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

On Mon, Aug 03, 2026 at 02:42:18PM +0200, Heiko Carstens wrote:
> On Mon, Aug 03, 2026 at 01:40:32PM +0200, Peter Zijlstra wrote:
> > 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.
> 
> True. Something like
> 
>   	/* READ_ONCE(get_lowcore()->preempt.count) (without PREEMPT_NEED_RESCHED) */
> 
> might be better.
> 

Thanks, I will update it.

Regards,
Boqun

> > >  	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;
> > >  }