r244036 kernel hangs under load.

[Konstantin Belousov]

On Tue, Dec 11, 2012 at 08:58:47PM -0500, Rick Macklem wrote:
> Ok, I'll test r243598 and then r243599 and r243835, just to
> see if it really is this.
> 
> I'll email when I have done this.
If you test only r243598, I am sure that you would experience corruption.
The r243599 should cause the deadlocks.

> 
> > >
> > >  Also, do you use the post-r244095 kernel ?
> > >
> > > Before and after. The most recent tests were post-r244095.
> > > (If anything the more recent kernels hang more easily.)
> > >
> > >
> > > >
> > > > Is your machine SMP ?
> > >
> > > Old, slow single core i386.
> > 
> > Try this. Please note that this is mostly a debugging facility.
> > 
> It seemed to help, but didn't stop the hangs completely.
> r244125 without the patch would hang somewhere in a kernel
> build. r244125 plus this patch ran almost 2 kernel builds
> before it got hung.

Can you try to look into the system state on the hang (on the kernel
with the if (1 || patch applied) ? Using the ddb and recipe from the
web page. Basically watch for a thread looping in the mnt_active
iterator and threads owning vnode interlocks.
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