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Commit 4e149479 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Greg Kroah-Hartman
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xen/manage: don't complain about an empty value in control/sysrq node 



[ Upstream commit 87dffe86d406bee8782cac2db035acb9a28620a7 ]

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: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: default avatarWei Liu <wei.liu2@citrix.com>
Signed-off-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent dfb29d69

drivers/xen/manage.c

+4 −2
Original line number Diff line number Diff line
@@ -283,9 +283,11 @@ 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);