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

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    1 /*-
    2  * Copyright (c) 2008 Isilon Systems, Inc.
    3  * Copyright (c) 2008 Ilya Maykov <ivmaykov@gmail.com>
    4  * Copyright (c) 1998 Berkeley Software Design, Inc.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Berkeley Software Design Inc's name may not be used to endorse or
   16  *    promote products derived from this software without specific prior
   17  *    written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  *
   31  *      from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
   32  *      and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
   33  */
   34 
   35 /*
   36  * Implementation of the `witness' lock verifier.  Originally implemented for
   37  * mutexes in BSD/OS.  Extended to handle generic lock objects and lock
   38  * classes in FreeBSD.
   39  */
   40 
   41 /*
   42  *      Main Entry: witness
   43  *      Pronunciation: 'wit-n&s
   44  *      Function: noun
   45  *      Etymology: Middle English witnesse, from Old English witnes knowledge,
   46  *          testimony, witness, from 2wit
   47  *      Date: before 12th century
   48  *      1 : attestation of a fact or event : TESTIMONY
   49  *      2 : one that gives evidence; specifically : one who testifies in
   50  *          a cause or before a judicial tribunal
   51  *      3 : one asked to be present at a transaction so as to be able to
   52  *          testify to its having taken place
   53  *      4 : one who has personal knowledge of something
   54  *      5 a : something serving as evidence or proof : SIGN
   55  *        b : public affirmation by word or example of usually
   56  *            religious faith or conviction <the heroic witness to divine
   57  *            life -- Pilot>
   58  *      6 capitalized : a member of the Jehovah's Witnesses 
   59  */
   60 
   61 /*
   62  * Special rules concerning Giant and lock orders:
   63  *
   64  * 1) Giant must be acquired before any other mutexes.  Stated another way,
   65  *    no other mutex may be held when Giant is acquired.
   66  *
   67  * 2) Giant must be released when blocking on a sleepable lock.
   68  *
   69  * This rule is less obvious, but is a result of Giant providing the same
   70  * semantics as spl().  Basically, when a thread sleeps, it must release
   71  * Giant.  When a thread blocks on a sleepable lock, it sleeps.  Hence rule
   72  * 2).
   73  *
   74  * 3) Giant may be acquired before or after sleepable locks.
   75  *
   76  * This rule is also not quite as obvious.  Giant may be acquired after
   77  * a sleepable lock because it is a non-sleepable lock and non-sleepable
   78  * locks may always be acquired while holding a sleepable lock.  The second
   79  * case, Giant before a sleepable lock, follows from rule 2) above.  Suppose
   80  * you have two threads T1 and T2 and a sleepable lock X.  Suppose that T1
   81  * acquires X and blocks on Giant.  Then suppose that T2 acquires Giant and
   82  * blocks on X.  When T2 blocks on X, T2 will release Giant allowing T1 to
   83  * execute.  Thus, acquiring Giant both before and after a sleepable lock
   84  * will not result in a lock order reversal.
   85  */
   86 
   87 #include <sys/cdefs.h>
   88 __FBSDID("$FreeBSD: releng/8.3/sys/kern/subr_witness.c 219107 2011-02-28 23:28:35Z rwatson $");
   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_mtx_sleep },
  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 #if defined(SMP) && defined(__sparc64__)
  667         { "ipi", &lock_class_mtx_spin },
  668 #endif
  669 #ifdef __i386__
  670         { "allpmaps", &lock_class_mtx_spin },
  671         { "descriptor tables", &lock_class_mtx_spin },
  672 #endif
  673         { "clk", &lock_class_mtx_spin },
  674         { "cpuset", &lock_class_mtx_spin },
  675         { "mprof lock", &lock_class_mtx_spin },
  676         { "zombie lock", &lock_class_mtx_spin },
  677         { "ALD Queue", &lock_class_mtx_spin },
  678 #ifdef __ia64__
  679         { "MCA spin lock", &lock_class_mtx_spin },
  680 #endif
  681 #if defined(__i386__) || defined(__amd64__)
  682         { "pcicfg", &lock_class_mtx_spin },
  683         { "NDIS thread lock", &lock_class_mtx_spin },
  684 #endif
  685         { "tw_osl_io_lock", &lock_class_mtx_spin },
  686         { "tw_osl_q_lock", &lock_class_mtx_spin },
  687         { "tw_cl_io_lock", &lock_class_mtx_spin },
  688         { "tw_cl_intr_lock", &lock_class_mtx_spin },
  689         { "tw_cl_gen_lock", &lock_class_mtx_spin },
  690 #ifdef  HWPMC_HOOKS
  691         { "pmc-leaf", &lock_class_mtx_spin },
  692 #endif
  693         { "blocked lock", &lock_class_mtx_spin },
  694         { NULL, NULL },
  695         { NULL, NULL }
  696 };
  697 
  698 #ifdef BLESSING
  699 /*
  700  * Pairs of locks which have been blessed
  701  * Don't complain about order problems with blessed locks
  702  */
  703 static struct witness_blessed blessed_list[] = {
  704 };
  705 static int blessed_count =
  706         sizeof(blessed_list) / sizeof(struct witness_blessed);
  707 #endif
  708 
  709 /*
  710  * This global is set to 0 once it becomes safe to use the witness code.
  711  */
  712 static int witness_cold = 1;
  713 
  714 /*
  715  * This global is set to 1 once the static lock orders have been enrolled
  716  * so that a warning can be issued for any spin locks enrolled later.
  717  */
  718 static int witness_spin_warn = 0;
  719 
  720 /*
  721  * The WITNESS-enabled diagnostic code.  Note that the witness code does
  722  * assume that the early boot is single-threaded at least until after this
  723  * routine is completed.
  724  */
  725 static void
  726 witness_initialize(void *dummy __unused)
  727 {
  728         struct lock_object *lock;
  729         struct witness_order_list_entry *order;
  730         struct witness *w, *w1;
  731         int i;
  732 
  733         w_data = malloc(sizeof (struct witness) * WITNESS_COUNT, M_WITNESS,
  734             M_NOWAIT | M_ZERO);
  735 
  736         /*
  737          * We have to release Giant before initializing its witness
  738          * structure so that WITNESS doesn't get confused.
  739          */
  740         mtx_unlock(&Giant);
  741         mtx_assert(&Giant, MA_NOTOWNED);
  742 
  743         CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
  744         mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET |
  745             MTX_NOWITNESS | MTX_NOPROFILE);
  746         for (i = WITNESS_COUNT - 1; i >= 0; i--) {
  747                 w = &w_data[i];
  748                 memset(w, 0, sizeof(*w));
  749                 w_data[i].w_index = i;  /* Witness index never changes. */
  750                 witness_free(w);
  751         }
  752         KASSERT(STAILQ_FIRST(&w_free)->w_index == 0,
  753             ("%s: Invalid list of free witness objects", __func__));
  754 
  755         /* Witness with index 0 is not used to aid in debugging. */
  756         STAILQ_REMOVE_HEAD(&w_free, w_list);
  757         w_free_cnt--;
  758 
  759         memset(w_rmatrix, 0,
  760             (sizeof(**w_rmatrix) * (WITNESS_COUNT+1) * (WITNESS_COUNT+1)));
  761 
  762         for (i = 0; i < LOCK_CHILDCOUNT; i++)
  763                 witness_lock_list_free(&w_locklistdata[i]);
  764         witness_init_hash_tables();
  765 
  766         /* First add in all the specified order lists. */
  767         for (order = order_lists; order->w_name != NULL; order++) {
  768                 w = enroll(order->w_name, order->w_class);
  769                 if (w == NULL)
  770                         continue;
  771                 w->w_file = "order list";
  772                 for (order++; order->w_name != NULL; order++) {
  773                         w1 = enroll(order->w_name, order->w_class);
  774                         if (w1 == NULL)
  775                                 continue;
  776                         w1->w_file = "order list";
  777                         itismychild(w, w1);
  778                         w = w1;
  779                 }
  780         }
  781         witness_spin_warn = 1;
  782 
  783         /* Iterate through all locks and add them to witness. */
  784         for (i = 0; pending_locks[i].wh_lock != NULL; i++) {
  785                 lock = pending_locks[i].wh_lock;
  786                 KASSERT(lock->lo_flags & LO_WITNESS,
  787                     ("%s: lock %s is on pending list but not LO_WITNESS",
  788                     __func__, lock->lo_name));
  789                 lock->lo_witness = enroll(pending_locks[i].wh_type,
  790                     LOCK_CLASS(lock));
  791         }
  792 
  793         /* Mark the witness code as being ready for use. */
  794         witness_cold = 0;
  795 
  796         mtx_lock(&Giant);
  797 }
  798 SYSINIT(witness_init, SI_SUB_WITNESS, SI_ORDER_FIRST, witness_initialize,
  799     NULL);
  800 
  801 void
  802 witness_init(struct lock_object *lock, const char *type)
  803 {
  804         struct lock_class *class;
  805 
  806         /* Various sanity checks. */
  807         class = LOCK_CLASS(lock);
  808         if ((lock->lo_flags & LO_RECURSABLE) != 0 &&
  809             (class->lc_flags & LC_RECURSABLE) == 0)
  810                 panic("%s: lock (%s) %s can not be recursable", __func__,
  811                     class->lc_name, lock->lo_name);
  812         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
  813             (class->lc_flags & LC_SLEEPABLE) == 0)
  814                 panic("%s: lock (%s) %s can not be sleepable", __func__,
  815                     class->lc_name, lock->lo_name);
  816         if ((lock->lo_flags & LO_UPGRADABLE) != 0 &&
  817             (class->lc_flags & LC_UPGRADABLE) == 0)
  818                 panic("%s: lock (%s) %s can not be upgradable", __func__,
  819                     class->lc_name, lock->lo_name);
  820 
  821         /*
  822          * If we shouldn't watch this lock, then just clear lo_witness.
  823          * Otherwise, if witness_cold is set, then it is too early to
  824          * enroll this lock, so defer it to witness_initialize() by adding
  825          * it to the pending_locks list.  If it is not too early, then enroll
  826          * the lock now.
