linux-kernel - Re: i865, drm_modeset_lock_all: BUG: unable to handle kernel NULL pointer dereference at 00000104

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Message-ID: <alpine.LRH.2.20.1608231445550.17020@math.ut.ee>
Date:   Tue, 23 Aug 2016 14:46:15 +0300 (EEST)
From:   Meelis Roos <mroos@...ux.ee>
To:     Chris Wilson <chris@...is-wilson.co.uk>
cc:     Linux Kernel list <linux-kernel@...r.kernel.org>,
        dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org
Subject: Re: i865, drm_modeset_lock_all: BUG: unable to handle kernel NULL
 pointer dereference at 00000104

> > > Looks like an incorrect call to drm_encoder_cleanup() from the error
> > > path. If we hit the error path we have never called drm_encoder_init.
> > > Please try:
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_dvo.c b/drivers/gpu/drm/i915/intel_dvo.c
> > > index 47bdf9dad0d3..b9e5a63a7c9e 100644
> > > --- a/drivers/gpu/drm/i915/intel_dvo.c
> > > +++ b/drivers/gpu/drm/i915/intel_dvo.c
> > > @@ -554,7 +554,6 @@ void intel_dvo_init(struct drm_device *dev)
> > >  		return;
> > >  	}
> > >  
> > > -	drm_encoder_cleanup(&intel_encoder->base);
> > >  	kfree(intel_dvo);
> > >  	kfree(intel_connector);
> > >  }
> > 
> > It works - the BUG is gone.
> > 
> > Now I get just 
> > [drm:__intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR* pipe A underrun
> 
> Other than the annoying underrun, is everything else as expected? i.e.
> no connected outputs? Have we lost dvo detection?

Yes, as expected - there is no monitor connected.

-- 
Meelis Roos (mroos@...ux.ee)