Re: [PATCH -next v7 5/7] arm64: entry: Refactor preempt_schedule_irq() check code

[Jinjie Ruan <ruanjinjie@xxxxxxxxxx>]

On 2025/8/12 0:02, Ada Couprie Diaz wrote:
> On 29/07/2025 02:54, Jinjie Ruan wrote:
> 
>> ARM64 requires an additional check whether to reschedule on return
>> from interrupt. So add arch_irqentry_exit_need_resched() as the default
>> NOP implementation and hook it up into the need_resched() condition in
>> raw_irqentry_exit_cond_resched(). This allows ARM64 to implement
>> the architecture specific version for switching over to
>> the generic entry code.
>>
>> To align the structure of the code with irqentry_exit_cond_resched()
>> from the generic entry code, hoist the need_irq_preemption()
>> and IS_ENABLED() check earlier. And different preemption check functions
>> are defined based on whether dynamic preemption is enabled.
>>
>> Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
>> Suggested-by: Kevin Brodsky <kevin.brodsky@xxxxxxx>
>> Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>> Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
>> ---
> Unrelated to the other thread : I noticed that compiling this patch
> with `allnoconfig` would fail :
> - `raw_irqentry_exit_cond_resched` has no previous prototype,
>   as it is defined within `#ifdef CONFIG_PREEMPTION`
> - `irqentry_exit_cond_resched()` is not declared, as it is also within
>   `#ifdef CONFIG_PREEMPTION`

You are right, thank you! I'll fix it.

> 
> The patch below fixes the issue, but introduces merge conflicts in
> patches 6 and 7, plus the `#ifdef` needs to be moved accordingly
> in patch 6 and the empty "without preemption" `irq_exit_cond_resched()`
> needs to be removed in patch 7.
> 
> I hope this can be useful,
> Ada
> 
> ---
> diff --git a/arch/arm64/include/asm/preempt.h
> b/arch/arm64/include/asm/preempt.h
> index 0f0ba250efe8..d9aba8b1e466 100644
> --- a/arch/arm64/include/asm/preempt.h
> +++ b/arch/arm64/include/asm/preempt.h
> @@ -103,6 +103,8 @@ void dynamic_irqentry_exit_cond_resched(void);
>  #define irqentry_exit_cond_resched() raw_irqentry_exit_cond_resched()
> 
>  #endif /* CONFIG_PREEMPT_DYNAMIC */
> +#else /* CONFIG_PREEMPTION */
> +#define irqentry_exit_cond_resched() {}
>  #endif /* CONFIG_PREEMPTION */
> 
>  #endif /* __ASM_PREEMPT_H */
> diff --git a/arch/arm64/kernel/entry-common.c
> b/arch/arm64/kernel/entry-common.c
> index 4f92664fd46c..abd7a315145e 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -661,6 +661,7 @@ static __always_inline void __el1_pnmi(struct
> pt_regs *regs,
>         arm64_exit_nmi(regs, state);
>  }
> 
> +#ifdef CONFIG_PREEMPTION
>  void raw_irqentry_exit_cond_resched(void)
>  {
>         if (!preempt_count()) {
> @@ -668,6 +669,7 @@ void raw_irqentry_exit_cond_resched(void)
>                         preempt_schedule_irq();
>         }
>  }
> +#endif
> 
>  #ifdef CONFIG_PREEMPT_DYNAMIC
>  DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
> 
>