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| author | Alexander Korotkov <akorotkov@postgresql.org> | 2018-12-13 06:12:25 +0300 |
|---|---|---|
| committer | Alexander Korotkov <akorotkov@postgresql.org> | 2018-12-13 06:31:16 +0300 |
| commit | f6c44e1b55c1bc98fca275f2040912cd89b8196a (patch) | |
| tree | 41d5fe800efab2d8cc315f3135cafa3b58686610 | |
| parent | 6548d62a98f9801fa0e6c1528568560f1b218477 (diff) | |
| download | postgresql-f6c44e1b55c1bc98fca275f2040912cd89b8196a.tar.gz postgresql-f6c44e1b55c1bc98fca275f2040912cd89b8196a.zip | |
Prevent deadlock in ginRedoDeletePage()
On standby ginRedoDeletePage() can work concurrently with read-only queries.
Those queries can traverse posting tree in two ways.
1) Using rightlinks by ginStepRight(), which locks the next page before
unlocking its left sibling.
2) Using downlinks by ginFindLeafPage(), which locks at most one page at time.
Original lock order was: page, parent, left sibling. That lock order can
deadlock with ginStepRight(). In order to prevent deadlock this commit changes
lock order to: left sibling, page, parent. Note, that position of parent in
locking order seems insignificant, because we only lock one page at time while
traversing downlinks.
Reported-by: Chen Huajun
Diagnosed-by: Chen Huajun, Peter Geoghegan, Andrey Borodin
Discussion: https://postgr.es/m/31a702a.14dd.166c1366ac1.Coremail.chjischj%40163.com
Author: Alexander Korotkov
Backpatch-through: 9.4
| -rw-r--r-- | src/backend/access/gin/ginxlog.c | 22 |
1 files changed, 13 insertions, 9 deletions
diff --git a/src/backend/access/gin/ginxlog.c b/src/backend/access/gin/ginxlog.c index 57ed81a8366..53b165326c5 100644 --- a/src/backend/access/gin/ginxlog.c +++ b/src/backend/access/gin/ginxlog.c @@ -511,6 +511,19 @@ ginRedoDeletePage(XLogReaderState *record) Buffer lbuffer; Page page; + /* + * Lock left page first in order to prevent possible deadlock with + * ginStepRight(). + */ + if (XLogReadBufferForRedo(record, 2, &lbuffer) == BLK_NEEDS_REDO) + { + page = BufferGetPage(lbuffer); + Assert(GinPageIsData(page)); + GinPageGetOpaque(page)->rightlink = data->rightLink; + PageSetLSN(page, lsn); + MarkBufferDirty(lbuffer); + } + if (XLogReadBufferForRedo(record, 0, &dbuffer) == BLK_NEEDS_REDO) { page = BufferGetPage(dbuffer); @@ -530,15 +543,6 @@ ginRedoDeletePage(XLogReaderState *record) MarkBufferDirty(pbuffer); } - if (XLogReadBufferForRedo(record, 2, &lbuffer) == BLK_NEEDS_REDO) - { - page = BufferGetPage(lbuffer); - Assert(GinPageIsData(page)); - GinPageGetOpaque(page)->rightlink = data->rightLink; - PageSetLSN(page, lsn); - MarkBufferDirty(lbuffer); - } - if (BufferIsValid(lbuffer)) UnlockReleaseBuffer(lbuffer); if (BufferIsValid(pbuffer)) |