MDEV-31602: Race on rpl_global_gtid_slave_state when starting IO thread

Fix that rpl_slave_state::load() was calling rpl_slave_state::update() without
holding LOCK_slave_state.
Reviewed-by: Monty <monty@mariadb.org>
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>

sql/rpl_gtid.cc

@@ -45,9 +45,7 @@ rpl_slave_state::update_state_hash(uint64 sub_id, rpl_gtid *gtid, void *hton,
     there will not be an attempt to delete the corresponding table row before
     it is even committed.
   */
-  mysql_mutex_lock(&LOCK_slave_state);
   err= update(gtid->domain_id, gtid->server_id, sub_id, gtid->seq_no, hton, rgi);
-  mysql_mutex_unlock(&LOCK_slave_state);
   if (err)
   {
     sql_print_warning("Slave: Out of memory during slave state maintenance. "
@@ -290,11 +288,24 @@ rpl_slave_state::truncate_hash()
 int
 rpl_slave_state::update(uint32 domain_id, uint32 server_id, uint64 sub_id,
                         uint64 seq_no, void *hton, rpl_group_info *rgi)
+{
+  int res;
+  mysql_mutex_lock(&LOCK_slave_state);
+  res= update_nolock(domain_id, server_id, sub_id, seq_no, hton, rgi);
+  mysql_mutex_unlock(&LOCK_slave_state);
+  return res;
+}
+
+
+int
+rpl_slave_state::update_nolock(uint32 domain_id, uint32 server_id, uint64 sub_id,
+                               uint64 seq_no, void *hton, rpl_group_info *rgi)
 {
   element *elem= NULL;
   list_element *list_elem= NULL;
 
   DBUG_ASSERT(hton || !loaded);
+  mysql_mutex_assert_owner(&LOCK_slave_state);
   if (!(elem= get_element(domain_id)))
     return 1;
 
@@ -308,7 +319,6 @@ rpl_slave_state::update(uint32 domain_id, uint32 server_id, uint64 sub_id,
       of all pending MASTER_GTID_WAIT(), so we do not slow down the
       replication SQL thread.
     */
-    mysql_mutex_assert_owner(&LOCK_slave_state);
     elem->gtid_waiter= NULL;
     mysql_cond_broadcast(&elem->COND_wait_gtid);
   }
@@ -1356,6 +1366,7 @@ rpl_slave_state::load(THD *thd, const char *state_from_master, size_t len,
 {
   const char *end= state_from_master + len;
 
+  mysql_mutex_assert_not_owner(&LOCK_slave_state);
   if (reset)
   {
     if (truncate_state_table(thd))

sql/rpl_gtid.h

@@ -231,6 +231,8 @@ struct rpl_slave_state
   ulong count() const { return hash.records; }
   int update(uint32 domain_id, uint32 server_id, uint64 sub_id,
              uint64 seq_no, void *hton, rpl_group_info *rgi);
+  int update_nolock(uint32 domain_id, uint32 server_id, uint64 sub_id,
+                    uint64 seq_no, void *hton, rpl_group_info *rgi);
   int truncate_state_table(THD *thd);
   void select_gtid_pos_table(THD *thd, LEX_CSTRING *out_tablename);
   int record_gtid(THD *thd, const rpl_gtid *gtid, uint64 sub_id,

sql/rpl_rli.cc

@@ -1927,7 +1927,7 @@ rpl_load_gtid_slave_state(THD *thd)
   for (i= 0; i < array.elements; ++i)
   {
     get_dynamic(&array, (uchar *)&tmp_entry, i);
-    if ((err= rpl_global_gtid_slave_state->update(tmp_entry.gtid.domain_id,
+    if ((err= rpl_global_gtid_slave_state->update_nolock(tmp_entry.gtid.domain_id,
                                                   tmp_entry.gtid.server_id,
                                                   tmp_entry.sub_id,
                                                   tmp_entry.gtid.seq_no,