diff --git a/demo/chat/main.cpp b/demo/chat/main.cpp
index 7f88e6f..715dd0d 100755
--- a/demo/chat/main.cpp
+++ b/demo/chat/main.cpp
@@ -50,20 +50,18 @@ int main() {
             }
             std::cout << dat << std::endl;
         }
+        std::cout << id << " receiver is quit..." << std::endl;
     }};
 
     for (/*int i = 1*/;; /*++i*/) {
         std::cin >> buf;
-        if (buf.empty()) break;
+        if (buf.empty() || (buf == quit__)) break;
 //        std::cout << "[" << i << "]" << std::endl;
         sender__.send(id + "> " + buf);
-        if (buf == quit__) {
-            receiver__.disconnect();
-            break;
-        }
     }
 
+    receiver__.disconnect();
     r.join();
-    std::cout << id << " is quit..." << std::endl;
+    std::cout << id << " sender is quit..." << std::endl;
     return 0;
 }
diff --git a/src/libipc/platform/waiter_linux.h b/src/libipc/platform/waiter_linux.h
index b84644b..0fe0ed2 100755
--- a/src/libipc/platform/waiter_linux.h
+++ b/src/libipc/platform/waiter_linux.h
@@ -241,6 +241,11 @@ class waiter_helper {
     std::atomic<unsigned> waiting_ { 0 };
     long counter_ = 0;
 
+    enum : unsigned {
+        destruct_mask = (std::numeric_limits<unsigned>::max)() >> 1,
+        destruct_flag = ~destruct_mask
+    };
+
 public:
     using handle_t = std::tuple<ipc::string, sem_helper::handle_t, sem_helper::handle_t>;
 
@@ -280,24 +285,33 @@ public:
     }
 
     template <typename F>
-    bool wait_if(handle_t const & h, F&& pred, std::size_t tm = invalid_value) {
+    bool wait_if(handle_t const & h, std::atomic<bool> const & enabled, F&& pred, std::size_t tm = invalid_value) {
+        if (!enabled.load(std::memory_order_acquire)) {
+            return false;
+        }
         waiting_.fetch_add(1, std::memory_order_release);
         auto finally = ipc::guard([this] {
-            waiting_->fetch_sub(1, std::memory_order_release);
+            waiting_.fetch_sub(1, std::memory_order_release);
         });
         {
             IPC_UNUSED_ auto guard = ipc::detail::unique_lock(lock_);
             if (!std::forward<F>(pred)()) return true;
             ++ counter_;
         }
-        bool ret = sem_helper::wait(std::get<1>(h), tm);
+        bool ret = false;
+        do {
+            if (!enabled.load(std::memory_order_acquire)) {
+                break;
+            }
+            ret = sem_helper::wait(std::get<1>(h), tm);
+        } while (waiting_.load(std::memory_order_acquire) & destruct_flag);
         finally.do_exit();
         ret = sem_helper::post(std::get<2>(h)) && ret;
         return ret;
     }
 
     bool notify(handle_t const & h) {
-        if (waiting_.load(std::memory_order_acquire) == 0) {
+        if ((waiting_.load(std::memory_order_acquire) & destruct_mask) == 0) {
             return true;
         }
         bool ret = true;
@@ -311,7 +325,7 @@ public:
     }
 
     bool broadcast(handle_t const & h) {
-        if (waiting_.load(std::memory_order_acquire) == 0) {
+        if ((waiting_.load(std::memory_order_acquire) & destruct_mask) == 0) {
             return true;
         }
         bool ret = true;
@@ -327,6 +341,28 @@ public:
         }
         return ret;
     }
+
+    bool emit_destruction(handle_t const & h) {
+        if ((waiting_.load(std::memory_order_acquire) & destruct_mask) == 0) {
+            return true;
+        }
+        bool ret = true;
+        IPC_UNUSED_ auto guard = ipc::detail::unique_lock(lock_);
+        waiting_.fetch_or(destruct_flag, std::memory_order_relaxed);
+        IPC_UNUSED_ auto finally = ipc::guard([this] {
+            waiting_.fetch_and(destruct_mask, std::memory_order_relaxed);
+        });
+        if (counter_ > 0) {
+            for (long i = 0; i < counter_; ++i) {
+                ret = ret && sem_helper::post(std::get<1>(h));
+            }
+            do {
+                -- counter_;
+                ret = ret && sem_helper::wait(std::get<2>(h), default_timeout);
+            } while (counter_ > 0);
+        }
+        return ret;
+    }
 };
 
 class waiter {
@@ -360,19 +396,24 @@ public:
     }
 
     template <typename F>
-    bool wait_if(handle_t h, F&& pred, std::size_t tm = invalid_value) {
+    bool wait_if(handle_t h, std::atomic<bool> const & enabled, F && pred, std::size_t tm = invalid_value) {
         if (h == invalid()) return false;
-        return helper_.wait_if(h, std::forward<F>(pred), tm);
+        return helper_.wait_if(h, enabled, std::forward<F>(pred), tm);
     }
 
-    void notify(handle_t h) {
-        if (h == invalid()) return;
-        helper_.notify(h);
+    bool notify(handle_t h) {
+        if (h == invalid()) return false;
+        return helper_.notify(h);
     }
 
-    void broadcast(handle_t h) {
-        if (h == invalid()) return;
-        helper_.broadcast(h);
+    bool broadcast(handle_t h) {
+        if (h == invalid()) return false;
+        return helper_.broadcast(h);
+    }
+
+    bool emit_destruction(handle_t h) {
+        if (h == invalid()) return false;
+        return helper_.emit_destruction(h);
     }
 };
 
diff --git a/src/libipc/platform/waiter_wrapper.h b/src/libipc/platform/waiter_wrapper.h
index 8242d31..4c30094 100755
--- a/src/libipc/platform/waiter_wrapper.h
+++ b/src/libipc/platform/waiter_wrapper.h
@@ -241,7 +241,7 @@ public:
     }
 
     template <typename F>
-    bool wait_if(F&& pred, std::size_t tm = invalid_value) {
+    bool wait_if(F && pred, std::size_t tm = invalid_value) {
         if (!valid()) return false;
         return w_->wait_if(h_, enabled_, std::forward<F>(pred), tm);
     }