Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754531Ab0AURNT (ORCPT ); Thu, 21 Jan 2010 12:13:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753801Ab0AURNS (ORCPT ); Thu, 21 Jan 2010 12:13:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:2072 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752631Ab0AURNR (ORCPT ); Thu, 21 Jan 2010 12:13:17 -0500 Message-ID: <4B588B29.2050100@redhat.com> Date: Thu, 21 Jan 2010 19:13:13 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091209 Fedora/3.0-4.fc12 Thunderbird/3.0 MIME-Version: 1.0 To: Davide Libenzi CC: "Michael S. Tsirkin" , mtosatti@redhat.com, kvm@vger.kernel.org, Linux Kernel Mailing List Subject: Re: [PATCHv2 1/3] eventfd: allow atomic read and waitqueue remove References: <20100121162648.GA16458@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1576 Lines: 42 On 01/21/2010 06:58 PM, Davide Libenzi wrote: > 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 >> --- >> >> 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. > I agree. But I think we can solve this in another way in .32: we can clear the eventfd from irqfd->inject work, which is in process context. The new stuff is only needed for lockless clearing, no? -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/