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txn.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *    Sleepycat Software.  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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the University of
 *    California, Berkeley and its contributors.
 * 4. 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.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)txn.c   10.66 (Sleepycat) 1/3/99";
#endif /* not lint */


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

#include <errno.h>
#include <string.h>
#include <time.h>
#endif

#include "db_int.h"
#include "shqueue.h"
#include "db_page.h"
#include "db_shash.h"
#include "txn.h"
#include "db_dispatch.h"
#include "lock.h"
#include "log.h"
#include "db_am.h"
#include "common_ext.h"

static int  __txn_begin __P((DB_TXN *));
static int  __txn_check_running __P((const DB_TXN *, TXN_DETAIL **));
static int  __txn_end __P((DB_TXN *, int));
static void __txn_freekids __P((DB_TXN *));
static int  __txn_grow_region __P((DB_TXNMGR *));
static int  __txn_init __P((DB_TXNREGION *));
static int  __txn_undo __P((DB_TXN *));
static int  __txn_validate_region __P((DB_TXNMGR *));

/*
 * This file contains the top level routines of the transaction library.
 * It assumes that a lock manager and log manager that conform to the db_log(3)
 * and db_lock(3) interfaces exist.
 *
 * Initialize a transaction region in shared memory.
 * Return 0 on success, errno on failure.
 */
static int
__txn_init(txn_region)
      DB_TXNREGION *txn_region;
{
      time_t now;

      (void)time(&now);

      /* maxtxns is already initialized. */
      txn_region->magic = DB_TXNMAGIC;
      txn_region->version = DB_TXNVERSION;
      txn_region->last_txnid = TXN_MINIMUM;
      /*
       * XXX
       * If we ever do more types of locking and logging, this changes.
       */
      txn_region->logtype = 0;
      txn_region->locktype = 0;
      txn_region->time_ckp = now;
      ZERO_LSN(txn_region->last_ckp);
      ZERO_LSN(txn_region->pending_ckp);
      SH_TAILQ_INIT(&txn_region->active_txn);
      __db_shalloc_init((void *)&txn_region[1],
          TXN_REGION_SIZE(txn_region->maxtxns) - sizeof(DB_TXNREGION));

      return (0);
}

int
txn_open(path, flags, mode, dbenv, mgrpp)
      const char *path;
      u_int32_t flags;
      int mode;
      DB_ENV *dbenv;
      DB_TXNMGR **mgrpp;
{
      DB_TXNMGR *tmgrp;
      u_int32_t maxtxns;
      int ret;

      /* Validate arguments. */
      if (dbenv == NULL)
            return (EINVAL);
#ifdef HAVE_SPINLOCKS
#define     OKFLAGS     (DB_CREATE | DB_THREAD | DB_TXN_NOSYNC)
#else
#define     OKFLAGS     (DB_CREATE | DB_TXN_NOSYNC)
#endif
      if ((ret = __db_fchk(dbenv, "txn_open", flags, OKFLAGS)) != 0)
            return (ret);

      maxtxns = dbenv->tx_max != 0 ? dbenv->tx_max : 20;

      /* Now, create the transaction manager structure and set its fields. */
      if ((ret = __os_calloc(1, sizeof(DB_TXNMGR), &tmgrp)) != 0)
            return (ret);

      /* Initialize the transaction manager structure. */
      tmgrp->mutexp = NULL;
      tmgrp->dbenv = dbenv;
      tmgrp->recover =
          dbenv->tx_recover == NULL ? __db_dispatch : dbenv->tx_recover;
      tmgrp->flags = LF_ISSET(DB_TXN_NOSYNC | DB_THREAD);
      TAILQ_INIT(&tmgrp->txn_chain);

