From 09cf7c9a1299c386525d31305fd50591acf49a9a Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 13 Jul 2012 14:14:08 +0100 Subject: [PATCH] drm/i915: Insert a flush between batches if the breadcrumb was dropped If we drop the breadcrumb request after a batch due to a signal for example we aim to fix it up at the next opportunity. In this case we emit a second batchbuffer with no waits upon the first and so no opportunity to insert the missing request, so we need to emit the missing flush for coherency. (Note that that invalidating the render cache is the same as flushing it, so there should have been no observable corruption.) Note that beside simply adding the missing flush, avoiding potential render corruption, this will also fix at least parts of the problem introduced by some funny interaction of these two commits: commit de2b998552c1534e87bfbc51ec5734b02bc89020 Author: Daniel Vetter Date: Wed Jul 4 22:52:50 2012 +0200 drm/i915: don't return a spurious -EIO from intel_ring_begin which allowed intel_ring_begin to return -ERESTARTSYS and commit cc889e0f6ce6a63c62db17d702ecfed86d58083f Author: Daniel Vetter Date: Wed Jun 13 20:45:19 2012 +0200 drm/i915: disable flushing_list/gpu_write_list which essentially disabled the flushing list. The issue happens when we submit a batch & emit it, but get interrupted (thanks to the first patch) while trying to emit the flush. On the next batch we still assume that the full gpu domain handling is in effect and hence compute the invalidate&flushing domains. But thanks to the 2nd patch we totally ignore these and only invalidate all gpu domains, presuming that any required flushes have been issued already. Which is wrong and eventually results in us updating the new write_domain values with the computed pending_write_domain values, which leaves an object with write_domain == 0 on the gpu_write_list. As soon as we try to unbind that object, things blow up. Fix this by emitting the missing flush according to the new ring->gpu_caches_dirty flag. Note that this does _not_ fix all the current cases where we end up with an object on the flushing_list that can't be flushed. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=52040 Signed-off-by: Chris Wilson [danvet: Add bug explanation to commit message.] Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/i915_gem_execbuffer.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c index 88e2e114189c..981e14f000e3 100644 --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c @@ -885,11 +885,16 @@ i915_gem_execbuffer_move_to_gpu(struct intel_ring_buffer *ring, return ret; } - /* Unconditionally invalidate gpu caches. */ - ret = i915_gem_flush_ring(ring, I915_GEM_GPU_DOMAINS, 0); + /* Unconditionally invalidate gpu caches and ensure that we do flush + * any residual writes from the previous batch. + */ + ret = i915_gem_flush_ring(ring, + I915_GEM_GPU_DOMAINS, + ring->gpu_caches_dirty ? I915_GEM_GPU_DOMAINS : 0); if (ret) return ret; + ring->gpu_caches_dirty = false; return 0; } -- 2.20.1