From 92061467a3c4c0fdc3ea45d80c4bf5e971223f8e Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Sun, 26 Feb 2023 20:37:25 +0800
Subject: [PATCH 01/13] Fix asset_debug_server hang. There should be at most
 one ThreadExecutor's ticker for one thread.

---
 .../src/schedule/executor/multi_threaded.rs   | 10 +++++--
 crates/bevy_tasks/src/task_pool.rs            | 19 ++++++++++---
 crates/bevy_tasks/src/thread_executor.rs      | 27 ++++++++++++++++---
 3 files changed, 47 insertions(+), 9 deletions(-)

diff --git a/crates/bevy_ecs/src/schedule/executor/multi_threaded.rs b/crates/bevy_ecs/src/schedule/executor/multi_threaded.rs
index 16ab5f789675d..4d0dbfe2497cc 100644
--- a/crates/bevy_ecs/src/schedule/executor/multi_threaded.rs
+++ b/crates/bevy_ecs/src/schedule/executor/multi_threaded.rs
@@ -619,11 +619,17 @@ fn evaluate_and_fold_conditions(conditions: &mut [BoxedCondition], world: &World
 }
 
 /// New-typed [`ThreadExecutor`] [`Resource`] that is used to run systems on the main thread
-#[derive(Resource, Default, Clone)]
+#[derive(Resource, Clone)]
 pub struct MainThreadExecutor(pub Arc<ThreadExecutor<'static>>);
 
+impl Default for MainThreadExecutor {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl MainThreadExecutor {
     pub fn new() -> Self {
-        MainThreadExecutor(Arc::new(ThreadExecutor::new()))
+        MainThreadExecutor(TaskPool::get_thread_executor().clone())
     }
 }
diff --git a/crates/bevy_tasks/src/task_pool.rs b/crates/bevy_tasks/src/task_pool.rs
index 4f37a8f34fbd4..9962200e08286 100644
--- a/crates/bevy_tasks/src/task_pool.rs
+++ b/crates/bevy_tasks/src/task_pool.rs
@@ -112,7 +112,12 @@ pub struct TaskPool {
 impl TaskPool {
     thread_local! {
         static LOCAL_EXECUTOR: async_executor::LocalExecutor<'static> = async_executor::LocalExecutor::new();
-        static THREAD_EXECUTOR: ThreadExecutor<'static> = ThreadExecutor::new();
+        static THREAD_EXECUTOR: Arc<ThreadExecutor<'static>> = Arc::new(ThreadExecutor::new());
+    }
+
+    /// Each thread can only create one thread_executor, otherwise, there are good chances they will deadlock
+    pub fn get_thread_executor() -> Arc<ThreadExecutor<'static>> {
+        Self::THREAD_EXECUTOR.with(|executor| executor.clone())
     }
 
     /// Create a `TaskPool` with the default configuration.
@@ -412,7 +417,11 @@ impl TaskPool {
             loop {
                 let tick_forever = async {
                     loop {
-                        external_ticker.tick().or(scope_ticker.tick()).await;
+                        if external_ticker.conflict_with(&scope_ticker) {
+                            external_ticker.tick().await
+                        } else {
+                            external_ticker.tick().or(scope_ticker.tick()).await;
+                        }
                     }
                 };
                 // we don't care if it errors. If a scoped task errors it will propagate
@@ -436,7 +445,11 @@ impl TaskPool {
             loop {
                 let tick_forever = async {
                     loop {
-                        external_ticker.tick().or(scope_ticker.tick()).await;
+                        if external_ticker.conflict_with(&scope_ticker) {
+                            external_ticker.tick().await;
+                        } else {
+                            external_ticker.tick().or(scope_ticker.tick()).await;
+                        }
                     }
                 };
                 let _result = AssertUnwindSafe(tick_forever).catch_unwind().await.is_ok();
diff --git a/crates/bevy_tasks/src/thread_executor.rs b/crates/bevy_tasks/src/thread_executor.rs
index 0ba66571db982..63ffb59f8d9b9 100644
--- a/crates/bevy_tasks/src/thread_executor.rs
+++ b/crates/bevy_tasks/src/thread_executor.rs
@@ -62,6 +62,19 @@ impl<'task> ThreadExecutor<'task> {
         Self::default()
     }
 
