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

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Date:   Thu, 13 Apr 2023 11:02:44 +0100
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Pierre Gondois <pierre.gondois@....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 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?

Cheers,
Conor.

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