There was a minor typo in the test module. I built and ran the
test_dsm_registry extension before submitting the patch but perhaps it
got mixed up with an older version.
From 06ddb42e39b3bd0e411a9bc96467ca6797673b8a Mon Sep 17 00:00:00 2001
From: swchangdev <[email protected]>
Date: Fri, 14 Mar 2025 10:00:12 +0900
Subject: [PATCH] Add detach and destroy feature to dsm_registry
---
src/backend/storage/ipc/dsm_registry.c | 167 +++++++++++++++++-
src/include/storage/dsm_registry.h | 8 +
.../expected/test_dsm_registry.out | 11 ++
.../sql/test_dsm_registry.sql | 2 +
.../test_dsm_registry--1.0.sql | 6 +
.../test_dsm_registry/test_dsm_registry.c | 28 +++
6 files changed, 221 insertions(+), 1 deletion(-)
diff --git a/src/backend/storage/ipc/dsm_registry.c b/src/backend/storage/ipc/dsm_registry.c
index 1d4fd31ffed..7915b70e47d 100644
--- a/src/backend/storage/ipc/dsm_registry.c
+++ b/src/backend/storage/ipc/dsm_registry.c
@@ -47,6 +47,12 @@ typedef struct DSMRegistryEntry
size_t size;
} DSMRegistryEntry;
+typedef struct DSMDetachCallbackContext
+{
+ void (*on_detach_callback) (void *);
+ void *arg;
+} DSMDetachCallbackContext;
+
static const dshash_parameters dsh_params = {
offsetof(DSMRegistryEntry, handle),
sizeof(DSMRegistryEntry),
@@ -121,6 +127,36 @@ init_dsm_registry(void)
LWLockRelease(DSMRegistryLock);
}
+static void
+call_on_detach_callback(dsm_segment *seg, Datum arg)
+{
+ char *ptr = DatumGetPointer(arg);
+ DSMDetachCallbackContext *cb_ctx = (DSMDetachCallbackContext *)ptr;
+ cb_ctx->on_detach_callback(cb_ctx->arg);
+}
+
+static void
+detach_dsm_segment(dsm_handle handle, void (*detach_cb) (void *), void *arg)
+{
+ dsm_segment *seg = dsm_find_mapping(handle);
+
+ /* Detach the segment only if it is already attached */
+ if (seg != NULL)
+ {
+ if (detach_cb != NULL)
+ {
+ DSMDetachCallbackContext *cb_ctx = palloc(sizeof(DSMDetachCallbackContext));
+ cb_ctx->on_detach_callback = detach_cb;
+ cb_ctx->arg = arg;
+
+ on_dsm_detach(seg, call_on_detach_callback, PointerGetDatum(cb_ctx));
+ }
+
+ dsm_unpin_mapping(seg);
+ dsm_detach(seg);
+ }
+}
+
/*
* Initialize or attach a named DSM segment.
*
@@ -172,6 +208,8 @@ GetNamedDSMSegment(const char *name, size_t size,
}
else if (entry->size != size)
{
+ dshash_release_lock(dsm_registry_table, entry);
+ MemoryContextSwitchTo(oldcontext);
ereport(ERROR,
(errmsg("requested DSM segment size does not match size of "
"existing segment")));
@@ -185,8 +223,11 @@ GetNamedDSMSegment(const char *name, size_t size,
{
seg = dsm_attach(entry->handle);
if (seg == NULL)
+ {
+ dshash_release_lock(dsm_registry_table, entry);
+ MemoryContextSwitchTo(oldcontext);
elog(ERROR, "could not map dynamic shared memory segment");
-
+ }
dsm_pin_mapping(seg);
}
@@ -198,3 +239,127 @@ GetNamedDSMSegment(const char *name, size_t size,
return ret;
}
+
+/*
+ * Detach a named DSM segment
+ *
+ * This routine detaches the DSM segment. If the DSM segment was not attached
+ * by this process, then the routine just returns. on_detach_callback is passed
+ * on to dsm_segment by calling on_dsm_detach for the corresponding dsm_segment
+ * before actually detaching.
