Re: [PATCH] mm: don't rely on system state to detect hot-plug operations

From: Greg Kroah-Hartman
Date: Wed Sep 09 2020 - 08:38:01 EST

On Wed, Sep 09, 2020 at 11:24:24AM +0200, David Hildenbrand wrote:
> >> I am not sure an enum is going to make the existing situation less
> >> messy. Sure we somehow have to distinguish boot init and runtime hotplug
> >> because they have different constrains. I am arguing that a) we should
> >> have a consistent way to check for those and b) we shouldn't blow up
> >> easily just because sysfs infrastructure has failed to initialize.
> >
> > For the point a, using the enum allows to know in register_mem_sect_under_node()
> > if the link operation is due to a hotplug operation or done at boot time.
> >
> > For the point b, one option would be ignore the link error in the case the link
> > is already existing, but that BUG_ON() had the benefit to highlight the root issue.
> >
> WARN_ON_ONCE() would be preferred - not crash the system but still
> highlight the issue.

Many many systems now run with 'panic on warn' enabled, so that wouldn't
change much :(

If you can warn, you can properly just print an error message and
recover from the problem.


greg k-h