      /* Join/create the txn region. */
      tmgrp->reginfo.dbenv = dbenv;
      tmgrp->reginfo.appname = DB_APP_NONE;
      if (path == NULL)
            tmgrp->reginfo.path = NULL;
      else
            if ((ret = __os_strdup(path, &tmgrp->reginfo.path)) != 0)
                  goto err;
      tmgrp->reginfo.file = DEFAULT_TXN_FILE;
      tmgrp->reginfo.mode = mode;
      tmgrp->reginfo.size = TXN_REGION_SIZE(maxtxns);
      tmgrp->reginfo.dbflags = flags;
      tmgrp->reginfo.addr = NULL;
      tmgrp->reginfo.fd = -1;
      tmgrp->reginfo.flags = dbenv->tx_max == 0 ? REGION_SIZEDEF : 0;
      if ((ret = __db_rattach(&tmgrp->reginfo)) != 0)
            goto err;

      /* Fill in region-related fields. */
      tmgrp->region = tmgrp->reginfo.addr;
      tmgrp->mem = &tmgrp->region[1];

      if (F_ISSET(&tmgrp->reginfo, REGION_CREATED)) {
            tmgrp->region->maxtxns = maxtxns;
            if ((ret = __txn_init(tmgrp->region)) != 0)
                  goto err;

      } else if (tmgrp->region->magic != DB_TXNMAGIC) {
            /* Check if valid region. */
            __db_err(dbenv, "txn_open: Bad magic number");
            ret = EINVAL;
            goto err;
      }

      if (LF_ISSET(DB_THREAD)) {
            if ((ret = __db_shalloc(tmgrp->mem, sizeof(db_mutex_t),
                MUTEX_ALIGNMENT, &tmgrp->mutexp)) == 0)
                  /*
                   * Since we only get here if threading is turned on, we
                   * know that we have spinlocks, so the offset is going
                   * to be ignored.  We put 0 here as a valid placeholder.
                   */
                  __db_mutex_init(tmgrp->mutexp, 0);
            if (ret != 0)
                  goto err;
      }

      UNLOCK_TXNREGION(tmgrp);
      *mgrpp = tmgrp;
      return (0);

err:  if (tmgrp->reginfo.addr != NULL) {
            if (tmgrp->mutexp != NULL)
                  __db_shalloc_free(tmgrp->mem, tmgrp->mutexp);

            UNLOCK_TXNREGION(tmgrp);
            (void)__db_rdetach(&tmgrp->reginfo);
            if (F_ISSET(&tmgrp->reginfo, REGION_CREATED))
                  (void)txn_unlink(path, 1, dbenv);
      }

      if (tmgrp->reginfo.path != NULL)
            __os_freestr(tmgrp->reginfo.path);
      __os_free(tmgrp, sizeof(*tmgrp));
      return (ret);
}

/*
 * __txn_panic --
 *    Panic a transaction region.
 *
 * PUBLIC: void __txn_panic __P((DB_ENV *));
 */
void
__txn_panic(dbenv)
      DB_ENV *dbenv;
{
      if (dbenv->tx_info != NULL)
            dbenv->tx_info->region->hdr.panic = 1;
}

/*
 * txn_begin --
 *    This is a wrapper to the actual begin process.  Normal txn_begin()
 * allocates a DB_TXN structure for the caller, while txn_xa_begin() does
 * not.  Other than that, both call into the common __txn_begin 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.
 */
int
txn_begin(tmgrp, parent, txnpp)
      DB_TXNMGR *tmgrp;
      DB_TXN *parent, **txnpp;
{
      DB_TXN *txn;
      int ret;

      TXN_PANIC_CHECK(tmgrp);

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

      txn->parent = parent;
      TAILQ_INIT(&txn->kids);
      txn->mgrp = tmgrp;
      txn->flags = TXN_MALLOC;
      if ((ret = __txn_begin(txn)) != 0) {
            __os_free(txn, sizeof(DB_TXN));
            txn = NULL;
      }
      if (txn != NULL && parent != NULL)
            TAILQ_INSERT_HEAD(&parent->kids, txn, klinks);
      *txnpp = 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;
{
      TXN_PANIC_CHECK(dbenv->tx_info);

      memset(txn, 0, sizeof(DB_TXN));

      txn->mgrp = dbenv->tx_info;

      return (__txn_begin(txn));
}

/*
 * __txn_begin --
 *    Normal DB version of txn_begin.
 */
static int
__txn_begin(txn)
      DB_TXN *txn;
{
      DB_LSN begin_lsn;
      DB_TXNMGR *mgr;
      TXN_DETAIL *td;
      size_t off;
      u_int32_t id;
      int ret;

