Re: [PATCH v9 02/24] x86/resctrl: kfree() rmid_ptrs from resctrl_exit()

[David Hildenbrand]

On 13.02.24 19:44, James Morse wrote:
> rmid_ptrs[] is allocated from dom_data_init() but never free()d.
>
> While the exit text ends up in the linker script's DISCARD section,
> the direction of travel is for resctrl to be/have loadable modules.
>
> Add resctrl_put_mon_l3_config() to cleanup any memory allocated
> by rdt_get_mon_l3_config().
>
> There is no reason to backport this to a stable kernel.
>
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> Tested-by: Babu Moger <babu.moger@xxxxxxx>
> Tested-by: Carl Worth <carl@xxxxxxxxxxxxxxxxxxxxxx> # arm64
> Reviewed-by: Babu Moger <babu.moger@xxxxxxx>
> ---

[...]


> +static void __exit dom_data_exit(void)
> +{
> +	mutex_lock(&rdtgroup_mutex);
> +
> +	kfree(rmid_ptrs);
> +	rmid_ptrs = NULL;
> +
> +	mutex_unlock(&rdtgroup_mutex);

Just curious: is grabbing that mutex really required?

Against which race are we trying to protect ourselves?

I suspect this mutex is not required here: if we could racing with 
someone else, likely freeing that memory would not be safe either.

Apart from that LGTM.

--
Cheers,

David / dhildenb