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