From 1248a55d32f5fc64c7a26cd606fdf4c2908ce09c Mon Sep 17 00:00:00 2001
From: Sebastian Ullrich <sebasti@nullri.ch>
Date: Fri, 7 Feb 2025 11:14:35 +0100
Subject: [PATCH] perf: avoid taking mutex on already-resolved promises (#6984)

---
 src/runtime/object.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/runtime/object.cpp b/src/runtime/object.cpp
index 636d7a1440..82e427abc6 100644
--- a/src/runtime/object.cpp
+++ b/src/runtime/object.cpp
@@ -842,6 +842,10 @@ public:
     }
 
     void resolve(lean_task_object * t, object * v) {
+        if (t->m_value) {
+            dec(v);
+            return;
+        }
         unique_lock<mutex> lock(m_mutex);
         if (t->m_value) {
             lock.unlock(); // `dec(v)` could lead to `deactivate_task` trying to take the lock