Re: Affinity managed interrupts vs non-managed interrupts

[Christoph Hellwig]

On Thu, Sep 06, 2018 at 01:46:46PM +0200, Thomas Gleixner wrote:
> There are a few things we need to clarify upfront:
> 
> Right now the pre and post vectors are marked managed and their
> affinity mask is set to the irq default affinity mask.
> 
> The default affinity mask is by default ALL cpus, but it can be tweaked
> both on the kernel command line and via proc.
> 
> If that mask is only a subset of CPUs and all of them go offline
> then these vectors are shutdown in managed mode.
> 
> That means we need to set the affinity mask of the pre and post vectors to
> possible mask, but that doesn't make much sense either, unless there is a
> reason to have them marked managed.
> 
> I think the right solution for these pre/post vectors is to _NOT_ mark
> them managed and leave them as regular interrupts which can be affinity
> controlled and also can move freely on hotplug.

Yes, agreed.  Marking the pre/post vector as managed was a mistake
(and I don't think it even was intentional, at least on my part).