+    /// check whether same executor, if yes, then the `Ticker` should not
+    /// be used in same task. E.g, ticker_1.or(ticker_2).await. This will leak
+    /// the ticker and cause dead lock
+    pub fn is_same_executor(&self, other: &Self) -> bool {
+        if self.thread_id == other.thread_id {
+            // for same thread, we assert they are same object
+            assert!(std::ptr::eq(self, other));
+            true
+        } else {
+            false
+        }
+    }
+
     /// Spawn a task on the thread executor
     pub fn spawn<T: Send + 'task>(
         &self,
@@ -77,7 +90,7 @@ impl<'task> ThreadExecutor<'task> {
     pub fn ticker<'ticker>(&'ticker self) -> Option<ThreadExecutorTicker<'task, 'ticker>> {
         if thread::current().id() == self.thread_id {
             return Some(ThreadExecutorTicker {
-                executor: &self.executor,
+                executor: self,
                 _marker: PhantomData::default(),
             });
         }
@@ -90,20 +103,26 @@ impl<'task> ThreadExecutor<'task> {
 /// created on.
 #[derive(Debug)]
 pub struct ThreadExecutorTicker<'task, 'ticker> {
-    executor: &'ticker Executor<'task>,
+    executor: &'ticker ThreadExecutor<'task>,
     // make type not send or sync
     _marker: PhantomData<*const ()>,
 }
 impl<'task, 'ticker> ThreadExecutorTicker<'task, 'ticker> {
+    /// if executor is same, then the Ticker should not used
+    /// in same task
+    pub fn conflict_with(&self, other: &Self) -> bool {
+        self.executor.is_same_executor(other.executor)
+    }
+
     /// Tick the thread executor.
     pub async fn tick(&self) {
-        self.executor.tick().await;
+        self.executor.executor.tick().await;
     }
 
     /// Synchronously try to tick a task on the executor.
     /// Returns false if if does not find a task to tick.
     pub fn try_tick(&self) -> bool {
-        self.executor.try_tick()
+        self.executor.executor.try_tick()
     }
 }
 

From 3bc434c1ffcc20b1ccc271dcb8203e5798174b3a Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Sun, 26 Feb 2023 21:05:25 +0800
Subject: [PATCH 02/13] fix clippy

---
 crates/bevy_ecs/src/schedule/executor/multi_threaded.rs | 2 +-
 crates/bevy_tasks/src/task_pool.rs                      | 4 ++--
 crates/bevy_tasks/src/thread_executor.rs                | 4 ++--
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/crates/bevy_ecs/src/schedule/executor/multi_threaded.rs b/crates/bevy_ecs/src/schedule/executor/multi_threaded.rs
index 4d0dbfe2497cc..4a330890ecf01 100644
--- a/crates/bevy_ecs/src/schedule/executor/multi_threaded.rs
+++ b/crates/bevy_ecs/src/schedule/executor/multi_threaded.rs
@@ -630,6 +630,6 @@ impl Default for MainThreadExecutor {
 
 impl MainThreadExecutor {
     pub fn new() -> Self {
-        MainThreadExecutor(TaskPool::get_thread_executor().clone())
+        MainThreadExecutor(TaskPool::get_thread_executor())
     }
 }
diff --git a/crates/bevy_tasks/src/task_pool.rs b/crates/bevy_tasks/src/task_pool.rs
index 9962200e08286..f5aa295a18c7c 100644
--- a/crates/bevy_tasks/src/task_pool.rs
+++ b/crates/bevy_tasks/src/task_pool.rs
@@ -115,7 +115,7 @@ impl TaskPool {
         static THREAD_EXECUTOR: Arc<ThreadExecutor<'static>> = Arc::new(ThreadExecutor::new());
     }
 
-    /// Each thread can only create one thread_executor, otherwise, there are good chances they will deadlock
+    /// Each thread should only create one `ThreadExecutor`, otherwise, there are good chances they will deadlock
     pub fn get_thread_executor() -> Arc<ThreadExecutor<'static>> {
         Self::THREAD_EXECUTOR.with(|executor| executor.clone())
     }
@@ -418,7 +418,7 @@ impl TaskPool {
                 let tick_forever = async {
                     loop {
                         if external_ticker.conflict_with(&scope_ticker) {
-                            external_ticker.tick().await
+                            external_ticker.tick().await;
                         } else {
                             external_ticker.tick().or(scope_ticker.tick()).await;
                         }
diff --git a/crates/bevy_tasks/src/thread_executor.rs b/crates/bevy_tasks/src/thread_executor.rs
index 63ffb59f8d9b9..397b440811040 100644
--- a/crates/bevy_tasks/src/thread_executor.rs
+++ b/crates/bevy_tasks/src/thread_executor.rs
@@ -63,11 +63,11 @@ impl<'task> ThreadExecutor<'task> {
     }
 
