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The default of lazy symbol resolution means that when the postmaster first reaches the select() call in ServerLoop, it'll need to resolve the link to that libc entry point. NetBSD's dynamic loader takes an internal lock while doing that, and if a signal interrupts the operation then there is a risk of self-deadlock should the signal handler do anything that requires that lock, as several of the postmaster signal handlers do. The window for this is pretty narrow, and timing considerations make it unlikely that a signal would arrive right then anyway. But it's semi-repeatable on slow single-CPU machines, and in principle the race could happen with any hardware. The least messy solution to this is to force binding of dynamic symbols at postmaster start, using the "-z now" linker option. While we're at it, also use "-z relro" so as to provide a small security gain. It's not entirely clear whether any other platforms share this issue, but for now we'll assume it's NetBSD-specific. (We might later try to use "-z now" on more platforms for performance reasons, but that would not likely be something to back-patch.) Report and patch by me; the idea to fix it this way is from Andres Freund. Discussion: https://postgr.es/m/3384826.1661802235@sss.pgh.pa.us |
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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/.