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txn.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996,2007 Oracle.  All rights reserved.
 */
/*
 * Copyright (c) 1995, 1996
 *    The President and Fellows of Harvard University.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Margo Seltzer.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $Id: txn.c,v 12.78 2007/06/29 00:25:02 margo Exp $
 */

#include "db_config.h"

#include "db_int.h"
#include "dbinc/crypto.h"
#include "dbinc/hmac.h"
#include "dbinc/db_page.h"
#include "dbinc/hash.h"
#include "dbinc/lock.h"
#include "dbinc/log.h"
#include "dbinc/mp.h"
#include "dbinc/txn.h"

#define     LOG_FLAGS(txn)                                  \
            (DB_LOG_COMMIT | (F_ISSET(txn, TXN_SYNC) ?      \
            DB_FLUSH : (F_ISSET(txn, TXN_WRITE_NOSYNC) ?    \
            DB_LOG_WRNOSYNC : 0)))

/*
 * __txn_isvalid enumerated types.  We cannot simply use the transaction
 * statuses, because different statuses need to be handled differently
 * depending on the caller.
 */
typedef enum {
      TXN_OP_ABORT,
      TXN_OP_COMMIT,
      TXN_OP_DISCARD,
      TXN_OP_PREPARE
} txnop_t;

static int  __txn_abort_pp __P((DB_TXN *));
static int  __txn_begin_int __P((DB_TXN *));
static int  __txn_commit_pp __P((DB_TXN *, u_int32_t));
static int  __txn_discard __P((DB_TXN *, u_int32_t));
static int  __txn_dispatch_undo
            __P((DB_ENV *, DB_TXN *, DBT *, DB_LSN *, DB_TXNHEAD *));
static int  __txn_end __P((DB_TXN *, int));
static int  __txn_isvalid __P((const DB_TXN *, txnop_t));
static int  __txn_undo __P((DB_TXN *));
static void __txn_set_txn_lsnp __P((DB_TXN *, DB_LSN **, DB_LSN **));

/*
 * __txn_begin_pp --
 *    DB_ENV->txn_begin pre/post processing.
 *
 * PUBLIC: int __txn_begin_pp __P((DB_ENV *, DB_TXN *, DB_TXN **, u_int32_t));
 */
int
__txn_begin_pp(dbenv, parent, txnpp, flags)
      DB_ENV *dbenv;
      DB_TXN *parent, **txnpp;
      u_int32_t flags;
{
      DB_THREAD_INFO *ip;
      int rep_check, ret;

      PANIC_CHECK(dbenv);
      ENV_REQUIRES_CONFIG(dbenv, dbenv->tx_handle, "txn_begin", DB_INIT_TXN);

      if ((ret = __db_fchk(dbenv,
          "txn_begin", flags,
          DB_READ_COMMITTED | DB_READ_UNCOMMITTED |
          DB_TXN_NOSYNC | DB_TXN_SNAPSHOT | DB_TXN_SYNC |
          DB_TXN_WAIT | DB_TXN_WRITE_NOSYNC | DB_TXN_NOWAIT)) != 0)
            return (ret);
      if ((ret = __db_fcchk(dbenv, "txn_begin", flags,
          DB_TXN_WRITE_NOSYNC | DB_TXN_NOSYNC, DB_TXN_SYNC)) != 0)
            return (ret);
      if ((ret = __db_fcchk(dbenv, "txn_begin",
          flags, DB_TXN_WRITE_NOSYNC, DB_TXN_NOSYNC)) != 0)
            return (ret);
      if (parent != NULL && !F_ISSET(parent, TXN_SNAPSHOT) &&
          LF_ISSET(DB_TXN_SNAPSHOT)) {
            __db_errx(dbenv,
                "Child transaction snapshot setting must match parent");
            return (EINVAL);
      }

      ENV_ENTER(dbenv, ip);

      if (parent == NULL) {
            rep_check = IS_ENV_REPLICATED(dbenv) ? 1 : 0;
            if (rep_check && (ret = __op_rep_enter(dbenv)) != 0)
                  goto err;
      } else
            rep_check = 0;
      ret = __txn_begin(dbenv, parent, txnpp, flags);
      /*
       * We only decrement the count if the operation fails.
       * Otherwise the count will be decremented when the
       * txn is resolved by txn_commit, txn_abort, etc.
       */
      if (ret != 0 && rep_check)
            (void)__op_rep_exit(dbenv);

err:  ENV_LEAVE(dbenv, ip);
      return (ret);
}

/*
 * __txn_begin --
 *    DB_ENV->txn_begin.
 *
 * This is a wrapper to the actual begin process.  Normal transaction begin
 * allocates a DB_TXN structure for the caller, while XA transaction begin
 * does not.  Other than that, both call into common __txn_begin_int code.
 *
 * Internally, we use TXN_DETAIL structures, but the DB_TXN structure
 * provides access to the transaction ID and the offset in the transaction
 * region of the TXN_DETAIL structure.
 *
 * PUBLIC: int __txn_begin __P((DB_ENV *, DB_TXN *, DB_TXN **, u_int32_t));
 */
int
__txn_begin(dbenv, parent, txnpp, flags)
      DB_ENV *dbenv;
      DB_TXN *parent, **txnpp;
      u_int32_t flags;
{
      DB_LOCKREGION *region;
      DB_TXN *txn;
      TXN_DETAIL *ptd, *td;
      int ret;

      *txnpp = NULL;
      if ((ret = __os_calloc(dbenv, 1, sizeof(DB_TXN), &txn)) != 0)
            return (ret);

      txn->mgrp = dbenv->tx_handle;
      txn->parent = parent;
      TAILQ_INIT(&txn->kids);
      TAILQ_INIT(&txn->events);
      STAILQ_INIT(&txn->logs);
      txn->flags = TXN_MALLOC;

      /*
       * Set the sync mode for commit.  Any local bits override those
       * in the environment.  SYNC is the default.
       */
      if (LF_ISSET(DB_TXN_SYNC))
            F_SET(txn, TXN_SYNC);
      else if (LF_ISSET(DB_TXN_NOSYNC))
            F_SET(txn, TXN_NOSYNC);
      else if (LF_ISSET(DB_TXN_WRITE_NOSYNC))
            F_SET(txn, TXN_WRITE_NOSYNC);
      else if (F_ISSET(dbenv, DB_ENV_TXN_NOSYNC))
            F_SET(txn, TXN_NOSYNC);
      else if (F_ISSET(dbenv, DB_ENV_TXN_WRITE_NOSYNC))
            F_SET(txn, TXN_WRITE_NOSYNC);
      else
            F_SET(txn, TXN_SYNC);

      if (LF_ISSET(DB_TXN_NOWAIT) ||
          (F_ISSET(dbenv, DB_ENV_TXN_NOWAIT) && !LF_ISSET(DB_TXN_WAIT)))
            F_SET(txn, TXN_NOWAIT);
      if (LF_ISSET(DB_READ_COMMITTED))
            F_SET(txn, TXN_READ_COMMITTED);
      if (LF_ISSET(DB_READ_UNCOMMITTED))
            F_SET(txn, TXN_READ_UNCOMMITTED);
      if (LF_ISSET(DB_TXN_SNAPSHOT) || F_ISSET(dbenv, DB_ENV_TXN_SNAPSHOT) ||
          (parent != NULL && F_ISSET(parent, TXN_SNAPSHOT)))
            F_SET(txn, TXN_SNAPSHOT);

      if ((ret = __txn_begin_int(txn)) != 0)
            goto err;
      td = txn->td;

      if (parent != NULL) {
            ptd = parent->td;
            TAILQ_INSERT_HEAD(&parent->kids, txn, klinks);
            SH_TAILQ_INSERT_HEAD(&ptd->kids, td, klinks, __txn_detail);
      }

      if (LOCKING_ON(dbenv)) {
            region = dbenv->lk_handle->reginfo.primary;
            if (parent != NULL) {
                  ret = __lock_inherit_timeout(dbenv,
                      parent->locker, txn->locker);
                  /* No parent locker set yet. */
                  if (ret == EINVAL) {
                        parent = NULL;
                        ret = 0;
                  }
                  if (ret != 0)
                        goto err;
            }

