1 /*-
2 * See the file LICENSE for redistribution information.
3 *
4 * Copyright (c) 1996, 1997, 1998
5 * Sleepycat Software. All rights reserved.
6 */
7
8 #include "config.h"
9
10 #ifndef lint
11 static const char sccsid[] = "@(#)lock_deadlock.c 10.37 (Sleepycat) 10/4/98";
12 #endif /* not lint */
13
14 #ifndef NO_SYSTEM_INCLUDES
15 #include <sys/types.h>
16
17 #include <errno.h>
18 #include <string.h>
19 #endif
20
21 #include "db_int.h"
22 #include "shqueue.h"
23 #include "db_shash.h"
24 #include "lock.h"
25 #include "common_ext.h"
26
27 #define ISSET_MAP(M, N) (M[(N) / 32] & (1 << (N) % 32))
28
29 #define CLEAR_MAP(M, N) { \
30 u_int32_t __i; \
31 for (__i = 0; __i < (N); __i++) \
32 M[__i] = 0; \
33 }
34
35 #define SET_MAP(M, B) (M[(B) / 32] |= (1 << ((B) % 32)))
36 #define CLR_MAP(M, B) (M[(B) / 32] &= ~(1 << ((B) % 32)))
37
38 #define OR_MAP(D, S, N) { \
39 u_int32_t __i; \
40 for (__i = 0; __i < (N); __i++) \
41 D[__i] |= S[__i]; \
42 }
43 #define BAD_KILLID 0xffffffff
44
45 typedef struct {
46 int valid;
47 u_int32_t id;
48 DB_LOCK last_lock;
49 db_pgno_t pgno;
50 } locker_info;
51
52 static int __dd_abort __P((DB_ENV *, locker_info *));
53 static int __dd_build
54 __P((DB_ENV *, u_int32_t **, u_int32_t *, locker_info **));
55 static u_int32_t
56 *__dd_find __P((u_int32_t *, locker_info *, u_int32_t));
57
58 #ifdef DIAGNOSTIC
59 static void __dd_debug __P((DB_ENV *, locker_info *, u_int32_t *, u_int32_t));
60 #endif
61
62 int
lock_detect(lt,flags,atype)63 lock_detect(lt, flags, atype)
64 DB_LOCKTAB *lt;
65 u_int32_t flags, atype;
66 {
67 DB_ENV *dbenv;
68 locker_info *idmap;
69 u_int32_t *bitmap, *deadlock, i, killid, nentries, nlockers;
70 int do_pass, ret;
71
72 LOCK_PANIC_CHECK(lt);
73
74 /* Validate arguments. */
75 if ((ret =
76 __db_fchk(lt->dbenv, "lock_detect", flags, DB_LOCK_CONFLICT)) != 0)
77 return (ret);
78
79 /* Check if a detector run is necessary. */
80 dbenv = lt->dbenv;
81 if (LF_ISSET(DB_LOCK_CONFLICT)) {
82 /* Make a pass every time a lock waits. */
83 LOCK_LOCKREGION(lt);
84 do_pass = dbenv->lk_info->region->need_dd != 0;
85 UNLOCK_LOCKREGION(lt);
86
87 if (!do_pass)
88 return (0);
89 }
90
91 /* Build the waits-for bitmap. */
92 if ((ret = __dd_build(dbenv, &bitmap, &nlockers, &idmap)) != 0)
93 return (ret);
94
95 if (nlockers == 0)
96 return (0);
97 #ifdef DIAGNOSTIC
98 if (dbenv->db_verbose != 0)
99 __dd_debug(dbenv, idmap, bitmap, nlockers);
100 #endif
101 /* Find a deadlock. */
102 deadlock = __dd_find(bitmap, idmap, nlockers);
103 nentries = ALIGN(nlockers, 32) / 32;
104 killid = BAD_KILLID;
105 if (deadlock != NULL) {
106 /* Kill someone. */
107 switch (atype) {
108 case DB_LOCK_OLDEST:
109 /*
110 * Find the first bit set in the current
111 * array and then look for a lower tid in
112 * the array.
113 */
114 for (i = 0; i < nlockers; i++)
115 if (ISSET_MAP(deadlock, i))
116 killid = i;
117
118 if (killid == BAD_KILLID) {
119 __db_err(dbenv,
120 "warning: could not find locker to abort");
121 break;
122 }
123
124 /*
125 * The oldest transaction has the lowest
126 * transaction id.
127 */
128 for (i = killid + 1; i < nlockers; i++)
129 if (ISSET_MAP(deadlock, i) &&
130 idmap[i].id < idmap[killid].id)
131 killid = i;
132 break;
133 case DB_LOCK_DEFAULT:
134 case DB_LOCK_RANDOM:
135 /*
136 * We are trying to calculate the id of the
137 * locker whose entry is indicated by deadlock.