  827          */
  828         if (witness_watch < 1 || panicstr != NULL ||
  829             (lock->lo_flags & LO_WITNESS) == 0)
  830                 lock->lo_witness = NULL;
  831         else if (witness_cold) {
  832                 pending_locks[pending_cnt].wh_lock = lock;
  833                 pending_locks[pending_cnt++].wh_type = type;
  834                 if (pending_cnt > WITNESS_PENDLIST)
  835                         panic("%s: pending locks list is too small, bump it\n",
  836                             __func__);
  837         } else
  838                 lock->lo_witness = enroll(type, class);
  839 }
  840 
  841 void
  842 witness_destroy(struct lock_object *lock)
  843 {
  844         struct lock_class *class;
  845         struct witness *w;
  846 
  847         class = LOCK_CLASS(lock);
  848 
  849         if (witness_cold)
  850                 panic("lock (%s) %s destroyed while witness_cold",
  851                     class->lc_name, lock->lo_name);
  852 
  853         /* XXX: need to verify that no one holds the lock */
  854         if ((lock->lo_flags & LO_WITNESS) == 0 || lock->lo_witness == NULL)
  855                 return;
  856         w = lock->lo_witness;
  857 
  858         mtx_lock_spin(&w_mtx);
  859         MPASS(w->w_refcount > 0);
  860         w->w_refcount--;
  861 
  862         if (w->w_refcount == 0)
  863                 depart(w);
  864         mtx_unlock_spin(&w_mtx);
  865 }
  866 
  867 #ifdef DDB
  868 static void
  869 witness_ddb_compute_levels(void)
  870 {
  871         struct witness *w;
  872 
  873         /*
  874          * First clear all levels.
  875          */
  876         STAILQ_FOREACH(w, &w_all, w_list)
  877                 w->w_ddb_level = -1;
  878 
  879         /*
  880          * Look for locks with no parents and level all their descendants.
  881          */
  882         STAILQ_FOREACH(w, &w_all, w_list) {
  883 
  884                 /* If the witness has ancestors (is not a root), skip it. */
  885                 if (w->w_num_ancestors > 0)
  886                         continue;
  887                 witness_ddb_level_descendants(w, 0);
  888         }
  889 }
  890 
  891 static void
  892 witness_ddb_level_descendants(struct witness *w, int l)
  893 {
  894         int i;
  895 
  896         if (w->w_ddb_level >= l)
  897                 return;
  898 
  899         w->w_ddb_level = l;
  900         l++;
  901 
  902         for (i = 1; i <= w_max_used_index; i++) {
  903                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
  904                         witness_ddb_level_descendants(&w_data[i], l);
  905         }
  906 }
  907 
  908 static void
  909 witness_ddb_display_descendants(int(*prnt)(const char *fmt, ...),
  910     struct witness *w, int indent)
  911 {
  912         int i;
  913 
  914         for (i = 0; i < indent; i++)
  915                 prnt(" ");
  916         prnt("%s (type: %s, depth: %d, active refs: %d)",
  917              w->w_name, w->w_class->lc_name,
  918              w->w_ddb_level, w->w_refcount);
  919         if (w->w_displayed) {
  920                 prnt(" -- (already displayed)\n");
  921                 return;
  922         }
  923         w->w_displayed = 1;
  924         if (w->w_file != NULL && w->w_line != 0)
  925                 prnt(" -- last acquired @ %s:%d\n", w->w_file,
  926                     w->w_line);
  927         else
  928                 prnt(" -- never acquired\n");
  929         indent++;
  930         WITNESS_INDEX_ASSERT(w->w_index);
  931         for (i = 1; i <= w_max_used_index; i++) {
  932                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
  933                         witness_ddb_display_descendants(prnt, &w_data[i],
  934                             indent);
  935         }
  936 }
  937 
  938 static void
  939 witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
  940     struct witness_list *list)
  941 {
  942         struct witness *w;
  943 
  944         STAILQ_FOREACH(w, list, w_typelist) {
  945                 if (w->w_file == NULL || w->w_ddb_level > 0)
  946                         continue;
  947 
  948                 /* This lock has no anscestors - display its descendants. */
  949                 witness_ddb_display_descendants(prnt, w, 0);
  950         }
  951 }
  952         
  953 static void
  954 witness_ddb_display(int(*prnt)(const char *fmt, ...))
  955 {
  956         struct witness *w;
  957 
  958         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
  959         witness_ddb_compute_levels();
  960 
  961         /* Clear all the displayed flags. */
  962         STAILQ_FOREACH(w, &w_all, w_list)
  963                 w->w_displayed = 0;
  964 
  965         /*
  966          * First, handle sleep locks which have been acquired at least
  967          * once.
  968          */
  969         prnt("Sleep locks:\n");
  970         witness_ddb_display_list(prnt, &w_sleep);
  971         
  972         /*
  973          * Now do spin locks which have been acquired at least once.
  974          */
  975         prnt("\nSpin locks:\n");
  976         witness_ddb_display_list(prnt, &w_spin);
  977         
  978         /*
  979          * Finally, any locks which have not been acquired yet.
  980          */
  981         prnt("\nLocks which were never acquired:\n");
  982         STAILQ_FOREACH(w, &w_all, w_list) {
  983                 if (w->w_file != NULL || w->w_refcount == 0)
  984                         continue;
  985                 prnt("%s (type: %s, depth: %d)\n", w->w_name,
  986                     w->w_class->lc_name, w->w_ddb_level);
  987         }
  988 }
  989 #endif /* DDB */
  990 
  991 /* Trim useless garbage from filenames. */
  992 static const char *
  993 fixup_filename(const char *file)
  994 {
  995 
  996         if (file == NULL)
  997                 return (NULL);
  998         while (strncmp(file, "../", 3) == 0)
  999                 file += 3;
 1000         return (file);
 1001 }
 1002 
 1003 int
 1004 witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
 1005 {
 1006 
 1007         if (witness_watch == -1 || panicstr != NULL)
 1008                 return (0);
 1009 
 1010         /* Require locks that witness knows about. */
 1011         if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL ||
 1012             lock2->lo_witness == NULL)
 1013                 return (EINVAL);
 1014 
 1015         mtx_assert(&w_mtx, MA_NOTOWNED);
 1016         mtx_lock_spin(&w_mtx);
 1017 
 1018         /*
 1019          * If we already have either an explicit or implied lock order that
 1020          * is the other way around, then return an error.
 1021          */
 1022         if (witness_watch &&
 1023             isitmydescendant(lock2->lo_witness, lock1->lo_witness)) {
 1024                 mtx_unlock_spin(&w_mtx);
 1025                 return (EDOOFUS);
 1026         }
 1027         
 1028         /* Try to add the new order. */
 1029         CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 1030             lock2->lo_witness->w_name, lock1->lo_witness->w_name);
 1031         itismychild(lock1->lo_witness, lock2->lo_witness);
 1032         mtx_unlock_spin(&w_mtx);
 1033         return (0);
 1034 }
 1035 
 1036 void
 1037 witness_checkorder(struct lock_object *lock, int flags, const char *file,
 1038     int line, struct lock_object *interlock)
 1039 {
 1040         struct lock_list_entry *lock_list, *lle;
 1041         struct lock_instance *lock1, *lock2, *plock;
 1042         struct lock_class *class;
 1043         struct witness *w, *w1;
 1044         struct thread *td;
 1045         int i, j;
 1046 
 1047         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL ||
 1048             panicstr != NULL)
 1049                 return;
 1050 
 1051         w = lock->lo_witness;
 1052         class = LOCK_CLASS(lock);
 1053         td = curthread;
 1054         file = fixup_filename(file);
 1055 
 1056         if (class->lc_flags & LC_SLEEPLOCK) {
 1057 
 1058                 /*
 1059                  * Since spin locks include a critical section, this check
 1060                  * implicitly enforces a lock order of all sleep locks before
 1061                  * all spin locks.
 1062                  */
 1063                 if (td->td_critnest != 0 && !kdb_active)
 1064                         panic("blockable sleep lock (%s) %s @ %s:%d",
 1065                             class->lc_name, lock->lo_name, file, line);
 1066 
 1067                 /*
 1068                  * If this is the first lock acquired then just return as
 1069                  * no order checking is needed.
 1070                  */
 1071                 lock_list = td->td_sleeplocks;
 1072                 if (lock_list == NULL || lock_list->ll_count == 0)
 1073                         return;
 1074         } else {
 1075 
 1076                 /*
 1077                  * If this is the first lock, just return as no order
 1078                  * checking is needed.  Avoid problems with thread
 1079                  * migration pinning the thread while checking if
 1080                  * spinlocks are held.  If at least one spinlock is held
 1081                  * the thread is in a safe path and it is allowed to
 1082                  * unpin it.
 1083                  */
 1084                 sched_pin();
 1085                 lock_list = PCPU_GET(spinlocks);
 1086                 if (lock_list == NULL || lock_list->ll_count == 0) {
 1087                         sched_unpin();
 1088                         return;
 1089                 }
 1090                 sched_unpin();
 1091         }
 1092 
 1093         /*
 1094          * Check to see if we are recursing on a lock we already own.  If
 1095          * so, make sure that we don't mismatch exclusive and shared lock
 1096          * acquires.
 1097          */
 1098         lock1 = find_instance(lock_list, lock);
 1099         if (lock1 != NULL) {
 1100                 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 &&
 1101                     (flags & LOP_EXCLUSIVE) == 0) {
 1102                         printf("shared lock of (%s) %s @ %s:%d\n",
 1103                             class->lc_name, lock->lo_name, file, line);
 1104                         printf("while exclusively locked from %s:%d\n",
 1105                             lock1->li_file, lock1->li_line);
 1106                         panic("share->excl");
 1107                 }
 1108                 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
 1109                     (flags & LOP_EXCLUSIVE) != 0) {
 1110                         printf("exclusive lock of (%s) %s @ %s:%d\n",
 1111                             class->lc_name, lock->lo_name, file, line);
 1112                         printf("while share locked from %s:%d\n",
 1113                             lock1->li_file, lock1->li_line);
 1114                         panic("excl->share");
 1115                 }
 1116                 return;
 1117         }
 1118 
 1119         /*
 1120          * Find the previously acquired lock, but ignore interlocks.
 1121          */
 1122         plock = &lock_list->ll_children[lock_list->ll_count - 1];
 1123         if (interlock != NULL && plock->li_lock == interlock) {
 1124                 if (lock_list->ll_count > 1)
 1125                         plock =
 1126                             &lock_list->ll_children[lock_list->ll_count - 2];
 1127                 else {
 1128                         lle = lock_list->ll_next;
 1129 
 1130                         /*
 1131                          * The interlock is the only lock we hold, so
 1132                          * simply return.
 1133                          */
 1134                         if (lle == NULL)
 1135                                 return;
 1136                         plock = &lle->ll_children[lle->ll_count - 1];
 1137                 }
 1138         }
 1139         
 1140         /*
 1141          * Try to perform most checks without a lock.  If this succeeds we
 1142          * can skip acquiring the lock and return success.
 1143          */
 1144         w1 = plock->li_lock->lo_witness;
 1145         if (witness_lock_order_check(w1, w))
 1146                 return;
 1147 
 1148         /*
 1149          * Check for duplicate locks of the same type.  Note that we only
 1150          * have to check for this on the last lock we just acquired.  Any
 1151          * other cases will be caught as lock order violations.
