From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752694AbbDPVVX (ORCPT ); Thu, 16 Apr 2015 17:21:23 -0400 Received: from mail-pa0-f47.google.com ([209.85.220.47]:35517 "EHLO mail-pa0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751988AbbDPVVG (ORCPT ); Thu, 16 Apr 2015 17:21:06 -0400 Date: Thu, 16 Apr 2015 14:21:10 -0700 From: Stephen Hemminger To: "Michael S. Tsirkin" Cc: "Hans J. Koch" , Greg Kroah-Hartman , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] uio: add irq control support to uio_pci_generic Message-ID: <20150416142110.2fc80b15@urahara> In-Reply-To: <20150416094105-mutt-send-email-mst@redhat.com> References: <20150415095934.09966367@urahara> <20150416094105-mutt-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 16 Apr 2015 09:43:24 +0200 "Michael S. Tsirkin" wrote: > On Wed, Apr 15, 2015 at 09:59:34AM -0700, Stephen Hemminger wrote: > > The driver already supported INTX interrupts but had no in kernel > > function to enable and disable them. > > > > It is possible for userspace to do this by accessing PCI config > > directly, but this racy > > How is it racy? We have userspace using this interface, > if there's a race I want to fix it. There is nothing to prevent two threads in user space doing read/modify write at the same time. The bigger issue is that DPDK needs to support multiple UIO interface types. And with current model there is no abstraction. The way to enable/disable IRQ is different depending on the UIO drivers.