Remove dynamic_shared_memory_type=none

PostgreSQL nowadays offers some kind of dynamic shared memory feature on
all supported platforms.  Having the choice of "none" prevents us from
relying on DSM in core features.  So this patch removes the choice of
"none".

Author: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>

7 files changed, 14 insertions, 37 deletions

diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
index 1d631b72755..4e32cfff500 100644
--- a/src/backend/access/transam/parallel.c
+++ b/src/backend/access/transam/parallel.c
@@ -162,13 +162,6 @@ CreateParallelContext(const char *library_name, const char *function_name,
 	Assert(nworkers >= 0);
 
 	/*
-	 * If dynamic shared memory is not available, we won't be able to use
-	 * background workers.
-	 */
-	if (dynamic_shared_memory_type == DSM_IMPL_NONE)
-		nworkers = 0;
-
-	/*
 	 * If we are running under serializable isolation, we can't use parallel
 	 * workers, at least not until somebody enhances that mechanism to be
 	 * parallel-aware.  Utility statement callers may ask us to ignore this
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index fd45c9767df..eeebf775a40 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -335,7 +335,6 @@ standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
 	 */
 	if ((cursorOptions & CURSOR_OPT_PARALLEL_OK) != 0 &&
 		IsUnderPostmaster &&
-		dynamic_shared_memory_type != DSM_IMPL_NONE &&
 		parse->commandType == CMD_SELECT &&
 		!parse->hasModifyingCTE &&
 		max_parallel_workers_per_gather > 0 &&
@@ -6050,8 +6049,7 @@ plan_create_index_workers(Oid tableOid, Oid indexOid)
 	double		allvisfrac;
 
 	/* Return immediately when parallelism disabled */
-	if (dynamic_shared_memory_type == DSM_IMPL_NONE ||
-		max_parallel_maintenance_workers == 0)
+	if (max_parallel_maintenance_workers == 0)
 		return 0;
 
 	/* Set up largely-dummy planner state */
diff --git a/src/backend/storage/ipc/dsm.c b/src/backend/storage/ipc/dsm.c
index f1f75b73f50..9629f22f7af 100644
--- a/src/backend/storage/ipc/dsm.c
+++ b/src/backend/storage/ipc/dsm.c
@@ -150,10 +150,6 @@ dsm_postmaster_startup(PGShmemHeader *shim)
 
 	Assert(!IsUnderPostmaster);
 
-	/* If dynamic shared memory is disabled, there's nothing to do. */
-	if (dynamic_shared_memory_type == DSM_IMPL_NONE)
-		return;
-
 	/*
 	 * If we're using the mmap implementations, clean up any leftovers.
 	 * Cleanup isn't needed on Windows, and happens earlier in startup for
@@ -219,10 +215,6 @@ dsm_cleanup_using_control_segment(dsm_handle old_control_handle)
 	uint32		i;
 	dsm_control_header *old_control;
 
-	/* If dynamic shared memory is disabled, there's nothing to do. */
-	if (dynamic_shared_memory_type == DSM_IMPL_NONE)
-		return;
-
 	/*
 	 * Try to attach the segment.  If this fails, it probably just means that
 	 * the operating system has been rebooted and the segment no longer
@@ -391,13 +383,6 @@ dsm_postmaster_shutdown(int code, Datum arg)
 static void
 dsm_backend_startup(void)
 {
-	/* If dynamic shared memory is disabled, reject this. */
-	if (dynamic_shared_memory_type == DSM_IMPL_NONE)
-		ereport(ERROR,
-				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-				 errmsg("dynamic shared memory is disabled"),
-				 errhint("Set dynamic_shared_memory_type to a value other than \"none\".")));
-
 #ifdef EXEC_BACKEND
 	{
 		void	   *control_address = NULL;
diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c
index c6382ec031b..77e1bab54be 100644
--- a/src/backend/storage/ipc/dsm_impl.c
+++ b/src/backend/storage/ipc/dsm_impl.c
@@ -106,7 +106,6 @@ const struct config_enum_entry dynamic_shared_memory_options[] = {
 #ifdef USE_DSM_MMAP
 	{"mmap", DSM_IMPL_MMAP, false},
 #endif
-	{"none", DSM_IMPL_NONE, false},
 	{NULL, 0, false}
 };
 
@@ -210,8 +209,6 @@ dsm_impl_can_resize(void)
 {
 	switch (dynamic_shared_memory_type)
 	{
-		case DSM_IMPL_NONE:
-			return false;
 		case DSM_IMPL_POSIX:
 			return true;
 		case DSM_IMPL_SYSV:
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 9e39baf4668..657c3f81f8f 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -133,7 +133,6 @@
 					#   sysv
 					#   windows
 					#   mmap
-					# use none to disable dynamic shared memory
 					# (change requires restart)
 
 # - Disk -
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index ae22e7d9fb8..3f203c6ca6d 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -984,6 +984,15 @@ test_config_settings(void)
 				ok_buffers = 0;
 
 
+	/*
+	 * Need to determine working DSM implementation first so that subsequent
+	 * tests don't fail because DSM setting doesn't work.
+	 */
+	printf(_("selecting dynamic shared memory implementation ... "));
+	fflush(stdout);
+	dynamic_shared_memory_type = choose_dsm_implementation();
+	printf("%s\n", dynamic_shared_memory_type);
+
 	printf(_("selecting default max_connections ... "));
 	fflush(stdout);
 
@@ -996,10 +1005,11 @@ test_config_settings(void)
 				 "\"%s\" --boot -x0 %s "
 				 "-c max_connections=%d "
 				 "-c shared_buffers=%d "
-				 "-c dynamic_shared_memory_type=none "
+				 "-c dynamic_shared_memory_type=%s "
 				 "< \"%s\" > \"%s\" 2>&1",
 				 backend_exec, boot_options,
 				 test_conns, test_buffs,
+				 dynamic_shared_memory_type,
 				 DEVNULL, DEVNULL);
 		status = system(cmd);
 		if (status == 0)
@@ -1031,10 +1041,11 @@ test_config_settings(void)
 				 "\"%s\" --boot -x0 %s "
 				 "-c max_connections=%d "
 				 "-c shared_buffers=%d "
-				 "-c dynamic_shared_memory_type=none "
+				 "-c dynamic_shared_memory_type=%s "
 				 "< \"%s\" > \"%s\" 2>&1",
 				 backend_exec, boot_options,
 				 n_connections, test_buffs,
+				 dynamic_shared_memory_type,
 				 DEVNULL, DEVNULL);
 		status = system(cmd);
 		if (status == 0)
@@ -1046,11 +1057,6 @@ test_config_settings(void)
 		printf("%dMB\n", (n_buffers * (BLCKSZ / 1024)) / 1024);
 	else
 		printf("%dkB\n", n_buffers * (BLCKSZ / 1024));
-
-	printf(_("selecting dynamic shared memory implementation ... "));
-	fflush(stdout);
-	dynamic_shared_memory_type = choose_dsm_implementation();
-	printf("%s\n", dynamic_shared_memory_type);
 }
 
 /*
diff --git a/src/include/storage/dsm_impl.h b/src/include/storage/dsm_impl.h
index 0e5730f7c5b..e7acdff3552 100644
--- a/src/include/storage/dsm_impl.h
+++ b/src/include/storage/dsm_impl.h
@@ -14,7 +14,6 @@
 #define DSM_IMPL_H
 
 /* Dynamic shared memory implementations. */
-#define DSM_IMPL_NONE			0
 #define DSM_IMPL_POSIX			1
 #define DSM_IMPL_SYSV			2
 #define DSM_IMPL_WINDOWS		3