            /*
             * Parent is NULL if we have no parent
             * or it has no timeouts set.
             */
            if (parent == NULL && region->tx_timeout != 0)
                  if ((ret = __lock_set_timeout(dbenv, txn->locker,
                      region->tx_timeout, DB_SET_TXN_TIMEOUT)) != 0)
                        goto err;
      }

      *txnpp = txn;
      return (0);

err:
      __os_free(dbenv, txn);
      return (ret);
}

/*
 * __txn_xa_begin --
 *    XA version of txn_begin.
 *
 * PUBLIC: int __txn_xa_begin __P((DB_ENV *, DB_TXN *));
 */
int
__txn_xa_begin(dbenv, txn)
      DB_ENV *dbenv;
      DB_TXN *txn;
{
      PANIC_CHECK(dbenv);

      /*
       * We need to initialize the transaction structure, but must be careful
       * not to smash the links.  We manually initialize the structure.
       */
      txn->mgrp = dbenv->tx_handle;
      TAILQ_INIT(&txn->kids);
      TAILQ_INIT(&txn->events);
      STAILQ_INIT(&txn->logs);
      txn->parent = NULL;
      txn->txnid = TXN_INVALID;
      txn->cursors = 0;
      memset(&txn->lock_timeout, 0, sizeof(db_timeout_t));
      memset(&txn->expire, 0, sizeof(db_timeout_t));

      return (__txn_begin_int(txn));
}

/*
 * __txn_recycle_id --
 *    Find a range of useable transaction ids.
 *
 * PUBLIC: int __txn_recycle_id __P((DB_ENV *));
 */
int
__txn_recycle_id(dbenv)
      DB_ENV *dbenv;
{
      DB_LSN null_lsn;
      DB_TXNMGR *mgr;
      DB_TXNREGION *region;
      TXN_DETAIL *td;
      u_int32_t *ids;
      int nids, ret;

      mgr = dbenv->tx_handle;
      region = mgr->reginfo.primary;

      if ((ret = __os_malloc(dbenv,
          sizeof(u_int32_t) * region->maxtxns, &ids)) != 0)
            return (ret);
      nids = 0;
      SH_TAILQ_FOREACH(td, &region->active_txn, links, __txn_detail)
            ids[nids++] = td->txnid;
      region->last_txnid = TXN_MINIMUM - 1;
      region->cur_maxid = TXN_MAXIMUM;
      if (nids != 0)
            __db_idspace(ids, nids,
                &region->last_txnid, &region->cur_maxid);
      __os_free(dbenv, ids);

      /*
       * Check LOGGING_ON rather than DBENV_LOGGING as we want to emit this
       * record at the end of recovery.
       */
      if (LOGGING_ON(dbenv))
          ret = __txn_recycle_log(dbenv, NULL, &null_lsn,
            0, region->last_txnid + 1, region->cur_maxid);

      return (ret);
}

/*
 * __txn_compensate_begin
 *    Begin an compensation transaction.  This is a special interface
 * that is used only for transactions that must be started to compensate
 * for actions during an abort.  Currently only used for allocations.
 *
 * PUBLIC: int __txn_compensate_begin __P((DB_ENV *, DB_TXN **));
 */
int
__txn_compensate_begin(dbenv, txnpp)
      DB_ENV *dbenv;
      DB_TXN **txnpp;
{
      DB_TXN *txn;
      int ret;

      PANIC_CHECK(dbenv);

      if ((ret = __os_calloc(dbenv, 1, sizeof(DB_TXN), &txn)) != 0)
            return (ret);

      txn->mgrp = dbenv->tx_handle;
      TAILQ_INIT(&txn->kids);
      TAILQ_INIT(&txn->events);
      STAILQ_INIT(&txn->logs);
      txn->flags = TXN_COMPENSATE | TXN_MALLOC;

      *txnpp = txn;
      return (__txn_begin_int(txn));
}

/*
 * __txn_begin_int --
 *    Normal DB version of txn_begin.
 */
static int
__txn_begin_int(txn)
      DB_TXN *txn;
{
      DB_ENV *dbenv;
      DB_TXNMGR *mgr;
      DB_TXNREGION *region;
      TXN_DETAIL *td;
      u_int32_t id;
      int ret;

      mgr = txn->mgrp;
      dbenv = mgr->dbenv;
      region = mgr->reginfo.primary;

      TXN_SYSTEM_LOCK(dbenv);
      if (!F_ISSET(txn, TXN_COMPENSATE) && F_ISSET(region, TXN_IN_RECOVERY)) {
            __db_errx(dbenv, "operation not permitted during recovery");
            ret = EINVAL;
            goto err;
      }

      /*
       * Allocate a new transaction id. Our current valid range can span
       * the maximum valid value, so check for it and wrap manually.
       */
      if (region->last_txnid == TXN_MAXIMUM &&
          region->cur_maxid != TXN_MAXIMUM)
            region->last_txnid = TXN_MINIMUM - 1;

      if (region->last_txnid == region->cur_maxid &&
          (ret = __txn_recycle_id(dbenv)) != 0)
            goto err;

      /* Allocate a new transaction detail structure. */
      if ((ret =
          __env_alloc(&mgr->reginfo, sizeof(TXN_DETAIL), &td)) != 0) {
            __db_errx(dbenv,
                "Unable to allocate memory for transaction detail");
            goto err;
      }

      /* Place transaction on active transaction list. */
      SH_TAILQ_INSERT_HEAD(&region->active_txn, td, links, __txn_detail);

      id = ++region->last_txnid;

#ifdef HAVE_STATISTICS
      ++region->stat.st_nbegins;
      if (++region->stat.st_nactive > region->stat.st_maxnactive)
            region->stat.st_maxnactive = region->stat.st_nactive;
#endif

      td->txnid = id;
      dbenv->thread_id(dbenv, &td->pid, &td->tid);

      /* allocate a locker for this txn */
      if (LOCKING_ON(dbenv) && (ret =
          __lock_getlocker(dbenv->lk_handle, id, 1, &txn->locker)) != 0)
            goto err;

      ZERO_LSN(td->last_lsn);
      ZERO_LSN(td->begin_lsn);
      SH_TAILQ_INIT(&td->kids);
      if (txn->parent != NULL)
            td->parent = R_OFFSET(&mgr->reginfo, txn->parent->td);
      else
            td->parent = INVALID_ROFF;
      td->name = INVALID_ROFF;
      MAX_LSN(td->read_lsn);
      MAX_LSN(td->visible_lsn);
      td->mvcc_ref = 0;
      td->mvcc_mtx = MUTEX_INVALID;
      td->status = TXN_RUNNING;
      td->flags = 0;
      td->xa_status = 0;
      td->nlog_dbs = 0;
      td->nlog_slots = TXN_NSLOTS;
      td->log_dbs = R_OFFSET(&mgr->reginfo, td->slots);

