From cd2a8579b9dbd2ed2023d4da2d24b6219861c25e Mon Sep 17 00:00:00 2001
From: Antonio Scandurra <me@as-cii.com>
Date: Mon, 28 Nov 2022 19:35:33 +0100
Subject: [PATCH] Capture runnable backtraces only when detecting
 nondeterminism

---
 crates/gpui/src/executor.rs | 30 +++++++++++++++++++++---------
 crates/gpui/src/test.rs     |  4 ++++
 2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/crates/gpui/src/executor.rs b/crates/gpui/src/executor.rs
index 5231f8a51a..876e48351d 100644
--- a/crates/gpui/src/executor.rs
+++ b/crates/gpui/src/executor.rs
@@ -75,6 +75,7 @@ struct DeterministicState {
     waiting_backtrace: Option<backtrace::Backtrace>,
     next_runnable_id: usize,
     poll_history: Vec<usize>,
+    enable_runnable_backtraces: bool,
     runnable_backtraces: collections::HashMap<usize, backtrace::Backtrace>,
 }
 
@@ -129,6 +130,7 @@ impl Deterministic {
                 waiting_backtrace: None,
                 next_runnable_id: 0,
                 poll_history: Default::default(),
+                enable_runnable_backtraces: false,
                 runnable_backtraces: Default::default(),
             })),
             parker: Default::default(),
@@ -139,6 +141,10 @@ impl Deterministic {
         self.state.lock().poll_history.clone()
     }
 
+    pub fn enable_runnable_backtrace(&self) {
+        self.state.lock().enable_runnable_backtraces = true;
+    }
+
     pub fn runnable_backtrace(&self, runnable_id: usize) -> backtrace::Backtrace {
         let mut backtrace = self.state.lock().runnable_backtraces[&runnable_id].clone();
         backtrace.resolve();
@@ -169,9 +175,11 @@ impl Deterministic {
         {
             let mut state = state.lock();
             id = util::post_inc(&mut state.next_runnable_id);
-            state
-                .runnable_backtraces
-                .insert(id, backtrace::Backtrace::new_unresolved());
+            if state.enable_runnable_backtraces {
+                state
+                    .runnable_backtraces
+                    .insert(id, backtrace::Backtrace::new_unresolved());
+            }
         }
 
         let unparker = self.parker.lock().unparker();
@@ -194,9 +202,11 @@ impl Deterministic {
         {
             let mut state = state.lock();
             id = util::post_inc(&mut state.next_runnable_id);
-            state
-                .runnable_backtraces
-                .insert(id, backtrace::Backtrace::new_unresolved());
+            if state.enable_runnable_backtraces {
+                state
+                    .runnable_backtraces
+                    .insert(id, backtrace::Backtrace::new_unresolved());
+            }
         }
 
         let unparker = self.parker.lock().unparker();
@@ -225,9 +235,11 @@ impl Deterministic {
         {
             let mut state = state.lock();
             id = util::post_inc(&mut state.next_runnable_id);
-            state
-                .runnable_backtraces
-                .insert(id, backtrace::Backtrace::new());
+            if state.enable_runnable_backtraces {
+                state
+                    .runnable_backtraces
+                    .insert(id, backtrace::Backtrace::new_unresolved());
+            }
         }
 
         let unparker = self.parker.lock().unparker();
diff --git a/crates/gpui/src/test.rs b/crates/gpui/src/test.rs
index 665033a71c..aade1054a8 100644
--- a/crates/gpui/src/test.rs
+++ b/crates/gpui/src/test.rs
@@ -72,6 +72,10 @@ pub fn run_test(
                 }
 
                 let deterministic = executor::Deterministic::new(seed);
+                if detect_nondeterminism {
+                    deterministic.enable_runnable_backtrace();
+                }
+
                 let leak_detector = Arc::new(Mutex::new(LeakDetector::default()));
                 let mut cx = TestAppContext::new(
                     foreground_platform.clone(),