On 19/02/2018 18:35, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2018-02-19 18:31:31)

On 19/02/2018 14:01, Chris Wilson wrote:
If we fail to unbind the vma (due to a signal on an active buffer that
needs to be moved for the next execbuf), then we need to clear the
persistent tracking state we setup for this execbuf.

Fixes: c7c6e46f913b ("drm/i915: Convert execbuf to use struct-of-array packing for 
critical fields")
Testcase: igt/gem_fenced_exec_thrash/no-spare-fences-busy*
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
Cc: <sta...@vger.kernel.org> # v4.14+
   drivers/gpu/drm/i915/i915_gem_execbuffer.c | 2 ++
   1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c 
index 51f3c32c64bf..4eb28e84fda4 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -505,6 +505,8 @@ eb_add_vma(struct i915_execbuffer *eb, unsigned int i, 
struct i915_vma *vma)
               list_add_tail(&vma->exec_link, &eb->unbound);
               if (drm_mm_node_allocated(&vma->node))
                       err = i915_vma_unbind(vma);
+             if (unlikely(err))
+                     vma->exec_flags = NULL;
       return err;

I was trying to track down what actually explodes for like 15 minutes.

My track was:

eb_relocate -> eb_lookup_vmas fails -> eb_relocate -> eb_relocate_slow
-> eb_reset_vmas -> second pass to eb_lookup_vmas -> resets
vma->exec_flags. So no explosion.

So in other words I've failed to find what goes wrong and under which

The first eb_relocate calls eb_lookup_vma triggers the failure and exit
from execbuf. In that path, we mark the current index as the sentinel
(err_vma: eb->vma[i] = NULL) which means we do not clear the last vma
when unwinding in eb_release_vmas. So the vma->exec_flags was carried
over into the next execbuf call from userspace.

Ah yes, I missed the !vma continue bit in eb_release vmas.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com>



Intel-gfx mailing list

Reply via email to