Messages in this thread Patch in this message | | | From | Vitaly Kuznetsov <> | Subject | [PATCH] xen/manage: don't complain about an empty value in control/sysrq node | Date | Thu, 6 Sep 2018 13:26:08 +0200 |
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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> --- This is a follow-up to my Xen toolstack patch: https://lists.xenproject.org/archives/html/xen-devel/2018-09/msg00266.html without it we're seeing -EPERM on write and the issue I'm trying to address here stays hidden. --- drivers/xen/manage.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c index c93d8ef8df34..5bb01a62f214 100644 --- a/drivers/xen/manage.c +++ b/drivers/xen/manage.c @@ -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); -- 2.14.4
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