Created attachment 743143 [details]
Proposed patch - part 1 - Free confdb message holder list on confdb exit

Description of problem:
objdb_notify_dispatch traverse thru confdb_ipc_message_holder_list list
until it's empty. If IPC connection is still feeding confdb/objdb with
changes then iteration will never end. To prevent this and let corosync
properly preempt, terminal condition is enhanced with maximum number of
processed items from list. Change makes confdb preemptable so corosync
can accept new connections, receive/send token, ...

Also when confdb service is unloaded. it's needed to free confdb message holder list. This operation will not only properly free memory, but also decreases
connection reference(s). This should solve deadloop in
coroipcs_ipc_service_exit, because confdb_exit_fn removes not only
notify_pipe but also deletes poll_dispatch, so nobody is left to
unreference connections.

Version-Release number of selected component (if applicable):
Flatiron

How reproducible:
98.76

Steps to Reproduce:
1. Start corosync -p
2. Start IPC client which track key changes and also make changes of that key
3. Exit corosync (sending SIGINT)

"Unit" test:
https://github.com/jfriesse/csts/blob/master/tests/stop-with-confdb-load.sh

Actual results:
Corosync will not exit (unit test $? != 0)

Expected results:
Corosync will properly exit (unit test $? == 0)

Additional info: