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