Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Implements PriorityTaskQueue with std's LinkedList rather than a custom linked list implementation #706

Merged
merged 3 commits into from
Apr 18, 2023
Merged

Implements PriorityTaskQueue with std's LinkedList rather than a custom linked list implementation #706

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
3f45497
Implements PriorityTaskQueue with std's LinkedList rather than a cust…
michaelRichards99 Apr 12, 2023
02ccc14
Fixed clippy error.
michaelRichards99 Apr 12, 2023
7445ef1
Use Iterator::position, extract task removal to a separate method, an…
michaelRichards99 Apr 18, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
149 changes: 41 additions & 108 deletions src/scheduler/task.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -237,33 +237,18 @@ impl TaskHandlePriorityQueue {
}
}

#[derive(Default)]
struct QueueHead {
head: Option<Rc<RefCell<Task>>>,
tail: Option<Rc<RefCell<Task>>>,
}

impl QueueHead {
pub const fn new() -> Self {
Self {
head: None,
tail: None,
}
}
}

/// Realize a priority queue for tasks
pub struct PriorityTaskQueue {
queues: [QueueHead; NO_PRIORITIES],
queues: [LinkedList<Rc<RefCell<Task>>>; NO_PRIORITIES],
prio_bitmap: u64,
}

impl PriorityTaskQueue {
/// Creates an empty priority queue for tasks
pub const fn new() -> PriorityTaskQueue {
const QUEUE_HEAD: QueueHead = QueueHead::new();
const EMPTY_LIST: LinkedList<Rc<RefCell<Task>>> = LinkedList::new();
PriorityTaskQueue {
queues: [QUEUE_HEAD; NO_PRIORITIES],
queues: [EMPTY_LIST; NO_PRIORITIES],
prio_bitmap: 0,
}
}
Expand All @@ -274,53 +259,41 @@ impl PriorityTaskQueue {
//assert!(i < NO_PRIORITIES, "Priority {} is too high", i);

self.prio_bitmap |= (1 << i) as u64;
match self.queues[i].tail {
None => {
// first element in the queue
self.queues[i].head = Some(task.clone());

let mut borrow = task.borrow_mut();
borrow.next = None;
borrow.prev = None;
}
Some(ref mut tail) => {
// add task at the end of the node
tail.borrow_mut().next = Some(task.clone());
let queue = &mut self.queues[i];
queue.push_back(task);
}

let mut borrow = task.borrow_mut();
borrow.next = None;
borrow.prev = Some(tail.clone());
}
fn pop_from_queue(&mut self, queue_index: usize) -> Option<Rc<RefCell<Task>>> {
let task = self.queues[queue_index].pop_back();
if self.queues[queue_index].is_empty() {
self.prio_bitmap &= !(1 << queue_index as u64);
}

self.queues[i].tail = Some(task);
task
}

fn pop_from_queue(&mut self, queue_index: usize) -> Option<Rc<RefCell<Task>>> {
let (new_head, task) = {
let head = self.queues[queue_index].head.as_mut()?;
let mut borrow = head.borrow_mut();
/// Remove the task at index from the queue and return that task,
/// or None if the index is out of range or the list is empty.
fn remove_from_queue(
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Ah, nice! You even made this a fully fledged method. 👍

&mut self,
task_index: usize,
queue_index: usize,
) -> Option<Rc<RefCell<Task>>> {
//assert!(prio < NO_PRIORITIES, "Priority {} is too high", prio);

if let Some(ref mut nhead) = borrow.next {
nhead.borrow_mut().prev = None;
let queue = &mut self.queues[queue_index];
if task_index <= queue.len() {
// Calling remove is unstable: https://github.com/rust-lang/rust/issues/69210
let mut split_list = queue.split_off(task_index);
let element = split_list.pop_front();
queue.append(&mut split_list);
if queue.is_empty() {
self.prio_bitmap &= !(1 << queue_index as u64);
}

let new_head = borrow.next.clone();
borrow.next = None;
borrow.prev = None;

let task = head.clone();

(new_head, task)
};

self.queues[queue_index].head = new_head;
if self.queues[queue_index].head.is_none() {
self.queues[queue_index].tail = None;
self.prio_bitmap &= !(1 << queue_index as u64);
element
} else {
None
}

Some(task)
}

/// Pop the task with the highest priority from the queue
Expand Down Expand Up @@ -355,50 +328,18 @@ impl PriorityTaskQueue {

/// Change priority of specific task
pub fn set_priority(&mut self, handle: TaskHandle, prio: Priority) -> Result<(), ()> {
let i = handle.get_priority().into() as usize;
let mut pos = self.queues[i].head.as_mut().ok_or(())?;

loop {
if handle.id == pos.borrow().id {
let task = pos.clone();

// Extract found task from queue and set new priority
{
let mut borrow = task.borrow_mut();

let new = borrow.next.as_ref().cloned();
if let Some(prev) = borrow.prev.as_mut() {
prev.borrow_mut().next = new;
}

let new = borrow.prev.as_ref().cloned();
if let Some(next) = borrow.next.as_mut() {
next.borrow_mut().prev = new;
}

if borrow.prev.as_mut().is_none() {
// Ok, the task is head of the list
self.queues[i].head = borrow.next.as_ref().cloned();
}

if borrow.next.as_mut().is_none() {
// Ok, the task is tail of the list
self.queues[i].tail = borrow.prev.as_ref().cloned();
}

borrow.prio = prio;
borrow.next = None;
borrow.prev = None;
}

self.push(task);

return Ok(());
}

let ptr = pos.as_ptr();
pos = unsafe { (*ptr).next.as_mut().ok_or(())? };
let old_priority = handle.get_priority().into() as usize;
if let Some(index) = self.queues[old_priority]
.iter()
.position(|current_task| current_task.borrow().id == handle.id)
{
let Some(task) = self.remove_from_queue(index, old_priority) else { return Err(()) };
task.borrow_mut().prio = prio;
self.push(task);
return Ok(());
}

Err(())
}
}

Expand All @@ -425,10 +366,6 @@ pub struct Task {
pub core_id: CoreId,
/// Stack of the task
pub stacks: TaskStacks,
/// next task in queue
pub next: Option<Rc<RefCell<Task>>>,
/// previous task in queue
pub prev: Option<Rc<RefCell<Task>>>,
/// Task Thread-Local-Storage (TLS)
pub tls: Option<TaskTLS>,
/// lwIP error code for this task
Expand Down Expand Up @@ -460,8 +397,6 @@ impl Task {
last_fpu_state: arch::processor::FPUState::new(),
core_id,
stacks,
next: None,
prev: None,
tls: None,
#[cfg(feature = "newlib")]
lwip_errno: 0,
Expand All @@ -480,8 +415,6 @@ impl Task {
last_fpu_state: arch::processor::FPUState::new(),
core_id,
stacks: TaskStacks::from_boot_stacks(),
next: None,
prev: None,
tls: None,
#[cfg(feature = "newlib")]
lwip_errno: 0,
Expand Down