[Intel-gfx] [PATCH 16/37] drm/i915: Always defer fenced work to the worker

[Chris Wilson]

Currently, if an error is raised we always call the cleanup locally
[and skip the main work callback]. However, some future users may need
to take a mutex to cleanup and so we cannot immediately execute the
cleanup as we may still be in interrupt context. For example, if we have
committed sensitive changes [like evicting from the ppGTT layout] that
are visible but gated behind the fence, we need to ensure those changes
are completed even after an error. [This does suggest the split between
the work/release callback is artificial and we may be able to simplify
the worker api by only requiring a single callback.]

With the execute-immediate flag, for most cases this should result in
immediate cleanup of an error.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_sw_fence_work.c | 26 +++++++++++------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_sw_fence_work.c b/drivers/gpu/drm/i915/i915_sw_fence_work.c
index a3a81bb8f2c3..e094fd0a4202 100644
--- a/drivers/gpu/drm/i915/i915_sw_fence_work.c
+++ b/drivers/gpu/drm/i915/i915_sw_fence_work.c
@@ -16,11 +16,14 @@ static void fence_complete(struct dma_fence_work *f)
 static void fence_work(struct work_struct *work)
 {
 	struct dma_fence_work *f = container_of(work, typeof(*f), work);
-	int err;
 
-	err = f->ops->work(f);
-	if (err)
-		dma_fence_set_error(&f->dma, err);
+	if (!f->dma.error) {
+		int err;
+
+		err = f->ops->work(f);
+		if (err)
+			dma_fence_set_error(&f->dma, err);
+	}
 
 	fence_complete(f);
 	dma_fence_put(&f->dma);
@@ -36,15 +39,10 @@ fence_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state)
 		if (fence->error)
 			dma_fence_set_error(&f->dma, fence->error);
 
-		if (!f->dma.error) {
-			dma_fence_get(&f->dma);
-			if (test_bit(DMA_FENCE_WORK_IMM, &f->dma.flags))
-				fence_work(&f->work);
-			else
-				queue_work(system_unbound_wq, &f->work);
-		} else {
-			fence_complete(f);
-		}
+		if (test_bit(DMA_FENCE_WORK_IMM, &f->dma.flags))
+			fence_work(&f->work);
+		else
+			queue_work(system_unbound_wq, &f->work);
 		break;
 
 	case FENCE_FREE:
@@ -91,6 +89,8 @@ void dma_fence_work_init(struct dma_fence_work *f,
 	dma_fence_init(&f->dma, &fence_ops, &f->lock, 0, 0);
 	i915_sw_fence_init(&f->chain, fence_notify);
 	INIT_WORK(&f->work, fence_work);
+
+	dma_fence_get(&f->dma); /* once for the chain; once for the work */
 }
 
 int dma_fence_work_chain(struct dma_fence_work *f, struct dma_fence *signal)
-- 
2.20.1