Re: [PATCH v2 10/12] preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITS

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Using `select HAS_SEPARATE_PREEMPT_RESCHED_BITS` in arch/x86/Kconfig violates Kconfig dependencies and causes build warnings when PREEMPT_COUNT is disabled.
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commit 0d7b7073a61462aad1916eef1d66b478cea3f90c
Author: Boqun Feng <boqun@kernel.org>

preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITS

This patch introduces HAS_SEPARATE_PREEMPT_RESCHED_BITS to allow architectures
with 64-bit preempt count support to keep NMI nesting bits in the 32-bit count,
avoiding the need for a separate cache line. It also enables this new
configuration for x86_64.

> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index f3f7cb01d69d0..bf8288b3d52be 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -327,6 +327,7 @@ config X86
>  	select USER_STACKTRACE_SUPPORT
>  	select HAVE_ARCH_KCSAN			if X86_64
>  	select PROC_PID_ARCH_STATUS		if PROC_FS
> +	select HAS_SEPARATE_PREEMPT_RESCHED_BITS		if X86_64

[Severity: Low]
Will this select cause a Kconfig warning about unmet direct dependencies when
PREEMPT_COUNT is disabled?

HAS_SEPARATE_PREEMPT_RESCHED_BITS depends on PREEMPT_COUNT and 64BIT, as
defined in kernel/Kconfig.preempt. Kconfig's select statement forces the target
symbol to 'y' without inheriting or checking its dependencies.

If the kernel is built with CONFIG_PREEMPT_NONE=y and lock debugging disabled
(leaving PREEMPT_COUNT disabled), this select will produce an unmet dependency
warning.

[ ... ]

> diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
> index 88c594c6d7fcd..35f546a042b10 100644
> --- a/kernel/Kconfig.preempt
> +++ b/kernel/Kconfig.preempt
> @@ -122,6 +122,10 @@ config PREEMPT_RT_NEEDS_BH_LOCK
>  config PREEMPT_COUNT
>         bool
>  
> +config HAS_SEPARATE_PREEMPT_RESCHED_BITS
> +	bool
> +	depends on PREEMPT_COUNT && 64BIT

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Sashiko AI review · https://sashiko.dev/#/patchset/20260526152148.30514-1-boqun@kernel.org?part=10