Re: [PATCH 1/3] drivers/edac: Add L1 and L2 error detection for A72

[Vijay Balakrishna <vijayb@linux.microsoft.com>]

On 5/20/2025 1:04 PM, Borislav Petkov wrote:
> On Tue, May 20, 2025 at 12:54:32PM -0700, Vijay Balakrishna wrote:
>> On 5/20/2025 9:09 AM, Vijay Balakrishna wrote:
>>> On 5/19/2025 1:51 AM, Borislav Petkov wrote:
>>>> I'd venture a guess you need to protect here against CPU hotplug...
>>>>
>>>>> +    for_each_cpu_and(cpu, cpu_online_mask, &compat_mask) {
>>>>> +        smp_call_function_single(cpu, read_errors, &merrsr, true);
>>>>> +        report_errors(edac_ctl, cpu, &merrsr);
>>>>> +    }
>>>>> +}
>>>>> +
>>>
>>> Hi Boris,
>>>
>>> I appreciate you highlighting the CPU hotplug issue. Upon further review
>>> of surrounding code, I realized we must ensure that the data passed to
>>> read_errors() is per-CPU.
>>
>> Actually, per-CPU data not needed as we are passing true -- wait until
>> function has completed on other CPUs.
> 
> What happens if @cpu above gets offlined right before you do
> smp_call_function_single() ?

We can see inconsistent behavior or kernel crash/hang. You are correct, 
we need to protect against CPU hotplug. I will add 
cpus_read_lock()/cpus_read_unlock().

Thanks,
Vijay