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[24.6.151.244]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2e8e3555c1dsm7314523a91.4.2024.10.28.08.50.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Oct 2024 08:50:41 -0700 (PDT) Date: Mon, 28 Oct 2024 08:50:38 -0700 From: Joe Damato To: "Lifshits, Vitaly" Cc: "netdev@vger.kernel.org" , "Keller, Jacob E" , "kurt@linutronix.de" , "Gomes, Vinicius" , "Nguyen, Anthony L" , "Kitszel, Przemyslaw" , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , "moderated list:INTEL ETHERNET DRIVERS" , open list , "open list:XDP (eXpress Data Path)" , stanislaw.gruszka@linux.intel.com Subject: Re: [Intel-wired-lan] [iwl-next v4 2/2] igc: Link queues to NAPI instances Message-ID: Mail-Followup-To: Joe Damato , "Lifshits, Vitaly" , "netdev@vger.kernel.org" , "Keller, Jacob E" , "kurt@linutronix.de" , "Gomes, Vinicius" , "Nguyen, Anthony L" , "Kitszel, Przemyslaw" , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , "moderated list:INTEL ETHERNET DRIVERS" , open list , "open list:XDP (eXpress Data Path)" , stanislaw.gruszka@linux.intel.com References: <20241022215246.307821-1-jdamato@fastly.com> <20241022215246.307821-3-jdamato@fastly.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Sun, Oct 27, 2024 at 11:49:33AM +0200, Lifshits, Vitaly wrote: > > On 10/23/2024 12:52 AM, Joe Damato wrote: > > Link queues to NAPI instances via netdev-genl API so that users can > > query this information with netlink. Handle a few cases in the driver: > > 1. Link/unlink the NAPIs when XDP is enabled/disabled > > 2. Handle IGC_FLAG_QUEUE_PAIRS enabled and disabled > > > > Example output when IGC_FLAG_QUEUE_PAIRS is enabled: > > > > $ ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \ > > --dump queue-get --json='{"ifindex": 2}' > > > > [{'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'rx'}, > > {'id': 1, 'ifindex': 2, 'napi-id': 8194, 'type': 'rx'}, > > {'id': 2, 'ifindex': 2, 'napi-id': 8195, 'type': 'rx'}, > > {'id': 3, 'ifindex': 2, 'napi-id': 8196, 'type': 'rx'}, > > {'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'tx'}, > > {'id': 1, 'ifindex': 2, 'napi-id': 8194, 'type': 'tx'}, > > {'id': 2, 'ifindex': 2, 'napi-id': 8195, 'type': 'tx'}, > > {'id': 3, 'ifindex': 2, 'napi-id': 8196, 'type': 'tx'}] > > > > Since IGC_FLAG_QUEUE_PAIRS is enabled, you'll note that the same NAPI ID > > is present for both rx and tx queues at the same index, for example > > index 0: > > > > {'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'rx'}, > > {'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'tx'}, > > > > To test IGC_FLAG_QUEUE_PAIRS disabled, a test system was booted using > > the grub command line option "maxcpus=2" to force > > igc_set_interrupt_capability to disable IGC_FLAG_QUEUE_PAIRS. > > > > Example output when IGC_FLAG_QUEUE_PAIRS is disabled: > > > > $ lscpu | grep "On-line CPU" > > On-line CPU(s) list: 0,2 > > > > $ ethtool -l enp86s0 | tail -5 > > Current hardware settings: > > RX: n/a > > TX: n/a > > Other: 1 > > Combined: 2 > > > > $ cat /proc/interrupts | grep enp > > 144: [...] enp86s0 > > 145: [...] enp86s0-rx-0 > > 146: [...] enp86s0-rx-1 > > 147: [...] enp86s0-tx-0 > > 148: [...] enp86s0-tx-1 > > > > 1 "other" IRQ, and 2 IRQs for each of RX and Tx, so we expect netlink to > > report 4 IRQs with unique NAPI IDs: > > > > $ ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \ > > --dump napi-get --json='{"ifindex": 2}' > > [{'id': 8196, 'ifindex': 2, 'irq': 148}, > > {'id': 8195, 'ifindex': 2, 'irq': 147}, > > {'id': 8194, 'ifindex': 2, 'irq': 146}, > > {'id': 8193, 'ifindex': 2, 'irq': 145}] > > > > Now we examine which queues these NAPIs are associated with, expecting > > that since IGC_FLAG_QUEUE_PAIRS is disabled each RX and TX queue will > > have its own NAPI instance: > > > > $ ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \ > > --dump queue-get --json='{"ifindex": 2}' > > [{'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'rx'}, > > {'id': 1, 'ifindex': 2, 'napi-id': 8194, 'type': 'rx'}, > > {'id': 0, 'ifindex': 2, 'napi-id': 8195, 'type': 'tx'}, > > {'id': 1, 'ifindex': 2, 'napi-id': 8196, 'type': 'tx'}] > > > > Signed-off-by: Joe Damato > > Acked-by: Vinicius Costa Gomes > > --- > > v4: > > - Add rtnl_lock/rtnl_unlock in two paths: igc_resume and > > igc_io_error_detected. The code added to the latter is inspired by > > a similar implementation in ixgbe's ixgbe_io_error_detected. > > > > v3: > > - Replace igc_unset_queue_napi with igc_set_queue_napi(adapater, i, > > NULL), as suggested by Vinicius Costa Gomes > > - Simplify implemention of igc_set_queue_napi as suggested by Kurt > > Kanzenbach, with a tweak to use ring->queue_index > > > > v2: > > - Update commit message to include tests for IGC_FLAG_QUEUE_PAIRS > > disabled > > - Refactored code to move napi queue mapping and unmapping to helper > > functions igc_set_queue_napi and igc_unset_queue_napi > > - Adjust the code to handle IGC_FLAG_QUEUE_PAIRS disabled > > - Call helpers to map/unmap queues to NAPIs in igc_up, __igc_open, > > igc_xdp_enable_pool, and igc_xdp_disable_pool > > > > drivers/net/ethernet/intel/igc/igc.h | 2 ++ > > drivers/net/ethernet/intel/igc/igc_main.c | 41 ++++++++++++++++++++--- > > drivers/net/ethernet/intel/igc/igc_xdp.c | 2 ++ > > 3 files changed, 40 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h > > index eac0f966e0e4..b8111ad9a9a8 100644 > > --- a/drivers/net/ethernet/intel/igc/igc.h > > +++ b/drivers/net/ethernet/intel/igc/igc.h > > @@ -337,6 +337,8 @@ struct igc_adapter { > > struct igc_led_classdev *leds; > > }; > > +void igc_set_queue_napi(struct igc_adapter *adapter, int q_idx, > > + struct napi_struct *napi); > > void igc_up(struct igc_adapter *adapter); > > void igc_down(struct igc_adapter *adapter); > > int igc_open(struct net_device *netdev); > > diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c > > index 7964bbedb16c..04aa216ef612 100644 > > --- a/drivers/net/ethernet/intel/igc/igc_main.c > > +++ b/drivers/net/ethernet/intel/igc/igc_main.c > > @@ -4948,6 +4948,22 @@ static int igc_sw_init(struct igc_adapter *adapter) > > return 0; > > } > > +void igc_set_queue_napi(struct igc_adapter *adapter, int vector, > > + struct napi_struct *napi) > > +{ > > + struct igc_q_vector *q_vector = adapter->q_vector[vector]; > > + > > + if (q_vector->rx.ring) > > + netif_queue_set_napi(adapter->netdev, > > + q_vector->rx.ring->queue_index, > > + NETDEV_QUEUE_TYPE_RX, napi); > > + > > + if (q_vector->tx.ring) > > + netif_queue_set_napi(adapter->netdev, > > + q_vector->tx.ring->queue_index, > > + NETDEV_QUEUE_TYPE_TX, napi); > > +} > > + > > /** > > * igc_up - Open the interface and prepare it to handle traffic > > * @adapter: board private structure > > @@ -4955,6 +4971,7 @@ static int igc_sw_init(struct igc_adapter *adapter) > > void igc_up(struct igc_adapter *adapter) > > { > > struct igc_hw *hw = &adapter->hw; > > + struct napi_struct *napi; > > int i = 0; > > /* hardware has been reset, we need to reload some things */ > > @@ -4962,8 +4979,11 @@ void igc_up(struct igc_adapter *adapter) > > clear_bit(__IGC_DOWN, &adapter->state); > > - for (i = 0; i < adapter->num_q_vectors; i++) > > - napi_enable(&adapter->q_vector[i]->napi); > > + for (i = 0; i < adapter->num_q_vectors; i++) { > > + napi = &adapter->q_vector[i]->napi; > > + napi_enable(napi); > > + igc_set_queue_napi(adapter, i, napi); > > + } > > if (adapter->msix_entries) > > igc_configure_msix(adapter); > > @@ -5192,6 +5212,7 @@ void igc_down(struct igc_adapter *adapter) > > for (i = 0; i < adapter->num_q_vectors; i++) { > > if (adapter->q_vector[i]) { > > napi_synchronize(&adapter->q_vector[i]->napi); > > + igc_set_queue_napi(adapter, i, NULL); > > napi_disable(&adapter->q_vector[i]->napi); > > } > > } > > @@ -6021,6 +6042,7 @@ static int __igc_open(struct net_device *netdev, bool resuming) > > struct igc_adapter *adapter = netdev_priv(netdev); > > struct pci_dev *pdev = adapter->pdev; > > struct igc_hw *hw = &adapter->hw; > > + struct napi_struct *napi; > > int err = 0; > > int i = 0; > > @@ -6056,8 +6078,11 @@ static int __igc_open(struct net_device *netdev, bool resuming) > > clear_bit(__IGC_DOWN, &adapter->state); > > - for (i = 0; i < adapter->num_q_vectors; i++) > > - napi_enable(&adapter->q_vector[i]->napi); > > + for (i = 0; i < adapter->num_q_vectors; i++) { > > + napi = &adapter->q_vector[i]->napi; > > + napi_enable(napi); > > + igc_set_queue_napi(adapter, i, napi); > > + } > > /* Clear any pending interrupts. */ > > rd32(IGC_ICR); > > @@ -7385,7 +7410,9 @@ static int igc_resume(struct device *dev) > > wr32(IGC_WUS, ~0); > > if (netif_running(netdev)) { > > + rtnl_lock(); > > This change will bring back the deadlock issue that was fixed in commit: > 6f31d6b: "igc: Refactor runtime power management flow". OK, thanks for letting me know. I think I better understand what the issue is. It seems that: - igc_resume can be called with rtnl held via ethtool (which I didn't know), which calls __igc_open - __igc_open re-enables NAPIs and re-links queues to NAPI IDs (which requires rtnl) so, it seems like the rtnl_lock() I've added to igc_resume is unnecessary. I suppose I don't know all of the paths where the pm functions can be called -- are there others where RTNL is _not_ already held? I looked at e1000e and it seems that driver does not re-enable NAPIs in its resume path and thus does not suffer from the same issue as igc. So my questions are: 1. Are there are other contexts where igc_resume is called where RTNL is not held? 2. If the answer is that RTNL is always held when igc_resume is called, then I can send a v5 that removes the rtnl_lock/rtnl_unlock. What do you think? [...] > > Hi Joe, > > > The current version will cause a regression, a possible deadlock, due to the > addition of the rtnl_lock in igc_resume that was fixed previously. > > You can refer to the following link: > > https://github.com/torvalds/linux/commit/6f31d6b643a32cc126cf86093fca1ea575948bf0#diff-d5b32b873e9902b496280a5f42c246043c8f0691d8b3a6bbd56df99ce8ceb394L7190 Thanks for the link.