diff options
Diffstat (limited to 'db2/lock/lock_deadlock.c')
| -rw-r--r-- | db2/lock/lock_deadlock.c | 496 |
1 files changed, 496 insertions, 0 deletions
diff --git a/db2/lock/lock_deadlock.c b/db2/lock/lock_deadlock.c new file mode 100644 index 0000000000..54a73afd1b --- /dev/null +++ b/db2/lock/lock_deadlock.c @@ -0,0 +1,496 @@ +/*- + * See the file LICENSE for redistribution information. + * + * Copyright (c) 1996, 1997 + * Sleepycat Software. All rights reserved. + */ + +#include "config.h" + +#ifndef lint +static const char copyright[] = +"@(#) Copyright (c) 1997\n\ + Sleepycat Software Inc. All rights reserved.\n"; +static const char sccsid[] = "@(#)lock_deadlock.c 10.20 (Sleepycat) 8/21/97"; +#endif + +#ifndef NO_SYSTEM_INCLUDES +#include <sys/types.h> + +#include <errno.h> +#include <string.h> +#include <stdlib.h> +#endif + +#include "db_int.h" +#include "shqueue.h" +#include "db_shash.h" +#include "lock.h" +#include "common_ext.h" + +#define ISSET_MAP(M, N) (M[(N) / 32] & (1 << (N) % 32)) + +#define CLEAR_MAP(M, N) { \ + u_int32_t __i; \ + for (__i = 0; __i < (N); __i++) \ + M[__i] = 0; \ +} + +#define SET_MAP(M, B) (M[(B) / 32] |= (1 << ((B) % 32))) +#define CLR_MAP(M, B) (M[(B) / 32] &= ~(1 << ((B) % 32))) + +#define OR_MAP(D, S, N) { \ + u_int32_t __i; \ + for (__i = 0; __i < (N); __i++) \ + D[__i] |= S[__i]; \ +} +#define BAD_KILLID 0xffffffff + +typedef struct { + int valid; + u_int32_t id; + DB_LOCK last_lock; +} locker_info; + +static int __dd_abort __P((DB_ENV *, locker_info *)); +static int __dd_build __P((DB_ENV *, u_int32_t **, int *, locker_info **)); +#ifdef DEBUG +static void __dd_debug __P((DB_ENV *, locker_info *, u_int32_t *, int)); +#endif +static u_int32_t + *__dd_find __P((u_int32_t *, locker_info *, u_int32_t)); + +int +lock_detect(lt, flags, atype) + DB_LOCKTAB *lt; + int flags; + u_int32_t atype; +{ + DB_ENV *dbenv; + locker_info *idmap; + u_int32_t *bitmap, *deadlock, killid; + int do_pass, i, nlockers, nentries, ret; + + /* Validate arguments. */ + if ((ret = + __db_fchk(lt->dbenv, "lock_detect", flags, DB_LOCK_CONFLICT)) != 0) + return (ret); + + /* Check if a detector run is necessary. */ + do_pass = 1; + dbenv = lt->dbenv; + if (LF_ISSET(DB_LOCK_CONFLICT)) { + /* Make a pass every time a lock waits. */ + LOCK_LOCKREGION(lt); + do_pass = dbenv->lk_info->region->need_dd != 0; + UNLOCK_LOCKREGION(lt); + } + + if (!do_pass) + return (0); + + /* Build the waits-for bitmap. */ + if ((ret = __dd_build(dbenv, &bitmap, &nlockers, &idmap)) != 0) + return (ret); + + if (nlockers == 0) + return (0); +#ifdef DEBUG + if (dbenv->db_verbose != 0) + __dd_debug(dbenv, idmap, bitmap, nlockers); +#endif + /* Find a deadlock. */ + deadlock = __dd_find(bitmap, idmap, nlockers); + nentries = ALIGN(nlockers, 32) / 32; + killid = BAD_KILLID; + if (deadlock != NULL) { + /* Kill someone. */ + switch (atype) { + case DB_LOCK_OLDEST: + /* + * Find the first bit set in the current + * array and then look for a lower tid in + * the array. + */ + for (i = 0; i < nlockers; i++) + if (ISSET_MAP(deadlock, i)) + killid = i; + + if (killid == BAD_KILLID) { + __db_err(dbenv, + "warning: could not find %s", + "locker to abort"); + break; + } + + /* + * The oldest transaction has the lowest + * transaction id. + */ + for (i = killid + 1; i < nlockers; i++) + if (ISSET_MAP(deadlock, i) && + idmap[i].id < idmap[killid].id) + killid = i; + break; + case DB_LOCK_DEFAULT: + case DB_LOCK_RANDOM: + /* + * We are trying to calculate the id of the + * locker whose entry is indicated by deadlock. + * We know that this is less than nlockers, so + * the cast below is valid. + */ + killid = + (u_int32_t)((deadlock - bitmap) / nentries); + break; + case DB_LOCK_YOUNGEST: + /* + * Find the first bit set in the current + * array and then look for a lower tid in + * the array. + */ + for (i = 0; i < nlockers; i++) + if (ISSET_MAP(deadlock, i)) + killid = i; + + if (killid == BAD_KILLID) { + __db_err(dbenv, + "warning: could not find %s", + "locker to abort"); + break; + } + /* + * The youngest transaction has the highest + * transaction id. + */ + for (i = killid + 1; i < nlockers; i++) + if (ISSET_MAP(deadlock, i) && + idmap[i].id > idmap[killid].id) + killid = i; + break; + default: + killid = BAD_KILLID; + ret = EINVAL; + } + + /* Kill the locker with lockid idmap[killid]. */ + if (dbenv->db_verbose != 0 && killid != BAD_KILLID) + __db_err(dbenv, "Aborting locker %lx", + (u_long)idmap[killid].id); + + if (killid != BAD_KILLID && + (ret = __dd_abort(dbenv, &idmap[killid])) != 0) + __db_err(dbenv, + "warning: unable to abort locker %lx", + (u_long)idmap[killid].id); + } + free(bitmap); + free(idmap); + + return (ret); +} + +/* + * ======================================================================== + * Utilities + */ +static int +__dd_build(dbenv, bmp, nlockers, idmap) + DB_ENV *dbenv; + u_int32_t **bmp; + int *nlockers; + locker_info **idmap; +{ + DB_LOCKTAB *lt; + DB_LOCKOBJ *op, *lockerp; + struct __db_lock *lp; + u_int32_t *bitmap, count, *entryp, i, id, nentries, *tmpmap; + locker_info *id_array; + int is_first, ret; + + lt = dbenv->lk_info; + + /* + * We'll check how many lockers there are, add a few more in for + * good measure and then allocate all the structures. Then we'll + * verify that we have enough room when we go back in and get the + * mutex the second time. + */ + LOCK_LOCKREGION(lt); +retry: count = lt->region->nlockers; + lt->region->need_dd = 0; + UNLOCK_LOCKREGION(lt); + + if (count == 0) { + *nlockers = 0; + return (0); + } + + if (dbenv->db_verbose) + __db_err(dbenv, "%lu lockers", (u_long)count); + + count += 10; + nentries = ALIGN(count, 32) / 32; + /* + * Allocate enough space for a count by count bitmap matrix. + * + * XXX + * We can probably save the malloc's between iterations just + * reallocing if necessary because count grew by too much. + */ + if ((bitmap = (u_int32_t *)calloc((size_t)count, + sizeof(u_int32_t) * nentries)) == NULL) { + __db_err(dbenv, "%s", strerror(ENOMEM)); + return (ENOMEM); + } + + if ((tmpmap = + (u_int32_t *)calloc(sizeof(u_int32_t), nentries)) == NULL) { + __db_err(dbenv, "%s", strerror(ENOMEM)); + free(bitmap); + return (ENOMEM); + } + + if ((id_array = (locker_info *)calloc((size_t)count, + sizeof(locker_info))) == NULL) { + __db_err(dbenv, "%s", strerror(ENOMEM)); + free(bitmap); + free(tmpmap); + return (ENOMEM); + } + + /* + * Now go back in and actually fill in the matrix. + */ + LOCK_LOCKREGION(lt); + if (lt->region->nlockers > count) { + free(bitmap); + free(tmpmap); + free(id_array); + goto retry; + } + + /* + * First we go through and assign each locker a deadlock detector id. + * Note that we fill in the idmap in the next loop since that's the + * only place where we conveniently have both the deadlock id and the + * actual locker. + */ + for (id = 0, i = 0; i < lt->region->table_size; i++) + for (op = SH_TAILQ_FIRST(<->hashtab[i], __db_lockobj); + op != NULL; op = SH_TAILQ_NEXT(op, links, __db_lockobj)) + if (op->type == DB_LOCK_LOCKER) + op->dd_id = id++; + /* + * We go through the hash table and find each object. For each object, + * we traverse the waiters list and add an entry in the waitsfor matrix + * for each waiter/holder combination. + */ + for (i = 0; i < lt->region->table_size; i++) { + for (op = SH_TAILQ_FIRST(<->hashtab[i], __db_lockobj); + op != NULL; op = SH_TAILQ_NEXT(op, links, __db_lockobj)) { + if (op->type != DB_LOCK_OBJTYPE) + continue; + CLEAR_MAP(tmpmap, nentries); + + /* + * First we go through and create a bit map that + * represents all the holders of this object. + */ + for (lp = SH_TAILQ_FIRST(&op->holders, __db_lock); + lp != NULL; + lp = SH_TAILQ_NEXT(lp, links, __db_lock)) { + if ((errno = __lock_getobj(lt, lp->holder, + NULL, DB_LOCK_LOCKER, &lockerp)) != 0) { + __db_err(dbenv, + "warning unable to find object"); + continue; + } + id_array[lockerp->dd_id].id = lp->holder; + id_array[lockerp->dd_id].valid = 1; + + /* + * If the holder has already been aborted, then + * we should ignore it for now. + */ + if (lp->status == DB_LSTAT_HELD) + SET_MAP(tmpmap, lockerp->dd_id); + } + + /* + * Next, for each waiter, we set its row in the matrix + * equal to the map of holders we set up above. + */ + for (is_first = 1, + lp = SH_TAILQ_FIRST(&op->waiters, __db_lock); + lp != NULL; + is_first = 0, + lp = SH_TAILQ_NEXT(lp, links, __db_lock)) { + if ((ret = __lock_getobj(lt, + lp->holder, NULL, DB_LOCK_LOCKER, &lockerp)) + != 0) { + __db_err(dbenv, + "warning unable to find object"); + continue; + } + id_array[lockerp->dd_id].id = lp->holder; + id_array[lockerp->dd_id].valid = 1; + + /* + * If the transaction is pending abortion, then + * ignore it on this iteration. + */ + if (lp->status != DB_LSTAT_WAITING) + continue; + + entryp = bitmap + (nentries * lockerp->dd_id); + OR_MAP(entryp, tmpmap, nentries); + /* + * If this is the first waiter on the queue, + * then we remove the waitsfor relationship + * with oneself. However, if it's anywhere + * else on the queue, then we have to keep + * it and we have an automatic deadlock. + */ + if (is_first) + CLR_MAP(entryp, lockerp->dd_id); + } + } + } + + /* Now for each locker; record its last lock. */ + for (id = 0; id < count; id++) { + if (!id_array[id].valid) + continue; + if ((ret = __lock_getobj(lt, + id_array[id].id, NULL, DB_LOCK_LOCKER, &lockerp)) != 0) { + __db_err(dbenv, + "No locks for locker %lu", (u_long)id_array[id].id); + continue; + } + lp = SH_LIST_FIRST(&lockerp->heldby, __db_lock); + if (lp != NULL) + id_array[id].last_lock = LOCK_TO_OFFSET(lt, lp); + } + + /* Pass complete, reset the deadlock detector bit. */ + lt->region->need_dd = 0; + UNLOCK_LOCKREGION(lt); + + /* + * Now we can release everything except the bitmap matrix that we + * created. + */ + *nlockers = id; + *idmap = id_array; + *bmp = bitmap; + free(tmpmap); + return (0); +} + +static u_int32_t * +__dd_find(bmp, idmap, nlockers) + u_int32_t *bmp; + locker_info *idmap; + u_int32_t nlockers; +{ + u_int32_t i, j, nentries, *mymap, *tmpmap; + + /* + * For each locker, or in the bits from the lockers + * on which that locker is waiting. + */ + nentries = ALIGN(nlockers, 32) / 32; + for (mymap = bmp, i = 0; i < nlockers; i++, mymap += nentries) { + if (!idmap[i].valid) + continue; + for (j = 0; j < nlockers; j++) { + if (ISSET_MAP(mymap, j)) { + /* Find the map for this bit. */ + tmpmap = bmp + (nentries * j); + OR_MAP(mymap, tmpmap, nentries); + if (ISSET_MAP(mymap, i)) + return (mymap); + } + } + } + return (NULL); +} + +static int +__dd_abort(dbenv, info) + DB_ENV *dbenv; + locker_info *info; +{ + DB_LOCKTAB *lt; + DB_LOCKOBJ *lockerp, *sh_obj; + struct __db_lock *lockp; + int ret; + + lt = dbenv->lk_info; + LOCK_LOCKREGION(lt); + + /* Find the locker's last lock. */ + if ((ret = + __lock_getobj(lt, info->id, NULL, DB_LOCK_LOCKER, &lockerp)) != 0) + goto out; + + lockp = SH_LIST_FIRST(&lockerp->heldby, __db_lock); + if (LOCK_TO_OFFSET(lt, lockp) != info->last_lock || + lockp == NULL || lockp->status != DB_LSTAT_WAITING) + goto out; + + /* Abort lock, take it off list, and wake up this lock. */ + lockp->status = DB_LSTAT_ABORTED; + lt->region->ndeadlocks++; + SH_LIST_REMOVE(lockp, locker_links, __db_lock); + sh_obj = (DB_LOCKOBJ *)((u_int8_t *)lockp + lockp->obj); + SH_TAILQ_REMOVE(&sh_obj->waiters, lockp, links, __db_lock); + (void)__db_mutex_unlock(&lockp->mutex, lt->fd); + + ret = 0; + +out: UNLOCK_LOCKREGION(lt); + return (ret); +} + +#ifdef DEBUG +static void +__dd_debug(dbenv, idmap, bitmap, nlockers) + DB_ENV *dbenv; + locker_info *idmap; + u_int32_t *bitmap; + int nlockers; +{ + u_int32_t *mymap; + int i, j, nentries; + char *msgbuf; + + __db_err(dbenv, "Waitsfor array"); + __db_err(dbenv, "waiter\twaiting on"); + /* + * Alloc space to print 10 bytes per item waited on. + */ + if ((msgbuf = (char *)malloc((nlockers + 1) * 10 + 64)) == NULL) { + errno = ENOMEM; + __db_err(dbenv, "%s", strerror(errno)); + return; + } + + nentries = ALIGN(nlockers, 32) / 32; + for (mymap = bitmap, i = 0; i < nlockers; i++, mymap += nentries) { + if (!idmap[i].valid) + continue; + sprintf(msgbuf, "%lx\t\t", (u_long)idmap[i].id);/* Waiter. */ + for (j = 0; j < nlockers; j++) + if (ISSET_MAP(mymap, j)) + sprintf(msgbuf, "%s %lx", msgbuf, + (u_long)idmap[j].id); + (void)sprintf(msgbuf, + "%s %lu", msgbuf, (u_long)idmap[i].last_lock); + __db_err(dbenv, msgbuf); + } + + free(msgbuf); +} +#endif |