From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751182AbdE3RKw (ORCPT ); Tue, 30 May 2017 13:10:52 -0400 Received: from mx2.suse.de ([195.135.220.15]:41028 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750733AbdE3RKv (ORCPT ); Tue, 30 May 2017 13:10:51 -0400 Subject: Re: [PATCH] xen: don't print error message in case of missing Xenstore entry To: Boris Ostrovsky , linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org References: <20170529091339.1449-1-jgross@suse.com> <69e13959-26a5-a794-2fa7-3933bc6f22f0@oracle.com> <78ae3bc7-fbd9-5f69-3177-67eeb3f43201@suse.com> From: Juergen Gross Message-ID: <43221609-cc69-8643-3ce3-82a531e3b904@suse.com> Date: Tue, 30 May 2017 19:10:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Language: de-DE Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/05/17 19:08, Boris Ostrovsky wrote: > On 05/30/2017 11:03 AM, Juergen Gross wrote: >> On 30/05/17 15:25, Boris Ostrovsky wrote: >>> On 05/29/2017 05:13 AM, Juergen Gross wrote: >>>> When registering for the Xenstore watch of the node control/sysrq the >>>> handler will be called at once. Don't issue an error message if the >>>> Xenstore node isn't there, as it will be created only when an event >>>> is being triggered. >>>> >>>> Signed-off-by: Juergen Gross >>>> --- >>>> drivers/xen/manage.c | 7 +++++-- >>>> 1 file changed, 5 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c >>>> index c1ec8ee80924..7ddd0803da23 100644 >>>> --- a/drivers/xen/manage.c >>>> +++ b/drivers/xen/manage.c >>>> @@ -277,8 +277,11 @@ static void sysrq_handler(struct xenbus_watch *watch, const char *path, >>>> err = xenbus_transaction_start(&xbt); >>>> if (err) >>>> return; >>>> - if (xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key) < 0) { >>>> - pr_err("Unable to read sysrq code in control/sysrq\n"); >>>> + err = xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key); >>>> + if (err < 0) { >>>> + if (err != -ENOENT) >>> Can we distinguish initialization invocation from actual watch firing? >>> E.g. '|| (system_state >= SYSTEM_RUNNING)'? >> The watch will fire again after suspend/resume (e.g. live migration). > > > That's unfortunate. (And system_state check would also not be a good > solution btw since the watch might be processed by the watch thread > after we enter SYSTEM_RUNNING). > > Can you add a comment explaining why we are ignoring ENOENT? Sure. Juergen