     /// check whether same executor, if yes, then the `Ticker` should not
-    /// be used in same task. E.g, ticker_1.or(ticker_2).await. This will leak
+    /// be used in same task. E.g, `ticker_1.or(ticker_2).await`. This will leak
     /// the ticker and cause dead lock
     pub fn is_same_executor(&self, other: &Self) -> bool {
         if self.thread_id == other.thread_id {
-            // for same thread, we assert they are same object
+            // for same thread, there should be only one instance
             assert!(std::ptr::eq(self, other));
             true
         } else {

From cb1929815d817297c892fd91c105b4abf3d41e11 Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Sun, 26 Feb 2023 21:32:49 +0800
Subject: [PATCH 03/13] fix wasm build

---
 crates/bevy_tasks/src/single_threaded_task_pool.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/crates/bevy_tasks/src/single_threaded_task_pool.rs b/crates/bevy_tasks/src/single_threaded_task_pool.rs
index 83e8084a6d3cd..b1546884bce51 100644
--- a/crates/bevy_tasks/src/single_threaded_task_pool.rs
+++ b/crates/bevy_tasks/src/single_threaded_task_pool.rs
@@ -56,6 +56,11 @@ impl TaskPoolBuilder {
 pub struct TaskPool {}
 
 impl TaskPool {
+    /// Just create a new `ThreadExecutor` for wasm
+    pub fn get_thread_executor() -> Arc<ThreadExecutor<'static>> {
+        Arc::new(ThreadExecutor::new())
+    }
+
     /// Create a `TaskPool` with the default configuration.
     pub fn new() -> Self {
         TaskPoolBuilder::new().build()

From f15ac4fee816af2f8f86bce4869b303a3ad425d4 Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Mon, 27 Feb 2023 08:33:51 +0800
Subject: [PATCH 04/13] move ticker conflict check out of loop

---
 crates/bevy_tasks/src/task_pool.rs | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/crates/bevy_tasks/src/task_pool.rs b/crates/bevy_tasks/src/task_pool.rs
index f5aa295a18c7c..d19183f3fb56f 100644
--- a/crates/bevy_tasks/src/task_pool.rs
+++ b/crates/bevy_tasks/src/task_pool.rs
@@ -416,10 +416,12 @@ impl TaskPool {
         let execute_forever = async move {
             loop {
                 let tick_forever = async {
-                    loop {
-                        if external_ticker.conflict_with(&scope_ticker) {
+                    if external_ticker.conflict_with(&scope_ticker) {
+                        loop {
                             external_ticker.tick().await;
-                        } else {
+                        }
+                    } else {
+                        loop {
                             external_ticker.tick().or(scope_ticker.tick()).await;
                         }
                     }
@@ -444,10 +446,12 @@ impl TaskPool {
         let execute_forever = async {
             loop {
                 let tick_forever = async {
-                    loop {
-                        if external_ticker.conflict_with(&scope_ticker) {
+                    if external_ticker.conflict_with(&scope_ticker) {
+                        loop {
                             external_ticker.tick().await;
-                        } else {
+                        }
+                    } else {
+                        loop {
                             external_ticker.tick().or(scope_ticker.tick()).await;
                         }
                     }

From 6d22cc51b447b1105bff60ad815ebde0d519b8ea Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Mon, 27 Feb 2023 15:15:35 +0800
Subject: [PATCH 05/13] Add nested app example to show ThreadExecutor deadlock.
 Disable the conflict check, it would block.

