From 678f51a7453ccebd1863ab8f87fc0ddb0d29f596 Mon Sep 17 00:00:00 2001
From: Micha Reiser <micha@reiser.io>
Date: Thu, 22 May 2025 11:26:17 +0200
Subject: [PATCH] Short-circuit `block-on` if same thread (#862)

* Short-circuit `block_on` if same thread

* Avoid acquiring the lock
---
 src/runtime.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/runtime.rs b/src/runtime.rs
index 84e1bae9..3eb80442 100644
--- a/src/runtime.rs
+++ b/src/runtime.rs
@@ -172,8 +172,13 @@ impl Runtime {
         other_id: ThreadId,
         query_mutex_guard: QueryMutexGuard,
     ) -> BlockResult {
-        let dg = self.dependency_graph.lock();
         let thread_id = thread::current().id();
+        // Cycle in the same thread.
+        if thread_id == other_id {
+            return BlockResult::Cycle;
+        }
+
+        let dg = self.dependency_graph.lock();
 
         if dg.depends_on(other_id, thread_id) {
             return BlockResult::Cycle;