netdev - Re: [PATCH] net: apm: xgene: force XGene enet driver to re-balance IRQ usage

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Message-ID: <cdb8a00c-a3bf-72e0-38b2-3c4b2427270a@gmail.com>
Date:   Tue, 18 Sep 2018 16:21:14 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     ahs3@...hat.com, "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        David Miller <davem@...emloft.net>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "isubramanian@....com" <isubramanian@....com>,
        "kchudgar@....com" <kchudgar@....com>,
        "qnguyen@....com" <qnguyen@....com>
Subject: Re: [PATCH] net: apm: xgene: force XGene enet driver to re-balance
 IRQ usage

On 09/18/2018 04:15 PM, Al Stone wrote:
> On 09/18/2018 05:09 PM, Lendacky, Thomas wrote:
>>
>>
>> On 09/17/2018 09:35 PM, David Miller wrote:
>>> From: Al Stone <ahs3@...hat.com>
>>> Date: Mon, 17 Sep 2018 17:35:33 -0600
>>>
>>>> @@ -866,8 +866,11 @@ static int xgene_enet_napi(struct napi_struct *napi, const int budget)
>>>>  	processed = xgene_enet_process_ring(ring, budget);
>>>>  
>>>>  	if (processed != budget) {
>>>> +		struct irq_desc *desc = irq_to_desc(ring->irq);
>>>> +
>>>>  		napi_complete_done(napi, processed);
>>
>> The problem could be that the driver isn't checking the
>> napi_complete_done() return code.  It was changed to return a bool and
>> the check should be more like:
>>
>>   if ((processed != budget) && napi_complete_done(napi, processed)) {
>>
>> If it returns false, then the driver will get called for polling again
>> after having issued enable_irq() and it well then issue the enable_irq()
>> a second (or more) time without having the matching diable_irq().
>>
>> Thanks,
>> Tom
> 
> Aha, that might be.  My apologies -- I play in ACPI but seldom in the network
> drivers, so was not fully aware of that change.  I can give that a try.
> 
> Thanks for the pointer.

FWIW this is being discussed in this thread as well:

https://www.spinics.net/lists/netdev/msg523760.html

there should be an update to drivers that have a ndo_poll_controller()
and don't check napi_complete_done(), though I am not clear who is doing
that yet.
-- 
Florian