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[67.180.167.114]) by smtp.gmail.com with ESMTPSA id d12-v6sm25095564pfn.118.2018.09.18.19.32.54 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Sep 2018 19:32:55 -0700 (PDT) Subject: Re: [PATCH] net: apm: xgene: force XGene enet driver to re-balance IRQ usage To: Florian Fainelli , ahs3@redhat.com, "Lendacky, Thomas" , David Miller Cc: "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "isubramanian@apm.com" , "kchudgar@apm.com" , "qnguyen@apm.com" References: <20180917233533.28626-1-ahs3@redhat.com> <20180917.193531.1424852853827678152.davem@davemloft.net> <4929e93d-508a-4670-9450-66e4fc85be7e@redhat.com> <29258606-8255-847c-b22f-8793999ce6fe@gmail.com> <0e0f3aa6-9b6e-edd5-226f-2e23de9b5a0f@gmail.com> From: Eric Dumazet Message-ID: <95391269-73b7-933f-27ee-2c4a17c8c6b1@gmail.com> Date: Tue, 18 Sep 2018 19:32:54 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <0e0f3aa6-9b6e-edd5-226f-2e23de9b5a0f@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/18/2018 05:03 PM, Florian Fainelli wrote: > On 09/18/2018 04:56 PM, Eric Dumazet wrote: >> >> >> On 09/18/2018 04:27 PM, Eric Dumazet wrote: >>> >> >>> I remember one of the napi_complete_done() change had to be reverted, >>> for some obscure reason. >> >> >> >> That was not exactly a revert, : > > This is what I have so far for the drivers that both use > napi_complete_done() without checking the return value and implement a > ndo_poll_controller() callback: > > https://github.com/ffainelli/linux/commits/napi-check In fact, there is still to explain what the bug is. napi_complete_done() return value can be ignored, unless drivers have to disable IRQ in their interrupt handler, using the following construct : if (napi_schedule_prep(napi)) { .... disable interrupt .... __napi_schedule_irqoff(napi); } It _can_ be used by other drivers to not rearm interrupts needlessly. The bug discussed in this thread (re-balance IRQ usage) is of the same kind than the one fixed in commit d7aba644ffdebf756e51e26a2229055211838e89 ("amd-xgbe: Enable IRQs only if napi_complete_done() is true")