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MDEV-41450 Purge coordinator loops forever in purge_sys_t::close_and_reopen() and leaks THD mem_root (22+ GB in < 2 min) for tables with an indexed virtual column #5854

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MDEV-41450 Purge coordinator loops forever in purge_sys_t::close_and_reopen() and leaks THD mem_root (22+ GB in < 2 min) for tables with an indexed virtual column #5854

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7 changes: 5 additions & 2 deletions sql/sql_class.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -5168,8 +5168,11 @@ TABLE *open_purge_table(THD *thd, const char *db, size_t dblen,
DBUG_ENTER("open_purge_table");
DBUG_ASSERT(thd->locked_tables_mode < LTM_PRELOCKED);

/* Purge already hold the MDL for the table */
Open_table_context ot_ctx(thd, MYSQL_OPEN_HAS_MDL_LOCK);
/* Purge already hold the MDL for the table. A kill flag on a purge THD
(for example from a Galera BF abort) is never reset, and purge has no
statement to abort; it must not make every subsequent open_table() fail. */
Open_table_context ot_ctx(thd, MYSQL_OPEN_HAS_MDL_LOCK |
MYSQL_OPEN_IGNORE_KILLED);
TABLE_LIST *tl= (TABLE_LIST*)thd->alloc(sizeof(TABLE_LIST));
LEX_CSTRING db_name= {db, dblen };
LEX_CSTRING table_name= { tb, tblen };
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13 changes: 13 additions & 0 deletions sql/wsrep_mysqld.cc
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Expand Up @@ -3626,6 +3626,19 @@ void wsrep_handle_mdl_conflict(MDL_context *requestor_ctx,
// Granted thread is either TOI or applying
wsrep_handle_granted_bf(request_thd, granted_thd, ticket, key);
}
else if (granted_thd->system_thread != NON_SYSTEM_THREAD &&
granted_thd->mdl_context.has_explicit_locks())
{
/* Granted thread is a server-internal background thread holding an
explicit MDL, e.g. the InnoDB purge coordinator holding MDL_SHARED
on a table for the duration of a purge batch. Such a thread has no
wsrep transaction to roll back and never resets THD::killed, so a
BF abort would leave it killed for the rest of the server lifetime
(MDEV-41450). It releases its locks on its own; the requestor waits,
as it did before MDEV-38218. */
wsrep_mdl_log(WSREP_MDL_DEBUG, "MDL conflict, waiting for system thread",
request_thd, granted_thd, ticket, key);
}
else
{
// Granted thread is not brute-force thread, we can abort it
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9 changes: 7 additions & 2 deletions storage/innobase/trx/trx0purge.cc
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Expand Up @@ -48,7 +48,7 @@ Created 3/26/1996 Heikki Tuuri
TABLE *open_purge_table(THD *thd, const char *db, size_t dblen,
const char *tb, size_t tblen,
MDL_ticket *mdl_ticket) noexcept;
int close_thread_tables(THD* thd) noexcept;
void reset_thd(MYSQL_THD thd);
MDL_ticket *get_mdl_ticket(TABLE *table) noexcept;

/** Maximum allowable purge history length. <=0 means 'infinite'. */
Expand Down Expand Up @@ -1106,7 +1106,12 @@ static void trx_purge_close_tables(THD *thd, purge_table *last_entry,
node->tables.clear();
}

close_thread_tables(thd);
/* Close the tables and free thd->mem_root, which holds the TABLE_LIST
allocated by every open_purge_table() call. Nothing else in the
coordinator's mem_root outlives its open tables, and without this
every batch (and every close_and_reopen() retry) would leak one
TABLE_LIST per opened table. */
reset_thd(thd);

for (auto mdl : mdl_tickets)
{
Expand Down