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[CI,6/6] drm/i915: Remove completed fences after a wait

Message ID 20170217151304.16665-6-chris@chris-wilson.co.uk (mailing list archive)
State New, archived
Headers show

Commit Message

Chris Wilson Feb. 17, 2017, 3:13 p.m. UTC 
If we wait upon the full (i.e. all shared fences, or upon an exclusive fence)
reservation object successfully, we know that all fences beneath it have
been signaled, so long as no new fences were added whilst we slept. If the
reservation_object remains the same, as detected by its seqcount, we can
then reap all the fences upon completion.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)
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Patch

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 5f7b8c88eb7e..d93032875f28 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -427,7 +427,9 @@  i915_gem_object_wait_reservation(struct reservation_object *resv,
 				 long timeout,
 				 struct intel_rps_client *rps)
 {
+	unsigned int seq = __read_seqcount_begin(&resv->seq);
 	struct dma_fence *excl;
+	bool prune_fences = false;
 
 	if (flags & I915_WAIT_ALL) {
 		struct dma_fence **shared;
@@ -452,15 +454,26 @@  i915_gem_object_wait_reservation(struct reservation_object *resv,
 		for (; i < count; i++)
 			dma_fence_put(shared[i]);
 		kfree(shared);
+
+		prune_fences = count && timeout >= 0;
 	} else {
 		excl = reservation_object_get_excl_rcu(resv);
 	}
 
-	if (excl && timeout >= 0)
+	if (excl && timeout >= 0) {
 		timeout = i915_gem_object_wait_fence(excl, flags, timeout, rps);
+		prune_fences = timeout >= 0;
+	}
 
 	dma_fence_put(excl);
 
+	if (prune_fences && !__read_seqcount_retry(&resv->seq, seq)) {
+		reservation_object_lock(resv, NULL);
+		if (!__read_seqcount_retry(&resv->seq, seq))
+			reservation_object_add_excl_fence(resv, NULL);
+		reservation_object_unlock(resv);
+	}
+
 	return timeout;
 }