linux-kernel - Re: [PATCH v2 06/35] thread_info: define __tif_need_resched(resched

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Date: Tue, 28 May 2024 18:03:10 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Ankur Arora <ankur.a.arora@...cle.com>
Cc: linux-kernel@...r.kernel.org, tglx@...utronix.de,
	torvalds@...ux-foundation.org, paulmck@...nel.org,
	rostedt@...dmis.org, mark.rutland@....com, juri.lelli@...hat.com,
	joel@...lfernandes.org, raghavendra.kt@....com,
	sshegde@...ux.ibm.com, boris.ostrovsky@...cle.com,
	konrad.wilk@...cle.com, Arnd Bergmann <arnd@...db.de>,
	Ingo Molnar <mingo@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH v2 06/35] thread_info: define
 __tif_need_resched(resched_t)

On Mon, May 27, 2024 at 05:34:52PM -0700, Ankur Arora wrote:

> diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
> index 65e5beedc915..e246b01553a5 100644
> --- a/include/linux/thread_info.h
> +++ b/include/linux/thread_info.h
> @@ -216,22 +216,44 @@ static __always_inline unsigned long read_ti_thread_flags(struct thread_info *ti
>  
>  #ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
>  
> -static __always_inline bool tif_need_resched(void)
> +static __always_inline bool __tif_need_resched_bitop(int nr_flag)
>  {
> -	return arch_test_bit(TIF_NEED_RESCHED,
> -			     (unsigned long *)(&current_thread_info()->flags));
> +	return arch_test_bit(nr_flag,
> +		     (unsigned long *)(&current_thread_info()->flags));
>  }
>  
>  #else
>  
> -static __always_inline bool tif_need_resched(void)
> +static __always_inline bool __tif_need_resched_bitop(int nr_flag)
>  {
> -	return test_bit(TIF_NEED_RESCHED,
> -			(unsigned long *)(&current_thread_info()->flags));
> +	return test_bit(nr_flag,
> +		(unsigned long *)(&current_thread_info()->flags));
>  }

:se cino=(0:0

That is, you're wrecking the indentation here.

>  
>  #endif /* _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H */
>  
> +static __always_inline bool __tif_need_resched(resched_t rs)
> +{
> +	/*
> +	 * With !PREEMPT_AUTO, this check is only meaningful if we
> +	 * are checking if tif_resched(RESCHED_NOW) is set.
> +	 */
> +	if (IS_ENABLED(CONFIG_PREEMPT_AUTO) || rs == RESCHED_NOW)
> +		return __tif_need_resched_bitop(tif_resched(rs));
> +	else
> +		return false;
> +}

	if (!IS_ENABLED(CONFIG_PREEMPT_AUTO) && rs == RESCHED_LAZY)
		return false;

	return __tif_need_resched_bitop(tif_resched(rs));


> +
> +static __always_inline bool tif_need_resched(void)
> +{
> +	return __tif_need_resched(RESCHED_NOW);
> +}
> +
> +static __always_inline bool tif_need_resched_lazy(void)
> +{
> +	return __tif_need_resched(RESCHED_LAZY);
> +}
> +
>  #ifndef CONFIG_HAVE_ARCH_WITHIN_STACK_FRAMES
>  static inline int arch_within_stack_frames(const void * const stack,
>  					   const void * const stackend,
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 233d1af39fff..ed229527be05 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2511,7 +2511,7 @@ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status)
>  	if (softirq_count() >> (SOFTIRQ_SHIFT + 1))
>  		trace_flags |= TRACE_FLAG_BH_OFF;
>  
> -	if (tif_need_resched())
> +	if (__tif_need_resched(RESCHED_NOW))
>  		trace_flags |= TRACE_FLAG_NEED_RESCHED;

Per the above this is a NO-OP.