class->lc_name, lock->lo_name,
 1556                             fixup_filename(file), line);
 1557                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
 1558                         kassert_panic(
 1559                             "downgrade of recursed lock (%s) %s r=%d @ %s:%d",
 1560                             class->lc_name, lock->lo_name,
 1561                             instance->li_flags & LI_RECURSEMASK,
 1562                             fixup_filename(file), line);
 1563         }
 1564         instance->li_flags &= ~LI_EXCLUSIVE;
 1565 }
 1566 
 1567 void
 1568 witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
 1569 {
 1570         struct lock_list_entry **lock_list, *lle;
 1571         struct lock_instance *instance;
 1572         struct lock_class *class;
 1573         struct thread *td;
 1574         register_t s;
 1575         int i, j;
 1576 
 1577         if (witness_cold || lock->lo_witness == NULL || panicstr != NULL)
 1578                 return;
 1579         td = curthread;
 1580         class = LOCK_CLASS(lock);
 1581 
 1582         /* Find lock instance associated with this lock. */
 1583         if (class->lc_flags & LC_SLEEPLOCK)
 1584                 lock_list = &td->td_sleeplocks;
 1585         else
 1586                 lock_list = PCPU_PTR(spinlocks);
 1587         lle = *lock_list;
 1588         for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next)
 1589                 for (i = 0; i < (*lock_list)->ll_count; i++) {
 1590                         instance = &(*lock_list)->ll_children[i];
 1591                         if (instance->li_lock == lock)
 1592                                 goto found;
 1593                 }
 1594 
 1595         /*
 1596          * When disabling WITNESS through witness_watch we could end up in
 1597          * having registered locks in the td_sleeplocks queue.
 1598          * We have to make sure we flush these queues, so just search for
 1599          * eventual register locks and remove them.
 1600          */
 1601         if (witness_watch > 0) {
 1602                 kassert_panic("lock (%s) %s not locked @ %s:%d", class->lc_name,
 1603                     lock->lo_name, fixup_filename(file), line);
 1604                 return;
 1605         } else {
 1606                 return;
 1607         }
 1608 found:
 1609 
 1610         /* First, check for shared/exclusive mismatches. */
 1611         if ((instance->li_flags & LI_EXCLUSIVE) != 0 && witness_watch > 0 &&
 1612             (flags & LOP_EXCLUSIVE) == 0) {
 1613                 witness_output("shared unlock of (%s) %s @ %s:%d\n",
 1614                     class->lc_name, lock->lo_name, fixup_filename(file), line);
 1615                 witness_output("while exclusively locked from %s:%d\n",
 1616                     fixup_filename(instance->li_file), instance->li_line);
 1617                 kassert_panic("excl->ushare");
 1618         }
 1619         if ((instance->li_flags & LI_EXCLUSIVE) == 0 && witness_watch > 0 &&
 1620             (flags & LOP_EXCLUSIVE) != 0) {
 1621                 witness_output("exclusive unlock of (%s) %s @ %s:%d\n",
 1622                     class->lc_name, lock->lo_name, fixup_filename(file), line);
 1623                 witness_output("while share locked from %s:%d\n",
 1624                     fixup_filename(instance->li_file),
 1625                     instance->li_line);
 1626                 kassert_panic("share->uexcl");
 1627         }
 1628         /* If we are recursed, unrecurse. */
 1629         if ((instance->li_flags & LI_RECURSEMASK) > 0) {
 1630                 CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__,
 1631                     td->td_proc->p_pid, instance->li_lock->lo_name,
 1632                     instance->li_flags);
 1633                 instance->li_flags--;
 1634                 return;
 1635         }
 1636         /* The lock is now being dropped, check for NORELEASE flag */
 1637         if ((instance->li_flags & LI_NORELEASE) != 0 && witness_watch > 0) {
 1638                 witness_output("forbidden unlock of (%s) %s @ %s:%d\n",
 1639                     class->lc_name, lock->lo_name, fixup_filename(file), line);
 1640                 kassert_panic("lock marked norelease");
 1641         }
 1642 
 1643         /* Otherwise, remove this item from the list. */
 1644         s = intr_disable();
 1645         CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__,
 1646             td->td_proc->p_pid, instance->li_lock->lo_name,
 1647             (*lock_list)->ll_count - 1);
 1648         for (j = i; j < (*lock_list)->ll_count - 1; j++)
 1649                 (*lock_list)->ll_children[j] =
 1650                     (*lock_list)->ll_children[j + 1];
 1651         (*lock_list)->ll_count--;
 1652         intr_restore(s);
 1653 
 1654         /*
 1655          * In order to reduce contention on w_mtx, we want to keep always an
 1656          * head object into lists so that frequent allocation from the 
 1657          * free witness pool (and subsequent locking) is avoided.
 1658          * In order to maintain the current code simple, when the head
 1659          * object is totally unloaded it means also that we do not have
 1660          * further objects in the list, so the list ownership needs to be
 1661          * hand over to another object if the current head needs to be freed.
 1662          */
 1663         if ((*lock_list)->ll_count == 0) {
 1664                 if (*lock_list == lle) {
 1665                         if (lle->ll_next == NULL)
 1666                                 return;
 1667                 } else
 1668                         lle = *lock_list;
 1669                 *lock_list = lle->ll_next;
 1670                 CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__,
 1671                     td->td_proc->p_pid, lle);
 1672                 witness_lock_list_free(lle);
 1673         }
 1674 }
 1675 
 1676 void
 1677 witness_thread_exit(struct thread *td)
 1678 {
 1679         struct lock_list_entry *lle;
 1680         int i, n;
 1681 
 1682         lle = td->td_sleeplocks;
 1683         if (lle == NULL || panicstr != NULL)
 1684                 return;
 1685         if (lle->ll_count != 0) {
 1686                 for (n = 0; lle != NULL; lle = lle->ll_next)
 1687                         for (i = lle->ll_count - 1; i >= 0; i--) {
 1688                                 if (n == 0)
 1689                                         witness_output(
 1690                     "Thread %p exiting with the following locks held:\n", td);
 1691                                 n++;
 1692                                 witness_list_lock(&lle->ll_children[i],
 1693                                     witness_output);
 1694                                 
 1695                         }
 1696                 kassert_panic(
 1697                     "Thread %p cannot exit while holding sleeplocks\n", td);
 1698         }
 1699         witness_lock_list_free(lle);
 1700 }
 1701 
 1702 /*
 1703  * Warn if any locks other than 'lock' are held.  Flags can be passed in to
 1704  * exempt Giant and sleepable locks from the checks as well.  If any
 1705  * non-exempt locks are held, then a supplied message is printed to the
 1706  * output channel along with a list of the offending locks.  If indicated in the
 1707  * flags then a failure results in a panic as well.
