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Commit41803d5

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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
@@ -3796,8 +3796,9 @@ restore_toc_entries_prefork(ArchiveHandle *AH, TocEntry *pending_list)
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*
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* Note: as of 9.2, it should be guaranteed that all PRE_DATA items appear
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* before DATA items, and all DATA items before POST_DATA items. That is
3799-
* not certain to be true in older archives, though, so this loop is coded
3800-
* to not assume it.
3799+
* not certain to be true in older archives, though, and in any case use
3800+
* of a list file would destroy that ordering (cf. SortTocFromFile). So
3801+
* this loop cannot assume that it holds.
38013802
*/
38023803
AH->restorePass=RESTORE_PASS_MAIN;
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skipped_some= false;
@@ -3844,7 +3845,7 @@ restore_toc_entries_prefork(ArchiveHandle *AH, TocEntry *pending_list)
38443845

38453846
(void)restore_toc_entry(AH,next_work_item, false);
38463847

3847-
/*there should be no touch of ready_list here, so pass NULL */
3848+
/*Reduce dependencies, but don't move anything to ready_list */
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reduce_dependencies(AH,next_work_item,NULL);
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}
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else
@@ -4521,7 +4522,7 @@ identify_locking_dependencies(ArchiveHandle *AH, TocEntry *te)
45214522
/*
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* Remove the specified TOC entry from the depCounts of items that depend on
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* it, thereby possibly making them ready-to-run. Any pending item that
4524-
* becomes ready should be moved to theready list.
4525+
* becomes ready should be moved to theready_list, if that's provided.
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*/
45264527
staticvoid
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reduce_dependencies(ArchiveHandle*AH,TocEntry*te,TocEntry*ready_list)
@@ -4538,15 +4539,19 @@ reduce_dependencies(ArchiveHandle *AH, TocEntry *te, TocEntry *ready_list)
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otherte->depCount--;
45394540

45404541
/*
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* It's ready if it has no remaining dependencies and it belongs in
4542-
* the current restore pass. However, don't move it if it has not yet
4543-
* been put into the pending list.
4542+
* It's ready if it has no remaining dependencies, and it belongs in
4543+
* the current restore pass, and it is currently a member of the
4544+
* pending list (that check is needed to prevent double restore in
4545+
* some cases where a list-file forces out-of-order restoring).
4546+
* However, if ready_list == NULL then caller doesn't want any list
4547+
* memberships changed.
45444548
*/
45454549
if (otherte->depCount==0&&
45464550
_tocEntryRestorePass(otherte)==AH->restorePass&&
4547-
otherte->par_prev!=NULL)
4551+
otherte->par_prev!=NULL&&
4552+
ready_list!=NULL)
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{
4549-
/*It must be in thepending list, so remove it ... */
4554+
/*Remove it frompending list ... */
45504555
par_list_remove(otherte);
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/* ... and add to ready_list */
45524557
par_list_append(ready_list,otherte);

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