      /*
       * We do not have to write begin records (and if we do not, then we
       * need never write records for read-only transactions).  However,
       * we do need to find the current LSN so that we can store it in the
       * transaction structure, so we can know where to take checkpoints.
       */
      mgr = txn->mgrp;
      if (mgr->dbenv->lg_info != NULL && (ret =
          log_put(mgr->dbenv->lg_info, &begin_lsn, NULL, DB_CURLSN)) != 0)
            goto err2;

      LOCK_TXNREGION(mgr);

      /* Make sure that last_txnid is not going to wrap around. */
      if (mgr->region->last_txnid == TXN_INVALID) {
            __db_err(mgr->dbenv, "txn_begin: %s  %s",
                "Transaction ID wrapping.",
                "Snapshot your database and start a new log.");
            ret = EINVAL;
            goto err1;
      }

      if ((ret = __txn_validate_region(mgr)) != 0)
            goto err1;

      /* Allocate a new transaction detail structure. */
      if ((ret = __db_shalloc(mgr->mem, sizeof(TXN_DETAIL), 0, &td)) != 0
          && ret == ENOMEM && (ret = __txn_grow_region(mgr)) == 0)
            ret = __db_shalloc(mgr->mem, sizeof(TXN_DETAIL), 0, &td);
      if (ret != 0)
            goto err1;

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

      id = ++mgr->region->last_txnid;
      ++mgr->region->nbegins;

      td->txnid = id;
      td->begin_lsn = begin_lsn;
      ZERO_LSN(td->last_lsn);
      td->last_lock = 0;
      td->status = TXN_RUNNING;
      if (txn->parent != NULL)
            td->parent = txn->parent->off;
      else
            td->parent = 0;

      off = (u_int8_t *)td - (u_int8_t *)mgr->region;
      UNLOCK_TXNREGION(mgr);

      ZERO_LSN(txn->last_lsn);
      txn->txnid = id;
      txn->off = off;

      if (F_ISSET(txn, TXN_MALLOC)) {
            LOCK_TXNTHREAD(mgr);
            TAILQ_INSERT_TAIL(&mgr->txn_chain, txn, links);
            UNLOCK_TXNTHREAD(mgr);
      }

      return (0);

err1: UNLOCK_TXNREGION(mgr);

err2: return (ret);
}
/*
 * txn_commit --
 *    Commit a transaction.
 */
int
txn_commit(txnp)
      DB_TXN *txnp;
{
      DB_LOG *logp;
      DB_TXNMGR *mgr;
      int ret;

      mgr = txnp->mgrp;

      TXN_PANIC_CHECK(mgr);
      if ((ret = __txn_check_running(txnp, NULL)) != 0)
            return (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 if its parent aborts, it will abort too and its parent
       * (or ultimate ancestor) will write synchronously.
       */
      if ((logp = mgr->dbenv->lg_info) != NULL &&
          !IS_ZERO_LSN(txnp->last_lsn)) {
            if (txnp->parent == NULL)
                  ret = __txn_regop_log(logp, txnp, &txnp->last_lsn,
                      F_ISSET(mgr, DB_TXN_NOSYNC) ? 0 : DB_FLUSH,
                      TXN_COMMIT);
            else
                  ret = __txn_child_log(logp, txnp, &txnp->last_lsn, 0,
                      TXN_COMMIT, txnp->parent->txnid);
            if (ret != 0)
                  return (ret);
      }

      /*
       * If this is the senior ancestor (i.e., it has no children), then we
       * can release all the child transactions since everyone is committing.
       * Then we can release this transaction.  If this is not the ultimate
       * ancestor, then we can neither free it or its children.
       */
      if (txnp->parent == NULL)
            __txn_freekids(txnp);

      return (__txn_end(txnp, 1));
}

/*
 * txn_abort --
 *    Abort a transcation.
 */
int
txn_abort(txnp)
      DB_TXN *txnp;
{
      int ret;
      DB_TXN *kids;

