From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: Re: [PATCH net 1/3] kref: add kref_sub_return Date: Wed, 12 Feb 2014 08:56:30 -0800 Message-ID: <20140212165630.GA22991@kroah.com> References: <1392222846-26699-1-git-send-email-mst@redhat.com> <1392222846-26699-2-git-send-email-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1392222846-26699-2-git-send-email-mst@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" Cc: virtio-dev@lists.oasis-open.org, Joern Engel , Anatol Pomozov , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, qinchuanyu@huawei.com, davem@davemloft.net List-Id: virtualization@lists.linuxfoundation.org On Wed, Feb 12, 2014 at 06:38:21PM +0200, Michael S. Tsirkin wrote: > It is sometimes useful to get the value of the reference count after > decrement. > For example, vhost wants to execute some periodic cleanup operations > once number of references drops below a specific value, before it > reaches zero (for efficiency). You should never care about what the value of the kref is, if you are using it correctly :) So I really don't want to add this function, as I'm sure people will use it incorrectly. You should only care if the reference drops to 0, if not, then your usage doesn't really fit into the "kref" model, and so, just use an atomic variable. I really want to know why it matters for "efficiency" that you know this number. How does that help anything, as the number could then go up later on, and the work you did at a "lower" number is obsolete, right? thanks, greg k-h From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753367AbaBLQzR (ORCPT ); Wed, 12 Feb 2014 11:55:17 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:50879 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752647AbaBLQzO (ORCPT ); Wed, 12 Feb 2014 11:55:14 -0500 Date: Wed, 12 Feb 2014 08:56:30 -0800 From: Greg Kroah-Hartman To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, Jason Wang , virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, davem@davemloft.net, qinchuanyu@huawei.com, Joern Engel , Anatol Pomozov , Nicholas Bellinger Subject: Re: [PATCH net 1/3] kref: add kref_sub_return Message-ID: <20140212165630.GA22991@kroah.com> References: <1392222846-26699-1-git-send-email-mst@redhat.com> <1392222846-26699-2-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1392222846-26699-2-git-send-email-mst@redhat.com> User-Agent: Mutt/1.5.22 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 12, 2014 at 06:38:21PM +0200, Michael S. Tsirkin wrote: > It is sometimes useful to get the value of the reference count after > decrement. > For example, vhost wants to execute some periodic cleanup operations > once number of references drops below a specific value, before it > reaches zero (for efficiency). You should never care about what the value of the kref is, if you are using it correctly :) So I really don't want to add this function, as I'm sure people will use it incorrectly. You should only care if the reference drops to 0, if not, then your usage doesn't really fit into the "kref" model, and so, just use an atomic variable. I really want to know why it matters for "efficiency" that you know this number. How does that help anything, as the number could then go up later on, and the work you did at a "lower" number is obsolete, right? thanks, greg k-h