WITNESS bug

[John Baldwin]

On Tuesday 19 October 2004 05:25 pm, Julian Elischer wrote:
> John Baldwin wrote:
> >On Tuesday 19 October 2004 12:01 pm, Kris Kennaway wrote:
> >>On Tue, Oct 19, 2004 at 09:13:26AM -0400, Robert Huff wrote:
> >>>Brian Fundakowski Feldman writes:
> >>>> You should never not run with WITNESS_SKIPSPIN if you use
> >>>> modules.  Any spin mutexes not listed statically in the witness
> >>>> code will cause your machine to immediately panic.
> >>>
> >>>	If this is true (and I'm not disputing it), shouldn't it be
> >>>noted in GENERIC and/or NOTES?  For that matter, what's the penalty
> >>>for not automatically including it as part of WITNESS?
> >>
> >>Sometimes you don't want to use it, e.g. if you actually want to trace
> >>spinlock operations with witness.
> >
> >True spin mutexes should be rarely used anyways, so I don't think modules
> >needing spin mutexes is all that big of an issue.  Almost all mutexes
> > should just be regular mutexes.
>
> netgraph uses a spin mutex for it's node locks

This is likely a bug, esp. given that normal mutexes adaptively spin when it 
is advantageous to do so. :)

-- 

John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/