Fix flicker issue on external display.

Relnote: when primary and virtual display fences are already signaled
while external one is still pending, external display fence should be
overridden by merged fence of primary and virtual.

Bug: 264002998
Test: atest libsurfaceflinger_unittest
Change-Id: Ia1ac1fcc20cfd96d148c549c06777be387df1bde

1 files changed, 3 insertions, 4 deletions

diff --git a/services/surfaceflinger/TransactionCallbackInvoker.cpp b/services/surfaceflinger/TransactionCallbackInvoker.cpp
index e5de7591ef..3da98d4247 100644
--- a/services/surfaceflinger/TransactionCallbackInvoker.cpp
+++ b/services/surfaceflinger/TransactionCallbackInvoker.cpp
@@ -137,7 +137,6 @@ status_t TransactionCallbackInvoker::addCallbackHandle(const sp<CallbackHandle>&
             sp<Fence> currentFence = future.get().value_or(Fence::NO_FENCE);
             if (prevFence == nullptr && currentFence->getStatus() != Fence::Status::Invalid) {
                 prevFence = std::move(currentFence);
-                handle->previousReleaseFence = prevFence;
             } else if (prevFence != nullptr) {
                 // If both fences are signaled or both are unsignaled, we need to merge
                 // them to get an accurate timestamp.
@@ -147,8 +146,7 @@ status_t TransactionCallbackInvoker::addCallbackHandle(const sp<CallbackHandle>&
                     snprintf(fenceName, 32, "%.28s", handle->name.c_str());
                     sp<Fence> mergedFence = Fence::merge(fenceName, prevFence, currentFence);
                     if (mergedFence->isValid()) {
-                        handle->previousReleaseFence = std::move(mergedFence);
-                        prevFence = handle->previousReleaseFence;
+                        prevFence = std::move(mergedFence);
                     }
                 } else if (currentFence->getStatus() == Fence::Status::Unsignaled) {
                     // If one fence has signaled and the other hasn't, the unsignaled
@@ -158,10 +156,11 @@ status_t TransactionCallbackInvoker::addCallbackHandle(const sp<CallbackHandle>&
                     // by this point, they will have both signaled and only the timestamp
                     // will be slightly off; any dependencies after this point will
                     // already have been met.
-                    handle->previousReleaseFence = std::move(currentFence);
+                    prevFence = std::move(currentFence);
                 }
             }
         }
+        handle->previousReleaseFence = prevFence;
         handle->previousReleaseFences.clear();
 
         FrameEventHistoryStats eventStats(handle->frameNumber,