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

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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 <exclusion@gmail.com>
Reviewed-by: Sami Imseih <samimseih@gmail.com>
Discussion: https://postgr.es/m/dd36d384-55df-4fc2-825c-5bc56c950fa9%40gmail.com
Backpatch-through: 17
This commit is contained in:
Nathan Bossart
2025-11-12 14:30:11 -06:00
parent 0bdc777e80
commit 1165a933aa
1 changed files with 30 additions and 4 deletions
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34
src/backend/storage/ipc/dsm_registry.c
View File

@@ -93,6 +93,7 @@ typedef struct DSMRegistryEntry
{ {
char name[NAMEDATALEN]; char name[NAMEDATALEN];
DSMREntryType type; DSMREntryType type;
bool initialized;
union union
{ {
NamedDSMState dsm; NamedDSMState dsm;
@@ -216,6 +217,7 @@ GetNamedDSMSegment(const char *name, size_t size,
dsm_segment *seg; dsm_segment *seg;
entry->type = DSMR_ENTRY_TYPE_DSM; entry->type = DSMR_ENTRY_TYPE_DSM;
entry->initialized = false;
/* Initialize the segment. */ /* Initialize the segment. */
seg = dsm_create(size, 0); seg = dsm_create(size, 0);
@@ -228,13 +230,21 @@ GetNamedDSMSegment(const char *name, size_t size,
if (init_callback) if (init_callback)
(*init_callback) (ret); (*init_callback) (ret);
entry->initialized = true;
} }
else if (entry->type != DSMR_ENTRY_TYPE_DSM) else if (entry->type != DSMR_ENTRY_TYPE_DSM)
ereport(ERROR, 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) else if (entry->dsm.size != size)
ereport(ERROR, 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 else
{ {
NamedDSMState *state = &entry->dsm; NamedDSMState *state = &entry->dsm;
@@ -297,6 +307,7 @@ GetNamedDSA(const char *name, bool *found)
NamedDSAState *state = &entry->dsa; NamedDSAState *state = &entry->dsa;
entry->type = DSMR_ENTRY_TYPE_DSA; entry->type = DSMR_ENTRY_TYPE_DSA;
entry->initialized = false;
/* Initialize the LWLock tranche for the DSA. */ /* Initialize the LWLock tranche for the DSA. */
state->tranche = LWLockNewTrancheId(name); state->tranche = LWLockNewTrancheId(name);
@@ -308,10 +319,17 @@ GetNamedDSA(const char *name, bool *found)
/* Store handle for other backends to use. */ /* Store handle for other backends to use. */
state->handle = dsa_get_handle(ret); state->handle = dsa_get_handle(ret);
entry->initialized = true;
} }
else if (entry->type != DSMR_ENTRY_TYPE_DSA) else if (entry->type != DSMR_ENTRY_TYPE_DSA)
ereport(ERROR, 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 else
{ {
NamedDSAState *state = &entry->dsa; NamedDSAState *state = &entry->dsa;
@@ -372,6 +390,7 @@ GetNamedDSHash(const char *name, const dshash_parameters *params, bool *found)
dsa_area *dsa; dsa_area *dsa;
entry->type = DSMR_ENTRY_TYPE_DSH; entry->type = DSMR_ENTRY_TYPE_DSH;
entry->initialized = false;
/* Initialize the LWLock tranche for the hash table. */ /* Initialize the LWLock tranche for the hash table. */
dsh_state->tranche = LWLockNewTrancheId(name); 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. */ /* Store handles for other backends to use. */
dsh_state->dsa_handle = dsa_get_handle(dsa); dsh_state->dsa_handle = dsa_get_handle(dsa);
dsh_state->dsh_handle = dshash_get_hash_table_handle(ret); dsh_state->dsh_handle = dshash_get_hash_table_handle(ret);
entry->initialized = true;
} }
else if (entry->type != DSMR_ENTRY_TYPE_DSH) else if (entry->type != DSMR_ENTRY_TYPE_DSH)
ereport(ERROR, 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 else
{ {
NamedDSHState *dsh_state = &entry->dsh; NamedDSHState *dsh_state = &entry->dsh;