      TXN_SYSTEM_UNLOCK(dbenv);

      txn->txnid = id;
      txn->td  = td;

      txn->abort = __txn_abort_pp;
      txn->commit = __txn_commit_pp;
      txn->discard = __txn_discard;
      txn->get_name = __txn_get_name;
      txn->id = __txn_id;
      txn->prepare = __txn_prepare;
      txn->set_txn_lsnp = __txn_set_txn_lsnp;
      txn->set_name = __txn_set_name;
      txn->set_timeout = __txn_set_timeout;

      /*
       * If this is a transaction family, we must link the child to the
       * maximal grandparent in the lock table for deadlock detection.
       */
      if (txn->parent != NULL && LOCKING_ON(dbenv))
            if ((ret = __lock_addfamilylocker(dbenv,
                txn->parent->txnid, txn->txnid)) != 0)
                  return (ret);

      if (F_ISSET(txn, TXN_MALLOC)) {
            MUTEX_LOCK(dbenv, mgr->mutex);
            TAILQ_INSERT_TAIL(&mgr->txn_chain, txn, links);
            MUTEX_UNLOCK(dbenv, mgr->mutex);
      }

      return (0);

err:  TXN_SYSTEM_UNLOCK(dbenv);
      return (ret);
}

/*
 * __txn_continue
 *    Fill in the fields of the local transaction structure given
 *    the detail transaction structure.
 *
 * PUBLIC: int __txn_continue __P((DB_ENV *, DB_TXN *, TXN_DETAIL *));
 */
int
__txn_continue(env, txn, td)
      DB_ENV *env;
      DB_TXN *txn;
      TXN_DETAIL *td;
{
      int ret;

      ret = 0;

      txn->mgrp = env->tx_handle;
      txn->parent = NULL;
      txn->txnid = td->txnid;
      txn->td = td;

      txn->abort = __txn_abort_pp;
      txn->commit = __txn_commit_pp;
      txn->discard = __txn_discard;
      txn->get_name = __txn_get_name;
      txn->id = __txn_id;
      txn->prepare = __txn_prepare;
      txn->set_name = __txn_set_name;

      txn->flags = 0;
      /*
       * If this is a restored transaction, we need to propagate that fact
       * to the process-local structure.  However, if it's not a restored
       * transaction, then we're running in XA and we need to make sure
       * that we have a locker associated with this transaction.
       */
      if (F_ISSET(td, TXN_DTL_RESTORED))
            F_SET(txn, TXN_RESTORED);
      else
            ret = __lock_getlocker(env->lk_handle,
                txn->txnid, 0, &txn->locker);

      return (ret);
}

/*
 * __txn_commit_pp --
 *    Interface routine to TXN->commit.
 */
static int
__txn_commit_pp(txn, flags)
      DB_TXN *txn;
      u_int32_t flags;
{
      DB_ENV *dbenv;
      DB_THREAD_INFO *ip;
      int not_child, ret, t_ret;

      dbenv = txn->mgrp->dbenv;
      not_child = txn->parent == NULL;

      ENV_ENTER(dbenv, ip);

      ret = __txn_commit(txn, flags);
      if (not_child && IS_ENV_REPLICATED(dbenv) &&
          (t_ret = __op_rep_exit(dbenv)) != 0 && ret == 0)
            ret = t_ret;
      ENV_LEAVE(dbenv, ip);
      return (ret);
}

/*
 * __txn_commit --
 *    Commit a transaction.
 *
 * PUBLIC: int __txn_commit __P((DB_TXN *, u_int32_t));
 */
int
__txn_commit(txn, flags)
      DB_TXN *txn;
      u_int32_t flags;
{
      DBT list_dbt;
      DB_ENV *dbenv;
      DB_LOCKREQ request;
      DB_TXN *kid;
      REGENV *renv;
      REGINFO *infop;
      TXN_DETAIL *td;
      u_int32_t id;
      int ret, t_ret;

      dbenv = txn->mgrp->dbenv;
      td = txn->td;

      PANIC_CHECK(dbenv);

      /*
       * A common mistake in Berkeley DB programs is to mis-handle deadlock
       * return.  If the transaction deadlocked, they want abort, not commit.
       */
      if (F_ISSET(txn, TXN_DEADLOCK)) {
            ret = __db_txn_deadlock_err(dbenv, txn);
            goto err;
      }

      if ((ret = __txn_isvalid(txn, TXN_OP_COMMIT)) != 0)
            return (ret);

      infop = dbenv->reginfo;
      renv = infop->primary;
      /*
       * No mutex is needed as envid is read-only once it is set.
       */
      id = renv->envid;

      /*
       * We clear flags that are incorrect, ignoring any flag errors, and
       * default to synchronous operations.  By definition, transaction
       * handles are dead when we return, and this error should never
       * happen, but we don't want to fail in the field 'cause the app is
       * specifying the wrong flag for some reason.
       */
      if (__db_fchk(dbenv, "DB_TXN->commit", flags,
          DB_TXN_NOSYNC | DB_TXN_SYNC | DB_TXN_WRITE_NOSYNC) != 0)
            flags = DB_TXN_SYNC;
      if (__db_fcchk(dbenv, "DB_TXN->commit", flags,
          DB_TXN_SYNC, DB_TXN_NOSYNC | DB_TXN_WRITE_NOSYNC) != 0)
            flags = DB_TXN_SYNC;

      if (LF_ISSET(DB_TXN_WRITE_NOSYNC)) {
            F_CLR(txn, TXN_SYNC_FLAGS);
            F_SET(txn, TXN_WRITE_NOSYNC);
      }
      if (LF_ISSET(DB_TXN_NOSYNC)) {
            F_CLR(txn, TXN_SYNC_FLAGS);
            F_SET(txn, TXN_NOSYNC);
      }
      if (LF_ISSET(DB_TXN_SYNC)) {
            F_CLR(txn, TXN_SYNC_FLAGS);
            F_SET(txn, TXN_SYNC);
      }

      /*
       * Commit any unresolved children.  If anyone fails to commit,
       * then try to abort the rest of the kids and then abort the parent.
       * Abort should never fail; if it does, we bail out immediately.
       */
      while ((kid = TAILQ_FIRST(&txn->kids)) != NULL)
            if ((ret = __txn_commit(kid, flags)) != 0)
                  while ((kid = TAILQ_FIRST(&txn->kids)) != NULL)
                        if ((t_ret = __txn_abort(kid)) != 0)
                              return (__db_panic(dbenv, t_ret));