138 */
139 killid = (deadlock - bitmap) / nentries;
140 break;
141 case DB_LOCK_YOUNGEST:
142 /*
143 * Find the first bit set in the current
144 * array and then look for a lower tid in
145 * the array.
146 */
147 for (i = 0; i < nlockers; i++)
148 if (ISSET_MAP(deadlock, i))
149 killid = i;
150
151 if (killid == BAD_KILLID) {
152 __db_err(dbenv,
153 "warning: could not find locker to abort");
154 break;
155 }
156 /*
157 * The youngest transaction has the highest
158 * transaction id.
159 */
160 for (i = killid + 1; i < nlockers; i++)
161 if (ISSET_MAP(deadlock, i) &&
162 idmap[i].id > idmap[killid].id)
163 killid = i;
164 break;
165 default:
166 killid = BAD_KILLID;
167 ret = EINVAL;
168 }
169
170 /* Kill the locker with lockid idmap[killid]. */
171 if (dbenv->db_verbose != 0 && killid != BAD_KILLID)
172 __db_err(dbenv, "Aborting locker %lx",
173 (u_long)idmap[killid].id);
174
175 if (killid != BAD_KILLID &&
176 (ret = __dd_abort(dbenv, &idmap[killid])) != 0)
177 __db_err(dbenv,
178 "warning: unable to abort locker %lx",
179 (u_long)idmap[killid].id);
180 }
181 __os_free(bitmap, 0);
182 __os_free(idmap, 0);
183
184 return (ret);
185 }
186
187 /*
188 * ========================================================================
189 * Utilities
190 */
191 static int
__dd_build(dbenv,bmp,nlockers,idmap)192 __dd_build(dbenv, bmp, nlockers, idmap)
193 DB_ENV *dbenv;
194 u_int32_t **bmp, *nlockers;
195 locker_info **idmap;
196 {
197 struct __db_lock *lp;
198 DB_LOCKTAB *lt;
199 DB_LOCKOBJ *op, *lo, *lockerp;
200 u_int8_t *pptr;
201 locker_info *id_array;
202 u_int32_t *bitmap, count, *entryp, i, id, nentries, *tmpmap;
203 int is_first, ret;
204
205 lt = dbenv->lk_info;
206
207 /*
208 * We'll check how many lockers there are, add a few more in for
209 * good measure and then allocate all the structures. Then we'll
210 * verify that we have enough room when we go back in and get the
211 * mutex the second time.
212 */
213 LOCK_LOCKREGION(lt);
214 retry: count = lt->region->nlockers;
215 lt->region->need_dd = 0;
216 UNLOCK_LOCKREGION(lt);
217
218 if (count == 0) {
219 *nlockers = 0;
220 return (0);
221 }
222
223 if (dbenv->db_verbose)
224 __db_err(dbenv, "%lu lockers", (u_long)count);
225
226 count += 10;
227 nentries = ALIGN(count, 32) / 32;
228 /*
229 * Allocate enough space for a count by count bitmap matrix.
230 *
231 * XXX
232 * We can probably save the malloc's between iterations just
233 * reallocing if necessary because count grew by too much.
234 */
235 if ((ret = __os_calloc((size_t)count,
236 sizeof(u_int32_t) * nentries, &bitmap)) != 0)
237 return (ret);
238
239 if ((ret = __os_calloc(sizeof(u_int32_t), nentries, &tmpmap)) != 0) {
240 __os_free(bitmap, sizeof(u_int32_t) * nentries);
241 return (ret);
242 }
243
244 if ((ret =
245 __os_calloc((size_t)count, sizeof(locker_info), &id_array)) != 0) {
246 __os_free(bitmap, count * sizeof(u_int32_t) * nentries);
247 __os_free(tmpmap, sizeof(u_int32_t) * nentries);
248 return (ret);
249 }
250
251 /*
252 * Now go back in and actually fill in the matrix.
253 */
254 LOCK_LOCKREGION(lt);
255 if (lt->region->nlockers > count) {
256 __os_free(bitmap, count * sizeof(u_int32_t) * nentries);
257 __os_free(tmpmap, sizeof(u_int32_t) * nentries);
258 __os_free(id_array, count * sizeof(locker_info));
259 goto retry;
260 }
261
262 /*
263 * First we go through and assign each locker a deadlock detector id.
264 * Note that we fill in the idmap in the next loop since that's the
265 * only place where we conveniently have both the deadlock id and the
266 * actual locker.
