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/systm.h>
  110 
  111 #ifdef DDB
  112 #include <ddb/ddb.h>
  113 #endif
  114 
  115 #include <machine/stdarg.h>
  116 
  117 #if !defined(DDB) && !defined(STACK)
  118 #error "DDB or STACK options are required for WITNESS"
  119 #endif
  120 
  121 /* Note that these traces do not work with KTR_ALQ. */
  122 #if 0
  123 #define KTR_WITNESS     KTR_SUBSYS
  124 #else
  125 #define KTR_WITNESS     0
  126 #endif
  127 
  128 #define LI_RECURSEMASK  0x0000ffff      /* Recursion depth of lock instance. */
  129 #define LI_EXCLUSIVE    0x00010000      /* Exclusive lock instance. */
  130 #define LI_NORELEASE    0x00020000      /* Lock not allowed to be released. */
  131 
  132 /* Define this to check for blessed mutexes */
  133 #undef BLESSING
  134 
  135 #define WITNESS_COUNT           1024
  136 #define WITNESS_CHILDCOUNT      (WITNESS_COUNT * 4)
  137 #define WITNESS_HASH_SIZE       251     /* Prime, gives load factor < 2 */
  138 #define WITNESS_PENDLIST        768
  139 
  140 /* Allocate 256 KB of stack data space */
  141 #define WITNESS_LO_DATA_COUNT   2048
  142 
  143 /* Prime, gives load factor of ~2 at full load */
  144 #define WITNESS_LO_HASH_SIZE    1021
  145 
  146 /*
  147  * XXX: This is somewhat bogus, as we assume here that at most 2048 threads
  148  * will hold LOCK_NCHILDREN locks.  We handle failure ok, and we should
  149  * probably be safe for the most part, but it's still a SWAG.
  150  */
  151 #define LOCK_NCHILDREN  5
  152 #define LOCK_CHILDCOUNT 2048
  153 
  154 #define MAX_W_NAME      64
  155 
  156 #define BADSTACK_SBUF_SIZE      (256 * WITNESS_COUNT)
  157 #define CYCLEGRAPH_SBUF_SIZE    8192
  158 #define FULLGRAPH_SBUF_SIZE     32768
  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 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_empty(const struct witness_lock_order_key *key)
  310 {
  311 
  312         return (key->from == 0 && key->to == 0);
  313 }
  314 
  315 static __inline int
  316 witness_lock_order_key_equal(const struct witness_lock_order_key *a,
  317     const struct witness_lock_order_key *b)
  318 {
  319 
  320         return (a->from == b->from && a->to == b->to);
  321 }
  322 
  323 static int      _isitmyx(struct witness *w1, struct witness *w2, int rmask,
  324                     const char *fname);
  325 #ifdef KDB
  326 static void     _witness_debugger(int cond, const char *msg);
  327 #endif
  328 static void     adopt(struct witness *parent, struct witness *child);
  329 #ifdef BLESSING
  330 static int      blessed(struct witness *, struct witness *);
  331 #endif
  332 static void     depart(struct witness *w);
  333 static struct witness   *enroll(const char *description,
  334                             struct lock_class *lock_class);
  335 static struct lock_instance     *find_instance(struct lock_list_entry *list,
  336                                     struct lock_object *lock);
  337 static int      isitmychild(struct witness *parent, struct witness *child);
  338 static int      isitmydescendant(struct witness *parent, struct witness *child);
  339 static void     itismychild(struct witness *parent, struct witness *child);
  340 static int      sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS);
  341 static int      sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS);
  342 static int      sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS);
  343 static void     witness_add_fullgraph(struct sbuf *sb, struct witness *parent);
  344 #ifdef DDB
  345 static void     witness_ddb_compute_levels(void);
  346 static void     witness_ddb_display(int(*)(const char *fmt, ...));
  347 static void     witness_ddb_display_descendants(int(*)(const char *fmt, ...),
  348                     struct witness *, int indent);
  349 static void     witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
  350                     struct witness_list *list);
  351 static void     witness_ddb_level_descendants(struct witness *parent, int l);
  352 static void     witness_ddb_list(struct thread *td);
  353 #endif
  354 static void     witness_free(struct witness *m);
  355 static struct witness   *witness_get(void);
  356 static uint32_t witness_hash_djb2(const uint8_t *key, uint32_t size);
  357 static struct witness   *witness_hash_get(const char *key);
  358 static void     witness_hash_put(struct witness *w);
  359 static void     witness_init_hash_tables(void);
  360 static void     witness_increment_graph_generation(void);
  361 static void     witness_lock_list_free(struct lock_list_entry *lle);
  362 static struct lock_list_entry   *witness_lock_list_get(void);
  363 static int      witness_lock_order_add(struct witness *parent,
  364                     struct witness *child);
  365 static int      witness_lock_order_check(struct witness *parent,
  366                     struct witness *child);
  367 static struct witness_lock_order_data   *witness_lock_order_get(
  368                                             struct witness *parent,
  369                                             struct witness *child);
  370 static void     witness_list_lock(struct lock_instance *instance,
  371                     int (*prnt)(const char *fmt, ...));
  372 static void     witness_setflag(struct lock_object *lock, int flag, int set);
  373 
  374 #ifdef KDB
  375 #define witness_debugger(c)     _witness_debugger(c, __func__)
  376 #else
  377 #define witness_debugger(c)
  378 #endif
  379 
  380 SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW, NULL, "Witness Locking");
  381 
  382 /*
  383  * If set to 0, lock order checking is disabled.  If set to -1,
  384  * witness is completely disabled.  Otherwise witness performs full
  385  * lock order checking for all locks.  At runtime, lock order checking
  386  * may be toggled.  However, witness cannot be reenabled once it is
  387  * completely disabled.
  388  */
  389 static int witness_watch = 1;
  390 TUNABLE_INT("debug.witness.watch", &witness_watch);
  391 SYSCTL_PROC(_debug_witness, OID_AUTO, watch, CTLFLAG_RW | CTLTYPE_INT, NULL, 0,
  392     sysctl_debug_witness_watch, "I", "witness is watching lock operations");
  393 
  394 #ifdef KDB
  395 /*
  396  * When KDB is enabled and witness_kdb is 1, it will cause the system
  397  * to drop into kdebug() when:
  398  *      - a lock hierarchy violation occurs
  399  *      - locks are held when going to sleep.
  400  */
  401 #ifdef WITNESS_KDB
  402 int     witness_kdb = 1;
  403 #else
  404 int     witness_kdb = 0;
  405 #endif
  406 TUNABLE_INT("debug.witness.kdb", &witness_kdb);
  407 SYSCTL_INT(_debug_witness, OID_AUTO, kdb, CTLFLAG_RW, &witness_kdb, 0, "");
  408 
  409 /*
  410  * When KDB is enabled and witness_trace is 1, it will cause the system
  411  * to print a stack trace:
  412  *      - a lock hierarchy violation occurs
  413  *      - locks are held when going to sleep.
  414  */
  415 int     witness_trace = 1;
  416 TUNABLE_INT("debug.witness.trace", &witness_trace);
  417 SYSCTL_INT(_debug_witness, OID_AUTO, trace, CTLFLAG_RW, &witness_trace, 0, "");
  418 #endif /* KDB */
  419 
  420 #ifdef WITNESS_SKIPSPIN
  421 int     witness_skipspin = 1;
  422 #else
  423 int     witness_skipspin = 0;
  424 #endif
  425 TUNABLE_INT("debug.witness.skipspin", &witness_skipspin);
  426 SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN, &witness_skipspin,
  427     0, "");
  428 
  429 /*
  430  * Call this to print out the relations between locks.
  431  */
  432 SYSCTL_PROC(_debug_witness, OID_AUTO, fullgraph, CTLTYPE_STRING | CTLFLAG_RD,
  433     NULL, 0, sysctl_debug_witness_fullgraph, "A", "Show locks relation graphs");
  434 
  435 /*
  436  * Call this to print out the witness faulty stacks.
  437  */
  438 SYSCTL_PROC(_debug_witness, OID_AUTO, badstacks, CTLTYPE_STRING | CTLFLAG_RD,
  439     NULL, 0, sysctl_debug_witness_badstacks, "A", "Show bad witness stacks");
  440 
  441 static struct mtx w_mtx;
  442 
  443 /* w_list */
  444 static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free);
  445 static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all);
  446 
  447 /* w_typelist */
  448 static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin);
  449 static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep);
  450 
  451 /* lock list */
  452 static struct lock_list_entry *w_lock_list_free = NULL;
  453 static struct witness_pendhelp pending_locks[WITNESS_PENDLIST];
  454 static u_int pending_cnt;
  455 
  456 static int w_free_cnt, w_spin_cnt, w_sleep_cnt;
  457 SYSCTL_INT(_debug_witness, OID_AUTO, free_cnt, CTLFLAG_RD, &w_free_cnt, 0, "");
  458 SYSCTL_INT(_debug_witness, OID_AUTO, spin_cnt, CTLFLAG_RD, &w_spin_cnt, 0, "");
  459 SYSCTL_INT(_debug_witness, OID_AUTO, sleep_cnt, CTLFLAG_RD, &w_sleep_cnt, 0,
  460     "");
  461 
  462 static struct witness *w_data;
  463 static uint8_t w_rmatrix[WITNESS_COUNT+1][WITNESS_COUNT+1];
  464 static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT];
  465 static struct witness_hash w_hash;      /* The witness hash table. */
  466 
  467 /* The lock order data hash */
  468 static struct witness_lock_order_data w_lodata[WITNESS_LO_DATA_COUNT];
  469 static struct witness_lock_order_data *w_lofree = NULL;
  470 static struct witness_lock_order_hash w_lohash;
  471 static int w_max_used_index = 0;
  472 static unsigned int w_generation = 0;
  473 static const char w_notrunning[] = "Witness not running\n";
  474 static const char w_stillcold[] = "Witness is still cold\n";
  475 
  476 
  477 static struct witness_order_list_entry order_lists[] = {
  478         /*
  479          * sx locks
  480          */
  481         { "proctree", &lock_class_sx },
  482         { "allproc", &lock_class_sx },
  483         { "allprison", &lock_class_sx },
  484         { NULL, NULL },
  485         /*
  486          * Various mutexes
  487          */
  488         { "Giant", &lock_class_mtx_sleep },
  489         { "pipe mutex", &lock_class_mtx_sleep },
  490         { "sigio lock", &lock_class_mtx_sleep },
  491         { "process group", &lock_class_mtx_sleep },
  492         { "process lock", &lock_class_mtx_sleep },
  493         { "session", &lock_class_mtx_sleep },
  494         { "uidinfo hash", &lock_class_rw },
  495 #ifdef  HWPMC_HOOKS
  496         { "pmc-sleep", &lock_class_mtx_sleep },
  497 #endif
  498         { NULL, NULL },
  499         /*
  500          * Sockets
  501          */
  502         { "accept", &lock_class_mtx_sleep },
  503         { "so_snd", &lock_class_mtx_sleep },
  504         { "so_rcv", &lock_class_mtx_sleep },
  505         { "sellck", &lock_class_mtx_sleep },
  506         { NULL, NULL },
  507         /*
  508          * Routing
  509          */
  510         { "so_rcv", &lock_class_mtx_sleep },
  511         { "radix node head", &lock_class_rw },
  512         { "rtentry", &lock_class_mtx_sleep },
  513         { "ifaddr", &lock_class_mtx_sleep },
  514         { NULL, NULL },
  515         /*
  516          * IPv4 multicast:
  517          * protocol locks before interface locks, after UDP locks.
  518          */
  519         { "udpinp", &lock_class_rw },
  520         { "in_multi_mtx", &lock_class_mtx_sleep },
  521         { "igmp_mtx", &lock_class_mtx_sleep },
  522         { "if_addr_mtx", &lock_class_mtx_sleep },
  523         { NULL, NULL },
  524         /*
  525          * IPv6 multicast:
  526          * protocol locks before interface locks, after UDP locks.