 1708  */
 1709 int
 1710 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
 1711 {
 1712         struct lock_list_entry *lock_list, *lle;
 1713         struct lock_instance *lock1;
 1714         struct thread *td;
 1715         va_list ap;
 1716         int i, n;
 1717 
 1718         if (witness_cold || witness_watch < 1 || panicstr != NULL)
 1719                 return (0);
 1720         n = 0;
 1721         td = curthread;
 1722         for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next)
 1723                 for (i = lle->ll_count - 1; i >= 0; i--) {
 1724                         lock1 = &lle->ll_children[i];
 1725                         if (lock1->li_lock == lock)
 1726                                 continue;
 1727                         if (flags & WARN_GIANTOK &&
 1728                             lock1->li_lock == &Giant.lock_object)
 1729                                 continue;
 1730                         if (flags & WARN_SLEEPOK &&
 1731                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0)
 1732                                 continue;
 1733                         if (n == 0) {
 1734                                 va_start(ap, fmt);
 1735                                 vprintf(fmt, ap);
 1736                                 va_end(ap);
 1737                                 printf(" with the following %slocks held:\n",
 1738                                     (flags & WARN_SLEEPOK) != 0 ?
 1739                                     "non-sleepable " : "");
 1740                         }
 1741                         n++;
 1742                         witness_list_lock(lock1, printf);
 1743                 }
 1744 
 1745         /*
 1746          * Pin the thread in order to avoid problems with thread migration.
 1747          * Once that all verifies are passed about spinlocks ownership,
 1748          * the thread is in a safe path and it can be unpinned.
 1749          */
 1750         sched_pin();
 1751         lock_list = PCPU_GET(spinlocks);
 1752         if (lock_list != NULL && lock_list->ll_count != 0) {
 1753                 sched_unpin();
 1754 
 1755                 /*
 1756                  * We should only have one spinlock and as long as
 1757                  * the flags cannot match for this locks class,
 1758                  * check if the first spinlock is the one curthread
 1759                  * should hold.
 1760                  */
 1761                 lock1 = &lock_list->ll_children[lock_list->ll_count - 1];
 1762                 if (lock_list->ll_count == 1 && lock_list->ll_next == NULL &&
 1763                     lock1->li_lock == lock && n == 0)
 1764                         return (0);
 1765 
 1766                 va_start(ap, fmt);
 1767                 vprintf(fmt, ap);
 1768                 va_end(ap);
 1769                 printf(" with the following %slocks held:\n",
 1770                     (flags & WARN_SLEEPOK) != 0 ?  "non-sleepable " : "");
 1771                 n += witness_list_locks(&lock_list, printf);
 1772         } else
 1773                 sched_unpin();
 1774         if (flags & WARN_PANIC && n)
 1775                 kassert_panic("%s", __func__);
 1776         else
 1777                 witness_debugger(n, __func__);
 1778         return (n);
 1779 }
 1780 
 1781 const char *
 1782 witness_file(struct lock_object *lock)
 1783 {
 1784         struct witness *w;
 1785 
 1786         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
 1787                 return ("?");
 1788         w = lock->lo_witness;
 1789         return (w->w_file);
 1790 }
 1791 
 1792 int
 1793 witness_line(struct lock_object *lock)
 1794 {
 1795         struct witness *w;
 1796 
 1797         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
 1798                 return (0);
 1799         w = lock->lo_witness;
 1800         return (w->w_line);
 1801 }
 1802 
 1803 static struct witness *
 1804 enroll(const char *description, struct lock_class *lock_class)
 1805 {
 1806         struct witness *w;
 1807         struct witness_list *typelist;
 1808 
 1809         MPASS(description != NULL);
 1810 
 1811         if (witness_watch == -1 || panicstr != NULL)
 1812                 return (NULL);
 1813         if ((lock_class->lc_flags & LC_SPINLOCK)) {
 1814                 if (witness_skipspin)
 1815                         return (NULL);
 1816                 else
 1817                         typelist = &w_spin;
 1818         } else if ((lock_class->lc_flags & LC_SLEEPLOCK)) {
 1819                 typelist = &w_sleep;
 1820         } else {
 1821                 kassert_panic("lock class %s is not sleep or spin",
 1822                     lock_class->lc_name);
 1823                 return (NULL);
 1824         }
 1825 
 1826         mtx_lock_spin(&w_mtx);
 1827         w = witness_hash_get(description);
 1828         if (w)
 1829                 goto found;
 1830         if ((w = witness_get()) == NULL)
 1831                 return (NULL);
 1832         MPASS(strlen(description) < MAX_W_NAME);
 1833         strcpy(w->w_name, description);
 1834         w->w_class = lock_class;
 1835         w->w_refcount = 1;
 1836         STAILQ_INSERT_HEAD(&w_all, w, w_list);
 1837         if (lock_class->lc_flags & LC_SPINLOCK) {
 1838                 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist);
 1839                 w_spin_cnt++;
 1840         } else if (lock_class->lc_flags & LC_SLEEPLOCK) {
 1841                 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist);
 1842                 w_sleep_cnt++;
 1843         }
 1844 
 1845         /* Insert new witness into the hash */
 1846         witness_hash_put(w);
 1847         witness_increment_graph_generation();
 1848         mtx_unlock_spin(&w_mtx);
 1849         return (w);
 1850 found:
 1851         w->w_refcount++;
 1852         if (w->w_refcount == 1)
 1853                 w->w_class = lock_class;
 1854         mtx_unlock_spin(&w_mtx);
 1855         if (lock_class != w->w_class)
 1856                 kassert_panic(
 1857                     "lock (%s) %s does not match earlier (%s) lock",
 1858                     description, lock_class->lc_name,
 1859                     w->w_class->lc_name);
 1860         return (w);
 1861 }
 1862 
 1863 static void
 1864 depart(struct witness *w)
 1865 {
 1866         struct witness_list *list;
 1867 
 1868         MPASS(w->w_refcount == 0);
 1869         if (w->w_class->lc_flags & LC_SLEEPLOCK) {
 1870                 list = &w_sleep;
 1871                 w_sleep_cnt--;
 1872         } else {
 1873                 list = &w_spin;
 1874                 w_spin_cnt--;
 1875         }
 1876         /*
 1877          * Set file to NULL as it may point into a loadable module.
 1878          */
 1879         w->w_file = NULL;
 1880         w->w_line = 0;
 1881         witness_increment_graph_generation();
 1882 }
 1883 
 1884 
 1885 static void
 1886 adopt(struct witness *parent, struct witness *child)
 1887 {
 1888         int pi, ci, i, j;
 1889 
 1890         if (witness_cold == 0)
 1891                 mtx_assert(&w_mtx, MA_OWNED);
 1892 
 1893         /* If the relationship is already known, there's no work to be done. */
 1894         if (isitmychild(parent, child))
 1895                 return;
 1896 
 1897         /* When the structure of the graph changes, bump up the generation. */
 1898         witness_increment_graph_generation();
 1899 
 1900         /*
 1901          * The hard part ... create the direct relationship, then propagate all
 1902          * indirect relationships.
 1903          */
 1904         pi = parent->w_index;
 1905         ci = child->w_index;
 1906         WITNESS_INDEX_ASSERT(pi);
 1907         WITNESS_INDEX_ASSERT(ci);
 1908         MPASS(pi != ci);
 1909         w_rmatrix[pi][ci] |= WITNESS_PARENT;
 1910         w_rmatrix[ci][pi] |= WITNESS_CHILD;
 1911 
 1912         /*
 1913          * If parent was not already an ancestor of child,
 1914          * then we increment the descendant and ancestor counters.
