#include <stack>
#include <thread>
-using namespace llvm;
+namespace llvm {
+namespace parallel {
+namespace detail {
namespace {
#endif
}
-void parallel::detail::TaskGroup::spawn(std::function<void()> F) {
- L.inc();
- Executor::getDefaultExecutor()->add([&, F] {
+static std::atomic<int> TaskGroupInstances;
+
+// Latch::sync() called by the dtor may cause one thread to block. If is a dead
+// lock if all threads in the default executor are blocked. To prevent the dead
+// 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; }
+
+void TaskGroup::spawn(std::function<void()> F) {
+ if (Parallel) {
+ L.inc();
+ Executor::getDefaultExecutor()->add([&, F] {
+ F();
+ L.dec();
+ });
+ } else {
F();
- L.dec();
- });
+ }
}
+
+} // namespace detail
+} // namespace parallel
+} // namespace llvm
#endif // LLVM_ENABLE_THREADS