SF: Introduce background task executor

Extract logic to execute work outside of the main thread
from TransactionCallbackInvoker so we can reuse the
thread for other tasks that are not critical to drawing.

Bug: 206380307
Test: presubmit
Change-Id: I8128d2f333e3aab5639cd1200e820de39f0b3191

1 files changed, 5 insertions, 34 deletions

diff --git a/services/surfaceflinger/TransactionCallbackInvoker.cpp b/services/surfaceflinger/TransactionCallbackInvoker.cpp
index f3d46ea061..b705d9cf7b 100644
--- a/services/surfaceflinger/TransactionCallbackInvoker.cpp
+++ b/services/surfaceflinger/TransactionCallbackInvoker.cpp
@@ -24,6 +24,7 @@
 #define ATRACE_TAG ATRACE_TAG_GRAPHICS
 
 #include "TransactionCallbackInvoker.h"
+#include "BackgroundExecutor.h"
 
 #include <cinttypes>
 
@@ -49,31 +50,6 @@ static bool containsOnCommitCallbacks(const std::vector<CallbackId>& callbacks)
     return !callbacks.empty() && callbacks.front().type == CallbackId::Type::ON_COMMIT;
 }
 
-TransactionCallbackInvoker::TransactionCallbackInvoker() {
-    mThread = std::thread([&]() {
-          std::unique_lock lock(mCallbackThreadMutex);
-
-        while (mKeepRunning) {
-          while (mCallbackThreadWork.size() > 0) {
-              mCallbackThreadWork.front()();
-              mCallbackThreadWork.pop();
-          }
-          mCallbackConditionVariable.wait(lock);
-        }
-    });
-}
-
-TransactionCallbackInvoker::~TransactionCallbackInvoker() {
-    {
-          std::unique_lock lock(mCallbackThreadMutex);
-          mKeepRunning = false;
-          mCallbackConditionVariable.notify_all();
-    }
-    if (mThread.joinable()) {
-        mThread.join();
-    }
-}
-
 void TransactionCallbackInvoker::addEmptyTransaction(const ListenerCallbacks& listenerCallbacks) {
     auto& [listener, callbackIds] = listenerCallbacks;
     auto& transactionStatsDeque = mCompletedTransactions[listener];
@@ -242,15 +218,10 @@ void TransactionCallbackInvoker::sendCallbacks(bool onCommitOnly) {
                 // keep it as an IBinder due to consistency reasons: if we
                 // interface_cast at the IPC boundary when reading a Parcel,
                 // we get pointers that compare unequal in the SF process.
-                {
-                    std::unique_lock lock(mCallbackThreadMutex);
-                    mCallbackThreadWork.push(
-                        [stats = std::move(listenerStats)]() {
-                          interface_cast<ITransactionCompletedListener>(stats.listener)
-                              ->onTransactionCompleted(stats);
-                    });
-                    mCallbackConditionVariable.notify_all();
-                }
+                BackgroundExecutor::getInstance().execute([stats = std::move(listenerStats)]() {
+                    interface_cast<ITransactionCompletedListener>(stats.listener)
+                            ->onTransactionCompleted(stats);
+                });
             }
         }
         completedTransactionsItr++;