Re: [PATCH v4 12/17] s390/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS

Shrikanth Hegde <[email protected]> Wed, 5 Aug 2026 01:57:04 +0530

Newsgroups	org.kernel.vger.rust-for-linux,org.kernel.vger.linux-kernel
Message-ID	<[email protected]>

+maddy, christophe,

On 8/4/26 9:44 PM, Boqun Feng wrote:
> From: Heiko Carstens <[email protected]>
> 
> Convert s390's preempt_count to 64 bit, and change the preempt
> primitives accordingly.
> 

> +	union {
> +		struct {
> +			__u32	need_resched;	/* 0x03a8 */
> +			__u32	count;		/* 0x03ac */
> +		} preempt;
> +		__u64	preempt_count;		/* 0x03a8 */
> +	};

This is interesting. So arm64, s390 will have similar implementation
w.r.t to preempt_count.

I guess PoC that i was trying for ppc64 is worth pursuing even more,
since ppc64 is one missing major arch which still uses old method
of querying tif_need_resched.
With similar change ppc64 can set HAS_SEPARATE_PREEMPT_RESCHED_BITS too.