Re: [KVM PATCH v4 2/2] kvm: add support for irqfd via eventfd-notificationinterface

[Avi Kivity]

Davide Libenzi wrote:
> On Thu, 7 May 2009, Avi Kivity wrote:
>
>   
> > Davide Libenzi wrote:
> >     
> > >   
> > >       
> > > > What's your take on adding irq context safe callbacks to irqfd?
> > > >
> > > > To give some background here, we would like to use eventfd as a generic
> > > > connector between components, so the components do not know about each
> > > > other.
> > > > So far eventfd successfully abstracts among components in the same
> > > > process, in
> > > > different processes, and in the kernel.
> > > >
> > > > eventfd_signal() can be safely called from irq context, and will wake up a
> > > > waiting task.  But in some cases, if the consumer is in the kernel, it may
> > > > be
> > > > able to consume the event from irq context, saving a context switch.
> > > >
> > > > So, will you consider patches adding this capability to eventfd?
> > > >     
> > > >         
> > > Maybe I got lost in the thread, but inside the kernel we have callback-based
> > > wakeup since long time. This is what epoll uses, when hooking into the file*
> > > f_op->poll() subsystem.
> > > Did you mean something else?
> > >   
> > >       
> > Do you mean wait_queue_t::func?
> >     
>
> Yes, it is since long time ago that a wakeup in Linux can lead either to a 
> real wakeup (in scheduler terms), or to a simple function call.
> Isn't that enough?
>
>   

It's perfect.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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