[PATCH v2] powerpc/imc: Dont create debugfs files for cpu-less nodes

[Michael Ellerman]

Anju T Sudhakar <anju at linux.vnet.ibm.com> writes:
> Hi Qian,
>
> On 7/16/19 12:11 AM, Qian Cai wrote:
>> On Thu, 2019-07-11 at 14:53 +1000, Michael Ellerman wrote:
>>> Hi Maddy,
>>>
>>> Madhavan Srinivasan <maddy at linux.vnet.ibm.com> writes:
>>>> diff --git a/arch/powerpc/platforms/powernv/opal-imc.c
>>>> b/arch/powerpc/platforms/powernv/opal-imc.c
>>>> index 186109bdd41b..e04b20625cb9 100644
>>>> --- a/arch/powerpc/platforms/powernv/opal-imc.c
>>>> +++ b/arch/powerpc/platforms/powernv/opal-imc.c
>>>> @@ -69,20 +69,20 @@ static void export_imc_mode_and_cmd(struct device_node
>>>> *node,
>>>>   	if (of_property_read_u32(node, "cb_offset", &cb_offset))
>>>>   		cb_offset = IMC_CNTL_BLK_OFFSET;
>>>>   
>>>> -	for_each_node(nid) {
>>>> -		loc = (u64)(pmu_ptr->mem_info[chip].vbase) + cb_offset;
>>>> +	while (ptr->vbase != NULL) {
>>> This means you'll bail out as soon as you find a node with no vbase, but
>>> it's possible we could have a CPU-less node intermingled with other
>>> nodes.
>>>
>>> So I think you want to keep the for loop, but continue if you see a NULL
>>> vbase?
>> Not sure if this will also takes care of some of those messages during the boot
>> on today's linux-next even without this patch.
>>
>>
>> [   18.077780][    T1] debugfs: Directory 'imc' with parent 'powerpc' already
>> present!
>>
>>
>
> This is introduced by a recent commit: c33d442328f55 (debugfs: make 
> error message a bit more verbose).
>
> So basically, the debugfs imc_* file is created per node, and is created 
> by the first nest unit which is
>
> being registered. For the subsequent nest units, debugfs_create_dir() 
> will just return since the imc_* file already
>
> exist.
>
> The commit "c33d442328f55 (debugfs: make error message a bit more 
> verbose)", prints
>
> a message if the debugfs file already exists in debugfs_create_dir(). 
> That is why we are encountering these
>
> messages now.
>
>
> This patch (i.e, powerpc/imc: Dont create debugfs files for cpu-less 
> nodes) will address the initial issue, i.e
>
> "numa crash while reading imc_* debugfs files for cpu less nodes", and 
> will not address these debugfs messages.
>
>
> But yeah this is a good catch. We can have some checks to avoid these 
> debugfs messages.
>
>
> Hi Michael,
>
> Do we need to have a separate patch to address these debugfs messages, 
> or can we address the same
>
> in the next version of this patch itself?

No, please do one logical change per patch.

cheers