 1915          */
 1916         if ((w_rmatrix[pi][ci] & WITNESS_ANCESTOR) == 0) {
 1917                 parent->w_num_descendants++;
 1918                 child->w_num_ancestors++;
 1919         }
 1920 
 1921         /* 
 1922          * Find each ancestor of 'pi'. Note that 'pi' itself is counted as 
 1923          * an ancestor of 'pi' during this loop.
 1924          */
 1925         for (i = 1; i <= w_max_used_index; i++) {
 1926                 if ((w_rmatrix[i][pi] & WITNESS_ANCESTOR_MASK) == 0 && 
 1927                     (i != pi))
 1928                         continue;
 1929 
 1930                 /* Find each descendant of 'i' and mark it as a descendant. */
 1931                 for (j = 1; j <= w_max_used_index; j++) {
 1932 
 1933                         /* 
 1934                          * Skip children that are already marked as
 1935                          * descendants of 'i'.
 1936                          */
 1937                         if (w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK)
 1938                                 continue;
 1939 
 1940                         /*
 1941                          * We are only interested in descendants of 'ci'. Note
 1942                          * that 'ci' itself is counted as a descendant of 'ci'.
 1943                          */
 1944                         if ((w_rmatrix[ci][j] & WITNESS_ANCESTOR_MASK) == 0 && 
 1945                             (j != ci))
 1946                                 continue;
 1947                         w_rmatrix[i][j] |= WITNESS_ANCESTOR;
 1948                         w_rmatrix[j][i] |= WITNESS_DESCENDANT;
 1949                         w_data[i].w_num_descendants++;
 1950                         w_data[j].w_num_ancestors++;
 1951 
 1952                         /* 
 1953                          * Make sure we aren't marking a node as both an
 1954                          * ancestor and descendant. We should have caught 
 1955                          * this as a lock order reversal earlier.
 1956                          */
 1957                         if ((w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) &&
 1958                             (w_rmatrix[i][j] & WITNESS_DESCENDANT_MASK)) {
 1959                                 printf("witness rmatrix paradox! [%d][%d]=%d "
 1960                                     "both ancestor and descendant\n",
 1961                                     i, j, w_rmatrix[i][j]); 
 1962                                 kdb_backtrace();
 1963                                 printf("Witness disabled.\n");
 1964                                 witness_watch = -1;
 1965                         }
 1966                         if ((w_rmatrix[j][i] & WITNESS_ANCESTOR_MASK) &&
 1967                             (w_rmatrix[j][i] & WITNESS_DESCENDANT_MASK)) {
 1968                                 printf("witness rmatrix paradox! [%d][%d]=%d "
 1969                                     "both ancestor and descendant\n",
 1970                                     j, i, w_rmatrix[j][i]); 
 1971                                 kdb_backtrace();
 1972                                 printf("Witness disabled.\n");
 1973                                 witness_watch = -1;
 1974                         }
 1975                 }
 1976         }
 1977 }
 1978 
 1979 static void
 1980 itismychild(struct witness *parent, struct witness *child)
 1981 {
 1982         int unlocked;
 1983 
 1984         MPASS(child != NULL && parent != NULL);
 1985         if (witness_cold == 0)
 1986                 mtx_assert(&w_mtx, MA_OWNED);
 1987 
 1988         if (!witness_lock_type_equal(parent, child)) {
 1989                 if (witness_cold == 0) {
 1990                         unlocked = 1;
 1991                         mtx_unlock_spin(&w_mtx);
 1992                 } else {
 1993                         unlocked = 0;
 1994                 }
 1995                 kassert_panic(
 1996                     "%s: parent \"%s\" (%s) and child \"%s\" (%s) are not "
 1997                     "the same lock type", __func__, parent->w_name,
 1998                     parent->w_class->lc_name, child->w_name,
 1999                     child->w_class->lc_name);
 2000                 if (unlocked)
 2001                         mtx_lock_spin(&w_mtx);
 2002         }
 2003         adopt(parent, child);
 2004 }
 2005 
 2006 /*
 2007  * Generic code for the isitmy*() functions. The rmask parameter is the
 2008  * expected relationship of w1 to w2.
 2009  */
 2010 static int
 2011 _isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname)
 2012 {
 2013         unsigned char r1, r2;
 2014         int i1, i2;
 2015 
 2016         i1 = w1->w_index;
 2017         i2 = w2->w_index;
 2018         WITNESS_INDEX_ASSERT(i1);
 2019         WITNESS_INDEX_ASSERT(i2);
 2020         r1 = w_rmatrix[i1][i2] & WITNESS_RELATED_MASK;
 2021         r2 = w_rmatrix[i2][i1] & WITNESS_RELATED_MASK;
 2022 
 2023         /* The flags on one better be the inverse of the flags on the other */
 2024         if (!((WITNESS_ATOD(r1) == r2 && WITNESS_DTOA(r2) == r1) ||
 2025             (WITNESS_DTOA(r1) == r2 && WITNESS_ATOD(r2) == r1))) {
 2026                 /* Don't squawk if we're potentially racing with an update. */
 2027                 if (!mtx_owned(&w_mtx))
 2028                         return (0);
 2029                 printf("%s: rmatrix mismatch between %s (index %d) and %s "
 2030                     "(index %d): w_rmatrix[%d][%d] == %hhx but "
 2031                     "w_rmatrix[%d][%d] == %hhx\n",
 2032                     fname, w1->w_name, i1, w2->w_name, i2, i1, i2, r1,
 2033                     i2, i1, r2);
 2034                 kdb_backtrace();
 2035                 printf("Witness disabled.\n");
 2036                 witness_watch = -1;
 2037         }
 2038         return (r1 & rmask);
 2039 }
 2040 
 2041 /*
 2042  * Checks if @child is a direct child of @parent.
 2043  */
 2044 static int
 2045 isitmychild(struct witness *parent, struct witness *child)
 2046 {
 2047 
 2048         return (_isitmyx(parent, child, WITNESS_PARENT, __func__));
 2049 }
 2050 
 2051 /*
 2052  * Checks if @descendant is a direct or inderect descendant of @ancestor.