  527          */
  528         { "udpinp", &lock_class_rw },
  529         { "in6_multi_mtx", &lock_class_mtx_sleep },
  530         { "mld_mtx", &lock_class_mtx_sleep },
  531         { "if_addr_mtx", &lock_class_mtx_sleep },
  532         { NULL, NULL },
  533         /*
  534          * UNIX Domain Sockets
  535          */
  536         { "unp_global_rwlock", &lock_class_rw },
  537         { "unp_list_lock", &lock_class_mtx_sleep },
  538         { "unp", &lock_class_mtx_sleep },
  539         { "so_snd", &lock_class_mtx_sleep },
  540         { NULL, NULL },
  541         /*
  542          * UDP/IP
  543          */
  544         { "udp", &lock_class_rw },
  545         { "udpinp", &lock_class_rw },
  546         { "so_snd", &lock_class_mtx_sleep },
  547         { NULL, NULL },
  548         /*
  549          * TCP/IP
  550          */
  551         { "tcp", &lock_class_rw },
  552         { "tcpinp", &lock_class_rw },
  553         { "so_snd", &lock_class_mtx_sleep },
  554         { NULL, NULL },
  555         /*
  556          * SLIP
  557          */
  558         { "slip_mtx", &lock_class_mtx_sleep },
  559         { "slip sc_mtx", &lock_class_mtx_sleep },
  560         { NULL, NULL },
  561         /*
  562          * netatalk
  563          */
  564         { "ddp_list_mtx", &lock_class_mtx_sleep },
  565         { "ddp_mtx", &lock_class_mtx_sleep },
  566         { NULL, NULL },
  567         /*
  568          * BPF
  569          */
  570         { "bpf global lock", &lock_class_mtx_sleep },
  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         { "system map", &lock_class_mtx_sleep },
  602         { "vm page queue mutex", &lock_class_mtx_sleep },
  603         { "vnode interlock", &lock_class_mtx_sleep },
  604         { "cdev", &lock_class_mtx_sleep },
  605         { NULL, NULL },
  606         /*
  607          * kqueue/VFS interaction
  608          */
  609         { "kqueue", &lock_class_mtx_sleep },
  610         { "struct mount mtx", &lock_class_mtx_sleep },
  611         { "vnode interlock", &lock_class_mtx_sleep },
  612         { NULL, NULL },
  613         /*
  614          * ZFS locking
  615          */
  616         { "dn->dn_mtx", &lock_class_sx },
  617         { "dr->dt.di.dr_mtx", &lock_class_sx },
  618         { "db->db_mtx", &lock_class_sx },
  619         { NULL, NULL },
  620         /*
  621          * spin locks
  622          */
  623 #ifdef SMP
  624         { "ap boot", &lock_class_mtx_spin },
  625 #endif
  626         { "rm.mutex_mtx", &lock_class_mtx_spin },
  627         { "sio", &lock_class_mtx_spin },
  628         { "scrlock", &lock_class_mtx_spin },
  629 #ifdef __i386__
  630         { "cy", &lock_class_mtx_spin },
  631 #endif
  632 #ifdef __sparc64__
  633         { "pcib_mtx", &lock_class_mtx_spin },
  634         { "rtc_mtx", &lock_class_mtx_spin },
  635 #endif
  636         { "scc_hwmtx", &lock_class_mtx_spin },
  637         { "uart_hwmtx", &lock_class_mtx_spin },
  638         { "fast_taskqueue", &lock_class_mtx_spin },
  639         { "intr table", &lock_class_mtx_spin },
  640 #ifdef  HWPMC_HOOKS
  641         { "pmc-per-proc", &lock_class_mtx_spin },
  642 #endif
  643         { "process slock", &lock_class_mtx_spin },
  644         { "sleepq chain", &lock_class_mtx_spin },
  645         { "umtx lock", &lock_class_mtx_spin },
  646         { "rm_spinlock", &lock_class_mtx_spin },
  647         { "turnstile chain", &lock_class_mtx_spin },
  648         { "turnstile lock", &lock_class_mtx_spin },
  649         { "sched lock", &lock_class_mtx_spin },
  650         { "td_contested", &lock_class_mtx_spin },
  651         { "callout", &lock_class_mtx_spin },
  652         { "entropy harvest mutex", &lock_class_mtx_spin },
  653         { "syscons video lock", &lock_class_mtx_spin },
  654         { "time lock", &lock_class_mtx_spin },
  655 #ifdef SMP
  656         { "smp rendezvous", &lock_class_mtx_spin },
  657 #endif
  658 #ifdef __powerpc__
  659         { "tlb0", &lock_class_mtx_spin },
  660 #endif
  661         /*
  662          * leaf locks
  663          */
  664         { "intrcnt", &lock_class_mtx_spin },
  665         { "icu", &lock_class_mtx_spin },
  666 #ifdef __i386__
  667         { "allpmaps", &lock_class_mtx_spin },
  668         { "descriptor tables", &lock_class_mtx_spin },
  669 #endif
  670         { "clk", &lock_class_mtx_spin },
  671         { "cpuset", &lock_class_mtx_spin },
  672         { "mprof lock", &lock_class_mtx_spin },
  673         { "zombie lock", &lock_class_mtx_spin },
  674         { "ALD Queue", &lock_class_mtx_spin },
  675 #ifdef __ia64__
  676         { "MCA spin lock", &lock_class_mtx_spin },
  677 #endif
  678 #if defined(__i386__) || defined(__amd64__)
  679         { "pcicfg", &lock_class_mtx_spin },
  680         { "NDIS thread lock", &lock_class_mtx_spin },
  681 #endif
  682         { "tw_osl_io_lock", &lock_class_mtx_spin },
  683         { "tw_osl_q_lock", &lock_class_mtx_spin },
  684         { "tw_cl_io_lock", &lock_class_mtx_spin },
  685         { "tw_cl_intr_lock", &lock_class_mtx_spin },
  686         { "tw_cl_gen_lock", &lock_class_mtx_spin },
  687 #ifdef  HWPMC_HOOKS
  688         { "pmc-leaf", &lock_class_mtx_spin },
  689 #endif
  690         { "blocked lock", &lock_class_mtx_spin },
  691         { NULL, NULL },
  692         { NULL, NULL }
  693 };
  694 
  695 #ifdef BLESSING
  696 /*
  697  * Pairs of locks which have been blessed
  698  * Don't complain about order problems with blessed locks
  699  */
  700 static struct witness_blessed blessed_list[] = {
  701 };
  702 static int blessed_count =
  703         sizeof(blessed_list) / sizeof(struct witness_blessed);
  704 #endif
  705 
  706 /*
  707  * This global is set to 0 once it becomes safe to use the witness code.
  708  */
  709 static int witness_cold = 1;
  710 
  711 /*
  712  * This global is set to 1 once the static lock orders have been enrolled
  713  * so that a warning can be issued for any spin locks enrolled later.
  714  */
  715 static int witness_spin_warn = 0;
  716 
  717 /*
  718  * The WITNESS-enabled diagnostic code.  Note that the witness code does
  719  * assume that the early boot is single-threaded at least until after this
  720  * routine is completed.
  721  */
  722 static void
  723 witness_initialize(void *dummy __unused)
  724 {
  725         struct lock_object *lock;
  726         struct witness_order_list_entry *order;
  727         struct witness *w, *w1;
  728         int i;
  729 
  730         w_data = malloc(sizeof (struct witness) * WITNESS_COUNT, M_WITNESS,
  731             M_NOWAIT | M_ZERO);
  732 
  733         /*
  734          * We have to release Giant before initializing its witness
  735          * structure so that WITNESS doesn't get confused.
  736          */
  737         mtx_unlock(&Giant);
  738         mtx_assert(&Giant, MA_NOTOWNED);
  739 
  740         CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
  741         mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET |
  742             MTX_NOWITNESS | MTX_NOPROFILE);
  743         for (i = WITNESS_COUNT - 1; i >= 0; i--) {
  744                 w = &w_data[i];
  745                 memset(w, 0, sizeof(*w));
  746                 w_data[i].w_index = i;  /* Witness index never changes. */
  747                 witness_free(w);
  748         }
  749         KASSERT(STAILQ_FIRST(&w_free)->w_index == 0,
  750             ("%s: Invalid list of free witness objects", __func__));
  751 
  752         /* Witness with index 0 is not used to aid in debugging. */
  753         STAILQ_REMOVE_HEAD(&w_free, w_list);
  754         w_free_cnt--;
  755 
  756         memset(w_rmatrix, 0,
  757             (sizeof(**w_rmatrix) * (WITNESS_COUNT+1) * (WITNESS_COUNT+1)));
  758 
  759         for (i = 0; i < LOCK_CHILDCOUNT; i++)
  760                 witness_lock_list_free(&w_locklistdata[i]);
  761         witness_init_hash_tables();
  762 
  763         /* First add in all the specified order lists. */
  764         for (order = order_lists; order->w_name != NULL; order++) {
  765                 w = enroll(order->w_name, order->w_class);
  766                 if (w == NULL)
  767                         continue;
  768                 w->w_file = "order list";
  769                 for (order++; order->w_name != NULL; order++) {
  770                         w1 = enroll(order->w_name, order->w_class);
  771                         if (w1 == NULL)
  772                                 continue;
  773                         w1->w_file = "order list";
  774                         itismychild(w, w1);
  775                         w = w1;
  776                 }
  777         }
  778         witness_spin_warn = 1;
  779 
  780         /* Iterate through all locks and add them to witness. */
  781         for (i = 0; pending_locks[i].wh_lock != NULL; i++) {
  782                 lock = pending_locks[i].wh_lock;
  783                 KASSERT(lock->lo_flags & LO_WITNESS,
  784                     ("%s: lock %s is on pending list but not LO_WITNESS",
  785                     __func__, lock->lo_name));
  786                 lock->lo_witness = enroll(pending_locks[i].wh_type,
  787                     LOCK_CLASS(lock));
  788         }
  789 
  790         /* Mark the witness code as being ready for use. */
  791         witness_cold = 0;
  792 
  793         mtx_lock(&Giant);
  794 }
  795 SYSINIT(witness_init, SI_SUB_WITNESS, SI_ORDER_FIRST, witness_initialize,
  796     NULL);
  797 
  798 void
  799 witness_init(struct lock_object *lock, const char *type)
  800 {
  801         struct lock_class *class;
  802 
  803         /* Various sanity checks. */
  804         class = LOCK_CLASS(lock);
  805         if ((lock->lo_flags & LO_RECURSABLE) != 0 &&
  806             (class->lc_flags & LC_RECURSABLE) == 0)
  807                 panic("%s: lock (%s) %s can not be recursable", __func__,
  808                     class->lc_name, lock->lo_name);
  809         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
  810             (class->lc_flags & LC_SLEEPABLE) == 0)
  811                 panic("%s: lock (%s) %s can not be sleepable", __func__,
  812                     class->lc_name, lock->lo_name);
  813         if ((lock->lo_flags & LO_UPGRADABLE) != 0 &&
  814             (class->lc_flags & LC_UPGRADABLE) == 0)
  815                 panic("%s: lock (%s) %s can not be upgradable", __func__,
  816                     class->lc_name, lock->lo_name);
  817 
  818         /*
  819          * If we shouldn't watch this lock, then just clear lo_witness.
  820          * Otherwise, if witness_cold is set, then it is too early to
  821          * enroll this lock, so defer it to witness_initialize() by adding
  822          * it to the pending_locks list.  If it is not too early, then enroll
  823          * the lock now.
  824          */
  825         if (witness_watch < 1 || panicstr != NULL ||
  826             (lock->lo_flags & LO_WITNESS) == 0)
  827                 lock->lo_witness = NULL;
  828         else if (witness_cold) {
  829                 pending_locks[pending_cnt].wh_lock = lock;
  830                 pending_locks[pending_cnt++].wh_type = type;
  831                 if (pending_cnt > WITNESS_PENDLIST)
  832                         panic("%s: pending locks list is too small, bump it\n",
  833                             __func__);
  834         } else
  835                 lock->lo_witness = enroll(type, class);
  836 }
  837 
  838 void
  839 witness_destroy(struct lock_object *lock)
  840 {
  841         struct lock_class *class;
  842         struct witness *w;
  843 
  844         class = LOCK_CLASS(lock);
  845 
  846         if (witness_cold)
  847                 panic("lock (%s) %s destroyed while witness_cold",
  848                     class->lc_name, lock->lo_name);
  849 
  850         /* XXX: need to verify that no one holds the lock */
  851         if ((lock->lo_flags & LO_WITNESS) == 0 || lock->lo_witness == NULL)
  852                 return;
  853         w = lock->lo_witness;
  854 
  855         mtx_lock_spin(&w_mtx);
  856         MPASS(w->w_refcount > 0);
  857         w->w_refcount--;
  858 
  859         if (w->w_refcount == 0)
  860                 depart(w);
  861         mtx_unlock_spin(&w_mtx);
  862 }
  863 
  864 #ifdef DDB
  865 static void
  866 witness_ddb_compute_levels(void)
  867 {
  868         struct witness *w;
  869 
  870         /*
  871          * First clear all levels.
