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Assert lack of hazardous buffer locks before possible catalog read.

Browse Source 
Commit 0bada39c83 fixed a bug of this kind,
which existed in all branches for six days before detection.  While the
probability of reaching the trouble was low, the disruption was extreme.  No
new backends could start, and service restoration needed an immediate
shutdown.  Hence, add this to catch the next bug like it.

The new check in RelationIdGetRelation() suffices to make autovacuum detect
the bug in commit 243e9b40f1 that led to commit
0bada39.  This also checks in a number of similar places.  It replaces each
Assert(IsTransactionState()) that pertained to a conditional catalog read.

No back-patch for now, but a back-patch of commit 243e9b4 should back-patch
this, too.  A back-patch could omit the src/test/regress changes, since back
branches won't gain new index columns.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/20250410191830.0e.nmisch@google.com
Discussion: https://postgr.es/m/10ec0bc3-5933-1189-6bb8-5dec4114558e@gmail.com
This commit is contained in:
Noah Misch
2025-04-17 05:00:30 -07:00
parent b669293e34
commit f4ece891fc
15 changed files with 248 additions and 24 deletions
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51
src/backend/utils/cache/catcache.c vendored
View File

@@ -1054,12 +1054,41 @@ RehashCatCacheLists(CatCache *cp)
cp->cc_lbucket = newbucket;
}
/*
* ConditionalCatalogCacheInitializeCache
*
* Call CatalogCacheInitializeCache() if not yet done.
*/
pg_attribute_always_inline
static void
ConditionalCatalogCacheInitializeCache(CatCache *cache)
{
#ifdef USE_ASSERT_CHECKING
/*
* TypeCacheRelCallback() runs outside transactions and relies on TYPEOID
* for hashing. This isn't ideal. Since lookup_type_cache() both
* registers the callback and searches TYPEOID, reaching trouble likely
* requires OOM at an unlucky moment.
*
* InvalidateAttoptCacheCallback() runs outside transactions and likewise
* relies on ATTNUM. InitPostgres() initializes ATTNUM, so it's reliable.
*/
if (!(cache->id == TYPEOID || cache->id == ATTNUM) ||
IsTransactionState())
AssertCouldGetRelation();
else
Assert(cache->cc_tupdesc != NULL);
#endif
if (unlikely(cache->cc_tupdesc == NULL))
CatalogCacheInitializeCache(cache);
}
/*
* CatalogCacheInitializeCache
*
* This function does final initialization of a catcache: obtain the tuple
* descriptor and set up the hash and equality function links. We assume
* that the relcache entry can be opened at this point!
* descriptor and set up the hash and equality function links.
*/
#ifdef CACHEDEBUG
#define CatalogCacheInitializeCache_DEBUG1 \
@@ -1194,8 +1223,7 @@ CatalogCacheInitializeCache(CatCache *cache)
void
InitCatCachePhase2(CatCache *cache, bool touch_index)
{
if (cache->cc_tupdesc == NULL)
CatalogCacheInitializeCache(cache);
ConditionalCatalogCacheInitializeCache(cache);
if (touch_index &&
cache->id != AMOID &&
@@ -1374,16 +1402,12 @@ SearchCatCacheInternal(CatCache *cache,
dlist_head *bucket;
CatCTup *ct;
/* Make sure we're in an xact, even if this ends up being a cache hit */
Assert(IsTransactionState());
Assert(cache->cc_nkeys == nkeys);
/*
* one-time startup overhead for each cache
*/
if (unlikely(cache->cc_tupdesc == NULL))
CatalogCacheInitializeCache(cache);
ConditionalCatalogCacheInitializeCache(cache);
#ifdef CATCACHE_STATS
cache->cc_searches++;
@@ -1668,8 +1692,7 @@ GetCatCacheHashValue(CatCache *cache,
/*
* one-time startup overhead for each cache
*/
if (cache->cc_tupdesc == NULL)
CatalogCacheInitializeCache(cache);
ConditionalCatalogCacheInitializeCache(cache);
/*
* calculate the hash value
@@ -1720,8 +1743,7 @@ SearchCatCacheList(CatCache *cache,
/*
* one-time startup overhead for each cache
*/
if (unlikely(cache->cc_tupdesc == NULL))
CatalogCacheInitializeCache(cache);
ConditionalCatalogCacheInitializeCache(cache);
Assert(nkeys > 0 && nkeys < cache->cc_nkeys);
@@ -2390,8 +2412,7 @@ PrepareToInvalidateCacheTuple(Relation relation,
continue;
/* Just in case cache hasn't finished initialization yet... */
if (ccp->cc_tupdesc == NULL)
CatalogCacheInitializeCache(ccp);
ConditionalCatalogCacheInitializeCache(ccp);
hashvalue = CatalogCacheComputeTupleHashValue(ccp, ccp->cc_nkeys, tuple);
dbid = ccp->cc_relisshared ? (Oid) 0 : MyDatabaseId;