 2053  */
 2054 static int
 2055 isitmydescendant(struct witness *ancestor, struct witness *descendant)
 2056 {
 2057 
 2058         return (_isitmyx(ancestor, descendant, WITNESS_ANCESTOR_MASK,
 2059             __func__));
 2060 }
 2061 
 2062 #ifdef BLESSING
 2063 static int
 2064 blessed(struct witness *w1, struct witness *w2)
 2065 {
 2066         int i;
 2067         struct witness_blessed *b;
 2068 
 2069         for (i = 0; i < nitems(blessed_list); i++) {
 2070                 b = &blessed_list[i];
 2071                 if (strcmp(w1->w_name, b->b_lock1) == 0) {
 2072                         if (strcmp(w2->w_name, b->b_lock2) == 0)
 2073                                 return (1);
 2074                         continue;
 2075                 }
 2076                 if (strcmp(w1->w_name, b->b_lock2) == 0)
 2077                         if (strcmp(w2->w_name, b->b_lock1) == 0)
 2078                                 return (1);
 2079         }
 2080         return (0);
 2081 }
 2082 #endif
 2083 
 2084 static struct witness *
 2085 witness_get(void)
 2086 {
 2087         struct witness *w;
 2088         int index;
 2089 
 2090         if (witness_cold == 0)
 2091                 mtx_assert(&w_mtx, MA_OWNED);
 2092 
 2093         if (witness_watch == -1) {
 2094                 mtx_unlock_spin(&w_mtx);
 2095                 return (NULL);
 2096         }
 2097         if (STAILQ_EMPTY(&w_free)) {
 2098                 witness_watch = -1;
 2099                 mtx_unlock_spin(&w_mtx);
 2100                 printf("WITNESS: unable to allocate a new witness object\n");
 2101                 return (NULL);
 2102         }
 2103         w = STAILQ_FIRST(&w_free);
 2104         STAILQ_REMOVE_HEAD(&w_free, w_list);
 2105         w_free_cnt--;
 2106         index = w->w_index;
 2107         MPASS(index > 0 && index == w_max_used_index+1 &&
 2108             index < witness_count);
 2109         bzero(w, sizeof(*w));
 2110         w->w_index = index;
 2111         if (index > w_max_used_index)
 2112                 w_max_used_index = index;
 2113         return (w);
 2114 }
 2115 
 2116 static void
 2117 witness_free(struct witness *w)
 2118 {
 2119 
 2120         STAILQ_INSERT_HEAD(&w_free, w, w_list);
 2121         w_free_cnt++;
 2122 }
 2123 
 2124 static struct lock_list_entry *
 2125 witness_lock_list_get(void)
 2126 {
 2127         struct lock_list_entry *lle;
 2128 
 2129         if (witness_watch == -1)
 2130                 return (NULL);
 2131         mtx_lock_spin(&w_mtx);
 2132         lle = w_lock_list_free;
 2133         if (lle == NULL) {
 2134                 witness_watch = -1;
 2135                 mtx_unlock_spin(&w_mtx);
 2136                 printf("%s: witness exhausted\n", __func__);
 2137                 return (NULL);
 2138         }
 2139         w_lock_list_free = lle->ll_next;
 2140         mtx_unlock_spin(&w_mtx);
 2141         bzero(lle, sizeof(*lle));
 2142         return (lle);
 2143 }
 2144                 
 2145 static void
 2146 witness_lock_list_free(struct lock_list_entry *lle)
 2147 {
 2148 
 2149         mtx_lock_spin(&w_mtx);
 2150         lle->ll_next = w_lock_list_free;
 2151         w_lock_list_free = lle;
 2152         mtx_unlock_spin(&w_mtx);
 2153 }
 2154 
 2155 static struct lock_instance *
 2156 find_instance(struct lock_list_entry *list, const struct lock_object *lock)
 2157 {
 2158         struct lock_list_entry *lle;
 2159         struct lock_instance *instance;
 2160         int i;
 2161 
 2162         for (lle = list; lle != NULL; lle = lle->ll_next)
 2163                 for (i = lle->ll_count - 1; i >= 0; i--) {
 2164                         instance = &lle->ll_children[i];
 2165                         if (instance->li_lock == lock)
 2166                                 return (instance);
 2167                 }
 2168         return (NULL);
 2169 }
 2170 
 2171 static void
 2172 witness_list_lock(struct lock_instance *instance,
 2173     int (*prnt)(const char *fmt, ...))
 2174 {
 2175         struct lock_object *lock;
 2176 
 2177         lock = instance->li_lock;
 2178         prnt("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ?
 2179             "exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name);
 2180         if (lock->lo_witness->w_name != lock->lo_name)
 2181                 prnt(" (%s)", lock->lo_witness->w_name);
 2182         prnt(" r = %d (%p) locked @ %s:%d\n",
 2183             instance->li_flags & LI_RECURSEMASK, lock,
 2184             fixup_filename(instance->li_file), instance->li_line);
 2185 }
 2186 
 2187 static int
 2188 witness_output(const char *fmt, ...)
 2189 {
 2190         va_list ap;
 2191         int ret;
 2192 
 2193         va_start(ap, fmt);
 2194         ret = witness_voutput(fmt, ap);
 2195         va_end(ap);
 2196         return (ret);
 2197 }
 2198 
 2199 static int
 2200 witness_voutput(const char *fmt, va_list ap)
 2201 {
 2202         int ret;
 2203 
 2204         ret = 0;
 2205         switch (witness_channel) {
 2206         case WITNESS_CONSOLE:
 2207                 ret = vprintf(fmt, ap);
 2208                 break;
 2209         case WITNESS_LOG:
 2210                 vlog(LOG_NOTICE, fmt, ap);
 2211                 break;
 2212         case WITNESS_NONE:
 2213                 break;
 2214         }
 2215         return (ret);
 2216 }
 2217 
 2218 #ifdef DDB
 2219 static int
 2220 witness_thread_has_locks(struct thread *td)
 2221 {
 2222 
 2223         if (td->td_sleeplocks == NULL)
 2224                 return (0);
 2225         return (td->td_sleeplocks->ll_count != 0);
 2226 }
 2227 
 2228 static int
 2229 witness_proc_has_locks(struct proc *p)
 2230 {
 2231         struct thread *td;
 2232 
 2233         FOREACH_THREAD_IN_PROC(p, td) {
 2234                 if (witness_thread_has_locks(td))
 2235                         return (1);
 2236         }
 2237         return (0);
 2238 }
 2239 #endif
 2240 
 2241 int
 2242 witness_list_locks(struct lock_list_entry **lock_list,
 2243     int (*prnt)(const char *fmt, ...))
 2244 {
 2245         struct lock_list_entry *lle;
 2246         int i, nheld;
 2247 
 2248         nheld = 0;
 2249         for (lle = *lock_list; lle != NULL; lle = lle->ll_next)
 2250                 for (i = lle->ll_count - 1; i >= 0; i--) {
 2251                         witness_list_lock(&lle->ll_children[i], prnt);
 2252                         nheld++;
 2253                 }
 2254         return (nheld);
 2255 }
 2256 
 2257 /*
 2258  * This is a bit risky at best.  We call this function when we have timed
 2259  * out acquiring a spin lock, and we assume that the other CPU is stuck
 2260  * with this lock held.  So, we go groveling around in the other CPU's
 2261  * per-cpu data to try to find the lock instance for this spin lock to
 2262  * see when it was last acquired.
 2263  */
 2264 void
 2265 witness_display_spinlock(struct lock_object *lock, struct thread *owner,
 2266     int (*prnt)(const char *fmt, ...))
 2267 {
 2268         struct lock_instance *instance;
 2269         struct pcpu *pc;
 2270 
 2271         if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU)
 2272                 return;
 2273         pc = pcpu_find(owner->td_oncpu);
 2274         instance = find_instance(pc->pc_spinlocks, lock);
 2275         if (instance != NULL)
 2276                 witness_list_lock(instance, prnt);
 2277 }
 2278 
 2279 void
 2280 witness_save(struct lock_object *lock, const char **filep, int *linep)
 2281 {
 2282         struct lock_list_entry *lock_list;
 2283         struct lock_instance *instance;
 2284         struct lock_class *class;
 2285 
 2286         /*
 2287          * This function is used independently in locking code to deal with
 2288          * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
 2289          * is gone.
