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kmc-solid: Fix wait queue manipulation errors in the Condvar implementation #93843

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merged 2 commits into from
Feb 10, 2022
Merged

kmc-solid: Fix wait queue manipulation errors in the Condvar implementation #93843

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bdc9508
kmc-solid: Fix wait queue manipulation errors in the `Condvar` implem…
kawadakk Feb 9, 2022
1d180ca
kmc-solid: Wait queue should be sorted in the descending order of tas…
kawadakk Feb 10, 2022
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13 changes: 9 additions & 4 deletions library/std/src/sys/itron/condvar.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,10 +15,12 @@ unsafe impl Sync for Condvar {}
pub type MovableCondvar = Condvar;

impl Condvar {
#[inline]
pub const fn new() -> Condvar {
Condvar { waiters: SpinMutex::new(waiter_queue::WaiterQueue::new()) }
}

#[inline]
pub unsafe fn init(&mut self) {}

pub unsafe fn notify_one(&self) {
Expand Down Expand Up @@ -190,7 +192,7 @@ mod waiter_queue {
let insert_after = {
let mut cursor = head.last;
loop {
if waiter.priority <= cursor.as_ref().priority {
if waiter.priority >= cursor.as_ref().priority {
// `cursor` and all previous waiters have the same or higher
// priority than `current_task_priority`. Insert the new
// waiter right after `cursor`.
Expand All @@ -206,14 +208,16 @@ mod waiter_queue {

if let Some(mut insert_after) = insert_after {
// Insert `waiter` after `insert_after`
let insert_before = insert_after.as_ref().prev;
let insert_before = insert_after.as_ref().next;

waiter.prev = Some(insert_after);
insert_after.as_mut().next = Some(waiter_ptr);

waiter.next = insert_before;
if let Some(mut insert_before) = insert_before {
insert_before.as_mut().prev = Some(waiter_ptr);
} else {
head.last = waiter_ptr;
}
} else {
// Insert `waiter` to the front
Expand All @@ -240,11 +244,11 @@ mod waiter_queue {
match (waiter.prev, waiter.next) {
(Some(mut prev), Some(mut next)) => {
prev.as_mut().next = Some(next);
next.as_mut().next = Some(prev);
next.as_mut().prev = Some(prev);
}
(None, Some(mut next)) => {
head.first = next;
next.as_mut().next = None;
next.as_mut().prev = None;
}
(Some(mut prev), None) => {
prev.as_mut().next = None;
Expand All @@ -271,6 +275,7 @@ mod waiter_queue {
unsafe { waiter.as_ref().task != 0 }
}

#[inline]
pub fn pop_front(&mut self) -> Option<abi::ID> {
unsafe {
let head = self.head.as_mut()?;
Expand Down