linux-kernel - Re: [PATCH v2] drm: use mgr->dev in drm_dbg_kms in drm_dp_add_payload

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Message-ID: <3d47da79a59817b69d5ed7cdaf4fbec227be00d9.camel@redhat.com>
Date:   Tue, 20 Jun 2023 15:59:24 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     Jeff Layton <jlayton@...nel.org>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     Wayne.Lin@....com, alexdeucher@...il.com,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm: use mgr->dev in drm_dbg_kms in
 drm_dp_add_payload_part2

Also since I forgot, so patchwork picks this up:

Reviewed-by: Lyude Paul <lyude@...hat.com>

On Tue, 2023-06-20 at 15:50 -0400, Lyude Paul wrote:
> Eek - this might have been a situation where everyone involved assumed someone
> else would push it, whoops. I'll make sure this is pushed upstream :).
> 
> FWIW: You could definitely send an MR to the fedora kernel's gitlab to get
> this included earlier. If you don't get to it before me I'll try to do that
> today
> 
> On Tue, 2023-06-20 at 07:18 -0400, Jeff Layton wrote:
> > I've noticed that this patch is not included in linux-next currently.
> > 
> > Can I get some confirmation that this is going to be included in v6.5?
> > Currently, I've been having to rebuild Fedora kernels to avoid this
> > panic, and I'd like to know there is a light at the end of that tunnel.
> > 
> > Thanks,
> > Jeff
> > 
> > On Wed, 2023-04-19 at 16:54 -0400, Lyude Paul wrote:
> > > Reviewed-by: Lyude Paul <lyude@...hat.com>
> > > 
> > > Thanks!
> > > 
> > > On Wed, 2023-04-19 at 07:24 -0400, Jeff Layton wrote:
> > > > I've been experiencing some intermittent crashes down in the display
> > > > driver code. The symptoms are ususally a line like this in dmesg:
> > > > 
> > > >     amdgpu 0000:30:00.0: [drm] Failed to create MST payload for port 000000006d3a3885: -5
> > > > 
> > > > ...followed by an Oops due to a NULL pointer dereference.
> > > > 
> > > > Switch to using mgr->dev instead of state->dev since "state" can be
> > > > NULL in some cases.
> > > > 
> > > > Link: https://bugzilla.redhat.com/show_bug.cgi?id=2184855
> > > > Suggested-by: Jani Nikula <jani.nikula@...ux.intel.com>
> > > > Signed-off-by: Jeff Layton <jlayton@...nel.org>
> > > > ---
> > > >  drivers/gpu/drm/display/drm_dp_mst_topology.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > I've been running this patch for a couple of days, but the problem
> > > > hasn't occurred again as of yet. It seems sane though as long as we can
> > > > assume that mgr->dev will be valid even when "state" is a NULL pointer.
> > > > 
> > > > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > > index 38dab76ae69e..e2e21ce79510 100644
> > > > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > > @@ -3404,7 +3404,7 @@ int drm_dp_add_payload_part2(struct drm_dp_mst_topology_mgr *mgr,
> > > >  
> > > >  	/* Skip failed payloads */
> > > >  	if (payload->vc_start_slot == -1) {
> > > > -		drm_dbg_kms(state->dev, "Part 1 of payload creation for %s failed, skipping part 2\n",
> > > > +		drm_dbg_kms(mgr->dev, "Part 1 of payload creation for %s failed, skipping part 2\n",
> > > >  			    payload->port->connector->name);
> > > >  		return -EIO;
> > > >  	}
> > > 
> > 
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat