[Intel-gfx] [PATCH] drm/i915: Distinguish last emitted request from last submitted request

[Chris Wilson]

In order not to trigger hangcheck on a idle-but-waiting engine, we need
to distinguish between the pending request queue and the actual
execution queue. This is done later in "drm/i915: Enable multiple
timelines" but for now we need a temporary fix to prevent blaming the
wrong engine for a GPU hang.

Fixes: 0a046a0e93d2 ("drm/i915: Nonblocking request submission")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/i915_gem_request.c | 5 +++--
 drivers/gpu/drm/i915/intel_ringbuffer.h | 1 +
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 40978bc12ceb..8832f8ec1583 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -328,6 +328,7 @@ submit_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state)
 
 	switch (state) {
 	case FENCE_COMPLETE:
+		request->engine->last_submitted_seqno = request->fence.seqno;
 		request->engine->submit_request(request);
 		break;
 
@@ -641,8 +642,8 @@ void __i915_add_request(struct drm_i915_gem_request *request, bool flush_caches)
 					     &request->submitq);
 
 	request->emitted_jiffies = jiffies;
-	request->previous_seqno = engine->last_submitted_seqno;
-	engine->last_submitted_seqno = request->fence.seqno;
+	request->previous_seqno = engine->last_pending_seqno;
+	engine->last_pending_seqno = request->fence.seqno;
 	i915_gem_active_set(&engine->last_request, request);
 	list_add_tail(&request->link, &engine->request_list);
 	list_add_tail(&request->ring_link, &ring->request_list);
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 498931f0b1f1..34954ca03a4a 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -355,6 +355,7 @@ struct intel_engine_cs {
 	 * inspecting request list.
 	 */
 	u32 last_submitted_seqno;
+	u32 last_pending_seqno;
 
 	/* An RCU guarded pointer to the last request. No reference is
 	 * held to the request, users must carefully acquire a reference to
-- 
2.9.3