Ensure transaction commit callbacks are called at most once.

Bug: 288781573
Bug: 292443283
Test: atest LayerTransactionTest
Change-Id: Ide66601b8a892b4bf5a331d83d38b4bd50919751

2 files changed, 34 insertions, 1 deletions

diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index 5bc05ef0d8..db99726739 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -377,7 +377,6 @@ void TransactionCompletedListener::onTransactionCompleted(ListenerStats listener
             }
             auto& [callbackFunction, callbackSurfaceControls] = callbacksMap[callbackId];
             if (!callbackFunction) {
-                ALOGE("cannot call null callback function, skipping");
                 continue;
             }
             std::vector<SurfaceControlStats> surfaceControlStats;
@@ -394,6 +393,11 @@ void TransactionCompletedListener::onTransactionCompleted(ListenerStats listener
 
             callbackFunction(transactionStats.latchTime, transactionStats.presentFence,
                              surfaceControlStats);
+
+            // More than one transaction may contain the same callback id. Erase the callback from
+            // the map to ensure that it is only called once. This can happen if transactions are
+            // parcelled out of process and applied in both processes.
+            callbacksMap.erase(callbackId);
         }
 
         // handle on complete callbacks
diff --git a/services/surfaceflinger/tests/LayerTransaction_test.cpp b/services/surfaceflinger/tests/LayerTransaction_test.cpp
index cbd54e7aa9..03de8d0b6d 100644
--- a/services/surfaceflinger/tests/LayerTransaction_test.cpp
+++ b/services/surfaceflinger/tests/LayerTransaction_test.cpp
@@ -184,6 +184,35 @@ TEST_F(LayerTransactionTest, BufferTakesPriorityOverColor) {
     }
 }
 
+TEST_F(LayerTransactionTest, CommitCallbackCalledOnce) {
+    auto callCount = 0;
+    auto commitCallback =
+            [&callCount](void* /* context */, nsecs_t /* latchTime */,
+                         const sp<Fence>& /* presentFence */,
+                         const std::vector<SurfaceControlStats>& /* stats */) mutable {
+                callCount++;
+            };
+
+    // Create two transactions that both contain the same callback id.
+    Transaction t1;
+    t1.addTransactionCommittedCallback(commitCallback, nullptr);
+    Parcel parcel;
+    t1.writeToParcel(&parcel);
+    parcel.setDataPosition(0);
+    Transaction t2;
+    t2.readFromParcel(&parcel);
+
+    // Apply the two transactions. There is a race here as we can't guarantee that the two
+    // transactions will be applied within the same SurfaceFlinger commit. If the transactions are
+    // applied within the same commit then we verify that callback ids are deduplicated within a
+    // single commit. Otherwise, we verify that commit callbacks are deduplicated across separate
+    // commits.
+    t1.apply();
+    t2.apply(/*synchronous=*/true);
+
+    ASSERT_EQ(callCount, 1);
+}
+
 } // namespace android
 
 // TODO(b/129481165): remove the #pragma below and fix conversion issues