From 4605d1c98b305567a7addb22643a9cc7519315e9 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 3 Jan 2009 20:03:08 +0000
Subject: [PATCH] Allow loadable modules to create PGC_POSTMASTER GUC
variables, but only when loaded via shared_preload_libraries. Needed for
support of pg_stat_statements, or pretty much anything else that wants a GUC
to control size of a shared memory allocation.
---
src/backend/utils/init/miscinit.c | 7 ++++++-
src/backend/utils/misc/guc.c | 23 +++++++++++++++++++++--
src/include/miscadmin.h | 3 ++-
3 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c
index 8e449487cc5..461918ed309 100644
--- a/src/backend/utils/init/miscinit.c
+++ b/src/backend/utils/init/miscinit.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.170 2009/01/01 17:23:51 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.171 2009/01/03 20:03:08 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1131,6 +1131,9 @@ ValidatePgVersion(const char *path)
char *shared_preload_libraries_string = NULL;
char *local_preload_libraries_string = NULL;
+/* Flag telling that we are loading shared_preload_libraries */
+bool process_shared_preload_libraries_in_progress = false;
+
/*
* load the shared libraries listed in 'libraries'
*
@@ -1197,9 +1200,11 @@ load_libraries(const char *libraries, const char *gucname, bool restricted)
void
process_shared_preload_libraries(void)
{
+ process_shared_preload_libraries_in_progress = true;
load_libraries(shared_preload_libraries_string,
"shared_preload_libraries",
false);
+ process_shared_preload_libraries_in_progress = false;
}
/*
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 1290af8dee0..303329167a8 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -10,7 +10,7 @@
* Written by Peter Eisentraut <peter_e@gmx.net>.
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.487 2009/01/02 10:33:20 mha Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.488 2009/01/03 20:03:08 tgl Exp $
*
*--------------------------------------------------------------------
*/
@@ -5625,6 +5625,17 @@ init_custom_variable(const char *name,
{
struct config_generic *gen;
+ /*
+ * Only allow custom PGC_POSTMASTER variables to be created during
+ * shared library preload; any later than that, we can't ensure that
+ * the value doesn't change after startup. This is a fatal elog if it
+ * happens; just erroring out isn't safe because we don't know what
+ * the calling loadable module might already have hooked into.
+ */
+ if (context == PGC_POSTMASTER &&
+ !process_shared_preload_libraries_in_progress)
+ elog(FATAL, "cannot create PGC_POSTMASTER variables after startup");
+
gen = (struct config_generic *) guc_malloc(ERROR, sz);
memset(gen, 0, sz);
@@ -5707,7 +5718,15 @@ define_custom_variable(struct config_generic * variable)
case PGC_S_ENV_VAR:
case PGC_S_FILE:
case PGC_S_ARGV:
- phcontext = PGC_SIGHUP;
+ /*
+ * If we got past the check in init_custom_variable, we can
+ * safely assume that any existing value for a PGC_POSTMASTER
+ * variable was set in postmaster context.
+ */
+ if (variable->context == PGC_POSTMASTER)
+ phcontext = PGC_POSTMASTER;
+ else
+ phcontext = PGC_SIGHUP;
break;
case PGC_S_DATABASE:
case PGC_S_USER:
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index ccef61f1bab..e1c1042d681 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -13,7 +13,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.207 2009/01/01 17:23:55 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.208 2009/01/03 20:03:08 tgl Exp $
*
* NOTES
* some of the information in this file should be moved to other files.
@@ -328,6 +328,7 @@ extern void BaseInit(void);
/* in utils/init/miscinit.c */
extern bool IgnoreSystemIndexes;
+extern PGDLLIMPORT bool process_shared_preload_libraries_in_progress;
extern char *shared_preload_libraries_string;
extern char *local_preload_libraries_string;
--
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