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use compare_exchange_strong to protect agianst spurious failures #40540

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Merged
merged 1 commit into from
Jan 24, 2022
Merged

use compare_exchange_strong to protect agianst spurious failures #40540

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10 changes: 5 additions & 5 deletions stdlib/public/Concurrency/TaskGroup.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -394,14 +394,14 @@ class TaskGroupImpl: public TaskGroupTaskStatusRecord {
///
/// This is used to atomically perform a waiting task completion.
bool statusCompletePendingReadyWaiting(GroupStatus &old) {
return status.compare_exchange_weak(
return status.compare_exchange_strong(
old.status, old.completingPendingReadyWaiting().status,
/*success*/ std::memory_order_relaxed,
/*failure*/ std::memory_order_relaxed);
}

bool statusCompletePendingReady(GroupStatus &old) {
return status.compare_exchange_weak(
return status.compare_exchange_strong(
old.status, old.completingPendingReady().status,
/*success*/ std::memory_order_relaxed,
/*failure*/ std::memory_order_relaxed);
Expand Down Expand Up @@ -588,7 +588,7 @@ void TaskGroupImpl::offer(AsyncTask *completedTask, AsyncContext *context) {
assert(assumed.pendingTasks() && "offered to group with no pending tasks!");
// We are the "first" completed task to arrive,
// and since there is a task waiting we immediately claim and complete it.
if (waitQueue.compare_exchange_weak(
if (waitQueue.compare_exchange_strong(
waitingTask, nullptr,
/*success*/ std::memory_order_release,
/*failure*/ std::memory_order_acquire) &&
Expand Down Expand Up @@ -755,7 +755,7 @@ PollResult TaskGroupImpl::poll(AsyncTask *waitingTask) {

auto assumedStatus = assumed.status;
auto newStatus = TaskGroupImpl::GroupStatus{assumedStatus};
if (status.compare_exchange_weak(
if (status.compare_exchange_strong(
assumedStatus, newStatus.completingPendingReadyWaiting().status,
/*success*/ std::memory_order_relaxed,
/*failure*/ std::memory_order_acquire)) {
Expand Down Expand Up @@ -821,7 +821,7 @@ PollResult TaskGroupImpl::poll(AsyncTask *waitingTask) {
waitingTask->flagAsSuspended();
}
// Put the waiting task at the beginning of the wait queue.
if (waitQueue.compare_exchange_weak(
if (waitQueue.compare_exchange_strong(
waitHead, waitingTask,
/*success*/ std::memory_order_release,
/*failure*/ std::memory_order_acquire)) {
Expand Down