358cde320b
If a call to WaitForXLogInsertionsToFinish() returned a value in the middle of a page, and another backend then started to insert a record to the same page, and then you called WaitXLogInsertionsToFinish() again, the second call might return a smaller value than the first call. The problem was in GetXLogBuffer(), which always updated the insertingAt value to the beginning of the requested page, not the actual requested location. Because of that, the second call might return a xlog pointer to the beginning of the page, while the first one returned a later position on the same page. XLogFlush() performs two calls to WaitXLogInsertionsToFinish() in succession, and holds WALWriteLock on the second call, which can deadlock if the second call to WaitXLogInsertionsToFinish() blocks. Reported by Spiros Ioannou. Backpatch to 9.4, where the more scalable WALInsertLock mechanism, and this bug, was introduced.
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/.