---
 Cargo.toml                 | 10 ++++++++++
 examples/app/nested_app.rs | 19 +++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 examples/app/nested_app.rs

diff --git a/Cargo.toml b/Cargo.toml
index 0b1427689d214..e611be4ec2a7f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -687,6 +687,16 @@ description = "Demonstrates the creation and registration of a custom plugin"
 category = "Application"
 wasm = true
 
+[[example]]
+name = "nested_app"
+path = "examples/app/nested_app.rs"
+
+[package.metadata.example.nested_app]
+name = "Nested"
+description = "Demonstrates the creation of nested app"
+category = "Application"
+wasm = false
+
 [[example]]
 name = "plugin_group"
 path = "examples/app/plugin_group.rs"
diff --git a/examples/app/nested_app.rs b/examples/app/nested_app.rs
new file mode 100644
index 0000000000000..8dd99a11556a9
--- /dev/null
+++ b/examples/app/nested_app.rs
@@ -0,0 +1,19 @@
+use bevy::prelude::*;
+
+fn run_sub_app(mut sub_app: NonSendMut<DebugApp>) {
+    sub_app.app.update();
+}
+
+struct DebugApp {
+    app: App,
+}
+
+fn main() {
+    let mut app = App::new();
+
+    let sub_app = App::new();
+    app.insert_non_send_resource(DebugApp { app: sub_app });
+    app.add_system(run_sub_app);
+
+    app.update();
+}

From 6d45a1853169fa8a519f6d1a6738b30fe113cee3 Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Mon, 27 Feb 2023 15:21:51 +0800
Subject: [PATCH 06/13] fix ci

---
 examples/README.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/examples/README.md b/examples/README.md
index c54ca491ec420..f1b62cd37e47d 100644
--- a/examples/README.md
+++ b/examples/README.md
@@ -153,6 +153,7 @@ Example | Description
 [Empty with Defaults](../examples/app/empty_defaults.rs) | An empty application with default plugins
 [Headless](../examples/app/headless.rs) | An application that runs without default plugins
 [Logs](../examples/app/logs.rs) | Illustrate how to use generate log output
+[Nested](../examples/app/nested_app.rs) | Demonstrates the creation of nested app
 [No Renderer](../examples/app/no_renderer.rs) | An application that runs with default plugins and displays an empty window, but without an actual renderer
 [Plugin](../examples/app/plugin.rs) | Demonstrates the creation and registration of a custom plugin
 [Plugin Group](../examples/app/plugin_group.rs) | Demonstrates the creation and registration of a custom plugin group

From f6b7b4538fa3d2209b69aaafc3513c5bfecc36d9 Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Tue, 28 Feb 2023 20:40:56 +0800
Subject: [PATCH 07/13] clean code for review

---
 Cargo.toml                               | 10 -------
 crates/bevy_tasks/src/task_pool.rs       | 20 +++----------
 crates/bevy_tasks/src/thread_executor.rs | 36 +++++++++++-------------
 examples/app/nested_app.rs               | 19 -------------
 4 files changed, 20 insertions(+), 65 deletions(-)
 delete mode 100644 examples/app/nested_app.rs

diff --git a/Cargo.toml b/Cargo.toml
index e611be4ec2a7f..0b1427689d214 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -687,16 +687,6 @@ description = "Demonstrates the creation and registration of a custom plugin"
 category = "Application"
 wasm = true
 
-[[example]]
-name = "nested_app"
-path = "examples/app/nested_app.rs"
-
-[package.metadata.example.nested_app]
-name = "Nested"
-description = "Demonstrates the creation of nested app"
-category = "Application"
-wasm = false
-
 [[example]]
 name = "plugin_group"
 path = "examples/app/plugin_group.rs"
diff --git a/crates/bevy_tasks/src/task_pool.rs b/crates/bevy_tasks/src/task_pool.rs
index d19183f3fb56f..1630e976edc19 100644
--- a/crates/bevy_tasks/src/task_pool.rs
+++ b/crates/bevy_tasks/src/task_pool.rs
@@ -416,14 +416,8 @@ impl TaskPool {
         let execute_forever = async move {
             loop {
                 let tick_forever = async {
-                    if external_ticker.conflict_with(&scope_ticker) {
-                        loop {
-                            external_ticker.tick().await;
-                        }
-                    } else {
-                        loop {
-                            external_ticker.tick().or(scope_ticker.tick()).await;
-                        }
+                    loop {
+                        external_ticker.or_tick(&scope_ticker).await;
                     }
                 };
                 // we don't care if it errors. If a scoped task errors it will propagate
@@ -446,14 +440,8 @@ impl TaskPool {
         let execute_forever = async {
             loop {
                 let tick_forever = async {
-                    if external_ticker.conflict_with(&scope_ticker) {
-                        loop {
-                            external_ticker.tick().await;
-                        }
-                    } else {
-                        loop {
-                            external_ticker.tick().or(scope_ticker.tick()).await;
-                        }
+                    loop {
+                        external_ticker.or_tick(&scope_ticker).await;
                     }
                 };
                 let _result = AssertUnwindSafe(tick_forever).catch_unwind().await.is_ok();
diff --git a/crates/bevy_tasks/src/thread_executor.rs b/crates/bevy_tasks/src/thread_executor.rs
index 397b440811040..f87c6c978e541 100644
--- a/crates/bevy_tasks/src/thread_executor.rs
+++ b/crates/bevy_tasks/src/thread_executor.rs
@@ -4,7 +4,7 @@ use std::{
 };
 
 use async_executor::{Executor, Task};
-use futures_lite::Future;
+use futures_lite::{Future, FutureExt};
 
