[PATCH v2] xen: don't print error message in case of missing Xenstore entry

[PATCH v2] xen: don't print error message in case of missing Xenstore entry

[Juergen Gross]

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 <jgross@suse.com>
---
 drivers/xen/manage.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index c1ec8ee80924..60cf71f1b256 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -277,8 +277,16 @@ 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) {
+		/*
+		 * The Xenstore watch fires directly after registering it and
+		 * after a suspend/resume cycle. So ENOENT is no error but
+		 * might happen in those cases.
+		 */
+		if (err != -ENOENT)
+			pr_err("Error %d reading sysrq code in control/sysrq\n",
+			       err);
 		xenbus_transaction_end(xbt, 1);
 		return;
 	}
-- 
2.12.3

Re: [PATCH v2] xen: don't print error message in case of missing Xenstore entry

[Boris Ostrovsky]

On 05/30/2017 02:52 PM, 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 <jgross@suse.com>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>