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If we failed to fork a worker process, or create a communication pipe for one, WaitForTerminatingWorkers would suffer an assertion failure if assert-enabled, otherwise crash or go into an infinite loop. This was a consequence of not accounting for the startup condition where we've not yet forked all the workers. The original bug was that ParallelBackupStart would set workerStatus to WRKR_IDLE before it had successfully forked a worker. I made things worse in commit b7b8cc0cf by not understanding the undocumented fact that the WRKR_TERMINATED state was also meant to represent the case where a worker hadn't been started yet: I changed enum T_WorkerStatus so that *all* the worker slots were initially in WRKR_IDLE state. But this wasn't any more broken in practice, since even one slot in the wrong state would keep WaitForTerminatingWorkers from terminating. In v10 and later, introduce an explicit T_WorkerStatus value for worker-not-started, in hopes of preventing future oversights of the same ilk. Before that, just document that WRKR_TERMINATED is supposed to cover that case (partly because it wasn't actively broken, and partly because the enum is exposed outside parallel.c in those branches, so there's microscopically more risk involved in changing it). In all branches, introduce a WORKER_IS_RUNNING status test macro to hide which T_WorkerStatus values mean that, and be more careful not to access ParallelSlot fields till we're sure they're valid. Per report from Vignesh C, though this is my patch not his. Back-patch to all supported branches. Discussion: https://postgr.es/m/CALDaNm1Luv-E3sarR+-unz-BjchquHHyfP+YC+2FS2pt_J+wxg@mail.gmail.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/.