Re: [PATCHv2 1/3] eventfd: allow atomic read and waitqueue remove

Davide Libenzi
2010-01-21T16:58:50Z

On Thu, 21 Jan 2010, Michael S. Tsirkin wrote:

> This is a backport of commit: 03db343a6320f780937078433fa7d8da955e6fce
> modified in a way that introduces some code duplication on the one hand,
> but reduces the risk of regressing existing eventfd users on the other
> hand.
>
> KVM needs a wait to atomically remove themselves from the eventfd
> ->poll() wait queue head, in order to handle correctly their IRQfd
> deassign operation.
>
> This patch introduces such API, plus a way to read an eventfd from its
> context.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>
> Avi, Davidel, how about only including the following part for -stable
> then? Reason is, I still would like to be able to use irqfd there, and
> getting spurious interrupts 100% of times unmask is done isn't a very
> good idea IMO ...

It's the same thing. Unless there are *real* problems in KVM due to the
spurious ints, I still think this is .33 material.

- Davide