Re: [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag

Michal Hocko
2020-08-13T16:14:01Z

On Thu 13-08-20 09:04:42, Paul E. McKenney wrote:
> On Thu, Aug 13, 2020 at 05:54:12PM +0200, Michal Hocko wrote:
[...]
> > If the whole bailout is guarded by CONFIG_PREEMPT_RT specific atomicity
> > check then there is no functional problem - GFP_RT_SAFE would still be
> > GFP_NOWAIT so functional wise the allocator will still do the right
> > thing.
>
> Perhaps it was just me getting confused, early hour Pacific Time and
> whatever other excuses might apply. But I thought that you still had
> an objection to GFP_RT_SAFE based on changes in allocator semantics for
> other users.

There is still that problem with lockdep complaining about raw->regular
spinlock on !PREEMPT_RT that would need to get resolved somehow. Thomas
is not really keen on adding some lockdep annotation mechanism and
unfortunatelly I do not have a different idea how to get rid of those.
--
Michal Hocko
SUSE Labs