drm/i915: Remove walk over obj->vma_list for the shrinker

In the next patch, we want to reduce the lock coverage within the
shrinker, and one of the dangerous walks we have is over obj->vma_list.
We are only walking the obj->vma_list in order to check whether it has
been permanently pinned by HW access, typically via use on the scanout.
But we have a couple of other long term pins, the context objects for
which we currently have to check the individual vma pin_count. If we
instead mark these using obj->pin_display, we can forgo the dangerous
and sometimes slow list iteration.

v2: Rearrange code to try and avoid confusion from false associations
due to arrangement of whitespace along with rebasing on obj->pin_global.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171013202621.7276-4-chris@chris-wilson.co.uk

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 766552f2cfae..7f45dd7dc3e5 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1093,6 +1093,7 @@ execlists_context_pin(struct intel_engine_cs *engine,
 		i915_ggtt_offset(ce->ring->vma);
 
 	ce->state->obj->mm.dirty = true;
+	ce->state->obj->pin_global++;
 
 	i915_gem_context_get(ctx);
 out:
@@ -1120,6 +1121,7 @@ static void execlists_context_unpin(struct intel_engine_cs *engine,
 
 	intel_ring_unpin(ce->ring);
 
+	ce->state->obj->pin_global--;
 	i915_gem_object_unpin_map(ce->state->obj);
 	i915_vma_unpin(ce->state);