the fill_schema_processlist function accesses THD::query() without proper protection
    so the parallel thread killing can lead to access to the freed meemory.

per-file comments:
  sql/sql_load.cc
Bug#51377      Crash in information_schema / processlist on concurrent DDL workload
    the THD::set_query_inner() call needs to be protected.
    But here we don't need to change the original thd->query() at all.
  sql/sql_show.cc
Bug#51377      Crash in information_schema / processlist on concurrent DDL workload
    protect the THD::query() access with the THD::LOCK_thd_data mutex.