1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 2008 Isilon Systems, Inc.
5 * Copyright (c) 2008 Ilya Maykov <ivmaykov@gmail.com>
6 * Copyright (c) 1998 Berkeley Software Design, Inc.
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. Berkeley Software Design Inc's name may not be used to endorse or
18 * promote products derived from this software without specific prior
19 * written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
34 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
35 */
36
37 /*
38 * Implementation of the `witness' lock verifier. Originally implemented for
39 * mutexes in BSD/OS. Extended to handle generic lock objects and lock
40 * classes in FreeBSD.
41 */
42
43 /*
44 * Main Entry: witness
45 * Pronunciation: 'wit-n&s
46 * Function: noun
47 * Etymology: Middle English witnesse, from Old English witnes knowledge,
48 * testimony, witness, from 2wit
49 * Date: before 12th century
50 * 1 : attestation of a fact or event : TESTIMONY
51 * 2 : one that gives evidence; specifically : one who testifies in
52 * a cause or before a judicial tribunal
53 * 3 : one asked to be present at a transaction so as to be able to
54 * testify to its having taken place
55 * 4 : one who has personal knowledge of something
56 * 5 a : something serving as evidence or proof : SIGN
57 * b : public affirmation by word or example of usually
58 * religious faith or conviction <the heroic witness to divine
59 * life -- Pilot>
60 * 6 capitalized : a member of the Jehovah's Witnesses
61 */
62
63 /*
64 * Special rules concerning Giant and lock orders:
65 *
66 * 1) Giant must be acquired before any other mutexes. Stated another way,
67 * no other mutex may be held when Giant is acquired.
68 *
69 * 2) Giant must be released when blocking on a sleepable lock.
70 *
71 * This rule is less obvious, but is a result of Giant providing the same
72 * semantics as spl(). Basically, when a thread sleeps, it must release
73 * Giant. When a thread blocks on a sleepable lock, it sleeps. Hence rule
74 * 2).
75 *
76 * 3) Giant may be acquired before or after sleepable locks.
77 *
78 * This rule is also not quite as obvious. Giant may be acquired after
79 * a sleepable lock because it is a non-sleepable lock and non-sleepable
80 * locks may always be acquired while holding a sleepable lock. The second
81 * case, Giant before a sleepable lock, follows from rule 2) above. Suppose
82 * you have two threads T1 and T2 and a sleepable lock X. Suppose that T1
83 * acquires X and blocks on Giant. Then suppose that T2 acquires Giant and
84 * blocks on X. When T2 blocks on X, T2 will release Giant allowing T1 to
85 * execute. Thus, acquiring Giant both before and after a sleepable lock
86 * will not result in a lock order reversal.
87 */
88
89 #include <sys/cdefs.h>
90 __FBSDID("$FreeBSD$");
91
92 #include "opt_ddb.h"
93 #include "opt_hwpmc_hooks.h"
94 #include "opt_stack.h"
95 #include "opt_witness.h"
96
97 #include <sys/param.h>
98 #include <sys/bus.h>
99 #include <sys/kdb.h>
100 #include <sys/kernel.h>
101 #include <sys/ktr.h>
102 #include <sys/lock.h>
103 #include <sys/malloc.h>
104 #include <sys/mutex.h>
105 #include <sys/priv.h>
106 #include <sys/proc.h>
107 #include <sys/sbuf.h>
108 #include <sys/sched.h>
109 #include <sys/stack.h>
110 #include <sys/sysctl.h>
111 #include <sys/syslog.h>
112 #include <sys/systm.h>
113
114 #ifdef DDB
115 #include <ddb/ddb.h>
116 #endif
117
118 #include <machine/stdarg.h>
119
120 #if !defined(DDB) && !defined(STACK)
121 #error "DDB or STACK options are required for WITNESS"
122 #endif
123
124 /* Note that these traces do not work with KTR_ALQ. */
125 #if 0
126 #define KTR_WITNESS KTR_SUBSYS
127 #else
128 #define KTR_WITNESS 0
129 #endif
130
131 #define LI_RECURSEMASK 0x0000ffff /* Recursion depth of lock instance. */
132 #define LI_EXCLUSIVE 0x00010000 /* Exclusive lock instance. */
133 #define LI_NORELEASE 0x00020000 /* Lock not allowed to be released. */
134 #define LI_SLEEPABLE 0x00040000 /* Lock may be held while sleeping. */
135
136 #ifndef WITNESS_COUNT
137 #define WITNESS_COUNT 1536
138 #endif
139 #define WITNESS_HASH_SIZE 251 /* Prime, gives load factor < 2 */
140 #define WITNESS_PENDLIST (512 + (MAXCPU * 4))
141
142 /* Allocate 256 KB of stack data space */
143 #define WITNESS_LO_DATA_COUNT 2048
144
145 /* Prime, gives load factor of ~2 at full load */
146 #define WITNESS_LO_HASH_SIZE 1021
147
148 /*
149 * XXX: This is somewhat bogus, as we assume here that at most 2048 threads
150 * will hold LOCK_NCHILDREN locks. We handle failure ok, and we should
151 * probably be safe for the most part, but it's still a SWAG.
152 */
153 #define LOCK_NCHILDREN 5
154 #define LOCK_CHILDCOUNT 2048
155
156 #define MAX_W_NAME 64
157
158 #define FULLGRAPH_SBUF_SIZE 512
159
160 /*
161 * These flags go in the witness relationship matrix and describe the
162 * relationship between any two struct witness objects.
163 */
164 #define WITNESS_UNRELATED 0x00 /* No lock order relation. */
165 #define WITNESS_PARENT 0x01 /* Parent, aka direct ancestor. */
166 #define WITNESS_ANCESTOR 0x02 /* Direct or indirect ancestor. */
167 #define WITNESS_CHILD 0x04 /* Child, aka direct descendant. */
168 #define WITNESS_DESCENDANT 0x08 /* Direct or indirect descendant. */
169 #define WITNESS_ANCESTOR_MASK (WITNESS_PARENT | WITNESS_ANCESTOR)
170 #define WITNESS_DESCENDANT_MASK (WITNESS_CHILD | WITNESS_DESCENDANT)
171 #define WITNESS_RELATED_MASK \
172 (WITNESS_ANCESTOR_MASK | WITNESS_DESCENDANT_MASK)
173 #define WITNESS_REVERSAL 0x10 /* A lock order reversal has been
174 * observed. */
175 #define WITNESS_RESERVED1 0x20 /* Unused flag, reserved. */
176 #define WITNESS_RESERVED2 0x40 /* Unused flag, reserved. */
177 #define WITNESS_LOCK_ORDER_KNOWN 0x80 /* This lock order is known. */
178
179 /* Descendant to ancestor flags */
180 #define WITNESS_DTOA(x) (((x) & WITNESS_RELATED_MASK) >> 2)
181
182 /* Ancestor to descendant flags */
183 #define WITNESS_ATOD(x) (((x) & WITNESS_RELATED_MASK) << 2)
184
185 #define WITNESS_INDEX_ASSERT(i) \
186 MPASS((i) > 0 && (i) <= w_max_used_index && (i) < witness_count)
187
188 static MALLOC_DEFINE(M_WITNESS, "Witness", "Witness");
189
190 /*
191 * Lock instances. A lock instance is the data associated with a lock while
192 * it is held by witness. For example, a lock instance will hold the
193 * recursion count of a lock. Lock instances are held in lists. Spin locks
194 * are held in a per-cpu list while sleep locks are held in per-thread list.
195 */
196 struct lock_instance {
197 struct lock_object *li_lock;
198 const char *li_file;
199 int li_line;
200 u_int li_flags;
201 };
202
203 /*
204 * A simple list type used to build the list of locks held by a thread
205 * or CPU. We can't simply embed the list in struct lock_object since a
206 * lock may be held by more than one thread if it is a shared lock. Locks
207 * are added to the head of the list, so we fill up each list entry from
208 * "the back" logically. To ease some of the arithmetic, we actually fill
209 * in each list entry the normal way (children[0] then children[1], etc.) but
210 * when we traverse the list we read children[count-1] as the first entry
211 * down to children[0] as the final entry.
212 */
213 struct lock_list_entry {
214 struct lock_list_entry *ll_next;
215 struct lock_instance ll_children[LOCK_NCHILDREN];
216 u_int ll_count;
217 };
218
219 /*
220 * The main witness structure. One of these per named lock type in the system
221 * (for example, "vnode interlock").
222 */
223 struct witness {
224 char w_name[MAX_W_NAME];
225 uint32_t w_index; /* Index in the relationship matrix */
226 struct lock_class *w_class;
227 STAILQ_ENTRY(witness) w_list; /* List of all witnesses. */
228 STAILQ_ENTRY(witness) w_typelist; /* Witnesses of a type. */
229 struct witness *w_hash_next; /* Linked list in hash buckets. */
230 const char *w_file; /* File where last acquired */
231 uint32_t w_line; /* Line where last acquired */
232 uint32_t w_refcount;
233 uint16_t w_num_ancestors; /* direct/indirect
234 * ancestor count */
235 uint16_t w_num_descendants; /* direct/indirect
236 * descendant count */
237 int16_t w_ddb_level;
238 unsigned w_displayed:1;
239 unsigned w_reversed:1;
240 };
241
242 STAILQ_HEAD(witness_list, witness);
243
244 /*
245 * The witness hash table. Keys are witness names (const char *), elements are
246 * witness objects (struct witness *).
247 */
248 struct witness_hash {
249 struct witness *wh_array[WITNESS_HASH_SIZE];
250 uint32_t wh_size;
251 uint32_t wh_count;
252 };
253
254 /*
255 * Key type for the lock order data hash table.
256 */
257 struct witness_lock_order_key {
258 uint16_t from;
259 uint16_t to;
260 };
261
262 struct witness_lock_order_data {
263 struct stack wlod_stack;
264 struct witness_lock_order_key wlod_key;
265 struct witness_lock_order_data *wlod_next;
266 };
267
268 /*
269 * The witness lock order data hash table. Keys are witness index tuples
270 * (struct witness_lock_order_key), elements are lock order data objects
271 * (struct witness_lock_order_data).
272 */
273 struct witness_lock_order_hash {
274 struct witness_lock_order_data *wloh_array[WITNESS_LO_HASH_SIZE];
275 u_int wloh_size;
276 u_int wloh_count;
277 };
278
279 struct witness_blessed {
280 const char *b_lock1;
281 const char *b_lock2;
282 };
283
284 struct witness_pendhelp {
285 const char *wh_type;
286 struct lock_object *wh_lock;
287 };
288
289 struct witness_order_list_entry {
290 const char *w_name;
291 struct lock_class *w_class;
292 };
293
294 /*
295 * Returns 0 if one of the locks is a spin lock and the other is not.
296 * Returns 1 otherwise.
297 */
298 static __inline int
299 witness_lock_type_equal(struct witness *w1, struct witness *w2)
300 {
301
302 return ((w1->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) ==
303 (w2->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)));
304 }
305
306 static __inline int
307 witness_lock_order_key_equal(const struct witness_lock_order_key *a,
308 const struct witness_lock_order_key *b)
309 {
310
311 return (a->from == b->from && a->to == b->to);
312 }
313
314 static int _isitmyx(struct witness *w1, struct witness *w2, int rmask,
315 const char *fname);
316 static void adopt(struct witness *parent, struct witness *child);
317 static int blessed(struct witness *, struct witness *);
318 static void depart(struct witness *w);
319 static struct witness *enroll(const char *description,
320 struct lock_class *lock_class);
321 static struct lock_instance *find_instance(struct lock_list_entry *list,
322 const struct lock_object *lock);
323 static int isitmychild(struct witness *parent, struct witness *child);
324 static int isitmydescendant(struct witness *parent, struct witness *child);
325 static void itismychild(struct witness *parent, struct witness *child);
326 static int sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS);
327 static int sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS);
328 static int sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS);
329 static int sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS);
330 static void witness_add_fullgraph(struct sbuf *sb, struct witness *parent);
331 #ifdef DDB
332 static void witness_ddb_compute_levels(void);
333 static void witness_ddb_display(int(*)(const char *fmt, ...));
334 static void witness_ddb_display_descendants(int(*)(const char *fmt, ...),
335 struct witness *, int indent);
336 static void witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
337 struct witness_list *list);
338 static void witness_ddb_level_descendants(struct witness *parent, int l);
339 static void witness_ddb_list(struct thread *td);
340 #endif
341 static void witness_enter_debugger(const char *msg);
342 static void witness_debugger(int cond, const char *msg);
343 static void witness_free(struct witness *m);
344 static struct witness *witness_get(void);
345 static uint32_t witness_hash_djb2(const uint8_t *key, uint32_t size);
346 static struct witness *witness_hash_get(const char *key);
347 static void witness_hash_put(struct witness *w);
348 static void witness_init_hash_tables(void);
349 static void witness_increment_graph_generation(void);
350 static void witness_lock_list_free(struct lock_list_entry *lle);
351 static struct lock_list_entry *witness_lock_list_get(void);
352 static int witness_lock_order_add(struct witness *parent,
353 struct witness *child);
354 static int witness_lock_order_check(struct witness *parent,
355 struct witness *child);
356 static struct witness_lock_order_data *witness_lock_order_get(
357 struct witness *parent,
358 struct witness *child);
359 static void witness_list_lock(struct lock_instance *instance,
360 int (*prnt)(const char *fmt, ...));
361 static int witness_output(const char *fmt, ...) __printflike(1, 2);
362 static int witness_output_drain(void *arg __unused, const char *data,
363 int len);
364 static int witness_voutput(const char *fmt, va_list ap) __printflike(1, 0);
365 static void witness_setflag(struct lock_object *lock, int flag, int set);
366
367 FEATURE(witness, "kernel has witness(9) support");
368
369 static SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
370 "Witness Locking");
371
372 /*
373 * If set to 0, lock order checking is disabled. If set to -1,
374 * witness is completely disabled. Otherwise witness performs full
375 * lock order checking for all locks. At runtime, lock order checking
376 * may be toggled. However, witness cannot be reenabled once it is
377 * completely disabled.
