Messages in this thread | | | From | Jani Nikula <> | Subject | Re: [PATCH] drm: make drm_dp_add_payload_part2 gracefully handle NULL state pointer | Date | Mon, 17 Apr 2023 11:44:47 +0300 |
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On Fri, 14 Apr 2023, Lyude Paul <lyude@redhat.com> wrote: > On Fri, 2023-04-14 at 13:35 +0300, Jani Nikula wrote: >> On Fri, 14 Apr 2023, Jeff Layton <jlayton@kernel.org> wrote: >> > On Fri, 2023-04-14 at 04:40 +0000, Lin, Wayne wrote: >> > > [Public] >> > > >> > > Hi Jeff, >> > > >> > > Thanks. I might need more information to understand why we can't retrieve >> > > the drm atomic state. Also , "Failed to create MST payload for port" indicates >> > > error while configuring DPCD payload ID table. Could you help to provide log >> > > with KMS + ATOMIC + DP debug on please? Thanks in advance! >> > > >> > > Regards, >> > > Wayne >> > > >> > >> > Possibly. I'm not that familiar with display driver debugging. Can you >> > send me some directions on how to crank up that sort of debug logging? >> > >> > Note that this problem is _very_ intermittent too: I went about 2 weeks >> > between crashes, and then I got 3 in one day. I'd rather not run with a >> > lot of debug logging for a long time if that's what this is going to >> > require, as this is my main workstation. >> > >> > The last time I got this log message, my proposed patch did prevent the >> > box from oopsing, so I'd really like to see it go in unless it's just >> > categorically wrong for the caller to pass down a NULL state pointer to >> > drm_dp_add_payload_part2. >> >> Cc: Lyude. >> >> Looks like the state parameter was added in commit 4d07b0bc4034 >> ("drm/display/dp_mst: Move all payload info into the atomic state") and >> its only use is to get at state->dev for debug logging. >> >> What's the plan for the parameter? Surely something more than that! :) > > I don't think there was any plan for that, or at least I certainly don't even > remember adding that D:. It must totally have been by mistake and snuck by > review, if that's the only thing that we're using it for I'd say it's > definitely fine to just drop it entirely
I guess we could use two patches then, first replace state->dev with mgr->dev as something that can be backported as needed, and second drop the state parameter altogether.
Jeff, up for it? At least the first one?
BR, Jani.
> >> >> Instead of "state ? state->dev : NULL" I guess we could use mgr->dev >> like the other logging calls do. It's papering over the NULL parameter >> too, but perhaps in a slightly cleaner way... >> >> >> BR, >> Jani. >> >> >> > >> > > > -----Original Message----- >> > > > From: Alex Deucher <alexdeucher@gmail.com> >> > > > Sent: Thursday, April 13, 2023 8:59 PM >> > > > To: Jani Nikula <jani.nikula@linux.intel.com>; Lin, Wayne >> > > > <Wayne.Lin@amd.com> >> > > > Cc: Jeff Layton <jlayton@kernel.org>; David Airlie <airlied@gmail.com>; >> > > > Daniel Vetter <daniel@ffwll.ch>; Deucher, Alexander >> > > > <Alexander.Deucher@amd.com>; linux-kernel@vger.kernel.org; dri- >> > > > devel@lists.freedesktop.org >> > > > Subject: Re: [PATCH] drm: make drm_dp_add_payload_part2 gracefully >> > > > handle NULL state pointer >> > > > >> > > > + Wayne >> > > > >> > > > On Thu, Apr 13, 2023 at 8:31 AM Jani Nikula <jani.nikula@linux.intel.com> >> > > > wrote: >> > > > > >> > > > > On Thu, 13 Apr 2023, Jeff Layton <jlayton@kernel.org> 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. >> > > > > > >> > > > > > The real bug is probably in the caller of this function, which is >> > > > > > passing it a NULL state pointer, but this patch at least keeps my >> > > > > > machine from oopsing when this occurs. >> > > > > >> > > > > My fear is that papering over this makes the root cause harder to find. >> > > > > >> > > > > Cc: Harry, Alex >> > > > > >> > > > > >> > > > > BR, >> > > > > Jani. >> > > > > >> > > > > >> > > > > > >> > > > > > Link: https://bugzilla.redhat.com/show_bug.cgi?id=2184855 >> > > > > > Signed-off-by: Jeff Layton <jlayton@kernel.org> >> > > > > > --- >> > > > > > drivers/gpu/drm/display/drm_dp_mst_topology.c | 3 ++- >> > > > > > 1 file changed, 2 insertions(+), 1 deletion(-) >> > > > > > >> > > > > > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c >> > > > > > b/drivers/gpu/drm/display/drm_dp_mst_topology.c >> > > > > > index 38dab76ae69e..87ad406c50f9 100644 >> > > > > > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c >> > > > > > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c >> > > > > > @@ -3404,7 +3404,8 @@ 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(state ? state->dev : NULL, >> > > > > > + "Part 1 of payload creation for %s failed, >> > > > > > + skipping part 2\n", >> > > > > > payload->port->connector->name); >> > > > > > return -EIO; >> > > > > > } >> > > > > >> > > > > -- >> > > > > Jani Nikula, Intel Open Source Graphics Center >>
-- Jani Nikula, Intel Open Source Graphics Center
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