Re: [PATCH v2 4/6] sched: dynamic: Simplify irqentry_exit_cond_resched()

[Jinjie Ruan]

在 2026/8/4 3:17, Mark Rutland 写道:
> PREEMPT_DYNAMIC is now limited to the FULL and LAZY preemption models.
> In either model, irqentry_exit_cond_resched() is always called and never
> disabled.

Hi Mark,

Is it necessary to mention that all architectures supporting generic irq
entry support PREEMPT_DYNAMIC?

> 
> Remove the unnecessary code for this when PREEMPT_DYNAMIC is selected.
> 
> Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
> Reviewed-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
> Cc: Frederic Weisbecker <frederic@xxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: John Stultz <jstultz@xxxxxxxxxx>
> Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
> Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
> ---
>  include/linux/irq-entry-common.h | 17 +----------------
>  kernel/entry/common.c            | 17 ++---------------
>  kernel/sched/core.c              |  7 -------
>  3 files changed, 3 insertions(+), 38 deletions(-)
> 
> diff --git a/include/linux/irq-entry-common.h b/include/linux/irq-entry-common.h
> index 1fabf0f5ea8e7..de7e10de91d04 100644
> --- a/include/linux/irq-entry-common.h
> +++ b/include/linux/irq-entry-common.h
> @@ -346,22 +346,7 @@ typedef struct irqentry_state {
>   *
>   * Conditional reschedule with additional sanity checks.
>   */
> -void raw_irqentry_exit_cond_resched(void);
> -
> -#ifdef CONFIG_PREEMPT_DYNAMIC
> -#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
> -#define irqentry_exit_cond_resched_dynamic_enabled	raw_irqentry_exit_cond_resched
> -#define irqentry_exit_cond_resched_dynamic_disabled	NULL
> -DECLARE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
> -#define irqentry_exit_cond_resched()	static_call(irqentry_exit_cond_resched)()
> -#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
> -DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
> -void dynamic_irqentry_exit_cond_resched(void);
> -#define irqentry_exit_cond_resched()	dynamic_irqentry_exit_cond_resched()
> -#endif
> -#else /* CONFIG_PREEMPT_DYNAMIC */
> -#define irqentry_exit_cond_resched()	raw_irqentry_exit_cond_resched()
> -#endif /* CONFIG_PREEMPT_DYNAMIC */
> +void irqentry_exit_cond_resched(void);
>  
>  /**
>   * irqentry_enter_from_kernel_mode - Establish state before invoking the irq handler
> diff --git a/kernel/entry/common.c b/kernel/entry/common.c
> index e3d381fd3d251..e234b04373fea 100644
> --- a/kernel/entry/common.c
> +++ b/kernel/entry/common.c
> @@ -123,7 +123,7 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
>  /**
>   * arch_irqentry_exit_need_resched - Architecture specific need resched function
>   *
> - * Invoked from raw_irqentry_exit_cond_resched() to check if resched is needed.
> + * Invoked from irqentry_exit_cond_resched() to check if resched is needed.
>   * Defaults return true.
>   *
>   * The main purpose is to permit arch to avoid preemption of a task from an IRQ.
> @@ -134,7 +134,7 @@ static inline bool arch_irqentry_exit_need_resched(void);
>  static inline bool arch_irqentry_exit_need_resched(void) { return true; }
>  #endif
>  
> -void raw_irqentry_exit_cond_resched(void)
> +void irqentry_exit_cond_resched(void)
>  {
>  	if (!preempt_count()) {
>  		/* Sanity check RCU and thread stack */
> @@ -145,19 +145,6 @@ void raw_irqentry_exit_cond_resched(void)
>  			preempt_schedule_irq();
>  	}
>  }

Otherwise, LGTM
Reviewed-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>

> -#ifdef CONFIG_PREEMPT_DYNAMIC
> -#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
> -DEFINE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
> -#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
> -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
> -#endif
>  
>  noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
>  {
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index f88b9ef70a0dd..4f754f4a472f8 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7788,9 +7788,6 @@ EXPORT_SYMBOL(__cond_resched_rwlock_write);
>  # endif
>  
>  /*
> - * SC:irqentry_exit_cond_resched
> - *
> - *
>   * NONE:
>   *   (unselectable)
>   *
> @@ -7798,11 +7795,9 @@ EXPORT_SYMBOL(__cond_resched_rwlock_write);
>   *   (unselectable)
>   *
>   * FULL:
> - *   irqentry_exit_cond_resched <- irqentry_exit_cond_resched
>   *   dynamic_preempt_lazy       <- false
>   *
>   * LAZY:
> - *   irqentry_exit_cond_resched <- irqentry_exit_cond_resched
>   *   dynamic_preempt_lazy       <- true
>   */
>  
> @@ -7846,14 +7841,12 @@ static void __sched_dynamic_update(int mode)
>  {
>  	switch (mode) {
>  	case preempt_dynamic_full:
> -		preempt_dynamic_enable(irqentry_exit_cond_resched);
>  		preempt_dynamic_key_disable(preempt_lazy);
>  		if (mode != preempt_dynamic_mode)
>  			pr_info("Dynamic Preempt: full\n");
>  		break;
>  
>  	case preempt_dynamic_lazy:
> -		preempt_dynamic_enable(irqentry_exit_cond_resched);
>  		preempt_dynamic_key_enable(preempt_lazy);
>  		if (mode != preempt_dynamic_mode)
>  			pr_info("Dynamic Preempt: lazy\n");