      /*
       * If there are any log records, write a log record and sync the log,
       * else do no log writes.  If the commit is for a child transaction,
       * we do not need to commit the child synchronously since it may still
       * abort (if its parent aborts), and otherwise its parent or ultimate
       * ancestor will write synchronously.
       */
      if (DBENV_LOGGING(dbenv) && (!IS_ZERO_LSN(td->last_lsn) ||
          STAILQ_FIRST(&txn->logs) != NULL)) {
            if (txn->parent == NULL) {
                  /*
                   * We are about to free all the read locks for this
                   * transaction below.  Some of those locks might be
                   * handle locks which should not be freed, because
                   * they will be freed when the handle is closed. Check
                   * the events and preprocess any trades now so we don't
                   * release the locks below.
                   */
                  if ((ret =
                      __txn_doevents(dbenv, txn, TXN_PREPARE, 1)) != 0)
                        goto err;

                  memset(&request, 0, sizeof(request));
                  if (LOCKING_ON(dbenv)) {
                        request.op = DB_LOCK_PUT_READ;
                        if (IS_REP_MASTER(dbenv) &&
                            !IS_ZERO_LSN(td->last_lsn)) {
                              memset(&list_dbt, 0, sizeof(list_dbt));
                              request.obj = &list_dbt;
                        }
                        ret = __lock_vec(dbenv,
                            txn->locker, 0, &request, 1, NULL);
                  }

                  if (ret == 0 && !IS_ZERO_LSN(td->last_lsn)) {
                        ret = __txn_regop_log(dbenv, txn,
                            &td->visible_lsn, LOG_FLAGS(txn),
                            TXN_COMMIT,
                            (int32_t)time(NULL), id, request.obj);
                        if (ret == 0)
                              td->last_lsn = td->visible_lsn;
#ifdef DIAGNOSTIC
                        if (ret == 0) {
                              DB_LSN s_lsn;

                              DB_ASSERT(dbenv, __log_current_lsn(
                                  dbenv, &s_lsn, NULL, NULL) == 0);
                              DB_ASSERT(dbenv, LOG_COMPARE(
                                  &td->visible_lsn, &s_lsn) <= 0);
                              COMPQUIET(s_lsn.file, 0);
                        }
#endif
                  }

                  if (request.obj != NULL && request.obj->data != NULL)
                        __os_free(dbenv, request.obj->data);
                  if (ret != 0)
                        goto err;
            } else {
                  /* Log the commit in the parent! */
                  if (!IS_ZERO_LSN(td->last_lsn) &&
                      (ret = __txn_child_log(dbenv, txn->parent,
                      &((TXN_DETAIL *)txn->parent->td)->last_lsn,
                      0, txn->txnid, &td->last_lsn)) != 0) {
                        goto err;
                  }
                  if (STAILQ_FIRST(&txn->logs) != NULL) {
                        /*
                         * Put the child first so we back it out first.
                         * All records are undone in reverse order.
                         */
                        STAILQ_CONCAT(&txn->logs, &txn->parent->logs);
                        txn->parent->logs = txn->logs;
                        STAILQ_INIT(&txn->logs);
                  }

                  F_SET(txn->parent, TXN_CHILDCOMMIT);
            }
      }

      /*
       * Process any aborted pages from our children.  We delay putting pages
       * on the free list that are newly allocated and then aborted so we can
       * undo other allocations, if necessary, without worrying about these
       * pages which were not on the free list before.
       */
      if (txn->txn_list != NULL) {
#ifndef HAVE_FTRUNCATE
            t_ret = __db_do_the_limbo(dbenv,
                  NULL, txn, txn->txn_list, LIMBO_NORMAL);
            if (t_ret != 0 && ret == 0)
                  ret = t_ret;
#endif
            __db_txnlist_end(dbenv, txn->txn_list);
            txn->txn_list = NULL;
      }

      if (ret != 0)
            goto err;

      /* This is OK because __txn_end can only fail with a panic. */
      return (__txn_end(txn, 1));

err:  /*
       * If we are prepared, then we "must" be able to commit.  We panic here
       * because even though the coordinator might be able to retry it is not
       * clear it would know to do that.  Otherwise  we'll try to abort.  If
       * that is successful, then we return whatever was in ret (that is, the
       * reason we failed).  If the abort was unsuccessful, abort probably
       * returned DB_RUNRECOVERY and we need to propagate that up.
       */
      if (td->status == TXN_PREPARED)
            return (__db_panic(dbenv, ret));

      if ((t_ret = __txn_abort(txn)) != 0)
            ret = t_ret;
      return (ret);
}

/*
 * __txn_abort_pp --
 *    Interface routine to TXN->abort.
 */
static int
__txn_abort_pp(txn)
      DB_TXN *txn;
{
      DB_ENV *dbenv;
      DB_THREAD_INFO *ip;
      int not_child, ret, t_ret;

      dbenv = txn->mgrp->dbenv;
      not_child = txn->parent == NULL;

      ENV_ENTER(dbenv, ip);

      ret = __txn_abort(txn);
      if (not_child && IS_ENV_REPLICATED(dbenv) &&
          (t_ret = __op_rep_exit(dbenv)) != 0 && ret == 0)
            ret = t_ret;
      ENV_LEAVE(dbenv, ip);
      return (ret);
}

/*
 * __txn_abort --
 *    Abort a transaction.
 *
 * PUBLIC: int __txn_abort __P((DB_TXN *));
 */
int
__txn_abort(txn)
      DB_TXN *txn;
{
      DB_ENV *dbenv;
      DB_LOCKREQ request;
      DB_TXN *kid;
      REGENV *renv;
      REGINFO *infop;
      TXN_DETAIL *td;
      u_int32_t id;
      int ret;

      dbenv = txn->mgrp->dbenv;
      td = txn->td;

      PANIC_CHECK(dbenv);

      /* Ensure that abort always fails fatally. */
      if ((ret = __txn_isvalid(txn, TXN_OP_ABORT)) != 0)
            return (__db_panic(dbenv, ret));

      /*
       * Try to abort any unresolved children.
       *
       * Abort either succeeds or panics the region.  As soon as we
       * see any failure, we just get out of here and return the panic
       * up.
       */
      while ((kid = TAILQ_FIRST(&txn->kids)) != NULL)
            if ((ret = __txn_abort(kid)) != 0)
                  return (ret);

      infop = dbenv->reginfo;
      renv = infop->primary;
      /*
       * No mutex is needed as envid is read-only once it is set.
       */
      id = renv->envid;

      /*
       * Fast path -- no need to do anything fancy if there were no
       * modifications (e.g., log records) for this transaction.
       * We still call txn_undo to cleanup the txn_list from our
       * children.
       */
      if (IS_ZERO_LSN(td->last_lsn) && STAILQ_FIRST(&txn->logs) == NULL) {
            if (txn->txn_list == NULL)
                  goto done;
            else
                  goto undo;
      }

      if (LOCKING_ON(dbenv)) {
            /* Allocate a locker for this restored txn if necessary. */
            if (txn->locker == NULL &&
                (ret = __lock_getlocker(dbenv->lk_handle,
                txn->txnid, 1, &txn->locker)) != 0)
                  return (__db_panic(dbenv, ret));
            /*
             * We are about to free all the read locks for this transaction
             * below.  Some of those locks might be handle locks which
             * should not be freed, because they will be freed when the
             * handle is closed.  Check the events and preprocess any
             * trades now so that we don't release the locks below.
             */
            if ((ret = __txn_doevents(dbenv, txn, TXN_ABORT, 1)) != 0)
                  return (__db_panic(dbenv, ret));

