Hello Everyone, Google led me here with a search for a "soft lockup CPU#" error I am experiencing.
I run Ubuntu Server on Citrix XenServer and have never had this issue with Ubuntu Server 12.04, 14.04 or 16.04. I am here because 18.04 has this issue upon using 'reboot', although 'poweroff' does as intended. If I be of any assistance to yourselves in retrieving log files, testing or what-ever to remedy this bug for the good of everyone then please let me know. Keen to improve Ubuntu for all. Thank you and best regards, Modiford. -- 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/1730717 Title: Some VMs fail to reboot with "watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [systemd:1]" Status in linux package in Ubuntu: Fix Committed Status in qemu-kvm package in Ubuntu: Confirmed Status in linux source package in Zesty: Won't Fix Status in qemu-kvm source package in Zesty: New Status in linux source package in Artful: Fix Committed Status in qemu-kvm source package in Artful: Confirmed Status in linux source package in Bionic: Fix Committed Status in qemu-kvm source package in Bionic: Confirmed Bug description: == SRU Justification == The fix to bug 1672819 can cause an lockup because it can spin indefinitely waiting for a child to exit. [FIX] Add a sauce patch to the original fix to insert a reasonable small delay and an upper bounds to the number of retries that are made before bailing out with an error. This avoids the lockup and also is less aggressive in the retry loop. [TEST] Without the fix the machine hangs. With the fix, the lockup no longer occurs. [REGRESSION POTENTIAL] There may be an issue with the interruptible sleep having some unforeseen impact with userspace racy code that expects the system call to return quickly when the race condition occurs and instead it gets delayed by a few milliseconds while the retry loop spins. However, code that relies on timing on fork/exec inside pthreads where this particular code path could bite is generally non-POSIX conforming racy code anyhow. ----------------------------------- This is impacting us for ubuntu autopkgtests. Eventually the whole region ends up dying because each worker is hit by this bug in turn and backs off until the next reset (6 hourly). 17.10 (and bionic) guests are sometimes failing to reboot. When this happens, you see the following in the console [[0;32m OK [0m] Reached target Shutdown. [ 191.698969] watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [systemd:1] [ 219.698438] watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [systemd:1] [ 226.702150] INFO: rcu_sched detected stalls on CPUs/tasks: [ 226.704958] »(detected by 0, t=15002 jiffies, g=5347, c=5346, q=187) [ 226.706093] All QSes seen, last rcu_sched kthread activity 15002 (4294949060-4294934058), jiffies_till_next_fqs=1, root ->qsmask 0x0 [ 226.708202] rcu_sched kthread starved for 15002 jiffies! g5347 c5346 f0x2 RCU_GP_WAIT_FQS(3) ->state=0x0 One host that exhibits this behaviour was: Linux klock 4.4.0-98-generic #121-Ubuntu SMP Tue Oct 10 14:24:03 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux guest running: Linux version 4.13.0-16-generic (buildd@lcy01-02) (gcc version 7.2.0 (Ubuntu 7.2.0-8ubuntu2)) #19-Ubuntu SMP Wed Oct 11 18:35:14 UTC 2017 (Ubuntu 4.13.0-16.19-generic 4.13.4) The affected cloud region is running the xenial/Ocata cloud archive, so the version of qemu-kvm in there may also be relevant. Here's how I reproduced it in lcy01: $ for n in {1..30}; do nova boot --flavor m1.small --image ubuntu/ubuntu-artful-17.10-amd64-server-20171026.1-disk1.img --key-name testbed-`hostname` --nic net-name=net_ues_proposed_migration laney-test${n}; done $ <ssh to each instance> sudo reboot # wait a minute or so for the instances to all reboot $ for n in {1..30}; do echo "=== ${n} ==="; nova console-log laney-test${n} | tail; done On bad instances you'll see the "soft lockup" message - on good it'll reboot as normal. We've seen good and bad instances on multiple compute hosts - it doesn't feel to me like a host problem but rather a race condition somewhere that's somehow either triggered or triggered much more often by what lcy01 is running. I always saw this on the first reboot - never on first boot, and never on n>1th boot. (But if it's a race then that might not mean much.) I'll attach a bad and a good console-log for reference. If you're at Canonical then see internal rt #107135 for some other details. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1730717/+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
