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Merge #706
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706: Implements PriorityTaskQueue with std's LinkedList rather than a custom linked list implementation r=mkroening a=michaelRichards99

Fixes #377.

Co-authored-by: michael <michaelsrichards1999@gmail.com>
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@bors @michaelRichards99
bors[bot] and michaelRichards99 committed Apr 18, 2023
2 parents 837b76e + 7445ef1 commit 05fd31d
Showing 1 changed file with 41 additions and 108 deletions.
149 changes: 41 additions & 108 deletions src/scheduler/task.rs
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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(
&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

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