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Although the postmaster doesn't currently create a self-pipe or any latches, there's discussion of it doing so in future. It's also conceivable that a shared_preload_libraries extension would try to create such a thing in the postmaster process today. In that case the self-pipe FDs would be inherited by forked child processes. latch.c was entirely unprepared for such a case and could suffer an assertion failure, or worse try to use the inherited pipe if somebody called WaitLatch without having called InitializeLatchSupport in that process. Make it keep track of whether InitializeLatchSupport has been called in the *current* process, and do the right thing if state has been inherited from a parent. Apply FD_CLOEXEC to file descriptors created in latch.c (the self-pipe, as well as epoll event sets). This ensures that child processes spawned in backends, the archiver, etc cannot accidentally or intentionally mess with these FDs. It also ensures that we end up with the right state for the self-pipe in EXEC_BACKEND processes, which otherwise wouldn't know to close the postmaster's self-pipe FDs. Back-patch to 9.6, mainly to keep latch.c looking similar in all branches it exists in. Discussion: https://postgr.es/m/8322.1493240739@sss.pgh.pa.us
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/.