Re: [syzbot] [mm?] INFO: rcu detected stall in unmap_region

[Nikolay Ivchenko <nivchenko.dev@gmail.com>]

> A known issue, feel free to grep broken in the 2025 report [1].
>
> [1] Subject: Re: [syzbot] [net?] [mm?] INFO: rcu detected stall in inet_rtm_newaddr (2)
> https://lore.kernel.org/lkml/CANn89iLjjtXV3ZMxfQDb1bbsVJ6a_Chexu4FwqeejxGTwsR_kg@mail.gmail.com/

Thanks for the link, Hillf. I read through that thread and also looked at
several other open syzbot reports with "stall" in the subject line that have
replies from other developers:

  - https://syzkaller.appspot.com/bug?extid=385468161961cee80c31
  - https://syzkaller.appspot.com/bug?extid=111bc509cd9740d7e4aa
  - https://syzkaller.appspot.com/bug?extid=c28b5fee66fd3b7f766e
  - https://syzkaller.appspot.com/bug?extid=9f78d5c664a8c33f4cce
  - https://syzkaller.appspot.com/bug?extid=69904c3b4a09e8fa2e1b
  - https://syzkaller.appspot.com/bug?extid=51cd74c5dfeafd65e488
  - https://syzkaller.appspot.com/bug?extid=5b4f4f81240931b16844
  - https://syzkaller.appspot.com/bug?extid=4507914ec56d21bb39ed
  - https://syzkaller.appspot.com/bug?extid=0635dc2e2c3c21a6aa04

In the reports similar to this one, all the attached reproducers configure
taprio with very small timer intervals. I haven't gone through all the
comments and proposed patches in those other reports yet, but I'm looking
into them now.

> How many hours were spent?
>
> And my 2cents suggestion sounds like sit back with netflix on.

I would gladly do that, but it really bothers me that there's a single
issue generating a flood of different bug reports on syzbot. As you
rightly pointed out - how many hours have already been spent investigating
them, and how many more will be wasted?

From what I can tell so far, this remains unfixed simply because no one
has fixed it yet, correct? Please correct me if I'm wrong and missed
other discussions on this topic. If that's the case, I'll try to propose
some solutions for this issue.

Best regards,
Nikolay Ivchenko