[Intel-gfx] [PATCH 06/16] drm/gem/shrinker: Wait before acquiring struct_mutex under oom

[Chris Wilson]

We can now wait for the GPU (all engines) to become idle without
requiring the struct_mutex. Inside the shrinker, we need to currently
take the struct_mutex in order to purge objects and to purge the objects
we need the GPU to be idle - causing a stall whilst we hold the
struct_mutex. We can hide most of that stall by performing the wait
before taking the struct_mutex and only doing essential waits for
new rendering on objects to be freed.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_shrinker.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index 1341cb55b6f1..43e53e419982 100644
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -326,9 +326,14 @@ i915_gem_shrinker_lock_uninterruptible(struct drm_i915_private *dev_priv,
 	unsigned long timeout = msecs_to_jiffies(timeout_ms) + 1;
 
 	while (!i915_gem_shrinker_lock(&dev_priv->drm, &slu->unlock)) {
+		if (i915_gem_wait_for_idle(dev_priv) == 0 &&
+		    i915_gem_shrinker_lock(&dev_priv->drm, &slu->unlock))
+			break;
+
 		schedule_timeout_killable(1);
 		if (fatal_signal_pending(current))
 			return false;
+
 		if (--timeout == 0) {
 			pr_err("Unable to lock GPU to purge memory.\n");
 			return false;
-- 
2.8.1