  872          */
  873         STAILQ_FOREACH(w, &w_all, w_list)
  874                 w->w_ddb_level = -1;
  875 
  876         /*
  877          * Look for locks with no parents and level all their descendants.
  878          */
  879         STAILQ_FOREACH(w, &w_all, w_list) {
  880 
  881                 /* If the witness has ancestors (is not a root), skip it. */
  882                 if (w->w_num_ancestors > 0)
  883                         continue;
  884                 witness_ddb_level_descendants(w, 0);
  885         }
  886 }
  887 
  888 static void
  889 witness_ddb_level_descendants(struct witness *w, int l)
  890 {
  891         int i;
  892 
  893         if (w->w_ddb_level >= l)
  894                 return;
  895 
  896         w->w_ddb_level = l;
  897         l++;
  898 
  899         for (i = 1; i <= w_max_used_index; i++) {
  900                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
  901                         witness_ddb_level_descendants(&w_data[i], l);
  902         }
  903 }
  904 
  905 static void
  906 witness_ddb_display_descendants(int(*prnt)(const char *fmt, ...),
  907     struct witness *w, int indent)
  908 {
  909         int i;
  910 
  911         for (i = 0; i < indent; i++)
  912                 prnt(" ");
  913         prnt("%s (type: %s, depth: %d, active refs: %d)",
  914              w->w_name, w->w_class->lc_name,
  915              w->w_ddb_level, w->w_refcount);
  916         if (w->w_displayed) {
  917                 prnt(" -- (already displayed)\n");
  918                 return;
  919         }
  920         w->w_displayed = 1;
  921         if (w->w_file != NULL && w->w_line != 0)
  922                 prnt(" -- last acquired @ %s:%d\n", w->w_file,
  923                     w->w_line);
  924         else
  925                 prnt(" -- never acquired\n");
  926         indent++;
  927         WITNESS_INDEX_ASSERT(w->w_index);
  928         for (i = 1; i <= w_max_used_index; i++) {
  929                 if (db_pager_quit)
  930                         return;
  931                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
  932                         witness_ddb_display_descendants(prnt, &w_data[i],
  933                             indent);
  934         }
  935 }
  936 
  937 static void
  938 witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
  939     struct witness_list *list)
  940 {
  941         struct witness *w;
  942 
  943         STAILQ_FOREACH(w, list, w_typelist) {
  944                 if (w->w_file == NULL || w->w_ddb_level > 0)
  945                         continue;
  946 
  947                 /* This lock has no anscestors - display its descendants. */
  948                 witness_ddb_display_descendants(prnt, w, 0);
  949                 if (db_pager_quit)
  950                         return;
  951         }
  952 }
  953         
  954 static void
  955 witness_ddb_display(int(*prnt)(const char *fmt, ...))
  956 {
  957         struct witness *w;
  958 
  959         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
  960         witness_ddb_compute_levels();
  961 
  962         /* Clear all the displayed flags. */
  963         STAILQ_FOREACH(w, &w_all, w_list)
  964                 w->w_displayed = 0;
  965 
  966         /*
  967          * First, handle sleep locks which have been acquired at least
  968          * once.
  969          */
  970         prnt("Sleep locks:\n");
  971         witness_ddb_display_list(prnt, &w_sleep);
  972         if (db_pager_quit)
  973                 return;
  974         
  975         /*
  976          * Now do spin locks which have been acquired at least once.
  977          */
  978         prnt("\nSpin locks:\n");
  979         witness_ddb_display_list(prnt, &w_spin);
  980         if (db_pager_quit)
  981                 return;
  982         
  983         /*
  984          * Finally, any locks which have not been acquired yet.
  985          */
  986         prnt("\nLocks which were never acquired:\n");
  987         STAILQ_FOREACH(w, &w_all, w_list) {
  988                 if (w->w_file != NULL || w->w_refcount == 0)
  989                         continue;
  990                 prnt("%s (type: %s, depth: %d)\n", w->w_name,
  991                     w->w_class->lc_name, w->w_ddb_level);
  992                 if (db_pager_quit)
  993                         return;
  994         }
  995 }
  996 #endif /* DDB */
  997 
  998 /* Trim useless garbage from filenames. */
  999 static const char *
 1000 fixup_filename(const char *file)
 1001 {
 1002 
 1003         if (file == NULL)
 1004                 return (NULL);
 1005         while (strncmp(file, "../", 3) == 0)
 1006                 file += 3;
 1007         return (file);
 1008 }
 1009 
 1010 int
 1011 witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
 1012 {
 1013 
 1014         if (witness_watch == -1 || panicstr != NULL)
 1015                 return (0);
 1016 
 1017         /* Require locks that witness knows about. */
 1018         if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL ||
 1019             lock2->lo_witness == NULL)
 1020                 return (EINVAL);
 1021 
 1022         mtx_assert(&w_mtx, MA_NOTOWNED);
 1023         mtx_lock_spin(&w_mtx);
 1024 
 1025         /*
 1026          * If we already have either an explicit or implied lock order that
 1027          * is the other way around, then return an error.
 1028          */
 1029         if (witness_watch &&
 1030             isitmydescendant(lock2->lo_witness, lock1->lo_witness)) {
 1031                 mtx_unlock_spin(&w_mtx);
 1032                 return (EDOOFUS);
 1033         }
 1034         
 1035         /* Try to add the new order. */
 1036         CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 1037             lock2->lo_witness->w_name, lock1->lo_witness->w_name);
 1038         itismychild(lock1->lo_witness, lock2->lo_witness);
 1039         mtx_unlock_spin(&w_mtx);
 1040         return (0);
 1041 }
 1042 
 1043 void
 1044 witness_checkorder(struct lock_object *lock, int flags, const char *file,
 1045     int line, struct lock_object *interlock)
 1046 {
 1047         struct lock_list_entry *lock_list, *lle;
 1048         struct lock_instance *lock1, *lock2, *plock;
 1049         struct lock_class *class;
 1050         struct witness *w, *w1;
 1051         struct thread *td;
 1052         int i, j;
 1053 
 1054         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL ||
 1055             panicstr != NULL)
 1056                 return;
 1057 
 1058         w = lock->lo_witness;
 1059         class = LOCK_CLASS(lock);
 1060         td = curthread;
 1061         file = fixup_filename(file);
 1062 
 1063         if (class->lc_flags & LC_SLEEPLOCK) {
 1064 
 1065                 /*
 1066                  * Since spin locks include a critical section, this check
 1067                  * implicitly enforces a lock order of all sleep locks before
 1068                  * all spin locks.
 1069                  */
 1070                 if (td->td_critnest != 0 && !kdb_active)
 1071                         panic("blockable sleep lock (%s) %s @ %s:%d",
 1072                             class->lc_name, lock->lo_name, file, line);
 1073 
 1074                 /*
 1075                  * If this is the first lock acquired then just return as
 1076                  * no order checking is needed.
 1077                  */
 1078                 lock_list = td->td_sleeplocks;
 1079                 if (lock_list == NULL || lock_list->ll_count == 0)
 1080                         return;
 1081         } else {
 1082 
 1083                 /*
 1084                  * If this is the first lock, just return as no order
 1085                  * checking is needed.  Avoid problems with thread
 1086                  * migration pinning the thread while checking if
 1087                  * spinlocks are held.  If at least one spinlock is held
 1088                  * the thread is in a safe path and it is allowed to
 1089                  * unpin it.
 1090                  */
 1091                 sched_pin();
 1092                 lock_list = PCPU_GET(spinlocks);
 1093                 if (lock_list == NULL || lock_list->ll_count == 0) {
 1094                         sched_unpin();
 1095                         return;
 1096                 }
 1097                 sched_unpin();
 1098         }
 1099 
 1100         /*
 1101          * Check to see if we are recursing on a lock we already own.  If
 1102          * so, make sure that we don't mismatch exclusive and shared lock
 1103          * acquires.
 1104          */
 1105         lock1 = find_instance(lock_list, lock);
 1106         if (lock1 != NULL) {
 1107                 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 &&
 1108                     (flags & LOP_EXCLUSIVE) == 0) {
 1109                         printf("shared lock of (%s) %s @ %s:%d\n",
 1110                             class->lc_name, lock->lo_name, file, line);
 1111                         printf("while exclusively locked from %s:%d\n",
 1112                             lock1->li_file, lock1->li_line);
 1113                         panic("share->excl");
 1114                 }
 1115                 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
 1116                     (flags & LOP_EXCLUSIVE) != 0) {
 1117                         printf("exclusive lock of (%s) %s @ %s:%d\n",
 1118                             class->lc_name, lock->lo_name, file, line);
 1119                         printf("while share locked from %s:%d\n",
 1120                             lock1->li_file, lock1->li_line);
 1121                         panic("excl->share");
 1122                 }
 1123                 return;
 1124         }
 1125 
 1126         /*
 1127          * Find the previously acquired lock, but ignore interlocks.
 1128          */
 1129         plock = &lock_list->ll_children[lock_list->ll_count - 1];
 1130         if (interlock != NULL && plock->li_lock == interlock) {
 1131                 if (lock_list->ll_count > 1)
 1132                         plock =
 1133                             &lock_list->ll_children[lock_list->ll_count - 2];
 1134                 else {
 1135                         lle = lock_list->ll_next;
 1136 
 1137                         /*
 1138                          * The interlock is the only lock we hold, so
 1139                          * simply return.
 1140                          */
 1141                         if (lle == NULL)
 1142                                 return;
 1143                         plock = &lle->ll_children[lle->ll_count - 1];
 1144                 }
 1145         }
 1146         
 1147         /*
 1148          * Try to perform most checks without a lock.  If this succeeds we
 1149          * can skip acquiring the lock and return success.
 1150          */
 1151         w1 = plock->li_lock->lo_witness;
 1152         if (witness_lock_order_check(w1, w))
 1153                 return;
 1154 
 1155         /*
 1156          * Check for duplicate locks of the same type.  Note that we only
 1157          * have to check for this on the last lock we just acquired.  Any
 1158          * other cases will be caught as lock order violations.
 1159          */
 1160         mtx_lock_spin(&w_mtx);
 1161         witness_lock_order_add(w1, w);
 1162         if (w1 == w) {
 1163                 i = w->w_index;
 1164                 if (!(lock->lo_flags & LO_DUPOK) && !(flags & LOP_DUPOK) &&
 1165                     !(w_rmatrix[i][i] & WITNESS_REVERSAL)) {
 1166                     w_rmatrix[i][i] |= WITNESS_REVERSAL;
 1167                         w->w_reversed = 1;
 1168                         mtx_unlock_spin(&w_mtx);
 1169                         printf(
 1170                             "acquiring duplicate lock of same type: \"%s\"\n", 
 1171                             w->w_name);
 1172                         printf(" 1st %s @ %s:%d\n", plock->li_lock->lo_name,
 1173                                plock->li_file, plock->li_line);
 1174                         printf(" 2nd %s @ %s:%d\n", lock->lo_name, file, line);
 1175                         witness_debugger(1);
 1176                     } else
 1177                             mtx_unlock_spin(&w_mtx);
 1178                 return;
 1179         }
 1180         mtx_assert(&w_mtx, MA_OWNED);
 1181 
 1182         /*
 1183          * If we know that the lock we are acquiring comes after
 1184          * the lock we most recently acquired in the lock order tree,
 1185          * then there is no need for any further checks.
 1186          */
 1187         if (isitmychild(w1, w))
 1188                 goto out;
 1189 
 1190         for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) {
 1191                 for (i = lle->ll_count - 1; i >= 0; i--, j++) {
 1192 
 1193                         MPASS(j < WITNESS_COUNT);
 1194                         lock1 = &lle->ll_children[i];
 1195 
 1196                         /*
 1197                          * Ignore the interlock the first time we see it.
 1198                          */
 1199                         if (interlock != NULL && interlock == lock1->li_lock) {
 1200                                 interlock = NULL;
 1201                                 continue;
 1202                         }
 1203 
 1204                         /*
 1205                          * If this lock doesn't undergo witness checking,
 1206                          * then skip it.
 1207                          */
 1208                         w1 = lock1->li_lock->lo_witness;
 1209                         if (w1 == NULL) {
 1210                                 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0,
 1211                                     ("lock missing witness structure"));
 1212                                 continue;
 1213                         }
 1214 
 1215                         /*
 1216                          * If we are locking Giant and this is a sleepable
 1217                          * lock, then skip it.
 1218                          */
 1219                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1220                             lock == &Giant.lock_object)
 1221                                 continue;
 1222 
 1223                         /*
 1224                          * If we are locking a sleepable lock and this lock
 1225                          * is Giant, then skip it.
