stuck when closing a serial session

the serial session may randomly stuck,
when try to close the sessiobor restart it, it will fall into a infinate loop and stuck the whole program.

note: the serial session has 70k+ lines of log history.


Start by reproducing the hang with a serial session containing 70k+ lines of log history, then compare closing and restarting the session. Trace the path that loops during the hang and verify that both actions complete without freezing the program.

Written by the indexing model from the issue text.