This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed- bionic' to 'verification-done-bionic'. If the problem still exists, change the tag 'verification-needed-bionic' to 'verification-failed- bionic'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: verification-needed-bionic -- 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/1797202 Title: [Bionic] arm64: topology: Avoid checking numa mask for scheduler MC selection Status in linux package in Ubuntu: Invalid Status in linux source package in Bionic: Fix Committed Bug description: [Impact] The numa mask subset check can often lead to system hang or crash during CPU hotplug and system suspend operation if NUMA is disabled. This is mostly observed on HMP systems where the CPU compute capacities are different and ends up in different scheduler domains. Since cpumask_of_node is returned instead core_sibling, the scheduler is confused with incorrect cpumasks(e.g. one CPU in two different sched domains at the same time) on CPU hotplug. [Fix] The following patch fixes this issue: e156ab71a974 arm64: topology: Avoid checking numa mask for scheduler MC selection [Test] -- testcase -- #!/bin/bash stress-ng -q --vm 100 --vm-bytes 1G --cpu 210 --timeout 2400s --metrics-brief & pid=$! for i in {1..210}; do num=$((RANDOM%10+$i)) echo "Offline CPU $num" echo 0 > /sys/devices/system/cpu/cpu$num/online || exit 1 sleep 3s echo "Online CPU $num" echo 1 > /sys/devices/system/cpu/cpu$num/online || exit 1 done kill -9 $pid ---------------- Executed the test case with stock Bionic kernel and with Bionic kernel with patches applied. No system hang or crash was observed. On Cavium CN99XX Thunder X2 system. [Regression Potential] Regression tested on Cavium Thunder X2 CN99XX system, and none were found. Regression risk is low. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1797202/+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
