9e149c847f
While debugging issues on HEAD for the new slot forwarding feature of Postgres 11, some monitoring of the code surrounding in-memory slot data has proved that the lock handling may cause inconsistent data to be read by read-only callers of slot functions, particularly pg_get_replication_slots() which fetches data for the system view pg_replication_slots, or modules looking directly at slot information. The code paths involved in those problems concern logical decoding initialization (down to 9.4) and WAL reservation for slots (new as of 10). A set of comments documenting all the lock handlings, particularly the dependency with LW locks for slots and the in_use flag as well as the internal mutex lock is added, based on a suggested by Simon Riggs. Some of the fixed code exists down to 9.4 where WAL decoding has been introduced, but as those race conditions are really unlikely going to happen as those concern code paths for slot and decoding creation, just fix the problem on HEAD. Author: Michael Paquier Discussion: https://postgr.es/m/20180528085747.GA27845@paquier.xyz |
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README
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/.