Re: [PATCH v2 2/3] sched: make migrate_enable/migrate_disable inline

[Peter Zijlstra]

On Tue, Aug 19, 2025 at 09:58:31AM +0800, Menglong Dong wrote:

> The "struct rq" is not available in include/linux/sched.h, so we can't
> access the "runqueues" with this_cpu_ptr(), as the compilation will fail
> in this_cpu_ptr() -> raw_cpu_ptr() -> __verify_pcpu_ptr():
>   typeof((ptr) + 0)
> 
> So we introduce the this_rq_raw() and access the runqueues with
> arch_raw_cpu_ptr() directly.

^ That, wants to be a comment near here:

> @@ -2312,4 +2315,78 @@ static __always_inline void alloc_tag_restore(struct alloc_tag *tag, struct allo
>  #define alloc_tag_restore(_tag, _old)		do {} while (0)
>  #endif
>  
> +#ifndef COMPILE_OFFSETS
> +
> +extern void __migrate_enable(void);
> +
> +struct rq;
> +DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
> +
> +#ifdef CONFIG_SMP
> +#define this_rq_raw() arch_raw_cpu_ptr(&runqueues)
> +#else
> +#define this_rq_raw() PERCPU_PTR(&runqueues)
> +#endif

Because that arch_ thing really is weird.

> +	(*(unsigned int *)((void *)this_rq_raw() + RQ_nr_pinned))--;
> +	(*(unsigned int *)((void *)this_rq_raw() + RQ_nr_pinned))++;

And since you did a macro anyway, why not fold that magic in there,
instead of duplicating it?

#define __this_rq_raw()  ((void *)arch_raw_cpu_ptr(&runqueues))
#define this_rq_pinned() (*(unsigned int *)(__this_rq_raw() + RQ_nr_pinned))

	this_rq_pinned()--;
	this_rq_pinned()++;

is nicer, no?