Re: [PATCH v7 1/3] cacheinfo: Allocate memory during CPU hotplug if not done from the primary CPU

[Borislav Petkov]

On Fri, Sep 13, 2024 at 01:31:53AM -0700, Ricardo Neri wrote:
> The motivation for commit 5944ce092b97 was to prevent a BUG splat in
> PREEMPT_RT kernels during memory allocation. This splat is not observed on
> x86 because the memory allocation for cacheinfo happens in
> detect_cache_attributes() from the cacheinfo CPU hotplug callback.
> 
> The dereference of a NULL cacheinfo is not observed today because
> cache_leaves(cpu) is zero until after init_cache_level() is called
> (during the CPU hotplug callback). A subsequent changeset will set
> the number of cache leaves earlier and the NULL-pointer dereference
> will be observed.

Lemme get this straight: this NULL ptr deref will happen after your changes so
we don't really need this patch in stable and thus no Fixes: tag at all,
right?

-- 
Regards/Gruss,
    Boris.

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