svn commit: r311952 - head/sys/ddb

[Slawa Olhovchenkov]

On Sun, Jan 15, 2017 at 01:07:58PM +0800, Julian Elischer wrote:

> 
> the old DEC machines had (from memory) ^O  which dropped all pending 
> output.
> Not so useful when there is 2MB of network buffers queued up to you, 
> but very useful on
> and asr-33 teletype.

Now it useful too, on serial console.
^O processing be present years ago in FreeBSD, but removed at time of
tty code rewrite. As I know patch for restore exist, nobody
review/commit.