mariadb/storage/xtradb/trx/trx0sys.cc

/*****************************************************************************

Copyright (c) 1996, 2017, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2017, MariaDB Corporation.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA

*****************************************************************************/

/**************************************************//**
@file trx/trx0sys.cc
Transaction system

Created 3/26/1996 Heikki Tuuri
*******************************************************/

#include "trx0sys.h"

#ifdef UNIV_NONINL
#include "trx0sys.ic"
#endif

#ifdef UNIV_HOTBACKUP
#include "fsp0types.h"

#else	/* !UNIV_HOTBACKUP */
#include "fsp0fsp.h"
#include "mtr0log.h"
#include "mtr0log.h"
#include "trx0trx.h"
#include "trx0rseg.h"
#include "trx0undo.h"
#include "srv0srv.h"
#include "srv0start.h"
#include "trx0purge.h"
#include "log0log.h"
#include "log0recv.h"
#include "os0file.h"
#include "read0read.h"

#ifdef WITH_WSREP
#include "ha_prototypes.h" /* wsrep_is_wsrep_xid() */
#endif /* */

#include <mysql/service_wsrep.h>

/** The file format tag structure with id and name. */
struct file_format_t {
	ulint		id;		/*!< id of the file format */
	const char*	name;		/*!< text representation of the
					file format */
	ib_mutex_t		mutex;		/*!< covers changes to the above
					fields */
};

/** The transaction system */
UNIV_INTERN trx_sys_t*		trx_sys		= NULL;

/** In a MySQL replication slave, in crash recovery we store the master log
file name and position here. */
/* @{ */
/** Master binlog file name */
UNIV_INTERN char	trx_sys_mysql_master_log_name[TRX_SYS_MYSQL_LOG_NAME_LEN];
/** Master binlog file position.  We have successfully got the updates
up to this position.  -1 means that no crash recovery was needed, or
there was no master log position info inside InnoDB.*/
UNIV_INTERN ib_int64_t	trx_sys_mysql_master_log_pos	= -1;
/* @} */

/** If this MySQL server uses binary logging, after InnoDB has been inited
and if it has done a crash recovery, we store the binlog file name and position
here. */
/* @{ */
/** Binlog file name */
UNIV_INTERN char	trx_sys_mysql_bin_log_name[TRX_SYS_MYSQL_LOG_NAME_LEN];
/** Binlog file position, or -1 if unknown */
UNIV_INTERN ib_int64_t	trx_sys_mysql_bin_log_pos	= -1;
/* @} */
#endif /* !UNIV_HOTBACKUP */

/** List of animal names representing file format. */
static const char*	file_format_name_map[] = {
	"Antelope",
	"Barracuda",
	"Cheetah",
	"Dragon",
	"Elk",
	"Fox",
	"Gazelle",
	"Hornet",
	"Impala",
	"Jaguar",
	"Kangaroo",
	"Leopard",
	"Moose",
	"Nautilus",
	"Ocelot",
	"Porpoise",
	"Quail",
	"Rabbit",
	"Shark",
	"Tiger",
	"Urchin",
	"Viper",
	"Whale",
	"Xenops",
	"Yak",
	"Zebra"
};

/** The number of elements in the file format name array. */
static const ulint	FILE_FORMAT_NAME_N
	= sizeof(file_format_name_map) / sizeof(file_format_name_map[0]);

#ifdef UNIV_PFS_MUTEX
/* Key to register the mutex with performance schema */
UNIV_INTERN mysql_pfs_key_t	file_format_max_mutex_key;
UNIV_INTERN mysql_pfs_key_t	trx_sys_mutex_key;
#endif /* UNIV_PFS_RWLOCK */

#ifndef UNIV_HOTBACKUP
#ifdef UNIV_DEBUG
/* Flag to control TRX_RSEG_N_SLOTS behavior debugging. */
UNIV_INTERN uint	trx_rseg_n_slots_debug = 0;
#endif

/** This is used to track the maximum file format id known to InnoDB. It's
updated via SET GLOBAL innodb_file_format_max = 'x' or when we open
or create a table. */
static	file_format_t	file_format_max;

#ifdef UNIV_DEBUG
/****************************************************************//**
Checks whether a trx is in one of rw_trx_list or ro_trx_list.
@return	TRUE if is in */
UNIV_INTERN
ibool
trx_in_trx_list(
/*============*/
	const trx_t*	in_trx)	/*!< in: transaction */
{
	const trx_t*	trx;
	trx_list_t*	trx_list;

	/* Non-locking autocommits should not hold any locks. */
	assert_trx_in_list(in_trx);

	trx_list = in_trx->read_only
		? &trx_sys->ro_trx_list : &trx_sys->rw_trx_list;

	ut_ad(mutex_own(&trx_sys->mutex));

	ut_ad(trx_assert_started(in_trx));

	for (trx = UT_LIST_GET_FIRST(*trx_list);
	     trx != NULL && trx != in_trx;
	     trx = UT_LIST_GET_NEXT(trx_list, trx)) {

		assert_trx_in_list(trx);
		ut_ad(trx->read_only == (trx_list == &trx_sys->ro_trx_list));
	}

	return(trx != NULL);
}
#endif /* UNIV_DEBUG */

/*****************************************************************//**
Writes the value of max_trx_id to the file based trx system header. */
UNIV_INTERN
void
trx_sys_flush_max_trx_id(void)
/*==========================*/
{
	mtr_t		mtr;
	trx_sysf_t*	sys_header;

	ut_ad(mutex_own(&trx_sys->mutex));

	if (!srv_read_only_mode) {
		mtr_start(&mtr);

		sys_header = trx_sysf_get(&mtr);

		mlog_write_ull(
			sys_header + TRX_SYS_TRX_ID_STORE,
			trx_sys->max_trx_id, &mtr);

		mtr_commit(&mtr);
	}
}

/*****************************************************************//**
Updates the offset information about the end of the MySQL binlog entry
which corresponds to the transaction just being committed. In a MySQL
replication slave updates the latest master binlog position up to which
replication has proceeded. */
UNIV_INTERN
void
trx_sys_update_mysql_binlog_offset(
/*===============================*/
	const char*	file_name,/*!< in: MySQL log file name */
	ib_int64_t	offset,	/*!< in: position in that log file */
	ulint		field,	/*!< in: offset of the MySQL log info field in
				the trx sys header */
#ifdef WITH_WSREP
        trx_sysf_t*     sys_header, /*!< in: trx sys header */
#endif /* WITH_WSREP */
	mtr_t*		mtr)	/*!< in: mtr */
{
#ifndef WITH_WSREP
	trx_sysf_t*	sys_header;
#endif /* !WITH_WSREP */