 2290          */
 2291         if (SCHEDULER_STOPPED())
 2292                 return;
 2293         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2294         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2295                 return;
 2296         class = LOCK_CLASS(lock);
 2297         if (class->lc_flags & LC_SLEEPLOCK)
 2298                 lock_list = curthread->td_sleeplocks;
 2299         else {
 2300                 if (witness_skipspin)
 2301                         return;
 2302                 lock_list = PCPU_GET(spinlocks);
 2303         }
 2304         instance = find_instance(lock_list, lock);
 2305         if (instance == NULL) {
 2306                 kassert_panic("%s: lock (%s) %s not locked", __func__,
 2307                     class->lc_name, lock->lo_name);
 2308                 return;
 2309         }
 2310         *filep = instance->li_file;
 2311         *linep = instance->li_line;
 2312 }
 2313 
 2314 void
 2315 witness_restore(struct lock_object *lock, const char *file, int line)
 2316 {
 2317         struct lock_list_entry *lock_list;
 2318         struct lock_instance *instance;
 2319         struct lock_class *class;
 2320 
 2321         /*
 2322          * This function is used independently in locking code to deal with
 2323          * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
 2324          * is gone.
 2325          */
 2326         if (SCHEDULER_STOPPED())
 2327                 return;
 2328         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2329         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2330                 return;
 2331         class = LOCK_CLASS(lock);
 2332         if (class->lc_flags & LC_SLEEPLOCK)
 2333                 lock_list = curthread->td_sleeplocks;
 2334         else {
 2335                 if (witness_skipspin)
 2336                         return;
 2337                 lock_list = PCPU_GET(spinlocks);
 2338         }
 2339         instance = find_instance(lock_list, lock);
 2340         if (instance == NULL)
 2341                 kassert_panic("%s: lock (%s) %s not locked", __func__,
 2342                     class->lc_name, lock->lo_name);
 2343         lock->lo_witness->w_file = file;
 2344         lock->lo_witness->w_line = line;
 2345         if (instance == NULL)
 2346                 return;
 2347         instance->li_file = file;
 2348         instance->li_line = line;
 2349 }
 2350 
 2351 void
 2352 witness_assert(const struct lock_object *lock, int flags, const char *file,
 2353     int line)
 2354 {
 2355 #ifdef INVARIANT_SUPPORT
 2356         struct lock_instance *instance;
 2357         struct lock_class *class;
 2358 
 2359         if (lock->lo_witness == NULL || witness_watch < 1 || panicstr != NULL)
 2360                 return;
 2361         class = LOCK_CLASS(lock);
 2362         if ((class->lc_flags & LC_SLEEPLOCK) != 0)
 2363                 instance = find_instance(curthread->td_sleeplocks, lock);
 2364         else if ((class->lc_flags & LC_SPINLOCK) != 0)
 2365                 instance = find_instance(PCPU_GET(spinlocks), lock);
 2366         else {
 2367                 kassert_panic("Lock (%s) %s is not sleep or spin!",
 2368                     class->lc_name, lock->lo_name);
 2369                 return;
 2370         }
 2371         switch (flags) {
 2372         case LA_UNLOCKED:
 2373                 if (instance != NULL)
 2374                         kassert_panic("Lock (%s) %s locked @ %s:%d.",
 2375                             class->lc_name, lock->lo_name,
 2376                             fixup_filename(file), line);
 2377                 break;
 2378         case LA_LOCKED:
 2379         case LA_LOCKED | LA_RECURSED:
 2380         case LA_LOCKED | LA_NOTRECURSED:
 2381         case LA_SLOCKED:
 2382         case LA_SLOCKED | LA_RECURSED:
 2383         case LA_SLOCKED | LA_NOTRECURSED:
 2384         case LA_XLOCKED:
 2385         case LA_XLOCKED | LA_RECURSED:
 2386         case LA_XLOCKED | LA_NOTRECURSED:
 2387                 if (instance == NULL) {
 2388                         kassert_panic("Lock (%s) %s not locked @ %s:%d.",
 2389                             class->lc_name, lock->lo_name,
 2390                             fixup_filename(file), line);
 2391                         break;
 2392                 }
 2393                 if ((flags & LA_XLOCKED) != 0 &&
 2394                     (instance->li_flags & LI_EXCLUSIVE) == 0)
 2395                         kassert_panic(
 2396                             "Lock (%s) %s not exclusively locked @ %s:%d.",
 2397                             class->lc_name, lock->lo_name,
 2398                             fixup_filename(file), line);
 2399                 if ((flags & LA_SLOCKED) != 0 &&
 2400                     (instance->li_flags & LI_EXCLUSIVE) != 0)
 2401                         kassert_panic(
 2402                             "Lock (%s) %s exclusively locked @ %s:%d.",
 2403                             class->lc_name, lock->lo_name,
 2404                             fixup_filename(file), line);
 2405                 if ((flags & LA_RECURSED) != 0 &&
 2406                     (instance->li_flags & LI_RECURSEMASK) == 0)
 2407                         kassert_panic("Lock (%s) %s not recursed @ %s:%d.",
 2408                             class->lc_name, lock->lo_name,
 2409                             fixup_filename(file), line);
 2410                 if ((flags & LA_NOTRECURSED) != 0 &&
 2411                     (instance->li_flags & LI_RECURSEMASK) != 0)
 2412                         kassert_panic("Lock (%s) %s recursed @ %s:%d.",
 2413                             class->lc_name, lock->lo_name,
 2414                             fixup_filename(file), line);
 2415                 break;
 2416         default:
 2417                 kassert_panic("Invalid lock assertion at %s:%d.",
 2418                     fixup_filename(file), line);
 2419 
 2420         }
 2421 #endif  /* INVARIANT_SUPPORT */
 2422 }
 2423 
 2424 static void
 2425 witness_setflag(struct lock_object *lock, int flag, int set)
 2426 {
 2427         struct lock_list_entry *lock_list;
 2428         struct lock_instance *instance;
 2429         struct lock_class *class;
 2430 
 2431         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2432                 return;
 2433         class = LOCK_CLASS(lock);
 2434         if (class->lc_flags & LC_SLEEPLOCK)
 2435                 lock_list = curthread->td_sleeplocks;
 2436         else {
 2437                 if (witness_skipspin)
 2438                         return;
 2439                 lock_list = PCPU_GET(spinlocks);
 2440         }
 2441         instance = find_instance(lock_list, lock);
 2442         if (instance == NULL) {
 2443                 kassert_panic("%s: lock (%s) %s not locked", __func__,
 2444                     class->lc_name, lock->lo_name);
 2445                 return;
 2446         }
 2447 
 2448         if (set)
 2449                 instance->li_flags |= flag;
 2450         else
 2451                 instance->li_flags &= ~flag;
 2452 }
 2453 
 2454 void
 2455 witness_norelease(struct lock_object *lock)
 2456 {
 2457 
 2458         witness_setflag(lock, LI_NORELEASE, 1);
 2459 }
 2460 
 2461 void
 2462 witness_releaseok(struct lock_object *lock)
 2463 {
 2464 
 2465         witness_setflag(lock, LI_NORELEASE, 0);
 2466 }
 2467 
 2468 #ifdef DDB
 2469 static void
 2470 witness_ddb_list(struct thread *td)
 2471 {
 2472 
 2473         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2474         KASSERT(kdb_active, ("%s: not in the debugger", __func__));
 2475 
 2476         if (witness_watch < 1)
 2477                 return;
 2478 
 2479         witness_list_locks(&td->td_sleeplocks, db_printf);
 2480 
 2481         /*
 2482          * We only handle spinlocks if td == curthread.  This is somewhat broken
 2483          * if td is currently executing on some other CPU and holds spin locks
 2484          * as we won't display those locks.  If we had a MI way of getting
 2485          * the per-cpu data for a given cpu then we could use
 2486          * td->td_oncpu to get the list of spinlocks for this thread
 2487          * and "fix" this.