 1226                          */
 1227                         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1228                             lock1->li_lock == &Giant.lock_object)
 1229                                 continue;
 1230 
 1231                         /*
 1232                          * If we are locking a sleepable lock and this lock
 1233                          * isn't sleepable, we want to treat it as a lock
 1234                          * order violation to enfore a general lock order of
 1235                          * sleepable locks before non-sleepable locks.
 1236                          */
 1237                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1238                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
 1239                                 goto reversal;
 1240 
 1241                         /*
 1242                          * If we are locking Giant and this is a non-sleepable
 1243                          * lock, then treat it as a reversal.
 1244                          */
 1245                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0 &&
 1246                             lock == &Giant.lock_object)
 1247                                 goto reversal;
 1248 
 1249                         /*
 1250                          * Check the lock order hierarchy for a reveresal.
 1251                          */
 1252                         if (!isitmydescendant(w, w1))
 1253                                 continue;
 1254                 reversal:
 1255 
 1256                         /*
 1257                          * We have a lock order violation, check to see if it
 1258                          * is allowed or has already been yelled about.
 1259                          */
 1260 #ifdef BLESSING
 1261 
 1262                         /*
 1263                          * If the lock order is blessed, just bail.  We don't
 1264                          * look for other lock order violations though, which
 1265                          * may be a bug.
 1266                          */
 1267                         if (blessed(w, w1))
 1268                                 goto out;
 1269 #endif
 1270 
 1271                         /* Bail if this violation is known */
 1272                         if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL)
 1273                                 goto out;
 1274 
 1275                         /* Record this as a violation */
 1276                         w_rmatrix[w1->w_index][w->w_index] |= WITNESS_REVERSAL;
 1277                         w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL;
 1278                         w->w_reversed = w1->w_reversed = 1;
 1279                         witness_increment_graph_generation();
 1280                         mtx_unlock_spin(&w_mtx);
 1281                         
 1282                         /*
 1283                          * Ok, yell about it.
 1284                          */
 1285                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1286                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
 1287                                 printf(
 1288                 "lock order reversal: (sleepable after non-sleepable)\n");
 1289                         else if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0
 1290                             && lock == &Giant.lock_object)
 1291                                 printf(
 1292                 "lock order reversal: (Giant after non-sleepable)\n");
 1293                         else
 1294                                 printf("lock order reversal:\n");
 1295 
 1296                         /*
 1297                          * Try to locate an earlier lock with
 1298                          * witness w in our list.
 1299                          */
 1300                         do {
 1301                                 lock2 = &lle->ll_children[i];
 1302                                 MPASS(lock2->li_lock != NULL);
 1303                                 if (lock2->li_lock->lo_witness == w)
 1304                                         break;
 1305                                 if (i == 0 && lle->ll_next != NULL) {
 1306                                         lle = lle->ll_next;
 1307                                         i = lle->ll_count - 1;
 1308                                         MPASS(i >= 0 && i < LOCK_NCHILDREN);
 1309                                 } else
 1310                                         i--;
 1311                         } while (i >= 0);
 1312                         if (i < 0) {
 1313                                 printf(" 1st %p %s (%s) @ %s:%d\n",
 1314                                     lock1->li_lock, lock1->li_lock->lo_name,
 1315                                     w1->w_name, lock1->li_file, lock1->li_line);
 1316                                 printf(" 2nd %p %s (%s) @ %s:%d\n", lock,
 1317                                     lock->lo_name, w->w_name, file, line);
 1318                         } else {
 1319                                 printf(" 1st %p %s (%s) @ %s:%d\n",
 1320                                     lock2->li_lock, lock2->li_lock->lo_name,
 1321                                     lock2->li_lock->lo_witness->w_name,
 1322                                     lock2->li_file, lock2->li_line);
 1323                                 printf(" 2nd %p %s (%s) @ %s:%d\n",
 1324                                     lock1->li_lock, lock1->li_lock->lo_name,
 1325                                     w1->w_name, lock1->li_file, lock1->li_line);
 1326                                 printf(" 3rd %p %s (%s) @ %s:%d\n", lock,
 1327                                     lock->lo_name, w->w_name, file, line);
 1328                         }
 1329                         witness_debugger(1);
 1330                         return;
 1331                 }
 1332         }
 1333 
 1334         /*
 1335          * If requested, build a new lock order.  However, don't build a new
 1336          * relationship between a sleepable lock and Giant if it is in the
 1337          * wrong direction.  The correct lock order is that sleepable locks
 1338          * always come before Giant.
 1339          */
 1340         if (flags & LOP_NEWORDER &&
 1341             !(plock->li_lock == &Giant.lock_object &&
 1342             (lock->lo_flags & LO_SLEEPABLE) != 0)) {
 1343                 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 1344                     w->w_name, plock->li_lock->lo_witness->w_name);
 1345                 itismychild(plock->li_lock->lo_witness, w);
 1346         }
 1347 out:
 1348         mtx_unlock_spin(&w_mtx);
 1349 }
 1350 
 1351 void
 1352 witness_lock(struct lock_object *lock, int flags, const char *file, int line)
 1353 {
 1354         struct lock_list_entry **lock_list, *lle;
 1355         struct lock_instance *instance;
 1356         struct witness *w;
 1357         struct thread *td;
 1358 
 1359         if (witness_cold || witness_watch == -1 || lock->lo_witness == NULL ||
 1360             panicstr != NULL)
 1361                 return;
 1362         w = lock->lo_witness;
 1363         td = curthread;
 1364         file = fixup_filename(file);
 1365 
 1366         /* Determine lock list for this lock. */
 1367         if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK)
 1368                 lock_list = &td->td_sleeplocks;
 1369         else
 1370                 lock_list = PCPU_PTR(spinlocks);
 1371 
 1372         /* Check to see if we are recursing on a lock we already own. */
 1373         instance = find_instance(*lock_list, lock);
 1374         if (instance != NULL) {
 1375                 instance->li_flags++;
 1376                 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__,
 1377                     td->td_proc->p_pid, lock->lo_name,
 1378                     instance->li_flags & LI_RECURSEMASK);
 1379                 instance->li_file = file;
 1380                 instance->li_line = line;
 1381                 return;
 1382         }
 1383 
 1384         /* Update per-witness last file and line acquire. */
 1385         w->w_file = file;
 1386         w->w_line = line;
 1387 
 1388         /* Find the next open lock instance in the list and fill it. */
 1389         lle = *lock_list;
 1390         if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
 1391                 lle = witness_lock_list_get();
 1392                 if (lle == NULL)
 1393                         return;
 1394                 lle->ll_next = *lock_list;
 1395                 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__,
 1396                     td->td_proc->p_pid, lle);
 1397                 *lock_list = lle;
 1398         }
 1399         instance = &lle->ll_children[lle->ll_count++];
 1400         instance->li_lock = lock;
 1401         instance->li_line = line;
 1402         instance->li_file = file;
 1403         if ((flags & LOP_EXCLUSIVE) != 0)
 1404                 instance->li_flags = LI_EXCLUSIVE;
 1405         else
 1406                 instance->li_flags = 0;
 1407         CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__,
 1408             td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1);
 1409 }
 1410 
 1411 void
 1412 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line)
 1413 {
 1414         struct lock_instance *instance;
 1415         struct lock_class *class;
 1416 
 1417         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 1418         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 1419                 return;
 1420         class = LOCK_CLASS(lock);
 1421         file = fixup_filename(file);
 1422         if (witness_watch) {
 1423                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
 1424                         panic("upgrade of non-upgradable lock (%s) %s @ %s:%d",
 1425                             class->lc_name, lock->lo_name, file, line);
 1426                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
 1427                         panic("upgrade of non-sleep lock (%s) %s @ %s:%d",
 1428                             class->lc_name, lock->lo_name, file, line);
 1429         }
 1430         instance = find_instance(curthread->td_sleeplocks, lock);
 1431         if (instance == NULL)
 1432                 panic("upgrade of unlocked lock (%s) %s @ %s:%d",
 1433                     class->lc_name, lock->lo_name, file, line);
 1434         if (witness_watch) {
 1435                 if ((instance->li_flags & LI_EXCLUSIVE) != 0)
 1436                         panic("upgrade of exclusive lock (%s) %s @ %s:%d",
 1437                             class->lc_name, lock->lo_name, file, line);
 1438                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
 1439                         panic("upgrade of recursed lock (%s) %s r=%d @ %s:%d",
 1440                             class->lc_name, lock->lo_name,
 1441                             instance->li_flags & LI_RECURSEMASK, file, line);
 1442         }
 1443         instance->li_flags |= LI_EXCLUSIVE;
 1444 }
 1445 
 1446 void
 1447 witness_downgrade(struct lock_object *lock, int flags, const char *file,
 1448     int line)
 1449 {
 1450         struct lock_instance *instance;
 1451         struct lock_class *class;
 1452 
 1453         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 1454         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 1455                 return;
 1456         class = LOCK_CLASS(lock);
 1457         file = fixup_filename(file);
 1458         if (witness_watch) {
 1459                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
 1460                 panic("downgrade of non-upgradable lock (%s) %s @ %s:%d",
 1461                             class->lc_name, lock->lo_name, file, line);
 1462                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
 1463                         panic("downgrade of non-sleep lock (%s) %s @ %s:%d",
 1464                             class->lc_name, lock->lo_name, file, line);
 1465         }
 1466         instance = find_instance(curthread->td_sleeplocks, lock);
 1467         if (instance == NULL)
 1468                 panic("downgrade of unlocked lock (%s) %s @ %s:%d",
 1469                     class->lc_name, lock->lo_name, file, line);
 1470         if (witness_watch) {
 1471                 if ((instance->li_flags & LI_EXCLUSIVE) == 0)
 1472                         panic("downgrade of shared lock (%s) %s @ %s:%d",
 1473                             class->lc_name, lock->lo_name, file, line);
 1474                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
 1475                         panic("downgrade of recursed lock (%s) %s r=%d @ %s:%d",
 1476                             class->lc_name, lock->lo_name,
 1477                             instance->li_flags & LI_RECURSEMASK, file, line);
 1478         }
 1479         instance->li_flags &= ~LI_EXCLUSIVE;
 1480 }
 1481 
 1482 void
 1483 witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
 1484 {
 1485         struct lock_list_entry **lock_list, *lle;
 1486         struct lock_instance *instance;
 1487         struct lock_class *class;
 1488         struct thread *td;
 1489         register_t s;
 1490         int i, j;
 1491 
 1492         if (witness_cold || lock->lo_witness == NULL || panicstr != NULL)
 1493                 return;
 1494         td = curthread;
 1495         class = LOCK_CLASS(lock);
 1496         file = fixup_filename(file);
 1497 
 1498         /* Find lock instance associated with this lock. */
 1499         if (class->lc_flags & LC_SLEEPLOCK)
 1500                 lock_list = &td->td_sleeplocks;
 1501         else
 1502                 lock_list = PCPU_PTR(spinlocks);
 1503         lle = *lock_list;
 1504         for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next)
 1505                 for (i = 0; i < (*lock_list)->ll_count; i++) {
 1506                         instance = &(*lock_list)->ll_children[i];
 1507                         if (instance->li_lock == lock)
 1508                                 goto found;
 1509                 }
 1510 
 1511         /*
 1512          * When disabling WITNESS through witness_watch we could end up in
 1513          * having registered locks in the td_sleeplocks queue.
 1514          * We have to make sure we flush these queues, so just search for
 1515          * eventual register locks and remove them.
