From 29c29dd0a778e952cdf6f55c7be08a33436515e2 Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Wed, 17 Jun 2026 12:59:40 +0900 Subject: [PATCH] Fix potential PANICs with concurrent drop of pgstats entries --- src/include/utils/pgstat_internal.h | 3 ++- src/backend/utils/activity/pgstat.c | 2 +- src/backend/utils/activity/pgstat_function.c | 2 +- src/backend/utils/activity/pgstat_replslot.c | 2 +- src/backend/utils/activity/pgstat_shmem.c | 17 ++++++++++++++++- src/backend/utils/activity/pgstat_xact.c | 8 ++++---- .../test_custom_stats/test_custom_var_stats.c | 2 +- 7 files changed, 26 insertions(+), 10 deletions(-) diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h index fe463faaf639..3ca4f4548956 100644 --- a/src/include/utils/pgstat_internal.h +++ b/src/include/utils/pgstat_internal.h @@ -807,7 +807,8 @@ extern PgStat_EntryRef *pgstat_get_entry_ref(PgStat_Kind kind, Oid dboid, uint64 extern bool pgstat_lock_entry(PgStat_EntryRef *entry_ref, bool nowait); extern bool pgstat_lock_entry_shared(PgStat_EntryRef *entry_ref, bool nowait); extern void pgstat_unlock_entry(PgStat_EntryRef *entry_ref); -extern bool pgstat_drop_entry(PgStat_Kind kind, Oid dboid, uint64 objid); +extern bool pgstat_drop_entry(PgStat_Kind kind, Oid dboid, uint64 objid, + bool missing_ok); extern void pgstat_drop_all_entries(void); extern void pgstat_drop_matching_entries(bool (*do_drop) (PgStatShared_HashEntry *, Datum), Datum match_data); diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c index b67da88c7dc2..c4fa14f138fa 100644 --- a/src/backend/utils/activity/pgstat.c +++ b/src/backend/utils/activity/pgstat.c @@ -650,7 +650,7 @@ pgstat_shutdown_hook(int code, Datum arg) dlist_init(&pgStatPending); /* drop the backend stats entry */ - if (!pgstat_drop_entry(PGSTAT_KIND_BACKEND, InvalidOid, MyProcNumber)) + if (!pgstat_drop_entry(PGSTAT_KIND_BACKEND, InvalidOid, MyProcNumber, false)) pgstat_request_entry_refs_gc(); pgstat_detach_shmem(); diff --git a/src/backend/utils/activity/pgstat_function.c b/src/backend/utils/activity/pgstat_function.c index d47d05e3d922..f0366e139907 100644 --- a/src/backend/utils/activity/pgstat_function.c +++ b/src/backend/utils/activity/pgstat_function.c @@ -113,7 +113,7 @@ pgstat_init_function_usage(FunctionCallInfo fcinfo, if (!SearchSysCacheExists1(PROCOID, ObjectIdGetDatum(fcinfo->flinfo->fn_oid))) { pgstat_drop_entry(PGSTAT_KIND_FUNCTION, MyDatabaseId, - fcinfo->flinfo->fn_oid); + fcinfo->flinfo->fn_oid, true); ereport(ERROR, errcode(ERRCODE_UNDEFINED_FUNCTION), errmsg("function call to dropped function")); } diff --git a/src/backend/utils/activity/pgstat_replslot.c b/src/backend/utils/activity/pgstat_replslot.c index 0d00dd5d93aa..a32b70a03736 100644 --- a/src/backend/utils/activity/pgstat_replslot.c +++ b/src/backend/utils/activity/pgstat_replslot.c @@ -188,7 +188,7 @@ pgstat_drop_replslot(ReplicationSlot *slot) Assert(LWLockHeldByMeInMode(ReplicationSlotAllocationLock, LW_EXCLUSIVE)); if (!pgstat_drop_entry(PGSTAT_KIND_REPLSLOT, InvalidOid, - ReplicationSlotIndex(slot))) + ReplicationSlotIndex(slot), false)) pgstat_request_entry_refs_gc(); } diff --git a/src/backend/utils/activity/pgstat_shmem.c b/src/backend/utils/activity/pgstat_shmem.c index b8f354c818a0..ae35332a3347 100644 --- a/src/backend/utils/activity/pgstat_shmem.c +++ b/src/backend/utils/activity/pgstat_shmem.c @@ -1000,13 +1000,16 @@ pgstat_drop_database_and_contents(Oid dboid) * This routine returns false if the stats entry of the dropped object could * not be freed, true otherwise. * + * If missing_ok is true, skip entries that have been concurrently dropped. + * * The callers of this function should call pgstat_request_entry_refs_gc() * if the stats entry could not be freed, to ensure that this entry's memory * can be reclaimed later by a different backend calling * pgstat_gc_entry_refs(). */ bool -pgstat_drop_entry(PgStat_Kind kind, Oid dboid, uint64 objid) +pgstat_drop_entry(PgStat_Kind kind, Oid dboid, uint64 objid, + bool missing_ok) { PgStat_HashKey key = {0}; PgStatShared_HashEntry *shent; @@ -1031,6 +1034,18 @@ pgstat_drop_entry(PgStat_Kind kind, Oid dboid, uint64 objid) shent = dshash_find(pgStatLocal.shared_hash, &key, true); if (shent) { + if (shent->dropped) + { + if (!missing_ok) + elog(ERROR, + "trying to drop stats entry already dropped: kind=%s dboid=%u objid=%" PRIu64, + pgstat_get_kind_info(shent->key.kind)->name, + shent->key.dboid, + shent->key.objid); + dshash_release_lock(pgStatLocal.shared_hash, shent); + return true; + } + freed = pgstat_drop_entry_internal(shent, NULL); /* diff --git a/src/backend/utils/activity/pgstat_xact.c b/src/backend/utils/activity/pgstat_xact.c index 5e2d69e62979..3e1978775e16 100644 --- a/src/backend/utils/activity/pgstat_xact.c +++ b/src/backend/utils/activity/pgstat_xact.c @@ -85,7 +85,7 @@ AtEOXact_PgStat_DroppedStats(PgStat_SubXactStatus *xact_state, bool isCommit) * Transaction that dropped an object committed. Drop the stats * too. */ - if (!pgstat_drop_entry(it->kind, it->dboid, objid)) + if (!pgstat_drop_entry(it->kind, it->dboid, objid, true)) not_freed_count++; } else if (!isCommit && pending->is_create) @@ -94,7 +94,7 @@ AtEOXact_PgStat_DroppedStats(PgStat_SubXactStatus *xact_state, bool isCommit) * Transaction that created an object aborted. Drop the stats * associated with the object. */ - if (!pgstat_drop_entry(it->kind, it->dboid, objid)) + if (!pgstat_drop_entry(it->kind, it->dboid, objid, true)) not_freed_count++; } @@ -160,7 +160,7 @@ AtEOSubXact_PgStat_DroppedStats(PgStat_SubXactStatus *xact_state, * Subtransaction creating a new stats object aborted. Drop the * stats object. */ - if (!pgstat_drop_entry(it->kind, it->dboid, objid)) + if (!pgstat_drop_entry(it->kind, it->dboid, objid, true)) not_freed_count++; pfree(pending); } @@ -323,7 +323,7 @@ pgstat_execute_transactional_drops(int ndrops, struct xl_xact_stats_item *items, xl_xact_stats_item *it = &items[i]; uint64 objid = ((uint64) it->objid_hi) << 32 | it->objid_lo; - if (!pgstat_drop_entry(it->kind, it->dboid, objid)) + if (!pgstat_drop_entry(it->kind, it->dboid, objid, true)) not_freed_count++; } diff --git a/src/test/modules/test_custom_stats/test_custom_var_stats.c b/src/test/modules/test_custom_stats/test_custom_var_stats.c index 5c4871ed37ca..863d6a524925 100644 --- a/src/test/modules/test_custom_stats/test_custom_var_stats.c +++ b/src/test/modules/test_custom_stats/test_custom_var_stats.c @@ -600,7 +600,7 @@ test_custom_stats_var_drop(PG_FUNCTION_ARGS) /* Drop entry and request GC if the entry could not be freed */ if (!pgstat_drop_entry(PGSTAT_KIND_TEST_CUSTOM_VAR_STATS, InvalidOid, - PGSTAT_CUSTOM_VAR_STATS_IDX(stat_name))) + PGSTAT_CUSTOM_VAR_STATS_IDX(stat_name), false)) pgstat_request_entry_refs_gc(); PG_RETURN_VOID(); -- 2.54.0