Add task cancellation test

It doesn't currently pass, but should in the near future.

Signed-off-by: Klim Tsoutsman <[email protected]>

applications/test_task_cancel/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "test_task_cancel"
+version = "0.1.0"
+authors = ["Klim Tsoutsman <[email protected]>"]
+description = "Task cancellation test"
+edition = "2021"
+
+[dependencies]
+log = "0.4"
+spawn = { path = "../../kernel/spawn" }
+spin = "0.9"
+task = { path = "../../kernel/task" }

applications/test_task_cancel/src/lib.rs

@@ -0,0 +1,49 @@
+// TODO: Properly implement Task::kill so the test passes.
+
+#![no_std]
+
+extern crate alloc;
+
+use alloc::{string::String, sync::Arc, vec::Vec};
+use core::sync::atomic::{AtomicUsize, Ordering};
+use spin::Mutex;
+
+pub fn main(_: Vec<String>) -> isize {
+    let lock = Arc::new(Mutex::new(()));
+    let task = spawn::new_task_builder(other, lock.clone())
+        .spawn()
+        .expect("failed to spawn task");
+
+    while !lock.is_locked() {}
+
+    task.kill(task::KillReason::Requested)
+        .expect("failed to abort task");
+
+    log::debug!("waiting for lock to be unlocked");
+
+    // For us to acquire the lock, the drop handler of the other thread's guard must
+    // have been invoked.
+    let _ = lock.lock();
+
+    0
+}
+
+#[inline(never)]
+fn other(lock: Arc<Mutex<()>>) {
+    let _guard = lock.lock();
+    loop {
+        // In order to properly unwind the task we need to reach an instruction that is
+        // covered by the unwind tables. Rust generates an unwind row for all call
+        // sites so by placing a call site in the loop we ensure that the task will
+        // reach an instruction from which it can unwind when it is told to cancel.
+        unwind_row_generator();
+    }
+}
+
+#[inline(never)]
+fn unwind_row_generator() {
+    static __COUNTER: AtomicUsize = AtomicUsize::new(0);
+
+    // Prevents unwind_row_generator from being optimised away.
+    __COUNTER.fetch_add(1, Ordering::Relaxed);
+}

theseus_features/Cargo.toml

@@ -63,6 +63,7 @@ test_realtime = { path = "../applications/test_realtime", optional = true }
 test_restartable = { path = "../applications/test_restartable", optional = true }
 test_serial_echo = { path = "../applications/test_serial_echo", optional = true }
 test_std_fs = { path = "../applications/test_std_fs", optional = true }
+test_task_cancel = { path = "../applications/test_task_cancel", optional = true }
 test_wait_queue = { path = "../applications/test_wait_queue", optional = true }
 test_wasmtime = { path = "../applications/test_wasmtime", optional = true }
 tls_test = { path = "../applications/tls_test", optional = true }
@@ -147,6 +148,7 @@ theseus_tests = [
     "test_restartable",
     "test_serial_echo",
     "test_std_fs",
+    "test_task_cancel",
     "test_wait_queue",
     "test_wasmtime",
     "tls_test",