 1516          */
 1517         if (witness_watch > 0)
 1518                 panic("lock (%s) %s not locked @ %s:%d", class->lc_name,
 1519                     lock->lo_name, file, line);
 1520         else
 1521                 return;
 1522 found:
 1523 
 1524         /* First, check for shared/exclusive mismatches. */
 1525         if ((instance->li_flags & LI_EXCLUSIVE) != 0 && witness_watch > 0 &&
 1526             (flags & LOP_EXCLUSIVE) == 0) {
 1527                 printf("shared unlock of (%s) %s @ %s:%d\n", class->lc_name,
 1528                     lock->lo_name, file, line);
 1529                 printf("while exclusively locked from %s:%d\n",
 1530                     instance->li_file, instance->li_line);
 1531                 panic("excl->ushare");
 1532         }
 1533         if ((instance->li_flags & LI_EXCLUSIVE) == 0 && witness_watch > 0 &&
 1534             (flags & LOP_EXCLUSIVE) != 0) {
 1535                 printf("exclusive unlock of (%s) %s @ %s:%d\n", class->lc_name,
 1536                     lock->lo_name, file, line);
 1537                 printf("while share locked from %s:%d\n", instance->li_file,
 1538                     instance->li_line);
 1539                 panic("share->uexcl");
 1540         }
 1541         /* If we are recursed, unrecurse. */
 1542         if ((instance->li_flags & LI_RECURSEMASK) > 0) {
 1543                 CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__,
 1544                     td->td_proc->p_pid, instance->li_lock->lo_name,
 1545                     instance->li_flags);
 1546                 instance->li_flags--;
 1547                 return;
 1548         }
 1549         /* The lock is now being dropped, check for NORELEASE flag */
 1550         if ((instance->li_flags & LI_NORELEASE) != 0 && witness_watch > 0) {
 1551                 printf("forbidden unlock of (%s) %s @ %s:%d\n", class->lc_name,
 1552                     lock->lo_name, file, line);
 1553                 panic("lock marked norelease");
 1554         }
 1555 
 1556         /* Otherwise, remove this item from the list. */
 1557         s = intr_disable();
 1558         CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__,
 1559             td->td_proc->p_pid, instance->li_lock->lo_name,
 1560             (*lock_list)->ll_count - 1);
 1561         for (j = i; j < (*lock_list)->ll_count - 1; j++)
 1562                 (*lock_list)->ll_children[j] =
 1563                     (*lock_list)->ll_children[j + 1];
 1564         (*lock_list)->ll_count--;
 1565         intr_restore(s);
 1566 
 1567         /*
 1568          * In order to reduce contention on w_mtx, we want to keep always an
 1569          * head object into lists so that frequent allocation from the 
 1570          * free witness pool (and subsequent locking) is avoided.
 1571          * In order to maintain the current code simple, when the head
 1572          * object is totally unloaded it means also that we do not have
 1573          * further objects in the list, so the list ownership needs to be
 1574          * hand over to another object if the current head needs to be freed.
 1575          */
 1576         if ((*lock_list)->ll_count == 0) {
 1577                 if (*lock_list == lle) {
 1578                         if (lle->ll_next == NULL)
 1579                                 return;
 1580                 } else
 1581                         lle = *lock_list;
 1582                 *lock_list = lle->ll_next;
 1583                 CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__,
 1584                     td->td_proc->p_pid, lle);
 1585                 witness_lock_list_free(lle);
 1586         }
 1587 }
 1588 
 1589 void
 1590 witness_thread_exit(struct thread *td)
 1591 {
 1592         struct lock_list_entry *lle;
 1593         int i, n;
 1594 
 1595         lle = td->td_sleeplocks;
 1596         if (lle == NULL || panicstr != NULL)
 1597                 return;
 1598         if (lle->ll_count != 0) {
 1599                 for (n = 0; lle != NULL; lle = lle->ll_next)
 1600                         for (i = lle->ll_count - 1; i >= 0; i--) {
 1601                                 if (n == 0)
 1602                 printf("Thread %p exiting with the following locks held:\n",
 1603                                             td);
 1604                                 n++;
 1605                                 witness_list_lock(&lle->ll_children[i], printf);
 1606                                 
 1607                         }
 1608                 panic("Thread %p cannot exit while holding sleeplocks\n", td);
 1609         }
 1610         witness_lock_list_free(lle);
 1611 }
 1612 
 1613 /*
 1614  * Warn if any locks other than 'lock' are held.  Flags can be passed in to
 1615  * exempt Giant and sleepable locks from the checks as well.  If any
 1616  * non-exempt locks are held, then a supplied message is printed to the
 1617  * console along with a list of the offending locks.  If indicated in the
 1618  * flags then a failure results in a panic as well.
 1619  */
 1620 int
 1621 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
 1622 {
 1623         struct lock_list_entry *lock_list, *lle;
 1624         struct lock_instance *lock1;
 1625         struct thread *td;
 1626         va_list ap;
 1627         int i, n;
 1628 
 1629         if (witness_cold || witness_watch < 1 || panicstr != NULL)
 1630                 return (0);
 1631         n = 0;
 1632         td = curthread;
 1633         for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next)
 1634                 for (i = lle->ll_count - 1; i >= 0; i--) {
 1635                         lock1 = &lle->ll_children[i];
 1636                         if (lock1->li_lock == lock)
 1637                                 continue;
 1638                         if (flags & WARN_GIANTOK &&
 1639                             lock1->li_lock == &Giant.lock_object)
 1640                                 continue;
 1641                         if (flags & WARN_SLEEPOK &&
 1642                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0)
 1643                                 continue;
 1644                         if (n == 0) {
 1645                                 va_start(ap, fmt);
 1646                                 vprintf(fmt, ap);
 1647                                 va_end(ap);
 1648                                 printf(" with the following");
 1649                                 if (flags & WARN_SLEEPOK)
 1650                                         printf(" non-sleepable");
 1651                                 printf(" locks held:\n");
 1652                         }
 1653                         n++;
 1654                         witness_list_lock(lock1, printf);
 1655                 }
 1656 
 1657         /*
 1658          * Pin the thread in order to avoid problems with thread migration.
 1659          * Once that all verifies are passed about spinlocks ownership,
 1660          * the thread is in a safe path and it can be unpinned.
 1661          */
 1662         sched_pin();
 1663         lock_list = PCPU_GET(spinlocks);
 1664         if (lock_list != NULL && lock_list->ll_count != 0) {
 1665                 sched_unpin();
 1666 
 1667                 /*
 1668                  * We should only have one spinlock and as long as
 1669                  * the flags cannot match for this locks class,
 1670                  * check if the first spinlock is the one curthread
 1671                  * should hold.
 1672                  */
 1673                 lock1 = &lock_list->ll_children[lock_list->ll_count - 1];
 1674                 if (lock_list->ll_count == 1 && lock_list->ll_next == NULL &&
 1675                     lock1->li_lock == lock && n == 0)
 1676                         return (0);
 1677 
 1678                 va_start(ap, fmt);
 1679                 vprintf(fmt, ap);
 1680                 va_end(ap);
 1681                 printf(" with the following");
 1682                 if (flags & WARN_SLEEPOK)
 1683                         printf(" non-sleepable");
 1684                 printf(" locks held:\n");
 1685                 n += witness_list_locks(&lock_list, printf);
 1686         } else
 1687                 sched_unpin();
 1688         if (flags & WARN_PANIC && n)
 1689                 panic("%s", __func__);
 1690         else
 1691                 witness_debugger(n);
 1692         return (n);
 1693 }
 1694 
 1695 const char *
 1696 witness_file(struct lock_object *lock)
 1697 {
 1698         struct witness *w;
 1699 
 1700         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
 1701                 return ("?");
 1702         w = lock->lo_witness;
 1703         return (w->w_file);
 1704 }
 1705 
 1706 int
 1707 witness_line(struct lock_object *lock)
 1708 {
 1709         struct witness *w;
 1710 
 1711         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
 1712                 return (0);
 1713         w = lock->lo_witness;
 1714         return (w->w_line);
 1715 }
 1716 
 1717 static struct witness *
 1718 enroll(const char *description, struct lock_class *lock_class)
 1719 {
 1720         struct witness *w;
 1721         struct witness_list *typelist;
 1722 
 1723         MPASS(description != NULL);
 1724 
 1725         if (witness_watch == -1 || panicstr != NULL)
 1726                 return (NULL);
 1727         if ((lock_class->lc_flags & LC_SPINLOCK)) {
 1728                 if (witness_skipspin)
 1729                         return (NULL);
 1730                 else
 1731                         typelist = &w_spin;
 1732         } else if ((lock_class->lc_flags & LC_SLEEPLOCK))
 1733                 typelist = &w_sleep;
 1734         else
 1735                 panic("lock class %s is not sleep or spin",
 1736                     lock_class->lc_name);
 1737 
 1738         mtx_lock_spin(&w_mtx);
 1739         w = witness_hash_get(description);
 1740         if (w)
 1741                 goto found;
 1742         if ((w = witness_get()) == NULL)
 1743                 return (NULL);
 1744         MPASS(strlen(description) < MAX_W_NAME);
 1745         strcpy(w->w_name, description);
 1746         w->w_class = lock_class;
 1747         w->w_refcount = 1;
 1748         STAILQ_INSERT_HEAD(&w_all, w, w_list);
 1749         if (lock_class->lc_flags & LC_SPINLOCK) {
 1750                 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist);
 1751                 w_spin_cnt++;
 1752         } else if (lock_class->lc_flags & LC_SLEEPLOCK) {
 1753                 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist);
 1754                 w_sleep_cnt++;
 1755         }
 1756 
 1757         /* Insert new witness into the hash */
 1758         witness_hash_put(w);
 1759         witness_increment_graph_generation();
 1760         mtx_unlock_spin(&w_mtx);
 1761         return (w);
 1762 found:
 1763         w->w_refcount++;
 1764         mtx_unlock_spin(&w_mtx);
 1765         if (lock_class != w->w_class)
 1766                 panic(
 1767                         "lock (%s) %s does not match earlier (%s) lock",
 1768                         description, lock_class->lc_name,
 1769                         w->w_class->lc_name);
 1770         return (w);
 1771 }
 1772 
 1773 static void
 1774 depart(struct witness *w)
 1775 {
 1776         struct witness_list *list;
 1777 
 1778         MPASS(w->w_refcount == 0);
 1779         if (w->w_class->lc_flags & LC_SLEEPLOCK) {
 1780                 list = &w_sleep;
 1781                 w_sleep_cnt--;
 1782         } else {
 1783                 list = &w_spin;
 1784                 w_spin_cnt--;
 1785         }
 1786         /*
 1787          * Set file to NULL as it may point into a loadable module.
 1788          */
 1789         w->w_file = NULL;
 1790         w->w_line = 0;
 1791         witness_increment_graph_generation();
 1792 }
 1793 
 1794 
 1795 static void
 1796 adopt(struct witness *parent, struct witness *child)
 1797 {
 1798         int pi, ci, i, j;
 1799 
 1800         if (witness_cold == 0)
 1801                 mtx_assert(&w_mtx, MA_OWNED);
 1802 
 1803         /* If the relationship is already known, there's no work to be done. */
 1804         if (isitmychild(parent, child))
 1805                 return;
 1806 
 1807         /* When the structure of the graph changes, bump up the generation. */
 1808         witness_increment_graph_generation();
 1809 
 1810         /*
 1811          * The hard part ... create the direct relationship, then propagate all
 1812          * indirect relationships.
 1813          */
 1814         pi = parent->w_index;
 1815         ci = child->w_index;
 1816         WITNESS_INDEX_ASSERT(pi);
 1817         WITNESS_INDEX_ASSERT(ci);
 1818         MPASS(pi != ci);
 1819         w_rmatrix[pi][ci] |= WITNESS_PARENT;
 1820         w_rmatrix[ci][pi] |= WITNESS_CHILD;
 1821 
 1822         /*
 1823          * If parent was not already an ancestor of child,
 1824          * then we increment the descendant and ancestor counters.
 1825          */
 1826         if ((w_rmatrix[pi][ci] & WITNESS_ANCESTOR) == 0) {
 1827                 parent->w_num_descendants++;
 1828                 child->w_num_ancestors++;
 1829         }
 1830 
 1831         /* 
 1832          * Find each ancestor of 'pi'. Note that 'pi' itself is counted as 
 1833          * an ancestor of 'pi' during this loop.
 1834          */
 1835         for (i = 1; i <= w_max_used_index; i++) {
 1836                 if ((w_rmatrix[i][pi] & WITNESS_ANCESTOR_MASK) == 0 && 
 1837                     (i != pi))
 1838                         continue;
 1839 
 1840                 /* Find each descendant of 'i' and mark it as a descendant. */
 1841                 for (j = 1; j <= w_max_used_index; j++) {
 1842 
 1843                         /* 
 1844                          * Skip children that are already marked as
 1845                          * descendants of 'i'.
 1846                          */
 1847                         if (w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK)
 1848                                 continue;
 1849 
 1850                         /*
 1851                          * We are only interested in descendants of 'ci'. Note
 1852                          * that 'ci' itself is counted as a descendant of 'ci'.
 1853                          */
 1854                         if ((w_rmatrix[ci][j] & WITNESS_ANCESTOR_MASK) == 0 && 
 1855                             (j != ci))
 1856                                 continue;
 1857                         w_rmatrix[i][j] |= WITNESS_ANCESTOR;
 1858                         w_rmatrix[j][i] |= WITNESS_DESCENDANT;
 1859                         w_data[i].w_num_descendants++;
 1860                         w_data[j].w_num_ancestors++;
 1861 
 1862                         /* 
 1863                          * Make sure we aren't marking a node as both an
 1864                          * ancestor and descendant. We should have caught 
 1865                          * this as a lock order reversal earlier.
 1866                          */
 1867                         if ((w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) &&
 1868                             (w_rmatrix[i][j] & WITNESS_DESCENDANT_MASK)) {
 1869                                 printf("witness rmatrix paradox! [%d][%d]=%d "
 1870                                     "both ancestor and descendant\n",
 1871                                     i, j, w_rmatrix[i][j]); 
 1872                                 kdb_backtrace();
 1873                                 printf("Witness disabled.\n");
 1874                                 witness_watch = -1;
 1875                         }
 1876                         if ((w_rmatrix[j][i] & WITNESS_ANCESTOR_MASK) &&
 1877                             (w_rmatrix[j][i] & WITNESS_DESCENDANT_MASK)) {
 1878                                 printf("witness rmatrix paradox! [%d][%d]=%d "
 1879                                     "both ancestor and descendant\n",
 1880                                     j, i, w_rmatrix[j][i]); 
 1881                                 kdb_backtrace();
 1882                                 printf("Witness disabled.\n");
 1883                                 witness_watch = -1;
 1884                         }
 1885                 }
 1886         }
 1887 }
 1888 
 1889 static void
 1890 itismychild(struct witness *parent, struct witness *child)
 1891 {
 1892 
 1893         MPASS(child != NULL && parent != NULL);
 1894         if (witness_cold == 0)
 1895                 mtx_assert(&w_mtx, MA_OWNED);
 1896 
 1897         if (!witness_lock_type_equal(parent, child)) {
 1898                 if (witness_cold == 0)
 1899                         mtx_unlock_spin(&w_mtx);
 1900                 panic("%s: parent \"%s\" (%s) and child \"%s\" (%s) are not "
 1901                     "the same lock type", __func__, parent->w_name,
 1902                     parent->w_class->lc_name, child->w_name,
 1903                     child->w_class->lc_name);
 1904         }
 1905         adopt(parent, child);
 1906 }
 1907 
 1908 /*
 1909  * Generic code for the isitmy*() functions. The rmask parameter is the
 1910  * expected relationship of w1 to w2.
 1911  */
 1912 static int
 1913 _isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname)
 1914 {
 1915         unsigned char r1, r2;
 1916         int i1, i2;
 1917 
 1918         i1 = w1->w_index;
 1919         i2 = w2->w_index;
 1920         WITNESS_INDEX_ASSERT(i1);
 1921         WITNESS_INDEX_ASSERT(i2);
 1922         r1 = w_rmatrix[i1][i2] & WITNESS_RELATED_MASK;
 1923         r2 = w_rmatrix[i2][i1] & WITNESS_RELATED_MASK;
 1924 
 1925         /* The flags on one better be the inverse of the flags on the other */
 1926         if (!((WITNESS_ATOD(r1) == r2 && WITNESS_DTOA(r2) == r1) ||
 1927                 (WITNESS_DTOA(r1) == r2 && WITNESS_ATOD(r2) == r1))) {
 1928                 printf("%s: rmatrix mismatch between %s (index %d) and %s "
 1929                     "(index %d): w_rmatrix[%d][%d] == %hhx but "
 1930                     "w_rmatrix[%d][%d] == %hhx\n",
 1931                     fname, w1->w_name, i1, w2->w_name, i2, i1, i2, r1,
 1932                     i2, i1, r2);
 1933                 kdb_backtrace();
 1934                 printf("Witness disabled.\n");
 1935                 witness_watch = -1;
 1936         }
 1937         return (r1 & rmask);
 1938 }
 1939 
 1940 /*
 1941  * Checks if @child is a direct child of @parent.
 1942  */
 1943 static int
 1944 isitmychild(struct witness *parent, struct witness *child)
 1945 {
 1946 
 1947         return (_isitmyx(parent, child, WITNESS_PARENT, __func__));
 1948 }
 1949 
 1950 /*
 1951  * Checks if @descendant is a direct or inderect descendant of @ancestor.
 1952  */
 1953 static int
 1954 isitmydescendant(struct witness *ancestor, struct witness *descendant)
 1955 {
 1956 
 1957         return (_isitmyx(ancestor, descendant, WITNESS_ANCESTOR_MASK,
 1958             __func__));
 1959 }
 1960 
 1961 #ifdef BLESSING
 1962 static int
 1963 blessed(struct witness *w1, struct witness *w2)
 1964 {
 1965         int i;
 1966         struct witness_blessed *b;
 1967 
 1968         for (i = 0; i < blessed_count; i++) {
 1969                 b = &blessed_list[i];
 1970                 if (strcmp(w1->w_name, b->b_lock1) == 0) {
 1971                         if (strcmp(w2->w_name, b->b_lock2) == 0)
 1972                                 return (1);
 1973                         continue;
 1974                 }
 1975                 if (strcmp(w1->w_name, b->b_lock2) == 0)
 1976                         if (strcmp(w2->w_name, b->b_lock1) == 0)
 1977                                 return (1);
 1978         }
 1979         return (0);
 1980 }
 1981 #endif
 1982 
 1983 static struct witness *
 1984 witness_get(void)
 1985 {
 1986         struct witness *w;
 1987         int index;
 1988 
 1989         if (witness_cold == 0)
 1990                 mtx_assert(&w_mtx, MA_OWNED);
 1991 
 1992         if (witness_watch == -1) {
 1993                 mtx_unlock_spin(&w_mtx);
 1994                 return (NULL);
 1995         }
 1996         if (STAILQ_EMPTY(&w_free)) {
 1997                 witness_watch = -1;
 1998                 mtx_unlock_spin(&w_mtx);
 1999                 printf("WITNESS: unable to allocate a new witness object\n");
 2000                 return (NULL);
 2001         }
 2002         w = STAILQ_FIRST(&w_free);
 2003         STAILQ_REMOVE_HEAD(&w_free, w_list);
 2004         w_free_cnt--;
 2005         index = w->w_index;
 2006         MPASS(index > 0 && index == w_max_used_index+1 &&
 2007             index < WITNESS_COUNT);
 2008         bzero(w, sizeof(*w));
 2009         w->w_index = index;
 2010         if (index > w_max_used_index)
 2011                 w_max_used_index = index;
 2012         return (w);
 2013 }
 2014 
 2015 static void
 2016 witness_free(struct witness *w)
 2017 {
 2018 
 2019         STAILQ_INSERT_HEAD(&w_free, w, w_list);
 2020         w_free_cnt++;
 2021 }
 2022 
 2023 static struct lock_list_entry *
 2024 witness_lock_list_get(void)
 2025 {
 2026         struct lock_list_entry *lle;
 2027 
 2028         if (witness_watch == -1)
 2029                 return (NULL);
 2030         mtx_lock_spin(&w_mtx);
 2031         lle = w_lock_list_free;
 2032         if (lle == NULL) {
 2033                 witness_watch = -1;
 2034                 mtx_unlock_spin(&w_mtx);
 2035                 printf("%s: witness exhausted\n", __func__);
 2036                 return (NULL);
 2037         }
 2038         w_lock_list_free = lle->ll_next;
 2039         mtx_unlock_spin(&w_mtx);
 2040         bzero(lle, sizeof(*lle));
 2041         return (lle);
 2042 }
 2043                 
 2044 static void
 2045 witness_lock_list_free(struct lock_list_entry *lle)
 2046 {
 2047 
 2048         mtx_lock_spin(&w_mtx);
 2049         lle->ll_next = w_lock_list_free;
 2050         w_lock_list_free = lle;
 2051         mtx_unlock_spin(&w_mtx);
 2052 }
 2053 
 2054 static struct lock_instance *
 2055 find_instance(struct lock_list_entry *list, struct lock_object *lock)
 2056 {
 2057         struct lock_list_entry *lle;
 2058         struct lock_instance *instance;
 2059         int i;
 2060 
 2061         for (lle = list; lle != NULL; lle = lle->ll_next)
 2062                 for (i = lle->ll_count - 1; i >= 0; i--) {
 2063                         instance = &lle->ll_children[i];
 2064                         if (instance->li_lock == lock)
 2065                                 return (instance);
 2066                 }
 2067         return (NULL);
 2068 }
 2069 
 2070 static void
 2071 witness_list_lock(struct lock_instance *instance,
 2072     int (*prnt)(const char *fmt, ...))
 2073 {
 2074         struct lock_object *lock;
 2075 
 2076         lock = instance->li_lock;
 2077         prnt("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ?
 2078             "exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name);
 2079         if (lock->lo_witness->w_name != lock->lo_name)
 2080                 prnt(" (%s)", lock->lo_witness->w_name);
 2081         prnt(" r = %d (%p) locked @ %s:%d\n",
 2082             instance->li_flags & LI_RECURSEMASK, lock, instance->li_file,
 2083             instance->li_line);
 2084 }
 2085 
 2086 #ifdef DDB
 2087 static int
 2088 witness_thread_has_locks(struct thread *td)
 2089 {
 2090 
 2091         if (td->td_sleeplocks == NULL)
 2092                 return (0);
 2093         return (td->td_sleeplocks->ll_count != 0);
 2094 }
 2095 
 2096 static int
 2097 witness_proc_has_locks(struct proc *p)
 2098 {
 2099         struct thread *td;
 2100 
 2101         FOREACH_THREAD_IN_PROC(p, td) {
 2102                 if (witness_thread_has_locks(td))
 2103                         return (1);
 2104         }
 2105         return (0);
 2106 }
 2107 #endif
 2108 
 2109 int
 2110 witness_list_locks(struct lock_list_entry **lock_list,
 2111     int (*prnt)(const char *fmt, ...))
 2112 {
 2113         struct lock_list_entry *lle;
 2114         int i, nheld;
 2115 
 2116         nheld = 0;
 2117         for (lle = *lock_list; lle != NULL; lle = lle->ll_next)
 2118                 for (i = lle->ll_count - 1; i >= 0; i--) {
 2119                         witness_list_lock(&lle->ll_children[i], prnt);
 2120                         nheld++;
 2121                 }
 2122         return (nheld);
 2123 }
 2124 
 2125 /*
 2126  * This is a bit risky at best.  We call this function when we have timed
 2127  * out acquiring a spin lock, and we assume that the other CPU is stuck
 2128  * with this lock held.  So, we go groveling around in the other CPU's
 2129  * per-cpu data to try to find the lock instance for this spin lock to
 2130  * see when it was last acquired.
 2131  */
 2132 void
 2133 witness_display_spinlock(struct lock_object *lock, struct thread *owner,
 2134     int (*prnt)(const char *fmt, ...))
 2135 {
 2136         struct lock_instance *instance;
 2137         struct pcpu *pc;
 2138 
 2139         if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU)
 2140                 return;
 2141         pc = pcpu_find(owner->td_oncpu);
 2142         instance = find_instance(pc->pc_spinlocks, lock);
 2143         if (instance != NULL)
 2144                 witness_list_lock(instance, prnt);
 2145 }
 2146 
 2147 void
 2148 witness_save(struct lock_object *lock, const char **filep, int *linep)
 2149 {
 2150         struct lock_list_entry *lock_list;
 2151         struct lock_instance *instance;
 2152         struct lock_class *class;
 2153 
 2154         /*
 2155          * This function is used independently in locking code to deal with
 2156          * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
 2157          * is gone.
 2158          */
 2159         if (SCHEDULER_STOPPED())
 2160                 return;
 2161         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2162         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2163                 return;
 2164         class = LOCK_CLASS(lock);
 2165         if (class->lc_flags & LC_SLEEPLOCK)
 2166                 lock_list = curthread->td_sleeplocks;
 2167         else {
 2168                 if (witness_skipspin)
 2169                         return;
 2170                 lock_list = PCPU_GET(spinlocks);
 2171         }
 2172         instance = find_instance(lock_list, lock);
 2173         if (instance == NULL)
 2174                 panic("%s: lock (%s) %s not locked", __func__,
 2175                     class->lc_name, lock->lo_name);
 2176         *filep = instance->li_file;
 2177         *linep = instance->li_line;
 2178 }
 2179 
 2180 void
 2181 witness_restore(struct lock_object *lock, const char *file, int line)
 2182 {
 2183         struct lock_list_entry *lock_list;
 2184         struct lock_instance *instance;
 2185         struct lock_class *class;
 2186 
 2187         /*
 2188          * This function is used independently in locking code to deal with
 2189          * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
 2190          * is gone.
