Re: [PATCH 12/24] s390/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS

[Peter Zijlstra <peterz@infradead.org>]

On Fri, Jul 31, 2026 at 01:30:13PM -0700, Boqun Feng wrote:

> @@ -26,25 +23,25 @@
>   */
>  static __always_inline int preempt_count(void)
>  {
> -	unsigned long lc_preempt, count;
> +	unsigned long lc_preempt;
> +	int count;
>  
> -	BUILD_BUG_ON(sizeof_field(struct lowcore, preempt_count) != sizeof(int));
> -	lc_preempt = offsetof(struct lowcore, preempt_count);
> +	lc_preempt = offsetof(struct lowcore, preempt.count);
>  	/* READ_ONCE(get_lowcore()->preempt_count) & ~PREEMPT_NEED_RESCHED */

If I'm not mistaken, this comment is no longer accurate, since
NEED_RESCHED lives in the high word and you're only loading the low
word.

>  	asm_inline(
> -		ALTERNATIVE("llgt	%[count],%[offzero](%%r0)\n",
> -			    "llgt	%[count],%[offalt](%%r0)\n",
> +		ALTERNATIVE("ly		%[count],%[offzero](%%r0)\n",
> +			    "ly		%[count],%[offalt](%%r0)\n",
>  			    ALT_FEATURE(MFEATURE_LOWCORE))
>  		: [count] "=d" (count)
>  		: [offzero] "i" (lc_preempt),
>  		  [offalt] "i" (lc_preempt + LOWCORE_ALT_ADDRESS),
> -		  "m" (((struct lowcore *)0)->preempt_count));
> +		  "m" (((struct lowcore *)0)->preempt.count));
>  	return count;
>  }