[PATCH 4/4] um: allow PM with suspend-to-idle

[Johannes Berg]

On Fri, 2020-11-20 at 22:29 +0100, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg at intel.com>
> 
> In order to be able to experiment with suspend in UML,
> add the minimal work to be able to suspend (s2idle) an
> instance of UML, and be able to wake it back up from
> that state with the USR1 signal sent to the main UML
> process.

So what I said about rtcwake ... maybe that's an argument for removing
the USR1 handling? I wasn't really too sure about it.

But on the other hand, typically real systems will have at least *some*
kind of wakeup source that you can manually use and that's always
enabled, perhaps the power button for example; the SIGUSR1 handling was
meant to simulate such a thing.

(Today, if you send SIGUSR1 to the main 'linux' process, it just dies,
but I hope nobody relies on that ...?)

johannes