 2488          *
 2489          * That still wouldn't really fix this unless we locked the scheduler
 2490          * lock or stopped the other CPU to make sure it wasn't changing the
 2491          * list out from under us.  It is probably best to just not try to
 2492          * handle threads on other CPU's for now.
 2493          */
 2494         if (td == curthread && PCPU_GET(spinlocks) != NULL)
 2495                 witness_list_locks(PCPU_PTR(spinlocks), db_printf);
 2496 }
 2497 
 2498 DB_SHOW_COMMAND(locks, db_witness_list)
 2499 {
 2500         struct thread *td;
 2501 
 2502         if (have_addr)
 2503                 td = db_lookup_thread(addr, true);
 2504         else
 2505                 td = kdb_thread;
 2506         witness_ddb_list(td);
 2507 }
 2508 
 2509 DB_SHOW_ALL_COMMAND(locks, db_witness_list_all)
 2510 {
 2511         struct thread *td;
 2512         struct proc *p;
 2513 
 2514         /*
 2515          * It would be nice to list only threads and processes that actually
 2516          * held sleep locks, but that information is currently not exported
 2517          * by WITNESS.
 2518          */
 2519         FOREACH_PROC_IN_SYSTEM(p) {
 2520                 if (!witness_proc_has_locks(p))
 2521                         continue;
 2522                 FOREACH_THREAD_IN_PROC(p, td) {
 2523                         if (!witness_thread_has_locks(td))
 2524                                 continue;
 2525                         db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid,
 2526                             p->p_comm, td, td->td_tid);
 2527                         witness_ddb_list(td);
 2528                         if (db_pager_quit)
 2529                                 return;
 2530                 }
 2531         }
 2532 }
 2533 DB_SHOW_ALIAS(alllocks, db_witness_list_all)
 2534 
 2535 DB_SHOW_COMMAND(witness, db_witness_display)
 2536 {
 2537 
 2538         witness_ddb_display(db_printf);
 2539 }
 2540 #endif
 2541 
 2542 static int
 2543 sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS)
 2544 {
 2545         struct witness_lock_order_data *data1, *data2, *tmp_data1, *tmp_data2;
 2546         struct witness *tmp_w1, *tmp_w2, *w1, *w2;
 2547         struct sbuf *sb;
 2548         u_int w_rmatrix1, w_rmatrix2;
 2549         int error, generation, i, j;
 2550 
 2551         tmp_data1 = NULL;
 2552         tmp_data2 = NULL;
 2553         tmp_w1 = NULL;
 2554         tmp_w2 = NULL;
 2555         if (witness_watch < 1) {
 2556                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
 2557                 return (error);
 2558         }
 2559         if (witness_cold) {
 2560                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
 2561                 return (error);
 2562         }
 2563         error = 0;
 2564         sb = sbuf_new(NULL, NULL, badstack_sbuf_size, SBUF_AUTOEXTEND);
 2565         if (sb == NULL)
 2566                 return (ENOMEM);
 2567 
 2568         /* Allocate and init temporary storage space. */
 2569         tmp_w1 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
 2570         tmp_w2 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
 2571         tmp_data1 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 
 2572             M_WAITOK | M_ZERO);
 2573         tmp_data2 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 
 2574             M_WAITOK | M_ZERO);
 2575         stack_zero(&tmp_data1->wlod_stack);
 2576         stack_zero(&tmp_data2->wlod_stack);
 2577 
 2578 restart:
 2579         mtx_lock_spin(&w_mtx);
 2580         generation = w_generation;
 2581         mtx_unlock_spin(&w_mtx);
 2582         sbuf_printf(sb, "Number of known direct relationships is %d\n",
 2583             w_lohash.wloh_count);
 2584         for (i = 1; i < w_max_used_index; i++) {
 2585                 mtx_lock_spin(&w_mtx);
 2586                 if (generation != w_generation) {
 2587                         mtx_unlock_spin(&w_mtx);
 2588 
 2589                         /* The graph has changed, try again. */
 2590                         req->oldidx = 0;
 2591                         sbuf_clear(sb);
 2592                         goto restart;
 2593                 }
 2594 
 2595                 w1 = &w_data[i];
 2596                 if (w1->w_reversed == 0) {
 2597                         mtx_unlock_spin(&w_mtx);
 2598                         continue;
 2599                 }
 2600 
 2601                 /* Copy w1 locally so we can release the spin lock. */
 2602                 *tmp_w1 = *w1;
 2603                 mtx_unlock_spin(&w_mtx);
 2604 
 2605                 if (tmp_w1->w_reversed == 0)
 2606                         continue;
 2607                 for (j = 1; j < w_max_used_index; j++) {
 2608                         if ((w_rmatrix[i][j] & WITNESS_REVERSAL) == 0 || i > j)
 2609                                 continue;
 2610 
 2611                         mtx_lock_spin(&w_mtx);
 2612                         if (generation != w_generation) {
 2613                                 mtx_unlock_spin(&w_mtx);
 2614 
 2615                                 /* The graph has changed, try again. */
 2616                                 req->oldidx = 0;
 2617                                 sbuf_clear(sb);
 2618                                 goto restart;
 2619                         }
 2620 
 2621                         w2 = &w_data[j];
 2622                         data1 = witness_lock_order_get(w1, w2);
 2623                         data2 = witness_lock_order_get(w2, w1);
 2624 
 2625                         /*
 2626                          * Copy information locally so we can release the
 2627                          * spin lock.
 2628                          */
 2629                         *tmp_w2 = *w2;
 2630                         w_rmatrix1 = (unsigned int)w_rmatrix[i][j];
 2631                         w_rmatrix2 = (unsigned int)w_rmatrix[j][i];
 2632 
 2633                         if (data1) {
 2634                                 stack_zero(&tmp_data1->wlod_stack);
 2635                                 stack_copy(&data1->wlod_stack,
 2636                                     &tmp_data1->wlod_stack);
 2637                         }
 2638                         if (data2 && data2 != data1) {
 2639                                 stack_zero(&tmp_data2->wlod_stack);
 2640                                 stack_copy(&data2->wlod_stack,
 2641                                     &tmp_data2->wlod_stack);
 2642                         }
 2643                         mtx_unlock_spin(&w_mtx);
 2644 
 2645                         sbuf_printf(sb,
 2646             "\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n",
 2647                             tmp_w1->w_name, tmp_w1->w_class->lc_name, 
 2648                             tmp_w2->w_name, tmp_w2->w_class->lc_name);
 2649                         if (data1) {
 2650                                 sbuf_printf(sb,
 2651                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
 2652                                     tmp_w1->w_name, tmp_w1->w_class->lc_name, 
 2653                                     tmp_w2->w_name, tmp_w2->w_class->lc_name);
 2654                                 stack_sbuf_print(sb, &tmp_data1->wlod_stack);
 2655                                 sbuf_printf(sb, "\n");
 2656                         }
 2657                         if (data2 && data2 != data1) {
 2658                                 sbuf_printf(sb,
 2659                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
 2660                                     tmp_w2->w_name, tmp_w2->w_class->lc_name, 
 2661                                     tmp_w1->w_name, tmp_w1->w_class->lc_name);
 2662                                 stack_sbuf_print(sb, &tmp_data2->wlod_stack);
 2663                                 sbuf_printf(sb, "\n");
 2664                         }
 2665                 }
 2666         }
 2667         mtx_lock_spin(&w_mtx);
 2668         if (generation != w_generation) {
 2669                 mtx_unlock_spin(&w_mtx);
 2670 
 2671                 /*
 2672                  * The graph changed while we were printing stack data,
 2673                  * try again.
 2674                  */
 2675                 req->oldidx = 0;
 2676                 sbuf_clear(sb);
 2677                 goto restart;
 2678         }
 2679         mtx_unlock_spin(&w_mtx);
 2680 
 2681         /* Free temporary storage space. */
 2682         free(tmp_data1, M_TEMP);
 2683         free(tmp_data2, M_TEMP);
 2684         free(tmp_w1, M_TEMP);
 2685         free(tmp_w2, M_TEMP);
 2686 
 2687         sbuf_finish(sb);
 2688         error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
 2689         sbuf_delete(sb);
 2690 
 2691         return (error);
 2692 }
 2693 
 2694 static int
 2695 sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS)
 2696 {
 2697         static const struct {
 2698                 enum witness_channel channel;
 2699                 const char *name;
 2700         } channels[] = {
 2701                 { WITNESS_CONSOLE, "console" },
 2702                 { WITNESS_LOG, "log" },
 2703                 { WITNESS_NONE, "none" },
 2704         };
 2705         char buf[16];
 2706         u_int i;
 2707         int error;
 2708 
 2709         buf[0] = '\0';
 2710         for (i = 0; i < nitems(channels); i++)
 2711                 if (witness_channel == channels[i].channel) {
 2712                         snprintf(buf, sizeof(buf), "%s", channels[i].name);
 2713                         break;
 2714                 }
 2715 
 2716         error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
 2717         if (error != 0 || req->newptr == NULL)
 2718                 return (error);
 2719 
 2720         error = EINVAL;
 2721         for (i = 0; i < nitems(channels); i++)
 2722                 if (strcmp(channels[i].name, buf) == 0) {
 2723                         witness_channel = channels[i].channel;
 2724                         error = 0;
 2725                         break;
 2726                 }
 2727         return (error);
 2728 }
 2729 
 2730 static int
 2731 sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS)
 2732 {
 2733         struct witness *w;
 2734         struct sbuf *sb;
 2735         int error;
 2736 
 2737         if (witness_watch < 1) {
 2738                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
 2739                 return (error);
 2740         }
 2741         if (witness_cold) {
 2742                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
 2743                 return (error);
 2744         }
 2745         error = 0;
 2746 
 2747         error = sysctl_wire_old_buffer(req, 0);
 2748         if (error != 0)
 2749                 return (error);
 2750         sb = sbuf_new_for_sysctl(NULL, NULL, FULLGRAPH_SBUF_SIZE, req);
 2751         if (sb == NULL)
 2752                 return (ENOMEM);
 2753         sbuf_printf(sb, "\n");
 2754 
 2755         mtx_lock_spin(&w_mtx);
 2756         STAILQ_FOREACH(w, &w_all, w_list)
 2757                 w->w_displayed = 0;
 2758         STAILQ_FOREACH(w, &w_all, w_list)
 2759                 witness_add_fullgraph(sb, w);
 2760         mtx_unlock_spin(&w_mtx);
 2761 
 2762         /*
 2763          * Close the sbuf and return to userland.
 2764          */
 2765         error = sbuf_finish(sb);
 2766         sbuf_delete(sb);
 2767 
 2768         return (error);
 2769 }
 2770 
 2771 static int
 2772 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS)
 2773 {
 2774         int error, value;
 2775 
 2776         value = witness_watch;
 2777         error = sysctl_handle_int(oidp, &value, 0, req);
 2778         if (error != 0 || req->newptr == NULL)
 2779                 return (error);
 2780         if (value > 1 || value < -1 ||
 2781             (witness_watch == -1 && value != witness_watch))
 2782                 return (EINVAL);
 2783         witness_watch = value;
 2784         return (0);
 2785 }
 2786 
 2787 static void
 2788 witness_add_fullgraph(struct sbuf *sb, struct witness *w)
 2789 {
 2790         int i;
 2791 
 2792         if (w->w_displayed != 0 || (w->w_file == NULL && w->w_line == 0))
 2793                 return;
 2794         w->w_displayed = 1;
 2795 
 2796         WITNESS_INDEX_ASSERT(w->w_index);
 2797         for (i = 1; i <= w_max_used_index; i++) {
 2798                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) {
 2799                         sbuf_printf(sb, "\"%s\",\"%s\"\n", w->w_name,
 2800                             w_data[i].w_name);
 2801                         witness_add_fullgraph(sb, &w_data[i]);
 2802                 }
 2803         }
 2804 }
 2805 
 2806 /*
 2807  * A simple hash function. Takes a key pointer and a key size. If size == 0,
 2808  * interprets the key as a string and reads until the null
 2809  * terminator. Otherwise, reads the first size bytes. Returns an unsigned 32-bit
 2810  * hash value computed from the key.
 2811  */
 2812 static uint32_t
 2813 witness_hash_djb2(const uint8_t *key, uint32_t size)
 2814 {
 2815         unsigned int hash = 5381;
 2816         int i;
 2817 
 2818         /* hash = hash * 33 + key[i] */
 2819         if (size)
 2820                 for (i = 0; i < size; i++)
 2821                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
 2822         else
 2823                 for (i = 0; key[i] != 0; i++)
 2824                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
 2825 
 2826         return (hash);
 2827 }
 2828 
 2829 
 2830 /*
 2831  * Initializes the two witness hash tables. Called exactly once from
 2832  * witness_initialize().
 2833  */
 2834 static void
 2835 witness_init_hash_tables(void)
 2836 {
 2837         int i;
 2838 
 2839         MPASS(witness_cold);
 2840 
 2841         /* Initialize the hash tables. */
 2842         for (i = 0; i < WITNESS_HASH_SIZE; i++)
 2843                 w_hash.wh_array[i] = NULL;
 2844 
 2845         w_hash.wh_size = WITNESS_HASH_SIZE;
 2846         w_hash.wh_count = 0;
 2847 
 2848         /* Initialize the lock order data hash. */
 2849         w_lofree = NULL;
 2850         for (i = 0; i < WITNESS_LO_DATA_COUNT; i++) {
 2851                 memset(&w_lodata[i], 0, sizeof(w_lodata[i]));
 2852                 w_lodata[i].wlod_next = w_lofree;
 2853                 w_lofree = &w_lodata[i];
 2854         }
 2855         w_lohash.wloh_size = WITNESS_LO_HASH_SIZE;
 2856         w_lohash.wloh_count = 0;
 2857         for (i = 0; i < WITNESS_LO_HASH_SIZE; i++)
 2858                 w_lohash.wloh_array[i] = NULL;
 2859 }
 2860 
 2861 static struct witness *
 2862 witness_hash_get(const char *key)
 2863 {
 2864         struct witness *w;
 2865         uint32_t hash;
 2866         
 2867         MPASS(key != NULL);
 2868         if (witness_cold == 0)
 2869                 mtx_assert(&w_mtx, MA_OWNED);
 2870         hash = witness_hash_djb2(key, 0) % w_hash.wh_size;
 2871         w = w_hash.wh_array[hash];
 2872         while (w != NULL) {
 2873                 if (strcmp(w->w_name, key) == 0)
 2874                         goto out;
 2875                 w = w->w_hash_next;
 2876         }
 2877 
 2878 out:
 2879         return (w);
 2880 }
 2881 
 2882 static void
 2883 witness_hash_put(struct witness *w)
 2884 {
 2885         uint32_t hash;
 2886 
 2887         MPASS(w != NULL);
 2888         MPASS(w->w_name != NULL);
 2889         if (witness_cold == 0)
 2890                 mtx_assert(&w_mtx, MA_OWNED);
 2891         KASSERT(witness_hash_get(w->w_name) == NULL,
 2892             ("%s: trying to add a hash entry that already exists!", __func__));
 2893         KASSERT(w->w_hash_next == NULL,
 2894             ("%s: w->w_hash_next != NULL", __func__));
 2895 
 2896         hash = witness_hash_djb2(w->w_name, 0) % w_hash.wh_size;
 2897         w->w_hash_next = w_hash.wh_array[hash];
 2898         w_hash.wh_array[hash] = w;
 2899         w_hash.wh_count++;
 2900 }
 2901 
 2902 
 2903 static struct witness_lock_order_data *
 2904 witness_lock_order_get(struct witness *parent, struct witness *child)
 2905 {
 2906         struct witness_lock_order_data *data = NULL;
 2907         struct witness_lock_order_key key;
 2908         unsigned int hash;
 2909 
 2910         MPASS(parent != NULL && child != NULL);
 2911         key.from = parent->w_index;
 2912         key.to = child->w_index;
 2913         WITNESS_INDEX_ASSERT(key.from);
 2914         WITNESS_INDEX_ASSERT(key.to);
 2915         if ((w_rmatrix[parent->w_index][child->w_index]
 2916             & WITNESS_LOCK_ORDER_KNOWN) == 0)
 2917                 goto out;
 2918 
 2919         hash = witness_hash_djb2((const char*)&key,
 2920             sizeof(key)) % w_lohash.wloh_size;
 2921         data = w_lohash.wloh_array[hash];
 2922         while (data != NULL) {
 2923                 if (witness_lock_order_key_equal(&data->wlod_key, &key))
 2924                         break;
 2925                 data = data->wlod_next;
 2926         }
 2927 
 2928 out:
 2929         return (data);
 2930 }
 2931 
 2932 /*
 2933  * Verify that parent and child have a known relationship, are not the same,
 2934  * and child is actually a child of parent.  This is done without w_mtx
 2935  * to avoid contention in the common case.
 2936  */
 2937 static int
 2938 witness_lock_order_check(struct witness *parent, struct witness *child)
 2939 {
 2940 
 2941         if (parent != child &&
 2942             w_rmatrix[parent->w_index][child->w_index]
 2943             & WITNESS_LOCK_ORDER_KNOWN &&
 2944             isitmychild(parent, child))
 2945                 return (1);
 2946 
 2947         return (0);
 2948 }
 2949 
 2950 static int
 2951 witness_lock_order_add(struct witness *parent, struct witness *child)
 2952 {
 2953         struct witness_lock_order_data *data = NULL;
 2954         struct witness_lock_order_key key;
 2955         unsigned int hash;
 2956         
 2957         MPASS(parent != NULL && child != NULL);
 2958         key.from = parent->w_index;
 2959         key.to = child->w_index;
 2960         WITNESS_INDEX_ASSERT(key.from);
 2961         WITNESS_INDEX_ASSERT(key.to);
 2962         if (w_rmatrix[parent->w_index][child->w_index]
 2963             & WITNESS_LOCK_ORDER_KNOWN)
 2964                 return (1);
 2965 
 2966         hash = witness_hash_djb2((const char*)&key,
 2967             sizeof(key)) % w_lohash.wloh_size;
 2968         w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN;
 2969         data = w_lofree;
 2970         if (data == NULL)
 2971                 return (0);
 2972         w_lofree = data->wlod_next;
 2973         data->wlod_next = w_lohash.wloh_array[hash];
 2974         data->wlod_key = key;
 2975         w_lohash.wloh_array[hash] = data;
 2976         w_lohash.wloh_count++;
 2977         stack_zero(&data->wlod_stack);
 2978         stack_save(&data->wlod_stack);
 2979         return (1);
 2980 }
 2981 
 2982 /* Call this whenever the structure of the witness graph changes. */
 2983 static void
 2984 witness_increment_graph_generation(void)
 2985 {
 2986 
 2987         if (witness_cold == 0)
 2988                 mtx_assert(&w_mtx, MA_OWNED);
 2989         w_generation++;
 2990 }
 2991 
 2992 static int
 2993 witness_output_drain(void *arg __unused, const char *data, int len)
 2994 {
 2995 
 2996         witness_output("%.*s", len, data);
 2997         return (len);
 2998 }
 2999 
 3000 static void
 3001 witness_debugger(int cond, const char *msg)
 3002 {
 3003         char buf[32];
 3004         struct sbuf sb;
 3005         struct stack st;
 3006 
 3007         if (!cond)
 3008                 return;
 3009 
 3010         if (witness_trace) {
 3011                 sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN);
 3012                 sbuf_set_drain(&sb, witness_output_drain, NULL);
 3013 
 3014                 stack_zero(&st);
 3015                 stack_save(&st);
 3016                 witness_output("stack backtrace:\n");
 3017                 stack_sbuf_print_ddb(&sb, &st);
 3018 
 3019                 sbuf_finish(&sb);
 3020         }
 3021 
 3022 #ifdef KDB
 3023         if (witness_kdb)
 3024                 kdb_enter(KDB_WHY_WITNESS, msg);
 3025 #endif
 3026 }

Cache object: e66117eb7478582b844f234eb90bb9f1


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.