[Intel-gfx] [PATCH 2/2] drm/i915: drm/i915: Fix recursive calls to unmap

[Ben Widawsky]

After the ILK vt-d workaround patches it became clear that we had
introduced a bug.  Chris Wilson tracked down the issue to recursive
calls to unmap. This happens because we try to optimize waiting on
requests by calling retire requests after the wait, which may drop the
last reference on an object and end up freeing the object (and then
unmap the object from the gtt).

After the last patch we can now choose to defer processing the retire
list.

Kudos to Chris Wilson for tracking this one down.

This fixes tests/gem_linear_blits in intel-gpu-tools.

v2: v1 used a global, v2 directly modified the call chain.

v3: As Keith Packard pointed out, v2 changed retirement behavior. While
it was intentional, it wasn't related to the bugfix, and so has been
removed.  To do this, changed i915_wait_request to be a macro to assure
old behavior is kept.

v4: Rebased and renamed strictly_idle to defer_retirement.

V5: Don't use a macro port new code, just change all the callers.
Also had a badly named argument in the function definition.

This patch fixes gem_unref_active_buffers from i-g-t in the non-VTd
case (ie. do_idle_maps forced to true).

Reported-by: guang.a.yang at intel.com
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=42180
Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 11bddd5..e050b90 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -55,7 +55,7 @@ static bool do_idling(struct drm_i915_private *dev_priv)
 
 	if (unlikely(dev_priv->mm.gtt->do_idle_maps)) {
 		dev_priv->mm.interruptible = false;
-		if (i915_gpu_idle(dev_priv->dev, false)) {
+		if (i915_gpu_idle(dev_priv->dev, true)) {
 			DRM_ERROR("Couldn't idle GPU\n");
 			/* Wait a bit, in hopes it avoids the hang */
 			udelay(10);
-- 
1.7.8.4