The issue of the current bug is unguarded access to mi->slave_running
by the shutdown thread calling end_slave() that is bug#29968
(alas happened not to be cross-linked with the current bug)
Fixed:
with removing the unguarded read of the running status
and perform reading it in terminate_slave_thread()
at time run_lock is taken (mostly bug#29968 backporting, still with some
improvements over that patch - see the error reporting from
terminate_slave_thread()).
Issue of bug#38716 is fixed here for 5.0 branch as well.
Note:
There has been a separate artifact identified -
a race condition between init_slave() and end_slave() -
reported as Bug#44467.
mysql-test/r/rpl_bug38694.result:
a new results file is added.
mysql-test/t/rpl_bug38694-slave.opt:
simulating delay at slave threads shutdown.
mysql-test/t/rpl_bug38694.test:
A new test to check if a delay at the termination phase of slave threads
could cause any issue.
sql/slave.cc:
The unguarded read of the running status is removed. Its reading is done in
terminate_slave_thread() at time run_lock is taken;
Calling terminate_slave_threads(skip_lock := !need_slave_mutex) in the failing branch of start_slave_threads() which is bug#38716 issue.
sql/slave.h:
removing terminate_slave_thread() out of the global interface scope.
