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Commitb1c2d76

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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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‎src/bin/pg_dump/pg_backup_archiver.c

Lines changed: 14 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -3851,8 +3851,9 @@ restore_toc_entries_prefork(ArchiveHandle *AH, TocEntry *pending_list)
38513851
*
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* Note: as of 9.2, it should be guaranteed that all PRE_DATA items appear
38533853
* before DATA items, and all DATA items before POST_DATA items. That is
3854-
* not certain to be true in older archives, though, so this loop is coded
3855-
* to not assume it.
3854+
* not certain to be true in older archives, though, and in any case use
3855+
* of a list file would destroy that ordering (cf. SortTocFromFile). So
3856+
* this loop cannot assume that it holds.
38563857
*/
38573858
AH->restorePass=RESTORE_PASS_MAIN;
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skipped_some= false;
@@ -3899,7 +3900,7 @@ restore_toc_entries_prefork(ArchiveHandle *AH, TocEntry *pending_list)
38993900

39003901
(void)restore_toc_entry(AH,next_work_item, false);
39013902

3902-
/*there should be no touch of ready_list here, so pass NULL */
3903+
/*Reduce dependencies, but don't move anything to ready_list */
39033904
reduce_dependencies(AH,next_work_item,NULL);
39043905
}
39053906
else
@@ -4545,7 +4546,7 @@ identify_locking_dependencies(ArchiveHandle *AH, TocEntry *te)
45454546
/*
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* Remove the specified TOC entry from the depCounts of items that depend on
45474548
* it, thereby possibly making them ready-to-run. Any pending item that
4548-
* becomes ready should be moved to theready list.
4549+
* becomes ready should be moved to theready_list, if that's provided.
45494550
*/
45504551
staticvoid
45514552
reduce_dependencies(ArchiveHandle*AH,TocEntry*te,TocEntry*ready_list)
@@ -4562,15 +4563,19 @@ reduce_dependencies(ArchiveHandle *AH, TocEntry *te, TocEntry *ready_list)
45624563
otherte->depCount--;
45634564

45644565
/*
4565-
* It's ready if it has no remaining dependencies and it belongs in
4566-
* the current restore pass. However, don't move it if it has not yet
4567-
* been put into the pending list.
4566+
* It's ready if it has no remaining dependencies, and it belongs in
4567+
* the current restore pass, and it is currently a member of the
4568+
* pending list (that check is needed to prevent double restore in
4569+
* some cases where a list-file forces out-of-order restoring).
4570+
* However, if ready_list == NULL then caller doesn't want any list
4571+
* memberships changed.
45684572
*/
45694573
if (otherte->depCount==0&&
45704574
_tocEntryRestorePass(otherte)==AH->restorePass&&
4571-
otherte->par_prev!=NULL)
4575+
otherte->par_prev!=NULL&&
4576+
ready_list!=NULL)
45724577
{
4573-
/*It must be in thepending list, so remove it ... */
4578+
/*Remove it frompending list ... */
45744579
par_list_remove(otherte);
45754580
/* ... and add to ready_list */
45764581
par_list_append(ready_list,otherte);

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