db2/lock/lock_deadlock.c

   1 /*-
   2  * See the file LICENSE for redistribution information.
   3  *
   4  * Copyright (c) 1996, 1997
   5  *      Sleepycat Software.  All rights reserved.
   6  */
   7
   8 #include "config.h"
   9
  10 #ifndef lint
  11 static const char copyright[] =
  12 "@(#) Copyright (c) 1997\n\
  13         Sleepycat Software Inc.  All rights reserved.\n";
  14 static const char sccsid[] = "@(#)lock_deadlock.c       10.25 (Sleepycat) 11/1/97";
  15 #endif
  16
  17 #ifndef NO_SYSTEM_INCLUDES
  18 #include <sys/types.h>
  19
  20 #include <errno.h>
  21 #include <string.h>
  22 #include <stdlib.h>
  23 #endif
  24
  25 #include "db_int.h"
  26 #include "shqueue.h"
  27 #include "db_shash.h"
  28 #include "lock.h"
  29 #include "common_ext.h"
  30
  31 #define ISSET_MAP(M, N) (M[(N) / 32] & (1 << (N) % 32))
  32
  33 #define CLEAR_MAP(M, N) {                                               \
  34         u_int32_t __i;                                                  \
  35         for (__i = 0; __i < (N); __i++)                                 \
  36                 M[__i] = 0;                                             \
  37 }
  38
  39 #define SET_MAP(M, B)   (M[(B) / 32] |= (1 << ((B) % 32)))
  40 #define CLR_MAP(M, B)   (M[(B) / 32] &= ~(1 << ((B) % 32)))
  41
  42 #define OR_MAP(D, S, N) {                                               \
  43         u_int32_t __i;                                                  \
  44         for (__i = 0; __i < (N); __i++)                                 \
  45                 D[__i] |= S[__i];                                       \
  46 }
  47 #define BAD_KILLID      0xffffffff
  48
  49 typedef struct {
  50         int             valid;
  51         u_int32_t       id;
  52         DB_LOCK         last_lock;
  53         db_pgno_t       pgno;
  54 } locker_info;
  55
  56 static int  __dd_abort __P((DB_ENV *, locker_info *));
  57 static int  __dd_build
  58         __P((DB_ENV *, u_int32_t **, u_int32_t *, locker_info **));
  59 static u_int32_t
  60            *__dd_find __P((u_int32_t *, locker_info *, u_int32_t));
  61
  62 #ifdef DEBUG
  63 static void __dd_debug __P((DB_ENV *, locker_info *, u_int32_t *, u_int32_t));
  64 #endif
  65
  66 int
  67 lock_detect(lt, flags, atype)
  68         DB_LOCKTAB *lt;
  69         int flags;
  70         u_int32_t atype;
  71 {
  72         DB_ENV *dbenv;
  73         locker_info *idmap;
  74         u_int32_t *bitmap, *deadlock, i, killid, nentries, nlockers;
  75         int do_pass, ret;
  76
  77         /* Validate arguments. */
  78         if ((ret =
  79             __db_fchk(lt->dbenv, "lock_detect", flags, DB_LOCK_CONFLICT)) != 0)
  80                 return (ret);
  81
  82         /* Check if a detector run is necessary. */
  83         dbenv = lt->dbenv;
  84         if (LF_ISSET(DB_LOCK_CONFLICT)) {
  85                 /* Make a pass every time a lock waits. */
  86                 LOCK_LOCKREGION(lt);
  87                 do_pass = dbenv->lk_info->region->need_dd != 0;
  88                 UNLOCK_LOCKREGION(lt);
  89
  90                 if (!do_pass)
  91                         return (0);
  92         }
  93
  94         /* Build the waits-for bitmap. */
  95         if ((ret = __dd_build(dbenv, &bitmap, &nlockers, &idmap)) != 0)
  96                 return (ret);
  97
  98         if (nlockers == 0)
  99                 return (0);
 100 #ifdef DEBUG
 101         if (dbenv->db_verbose != 0)
 102                 __dd_debug(dbenv, idmap, bitmap, nlockers);
 103 #endif
 104         /* Find a deadlock. */
 105         deadlock = __dd_find(bitmap, idmap, nlockers);
 106         nentries = ALIGN(nlockers, 32) / 32;
 107         killid = BAD_KILLID;
 108         if (deadlock != NULL) {
 109                 /* Kill someone. */
 110                 switch (atype) {
 111                 case DB_LOCK_OLDEST:
 112                         /*
 113                          * Find the first bit set in the current
 114                          * array and then look for a lower tid in
 115                          * the array.
