Add num tasks in scheduler

src/cfs.rs

@@ -187,4 +187,8 @@ impl<T> BaseScheduler for CFScheduler<T> {
             false
         }
     }
+
+    fn num_tasks(&self) -> usize {
+        self.ready_queue.len()
+    }
 }

src/fifo.rs

@@ -56,13 +56,15 @@ impl<T> Deref for FifoTask<T> {
 /// It internally uses a linked list as the ready queue.
 pub struct FifoScheduler<T> {
     ready_queue: List<Arc<FifoTask<T>>>,
+    num_tasks: usize,
 }
 
 impl<T> FifoScheduler<T> {
     /// Creates a new empty [`FifoScheduler`].
     pub const fn new() -> Self {
         Self {
             ready_queue: List::new(),
+            num_tasks: 0,
         }
     }
     /// get the name of scheduler
@@ -77,18 +79,30 @@ impl<T> BaseScheduler for FifoScheduler<T> {
     fn init(&mut self) {}
 
     fn add_task(&mut self, task: Self::SchedItem) {
+        self.num_tasks += 1;
         self.ready_queue.push_back(task);
     }
 
     fn remove_task(&mut self, task: &Self::SchedItem) -> Option<Self::SchedItem> {
-        unsafe { self.ready_queue.remove(task) }
+        let res = unsafe { self.ready_queue.remove(task) };
+        if res.is_some() {
+            // Only decrement the number of tasks if the task is removed.
+            self.num_tasks -= 1;
+        }
+        res
     }
 
     fn pick_next_task(&mut self) -> Option<Self::SchedItem> {
-        self.ready_queue.pop_front()
+        let res = self.ready_queue.pop_front();
+        if res.is_some() {
+            // Only decrement the number of tasks if the task is picked.
+            self.num_tasks -= 1;
+        }
+        res
     }
 
     fn put_prev_task(&mut self, prev: Self::SchedItem, _preempt: bool) {
+        self.num_tasks += 1;
         self.ready_queue.push_back(prev);
     }
 
@@ -99,4 +113,8 @@ impl<T> BaseScheduler for FifoScheduler<T> {
     fn set_priority(&mut self, _task: &Self::SchedItem, _prio: isize) -> bool {
         false
     }
+
+    fn num_tasks(&self) -> usize {
+        self.num_tasks
+    }
 }

src/lib.rs

@@ -63,6 +63,9 @@ pub trait BaseScheduler {
     /// `current` is the current running task.
     fn task_tick(&mut self, current: &Self::SchedItem) -> bool;
 
-    /// set priority for a task
+    /// Set priority for a task.
     fn set_priority(&mut self, task: &Self::SchedItem, prio: isize) -> bool;
+
+    /// Returns the number of tasks in the scheduler.
+    fn num_tasks(&self) -> usize;
 }

src/round_robin.rs

@@ -110,4 +110,8 @@ impl<T, const S: usize> BaseScheduler for RRScheduler<T, S> {
     fn set_priority(&mut self, _task: &Self::SchedItem, _prio: isize) -> bool {
         false
     }
+
+    fn num_tasks(&self) -> usize {
+        self.ready_queue.len()
+    }
 }