commit f01a6f1491ec94dca77d80d3c76c473e806226da
author Vishnu Nair <vishnun@google.com> Mon Apr 03 22:34:17 2023 +0000
committer Vishnu Nair <vishnun@google.com> Tue Apr 04 00:07:45 2023 +0000
tree 5c1793a4a0248f468851f6acc2a74aea3d84d793
parent f9c1b98e54aa996d2a4412916a09e6fe504be560

[sf] Fix latch unsignaled issues

With LatchUnsignaledConfig::AutoSingleLayer flag, we should only
apply a transaction with an unsignaled fence if its the only transaction.
If we pass an unsignaled fence to HWC, HWC might miss presenting
the frame if the fence does not fire in time. If we apply another
transaction we may penalize the other transaction unfairly.

With LatchUnsignaledConfig::Always flag, respect backpressure flag
and take the opportunity to simplify the logic by treating the flag as
a signal to ignore the fence when applying transactions.

Test: surfaceflinger unit tests
Bug: 276229937
Change-Id: Ib5cd8205d62fdf8912b7f5c2cad312a01cae4300

services/surfaceflinger/FrontEnd/TransactionHandler.h

diff --git a/services/surfaceflinger/FrontEnd/TransactionHandler.h b/services/surfaceflinger/FrontEnd/TransactionHandler.h
index 7fc825e..865835f 100644
--- a/services/surfaceflinger/FrontEnd/TransactionHandler.h
+++ b/services/surfaceflinger/FrontEnd/TransactionHandler.h
@@ -40,14 +40,20 @@
         // Layer handles that have transactions with buffers that are ready to be applied.
         ftl::SmallMap<IBinder* /* binder address */, uint64_t /* framenumber */, 15>
                 bufferLayersReadyToPresent = {};
-        ftl::SmallVector<IBinder* /* queueToken */, 15> queuesWithUnsignaledBuffers;
+        // Tracks the queue with an unsignaled buffer. This is used to handle
+        // LatchUnsignaledConfig::AutoSingleLayer to ensure we only apply an unsignaled buffer
+        // if it's the only transaction that is ready to be applied.
+        sp<IBinder> queueWithUnsignaledBuffer = nullptr;
     };
     enum class TransactionReadiness {
-        NotReady,
-        NotReadyBarrier,
+        // Transaction is ready to be applied
         Ready,
-        ReadyUnsignaled,
-        ReadyUnsignaledSingle,
+        // Transaction has unmet conditions (fence, present time, etc) and cannot be applied.
+        NotReady,
+        // Transaction is waiting on a barrier (another buffer to be latched first)
+        NotReadyBarrier,
+        // Transaction has an unsignaled fence but can be applied if it's the only transaction
+        NotReadyUnsignaled,
     };
     using TransactionFilter = std::function<TransactionReadiness(const TransactionFlushState&)>;
 
@@ -64,6 +70,9 @@
     friend class ::android::TestableSurfaceFlinger;
 
     int flushPendingTransactionQueues(std::vector<TransactionState>&, TransactionFlushState&);
+    void applyUnsignaledBufferTransaction(std::vector<TransactionState>&, TransactionFlushState&);
+    void popTransactionFromPending(std::vector<TransactionState>&, TransactionFlushState&,
+                                   std::queue<TransactionState>&);
     TransactionReadiness applyFilters(TransactionFlushState&);
     std::unordered_map<sp<IBinder>, std::queue<TransactionState>, IListenerHash>
             mPendingTransactionQueues;