	if (ut_strlen(file_name) >= TRX_SYS_MYSQL_LOG_NAME_LEN) {

		/* We cannot fit the name to the 512 bytes we have reserved */

		return;
	}

#ifndef WITH_WSREP
	sys_header = trx_sysf_get(mtr);
#endif /* !WITH_WSREP */

	if (mach_read_from_4(sys_header + field
			     + TRX_SYS_MYSQL_LOG_MAGIC_N_FLD)
	    != TRX_SYS_MYSQL_LOG_MAGIC_N) {

		mlog_write_ulint(sys_header + field
				 + TRX_SYS_MYSQL_LOG_MAGIC_N_FLD,
				 TRX_SYS_MYSQL_LOG_MAGIC_N,
				 MLOG_4BYTES, mtr);
	}

	if (0 != strcmp((char*) (sys_header + field + TRX_SYS_MYSQL_LOG_NAME),
			file_name)) {

		mlog_write_string(sys_header + field
				  + TRX_SYS_MYSQL_LOG_NAME,
				  (byte*) file_name, 1 + ut_strlen(file_name),
				  mtr);
	}

	if (mach_read_from_4(sys_header + field
			     + TRX_SYS_MYSQL_LOG_OFFSET_HIGH) > 0
	    || (offset >> 32) > 0) {

		mlog_write_ulint(sys_header + field
				 + TRX_SYS_MYSQL_LOG_OFFSET_HIGH,
				 (ulint)(offset >> 32),
				 MLOG_4BYTES, mtr);
	}

	mlog_write_ulint(sys_header + field
			 + TRX_SYS_MYSQL_LOG_OFFSET_LOW,
			 (ulint)(offset & 0xFFFFFFFFUL),
			 MLOG_4BYTES, mtr);
}

/*****************************************************************//**
Stores the MySQL binlog offset info in the trx system header if
the magic number shows it valid, and print the info to stderr */
UNIV_INTERN
void
trx_sys_print_mysql_binlog_offset(void)
/*===================================*/
{
	trx_sysf_t*	sys_header;
	mtr_t		mtr;
	ulint		trx_sys_mysql_bin_log_pos_high;
	ulint		trx_sys_mysql_bin_log_pos_low;

	mtr_start(&mtr);

	sys_header = trx_sysf_get(&mtr);

	if (mach_read_from_4(sys_header + TRX_SYS_MYSQL_LOG_INFO
			     + TRX_SYS_MYSQL_LOG_MAGIC_N_FLD)
	    != TRX_SYS_MYSQL_LOG_MAGIC_N) {

		mtr_commit(&mtr);

		return;
	}

	trx_sys_mysql_bin_log_pos_high = mach_read_from_4(
		sys_header + TRX_SYS_MYSQL_LOG_INFO
		+ TRX_SYS_MYSQL_LOG_OFFSET_HIGH);
	trx_sys_mysql_bin_log_pos_low = mach_read_from_4(
		sys_header + TRX_SYS_MYSQL_LOG_INFO
		+ TRX_SYS_MYSQL_LOG_OFFSET_LOW);

	trx_sys_mysql_bin_log_pos
		= (((ib_int64_t) trx_sys_mysql_bin_log_pos_high) << 32)
		+ (ib_int64_t) trx_sys_mysql_bin_log_pos_low;

	ut_memcpy(trx_sys_mysql_bin_log_name,
		  sys_header + TRX_SYS_MYSQL_LOG_INFO
		  + TRX_SYS_MYSQL_LOG_NAME, TRX_SYS_MYSQL_LOG_NAME_LEN);

	fprintf(stderr,
		"InnoDB: Last MySQL binlog file position %lu %lu,"
		" file name %s\n",
		trx_sys_mysql_bin_log_pos_high, trx_sys_mysql_bin_log_pos_low,
		trx_sys_mysql_bin_log_name);

	mtr_commit(&mtr);
}

#ifdef WITH_WSREP

#ifdef UNIV_DEBUG
static long long trx_sys_cur_xid_seqno = -1;
static unsigned char trx_sys_cur_xid_uuid[16];

/** Read WSREP XID seqno */
static inline long long read_wsrep_xid_seqno(const XID* xid)
{
	long long seqno;
	memcpy(&seqno, xid->data + 24, sizeof(long long));
	return seqno;
}

/** Read WSREP XID UUID */
static inline void read_wsrep_xid_uuid(const XID* xid, unsigned char* buf)
{
	memcpy(buf, xid->data + 8, 16);
}

#endif /* UNIV_DEBUG */

/** Update WSREP XID info in sys_header of TRX_SYS_PAGE_NO = 5.
@param[in]	xid		Transaction XID
@param[in,out]	sys_header	sys_header
@param[in]	mtr		minitransaction */
UNIV_INTERN
void
trx_sys_update_wsrep_checkpoint(
	const XID*	xid,
	trx_sysf_t*	sys_header,
	mtr_t*		mtr)
{
#ifdef UNIV_DEBUG
	if (xid->formatID != -1
	    && mach_read_from_4(sys_header + TRX_SYS_WSREP_XID_INFO
			+ TRX_SYS_WSREP_XID_MAGIC_N_FLD)
		== TRX_SYS_WSREP_XID_MAGIC_N) {
		/* Check that seqno is monotonically increasing */
		unsigned char xid_uuid[16];
		long long xid_seqno = read_wsrep_xid_seqno(xid);
		read_wsrep_xid_uuid(xid, xid_uuid);

		if (!memcmp(xid_uuid, trx_sys_cur_xid_uuid, 8)) {
			ut_ad(xid_seqno > trx_sys_cur_xid_seqno);
			trx_sys_cur_xid_seqno = xid_seqno;
		} else {
			memcpy(trx_sys_cur_xid_uuid, xid_uuid, 16);
		}

		trx_sys_cur_xid_seqno = xid_seqno;
	}
#endif /* UNIV_DEBUG */

	ut_ad(xid && mtr);
	ut_a(xid->formatID == -1 || wsrep_is_wsrep_xid((const XID *)xid));

