From 6a1952737262e9584098f37ade1f4406172c890f Mon Sep 17 00:00:00 2001
From: chaviw <chaviw@google.com>
Date: Fri, 3 Sep 2021 16:14:25 -0500
Subject: Add applyPendingTransactions

It's possible for a caller to request mergeWithNextTransaction, but
the main frame had nothing new to draw. If that's the case, the
mergeWithNextTransactions will be stuck and never applied (or applied
much later). Since this could end up blocking Transactions, it's better
to force apply these when we know a frame wasn't going to draw this
vsync.

Adding applyPendingTransactions to allows callers to force apply
these transactions.

Test: Existing tests pass
Bug: 195262673
Change-Id: I3082b54e35dfae2b3f7fe589c6f665f781d8b07b
---
 libs/gui/BLASTBufferQueue.cpp | 42 +++++++++++++++++++++++++++---------------
 1 file changed, 27 insertions(+), 15 deletions(-)

(limited to 'libs/gui/BLASTBufferQueue.cpp')

diff --git a/libs/gui/BLASTBufferQueue.cpp b/libs/gui/BLASTBufferQueue.cpp
index 982dd63a8c..379b090c5b 100644
--- a/libs/gui/BLASTBufferQueue.cpp
+++ b/libs/gui/BLASTBufferQueue.cpp
@@ -508,21 +508,7 @@ void BLASTBufferQueue::processNextBufferLocked(bool useNextTransaction) {
         }
     }
 
-    auto mergeTransaction =
-            [&t, currentFrameNumber = bufferItem.mFrameNumber](
-                    std::tuple<uint64_t, SurfaceComposerClient::Transaction> pendingTransaction) {
-                auto& [targetFrameNumber, transaction] = pendingTransaction;
-                if (currentFrameNumber < targetFrameNumber) {
-                    return false;
-                }
-                t->merge(std::move(transaction));
-                return true;
-            };
-
-    mPendingTransactions.erase(std::remove_if(mPendingTransactions.begin(),
-                                              mPendingTransactions.end(), mergeTransaction),
-                               mPendingTransactions.end());
-
+    mergePendingTransactions(t, bufferItem.mFrameNumber);
     if (applyTransaction) {
         t->setApplyToken(mApplyToken).apply();
     }
@@ -726,6 +712,32 @@ void BLASTBufferQueue::mergeWithNextTransaction(SurfaceComposerClient::Transacti
     }
 }
 
+void BLASTBufferQueue::applyPendingTransactions(uint64_t frameNumber) {
+    std::lock_guard _lock{mMutex};
+
+    SurfaceComposerClient::Transaction t;
+    mergePendingTransactions(&t, frameNumber);
+    t.setApplyToken(mApplyToken).apply();
+}
+
+void BLASTBufferQueue::mergePendingTransactions(SurfaceComposerClient::Transaction* t,
+                                                uint64_t frameNumber) {
+    auto mergeTransaction =
+            [&t, currentFrameNumber = frameNumber](
+                    std::tuple<uint64_t, SurfaceComposerClient::Transaction> pendingTransaction) {
+                auto& [targetFrameNumber, transaction] = pendingTransaction;
+                if (currentFrameNumber < targetFrameNumber) {
+                    return false;
+                }
+                t->merge(std::move(transaction));
+                return true;
+            };
+
+    mPendingTransactions.erase(std::remove_if(mPendingTransactions.begin(),
+                                              mPendingTransactions.end(), mergeTransaction),
+                               mPendingTransactions.end());
+}
+
 // Maintains a single worker thread per process that services a list of runnables.
 class AsyncWorker : public Singleton<AsyncWorker> {
 private:
-- 
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