From ddf6d1b38c01b36b28e98953e680aabf6aefbdbf Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Wed, 1 Apr 2026 18:10:31 +0300 Subject: [PATCH 03/14] Add test module to test after-startup shmem allocations None of the existing modules could make use of the lazy shmem allocation after postmaster startup: - pg_stat_statements needs to load and dump stats file on startup and shutdown, which doesn't really work if the library is not loaded into postmaster - test_aio registers injection points, which reference the library itself, which creates a weird initialization loop if you try to do that directly from _PG_init() in a backend. The initialization really needs to happen after _PG_init() - injection_points would be a candidate, but it already knows to use DSM when it's not loaded from shared_preload_libraries. --- src/test/modules/Makefile | 1 + src/test/modules/meson.build | 1 + src/test/modules/test_shmem/Makefile | 24 ++++ src/test/modules/test_shmem/meson.build | 33 ++++++ .../test_shmem/t/001_late_shmem_alloc.pl | 49 ++++++++ .../modules/test_shmem/test_shmem--1.0.sql | 9 ++ src/test/modules/test_shmem/test_shmem.c | 105 ++++++++++++++++++ .../modules/test_shmem/test_shmem.control | 3 + src/tools/pgindent/typedefs.list | 1 + 9 files changed, 226 insertions(+) create mode 100644 src/test/modules/test_shmem/Makefile create mode 100644 src/test/modules/test_shmem/meson.build create mode 100644 src/test/modules/test_shmem/t/001_late_shmem_alloc.pl create mode 100644 src/test/modules/test_shmem/test_shmem--1.0.sql create mode 100644 src/test/modules/test_shmem/test_shmem.c create mode 100644 src/test/modules/test_shmem/test_shmem.control diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile index 864b407abcf..f1b04c99969 100644 --- a/src/test/modules/Makefile +++ b/src/test/modules/Makefile @@ -48,6 +48,7 @@ SUBDIRS = \ test_resowner \ test_rls_hooks \ test_saslprep \ + test_shmem \ test_shm_mq \ test_slru \ test_tidstore \ diff --git a/src/test/modules/meson.build b/src/test/modules/meson.build index e5acacd5083..fc99552d9ab 100644 --- a/src/test/modules/meson.build +++ b/src/test/modules/meson.build @@ -49,6 +49,7 @@ subdir('test_regex') subdir('test_resowner') subdir('test_rls_hooks') subdir('test_saslprep') +subdir('test_shmem') subdir('test_shm_mq') subdir('test_slru') subdir('test_tidstore') diff --git a/src/test/modules/test_shmem/Makefile b/src/test/modules/test_shmem/Makefile new file mode 100644 index 00000000000..2407f7462fe --- /dev/null +++ b/src/test/modules/test_shmem/Makefile @@ -0,0 +1,24 @@ +# src/test/modules/test_shmem/Makefile + +PGFILEDESC = "test_shmem - test code for shmem allocations" + +MODULE_big = test_shmem +OBJS = \ + $(WIN32RES) \ + test_shmem.o + +EXTENSION = test_shmem +DATA = test_shmem--1.0.sql + +TAP_TESTS = 1 + +ifdef USE_PGXS +PG_CONFIG = pg_config +PGXS := $(shell $(PG_CONFIG) --pgxs) +include $(PGXS) +else +subdir = src/test/modules/test_shmem +top_builddir = ../../../.. +include $(top_builddir)/src/Makefile.global +include $(top_srcdir)/contrib/contrib-global.mk +endif diff --git a/src/test/modules/test_shmem/meson.build b/src/test/modules/test_shmem/meson.build new file mode 100644 index 00000000000..fb4bf328b8f --- /dev/null +++ b/src/test/modules/test_shmem/meson.build @@ -0,0 +1,33 @@ +# Copyright (c) 2024-2026, PostgreSQL Global Development Group + +test_shmem_sources = files( + 'test_shmem.c', +) + +if host_system == 'windows' + test_shmem_sources += rc_lib_gen.process(win32ver_rc, extra_args: [ + '--NAME', 'test_shmem', + '--FILEDESC', 'test_shmem - test code for shmem allocations',]) +endif + +test_shmem = shared_module('test_shmem', + test_shmem_sources, + kwargs: pg_test_mod_args, +) +test_install_libs += test_shmem + +test_install_data += files( + 'test_shmem.control', + 'test_shmem--1.0.sql', +) + +tests += { + 'name': 'test_shmem', + 'sd': meson.current_source_dir(), + 'bd': meson.current_build_dir(), + 'tap': { + 'tests': [ + 't/001_late_shmem_alloc.pl', + ], + }, +} diff --git a/src/test/modules/test_shmem/t/001_late_shmem_alloc.pl b/src/test/modules/test_shmem/t/001_late_shmem_alloc.pl new file mode 100644 index 00000000000..c154f57682a --- /dev/null +++ b/src/test/modules/test_shmem/t/001_late_shmem_alloc.pl @@ -0,0 +1,49 @@ +# Copyright (c) 2025-2026, PostgreSQL Global Development Group + +use strict; +use warnings FATAL => 'all'; + +use PostgreSQL::Test::Cluster; +use PostgreSQL::Test::Utils; +use Test::More; + +### +# Test allocating memory after startup, i.e. when the library is not +# in shared_preload_libraries +### +my $node = PostgreSQL::Test::Cluster->new('main'); +$node->init; +$node->start; + + +$node->safe_psql("postgres", "CREATE EXTENSION test_shmem;"); + +# Check that the attach counter is incremented on a new connection +my $attach_count1 = $node->safe_psql("postgres", "SELECT get_test_shmem_attach_count();"); +my $attach_count2 = $node->safe_psql("postgres", "SELECT get_test_shmem_attach_count();"); +cmp_ok($attach_count2, '>', $attach_count1, "attach callback is called