 /// An executor that can only be ticked on the thread it was instantiated on. But
 /// can spawn `Send` tasks from other threads.
@@ -62,19 +62,6 @@ impl<'task> ThreadExecutor<'task> {
         Self::default()
     }
 
-    /// check whether same executor, if yes, then the `Ticker` should not
-    /// be used in same task. E.g, `ticker_1.or(ticker_2).await`. This will leak
-    /// the ticker and cause dead lock
-    pub fn is_same_executor(&self, other: &Self) -> bool {
-        if self.thread_id == other.thread_id {
-            // for same thread, there should be only one instance
-            assert!(std::ptr::eq(self, other));
-            true
-        } else {
-            false
-        }
-    }
-
     /// Spawn a task on the thread executor
     pub fn spawn<T: Send + 'task>(
         &self,
@@ -96,6 +83,11 @@ impl<'task> ThreadExecutor<'task> {
         }
         None
     }
+
+    /// check whether `self` and `other` is the same executor
+    fn is_same_executor(&self, other: &Self) -> bool {
+        std::ptr::eq(self, other)
+    }
 }
 
 /// Used to tick the [`ThreadExecutor`]. The executor does not
@@ -108,12 +100,6 @@ pub struct ThreadExecutorTicker<'task, 'ticker> {
     _marker: PhantomData<*const ()>,
 }
 impl<'task, 'ticker> ThreadExecutorTicker<'task, 'ticker> {
-    /// if executor is same, then the Ticker should not used
-    /// in same task
-    pub fn conflict_with(&self, other: &Self) -> bool {
-        self.executor.is_same_executor(other.executor)
-    }
-
     /// Tick the thread executor.
     pub async fn tick(&self) {
         self.executor.executor.tick().await;
@@ -124,6 +110,16 @@ impl<'task, 'ticker> ThreadExecutorTicker<'task, 'ticker> {
     pub fn try_tick(&self) -> bool {
         self.executor.executor.try_tick()
     }
+
+    /// join tick `self` and `other` with `or`
+    /// ref: https://github.com/bevyengine/bevy/pull/7825
+    pub async fn or_tick(&self, other: &Self) {
+        if self.executor.is_same_executor(other.executor) {
+            self.tick().await
+        } else {
+            self.tick().or(other.tick()).await
+        }
+    }
 }
 
 #[cfg(test)]
diff --git a/examples/app/nested_app.rs b/examples/app/nested_app.rs
deleted file mode 100644
index 8dd99a11556a9..0000000000000
--- a/examples/app/nested_app.rs
+++ /dev/null
@@ -1,19 +0,0 @@
-use bevy::prelude::*;
-
-fn run_sub_app(mut sub_app: NonSendMut<DebugApp>) {
-    sub_app.app.update();
-}
-
-struct DebugApp {
-    app: App,
-}
-
-fn main() {
-    let mut app = App::new();
-
-    let sub_app = App::new();
-    app.insert_non_send_resource(DebugApp { app: sub_app });
-    app.add_system(run_sub_app);
-
-    app.update();
-}

From 46bf6e6514756e4b4a3c8491bf8e3dd10b80e8b0 Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Tue, 28 Feb 2023 20:46:21 +0800
Subject: [PATCH 08/13] fix ci

---
 crates/bevy_tasks/src/thread_executor.rs | 8 ++++----
 examples/README.md                       | 1 -
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/crates/bevy_tasks/src/thread_executor.rs b/crates/bevy_tasks/src/thread_executor.rs
index f87c6c978e541..95bb5ce611f39 100644
--- a/crates/bevy_tasks/src/thread_executor.rs
+++ b/crates/bevy_tasks/src/thread_executor.rs
@@ -111,13 +111,13 @@ impl<'task, 'ticker> ThreadExecutorTicker<'task, 'ticker> {
         self.executor.executor.try_tick()
     }
 
