From 25e8b28935f92e2bdf15bea992301fbd35a5bbde Mon Sep 17 00:00:00 2001
From: yuzubot <yuzu@yuzu-emu.org>
Date: Thu, 12 Dec 2019 13:01:22 +0000
Subject: [PATCH] "Merge Tagged PR 3173"

---
 src/common/threadsafe_queue.h | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/common/threadsafe_queue.h b/src/common/threadsafe_queue.h
index e714ba5b3..dda7b3a09 100644
--- a/src/common/threadsafe_queue.h
+++ b/src/common/threadsafe_queue.h
@@ -46,9 +46,19 @@ public:
         ElementPtr* new_ptr = new ElementPtr();
         write_ptr->next.store(new_ptr, std::memory_order_release);
         write_ptr = new_ptr;
-        cv.notify_one();
 
+        const size_t previous_size{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();
+        } else {
+            cv.notify_one();
+        }
     }
 
     void Pop() {