I confirm, there is no problem in single-threaded programs, and
there is no problem if all bm_send_event() and bm_flush_cache() are called
from the same thread.

> ... instead of struggling with all your locks.

it is better to have midas fully thread safe. ODB has been so for a long time,
event buffer partially (except for this bug), now fully.

without that the problem still exists, because in many frontends,
bm_flush_buffer() is called from the main thread, and will race
against the "bm_send_event() thread". Of course you can do
everything on the main thread, but this opens you to RPC timeouts
during run transitions (if you sleep in bm_wait_for_free_space()).

also the SYSMSG buffer is subject to the same bug. cm_msg() is of course
safe to call from anywhere, but cm_msg_flush_buffer() and cm_periodic_tasks()
can be called from any thread, and they issue bm_send_event(SYSMSG),
and there will be mysterious crashes and SYSMSG corruptions, probably
only during message storms, but still!

K.O.