updated

Tsung-Wei Huang · Tsung-Wei Huang · commit 0c423defa742 · 2025-07-21T12:07:21.000-05:00
diff --git a/taskflow/core/atomic_notifier.hpp b/taskflow/core/atomic_notifier.hpp
@@ -69,13 +69,8 @@ inline size_t AtomicNotifier::num_waiters() const noexcept {
 
 inline void AtomicNotifier::notify_one() noexcept {
   std::atomic_thread_fence(std::memory_order_seq_cst);
-  //if((_state.load(std::memory_order_acquire) & WAITER_MASK) != 0) {
-  //  _state.fetch_add(EPOCH_INC, std::memory_order_relaxed);
-  //  _state.notify_one(); 
-  //}
-
   for(uint64_t state = _state.load(std::memory_order_acquire); state & WAITER_MASK;) {
-    if(_state.compare_exchange_weak(state, state + EPOCH_INC, std::memory_order_acquire)) {
+    if(_state.compare_exchange_weak(state, state + EPOCH_INC, std::memory_order_acq_rel)) {
       _state.notify_one(); 
       break;
     }
@@ -84,12 +79,8 @@ inline void AtomicNotifier::notify_one() noexcept {
 
 inline void AtomicNotifier::notify_all() noexcept {
   std::atomic_thread_fence(std::memory_order_seq_cst);
-  //if((_state.load(std::memory_order_acquire) & WAITER_MASK) != 0) {
-  //  _state.fetch_add(EPOCH_INC, std::memory_order_relaxed);
-  //  _state.notify_all(); 
-  //}
   for(uint64_t state = _state.load(std::memory_order_acquire); state & WAITER_MASK;) {
-    if(_state.compare_exchange_weak(state, state + EPOCH_INC, std::memory_order_acquire)) {
+    if(_state.compare_exchange_weak(state, state + EPOCH_INC, std::memory_order_acq_rel)) {
       _state.notify_all(); 
       break;
     }
@@ -123,9 +114,6 @@ inline void AtomicNotifier::commit_wait(Waiter* waiter) noexcept {
     _state.wait(prev, std::memory_order_acquire); 
     prev = _state.load(std::memory_order_acquire);
   }
-  // memory_order_relaxed would suffice for correctness, but the faster
-  // #waiters gets to 0, the less likely it is that we'll do spurious wakeups
-  // (and thus system calls)
   _state.fetch_sub(WAITER_INC, std::memory_order_seq_cst);
 }
 