+ */
+void
+DetachNamedDSMSegment(const char *name, size_t size,
+ void (*on_detach_callback) (void *), void *arg)
+{
+ DSMRegistryEntry *entry;
+ MemoryContext oldcontext;
+
+ if (!name || *name == '\0')
+ ereport(ERROR,
+ (errmsg("DSM segment name cannot be empty")));
+
+ if (strlen(name) >= offsetof(DSMRegistryEntry, handle))
+ ereport(ERROR,
+ (errmsg("DSM segment name too long")));
+
+ if (size == 0)
+ ereport(ERROR,
+ (errmsg("DSM segment size must be nonzero")));
+
+ /* Be sure any local memory allocated by DSM/DSA routines is persistent. */
+ oldcontext = MemoryContextSwitchTo(TopMemoryContext);
+
+ /* Connect to the registry. */
+ init_dsm_registry();
+
+ entry = dshash_find(dsm_registry_table, name, true);
+
+ if (entry == NULL)
+ {
+ MemoryContextSwitchTo(oldcontext);
+ ereport(ERROR,
+ (errmsg("cannot detach a DSM segment that does not exist")));
+ }
+
+ if (entry->size != size)
+ {
+ dshash_release_lock(dsm_registry_table, entry);
+ MemoryContextSwitchTo(oldcontext);
+ ereport(ERROR,
+ (errmsg("requested DSM segment size does not match size of "
+ "existing segment")));
+ }
+
+ detach_dsm_segment(entry->handle, on_detach_callback, arg);
+
+ dshash_release_lock(dsm_registry_table, entry);
+ MemoryContextSwitchTo(oldcontext);
+}
+
+/*
+ * Attempt to destroy a named DSM segment
+ *
+ * This routine attempts to destroy the DSM segment. We unpin the dsm_segment
+ * and delete the entry from dsm_registry_table. This may not destroy the
+ * dsm_segment instantly, but it would die out once all the other processes
+ * attached to this dsm_segment either exit or manually detach from the
+ * dsm_segment.
+ *
+ * Because we deleted the key from dsm_registry_table, calling
+ * GetNamedDSMSegment with the same key would result into creating a new
+ * dsm_segment instead of retrieving the old unpinned dsm_segment.
+ */
+void
+DestroyNamedDSMSegment(const char *name, size_t size,
+ void (*on_detach_callback) (void *), void *arg)
+{
+ DSMRegistryEntry *entry;
+ MemoryContext oldcontext;
+
+ if (!name || *name == '\0')
+ ereport(ERROR,
+ (errmsg("DSM segment name cannot be empty")));
+
+ if (strlen(name) >= offsetof(DSMRegistryEntry, handle))
+ ereport(ERROR,
+ (errmsg("DSM segment name too long")));
+
+ if (size == 0)
+ ereport(ERROR,
+ (errmsg("DSM segment size must be nonzero")));
+
+ /* Be sure any local memory allocated by DSM/DSA routines is persistent. */
+ oldcontext = MemoryContextSwitchTo(TopMemoryContext);
+
+ /* Connect to the registry. */
+ init_dsm_registry();
+
+ entry = dshash_find(dsm_registry_table, name, true);
+
+ if (entry == NULL)
+ {
+ MemoryContextSwitchTo(oldcontext);
+ ereport(ERROR,
+ (errmsg("cannot destroy a DSM segment that does not exist")));
+ }
+
+ if (entry->size != size)
+ {
+ dshash_release_lock(dsm_registry_table, entry);
+ MemoryContextSwitchTo(oldcontext);
+ ereport(ERROR,
+ (errmsg("requested DSM segment size does not match size of "
+ "existing segment")));
+ }
+
+ detach_dsm_segment(entry->handle, on_detach_callback, arg);
+ dsm_unpin_segment(entry->handle);
+
+ /* dshash_delete_entry calls LWLockRelease internally. We shouldn't
+ * release lock twice */
+ dshash_delete_entry(dsm_registry_table, entry);
+ dshash_delete_key(dsm_registry_table, name);
+
+ MemoryContextSwitchTo(oldcontext);
+}
\ No newline at end of file
diff --git a/src/include/storage/dsm_registry.h b/src/include/storage/dsm_registry.h
