Re: [PATCH v8 0/7] freezer for cgroup v2

From: Oleg Nesterov
Date: Fri Feb 22 2019 - 11:34:47 EST


On 02/21, Tejun Heo wrote:
> So, I really wanna avoid allowing userspace to cause D state sleeps.
> ptrace support is a lot less important than kill for sure but if at
> all possible I think it'd be better to have it

Tejun, I agree it would be better. I did not argue with that.

The question is how this can be implemented. And how much uglifications^W
complications in the core kernel code this needs.

> To summarize, the ideal result is the frozen state to be "stuck in
> jobctl stop loop"

Not sure I understand, but I don't think this can work...

Let me repeat, imo the freezer should be "reliable", it shouldn't stuck
in CGRP_FREEZE state forever if, say, it races with vfork(). And personally
I think this is more important than (very limited) ptrace support.

So I think it too should somehow interact with freezable_schedule/etc.