Partially revert this commit:
commit 6a1cb449fe
Author: Sergei Golubchik <serg@mariadb.org>
Date: Mon Jan 18 18:02:16 2021 +0100
cleanup: remove slave background thread, use handle_manager thread instead
This restores running the parallel replication deadlock killing in its own
dedicated thread, not in the manager thread shared with other unrelated
processing.
When a parallel replication conflict is detected, multiple threads can be
waiting for each other, potentially in a loop. It is critical for
correctness (as well as performance) that the blocking thread is killed
immediately to allow other threads to continue. If one of the threads being
blocked was the manager thread itself in some unrelated job, the kill could
end up being blocked indefinitely, causing replication to hang, usually
eventually timing out on innodb_lock_wait_timeout and failing replication
with an error like:
[ERROR] Slave worker thread retried transaction 10 time(s) in vain, giving up
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
53468695ad