	if (mach_read_from_4(sys_header + TRX_SYS_WSREP_XID_INFO
			+ TRX_SYS_WSREP_XID_MAGIC_N_FLD)
		!= TRX_SYS_WSREP_XID_MAGIC_N) {
		mlog_write_ulint(sys_header + TRX_SYS_WSREP_XID_INFO
			+ TRX_SYS_WSREP_XID_MAGIC_N_FLD,
			TRX_SYS_WSREP_XID_MAGIC_N,
			MLOG_4BYTES, mtr);
	}

	mlog_write_ulint(sys_header + TRX_SYS_WSREP_XID_INFO
		+ TRX_SYS_WSREP_XID_FORMAT,
		(int)xid->formatID,
		MLOG_4BYTES, mtr);
	mlog_write_ulint(sys_header + TRX_SYS_WSREP_XID_INFO
		+ TRX_SYS_WSREP_XID_GTRID_LEN,
		(int)xid->gtrid_length,
		MLOG_4BYTES, mtr);
	mlog_write_ulint(sys_header + TRX_SYS_WSREP_XID_INFO
		+ TRX_SYS_WSREP_XID_BQUAL_LEN,
		(int)xid->bqual_length,
		MLOG_4BYTES, mtr);
	mlog_write_string(sys_header + TRX_SYS_WSREP_XID_INFO
		+ TRX_SYS_WSREP_XID_DATA,
		(const unsigned char*) xid->data,
		XIDDATASIZE, mtr);
}

/** Read WSREP XID from sys_header of TRX_SYS_PAGE_NO = 5.
@param[out]	xid	Transaction XID
@retval true if found, false if not */
UNIV_INTERN
bool
trx_sys_read_wsrep_checkpoint(XID* xid)
{
	trx_sysf_t*	sys_header;
	mtr_t		mtr;
	ulint		magic;

	ut_ad(xid);

	mtr_start(&mtr);

	sys_header = trx_sysf_get(&mtr);

	if ((magic = mach_read_from_4(sys_header + TRX_SYS_WSREP_XID_INFO
				+ TRX_SYS_WSREP_XID_MAGIC_N_FLD))
		!= TRX_SYS_WSREP_XID_MAGIC_N) {
		memset(xid, 0, sizeof(*xid));
		xid->formatID = -1;
		trx_sys_update_wsrep_checkpoint(xid, sys_header, &mtr);
		mtr_commit(&mtr);
		return false;
	}

	xid->formatID     = (int)mach_read_from_4(
		sys_header
		+ TRX_SYS_WSREP_XID_INFO + TRX_SYS_WSREP_XID_FORMAT);
	xid->gtrid_length = (int)mach_read_from_4(
		sys_header
		+ TRX_SYS_WSREP_XID_INFO + TRX_SYS_WSREP_XID_GTRID_LEN);
	xid->bqual_length = (int)mach_read_from_4(
		sys_header
		+ TRX_SYS_WSREP_XID_INFO + TRX_SYS_WSREP_XID_BQUAL_LEN);
	ut_memcpy(xid->data,
		sys_header + TRX_SYS_WSREP_XID_INFO + TRX_SYS_WSREP_XID_DATA,
		XIDDATASIZE);

	mtr_commit(&mtr);
	return true;
}

#endif /* WITH_WSREP */

/*****************************************************************//**
Prints to stderr the MySQL master log offset info in the trx system header if
the magic number shows it valid. */
UNIV_INTERN
void
trx_sys_print_mysql_master_log_pos(void)
/*====================================*/
{
	trx_sysf_t*	sys_header;
	mtr_t		mtr;

	mtr_start(&mtr);

	sys_header = trx_sysf_get(&mtr);

	if (mach_read_from_4(sys_header + TRX_SYS_MYSQL_MASTER_LOG_INFO
			     + TRX_SYS_MYSQL_LOG_MAGIC_N_FLD)
	    != TRX_SYS_MYSQL_LOG_MAGIC_N) {

		mtr_commit(&mtr);

		return;
	}

	fprintf(stderr,
		"InnoDB: In a MySQL replication slave the last"
		" master binlog file\n"
		"InnoDB: position %lu %lu, file name %s\n",
		(ulong) mach_read_from_4(sys_header
					 + TRX_SYS_MYSQL_MASTER_LOG_INFO
					 + TRX_SYS_MYSQL_LOG_OFFSET_HIGH),
		(ulong) mach_read_from_4(sys_header
					 + TRX_SYS_MYSQL_MASTER_LOG_INFO
					 + TRX_SYS_MYSQL_LOG_OFFSET_LOW),
		sys_header + TRX_SYS_MYSQL_MASTER_LOG_INFO
		+ TRX_SYS_MYSQL_LOG_NAME);
	/* Copy the master log position info to global variables we can
	use in ha_innobase.cc to initialize glob_mi to right values */

	ut_memcpy(trx_sys_mysql_master_log_name,
		  sys_header + TRX_SYS_MYSQL_MASTER_LOG_INFO
		  + TRX_SYS_MYSQL_LOG_NAME,
		  TRX_SYS_MYSQL_LOG_NAME_LEN);

	trx_sys_mysql_master_log_pos
		= (((ib_int64_t) mach_read_from_4(
			    sys_header + TRX_SYS_MYSQL_MASTER_LOG_INFO
			    + TRX_SYS_MYSQL_LOG_OFFSET_HIGH)) << 32)
		+ ((ib_int64_t) mach_read_from_4(
			   sys_header + TRX_SYS_MYSQL_MASTER_LOG_INFO
			   + TRX_SYS_MYSQL_LOG_OFFSET_LOW));
	mtr_commit(&mtr);
}

/****************************************************************//**
Looks for a free slot for a rollback segment in the trx system file copy.
@return	slot index or ULINT_UNDEFINED if not found */
UNIV_INTERN
ulint
trx_sysf_rseg_find_free(
/*====================*/
	mtr_t*	mtr)	/*!< in: mtr */
{
	ulint		i;
	trx_sysf_t*	sys_header;

	sys_header = trx_sysf_get(mtr);

	for (i = 0; i < TRX_SYS_N_RSEGS; i++) {
		ulint	page_no;

		page_no = trx_sysf_rseg_get_page_no(sys_header, i, mtr);

		if (page_no == FIL_NULL) {

			return(i);
		}
	}

	return(ULINT_UNDEFINED);
}

/*****************************************************************//**
Creates the file page for the transaction system. This function is called only
at the database creation, before trx_sys_init. */
static
void
trx_sysf_create(
/*============*/
	mtr_t*	mtr)	/*!< in: mtr */
{
	trx_sysf_t*	sys_header;
	ulint		slot_no;
	buf_block_t*	block;
	page_t*		page;
	ulint		page_no;
	byte*		ptr;
	ulint		len;

	ut_ad(mtr);

