Re: [RFC PATCH 2/3] futex: Add basic infrastructure for local task local hash.

[Peter Zijlstra <peterz@infradead.org>]

On Thu, Oct 31, 2024 at 12:14:16AM +0100, Thomas Gleixner wrote:

> If that's handled, then it falls flat when a futex is used as a wait
> queue. There might be a thread sitting on it waiting for an event which
> never happens, which means the old hash never gets removed. Then the
> process gets another pile of threads and can't expand the hash because
> there are already two instances.

Damn... I mean it means a userspace thread is basically stuck forever,
but that's not our problem. Yes this is annoying.

The whole requeue on lookup and hb->waiters thing looks simple enough,
but this is a bit annoying. I can probably make it work though,
however..

> I really want to start simple and let the process' futex usage come to a
> grinding halt when the resizing and rehashing takes place.

Fair enough. Lets do the simple thing first.

> I really want to know who thought that futexes are a good idea to begin
> with. Once we figured that out I need to find those who added all the
> other complexity on top of that bad idea :)

If memory serves me, it was some tall German dude that did most of that.