From e7bcfa563e568ca8d3474432fd094a38205c78f0 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Fri, 2 Apr 2021 03:43:26 +1300
Subject: [PATCH] Use POSIX_NAMED_SEMAPHORES on OpenBSD.

For PostgreSQL to work out of the box without sysctl changes, let's use
POSIX semaphores instead of System V ones.  The "unamed" kind aren't
supported in shared memory, so we use the "named" kind.

Discussion: https://postgr.es/m/27582.1546928073%40sss.pgh.pa.us
---
 doc/src/sgml/runtime.sgml |  6 +-----
 src/template/openbsd      | 11 +++++++++++
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index bf877c0e0c..9aa3129aba 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -998,11 +998,7 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such
        <para>
         The default shared memory settings are usually good enough, unless
         you have set <literal>shared_memory_type</literal> to <literal>sysv</literal>.
-        You will usually want to
-        increase <literal>kern.seminfo.semmni</literal>
-        and <literal>kern.seminfo.semmns</literal>,
-        as <systemitem class="osname">OpenBSD</systemitem>'s default settings
-        for these are uncomfortably small.
+        System V semaphores are not used on this platform (since OpenBSD 5.5).
        </para>
 
        <para>
diff --git a/src/template/openbsd b/src/template/openbsd
index 365268c489..d3b6bf464a 100644
--- a/src/template/openbsd
+++ b/src/template/openbsd
@@ -2,3 +2,14 @@
 
 # Extra CFLAGS for code that will go into a shared library
 CFLAGS_SL="-fPIC -DPIC"
+
+# OpenBSD 5.5 (2014) gained named POSIX semaphores.  They work out of the box
+# without changing any sysctl settings, unlike System V semaphores.
+case $host_os in
+  openbsd5.[01234]*)
+    USE_SYSV_SEMAPHORES=1
+    ;;
+  *)
+    USE_NAMED_POSIX_SEMAPHORES=1
+    ;;
+esac
-- 
2.30.1