index b381e44bc9d..2bd20b82ffd 100644
--- a/src/include/storage/dsm_registry.h
+++ b/src/include/storage/dsm_registry.h
@@ -17,6 +17,14 @@ extern void *GetNamedDSMSegment(const char *name, size_t size,
void (*init_callback) (void *ptr),
bool *found);
+extern void DetachNamedDSMSegment(const char *name, size_t size,
+ void (*on_detach_callback) (void *),
+ void *arg);
+
+extern void DestroyNamedDSMSegment(const char *name, size_t size,
+ void (*on_detach_callback) (void *),
+ void *arg);
+
extern Size DSMRegistryShmemSize(void);
extern void DSMRegistryShmemInit(void);
diff --git a/src/test/modules/test_dsm_registry/expected/test_dsm_registry.out b/src/test/modules/test_dsm_registry/expected/test_dsm_registry.out
index 8ffbd343a05..f5c85a976a9 100644
--- a/src/test/modules/test_dsm_registry/expected/test_dsm_registry.out
+++ b/src/test/modules/test_dsm_registry/expected/test_dsm_registry.out
@@ -12,3 +12,14 @@ SELECT get_val_in_shmem();
1236
(1 row)
+SELECT detach_from_tdr_segment();
+ detach_from_tdr_segment
+-------------------------
+ t
+(1 row)
+
+SELECT destroy_tdr_segment();
+ destroy_tdr_segment
+---------------------
+
+(1 row)
diff --git a/src/test/modules/test_dsm_registry/sql/test_dsm_registry.sql b/src/test/modules/test_dsm_registry/sql/test_dsm_registry.sql
index b3351be0a16..24f90658f83 100644
--- a/src/test/modules/test_dsm_registry/sql/test_dsm_registry.sql
+++ b/src/test/modules/test_dsm_registry/sql/test_dsm_registry.sql
@@ -2,3 +2,5 @@ CREATE EXTENSION test_dsm_registry;
SELECT set_val_in_shmem(1236);
\c
SELECT get_val_in_shmem();
+SELECT detach_from_tdr_segment();
+SELECT destroy_tdr_segment();
\ No newline at end of file
diff --git a/src/test/modules/test_dsm_registry/test_dsm_registry--1.0.sql b/src/test/modules/test_dsm_registry/test_dsm_registry--1.0.sql
index 8c55b0919b1..74d8dc50d8a 100644
--- a/src/test/modules/test_dsm_registry/test_dsm_registry--1.0.sql
+++ b/src/test/modules/test_dsm_registry/test_dsm_registry--1.0.sql
@@ -8,3 +8,9 @@ CREATE FUNCTION set_val_in_shmem(val INT) RETURNS VOID
CREATE FUNCTION get_val_in_shmem() RETURNS INT
AS 'MODULE_PATHNAME' LANGUAGE C;
+
+CREATE FUNCTION detach_from_tdr_segment() RETURNS BOOL
+ AS 'MODULE_PATHNAME' LANGUAGE C;
+
+CREATE FUNCTION destroy_tdr_segment() RETURNS VOID
+ AS 'MODULE_PATHNAME' LANGUAGE C;
\ No newline at end of file
diff --git a/src/test/modules/test_dsm_registry/test_dsm_registry.c b/src/test/modules/test_dsm_registry/test_dsm_registry.c
index 462a80f8790..bdbb45e745c 100644
--- a/src/test/modules/test_dsm_registry/test_dsm_registry.c
+++ b/src/test/modules/test_dsm_registry/test_dsm_registry.c
@@ -35,6 +35,12 @@ tdr_init_shmem(void *ptr)
state->val = 0;
}
+static void
+reset_tdr_state_to_null(void *arg)
+{
+ tdr_state = NULL;
+}
+
static void
tdr_attach_shmem(void)
{
@@ -74,3 +80,25 @@ get_val_in_shmem(PG_FUNCTION_ARGS)
PG_RETURN_UINT32(ret);
}
+
+PG_FUNCTION_INFO_V1(detach_from_tdr_segment);
+Datum
+detach_from_tdr_segment(PG_FUNCTION_ARGS)
+{
+ DetachNamedDSMSegment("test_dsm_registry",
+ sizeof(TestDSMRegistryStruct),
+ reset_tdr_state_to_null, NULL);
+
+ PG_RETURN_BOOL(tdr_state == NULL);
+}
+
+PG_FUNCTION_INFO_V1(destroy_tdr_segment);
+Datum
+destroy_tdr_segment(PG_FUNCTION_ARGS)
+{
+ DestroyNamedDSMSegment("test_dsm_registry",
+ sizeof(TestDSMRegistryStruct),
+ NULL, NULL);
+
+ PG_RETURN_VOID();
+}
\ No newline at end of file
--
2.48.1
