Re: [PATCH v2 2/6] sched: dynamic: Simplify {cond,might}_resched()

[Jinjie Ruan <ruanjinjie@huawei.com>]

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, both cond_resched() and might_resched() are always
> disabled and do nothing.
> 
> Remove the unnecessary code for these when PREEMPT_DYNAMIC is selected.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
> Cc: Frederic Weisbecker <frederic@kernel.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: John Stultz <jstultz@google.com>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Shrikanth Hegde <sshegde@linux.ibm.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Valentin Schneider <vschneid@redhat.com>
> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> ---
>  include/linux/kernel.h | 20 -------------------
>  include/linux/sched.h  | 31 +++--------------------------
>  kernel/sched/core.c    | 44 +-----------------------------------------
>  3 files changed, 4 insertions(+), 91 deletions(-)
> 
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index e5570a16cbb1a..533ee1e6e1cb7 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -43,30 +43,10 @@ struct completion;
>  struct user;
>  
>  #ifdef CONFIG_PREEMPT_VOLUNTARY_BUILD
> -
>  extern int __cond_resched(void);
>  # define might_resched() __cond_resched()
> -
> -#elif defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
> -
> -extern int __cond_resched(void);
> -
> -DECLARE_STATIC_CALL(might_resched, __cond_resched);
> -
> -static __always_inline void might_resched(void)
> -{
> -	static_call_mod(might_resched)();
> -}
> -
> -#elif defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
> -
> -extern int dynamic_might_resched(void);
> -# define might_resched() dynamic_might_resched()
> -
>  #else
> -
>  # define might_resched() do { } while (0)
> -
>  #endif /* CONFIG_PREEMPT_* */
>  
>  #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 373bcc0598d10..1a44c5261c2dd 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2119,44 +2119,19 @@ static inline void set_need_resched_current(void)
>   * value indicates whether a reschedule was done in fact.
>   * cond_resched_lock() will drop the spinlock before scheduling,
>   */
> -#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
> +#if !defined(CONFIG_PREEMPTION)
>  extern int __cond_resched(void);
>  
> -#if defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
> -
> -DECLARE_STATIC_CALL(cond_resched, __cond_resched);
> -
> -static __always_inline int _cond_resched(void)
> -{
> -	return static_call_mod(cond_resched)();
> -}
> -
> -#elif defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
> -
> -extern int dynamic_cond_resched(void);
> -
> -static __always_inline int _cond_resched(void)
> -{
> -	return dynamic_cond_resched();
> -}
> -
> -#else /* !CONFIG_PREEMPTION */
> -
>  static inline int _cond_resched(void)
>  {
>  	return __cond_resched();
>  }
> -
> -#endif /* PREEMPT_DYNAMIC && CONFIG_HAVE_PREEMPT_DYNAMIC_CALL */
> -
> -#else /* CONFIG_PREEMPTION && !CONFIG_PREEMPT_DYNAMIC */
> -
> +#else
>  static inline int _cond_resched(void)
>  {
>  	return 0;
>  }
> -
> -#endif /* !CONFIG_PREEMPTION || CONFIG_PREEMPT_DYNAMIC */
> +#endif
>  
>  #define cond_resched() ({			\
>  	__might_resched(__FILE__, __LINE__, 0);	\
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 2db78826a484b..84ec93694d718 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7733,7 +7733,7 @@ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
>  }
>  #endif /* CONFIG_RT_MUTEXES */
>  
> -#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
> +#if !defined(CONFIG_PREEMPTION)
>  int __sched __cond_resched(void)
>  {
>  	if (should_resched(0) && !irqs_disabled()) {
> @@ -7761,38 +7761,6 @@ int __sched __cond_resched(void)
>  EXPORT_SYMBOL(__cond_resched);
>  #endif
>  
> -#ifdef CONFIG_PREEMPT_DYNAMIC
> -# ifdef CONFIG_HAVE_PREEMPT_DYNAMIC_CALL
> -#  define cond_resched_dynamic_enabled	__cond_resched
> -#  define cond_resched_dynamic_disabled	((void *)&__static_call_return0)
> -DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched);
> -EXPORT_STATIC_CALL_TRAMP(cond_resched);
> -
> -#  define might_resched_dynamic_enabled	__cond_resched
> -#  define might_resched_dynamic_disabled ((void *)&__static_call_return0)
> -DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched);
> -EXPORT_STATIC_CALL_TRAMP(might_resched);
> -# elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
> -static DEFINE_STATIC_KEY_FALSE(sk_dynamic_cond_resched);
> -int __sched dynamic_cond_resched(void)
> -{
> -	if (!static_branch_unlikely(&sk_dynamic_cond_resched))
> -		return 0;
> -	return __cond_resched();
> -}
> -EXPORT_SYMBOL(dynamic_cond_resched);
> -
> -static DEFINE_STATIC_KEY_FALSE(sk_dynamic_might_resched);
> -int __sched dynamic_might_resched(void)
> -{
> -	if (!static_branch_unlikely(&sk_dynamic_might_resched))
> -		return 0;
> -	return __cond_resched();
> -}
> -EXPORT_SYMBOL(dynamic_might_resched);
> -# endif
> -#endif /* CONFIG_PREEMPT_DYNAMIC */
> -
>  /*
>   * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
>   * call schedule, and on return reacquire the lock.
> @@ -7862,8 +7830,6 @@ EXPORT_SYMBOL(__cond_resched_rwlock_write);
>  # endif
>  
>  /*
> - * SC:cond_resched
> - * SC:might_resched
>   * SC:preempt_schedule
>   * SC:preempt_schedule_notrace
>   * SC:irqentry_exit_cond_resched
> @@ -7876,16 +7842,12 @@ EXPORT_SYMBOL(__cond_resched_rwlock_write);
>   *   (unselectable)
>   *
>   * FULL:
> - *   cond_resched               <- RET0
> - *   might_resched              <- RET0
>   *   preempt_schedule           <- preempt_schedule
>   *   preempt_schedule_notrace   <- preempt_schedule_notrace
>   *   irqentry_exit_cond_resched <- irqentry_exit_cond_resched
>   *   dynamic_preempt_lazy       <- false
>   *
>   * LAZY:
> - *   cond_resched               <- RET0
> - *   might_resched              <- RET0
>   *   preempt_schedule           <- preempt_schedule
>   *   preempt_schedule_notrace   <- preempt_schedule_notrace
>   *   irqentry_exit_cond_resched <- irqentry_exit_cond_resched
> @@ -7932,8 +7894,6 @@ static void __sched_dynamic_update(int mode)
>  {
>  	switch (mode) {
>  	case preempt_dynamic_full:
> -		preempt_dynamic_disable(cond_resched);
> -		preempt_dynamic_disable(might_resched);
>  		preempt_dynamic_enable(preempt_schedule);
>  		preempt_dynamic_enable(preempt_schedule_notrace);
>  		preempt_dynamic_enable(irqentry_exit_cond_resched);
> @@ -7943,8 +7903,6 @@ static void __sched_dynamic_update(int mode)
>  		break;
>  
>  	case preempt_dynamic_lazy:
> -		preempt_dynamic_disable(cond_resched);
> -		preempt_dynamic_disable(might_resched);

Reviewed-by: Jinjie Ruan <ruanjinjie@huawei.com>

>  		preempt_dynamic_enable(preempt_schedule);
>  		preempt_dynamic_enable(preempt_schedule_notrace);
>  		preempt_dynamic_enable(irqentry_exit_cond_resched);