Teach DSM registry to ERROR if attaching to an uninitialized entry.HEADmaster

If DSM entry initialization fails, backends could try to use an
uninitialized DSM segment, DSA, or dshash table (since the entry is
still added to the registry).  To fix, keep track of whether
initialization completed, and ERROR if a backend tries to attach to
an uninitialized entry.  We could instead retry initialization as
needed, but that seemed complicated, error prone, and unlikely to
help most cases.  Furthermore, such problems probably indicate a
coding error.

Reported-by: Alexander Lakhin <[email protected]>
Reviewed-by: Sami Imseih <[email protected]>
Discussion: https://postgr.es/m/dd36d384-55df-4fc2-825c-5bc56c950fa9%40gmail.com
Backpatch-through: 17

1 files changed, 30 insertions, 4 deletions

diff --git a/src/backend/storage/ipc/dsm_registry.c b/src/backend/storage/ipc/dsm_registry.c
index a926b9c3f32..7eba8a8cffb 100644
--- a/src/backend/storage/ipc/dsm_registry.c
+++ b/src/backend/storage/ipc/dsm_registry.c
@@ -93,6 +93,7 @@ typedef struct DSMRegistryEntry
 {
 	char		name[NAMEDATALEN];
 	DSMREntryType type;
+	bool		initialized;
 	union
 	{
 		NamedDSMState dsm;
@@ -216,6 +217,7 @@ GetNamedDSMSegment(const char *name, size_t size,
 		dsm_segment *seg;
 
 		entry->type = DSMR_ENTRY_TYPE_DSM;
+		entry->initialized = false;
 
 		/* Initialize the segment. */
 		seg = dsm_create(size, 0);
@@ -228,13 +230,21 @@ GetNamedDSMSegment(const char *name, size_t size,
 
 		if (init_callback)
 			(*init_callback) (ret);
+
+		entry->initialized = true;
 	}
 	else if (entry->type != DSMR_ENTRY_TYPE_DSM)
 		ereport(ERROR,
-				(errmsg("requested DSM segment does not match type of existing entry")));
+				(errmsg("requested DSM segment \"%s\" does not match type of existing entry",
+						name)));
+	else if (!entry->initialized)
+		ereport(ERROR,
+				(errmsg("requested DSM segment \"%s\" failed initialization",
+						name)));
 	else if (entry->dsm.size != size)
 		ereport(ERROR,
-				(errmsg("requested DSM segment size does not match size of existing segment")));
+				(errmsg("requested DSM segment \"%s\" does not match size of existing entry",
+						name)));
 	else
 	{
 		NamedDSMState *state = &entry->dsm;
@@ -297,6 +307,7 @@ GetNamedDSA(const char *name, bool *found)
 		NamedDSAState *state = &entry->dsa;
 
 		entry->type = DSMR_ENTRY_TYPE_DSA;
+		entry->initialized = false;
 
 		/* Initialize the LWLock tranche for the DSA. */
 		state->tranche = LWLockNewTrancheId(name);
@@ -308,10 +319,17 @@ GetNamedDSA(const char *name, bool *found)
 
 		/* Store handle for other backends to use. */
 		state->handle = dsa_get_handle(ret);
+
+		entry->initialized = true;
 	}
 	else if (entry->type != DSMR_ENTRY_TYPE_DSA)
 		ereport(ERROR,
-				(errmsg("requested DSA does not match type of existing entry")));
+				(errmsg("requested DSA \"%s\" does not match type of existing entry",
+						name)));
+	else if (!entry->initialized)
+		ereport(ERROR,
+				(errmsg("requested DSA \"%s\" failed initialization",
+						name)));
 	else
 	{
 		NamedDSAState *state = &entry->dsa;
@@ -372,6 +390,7 @@ GetNamedDSHash(const char *name, const dshash_parameters *params, bool *found)
 		dsa_area   *dsa;
 
 		entry->type = DSMR_ENTRY_TYPE_DSH;
+		entry->initialized = false;
 
 		/* Initialize the LWLock tranche for the hash table. */
 		dsh_state->tranche = LWLockNewTrancheId(name);
@@ -389,10 +408,17 @@ GetNamedDSHash(const char *name, const dshash_parameters *params, bool *found)
 		/* Store handles for other backends to use. */
 		dsh_state->dsa_handle = dsa_get_handle(dsa);
 		dsh_state->dsh_handle = dshash_get_hash_table_handle(ret);
+
+		entry->initialized = true;
 	}
 	else if (entry->type != DSMR_ENTRY_TYPE_DSH)
 		ereport(ERROR,
-				(errmsg("requested DSHash does not match type of existing entry")));
+				(errmsg("requested DSHash \"%s\" does not match type of existing entry",
+						name)));
+	else if (!entry->initialized)
+		ereport(ERROR,
+				(errmsg("requested DSHash \"%s\" failed initialization",
+						name)));
 	else
 	{
 		NamedDSHState *dsh_state = &entry->dsh;