This is an attempt to fix the situation described by https://reviews.llvm.org/D104207#2826290 and PR41508.
See sequence of operations leading to the bug in https://reviews.llvm.org/D104207#3004689
We ensure that the Latch is completely "free" before decrementing the number of TaskGroupInstances.
Differential revision: https://reviews.llvm.org/D109914
public:
explicit Latch(uint32_t Count = 0) : Count(Count) {}
- ~Latch() { sync(); }
+ ~Latch() {
+ // Ensure at least that sync() was called.
+ assert(Count == 0);
+ }
void inc() {
std::lock_guard<std::mutex> lock(Mutex);
// lock, only allow the first TaskGroup to run tasks parallelly. In the scenario
// of nested parallel_for_each(), only the outermost one runs parallelly.
TaskGroup::TaskGroup() : Parallel(TaskGroupInstances++ == 0) {}
-TaskGroup::~TaskGroup() { --TaskGroupInstances; }
+TaskGroup::~TaskGroup() {
+ // We must ensure that all the workloads have finished before decrementing the
+ // instances count.
+ L.sync();
+ --TaskGroupInstances;
+}
void TaskGroup::spawn(std::function<void()> F) {
if (Parallel) {