-    /// join tick `self` and `other` with `or`
-    /// ref: https://github.com/bevyengine/bevy/pull/7825
+    /// join tick `self` and `other` with `or`.
+    /// check [this pr](https://github.com/bevyengine/bevy/pull/7825) for reference
     pub async fn or_tick(&self, other: &Self) {
         if self.executor.is_same_executor(other.executor) {
-            self.tick().await
+            self.tick().await;
         } else {
-            self.tick().or(other.tick()).await
+            self.tick().or(other.tick()).await;
         }
     }
 }
diff --git a/examples/README.md b/examples/README.md
index f1b62cd37e47d..c54ca491ec420 100644
--- a/examples/README.md
+++ b/examples/README.md
@@ -153,7 +153,6 @@ Example | Description
 [Empty with Defaults](../examples/app/empty_defaults.rs) | An empty application with default plugins
 [Headless](../examples/app/headless.rs) | An application that runs without default plugins
 [Logs](../examples/app/logs.rs) | Illustrate how to use generate log output
-[Nested](../examples/app/nested_app.rs) | Demonstrates the creation of nested app
 [No Renderer](../examples/app/no_renderer.rs) | An application that runs with default plugins and displays an empty window, but without an actual renderer
 [Plugin](../examples/app/plugin.rs) | Demonstrates the creation and registration of a custom plugin
 [Plugin Group](../examples/app/plugin_group.rs) | Demonstrates the creation and registration of a custom plugin group

From 4f9af7f80f4a44a69067bb79a4228115a6ae3d1c Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Wed, 1 Mar 2023 10:16:52 +0800
Subject: [PATCH 09/13] add `same executor checking` to existing executor
 branching code

---
 crates/bevy_tasks/src/task_pool.rs       | 24 +++++++++++++++---------
 crates/bevy_tasks/src/thread_executor.rs | 10 +++-------
 2 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/crates/bevy_tasks/src/task_pool.rs b/crates/bevy_tasks/src/task_pool.rs
index 1630e976edc19..b8f4131b89af7 100644
--- a/crates/bevy_tasks/src/task_pool.rs
+++ b/crates/bevy_tasks/src/task_pool.rs
@@ -382,8 +382,10 @@ impl TaskPool {
 
                 // we get this from a thread local so we should always be on the scope executors thread.
                 let scope_ticker = scope_executor.ticker().unwrap();
-                if let Some(external_ticker) = external_executor.ticker() {
-                    if tick_task_pool_executor {
+                match (external_executor.ticker(), tick_task_pool_executor) {
+                    (Some(external_ticker), true)
+                        if !external_ticker.is_same_executor(&scope_ticker) =>
+                    {
                         Self::execute_global_external_scope(
                             executor,
                             external_ticker,
@@ -391,14 +393,18 @@ impl TaskPool {
                             get_results,
                         )
                         .await
-                    } else {
+                    }
+                    (Some(external_ticker), false)
+                        if !external_ticker.is_same_executor(&scope_ticker) =>
+                    {
                         Self::execute_external_scope(external_ticker, scope_ticker, get_results)
                             .await
                     }
-                } else if tick_task_pool_executor {
-                    Self::execute_global_scope(executor, scope_ticker, get_results).await
-                } else {
-                    Self::execute_scope(scope_ticker, get_results).await
+                    // either external_executor is none or it is same as scope_executor
+                    (_, true) => {
+                        Self::execute_global_scope(executor, scope_ticker, get_results).await
+                    }
+                    (_, false) => Self::execute_scope(scope_ticker, get_results).await,
                 }
             })
         }
@@ -417,7 +423,7 @@ impl TaskPool {
             loop {
                 let tick_forever = async {
                     loop {
-                        external_ticker.or_tick(&scope_ticker).await;
+                        external_ticker.tick().or(scope_ticker.tick()).await;
                     }
                 };
                 // we don't care if it errors. If a scoped task errors it will propagate
@@ -441,7 +447,7 @@ impl TaskPool {
             loop {
                 let tick_forever = async {
                     loop {
-                        external_ticker.or_tick(&scope_ticker).await;
+                        external_ticker.tick().or(scope_ticker.tick()).await;
                     }
                 };
                 let _result = AssertUnwindSafe(tick_forever).catch_unwind().await.is_ok();
diff --git a/crates/bevy_tasks/src/thread_executor.rs b/crates/bevy_tasks/src/thread_executor.rs
index 95bb5ce611f39..5f21c801f690a 100644
--- a/crates/bevy_tasks/src/thread_executor.rs
+++ b/crates/bevy_tasks/src/thread_executor.rs
@@ -111,14 +111,10 @@ impl<'task, 'ticker> ThreadExecutorTicker<'task, 'ticker> {
         self.executor.executor.try_tick()
     }
 
