LocklessQueue cleanup
Bug: 353354073
Test: presubmits
Flag: EXEMPT refactor
Change-Id: I8554a448558d56a40bc382a531f0c10e8593846f
diff --git a/services/surfaceflinger/LocklessQueue.h b/services/surfaceflinger/LocklessQueue.h
index 6b63360..4d0b261 100644
--- a/services/surfaceflinger/LocklessQueue.h
+++ b/services/surfaceflinger/LocklessQueue.h
@@ -15,11 +15,11 @@
*/
#pragma once
+
#include <atomic>
#include <optional>
-template <typename T>
-// Single consumer multi producer stack. We can understand the two operations independently to see
+// Single consumer multi producer queue. We can understand the two operations independently to see
// why they are without race condition.
//
// push is responsible for maintaining a linked list stored in mPush, and called from multiple
@@ -36,33 +36,27 @@
// then store the list and pop one element.
//
// If we already had something in the pop list we just pop directly.
+template <typename T>
class LocklessQueue {
public:
- class Entry {
- public:
- T mValue;
- std::atomic<Entry*> mNext;
- Entry(T value) : mValue(value) {}
- };
- std::atomic<Entry*> mPush = nullptr;
- std::atomic<Entry*> mPop = nullptr;
bool isEmpty() { return (mPush.load() == nullptr) && (mPop.load() == nullptr); }
void push(T value) {
- Entry* entry = new Entry(value);
+ Entry* entry = new Entry(std::move(value));
Entry* previousHead = mPush.load(/*std::memory_order_relaxed*/);
do {
entry->mNext = previousHead;
} while (!mPush.compare_exchange_weak(previousHead, entry)); /*std::memory_order_release*/
}
+
std::optional<T> pop() {
Entry* popped = mPop.load(/*std::memory_order_acquire*/);
if (popped) {
// Single consumer so this is fine
mPop.store(popped->mNext /* , std::memory_order_release */);
- auto value = popped->mValue;
+ auto value = std::move(popped->mValue);
delete popped;
- return std::move(value);
+ return value;
} else {
Entry* grabbedList = mPush.exchange(nullptr /* , std::memory_order_acquire */);
if (!grabbedList) return std::nullopt;
@@ -74,9 +68,19 @@
grabbedList = next;
}
mPop.store(popped /* , std::memory_order_release */);
- auto value = grabbedList->mValue;
+ auto value = std::move(grabbedList->mValue);
delete grabbedList;
- return std::move(value);
+ return value;
}
}
+
+private:
+ class Entry {
+ public:
+ T mValue;
+ std::atomic<Entry*> mNext;
+ Entry(T value) : mValue(value) {}
+ };
+ std::atomic<Entry*> mPush = nullptr;
+ std::atomic<Entry*> mPop = nullptr;
};