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

Waiman Long
2024-10-08T19:44:29Z

On 10/8/24 1:38 PM, Peter Zijlstra wrote:
> 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.

Regarding the futex-numa patches, are you planning to get them merged
soon? We have customers asking for that.

Cheers,
Longman