linux-kernel - Re: [KVM PATCH v4 2/2] kvm: add support for irqfd via eventfd-notification interface

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Message-ID: <alpine.DEB.1.10.0905070744490.30708@makko.or.mcafeemobile.com>
Date:	Thu, 7 May 2009 07:46:37 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Avi Kivity <avi@...hat.com>
cc:	Gregory Haskins <ghaskins@...ell.com>, viro@...IV.linux.org.uk,
	kvm@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [KVM PATCH v4 2/2] kvm: add support for irqfd via eventfd-notification
 interface

On Thu, 7 May 2009, Avi Kivity 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?


- Davide


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