378 */
379 static int witness_watch = 1;
380 SYSCTL_PROC(_debug_witness, OID_AUTO, watch,
381 CTLFLAG_RWTUN | CTLTYPE_INT | CTLFLAG_MPSAFE, NULL, 0,
382 sysctl_debug_witness_watch, "I",
383 "witness is watching lock operations");
384
385 #ifdef KDB
386 /*
387 * When KDB is enabled and witness_kdb is 1, it will cause the system
388 * to drop into kdebug() when:
389 * - a lock hierarchy violation occurs
390 * - locks are held when going to sleep.
391 */
392 #ifdef WITNESS_KDB
393 int witness_kdb = 1;
394 #else
395 int witness_kdb = 0;
396 #endif
397 SYSCTL_INT(_debug_witness, OID_AUTO, kdb, CTLFLAG_RWTUN, &witness_kdb, 0, "");
398 #endif /* KDB */
399
400 #if defined(DDB) || defined(KDB)
401 /*
402 * When DDB or KDB is enabled and witness_trace is 1, it will cause the system
403 * to print a stack trace:
404 * - a lock hierarchy violation occurs
405 * - locks are held when going to sleep.
406 */
407 int witness_trace = 1;
408 SYSCTL_INT(_debug_witness, OID_AUTO, trace, CTLFLAG_RWTUN, &witness_trace, 0, "");
409 #endif /* DDB || KDB */
410
411 #ifdef WITNESS_SKIPSPIN
412 int witness_skipspin = 1;
413 #else
414 int witness_skipspin = 0;
415 #endif
416 SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN, &witness_skipspin, 0, "");
417
418 int badstack_sbuf_size;
419
420 int witness_count = WITNESS_COUNT;
421 SYSCTL_INT(_debug_witness, OID_AUTO, witness_count, CTLFLAG_RDTUN,
422 &witness_count, 0, "");
423
424 /*
425 * Output channel for witness messages. By default we print to the console.
426 */
427 enum witness_channel {
428 WITNESS_CONSOLE,
429 WITNESS_LOG,
430 WITNESS_NONE,
431 };
432
433 static enum witness_channel witness_channel = WITNESS_CONSOLE;
434 SYSCTL_PROC(_debug_witness, OID_AUTO, output_channel,
435 CTLTYPE_STRING | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, NULL, 0,
436 sysctl_debug_witness_channel, "A",
437 "Output channel for warnings");
438
439 /*
440 * Call this to print out the relations between locks.
441 */
442 SYSCTL_PROC(_debug_witness, OID_AUTO, fullgraph,
443 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
444 sysctl_debug_witness_fullgraph, "A",
445 "Show locks relation graphs");
446
447 /*
448 * Call this to print out the witness faulty stacks.
449 */
450 SYSCTL_PROC(_debug_witness, OID_AUTO, badstacks,
451 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
452 sysctl_debug_witness_badstacks, "A",
453 "Show bad witness stacks");
454
455 static struct mtx w_mtx;
456
457 /* w_list */
458 static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free);
459 static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all);
460
461 /* w_typelist */
462 static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin);
463 static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep);
464
465 /* lock list */
466 static struct lock_list_entry *w_lock_list_free = NULL;
467 static struct witness_pendhelp pending_locks[WITNESS_PENDLIST];
468 static u_int pending_cnt;
469
470 static int w_free_cnt, w_spin_cnt, w_sleep_cnt;
471 SYSCTL_INT(_debug_witness, OID_AUTO, free_cnt, CTLFLAG_RD, &w_free_cnt, 0, "");
472 SYSCTL_INT(_debug_witness, OID_AUTO, spin_cnt, CTLFLAG_RD, &w_spin_cnt, 0, "");
473 SYSCTL_INT(_debug_witness, OID_AUTO, sleep_cnt, CTLFLAG_RD, &w_sleep_cnt, 0,
474 "");
475
476 static struct witness *w_data;
477 static uint8_t **w_rmatrix;
478 static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT];
479 static struct witness_hash w_hash; /* The witness hash table. */
480
481 /* The lock order data hash */
482 static struct witness_lock_order_data w_lodata[WITNESS_LO_DATA_COUNT];
483 static struct witness_lock_order_data *w_lofree = NULL;
484 static struct witness_lock_order_hash w_lohash;
485 static int w_max_used_index = 0;
486 static unsigned int w_generation = 0;
487 static const char w_notrunning[] = "Witness not running\n";
488 static const char w_stillcold[] = "Witness is still cold\n";
489 #ifdef __i386__
490 static const char w_notallowed[] = "The sysctl is disabled on the arch\n";
491 #endif
492
493 static struct witness_order_list_entry order_lists[] = {
494 /*
495 * sx locks
496 */
497 { "proctree", &lock_class_sx },
498 { "allproc", &lock_class_sx },
499 { "allprison", &lock_class_sx },
500 { NULL, NULL },
501 /*
502 * Various mutexes
503 */
504 { "Giant", &lock_class_mtx_sleep },
505 { "pipe mutex", &lock_class_mtx_sleep },
506 { "sigio lock", &lock_class_mtx_sleep },
507 { "process group", &lock_class_mtx_sleep },
508 #ifdef HWPMC_HOOKS
509 { "pmc-sleep", &lock_class_mtx_sleep },
510 #endif
511 { "process lock", &lock_class_mtx_sleep },
512 { "session", &lock_class_mtx_sleep },
513 { "uidinfo hash", &lock_class_rw },
514 { "time lock", &lock_class_mtx_sleep },
515 { NULL, NULL },
516 /*
517 * umtx
518 */
519 { "umtx lock", &lock_class_mtx_sleep },
520 { NULL, NULL },
521 /*
522 * Sockets
523 */
524 { "accept", &lock_class_mtx_sleep },
525 { "so_snd", &lock_class_mtx_sleep },
526 { "so_rcv", &lock_class_mtx_sleep },
527 { "sellck", &lock_class_mtx_sleep },
528 { NULL, NULL },
529 /*
530 * Routing
531 */
532 { "so_rcv", &lock_class_mtx_sleep },
533 { "radix node head", &lock_class_rm },
534 { "ifaddr", &lock_class_mtx_sleep },
535 { NULL, NULL },
536 /*
537 * IPv4 multicast:
538 * protocol locks before interface locks, after UDP locks.
539 */
540 { "in_multi_sx", &lock_class_sx },
541 { "udpinp", &lock_class_rw },
542 { "in_multi_list_mtx", &lock_class_mtx_sleep },
543 { "igmp_mtx", &lock_class_mtx_sleep },
544 { "ifnet_rw", &lock_class_rw },
545 { "if_addr_lock", &lock_class_mtx_sleep },
546 { NULL, NULL },
547 /*
548 * IPv6 multicast:
549 * protocol locks before interface locks, after UDP locks.
550 */
551 { "in6_multi_sx", &lock_class_sx },
552 { "udpinp", &lock_class_rw },
553 { "in6_multi_list_mtx", &lock_class_mtx_sleep },
554 { "mld_mtx", &lock_class_mtx_sleep },
555 { "ifnet_rw", &lock_class_rw },
556 { "if_addr_lock", &lock_class_mtx_sleep },
557 { NULL, NULL },
558 /*
559 * UNIX Domain Sockets
560 */
561 { "unp_link_rwlock", &lock_class_rw },
562 { "unp_list_lock", &lock_class_mtx_sleep },
563 { "unp", &lock_class_mtx_sleep },
564 { "so_snd", &lock_class_mtx_sleep },
565 { NULL, NULL },
566 /*
567 * UDP/IP
568 */
569 { "udp", &lock_class_mtx_sleep },
570 { "udpinp", &lock_class_rw },
571 { "so_snd", &lock_class_mtx_sleep },
572 { NULL, NULL },
573 /*
574 * TCP/IP
575 */
576 { "tcp", &lock_class_mtx_sleep },
577 { "tcpinp", &lock_class_rw },
578 { "so_snd", &lock_class_mtx_sleep },
579 { NULL, NULL },
580 /*
581 * BPF
582 */
583 { "bpf global lock", &lock_class_sx },
584 { "bpf cdev lock", &lock_class_mtx_sleep },
585 { NULL, NULL },
586 /*
587 * NFS server
588 */
589 { "nfsd_mtx", &lock_class_mtx_sleep },
590 { "so_snd", &lock_class_mtx_sleep },
591 { NULL, NULL },
592
593 /*
594 * IEEE 802.11
595 */
596 { "802.11 com lock", &lock_class_mtx_sleep},
597 { NULL, NULL },
598 /*
599 * Network drivers
600 */
601 { "network driver", &lock_class_mtx_sleep},
602 { NULL, NULL },
603
604 /*
605 * Netgraph
606 */
607 { "ng_node", &lock_class_mtx_sleep },
608 { "ng_worklist", &lock_class_mtx_sleep },
609 { NULL, NULL },
610 /*
611 * CDEV
612 */
613 { "vm map (system)", &lock_class_mtx_sleep },
614 { "vnode interlock", &lock_class_mtx_sleep },
615 { "cdev", &lock_class_mtx_sleep },
616 { "devthrd", &lock_class_mtx_sleep },
617 { NULL, NULL },
618 /*
619 * VM
620 */
621 { "vm map (user)", &lock_class_sx },
622 { "vm object", &lock_class_rw },
623 { "vm page", &lock_class_mtx_sleep },
624 { "pmap pv global", &lock_class_rw },
625 { "pmap", &lock_class_mtx_sleep },
626 { "pmap pv list", &lock_class_rw },
627 { "vm page free queue", &lock_class_mtx_sleep },
628 { "vm pagequeue", &lock_class_mtx_sleep },
629 { NULL, NULL },
630 /*
631 * kqueue/VFS interaction
632 */
633 { "kqueue", &lock_class_mtx_sleep },
634 { "struct mount mtx", &lock_class_mtx_sleep },
635 { "vnode interlock", &lock_class_mtx_sleep },
636 { NULL, NULL },
637 /*
638 * VFS namecache
639 */
640 { "ncvn", &lock_class_mtx_sleep },
641 { "ncbuc", &lock_class_mtx_sleep },
642 { "vnode interlock", &lock_class_mtx_sleep },
643 { "ncneg", &lock_class_mtx_sleep },
644 { NULL, NULL },
645 /*
646 * ZFS locking
647 */
648 { "dn->dn_mtx", &lock_class_sx },
649 { "dr->dt.di.dr_mtx", &lock_class_sx },
650 { "db->db_mtx", &lock_class_sx },
651 { NULL, NULL },
652 /*
653 * TCP log locks
654 */
655 { "TCP ID tree", &lock_class_rw },
656 { "tcp log id bucket", &lock_class_mtx_sleep },
657 { "tcpinp", &lock_class_rw },
658 { "TCP log expireq", &lock_class_mtx_sleep },
659 { NULL, NULL },
660 /*
661 * spin locks
662 */
663 #ifdef SMP
664 { "ap boot", &lock_class_mtx_spin },
665 #endif
666 { "rm.mutex_mtx", &lock_class_mtx_spin },
667 { "sio", &lock_class_mtx_spin },
668 #ifdef __i386__
669 { "cy", &lock_class_mtx_spin },
670 #endif
671 { "scc_hwmtx", &lock_class_mtx_spin },
672 { "uart_hwmtx", &lock_class_mtx_spin },
673 { "fast_taskqueue", &lock_class_mtx_spin },
674 { "intr table", &lock_class_mtx_spin },
675 { "process slock", &lock_class_mtx_spin },
676 { "syscons video lock", &lock_class_mtx_spin },
677 { "sleepq chain", &lock_class_mtx_spin },
678 { "rm_spinlock", &lock_class_mtx_spin },
679 { "turnstile chain", &lock_class_mtx_spin },
680 { "turnstile lock", &lock_class_mtx_spin },
681 { "sched lock", &lock_class_mtx_spin },
682 { "td_contested", &lock_class_mtx_spin },
683 { "callout", &lock_class_mtx_spin },
684 { "entropy harvest mutex", &lock_class_mtx_spin },
685 #ifdef SMP
686 { "smp rendezvous", &lock_class_mtx_spin },
687 #endif
688 #ifdef __powerpc__
689 { "tlb0", &lock_class_mtx_spin },
690 #endif
691 { NULL, NULL },
692 { "sched lock", &lock_class_mtx_spin },
693 #ifdef HWPMC_HOOKS
694 { "pmc-per-proc", &lock_class_mtx_spin },
695 #endif
696 { NULL, NULL },
697 /*
698 * leaf locks
699 */
700 { "intrcnt", &lock_class_mtx_spin },
701 { "icu", &lock_class_mtx_spin },
702 #ifdef __i386__
703 { "allpmaps", &lock_class_mtx_spin },
704 { "descriptor tables", &lock_class_mtx_spin },
705 #endif
706 { "clk", &lock_class_mtx_spin },
707 { "cpuset", &lock_class_mtx_spin },
708 { "mprof lock", &lock_class_mtx_spin },
709 { "zombie lock", &lock_class_mtx_spin },
710 { "ALD Queue", &lock_class_mtx_spin },
711 #if defined(__i386__) || defined(__amd64__)
712 { "pcicfg", &lock_class_mtx_spin },
713 { "NDIS thread lock", &lock_class_mtx_spin },
714 #endif
715 { "tw_osl_io_lock", &lock_class_mtx_spin },
716 { "tw_osl_q_lock", &lock_class_mtx_spin },
717 { "tw_cl_io_lock", &lock_class_mtx_spin },
718 { "tw_cl_intr_lock", &lock_class_mtx_spin },
719 { "tw_cl_gen_lock", &lock_class_mtx_spin },
720 #ifdef HWPMC_HOOKS
721 { "pmc-leaf", &lock_class_mtx_spin },
722 #endif
723 { "blocked lock", &lock_class_mtx_spin },
724 { NULL, NULL },
725 { NULL, NULL }
726 };
727
728 /*
729 * Pairs of locks which have been blessed. Witness does not complain about
730 * order problems with blessed lock pairs. Please do not add an entry to the
731 * table without an explanatory comment.
