I've seen this for a long time when using ddb over an IPMI serial console and people were saying that it could be because of IPMI and whatever.
Now I had a KDB: enter: manua escape to debugger situation (unclear where from yet) on my laptop. I said "db> cont" on v0 and it is stuck at that, not bringing back the shell session alive. However I can switch to v1 v2 v3 and all these shells are perfectly working fine.
I wonder what is broken that returning from ddb doesn't work anymore?
Coming back hours later pressing <Enter> again on the "cont" line which didn't show a shell prompt, gave me the 4 <Enter>s I pressed in total (3 earlier, 1 now) and the command prompt came back. Something is still fishy.
Anyone else with other experience (IPMI, serial, tty) would be welcome.
And I currently had this on a classic serial line machine as well.
I still get kernel printfs coming but typing anything doesn't work.
I hope someone has an idea... It's annoying if you cannot remotely power cycle a machine and need hands-on.
(In reply to Bjoern A. Zeeb from comment #2)
I gave this a try in vt0 and, after entering cont in the ddb prompt the terminal recovered and my bash prompt reappeared. A number of carriage returns were apparently emitted by the kernel, but that was not a problem.
BUT I'm using sc and NOT vt. What are you using?