-    /// join tick `self` and `other` with `or`.
+    /// Returns true if `self` and `other`'s executor is same
     /// check [this pr](https://github.com/bevyengine/bevy/pull/7825) for reference
-    pub async fn or_tick(&self, other: &Self) {
-        if self.executor.is_same_executor(other.executor) {
-            self.tick().await;
-        } else {
-            self.tick().or(other.tick()).await;
-        }
+    pub fn is_same_executor(&self, other: &Self) -> bool {
+        std::ptr::eq(self.executor, other.executor)
     }
 }
 

From 45beaba764f2f9233aa398617391e3d84ebc82af Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Wed, 1 Mar 2023 10:27:41 +0800
Subject: [PATCH 10/13] remove unused code

---
 crates/bevy_tasks/src/thread_executor.rs | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/crates/bevy_tasks/src/thread_executor.rs b/crates/bevy_tasks/src/thread_executor.rs
index 5f21c801f690a..1df9edf0468a6 100644
--- a/crates/bevy_tasks/src/thread_executor.rs
+++ b/crates/bevy_tasks/src/thread_executor.rs
@@ -4,7 +4,7 @@ use std::{
 };
 
 use async_executor::{Executor, Task};
-use futures_lite::{Future, FutureExt};
+use futures_lite::Future;
 
 /// An executor that can only be ticked on the thread it was instantiated on. But
 /// can spawn `Send` tasks from other threads.
@@ -83,11 +83,6 @@ impl<'task> ThreadExecutor<'task> {
         }
         None
     }
-
-    /// check whether `self` and `other` is the same executor
-    fn is_same_executor(&self, other: &Self) -> bool {
-        std::ptr::eq(self, other)
-    }
 }
 
 /// Used to tick the [`ThreadExecutor`]. The executor does not

From c2bd15866496e65eb6a1b29c364ff69da6f0a5c5 Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Thu, 2 Mar 2023 09:34:18 +0800
Subject: [PATCH 11/13] fix comment

---
 crates/bevy_tasks/src/task_pool.rs       | 2 ++
 crates/bevy_tasks/src/thread_executor.rs | 1 -
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/crates/bevy_tasks/src/task_pool.rs b/crates/bevy_tasks/src/task_pool.rs
index b8f4131b89af7..247a8faeb93d3 100644
--- a/crates/bevy_tasks/src/task_pool.rs
+++ b/crates/bevy_tasks/src/task_pool.rs
@@ -381,6 +381,8 @@ impl TaskPool {
                 let tick_task_pool_executor = tick_task_pool_executor || self.threads.is_empty();
 
                 // we get this from a thread local so we should always be on the scope executors thread.
+                // note: it is possible `scope_executor` and `external_executor` is the same executor,
+                // in that case, we should only tick one of them, otherwise, it may cause deadlock.
                 let scope_ticker = scope_executor.ticker().unwrap();
                 match (external_executor.ticker(), tick_task_pool_executor) {
                     (Some(external_ticker), true)
diff --git a/crates/bevy_tasks/src/thread_executor.rs b/crates/bevy_tasks/src/thread_executor.rs
index 1df9edf0468a6..9ec860bb0fb43 100644
--- a/crates/bevy_tasks/src/thread_executor.rs
+++ b/crates/bevy_tasks/src/thread_executor.rs
@@ -107,7 +107,6 @@ impl<'task, 'ticker> ThreadExecutorTicker<'task, 'ticker> {
     }
 
     /// Returns true if `self` and `other`'s executor is same
-    /// check [this pr](https://github.com/bevyengine/bevy/pull/7825) for reference
     pub fn is_same_executor(&self, other: &Self) -> bool {
         std::ptr::eq(self.executor, other.executor)
     }

From 90e1d0bf319fbac264bbfbe7a7f19763add1acef Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Thu, 2 Mar 2023 14:26:02 +0800
Subject: [PATCH 12/13] remove default branch from match

