Re: [PATCH] drm/i915/gen9: fix error path in intel_init_workaround_bb

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Jun 23, 2015 at 05:21:16PM +0100, Siluvery, Arun wrote:
> On 23/06/2015 17:01, Chris Wilson wrote:
> >On Tue, Jun 23, 2015 at 06:58:42PM +0300, Imre Deak wrote:
> >>On ti, 2015-06-23 at 16:44 +0100, Chris Wilson wrote:
> >>>On Tue, Jun 23, 2015 at 06:18:21PM +0300, Imre Deak wrote:
> >>>>On ti, 2015-06-23 at 16:13 +0100, Siluvery, Arun wrote:
> >>>>>On 23/06/2015 15:36, Imre Deak wrote:
> >>>>>>On ti, 2015-06-23 at 15:31 +0100, Chris Wilson wrote:
> >>>>>>>On Tue, Jun 23, 2015 at 05:26:13PM +0300, Imre Deak wrote:
> >>>>>>>>On the GEN!=8 error path we call kmap_atomic() which returns in atomic
> >>>>>>>>context and then lrc_destroy_wa_ctx_obj() which can be called only in
> >>>>>>>>process context. Fix this by preserving the correct cleanup order on
> >>>>>>>>this error path.
> >>>>>>>>
> >>>>>>>>Also convert the WARN to DRM_ERROR the stack trace isn't really useful.
> >>>>>>>>
> >>>>>>>>Signed-off-by: Imre Deak <imre.deak@intel.com>
> >>>>>>>>---
> >>>>>>>>   drivers/gpu/drm/i915/intel_lrc.c | 10 +++++++---
> >>>>>>>>   1 file changed, 7 insertions(+), 3 deletions(-)
> >>>>>>>>
> >>>>>>>>diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> >>>>>>>>index 1b50dd7..8bff1a2 100644
> >>>>>>>>--- a/drivers/gpu/drm/i915/intel_lrc.c
> >>>>>>>>+++ b/drivers/gpu/drm/i915/intel_lrc.c
> >>>>>>>>@@ -1289,10 +1289,14 @@ static int intel_init_workaround_bb(struct intel_engine_cs *ring)
> >>>>>>>>   		if (ret)
> >>>>>>>>   			goto out;
> >>>>>>>>   	} else {
> >>>>>>>>-		WARN(INTEL_INFO(ring->dev)->gen >= 8,
> >>>>>>>>-		     "WA batch buffer is not initialized for Gen%d\n",
> >>>>>>>>-		     INTEL_INFO(ring->dev)->gen);
> >>>>>>>>+		if (INTEL_INFO(ring->dev)->gen >= 8)
> >>>>>>>>+			DRM_ERROR("WA batch buffer is not initialized for Gen%d\n",
> >>>>>>>>+				  INTEL_INFO(ring->dev)->gen);
> >>>>>>>>+
> >>>>>>>
> >>>>>>>Do this test upfront, then we don't have multiple error paths.
> >>>>>>>http://paste.debian.net/255769
> >>>>>>
> >>>>>>I didn't bother moving it, I suppose GEN9 support will be added soon
> >>>>>>anyway and we get a bit more test coverage on GEN9 meanwhile. But if you
> >>>>>>insist I can move it.
> >>>>>
> >>>>>Hi Imre,
> >>>>>
> >>>>>I sent the following patch with the changes suggested by Chris.
> >>>>>https://patchwork.kernel.org/patch/6661891/
> >>>>>Since you sent it first, my patch can be ignored if your patch is updated.
> >>>>
> >>>>I'm fine applying your patch, but I would ask to convert the WARN to
> >>>>DRM_ERROR. The stack trace doesn't add much to the error message and the
> >>>>WARN is needlessly verbose now on BXT,SKL..
> >>>
> >>>I presumed Arun choose WARN because we are missing w/a and wanted
> >>>someone to step forward and prove the fixes?
> >>
> >>Imo it's unnecessarily verbose, during development when loading the
> >>driver I know that things are mostly ok if I can't see any such
> >>backtraces. But no strong opinion, I can also change this locally.
> 
> Error message can easily get lost and also it is not an error to not apply
> these WA which is why we also continue. I thought WARN will probably get
> more attention and help in adding missing WA quickly.

Friendly inquiry from your maintainer: Can we perhaps not bikeshed the
benefits of DRM_ERROR vs. WARN_ON and just get this reviewed&merged?

From an igt/piglit pov both cause a test failure and so are equivalent.
And I'm hopeful that the new QA team actually catches dmesg fallout
reliable rsn.

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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