            /* Turn off timeouts. */
            if ((ret = __lock_set_timeout(dbenv,
                txn->locker, 0, DB_SET_TXN_TIMEOUT)) != 0)
                  return (__db_panic(dbenv, ret));

            if ((ret = __lock_set_timeout(dbenv,
                txn->locker, 0, DB_SET_LOCK_TIMEOUT)) != 0)
                  return (__db_panic(dbenv, ret));

            request.op = DB_LOCK_UPGRADE_WRITE;
            request.obj = NULL;
            if ((ret = __lock_vec(
                dbenv, txn->locker, DB_LOCK_ABORT, &request, 1, NULL)) != 0)
                  return (__db_panic(dbenv, ret));
      }
undo: if ((ret = __txn_undo(txn)) != 0)
            return (__db_panic(dbenv, ret));

      /*
       * Normally, we do not need to log aborts.  However, if we
       * are a distributed transaction (i.e., we have a prepare),
       * then we log the abort so we know that this transaction
       * was actually completed.
       */
done:  if (DBENV_LOGGING(dbenv) && td->status == TXN_PREPARED &&
          (ret = __txn_regop_log(dbenv, txn, &td->last_lsn,
          LOG_FLAGS(txn), TXN_ABORT, (int32_t)time(NULL), id, NULL)) != 0)
            return (__db_panic(dbenv, ret));

      /* __txn_end always panics if it errors, so pass the return along. */
      return (__txn_end(txn, 0));
}

/*
 * __txn_discard --
 *    Interface routine to TXN->discard.
 */
static int
__txn_discard(txn, flags)
      DB_TXN *txn;
      u_int32_t flags;
{
      DB_ENV *dbenv;
      DB_THREAD_INFO *ip;
      int ret, t_ret;

      dbenv = txn->mgrp->dbenv;

      ENV_ENTER(dbenv, ip);
      ret = __txn_discard_int(txn, flags);
      if (IS_ENV_REPLICATED(dbenv) &&
          (t_ret = __op_rep_exit(dbenv)) != 0 && ret == 0)
            ret = t_ret;
      ENV_LEAVE(dbenv, ip);
      return (ret);
}

/*
 * __txn_discard --
 *    Free the per-process resources associated with this txn handle.
 *
 * PUBLIC: int __txn_discard_int __P((DB_TXN *, u_int32_t flags));
 */
int
__txn_discard_int(txn, flags)
      DB_TXN *txn;
      u_int32_t flags;
{
      DB_ENV *dbenv;
      DB_TXN *freep;
      DB_TXNMGR *mgr;
      int ret;

      COMPQUIET(flags, 0);

      mgr = txn->mgrp;
      dbenv = mgr->dbenv;
      freep = NULL;

      PANIC_CHECK(dbenv);

      if ((ret = __txn_isvalid(txn, TXN_OP_DISCARD)) != 0)
            return (ret);

      /* Should be no children. */
      DB_ASSERT(dbenv, TAILQ_FIRST(&txn->kids) == NULL);

      /* Free the space. */
      MUTEX_LOCK(dbenv, mgr->mutex);
      mgr->n_discards++;
      if (F_ISSET(txn, TXN_MALLOC)) {
            TAILQ_REMOVE(&mgr->txn_chain, txn, links);
            freep = txn;
      }
      MUTEX_UNLOCK(dbenv, mgr->mutex);
      if (freep != NULL)
            __os_free(dbenv, freep);

      return (0);
}

/*
 * __txn_prepare --
 *    Flush the log so a future commit is guaranteed to succeed.
 *
 * PUBLIC: int __txn_prepare __P((DB_TXN *, u_int8_t *));
 */
int
__txn_prepare(txn, gid)
      DB_TXN *txn;
      u_int8_t *gid;
{
      DBT list_dbt, xid;
      DB_ENV *dbenv;
      DB_LOCKREQ request;
      DB_THREAD_INFO *ip;
      DB_TXN *kid;
      TXN_DETAIL *td;
      u_int32_t lflags;
      int ret;

      dbenv = txn->mgrp->dbenv;
      td = txn->td;

      PANIC_CHECK(dbenv);

      if ((ret = __txn_isvalid(txn, TXN_OP_PREPARE)) != 0)
            return (ret);
      if (F_ISSET(txn, TXN_DEADLOCK))
            return (__db_txn_deadlock_err(dbenv, txn));

      ENV_ENTER(dbenv, ip);

      /* Commit any unresolved children. */
      while ((kid = TAILQ_FIRST(&txn->kids)) != NULL)
            if ((ret = __txn_commit(kid, DB_TXN_NOSYNC)) != 0)
                  goto err;

#ifndef HAVE_FTRUNCATE
      if (txn->txn_list != NULL  &&
          (ret = __db_do_the_limbo(dbenv,
          NULL, txn, txn->txn_list, LIMBO_PREPARE)) != 0)
            goto err;
#endif
      /*
       * In XA, the global transaction ID in the txn_detail structure is
       * already set; in a non-XA environment, we must set it here.  XA
       * requires that the transaction be either ENDED or SUSPENDED when
       * prepare is called, so we know that if the xa_status isn't in one
       * of those states, then we are calling prepare directly and we need
       * to fill in the td->xid.
       */
      if ((ret = __txn_doevents(dbenv, txn, TXN_PREPARE, 1)) != 0)
            goto err;
      memset(&request, 0, sizeof(request));
      if (LOCKING_ON(dbenv)) {
            request.op = DB_LOCK_PUT_READ;
            if (!IS_ZERO_LSN(td->last_lsn)) {
                  memset(&list_dbt, 0, sizeof(list_dbt));
                  request.obj = &list_dbt;
            }
            if ((ret = __lock_vec(dbenv,
                txn->locker, 0, &request, 1, NULL)) != 0)
                  goto err;

      }
      if (DBENV_LOGGING(dbenv)) {
            memset(&xid, 0, sizeof(xid));
            if (td->xa_status != TXN_XA_ENDED &&
                td->xa_status != TXN_XA_SUSPENDED)
                  /* Regular prepare; fill in the gid. */
                  memcpy(td->xid, gid, sizeof(td->xid));

            xid.size = sizeof(td->xid);
            xid.data = td->xid;

            lflags = DB_LOG_COMMIT | DB_FLUSH;
            if ((ret = __txn_xa_regop_log(dbenv, txn, &td->last_lsn,
                lflags, TXN_PREPARE, &xid, td->format, td->gtrid, td->bqual,
                &td->begin_lsn, request.obj)) != 0)
                  __db_err(
                      dbenv, ret, "DB_TXN->prepare: log_write failed");

            if (request.obj != NULL && request.obj->data != NULL)
                  __os_free(dbenv, request.obj->data);
            if (ret != 0)
                  goto err;

      }

      MUTEX_LOCK(dbenv, txn->mgrp->mutex);
      td->status = TXN_PREPARED;
      MUTEX_UNLOCK(dbenv, txn->mgrp->mutex);
err:  ENV_LEAVE(dbenv, ip);
      return (ret);
}

/*
 * __txn_id --
 *    Return the transaction ID.
 *
 * PUBLIC: u_int32_t __txn_id __P((DB_TXN *));
 */
u_int32_t
__txn_id(txn)
      DB_TXN *txn;
{
      return (txn->txnid);
}