	/* Note that below we first reserve the file space x-latch, and
	then enter the kernel: we must do it in this order to conform
	to the latching order rules. */

	mtr_x_lock(fil_space_get_latch(TRX_SYS_SPACE, NULL), mtr);

	/* Create the trx sys file block in a new allocated file segment */
	block = fseg_create(TRX_SYS_SPACE, 0, TRX_SYS + TRX_SYS_FSEG_HEADER,
			    mtr);
	buf_block_dbg_add_level(block, SYNC_TRX_SYS_HEADER);

	ut_a(buf_block_get_page_no(block) == TRX_SYS_PAGE_NO);

	page = buf_block_get_frame(block);

	mlog_write_ulint(page + FIL_PAGE_TYPE, FIL_PAGE_TYPE_TRX_SYS,
			 MLOG_2BYTES, mtr);

	/* Reset the doublewrite buffer magic number to zero so that we
	know that the doublewrite buffer has not yet been created (this
	suppresses a Valgrind warning) */

	mlog_write_ulint(page + TRX_SYS_DOUBLEWRITE
			 + TRX_SYS_DOUBLEWRITE_MAGIC, 0, MLOG_4BYTES, mtr);

	sys_header = trx_sysf_get(mtr);

	/* Start counting transaction ids from number 1 up */
	mach_write_to_8(sys_header + TRX_SYS_TRX_ID_STORE, 1);

	/* Reset the rollback segment slots.  Old versions of InnoDB
	define TRX_SYS_N_RSEGS as 256 (TRX_SYS_OLD_N_RSEGS) and expect
	that the whole array is initialized. */
	ptr = TRX_SYS_RSEGS + sys_header;
	len = ut_max(TRX_SYS_OLD_N_RSEGS, TRX_SYS_N_RSEGS)
		* TRX_SYS_RSEG_SLOT_SIZE;
	memset(ptr, 0xff, len);
	ptr += len;
	ut_a(ptr <= page + (UNIV_PAGE_SIZE - FIL_PAGE_DATA_END));

	/* Initialize all of the page.  This part used to be uninitialized. */
	memset(ptr, 0, UNIV_PAGE_SIZE - FIL_PAGE_DATA_END + page - ptr);

	mlog_log_string(sys_header, UNIV_PAGE_SIZE - FIL_PAGE_DATA_END
			+ page - sys_header, mtr);

	/* Create the first rollback segment in the SYSTEM tablespace */
	slot_no = trx_sysf_rseg_find_free(mtr);
	page_no = trx_rseg_header_create(TRX_SYS_SPACE, 0, ULINT_MAX, slot_no,
					 mtr);

	ut_a(slot_no == TRX_SYS_SYSTEM_RSEG_ID);
	ut_a(page_no == FSP_FIRST_RSEG_PAGE_NO);
}

/*****************************************************************//**
Compare two trx_rseg_t instances on last_trx_no. */
static
int
trx_rseg_compare_last_trx_no(
/*=========================*/
	const void*	p1,		/*!< in: elem to compare */
	const void*	p2)		/*!< in: elem to compare */
{
	ib_int64_t	cmp;

	const rseg_queue_t*	rseg_q1 = (const rseg_queue_t*) p1;
	const rseg_queue_t*	rseg_q2 = (const rseg_queue_t*) p2;

	cmp = rseg_q1->trx_no - rseg_q2->trx_no;

	if (cmp < 0) {
		return(-1);
	} else if (cmp > 0) {
		return(1);
	}

	return(0);
}

/*****************************************************************//**
Creates and initializes the central memory structures for the transaction
system. This is called when the database is started.
@return min binary heap of rsegs to purge */
UNIV_INTERN
ib_bh_t*
trx_sys_init_at_db_start(void)
/*==========================*/
{
	mtr_t		mtr;
	ib_bh_t*	ib_bh;
	trx_sysf_t*	sys_header;
	ib_uint64_t	rows_to_undo	= 0;
	const char*	unit		= "";

	/* We create the min binary heap here and pass ownership to
	purge when we init the purge sub-system. Purge is responsible
	for freeing the binary heap. */

	ib_bh = ib_bh_create(
		trx_rseg_compare_last_trx_no,
		sizeof(rseg_queue_t), TRX_SYS_N_RSEGS);

	mtr_start(&mtr);

	/* Allocate the trx descriptors array */
	trx_sys->descriptors = static_cast<trx_id_t*>(
		ut_malloc(sizeof(trx_id_t) *
			  TRX_DESCR_ARRAY_INITIAL_SIZE));
	trx_sys->descr_n_max = TRX_DESCR_ARRAY_INITIAL_SIZE;
	trx_sys->descr_n_used = 0;
	srv_descriptors_memory = TRX_DESCR_ARRAY_INITIAL_SIZE *
		sizeof(trx_id_t);

	sys_header = trx_sysf_get(&mtr);

	if (srv_force_recovery < SRV_FORCE_NO_UNDO_LOG_SCAN) {
		trx_rseg_array_init(sys_header, ib_bh, &mtr);
	}

	/* VERY important: after the database is started, max_trx_id value is
	divisible by TRX_SYS_TRX_ID_WRITE_MARGIN, and the 'if' in
	trx_sys_get_new_trx_id will evaluate to TRUE when the function
	is first time called, and the value for trx id will be written
	to the disk-based header! Thus trx id values will not overlap when
	the database is repeatedly started! */

	trx_sys->max_trx_id = 2 * TRX_SYS_TRX_ID_WRITE_MARGIN
		+ ut_uint64_align_up(mach_read_from_8(sys_header
						   + TRX_SYS_TRX_ID_STORE),
				     TRX_SYS_TRX_ID_WRITE_MARGIN);

	ut_d(trx_sys->rw_max_trx_id = trx_sys->max_trx_id);

	UT_LIST_INIT(trx_sys->mysql_trx_list);

	trx_dummy_sess = sess_open();

	trx_lists_init_at_db_start();

