gdb doesn't notice when a target resumes

In a setup like this:
gdb --- OpenOCD --- hardware target

I can download a program, debug, everything is fine. Let's say we're halted
somewhere.
Now something happens that causes the hardware target to be running again
and no longer halted. OpenOCD notices quickly because it polls the target.
But gdb doesn't ever notice that the target was resumed. There doesn't
appear to be a notification packet
<https://sourceware.org/gdb/onlinedocs/gdb/Notification-Packets.html#Notification-Packets>
for
OpenOCD to even communicate to gdb that the target has resumed.

Am I missing something? Have people attempted to tackle this problem?

Tim