netdev - Re: [PATCH] net: Handle threadirqs in __napi_schedule

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Message-ID: <CANn89iL-fgyZo=NbyDFA5ebSn4nqvNASFyXq2GVGpCpH049+Lg@mail.gmail.com>
Date: Fri, 13 Sep 2024 17:16:45 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Sean Anderson <sean.anderson@...ux.dev>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	Juri Lelli <juri.lelli@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: Handle threadirqs in __napi_schedule_irqoff

On Fri, Sep 13, 2024 at 5:10 PM Sean Anderson <sean.anderson@...ux.dev> wrote:
>
> The threadirqs kernel parameter can be used to force threaded IRQs even
> on non-PREEMPT_RT kernels. Use force_irqthreads to determine if we can
> skip disabling local interrupts. This defaults to false on regular
> kernels, and is always true on PREEMPT_RT kernels.
>
> Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
> ---
>
>  net/core/dev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 1e740faf9e78..112e871bc2b0 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6202,7 +6202,7 @@ EXPORT_SYMBOL(napi_schedule_prep);
>   */
>  void __napi_schedule_irqoff(struct napi_struct *n)
>  {
> -       if (!IS_ENABLED(CONFIG_PREEMPT_RT))
> +       if (!force_irqthreads())
>                 ____napi_schedule(this_cpu_ptr(&softnet_data), n);
>         else
>                 __napi_schedule(n);
> --
> 2.35.1.1320.gc452695387.dirty
>

Seems reasonable, can you update the comment (kdoc) as well ?

It says :

 * On PREEMPT_RT enabled kernels this maps to __napi_schedule()
 * because the interrupt disabled assumption might not be true
 * due to force-threaded interrupts and spinlock substitution.

Also always specify net or net-next for networking patches.

Thanks.