      TXN_PANIC_CHECK(txnp->mgrp);
      if ((ret = __txn_check_running(txnp, NULL)) != 0)
            return (ret);

      for (kids = TAILQ_FIRST(&txnp->kids);
          kids != NULL;
          kids = TAILQ_FIRST(&txnp->kids))
            txn_abort(kids);

      if ((ret = __txn_undo(txnp)) != 0) {
            __db_err(txnp->mgrp->dbenv,
                "txn_abort: Log undo failed %s", strerror(ret));
            return (ret);
      }
      return (__txn_end(txnp, 0));
}

/*
 * txn_prepare --
 *    Flush the log so a future commit is guaranteed to succeed.
 */
int
txn_prepare(txnp)
      DB_TXN *txnp;
{
      DBT xid;
      DB_ENV *dbenv;
      TXN_DETAIL *td;
      int ret;

      if ((ret = __txn_check_running(txnp, &td)) != 0)
            return (ret);

      dbenv = txnp->mgrp->dbenv;
      memset(&xid, 0, sizeof(xid));
      xid.data = td->xid;
      /*
       * We indicate that a transaction is an XA transaction by putting
       * a valid size in the xid.size fiels.  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, but we are
       * calling prepare that we are not an XA transaction.
       */
      xid.size =
          td->xa_status != TXN_XA_ENDED && td->xa_status != TXN_XA_SUSPENDED ?
          0 : sizeof(td->xid);
      if (dbenv->lg_info != NULL &&
          (ret = __txn_xa_regop_log(dbenv->lg_info, txnp, &txnp->last_lsn,
          F_ISSET(txnp->mgrp, DB_TXN_NOSYNC) ? 0 : DB_FLUSH, TXN_PREPARE,
          &xid, td->format, td->gtrid, td->bqual, &td->begin_lsn)) != 0) {
            __db_err(dbenv,
                "txn_prepare: log_write failed %s\n", strerror(ret));
            return (ret);
      }

      LOCK_TXNTHREAD(txnp->mgrp);
      td->status = TXN_PREPARED;
      UNLOCK_TXNTHREAD(txnp->mgrp);
      return (ret);
}

/*
 * Return the transaction ID associated with a particular transaction
 */
u_int32_t
txn_id(txnp)
      DB_TXN *txnp;
{
      return (txnp->txnid);
}

/*
 * txn_close --
 *    Close the transaction region, does not imply a checkpoint.
 */
int
txn_close(tmgrp)
      DB_TXNMGR *tmgrp;
{
      DB_TXN *txnp;
      int ret, t_ret;

      TXN_PANIC_CHECK(tmgrp);

      ret = 0;

      /*
       * This function had better only be called once per process
       * (i.e., not per thread), so there should be no synchronization
       * required.
       */
      while ((txnp =
          TAILQ_FIRST(&tmgrp->txn_chain)) != TAILQ_END(&tmgrp->txn_chain))
            if ((t_ret = txn_abort(txnp)) != 0) {
                  __txn_end(txnp, 0);
                  if (ret == 0)
                        ret = t_ret;
            }

      if (tmgrp->dbenv->lg_info &&
          (t_ret = log_flush(tmgrp->dbenv->lg_info, NULL)) != 0 && ret == 0)
            ret = t_ret;

      if (tmgrp->mutexp != NULL) {
            LOCK_TXNREGION(tmgrp);
            __db_shalloc_free(tmgrp->mem, tmgrp->mutexp);
            UNLOCK_TXNREGION(tmgrp);
      }

      if ((t_ret = __db_rdetach(&tmgrp->reginfo)) != 0 && ret == 0)
            ret = t_ret;

      if (tmgrp->reginfo.path != NULL)
            __os_freestr(tmgrp->reginfo.path);
      __os_free(tmgrp, sizeof(*tmgrp));

      return (ret);
}

/*
 * txn_unlink --
 *    Remove the transaction region.
 */
int
txn_unlink(path, force, dbenv)
      const char *path;
      int force;
      DB_ENV *dbenv;
{
      REGINFO reginfo;
      int ret;

      memset(&reginfo, 0, sizeof(reginfo));
      reginfo.dbenv = dbenv;
      reginfo.appname = DB_APP_NONE;
      if (path != NULL && (ret = __os_strdup(path, &reginfo.path)) != 0)
            return (ret);
      reginfo.file = DEFAULT_TXN_FILE;
      ret = __db_runlink(&reginfo, force);
      if (reginfo.path != NULL)
            __os_freestr(reginfo.path);
      return (ret);
}

