Re: [PATCH] mips: mm: Call rcutree_report_cpu_starting() even earlier

[Maciej W. Rozycki]

On Tue, 7 Apr 2026, Stefan Wiehler wrote:

> diff --git a/arch/mips/mm/tlb-r4k.c b/arch/mips/mm/tlb-r4k.c
> index 24fe85fa169d..49cb5262df1e 100644
> --- a/arch/mips/mm/tlb-r4k.c
> +++ b/arch/mips/mm/tlb-r4k.c
> @@ -744,12 +745,18 @@ static void __ref r4k_tlb_uniquify_write(struct tlbent *tlb_vpns, int tlbsize)
>   */
>  static void __ref r4k_tlb_uniquify(void)
>  {
> +	unsigned int cpu = raw_smp_processor_id();
>  	int tlbsize = current_cpu_data.tlbsize;
>  	bool use_slab = slab_is_available();
> +	static bool secondary = false;
>  	phys_addr_t tlb_vpn_size;
>  	struct tlbent *tlb_vpns;
>  
>  	tlb_vpn_size = tlbsize * sizeof(*tlb_vpns);
> +	if (secondary)
> +		rcu_cpu_starting(cpu);
> +	else
> +		secondary = true;

 You could use `use_slab' to figure out whether it is a secondary CPU, but 
the right fix AFAICT is to reorder the `rcutree_report_cpu_starting' ahead 
of `per_cpu_trap_init' in `start_secondary', possibly even to the start of 
the function (does it rely on any of the initialisation done earlier on?).

 NB is `rcu_cpu_starting' the right function call to make, and where does 
`cpu' come from here?

 Thanks for the report!

  Maciej