732 */
733 static struct witness_blessed blessed_list[] = {
734 /*
735 * See the comment in ufs_dirhash.c. Basically, a vnode lock serializes
736 * both lock orders, so a deadlock cannot happen as a result of this
737 * LOR.
738 */
739 { "dirhash", "bufwait" },
740
741 /*
742 * A UFS vnode may be locked in vget() while a buffer belonging to the
743 * parent directory vnode is locked.
744 */
745 { "ufs", "bufwait" },
746 };
747
748 /*
749 * This global is set to 0 once it becomes safe to use the witness code.
750 */
751 static int witness_cold = 1;
752
753 /*
754 * This global is set to 1 once the static lock orders have been enrolled
755 * so that a warning can be issued for any spin locks enrolled later.
756 */
757 static int witness_spin_warn = 0;
758
759 /* Trim useless garbage from filenames. */
760 static const char *
761 fixup_filename(const char *file)
762 {
763
764 if (file == NULL)
765 return (NULL);
766 while (strncmp(file, "../", 3) == 0)
767 file += 3;
768 return (file);
769 }
770
771 /*
772 * Calculate the size of early witness structures.
773 */
774 int
775 witness_startup_count(void)
776 {
777 int sz;
778
779 sz = sizeof(struct witness) * witness_count;
780 sz += sizeof(*w_rmatrix) * (witness_count + 1);
781 sz += sizeof(*w_rmatrix[0]) * (witness_count + 1) *
782 (witness_count + 1);
783
784 return (sz);
785 }
786
787 /*
788 * The WITNESS-enabled diagnostic code. Note that the witness code does
789 * assume that the early boot is single-threaded at least until after this
790 * routine is completed.
791 */
792 void
793 witness_startup(void *mem)
794 {
795 struct lock_object *lock;
796 struct witness_order_list_entry *order;
797 struct witness *w, *w1;
798 uintptr_t p;
799 int i;
800
801 p = (uintptr_t)mem;
802 w_data = (void *)p;
803 p += sizeof(struct witness) * witness_count;
804
805 w_rmatrix = (void *)p;
806 p += sizeof(*w_rmatrix) * (witness_count + 1);
807
808 for (i = 0; i < witness_count + 1; i++) {
809 w_rmatrix[i] = (void *)p;
810 p += sizeof(*w_rmatrix[i]) * (witness_count + 1);
811 }
812 badstack_sbuf_size = witness_count * 256;
813
814 /*
815 * We have to release Giant before initializing its witness
816 * structure so that WITNESS doesn't get confused.
817 */
818 mtx_unlock(&Giant);
819 mtx_assert(&Giant, MA_NOTOWNED);
820
821 CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
822 mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET |
823 MTX_NOWITNESS | MTX_NOPROFILE);
824 for (i = witness_count - 1; i >= 0; i--) {
825 w = &w_data[i];
826 memset(w, 0, sizeof(*w));
827 w_data[i].w_index = i; /* Witness index never changes. */
828 witness_free(w);
829 }
830 KASSERT(STAILQ_FIRST(&w_free)->w_index == 0,
831 ("%s: Invalid list of free witness objects", __func__));
832
833 /* Witness with index 0 is not used to aid in debugging. */
834 STAILQ_REMOVE_HEAD(&w_free, w_list);
835 w_free_cnt--;
836
837 for (i = 0; i < witness_count; i++) {
838 memset(w_rmatrix[i], 0, sizeof(*w_rmatrix[i]) *
839 (witness_count + 1));
840 }
841
842 for (i = 0; i < LOCK_CHILDCOUNT; i++)
843 witness_lock_list_free(&w_locklistdata[i]);
844 witness_init_hash_tables();
845
846 /* First add in all the specified order lists. */
847 for (order = order_lists; order->w_name != NULL; order++) {
848 w = enroll(order->w_name, order->w_class);
849 if (w == NULL)
850 continue;
851 w->w_file = "order list";
852 for (order++; order->w_name != NULL; order++) {
853 w1 = enroll(order->w_name, order->w_class);
854 if (w1 == NULL)
855 continue;
856 w1->w_file = "order list";
857 itismychild(w, w1);
858 w = w1;
859 }
860 }
861 witness_spin_warn = 1;
862
863 /* Iterate through all locks and add them to witness. */
864 for (i = 0; pending_locks[i].wh_lock != NULL; i++) {
865 lock = pending_locks[i].wh_lock;
866 KASSERT(lock->lo_flags & LO_WITNESS,
867 ("%s: lock %s is on pending list but not LO_WITNESS",
868 __func__, lock->lo_name));
869 lock->lo_witness = enroll(pending_locks[i].wh_type,
870 LOCK_CLASS(lock));
871 }
872
873 /* Mark the witness code as being ready for use. */
874 witness_cold = 0;
875
876 mtx_lock(&Giant);
877 }
878
879 void
880 witness_init(struct lock_object *lock, const char *type)
881 {
882 struct lock_class *class;
883
884 /* Various sanity checks. */
885 class = LOCK_CLASS(lock);
886 if ((lock->lo_flags & LO_RECURSABLE) != 0 &&
887 (class->lc_flags & LC_RECURSABLE) == 0)
888 kassert_panic("%s: lock (%s) %s can not be recursable",
889 __func__, class->lc_name, lock->lo_name);
890 if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
891 (class->lc_flags & LC_SLEEPABLE) == 0)
892 kassert_panic("%s: lock (%s) %s can not be sleepable",
893 __func__, class->lc_name, lock->lo_name);
894 if ((lock->lo_flags & LO_UPGRADABLE) != 0 &&
895 (class->lc_flags & LC_UPGRADABLE) == 0)
896 kassert_panic("%s: lock (%s) %s can not be upgradable",
897 __func__, class->lc_name, lock->lo_name);
898
899 /*
900 * If we shouldn't watch this lock, then just clear lo_witness.
901 * Otherwise, if witness_cold is set, then it is too early to
902 * enroll this lock, so defer it to witness_initialize() by adding
903 * it to the pending_locks list. If it is not too early, then enroll
904 * the lock now.
905 */
906 if (witness_watch < 1 || KERNEL_PANICKED() ||
907 (lock->lo_flags & LO_WITNESS) == 0)
908 lock->lo_witness = NULL;
909 else if (witness_cold) {
910 pending_locks[pending_cnt].wh_lock = lock;
911 pending_locks[pending_cnt++].wh_type = type;
912 if (pending_cnt > WITNESS_PENDLIST)
913 panic("%s: pending locks list is too small, "
914 "increase WITNESS_PENDLIST\n",
915 __func__);
916 } else
917 lock->lo_witness = enroll(type, class);
918 }
919
920 void
921 witness_destroy(struct lock_object *lock)
922 {
923 struct lock_class *class;
924 struct witness *w;
925
926 class = LOCK_CLASS(lock);
927
928 if (witness_cold)
929 panic("lock (%s) %s destroyed while witness_cold",
930 class->lc_name, lock->lo_name);
931
932 /* XXX: need to verify that no one holds the lock */
933 if ((lock->lo_flags & LO_WITNESS) == 0 || lock->lo_witness == NULL)
934 return;
935 w = lock->lo_witness;
936
937 mtx_lock_spin(&w_mtx);
938 MPASS(w->w_refcount > 0);
939 w->w_refcount--;
940
941 if (w->w_refcount == 0)
942 depart(w);
943 mtx_unlock_spin(&w_mtx);
944 }
945
946 #ifdef DDB
947 static void
948 witness_ddb_compute_levels(void)
949 {
950 struct witness *w;
951
952 /*
953 * First clear all levels.
954 */
955 STAILQ_FOREACH(w, &w_all, w_list)
956 w->w_ddb_level = -1;
957
958 /*
959 * Look for locks with no parents and level all their descendants.
960 */
961 STAILQ_FOREACH(w, &w_all, w_list) {
962 /* If the witness has ancestors (is not a root), skip it. */
963 if (w->w_num_ancestors > 0)
964 continue;
965 witness_ddb_level_descendants(w, 0);
966 }
967 }
968
969 static void
970 witness_ddb_level_descendants(struct witness *w, int l)
971 {
972 int i;
973
974 if (w->w_ddb_level >= l)
975 return;
976
977 w->w_ddb_level = l;
978 l++;
979
980 for (i = 1; i <= w_max_used_index; i++) {
981 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
982 witness_ddb_level_descendants(&w_data[i], l);
983 }
984 }
985
986 static void
987 witness_ddb_display_descendants(int(*prnt)(const char *fmt, ...),
988 struct witness *w, int indent)
989 {
990 int i;
991
992 for (i = 0; i < indent; i++)
993 prnt(" ");
994 prnt("%s (type: %s, depth: %d, active refs: %d)",
995 w->w_name, w->w_class->lc_name,
996 w->w_ddb_level, w->w_refcount);
997 if (w->w_displayed) {
998 prnt(" -- (already displayed)\n");
999 return;
1000 }
1001 w->w_displayed = 1;
1002 if (w->w_file != NULL && w->w_line != 0)
1003 prnt(" -- last acquired @ %s:%d\n", fixup_filename(w->w_file),
1004 w->w_line);
1005 else
1006 prnt(" -- never acquired\n");
1007 indent++;
1008 WITNESS_INDEX_ASSERT(w->w_index);
1009 for (i = 1; i <= w_max_used_index; i++) {
1010 if (db_pager_quit)
1011 return;
1012 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
1013 witness_ddb_display_descendants(prnt, &w_data[i],
1014 indent);
1015 }
1016 }
1017
1018 static void
1019 witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
1020 struct witness_list *list)
1021 {
1022 struct witness *w;
1023
1024 STAILQ_FOREACH(w, list, w_typelist) {
1025 if (w->w_file == NULL || w->w_ddb_level > 0)
1026 continue;
1027
1028 /* This lock has no anscestors - display its descendants. */
1029 witness_ddb_display_descendants(prnt, w, 0);
1030 if (db_pager_quit)
1031 return;
1032 }
1033 }
1034
1035 static void
1036 witness_ddb_display(int(*prnt)(const char *fmt, ...))
1037 {
1038 struct witness *w;
1039
1040 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
1041 witness_ddb_compute_levels();
1042
1043 /* Clear all the displayed flags. */
1044 STAILQ_FOREACH(w, &w_all, w_list)
1045 w->w_displayed = 0;
1046
1047 /*
1048 * First, handle sleep locks which have been acquired at least
1049 * once.
1050 */
1051 prnt("Sleep locks:\n");
1052 witness_ddb_display_list(prnt, &w_sleep);
1053 if (db_pager_quit)
1054 return;
1055
1056 /*
1057 * Now do spin locks which have been acquired at least once.
1058 */
1059 prnt("\nSpin locks:\n");
1060 witness_ddb_display_list(prnt, &w_spin);
1061 if (db_pager_quit)
1062 return;
1063
1064 /*
1065 * Finally, any locks which have not been acquired yet.
1066 */
1067 prnt("\nLocks which were never acquired:\n");
1068 STAILQ_FOREACH(w, &w_all, w_list) {
1069 if (w->w_file != NULL || w->w_refcount == 0)
1070 continue;
1071 prnt("%s (type: %s, depth: %d)\n", w->w_name,
1072 w->w_class->lc_name, w->w_ddb_level);
1073 if (db_pager_quit)
1074 return;
1075 }
1076 }
1077 #endif /* DDB */
1078
1079 int
1080 witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
1081 {
1082
1083 if (witness_watch == -1 || KERNEL_PANICKED())
1084 return (0);
1085
1086 /* Require locks that witness knows about. */
1087 if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL ||
1088 lock2->lo_witness == NULL)
1089 return (EINVAL);
1090
1091 mtx_assert(&w_mtx, MA_NOTOWNED);
1092 mtx_lock_spin(&w_mtx);
1093
1094 /*
1095 * If we already have either an explicit or implied lock order that
1096 * is the other way around, then return an error.
1097 */
1098 if (witness_watch &&
1099 isitmydescendant(lock2->lo_witness, lock1->lo_witness)) {
1100 mtx_unlock_spin(&w_mtx);
1101 return (EDOOFUS);
1102 }
1103
1104 /* Try to add the new order. */
1105 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
1106 lock2->lo_witness->w_name, lock1->lo_witness->w_name);
1107 itismychild(lock1->lo_witness, lock2->lo_witness);
1108 mtx_unlock_spin(&w_mtx);
1109 return (0);
1110 }
1111
1112 void
1113 witness_checkorder(struct lock_object *lock, int flags, const char *file,
1114 int line, struct lock_object *interlock)
1115 {
1116 struct lock_list_entry *lock_list, *lle;
1117 struct lock_instance *lock1, *lock2, *plock;
1118 struct lock_class *class, *iclass;
1119 struct witness *w, *w1;
1120 struct thread *td;
1121 int i, j;
1122
1123 if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL ||
1124 KERNEL_PANICKED())
1125 return;
1126
1127 w = lock->lo_witness;
1128 class = LOCK_CLASS(lock);
1129 td = curthread;
1130
1131 if (class->lc_flags & LC_SLEEPLOCK) {
1132 /*
1133 * Since spin locks include a critical section, this check
1134 * implicitly enforces a lock order of all sleep locks before
1135 * all spin locks.
1136 */
1137 if (td->td_critnest != 0 && !kdb_active)
1138 kassert_panic("acquiring blockable sleep lock with "
1139 "spinlock or critical section held (%s) %s @ %s:%d",
1140 class->lc_name, lock->lo_name,
1141 fixup_filename(file), line);
1142
1143 /*
1144 * If this is the first lock acquired then just return as
1145 * no order checking is needed.
1146 */
1147 lock_list = td->td_sleeplocks;
1148 if (lock_list == NULL || lock_list->ll_count == 0)
1149 return;
1150 } else {
1151 /*
1152 * If this is the first lock, just return as no order
1153 * checking is needed. Avoid problems with thread
1154 * migration pinning the thread while checking if
1155 * spinlocks are held. If at least one spinlock is held
1156 * the thread is in a safe path and it is allowed to
1157 * unpin it.