/* Internal routines. */

/*
 * Return 0 if the txnp is reasonable, otherwise returns EINVAL.
 */
static int
__txn_check_running(txnp, tdp)
      const DB_TXN *txnp;
      TXN_DETAIL **tdp;
{
      TXN_DETAIL *tp;

      tp = NULL;
      if (txnp != NULL && txnp->mgrp != NULL && txnp->mgrp->region != NULL) {
            tp = (TXN_DETAIL *)((u_int8_t *)txnp->mgrp->region + txnp->off);
            /*
             * Child transactions could be marked committed which is OK.
             */
            if (tp->status != TXN_RUNNING &&
                tp->status != TXN_PREPARED && tp->status != TXN_COMMITTED)
                  tp = NULL;
            if (tdp != NULL)
                  *tdp = tp;
      }

      return (tp == NULL ? EINVAL : 0);
}

static int
__txn_end(txnp, is_commit)
      DB_TXN *txnp;
      int is_commit;
{
      DB_LOCKREQ request;
      DB_TXNMGR *mgr;
      TXN_DETAIL *tp;
      u_int32_t locker;
      int ret;

      mgr = txnp->mgrp;

      /* Release the locks. */
      locker = txnp->txnid;
      request.op = txnp->parent == NULL ||
          is_commit == 0 ? DB_LOCK_PUT_ALL : DB_LOCK_INHERIT;

      if (mgr->dbenv->lk_info) {
            ret =
                lock_tvec(mgr->dbenv->lk_info, txnp, 0, &request, 1, NULL);
            if (ret != 0 && (ret != DB_LOCK_DEADLOCK || is_commit)) {
                  __db_err(mgr->dbenv, "%s: release locks failed %s",
                      is_commit ? "txn_commit" : "txn_abort",
                      strerror(ret));
                  return (ret);
            }
      }

      /* End the transaction. */
      LOCK_TXNREGION(mgr);

      /*
       * Child transactions that are committing cannot be released until
       * the parent commits, since the parent may abort, causing the child
       * to abort as well.
       */
      tp = (TXN_DETAIL *)((u_int8_t *)mgr->region + txnp->off);
      if (txnp->parent == NULL || !is_commit) {
            SH_TAILQ_REMOVE(&mgr->region->active_txn,
                tp, links, __txn_detail);

            __db_shalloc_free(mgr->mem, tp);
      } else
            tp->status = is_commit ? TXN_COMMITTED : TXN_ABORTED;

      if (is_commit)
            mgr->region->ncommits++;
      else
            mgr->region->naborts++;

      UNLOCK_TXNREGION(mgr);

      /*
       * If the transaction aborted, we can remove it from its parent links.
       * If it committed, then we need to leave it on, since the parent can
       * still abort.
       */
      if (txnp->parent != NULL && !is_commit)
            TAILQ_REMOVE(&txnp->parent->kids, txnp, klinks);

      /* Free the space. */
      if (F_ISSET(txnp, TXN_MALLOC) && (txnp->parent == NULL || !is_commit)) {
            LOCK_TXNTHREAD(mgr);
            TAILQ_REMOVE(&mgr->txn_chain, txnp, links);
            UNLOCK_TXNTHREAD(mgr);

