[TUHS] FD 2

Dan Cross crossd at gmail.com
Tue Jan 31 02:17:59 AEST 2023


On Mon, Jan 30, 2023 at 11:07 AM Larry McVoy <lm at mcvoy.com> wrote:
> On Mon, Jan 30, 2023 at 08:03:42AM -0800, Bakul Shah wrote:
> > > On Jan 30, 2023, at 7:18 AM, Dan Cross <crossd at gmail.com> wrote:
> > > There was no job control on plan9 and I can't say I ever missed it.
> >
> > Just yesterday I realized running two ???make -j 8??? in parallel was making
> > them both go real slow so I  stopped one of them with ^Z and continued
> > it once the other make finished. This use case can???t be handled with more
> > windows.
>
> If you don't have job control, do you not have ^C to kill one of the
> make jobs?  I guess you open another window and ps and kill it but
> if the machine is already thrashing that is gonna be unpleasant.

You do, but it's not a kernel-level thing; there's no TTY abstraction
with an attendant driver. Instead, the window system will interpret
DEL as an interrupt request and send a note to the process group
running in that window.

Plan 9 didn't have signals; rather, there were "notes", that were
little strings that could be sent between processes. It was the
responsibility of the receiver to parse these and take appropriate
action in a note handler; there was a "stop" note that could be used
to pause a process. One could presumably use that to pause a process
group that was using excessive CPU.


        - Dan C.


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