4aec49899e
Post-commit review by Andres Freund discovered a couple of concurrency bugs in the original patch: specifically, if the leader cleared a follower's XID before it reached PGSemaphoreLock, the semaphore would be left in the wrong state; and if another process did PGSemaphoreUnlock for some unrelated reason, we might resume execution before the fact that our XID was cleared was globally visible. Also, improve the wording of some comments, rename nextClearXidElem to firstClearXidElem in PROC_HDR for clarity, and drop some volatile qualifiers that aren't necessary. Amit Kapila, reviewed and slightly revised by me.
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: http://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 http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.