From 67b8ecc73e4201ee98f812c2a43ff9e93414faea Mon Sep 17 00:00:00 2001
From: bunnei <bunneidev@gmail.com>
Date: Mon, 16 Dec 2019 20:39:53 -0500
Subject: [PATCH] common: SPSCQueue: Notify after incrementing queue size.

---
 src/common/threadsafe_queue.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/common/threadsafe_queue.h b/src/common/threadsafe_queue.h
index e714ba5b3..8268bbd5c 100644
--- a/src/common/threadsafe_queue.h
+++ b/src/common/threadsafe_queue.h
@@ -46,9 +46,16 @@ public:
         ElementPtr* new_ptr = new ElementPtr();
         write_ptr->next.store(new_ptr, std::memory_order_release);
         write_ptr = new_ptr;
-        cv.notify_one();
 
-        ++size;
+        const size_t previous_size{size++};
+
+        // Acquire the mutex and then immediately release it as a fence.
+        // TODO(bunnei): This can be replaced with C++20 waitable atomics when properly supported.
+        // See discussion on https://github.com/yuzu-emu/yuzu/pull/3173 for details.
+        if (previous_size == 0) {
+            std::lock_guard lock{cv_mutex};
+        }
+        cv.notify_one();
     }
 
     void Pop() {