---
 crates/bevy_tasks/src/task_pool.rs | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/crates/bevy_tasks/src/task_pool.rs b/crates/bevy_tasks/src/task_pool.rs
index 247a8faeb93d3..e52dd744d7c07 100644
--- a/crates/bevy_tasks/src/task_pool.rs
+++ b/crates/bevy_tasks/src/task_pool.rs
@@ -384,10 +384,12 @@ impl TaskPool {
                 // note: it is possible `scope_executor` and `external_executor` is the same executor,
                 // in that case, we should only tick one of them, otherwise, it may cause deadlock.
                 let scope_ticker = scope_executor.ticker().unwrap();
-                match (external_executor.ticker(), tick_task_pool_executor) {
-                    (Some(external_ticker), true)
-                        if !external_ticker.is_same_executor(&scope_ticker) =>
-                    {
+                let external_ticker = external_executor
+                    .ticker()
+                    .filter(|external_ticker| !external_ticker.is_same_executor(&scope_ticker));
+
+                match (external_ticker, tick_task_pool_executor) {
+                    (Some(external_ticker), true) => {
                         Self::execute_global_external_scope(
                             executor,
                             external_ticker,
@@ -396,17 +398,15 @@ impl TaskPool {
                         )
                         .await
                     }
-                    (Some(external_ticker), false)
-                        if !external_ticker.is_same_executor(&scope_ticker) =>
-                    {
+                    (Some(external_ticker), false) => {
                         Self::execute_external_scope(external_ticker, scope_ticker, get_results)
                             .await
                     }
                     // either external_executor is none or it is same as scope_executor
-                    (_, true) => {
+                    (None, true) => {
                         Self::execute_global_scope(executor, scope_ticker, get_results).await
                     }
-                    (_, false) => Self::execute_scope(scope_ticker, get_results).await,
+                    (None, false) => Self::execute_scope(scope_ticker, get_results).await,
                 }
             })
         }

From 9312549c89c47a88e60a529fc2bc7c2bf28b1429 Mon Sep 17 00:00:00 2001
From: shuo <shuoli84@gmail.com>
Date: Thu, 2 Mar 2023 14:29:17 +0800
Subject: [PATCH 13/13] refine code a bit

---
 crates/bevy_tasks/src/task_pool.rs       |  8 +++++---
 crates/bevy_tasks/src/thread_executor.rs | 10 +++++-----
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/crates/bevy_tasks/src/task_pool.rs b/crates/bevy_tasks/src/task_pool.rs
index e52dd744d7c07..f66d1cd615d52 100644
--- a/crates/bevy_tasks/src/task_pool.rs
+++ b/crates/bevy_tasks/src/task_pool.rs
@@ -384,9 +384,11 @@ impl TaskPool {
                 // note: it is possible `scope_executor` and `external_executor` is the same executor,
                 // in that case, we should only tick one of them, otherwise, it may cause deadlock.
                 let scope_ticker = scope_executor.ticker().unwrap();
-                let external_ticker = external_executor
-                    .ticker()
-                    .filter(|external_ticker| !external_ticker.is_same_executor(&scope_ticker));
+                let external_ticker = if !external_executor.is_same(scope_executor) {
+                    external_executor.ticker()
+                } else {
+                    None
+                };
 
                 match (external_ticker, tick_task_pool_executor) {
                     (Some(external_ticker), true) => {
diff --git a/crates/bevy_tasks/src/thread_executor.rs b/crates/bevy_tasks/src/thread_executor.rs
index 9ec860bb0fb43..7495fe525e052 100644
--- a/crates/bevy_tasks/src/thread_executor.rs
+++ b/crates/bevy_tasks/src/thread_executor.rs
@@ -83,6 +83,11 @@ impl<'task> ThreadExecutor<'task> {
         }
         None
     }
+
+    /// Returns true if `self` and `other`'s executor is same
+    pub fn is_same(&self, other: &Self) -> bool {
+        std::ptr::eq(self, other)
+    }
 }
 
 /// Used to tick the [`ThreadExecutor`]. The executor does not
@@ -105,11 +110,6 @@ impl<'task, 'ticker> ThreadExecutorTicker<'task, 'ticker> {
     pub fn try_tick(&self) -> bool {
         self.executor.executor.try_tick()
     }
-
-    /// Returns true if `self` and `other`'s executor is same
-    pub fn is_same_executor(&self, other: &Self) -> bool {
-        std::ptr::eq(self.executor, other.executor)
-    }
 }
 
 #[cfg(test)]