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Writing correct code using atomic variables is often difficult due to the memory barrier semantics (or lack thereof) of the underlying operations. This commit introduces atomic read/write functions with full barrier semantics to ease this cognitive load. For example, some spinlocks protect a single value, and these new functions make it easy to convert the value to an atomic variable (thus eliminating the need for the spinlock) without modifying the barrier semantics previously provided by the spinlock. Since these functions may be less performant than the other atomic reads and writes, they are not suitable for every use-case. However, using a single atomic operation with full barrier semantics may be more performant in cases where a separate explicit barrier would otherwise be required. The base implementations for these new functions are atomic exchanges (for writes) and atomic fetch/adds with 0 (for reads). These implementations can be overwritten with better architecture- specific versions as they are discovered. This commit leaves converting existing code to use these new functions as a future exercise. Reviewed-by: Andres Freund, Yong Li, Jeff Davis Discussion: https://postgr.es/m/20231110205128.GB1315705%40nathanxps13 |
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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.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at:
https://www.postgresql.org/docs/devel/
In particular, information about building PostgreSQL from the source
code can be found at:
https://www.postgresql.org/docs/devel/installation.html
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.