linux-kernel - Re: [PATCH v3 3/4] arch_topology: Remove early cacheinfo error message

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Date:   Thu, 13 Apr 2023 17:25:25 +0200
From:   Pierre Gondois <pierre.gondois@....com>
To:     Conor Dooley <conor.dooley@...rochip.com>
Cc:     linux-kernel@...r.kernel.org, Radu Rendec <rrendec@...hat.com>,
        Alexandre Ghiti <alexghiti@...osinc.com>,
        Will Deacon <will@...nel.org>, Conor Dooley <conor@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Gavin Shan <gshan@...hat.com>
Subject: Re: [PATCH v3 3/4] arch_topology: Remove early cacheinfo error
 message



On 4/13/23 12:02, Conor Dooley wrote:
> On Thu, Apr 13, 2023 at 11:14:33AM +0200, Pierre Gondois wrote:
>> fetch_cache_info() tries to get the number of cache leaves/levels
>> for each CPU in order to pre-allocate memory for cacheinfo struct.
>> Allocating this memory later triggers a:
>>    'BUG: sleeping function called from invalid context'
>> in PREEMPT_RT kernels.
>>
>> If there is no cache related information available in DT or ACPI,
>> fetch_cache_info() fails and an error message is printed:
>>    'Early cacheinfo failed, ret = ...'
>>
>> Not having cache information should be a valid configuration.
>> Remove the error message if fetch_cache_info() fails.
>>
>> Suggested-by: Conor Dooley <conor@...nel.org>
> 
> Not that it really matters for suggested-by, and there's no way really
> for you to know, but the corporate overlords prefer:
> s/conor@...nel.org/conor.dooley@...rochip.com/
> 
>> Link: https://lore.kernel.org/all/20230404-hatred-swimmer-6fecdf33b57a@spud/
>> Signed-off-by: Pierre Gondois <pierre.gondois@....com>
>> ---
>>   drivers/base/arch_topology.c | 4 +---
>>   1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
>> index b1c1dd38ab01..1f071eaede5b 100644
>> --- a/drivers/base/arch_topology.c
>> +++ b/drivers/base/arch_topology.c
>> @@ -843,10 +843,8 @@ void __init init_cpu_topology(void)
>>   
>>   	for_each_possible_cpu(cpu) {
>>   		ret = fetch_cache_info(cpu);
>> -		if (ret) {
>> -			pr_err("Early cacheinfo failed, ret = %d\n", ret);
> 
> Hmm do you really want to remove the print altogether? This can fail
> with -EINVAL and -ENOMEM too, so should we just check for
> | if (ret && ret != -ENOENT)
> instead, since in the other cases it really did fail?

I think [PATCH 2/4] requires the following update in this case:

--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -288,8 +288,10 @@ int init_of_cache_level(unsigned int cpu)
         struct device_node *prev = NULL;
         unsigned int levels = 0, leaves, level;
  
-       if (!of_check_cache_nodes(np))
-               goto err_out;
+       if (!of_check_cache_nodes(np)) {
+               of_node_put(np);
+               return -ENOENT;
+       }
  
         leaves = of_count_cache_leaves(np);
         if (leaves > 0)

Is it ok to do this and keep your Reviewed-by ?

Thanks for the review,
Regards,
Pierre