 1152          */
 1153         mtx_lock_spin(&w_mtx);
 1154         witness_lock_order_add(w1, w);
 1155         if (w1 == w) {
 1156                 i = w->w_index;
 1157                 if (!(lock->lo_flags & LO_DUPOK) && !(flags & LOP_DUPOK) &&
 1158                     !(w_rmatrix[i][i] & WITNESS_REVERSAL)) {
 1159                     w_rmatrix[i][i] |= WITNESS_REVERSAL;
 1160                         w->w_reversed = 1;
 1161                         mtx_unlock_spin(&w_mtx);
 1162                         printf(
 1163                             "acquiring duplicate lock of same type: \"%s\"\n", 
 1164                             w->w_name);
 1165                         printf(" 1st %s @ %s:%d\n", plock->li_lock->lo_name,
 1166                                plock->li_file, plock->li_line);
 1167                         printf(" 2nd %s @ %s:%d\n", lock->lo_name, file, line);
 1168                         witness_debugger(1);
 1169                     } else
 1170                             mtx_unlock_spin(&w_mtx);
 1171                 return;
 1172         }
 1173         mtx_assert(&w_mtx, MA_OWNED);
 1174 
 1175         /*
 1176          * If we know that the lock we are acquiring comes after
 1177          * the lock we most recently acquired in the lock order tree,
 1178          * then there is no need for any further checks.
 1179          */
 1180         if (isitmychild(w1, w))
 1181                 goto out;
 1182 
 1183         for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) {
 1184                 for (i = lle->ll_count - 1; i >= 0; i--, j++) {
 1185 
 1186                         MPASS(j < WITNESS_COUNT);
 1187                         lock1 = &lle->ll_children[i];
 1188 
 1189                         /*
 1190                          * Ignore the interlock the first time we see it.
 1191                          */
 1192                         if (interlock != NULL && interlock == lock1->li_lock) {
 1193                                 interlock = NULL;
 1194                                 continue;
 1195                         }
 1196 
 1197                         /*
 1198                          * If this lock doesn't undergo witness checking,
 1199                          * then skip it.
 1200                          */
 1201                         w1 = lock1->li_lock->lo_witness;
 1202                         if (w1 == NULL) {
 1203                                 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0,
 1204                                     ("lock missing witness structure"));
 1205                                 continue;
 1206                         }
 1207 
 1208                         /*
 1209                          * If we are locking Giant and this is a sleepable
 1210                          * lock, then skip it.
 1211                          */
 1212                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1213                             lock == &Giant.lock_object)
 1214                                 continue;
 1215 
 1216                         /*
 1217                          * If we are locking a sleepable lock and this lock
 1218                          * is Giant, then skip it.
 1219                          */
 1220                         if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1221                             lock1->li_lock == &Giant.lock_object)
 1222                                 continue;
 1223 
 1224                         /*
 1225                          * If we are locking a sleepable lock and this lock
 1226                          * isn't sleepable, we want to treat it as a lock
 1227                          * order violation to enfore a general lock order of
 1228                          * sleepable locks before non-sleepable locks.
 1229                          */
 1230                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1231                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
 1232                                 goto reversal;
 1233 
 1234                         /*
 1235                          * If we are locking Giant and this is a non-sleepable
 1236                          * lock, then treat it as a reversal.
 1237                          */
 1238                         if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0 &&
 1239                             lock == &Giant.lock_object)
 1240                                 goto reversal;
 1241 
 1242                         /*
 1243                          * Check the lock order hierarchy for a reveresal.
 1244                          */
 1245                         if (!isitmydescendant(w, w1))
 1246                                 continue;
 1247                 reversal:
 1248 
 1249                         /*
 1250                          * We have a lock order violation, check to see if it
 1251                          * is allowed or has already been yelled about.
 1252                          */
 1253 #ifdef BLESSING
 1254 
 1255                         /*
 1256                          * If the lock order is blessed, just bail.  We don't
 1257                          * look for other lock order violations though, which
 1258                          * may be a bug.
 1259                          */
 1260                         if (blessed(w, w1))
 1261                                 goto out;
 1262 #endif
 1263 
 1264                         /* Bail if this violation is known */
 1265                         if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL)
 1266                                 goto out;
 1267 
 1268                         /* Record this as a violation */
 1269                         w_rmatrix[w1->w_index][w->w_index] |= WITNESS_REVERSAL;
 1270                         w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL;
 1271                         w->w_reversed = w1->w_reversed = 1;
 1272                         witness_increment_graph_generation();
 1273                         mtx_unlock_spin(&w_mtx);
 1274                         
 1275                         /*
 1276                          * Ok, yell about it.
 1277                          */
 1278                         if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
 1279                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
 1280                                 printf(
 1281                 "lock order reversal: (sleepable after non-sleepable)\n");
 1282                         else if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0
 1283                             && lock == &Giant.lock_object)
 1284                                 printf(
 1285                 "lock order reversal: (Giant after non-sleepable)\n");
 1286                         else
 1287                                 printf("lock order reversal:\n");
 1288 
 1289                         /*
 1290                          * Try to locate an earlier lock with
 1291                          * witness w in our list.
 1292                          */
 1293                         do {
 1294                                 lock2 = &lle->ll_children[i];
 1295                                 MPASS(lock2->li_lock != NULL);
 1296                                 if (lock2->li_lock->lo_witness == w)
 1297                                         break;
 1298                                 if (i == 0 && lle->ll_next != NULL) {
 1299                                         lle = lle->ll_next;
 1300                                         i = lle->ll_count - 1;
 1301                                         MPASS(i >= 0 && i < LOCK_NCHILDREN);
 1302                                 } else
 1303                                         i--;
 1304                         } while (i >= 0);
 1305                         if (i < 0) {
 1306                                 printf(" 1st %p %s (%s) @ %s:%d\n",
 1307                                     lock1->li_lock, lock1->li_lock->lo_name,
 1308                                     w1->w_name, lock1->li_file, lock1->li_line);
 1309                                 printf(" 2nd %p %s (%s) @ %s:%d\n", lock,
 1310                                     lock->lo_name, w->w_name, file, line);
 1311                         } else {
 1312                                 printf(" 1st %p %s (%s) @ %s:%d\n",
 1313                                     lock2->li_lock, lock2->li_lock->lo_name,
 1314                                     lock2->li_lock->lo_witness->w_name,
 1315                                     lock2->li_file, lock2->li_line);
 1316                                 printf(" 2nd %p %s (%s) @ %s:%d\n",
 1317                                     lock1->li_lock, lock1->li_lock->lo_name,
 1318                                     w1->w_name, lock1->li_file, lock1->li_line);
 1319                                 printf(" 3rd %p %s (%s) @ %s:%d\n", lock,
 1320                                     lock->lo_name, w->w_name, file, line);
 1321                         }
 1322                         witness_debugger(1);
 1323                         return;
 1324                 }
 1325         }
 1326 
 1327         /*
 1328          * If requested, build a new lock order.  However, don't build a new
 1329          * relationship between a sleepable lock and Giant if it is in the
 1330          * wrong direction.  The correct lock order is that sleepable locks
 1331          * always come before Giant.
 1332          */
 1333         if (flags & LOP_NEWORDER &&
 1334             !(plock->li_lock == &Giant.lock_object &&
 1335             (lock->lo_flags & LO_SLEEPABLE) != 0)) {
 1336                 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
 1337                     w->w_name, plock->li_lock->lo_witness->w_name);
 1338                 itismychild(plock->li_lock->lo_witness, w);
 1339         }
 1340 out:
 1341         mtx_unlock_spin(&w_mtx);
 1342 }
 1343 
 1344 void
 1345 witness_lock(struct lock_object *lock, int flags, const char *file, int line)
 1346 {
 1347         struct lock_list_entry **lock_list, *lle;
 1348         struct lock_instance *instance;
 1349         struct witness *w;
 1350         struct thread *td;
 1351 
 1352         if (witness_cold || witness_watch == -1 || lock->lo_witness == NULL ||
 1353             panicstr != NULL)
 1354                 return;
 1355         w = lock->lo_witness;
 1356         td = curthread;
 1357         file = fixup_filename(file);
 1358 
 1359         /* Determine lock list for this lock. */
 1360         if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK)
 1361                 lock_list = &td->td_sleeplocks;
 1362         else
 1363                 lock_list = PCPU_PTR(spinlocks);
 1364 
 1365         /* Check to see if we are recursing on a lock we already own. */
 1366         instance = find_instance(*lock_list, lock);
 1367         if (instance != NULL) {
 1368                 instance->li_flags++;
 1369                 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__,
 1370                     td->td_proc->p_pid, lock->lo_name,
 1371                     instance->li_flags & LI_RECURSEMASK);
 1372                 instance->li_file = file;
 1373                 instance->li_line = line;
 1374                 return;
 1375         }
 1376 
 1377         /* Update per-witness last file and line acquire. */
 1378         w->w_file = file;
 1379         w->w_line = line;
 1380 
 1381         /* Find the next open lock instance in the list and fill it. */
 1382         lle = *lock_list;
 1383         if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
 1384                 lle = witness_lock_list_get();
 1385                 if (lle == NULL)
 1386                         return;
 1387                 lle->ll_next = *lock_list;
 1388                 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__,
 1389                     td->td_proc->p_pid, lle);
 1390                 *lock_list = lle;
 1391         }
 1392         instance = &lle->ll_children[lle->ll_count++];
 1393         instance->li_lock = lock;
 1394         instance->li_line = line;
 1395         instance->li_file = file;
 1396         if ((flags & LOP_EXCLUSIVE) != 0)
 1397                 instance->li_flags = LI_EXCLUSIVE;
 1398         else
 1399                 instance->li_flags = 0;
 1400         CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__,
 1401             td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1);
 1402 }
 1403 
 1404 void
 1405 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line)
 1406 {
 1407         struct lock_instance *instance;
 1408         struct lock_class *class;
 1409 
 1410         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 1411         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 1412                 return;
 1413         class = LOCK_CLASS(lock);
 1414         file = fixup_filename(file);
 1415         if (witness_watch) {
 1416                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
 1417                         panic("upgrade of non-upgradable lock (%s) %s @ %s:%d",
 1418                             class->lc_name, lock->lo_name, file, line);
 1419                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
 1420                         panic("upgrade of non-sleep lock (%s) %s @ %s:%d",
 1421                             class->lc_name, lock->lo_name, file, line);
 1422         }
 1423         instance = find_instance(curthread->td_sleeplocks, lock);
 1424         if (instance == NULL)
 1425                 panic("upgrade of unlocked lock (%s) %s @ %s:%d",
 1426                     class->lc_name, lock->lo_name, file, line);
 1427         if (witness_watch) {
 1428                 if ((instance->li_flags & LI_EXCLUSIVE) != 0)
 1429                         panic("upgrade of exclusive lock (%s) %s @ %s:%d",
 1430                             class->lc_name, lock->lo_name, file, line);
 1431                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
 1432                         panic("upgrade of recursed lock (%s) %s r=%d @ %s:%d",
 1433                             class->lc_name, lock->lo_name,
 1434                             instance->li_flags & LI_RECURSEMASK, file, line);
 1435         }
 1436         instance->li_flags |= LI_EXCLUSIVE;
 1437 }
 1438 
 1439 void
 1440 witness_downgrade(struct lock_object *lock, int flags, const char *file,
 1441     int line)
 1442 {
 1443         struct lock_instance *instance;
 1444         struct lock_class *class;
 1445 
 1446         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 1447         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 1448                 return;
 1449         class = LOCK_CLASS(lock);
 1450         file = fixup_filename(file);
 1451         if (witness_watch) {
 1452                 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
 1453                 panic("downgrade of non-upgradable lock (%s) %s @ %s:%d",
 1454                             class->lc_name, lock->lo_name, file, line);
 1455                 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
 1456                         panic("downgrade of non-sleep lock (%s) %s @ %s:%d",
 1457                             class->lc_name, lock->lo_name, file, line);
 1458         }
 1459         instance = find_instance(curthread->td_sleeplocks, lock);
 1460         if (instance == NULL)
 1461                 panic("downgrade of unlocked lock (%s) %s @ %s:%d",
 1462                     class->lc_name, lock->lo_name, file, line);
 1463         if (witness_watch) {
 1464                 if ((instance->li_flags & LI_EXCLUSIVE) == 0)
 1465                         panic("downgrade of shared lock (%s) %s @ %s:%d",
 1466                             class->lc_name, lock->lo_name, file, line);
 1467                 if ((instance->li_flags & LI_RECURSEMASK) != 0)
 1468                         panic("downgrade of recursed lock (%s) %s r=%d @ %s:%d",
 1469                             class->lc_name, lock->lo_name,
 1470                             instance->li_flags & LI_RECURSEMASK, file, line);
 1471         }
 1472         instance->li_flags &= ~LI_EXCLUSIVE;
 1473 }
 1474 
 1475 void
 1476 witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
 1477 {
 1478         struct lock_list_entry **lock_list, *lle;
 1479         struct lock_instance *instance;
 1480         struct lock_class *class;
 1481         struct thread *td;
 1482         register_t s;
 1483         int i, j;
 1484 
 1485         if (witness_cold || lock->lo_witness == NULL || panicstr != NULL)
 1486                 return;
 1487         td = curthread;
 1488         class = LOCK_CLASS(lock);
 1489         file = fixup_filename(file);
 1490 
 1491         /* Find lock instance associated with this lock. */
 1492         if (class->lc_flags & LC_SLEEPLOCK)
 1493                 lock_list = &td->td_sleeplocks;
 1494         else
 1495                 lock_list = PCPU_PTR(spinlocks);
 1496         lle = *lock_list;
 1497         for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next)
 1498                 for (i = 0; i < (*lock_list)->ll_count; i++) {
 1499                         instance = &(*lock_list)->ll_children[i];
 1500                         if (instance->li_lock == lock)
 1501                                 goto found;
 1502                 }
 1503 
 1504         /*
 1505          * When disabling WITNESS through witness_watch we could end up in
 1506          * having registered locks in the td_sleeplocks queue.
