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Don’t start executing a task when cancelToBeRescheduled is called before execute #1370

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Merged
merged 2 commits into from
Jun 1, 2024
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Don’t start executing a task when cancelToBeRescheduled is called before execute #1370

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02576d6
Change `QueuedTask.cancelledToBeRescheduled` to be a normal Bool inst…
ahoppen May 31, 2024
cc1280f
Don’t start executing a task when `cancelToBeRescheduled` is called b…
ahoppen May 31, 2024
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17 changes: 13 additions & 4 deletions Sources/SKCore/TaskScheduler.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -144,7 +144,7 @@ public actor QueuedTask<TaskDescription: TaskDescriptionProtocol> {
/// Whether `cancelToBeRescheduled` has been called on this `QueuedTask`.
///
/// Gets reset every time `executionTask` finishes.
nonisolated(unsafe) private var cancelledToBeRescheduled: AtomicBool = .init(initialValue: false)
private var cancelledToBeRescheduled: Bool = false

/// Whether `resultTask` has been cancelled.
private nonisolated(unsafe) var resultTaskCancelled: AtomicBool = .init(initialValue: false)
Expand Down Expand Up @@ -228,6 +228,15 @@ public actor QueuedTask<TaskDescription: TaskDescriptionProtocol> {
/// Execution might be canceled to be rescheduled, in which case this returns `.cancelledToBeRescheduled`. In that
/// case the `TaskScheduler` is expected to call `execute` again.
func execute() async -> ExecutionTaskFinishStatus {
if cancelledToBeRescheduled {
// `QueuedTask.execute` is called from a detached task in `TaskScheduler.poke` but we insert it into the
// `currentlyExecutingTasks` queue beforehand. This leaves a short windows in which we could cancel the task to
// reschedule it before it actually starts executing.
// If this happens, we don't have to do anything in `execute` and can immediately return. `execute` will be called
// again when the task gets rescheduled.
cancelledToBeRescheduled = false
return .cancelledToBeRescheduled
}
precondition(executionTask == nil, "Task started twice")
let task = Task.detached(priority: self.priority) {
if !Task.isCancelled && !self.resultTaskCancelled.value {
Expand All @@ -246,9 +255,9 @@ public actor QueuedTask<TaskDescription: TaskDescriptionProtocol> {
private func finalizeExecution() async -> ExecutionTaskFinishStatus {
self.executionTask = nil
_isExecuting.value = false
if Task.isCancelled && self.cancelledToBeRescheduled.value {
if Task.isCancelled && self.cancelledToBeRescheduled {
await executionStateChangedCallback?(self, .cancelledToBeRescheduled)
self.cancelledToBeRescheduled.value = false
self.cancelledToBeRescheduled = false
return ExecutionTaskFinishStatus.cancelledToBeRescheduled
} else {
await executionStateChangedCallback?(self, .finished)
Expand All @@ -260,10 +269,10 @@ public actor QueuedTask<TaskDescription: TaskDescriptionProtocol> {
///
/// If the task has not been started yet or has already finished execution, this is a no-op.
func cancelToBeRescheduled() {
self.cancelledToBeRescheduled = true
guard let executionTask else {
return
}
self.cancelledToBeRescheduled.value = true
executionTask.cancel()
self.executionTask = nil
}
Expand Down