in each backend"); +$node->stop; + +### +# Test that loading via shared_preload_libraries also works +### +$node->append_conf('postgresql.conf', "shared_preload_libraries = 'test_shmem'"); +$node->start; + +# When loaded via shared_preload_libraries, the attach callback is +# called or not, depending on whether this is an EXEC_BACKEND build. +my $exec_backend = $node->safe_psql("postgres", "SHOW debug_exec_backend;") eq 'on'; +$attach_count1 = $node->safe_psql("postgres", "SELECT get_test_shmem_attach_count();"); +$attach_count2 = $node->safe_psql("postgres", "SELECT get_test_shmem_attach_count();"); + +if ($exec_backend) +{ + cmp_ok($attach_count2, '>', $attach_count1, "attach callback is called in each backend when loaded via shared_preload_libraries"); +} +else +{ + ok($attach_count1 == 0 && $attach_count2 == 0, "attach callback is not called when loaded via shared_preload_libraries"); +} + +$node->stop; +done_testing(); diff --git a/src/test/modules/test_shmem/test_shmem--1.0.sql b/src/test/modules/test_shmem/test_shmem--1.0.sql new file mode 100644 index 00000000000..2d01fd9256c --- /dev/null +++ b/src/test/modules/test_shmem/test_shmem--1.0.sql @@ -0,0 +1,9 @@ +/* src/test/modules/test_shmem/test_shmem--1.0.sql */ + +-- complain if script is sourced in psql, rather than via CREATE EXTENSION +\echo Use "CREATE EXTENSION test_shmem" to load this file. \quit + + +CREATE FUNCTION get_test_shmem_attach_count() +RETURNS pg_catalog.int4 STRICT +AS 'MODULE_PATHNAME' LANGUAGE C; diff --git a/src/test/modules/test_shmem/test_shmem.c b/src/test/modules/test_shmem/test_shmem.c new file mode 100644 index 00000000000..31c735be570 --- /dev/null +++ b/src/test/modules/test_shmem/test_shmem.c @@ -0,0 +1,105 @@ +/*------------------------------------------------------------------------- + * + * test_shmem.c + * Helpers to test shmem allocation routines + * + * Test basic memory allocation in an extension module. One notable feature + * that is not exercised by any other module in the repository is the + * allocating (non-DSM) shared memory after postmaster startup. + * + * Copyright (c) 2020-2026, PostgreSQL Global Development Group + * + * IDENTIFICATION + * src/test/modules/test_shmem/test_shmem.c + * + *------------------------------------------------------------------------- + */ + +#include "postgres.h" + +#include "fmgr.h" +#include "miscadmin.h" +#include "storage/shmem.h" + + +PG_MODULE_MAGIC; + +typedef struct TestShmemData +{ + int value; + bool initialized; + int attach_count; +} TestShmemData; + +static TestShmemData *TestShmem; + +static bool attached_or_initialized = false; + +static void test_shmem_request(void *arg); +static void test_shmem_init(void *arg); +static void test_shmem_attach(void *arg); + +static const ShmemCallbacks TestShmemCallbacks = { + .flags = SHMEM_CALLBACKS_ALLOW_AFTER_STARTUP, + .request_fn = test_shmem_request, + .init_fn = test_shmem_init, + .attach_fn = test_shmem_attach, +}; + +static void +test_shmem_request(void *arg) +{ + static ShmemStructDesc TestShmemDesc; + + elog(LOG, "test_shmem_request callback called"); + + ShmemRequestStruct(&TestShmemDesc, + .name = "test_shmem area", + .size = sizeof(TestShmemData), + .ptr = (void **) &TestShmem, + ); +} + +static void +test_shmem_init(void *arg) +{ + elog(LOG, "init callback called"); + if (TestShmem->initialized) + elog(ERROR, "shmem area already initialized"); + TestShmem->initialized = true; + + if (attached_or_initialized) + elog(ERROR, "attach or initialize already called in this process"); + attached_or_initialized = true; +} + +static void +test_shmem_attach(void *arg) +{ + elog(LOG, "test_shmem_attach callback called"); + if (!TestShmem->initialized) + elog(ERROR, "shmem area not yet initialized"); + TestShmem->attach_count++; + + if (attached_or_initialized) + elog(ERROR, "attach or initialize already called in this process"); + attached_or_initialized = true; +} + +void +_PG_init(void) +{ + elog(LOG, "test_shmem module's _PG_init called"); + RegisterShmemCallbacks(&TestShmemCallbacks); +} + +PG_FUNCTION_INFO_V1(get_test_shmem_attach_count); +Datum +get_test_shmem_attach_count(PG_FUNCTION_ARGS) +{ + if (!attached_or_initialized) + elog(ERROR, "shmem area not attached or initialized in this process"); + if (!TestShmem->initialized) + elog(ERROR, "shmem area not yet initialized"); + PG_RETURN_INT32(TestShmem->attach_count); +} diff --git a/src/test/modules/test_shmem/test_shmem.control b/src/test/modules/test_shmem/test_shmem.control new file mode 100644 index 00000000000..f2f26f4537a --- /dev/null +++ b/src/test/modules/test_shmem/test_shmem.control @@ -0,0 +1,3 @@ +comment = 'Test code for shmem allocations' +default_version = '1.0' +module_pathname = '$libdir/test_shmem' diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 5894893997c..5358229b73f 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -3146,6 +3146,7 @@ TestDSMRegistryHashEntry TestDSMRegistryStruct TestDecodingData TestDecodingTxnData +TestShmemData TestSpec TestValueType TextFreq -- 2.47.3