I am not sure we could deterministically provoke the issue. At the very least to ensure no other regression was introduced, I would run it under heavy network load.
The environment in question which saw the issue had network load, contention for cpus and several other issues occur. The basic environment is: 1. For any 25Gb NIC/chipset that requires the 4.4 bnxt_en_bpo driver, set its 2 ports/interfaces up in bonding mode as follows: bond-lacp-rate fast bond-master bond0 bond-miimon 100 bond-mode 802.3ad bond-xmit-hash-policy layer3+4 mtu 9000 2. Run any heavy TCP network load test over the systems (e.g. iperf, netperf, file transfer, etc.) 3. Theoretically, it would appear that if the number of tx ring descriptors were lower, than that would be more likely to hit this (not successfully proven by testing here), but can lower it and see if that helps: # ethtool -G eno49 tx 128 // for example I am not sure if that helps, Scott. I'll try and smoke up more specific steps but I cannot guarantee you will see the issue. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1814095 Title: bnxt_en_po: TX timed out triggering Netdev Watchdog Timer Status in linux package in Ubuntu: Confirmed Status in linux source package in Xenial: Fix Committed Bug description: [Impact] The bnxt_en_bpo driver experienced tx timeouts causing the system to experience network stalls and fail to send data and heartbeat packets. The following 25Gb Broadcom NIC error was seen on Xenial running the 4.4.0-141-generic kernel on an amd64 host seeing moderate-heavy network traffic (just once): * The bnxt_en_po driver froze on a "TX timed out" error and triggered the Netdev Watchdog timer under load. * From kernel log: "NETDEV WATCHDOG: eno2d1 (bnxt_en_bpo): transmit queue 0 timed out" See attached kern.log excerpt file for full excerpt of error log. * Release = Xenial Kernel = 4.4.0-141-generic #167 eno2d1 = Product Name: Broadcom Adv. Dual 25Gb Ethernet * This caused the driver to reset in order to recover: "bnxt_en_bpo 0000:19:00.1 eno2d1: TX timeout detected, starting reset task!" driver: bnxt_en_bpo version: 1.8.1 source: ubuntu/bnxt/bnxt.c: bnxt_tx_timeout() * The loss of connectivity and softirq stall caused other failures on the system. * The bnxt_en_po driver is the imported Broadcom driver pulled in to support newer Broadcom HW (specific boards) while the bnx_en module continues to support the older HW. The current Linux upstream driver does not compile easily with the 4.4 kernel (too many changes). * This upstream and bnxt_en driver fix is a likely solution: "bnxt_en: Fix TX timeout during netpoll" commit: 73f21c653f930f438d53eed29b5e4c65c8a0f906 This fix has not been applied to the bnxt_en_po driver version, but review of the code indicates that it is susceptible to the bug, and the fix would be reasonable. [Test Case] * Unfortunately, this is not easy to reproduce. Also, it is only seen on 4.4 kernels with newer Broadcom NICs supported by the bnxt_en_bpo driver. [Regression Potential] * The patch is restricted to the bpo driver, with very constrained scope - just the newest Broadcom NICs being used by the Xenial 4.4 kernel (as opposed to the hwe 4.15 etc. kernels, which would have the in-tree fixed driver). * The patch is very small and backport is fairly minimal and simple. * The fix has been running on the in-tree driver in upstream mainline as well as the Ubuntu Linux in-tree driver, although the Broadcom driver has a lot of lower level code that is different, this piece is still the same. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1814095/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
