[Intel-gfx] [PATCH] drm/i915: Skip an engine reset if it recovered before our preparations

[Chris Wilson]

At the beginning of a reset, we disable the submission method and find
the stuck request. We expect to find a stuck request for we have
declared the engine stalled. However, if we find no active request, the
engine must have recovered from its stall before we could issue a reset,
so let the engine continue on without a reset. If the engine is truly
stuck, we will back soon enough with the next reset attempt.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Michel Thierry <michel.thierry at intel.com>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index ca9f4b2862eb..6f24435ddffe 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -2011,19 +2011,19 @@ int i915_reset_engine(struct intel_engine_cs *engine, unsigned int flags)
 
 	GEM_BUG_ON(!test_bit(I915_RESET_ENGINE + engine->id, &error->flags));
 
-	if (!(flags & I915_RESET_QUIET)) {
-		dev_notice(engine->i915->drm.dev,
-			   "Resetting %s after gpu hang\n", engine->name);
-	}
-	error->reset_engine_count[engine->id]++;
-
 	active_request = i915_gem_reset_prepare_engine(engine);
-	if (IS_ERR(active_request)) {
+	if (IS_ERR_OR_NULL(active_request)) {
 		DRM_DEBUG_DRIVER("Previous reset failed, promote to full reset\n");
 		ret = PTR_ERR(active_request);
 		goto out;
 	}
 
+	if (!(flags & I915_RESET_QUIET)) {
+		dev_notice(engine->i915->drm.dev,
+			   "Resetting %s after gpu hang\n", engine->name);
+	}
+	error->reset_engine_count[engine->id]++;
+
 	if (!engine->i915->guc.execbuf_client)
 		ret = intel_gt_reset_engine(engine->i915, engine);
 	else
-- 
2.15.1