Re: Problems with hangs under NetBSD-5.x

[Sverre Froyen <sverre%viewmark.com@localhost>]

On Tue July 28 2009 09:57:09 Mindaugas Rasiukevicius wrote:
> Sverre Froyen <sverre%viewmark.com@localhost> wrote:
> > Does this warrant a PR?  The information is pretty limited.  I've
> > attached the output from ps.
>
> Yes, but more information is definitely need. Few things before that:
>
> - Can you try to compile a latest kernel from netbsd-5 branch? There is one
>   deadlock fix in VFS layer.

I have a new netbsd-5 kernel and userland ready and will reboot the server 
tomorrow.

> - Can you get into DDB and get a backtrace of LWPs which are stuck?

I can get into DDB but I will have limited time to poke around as this is a 
production server.  Is there a specific set of data that would be useful.  As 
you can see from the ps output, many processes are hung (I count 57).  Surely 
we do not need backtraces from all of those.  A set of commands to run would 
be most helpful.

> - Have you tried to leave only one CPU online and see if problem still
> occurs? See cpuctl(8) man page.

I am reluctant to do this as it will impact the server performance.

> > > 5.  I'm not using WAPBL, in fact, I don't have it built in my kernel. 
> > > I am,however, using ffs with softdep.
> >
> > No softdep and I've now seen this with and without WAPBL.
>
> WAPBL is strongly recommended over softdep. Note that softdep is actually
> removed in -current, and wont be in further releases.

I'm using neither at the moment.  If I see no hangs with the new netbsd-5 
kernel, I may try WAPBL again.  With WAPBL I would get hangs maybe once per 
week.

Thanks,
Sverre