From 79a4d24f31e09eb3c421deb34829eee0bf6acd67 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 18 Mar 2014 07:58:53 -0400
Subject: [PATCH] Make it easy to detach completely from shared memory.
The new function dsm_detach_all() can be used either by postmaster
children that don't wish to take any risk of accidentally corrupting
shared memory; or by forked children of regular backends with
the same need. This patch also updates the postmaster children that
already do PGSharedMemoryDetach() to do dsm_detach_all() as well.
Per discussion with Tom Lane.
---
src/backend/postmaster/pgarch.c | 2 ++
src/backend/postmaster/pgstat.c | 2 ++
src/backend/postmaster/syslogger.c | 2 ++
src/backend/storage/ipc/dsm.c | 27 +++++++++++++++++++++++++++
src/include/storage/dsm.h | 1 +
5 files changed, 34 insertions(+)
diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c
index cf2ce46516b..815316055a7 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -40,6 +40,7 @@
#include "postmaster/fork_process.h"
#include "postmaster/pgarch.h"
#include "postmaster/postmaster.h"
+#include "storage/dsm.h"
#include "storage/fd.h"
#include "storage/ipc.h"
#include "storage/latch.h"
@@ -163,6 +164,7 @@ pgarch_start(void)
on_exit_reset();
/* Drop our connection to postmaster's shared memory, as well */
+ dsm_detach_all();
PGSharedMemoryDetach();
PgArchiverMain(0, NULL);
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 1ca5d130444..3dc280a48d7 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -50,6 +50,7 @@
#include "postmaster/postmaster.h"
#include "storage/proc.h"
#include "storage/backendid.h"
+#include "storage/dsm.h"
#include "storage/fd.h"
#include "storage/ipc.h"
#include "storage/latch.h"
@@ -709,6 +710,7 @@ pgstat_start(void)
on_exit_reset();
/* Drop our connection to postmaster's shared memory, as well */
+ dsm_detach_all();
PGSharedMemoryDetach();
PgstatCollectorMain(0, NULL);
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index e277a9a8a66..4731ab73fed 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -39,6 +39,7 @@
#include "postmaster/fork_process.h"
#include "postmaster/postmaster.h"
#include "postmaster/syslogger.h"
+#include "storage/dsm.h"
#include "storage/ipc.h"
#include "storage/latch.h"
#include "storage/pg_shmem.h"
@@ -626,6 +627,7 @@ SysLogger_Start(void)
on_exit_reset();
/* Drop our connection to postmaster's shared memory, as well */
+ dsm_detach_all();
PGSharedMemoryDetach();
/* do the work */
diff --git a/src/backend/storage/ipc/dsm.c b/src/backend/storage/ipc/dsm.c
index 232c099c18a..c967177c4b1 100644
--- a/src/backend/storage/ipc/dsm.c
+++ b/src/backend/storage/ipc/dsm.c
@@ -722,6 +722,8 @@ dsm_attach(dsm_handle h)
/*
* At backend shutdown time, detach any segments that are still attached.
+ * (This is similar to dsm_detach_all, except that there's no reason to
+ * unmap the control segment before exiting, so we don't bother.)
*/
void
dsm_backend_shutdown(void)
@@ -735,6 +737,31 @@ dsm_backend_shutdown(void)
}
}
+/*
+ * Detach all shared memory segments, including the control segments. This
+ * should be called, along with PGSharedMemoryDetach, in processes that
+ * might inherit mappings but are not intended to be connected to dynamic
+ * shared memory.
+ */
+void
+dsm_detach_all(void)
+{
+ void *control_address = dsm_control;
+
+ while (!dlist_is_empty(&dsm_segment_list))
+ {
+ dsm_segment *seg;
+
+ seg = dlist_head_element(dsm_segment, node, &dsm_segment_list);
+ dsm_detach(seg);
+ }
+
+ if (control_address != NULL)
+ dsm_impl_op(DSM_OP_DETACH, dsm_control_handle, 0,
+ &dsm_control_impl_private, &control_address,
+ &dsm_control_mapped_size, ERROR);
+}
+
/*
* Resize an existing shared memory segment.
*
diff --git a/src/include/storage/dsm.h b/src/include/storage/dsm.h
index 03dd7679ffd..e4669a1e3c1 100644
--- a/src/include/storage/dsm.h
+++ b/src/include/storage/dsm.h
@@ -20,6 +20,7 @@ typedef struct dsm_segment dsm_segment;
/* Startup and shutdown functions. */
extern void dsm_postmaster_startup(void);
extern void dsm_backend_shutdown(void);
+extern void dsm_detach_all(void);
/* Functions that create, update, or remove mappings. */
extern dsm_segment *dsm_create(Size size);
--
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