Thread: pgsql: Fix race condition between hot standby and restoring a full-page
pgsql: Fix race condition between hot standby and restoring a full-page
From
Heikki Linnakangas
Date:
Fix race condition between hot standby and restoring a full-page image. There was a window in RestoreBackupBlock where a page would be zeroed out, but not yet locked. If a backend pinned and locked the page in that window, it saw the zeroed page instead of the old page or new page contents, which could lead to missing rows in a result set, or errors. To fix, replace RBM_ZERO with RBM_ZERO_AND_LOCK, which atomically pins, zeroes, and locks the page, if it's not in the buffer cache already. In stable branches, the old RBM_ZERO constant is renamed to RBM_DO_NOT_USE, to avoid breaking any 3rd party extensions that might use RBM_ZERO. More importantly, this avoids renumbering the other enum values, which would cause even bigger confusion in extensions that use ReadBufferExtended, but haven't been recompiled. Backpatch to all supported versions; this has been racy since hot standby was introduced. Branch ------ master Details ------- http://git.postgresql.org/pg/commitdiff/81c45081960f39351c38cd53554bb3788af54023 Modified Files -------------- src/backend/access/hash/hashpage.c | 13 +++++----- src/backend/access/heap/heapam.c | 6 ++--- src/backend/access/transam/xlogutils.c | 44 ++++++++++++++++++++------------ src/backend/storage/buffer/bufmgr.c | 41 ++++++++++++++++++++++++++--- src/include/storage/bufmgr.h | 6 +++-- 5 files changed, 78 insertions(+), 32 deletions(-)