Re: [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early

[Michal Hocko]

On Wed 13-09-17 14:10:01, Michal Hocko wrote:
> On Wed 13-09-17 13:41:20, Vlastimil Babka wrote:
> > On 09/11/2017 10:17 AM, Michal Hocko wrote:
> [...]
> > > Yes, we should be able to distinguish the two and hopefully we can teach
> > > the migration code to distinguish between EBUSY (likely permanent) and
> > > EGAIN (temporal) failure. This sound like something we should aim for
> > > longterm I guess. Anyway as I've said in other email. If somebody really
> > > wants to have a guaratee of a bounded retry then it is trivial to set up
> > > an alarm and send a signal itself to bail out.
> > 
> > Sure, I would just be careful about not breaking existing userspace
> > (udev?) when offline triggered via ACPI from some management interface
> > (or whatever the exact mechanism is).
> 
> The thing is that there is absolutely no timing guarantee even with
> retry limit in place. We are doing allocations, potentially bouncing on
> locks which can be taken elsewhere etc... So if somebody really depend
> on this then it is pretty much broken already.
> 
> > > Do you think that the changelog should be more clear about this?
> > 
> > It certainly wouldn't hurt :)
> 
> So what do you think about the following wording:

Ups, wrong patch