Fix potential deadlock in job queue #3480
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…unction to enter an infinite loop.
ahojnnes
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Jul 14, 2025
ahojnnes
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Jul 16, 2025
Fix a bug where the Stop function's state issue may cause the Pop()
function to enter an infinite loop.
template <typename T>
void JobQueue<T>::Stop() {
stop_ = true; // problem code
push_condition_.notify_all();
pop_condition_.notify_all();
}
typename JobQueue<T>::Job JobQueue<T>::Pop() {
std::unique_lock<std::mutex> lock(mutex_);
while (jobs_.empty() && !stop_) {
push_condition_.wait(lock);
....
Bug Description:
There is a race condition between Stop() and Pop() that can lead to
deadlock. The sequence is:
In Pop(), the thread evaluates while (jobs_.empty() && !stop_) and sees
stop_ = false
Before entering push_condition_.wait(lock), the Stop() function gets
executed:
Sets stop_ = true
Calls push_condition_.notify_all()
The Pop() thread then proceeds to push_condition_.wait(lock)
Because the notification was sent before the wait began, it's missed
Now the thread is stuck waiting indefinitely with stop_ = true, causing
a deadlock
---------
Co-authored-by: 3000huyang <[email protected]>
Co-authored-by: Johannes Schönberger <[email protected]>
Co-authored-by: Johannes Schönberger <[email protected]>
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Fix a bug where the Stop function's state issue may cause the Pop() function to enter an infinite loop.
template
void JobQueue::Stop() {
stop_ = true; // problem code
push_condition_.notify_all();
pop_condition_.notify_all();
}
typename JobQueue::Job JobQueue::Pop() {
std::unique_lockstd::mutex lock(mutex_);
while (jobs_.empty() && !stop_) {
push_condition_.wait(lock);
....
Bug Description:
There is a race condition between Stop() and Pop() that can lead to deadlock. The sequence is:
In Pop(), the thread evaluates while (jobs_.empty() && !stop_) and sees stop_ = false
Before entering push_condition_.wait(lock), the Stop() function gets executed:
Sets stop_ = true
Calls push_condition_.notify_all()
The Pop() thread then proceeds to push_condition_.wait(lock)
Because the notification was sent before the wait began, it's missed
Now the thread is stuck waiting indefinitely with stop_ = true, causing a deadlock