/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *      Sleepycat Software.  All rights reserved.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)lock_deadlock.c       10.37 (Sleepycat) 10/4/98";
#endif /* not lint */

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <errno.h>
#include <string.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;
        db_pgno_t       pgno;
} locker_info;

static int  __dd_abort __P((DB_ENV *, locker_info *));
static int  __dd_build
        __P((DB_ENV *, u_int32_t **, u_int32_t *, locker_info **));
static u_int32_t
           *__dd_find __P((u_int32_t *, locker_info *, u_int32_t));

#ifdef DIAGNOSTIC
static void __dd_debug __P((DB_ENV *, locker_info *, u_int32_t *, u_int32_t));
#endif

int
lock_detect(lt, flags, atype)
        DB_LOCKTAB *lt;
        u_int32_t flags, atype;
{
        DB_ENV *dbenv;
        locker_info *idmap;
        u_int32_t *bitmap, *deadlock, i, killid, nentries, nlockers;
        int do_pass, ret;

        LOCK_PANIC_CHECK(lt);

        /* Validate arguments. */
        if ((ret =
            __db_fchk(lt->dbenv, "lock_detect", flags, DB_LOCK_CONFLICT)) != 0)
                return (ret);

        /* Check if a detector run is necessary. */
        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 DIAGNOSTIC
        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 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.
                         */
                        killid = (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 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);
        }
        __os_free(bitmap, 0);
        __os_free(idmap, 0);

        return (ret);
}

/*
 * ========================================================================
 * Utilities
 */
static int
__dd_build(dbenv, bmp, nlockers, idmap)
        DB_ENV *dbenv;
        u_int32_t **bmp, *nlockers;
        locker_info **idmap;
{
        struct __db_lock *lp;
        DB_LOCKTAB *lt;
        DB_LOCKOBJ *op, *lo, *lockerp;
        u_int8_t *pptr;
        locker_info *id_array;
        u_int32_t *bitmap, count, *entryp, i, id, nentries, *tmpmap;
        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 ((ret = __os_calloc((size_t)count,
            sizeof(u_int32_t) * nentries, &bitmap)) != 0)
                return (ret);

        if ((ret = __os_calloc(sizeof(u_int32_t), nentries, &tmpmap)) != 0) {
                __os_free(bitmap, sizeof(u_int32_t) * nentries);
                return (ret);
        }

        if ((ret =
            __os_calloc((size_t)count, sizeof(locker_info), &id_array)) != 0) {
                __os_free(bitmap, count * sizeof(u_int32_t) * nentries);
                __os_free(tmpmap, sizeof(u_int32_t) * nentries);
                return (ret);
        }

        /*
         * Now go back in and actually fill in the matrix.
         */
        LOCK_LOCKREGION(lt);
        if (lt->region->nlockers > count) {
                __os_free(bitmap, count * sizeof(u_int32_t) * nentries);
                __os_free(tmpmap, sizeof(u_int32_t) * nentries);
                __os_free(id_array, count * sizeof(locker_info));
                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(&lt->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(&lt->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 (__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 (__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 (__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);
                        lo = (DB_LOCKOBJ *)((u_int8_t *)lp + lp->obj);
                        pptr = SH_DBT_PTR(&lo->lockobj);
                        if (lo->lockobj.size >= sizeof(db_pgno_t))
                                memcpy(&id_array[id].pgno, pptr,
                                    sizeof(db_pgno_t));
                        else
                                id_array[id].pgno = 0;
                }
        }

        /* 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;
        __os_free(tmpmap, sizeof(u_int32_t) * nentries);
        return (0);
}

static u_int32_t *
__dd_find(bmp, idmap, nlockers)
        u_int32_t *bmp, nlockers;
        locker_info *idmap;
{
        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;
{
        struct __db_lock *lockp;
        DB_LOCKTAB *lt;
        DB_LOCKOBJ *lockerp, *sh_obj;
        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);

        /*
         * It's possible that this locker was already aborted.
         * If that's the case, make sure that we remove its
         * locker from the hash table.
         */
        if (lockp == NULL) {
                HASHREMOVE_EL(lt->hashtab, __db_lockobj,
                    links, lockerp, lt->region->table_size, __lock_lhash);
                SH_TAILQ_INSERT_HEAD(&lt->region->free_objs,
                    lockerp, links, __db_lockobj);
                lt->region->nlockers--;
                goto out;
        } else if (LOCK_TO_OFFSET(lt, lockp) != info->last_lock ||
            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->reginfo.fd);

        ret = 0;

out:    UNLOCK_LOCKREGION(lt);
        return (ret);
}

#ifdef DIAGNOSTIC
static void
__dd_debug(dbenv, idmap, bitmap, nlockers)
        DB_ENV *dbenv;
        locker_info *idmap;
        u_int32_t *bitmap, nlockers;
{
        u_int32_t i, j, *mymap, nentries;
        int ret;
        char *msgbuf;

        __db_err(dbenv, "Waitsfor array");
        __db_err(dbenv, "waiter\twaiting on");

        /* Allocate space to print 10 bytes per item waited on. */
#undef  MSGBUF_LEN
#define MSGBUF_LEN ((nlockers + 1) * 10 + 64)
        if ((ret = __os_malloc(MSGBUF_LEN, NULL, &msgbuf)) != 0)
                return;

        nentries = ALIGN(nlockers, 32) / 32;
        for (mymap = bitmap, i = 0; i < nlockers; i++, mymap += nentries) {
                if (!idmap[i].valid)
                        continue;
                sprintf(msgbuf,                                 /* Waiter. */
                    "%lx/%lu:\t", (u_long)idmap[i].id, (u_long)idmap[i].pgno);
                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);
        }

        __os_free(msgbuf, MSGBUF_LEN);
}
#endif