On 6/4/20 12:07 AM, Song Liu wrote:

The hang happens at expected place.

quoted

[Jun 3 09:02] INFO: task mdadm:2858 blocked for more than 120 seconds.
[  +0.060545]       Tainted: G            E     5.4.19-msl-00001-gbf39596faf12 #2
[  +0.062932] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

Could you please try disable the timeout message with

echo 0 > /proc/sys/kernel/hung_task_timeout_secs

And during this wait (after message
"r5c_recovery_flush_data_only_stripes before wait_event"),
checks whether the raid disks (not the journal disk) are taking IOs
(using tools like iostat).

No activity on component drives.