linux-kernel - Re: [RFC][PATCH 3/7] smp: Move irq_work_run() out of flush_smp_call_function

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Date:   Fri, 29 May 2020 15:04:54 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org, x86@...nel.org,
        cai@....pw, mgorman@...hsingularity.net
Subject: Re: [RFC][PATCH 3/7] smp: Move irq_work_run() out of
 flush_smp_call_function_queue()

On Tue, May 26, 2020 at 06:11:00PM +0200, Peter Zijlstra wrote:
> This ensures flush_smp_call_function_queue() is strictly about
> call_single_queue.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  kernel/smp.c |   17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -84,6 +84,7 @@ int smpcfd_dying_cpu(unsigned int cpu)
>  	 * still pending.
>  	 */
>  	flush_smp_call_function_queue(false);
> +	irq_work_run();
>  	return 0;
>  }
>  
> @@ -191,6 +192,14 @@ static int generic_exec_single(int cpu,
>  void generic_smp_call_function_single_interrupt(void)
>  {
>  	flush_smp_call_function_queue(true);
> +
> +	/*
> +	 * Handle irq works queued remotely by irq_work_queue_on().
> +	 * Smp functions above are typically synchronous so they
> +	 * better run first since some other CPUs may be busy waiting
> +	 * for them.
> +	 */

You may want to update that comment once you merge remote irq_work and csd.

Thanks.

> +	irq_work_run();
>  }
>  
>  /**
> @@ -267,14 +276,6 @@ static void flush_smp_call_function_queu
>  		csd_unlock(csd);
>  		func(info);
>  	}
> -
> -	/*
> -	 * Handle irq works queued remotely by irq_work_queue_on().
> -	 * Smp functions above are typically synchronous so they
> -	 * better run first since some other CPUs may be busy waiting
> -	 * for them.
> -	 */
> -	irq_work_run();
>  }
>  
>  /*
> 
>