boot message "xen:manage: Unable to read sysrq code in control/sysrq" ?

boot message "xen:manage: Unable to read sysrq code in control/sysrq" ?

[PGNet Dev]

Working with Xen 4.9.0 host on kernel 4.11.3

	dmesg | egrep -i "linux version|xen version"
		[    0.000000] Linux version 4.11.3-2.g7262353-default (geeko@buildhost) (gcc version 7.1.1 20170517 [gcc-7-branch revision 248152] (SUSE Linux) ) #1 SMP PREEMPT Thu May 25 17:55:04 UTC 2017 (7262353)
		[    0.000000] Xen version: 4.9.0_07-503 (preserve-AD)

I currently see in host boot

	dmesg | grep sysrq
		[   20.905146] xen:manage: Unable to read sysrq code in control/sysrq

That seems to originate at

	https://lkml.org/lkml/2016/11/8/134
		...
	+	if (xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key) < 0) {
			pr_err("Unable to read sysrq code in control/sysrq\n");
			xenbus_transaction_end(xbt, 1);
			return;
		...

Is this a config issue -- wrong or missing -- on my end?  Or a problem that needs some more diagnostic info here?

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Re: boot message "xen:manage: Unable to read sysrq code in control/sysrq" ?

[Juergen Gross]

On 28/05/17 21:55, PGNet Dev wrote:
> Working with Xen 4.9.0 host on kernel 4.11.3
> 
> 	dmesg | egrep -i "linux version|xen version"
> 		[    0.000000] Linux version 4.11.3-2.g7262353-default (geeko@buildhost) (gcc version 7.1.1 20170517 [gcc-7-branch revision 248152] (SUSE Linux) ) #1 SMP PREEMPT Thu May 25 17:55:04 UTC 2017 (7262353)
> 		[    0.000000] Xen version: 4.9.0_07-503 (preserve-AD)
> 
> I currently see in host boot
> 
> 	dmesg | grep sysrq
> 		[   20.905146] xen:manage: Unable to read sysrq code in control/sysrq
> 
> That seems to originate at
> 
> 	https://lkml.org/lkml/2016/11/8/134
> 		...
> 	+	if (xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key) < 0) {
> 			pr_err("Unable to read sysrq code in control/sysrq\n");
> 			xenbus_transaction_end(xbt, 1);
> 			return;
> 		...
> 
> Is this a config issue -- wrong or missing -- on my end?  Or a problem that needs some more diagnostic info here?

Its just a message which shouldn't be printed at all, as this is no
error. I'll send a patch.

Thanks for the notice!


Juergen

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