Re: [PATCH -next v5 06/22] arm64: entry: Expand the need_irq_preemption() macro ahead

Mark Rutland
2025-02-10T12:17:44Z

On Fri, Dec 06, 2024 at 06:17:28PM +0800, Jinjie Ruan wrote:
> The generic entry has the same logic as need_irq_preemption()
> macro and use a helper function to check other resched condition.
>
> In preparation for moving arm64 over to the generic entry code,
> check and expand need_irq_preemption() ahead and extract arm64 resched
> check code to a helper function.

I think this is just saying that the goal is to align the structure of
the code with raw_irqentry_exit_cond_resched() from the generic entry
code.

It'd be a bit clearer to say that, and to do this *before* moving the
call into __exit_to_kernel_mode().

Mark.

>
> No functional changes.
>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
> arch/arm64/include/asm/preempt.h | 1 +
> arch/arm64/kernel/entry-common.c | 28 +++++++++++++++++-----------
> 2 files changed, 18 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h
> index 0159b625cc7f..d0f93385bd85 100644
> --- a/arch/arm64/include/asm/preempt.h
> +++ b/arch/arm64/include/asm/preempt.h
> @@ -85,6 +85,7 @@ static inline bool should_resched(int preempt_offset)
> void preempt_schedule(void);
> void preempt_schedule_notrace(void);
>
> +void raw_irqentry_exit_cond_resched(void);
> #ifdef CONFIG_PREEMPT_DYNAMIC
>
> DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> index efd1a990d138..80b47ca02db2 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -77,17 +77,10 @@ static noinstr irqentry_state_t enter_from_kernel_mode(struct pt_regs *regs)
>
> #ifdef CONFIG_PREEMPT_DYNAMIC
> DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
> -#define need_irq_preemption() \
> - (static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
> -#else
> -#define need_irq_preemption() (IS_ENABLED(CONFIG_PREEMPTION))
> #endif
>
> static inline bool arm64_need_resched(void)
> {
> - if (!need_irq_preemption())
> - return false;
> -
> /*
> * DAIF.DA are cleared at the start of IRQ/FIQ handling, and when GIC
> * priority masking is used the GIC irqchip driver will clear DAIF.IF
> @@ -111,6 +104,22 @@ static inline bool arm64_need_resched(void)
> return true;
> }
>
> +void raw_irqentry_exit_cond_resched(void)
> +{
> +#ifdef CONFIG_PREEMPT_DYNAMIC
> + if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
> + return;
> +#else
> + if (!IS_ENABLED(CONFIG_PREEMPTION))
> + return;
> +#endif
> +
> + if (!preempt_count()) {
> + if (need_resched() && arm64_need_resched())
> + preempt_schedule_irq();
> + }
> +}
> +
> /*
> * Handle IRQ/context state management when exiting to kernel mode.
> * After this function returns it is not safe to call regular kernel code,
> @@ -133,10 +142,7 @@ static __always_inline void __exit_to_kernel_mode(struct pt_regs *regs,
> return;
> }
>
> - if (!preempt_count() && need_resched()) {
> - if (arm64_need_resched())
> - preempt_schedule_irq();
> - }
> + raw_irqentry_exit_cond_resched();
>
> trace_hardirqs_on();
> } else {
> --
> 2.34.1
>