Re: [PATCH 3/3] eventfd: add internal reference counting to fix notifier race conditions

Davide Libenzi
2009-06-19T22:00:40Z

On Fri, 19 Jun 2009, Gregory Haskins wrote:

> I am fairly confident it is not that simple after having thought about
> this issue over the last few days. But I've been wrong in the past.
> Propose a patch and I will review it for races/correctness, if you
> like. Perhaps a combination of that plus your asymmetrical locking
> scheme would work. One of the challenges you will hit is avoiding ABBA
> between your "get" lock and the wqh, but good luck!

A patch for what? The eventfd patch is a one-liner.
It seems hard to believe that the thing cannot be handled on your side.
Once the wake_up_locked() is turned into a wake_up(), what other races are
there?
Let's not try to find the problem that fits and justify the "cool"
solution, but let's see if a problem is there at all.

- Davide