 1507          * We have to make sure we flush these queues, so just search for
 1508          * eventual register locks and remove them.
 1509          */
 1510         if (witness_watch > 0)
 1511                 panic("lock (%s) %s not locked @ %s:%d", class->lc_name,
 1512                     lock->lo_name, file, line);
 1513         else
 1514                 return;
 1515 found:
 1516 
 1517         /* First, check for shared/exclusive mismatches. */
 1518         if ((instance->li_flags & LI_EXCLUSIVE) != 0 && witness_watch > 0 &&
 1519             (flags & LOP_EXCLUSIVE) == 0) {
 1520                 printf("shared unlock of (%s) %s @ %s:%d\n", class->lc_name,
 1521                     lock->lo_name, file, line);
 1522                 printf("while exclusively locked from %s:%d\n",
 1523                     instance->li_file, instance->li_line);
 1524                 panic("excl->ushare");
 1525         }
 1526         if ((instance->li_flags & LI_EXCLUSIVE) == 0 && witness_watch > 0 &&
 1527             (flags & LOP_EXCLUSIVE) != 0) {
 1528                 printf("exclusive unlock of (%s) %s @ %s:%d\n", class->lc_name,
 1529                     lock->lo_name, file, line);
 1530                 printf("while share locked from %s:%d\n", instance->li_file,
 1531                     instance->li_line);
 1532                 panic("share->uexcl");
 1533         }
 1534         /* If we are recursed, unrecurse. */
 1535         if ((instance->li_flags & LI_RECURSEMASK) > 0) {
 1536                 CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__,
 1537                     td->td_proc->p_pid, instance->li_lock->lo_name,
 1538                     instance->li_flags);
 1539                 instance->li_flags--;
 1540                 return;
 1541         }
 1542         /* The lock is now being dropped, check for NORELEASE flag */
 1543         if ((instance->li_flags & LI_NORELEASE) != 0 && witness_watch > 0) {
 1544                 printf("forbidden unlock of (%s) %s @ %s:%d\n", class->lc_name,
 1545                     lock->lo_name, file, line);
 1546                 panic("lock marked norelease");
 1547         }
 1548 
 1549         /* Otherwise, remove this item from the list. */
 1550         s = intr_disable();
 1551         CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__,
 1552             td->td_proc->p_pid, instance->li_lock->lo_name,
 1553             (*lock_list)->ll_count - 1);
 1554         for (j = i; j < (*lock_list)->ll_count - 1; j++)
 1555                 (*lock_list)->ll_children[j] =
 1556                     (*lock_list)->ll_children[j + 1];
 1557         (*lock_list)->ll_count--;
 1558         intr_restore(s);
 1559 
 1560         /*
 1561          * In order to reduce contention on w_mtx, we want to keep always an
 1562          * head object into lists so that frequent allocation from the 
 1563          * free witness pool (and subsequent locking) is avoided.
 1564          * In order to maintain the current code simple, when the head
 1565          * object is totally unloaded it means also that we do not have
 1566          * further objects in the list, so the list ownership needs to be
 1567          * hand over to another object if the current head needs to be freed.
 1568          */
 1569         if ((*lock_list)->ll_count == 0) {
 1570                 if (*lock_list == lle) {
 1571                         if (lle->ll_next == NULL)
 1572                                 return;
 1573                 } else
 1574                         lle = *lock_list;
 1575                 *lock_list = lle->ll_next;
 1576                 CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__,
 1577                     td->td_proc->p_pid, lle);
 1578                 witness_lock_list_free(lle);
 1579         }
 1580 }
 1581 
 1582 void
 1583 witness_thread_exit(struct thread *td)
 1584 {
 1585         struct lock_list_entry *lle;
 1586         int i, n;
 1587 
 1588         lle = td->td_sleeplocks;
 1589         if (lle == NULL || panicstr != NULL)
 1590                 return;
 1591         if (lle->ll_count != 0) {
 1592                 for (n = 0; lle != NULL; lle = lle->ll_next)
 1593                         for (i = lle->ll_count - 1; i >= 0; i--) {
 1594                                 if (n == 0)
 1595                 printf("Thread %p exiting with the following locks held:\n",
 1596                                             td);
 1597                                 n++;
 1598                                 witness_list_lock(&lle->ll_children[i], printf);
 1599                                 
 1600                         }
 1601                 panic("Thread %p cannot exit while holding sleeplocks\n", td);
 1602         }
 1603         witness_lock_list_free(lle);
 1604 }
 1605 
 1606 /*
 1607  * Warn if any locks other than 'lock' are held.  Flags can be passed in to
 1608  * exempt Giant and sleepable locks from the checks as well.  If any
 1609  * non-exempt locks are held, then a supplied message is printed to the
 1610  * console along with a list of the offending locks.  If indicated in the
 1611  * flags then a failure results in a panic as well.
 1612  */
 1613 int
 1614 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
 1615 {
 1616         struct lock_list_entry *lock_list, *lle;
 1617         struct lock_instance *lock1;
 1618         struct thread *td;
 1619         va_list ap;
 1620         int i, n;
 1621 
 1622         if (witness_cold || witness_watch < 1 || panicstr != NULL)
 1623                 return (0);
 1624         n = 0;
 1625         td = curthread;
 1626         for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next)
 1627                 for (i = lle->ll_count - 1; i >= 0; i--) {
 1628                         lock1 = &lle->ll_children[i];
 1629                         if (lock1->li_lock == lock)
 1630                                 continue;
 1631                         if (flags & WARN_GIANTOK &&
 1632                             lock1->li_lock == &Giant.lock_object)
 1633                                 continue;
 1634                         if (flags & WARN_SLEEPOK &&
 1635                             (lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0)
 1636                                 continue;
 1637                         if (n == 0) {
 1638                                 va_start(ap, fmt);
 1639                                 vprintf(fmt, ap);
 1640                                 va_end(ap);
 1641                                 printf(" with the following");
 1642                                 if (flags & WARN_SLEEPOK)
 1643                                         printf(" non-sleepable");
 1644                                 printf(" locks held:\n");
 1645                         }
 1646                         n++;
 1647                         witness_list_lock(lock1, printf);
 1648                 }
 1649 
 1650         /*
 1651          * Pin the thread in order to avoid problems with thread migration.
 1652          * Once that all verifies are passed about spinlocks ownership,
 1653          * the thread is in a safe path and it can be unpinned.
 1654          */
 1655         sched_pin();
 1656         lock_list = PCPU_GET(spinlocks);
 1657         if (lock_list != NULL && lock_list->ll_count != 0) {
 1658                 sched_unpin();
 1659 
 1660                 /*
 1661                  * We should only have one spinlock and as long as
 1662                  * the flags cannot match for this locks class,
 1663                  * check if the first spinlock is the one curthread
 1664                  * should hold.
