Re: [PATCH -next v5 08/22] arm64: entry: Use different helpers to check resched for PREEMPT_DYNAMIC

Mark Rutland
2025-02-10T12:17:45Z

On Fri, Dec 06, 2024 at 06:17:30PM +0800, Jinjie Ruan wrote:
> In generic entry, when PREEMPT_DYNAMIC is enabled or disabled, two
> different helpers are used to check whether resched is required
> and some common code is reused.
>
> In preparation for moving arm64 over to the generic entry code,
> use new helper to check resched when PREEMPT_DYNAMIC enabled and
> reuse common code for the disabled case.
>
> No functional changes.

Please fold this together with the last two patches; it's undoing
changes you made in patch 6, and it'd be far clearer to see that all at
once.

Mark.

>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
> arch/arm64/include/asm/preempt.h | 3 +++
> arch/arm64/kernel/entry-common.c | 21 +++++++++++----------
> 2 files changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h
> index d0f93385bd85..0f0ba250efe8 100644
> --- a/arch/arm64/include/asm/preempt.h
> +++ b/arch/arm64/include/asm/preempt.h
> @@ -93,11 +93,14 @@ void dynamic_preempt_schedule(void);
> #define __preempt_schedule() dynamic_preempt_schedule()
> void dynamic_preempt_schedule_notrace(void);
> #define __preempt_schedule_notrace() dynamic_preempt_schedule_notrace()
> +void dynamic_irqentry_exit_cond_resched(void);
> +#define irqentry_exit_cond_resched() dynamic_irqentry_exit_cond_resched()
>
> #else /* CONFIG_PREEMPT_DYNAMIC */
>
> #define __preempt_schedule() preempt_schedule()
> #define __preempt_schedule_notrace() preempt_schedule_notrace()
> +#define irqentry_exit_cond_resched() raw_irqentry_exit_cond_resched()
>
> #endif /* CONFIG_PREEMPT_DYNAMIC */
> #endif /* CONFIG_PREEMPTION */
> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> index 029f8bd72f8a..015a65d19b52 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -75,10 +75,6 @@ static noinstr irqentry_state_t enter_from_kernel_mode(struct pt_regs *regs)
> return state;
> }
>
> -#ifdef CONFIG_PREEMPT_DYNAMIC
> -DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
> -#endif
> -
> static inline bool arm64_need_resched(void)
> {
> /*
> @@ -106,17 +102,22 @@ static inline bool arm64_need_resched(void)
>
> void raw_irqentry_exit_cond_resched(void)
> {
> -#ifdef CONFIG_PREEMPT_DYNAMIC
> - if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
> - return;
> -#endif
> -
> if (!preempt_count()) {
> if (need_resched() && arm64_need_resched())
> preempt_schedule_irq();
> }
> }
>
> +#ifdef CONFIG_PREEMPT_DYNAMIC
> +DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
> +void dynamic_irqentry_exit_cond_resched(void)
> +{
> + if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
> + return;
> + raw_irqentry_exit_cond_resched();
> +}
> +#endif
> +
> /*
> * Handle IRQ/context state management when exiting to kernel mode.
> * After this function returns it is not safe to call regular kernel code,
> @@ -140,7 +141,7 @@ static __always_inline void __exit_to_kernel_mode(struct pt_regs *regs,
> }
>
> if (IS_ENABLED(CONFIG_PREEMPTION))
> - raw_irqentry_exit_cond_resched();
> + irqentry_exit_cond_resched();
>
> trace_hardirqs_on();
> } else {
> --
> 2.34.1
>