Server could hang during chasing dead record version [CORE4656]

[firebird-issue-importer]

Submitted by: @dmitry-starodubov

Assigned to: @dmitry-starodubov

In VIO_chase_record_version:
if (!(rpb->rpb_flags & rpb_chained) && rpb->rpb_flags & rpb_gc_active)
{
if (!rpb->rpb_transaction_nr) {
state = tra_active;
}

if \(state == tra\_committed\) \{
	state = TRA\_pc\_active\(tdbb, rpb\-\>rpb\_transaction\_nr\) ? tra\_precommitted : tra\_dead;
\}

if \(state == tra\_dead\) \{
	rpb\-\>rpb\_flags &= \~rpb\_gc\_active;
\}

}
If state is dead and record has rpb_gc_active flag turned on, this flag is reset and starts new iteration of chasing.
On new iteration if ATT_NO_CLEANUP flag turned on, version is read from disk again and compared with saved version:

record_param temp = *rpb;
...
VIO_data(tdbb, rpb, pool);
rpb->rpb_page = temp.rpb_page;
rpb->rpb_line = temp.rpb_line;
if (!(DPM_fetch(tdbb, rpb, LCK_read)))
{
if (!DPM_get(tdbb, rpb, LCK_read)) {
return false;
}
break;
}

if \(rpb\-\>rpb\_b\_page \!= temp\.rpb\_b\_page \|\| rpb\-\>rpb\_b\_line \!= temp\.rpb\_b\_line \|\|
    rpb\-\>rpb\_f\_page \!= temp\.rpb\_f\_page \|\| rpb\-\>rpb\_f\_line \!= temp\.rpb\_f\_line \|\|
    rpb\-\>rpb\_flags \!= temp\.rpb\_flags\)
\{
    CCH\_RELEASE\(tdbb, &rpb\-\>getWindow\(tdbb\)\);
    if \(\!DPM\_get\(tdbb, rpb, LCK\_read\)\) \{
        return false;
    \}
    break;
\}

"rpb" and "temp" versions can differ only by rpb_gc_active flag which was reset from saved version on previous iteration. Because of this current version considered as changed and it processed again. And so on. Loop inside VIO_chase_record_version becomes infinite.

Commits: 1c4aeb4 b260c1e FirebirdSQL/fbt-repository@53dc454 FirebirdSQL/fbt-repository@e3b3da1

[firebird-issue-importer]

Modified by: @dmitry-starodubov

assignee: Dmitriy Starodubov [ dmitriy starodubov ]

[firebird-issue-importer]

Modified by: @dyemanov

status: Open [ 1 ] => Resolved [ 5 ]

resolution: Fixed [ 1 ]

Fix Version: 3.0 Beta 2 [ 10586 ]

[firebird-issue-importer]

Commented by: Jesus Angel Garcia Zarco (cointec)

Will be fixed for 2.5.4?

I trink I have had this problem last week in one of our customers with 2.5.2 upd 1

[firebird-issue-importer]

Modified by: @pavel-zotov

status: Resolved [ 5 ] => Resolved [ 5 ]

QA Status: Cannot be tested

[firebird-issue-importer]

Modified by: @pcisar

status: Resolved [ 5 ] => Closed [ 6 ]

[firebird-issue-importer]

Commented by: @hvlad

Backported into v2.5.5

[firebird-issue-importer]

Modified by: @hvlad

Fix Version: 2.5.5 [ 10670 ]