linux-kernel - Re: [PATCH] HWPOISON: add a pr_err message when forcibly send a sigbus

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Message-ID: <c1d7c97e-d3fd-8099-9136-afb2f3b91ba8@linux.alibaba.com>
Date:   Thu, 12 Oct 2023 16:16:58 +0800
From:   Shuai Xue <xueshuai@...ux.alibaba.com>
To:     Helge Deller <deller@....de>, Will Deacon <will@...nel.org>,
        "Luck, Tony" <tony.luck@...el.com>
Cc:     catalin.marinas@....com, James.Bottomley@...senPartnership.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        hpa@...or.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-parisc@...r.kernel.org
Subject: Re: [PATCH] HWPOISON: add a pr_err message when forcibly send a
 sigbus



On 2023/9/4 18:40, Shuai Xue wrote:
> 
> 
> On 2023/8/31 17:06, Helge Deller wrote:
>> On 8/31/23 05:29, Shuai Xue wrote:
>>> On 2023/8/31 06:18, Will Deacon wrote:
>>>> On Mon, Aug 28, 2023 at 09:41:55AM +0800, Shuai Xue wrote:
>>>>> On 2023/8/22 09:15, Shuai Xue wrote:
>>>>>> On 2023/8/21 18:50, Will Deacon wrote:
>>>>>>>> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
>>>>>>>> index 3fe516b32577..38e2186882bd 100644
>>>>>>>> --- a/arch/arm64/mm/fault.c
>>>>>>>> +++ b/arch/arm64/mm/fault.c
>>>>>>>> @@ -679,6 +679,8 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
>>>>>>>>       } else if (fault & (VM_FAULT_HWPOISON_LARGE | VM_FAULT_HWPOISON)) {
>>>>>>>>           unsigned int lsb;
>>>>>>>>
>>>>>>>> +        pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
>>>>>>>> +               current->comm, current->pid, far);
>>>>>>>>           lsb = PAGE_SHIFT;
>>>>>>>>           if (fault & VM_FAULT_HWPOISON_LARGE)
>>>>>>>>               lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
>>>>>>>
>>>>>>> Hmm, I'm not convinced by this. We have 'show_unhandled_signals' already,
>>>>>>> and there's plenty of code in memory-failure.c for handling poisoned pages
>>>>>>> reported by e.g. GHES. I don't think dumping extra messages in dmesg from
>>>>>>> the arch code really adds anything.
>>>>>>
>>>>>> I see the show_unhandled_signals() will dump the stack but it rely on
>>>>>> /proc/sys/debug/exception-trace be set.
>>>>>>
>>>>>> The memory failure is the top issue in our production cloud and also other hyperscalers.
>>>>>> We have received complaints from our operations engineers and end users that processes
>>>>>> are being inexplicably killed :(. Could you please consider add a message?
>>>>
>>>> I don't have any objection to logging this stuff somehow, I'm just not
>>>> convinced that the console is the best place for that information in 2023.
>>>> Is there really nothing better?
>>
>>> I agree that console might not the better place, but it still plays an important role.
>>> IMO the most direct idea for end user to check what happened is to check by viewing
>>> the dmesg. In addition, we deployed some log store service collects all cluster dmesg
>>> from /var/log/kern.
>>
>> Right, pr_err() is not just console.
>> It ends up in the syslog, which ends up in a lot of places, e.g. through syslog forwarding.
>> Most monitoring tools monitor the syslog as well.
>>
>> So, IMHO pr_err() is the right thing.
>>
>> Helge
>>
> 
> Totally agreed.
> 
> Thank you.
> 
> Best Regards,
> Shuai
> 


Hi, Will,

Based our discussion in this thread, are you happy to queue this patch?

Thank you.
Best Regards,
Shuai