6.0-rc1 new RCU stall warning/stack trace

6.0-rc1 new RCU stall warning/stack trace

[Hans de Goede]

Hi All,

While dogfooding 6.0-rc1 on my main workstation I noticed the following
new RCU stall warning/stack trace after a suspend/resume:

[  290.653114] xhci_hcd 0000:16:00.0: xHC error in resume, USBSTS 0x401, Reinit
...
[  290.653253] usb usb1: root hub lost power or was reset
[  290.653255] usb usb2: root hub lost power or was reset
...
[  290.684960] rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 9-...D } 28 jiffies s: 985 root: 0x1/.
[  290.684972] rcu: blocking rcu_node structures (internal RCU debug): l=1:0-15:0x200/.
[  290.684975] Task dump for CPU 9:
[  290.684977] task:kworker/u64:20  state:R  running task     stack:    0 pid: 3993 ppid:     2 flags:0x00004008
[  290.684982] Workqueue: events_unbound async_run_entry_fn
[  290.684987] Call Trace:
[  290.684988]  <TASK>
[  290.684994]  ? lock_is_held_type+0xe3/0x140
[  290.684999]  ? find_held_lock+0x2b/0x80
[  290.685003]  ? lock_release+0x135/0x2d0
[  290.685008]  ? delay_halt+0x3b/0x60
[  290.685012]  ? xhci_handshake+0x3e/0xb0
[  290.685016]  ? xhci_reset+0x6a/0x100
[  290.685019]  ? xhci_resume+0x1ec/0x600
[  290.685023]  ? resume_common+0xa0/0x100
[  290.685026]  ? pci_pm_poweroff_noirq+0x100/0x100
[  290.685030]  ? dpm_run_callback+0x53/0xc0
[  290.685034]  ? device_resume+0xa8/0x200
[  290.685038]  ? async_resume+0x19/0x30
[  290.685040]  ? async_run_entry_fn+0x30/0x130
[  290.685043]  ? process_one_work+0x257/0x570
[  290.685050]  ? worker_thread+0x4f/0x3a0
[  290.685054]  ? process_one_work+0x570/0x570
[  290.685056]  ? kthread+0xf5/0x120
[  290.685058]  ? kthread_complete_and_exit+0x20/0x20
[  290.685062]  ? ret_from_fork+0x22/0x30
[  290.685072]  </TASK>

Note I've not seen any negative side-effects from this yet,
still I thought it would be good to report this.

Regards,

Hans