/*
 * __txn_get_name --
 *    Get a descriptive string from a transaction.
 *
 * PUBLIC: int __txn_get_name __P((DB_TXN *, const char **));
 */
int
__txn_get_name(txn, namep)
      DB_TXN *txn;
      const char **namep;
{
      *namep = txn->name;

      return (0);
}

/*
 * __txn_set_name --
 *    Set a descriptive string for a transaction.
 *
 * PUBLIC: int __txn_set_name __P((DB_TXN *, const char *));
 */
int
__txn_set_name(txn, name)
      DB_TXN *txn;
      const char *name;
{
      DB_ENV *dbenv;
      DB_THREAD_INFO *ip;
      DB_TXNMGR *mgr;
      TXN_DETAIL *td;
      size_t len;
      int ret;
      char *p;

      mgr = txn->mgrp;
      dbenv = mgr->dbenv;
      td = txn->td;
      len = strlen(name) + 1;

      if ((ret = __os_realloc(dbenv, len, &txn->name)) != 0)
            return (ret);
      memcpy(txn->name, name, len);

      ENV_ENTER(dbenv, ip);
      TXN_SYSTEM_LOCK(dbenv);
      if (td->name != INVALID_ROFF) {
            __env_alloc_free(
                &mgr->reginfo, R_ADDR(&mgr->reginfo, td->name));
            td->name = INVALID_ROFF;
      }
      if ((ret = __env_alloc(&mgr->reginfo, len, &p)) != 0) {
            TXN_SYSTEM_UNLOCK(dbenv);
            __db_errx(dbenv,
                "Unable to allocate memory for transaction name");

            __os_free(dbenv, txn->name);
            txn->name = NULL;

            ENV_LEAVE(dbenv, ip);
            return (ret);
      }
      TXN_SYSTEM_UNLOCK(dbenv);
      td->name = R_OFFSET(&mgr->reginfo, p);
      memcpy(p, name, len);

#ifdef DIAGNOSTIC
      /*
       * If DIAGNOSTIC is set, map the name into the log so users can track
       * operations through the log.
       */
      if (DBENV_LOGGING(dbenv))
            (void)__log_printf(dbenv, txn,
                "transaction %#lx named %s", (u_long)txn->txnid, name);
#endif

      ENV_LEAVE(dbenv, ip);
      return (0);
}

/*
 * __txn_set_timeout --
 *    DB_ENV->set_txn_timeout.
 * PUBLIC: int  __txn_set_timeout __P((DB_TXN *, db_timeout_t, u_int32_t));
 */
int
__txn_set_timeout(txn, timeout, op)
      DB_TXN *txn;
      db_timeout_t timeout;
      u_int32_t op;
{
      DB_ENV *dbenv;
      DB_THREAD_INFO *ip;
      int ret;

      dbenv = txn->mgrp->dbenv;

      if (op != DB_SET_TXN_TIMEOUT && op != DB_SET_LOCK_TIMEOUT)
            return (__db_ferr(dbenv, "DB_TXN->set_timeout", 0));

      ENV_ENTER(dbenv, ip);
      ret = __lock_set_timeout( dbenv, txn->locker, timeout, op);
      ENV_LEAVE(txn->mgrp->dbenv, ip);
      return (ret);
}

/*
 * __txn_isvalid --
 *    Return 0 if the DB_TXN is reasonable, otherwise panic.
 */
static int
__txn_isvalid(txn, op)
      const DB_TXN *txn;
      txnop_t op;
{
      DB_ENV *dbenv;
      DB_TXNMGR *mgr;
      DB_TXNREGION *region;
      TXN_DETAIL *td;

      mgr = txn->mgrp;
      dbenv = mgr->dbenv;
      region = mgr->reginfo.primary;

      /* Check for recovery. */
      if (!F_ISSET(txn, TXN_COMPENSATE) &&
          F_ISSET(region, TXN_IN_RECOVERY)) {
            __db_errx(dbenv, "operation not permitted during recovery");
            goto err;
      }

      /* Check for live cursors. */
      if (txn->cursors != 0) {
            __db_errx(dbenv, "transaction has active cursors");
            goto err;
      }

      /* Check transaction's state. */
      td = txn->td;

      /* Handle any operation specific checks. */
      switch (op) {
      case TXN_OP_DISCARD:
            /*
             * Since we're just tossing the per-process space; there are
             * a lot of problems with the transaction that we can tolerate.
             */

            /* Transaction is already been reused. */
            if (txn->txnid != td->txnid)
                  return (0);

            /*
             * What we've got had better be either a prepared or
             * restored transaction.
             */
            if (td->status != TXN_PREPARED &&
                !F_ISSET(td, TXN_DTL_RESTORED)) {
                  __db_errx(dbenv, "not a restored transaction");
                  return (__db_panic(dbenv, EINVAL));
            }

            return (0);
      case TXN_OP_PREPARE:
            if (txn->parent != NULL) {
                  /*
                   * This is not fatal, because you could imagine an
                   * application that simply prepares everybody because
                   * it doesn't distinguish between children and parents.
                   * I'm not arguing this is good, but I could imagine
                   * someone doing it.
                   */
                  __db_errx(dbenv,
                      "Prepare disallowed on child transactions");
                  return (EINVAL);
            }
            break;
      case TXN_OP_ABORT:
      case TXN_OP_COMMIT:
      default:
            break;
      }

      switch (td->status) {
      case TXN_PREPARED:
            if (op == TXN_OP_PREPARE) {
                  __db_errx(dbenv, "transaction already prepared");
                  /*
                   * Txn_prepare doesn't blow away the user handle, so
                   * in this case, give the user the opportunity to
                   * abort or commit.
                   */
                  return (EINVAL);
            }
            break;
      case TXN_RUNNING:
            break;
      case TXN_ABORTED:
      case TXN_COMMITTED:
      default:
            __db_errx(dbenv, "transaction already %s",
                td->status == TXN_COMMITTED ? "committed" : "aborted");
            goto err;
      }

      return (0);

err:  /*
       * If there's a serious problem with the transaction, panic.  TXN
       * handles are dead by definition when we return, and if you use
       * a cursor you forgot to close, we have no idea what will happen.
       */
      return (__db_panic(dbenv, EINVAL));
}

/*
 * __txn_end --
 *    Internal transaction end routine.
 */
static int
__txn_end(txn, is_commit)
      DB_TXN *txn;
      int is_commit;
{
      DB_ENV *dbenv;
      DB_LOCKREQ request;
      DB_TXNLOGREC *lr;
      DB_TXNMGR *mgr;
      DB_TXNREGION *region;
      TXN_DETAIL *ptd, *td;
      db_mutex_t mvcc_mtx;
      int do_closefiles, ret;

      mgr = txn->mgrp;
      dbenv = mgr->dbenv;
      region = mgr->reginfo.primary;
      do_closefiles = 0;

      /* Process commit events. */
      if ((ret = __txn_doevents(dbenv,
          txn, is_commit ? TXN_COMMIT : TXN_ABORT, 0)) != 0)
            return (__db_panic(dbenv, ret));

      /*
       * Release the locks.
       *
       * __txn_end cannot return an simple error, we MUST return
       * success/failure from commit or abort, ignoring any internal
       * errors.  So, we panic if something goes wrong.  We can't
       * deadlock here because we're not acquiring any new locks,
       * so DB_LOCK_DEADLOCK is just as fatal as any other error.
       */
      if (LOCKING_ON(dbenv)) {
            /* Allocate a locker for this restored txn if necessary. */
            if (txn->locker == NULL &&
                (ret = __lock_getlocker(dbenv->lk_handle,
                txn->txnid, 1, &txn->locker)) != 0)
                  return (__db_panic(dbenv, ret));
            request.op = txn->parent == NULL ||
                is_commit == 0 ? DB_LOCK_PUT_ALL : DB_LOCK_INHERIT;
            request.obj = NULL;
            if ((ret = __lock_vec(dbenv,
                txn->locker, 0, &request, 1, NULL)) != 0)
                  return (__db_panic(dbenv, ret));
      }