	/* This S lock is not strictly required, it is here only to satisfy
	the debug code (assertions). We are still running in single threaded
	bootstrap mode. */

	mutex_enter(&trx_sys->mutex);

	ut_a(UT_LIST_GET_LEN(trx_sys->ro_trx_list) == 0);

	if (UT_LIST_GET_LEN(trx_sys->rw_trx_list) > 0) {
		const trx_t*	trx;

		for (trx = UT_LIST_GET_FIRST(trx_sys->rw_trx_list);
		     trx != NULL;
		     trx = UT_LIST_GET_NEXT(trx_list, trx)) {

			ut_ad(trx->is_recovered);
			assert_trx_in_rw_list(trx);

			if (trx_state_eq(trx, TRX_STATE_ACTIVE)) {
				rows_to_undo += trx->undo_no;
			}
		}

		if (rows_to_undo > 1000000000) {
			unit = "M";
			rows_to_undo = rows_to_undo / 1000000;
		}

		fprintf(stderr,
			"InnoDB: %lu transaction(s) which must be"
			" rolled back or cleaned up\n"
			"InnoDB: in total %lu%s row operations to undo\n",
			(ulong) UT_LIST_GET_LEN(trx_sys->rw_trx_list),
			(ulong) rows_to_undo, unit);

		fprintf(stderr, "InnoDB: Trx id counter is " TRX_ID_FMT "\n",
			trx_sys->max_trx_id);
	}

	mutex_exit(&trx_sys->mutex);

	UT_LIST_INIT(trx_sys->view_list);

	mtr_commit(&mtr);

	return(ib_bh);
}

/*****************************************************************//**
Creates the trx_sys instance and initializes ib_bh and mutex. */
UNIV_INTERN
void
trx_sys_create(void)
/*================*/
{
	ut_ad(trx_sys == NULL);

	trx_sys = static_cast<trx_sys_t*>(mem_zalloc(sizeof(*trx_sys)));

	mutex_create(trx_sys_mutex_key, &trx_sys->mutex, SYNC_TRX_SYS);
}

/*****************************************************************//**
Creates and initializes the transaction system at the database creation. */
UNIV_INTERN
void
trx_sys_create_sys_pages(void)
/*==========================*/
{
	mtr_t	mtr;

	mtr_start(&mtr);

	trx_sysf_create(&mtr);

	mtr_commit(&mtr);
}

/*****************************************************************//**
Update the file format tag.
@return	always TRUE */
static
ibool
trx_sys_file_format_max_write(
/*==========================*/
	ulint		format_id,	/*!< in: file format id */
	const char**	name)		/*!< out: max file format name, can
					be NULL */
{
	mtr_t		mtr;
	byte*		ptr;
	buf_block_t*	block;
	ib_uint64_t	tag_value;

	mtr_start(&mtr);

	block = buf_page_get(
		TRX_SYS_SPACE, 0, TRX_SYS_PAGE_NO, RW_X_LATCH, &mtr);

	file_format_max.id = format_id;
	file_format_max.name = trx_sys_file_format_id_to_name(format_id);

	ptr = buf_block_get_frame(block) + TRX_SYS_FILE_FORMAT_TAG;
	tag_value = format_id + TRX_SYS_FILE_FORMAT_TAG_MAGIC_N;

	if (name) {
		*name = file_format_max.name;
	}

	mlog_write_ull(ptr, tag_value, &mtr);

	mtr_commit(&mtr);

	return(TRUE);
}

/*****************************************************************//**
Read the file format tag.
@return	the file format or ULINT_UNDEFINED if not set. */
static
ulint
trx_sys_file_format_max_read(void)
/*==============================*/
{
	mtr_t			mtr;
	const byte*		ptr;
	const buf_block_t*	block;
	ib_id_t			file_format_id;

	/* Since this is called during the startup phase it's safe to
	read the value without a covering mutex. */
	mtr_start(&mtr);

	block = buf_page_get(
		TRX_SYS_SPACE, 0, TRX_SYS_PAGE_NO, RW_X_LATCH, &mtr);

	ptr = buf_block_get_frame(block) + TRX_SYS_FILE_FORMAT_TAG;
	file_format_id = mach_read_from_8(ptr);

	mtr_commit(&mtr);

	file_format_id -= TRX_SYS_FILE_FORMAT_TAG_MAGIC_N;

	if (file_format_id >= FILE_FORMAT_NAME_N) {

		/* Either it has never been tagged, or garbage in it. */
		return(ULINT_UNDEFINED);
	}

	return((ulint) file_format_id);
}

/*****************************************************************//**
Get the name representation of the file format from its id.
@return	pointer to the name */
UNIV_INTERN
const char*
trx_sys_file_format_id_to_name(
/*===========================*/
	const ulint	id)	/*!< in: id of the file format */
{
	ut_a(id < FILE_FORMAT_NAME_N);

	return(file_format_name_map[id]);
}

/*****************************************************************//**
Check for the max file format tag stored on disk. Note: If max_format_id
is == UNIV_FORMAT_MAX + 1 then we only print a warning.
@return	DB_SUCCESS or error code */
UNIV_INTERN
dberr_t
trx_sys_file_format_max_check(
/*==========================*/
	ulint	max_format_id)	/*!< in: max format id to check */
{
	ulint	format_id;

	/* Check the file format in the tablespace. Do not try to
	recover if the file format is not supported by the engine
	unless forced by the user. */
	format_id = trx_sys_file_format_max_read();
	if (format_id == ULINT_UNDEFINED) {
		/* Format ID was not set. Set it to minimum possible
		value. */
		format_id = UNIV_FORMAT_MIN;
	}

	ib_logf(IB_LOG_LEVEL_INFO,
		"Highest supported file format is %s.",
		trx_sys_file_format_id_to_name(UNIV_FORMAT_MAX));

	if (format_id > UNIV_FORMAT_MAX) {

		ut_a(format_id < FILE_FORMAT_NAME_N);

		ib_logf(max_format_id <= UNIV_FORMAT_MAX
			? IB_LOG_LEVEL_ERROR : IB_LOG_LEVEL_WARN,
			"The system tablespace is in a file "
			"format that this version doesn't support - %s.",
			trx_sys_file_format_id_to_name(format_id));

		if (max_format_id <= UNIV_FORMAT_MAX) {
			return(DB_ERROR);
		}
	}

	format_id = (format_id > max_format_id) ? format_id : max_format_id;

