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SubjectRe: [PATCH v2] xen/mce: don't issue error message for failed /dev/mcelog registration
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On 13/06/17 21:30, Joe Perches wrote:
> On Tue, 2017-06-13 at 21:27 +0200, Juergen Gross wrote:
>> On 13/06/17 18:31, Joe Perches wrote:
>>> On Tue, 2017-06-13 at 18:13 +0200, Juergen Gross wrote:
>>>> On 13/06/17 17:20, Ingo Molnar wrote:
>>>>> * Juergen Gross <jgross@suse.com> wrote:
>>>>>
>>>>>> When running under Xen as dom0 /dev/mcelog is being registered by Xen
>>>>>> instead of the normal mcelog driver. Avoid an error message being
>>>>>> issued by the mcelog driver in this case. Instead issue an informative
>>>>>> message that Xen has registered the device.
>>>
>>> []
>>>>>> diff --git a/arch/x86/kernel/cpu/mcheck/dev-mcelog.c b/arch/x86/kernel/cpu/mcheck/dev-mcelog.c
>>>
>>> []
>>>>>> @@ -388,9 +388,16 @@ static __init int dev_mcelog_init_device(void)
>>>>>> /* register character device /dev/mcelog */
>>>>>> err = misc_register(&mce_chrdev_device);
>>>>>> if (err) {
>>>>>> - pr_err("Unable to init device /dev/mcelog (rc: %d)\n", err);
>>>>>> - return err;
>>>>>> + if (err == -EBUSY)
>>>>>> + /* Xen dom0 might have registered the device already. */
>>>>>> + pr_info("Unable to init device /dev/mcelog, already registered");
>>>>>> + else {
>>>>>> + pr_err("Unable to init device /dev/mcelog (rc: %d)\n",
>>>>>> + err);
>>>>>> + return err;
>>>>>> + }
>>>>>
>>>>> Please only use balanced curly braces in conditional statements.
>>>>
>>>> Okay, will change.
>>>
>>> Perhaps better is to reverse the test
>>>
>>> if (err != -EBUSY) {
>>> pr_err("Unable to ....", err);
>>> return err;
>>> }
>>> pr_info("etc...");
>>
>> Okay.
>>
>>>
>>> [ rest of code at this indentation ]
>>>
>>> but it looks like you added a logic defect too and
>>> this code should be:
>>>
>>> if (err) {
>>> if (err == -EBUSY)
>>> pr_info(...)
>>> else
>>> pr_err(...)
>>> return err;
>>> }
>>>
>>> or less indented using
>>>
>>> err = misc_register(&mce_chrdev_device);
>>> if (err == -EBUSY) {
>>> pr_info(...);
>>> return err;
>>> } else if (err) {
>>> pr_err(...);
>>> return err;
>>> }
>>
>> I didn't want to omit the call to mce_register_decode_chain() in the Xen
>> case.
>
> You should definitely mention that behavior change
> in the changelog.

Looking more thoroughly it seems I really don't need the call for Xen.
So thanks for bringing it up. :-)


Juergen

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