From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751105AbdE3RJv (ORCPT ); Tue, 30 May 2017 13:09:51 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:27307 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751030AbdE3RJs (ORCPT ); Tue, 30 May 2017 13:09:48 -0400 Subject: Re: [PATCH] xen: don't print error message in case of missing Xenstore entry To: Juergen Gross , 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: Boris Ostrovsky Message-ID: Date: Tue, 30 May 2017 13:08:25 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <78ae3bc7-fbd9-5f69-3177-67eeb3f43201@suse.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? -boris > > > Juergen > >> -boris >> >>> + pr_err("Error %d reading sysrq code in control/sysrq\n", >>> + err); >>> xenbus_transaction_end(xbt, 1); >>> return; >>> } >>