[Bug 1899106] Re: Kernel stack dump at reboot after upgrade from 20.04 to 20.10

And another quick question was the Ubuntu release you started the
upgrade on at the latest level, means 20.04.1 or was it still a 20.04 GA
(w/o having done an apt full-upgrade or so)?

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https://bugs.launchpad.net/bugs/1899106

Title:
Kernel stack dump at reboot after upgrade from 20.04 to 20.10

Status in Ubuntu on IBM z Systems:
New
Status in linux package in Ubuntu:
Incomplete

Bug description:
Upon reboot after upgrading a zVM guest from 20.04 to 20.10 the system
was slow to reboot, then dumped a kernel Call Trace to the console.
The guest boot to the upgrade OS on the next reboot.

Ý Ý0;32m OK Ý0m¨ Reached target Ý0;1;39mShutdown Ý0m.
Ý Ý0;32m OK Ý0m¨ Reached target Ý0;1;39mFinal Step Ý0m.
Ý Ý0;32m OK Ý0m¨ Finished Ý0;1;39mReboot Ý0m.
Ý Ý0;32m OK Ý0m¨ Reached target Ý0;1;39mReboot Ý0m.
Ý 977.915226¨ rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
Ý 1172.401646¨ (detected by 2, t=2102 jiffies, g=44453, q=4439)
Ý 1172.401654¨ rcu: All QSes seen, last rcu_sched kthread activity 2102 (4295035
060-4295032958), jiffies_till_next_fqs=1, root ->qsmask 0x0
Ý 1172.401662¨ Call Trace:
Ý 1172.401674¨ (Ý<000000008ee47f6a>¨ show_stack+0x7a/0xc0)
Ý 1172.401681¨ Ý<000000008eee1fcc>¨ sched_show_task.part.0+0xdc/0x100
Ý 1172.401689¨ Ý<000000008ef31244>¨ rcu_sched_clock_irq+0x904/0x980
Ý 1172.401698¨ Ý<000000008ef3fedc>¨ update_process_times+0x3c/0xa0
Ý 1172.401703¨ Ý<000000008ef51bba>¨ tick_sched_handle.isra.0+0x4a/0x70
Ý 1172.401705¨ Ý<000000008ef51e5e>¨ tick_sched_timer+0x5e/0xc0
Ý 1172.401708¨ Ý<000000008ef40ee8>¨ __hrtimer_run_queues+0x118/0x2f0
Ý 1172.401711¨ Ý<000000008ef41bac>¨ hrtimer_interrupt+0x12c/0x2b0
Ý 1173.451971¨ Ý<000000008ee40c9a>¨ do_IRQ+0xaa/0xb0
Ý 1173.451979¨ Ý<000000008f710918>¨ ext_int_handler+0x130/0x134
Ý 1173.451983¨ Ý<000000008ee375cc>¨ enabled_wait+0x3c/0xd0
Ý 1173.451991¨ rcu: rcu_sched kthread starved for 2102 jiffies! g44453 f0x2 RCU_
GP_WAIT_FQS(5) ->state=0x200 ->cpu=1
Ý 1173.451994¨ rcu: RCU grace-period kthread stack dump:
Ý 1173.452000¨ Call Trace:
Ý 1173.452005¨ (Ý<000000008f70ac04>¨ __schedule+0x304/0x7a0)
Ý 1173.452008¨ Ý<000000008f70b0ea>¨ schedule+0x4a/0xe0
Ý 1173.452012¨ Ý<000000008f70f246>¨ schedule_timeout+0x176/0x370
Ý 1173.452018¨ Ý<000000008ef2ed52>¨ rcu_gp_kthread+0x732/0xbc0
Ý 1173.452024¨ Ý<000000008eed89aa>¨ kthread+0x12a/0x160
Ý 1173.452032¨ Ý<000000008f710310>¨ ret_from_fork+0x2c/0x30
Ý 1173.452034¨ Ý<000000008f710314>¨ kernel_thread_starter+0x0/0x10
Ý 1173.452048¨ rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
Ý 1173.452059¨ (detected by 2, t=21655 jiffies, g=44453, q=4440)
Ý 1173.452061¨ rcu: All QSes seen, last rcu_sched kthread activity 21655 (429505
4613-4295032958), jiffies_till_next_fqs=1, root ->qsmask 0x0
Ý 1173.452066¨ Call Trace:
Ý 1173.452482¨ (Ý<000000008ee47f6a>¨ show_stack+0x7a/0xc0)
Ý 1173.452489¨ Ý<000000008eee1fcc>¨ sched_show_task.part.0+0xdc/0x100
Ý 1173.452495¨ Ý<000000008ef31244>¨ rcu_sched_clock_irq+0x904/0x980
Ý 1173.452501¨ Ý<000000008ef3fedc>¨ update_process_times+0x3c/0xa0
Ý 1173.452506¨ Ý<000000008ef51bba>¨ tick_sched_handle.isra.0+0x4a/0x70
Ý 1173.452510¨ Ý<000000008ef51e5e>¨ tick_sched_timer+0x5e/0xc0
Ý 1173.452513¨ Ý<000000008ef40ee8>¨ __hrtimer_run_queues+0x118/0x2f0
Ý 1173.452518¨ Ý<000000008ef41bac>¨ hrtimer_interrupt+0x12c/0x2b0
Ý 1173.452521¨ Ý<000000008ee40c9a>¨ do_IRQ+0xaa/0xb0
Ý 1173.452527¨ Ý<000000008f710918>¨ ext_int_handler+0x130/0x134
Ý 1173.452529¨ Ý<000000008ee375cc>¨ enabled_wait+0x3c/0xd0
Ý 1173.452532¨ rcu: rcu_sched kthread starved for 21655 jiffies! g44453 f0x2 RCU
_GP_WAIT_FQS(5) ->state=0x200 ->cpu=1
Ý 1173.452533¨ rcu: RCU grace-period kthread stack dump:
Ý 1173.452535¨ Call Trace:
Ý 1173.452537¨ (Ý<000000008f70ac04>¨ __schedule+0x304/0x7a0)
Ý 1173.452539¨ Ý<000000008f70b0ea>¨ schedule+0x4a/0xe0
Ý 1173.452541¨ Ý<000000008f70f246>¨ schedule_timeout+0x176/0x370
Ý 1173.452543¨ Ý<000000008ef2ed52>¨ rcu_gp_kthread+0x732/0xbc0
Ý 1173.452545¨ Ý<000000008eed89aa>¨ kthread+0x12a/0x160
Ý 1173.452547¨ Ý<000000008f710310>¨ ret_from_fork+0x2c/0x30
Ý 1173.452549¨ Ý<000000008f710314>¨ kernel_thread_starter+0x0/0x10

01: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP stop from
CPU 00.

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