From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Subject: Re: [Pv-drivers] [PATCH 05/12] VMCI: event handling implementation. Date: Tue, 30 Oct 2012 08:50:12 -0700 Message-ID: <20121030155012.GE14167@kroah.com> References: <20121030005923.17788.21797.stgit@promb-2n-dhcp175.eng.vmware.com> <20121030010420.17788.59187.stgit@promb-2n-dhcp175.eng.vmware.com> <20121030022446.GF1920@kroah.com> <20121030045821.GD32055@dtor-ws.eng.vmware.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20121030045821.GD32055@dtor-ws.eng.vmware.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: Dmitry Torokhov Cc: pv-drivers@vmware.com, linux-kernel@vger.kernel.org, George Zhang , virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On Mon, Oct 29, 2012 at 09:58:21PM -0700, Dmitry Torokhov wrote: > On Mon, Oct 29, 2012 at 07:24:46PM -0700, Greg KH wrote: > > On Mon, Oct 29, 2012 at 06:04:27PM -0700, George Zhang wrote: > > > +/* > > > + * Releases the given VMCISubscription. > > > + * Fires the destroy event if the reference count has gone to zero. > > > + */ > > > +static void event_release(struct vmci_subscription *entry) > > > +{ > > > + kref_put(&entry->kref, event_signal_destroy); > > > +} > > > > Same question as before with the kref_put() call, what is handling the > > locking here? It looks like a race to me. > > The reference is taken only if event is on the list (which managed by > RCU and a mutex), so it is not possible to go from 0->1 for that > refcount. Ok, as long as you have audited this. 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 S933668Ab2J3PuT (ORCPT ); Tue, 30 Oct 2012 11:50:19 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:51269 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753716Ab2J3PuQ (ORCPT ); Tue, 30 Oct 2012 11:50:16 -0400 Date: Tue, 30 Oct 2012 08:50:12 -0700 From: Greg KH To: Dmitry Torokhov Cc: George Zhang , pv-drivers@vmware.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [Pv-drivers] [PATCH 05/12] VMCI: event handling implementation. Message-ID: <20121030155012.GE14167@kroah.com> References: <20121030005923.17788.21797.stgit@promb-2n-dhcp175.eng.vmware.com> <20121030010420.17788.59187.stgit@promb-2n-dhcp175.eng.vmware.com> <20121030022446.GF1920@kroah.com> <20121030045821.GD32055@dtor-ws.eng.vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121030045821.GD32055@dtor-ws.eng.vmware.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 29, 2012 at 09:58:21PM -0700, Dmitry Torokhov wrote: > On Mon, Oct 29, 2012 at 07:24:46PM -0700, Greg KH wrote: > > On Mon, Oct 29, 2012 at 06:04:27PM -0700, George Zhang wrote: > > > +/* > > > + * Releases the given VMCISubscription. > > > + * Fires the destroy event if the reference count has gone to zero. > > > + */ > > > +static void event_release(struct vmci_subscription *entry) > > > +{ > > > + kref_put(&entry->kref, event_signal_destroy); > > > +} > > > > Same question as before with the kref_put() call, what is handling the > > locking here? It looks like a race to me. > > The reference is taken only if event is on the list (which managed by > RCU and a mutex), so it is not possible to go from 0->1 for that > refcount. Ok, as long as you have audited this. greg k-h