# Re: \[PATCH v4 00/15\] Add futex2 syscalls

- From: Zebediah Figura \<hidden\>
- Date: 2021-06-04 04:52:55 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2021/06/1402113
- Thread: https://ratatoskr.run/linux-api/2021/06/1401776/t.md

```text
On 6/3/21 2:59 PM, André Almeida wrote:
>   ** The wait on multiple problem
>
>   The use case lies in the Wine implementation of the Windows NT interface
>   WaitMultipleObjects. This Windows API function allows a thread to sleep
>   waiting on the first of a set of event sources (mutexes, timers, signal,
>   console input, etc) to signal.  Considering this is a primitive
>   synchronization operation for Windows applications, being able to quickly
>   signal events on the producer side, and quickly go to sleep on the
>   consumer side is essential for good performance of those running over Wine.
>

I know this is part of the cover letter, but I really do want to clarify that this isn't really accurate. The use case that this is referring to is not "the Wine implementation of WaitForMultipleObjects", it is an out-of-tree implementation of WaitForMultipleObjects that provides improved performance compared to the in-tree implementation.

This is especially salient because:

(1) this out-of-tree implementation is only in a small handful of cases any more performant than a different out-of-tree implementation which uses eventfd and poll() instead;

(2) these implementations will remain out-of-tree due to compatibility and robustness problems;

(3) I believe there is potential for an upstreamable implementation which does not rely on futex or futex2.
```