2016-10-30 23:32:44

by Larry Finger

[permalink] [raw]
Subject: Regression in kernel 4.9-rcX - bisected to commit a481daa88fd4

With the 4.9-rcX kernel, my Dell Latitude D600 laptop has a kernel panic on
shutdown in routine radeon_connector_unregister(). This problem has been
bisected to show that commit a481daa88fd4 ("drm/radeon: always apply pci
shutdown callbacks") is at fault.

In the routine that crashes, the ddc_bus member of the struct drm_connector is
NULL, thus the following one-line (line-wrapped) patch fixes the problem:

diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c
b/drivers/gpu/drm/radeon/radeon_connectors.c
--- a/drivers/gpu/drm/radeon/radeon_connectors.c
+++ b/drivers/gpu/drm/radeon/radeon_connectors.c
@@ -931,7 +931,7 @@ static void radeon_connector_unregister(struct drm_connector
*connector)
{
struct radeon_connector *radeon_connector = to_radeon_connector(connector);

- if (radeon_connector->ddc_bus->has_aux) {
+ if (radeon_connector->ddc_bus && radeon_connector->ddc_bus->has_aux) {
drm_dp_aux_unregister(&radeon_connector->ddc_bus->aux);
radeon_connector->ddc_bus->has_aux = false;
}

The above change will soon be submitted as a proper patch. This posting to LKML
is intended to publicize the regression as soon as possible.

Larry


2016-11-06 11:29:12

by Thorsten Leemhuis

[permalink] [raw]
Subject: Re: Regression in kernel 4.9-rcX - bisected to commit a481daa88fd4

On 31.10.2016 00:32, Larry Finger wrote:
> With the 4.9-rcX kernel, my Dell Latitude D600 laptop has a kernel panic on
> shutdown in routine radeon_connector_unregister(). This problem has been
> bisected to show that commit a481daa88fd4 ("drm/radeon: always apply pci
> shutdown callbacks") is at fault.
>
> In the routine that crashes, the ddc_bus member of the struct drm_connector is
> NULL, thus the following one-line (line-wrapped) patch fixes the problem:
> […]
> The above change will soon be submitted as a proper patch. This posting to LKML
> is intended to publicize the regression as soon as possible.

JFYI: I added this report to the list of regressions for Linux 4.9. I'll
watch this thread for further updates on this issue to document progress
in my weekly reports. Please let me know via [email protected]
in case the discussion moves to a different place (bugzilla or another
mail thread for example).

Current status (afaics): Patch available

tia! Ciao, Thorsten

P.S.: Thx for CCing me!