 2191          */
 2192         if (SCHEDULER_STOPPED())
 2193                 return;
 2194         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2195         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2196                 return;
 2197         class = LOCK_CLASS(lock);
 2198         if (class->lc_flags & LC_SLEEPLOCK)
 2199                 lock_list = curthread->td_sleeplocks;
 2200         else {
 2201                 if (witness_skipspin)
 2202                         return;
 2203                 lock_list = PCPU_GET(spinlocks);
 2204         }
 2205         instance = find_instance(lock_list, lock);
 2206         if (instance == NULL)
 2207                 panic("%s: lock (%s) %s not locked", __func__,
 2208                     class->lc_name, lock->lo_name);
 2209         lock->lo_witness->w_file = file;
 2210         lock->lo_witness->w_line = line;
 2211         instance->li_file = file;
 2212         instance->li_line = line;
 2213 }
 2214 
 2215 void
 2216 witness_assert(struct lock_object *lock, int flags, const char *file, int line)
 2217 {
 2218 #ifdef INVARIANT_SUPPORT
 2219         struct lock_instance *instance;
 2220         struct lock_class *class;
 2221 
 2222         if (lock->lo_witness == NULL || witness_watch < 1 || panicstr != NULL)
 2223                 return;
 2224         class = LOCK_CLASS(lock);
 2225         if ((class->lc_flags & LC_SLEEPLOCK) != 0)
 2226                 instance = find_instance(curthread->td_sleeplocks, lock);
 2227         else if ((class->lc_flags & LC_SPINLOCK) != 0)
 2228                 instance = find_instance(PCPU_GET(spinlocks), lock);
 2229         else {
 2230                 panic("Lock (%s) %s is not sleep or spin!",
 2231                     class->lc_name, lock->lo_name);
 2232         }
 2233         file = fixup_filename(file);
 2234         switch (flags) {
 2235         case LA_UNLOCKED:
 2236                 if (instance != NULL)
 2237                         panic("Lock (%s) %s locked @ %s:%d.",
 2238                             class->lc_name, lock->lo_name, file, line);
 2239                 break;
 2240         case LA_LOCKED:
 2241         case LA_LOCKED | LA_RECURSED:
 2242         case LA_LOCKED | LA_NOTRECURSED:
 2243         case LA_SLOCKED:
 2244         case LA_SLOCKED | LA_RECURSED:
 2245         case LA_SLOCKED | LA_NOTRECURSED:
 2246         case LA_XLOCKED:
 2247         case LA_XLOCKED | LA_RECURSED:
 2248         case LA_XLOCKED | LA_NOTRECURSED:
 2249                 if (instance == NULL) {
 2250                         panic("Lock (%s) %s not locked @ %s:%d.",
 2251                             class->lc_name, lock->lo_name, file, line);
 2252                         break;
 2253                 }
 2254                 if ((flags & LA_XLOCKED) != 0 &&
 2255                     (instance->li_flags & LI_EXCLUSIVE) == 0)
 2256                         panic("Lock (%s) %s not exclusively locked @ %s:%d.",
 2257                             class->lc_name, lock->lo_name, file, line);
 2258                 if ((flags & LA_SLOCKED) != 0 &&
 2259                     (instance->li_flags & LI_EXCLUSIVE) != 0)
 2260                         panic("Lock (%s) %s exclusively locked @ %s:%d.",
 2261                             class->lc_name, lock->lo_name, file, line);
 2262                 if ((flags & LA_RECURSED) != 0 &&
 2263                     (instance->li_flags & LI_RECURSEMASK) == 0)
 2264                         panic("Lock (%s) %s not recursed @ %s:%d.",
 2265                             class->lc_name, lock->lo_name, file, line);
 2266                 if ((flags & LA_NOTRECURSED) != 0 &&
 2267                     (instance->li_flags & LI_RECURSEMASK) != 0)
 2268                         panic("Lock (%s) %s recursed @ %s:%d.",
 2269                             class->lc_name, lock->lo_name, file, line);
 2270                 break;
 2271         default:
 2272                 panic("Invalid lock assertion at %s:%d.", file, line);
 2273 
 2274         }
 2275 #endif  /* INVARIANT_SUPPORT */
 2276 }
 2277 
 2278 static void
 2279 witness_setflag(struct lock_object *lock, int flag, int set)
 2280 {
 2281         struct lock_list_entry *lock_list;
 2282         struct lock_instance *instance;
 2283         struct lock_class *class;
 2284 
 2285         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2286                 return;
 2287         class = LOCK_CLASS(lock);
 2288         if (class->lc_flags & LC_SLEEPLOCK)
 2289                 lock_list = curthread->td_sleeplocks;
 2290         else {
 2291                 if (witness_skipspin)
 2292                         return;
 2293                 lock_list = PCPU_GET(spinlocks);
 2294         }
 2295         instance = find_instance(lock_list, lock);
 2296         if (instance == NULL)
 2297                 panic("%s: lock (%s) %s not locked", __func__,
 2298                     class->lc_name, lock->lo_name);
 2299 
 2300         if (set)
 2301                 instance->li_flags |= flag;
 2302         else
 2303                 instance->li_flags &= ~flag;
 2304 }
 2305 
 2306 void
 2307 witness_norelease(struct lock_object *lock)
 2308 {
 2309 
 2310         witness_setflag(lock, LI_NORELEASE, 1);
 2311 }
 2312 
 2313 void
 2314 witness_releaseok(struct lock_object *lock)
 2315 {
 2316 
 2317         witness_setflag(lock, LI_NORELEASE, 0);
 2318 }
 2319 
 2320 #ifdef DDB
 2321 static void
 2322 witness_ddb_list(struct thread *td)
 2323 {
 2324 
 2325         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2326         KASSERT(kdb_active, ("%s: not in the debugger", __func__));
 2327 
 2328         if (witness_watch < 1)
 2329                 return;
 2330 
 2331         witness_list_locks(&td->td_sleeplocks, db_printf);
 2332 
 2333         /*
 2334          * We only handle spinlocks if td == curthread.  This is somewhat broken
 2335          * if td is currently executing on some other CPU and holds spin locks
 2336          * as we won't display those locks.  If we had a MI way of getting
 2337          * the per-cpu data for a given cpu then we could use
 2338          * td->td_oncpu to get the list of spinlocks for this thread
 2339          * and "fix" this.
 2340          *
 2341          * That still wouldn't really fix this unless we locked the scheduler
 2342          * lock or stopped the other CPU to make sure it wasn't changing the
 2343          * list out from under us.  It is probably best to just not try to
 2344          * handle threads on other CPU's for now.
 2345          */
 2346         if (td == curthread && PCPU_GET(spinlocks) != NULL)
 2347                 witness_list_locks(PCPU_PTR(spinlocks), db_printf);
 2348 }
 2349 
 2350 DB_SHOW_COMMAND(locks, db_witness_list)
 2351 {
 2352         struct thread *td;
 2353 
 2354         if (have_addr)
 2355                 td = db_lookup_thread(addr, TRUE);
 2356         else
 2357                 td = kdb_thread;
 2358         witness_ddb_list(td);
 2359 }
 2360 
 2361 DB_SHOW_ALL_COMMAND(locks, db_witness_list_all)
 2362 {
 2363         struct thread *td;
 2364         struct proc *p;
 2365 
 2366         /*
 2367          * It would be nice to list only threads and processes that actually
 2368          * held sleep locks, but that information is currently not exported
 2369          * by WITNESS.
 2370          */
 2371         FOREACH_PROC_IN_SYSTEM(p) {
 2372                 if (!witness_proc_has_locks(p))
 2373                         continue;
 2374                 FOREACH_THREAD_IN_PROC(p, td) {
 2375                         if (!witness_thread_has_locks(td))
 2376                                 continue;
 2377                         db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid,
 2378                             p->p_comm, td, td->td_tid);
 2379                         witness_ddb_list(td);
 2380                         if (db_pager_quit)
 2381                                 return;
 2382                 }
 2383         }
 2384 }
 2385 DB_SHOW_ALIAS(alllocks, db_witness_list_all)
 2386 
 2387 DB_SHOW_COMMAND(witness, db_witness_display)
 2388 {
 2389 
 2390         witness_ddb_display(db_printf);
 2391 }
 2392 #endif
 2393 
 2394 static int
 2395 sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS)
 2396 {
 2397         struct witness_lock_order_data *data1, *data2, *tmp_data1, *tmp_data2;
 2398         struct witness *tmp_w1, *tmp_w2, *w1, *w2;
 2399         struct sbuf *sb;
 2400         u_int w_rmatrix1, w_rmatrix2;
 2401         int error, generation, i, j;
 2402 
 2403         tmp_data1 = NULL;
 2404         tmp_data2 = NULL;
 2405         tmp_w1 = NULL;
 2406         tmp_w2 = NULL;
 2407         if (witness_watch < 1) {
 2408                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
 2409                 return (error);
 2410         }
 2411         if (witness_cold) {
 2412                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
 2413                 return (error);
 2414         }
 2415         error = 0;
 2416         sb = sbuf_new(NULL, NULL, BADSTACK_SBUF_SIZE, SBUF_AUTOEXTEND);
 2417         if (sb == NULL)
 2418                 return (ENOMEM);
 2419 
 2420         /* Allocate and init temporary storage space. */
 2421         tmp_w1 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
 2422         tmp_w2 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
 2423         tmp_data1 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 
 2424             M_WAITOK | M_ZERO);
 2425         tmp_data2 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 
 2426             M_WAITOK | M_ZERO);
 2427         stack_zero(&tmp_data1->wlod_stack);
 2428         stack_zero(&tmp_data2->wlod_stack);
 2429 
 2430 restart:
 2431         mtx_lock_spin(&w_mtx);
 2432         generation = w_generation;
 2433         mtx_unlock_spin(&w_mtx);
 2434         sbuf_printf(sb, "Number of known direct relationships is %d\n",
 2435             w_lohash.wloh_count);
 2436         for (i = 1; i < w_max_used_index; i++) {
 2437                 mtx_lock_spin(&w_mtx);
 2438                 if (generation != w_generation) {
 2439                         mtx_unlock_spin(&w_mtx);
 2440 
 2441                         /* The graph has changed, try again. */
 2442                         req->oldidx = 0;
 2443                         sbuf_clear(sb);
 2444                         goto restart;
 2445                 }
 2446 
 2447                 w1 = &w_data[i];
 2448                 if (w1->w_reversed == 0) {
 2449                         mtx_unlock_spin(&w_mtx);
 2450                         continue;
 2451                 }
 2452 
 2453                 /* Copy w1 locally so we can release the spin lock. */
 2454                 *tmp_w1 = *w1;
 2455                 mtx_unlock_spin(&w_mtx);
 2456 
 2457                 if (tmp_w1->w_reversed == 0)
 2458                         continue;
 2459                 for (j = 1; j < w_max_used_index; j++) {
 2460                         if ((w_rmatrix[i][j] & WITNESS_REVERSAL) == 0 || i > j)
 2461                                 continue;
 2462 
 2463                         mtx_lock_spin(&w_mtx);
 2464                         if (generation != w_generation) {
 2465                                 mtx_unlock_spin(&w_mtx);
 2466 
 2467                                 /* The graph has changed, try again. */
 2468                                 req->oldidx = 0;
 2469                                 sbuf_clear(sb);
 2470                                 goto restart;
 2471                         }
 2472 
 2473                         w2 = &w_data[j];
 2474                         data1 = witness_lock_order_get(w1, w2);
 2475                         data2 = witness_lock_order_get(w2, w1);
 2476 
 2477                         /*
 2478                          * Copy information locally so we can release the
 2479                          * spin lock.