 1665                  */
 1666                 lock1 = &lock_list->ll_children[lock_list->ll_count - 1];
 1667                 if (lock_list->ll_count == 1 && lock_list->ll_next == NULL &&
 1668                     lock1->li_lock == lock && n == 0)
 1669                         return (0);
 1670 
 1671                 va_start(ap, fmt);
 1672                 vprintf(fmt, ap);
 1673                 va_end(ap);
 1674                 printf(" with the following");
 1675                 if (flags & WARN_SLEEPOK)
 1676                         printf(" non-sleepable");
 1677                 printf(" locks held:\n");
 1678                 n += witness_list_locks(&lock_list, printf);
 1679         } else
 1680                 sched_unpin();
 1681         if (flags & WARN_PANIC && n)
 1682                 panic("%s", __func__);
 1683         else
 1684                 witness_debugger(n);
 1685         return (n);
 1686 }
 1687 
 1688 const char *
 1689 witness_file(struct lock_object *lock)
 1690 {
 1691         struct witness *w;
 1692 
 1693         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
 1694                 return ("?");
 1695         w = lock->lo_witness;
 1696         return (w->w_file);
 1697 }
 1698 
 1699 int
 1700 witness_line(struct lock_object *lock)
 1701 {
 1702         struct witness *w;
 1703 
 1704         if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
 1705                 return (0);
 1706         w = lock->lo_witness;
 1707         return (w->w_line);
 1708 }
 1709 
 1710 static struct witness *
 1711 enroll(const char *description, struct lock_class *lock_class)
 1712 {
 1713         struct witness *w;
 1714         struct witness_list *typelist;
 1715 
 1716         MPASS(description != NULL);
 1717 
 1718         if (witness_watch == -1 || panicstr != NULL)
 1719                 return (NULL);
 1720         if ((lock_class->lc_flags & LC_SPINLOCK)) {
 1721                 if (witness_skipspin)
 1722                         return (NULL);
 1723                 else
 1724                         typelist = &w_spin;
 1725         } else if ((lock_class->lc_flags & LC_SLEEPLOCK))
 1726                 typelist = &w_sleep;
 1727         else
 1728                 panic("lock class %s is not sleep or spin",
 1729                     lock_class->lc_name);
 1730 
 1731         mtx_lock_spin(&w_mtx);
 1732         w = witness_hash_get(description);
 1733         if (w)
 1734                 goto found;
 1735         if ((w = witness_get()) == NULL)
 1736                 return (NULL);
 1737         MPASS(strlen(description) < MAX_W_NAME);
 1738         strcpy(w->w_name, description);
 1739         w->w_class = lock_class;
 1740         w->w_refcount = 1;
 1741         STAILQ_INSERT_HEAD(&w_all, w, w_list);
 1742         if (lock_class->lc_flags & LC_SPINLOCK) {
 1743                 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist);
 1744                 w_spin_cnt++;
 1745         } else if (lock_class->lc_flags & LC_SLEEPLOCK) {
 1746                 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist);
 1747                 w_sleep_cnt++;
 1748         }
 1749 
 1750         /* Insert new witness into the hash */
 1751         witness_hash_put(w);
 1752         witness_increment_graph_generation();
 1753         mtx_unlock_spin(&w_mtx);
 1754         return (w);
 1755 found:
 1756         w->w_refcount++;
 1757         mtx_unlock_spin(&w_mtx);
 1758         if (lock_class != w->w_class)
 1759                 panic(
 1760                         "lock (%s) %s does not match earlier (%s) lock",
 1761                         description, lock_class->lc_name,
 1762                         w->w_class->lc_name);
 1763         return (w);
 1764 }
 1765 
 1766 static void
 1767 depart(struct witness *w)
 1768 {
 1769         struct witness_list *list;
 1770 
 1771         MPASS(w->w_refcount == 0);
 1772         if (w->w_class->lc_flags & LC_SLEEPLOCK) {
 1773                 list = &w_sleep;
 1774                 w_sleep_cnt--;
 1775         } else {
 1776                 list = &w_spin;
 1777                 w_spin_cnt--;
 1778         }
 1779         /*
 1780          * Set file to NULL as it may point into a loadable module.
 1781          */
 1782         w->w_file = NULL;
 1783         w->w_line = 0;
 1784         witness_increment_graph_generation();
 1785 }
 1786 
 1787 
 1788 static void
 1789 adopt(struct witness *parent, struct witness *child)
 1790 {
 1791         int pi, ci, i, j;
 1792 
 1793         if (witness_cold == 0)
 1794                 mtx_assert(&w_mtx, MA_OWNED);
 1795 
 1796         /* If the relationship is already known, there's no work to be done. */
 1797         if (isitmychild(parent, child))
 1798                 return;
 1799 
 1800         /* When the structure of the graph changes, bump up the generation. */
 1801         witness_increment_graph_generation();
 1802 
 1803         /*
 1804          * The hard part ... create the direct relationship, then propagate all
 1805          * indirect relationships.
 1806          */
 1807         pi = parent->w_index;
 1808         ci = child->w_index;
 1809         WITNESS_INDEX_ASSERT(pi);
 1810         WITNESS_INDEX_ASSERT(ci);
 1811         MPASS(pi != ci);
 1812         w_rmatrix[pi][ci] |= WITNESS_PARENT;
 1813         w_rmatrix[ci][pi] |= WITNESS_CHILD;
 1814 
 1815         /*
 1816          * If parent was not already an ancestor of child,
 1817          * then we increment the descendant and ancestor counters.
 1818          */
 1819         if ((w_rmatrix[pi][ci] & WITNESS_ANCESTOR) == 0) {
 1820                 parent->w_num_descendants++;
 1821                 child->w_num_ancestors++;
 1822         }
 1823 
 1824         /* 
 1825          * Find each ancestor of 'pi'. Note that 'pi' itself is counted as 
 1826          * an ancestor of 'pi' during this loop.
 1827          */
 1828         for (i = 1; i <= w_max_used_index; i++) {
 1829                 if ((w_rmatrix[i][pi] & WITNESS_ANCESTOR_MASK) == 0 && 
 1830                     (i != pi))
 1831                         continue;
 1832 
 1833                 /* Find each descendant of 'i' and mark it as a descendant. */
 1834                 for (j = 1; j <= w_max_used_index; j++) {
 1835 
 1836                         /* 
 1837                          * Skip children that are already marked as
 1838                          * descendants of 'i'.
 1839                          */
 1840                         if (w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK)
 1841                                 continue;
 1842 
 1843                         /*
 1844                          * We are only interested in descendants of 'ci'. Note
 1845                          * that 'ci' itself is counted as a descendant of 'ci'.
 1846                          */
 1847                         if ((w_rmatrix[ci][j] & WITNESS_ANCESTOR_MASK) == 0 && 
 1848                             (j != ci))
 1849                                 continue;
 1850                         w_rmatrix[i][j] |= WITNESS_ANCESTOR;
 1851                         w_rmatrix[j][i] |= WITNESS_DESCENDANT;
 1852                         w_data[i].w_num_descendants++;
 1853                         w_data[j].w_num_ancestors++;
 1854 
 1855                         /* 
 1856                          * Make sure we aren't marking a node as both an
 1857                          * ancestor and descendant. We should have caught 
 1858                          * this as a lock order reversal earlier.
 1859                          */
 1860                         if ((w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) &&
 1861                             (w_rmatrix[i][j] & WITNESS_DESCENDANT_MASK)) {
 1862                                 printf("witness rmatrix paradox! [%d][%d]=%d "
 1863                                     "both ancestor and descendant\n",
 1864                                     i, j, w_rmatrix[i][j]); 
 1865                                 kdb_backtrace();
 1866                                 printf("Witness disabled.\n");
 1867                                 witness_watch = -1;
 1868                         }
 1869                         if ((w_rmatrix[j][i] & WITNESS_ANCESTOR_MASK) &&
 1870                             (w_rmatrix[j][i] & WITNESS_DESCENDANT_MASK)) {
 1871                                 printf("witness rmatrix paradox! [%d][%d]=%d "
 1872                                     "both ancestor and descendant\n",
 1873                                     j, i, w_rmatrix[j][i]); 
 1874                                 kdb_backtrace();
 1875                                 printf("Witness disabled.\n");
 1876                                 witness_watch = -1;
 1877                         }
 1878                 }
 1879         }
 1880 }
 1881 
 1882 static void
 1883 itismychild(struct witness *parent, struct witness *child)
 1884 {
 1885 
 1886         MPASS(child != NULL && parent != NULL);
 1887         if (witness_cold == 0)
 1888                 mtx_assert(&w_mtx, MA_OWNED);
 1889 
 1890         if (!witness_lock_type_equal(parent, child)) {
 1891                 if (witness_cold == 0)
 1892                         mtx_unlock_spin(&w_mtx);
 1893                 panic("%s: parent \"%s\" (%s) and child \"%s\" (%s) are not "
 1894                     "the same lock type", __func__, parent->w_name,
 1895                     parent->w_class->lc_name, child->w_name,
 1896                     child->w_class->lc_name);
 1897         }
 1898         adopt(parent, child);
 1899 }
 1900 
 1901 /*
 1902  * Generic code for the isitmy*() functions. The rmask parameter is the
 1903  * expected relationship of w1 to w2.
 1904  */
 1905 static int
 1906 _isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname)
 1907 {
 1908         unsigned char r1, r2;
 1909         int i1, i2;
 1910 
 1911         i1 = w1->w_index;
 1912         i2 = w2->w_index;
 1913         WITNESS_INDEX_ASSERT(i1);
 1914         WITNESS_INDEX_ASSERT(i2);
 1915         r1 = w_rmatrix[i1][i2] & WITNESS_RELATED_MASK;
 1916         r2 = w_rmatrix[i2][i1] & WITNESS_RELATED_MASK;
 1917 
 1918         /* The flags on one better be the inverse of the flags on the other */
 1919         if (!((WITNESS_ATOD(r1) == r2 && WITNESS_DTOA(r2) == r1) ||
 1920                 (WITNESS_DTOA(r1) == r2 && WITNESS_ATOD(r2) == r1))) {
 1921                 printf("%s: rmatrix mismatch between %s (index %d) and %s "
 1922                     "(index %d): w_rmatrix[%d][%d] == %hhx but "
 1923                     "w_rmatrix[%d][%d] == %hhx\n",
 1924                     fname, w1->w_name, i1, w2->w_name, i2, i1, i2, r1,
 1925                     i2, i1, r2);
 1926                 kdb_backtrace();
 1927                 printf("Witness disabled.\n");
 1928                 witness_watch = -1;
 1929         }
 1930         return (r1 & rmask);
 1931 }
 1932 
 1933 /*
 1934  * Checks if @child is a direct child of @parent.
 1935  */
 1936 static int
 1937 isitmychild(struct witness *parent, struct witness *child)
 1938 {
 1939 
 1940         return (_isitmyx(parent, child, WITNESS_PARENT, __func__));
 1941 }
 1942 
 1943 /*
 1944  * Checks if @descendant is a direct or inderect descendant of @ancestor.
