Re: [RFC PATCH 08/86] Revert "arm64: Support PREEMPT_DYNAMIC"

[Mark Rutland]

On Tue, Nov 07, 2023 at 01:56:54PM -0800, Ankur Arora wrote:
> This reverts commit 1b2d3451ee50a0968cb9933f726e50b368ba5073.

As the author of the commit being reverted, I'd appreciate being Cc'd on
subsequent versions of this patch (and ideally, for the series as a whole).

Mark.

> 
> Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
> ---
>  arch/arm64/Kconfig               |  1 -
>  arch/arm64/include/asm/preempt.h | 19 ++-----------------
>  arch/arm64/kernel/entry-common.c | 10 +---------
>  3 files changed, 3 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 78f20e632712..856d7be2ee45 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -221,7 +221,6 @@ config ARM64
>  	select HAVE_PERF_EVENTS_NMI if ARM64_PSEUDO_NMI
>  	select HAVE_PERF_REGS
>  	select HAVE_PERF_USER_STACK_DUMP
> -	select HAVE_PREEMPT_DYNAMIC_KEY
>  	select HAVE_REGS_AND_STACK_ACCESS_API
>  	select HAVE_POSIX_CPU_TIMERS_TASK_WORK
>  	select HAVE_FUNCTION_ARG_ACCESS_API
> diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h
> index 0159b625cc7f..e83f0982b99c 100644
> --- a/arch/arm64/include/asm/preempt.h
> +++ b/arch/arm64/include/asm/preempt.h
> @@ -2,7 +2,6 @@
>  #ifndef __ASM_PREEMPT_H
>  #define __ASM_PREEMPT_H
>  
> -#include <linux/jump_label.h>
>  #include <linux/thread_info.h>
>  
>  #define PREEMPT_NEED_RESCHED	BIT(32)
> @@ -81,24 +80,10 @@ static inline bool should_resched(int preempt_offset)
>  }
>  
>  #ifdef CONFIG_PREEMPTION
> -
>  void preempt_schedule(void);
> +#define __preempt_schedule() preempt_schedule()
>  void preempt_schedule_notrace(void);
> -
> -#ifdef CONFIG_PREEMPT_DYNAMIC
> -
> -DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
> -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()
> -
> -#else /* CONFIG_PREEMPT_DYNAMIC */
> -
> -#define __preempt_schedule()		preempt_schedule()
> -#define __preempt_schedule_notrace()	preempt_schedule_notrace()
> -
> -#endif /* CONFIG_PREEMPT_DYNAMIC */
> +#define __preempt_schedule_notrace() preempt_schedule_notrace()
>  #endif /* CONFIG_PREEMPTION */
>  
>  #endif /* __ASM_PREEMPT_H */
> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> index 0fc94207e69a..5d9c9951562b 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -225,17 +225,9 @@ static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs)
>  		lockdep_hardirqs_on(CALLER_ADDR0);
>  }
>  
> -#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 void __sched arm64_preempt_schedule_irq(void)
>  {
> -	if (!need_irq_preemption())
> +	if (!IS_ENABLED(CONFIG_PREEMPTION))
>  		return;
>  
>  	/*
> -- 
> 2.31.1
>