linux-kernel - Re: [PATCH] net: Handle threadirqs in __napi_schedule

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Message-ID: <e127f072-e034-4d21-a71f-4b140102118f@linux.dev>
Date: Fri, 13 Sep 2024 11:23:16 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Eric Dumazet <edumazet@...gle.com>
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 9/13/24 11:16, Eric Dumazet wrote:
> 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.

OK

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

Ah, sorry. Should be net-next.

--Sean