            __os_free(txnp, sizeof(*txnp));
      }

      return (0);
}


/*
 * __txn_undo --
 *    Undo the transaction with id txnid.  Returns 0 on success and
 *    errno on failure.
 */
static int
__txn_undo(txnp)
      DB_TXN *txnp;
{
      DBT rdbt;
      DB_LOG *logp;
      DB_LSN key_lsn;
      DB_TXNMGR *mgr;
      int ret;

      mgr = txnp->mgrp;
      logp = mgr->dbenv->lg_info;
      if (logp == NULL)
            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));
      if (F_ISSET(logp, DB_AM_THREAD))
            F_SET(&rdbt, DB_DBT_MALLOC);

      key_lsn = txnp->last_lsn;           /* structure assignment */
      for (ret = 0; ret == 0 && !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 = log_get(logp, &key_lsn, &rdbt, DB_SET)) == 0) {
                  ret =
                      mgr->recover(logp, &rdbt, &key_lsn, TXN_UNDO, NULL);
                  if (F_ISSET(logp, DB_AM_THREAD) && rdbt.data != NULL) {
                        __os_free(rdbt.data, rdbt.size);
                        rdbt.data = NULL;
                  }
            }
            if (ret != 0)
                  return (ret);
      }

      return (ret);
}

/*
 * Transaction checkpoint.
 * If either kbytes or minutes is non-zero, then we only take the checkpoint
 * more than "minutes" minutes have passed since the last checkpoint or if
 * more than "kbytes" of log data have been written since the last checkpoint.
 * When taking a checkpoint, find the oldest active transaction and figure out
 * its first LSN.  This is the lowest LSN we can checkpoint, since any record
 * written after since that point may be involved in a transaction and may
 * therefore need to be undone in the case of an abort.
 */
int
txn_checkpoint(mgr, kbytes, minutes)
      const DB_TXNMGR *mgr;
      u_int32_t kbytes, minutes;
{
      DB_LOG *dblp;
      DB_LSN ckp_lsn, sync_lsn, last_ckp;
      TXN_DETAIL *txnp;
      time_t last_ckp_time, now;
      u_int32_t kbytes_written;
      int ret;

      TXN_PANIC_CHECK(mgr);

      /*
       * Check if we need to run recovery.
       */
      ZERO_LSN(ckp_lsn);
      if (minutes != 0) {
            (void)time(&now);

            LOCK_TXNREGION(mgr);
            last_ckp_time = mgr->region->time_ckp;
            UNLOCK_TXNREGION(mgr);

            if (now - last_ckp_time >= (time_t)(minutes * 60))
                  goto do_ckp;
      }

      if (kbytes != 0) {
            dblp = mgr->dbenv->lg_info;
            LOCK_LOGREGION(dblp);
            kbytes_written =
                dblp->lp->stat.st_wc_mbytes * 1024 +
                dblp->lp->stat.st_wc_bytes / 1024;
            ckp_lsn = dblp->lp->lsn;
            UNLOCK_LOGREGION(dblp);
            if (kbytes_written >= (u_int32_t)kbytes)
                  goto do_ckp;
      }

      /*
       * If we checked time and data and didn't go to checkpoint,
       * we're done.
       */
      if (minutes != 0 || kbytes != 0)
            return (0);

do_ckp:
      if (IS_ZERO_LSN(ckp_lsn)) {
            dblp = mgr->dbenv->lg_info;
            LOCK_LOGREGION(dblp);
            ckp_lsn = dblp->lp->lsn;
            UNLOCK_LOGREGION(dblp);
      }

      /*
       * We have to find an LSN such that all transactions begun
       * before that LSN are complete.
       */
      LOCK_TXNREGION(mgr);

      if (!IS_ZERO_LSN(mgr->region->pending_ckp))
            ckp_lsn = mgr->region->pending_ckp;
      else
            for (txnp =
                SH_TAILQ_FIRST(&mgr->region->active_txn, __txn_detail);
                txnp != NULL;
                txnp = SH_TAILQ_NEXT(txnp, links, __txn_detail)) {

                  /*
                   * Look through the active transactions for the
                   * lowest begin lsn.
                   */
                  if (!IS_ZERO_LSN(txnp->begin_lsn) &&
                      log_compare(&txnp->begin_lsn, &ckp_lsn) < 0)
                        ckp_lsn = txnp->begin_lsn;
            }

      mgr->region->pending_ckp = ckp_lsn;
      UNLOCK_TXNREGION(mgr);

