add basic yield executor

Signed-off-by: Julien CLEMENT <julien.clement@epita.fr>

src/syscalls/mod.rs

@@ -1,7 +1,7 @@
 use crate::println;
 use crate::proc::thread::{resume_k_thread, RUNNING_THREAD};
 use crate::proc::scheduler::SCHEDULER;
-use crate::task::executor::EXECUTOR;
+use crate::task::yield_executor::YieldExecutor;
 use crate::task::Task;
 
 pub use ids::*;
@@ -25,8 +25,6 @@ impl SyscallContext {
     pub async fn run(&mut self) {
         println!("Running async syscall runner for {:?}", self.id);
         self.dispatch().await;
-        println!("Syscall {:?} end, unblocking thread", self.id);
-        SCHEDULER.lock().await.unblock(self.thread_id);
     }
 
     pub async fn dispatch(&mut self) {
@@ -51,18 +49,9 @@ pub fn syscall_routine(syscall_id: SyscallId) -> u64 {
     }));
     
     println!("Spawning async syscall runner");
-    EXECUTOR
-        .try_lock()
-        .unwrap()
-        .spawn(Task::new(syscall_runner(context.clone())));
-
-    println!("Blocking thread");
-    SCHEDULER
-        .try_lock()
-        .unwrap()
-        .block(context.borrow().thread_id);
-    println!("Returning to scheduler");
-    resume_k_thread();
+    let mut executor = YieldExecutor::new(context.borrow().thread_id);
+    executor.spawn(Task::new(syscall_runner(context.clone())));
+    executor.run();
 
     let res = context.borrow().res;
     res

src/syscalls/proc.rs

@@ -1,10 +1,11 @@
 use crate::println;
 use crate::proc::scheduler::SCHEDULER;
+use crate::proc::thread::resume_k_thread;
 
 use super::SyscallContext;
 
 pub async fn exit(context: &SyscallContext) {
     println!("Running exit(2)");
-    let mut scheduler = SCHEDULER.lock().await;
-    scheduler.exit(context.thread_id);
+    SCHEDULER.lock().await.exit(context.thread_id);
+    resume_k_thread();
 }

src/task/mod.rs

@@ -5,6 +5,7 @@ use core::sync::atomic::{AtomicU64, Ordering};
 use core::task::{Context, Poll};
 
 pub mod executor;
+pub mod yield_executor;
 pub mod keyboard;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]

src/task/yield_executor.rs

@@ -0,0 +1,119 @@
+
+use crate::println;
+use crate::proc::thread::{ThreadId, resume_k_thread};
+use crate::proc::scheduler::SCHEDULER;
+
+use super::{Task, TaskId};
+
+use alloc::{collections::BTreeMap, sync::Arc, task::Wake};
+use core::task::{Context, Poll, Waker};
+use crossbeam_queue::ArrayQueue;
+
+pub struct YieldExecutor {
+    tasks: BTreeMap<TaskId, Task>,
+    task_queue: Arc<ArrayQueue<TaskId>>,
+    waker_cache: BTreeMap<TaskId, Waker>,
+    thread_id: ThreadId,
+}
+
+impl YieldExecutor {
+    pub fn new(thread_id: ThreadId) -> Self {
+        YieldExecutor {
+            tasks: BTreeMap::new(),
+            task_queue: Arc::new(ArrayQueue::new(100)),
+            waker_cache: BTreeMap::new(),
+            thread_id: thread_id,
+        }
+    }
+
+    pub fn run(&mut self) {
+        loop {
+            self.run_ready_tasks();
+            if self.done() {
+                break;
+            } else {
+                println!("Blocking thread");
+                SCHEDULER
+                    .try_lock()
+                    .unwrap()
+                    .block(self.thread_id);
+                println!("Returning to scheduler");
+                resume_k_thread();
+            }
+        }
+    }
+
+    fn done(&self) -> bool {
+        self.tasks.is_empty()
+    }
+
+    pub fn spawn(&mut self, task: Task) {
+        let task_id = task.id;
+        if self.tasks.insert(task.id, task).is_some() {
+            panic!("Duplicate task ID");
+        }
+        self.task_queue.push(task_id).expect("Task queue full");
+    }
+
+    fn run_ready_tasks(&mut self) {
+        let Self {
+            tasks,
+            task_queue,
+            waker_cache,
+            thread_id,
+        } = self; // Executor destructuring
+
+        while let Ok(task_id) = task_queue.pop() {
+            let task = match tasks.get_mut(&task_id) {
+                Some(task) => task,
+                None => continue, // Task does not exist anymore
+            };
+            let waker = waker_cache
+                .entry(task_id)
+                .or_insert_with(|| YieldTaskWaker::new(task_id, task_queue.clone(), *thread_id));
+            let mut context = Context::from_waker(waker);
+            match task.poll(&mut context) {
+                Poll::Ready(()) => {
+                    // task is done
+                    tasks.remove(&task_id);
+                    waker_cache.remove(&task_id);
+                }
+                Poll::Pending => {}
+            }
+        }
+    }
+}
+
+struct YieldTaskWaker {
+    task_id: TaskId,
+    task_queue: Arc<ArrayQueue<TaskId>>,
+    thread_id: ThreadId,
+}
+
+impl YieldTaskWaker {
+    fn new(task_id: TaskId, task_queue: Arc<ArrayQueue<TaskId>>, thread_id: ThreadId) -> Waker {
+        Waker::from(Arc::new(YieldTaskWaker {
+            task_id,
+            task_queue,
+            thread_id
+        }))
+    }
+
+    fn wake_task(&self) {
+        self.task_queue.push(self.task_id).expect("Task queue full");
+        SCHEDULER
+            .try_lock()
+            .unwrap()
+            .unblock(self.thread_id);
+    }
+}
+
+impl Wake for YieldTaskWaker {
+    fn wake(self: Arc<Self>) {
+        self.wake_task();
+    }
+
+    fn wake_by_ref(self: &Arc<Self>) {
+        self.wake_task();
+    }
+}