Re: [PATCH 0/8] Suspend block api (version 6)

[Matthew Garrett <mjg@redhat.com>]

On Mon, May 17, 2010 at 10:53:36PM +0200, Linus WALLEIJ wrote:
> I understand the problem such that the scheduler cannot determine whether
> a certain process should be allowed to schedule or not.
> 
> It strikes me that the intuitive solution is to group all un-trusted 
> processes/threads/tasks that need to be shut off even if they are
> scheduling into a control group and let the idle code ignore the
> processes in this group.
> 
> Or is there something too naïve about this?

It gets most of the way there (and I spent a while playing with it), but 
the problem is that not all wakeup events get proxied through the 
trusted userspace runtime. Network packets are the easiest example - a 
packet may wake the system, but if the process it's delivered to is 
frozen then obviously things get trickier. It's also racy, in that if 
you're currently awake and receive a packet that would otherwise have 
woken the system you may go to sleep between the packet being received 
and bubbling up through the kernel to get to userspace.

-- 
Matthew Garrett | mjg59@srcf.ucam.org