267 */
268 for (id = 0, i = 0; i < lt->region->table_size; i++)
269 for (op = SH_TAILQ_FIRST(<->hashtab[i], __db_lockobj);
270 op != NULL; op = SH_TAILQ_NEXT(op, links, __db_lockobj))
271 if (op->type == DB_LOCK_LOCKER)
272 op->dd_id = id++;
273 /*
274 * We go through the hash table and find each object. For each object,
275 * we traverse the waiters list and add an entry in the waitsfor matrix
276 * for each waiter/holder combination.
277 */
278 for (i = 0; i < lt->region->table_size; i++) {
279 for (op = SH_TAILQ_FIRST(<->hashtab[i], __db_lockobj);
280 op != NULL; op = SH_TAILQ_NEXT(op, links, __db_lockobj)) {
281 if (op->type != DB_LOCK_OBJTYPE)
282 continue;
283 CLEAR_MAP(tmpmap, nentries);
284
285 /*
286 * First we go through and create a bit map that
287 * represents all the holders of this object.
288 */
289 for (lp = SH_TAILQ_FIRST(&op->holders, __db_lock);
290 lp != NULL;
291 lp = SH_TAILQ_NEXT(lp, links, __db_lock)) {
292 if (__lock_getobj(lt, lp->holder,
293 NULL, DB_LOCK_LOCKER, &lockerp) != 0) {
294 __db_err(dbenv,
295 "warning unable to find object");
296 continue;
297 }
298 id_array[lockerp->dd_id].id = lp->holder;
299 id_array[lockerp->dd_id].valid = 1;
300
301 /*
302 * If the holder has already been aborted, then
303 * we should ignore it for now.
304 */
305 if (lp->status == DB_LSTAT_HELD)
306 SET_MAP(tmpmap, lockerp->dd_id);
307 }
308
309 /*
310 * Next, for each waiter, we set its row in the matrix
311 * equal to the map of holders we set up above.
312 */
313 for (is_first = 1,
314 lp = SH_TAILQ_FIRST(&op->waiters, __db_lock);
315 lp != NULL;
316 is_first = 0,
317 lp = SH_TAILQ_NEXT(lp, links, __db_lock)) {
318 if (__lock_getobj(lt, lp->holder,
319 NULL, DB_LOCK_LOCKER, &lockerp) != 0) {
320 __db_err(dbenv,
321 "warning unable to find object");
322 continue;
323 }
324 id_array[lockerp->dd_id].id = lp->holder;
325 id_array[lockerp->dd_id].valid = 1;
326
327 /*
328 * If the transaction is pending abortion, then
329 * ignore it on this iteration.
330 */
331 if (lp->status != DB_LSTAT_WAITING)
332 continue;
333
334 entryp = bitmap + (nentries * lockerp->dd_id);
335 OR_MAP(entryp, tmpmap, nentries);
336 /*
337 * If this is the first waiter on the queue,
338 * then we remove the waitsfor relationship
339 * with oneself. However, if it's anywhere
340 * else on the queue, then we have to keep
341 * it and we have an automatic deadlock.
342 */
343 if (is_first)
344 CLR_MAP(entryp, lockerp->dd_id);
345 }
346 }
347 }
348
349 /* Now for each locker; record its last lock. */
350 for (id = 0; id < count; id++) {
351 if (!id_array[id].valid)
352 continue;
353 if (__lock_getobj(lt,
354 id_array[id].id, NULL, DB_LOCK_LOCKER, &lockerp) != 0) {
355 __db_err(dbenv,
356 "No locks for locker %lu", (u_long)id_array[id].id);
357 continue;
358 }
359 lp = SH_LIST_FIRST(&lockerp->heldby, __db_lock);
360 if (lp != NULL) {
361 id_array[id].last_lock = LOCK_TO_OFFSET(lt, lp);
362 lo = (DB_LOCKOBJ *)((u_int8_t *)lp + lp->obj);
363 pptr = SH_DBT_PTR(&lo->lockobj);
364 if (lo->lockobj.size >= sizeof(db_pgno_t))
365 memcpy(&id_array[id].pgno, pptr,
366 sizeof(db_pgno_t));
367 else
368 id_array[id].pgno = 0;
369 }
370 }
371
372 /* Pass complete, reset the deadlock detector bit. */
373 lt->region->need_dd = 0;
374 UNLOCK_LOCKREGION(lt);
375
376 /*
377 * Now we can release everything except the bitmap matrix that we
378 * created.
379 */
380 *nlockers = id;
381 *idmap = id_array;
382 *bmp = bitmap;
383 __os_free(tmpmap, sizeof(u_int32_t) * nentries);
384 return (0);
385 }
386
387 static u_int32_t *
__dd_find(bmp,idmap,nlockers)388 __dd_find(bmp, idmap, nlockers)
389 u_int32_t *bmp, nlockers;
390 locker_info *idmap;
391 {
392 u_int32_t i, j, nentries, *mymap, *tmpmap;
393
394 /*
395 * For each locker, OR in the bits from the lockers on which that
396 * locker is waiting.