	/* We don't need a mutex here, as this function should only
	be called once at start up. */
	file_format_max.id = format_id;
	file_format_max.name = trx_sys_file_format_id_to_name(format_id);

	return(DB_SUCCESS);
}

/*****************************************************************//**
Set the file format id unconditionally except if it's already the
same value.
@return	TRUE if value updated */
UNIV_INTERN
ibool
trx_sys_file_format_max_set(
/*========================*/
	ulint		format_id,	/*!< in: file format id */
	const char**	name)		/*!< out: max file format name or
					NULL if not needed. */
{
	ibool		ret = FALSE;

	ut_a(format_id <= UNIV_FORMAT_MAX);

	mutex_enter(&file_format_max.mutex);

	/* Only update if not already same value. */
	if (format_id != file_format_max.id) {

		ret = trx_sys_file_format_max_write(format_id, name);
	}

	mutex_exit(&file_format_max.mutex);

	return(ret);
}

/********************************************************************//**
Tags the system table space with minimum format id if it has not been
tagged yet.
WARNING: This function is only called during the startup and AFTER the
redo log application during recovery has finished. */
UNIV_INTERN
void
trx_sys_file_format_tag_init(void)
/*==============================*/
{
	ulint	format_id;

	format_id = trx_sys_file_format_max_read();

	/* If format_id is not set then set it to the minimum. */
	if (format_id == ULINT_UNDEFINED) {
		trx_sys_file_format_max_set(UNIV_FORMAT_MIN, NULL);
	}
}

/********************************************************************//**
Update the file format tag in the system tablespace only if the given
format id is greater than the known max id.
@return	TRUE if format_id was bigger than the known max id */
UNIV_INTERN
ibool
trx_sys_file_format_max_upgrade(
/*============================*/
	const char**	name,		/*!< out: max file format name */
	ulint		format_id)	/*!< in: file format identifier */
{
	ibool		ret = FALSE;

	ut_a(name);
	ut_a(file_format_max.name != NULL);
	ut_a(format_id <= UNIV_FORMAT_MAX);

	mutex_enter(&file_format_max.mutex);

	if (format_id > file_format_max.id) {

		ret = trx_sys_file_format_max_write(format_id, name);
	}

	mutex_exit(&file_format_max.mutex);

	return(ret);
}

/*****************************************************************//**
Get the name representation of the file format from its id.
@return	pointer to the max format name */
UNIV_INTERN
const char*
trx_sys_file_format_max_get(void)
/*=============================*/
{
	return(file_format_max.name);
}

/*****************************************************************//**
Initializes the tablespace tag system. */
UNIV_INTERN
void
trx_sys_file_format_init(void)
/*==========================*/
{
	mutex_create(file_format_max_mutex_key,
		     &file_format_max.mutex, SYNC_FILE_FORMAT_TAG);

	/* We don't need a mutex here, as this function should only
	be called once at start up. */
	file_format_max.id = UNIV_FORMAT_MIN;

	file_format_max.name = trx_sys_file_format_id_to_name(
		file_format_max.id);
}

/*****************************************************************//**
Closes the tablespace tag system. */
UNIV_INTERN
void
trx_sys_file_format_close(void)
/*===========================*/
{
	/* Does nothing at the moment */
}

/*********************************************************************
Creates the rollback segments.
@return number of rollback segments that are active. */
UNIV_INTERN
ulint
trx_sys_create_rsegs(
/*=================*/
	ulint	n_spaces,	/*!< number of tablespaces for UNDO logs */
	ulint	n_rsegs)	/*!< number of rollback segments to create */
{
	mtr_t	mtr;
	ulint	n_used;

	ut_a(n_spaces < TRX_SYS_N_RSEGS);
	ut_a(n_rsegs <= TRX_SYS_N_RSEGS);

	if (srv_read_only_mode) {
		return(ULINT_UNDEFINED);
	}

	/* This is executed in single-threaded mode therefore it is not
	necessary to use the same mtr in trx_rseg_create(). n_used cannot
	change while the function is executing. */

	mtr_start(&mtr);
	n_used = trx_sysf_rseg_find_free(&mtr);
	mtr_commit(&mtr);

	if (n_used == ULINT_UNDEFINED) {
		n_used = TRX_SYS_N_RSEGS;
	}

	/* Do not create additional rollback segments if innodb_force_recovery
	has been set and the database was not shutdown cleanly. */

	if (!srv_force_recovery && !recv_needed_recovery && n_used < n_rsegs) {
		ulint	i;
		ulint	new_rsegs = n_rsegs - n_used;

		for (i = 0; i < new_rsegs; ++i) {
			ulint	space_id;
			space_id = (n_spaces == 0) ? 0
				: (srv_undo_space_id_start + i % n_spaces);

			/* Tablespace 0 is the system tablespace. */
			if (trx_rseg_create(space_id) != NULL) {
				++n_used;
			} else {
				break;
			}
		}
	}

	ib_logf(IB_LOG_LEVEL_INFO,
		"%lu rollback segment(s) are active.", n_used);

	return(n_used);
}

#else /* !UNIV_HOTBACKUP */
/*****************************************************************//**
Prints to stderr the MySQL binlog info in the system header if the
magic number shows it valid. */
UNIV_INTERN
void
trx_sys_print_mysql_binlog_offset_from_page(
/*========================================*/
	const byte*	page)	/*!< in: buffer containing the trx
				system header page, i.e., page number
				TRX_SYS_PAGE_NO in the tablespace */
{
	const trx_sysf_t*	sys_header;

	sys_header = page + TRX_SYS;

	if (mach_read_from_4(sys_header + TRX_SYS_MYSQL_LOG_INFO
			     + TRX_SYS_MYSQL_LOG_MAGIC_N_FLD)
	    == TRX_SYS_MYSQL_LOG_MAGIC_N) {

		fprintf(stderr,
			"mysqlbackup: Last MySQL binlog file position %lu %lu,"
			" file name %s\n",
			(ulong) mach_read_from_4(
				sys_header + TRX_SYS_MYSQL_LOG_INFO
				+ TRX_SYS_MYSQL_LOG_OFFSET_HIGH),
			(ulong) mach_read_from_4(
				sys_header + TRX_SYS_MYSQL_LOG_INFO
				+ TRX_SYS_MYSQL_LOG_OFFSET_LOW),
			sys_header + TRX_SYS_MYSQL_LOG_INFO
			+ TRX_SYS_MYSQL_LOG_NAME);
	}
}