1158 */
1159 sched_pin();
1160 lock_list = PCPU_GET(spinlocks);
1161 if (lock_list == NULL || lock_list->ll_count == 0) {
1162 sched_unpin();
1163 return;
1164 }
1165 sched_unpin();
1166 }
1167
1168 /*
1169 * Check to see if we are recursing on a lock we already own. If
1170 * so, make sure that we don't mismatch exclusive and shared lock
1171 * acquires.
1172 */
1173 lock1 = find_instance(lock_list, lock);
1174 if (lock1 != NULL) {
1175 if ((lock1->li_flags & LI_EXCLUSIVE) != 0 &&
1176 (flags & LOP_EXCLUSIVE) == 0) {
1177 witness_output("shared lock of (%s) %s @ %s:%d\n",
1178 class->lc_name, lock->lo_name,
1179 fixup_filename(file), line);
1180 witness_output("while exclusively locked from %s:%d\n",
1181 fixup_filename(lock1->li_file), lock1->li_line);
1182 kassert_panic("excl->share");
1183 }
1184 if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
1185 (flags & LOP_EXCLUSIVE) != 0) {
1186 witness_output("exclusive lock of (%s) %s @ %s:%d\n",
1187 class->lc_name, lock->lo_name,
1188 fixup_filename(file), line);
1189 witness_output("while share locked from %s:%d\n",
1190 fixup_filename(lock1->li_file), lock1->li_line);
1191 kassert_panic("share->excl");
1192 }
1193 return;
1194 }
1195
1196 /* Warn if the interlock is not locked exactly once. */
1197 if (interlock != NULL) {
1198 iclass = LOCK_CLASS(interlock);
1199 lock1 = find_instance(lock_list, interlock);
1200 if (lock1 == NULL)
1201 kassert_panic("interlock (%s) %s not locked @ %s:%d",
1202 iclass->lc_name, interlock->lo_name,
1203 fixup_filename(file), line);
1204 else if ((lock1->li_flags & LI_RECURSEMASK) != 0)
1205 kassert_panic("interlock (%s) %s recursed @ %s:%d",
1206 iclass->lc_name, interlock->lo_name,
1207 fixup_filename(file), line);
1208 }
1209
1210 /*
1211 * Find the previously acquired lock, but ignore interlocks.
1212 */
1213 plock = &lock_list->ll_children[lock_list->ll_count - 1];
1214 if (interlock != NULL && plock->li_lock == interlock) {
1215 if (lock_list->ll_count > 1)
1216 plock =
1217 &lock_list->ll_children[lock_list->ll_count - 2];
1218 else {
1219 lle = lock_list->ll_next;
1220
1221 /*
1222 * The interlock is the only lock we hold, so
1223 * simply return.
1224 */
1225 if (lle == NULL)
1226 return;
1227 plock = &lle->ll_children[lle->ll_count - 1];
1228 }
1229 }
1230
1231 /*
1232 * Try to perform most checks without a lock. If this succeeds we
1233 * can skip acquiring the lock and return success. Otherwise we redo
1234 * the check with the lock held to handle races with concurrent updates.
1235 */
1236 w1 = plock->li_lock->lo_witness;
1237 if (witness_lock_order_check(w1, w))
1238 return;
1239
1240 mtx_lock_spin(&w_mtx);
1241 if (witness_lock_order_check(w1, w)) {
1242 mtx_unlock_spin(&w_mtx);
1243 return;
1244 }
1245 witness_lock_order_add(w1, w);
1246
1247 /*
1248 * Check for duplicate locks of the same type. Note that we only
1249 * have to check for this on the last lock we just acquired. Any
1250 * other cases will be caught as lock order violations.
1251 */
1252 if (w1 == w) {
1253 i = w->w_index;
1254 if (!(lock->lo_flags & LO_DUPOK) && !(flags & LOP_DUPOK) &&
1255 !(w_rmatrix[i][i] & WITNESS_REVERSAL)) {
1256 w_rmatrix[i][i] |= WITNESS_REVERSAL;
1257 w->w_reversed = 1;
1258 mtx_unlock_spin(&w_mtx);
1259 witness_output(
1260 "acquiring duplicate lock of same type: \"%s\"\n",
1261 w->w_name);
1262 witness_output(" 1st %s @ %s:%d\n", plock->li_lock->lo_name,
1263 fixup_filename(plock->li_file), plock->li_line);
1264 witness_output(" 2nd %s @ %s:%d\n", lock->lo_name,
1265 fixup_filename(file), line);
1266 witness_debugger(1, __func__);
1267 } else
1268 mtx_unlock_spin(&w_mtx);
1269 return;
1270 }
1271 mtx_assert(&w_mtx, MA_OWNED);
1272
1273 /*
1274 * If we know that the lock we are acquiring comes after
1275 * the lock we most recently acquired in the lock order tree,
1276 * then there is no need for any further checks.
1277 */
1278 if (isitmychild(w1, w))
1279 goto out;
1280
1281 for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) {
1282 for (i = lle->ll_count - 1; i >= 0; i--, j++) {
1283 struct stack pstack;
1284 bool pstackv, trace;
1285
1286 MPASS(j < LOCK_CHILDCOUNT * LOCK_NCHILDREN);
1287 lock1 = &lle->ll_children[i];
1288
1289 /*
1290 * Ignore the interlock.
1291 */
1292 if (interlock == lock1->li_lock)
1293 continue;
1294
1295 /*
1296 * If this lock doesn't undergo witness checking,
1297 * then skip it.
1298 */
1299 w1 = lock1->li_lock->lo_witness;
1300 if (w1 == NULL) {
1301 KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0,
1302 ("lock missing witness structure"));
1303 continue;
1304 }
1305
1306 /*
1307 * If we are locking Giant and this is a sleepable
1308 * lock, then skip it.
1309 */
1310 if ((lock1->li_flags & LI_SLEEPABLE) != 0 &&
1311 lock == &Giant.lock_object)
1312 continue;
1313
1314 /*
1315 * If we are locking a sleepable lock and this lock
1316 * is Giant, then skip it.
1317 */
1318 if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
1319 (flags & LOP_NOSLEEP) == 0 &&
1320 lock1->li_lock == &Giant.lock_object)
1321 continue;
1322
1323 /*
1324 * If we are locking a sleepable lock and this lock
1325 * isn't sleepable, we want to treat it as a lock
1326 * order violation to enfore a general lock order of
1327 * sleepable locks before non-sleepable locks.
1328 */
1329 if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
1330 (flags & LOP_NOSLEEP) == 0 &&
1331 (lock1->li_flags & LI_SLEEPABLE) == 0)
1332 goto reversal;
1333
1334 /*
1335 * If we are locking Giant and this is a non-sleepable
1336 * lock, then treat it as a reversal.
1337 */
1338 if ((lock1->li_flags & LI_SLEEPABLE) == 0 &&
1339 lock == &Giant.lock_object)
1340 goto reversal;
1341
1342 /*
1343 * Check the lock order hierarchy for a reveresal.
1344 */
1345 if (!isitmydescendant(w, w1))
1346 continue;
1347 reversal:
1348
1349 /*
1350 * We have a lock order violation, check to see if it
1351 * is allowed or has already been yelled about.
1352 */
1353
1354 /* Bail if this violation is known */
1355 if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL)
1356 goto out;
1357
1358 /* Record this as a violation */
1359 w_rmatrix[w1->w_index][w->w_index] |= WITNESS_REVERSAL;
1360 w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL;
1361 w->w_reversed = w1->w_reversed = 1;
1362 witness_increment_graph_generation();
1363
1364 /*
1365 * If the lock order is blessed, bail before logging
1366 * anything. We don't look for other lock order
1367 * violations though, which may be a bug.
1368 */
1369 if (blessed(w, w1))
1370 goto out;
1371
1372 trace = atomic_load_int(&witness_trace);
1373 if (trace) {
1374 struct witness_lock_order_data *data;
1375
1376 pstackv = false;
1377 data = witness_lock_order_get(w, w1);
1378 if (data != NULL) {
1379 stack_copy(&data->wlod_stack,
1380 &pstack);
1381 pstackv = true;
1382 }
1383 }
1384 mtx_unlock_spin(&w_mtx);
1385
1386 #ifdef WITNESS_NO_VNODE
1387 /*
1388 * There are known LORs between VNODE locks. They are
1389 * not an indication of a bug. VNODE locks are flagged
1390 * as such (LO_IS_VNODE) and we don't yell if the LOR
1391 * is between 2 VNODE locks.
1392 */
1393 if ((lock->lo_flags & LO_IS_VNODE) != 0 &&
1394 (lock1->li_lock->lo_flags & LO_IS_VNODE) != 0)
1395 return;
1396 #endif
1397
1398 /*
1399 * Ok, yell about it.
1400 */
1401 if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
1402 (flags & LOP_NOSLEEP) == 0 &&
1403 (lock1->li_flags & LI_SLEEPABLE) == 0)
1404 witness_output(
1405 "lock order reversal: (sleepable after non-sleepable)\n");
1406 else if ((lock1->li_flags & LI_SLEEPABLE) == 0
1407 && lock == &Giant.lock_object)
1408 witness_output(
1409 "lock order reversal: (Giant after non-sleepable)\n");
1410 else
1411 witness_output("lock order reversal:\n");
1412
1413 /*
1414 * Try to locate an earlier lock with
1415 * witness w in our list.
1416 */
1417 do {
1418 lock2 = &lle->ll_children[i];
1419 MPASS(lock2->li_lock != NULL);
1420 if (lock2->li_lock->lo_witness == w)
1421 break;
1422 if (i == 0 && lle->ll_next != NULL) {
1423 lle = lle->ll_next;
1424 i = lle->ll_count - 1;
1425 MPASS(i >= 0 && i < LOCK_NCHILDREN);
1426 } else
1427 i--;
1428 } while (i >= 0);
1429 if (i < 0) {
1430 witness_output(" 1st %p %s (%s, %s) @ %s:%d\n",
1431 lock1->li_lock, lock1->li_lock->lo_name,
1432 w1->w_name, w1->w_class->lc_name,
1433 fixup_filename(lock1->li_file),
1434 lock1->li_line);
1435 witness_output(" 2nd %p %s (%s, %s) @ %s:%d\n",
1436 lock, lock->lo_name, w->w_name,
1437 w->w_class->lc_name, fixup_filename(file),
1438 line);
1439 } else {
1440 struct witness *w2 = lock2->li_lock->lo_witness;
1441
1442 witness_output(" 1st %p %s (%s, %s) @ %s:%d\n",
1443 lock2->li_lock, lock2->li_lock->lo_name,
1444 w2->w_name, w2->w_class->lc_name,
1445 fixup_filename(lock2->li_file),
1446 lock2->li_line);
1447 witness_output(" 2nd %p %s (%s, %s) @ %s:%d\n",
1448 lock1->li_lock, lock1->li_lock->lo_name,
1449 w1->w_name, w1->w_class->lc_name,
1450 fixup_filename(lock1->li_file),
1451 lock1->li_line);
1452 witness_output(" 3rd %p %s (%s, %s) @ %s:%d\n", lock,
1453 lock->lo_name, w->w_name,
1454 w->w_class->lc_name, fixup_filename(file),
1455 line);
1456 }
1457 if (trace) {
1458 char buf[64];
1459 struct sbuf sb;
1460
1461 sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN);
1462 sbuf_set_drain(&sb, witness_output_drain,
1463 NULL);
1464
1465 if (pstackv) {
1466 sbuf_printf(&sb,
1467 "lock order %s -> %s established at:\n",
1468 w->w_name, w1->w_name);
1469 stack_sbuf_print_flags(&sb, &pstack,
1470 M_NOWAIT, STACK_SBUF_FMT_LONG);
1471 }
1472
1473 sbuf_printf(&sb,
1474 "lock order %s -> %s attempted at:\n",
1475 w1->w_name, w->w_name);
1476 stack_save(&pstack);
1477 stack_sbuf_print_flags(&sb, &pstack, M_NOWAIT,
1478 STACK_SBUF_FMT_LONG);
1479
1480 sbuf_finish(&sb);
1481 sbuf_delete(&sb);
1482 }
1483 witness_enter_debugger(__func__);
1484 return;
1485 }
1486 }
1487
1488 /*
1489 * If requested, build a new lock order. However, don't build a new
1490 * relationship between a sleepable lock and Giant if it is in the
1491 * wrong direction. The correct lock order is that sleepable locks
1492 * always come before Giant.
1493 */
1494 if (flags & LOP_NEWORDER &&
1495 !(plock->li_lock == &Giant.lock_object &&
1496 (lock->lo_flags & LO_SLEEPABLE) != 0 &&
1497 (flags & LOP_NOSLEEP) == 0)) {
1498 CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
1499 w->w_name, plock->li_lock->lo_witness->w_name);
1500 itismychild(plock->li_lock->lo_witness, w);
1501 }
1502 out:
1503 mtx_unlock_spin(&w_mtx);
1504 }
1505
1506 void
1507 witness_lock(struct lock_object *lock, int flags, const char *file, int line)
1508 {
1509 struct lock_list_entry **lock_list, *lle;
1510 struct lock_instance *instance;
1511 struct witness *w;
1512 struct thread *td;
1513
1514 if (witness_cold || witness_watch == -1 || lock->lo_witness == NULL ||
1515 KERNEL_PANICKED())
1516 return;
1517 w = lock->lo_witness;
1518 td = curthread;
1519
1520 /* Determine lock list for this lock. */
1521 if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK)
1522 lock_list = &td->td_sleeplocks;
1523 else
1524 lock_list = PCPU_PTR(spinlocks);
1525
1526 /* Check to see if we are recursing on a lock we already own. */
1527 instance = find_instance(*lock_list, lock);
1528 if (instance != NULL) {
1529 instance->li_flags++;
1530 CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__,
1531 td->td_proc->p_pid, lock->lo_name,
1532 instance->li_flags & LI_RECURSEMASK);
1533 instance->li_file = file;
1534 instance->li_line = line;
1535 return;
1536 }
1537
1538 /* Update per-witness last file and line acquire. */
1539 w->w_file = file;
1540 w->w_line = line;
1541
1542 /* Find the next open lock instance in the list and fill it. */
1543 lle = *lock_list;
1544 if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
1545 lle = witness_lock_list_get();
1546 if (lle == NULL)
1547 return;
1548 lle->ll_next = *lock_list;
1549 CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__,
1550 td->td_proc->p_pid, lle);
1551 *lock_list = lle;
1552 }
1553 instance = &lle->ll_children[lle->ll_count++];
1554 instance->li_lock = lock;
1555 instance->li_line = line;
1556 instance->li_file = file;
1557 instance->li_flags = 0;
1558 if ((flags & LOP_EXCLUSIVE) != 0)
1559 instance->li_flags |= LI_EXCLUSIVE;
1560 if ((lock->lo_flags & LO_SLEEPABLE) != 0 && (flags & LOP_NOSLEEP) == 0)
1561 instance->li_flags |= LI_SLEEPABLE;
1562 CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__,
1563 td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1);
1564 }
1565
1566 void
1567 witness_upgrade(struct lock_object *lock, int flags, const char *file, int line)
1568 {
1569 struct lock_instance *instance;
1570 struct lock_class *class;
1571
1572 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
1573 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED())
1574 return;
1575 class = LOCK_CLASS(lock);
1576 if (witness_watch) {
1577 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
1578 kassert_panic(
1579 "upgrade of non-upgradable lock (%s) %s @ %s:%d",
1580 class->lc_name, lock->lo_name,
1581 fixup_filename(file), line);
1582 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
1583 kassert_panic(
1584 "upgrade of non-sleep lock (%s) %s @ %s:%d",
1585 class->lc_name, lock->lo_name,
1586 fixup_filename(file), line);
1587 }
1588 instance = find_instance(curthread->td_sleeplocks, lock);
1589 if (instance == NULL) {
1590 kassert_panic("upgrade of unlocked lock (%s) %s @ %s:%d",
1591 class->lc_name, lock->lo_name,
1592 fixup_filename(file), line);
1593 return;
1594 }
1595 if (witness_watch) {
1596 if ((instance->li_flags & LI_EXCLUSIVE) != 0)
1597 kassert_panic(
1598 "upgrade of exclusive lock (%s) %s @ %s:%d",
1599 class->lc_name, lock->lo_name,
1600 fixup_filename(file), line);
1601 if ((instance->li_flags & LI_RECURSEMASK) != 0)
1602 kassert_panic(
1603 "upgrade of recursed lock (%s) %s r=%d @ %s:%d",
1604 class->lc_name, lock->lo_name,
1605 instance->li_flags & LI_RECURSEMASK,
1606 fixup_filename(file), line);
1607 }
1608 instance->li_flags |= LI_EXCLUSIVE;
1609 }
1610
1611 void
1612 witness_downgrade(struct lock_object *lock, int flags, const char *file,
1613 int line)
1614 {
1615 struct lock_instance *instance;
1616 struct lock_class *class;
1617
1618 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
1619 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED())
1620 return;
1621 class = LOCK_CLASS(lock);
1622 if (witness_watch) {
1623 if ((lock->lo_flags & LO_UPGRADABLE) == 0)
1624 kassert_panic(
1625 "downgrade of non-upgradable lock (%s) %s @ %s:%d",
1626 class->lc_name, lock->lo_name,
1627 fixup_filename(file), line);
1628 if ((class->lc_flags & LC_SLEEPLOCK) == 0)
1629 kassert_panic(
1630 "downgrade of non-sleep lock (%s) %s @ %s:%d",
1631 class->lc_name, lock->lo_name,
1632 fixup_filename(file), line);
1633 }
1634 instance = find_instance(curthread->td_sleeplocks, lock);
1635 if (instance == NULL) {
1636 kassert_panic("downgrade of unlocked lock (%s) %s @ %s:%d",
1637 class->lc_name, lock->lo_name,
1638 fixup_filename(file), line);
1639 return;
1640 }
1641 if (witness_watch) {
1642 if ((instance->li_flags & LI_EXCLUSIVE) == 0)
1643 kassert_panic(
1644 "downgrade of shared lock (%s) %s @ %s:%d",
1645 class->lc_name, lock->lo_name,
1646 fixup_filename(file), line);
1647 if ((instance->li_flags & LI_RECURSEMASK) != 0)
1648 kassert_panic(
1649 "downgrade of recursed lock (%s) %s r=%d @ %s:%d",
1650 class->lc_name, lock->lo_name,
1651 instance->li_flags & LI_RECURSEMASK,
1652 fixup_filename(file), line);
1653 }
1654 instance->li_flags &= ~LI_EXCLUSIVE;
1655 }
1656
1657 void
1658 witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
1659 {
1660 struct lock_list_entry **lock_list, *lle;
1661 struct lock_instance *instance;
1662 struct lock_class *class;
1663 struct thread *td;
1664 register_t s;
1665 int i, j;
1666
1667 if (witness_cold || lock->lo_witness == NULL || KERNEL_PANICKED())
1668 return;
1669 td = curthread;
1670 class = LOCK_CLASS(lock);
1671
1672 /* Find lock instance associated with this lock. */
1673 if (class->lc_flags & LC_SLEEPLOCK)
1674 lock_list = &td->td_sleeplocks;
1675 else
1676 lock_list = PCPU_PTR(spinlocks);
1677 lle = *lock_list;
1678 for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next)
1679 for (i = 0; i < (*lock_list)->ll_count; i++) {
1680 instance = &(*lock_list)->ll_children[i];
1681 if (instance->li_lock == lock)
1682 goto found;
1683 }
1684
1685 /*
1686 * When disabling WITNESS through witness_watch we could end up in
1687 * having registered locks in the td_sleeplocks queue.
1688 * We have to make sure we flush these queues, so just search for
1689 * eventual register locks and remove them.
1690 */
1691 if (witness_watch > 0) {
1692 kassert_panic("lock (%s) %s not locked @ %s:%d", class->lc_name,
1693 lock->lo_name, fixup_filename(file), line);
1694 return;
1695 } else {
1696 return;
1697 }
1698 found:
1699
1700 /* First, check for shared/exclusive mismatches. */
1701 if ((instance->li_flags & LI_EXCLUSIVE) != 0 && witness_watch > 0 &&
1702 (flags & LOP_EXCLUSIVE) == 0) {
1703 witness_output("shared unlock of (%s) %s @ %s:%d\n",
1704 class->lc_name, lock->lo_name, fixup_filename(file), line);
1705 witness_output("while exclusively locked from %s:%d\n",
1706 fixup_filename(instance->li_file), instance->li_line);
1707 kassert_panic("excl->ushare");
1708 }
1709 if ((instance->li_flags & LI_EXCLUSIVE) == 0 && witness_watch > 0 &&
1710 (flags & LOP_EXCLUSIVE) != 0) {
1711 witness_output("exclusive unlock of (%s) %s @ %s:%d\n",
1712 class->lc_name, lock->lo_name, fixup_filename(file), line);
1713 witness_output("while share locked from %s:%d\n",
1714 fixup_filename(instance->li_file),
1715 instance->li_line);
1716 kassert_panic("share->uexcl");
1717 }
1718 /* If we are recursed, unrecurse. */
1719 if ((instance->li_flags & LI_RECURSEMASK) > 0) {
1720 CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__,
1721 td->td_proc->p_pid, instance->li_lock->lo_name,
1722 instance->li_flags);
1723 instance->li_flags--;
1724 return;
1725 }
1726 /* The lock is now being dropped, check for NORELEASE flag */
1727 if ((instance->li_flags & LI_NORELEASE) != 0 && witness_watch > 0) {
1728 witness_output("forbidden unlock of (%s) %s @ %s:%d\n",
1729 class->lc_name, lock->lo_name, fixup_filename(file), line);
1730 kassert_panic("lock marked norelease");
1731 }
1732
1733 /* Otherwise, remove this item from the list. */
1734 s = intr_disable();
1735 CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__,
1736 td->td_proc->p_pid, instance->li_lock->lo_name,
1737 (*lock_list)->ll_count - 1);
1738 for (j = i; j < (*lock_list)->ll_count - 1; j++)
1739 (*lock_list)->ll_children[j] =
1740 (*lock_list)->ll_children[j + 1];
1741 (*lock_list)->ll_count--;
1742 intr_restore(s);
1743
1744 /*
1745 * In order to reduce contention on w_mtx, we want to keep always an
1746 * head object into lists so that frequent allocation from the
1747 * free witness pool (and subsequent locking) is avoided.
1748 * In order to maintain the current code simple, when the head
1749 * object is totally unloaded it means also that we do not have
1750 * further objects in the list, so the list ownership needs to be
1751 * hand over to another object if the current head needs to be freed.
1752 */
1753 if ((*lock_list)->ll_count == 0) {
1754 if (*lock_list == lle) {
1755 if (lle->ll_next == NULL)
1756 return;
1757 } else
1758 lle = *lock_list;
1759 *lock_list = lle->ll_next;
1760 CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__,
1761 td->td_proc->p_pid, lle);
1762 witness_lock_list_free(lle);
1763 }
1764 }
1765
1766 void
1767 witness_thread_exit(struct thread *td)
1768 {
1769 struct lock_list_entry *lle;
1770 int i, n;
1771
1772 lle = td->td_sleeplocks;
1773 if (lle == NULL || KERNEL_PANICKED())
1774 return;
1775 if (lle->ll_count != 0) {
1776 for (n = 0; lle != NULL; lle = lle->ll_next)
1777 for (i = lle->ll_count - 1; i >= 0; i--) {
1778 if (n == 0)
1779 witness_output(
1780 "Thread %p exiting with the following locks held:\n", td);
1781 n++;
1782 witness_list_lock(&lle->ll_children[i],
1783 witness_output);
1784
1785 }
1786 kassert_panic(
1787 "Thread %p cannot exit while holding sleeplocks\n", td);
1788 }
1789 witness_lock_list_free(lle);
1790 }
1791
1792 /*
1793 * Warn if any locks other than 'lock' are held. Flags can be passed in to
1794 * exempt Giant and sleepable locks from the checks as well. If any
1795 * non-exempt locks are held, then a supplied message is printed to the
1796 * output channel along with a list of the offending locks. If indicated in the
1797 * flags then a failure results in a panic as well.
1798 */
1799 int
1800 witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
1801 {
1802 struct lock_list_entry *lock_list, *lle;
1803 struct lock_instance *lock1;
1804 struct thread *td;
1805 va_list ap;
1806 int i, n;
1807
1808 if (witness_cold || witness_watch < 1 || KERNEL_PANICKED())
1809 return (0);
1810 n = 0;
1811 td = curthread;
1812 for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next)
1813 for (i = lle->ll_count - 1; i >= 0; i--) {
1814 lock1 = &lle->ll_children[i];
1815 if (lock1->li_lock == lock)
1816 continue;
1817 if (flags & WARN_GIANTOK &&
1818 lock1->li_lock == &Giant.lock_object)
1819 continue;
1820 if (flags & WARN_SLEEPOK &&
1821 (lock1->li_flags & LI_SLEEPABLE) != 0)
1822 continue;
1823 if (n == 0) {
1824 va_start(ap, fmt);
1825 vprintf(fmt, ap);
1826 va_end(ap);
1827 printf(" with the following %slocks held:\n",
1828 (flags & WARN_SLEEPOK) != 0 ?
1829 "non-sleepable " : "");
1830 }
1831 n++;
1832 witness_list_lock(lock1, printf);
1833 }
1834
1835 /*
1836 * Pin the thread in order to avoid problems with thread migration.
1837 * Once that all verifies are passed about spinlocks ownership,
1838 * the thread is in a safe path and it can be unpinned.
1839 */
1840 sched_pin();
1841 lock_list = PCPU_GET(spinlocks);
1842 if (lock_list != NULL && lock_list->ll_count != 0) {
1843 sched_unpin();
1844
1845 /*
1846 * We should only have one spinlock and as long as
1847 * the flags cannot match for this locks class,
1848 * check if the first spinlock is the one curthread
1849 * should hold.
1850 */
1851 lock1 = &lock_list->ll_children[lock_list->ll_count - 1];
1852 if (lock_list->ll_count == 1 && lock_list->ll_next == NULL &&
1853 lock1->li_lock == lock && n == 0)
1854 return (0);
1855
1856 va_start(ap, fmt);
1857 vprintf(fmt, ap);
1858 va_end(ap);
1859 printf(" with the following %slocks held:\n",
1860 (flags & WARN_SLEEPOK) != 0 ? "non-sleepable " : "");
1861 n += witness_list_locks(&lock_list, printf);
1862 } else
1863 sched_unpin();
1864 if (flags & WARN_PANIC && n)
1865 kassert_panic("%s", __func__);
1866 else
1867 witness_debugger(n, __func__);
1868 return (n);
1869 }
1870
1871 const char *
1872 witness_file(struct lock_object *lock)
1873 {
1874 struct witness *w;
1875
1876 if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
1877 return ("?");
1878 w = lock->lo_witness;
1879 return (w->w_file);
1880 }
1881
1882 int
1883 witness_line(struct lock_object *lock)
1884 {
1885 struct witness *w;
1886
1887 if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
1888 return (0);
1889 w = lock->lo_witness;
1890 return (w->w_line);
1891 }
1892
1893 static struct witness *
1894 enroll(const char *description, struct lock_class *lock_class)
1895 {
1896 struct witness *w;
1897
1898 MPASS(description != NULL);
1899
1900 if (witness_watch == -1 || KERNEL_PANICKED())
1901 return (NULL);
1902 if ((lock_class->lc_flags & LC_SPINLOCK)) {
1903 if (witness_skipspin)
1904 return (NULL);
1905 } else if ((lock_class->lc_flags & LC_SLEEPLOCK) == 0) {
1906 kassert_panic("lock class %s is not sleep or spin",
1907 lock_class->lc_name);
1908 return (NULL);
1909 }
1910
1911 mtx_lock_spin(&w_mtx);
1912 w = witness_hash_get(description);
1913 if (w)
1914 goto found;
1915 if ((w = witness_get()) == NULL)
1916 return (NULL);
1917 MPASS(strlen(description) < MAX_W_NAME);
1918 strcpy(w->w_name, description);
1919 w->w_class = lock_class;
1920 w->w_refcount = 1;
1921 STAILQ_INSERT_HEAD(&w_all, w, w_list);
1922 if (lock_class->lc_flags & LC_SPINLOCK) {
1923 STAILQ_INSERT_HEAD(&w_spin, w, w_typelist);
1924 w_spin_cnt++;
1925 } else if (lock_class->lc_flags & LC_SLEEPLOCK) {
1926 STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist);
1927 w_sleep_cnt++;
1928 }
1929
1930 /* Insert new witness into the hash */
1931 witness_hash_put(w);
1932 witness_increment_graph_generation();
1933 mtx_unlock_spin(&w_mtx);
1934 return (w);
1935 found:
1936 w->w_refcount++;
1937 if (w->w_refcount == 1)
1938 w->w_class = lock_class;
1939 mtx_unlock_spin(&w_mtx);
1940 if (lock_class != w->w_class)
1941 kassert_panic(
1942 "lock (%s) %s does not match earlier (%s) lock",
1943 description, lock_class->lc_name,
1944 w->w_class->lc_name);
1945 return (w);
1946 }
1947
1948 static void
1949 depart(struct witness *w)
1950 {
1951
1952 MPASS(w->w_refcount == 0);
1953 if (w->w_class->lc_flags & LC_SLEEPLOCK) {
1954 w_sleep_cnt--;
1955 } else {
1956 w_spin_cnt--;
1957 }
1958 /*
1959 * Set file to NULL as it may point into a loadable module.