397 */
398 nentries = ALIGN(nlockers, 32) / 32;
399 for (mymap = bmp, i = 0; i < nlockers; i++, mymap += nentries) {
400 if (!idmap[i].valid)
401 continue;
402 for (j = 0; j < nlockers; j++) {
403 if (ISSET_MAP(mymap, j)) {
404 /* Find the map for this bit. */
405 tmpmap = bmp + (nentries * j);
406 OR_MAP(mymap, tmpmap, nentries);
407 if (ISSET_MAP(mymap, i))
408 return (mymap);
409 }
410 }
411 }
412 return (NULL);
413 }
414
415 static int
__dd_abort(dbenv,info)416 __dd_abort(dbenv, info)
417 DB_ENV *dbenv;
418 locker_info *info;
419 {
420 struct __db_lock *lockp;
421 DB_LOCKTAB *lt;
422 DB_LOCKOBJ *lockerp, *sh_obj;
423 int ret;
424
425 lt = dbenv->lk_info;
426 LOCK_LOCKREGION(lt);
427
428 /* Find the locker's last lock. */
429 if ((ret =
430 __lock_getobj(lt, info->id, NULL, DB_LOCK_LOCKER, &lockerp)) != 0)
431 goto out;
432
433 lockp = SH_LIST_FIRST(&lockerp->heldby, __db_lock);
434
435 /*
436 * It's possible that this locker was already aborted.
437 * If that's the case, make sure that we remove its
438 * locker from the hash table.
439 */
440 if (lockp == NULL) {
441 HASHREMOVE_EL(lt->hashtab, __db_lockobj,
442 links, lockerp, lt->region->table_size, __lock_lhash);
443 SH_TAILQ_INSERT_HEAD(<->region->free_objs,
444 lockerp, links, __db_lockobj);
445 lt->region->nlockers--;
446 goto out;
447 } else if (LOCK_TO_OFFSET(lt, lockp) != info->last_lock ||
448 lockp->status != DB_LSTAT_WAITING)
449 goto out;
450
451 /* Abort lock, take it off list, and wake up this lock. */
452 lockp->status = DB_LSTAT_ABORTED;
453 lt->region->ndeadlocks++;
454 SH_LIST_REMOVE(lockp, locker_links, __db_lock);
455 sh_obj = (DB_LOCKOBJ *)((u_int8_t *)lockp + lockp->obj);
456 SH_TAILQ_REMOVE(&sh_obj->waiters, lockp, links, __db_lock);
457 (void)__db_mutex_unlock(&lockp->mutex, lt->reginfo.fd);
458
459 ret = 0;
460
461 out: UNLOCK_LOCKREGION(lt);
462 return (ret);
463 }
464
465 #ifdef DIAGNOSTIC
466 static void
__dd_debug(dbenv,idmap,bitmap,nlockers)467 __dd_debug(dbenv, idmap, bitmap, nlockers)
468 DB_ENV *dbenv;
469 locker_info *idmap;
470 u_int32_t *bitmap, nlockers;
471 {
472 u_int32_t i, j, *mymap, nentries;
473 int ret;
474 char *msgbuf;
475
476 __db_err(dbenv, "Waitsfor array");
477 __db_err(dbenv, "waiter\twaiting on");
478
479 /* Allocate space to print 10 bytes per item waited on. */
480 #undef MSGBUF_LEN
481 #define MSGBUF_LEN ((nlockers + 1) * 10 + 64)
482 if ((ret = __os_malloc(MSGBUF_LEN, NULL, &msgbuf)) != 0)
483 return;
484
485 nentries = ALIGN(nlockers, 32) / 32;
486 for (mymap = bitmap, i = 0; i < nlockers; i++, mymap += nentries) {
487 if (!idmap[i].valid)
488 continue;
489 sprintf(msgbuf, /* Waiter. */
490 "%lx/%lu:\t", (u_long)idmap[i].id, (u_long)idmap[i].pgno);
491 for (j = 0; j < nlockers; j++)
492 if (ISSET_MAP(mymap, j))
493 sprintf(msgbuf, "%s %lx", msgbuf,
494 (u_long)idmap[j].id);
495 (void)sprintf(msgbuf,
496 "%s %lu", msgbuf, (u_long)idmap[i].last_lock);
497 __db_err(dbenv, msgbuf);
498 }
499
500 __os_free(msgbuf, MSGBUF_LEN);
501 }
502 #endif
503