This sounds relevant:
There is a physical switch that cuts the connection between the PC in the “lock up” and the network connection to the rest of the world. When certain time comes the PC as allowed to communicate with the rest of the world by someone flipping the physical switch.
There are actually a few competing companies trying to get the same financial news information from the “lock up” to the outside in the automated trading world as fast as possible after the switch is flipped, so the milliseconds count.
I was passively involved in some of the discussions regarding this, and the partial solution to this was to insert a hub on each side of the physical cut-off switch to keep the link state as up, there are all sorts of other issues related to this that are unrelated to Linux itself and are not being mentioned.