linux-kernel - Re: [PATCH v8 3/7] crash: add generic infrastructure for crash hotplug support

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Message-ID: <1ef10873-c20f-afd8-e560-3b7fb5516f2b@redhat.com>
Date:   Wed, 15 Jun 2022 11:53:32 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Eric DeVolder <eric.devolder@...cle.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, ebiederm@...ssion.com,
        dyoung@...hat.com, bhe@...hat.com, vgoyal@...hat.com
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com,
        nramas@...ux.microsoft.com, thomas.lendacky@....com,
        robh@...nel.org, efault@....de, rppt@...nel.org,
        konrad.wilk@...cle.com, boris.ostrovsky@...cle.com
Subject: Re: [PATCH v8 3/7] crash: add generic infrastructure for crash
 hotplug support

On 01.06.22 00:25, Eric DeVolder wrote:
> 
> 
> On 5/31/22 08:15, David Hildenbrand wrote:
>> On 12.05.22 18:10, Eric DeVolder wrote:
>>> David,
>>> Great questions! See inline responses below.
>>> eric
>>
>> Sorry for the late reply, travel and vacation ...
> No problem, greatly appreciate the feedback!
> eric
> 
>>
>>>>
>>>>> +
>>>>> +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
>>>>> +void __weak arch_crash_handle_hotplug_event(struct kimage *image,
>>>>> +							unsigned int hp_action, unsigned int cpu)
>>>>> +{
>>>>> +	WARN(1, "crash hotplug handler not implemented");
>>>>
>>>>
>>>> Won't that trigger on any arch that has CONFIG_HOTPLUG_CPU and CONFIG_MEMORY_HOTPLUG?
>>>> I mean, you only implement it for x86 later in this series. Or what else stops this WARN from
>>>> triggering?
>>>>
>>> You're correct. What about: printk_once(KERN_DEBUG "...") ?
>>
>> Why even bother about printing anything? If the feature is not
>> supported, there should be some way for user space to figure out that it
>> sill has to reload on hot(un)plug manually, no?
> 
> I've changed this to WARN_ONCE(). If that isn't agreeable, I'll remove it.

Please don't use WARN* on expected error paths.

-- 
Thanks,

David / dhildenb