From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752380AbcGGNWe (ORCPT ); Thu, 7 Jul 2016 09:22:34 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:36667 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751058AbcGGNWb (ORCPT ); Thu, 7 Jul 2016 09:22:31 -0400 X-IronPort-AV: E=Sophos;i="5.28,324,1464652800"; d="scan'208";a="371782902" Subject: Re: [Xen-devel] [PATCH 1/2] xenbus: don't bail early from xenbus_dev_request_and_reply() To: David Vrabel , Jan Beulich References: <577E1FFE02000078000FBD8C@prv-mh.provo.novell.com> <577E219402000078000FBDB6@prv-mh.provo.novell.com> <577E3ED0.906@citrix.com> <577E629C02000078000FC32F@prv-mh.provo.novell.com> <577E4865.1080307@citrix.com> <577E65CB02000078000FC35B@prv-mh.provo.novell.com> <577E5565.40302@citrix.com> CC: Juergen Gross , , , From: David Vrabel Message-ID: <577E5793.5030209@citrix.com> Date: Thu, 7 Jul 2016 14:22:27 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.5.0 MIME-Version: 1.0 In-Reply-To: <577E5565.40302@citrix.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/07/16 14:13, David Vrabel wrote: > On 07/07/16 13:23, Jan Beulich wrote: >>>>> On 07.07.16 at 14:17, wrote: >>> On 07/07/16 13:09, Jan Beulich wrote: >>>>>>> On 07.07.16 at 13:36, wrote: >>>>> On 07/07/16 08:32, Jan Beulich wrote: >>>>>> We must not skip the transaction_end() call for a failed >>>>>> XS_TRANSACTION_START. The removed code fragment got introduced by >>>>>> commit 027bd7e899 ("xen/xenbus: Avoid synchronous wait on XenBus >>>>>> stalling shutdown/restart") without its description really indicating >>>>>> why it was added (and hence I can't identify whether a more complex >>>>>> change might be needed here). >>>>> >>>>> If sending the XS_TRANSACTION_END message failed, then the transaction >>>>> is still open and transaction_end() should not be called. >>>>> >>>>> However, if sending an XS_TRANSACTION_START failed, then >>>>> transaction_end() should be called. >>>>> >>>>> So, yes a more complex fix is needed here. >>>> >>>> Well, both of the things you name are what happens with the patch >>>> in place. So if those two conditions are all that needs to be satisfied, >>>> then no more complex change is needed afaict (and was the behavior >>>> before the cross referenced commit) - the question really is whether >>>> that other commit meant to deal with something _beyond_ those two >>>> things. >>> >>> You call transaction_end() if msg->type == XS_TRANSACTION_END, even if >>> xb_write() returned an error. >> >> When xb_write() returns an error, msg->type gets set to XS_ERROR. > > So? > > if ((msg->type == XS_TRANSACTION_END) || > (...)) > transaction_end(); > > We don't check msg->type for XS_TRANSACTION_END messages. Sorry, being stupid. Yeah, the change is fine but it needs a better commit message. David