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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 d80d5f0995
commit ac2800ddc1
1 changed files with 15 additions and 6 deletions
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21
src/backend/storage/ipc/dsm_registry.c
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@@ -45,6 +45,7 @@ typedef struct DSMRegistryEntry
char name[64];
dsm_handle handle;
size_t size;
bool initialized;
} DSMRegistryEntry;
static const dshash_parameters dsh_params = {
@@ -158,8 +159,12 @@ GetNamedDSMSegment(const char *name, size_t size,
entry = dshash_find_or_insert(dsm_registry_table, name, found);
if (!(*found))
{
dsm_segment *seg;
entry->initialized = false;
/* Initialize the segment. */
dsm_segment *seg = dsm_create(size, 0);
seg = dsm_create(size, 0);
dsm_pin_segment(seg);
dsm_pin_mapping(seg);
@@ -169,13 +174,17 @@ GetNamedDSMSegment(const char *name, size_t size,
if (init_callback)
(*init_callback) (ret);
entry->initialized = true;
}
else if (entry->size != size)
{
else if (!entry->initialized)
ereport(ERROR,
(errmsg("requested DSM segment size does not match size of "
"existing segment")));
}
(errmsg("requested DSM segment \"%s\" failed initialization",
name)));
else if (entry->size != size)
ereport(ERROR,
(errmsg("requested DSM segment \"%s\" does not match size of existing entry",
name)));
else
{
dsm_segment *seg = dsm_find_mapping(entry->handle);