As above, if the outer pane has smashed the train can remain in service until the end of that diagram
The remaining inner pane has to be marked and secured just in case it is smashed later
If both panes have smashed the train can continue at a reduced speed, with all passengers temporarily evacuated from the affected carriage
At the next possible station the train will either be taken out of service or a temporary window fitted
Smashed windows can also be caused by loose ballast, and it seems to happen quite often to LM units