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Holding just a buffer pin (with no buffer lock) on an nbtree buffer/page provides very weak guarantees, especially compared to heapam, where it's often safe to read a page while only holding a buffer pin. This commit has Valgrind enforce the following rule: it is never okay to access an nbtree buffer without holding both a pin and a lock on the buffer. A draft version of this patch detected questionable code that was cleaned up by commits fa7ff642 and 7154aa16. The code in question used to access an nbtree buffer page's special/opaque area with no buffer lock (only a buffer pin). This practice (which isn't obviously unsafe) is hereby formally disallowed in nbtree. There doesn't seem to be any reason to allow it, and banning it keeps things simple for Valgrind. The new checks are implemented by adding custom nbtree client requests (located in LockBuffer() wrapper functions); these requests are "superimposed" on top of the generic bufmgr.c Valgrind client requests added by commit 1e0dfd16. No custom resource management cleanup code is needed to undo the effects of marking buffers as non-accessible under this scheme. Author: Peter Geoghegan Reviewed-By: Anastasia Lubennikova, Georgios Kokolatos Discussion: https://postgr.es/m/CAH2-WzkLgyN3zBvRZ1pkNJThC=xi_0gpWRUb_45eexLH1+k2_Q@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/.