diff --git a/src/circ_elem_array.h b/src/circ_elem_array.h
index 2756955..79ec151 100644
--- a/src/circ_elem_array.h
+++ b/src/circ_elem_array.h
@@ -36,8 +36,9 @@ enum : std::size_t {
 template <std::size_t DataSize>
 class elem_array : private elem_array_head {
     struct head_t {
-        ac_t rf_; // read flag
-        ac_t wf_; // write flag
+        ac_t rf_;              // read flag
+        std::atomic_bool wf_;  // write flag
+        std::atomic_flag acq_; // acquire flag
     };
 
 public:
@@ -102,18 +103,27 @@ public:
     }
 
     void* acquire(void) {
-        auto el = elem(wt_.load(std::memory_order_consume));
-        // check read finished by all consumers
-        do {
-            uc_t expected = 0;
-            std::atomic_thread_fence(std::memory_order_acquire);
-            if (el->head_.rf_.compare_exchange_weak(
-                        expected, cc_.load(std::memory_order_relaxed), std::memory_order_release)) {
-                break;
+        elem_t* el;
+        while (1) {
+            // searching an available element
+            el = elem(wt_.fetch_add(1, std::memory_order_acquire));
+            if (el->head_.acq_.test_and_set(std::memory_order_release)) {
+                std::this_thread::yield();
+                continue;
             }
-            std::this_thread::yield();
-        } while(1);
-        wt_.fetch_add(1, std::memory_order_release);
+            // check read finished by all consumers
+            while(1) {
+                uc_t expected = 0;
+                std::atomic_thread_fence(std::memory_order_acquire);
+                if (el->head_.rf_.compare_exchange_weak(
+                            expected, cc_.load(std::memory_order_relaxed), std::memory_order_release)) {
+                    break;
+                }
+                std::this_thread::yield();
+            }
+            el->head_.acq_.clear(std::memory_order_release);
+            break;
+        }
         return el->data_;
     }
 
@@ -131,7 +141,7 @@ public:
                      * set wf_ for the other producer thread which is commiting
                      * the element matches cr_ could see it has commited
                     */
-                    el->head_.wf_.store(1, std::memory_order_release);
+                    el->head_.wf_.store(true, std::memory_order_release);
                 }
                 else {
                     /*
@@ -139,7 +149,7 @@ public:
                      * so we just increase the cursor & go check the next
                     */
                     ++next;
-                    el->head_.wf_.store(0, std::memory_order_release);
+                    el->head_.wf_.store(false, std::memory_order_release);
                 }
                 /*
                  * it needs to go back and judge again
@@ -155,7 +165,7 @@ public:
             /*
              * check next element has commited or not
             */
-        } while(el = elem(++wi), el->head_.wf_.exchange(0, std::memory_order_acq_rel));
+        } while(el = elem(++wi), el->head_.wf_.exchange(false, std::memory_order_acq_rel));
     }
 
     uc_t cursor(void) const {