1960 */
1961 w->w_file = NULL;
1962 w->w_line = 0;
1963 witness_increment_graph_generation();
1964 }
1965
1966 static void
1967 adopt(struct witness *parent, struct witness *child)
1968 {
1969 int pi, ci, i, j;
1970
1971 if (witness_cold == 0)
1972 mtx_assert(&w_mtx, MA_OWNED);
1973
1974 /* If the relationship is already known, there's no work to be done. */
1975 if (isitmychild(parent, child))
1976 return;
1977
1978 /* When the structure of the graph changes, bump up the generation. */
1979 witness_increment_graph_generation();
1980
1981 /*
1982 * The hard part ... create the direct relationship, then propagate all
1983 * indirect relationships.
1984 */
1985 pi = parent->w_index;
1986 ci = child->w_index;
1987 WITNESS_INDEX_ASSERT(pi);
1988 WITNESS_INDEX_ASSERT(ci);
1989 MPASS(pi != ci);
1990 w_rmatrix[pi][ci] |= WITNESS_PARENT;
1991 w_rmatrix[ci][pi] |= WITNESS_CHILD;
1992
1993 /*
1994 * If parent was not already an ancestor of child,
1995 * then we increment the descendant and ancestor counters.
1996 */
1997 if ((w_rmatrix[pi][ci] & WITNESS_ANCESTOR) == 0) {
1998 parent->w_num_descendants++;
1999 child->w_num_ancestors++;
2000 }
2001
2002 /*
2003 * Find each ancestor of 'pi'. Note that 'pi' itself is counted as
2004 * an ancestor of 'pi' during this loop.
2005 */
2006 for (i = 1; i <= w_max_used_index; i++) {
2007 if ((w_rmatrix[i][pi] & WITNESS_ANCESTOR_MASK) == 0 &&
2008 (i != pi))
2009 continue;
2010
2011 /* Find each descendant of 'i' and mark it as a descendant. */
2012 for (j = 1; j <= w_max_used_index; j++) {
2013 /*
2014 * Skip children that are already marked as
2015 * descendants of 'i'.
2016 */
2017 if (w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK)
2018 continue;
2019
2020 /*
2021 * We are only interested in descendants of 'ci'. Note
2022 * that 'ci' itself is counted as a descendant of 'ci'.
2023 */
2024 if ((w_rmatrix[ci][j] & WITNESS_ANCESTOR_MASK) == 0 &&
2025 (j != ci))
2026 continue;
2027 w_rmatrix[i][j] |= WITNESS_ANCESTOR;
2028 w_rmatrix[j][i] |= WITNESS_DESCENDANT;
2029 w_data[i].w_num_descendants++;
2030 w_data[j].w_num_ancestors++;
2031
2032 /*
2033 * Make sure we aren't marking a node as both an
2034 * ancestor and descendant. We should have caught
2035 * this as a lock order reversal earlier.
2036 */
2037 if ((w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) &&
2038 (w_rmatrix[i][j] & WITNESS_DESCENDANT_MASK)) {
2039 printf("witness rmatrix paradox! [%d][%d]=%d "
2040 "both ancestor and descendant\n",
2041 i, j, w_rmatrix[i][j]);
2042 kdb_backtrace();
2043 printf("Witness disabled.\n");
2044 witness_watch = -1;
2045 }
2046 if ((w_rmatrix[j][i] & WITNESS_ANCESTOR_MASK) &&
2047 (w_rmatrix[j][i] & WITNESS_DESCENDANT_MASK)) {
2048 printf("witness rmatrix paradox! [%d][%d]=%d "
2049 "both ancestor and descendant\n",
2050 j, i, w_rmatrix[j][i]);
2051 kdb_backtrace();
2052 printf("Witness disabled.\n");
2053 witness_watch = -1;
2054 }
2055 }
2056 }
2057 }
2058
2059 static void
2060 itismychild(struct witness *parent, struct witness *child)
2061 {
2062 int unlocked;
2063
2064 MPASS(child != NULL && parent != NULL);
2065 if (witness_cold == 0)
2066 mtx_assert(&w_mtx, MA_OWNED);
2067
2068 if (!witness_lock_type_equal(parent, child)) {
2069 if (witness_cold == 0) {
2070 unlocked = 1;
2071 mtx_unlock_spin(&w_mtx);
2072 } else {
2073 unlocked = 0;
2074 }
2075 kassert_panic(
2076 "%s: parent \"%s\" (%s) and child \"%s\" (%s) are not "
2077 "the same lock type", __func__, parent->w_name,
2078 parent->w_class->lc_name, child->w_name,
2079 child->w_class->lc_name);
2080 if (unlocked)
2081 mtx_lock_spin(&w_mtx);
2082 }
2083 adopt(parent, child);
2084 }
2085
2086 /*
2087 * Generic code for the isitmy*() functions. The rmask parameter is the
2088 * expected relationship of w1 to w2.
2089 */
2090 static int
2091 _isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname)
2092 {
2093 unsigned char r1, r2;
2094 int i1, i2;
2095
2096 i1 = w1->w_index;
2097 i2 = w2->w_index;
2098 WITNESS_INDEX_ASSERT(i1);
2099 WITNESS_INDEX_ASSERT(i2);
2100 r1 = w_rmatrix[i1][i2] & WITNESS_RELATED_MASK;
2101 r2 = w_rmatrix[i2][i1] & WITNESS_RELATED_MASK;
2102
2103 /* The flags on one better be the inverse of the flags on the other */
2104 if (!((WITNESS_ATOD(r1) == r2 && WITNESS_DTOA(r2) == r1) ||
2105 (WITNESS_DTOA(r1) == r2 && WITNESS_ATOD(r2) == r1))) {
2106 /* Don't squawk if we're potentially racing with an update. */
2107 if (!mtx_owned(&w_mtx))
2108 return (0);
2109 printf("%s: rmatrix mismatch between %s (index %d) and %s "
2110 "(index %d): w_rmatrix[%d][%d] == %hhx but "
2111 "w_rmatrix[%d][%d] == %hhx\n",
2112 fname, w1->w_name, i1, w2->w_name, i2, i1, i2, r1,
2113 i2, i1, r2);
2114 kdb_backtrace();
2115 printf("Witness disabled.\n");
2116 witness_watch = -1;
2117 }
2118 return (r1 & rmask);
2119 }
2120
2121 /*
2122 * Checks if @child is a direct child of @parent.
2123 */
2124 static int
2125 isitmychild(struct witness *parent, struct witness *child)
2126 {
2127
2128 return (_isitmyx(parent, child, WITNESS_PARENT, __func__));
2129 }
2130
2131 /*
2132 * Checks if @descendant is a direct or inderect descendant of @ancestor.
2133 */
2134 static int
2135 isitmydescendant(struct witness *ancestor, struct witness *descendant)
2136 {
2137
2138 return (_isitmyx(ancestor, descendant, WITNESS_ANCESTOR_MASK,
2139 __func__));
2140 }
2141
2142 static int
2143 blessed(struct witness *w1, struct witness *w2)
2144 {
2145 int i;
2146 struct witness_blessed *b;
2147
2148 for (i = 0; i < nitems(blessed_list); i++) {
2149 b = &blessed_list[i];
2150 if (strcmp(w1->w_name, b->b_lock1) == 0) {
2151 if (strcmp(w2->w_name, b->b_lock2) == 0)
2152 return (1);
2153 continue;
2154 }
2155 if (strcmp(w1->w_name, b->b_lock2) == 0)
2156 if (strcmp(w2->w_name, b->b_lock1) == 0)
2157 return (1);
2158 }
2159 return (0);
2160 }
2161
2162 static struct witness *
2163 witness_get(void)
2164 {
2165 struct witness *w;
2166 int index;
2167
2168 if (witness_cold == 0)
2169 mtx_assert(&w_mtx, MA_OWNED);
2170
2171 if (witness_watch == -1) {
2172 mtx_unlock_spin(&w_mtx);
2173 return (NULL);
2174 }
2175 if (STAILQ_EMPTY(&w_free)) {
2176 witness_watch = -1;
2177 mtx_unlock_spin(&w_mtx);
2178 printf("WITNESS: unable to allocate a new witness object\n");
2179 return (NULL);
2180 }
2181 w = STAILQ_FIRST(&w_free);
2182 STAILQ_REMOVE_HEAD(&w_free, w_list);
2183 w_free_cnt--;
2184 index = w->w_index;
2185 MPASS(index > 0 && index == w_max_used_index+1 &&
2186 index < witness_count);
2187 bzero(w, sizeof(*w));
2188 w->w_index = index;
2189 if (index > w_max_used_index)
2190 w_max_used_index = index;
2191 return (w);
2192 }
2193
2194 static void
2195 witness_free(struct witness *w)
2196 {
2197
2198 STAILQ_INSERT_HEAD(&w_free, w, w_list);
2199 w_free_cnt++;
2200 }
2201
2202 static struct lock_list_entry *
2203 witness_lock_list_get(void)
2204 {
2205 struct lock_list_entry *lle;
2206
2207 if (witness_watch == -1)
2208 return (NULL);
2209 mtx_lock_spin(&w_mtx);
2210 lle = w_lock_list_free;
2211 if (lle == NULL) {
2212 witness_watch = -1;
2213 mtx_unlock_spin(&w_mtx);
2214 printf("%s: witness exhausted\n", __func__);
2215 return (NULL);
2216 }
2217 w_lock_list_free = lle->ll_next;
2218 mtx_unlock_spin(&w_mtx);
2219 bzero(lle, sizeof(*lle));
2220 return (lle);
2221 }
2222
2223 static void
2224 witness_lock_list_free(struct lock_list_entry *lle)
2225 {
2226
2227 mtx_lock_spin(&w_mtx);
2228 lle->ll_next = w_lock_list_free;
2229 w_lock_list_free = lle;
2230 mtx_unlock_spin(&w_mtx);
2231 }
2232
2233 static struct lock_instance *
2234 find_instance(struct lock_list_entry *list, const struct lock_object *lock)
2235 {
2236 struct lock_list_entry *lle;
2237 struct lock_instance *instance;
2238 int i;
2239
2240 for (lle = list; lle != NULL; lle = lle->ll_next)
2241 for (i = lle->ll_count - 1; i >= 0; i--) {
2242 instance = &lle->ll_children[i];
2243 if (instance->li_lock == lock)
2244 return (instance);
2245 }
2246 return (NULL);
2247 }
2248
2249 static void
2250 witness_list_lock(struct lock_instance *instance,
2251 int (*prnt)(const char *fmt, ...))
2252 {
2253 struct lock_object *lock;
2254
2255 lock = instance->li_lock;
2256 prnt("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ?
2257 "exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name);
2258 if (lock->lo_witness->w_name != lock->lo_name)
2259 prnt(" (%s)", lock->lo_witness->w_name);
2260 prnt(" r = %d (%p) locked @ %s:%d\n",
2261 instance->li_flags & LI_RECURSEMASK, lock,
2262 fixup_filename(instance->li_file), instance->li_line);
2263 }
2264
2265 static int
2266 witness_output(const char *fmt, ...)
2267 {
2268 va_list ap;
2269 int ret;
2270
2271 va_start(ap, fmt);
2272 ret = witness_voutput(fmt, ap);
2273 va_end(ap);
2274 return (ret);
2275 }
2276
2277 static int
2278 witness_voutput(const char *fmt, va_list ap)
2279 {
2280 int ret;
2281
2282 ret = 0;
2283 switch (witness_channel) {
2284 case WITNESS_CONSOLE:
2285 ret = vprintf(fmt, ap);
2286 break;
2287 case WITNESS_LOG:
2288 vlog(LOG_NOTICE, fmt, ap);
2289 break;
2290 case WITNESS_NONE:
2291 break;
2292 }
2293 return (ret);
2294 }
2295
2296 #ifdef DDB
2297 static int
2298 witness_thread_has_locks(struct thread *td)
2299 {
2300
2301 if (td->td_sleeplocks == NULL)
2302 return (0);
2303 return (td->td_sleeplocks->ll_count != 0);
2304 }
2305
2306 static int
2307 witness_proc_has_locks(struct proc *p)
2308 {
2309 struct thread *td;
2310
2311 FOREACH_THREAD_IN_PROC(p, td) {
2312 if (witness_thread_has_locks(td))
2313 return (1);
2314 }
2315 return (0);
2316 }
2317 #endif
2318
2319 int
2320 witness_list_locks(struct lock_list_entry **lock_list,
2321 int (*prnt)(const char *fmt, ...))