 116                          */
 117                         for (i = 0; i < nlockers; i++)
 118                                 if (ISSET_MAP(deadlock, i))
 119                                         killid = i;
 120
 121                         if (killid == BAD_KILLID) {
 122                                 __db_err(dbenv,
 123                                     "warning: could not find locker to abort");
 124                                 break;
 125                         }
 126
 127                         /*
 128                          * The oldest transaction has the lowest
 129                          * transaction id.
 130                          */
 131                         for (i = killid + 1; i < nlockers; i++)
 132                                 if (ISSET_MAP(deadlock, i) &&
 133                                     idmap[i].id < idmap[killid].id)
 134                                         killid = i;
 135                         break;
 136                 case DB_LOCK_DEFAULT:
 137                 case DB_LOCK_RANDOM:
 138                         /*
 139                          * We are trying to calculate the id of the
 140                          * locker whose entry is indicated by deadlock.
 141                          */
 142                         killid = (deadlock - bitmap) / nentries;
 143                         break;
 144                 case DB_LOCK_YOUNGEST:
 145                         /*
 146                          * Find the first bit set in the current
 147                          * array and then look for a lower tid in
 148                          * the array.
 149                          */
 150                         for (i = 0; i < nlockers; i++)
 151                                 if (ISSET_MAP(deadlock, i))
 152                                         killid = i;
 153
 154                         if (killid == BAD_KILLID) {
 155                                 __db_err(dbenv,
 156                                     "warning: could not find locker to abort");
 157                                 break;
 158                         }
 159                         /*
 160                          * The youngest transaction has the highest
 161                          * transaction id.
 162                          */
 163                         for (i = killid + 1; i < nlockers; i++)
 164                                 if (ISSET_MAP(deadlock, i) &&
 165                                     idmap[i].id > idmap[killid].id)
 166                                         killid = i;
 167                         break;
 168                 default:
 169                         killid = BAD_KILLID;
 170                         ret = EINVAL;
 171                 }
 172
 173                 /* Kill the locker with lockid idmap[killid]. */
 174                 if (dbenv->db_verbose != 0 && killid != BAD_KILLID)
 175                         __db_err(dbenv, "Aborting locker %lx",
 176                             (u_long)idmap[killid].id);
 177
 178                 if (killid != BAD_KILLID &&
 179                     (ret = __dd_abort(dbenv, &idmap[killid])) != 0)
 180                         __db_err(dbenv,
 181                             "warning: unable to abort locker %lx",
 182                             (u_long)idmap[killid].id);
 183         }
 184         __db_free(bitmap);
 185         __db_free(idmap);
 186
 187         return (ret);
 188 }
 189
 190 /*
 191  * ========================================================================
 192  * Utilities
 193  */
 194 static int
 195 __dd_build(dbenv, bmp, nlockers, idmap)
 196         DB_ENV *dbenv;
 197         u_int32_t **bmp, *nlockers;
 198         locker_info **idmap;
 199 {
 200         struct __db_lock *lp;
 201         DB_LOCKTAB *lt;
 202         DB_LOCKOBJ *op, *lo, *lockerp;
 203         u_int8_t *pptr;
 204         locker_info *id_array;
 205         u_int32_t *bitmap, count, *entryp, i, id, nentries, *tmpmap;
 206         int is_first, ret;
 207
 208         lt = dbenv->lk_info;
 209
 210         /*
 211          * We'll check how many lockers there are, add a few more in for
 212          * good measure and then allocate all the structures.  Then we'll
 213          * verify that we have enough room when we go back in and get the
 214          * mutex the second time.
