Re: Hang when starting sshd on MP machine

[Andrew Doran <ad%NetBSD.org@localhost>]

On Sat, Mar 22, 2008 at 03:40:55PM -0400, Chris Ross wrote:

> 
> On Mar 22, 2008, at 10:25, Andrew Doran wrote:
> >It's a deadlock involving kernel_lock. Haven't figured out what the  
> >problem
> >is yet, but I've put kernel_lock back around the kqueue stuff which  
> >should
> >sort it for the time being.
> 
>   Putting kernel_lock back avoids the problem, helps figure out where  
> the problem is, or both? 

It avoids the problem.

> If the former, then is there any help those of us only testing and not yet
> needing any term of multiuser functionality could do to provide data to
> help track it down?

I think it's case of trying to understand where the dealock is coming from.
It looks like a lock order reversal. I think what is happening is that one
thread is acquiring:

        kernel_lock -> kq_lock

.. and another is acquiring:

        kq_lock -> kernel_lock.

They both deadlock waiting for each other's lock. Given a quick look I
haven't been able to find that.

Andrew