 1945  */
 1946 static int
 1947 isitmydescendant(struct witness *ancestor, struct witness *descendant)
 1948 {
 1949 
 1950         return (_isitmyx(ancestor, descendant, WITNESS_ANCESTOR_MASK,
 1951             __func__));
 1952 }
 1953 
 1954 #ifdef BLESSING
 1955 static int
 1956 blessed(struct witness *w1, struct witness *w2)
 1957 {
 1958         int i;
 1959         struct witness_blessed *b;
 1960 
 1961         for (i = 0; i < blessed_count; i++) {
 1962                 b = &blessed_list[i];
 1963                 if (strcmp(w1->w_name, b->b_lock1) == 0) {
 1964                         if (strcmp(w2->w_name, b->b_lock2) == 0)
 1965                                 return (1);
 1966                         continue;
 1967                 }
 1968                 if (strcmp(w1->w_name, b->b_lock2) == 0)
 1969                         if (strcmp(w2->w_name, b->b_lock1) == 0)
 1970                                 return (1);
 1971         }
 1972         return (0);
 1973 }
 1974 #endif
 1975 
 1976 static struct witness *
 1977 witness_get(void)
 1978 {
 1979         struct witness *w;
 1980         int index;
 1981 
 1982         if (witness_cold == 0)
 1983                 mtx_assert(&w_mtx, MA_OWNED);
 1984 
 1985         if (witness_watch == -1) {
 1986                 mtx_unlock_spin(&w_mtx);
 1987                 return (NULL);
 1988         }
 1989         if (STAILQ_EMPTY(&w_free)) {
 1990                 witness_watch = -1;
 1991                 mtx_unlock_spin(&w_mtx);
 1992                 printf("WITNESS: unable to allocate a new witness object\n");
 1993                 return (NULL);
 1994         }
 1995         w = STAILQ_FIRST(&w_free);
 1996         STAILQ_REMOVE_HEAD(&w_free, w_list);
 1997         w_free_cnt--;
 1998         index = w->w_index;
 1999         MPASS(index > 0 && index == w_max_used_index+1 &&
 2000             index < WITNESS_COUNT);
 2001         bzero(w, sizeof(*w));
 2002         w->w_index = index;
 2003         if (index > w_max_used_index)
 2004                 w_max_used_index = index;
 2005         return (w);
 2006 }
 2007 
 2008 static void
 2009 witness_free(struct witness *w)
 2010 {
 2011 
 2012         STAILQ_INSERT_HEAD(&w_free, w, w_list);
 2013         w_free_cnt++;
 2014 }
 2015 
 2016 static struct lock_list_entry *
 2017 witness_lock_list_get(void)
 2018 {
 2019         struct lock_list_entry *lle;
 2020 
 2021         if (witness_watch == -1)
 2022                 return (NULL);
 2023         mtx_lock_spin(&w_mtx);
 2024         lle = w_lock_list_free;
 2025         if (lle == NULL) {
 2026                 witness_watch = -1;
 2027                 mtx_unlock_spin(&w_mtx);
 2028                 printf("%s: witness exhausted\n", __func__);
 2029                 return (NULL);
 2030         }
 2031         w_lock_list_free = lle->ll_next;
 2032         mtx_unlock_spin(&w_mtx);
 2033         bzero(lle, sizeof(*lle));
 2034         return (lle);
 2035 }
 2036                 
 2037 static void
 2038 witness_lock_list_free(struct lock_list_entry *lle)
 2039 {
 2040 
 2041         mtx_lock_spin(&w_mtx);
 2042         lle->ll_next = w_lock_list_free;
 2043         w_lock_list_free = lle;
 2044         mtx_unlock_spin(&w_mtx);
 2045 }
 2046 
 2047 static struct lock_instance *
 2048 find_instance(struct lock_list_entry *list, struct lock_object *lock)
 2049 {
 2050         struct lock_list_entry *lle;
 2051         struct lock_instance *instance;
 2052         int i;
 2053 
 2054         for (lle = list; lle != NULL; lle = lle->ll_next)
 2055                 for (i = lle->ll_count - 1; i >= 0; i--) {
 2056                         instance = &lle->ll_children[i];
 2057                         if (instance->li_lock == lock)
 2058                                 return (instance);
 2059                 }
 2060         return (NULL);
 2061 }
 2062 
 2063 static void
 2064 witness_list_lock(struct lock_instance *instance,
 2065     int (*prnt)(const char *fmt, ...))
 2066 {
 2067         struct lock_object *lock;
 2068 
 2069         lock = instance->li_lock;
 2070         prnt("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ?
 2071             "exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name);
 2072         if (lock->lo_witness->w_name != lock->lo_name)
 2073                 prnt(" (%s)", lock->lo_witness->w_name);
 2074         prnt(" r = %d (%p) locked @ %s:%d\n",
 2075             instance->li_flags & LI_RECURSEMASK, lock, instance->li_file,
 2076             instance->li_line);
 2077 }
 2078 
 2079 #ifdef DDB
 2080 static int
 2081 witness_thread_has_locks(struct thread *td)
 2082 {
 2083 
 2084         if (td->td_sleeplocks == NULL)
 2085                 return (0);
 2086         return (td->td_sleeplocks->ll_count != 0);
 2087 }
 2088 
 2089 static int
 2090 witness_proc_has_locks(struct proc *p)
 2091 {
 2092         struct thread *td;
 2093 
 2094         FOREACH_THREAD_IN_PROC(p, td) {
 2095                 if (witness_thread_has_locks(td))
 2096                         return (1);
 2097         }
 2098         return (0);
 2099 }
 2100 #endif
 2101 
 2102 int
 2103 witness_list_locks(struct lock_list_entry **lock_list,
 2104     int (*prnt)(const char *fmt, ...))
 2105 {
 2106         struct lock_list_entry *lle;
 2107         int i, nheld;
 2108 
 2109         nheld = 0;
 2110         for (lle = *lock_list; lle != NULL; lle = lle->ll_next)
 2111                 for (i = lle->ll_count - 1; i >= 0; i--) {
 2112                         witness_list_lock(&lle->ll_children[i], prnt);
 2113                         nheld++;
 2114                 }
 2115         return (nheld);
 2116 }
 2117 
 2118 /*
 2119  * This is a bit risky at best.  We call this function when we have timed
 2120  * out acquiring a spin lock, and we assume that the other CPU is stuck
 2121  * with this lock held.  So, we go groveling around in the other CPU's
 2122  * per-cpu data to try to find the lock instance for this spin lock to
 2123  * see when it was last acquired.
 2124  */
 2125 void
 2126 witness_display_spinlock(struct lock_object *lock, struct thread *owner,
 2127     int (*prnt)(const char *fmt, ...))
 2128 {
 2129         struct lock_instance *instance;
 2130         struct pcpu *pc;
 2131 
 2132         if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU)
 2133                 return;
 2134         pc = pcpu_find(owner->td_oncpu);
 2135         instance = find_instance(pc->pc_spinlocks, lock);
 2136         if (instance != NULL)
 2137                 witness_list_lock(instance, prnt);
 2138 }
 2139 
 2140 void
 2141 witness_save(struct lock_object *lock, const char **filep, int *linep)
 2142 {
 2143         struct lock_list_entry *lock_list;
 2144         struct lock_instance *instance;
 2145         struct lock_class *class;
 2146 
 2147         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2148         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2149                 return;
 2150         class = LOCK_CLASS(lock);
 2151         if (class->lc_flags & LC_SLEEPLOCK)
 2152                 lock_list = curthread->td_sleeplocks;
 2153         else {
 2154                 if (witness_skipspin)
 2155                         return;
 2156                 lock_list = PCPU_GET(spinlocks);
 2157         }
 2158         instance = find_instance(lock_list, lock);
 2159         if (instance == NULL)
 2160                 panic("%s: lock (%s) %s not locked", __func__,
 2161                     class->lc_name, lock->lo_name);
 2162         *filep = instance->li_file;
 2163         *linep = instance->li_line;
 2164 }
 2165 
 2166 void
 2167 witness_restore(struct lock_object *lock, const char *file, int line)
 2168 {
 2169         struct lock_list_entry *lock_list;
 2170         struct lock_instance *instance;
 2171         struct lock_class *class;
 2172 
 2173         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2174         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2175                 return;
 2176         class = LOCK_CLASS(lock);
 2177         if (class->lc_flags & LC_SLEEPLOCK)
 2178                 lock_list = curthread->td_sleeplocks;
 2179         else {
 2180                 if (witness_skipspin)
 2181                         return;
 2182                 lock_list = PCPU_GET(spinlocks);
 2183         }
 2184         instance = find_instance(lock_list, lock);
 2185         if (instance == NULL)
 2186                 panic("%s: lock (%s) %s not locked", __func__,
 2187                     class->lc_name, lock->lo_name);
 2188         lock->lo_witness->w_file = file;
 2189         lock->lo_witness->w_line = line;
 2190         instance->li_file = file;
 2191         instance->li_line = line;
 2192 }
 2193 
 2194 void
 2195 witness_assert(struct lock_object *lock, int flags, const char *file, int line)
 2196 {
 2197 #ifdef INVARIANT_SUPPORT
 2198         struct lock_instance *instance;
 2199         struct lock_class *class;
 2200 
 2201         if (lock->lo_witness == NULL || witness_watch < 1 || panicstr != NULL)
 2202                 return;
 2203         class = LOCK_CLASS(lock);
 2204         if ((class->lc_flags & LC_SLEEPLOCK) != 0)
 2205                 instance = find_instance(curthread->td_sleeplocks, lock);
 2206         else if ((class->lc_flags & LC_SPINLOCK) != 0)
 2207                 instance = find_instance(PCPU_GET(spinlocks), lock);
 2208         else {
 2209                 panic("Lock (%s) %s is not sleep or spin!",
 2210                     class->lc_name, lock->lo_name);
 2211         }
 2212         file = fixup_filename(file);
 2213         switch (flags) {
 2214         case LA_UNLOCKED:
 2215                 if (instance != NULL)
 2216                         panic("Lock (%s) %s locked @ %s:%d.",
 2217                             class->lc_name, lock->lo_name, file, line);
 2218                 break;
 2219         case LA_LOCKED:
 2220         case LA_LOCKED | LA_RECURSED:
 2221         case LA_LOCKED | LA_NOTRECURSED:
 2222         case LA_SLOCKED:
 2223         case LA_SLOCKED | LA_RECURSED:
 2224         case LA_SLOCKED | LA_NOTRECURSED:
 2225         case LA_XLOCKED:
 2226         case LA_XLOCKED | LA_RECURSED:
 2227         case LA_XLOCKED | LA_NOTRECURSED:
 2228                 if (instance == NULL) {
 2229                         panic("Lock (%s) %s not locked @ %s:%d.",
 2230                             class->lc_name, lock->lo_name, file, line);
 2231                         break;
 2232                 }
 2233                 if ((flags & LA_XLOCKED) != 0 &&
 2234                     (instance->li_flags & LI_EXCLUSIVE) == 0)
 2235                         panic("Lock (%s) %s not exclusively locked @ %s:%d.",
 2236                             class->lc_name, lock->lo_name, file, line);
 2237                 if ((flags & LA_SLOCKED) != 0 &&
 2238                     (instance->li_flags & LI_EXCLUSIVE) != 0)
 2239                         panic("Lock (%s) %s exclusively locked @ %s:%d.",
 2240                             class->lc_name, lock->lo_name, file, line);
 2241                 if ((flags & LA_RECURSED) != 0 &&
 2242                     (instance->li_flags & LI_RECURSEMASK) == 0)
 2243                         panic("Lock (%s) %s not recursed @ %s:%d.",
 2244                             class->lc_name, lock->lo_name, file, line);
 2245                 if ((flags & LA_NOTRECURSED) != 0 &&
 2246                     (instance->li_flags & LI_RECURSEMASK) != 0)
 2247                         panic("Lock (%s) %s recursed @ %s:%d.",
 2248                             class->lc_name, lock->lo_name, file, line);
 2249                 break;
 2250         default:
 2251                 panic("Invalid lock assertion at %s:%d.", file, line);
 2252 
 2253         }
 2254 #endif  /* INVARIANT_SUPPORT */
 2255 }
 2256 
 2257 static void
 2258 witness_setflag(struct lock_object *lock, int flag, int set)
 2259 {
 2260         struct lock_list_entry *lock_list;
 2261         struct lock_instance *instance;
 2262         struct lock_class *class;
 2263 
 2264         if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
 2265                 return;
 2266         class = LOCK_CLASS(lock);
 2267         if (class->lc_flags & LC_SLEEPLOCK)
 2268                 lock_list = curthread->td_sleeplocks;
 2269         else {
 2270                 if (witness_skipspin)
 2271                         return;
 2272                 lock_list = PCPU_GET(spinlocks);
 2273         }
 2274         instance = find_instance(lock_list, lock);
 2275         if (instance == NULL)
 2276                 panic("%s: lock (%s) %s not locked", __func__,
 2277                     class->lc_name, lock->lo_name);
 2278 
 2279         if (set)
 2280                 instance->li_flags |= flag;
 2281         else
 2282                 instance->li_flags &= ~flag;
 2283 }
 2284 
 2285 void
 2286 witness_norelease(struct lock_object *lock)
 2287 {
 2288 
 2289         witness_setflag(lock, LI_NORELEASE, 1);
 2290 }
 2291 
 2292 void
 2293 witness_releaseok(struct lock_object *lock)
 2294 {
 2295 
 2296         witness_setflag(lock, LI_NORELEASE, 0);
 2297 }
 2298 
 2299 #ifdef DDB
 2300 static void
 2301 witness_ddb_list(struct thread *td)
 2302 {
 2303 
 2304         KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
 2305         KASSERT(kdb_active, ("%s: not in the debugger", __func__));
 2306 
 2307         if (witness_watch < 1)
 2308                 return;
 2309 
 2310         witness_list_locks(&td->td_sleeplocks, db_printf);
 2311 
 2312         /*
 2313          * We only handle spinlocks if td == curthread.  This is somewhat broken
 2314          * if td is currently executing on some other CPU and holds spin locks
 2315          * as we won't display those locks.  If we had a MI way of getting
 2316          * the per-cpu data for a given cpu then we could use
 2317          * td->td_oncpu to get the list of spinlocks for this thread
 2318          * and "fix" this.