/*****************************************************************//**
Reads the file format id from the first system table space file.
Even if the call succeeds and returns TRUE, the returned format id
may be ULINT_UNDEFINED signalling that the format id was not present
in the data file.
@return TRUE if call succeeds */
UNIV_INTERN
ibool
trx_sys_read_file_format_id(
/*========================*/
	const char *pathname,  /*!< in: pathname of the first system
				        table space file */
	ulint *format_id)      /*!< out: file format of the system table
				         space */
{
	os_file_t	file;
	ibool		success;
	byte		buf[UNIV_PAGE_SIZE * 2];
	page_t*		page = ut_align(buf, UNIV_PAGE_SIZE);
	const byte*	ptr;
	ib_id_t		file_format_id;

	*format_id = ULINT_UNDEFINED;

	file = os_file_create_simple_no_error_handling(
		innodb_file_data_key,
		pathname,
		OS_FILE_OPEN,
		OS_FILE_READ_ONLY,
		&success
	);
	if (!success) {
		/* The following call prints an error message */
		os_file_get_last_error(true);

		ut_print_timestamp(stderr);

		fprintf(stderr,
			"  mysqlbackup: Error: trying to read system "
			"tablespace file format,\n"
			"  mysqlbackup: but could not open the tablespace "
			"file %s!\n", pathname);
		return(FALSE);
	}

	/* Read the page on which file format is stored */

	success = os_file_read_no_error_handling(
		file, page, TRX_SYS_PAGE_NO * UNIV_PAGE_SIZE, UNIV_PAGE_SIZE);

	if (!success) {
		/* The following call prints an error message */
		os_file_get_last_error(true);

		ut_print_timestamp(stderr);

		fprintf(stderr,
			"  mysqlbackup: Error: trying to read system "
			"tablespace file format,\n"
			"  mysqlbackup: but failed to read the tablespace "
			"file %s!\n", pathname);

		os_file_close(file);
		return(FALSE);
	}
	os_file_close(file);

	/* get the file format from the page */
	ptr = page + TRX_SYS_FILE_FORMAT_TAG;
	file_format_id = mach_read_from_8(ptr);
	file_format_id -= TRX_SYS_FILE_FORMAT_TAG_MAGIC_N;

	if (file_format_id >= FILE_FORMAT_NAME_N) {

		/* Either it has never been tagged, or garbage in it. */
		return(TRUE);
	}

	*format_id = (ulint) file_format_id;

	return(TRUE);
}

/*****************************************************************//**
Reads the file format id from the given per-table data file.
@return TRUE if call succeeds */
UNIV_INTERN
ibool
trx_sys_read_pertable_file_format_id(
/*=================================*/
	const char *pathname,  /*!< in: pathname of a per-table
				        datafile */
	ulint *format_id)      /*!< out: file format of the per-table
				         data file */
{
	os_file_t	file;
	ibool		success;
	byte		buf[UNIV_PAGE_SIZE * 2];
	page_t*		page = ut_align(buf, UNIV_PAGE_SIZE);
	const byte*	ptr;
	ib_uint32_t	flags;

	*format_id = ULINT_UNDEFINED;

	file = os_file_create_simple_no_error_handling(
		innodb_file_data_key,
		pathname,
		OS_FILE_OPEN,
		OS_FILE_READ_ONLY,
		&success
	);
	if (!success) {
		/* The following call prints an error message */
		os_file_get_last_error(true);

		ut_print_timestamp(stderr);

		fprintf(stderr,
			"  mysqlbackup: Error: trying to read per-table "
			"tablespace format,\n"
			"  mysqlbackup: but could not open the tablespace "
			"file %s!\n", pathname);

		return(FALSE);
	}

	/* Read the first page of the per-table datafile */

	success = os_file_read_no_error_handling(file, page, 0, UNIV_PAGE_SIZE);

	if (!success) {
		/* The following call prints an error message */
		os_file_get_last_error(true);

		ut_print_timestamp(stderr);

		fprintf(stderr,
			"  mysqlbackup: Error: trying to per-table data file "
			"format,\n"
			"  mysqlbackup: but failed to read the tablespace "
			"file %s!\n", pathname);

		os_file_close(file);
		return(FALSE);
	}
	os_file_close(file);

	/* get the file format from the page */
	ptr = page + 54;
	flags = mach_read_from_4(ptr);

	if (!fsp_flags_is_valid(flags) {
		/* bad tablespace flags */
		return(FALSE);
	}

	*format_id = FSP_FLAGS_GET_POST_ANTELOPE(flags);

	return(TRUE);
}


/*****************************************************************//**
Get the name representation of the file format from its id.
@return	pointer to the name */
UNIV_INTERN
const char*
trx_sys_file_format_id_to_name(
/*===========================*/
	const ulint	id)	/*!< in: id of the file format */
{
	if (!(id < FILE_FORMAT_NAME_N)) {
		/* unknown id */
		return("Unknown");
	}

	return(file_format_name_map[id]);
}

#endif /* !UNIV_HOTBACKUP */

#ifndef UNIV_HOTBACKUP
/*********************************************************************
Shutdown/Close the transaction system. */
UNIV_INTERN
void
trx_sys_close(void)
/*===============*/
{
	ulint		i;
	trx_t*		trx;
	read_view_t*	view;

	ut_ad(trx_sys != NULL);
	ut_ad(srv_shutdown_state == SRV_SHUTDOWN_EXIT_THREADS);

	/* Check that all read views are closed except read view owned
	by a purge. */

	mutex_enter(&trx_sys->mutex);

	if (UT_LIST_GET_LEN(trx_sys->view_list) > 1) {
		fprintf(stderr,
			"InnoDB: Error: all read views were not closed"
			" before shutdown:\n"
			"InnoDB: %lu read views open \n",
			UT_LIST_GET_LEN(trx_sys->view_list) - 1);
	}

	mutex_exit(&trx_sys->mutex);

	sess_close(trx_dummy_sess);
	trx_dummy_sess = NULL;

	trx_purge_sys_close();

	/* Free the double write data structures. */
	if (buf_dblwr) {
		buf_dblwr_free();
	}


