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

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Message-ID: <53a6c904-161b-4665-a0c5-fda1cf838654@amd.com>
Date: Fri, 13 Sep 2024 09:08:07 -0700
From: Brett Creeley <bcreeley@....com>
To: Sean Anderson <sean.anderson@...ux.dev>,
 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 9/13/2024 8:23 AM, Sean Anderson wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> 
> 
> 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.

Is this worthy for a fixes/net tag?

Thanks,

Brett
> 
> --Sean
> 
>