 2480                          */
 2481                         *tmp_w2 = *w2;
 2482                         w_rmatrix1 = (unsigned int)w_rmatrix[i][j];
 2483                         w_rmatrix2 = (unsigned int)w_rmatrix[j][i];
 2484 
 2485                         if (data1) {
 2486                                 stack_zero(&tmp_data1->wlod_stack);
 2487                                 stack_copy(&data1->wlod_stack,
 2488                                     &tmp_data1->wlod_stack);
 2489                         }
 2490                         if (data2 && data2 != data1) {
 2491                                 stack_zero(&tmp_data2->wlod_stack);
 2492                                 stack_copy(&data2->wlod_stack,
 2493                                     &tmp_data2->wlod_stack);
 2494                         }
 2495                         mtx_unlock_spin(&w_mtx);
 2496 
 2497                         sbuf_printf(sb,
 2498             "\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n",
 2499                             tmp_w1->w_name, tmp_w1->w_class->lc_name, 
 2500                             tmp_w2->w_name, tmp_w2->w_class->lc_name);
 2501 #if 0
 2502                         sbuf_printf(sb,
 2503                         "w_rmatrix[%s][%s] == %x, w_rmatrix[%s][%s] == %x\n",
 2504                             tmp_w1->name, tmp_w2->w_name, w_rmatrix1,
 2505                             tmp_w2->name, tmp_w1->w_name, w_rmatrix2);
 2506 #endif
 2507                         if (data1) {
 2508                                 sbuf_printf(sb,
 2509                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
 2510                                     tmp_w1->w_name, tmp_w1->w_class->lc_name, 
 2511                                     tmp_w2->w_name, tmp_w2->w_class->lc_name);
 2512                                 stack_sbuf_print(sb, &tmp_data1->wlod_stack);
 2513                                 sbuf_printf(sb, "\n");
 2514                         }
 2515                         if (data2 && data2 != data1) {
 2516                                 sbuf_printf(sb,
 2517                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
 2518                                     tmp_w2->w_name, tmp_w2->w_class->lc_name, 
 2519                                     tmp_w1->w_name, tmp_w1->w_class->lc_name);
 2520                                 stack_sbuf_print(sb, &tmp_data2->wlod_stack);
 2521                                 sbuf_printf(sb, "\n");
 2522                         }
 2523                 }
 2524         }
 2525         mtx_lock_spin(&w_mtx);
 2526         if (generation != w_generation) {
 2527                 mtx_unlock_spin(&w_mtx);
 2528 
 2529                 /*
 2530                  * The graph changed while we were printing stack data,
 2531                  * try again.
 2532                  */
 2533                 req->oldidx = 0;
 2534                 sbuf_clear(sb);
 2535                 goto restart;
 2536         }
 2537         mtx_unlock_spin(&w_mtx);
 2538 
 2539         /* Free temporary storage space. */
 2540         free(tmp_data1, M_TEMP);
 2541         free(tmp_data2, M_TEMP);
 2542         free(tmp_w1, M_TEMP);
 2543         free(tmp_w2, M_TEMP);
 2544 
 2545         sbuf_finish(sb);
 2546         error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
 2547         sbuf_delete(sb);
 2548 
 2549         return (error);
 2550 }
 2551 
 2552 static int
 2553 sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS)
 2554 {
 2555         struct witness *w;
 2556         struct sbuf *sb;
 2557         int error;
 2558 
 2559         if (witness_watch < 1) {
 2560                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
 2561                 return (error);
 2562         }
 2563         if (witness_cold) {
 2564                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
 2565                 return (error);
 2566         }
 2567         error = 0;
 2568         sb = sbuf_new(NULL, NULL, FULLGRAPH_SBUF_SIZE, SBUF_FIXEDLEN);
 2569         if (sb == NULL)
 2570                 return (ENOMEM);
 2571         sbuf_printf(sb, "\n");
 2572 
 2573         mtx_lock_spin(&w_mtx);
 2574         STAILQ_FOREACH(w, &w_all, w_list)
 2575                 w->w_displayed = 0;
 2576         STAILQ_FOREACH(w, &w_all, w_list)
 2577                 witness_add_fullgraph(sb, w);
 2578         mtx_unlock_spin(&w_mtx);
 2579 
 2580         /*
 2581          * While using SBUF_FIXEDLEN, check if the sbuf overflowed.
 2582          */
 2583         if (sbuf_overflowed(sb)) {
 2584                 sbuf_delete(sb);
 2585                 panic("%s: sbuf overflowed, bump FULLGRAPH_SBUF_SIZE value\n",
 2586                     __func__);
 2587         }
 2588 
 2589         /*
 2590          * Close the sbuf and return to userland.
 2591          */
 2592         sbuf_finish(sb);
 2593         error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
 2594         sbuf_delete(sb);
 2595 
 2596         return (error);
 2597 }
 2598 
 2599 static int
 2600 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS)
 2601 {
 2602         int error, value;
 2603 
 2604         value = witness_watch;
 2605         error = sysctl_handle_int(oidp, &value, 0, req);
 2606         if (error != 0 || req->newptr == NULL)
 2607                 return (error);
 2608         if (value > 1 || value < -1 ||
 2609             (witness_watch == -1 && value != witness_watch))
 2610                 return (EINVAL);
 2611         witness_watch = value;
 2612         return (0);
 2613 }
 2614 
 2615 static void
 2616 witness_add_fullgraph(struct sbuf *sb, struct witness *w)
 2617 {
 2618         int i;
 2619 
 2620         if (w->w_displayed != 0 || (w->w_file == NULL && w->w_line == 0))
 2621                 return;
 2622         w->w_displayed = 1;
 2623 
 2624         WITNESS_INDEX_ASSERT(w->w_index);
 2625         for (i = 1; i <= w_max_used_index; i++) {
 2626                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) {
 2627                         sbuf_printf(sb, "\"%s\",\"%s\"\n", w->w_name,
 2628                             w_data[i].w_name);
 2629                         witness_add_fullgraph(sb, &w_data[i]);
 2630                 }
 2631         }
 2632 }
 2633 
 2634 /*
 2635  * A simple hash function. Takes a key pointer and a key size. If size == 0,
 2636  * interprets the key as a string and reads until the null
 2637  * terminator. Otherwise, reads the first size bytes. Returns an unsigned 32-bit
 2638  * hash value computed from the key.
 2639  */
 2640 static uint32_t
 2641 witness_hash_djb2(const uint8_t *key, uint32_t size)
 2642 {
 2643         unsigned int hash = 5381;
 2644         int i;
 2645 
 2646         /* hash = hash * 33 + key[i] */
 2647         if (size)
 2648                 for (i = 0; i < size; i++)
 2649                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
 2650         else
 2651                 for (i = 0; key[i] != 0; i++)
 2652                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
 2653 
 2654         return (hash);
 2655 }
 2656 
 2657 
 2658 /*
 2659  * Initializes the two witness hash tables. Called exactly once from
 2660  * witness_initialize().
 2661  */
 2662 static void
 2663 witness_init_hash_tables(void)
 2664 {
 2665         int i;
 2666 
 2667         MPASS(witness_cold);
 2668 
 2669         /* Initialize the hash tables. */
 2670         for (i = 0; i < WITNESS_HASH_SIZE; i++)
 2671                 w_hash.wh_array[i] = NULL;
 2672 
 2673         w_hash.wh_size = WITNESS_HASH_SIZE;
 2674         w_hash.wh_count = 0;
 2675 
 2676         /* Initialize the lock order data hash. */
 2677         w_lofree = NULL;
 2678         for (i = 0; i < WITNESS_LO_DATA_COUNT; i++) {
 2679                 memset(&w_lodata[i], 0, sizeof(w_lodata[i]));
 2680                 w_lodata[i].wlod_next = w_lofree;
 2681                 w_lofree = &w_lodata[i];
 2682         }
 2683         w_lohash.wloh_size = WITNESS_LO_HASH_SIZE;
 2684         w_lohash.wloh_count = 0;
 2685         for (i = 0; i < WITNESS_LO_HASH_SIZE; i++)
 2686                 w_lohash.wloh_array[i] = NULL;
 2687 }
 2688 
 2689 static struct witness *
 2690 witness_hash_get(const char *key)
 2691 {
 2692         struct witness *w;
 2693         uint32_t hash;
 2694         
 2695         MPASS(key != NULL);
 2696         if (witness_cold == 0)
 2697                 mtx_assert(&w_mtx, MA_OWNED);
 2698         hash = witness_hash_djb2(key, 0) % w_hash.wh_size;
 2699         w = w_hash.wh_array[hash];
 2700         while (w != NULL) {
 2701                 if (strcmp(w->w_name, key) == 0)
 2702                         goto out;
 2703                 w = w->w_hash_next;
 2704         }
 2705 
 2706 out:
 2707         return (w);
 2708 }
 2709 
 2710 static void
 2711 witness_hash_put(struct witness *w)
 2712 {
 2713         uint32_t hash;
 2714 
 2715         MPASS(w != NULL);
 2716         MPASS(w->w_name != NULL);
 2717         if (witness_cold == 0)
 2718                 mtx_assert(&w_mtx, MA_OWNED);
 2719         KASSERT(witness_hash_get(w->w_name) == NULL,
 2720             ("%s: trying to add a hash entry that already exists!", __func__));
 2721         KASSERT(w->w_hash_next == NULL,
 2722             ("%s: w->w_hash_next != NULL", __func__));
 2723 
 2724         hash = witness_hash_djb2(w->w_name, 0) % w_hash.wh_size;
 2725         w->w_hash_next = w_hash.wh_array[hash];
 2726         w_hash.wh_array[hash] = w;
 2727         w_hash.wh_count++;
 2728 }
 2729 
 2730 
 2731 static struct witness_lock_order_data *
 2732 witness_lock_order_get(struct witness *parent, struct witness *child)
 2733 {
 2734         struct witness_lock_order_data *data = NULL;
 2735         struct witness_lock_order_key key;
 2736         unsigned int hash;
 2737 
 2738         MPASS(parent != NULL && child != NULL);
 2739         key.from = parent->w_index;
 2740         key.to = child->w_index;
 2741         WITNESS_INDEX_ASSERT(key.from);
 2742         WITNESS_INDEX_ASSERT(key.to);
 2743         if ((w_rmatrix[parent->w_index][child->w_index]
 2744             & WITNESS_LOCK_ORDER_KNOWN) == 0)
 2745                 goto out;
 2746 
 2747         hash = witness_hash_djb2((const char*)&key,
 2748             sizeof(key)) % w_lohash.wloh_size;
 2749         data = w_lohash.wloh_array[hash];
 2750         while (data != NULL) {
 2751                 if (witness_lock_order_key_equal(&data->wlod_key, &key))
 2752                         break;
 2753                 data = data->wlod_next;
 2754         }
 2755 
 2756 out:
 2757         return (data);
 2758 }
 2759 
 2760 /*
 2761  * Verify that parent and child have a known relationship, are not the same,
 2762  * and child is actually a child of parent.  This is done without w_mtx
 2763  * to avoid contention in the common case.
 2764  */
 2765 static int
 2766 witness_lock_order_check(struct witness *parent, struct witness *child)
 2767 {
 2768 
 2769         if (parent != child &&
 2770             w_rmatrix[parent->w_index][child->w_index]
 2771             & WITNESS_LOCK_ORDER_KNOWN &&
 2772             isitmychild(parent, child))
 2773                 return (1);
 2774 
 2775         return (0);
 2776 }
 2777 
 2778 static int
 2779 witness_lock_order_add(struct witness *parent, struct witness *child)
 2780 {
 2781         struct witness_lock_order_data *data = NULL;
 2782         struct witness_lock_order_key key;
 2783         unsigned int hash;
 2784         
 2785         MPASS(parent != NULL && child != NULL);
 2786         key.from = parent->w_index;
 2787         key.to = child->w_index;
 2788         WITNESS_INDEX_ASSERT(key.from);
 2789         WITNESS_INDEX_ASSERT(key.to);
 2790         if (w_rmatrix[parent->w_index][child->w_index]
 2791             & WITNESS_LOCK_ORDER_KNOWN)
 2792                 return (1);
 2793 
 2794         hash = witness_hash_djb2((const char*)&key,
 2795             sizeof(key)) % w_lohash.wloh_size;
 2796         w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN;
 2797         data = w_lofree;
 2798         if (data == NULL)
 2799                 return (0);
 2800         w_lofree = data->wlod_next;
 2801         data->wlod_next = w_lohash.wloh_array[hash];
 2802         data->wlod_key = key;
 2803         w_lohash.wloh_array[hash] = data;
 2804         w_lohash.wloh_count++;
 2805         stack_zero(&data->wlod_stack);
 2806         stack_save(&data->wlod_stack);
 2807         return (1);
 2808 }
 2809 
 2810 /* Call this whenver the structure of the witness graph changes. */
 2811 static void
 2812 witness_increment_graph_generation(void)
 2813 {
 2814 
 2815         if (witness_cold == 0)
 2816                 mtx_assert(&w_mtx, MA_OWNED);
 2817         w_generation++;
 2818 }
 2819 
 2820 #ifdef KDB
 2821 static void
 2822 _witness_debugger(int cond, const char *msg)
 2823 {
 2824 
 2825         if (witness_trace && cond)
 2826                 kdb_backtrace();
 2827         if (witness_kdb && cond)
 2828                 kdb_enter(KDB_WHY_WITNESS, msg);
 2829 }
 2830 #endif

Cache object: 1679f60eb704d1303d9e1ae4a9edff6d


[ 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.