2322 {
2323 struct lock_list_entry *lle;
2324 int i, nheld;
2325
2326 nheld = 0;
2327 for (lle = *lock_list; lle != NULL; lle = lle->ll_next)
2328 for (i = lle->ll_count - 1; i >= 0; i--) {
2329 witness_list_lock(&lle->ll_children[i], prnt);
2330 nheld++;
2331 }
2332 return (nheld);
2333 }
2334
2335 /*
2336 * This is a bit risky at best. We call this function when we have timed
2337 * out acquiring a spin lock, and we assume that the other CPU is stuck
2338 * with this lock held. So, we go groveling around in the other CPU's
2339 * per-cpu data to try to find the lock instance for this spin lock to
2340 * see when it was last acquired.
2341 */
2342 void
2343 witness_display_spinlock(struct lock_object *lock, struct thread *owner,
2344 int (*prnt)(const char *fmt, ...))
2345 {
2346 struct lock_instance *instance;
2347 struct pcpu *pc;
2348
2349 if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU)
2350 return;
2351 pc = pcpu_find(owner->td_oncpu);
2352 instance = find_instance(pc->pc_spinlocks, lock);
2353 if (instance != NULL)
2354 witness_list_lock(instance, prnt);
2355 }
2356
2357 void
2358 witness_save(struct lock_object *lock, const char **filep, int *linep)
2359 {
2360 struct lock_list_entry *lock_list;
2361 struct lock_instance *instance;
2362 struct lock_class *class;
2363
2364 /*
2365 * This function is used independently in locking code to deal with
2366 * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
2367 * is gone.
2368 */
2369 if (SCHEDULER_STOPPED())
2370 return;
2371 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
2372 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED())
2373 return;
2374 class = LOCK_CLASS(lock);
2375 if (class->lc_flags & LC_SLEEPLOCK)
2376 lock_list = curthread->td_sleeplocks;
2377 else {
2378 if (witness_skipspin)
2379 return;
2380 lock_list = PCPU_GET(spinlocks);
2381 }
2382 instance = find_instance(lock_list, lock);
2383 if (instance == NULL) {
2384 kassert_panic("%s: lock (%s) %s not locked", __func__,
2385 class->lc_name, lock->lo_name);
2386 return;
2387 }
2388 *filep = instance->li_file;
2389 *linep = instance->li_line;
2390 }
2391
2392 void
2393 witness_restore(struct lock_object *lock, const char *file, int line)
2394 {
2395 struct lock_list_entry *lock_list;
2396 struct lock_instance *instance;
2397 struct lock_class *class;
2398
2399 /*
2400 * This function is used independently in locking code to deal with
2401 * Giant, SCHEDULER_STOPPED() check can be removed here after Giant
2402 * is gone.
2403 */
2404 if (SCHEDULER_STOPPED())
2405 return;
2406 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
2407 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED())
2408 return;
2409 class = LOCK_CLASS(lock);
2410 if (class->lc_flags & LC_SLEEPLOCK)
2411 lock_list = curthread->td_sleeplocks;
2412 else {
2413 if (witness_skipspin)
2414 return;
2415 lock_list = PCPU_GET(spinlocks);
2416 }
2417 instance = find_instance(lock_list, lock);
2418 if (instance == NULL)
2419 kassert_panic("%s: lock (%s) %s not locked", __func__,
2420 class->lc_name, lock->lo_name);
2421 lock->lo_witness->w_file = file;
2422 lock->lo_witness->w_line = line;
2423 if (instance == NULL)
2424 return;
2425 instance->li_file = file;
2426 instance->li_line = line;
2427 }
2428
2429 void
2430 witness_assert(const struct lock_object *lock, int flags, const char *file,
2431 int line)
2432 {
2433 #ifdef INVARIANT_SUPPORT
2434 struct lock_instance *instance;
2435 struct lock_class *class;
2436
2437 if (lock->lo_witness == NULL || witness_watch < 1 || KERNEL_PANICKED())
2438 return;
2439 class = LOCK_CLASS(lock);
2440 if ((class->lc_flags & LC_SLEEPLOCK) != 0)
2441 instance = find_instance(curthread->td_sleeplocks, lock);
2442 else if ((class->lc_flags & LC_SPINLOCK) != 0)
2443 instance = find_instance(PCPU_GET(spinlocks), lock);
2444 else {
2445 kassert_panic("Lock (%s) %s is not sleep or spin!",
2446 class->lc_name, lock->lo_name);
2447 return;
2448 }
2449 switch (flags) {
2450 case LA_UNLOCKED:
2451 if (instance != NULL)
2452 kassert_panic("Lock (%s) %s locked @ %s:%d.",
2453 class->lc_name, lock->lo_name,
2454 fixup_filename(file), line);
2455 break;
2456 case LA_LOCKED:
2457 case LA_LOCKED | LA_RECURSED:
2458 case LA_LOCKED | LA_NOTRECURSED:
2459 case LA_SLOCKED:
2460 case LA_SLOCKED | LA_RECURSED:
2461 case LA_SLOCKED | LA_NOTRECURSED:
2462 case LA_XLOCKED:
2463 case LA_XLOCKED | LA_RECURSED:
2464 case LA_XLOCKED | LA_NOTRECURSED:
2465 if (instance == NULL) {
2466 kassert_panic("Lock (%s) %s not locked @ %s:%d.",
2467 class->lc_name, lock->lo_name,
2468 fixup_filename(file), line);
2469 break;
2470 }
2471 if ((flags & LA_XLOCKED) != 0 &&
2472 (instance->li_flags & LI_EXCLUSIVE) == 0)
2473 kassert_panic(
2474 "Lock (%s) %s not exclusively locked @ %s:%d.",
2475 class->lc_name, lock->lo_name,
2476 fixup_filename(file), line);
2477 if ((flags & LA_SLOCKED) != 0 &&
2478 (instance->li_flags & LI_EXCLUSIVE) != 0)
2479 kassert_panic(
2480 "Lock (%s) %s exclusively locked @ %s:%d.",
2481 class->lc_name, lock->lo_name,
2482 fixup_filename(file), line);
2483 if ((flags & LA_RECURSED) != 0 &&
2484 (instance->li_flags & LI_RECURSEMASK) == 0)
2485 kassert_panic("Lock (%s) %s not recursed @ %s:%d.",
2486 class->lc_name, lock->lo_name,
2487 fixup_filename(file), line);
2488 if ((flags & LA_NOTRECURSED) != 0 &&
2489 (instance->li_flags & LI_RECURSEMASK) != 0)
2490 kassert_panic("Lock (%s) %s recursed @ %s:%d.",
2491 class->lc_name, lock->lo_name,
2492 fixup_filename(file), line);
2493 break;
2494 default:
2495 kassert_panic("Invalid lock assertion at %s:%d.",
2496 fixup_filename(file), line);
2497 }
2498 #endif /* INVARIANT_SUPPORT */
2499 }
2500
2501 static void
2502 witness_setflag(struct lock_object *lock, int flag, int set)
2503 {
2504 struct lock_list_entry *lock_list;
2505 struct lock_instance *instance;
2506 struct lock_class *class;
2507
2508 if (lock->lo_witness == NULL || witness_watch == -1 || KERNEL_PANICKED())
2509 return;
2510 class = LOCK_CLASS(lock);
2511 if (class->lc_flags & LC_SLEEPLOCK)
2512 lock_list = curthread->td_sleeplocks;
2513 else {
2514 if (witness_skipspin)
2515 return;
2516 lock_list = PCPU_GET(spinlocks);
2517 }
2518 instance = find_instance(lock_list, lock);
2519 if (instance == NULL) {
2520 kassert_panic("%s: lock (%s) %s not locked", __func__,
2521 class->lc_name, lock->lo_name);
2522 return;
2523 }
2524
2525 if (set)
2526 instance->li_flags |= flag;
2527 else
2528 instance->li_flags &= ~flag;
2529 }
2530
2531 void
2532 witness_norelease(struct lock_object *lock)
2533 {
2534
2535 witness_setflag(lock, LI_NORELEASE, 1);
2536 }
2537
2538 void
2539 witness_releaseok(struct lock_object *lock)
2540 {
2541
2542 witness_setflag(lock, LI_NORELEASE, 0);
2543 }
2544
2545 #ifdef DDB
2546 static void
2547 witness_ddb_list(struct thread *td)
2548 {
2549
2550 KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
2551 KASSERT(kdb_active, ("%s: not in the debugger", __func__));
2552
2553 if (witness_watch < 1)
2554 return;
2555
2556 witness_list_locks(&td->td_sleeplocks, db_printf);
2557
2558 /*
2559 * We only handle spinlocks if td == curthread. This is somewhat broken
2560 * if td is currently executing on some other CPU and holds spin locks
2561 * as we won't display those locks. If we had a MI way of getting
2562 * the per-cpu data for a given cpu then we could use
2563 * td->td_oncpu to get the list of spinlocks for this thread
2564 * and "fix" this.
2565 *
2566 * That still wouldn't really fix this unless we locked the scheduler
2567 * lock or stopped the other CPU to make sure it wasn't changing the
2568 * list out from under us. It is probably best to just not try to
2569 * handle threads on other CPU's for now.
2570 */
2571 if (td == curthread && PCPU_GET(spinlocks) != NULL)
2572 witness_list_locks(PCPU_PTR(spinlocks), db_printf);
2573 }
2574
2575 DB_SHOW_COMMAND(locks, db_witness_list)
2576 {
2577 struct thread *td;
2578
2579 if (have_addr)
2580 td = db_lookup_thread(addr, true);
2581 else
2582 td = kdb_thread;
2583 witness_ddb_list(td);
2584 }
2585
2586 DB_SHOW_ALL_COMMAND(locks, db_witness_list_all)
2587 {
2588 struct thread *td;
2589 struct proc *p;
2590
2591 /*
2592 * It would be nice to list only threads and processes that actually
2593 * held sleep locks, but that information is currently not exported
2594 * by WITNESS.
2595 */
2596 FOREACH_PROC_IN_SYSTEM(p) {
2597 if (!witness_proc_has_locks(p))
2598 continue;
2599 FOREACH_THREAD_IN_PROC(p, td) {
2600 if (!witness_thread_has_locks(td))
2601 continue;
2602 db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid,
2603 p->p_comm, td, td->td_tid);
2604 witness_ddb_list(td);
2605 if (db_pager_quit)
2606 return;
2607 }
2608 }
2609 }
2610 DB_SHOW_ALIAS(alllocks, db_witness_list_all)
2611
2612 DB_SHOW_COMMAND(witness, db_witness_display)
2613 {
2614
2615 witness_ddb_display(db_printf);
2616 }
2617 #endif
2618
2619 static void
2620 sbuf_print_witness_badstacks(struct sbuf *sb, size_t *oldidx)
2621 {
2622 struct witness_lock_order_data *data1, *data2, *tmp_data1, *tmp_data2;
2623 struct witness *tmp_w1, *tmp_w2, *w1, *w2;
2624 int generation, i, j;
2625
2626 tmp_data1 = NULL;
2627 tmp_data2 = NULL;
2628 tmp_w1 = NULL;
2629 tmp_w2 = NULL;
2630
2631 /* Allocate and init temporary storage space. */
2632 tmp_w1 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
2633 tmp_w2 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
2634 tmp_data1 = malloc(sizeof(struct witness_lock_order_data), M_TEMP,
2635 M_WAITOK | M_ZERO);
2636 tmp_data2 = malloc(sizeof(struct witness_lock_order_data), M_TEMP,
2637 M_WAITOK | M_ZERO);
2638 stack_zero(&tmp_data1->wlod_stack);
2639 stack_zero(&tmp_data2->wlod_stack);
2640
2641 restart:
2642 mtx_lock_spin(&w_mtx);
2643 generation = w_generation;
2644 mtx_unlock_spin(&w_mtx);
2645 sbuf_printf(sb, "Number of known direct relationships is %d\n",
2646 w_lohash.wloh_count);
2647 for (i = 1; i < w_max_used_index; i++) {
2648 mtx_lock_spin(&w_mtx);
2649 if (generation != w_generation) {
2650 mtx_unlock_spin(&w_mtx);
2651
2652 /* The graph has changed, try again. */
2653 *oldidx = 0;
2654 sbuf_clear(sb);
2655 goto restart;
2656 }
2657
2658 w1 = &w_data[i];
2659 if (w1->w_reversed == 0) {
2660 mtx_unlock_spin(&w_mtx);
2661 continue;
2662 }
2663
2664 /* Copy w1 locally so we can release the spin lock. */
2665 *tmp_w1 = *w1;
2666 mtx_unlock_spin(&w_mtx);
2667
2668 if (tmp_w1->w_reversed == 0)
2669 continue;
2670 for (j = 1; j < w_max_used_index; j++) {
2671 if ((w_rmatrix[i][j] & WITNESS_REVERSAL) == 0 || i > j)
2672 continue;
2673
2674 mtx_lock_spin(&w_mtx);
2675 if (generation != w_generation) {
2676 mtx_unlock_spin(&w_mtx);
2677
2678 /* The graph has changed, try again. */
2679 *oldidx = 0;
2680 sbuf_clear(sb);
2681 goto restart;
2682 }
2683
2684 w2 = &w_data[j];
2685 data1 = witness_lock_order_get(w1, w2);
2686 data2 = witness_lock_order_get(w2, w1);
2687
2688 /*
2689 * Copy information locally so we can release the
2690 * spin lock.
