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

[Pierre Gondois]

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@xxxxxxxxxx>
>
> 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@xxxxxxxxxx/conor.dooley@xxxxxxxxxxxxx/
>
> > Link: https://lore.kernel.org/all/20230404-hatred-swimmer-6fecdf33b57a@spud/
> > Signed-off-by: Pierre Gondois <pierre.gondois@xxxxxxx>
> > ---
> >   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