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| author | Jeff Davis <jdavis@postgresql.org> | 2023-12-19 17:35:54 -0800 |
|---|---|---|
| committer | Jeff Davis <jdavis@postgresql.org> | 2023-12-19 17:35:54 -0800 |
| commit | 766571be16598b401b5527208847145edc6be1f4 (patch) | |
| tree | 8b996fa24f62b557b285ff07123a1d7e79a56092 /src/backend/access/transam/xlog.c | |
| parent | c3a8e2a7cb16d55e3b757934b538cb8b8a0eab02 (diff) | |
| download | postgresql-766571be16598b401b5527208847145edc6be1f4.tar.gz postgresql-766571be16598b401b5527208847145edc6be1f4.zip | |
Additional write barrier in AdvanceXLInsertBuffer().
First, mark the xlblocks member with InvalidXLogRecPtr, then issue a
write barrier, then initialize it. That ensures that the xlblocks
member doesn't appear valid while the contents are being initialized.
In preparation for reading WAL buffer contents without a lock.
Author: Bharath Rupireddy
Discussion: https://postgr.es/m/CALj2ACVfFMfqD5oLzZSQQZWfXiJqd-NdX0_317veP6FuB31QWA@mail.gmail.com
Reviewed-by: Andres Freund
Diffstat (limited to 'src/backend/access/transam/xlog.c')
| -rw-r--r-- | src/backend/access/transam/xlog.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 1c77daa611a..56e4d6fb022 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -1933,6 +1933,14 @@ AdvanceXLInsertBuffer(XLogRecPtr upto, TimeLineID tli, bool opportunistic) NewPage = (XLogPageHeader) (XLogCtl->pages + nextidx * (Size) XLOG_BLCKSZ); /* + * Mark the xlblock with InvalidXLogRecPtr and issue a write barrier + * before initializing. Otherwise, the old page may be partially + * zeroed but look valid. + */ + pg_atomic_write_u64(&XLogCtl->xlblocks[nextidx], InvalidXLogRecPtr); + pg_write_barrier(); + + /* * Be sure to re-zero the buffer so that bytes beyond what we've * written will look like zeroes and not valid XLOG records... */ |