mirror of
https://github.com/postgres/postgres.git
synced 2025-04-22 23:02:54 +03:00
effe7d9552
When preparing a transaction in two-phase commit, a dummy PGPROC entry holding the GID used for the transaction is registered, which gets released once COMMIT PREPARED is run. Prior releasing its shared memory state, all the locks taken in the prepared transaction are released using a dedicated set of callbacks (pgstat and multixact having similar callbacks), which may cause the locks to be released before the GID is set free. Hence, there is a small window where lock conflicts could happen, for example: - Transaction A releases its locks, still holding its GID in shared memory. - Transaction B held a lock which conflicted with locks of transaction A. - Transaction B continues its processing, reusing the same GID as transaction A. - Transaction B fails because of a conflicting GID, already in use by transaction A. This commit changes the shared memory state release so as post-commit callbacks and predicate lock cleanup happen consistently with the shared memory state cleanup for the dummy PGPROC entry. The race window is small and 2PC had this issue from the start, so no backpatch is done. On top if that fixes discussed involved ABI breakages, which are not welcome in stable branches. Reported-by: Oleksii Kliukin, Ildar Musin Diagnosed-by: Oleksii Kliukin, Ildar Musin Author: Michael Paquier Reviewed-by: Masahiko Sawada, Oleksii Kliukin Discussion: https://postgr.es/m/BF9B38A4-2BFF-46E8-BA87-A2D00A8047A6@hintbits.com
PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.