2691 */
2692 *tmp_w2 = *w2;
2693
2694 if (data1) {
2695 stack_zero(&tmp_data1->wlod_stack);
2696 stack_copy(&data1->wlod_stack,
2697 &tmp_data1->wlod_stack);
2698 }
2699 if (data2 && data2 != data1) {
2700 stack_zero(&tmp_data2->wlod_stack);
2701 stack_copy(&data2->wlod_stack,
2702 &tmp_data2->wlod_stack);
2703 }
2704 mtx_unlock_spin(&w_mtx);
2705
2706 if (blessed(tmp_w1, tmp_w2))
2707 continue;
2708
2709 sbuf_printf(sb,
2710 "\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n",
2711 tmp_w1->w_name, tmp_w1->w_class->lc_name,
2712 tmp_w2->w_name, tmp_w2->w_class->lc_name);
2713 if (data1) {
2714 sbuf_printf(sb,
2715 "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
2716 tmp_w1->w_name, tmp_w1->w_class->lc_name,
2717 tmp_w2->w_name, tmp_w2->w_class->lc_name);
2718 stack_sbuf_print(sb, &tmp_data1->wlod_stack);
2719 sbuf_printf(sb, "\n");
2720 }
2721 if (data2 && data2 != data1) {
2722 sbuf_printf(sb,
2723 "Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
2724 tmp_w2->w_name, tmp_w2->w_class->lc_name,
2725 tmp_w1->w_name, tmp_w1->w_class->lc_name);
2726 stack_sbuf_print(sb, &tmp_data2->wlod_stack);
2727 sbuf_printf(sb, "\n");
2728 }
2729 }
2730 }
2731 mtx_lock_spin(&w_mtx);
2732 if (generation != w_generation) {
2733 mtx_unlock_spin(&w_mtx);
2734
2735 /*
2736 * The graph changed while we were printing stack data,
2737 * try again.
2738 */
2739 *oldidx = 0;
2740 sbuf_clear(sb);
2741 goto restart;
2742 }
2743 mtx_unlock_spin(&w_mtx);
2744
2745 /* Free temporary storage space. */
2746 free(tmp_data1, M_TEMP);
2747 free(tmp_data2, M_TEMP);
2748 free(tmp_w1, M_TEMP);
2749 free(tmp_w2, M_TEMP);
2750 }
2751
2752 static int
2753 sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS)
2754 {
2755 struct sbuf *sb;
2756 int error;
2757
2758 if (witness_watch < 1) {
2759 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
2760 return (error);
2761 }
2762 if (witness_cold) {
2763 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
2764 return (error);
2765 }
2766 error = 0;
2767 sb = sbuf_new(NULL, NULL, badstack_sbuf_size, SBUF_AUTOEXTEND);
2768 if (sb == NULL)
2769 return (ENOMEM);
2770
2771 sbuf_print_witness_badstacks(sb, &req->oldidx);
2772
2773 sbuf_finish(sb);
2774 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
2775 sbuf_delete(sb);
2776
2777 return (error);
2778 }
2779
2780 #ifdef DDB
2781 static int
2782 sbuf_db_printf_drain(void *arg __unused, const char *data, int len)
2783 {
2784
2785 return (db_printf("%.*s", len, data));
2786 }
2787
2788 DB_SHOW_COMMAND(badstacks, db_witness_badstacks)
2789 {
2790 struct sbuf sb;
2791 char buffer[128];
2792 size_t dummy;
2793
2794 sbuf_new(&sb, buffer, sizeof(buffer), SBUF_FIXEDLEN);
2795 sbuf_set_drain(&sb, sbuf_db_printf_drain, NULL);
2796 sbuf_print_witness_badstacks(&sb, &dummy);
2797 sbuf_finish(&sb);
2798 }
2799 #endif
2800
2801 static int
2802 sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS)
2803 {
2804 static const struct {
2805 enum witness_channel channel;
2806 const char *name;
2807 } channels[] = {
2808 { WITNESS_CONSOLE, "console" },
2809 { WITNESS_LOG, "log" },
2810 { WITNESS_NONE, "none" },
2811 };
2812 char buf[16];
2813 u_int i;
2814 int error;
2815
2816 buf[0] = '\0';
2817 for (i = 0; i < nitems(channels); i++)
2818 if (witness_channel == channels[i].channel) {
2819 snprintf(buf, sizeof(buf), "%s", channels[i].name);
2820 break;
2821 }
2822
2823 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
2824 if (error != 0 || req->newptr == NULL)
2825 return (error);
2826
2827 error = EINVAL;
2828 for (i = 0; i < nitems(channels); i++)
2829 if (strcmp(channels[i].name, buf) == 0) {
2830 witness_channel = channels[i].channel;
2831 error = 0;
2832 break;
2833 }
2834 return (error);
2835 }
2836
2837 static int
2838 sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS)
2839 {
2840 struct witness *w;
2841 struct sbuf *sb;
2842 int error;
2843
2844 #ifdef __i386__
2845 error = SYSCTL_OUT(req, w_notallowed, sizeof(w_notallowed));
2846 return (error);
2847 #endif
2848
2849 if (witness_watch < 1) {
2850 error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
2851 return (error);
2852 }
2853 if (witness_cold) {
2854 error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
2855 return (error);
2856 }
2857 error = 0;
2858
2859 error = sysctl_wire_old_buffer(req, 0);
2860 if (error != 0)
2861 return (error);
2862 sb = sbuf_new_for_sysctl(NULL, NULL, FULLGRAPH_SBUF_SIZE, req);
2863 if (sb == NULL)
2864 return (ENOMEM);
2865 sbuf_printf(sb, "\n");
2866
2867 mtx_lock_spin(&w_mtx);
2868 STAILQ_FOREACH(w, &w_all, w_list)
2869 w->w_displayed = 0;
2870 STAILQ_FOREACH(w, &w_all, w_list)
2871 witness_add_fullgraph(sb, w);
2872 mtx_unlock_spin(&w_mtx);
2873
2874 /*
2875 * Close the sbuf and return to userland.
2876 */
2877 error = sbuf_finish(sb);
2878 sbuf_delete(sb);
2879
2880 return (error);
2881 }
2882
2883 static int
2884 sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS)
2885 {
2886 int error, value;
2887
2888 value = witness_watch;
2889 error = sysctl_handle_int(oidp, &value, 0, req);
2890 if (error != 0 || req->newptr == NULL)
2891 return (error);
2892 if (value > 1 || value < -1 ||
2893 (witness_watch == -1 && value != witness_watch))
2894 return (EINVAL);
2895 witness_watch = value;
2896 return (0);
2897 }
2898
2899 static void
2900 witness_add_fullgraph(struct sbuf *sb, struct witness *w)
2901 {
2902 int i;
2903
2904 if (w->w_displayed != 0 || (w->w_file == NULL && w->w_line == 0))
2905 return;
2906 w->w_displayed = 1;
2907
2908 WITNESS_INDEX_ASSERT(w->w_index);
2909 for (i = 1; i <= w_max_used_index; i++) {
2910 if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) {
2911 sbuf_printf(sb, "\"%s\",\"%s\"\n", w->w_name,
2912 w_data[i].w_name);
2913 witness_add_fullgraph(sb, &w_data[i]);
2914 }
2915 }
2916 }
2917
2918 /*
2919 * A simple hash function. Takes a key pointer and a key size. If size == 0,
2920 * interprets the key as a string and reads until the null
2921 * terminator. Otherwise, reads the first size bytes. Returns an unsigned 32-bit
2922 * hash value computed from the key.
2923 */
2924 static uint32_t
2925 witness_hash_djb2(const uint8_t *key, uint32_t size)
2926 {
2927 unsigned int hash = 5381;
2928 int i;
2929
2930 /* hash = hash * 33 + key[i] */
2931 if (size)
2932 for (i = 0; i < size; i++)
2933 hash = ((hash << 5) + hash) + (unsigned int)key[i];
2934 else
2935 for (i = 0; key[i] != 0; i++)
2936 hash = ((hash << 5) + hash) + (unsigned int)key[i];
2937
2938 return (hash);
2939 }
2940
2941 /*
2942 * Initializes the two witness hash tables. Called exactly once from
2943 * witness_initialize().
2944 */
2945 static void
2946 witness_init_hash_tables(void)
2947 {
2948 int i;
2949
2950 MPASS(witness_cold);
2951
2952 /* Initialize the hash tables. */
2953 for (i = 0; i < WITNESS_HASH_SIZE; i++)
2954 w_hash.wh_array[i] = NULL;
2955
2956 w_hash.wh_size = WITNESS_HASH_SIZE;
2957 w_hash.wh_count = 0;
2958
2959 /* Initialize the lock order data hash. */
2960 w_lofree = NULL;
2961 for (i = 0; i < WITNESS_LO_DATA_COUNT; i++) {
2962 memset(&w_lodata[i], 0, sizeof(w_lodata[i]));
2963 w_lodata[i].wlod_next = w_lofree;
2964 w_lofree = &w_lodata[i];
2965 }
2966 w_lohash.wloh_size = WITNESS_LO_HASH_SIZE;
2967 w_lohash.wloh_count = 0;
2968 for (i = 0; i < WITNESS_LO_HASH_SIZE; i++)
2969 w_lohash.wloh_array[i] = NULL;
2970 }
2971
2972 static struct witness *
2973 witness_hash_get(const char *key)
2974 {
2975 struct witness *w;
2976 uint32_t hash;
2977
2978 MPASS(key != NULL);
2979 if (witness_cold == 0)
2980 mtx_assert(&w_mtx, MA_OWNED);
2981 hash = witness_hash_djb2(key, 0) % w_hash.wh_size;
2982 w = w_hash.wh_array[hash];
2983 while (w != NULL) {
2984 if (strcmp(w->w_name, key) == 0)
2985 goto out;
2986 w = w->w_hash_next;
2987 }
2988
2989 out:
2990 return (w);
2991 }
2992
2993 static void
2994 witness_hash_put(struct witness *w)
2995 {
2996 uint32_t hash;
2997
2998 MPASS(w != NULL);
2999 MPASS(w->w_name != NULL);
3000 if (witness_cold == 0)
3001 mtx_assert(&w_mtx, MA_OWNED);
3002 KASSERT(witness_hash_get(w->w_name) == NULL,
3003 ("%s: trying to add a hash entry that already exists!", __func__));
3004 KASSERT(w->w_hash_next == NULL,
3005 ("%s: w->w_hash_next != NULL", __func__));
3006
3007 hash = witness_hash_djb2(w->w_name, 0) % w_hash.wh_size;
3008 w->w_hash_next = w_hash.wh_array[hash];
3009 w_hash.wh_array[hash] = w;
3010 w_hash.wh_count++;
3011 }
3012
3013 static struct witness_lock_order_data *
3014 witness_lock_order_get(struct witness *parent, struct witness *child)
3015 {
3016 struct witness_lock_order_data *data = NULL;
3017 struct witness_lock_order_key key;
3018 unsigned int hash;
3019
3020 MPASS(parent != NULL && child != NULL);
3021 key.from = parent->w_index;
3022 key.to = child->w_index;
3023 WITNESS_INDEX_ASSERT(key.from);
3024 WITNESS_INDEX_ASSERT(key.to);
3025 if ((w_rmatrix[parent->w_index][child->w_index]
3026 & WITNESS_LOCK_ORDER_KNOWN) == 0)
3027 goto out;
3028
3029 hash = witness_hash_djb2((const char*)&key,
3030 sizeof(key)) % w_lohash.wloh_size;
3031 data = w_lohash.wloh_array[hash];
3032 while (data != NULL) {
3033 if (witness_lock_order_key_equal(&data->wlod_key, &key))
3034 break;
3035 data = data->wlod_next;
3036 }
3037
3038 out:
3039 return (data);
3040 }
3041
3042 /*
3043 * Verify that parent and child have a known relationship, are not the same,
3044 * and child is actually a child of parent. This is done without w_mtx
3045 * to avoid contention in the common case.
3046 */
3047 static int
3048 witness_lock_order_check(struct witness *parent, struct witness *child)
3049 {
3050
3051 if (parent != child &&
3052 w_rmatrix[parent->w_index][child->w_index]
3053 & WITNESS_LOCK_ORDER_KNOWN &&
3054 isitmychild(parent, child))
3055 return (1);
3056
3057 return (0);
3058 }
3059
3060 static int
3061 witness_lock_order_add(struct witness *parent, struct witness *child)
3062 {
3063 struct witness_lock_order_data *data = NULL;
3064 struct witness_lock_order_key key;
3065 unsigned int hash;
3066
3067 MPASS(parent != NULL && child != NULL);
3068 key.from = parent->w_index;
3069 key.to = child->w_index;
3070 WITNESS_INDEX_ASSERT(key.from);
3071 WITNESS_INDEX_ASSERT(key.to);
3072 if (w_rmatrix[parent->w_index][child->w_index]
3073 & WITNESS_LOCK_ORDER_KNOWN)
3074 return (1);
3075
3076 hash = witness_hash_djb2((const char*)&key,
3077 sizeof(key)) % w_lohash.wloh_size;
3078 w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN;
3079 data = w_lofree;
3080 if (data == NULL)
3081 return (0);
3082 w_lofree = data->wlod_next;
3083 data->wlod_next = w_lohash.wloh_array[hash];
3084 data->wlod_key = key;
3085 w_lohash.wloh_array[hash] = data;
3086 w_lohash.wloh_count++;
3087 stack_zero(&data->wlod_stack);
3088 stack_save(&data->wlod_stack);
3089 return (1);
3090 }
3091
3092 /* Call this whenever the structure of the witness graph changes. */
3093 static void
3094 witness_increment_graph_generation(void)
3095 {
3096
3097 if (witness_cold == 0)
3098 mtx_assert(&w_mtx, MA_OWNED);
3099 w_generation++;
3100 }
3101
3102 static int
3103 witness_output_drain(void *arg __unused, const char *data, int len)
3104 {
3105
3106 witness_output("%.*s", len, data);
3107 return (len);
3108 }
3109
3110 static void
3111 witness_debugger(int cond, const char *msg)
3112 {
3113 char buf[32];
3114 struct sbuf sb;
3115 struct stack st;
3116
3117 if (!cond)
3118 return;
3119
3120 if (witness_trace) {
3121 sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN);
3122 sbuf_set_drain(&sb, witness_output_drain, NULL);
3123
3124 stack_zero(&st);
3125 stack_save(&st);
3126 witness_output("stack backtrace:\n");
3127 stack_sbuf_print_ddb(&sb, &st);
3128
3129 sbuf_finish(&sb);
3130 }
3131
3132 witness_enter_debugger(msg);
3133 }
3134
3135 static void
3136 witness_enter_debugger(const char *msg)
3137 {
3138 #ifdef KDB
3139 if (witness_kdb)
3140 kdb_enter(KDB_WHY_WITNESS, msg);
3141 #endif
3142 }
Cache object: 661878e35da75d90120874cbb67fbbf1
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