	/* Only prepared transactions may be left in the system. Free them. */
	ut_a(UT_LIST_GET_LEN(trx_sys->rw_trx_list) == trx_sys->n_prepared_trx
	     || srv_read_only_mode
	     || srv_force_recovery >= SRV_FORCE_NO_TRX_UNDO
	     || srv_apply_log_only);

	while ((trx = UT_LIST_GET_FIRST(trx_sys->rw_trx_list)) != NULL) {
		trx_free_prepared(trx);
	}

	/* There can't be any active transactions. */
	for (i = 0; i < TRX_SYS_N_RSEGS; ++i) {
		trx_rseg_t*	rseg;

		rseg = trx_sys->rseg_array[i];

		if (rseg != NULL) {
			trx_rseg_mem_free(rseg);
		} else {
			break;
		}
	}

	view = UT_LIST_GET_FIRST(trx_sys->view_list);

	while (view != NULL) {
		read_view_t*	prev_view = view;

		view = UT_LIST_GET_NEXT(view_list, prev_view);

		/* Views are allocated from the trx_sys->global_read_view_heap.
		So, we simply remove the element here. */
		UT_LIST_REMOVE(view_list, trx_sys->view_list, prev_view);
	}

	if (!srv_apply_log_only) {
		ut_a(UT_LIST_GET_LEN(trx_sys->view_list) == 0);
		ut_a(UT_LIST_GET_LEN(trx_sys->ro_trx_list) == 0);
		ut_a(UT_LIST_GET_LEN(trx_sys->rw_trx_list) == 0);
		ut_a(UT_LIST_GET_LEN(trx_sys->mysql_trx_list) == 0);
	}

	mutex_free(&trx_sys->mutex);

	ut_ad(trx_sys->descr_n_used == 0);
	ut_free(trx_sys->descriptors);

	mem_free(trx_sys);

	trx_sys = NULL;
}

/** @brief Convert an undo log to TRX_UNDO_PREPARED state on shutdown.

If any prepared ACTIVE transactions exist, and their rollback was
prevented by innodb_force_recovery, we convert these transactions to
XA PREPARE state in the main-memory data structures, so that shutdown
will proceed normally. These transactions will again recover as ACTIVE
on the next restart, and they will be rolled back unless
innodb_force_recovery prevents it again.

@param[in]	trx	transaction
@param[in,out]	undo	undo log to convert to TRX_UNDO_PREPARED */
static
void
trx_undo_fake_prepared(
	const trx_t*	trx,
	trx_undo_t*	undo)
{
	ut_ad(srv_force_recovery >= SRV_FORCE_NO_TRX_UNDO);
	ut_ad(trx_state_eq(trx, TRX_STATE_ACTIVE));
	ut_ad(trx->is_recovered);

	if (undo != NULL) {
		ut_ad(undo->state == TRX_UNDO_ACTIVE);
		undo->state = TRX_UNDO_PREPARED;
	}
}

/*********************************************************************
Check if there are any active (non-prepared) transactions.
@return total number of active transactions or 0 if none */
UNIV_INTERN
ulint
trx_sys_any_active_transactions(void)
/*=================================*/
{
	if (srv_apply_log_only) {
		return(0);
	}
	mutex_enter(&trx_sys->mutex);

	ulint	total_trx = UT_LIST_GET_LEN(trx_sys->mysql_trx_list);

	if (total_trx == 0) {
		total_trx = UT_LIST_GET_LEN(trx_sys->rw_trx_list);
		ut_a(total_trx >= trx_sys->n_prepared_trx);

		if (total_trx > trx_sys->n_prepared_trx
		    && srv_force_recovery >= SRV_FORCE_NO_TRX_UNDO) {
			for (trx_t* trx = UT_LIST_GET_FIRST(
				     trx_sys->rw_trx_list);
			     trx != NULL;
			     trx = UT_LIST_GET_NEXT(trx_list, trx)) {
				if (!trx_state_eq(trx, TRX_STATE_ACTIVE)
				    || !trx->is_recovered) {
					continue;
				}
				/* This was a recovered transaction
				whose rollback was disabled by
				the innodb_force_recovery setting.
				Pretend that it is in XA PREPARE
				state so that shutdown will work. */
				trx_undo_fake_prepared(
					trx, trx->insert_undo);
				trx_undo_fake_prepared(
					trx, trx->update_undo);
				trx->state = TRX_STATE_PREPARED;
				trx_sys->n_prepared_trx++;
				trx_sys->n_prepared_recovered_trx++;
			}
		}

		ut_a(total_trx >= trx_sys->n_prepared_trx);
		total_trx -= trx_sys->n_prepared_trx;
	}

	mutex_exit(&trx_sys->mutex);

	return(total_trx);
}

#ifdef UNIV_DEBUG
/*************************************************************//**
Validate the trx_list_t.
@return TRUE if valid. */
static
ibool
trx_sys_validate_trx_list_low(
/*===========================*/
	trx_list_t*	trx_list)	/*!< in: &trx_sys->ro_trx_list
					or &trx_sys->rw_trx_list */
{
	const trx_t*	trx;
	const trx_t*	prev_trx = NULL;

	ut_ad(mutex_own(&trx_sys->mutex));

	ut_ad(trx_list == &trx_sys->ro_trx_list
	      || trx_list == &trx_sys->rw_trx_list);

	for (trx = UT_LIST_GET_FIRST(*trx_list);
	     trx != NULL;
	     prev_trx = trx, trx = UT_LIST_GET_NEXT(trx_list, prev_trx)) {

		assert_trx_in_list(trx);
		ut_ad(trx->read_only == (trx_list == &trx_sys->ro_trx_list));

		ut_a(prev_trx == NULL || prev_trx->id > trx->id);
	}

	return(TRUE);
}

/*************************************************************//**
Validate the trx_sys_t::ro_trx_list and trx_sys_t::rw_trx_list.
@return TRUE if lists are valid. */
UNIV_INTERN
ibool
trx_sys_validate_trx_list(void)
/*===========================*/
{
	ut_ad(mutex_own(&trx_sys->mutex));

	ut_a(trx_sys_validate_trx_list_low(&trx_sys->ro_trx_list));
	ut_a(trx_sys_validate_trx_list_low(&trx_sys->rw_trx_list));

	return(TRUE);
}
#endif /* UNIV_DEBUG */
#endif /* !UNIV_HOTBACKUP */