      /* End the transaction. */
      td = txn->td;
      if (td->nlog_dbs != 0 && (ret = __txn_dref_fname(dbenv, txn)) != 0)
            return (__db_panic(dbenv, ret));

      TXN_SYSTEM_LOCK(dbenv);

      td->status = is_commit ? TXN_COMMITTED : TXN_ABORTED;
      SH_TAILQ_REMOVE(&region->active_txn, td, links, __txn_detail);
      if (F_ISSET(td, TXN_DTL_RESTORED)) {
            region->stat.st_nrestores--;
            do_closefiles = region->stat.st_nrestores == 0;
      }

      if (td->name != INVALID_ROFF) {
            __env_alloc_free(
                &mgr->reginfo, R_ADDR(&mgr->reginfo, td->name));
            td->name = INVALID_ROFF;
      }
      if (txn->parent != NULL) {
            ptd = txn->parent->td;
            SH_TAILQ_REMOVE(&ptd->kids, td, klinks, __txn_detail);
      } else if ((mvcc_mtx = td->mvcc_mtx) != MUTEX_INVALID ||
          td->mvcc_ref != 0) {
            if (IS_MAX_LSN(td->visible_lsn))
                  td->visible_lsn = td->last_lsn;
            MUTEX_LOCK(dbenv, mvcc_mtx);
            if (td->mvcc_ref != 0) {
                  SH_TAILQ_INSERT_HEAD(&region->mvcc_txn,
                      td, links, __txn_detail);
#ifdef HAVE_STATISTICS
                  if (++region->stat.st_nsnapshot >
                      region->stat.st_maxnsnapshot)
                        region->stat.st_maxnsnapshot =
                            region->stat.st_nsnapshot;
#endif
                  td = NULL;
            }
            MUTEX_UNLOCK(dbenv, mvcc_mtx);
            if (td != NULL)
                  if ((ret = __mutex_free(dbenv, &td->mvcc_mtx)) != 0)
                        return (__db_panic(dbenv, ret));
      }

      if (td != NULL) {
            if (td->nlog_slots != TXN_NSLOTS)
                  __env_alloc_free(&mgr->reginfo,
                      R_ADDR(&mgr->reginfo, td->log_dbs));
            __env_alloc_free(&mgr->reginfo, td);
      }

#ifdef HAVE_STATISTICS
      if (is_commit)
            region->stat.st_ncommits++;
      else
            region->stat.st_naborts++;
      --region->stat.st_nactive;
#endif

      TXN_SYSTEM_UNLOCK(dbenv);

      /*
       * The transaction cannot get more locks, remove its locker info,
       * if any.
       */
      if (LOCKING_ON(dbenv) && (ret =
          __lock_freefamilylocker(dbenv->lk_handle, txn->locker)) != 0)
            return (__db_panic(dbenv, ret));
      if (txn->parent != NULL)
            TAILQ_REMOVE(&txn->parent->kids, txn, klinks);

      /* Free the space. */
      while ((lr = STAILQ_FIRST(&txn->logs)) != NULL) {
            STAILQ_REMOVE(&txn->logs, lr, __txn_logrec, links);
            __os_free(dbenv, lr);
      }
      if (txn->name != NULL) {
            __os_free(dbenv, txn->name);
            txn->name = NULL;
      }
      if (F_ISSET(txn, TXN_MALLOC)) {
            MUTEX_LOCK(dbenv, mgr->mutex);
            TAILQ_REMOVE(&mgr->txn_chain, txn, links);
            MUTEX_UNLOCK(dbenv, mgr->mutex);

            __os_free(dbenv, txn);
      }

      if (do_closefiles) {
            /*
             * Otherwise, we have resolved the last outstanding prepared
             * txn and need to invalidate the fileids that were left
             * open for those txns and then close them.
             */
            (void)__dbreg_invalidate_files(dbenv, 1);
            (void)__dbreg_close_files(dbenv, 1);
            if (IS_REP_MASTER(dbenv))
                  F_CLR(dbenv->rep_handle, DBREP_OPENFILES);
            F_CLR(dbenv->lg_handle, DBLOG_OPENFILES);
            mgr->n_discards = 0;
            (void)__txn_checkpoint(dbenv, 0, 0,
                DB_CKP_INTERNAL | DB_FORCE);
      }

      return (0);
}

static int
__txn_dispatch_undo(dbenv, txn, rdbt, key_lsn, txnlist)
      DB_ENV *dbenv;
      DB_TXN *txn;
      DBT *rdbt;
      DB_LSN *key_lsn;
      DB_TXNHEAD *txnlist;
{
      int ret;

      txnlist->td = txn->td;
      ret = __db_dispatch(dbenv, dbenv->recover_dtab,
          dbenv->recover_dtab_size, rdbt, key_lsn, DB_TXN_ABORT, txnlist);
      if (ret == DB_SURPRISE_KID) {
            F_SET(txn, TXN_CHILDCOMMIT);
            ret = 0;
      }
      if (ret == 0 && F_ISSET(txn, TXN_CHILDCOMMIT) && IS_ZERO_LSN(*key_lsn))
            ret = __db_txnlist_lsnget(dbenv, txnlist, key_lsn, 0);

      return (ret);
}

/*
 * __txn_undo --
 *    Undo the transaction with id txnid.
 */
static int
__txn_undo(txn)
      DB_TXN *txn;
{
      DBT rdbt;
      DB_ENV *dbenv;
      DB_LOGC *logc;
      DB_LSN key_lsn;
      DB_TXN *ptxn;
      DB_TXNHEAD *txnlist;
      DB_TXNLOGREC *lr;
      DB_TXNMGR *mgr;
      int ret, t_ret;

      mgr = txn->mgrp;
      dbenv = mgr->dbenv;
      logc = NULL;
      txnlist = NULL;
      ret = 0;

      if (!LOGGING_ON(dbenv))
            return (0);

      /*
       * This is the simplest way to code this, but if the mallocs during
       * recovery turn out to be a performance issue, we can do the
       * allocation here and use DB_DBT_USERMEM.
       */
      memset(&rdbt, 0, sizeof(rdbt));

      /*
       * Allocate a txnlist for children and aborted page allocs.
       * We need to associate the list with the maximal parent
       * so that aborted pages are recovered when that transaction
       * is committed or aborted.
       */
      for (ptxn = txn->parent; ptxn != NULL && ptxn->parent != NULL;)
            ptxn = ptxn->parent;

      if (ptxn != NULL && ptxn->txn_list != NULL)
            txnlist = ptxn->txn_list;
      else if (txn->txn_list != NULL)
            txnlist = txn->txn_list;
      else if ((ret = __db_txnlist_init(dbenv, 0, 0, NULL, &txnlist)) != 0)
            return (ret);
      else if (ptxn != NULL)
            ptxn->txn_list = txnlist;