      /*
       * memp_sync may change the lsn you pass it, so don't pass it
       * the actual ckp_lsn, pass it a temp instead.
       */
      sync_lsn = ckp_lsn;
      if (mgr->dbenv->mp_info != NULL &&
          (ret = memp_sync(mgr->dbenv->mp_info, &sync_lsn)) != 0) {
            /*
             * ret == DB_INCOMPLETE means that there are still buffers to
             * flush, the checkpoint is not complete.  Wait and try again.
             */
            if (ret > 0)
                  __db_err(mgr->dbenv,
                      "txn_checkpoint: system failure in memp_sync %s\n",
                      strerror(ret));
            return (ret);
      }
      if (mgr->dbenv->lg_info != NULL) {
            LOCK_TXNREGION(mgr);
            last_ckp = mgr->region->last_ckp;
            ZERO_LSN(mgr->region->pending_ckp);
            UNLOCK_TXNREGION(mgr);

            if ((ret = __txn_ckp_log(mgr->dbenv->lg_info,
               NULL, &ckp_lsn, DB_CHECKPOINT, &ckp_lsn, &last_ckp)) != 0) {
                  __db_err(mgr->dbenv,
                      "txn_checkpoint: log failed at LSN [%ld %ld] %s\n",
                      (long)ckp_lsn.file, (long)ckp_lsn.offset,
                      strerror(ret));
                  return (ret);
            }

            LOCK_TXNREGION(mgr);
            mgr->region->last_ckp = ckp_lsn;
            (void)time(&mgr->region->time_ckp);
            UNLOCK_TXNREGION(mgr);
      }
      return (0);
}

/*
 * __txn_validate_region --
 *    Called at every interface to verify if the region has changed size,
 *    and if so, to remap the region in and reset the process' pointers.
 */
static int
__txn_validate_region(tp)
      DB_TXNMGR *tp;
{
      int ret;

      if (tp->reginfo.size == tp->region->hdr.size)
            return (0);

      /* Detach/reattach the region. */
      if ((ret = __db_rreattach(&tp->reginfo, tp->region->hdr.size)) != 0)
            return (ret);

      /* Reset region information. */
      tp->region = tp->reginfo.addr;
      tp->mem = &tp->region[1];

      return (0);
}

static int
__txn_grow_region(tp)
      DB_TXNMGR *tp;
{
      size_t incr, oldsize;
      u_int32_t mutex_offset, oldmax;
      u_int8_t *curaddr;
      int ret;

      oldmax = tp->region->maxtxns;
      incr = oldmax * sizeof(DB_TXN);
      mutex_offset = tp->mutexp != NULL ?
          (u_int8_t *)tp->mutexp - (u_int8_t *)tp->region : 0;

      oldsize = tp->reginfo.size;
      if ((ret = __db_rgrow(&tp->reginfo, oldsize + incr)) != 0)
            return (ret);
      tp->region = tp->reginfo.addr;

      /* Throw the new space on the free list. */
      curaddr = (u_int8_t *)tp->region + oldsize;
      tp->mem = &tp->region[1];
      tp->mutexp = mutex_offset != 0 ?
          (db_mutex_t *)((u_int8_t *)tp->region + mutex_offset) : NULL;

      *((size_t *)curaddr) = incr - sizeof(size_t);
      curaddr += sizeof(size_t);
      __db_shalloc_free(tp->mem, curaddr);

      tp->region->maxtxns = 2 * oldmax;

      return (0);
}

int
txn_stat(mgr, statp, db_malloc)
      DB_TXNMGR *mgr;
      DB_TXN_STAT **statp;
      void *(*db_malloc) __P((size_t));
{
      DB_TXN_STAT *stats;
      TXN_DETAIL *txnp;
      size_t nbytes;
      u_int32_t nactive, ndx;
      int ret;

      TXN_PANIC_CHECK(mgr);

      LOCK_TXNREGION(mgr);
      nactive = mgr->region->nbegins -
          mgr->region->naborts - mgr->region->ncommits;
      UNLOCK_TXNREGION(mgr);

      /*
       * Allocate a bunch of extra active structures to handle any
       * that have been created since we unlocked the region.
       */
      nbytes = sizeof(DB_TXN_STAT) + sizeof(DB_TXN_ACTIVE) * (nactive + 200);
      if ((ret = __os_malloc(nbytes, db_malloc, &stats)) != 0)
            return (ret);

