Use semaphore instead of condition variable
BackgroundExecutor uses a condition variable to synchronize processing
to a work queue, which means that there is possible mutex contention on
the main thread in rare scenarios.
Instead, we can make the main thread non-blocking with a thread-safe
queue, and use semaphores for signaling the background thread to wake
up. Using semaphores saves a small number of instructions, but overall
reduces contention
Bug: 232113929
Test: bouncy ball
Change-Id: Iced25e8349bdb2a70cac1ed681059a0b14258407
diff --git a/services/surfaceflinger/TransactionCallbackInvoker.cpp b/services/surfaceflinger/TransactionCallbackInvoker.cpp
index e1f348f..9f4a6cd 100644
--- a/services/surfaceflinger/TransactionCallbackInvoker.cpp
+++ b/services/surfaceflinger/TransactionCallbackInvoker.cpp
@@ -184,6 +184,7 @@
void TransactionCallbackInvoker::sendCallbacks(bool onCommitOnly) {
// For each listener
auto completedTransactionsItr = mCompletedTransactions.begin();
+ BackgroundExecutor::Callbacks callbacks;
while (completedTransactionsItr != mCompletedTransactions.end()) {
auto& [listener, transactionStatsDeque] = *completedTransactionsItr;
ListenerStats listenerStats;
@@ -218,7 +219,7 @@
// 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.
- BackgroundExecutor::getInstance().execute([stats = std::move(listenerStats)]() {
+ callbacks.emplace_back([stats = std::move(listenerStats)]() {
interface_cast<ITransactionCompletedListener>(stats.listener)
->onTransactionCompleted(stats);
});
@@ -230,6 +231,8 @@
if (mPresentFence) {
mPresentFence.clear();
}
+
+ BackgroundExecutor::getInstance().sendCallbacks(std::move(callbacks));
}
// -----------------------------------------------------------------------