On 2021-01-08 08:45:14 [+0000], Ran Wang wrote:

Hi Sebastian, Peter

Hi,

quoted

I had a similar patch in -RT and dropped it in v5.10-rc7-rt16.
It was added because RT couldn't boot since creating the boot-threads didn't work before the ksoftirqd was up. This was fixed by commit
   26c7295be0c5e ("kthread: Do not preempt current task if it is going to call schedule()")

I tried applying above commit to linux-5.6.y-rt, it could resolve my problem on LX2160ARDB, THANKS!

so in other words all this could have been avoided by using a supported
or maintained RT series. The v5.4 series has this patch, v5.6 isn't
maintained anymore so it is likely that there is more missing.

Sebastian