 2319          *
 2320          * That still wouldn't really fix this unless we locked the scheduler
 2321          * lock or stopped the other CPU to make sure it wasn't changing the
 2322          * list out from under us.  It is probably best to just not try to
 2323          * handle threads on other CPU's for now.
 2324          */
 2325         if (td == curthread && PCPU_GET(spinlocks) != NULL)
 2326                 witness_list_locks(PCPU_PTR(spinlocks), db_printf);
 2327 }
 2328 
 2329 DB_SHOW_COMMAND(locks, db_witness_list)
 2330 {
 2331         struct thread *td;
 2332 
 2333         if (have_addr)
 2334                 td = db_lookup_thread(addr, TRUE);
 2335         else
 2336                 td = kdb_thread;
 2337         witness_ddb_list(td);
 2338 }
 2339 
 2340 DB_SHOW_ALL_COMMAND(locks, db_witness_list_all)
 2341 {
 2342         struct thread *td;
 2343         struct proc *p;
 2344 
 2345         /*
 2346          * It would be nice to list only threads and processes that actually
 2347          * held sleep locks, but that information is currently not exported
 2348          * by WITNESS.
 2349          */
 2350         FOREACH_PROC_IN_SYSTEM(p) {
 2351                 if (!witness_proc_has_locks(p))
 2352                         continue;
 2353                 FOREACH_THREAD_IN_PROC(p, td) {
 2354                         if (!witness_thread_has_locks(td))
 2355                                 continue;
 2356                         db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid,
 2357                             p->p_comm, td, td->td_tid);
 2358                         witness_ddb_list(td);
 2359                 }
 2360         }
 2361 }
 2362 DB_SHOW_ALIAS(alllocks, db_witness_list_all)
 2363 
 2364 DB_SHOW_COMMAND(witness, db_witness_display)
 2365 {
 2366 
 2367         witness_ddb_display(db_printf);
 2368 }
 2369 #endif
 2370 
 2371 static int
 2372 sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS)
 2373 {
 2374         struct witness_lock_order_data *data1, *data2, *tmp_data1, *tmp_data2;
 2375         struct witness *tmp_w1, *tmp_w2, *w1, *w2;
 2376         struct sbuf *sb;
 2377         u_int w_rmatrix1, w_rmatrix2;
 2378         int error, generation, i, j;
 2379 
 2380         tmp_data1 = NULL;
 2381         tmp_data2 = NULL;
 2382         tmp_w1 = NULL;
 2383         tmp_w2 = NULL;
 2384         if (witness_watch < 1) {
 2385                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
 2386                 return (error);
 2387         }
 2388         if (witness_cold) {
 2389                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
 2390                 return (error);
 2391         }
 2392         error = 0;
 2393         sb = sbuf_new(NULL, NULL, BADSTACK_SBUF_SIZE, SBUF_AUTOEXTEND);
 2394         if (sb == NULL)
 2395                 return (ENOMEM);
 2396 
 2397         /* Allocate and init temporary storage space. */
 2398         tmp_w1 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
 2399         tmp_w2 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
 2400         tmp_data1 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 
 2401             M_WAITOK | M_ZERO);
 2402         tmp_data2 = malloc(sizeof(struct witness_lock_order_data), M_TEMP, 
 2403             M_WAITOK | M_ZERO);
 2404         stack_zero(&tmp_data1->wlod_stack);
 2405         stack_zero(&tmp_data2->wlod_stack);
 2406 
 2407 restart:
 2408         mtx_lock_spin(&w_mtx);
 2409         generation = w_generation;
 2410         mtx_unlock_spin(&w_mtx);
 2411         sbuf_printf(sb, "Number of known direct relationships is %d\n",
 2412             w_lohash.wloh_count);
 2413         for (i = 1; i < w_max_used_index; i++) {
 2414                 mtx_lock_spin(&w_mtx);
 2415                 if (generation != w_generation) {
 2416                         mtx_unlock_spin(&w_mtx);
 2417 
 2418                         /* The graph has changed, try again. */
 2419                         req->oldidx = 0;
 2420                         sbuf_clear(sb);
 2421                         goto restart;
 2422                 }
 2423 
 2424                 w1 = &w_data[i];
 2425                 if (w1->w_reversed == 0) {
 2426                         mtx_unlock_spin(&w_mtx);
 2427                         continue;
 2428                 }
 2429 
 2430                 /* Copy w1 locally so we can release the spin lock. */
 2431                 *tmp_w1 = *w1;
 2432                 mtx_unlock_spin(&w_mtx);
 2433 
 2434                 if (tmp_w1->w_reversed == 0)
 2435                         continue;
 2436                 for (j = 1; j < w_max_used_index; j++) {
 2437                         if ((w_rmatrix[i][j] & WITNESS_REVERSAL) == 0 || i > j)
 2438                                 continue;
 2439 
 2440                         mtx_lock_spin(&w_mtx);
 2441                         if (generation != w_generation) {
 2442                                 mtx_unlock_spin(&w_mtx);
 2443 
 2444                                 /* The graph has changed, try again. */
 2445                                 req->oldidx = 0;
 2446                                 sbuf_clear(sb);
 2447                                 goto restart;
 2448                         }
 2449 
 2450                         w2 = &w_data[j];
 2451                         data1 = witness_lock_order_get(w1, w2);
 2452                         data2 = witness_lock_order_get(w2, w1);
 2453 
 2454                         /*
 2455                          * Copy information locally so we can release the
 2456                          * spin lock.
 2457                          */
 2458                         *tmp_w2 = *w2;
 2459                         w_rmatrix1 = (unsigned int)w_rmatrix[i][j];
 2460                         w_rmatrix2 = (unsigned int)w_rmatrix[j][i];
 2461 
 2462                         if (data1) {
 2463                                 stack_zero(&tmp_data1->wlod_stack);
 2464                                 stack_copy(&data1->wlod_stack,
 2465                                     &tmp_data1->wlod_stack);
 2466                         }
 2467                         if (data2 && data2 != data1) {
 2468                                 stack_zero(&tmp_data2->wlod_stack);
 2469                                 stack_copy(&data2->wlod_stack,
 2470                                     &tmp_data2->wlod_stack);
 2471                         }
 2472                         mtx_unlock_spin(&w_mtx);
 2473 
 2474                         sbuf_printf(sb,
 2475             "\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n",
 2476                             tmp_w1->w_name, tmp_w1->w_class->lc_name, 
 2477                             tmp_w2->w_name, tmp_w2->w_class->lc_name);
 2478 #if 0
 2479                         sbuf_printf(sb,
 2480                         "w_rmatrix[%s][%s] == %x, w_rmatrix[%s][%s] == %x\n",
 2481                             tmp_w1->name, tmp_w2->w_name, w_rmatrix1,
 2482                             tmp_w2->name, tmp_w1->w_name, w_rmatrix2);
 2483 #endif
 2484                         if (data1) {
 2485                                 sbuf_printf(sb,
 2486                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
 2487                                     tmp_w1->w_name, tmp_w1->w_class->lc_name, 
 2488                                     tmp_w2->w_name, tmp_w2->w_class->lc_name);
 2489                                 stack_sbuf_print(sb, &tmp_data1->wlod_stack);
 2490                                 sbuf_printf(sb, "\n");
 2491                         }
 2492                         if (data2 && data2 != data1) {
 2493                                 sbuf_printf(sb,
 2494                         "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
 2495                                     tmp_w2->w_name, tmp_w2->w_class->lc_name, 
 2496                                     tmp_w1->w_name, tmp_w1->w_class->lc_name);
 2497                                 stack_sbuf_print(sb, &tmp_data2->wlod_stack);
 2498                                 sbuf_printf(sb, "\n");
 2499                         }
 2500                 }
 2501         }
 2502         mtx_lock_spin(&w_mtx);
 2503         if (generation != w_generation) {
 2504                 mtx_unlock_spin(&w_mtx);
 2505 
 2506                 /*
 2507                  * The graph changed while we were printing stack data,
 2508                  * try again.
