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Subject: Re: [PATCH] net: apm: xgene: force XGene enet driver to re-balance
 IRQ usage
To:     ahs3@redhat.com, "Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
        David Miller <davem@davemloft.net>
Cc:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "isubramanian@apm.com" <isubramanian@apm.com>,
        "kchudgar@apm.com" <kchudgar@apm.com>,
        "qnguyen@apm.com" <qnguyen@apm.com>
References: <20180917233533.28626-1-ahs3@redhat.com>
 <20180917.193531.1424852853827678152.davem@davemloft.net>
 <a5adee73-dde7-d00f-e7ef-1f81dc7c813a@amd.com>
 <4929e93d-508a-4670-9450-66e4fc85be7e@redhat.com>
From:   Eric Dumazet <eric.dumazet@gmail.com>
Message-ID: <32ee17f8-8b89-9d8c-90a6-6d513be6b2b7@gmail.com>
Date:   Tue, 18 Sep 2018 16:25:38 -0700
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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@redhat.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.
> 

Yes, please look at commit d7aba644ffdebf756e51e26a2229055211838e89
("amd-xgbe: Enable IRQs only if napi_complete_done() is true")