 215          */
 216         LOCK_LOCKREGION(lt);
 217 retry:  count = lt->region->nlockers;
 218         lt->region->need_dd = 0;
 219         UNLOCK_LOCKREGION(lt);
 220
 221         if (count == 0) {
 222                 *nlockers = 0;
 223                 return (0);
 224         }
 225
 226         if (dbenv->db_verbose)
 227                 __db_err(dbenv, "%lu lockers", (u_long)count);
 228
 229         count += 10;
 230         nentries = ALIGN(count, 32) / 32;
 231         /*
 232          * Allocate enough space for a count by count bitmap matrix.
 233          *
 234          * XXX
 235          * We can probably save the malloc's between iterations just
 236          * reallocing if necessary because count grew by too much.
 237          */
 238         if ((bitmap = (u_int32_t *)__db_calloc((size_t)count,
 239             sizeof(u_int32_t) * nentries)) == NULL) {
 240                 __db_err(dbenv, "%s", strerror(ENOMEM));
 241                 return (ENOMEM);
 242         }
 243
 244         if ((tmpmap =
 245             (u_int32_t *)__db_calloc(sizeof(u_int32_t), nentries)) == NULL) {
 246                 __db_err(dbenv, "%s", strerror(ENOMEM));
 247                 __db_free(bitmap);
 248                 return (ENOMEM);
 249         }
 250
 251         if ((id_array = (locker_info *)__db_calloc((size_t)count,
 252             sizeof(locker_info))) == NULL) {
 253                 __db_err(dbenv, "%s", strerror(ENOMEM));
 254                 __db_free(bitmap);
 255                 __db_free(tmpmap);
 256                 return (ENOMEM);
 257         }
 258
 259         /*
 260          * Now go back in and actually fill in the matrix.
 261          */
 262         LOCK_LOCKREGION(lt);
 263         if (lt->region->nlockers > count) {
 264                 __db_free(bitmap);
 265                 __db_free(tmpmap);
 266                 __db_free(id_array);
 267                 goto retry;
 268         }
 269
 270         /*
 271          * First we go through and assign each locker a deadlock detector id.
 272          * Note that we fill in the idmap in the next loop since that's the
 273          * only place where we conveniently have both the deadlock id and the
 274          * actual locker.
 275          */
 276         for (id = 0, i = 0; i < lt->region->table_size; i++)
 277                 for (op = SH_TAILQ_FIRST(&lt->hashtab[i], __db_lockobj);
 278                     op != NULL; op = SH_TAILQ_NEXT(op, links, __db_lockobj))
 279                         if (op->type == DB_LOCK_LOCKER)
 280                                 op->dd_id = id++;
 281         /*
 282          * We go through the hash table and find each object.  For each object,
 283          * we traverse the waiters list and add an entry in the waitsfor matrix
 284          * for each waiter/holder combination.
 285          */
 286         for (i = 0; i < lt->region->table_size; i++) {
 287                 for (op = SH_TAILQ_FIRST(&lt->hashtab[i], __db_lockobj);
 288                     op != NULL; op = SH_TAILQ_NEXT(op, links, __db_lockobj)) {
 289                         if (op->type != DB_LOCK_OBJTYPE)
 290                                 continue;
 291                         CLEAR_MAP(tmpmap, nentries);
 292
 293                         /*
 294                          * First we go through and create a bit map that
 295                          * represents all the holders of this object.
 296                          */
 297                         for (lp = SH_TAILQ_FIRST(&op->holders, __db_lock);
 298                             lp != NULL;
 299                             lp = SH_TAILQ_NEXT(lp, links, __db_lock)) {
 300                                 if (__lock_getobj(lt, lp->holder,
 301                                     NULL, DB_LOCK_LOCKER, &lockerp) != 0) {
 302                                         __db_err(dbenv,
 303                                             "warning unable to find object");
 304                                         continue;
 305                                 }
 306                                 id_array[lockerp->dd_id].id = lp->holder;
 307                                 id_array[lockerp->dd_id].valid = 1;
 308
 309                                 /*
 310                                  * If the holder has already been aborted, then
 311                                  * we should ignore it for now.