 2509                  */
 2510                 req->oldidx = 0;
 2511                 sbuf_clear(sb);
 2512                 goto restart;
 2513         }
 2514         mtx_unlock_spin(&w_mtx);
 2515 
 2516         /* Free temporary storage space. */
 2517         free(tmp_data1, M_TEMP);
 2518         free(tmp_data2, M_TEMP);
 2519         free(tmp_w1, M_TEMP);
 2520         free(tmp_w2, M_TEMP);
 2521 
 2522         sbuf_finish(sb);
 2523         error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
 2524         sbuf_delete(sb);
 2525 
 2526         return (error);
 2527 }
 2528 
 2529 static int
 2530 sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS)
 2531 {
 2532         struct witness *w;
 2533         struct sbuf *sb;
 2534         int error;
 2535 
 2536         if (witness_watch < 1) {
 2537                 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
 2538                 return (error);
 2539         }
 2540         if (witness_cold) {
 2541                 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
 2542                 return (error);
 2543         }
 2544         error = 0;
 2545         sb = sbuf_new(NULL, NULL, FULLGRAPH_SBUF_SIZE, SBUF_FIXEDLEN);
 2546         if (sb == NULL)
 2547                 return (ENOMEM);
 2548         sbuf_printf(sb, "\n");
 2549 
 2550         mtx_lock_spin(&w_mtx);
 2551         STAILQ_FOREACH(w, &w_all, w_list)
 2552                 w->w_displayed = 0;
 2553         STAILQ_FOREACH(w, &w_all, w_list)
 2554                 witness_add_fullgraph(sb, w);
 2555         mtx_unlock_spin(&w_mtx);
 2556 
 2557         /*
 2558          * While using SBUF_FIXEDLEN, check if the sbuf overflowed.
 2559          */
 2560         if (sbuf_overflowed(sb)) {
 2561                 sbuf_delete(sb);
 2562                 panic("%s: sbuf overflowed, bump FULLGRAPH_SBUF_SIZE value\n",
 2563                     __func__);
 2564         }
 2565 
 2566         /*
 2567          * Close the sbuf and return to userland.
 2568          */
 2569         sbuf_finish(sb);
 2570         error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
 2571         sbuf_delete(sb);
 2572 
 2573         return (error);
 2574 }
 2575 
 2576 static int
 2577 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS)
 2578 {
 2579         int error, value;
 2580 
 2581         value = witness_watch;
 2582         error = sysctl_handle_int(oidp, &value, 0, req);
 2583         if (error != 0 || req->newptr == NULL)
 2584                 return (error);
 2585         if (value > 1 || value < -1 ||
 2586             (witness_watch == -1 && value != witness_watch))
 2587                 return (EINVAL);
 2588         witness_watch = value;
 2589         return (0);
 2590 }
 2591 
 2592 static void
 2593 witness_add_fullgraph(struct sbuf *sb, struct witness *w)
 2594 {
 2595         int i;
 2596 
 2597         if (w->w_displayed != 0 || (w->w_file == NULL && w->w_line == 0))
 2598                 return;
 2599         w->w_displayed = 1;
 2600 
 2601         WITNESS_INDEX_ASSERT(w->w_index);
 2602         for (i = 1; i <= w_max_used_index; i++) {
 2603                 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) {
 2604                         sbuf_printf(sb, "\"%s\",\"%s\"\n", w->w_name,
 2605                             w_data[i].w_name);
 2606                         witness_add_fullgraph(sb, &w_data[i]);
 2607                 }
 2608         }
 2609 }
 2610 
 2611 /*
 2612  * A simple hash function. Takes a key pointer and a key size. If size == 0,
 2613  * interprets the key as a string and reads until the null
 2614  * terminator. Otherwise, reads the first size bytes. Returns an unsigned 32-bit
 2615  * hash value computed from the key.
 2616  */
 2617 static uint32_t
 2618 witness_hash_djb2(const uint8_t *key, uint32_t size)
 2619 {
 2620         unsigned int hash = 5381;
 2621         int i;
 2622 
 2623         /* hash = hash * 33 + key[i] */
 2624         if (size)
 2625                 for (i = 0; i < size; i++)
 2626                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
 2627         else
 2628                 for (i = 0; key[i] != 0; i++)
 2629                         hash = ((hash << 5) + hash) + (unsigned int)key[i];
 2630 
 2631         return (hash);
 2632 }
 2633 
 2634 
 2635 /*
 2636  * Initializes the two witness hash tables. Called exactly once from
 2637  * witness_initialize().
 2638  */
 2639 static void
 2640 witness_init_hash_tables(void)
 2641 {
 2642         int i;
 2643 
 2644         MPASS(witness_cold);
 2645 
 2646         /* Initialize the hash tables. */
 2647         for (i = 0; i < WITNESS_HASH_SIZE; i++)
 2648                 w_hash.wh_array[i] = NULL;
 2649 
 2650         w_hash.wh_size = WITNESS_HASH_SIZE;
 2651         w_hash.wh_count = 0;
 2652 
 2653         /* Initialize the lock order data hash. */
 2654         w_lofree = NULL;
 2655         for (i = 0; i < WITNESS_LO_DATA_COUNT; i++) {
 2656                 memset(&w_lodata[i], 0, sizeof(w_lodata[i]));
 2657                 w_lodata[i].wlod_next = w_lofree;
 2658                 w_lofree = &w_lodata[i];
 2659         }
 2660         w_lohash.wloh_size = WITNESS_LO_HASH_SIZE;
 2661         w_lohash.wloh_count = 0;
 2662         for (i = 0; i < WITNESS_LO_HASH_SIZE; i++)
 2663                 w_lohash.wloh_array[i] = NULL;
 2664 }
 2665 
 2666 static struct witness *
 2667 witness_hash_get(const char *key)
 2668 {
 2669         struct witness *w;
 2670         uint32_t hash;
 2671         
 2672         MPASS(key != NULL);
 2673         if (witness_cold == 0)
 2674                 mtx_assert(&w_mtx, MA_OWNED);
 2675         hash = witness_hash_djb2(key, 0) % w_hash.wh_size;
 2676         w = w_hash.wh_array[hash];
 2677         while (w != NULL) {
 2678                 if (strcmp(w->w_name, key) == 0)
 2679                         goto out;
 2680                 w = w->w_hash_next;
 2681         }
 2682 
 2683 out:
 2684         return (w);
 2685 }
 2686 
 2687 static void
 2688 witness_hash_put(struct witness *w)
 2689 {
 2690         uint32_t hash;
 2691 
 2692         MPASS(w != NULL);
 2693         MPASS(w->w_name != NULL);
 2694         if (witness_cold == 0)
 2695                 mtx_assert(&w_mtx, MA_OWNED);
 2696         KASSERT(witness_hash_get(w->w_name) == NULL,
 2697             ("%s: trying to add a hash entry that already exists!", __func__));
 2698         KASSERT(w->w_hash_next == NULL,
 2699             ("%s: w->w_hash_next != NULL", __func__));
 2700 
 2701         hash = witness_hash_djb2(w->w_name, 0) % w_hash.wh_size;
 2702         w->w_hash_next = w_hash.wh_array[hash];
 2703         w_hash.wh_array[hash] = w;
 2704         w_hash.wh_count++;
 2705 }
 2706 
 2707 
 2708 static struct witness_lock_order_data *
 2709 witness_lock_order_get(struct witness *parent, struct witness *child)
 2710 {
 2711         struct witness_lock_order_data *data = NULL;
 2712         struct witness_lock_order_key key;
 2713         unsigned int hash;
 2714 
 2715         MPASS(parent != NULL && child != NULL);
 2716         key.from = parent->w_index;
 2717         key.to = child->w_index;
 2718         WITNESS_INDEX_ASSERT(key.from);
 2719         WITNESS_INDEX_ASSERT(key.to);
 2720         if ((w_rmatrix[parent->w_index][child->w_index]
 2721             & WITNESS_LOCK_ORDER_KNOWN) == 0)
 2722                 goto out;
 2723 
 2724         hash = witness_hash_djb2((const char*)&key,
 2725             sizeof(key)) % w_lohash.wloh_size;
 2726         data = w_lohash.wloh_array[hash];
 2727         while (data != NULL) {
 2728                 if (witness_lock_order_key_equal(&data->wlod_key, &key))
 2729                         break;
 2730                 data = data->wlod_next;
 2731         }
 2732 
 2733 out:
 2734         return (data);
 2735 }
 2736 
 2737 /*
 2738  * Verify that parent and child have a known relationship, are not the same,
 2739  * and child is actually a child of parent.  This is done without w_mtx
 2740  * to avoid contention in the common case.
 2741  */
 2742 static int
 2743 witness_lock_order_check(struct witness *parent, struct witness *child)
 2744 {
 2745 
 2746         if (parent != child &&
 2747             w_rmatrix[parent->w_index][child->w_index]
 2748             & WITNESS_LOCK_ORDER_KNOWN &&
 2749             isitmychild(parent, child))
 2750                 return (1);
 2751 
 2752         return (0);
 2753 }
 2754 
 2755 static int
 2756 witness_lock_order_add(struct witness *parent, struct witness *child)
 2757 {
 2758         struct witness_lock_order_data *data = NULL;
 2759         struct witness_lock_order_key key;
 2760         unsigned int hash;
 2761         
 2762         MPASS(parent != NULL && child != NULL);
 2763         key.from = parent->w_index;
 2764         key.to = child->w_index;
 2765         WITNESS_INDEX_ASSERT(key.from);
 2766         WITNESS_INDEX_ASSERT(key.to);
 2767         if (w_rmatrix[parent->w_index][child->w_index]
 2768             & WITNESS_LOCK_ORDER_KNOWN)
 2769                 return (1);
 2770 
 2771         hash = witness_hash_djb2((const char*)&key,
 2772             sizeof(key)) % w_lohash.wloh_size;
 2773         w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN;
 2774         data = w_lofree;
 2775         if (data == NULL)
 2776                 return (0);
 2777         w_lofree = data->wlod_next;
 2778         data->wlod_next = w_lohash.wloh_array[hash];
 2779         data->wlod_key = key;
 2780         w_lohash.wloh_array[hash] = data;
 2781         w_lohash.wloh_count++;
 2782         stack_zero(&data->wlod_stack);
 2783         stack_save(&data->wlod_stack);
 2784         return (1);
 2785 }
 2786 
 2787 /* Call this whenver the structure of the witness graph changes. */
 2788 static void
 2789 witness_increment_graph_generation(void)
 2790 {
 2791 
 2792         if (witness_cold == 0)
 2793                 mtx_assert(&w_mtx, MA_OWNED);
 2794         w_generation++;
 2795 }
 2796 
 2797 #ifdef KDB
 2798 static void
 2799 _witness_debugger(int cond, const char *msg)
 2800 {
 2801 
 2802         if (witness_trace && cond)
 2803                 kdb_backtrace();
 2804         if (witness_kdb && cond)
 2805                 kdb_enter(KDB_WHY_WITNESS, msg);
 2806 }
 2807 #endif

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