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

So with my 1st attempt to recreate (assuming 20.04.1 ans zFCP) I wasn't successful, means:
starting with a clean 20.04.1 (after doing a full-upgrade before kicking off the dist-upgrade -d) on z/VM using zFCP/SCSI multipath the upgrade to groovy worked in my case/my environment.

** Attachment added: "dist-upgrade from 20.04.1 to 20.10.txt"
https://bugs.launchpad.net/ubuntu-z-systems/+bug/1899106/+attachment/5419879/+files/dist-upgrade%20from%2020.04.1%20to%2020.10.txt

** Changed in: ubuntu-z-systems
Status: New => Incomplete

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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:
Incomplete
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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