Re: Bug: INFO_ task hung in lock_two_nondirectories

[Kun Hu]

> 
> Is there some political reason that collaboration isn't happening? I've
> found the syzbot people to be great to work with.
> 
> I'll give some analysis on this bug, but in general I won't in the
> future until you guys start collaborating (or at least tell us what the
> blocker is) - I don't want to be duplicating work I've already done for
> syzbot.

Thanks, no political reasons, simply just researching this area and not familiar enough with it, I'll keep an eye out for this later.


> 
> We need to know what the other threads are doing. Since lockdep didn't
> detect an actual deadlock, it seems most likely that the blocked thread
> is blocked because the thread holding the inode lock is spinning and
> livelocked.
> 
> That's not in the dump, so to debug this we'd need to reproduce this in
> a local VM and poke around with e.g. top/perf and see what's going on.
> 
> I've a tool to reproduce syzbot bugs locally in a single command [1], so
> that would be my starting point - except it doesn't work with your
> forked version. Doh.
> 
> Another thing we could do is write some additional code for the hung
> task detector that, when lockdep is enabled, uses it to figure out which
> task it's blocked on and additionally print a backtrace for that.
> 
> [1]: https://evilpiepirate.org/git/ktest.git/tree/tests/syzbot-repro.ktest
> 
>> 

Ok, I'll try it with this tool. For now, we are experimenting based on the early November 2024 version (df3dc63), let's see if we can debug this tool of yours.