      LOCK_TXNREGION(mgr);
      stats->st_last_txnid = mgr->region->last_txnid;
      stats->st_last_ckp = mgr->region->last_ckp;
      stats->st_maxtxns = mgr->region->maxtxns;
      stats->st_naborts = mgr->region->naborts;
      stats->st_nbegins = mgr->region->nbegins;
      stats->st_ncommits = mgr->region->ncommits;
      stats->st_pending_ckp = mgr->region->pending_ckp;
      stats->st_time_ckp = mgr->region->time_ckp;
      stats->st_nactive = stats->st_nbegins -
          stats->st_naborts - stats->st_ncommits;
      if (stats->st_nactive > nactive + 200)
            stats->st_nactive = nactive + 200;
      stats->st_txnarray = (DB_TXN_ACTIVE *)&stats[1];

      ndx = 0;
      for (txnp = SH_TAILQ_FIRST(&mgr->region->active_txn, __txn_detail);
          txnp != NULL;
          txnp = SH_TAILQ_NEXT(txnp, links, __txn_detail)) {
            stats->st_txnarray[ndx].txnid = txnp->txnid;
            stats->st_txnarray[ndx].lsn = txnp->begin_lsn;
            ndx++;

            if (ndx >= stats->st_nactive)
                  break;
      }

      stats->st_region_wait = mgr->region->hdr.lock.mutex_set_wait;
      stats->st_region_nowait = mgr->region->hdr.lock.mutex_set_nowait;
      stats->st_refcnt = mgr->region->hdr.refcnt;
      stats->st_regsize = mgr->region->hdr.size;

      UNLOCK_TXNREGION(mgr);
      *statp = stats;
      return (0);
}

static void
__txn_freekids(txnp)
      DB_TXN *txnp;
{
      DB_TXNMGR *mgr;
      TXN_DETAIL *tp;
      DB_TXN *kids;

      mgr = txnp->mgrp;

      for (kids = TAILQ_FIRST(&txnp->kids);
          kids != NULL;
          kids = TAILQ_FIRST(&txnp->kids)) {
            /* Free any children of this transaction. */
            __txn_freekids(kids);

            /* Free the transaction detail in the region. */
            LOCK_TXNREGION(mgr);
            tp = (TXN_DETAIL *)((u_int8_t *)mgr->region + kids->off);
            SH_TAILQ_REMOVE(&mgr->region->active_txn,
                tp, links, __txn_detail);

            __db_shalloc_free(mgr->mem, tp);
            UNLOCK_TXNREGION(mgr);

            /* Now remove from its parent. */
            TAILQ_REMOVE(&txnp->kids, kids, klinks);
            if (F_ISSET(txnp, TXN_MALLOC)) {
                  LOCK_TXNTHREAD(mgr);
                  TAILQ_REMOVE(&mgr->txn_chain, kids, links);
                  UNLOCK_TXNTHREAD(mgr);
                  __os_free(kids, sizeof(*kids));
            }
      }
}

/*
 * __txn_is_ancestor --
 *    Determine if a transaction is an ancestor of another transaction.
 * This is used during lock promotion when we do not have the per-process
 * data structures that link parents together.  Instead, we'll have to
 * follow the links in the transaction region.
 *
 * PUBLIC: int __txn_is_ancestor __P((DB_TXNMGR *, size_t, size_t));
 */
int
__txn_is_ancestor(mgr, hold_off, req_off)
      DB_TXNMGR *mgr;
      size_t hold_off, req_off;
{
      TXN_DETAIL *hold_tp, *req_tp;

      hold_tp = (TXN_DETAIL *)((u_int8_t *)mgr->region + hold_off);
      req_tp = (TXN_DETAIL *)((u_int8_t *)mgr->region + req_off);

      while (req_tp->parent != 0) {
            req_tp =
                (TXN_DETAIL *)((u_int8_t *)mgr->region + req_tp->parent);
            if (req_tp->txnid == hold_tp->txnid)
                  return (1);
      }

      return (0);
}

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