netdev - Re: [PATCH net-next v2 1/2] irq_work: Export symbol "irq_work_queue

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Date:   Wed, 8 Jul 2020 13:50:43 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>, xiangning.yu@...baba-inc.com
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/2] irq_work: Export symbol
 "irq_work_queue_on"



On 7/8/20 1:27 PM, Eric Dumazet wrote:
> 
> 
> On 7/8/20 12:37 PM, David Miller wrote:
>> From: "YU, Xiangning" <xiangning.yu@...baba-inc.com>
>> Date: Thu, 09 Jul 2020 00:38:16 +0800
>>
>>> @@ -111,7 +111,7 @@ bool irq_work_queue_on(struct irq_work *work, int cpu)
>>>  	return true;
>>>  #endif /* CONFIG_SMP */
>>>  }
>>> -
>>> +EXPORT_SYMBOL_GPL(irq_work_queue_on);
>>
>> You either removed the need for kthreads or you didn't.
>>
>> If you are queueing IRQ work like this, you're still using kthreads.
>>
>> That's why Eric is asking why you still need this export.
>>
> 
> I received my copy of the 2/2 patch very late, I probably misunderstood
> the v2 changes.
> 
> It seems irq_work_queue_on() is till heavily used, and this makes me nervous.
> 
> Has this thing being tested on 256 cores platform ?
> 

Oh well, the answer is no.
...
#define    MAX_CPU_COUNT       128 /* make it dynamic */ 
...
ltb->num_cpus = num_online_cpus();
if (ltb->num_cpus > MAX_CPU_COUNT)
    return (ltb->num_cpus > MAX_CPU_COUNT)