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Commitece4bd9

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Fix possible core dump in parallel restore when using a TOC list.
Commit3eb9a5e unintentionally introduced an ordering dependencyinto restore_toc_entries_prefork(). The existing coding ofreduce_dependencies() contains a check to skip moving a TOC entryto the ready_list if it wasn't initially in the pending_list.This used to suffice to prevent reduce_dependencies() from trying tomove anything into the ready_list during restore_toc_entries_prefork(),because the pending_list stayed empty throughout that phase; but it nolonger does. The problem doesn't manifest unless the TOC has beenreordered by SortTocFromFile, which is how I missed it in testing.To fix, just add a test for ready_list == NULL, converting the callwith NULL from a poor man's sanity check into an explicit commandnot to touch TOC items' list membership. Clarify some of the commentsaround this; in particular, note the primary purpose of the check forpending_list membership, which is to ensure that we can't try to restorethe same item twice, in case a TOC list forces it to be restored beforeits dependency count goes to zero.Per report from Fabrízio de Royes Mello. Back-patch to 9.3, like theprevious commit.Discussion:https://postgr.es/m/CAFcNs+pjuv0JL_x4+=71TPUPjdLHOXA4YfT32myj_OrrZb4ohA@mail.gmail.com
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1 file changed

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‎src/bin/pg_dump/pg_backup_archiver.c‎

Lines changed: 14 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -3536,8 +3536,9 @@ restore_toc_entries_prefork(ArchiveHandle *AH, TocEntry *pending_list)
35363536
*
35373537
* Note: as of 9.2, it should be guaranteed that all PRE_DATA items appear
35383538
* before DATA items, and all DATA items before POST_DATA items. That is
3539-
* not certain to be true in older archives, though, so this loop is coded
3540-
* to not assume it.
3539+
* not certain to be true in older archives, though, and in any case use
3540+
* of a list file would destroy that ordering (cf. SortTocFromFile). So
3541+
* this loop cannot assume that it holds.
35413542
*/
35423543
AH->restorePass=RESTORE_PASS_MAIN;
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skipped_some= false;
@@ -3584,7 +3585,7 @@ restore_toc_entries_prefork(ArchiveHandle *AH, TocEntry *pending_list)
35843585

35853586
(void)restore_toc_entry(AH,next_work_item,ropt, false);
35863587

3587-
/*there should be no touch of ready_list here, so pass NULL */
3588+
/*Reduce dependencies, but don't move anything to ready_list */
35883589
reduce_dependencies(AH,next_work_item,NULL);
35893590
}
35903591
else
@@ -4262,7 +4263,7 @@ identify_locking_dependencies(ArchiveHandle *AH, TocEntry *te)
42624263
/*
42634264
* Remove the specified TOC entry from the depCounts of items that depend on
42644265
* it, thereby possibly making them ready-to-run. Any pending item that
4265-
* becomes ready should be moved to theready list.
4266+
* becomes ready should be moved to theready_list, if that's provided.
42664267
*/
42674268
staticvoid
42684269
reduce_dependencies(ArchiveHandle*AH,TocEntry*te,TocEntry*ready_list)
@@ -4279,15 +4280,19 @@ reduce_dependencies(ArchiveHandle *AH, TocEntry *te, TocEntry *ready_list)
42794280
otherte->depCount--;
42804281

42814282
/*
4282-
* It's ready if it has no remaining dependencies and it belongs in
4283-
* the current restore pass. However, don't move it if it has not yet
4284-
* been put into the pending list.
4283+
* It's ready if it has no remaining dependencies, and it belongs in
4284+
* the current restore pass, and it is currently a member of the
4285+
* pending list (that check is needed to prevent double restore in
4286+
* some cases where a list-file forces out-of-order restoring).
4287+
* However, if ready_list == NULL then caller doesn't want any list
4288+
* memberships changed.
42854289
*/
42864290
if (otherte->depCount==0&&
42874291
_tocEntryRestorePass(otherte)==AH->restorePass&&
4288-
otherte->par_prev!=NULL)
4292+
otherte->par_prev!=NULL&&
4293+
ready_list!=NULL)
42894294
{
4290-
/*It must be in thepending list, so remove it ... */
4295+
/*Remove it frompending list ... */
42914296
par_list_remove(otherte);
42924297
/* ... and add to ready_list */
42934298
par_list_append(ready_list,otherte);

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