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.
v2 (Daniel Vetter): - Re-order to put the reverts first - Add ACKs from Daniel - Add better CC and Fixes tags
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" Revert "drm/i915: Propagate errors on awaiting already signaled fences" drm/i915: Remove allow_alloc from i915_gem_object_get_sg* drm/i915: Drop error handling from dma_fence_work 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(-)