SF: Force empty sync transactions to apply anyway

Following the change to not flush transactions in the screen shot
path, this enables the use of empty synchronous transactions as a
flush mechanism for previous asynchronous transactions.

Bug: 27098060
Change-Id: I282fdfffb72db148edcbf1ded65b15816fc714a2

2 files changed, 14 insertions, 0 deletions

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 466da8cfba..ce63ec290a 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -2165,6 +2165,13 @@ void SurfaceFlinger::setTransactionState(
         }
     }
 
+    // If a synchronous transaction is explicitly requested without any changes,
+    // force a transaction anyway. This can be used as a flush mechanism for
+    // previous async transactions.
+    if (transactionFlags == 0 && (flags & eSynchronous)) {
+        transactionFlags = eTransactionNeeded;
+    }
+
     if (transactionFlags) {
         // this triggers the transaction
         setTransactionFlags(transactionFlags);
diff --git a/services/surfaceflinger/SurfaceFlinger_hwc1.cpp b/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
index de46dfa0ff..3572acbf35 100644
--- a/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
+++ b/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
@@ -2181,6 +2181,13 @@ void SurfaceFlinger::setTransactionState(
         }
     }
 
+    // If a synchronous transaction is explicitly requested without any changes,
+    // force a transaction anyway. This can be used as a flush mechanism for
+    // previous async transactions.
+    if (transactionFlags == 0 && (flags & eSynchronous)) {
+        transactionFlags = eTransactionNeeded;
+    }
+
     if (transactionFlags) {
         // this triggers the transaction
         setTransactionFlags(transactionFlags);