Re: [Intel-gfx] [PATCH 0/5] drm/i915: Get rid of fence error propagation

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Jun 02, 2021 at 11:41:44AM -0500, Jason Ekstrand wrote:
> Fence error propagation is sketchy at best.  Instead of explicitly handling
> fences which might have errors set in the code which is aware of errors, we
> just kick them down the line and hope that userspace knows what to do when
> a wait eventually fails.  This is sketchy at best because most userspace
> isn't prepared to handle errors in those places.  To make things worse, it
> allows errors to propagate across processes in unpredictable ways.  This is
> causing hangs in one client to kill X11.
> 
> Unfortunately, there's no quick path from here to there thanks to the fact
> that we're now running the command parser asynchronously and relying on
> fence errors for when it fails.  This series first gets rid of asynchronous
> command parsing and then cleans up from there.  There was never any real
> use-case for asynchronous parsing and the platforms that rely heavily on
> the command parser are old enough (Gen7) that, when we changed the way the
> command parser works, it wasn't really a change anyone was asking for
> anyway.
> 
> I think we probably want this whole mess back-ported.  I'm happy to take
> suggestions on the strategy there because the history there is a bit
> annoying and I'm not 100% sure where the Linux release cuts land.  In any
> case, I'm happy to make a version of this series per-release if needed for
> Greg to back-port.

I think just the two reversts are enough to be backported, other 3 are
cleanups.

Also I guess this will need to come with an igt patch to adjust the
cmdparser test.

With all the nits addressed, on the series.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> 
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Jon Bloomfield <jon.bloomfield@intel.com>
> 
> Jason Ekstrand (5):
>   drm/i915: Revert "drm/i915/gem: Asynchronous cmdparser"
>   drm/i915: Remove allow_alloc from i915_gem_object_get_sg*
>   drm/i915: Drop error handling from dma_fence_work
>   Revert "drm/i915: Propagate errors on awaiting already signaled
>     fences"
>   Revert "drm/i915: Skip over MI_NOOP when parsing"
> 
>  drivers/gpu/drm/i915/gem/i915_gem_clflush.c   |   4 +-
>  .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 227 +-----------------
>  drivers/gpu/drm/i915/gem/i915_gem_object.h    |  10 +-
>  drivers/gpu/drm/i915/gem/i915_gem_pages.c     |  21 +-
>  .../i915/gem/selftests/i915_gem_execbuffer.c  |   4 +
>  drivers/gpu/drm/i915/gt/intel_ggtt.c          |   2 +-
>  drivers/gpu/drm/i915/i915_cmd_parser.c        | 199 ++++++++-------
>  drivers/gpu/drm/i915/i915_drv.h               |   7 +-
>  drivers/gpu/drm/i915/i915_request.c           |   8 +-
>  drivers/gpu/drm/i915/i915_sw_fence_work.c     |   5 +-
>  drivers/gpu/drm/i915/i915_sw_fence_work.h     |   2 +-
>  drivers/gpu/drm/i915/i915_vma.c               |   3 +-
>  12 files changed, 141 insertions(+), 351 deletions(-)
> 
> -- 
> 2.31.1
> 

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