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

Michael S. Tsirkin
2010-01-21T17:53:20Z

On Thu, Jan 21, 2010 at 09:50:34AM -0800, Davide Libenzi wrote:
> On Thu, 21 Jan 2010, Avi Kivity wrote:
>
> > On 01/21/2010 07:32 PM, Michael S. Tsirkin wrote:
> > >
> > > > Can't you read from the file?
> > > >
> > > IMO no, the read could block.
> > >
> >
> > But you're in process context. An eventfd never blocks.
>
> Can you control the eventfd flags? Because if yes, O_NONBLOCK will never
> block.
>

Userspace can but kvm can't.

>
> - Davide
>