 312                                  */
 313                                 if (lp->status == DB_LSTAT_HELD)
 314                                         SET_MAP(tmpmap, lockerp->dd_id);
 315                         }
 316
 317                         /*
 318                          * Next, for each waiter, we set its row in the matrix
 319                          * equal to the map of holders we set up above.
 320                          */
 321                         for (is_first = 1,
 322                             lp = SH_TAILQ_FIRST(&op->waiters, __db_lock);
 323                             lp != NULL;
 324                             is_first = 0,
 325                             lp = SH_TAILQ_NEXT(lp, links, __db_lock)) {
 326                                 if ((ret = __lock_getobj(lt, lp->holder,
 327                                     NULL, DB_LOCK_LOCKER, &lockerp)) != 0) {
 328                                         __db_err(dbenv,
 329                                             "warning unable to find object");
 330                                         continue;
 331                                 }
 332                                 id_array[lockerp->dd_id].id = lp->holder;
 333                                 id_array[lockerp->dd_id].valid = 1;
 334
 335                                 /*
 336                                  * If the transaction is pending abortion, then
 337                                  * ignore it on this iteration.
 338                                  */
 339                                 if (lp->status != DB_LSTAT_WAITING)
 340                                         continue;
 341
 342                                 entryp = bitmap + (nentries * lockerp->dd_id);
 343                                 OR_MAP(entryp, tmpmap, nentries);
 344                                 /*
 345                                  * If this is the first waiter on the queue,
 346                                  * then we remove the waitsfor relationship
 347                                  * with oneself.  However, if it's anywhere
 348                                  * else on the queue, then we have to keep
 349                                  * it and we have an automatic deadlock.
 350                                  */
 351                                 if (is_first)
 352                                         CLR_MAP(entryp, lockerp->dd_id);
 353                         }
 354                 }
 355         }
 356
 357         /* Now for each locker; record its last lock. */
 358         for (id = 0; id < count; id++) {
 359                 if (!id_array[id].valid)
 360                         continue;
 361                 if ((ret = __lock_getobj(lt,
 362                     id_array[id].id, NULL, DB_LOCK_LOCKER, &lockerp)) != 0) {
 363                         __db_err(dbenv,
 364                             "No locks for locker %lu", (u_long)id_array[id].id);
 365                         continue;
 366                 }
 367                 lp = SH_LIST_FIRST(&lockerp->heldby, __db_lock);
 368                 if (lp != NULL) {
 369                         id_array[id].last_lock = LOCK_TO_OFFSET(lt, lp);
 370                         lo = (DB_LOCKOBJ *)((u_int8_t *)lp + lp->obj);
 371                         pptr = SH_DBT_PTR(&lo->lockobj);
 372                         if (lo->lockobj.size >= sizeof(db_pgno_t))
 373                                 memcpy(&id_array[id].pgno, pptr,
 374                                     sizeof(db_pgno_t));
 375                         else
 376                                 id_array[id].pgno = 0;
 377                 }
 378         }
 379
 380         /* Pass complete, reset the deadlock detector bit. */
 381         lt->region->need_dd = 0;
 382         UNLOCK_LOCKREGION(lt);
 383
 384         /*
 385          * Now we can release everything except the bitmap matrix that we
 386          * created.
 387          */
 388         *nlockers = id;
 389         *idmap = id_array;
 390         *bmp = bitmap;
 391         __db_free(tmpmap);
 392         return (0);
 393 }
 394
 395 static u_int32_t *
 396 __dd_find(bmp, idmap, nlockers)
 397         u_int32_t *bmp, nlockers;
 398         locker_info *idmap;
 399 {
 400         u_int32_t i, j, nentries, *mymap, *tmpmap;
 401
 402         /*
 403          * For each locker, OR in the bits from the lockers on which that
 404          * locker is waiting.
