Re: Futex hash_bucket lock can break isolation and cause priority inversion on RT

Peter Zijlstra
2024-10-08T17:39:07Z

On Tue, Oct 08, 2024 at 04:22:26PM +0100, Juri Lelli wrote:
> Does this report make any sense? If it does, has this issue ever been
> reported and possibly discussed? I guess it’s kind of a corner case, but
> I wonder if anybody has suggestions already on how to possibly try to
> tackle it from a kernel perspective.

Any shared lock can cause such havoc. Futex hash buckets is just one of
a number of very popular ones that's relatively easy to hit.

I do have some futex-numa patches still pending, but they won't
magically sure this either. Userspace needs help at the very least.