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Andres Freund 332693e759 lwlock: Fix, currently harmless, bug in LWLockWakeup()
Accidentally the code in LWLockWakeup() checked the list of to-be-woken up
processes to see if LW_FLAG_HAS_WAITERS should be unset. That means that
HAS_WAITERS would not get unset immediately, but only during the next,
unnecessary, call to LWLockWakeup().

Luckily, as the code stands, this is just a small efficiency issue.

However, if there were (as in a patch of mine) a case in which LWLockWakeup()
would not find any backend to wake, despite the wait list not being empty,
we'd wrongly unset LW_FLAG_HAS_WAITERS, leading to potentially hanging.

While the consequences in the backbranches are limited, the code as-is
confusing, and it is possible that there are workloads where the additional
wait list lock acquisitions hurt, therefore backpatch.

Discussion: https://postgr.es/m/fvfmkr5kk4nyex56ejgxj3uzi63isfxovp2biecb4bspbjrze7@az2pljabhnff
Backpatch-through: 14
2025-11-24 17:39:42 -05:00
config Don't put library-supplied -L/-I switches before user-supplied ones. 2025-07-29 15:17:41 -04:00
contrib postgres_fdw: Add more test coverage for EvalPlanQual testing. 2025-11-06 12:15:05 +09:00
doc doc: Improve description of RLS policies applied by command type. 2025-11-13 12:05:17 +00:00
src lwlock: Fix, currently harmless, bug in LWLockWakeup() 2025-11-24 17:39:42 -05:00
.abi-compliance-history Update .abi-compliance-history for change to CreateStatistics(). 2025-11-17 14:14:41 -06:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Add .editorconfig 2019-12-18 09:13:13 +01:00
.git-blame-ignore-revs Add previous commit to .git-blame-ignore-revs. 2025-10-21 10:02:19 -05:00
.gitattributes Exclude LLVM files from whitespace checks 2024-11-27 11:10:00 +01:00
.gitignore Add portlock directory to .gitignore 2022-11-26 07:47:06 -05:00
aclocal.m4 Probe $PROVE not $PERL while checking for modules needed by TAP tests. 2021-11-22 12:54:52 -05:00
configure Stamp 14.20. 2025-11-10 16:58:00 -05:00
configure.ac Stamp 14.20. 2025-11-10 16:58:00 -05:00
COPYRIGHT Align organization wording in copyright statement 2025-05-16 11:20:07 -04:00
GNUmakefile.in Remove temporary portlock directory during make [dist]clean. 2022-11-26 10:30:53 -05:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Don't unset MAKEFLAGS in non-GNU Makefile. 2019-06-25 09:36:21 +12:00
README Canonicalize some URLs 2020-02-10 20:47:50 +01:00
README.git Canonicalize some URLs 2020-02-10 20:47:50 +01:00

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/.