Commit 87dffe86 authored Sep 06, 2018 by Vitaly Kuznetsov Committed by Boris Ostrovsky Sep 14, 2018

xen/manage: don't complain about an empty value in control/sysrq node



When guest receives a sysrq request from the host it acknowledges it by
writing '\0' to control/sysrq xenstore node. This, however, make xenstore
watch fire again but xenbus_scanf() fails to parse empty value with "%c"
format string:

 sysrq: SysRq : Emergency Sync
 Emergency Sync complete
 xen:manage: Error -34 reading sysrq code in control/sysrq

Ignore -ERANGE the same way we already ignore -ENOENT, empty value in
control/sysrq is totally legal.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

parent 11da3a7f

drivers/xen/manage.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -280,9 +280,11 @@ static void sysrq_handler(struct xenbus_watch watch, const char path,
		/*
		* 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.
		* might happen in those cases. ERANGE is observed when we get
		* an empty value (''), this happens when we acknowledge the
		* request by writing '\0' below.
		*/
		if (err != -ENOENT)
		if (err != -ENOENT && err != -ERANGE)
		pr_err("Error %d reading sysrq code in control/sysrq\n",
		err);
		xenbus_transaction_end(xbt, 1);

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