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Commit2c8dd05d6cadded the atomic variable writtenUpto into walreceiver's shared memory information. It's initialized only when walreceiver started up but could be read via pg_stat_wal_receiver view anytime, i.e., even before it's initialized. In the server built with --disable-atomics and --disable-spinlocks, this uninitialized atomic variable read could cause "invalid spinlock number: 0" error. This commit changed writtenUpto so that it's initialized at the postmaster startup, to avoid the uninitialized variable read via pg_stat_wal_receiver and fix the error. Also this commit moved the read of writtenUpto after the release of spinlock protecting walreceiver's shared variables. This is necessary to prevent new spinlock from being taken by atomic variable read while holding another spinlock, and to shorten the spinlock duration. This change leads writtenUpto not to be consistent with the other walreceiver's shared variables protected by a spinlock. But this is OK because writtenUpto should not be used for data integrity checks. Back-patch to v13 where commit2c8dd05d6cintroduced the bug. Author: Fujii Masao Reviewed-by: Michael Paquier, Thomas Munro, Andres Freund Discussion: https://postgr.es/m/7ef8708c-5b6b-edd3-2cf2-7783f1c7c175@oss.nttdata.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/.