panic on 5.2 BETA: blockable sleep lock

Stefan Ehmann shoesoft at
Fri Nov 28 00:31:21 PST 2003

On Fri, 2003-11-28 at 01:02, Don Lewis wrote:
> On 27 Nov, Stefan Ehmann wrote:
> > On Wed, 2003-11-26 at 08:33, Don Lewis wrote:
> >> The problem is that selrecord() wants to lock a MTX_DEF mutex, which can
> >> cause a context switch if the mutex is already locked by another thread.
> >> This is contrary to what bktr_poll() wants to accomplish by calling
> >> critical_enter().
> > 
> > Strange enough that does not seem to happen with a kernel built without
> > INVARIANTS and WITNESS. Does this make any sense or is this just by
> > chance?
> You might try the patch below with WITNESS enabled.  I don't have the
> hardware, so I can't test it.  It compiles for me, but for all I know it
> could delete all your files if you run it.

Tested it a few times and no panics - seems to work fine. Tested it
again without the patch: panics immediately after starting alevt (not
xawtv as initially stated).


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