      /*
       * Take log records from the linked list stored in the transaction,
       * then from the log.
       */
      STAILQ_FOREACH(lr, &txn->logs, links) {
            rdbt.data = lr->data;
            rdbt.size = 0;
            LSN_NOT_LOGGED(key_lsn);
            ret =
                __txn_dispatch_undo(dbenv, txn, &rdbt, &key_lsn, txnlist);
            if (ret != 0) {
                  __db_err(dbenv, ret,
                      "DB_TXN->abort: in-memory log undo failed");
                  goto err;
            }
      }

      key_lsn = ((TXN_DETAIL *)txn->td)->last_lsn;

      if (!IS_ZERO_LSN(key_lsn) &&
           (ret = __log_cursor(dbenv, &logc)) != 0)
            goto err;

      while (!IS_ZERO_LSN(key_lsn)) {
            /*
             * The dispatch routine returns the lsn of the record
             * before the current one in the key_lsn argument.
             */
            if ((ret = __logc_get(logc, &key_lsn, &rdbt, DB_SET)) == 0) {
                  ret = __txn_dispatch_undo(dbenv,
                      txn, &rdbt, &key_lsn, txnlist);
            }

            if (ret != 0) {
                  __db_err(dbenv, ret,
                "DB_TXN->abort: log undo failed for LSN: %lu %lu",
                      (u_long)key_lsn.file, (u_long)key_lsn.offset);
                  goto err;
            }
      }

#ifndef HAVE_FTRUNCATE
      ret = __db_do_the_limbo(dbenv, ptxn, txn, txnlist, LIMBO_NORMAL);
#endif

err:  if (logc != NULL && (t_ret = __logc_close(logc)) != 0 && ret == 0)
            ret = t_ret;

      if (ptxn == NULL && txnlist != NULL)
            __db_txnlist_end(dbenv, txnlist);
      return (ret);
}

/*
 * __txn_activekids --
 *    Return if this transaction has any active children.
 *
 * PUBLIC: int __txn_activekids __P((DB_ENV *, u_int32_t, DB_TXN *));
 */
int
__txn_activekids(dbenv, rectype, txn)
      DB_ENV *dbenv;
      u_int32_t rectype;
      DB_TXN *txn;
{
      /*
       * On a child commit, we know that there are children (i.e., the
       * committing child at the least.  In that case, skip this check.
       */
      if (F_ISSET(txn, TXN_COMPENSATE) || rectype == DB___txn_child)
            return (0);

      if (TAILQ_FIRST(&txn->kids) != NULL) {
            __db_errx(dbenv, "Child transaction is active");
            return (EPERM);
      }
      return (0);
}

/*
 * __txn_force_abort --
 *    Force an abort record into the log if the commit record
 *    failed to get to disk.
 *
 * PUBLIC: int __txn_force_abort __P((DB_ENV *, u_int8_t *));
 */
int
__txn_force_abort(dbenv, buffer)
      DB_ENV *dbenv;
      u_int8_t *buffer;
{
      DB_CIPHER *db_cipher;
      HDR hdr, *hdrp;
      u_int32_t offset, opcode, sum_len;
      u_int8_t *bp, *key, chksum[DB_MAC_KEY];
      size_t hdrsize, rec_len;
      int ret;

      db_cipher = dbenv->crypto_handle;

      /*
       * This routine depends on the layout of HDR and the __txn_regop
       * __txn_xa_regop records in txn.src.  We are passed the beginning
       * of the commit record in the log buffer and overwrite the
       * commit with an abort and recalculate the checksum.
       */
      hdrsize = CRYPTO_ON(dbenv) ? HDR_CRYPTO_SZ : HDR_NORMAL_SZ;

      hdrp = (HDR *)buffer;
      memcpy(&hdr.prev, buffer + SSZ(HDR, prev), sizeof(hdr.prev));
      memcpy(&hdr.len, buffer + SSZ(HDR, len), sizeof(hdr.len));
      rec_len = hdr.len - hdrsize;

      offset = sizeof(u_int32_t) + sizeof(u_int32_t) + sizeof(DB_LSN);
      if (CRYPTO_ON(dbenv)) {
            key = db_cipher->mac_key;
            sum_len = DB_MAC_KEY;
            if ((ret = db_cipher->decrypt(dbenv, db_cipher->data,
                &hdrp->iv[0], buffer + hdrsize, rec_len)) != 0)
                  return (__db_panic(dbenv, ret));
      } else {
            key = NULL;
            sum_len = sizeof(u_int32_t);
      }
      bp = buffer + hdrsize + offset;
      opcode = TXN_ABORT;
      memcpy(bp, &opcode, sizeof(opcode));

      if (CRYPTO_ON(dbenv) &&
          (ret = db_cipher->encrypt(dbenv,
          db_cipher->data, &hdrp->iv[0], buffer + hdrsize, rec_len)) != 0)
            return (__db_panic(dbenv, ret));

      __db_chksum(&hdr, buffer + hdrsize, rec_len, key, chksum);
      memcpy(buffer + SSZA(HDR, chksum), chksum, sum_len);

      return (0);
}

/*
 * __txn_preclose --
 *    Before we can close an environment, we need to check if we were in the
 *    middle of taking care of restored transactions.  If so, close the files
 *    we opened.
 *
 * PUBLIC: int __txn_preclose __P((DB_ENV *));
 */
int
__txn_preclose(dbenv)
      DB_ENV *dbenv;
{
      DB_TXNMGR *mgr;
      DB_TXNREGION *region;
      int do_closefiles, ret;

      mgr = dbenv->tx_handle;
      region = mgr->reginfo.primary;
      do_closefiles = 0;

      TXN_SYSTEM_LOCK(dbenv);
      if (region != NULL &&
          region->stat.st_nrestores <= mgr->n_discards &&
          mgr->n_discards != 0)
            do_closefiles = 1;
      TXN_SYSTEM_UNLOCK(dbenv);

      if (do_closefiles) {
            /*
             * Set the DBLOG_RECOVER flag while closing these files so they
             * do not create additional log records that will confuse future
             * recoveries.
             */
            F_SET(dbenv->lg_handle, DBLOG_RECOVER);
            ret = __dbreg_close_files(dbenv, 0);
            F_CLR(dbenv->lg_handle, DBLOG_RECOVER);
      } else
            ret = 0;

      return (ret);
}

/*
 * __txn_reset --
 *    Reset the last txnid to its minimum value, and log the reset.
 *
 * PUBLIC: int __txn_reset __P((DB_ENV *));
 */
int
__txn_reset(dbenv)
      DB_ENV *dbenv;
{
      DB_LSN scrap;
      DB_TXNREGION *region;

      region = dbenv->tx_handle->reginfo.primary;
      region->last_txnid = TXN_MINIMUM;

      DB_ASSERT(dbenv, LOGGING_ON(dbenv));
      return (__txn_recycle_log(dbenv,
          NULL, &scrap, 0, TXN_MINIMUM, TXN_MAXIMUM));
}

/*
 * txn_set_txn_lsnp --
 *    Set the pointer to the begin_lsn field if that field is zero.
 *    Set the pointer to the last_lsn field.
 */
static void
__txn_set_txn_lsnp(txn, blsnp, llsnp)
      DB_TXN *txn;
      DB_LSN **blsnp, **llsnp;
{
      TXN_DETAIL *td;

      td = txn->td;
      *llsnp = &td->last_lsn;

      while (txn->parent != NULL)
            txn = txn->parent;

      td = txn->td;
      if (IS_ZERO_LSN(td->begin_lsn))
            *blsnp = &td->begin_lsn;
}

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