drm/i915/gt: Convert timeline tracking to spinlock

Convert the active_list manipulation of timelines to use spinlocks so
that we can perform the updates from underneath a quick interrupt
callback, if need be.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190815205709.24285-2-chris@chris-wilson.co.uk

3 files changed, 14 insertions, 10 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_types.h b/drivers/gpu/drm/i915/gt/intel_gt_types.h
index adab4d2c29ac..143b2d78c2cc 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_types.h
@@ -40,7 +40,7 @@ struct intel_gt {
 	struct intel_uc uc;
 
 	struct intel_gt_timelines {
-		struct mutex mutex; /* protects list */
+		spinlock_t lock; /* protects active_list */
 		struct list_head active_list;
 
 		/* Pack multiple timelines' seqnos into the same page */
diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
index ec85740de942..077716442c90 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -811,7 +811,7 @@ static bool __intel_gt_unset_wedged(struct intel_gt *gt)
 	 *
 	 * No more can be submitted until we reset the wedged bit.
 	 */
-	mutex_lock(&timelines->mutex);
+	spin_lock(&timelines->lock);
 	list_for_each_entry(tl, &timelines->active_list, link) {
 		struct i915_request *rq;
 
@@ -819,6 +819,8 @@ static bool __intel_gt_unset_wedged(struct intel_gt *gt)
 		if (!rq)
 			continue;
 
+		spin_unlock(&timelines->lock);
+
 		/*
 		 * All internal dependencies (i915_requests) will have
 		 * been flushed by the set-wedge, but we may be stuck waiting
@@ -828,8 +830,12 @@ static bool __intel_gt_unset_wedged(struct intel_gt *gt)
 		 */
 		dma_fence_default_wait(&rq->fence, false, MAX_SCHEDULE_TIMEOUT);
 		i915_request_put(rq);
+
+		/* Restart iteration after droping lock */
+		spin_lock(&timelines->lock);
+		tl = list_entry(&timelines->active_list, typeof(*tl), link);
 	}
-	mutex_unlock(&timelines->mutex);
+	spin_unlock(&timelines->lock);
 
 	intel_gt_sanitize(gt, false);
 
diff --git a/drivers/gpu/drm/i915/gt/intel_timeline.c b/drivers/gpu/drm/i915/gt/intel_timeline.c
index 4af0b9801d91..355dfc52c804 100644
--- a/drivers/gpu/drm/i915/gt/intel_timeline.c
+++ b/drivers/gpu/drm/i915/gt/intel_timeline.c
@@ -266,7 +266,7 @@ static void timelines_init(struct intel_gt *gt)
 {
 	struct intel_gt_timelines *timelines = &gt->timelines;
 
-	mutex_init(&timelines->mutex);
+	spin_lock_init(&timelines->lock);
 	INIT_LIST_HEAD(&timelines->active_list);
 
 	spin_lock_init(&timelines->hwsp_lock);
@@ -345,9 +345,9 @@ void intel_timeline_enter(struct intel_timeline *tl)
 		return;
 	GEM_BUG_ON(!tl->active_count); /* overflow? */
 
-	mutex_lock(&timelines->mutex);
+	spin_lock(&timelines->lock);
 	list_add(&tl->link, &timelines->active_list);
-	mutex_unlock(&timelines->mutex);
+	spin_unlock(&timelines->lock);
 }
 
 void intel_timeline_exit(struct intel_timeline *tl)
@@ -358,9 +358,9 @@ void intel_timeline_exit(struct intel_timeline *tl)
 	if (--tl->active_count)
 		return;
 
-	mutex_lock(&timelines->mutex);
+	spin_lock(&timelines->lock);
 	list_del(&tl->link);
-	mutex_unlock(&timelines->mutex);
+	spin_unlock(&timelines->lock);
 
 	/*
 	 * Since this timeline is idle, all bariers upon which we were waiting
@@ -548,8 +548,6 @@ static void timelines_fini(struct intel_gt *gt)
 
 	GEM_BUG_ON(!list_empty(&timelines->active_list));
 	GEM_BUG_ON(!list_empty(&timelines->hwsp_free_list));
-
-	mutex_destroy(&timelines->mutex);
 }
 
 void intel_timelines_fini(struct drm_i915_private *i915)