From 837d2d8b158bdaa2615385e4cc6cd46956dea92a Mon Sep 17 00:00:00 2001
From: tianrking <10758833+tianrking@users.noreply.github.com>
Date: Mon, 27 Jul 2026 01:22:49 +0800
Subject: [PATCH] executor: support rtos-trace without pointer CAS

---
 embassy-executor/Cargo.toml       |  1 +
 embassy-executor/src/raw/trace.rs | 14 ++++++++++++--
 rust-toolchain.toml               |  1 +
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/embassy-executor/Cargo.toml b/embassy-executor/Cargo.toml
index f5a9f26e72..0d0787c921 100644
--- a/embassy-executor/Cargo.toml
+++ b/embassy-executor/Cargo.toml
@@ -40,6 +40,7 @@ build = [
     {target = "riscv32imac-unknown-none-elf", features = ["platform-riscv32"]},
     {target = "riscv32imac-unknown-none-elf", features = ["platform-riscv32", "executor-thread"]},
     {target = "riscv32imac-unknown-none-elf", features = ["platform-riscv32", "executor-thread", "trace"]},
+    {target = "riscv32imc-unknown-none-elf", features = ["platform-riscv32", "executor-thread", "rtos-trace"]},
     {target = "riscv64imac-unknown-none-elf", features = ["platform-riscv64"]},
     {target = "riscv64imac-unknown-none-elf", features = ["platform-riscv64", "executor-thread"]},
     {target = "riscv64imac-unknown-none-elf", features = ["platform-riscv64", "executor-thread", "trace"]},
diff --git a/embassy-executor/src/raw/trace.rs b/embassy-executor/src/raw/trace.rs
index 8301620394..88840e8c4c 100644
--- a/embassy-executor/src/raw/trace.rs
+++ b/embassy-executor/src/raw/trace.rs
@@ -122,14 +122,15 @@ impl TaskTracker {
     /// Adds a task to the tracker
     ///
     /// This method inserts a task at the head of the intrusive linked list.
-    /// The operation is thread-safe and lock-free, using atomic operations
-    /// to ensure consistency even when called from different contexts.
+    /// The operation is lock-free on targets with pointer compare-and-swap.
+    /// On targets without it, insertions are serialized by a critical section.
     ///
     /// # Arguments
     /// * `task` - The task reference to add to the tracker
     pub fn add(&self, task: TaskRef) {
         let task_ptr = task.as_ptr();
 
+        #[cfg(target_has_atomic = "ptr")]
         loop {
             let current_head = self.head.load(Ordering::Acquire);
             unsafe {
@@ -144,6 +145,15 @@ impl TaskTracker {
                 break;
             }
         }
+
+        #[cfg(not(target_has_atomic = "ptr"))]
+        critical_section::with(|_| {
+            let current_head = self.head.load(Ordering::Acquire);
+            unsafe {
+                (*task_ptr).all_tasks_next.store(current_head, Ordering::Relaxed);
+            }
+            self.head.store(task_ptr.cast_mut(), Ordering::Release);
+        });
     }
 
     /// Performs an operation on each task in the tracker
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
index 8bafea673c..f73e1e9a5b 100644
--- a/rust-toolchain.toml
+++ b/rust-toolchain.toml
@@ -8,6 +8,7 @@ targets = [
     "thumbv7em-none-eabihf",
     "thumbv8m.main-none-eabihf",
     "riscv32imac-unknown-none-elf",
+    "riscv32imc-unknown-none-elf",
     "riscv64imac-unknown-none-elf",
     "riscv64gc-unknown-none-elf",
     "wasm32-unknown-unknown",