Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756756AbZCSCGb (ORCPT ); Wed, 18 Mar 2009 22:06:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751528AbZCSCGR (ORCPT ); Wed, 18 Mar 2009 22:06:17 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:36064 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751223AbZCSCGQ (ORCPT ); Wed, 18 Mar 2009 22:06:16 -0400 Date: Wed, 18 Mar 2009 18:56:30 -0700 From: Andrew Morton To: Alexander Duyck Cc: "Kirsher, Jeffrey T" , "davem@davemloft.net" , "netdev@vger.kernel.org" , "gospo@redhat.com" , "linux-kernel@vger.kernel.org" , "greg@kroah.com" , "kvm@vger.kernel.org" , "Zhao, Yu" Subject: Re: [net-next PATCH 1/2] igbvf: add new driver to support 82576 virtual functions Message-Id: <20090318185630.11f3d557.akpm@linux-foundation.org> In-Reply-To: <49C1948F.1060300@intel.com> References: <20090311020928.23138.20790.stgit@lost.foo-projects.org> <20090310222154.4bc8c12c.akpm@linux-foundation.org> <49C03C80.5020203@intel.com> <20090317180826.8f3c596b.akpm@linux-foundation.org> <49C111C6.2010905@intel.com> <20090318145340.6b282829.akpm@linux-foundation.org> <49C1948F.1060300@intel.com> X-Mailer: Sylpheed 2.4.7 (GTK+ 2.12.1; x86_64-redhat-linux-gnu) 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 Content-Length: 2539 Lines: 52 On Wed, 18 Mar 2009 17:40:47 -0700 Alexander Duyck wrote: > Andrew Morton wrote: > > On Wed, 18 Mar 2009 08:22:46 -0700 Alexander Duyck wrote: > > > >>>>>> +static int igbvf_set_ringparam(struct net_device *netdev, > >>>>>> + struct ethtool_ringparam *ring) > >>>>>> +{ > >>>>>> + struct igbvf_adapter *adapter = netdev_priv(netdev); > >>>>>> + struct igbvf_ring *tx_ring, *tx_old; > >>>>>> + struct igbvf_ring *rx_ring, *rx_old; > >>>>>> + int err; > >>>>>> + > >>>>>> + if ((ring->rx_mini_pending) || (ring->rx_jumbo_pending)) > >>>>>> + return -EINVAL; > >>>>>> + > >>>>>> + while (test_and_set_bit(__IGBVF_RESETTING, &adapter->state)) > >>>>>> + msleep(1); > >>>>> No timeout needed here? Interrupts might not be working, for example.. > >>>> This bit isn't set in interrupt context. This is always used out of > >>>> interrupt context and is just to prevent multiple setting changes at the > >>>> same time. > >>> Oh. Can't use plain old mutex_lock()? > >> We have one or two spots that actually check to see if the bit is set > >> and just report a warning instead of actually waiting on the bit to clear. > > > > mutex_is_locked()? > > I suppose that would work, but I still would prefer to keep this bit of > code as it is. My main motivation is just to use what was already > proven, and the fact is the e1000, e1000e, igb, and several other > drivers all use this same approach and it works. OK, that's a reason. > I don't think we need the extra overhead of the mutex lock since most of > the calls that end up setting the __IGBVF_RESETTING bit will already be > wrapped within rtnl_lock/unlock calls. As far as I can tell it looks > like the only two threads that would ever be competing for the lock > would be the igbvf_reinit_locked and whatever ethtool or ifconfig > requests that decide to make changes to the configuration of the netdevice. You may well find that mutex_lock is more efficient than setting a timer and waking up once per millisecond. Certainly much lower latency on some setups given clock granularities of as much as 10 milliseconds. But it sounds like that's all a separate standalone exercise. -- 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/