 405          */
 406         nentries = ALIGN(nlockers, 32) / 32;
 407         for (mymap = bmp, i = 0; i < nlockers; i++, mymap += nentries) {
 408                 if (!idmap[i].valid)
 409                         continue;
 410                 for (j = 0; j < nlockers; j++) {
 411                         if (ISSET_MAP(mymap, j)) {
 412                                 /* Find the map for this bit. */
 413                                 tmpmap = bmp + (nentries * j);
 414                                 OR_MAP(mymap, tmpmap, nentries);
 415                                 if (ISSET_MAP(mymap, i))
 416                                         return (mymap);
 417                         }
 418                 }
 419         }
 420         return (NULL);
 421 }
 422
 423 static int
 424 __dd_abort(dbenv, info)
 425         DB_ENV *dbenv;
 426         locker_info *info;
 427 {
 428         struct __db_lock *lockp;
 429         DB_LOCKTAB *lt;
 430         DB_LOCKOBJ *lockerp, *sh_obj;
 431         int ret;
 432
 433         lt = dbenv->lk_info;
 434         LOCK_LOCKREGION(lt);
 435
 436         /* Find the locker's last lock. */
 437         if ((ret =
 438             __lock_getobj(lt, info->id, NULL, DB_LOCK_LOCKER, &lockerp)) != 0)
 439                 goto out;
 440
 441         lockp = SH_LIST_FIRST(&lockerp->heldby, __db_lock);
 442         if (LOCK_TO_OFFSET(lt, lockp) != info->last_lock ||
 443             lockp == NULL || lockp->status != DB_LSTAT_WAITING)
 444                 goto out;
 445
 446         /* Abort lock, take it off list, and wake up this lock. */
 447         lockp->status = DB_LSTAT_ABORTED;
 448         lt->region->ndeadlocks++;
 449         SH_LIST_REMOVE(lockp, locker_links, __db_lock);
 450         sh_obj = (DB_LOCKOBJ *)((u_int8_t *)lockp + lockp->obj);
 451         SH_TAILQ_REMOVE(&sh_obj->waiters, lockp, links, __db_lock);
 452         (void)__db_mutex_unlock(&lockp->mutex, lt->fd);
 453
 454         ret = 0;
 455
 456 out:    UNLOCK_LOCKREGION(lt);
 457         return (ret);
 458 }
 459
 460 #ifdef DEBUG
 461 static void
 462 __dd_debug(dbenv, idmap, bitmap, nlockers)
 463         DB_ENV *dbenv;
 464         locker_info *idmap;
 465         u_int32_t *bitmap, nlockers;
 466 {
 467         u_int32_t i, j, *mymap, nentries;
 468         char *msgbuf;
 469
 470         __db_err(dbenv, "Waitsfor array");
 471         __db_err(dbenv, "waiter\twaiting on");
 472         /*
 473          * Allocate space to print 10 bytes per item waited on.
 474          */
 475         if ((msgbuf = (char *)__db_malloc((nlockers + 1) * 10 + 64)) == NULL) {
 476                 __db_err(dbenv, "%s", strerror(ENOMEM));
 477                 return;
 478         }
 479
 480         nentries = ALIGN(nlockers, 32) / 32;
 481         for (mymap = bitmap, i = 0; i < nlockers; i++, mymap += nentries) {
 482                 if (!idmap[i].valid)
 483                         continue;
 484                 sprintf(msgbuf,                                 /* Waiter. */
 485                     "%lx/%lu:\t", (u_long)idmap[i].id, (u_long)idmap[i].pgno);
 486                 for (j = 0; j < nlockers; j++)
 487                         if (ISSET_MAP(mymap, j))
 488                                 sprintf(msgbuf, "%s %lx", msgbuf,
 489                                     (u_long)idmap[j].id);
 490                 (void)sprintf(msgbuf,
 491                     "%s %lu", msgbuf, (u_long)idmap[i].last_lock);
 492                 __db_err(dbenv, msgbuf);
 493         }
 494
 495         __db_free(msgbuf);
 496 }
 497 #endif