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Winsock only signals an FD_CLOSE event once if the other end of the socket shuts down gracefully. Because each WaitLatchOrSocket() call constructs and destroys a new event handle every time, with unlucky timing we can lose it and hang. We get away with this only if the other end disconnects non-gracefully, because FD_CLOSE is repeatedly signaled in that case. To fix this design flaw in our Windows socket support fundamentally, we'd probably need to rearchitect it so that a single event handle exists for the lifetime of a socket, or switch to completely different multiplexing or async I/O APIs. That's going to be a bigger job and probably wouldn't be back-patchable. This brute force kludge closes the race by explicitly polling with MSG_PEEK before sleeping. Back-patch to all supported releases. This should hopefully clear up some random build farm and CI hang failures reported over the years. It might also allow us to try using graceful shutdown in more places again (reverted in commit 29992a6) to fix instability in the transmission of FATAL error messages, but that isn't done by this commit. Reported-by: Tom Lane <tgl@sss.pgh.pa.us> Tested-by: Alexander Lakhin <exclusion@gmail.com> Discussion: https://postgr.es/m/176008.1715492071%40sss.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: 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/.