dummy pr to test deadlock solutions

src/cpp/fastdds/core/condition/WaitSetImpl.cpp

@@ -103,6 +103,8 @@ ReturnCode_t WaitSetImpl::wait(
         const fastrtps::Duration_t& timeout)
 {
     std::unique_lock<std::mutex> lock(mutex_);
+    // last notification processed
+    unsigned int old_counter = notifications_ - 1;
 
     if (is_waiting_)
     {
@@ -111,31 +113,54 @@ ReturnCode_t WaitSetImpl::wait(
 
     auto fill_active_conditions = [&]()
             {
-                bool ret_val = false;
-                active_conditions.clear();
-                for (const Condition* c : entries_)
+                bool ret_val;
+
+                if ( old_counter == notifications_ )
+                {
+                    // spurious wakeup
+                    return false;
+                }
+
+                // Loop if predicate may be outdated
+                do
                 {
-                    if (c->get_trigger_value())
+                    ret_val = false;
+                    old_counter = notifications_;
+                    active_conditions.clear();
+
+                    for (const Condition* c : entries_)
                     {
-                        ret_val = true;
-                        active_conditions.push_back(const_cast<Condition*>(c));
+                        if (c->get_trigger_value())
+                        {
+                            ret_val = true;
+                            active_conditions.push_back(const_cast<Condition*>(c));
+                        }
                     }
                 }
+                while (old_counter != notifications_
+                && active_conditions.size() != entries_.size());
+
                 return ret_val;
             };
 
     bool condition_value = false;
     is_waiting_ = true;
-    if (fastrtps::c_TimeInfinite == timeout)
-    {
-        cond_.wait(lock, fill_active_conditions);
-        condition_value = true;
-    }
-    else
+    auto missing_notification_outage = std::chrono::milliseconds(500);
+    auto now = std::chrono::steady_clock::now();
+    auto deadline = fastrtps::c_TimeInfinite == timeout ?
+            std::chrono::steady_clock::time_point::max() :
+            now + std::chrono::nanoseconds(timeout.to_ns());
+
+    do
     {
-        auto ns = timeout.to_ns();
-        condition_value = cond_.wait_for(lock, std::chrono::nanoseconds(ns), fill_active_conditions);
+        now = std::chrono::steady_clock::now();
+        auto next_outage_timeout = now + missing_notification_outage;
+        auto ctimeout = std::min(next_outage_timeout, deadline);
+
+        condition_value = cond_.wait_until(lock, ctimeout, fill_active_conditions);
     }
+    while (!condition_value && ( old_counter != notifications_ || deadline > now));
+
     is_waiting_ = false;
 
     return condition_value ? ReturnCode_t::RETCODE_OK : ReturnCode_t::RETCODE_TIMEOUT;
@@ -156,6 +181,7 @@ ReturnCode_t WaitSetImpl::get_conditions(
 
 void WaitSetImpl::wake_up()
 {
+    ++notifications_;
     cond_.notify_one();
 }
 

src/cpp/fastdds/core/condition/WaitSetImpl.hpp

@@ -19,6 +19,7 @@
 #ifndef _FASTDDS_CORE_CONDITION_WAITSETIMPL_HPP_
 #define _FASTDDS_CORE_CONDITION_WAITSETIMPL_HPP_
 
+#include <atomic>
 #include <condition_variable>
 #include <mutex>
 
@@ -113,6 +114,7 @@ struct WaitSetImpl
     std::condition_variable cond_;
     eprosima::utilities::collections::unordered_vector<const Condition*> entries_;
     bool is_waiting_ = false;
+    std::atomic_uint notifications_ = {1};
 };
 
 }  // namespace detail

test/unittest/dds/core/condition/WaitSetImplTests.cpp

@@ -13,6 +13,8 @@
 // limitations under the License.
 
 #include <algorithm>
+#include <future>
+#include <thread>
 
 #include <gtest/gtest.h>
 
@@ -33,7 +35,7 @@ class TestCondition : public Condition
 {
 public:
 
-    bool trigger_value = false;
+    volatile bool trigger_value = false;
 
     bool get_trigger_value() const override
     {
@@ -197,6 +199,73 @@ TEST(WaitSetImplTests, wait)
     }
 }
 
+TEST(WaitSetImplTests, fix_wait_notification_lost)
+{
+    ConditionSeq conditions;
+    WaitSetImpl wait_set;
+
+    // Waiting should return the added connection after the trigger value is updated and the wait_set waken.
+    {
+        TestCondition triggered_condition;
+
+        // Expecting calls on the notifier of triggered_condition.
+        auto notifier = triggered_condition.get_notifier();
+        EXPECT_CALL(*notifier, attach_to(_)).Times(1);
+        EXPECT_CALL(*notifier, will_be_deleted(_)).Times(1);
+
+        class AnotherTestCondition : public Condition
+        {
+        public:
+
+            bool get_trigger_value() const override
+            {
+                // Time to simulate thread context switch or something else
+                std::this_thread::sleep_for(std::chrono::seconds(2));
+                return false;
+            }
+
+        }
+        second_simulator_condition;
+
+        // Expecting calls on the notifier of second_simulator_condition.
+        notifier = second_simulator_condition.get_notifier();
+        EXPECT_CALL(*notifier, attach_to(_)).Times(1);
+        EXPECT_CALL(*notifier, will_be_deleted(_)).Times(1);
+
+        wait_set.attach_condition(triggered_condition);
+        wait_set.attach_condition(second_simulator_condition);
+
+        std::promise<void> promise;
+        std::future<void> future = promise.get_future();
+        ReturnCode_t ret = ReturnCode_t::RETCODE_ERROR;
+        std::thread wait_conditions([&]()
+                {
+                    // Not to use `WaitSetImpl::wait` with a timeout value, because the
+                    // `condition_variable::wait_for` could call _Predicate function again.
+                    ret = wait_set.wait(conditions, eprosima::fastrtps::c_TimeInfinite);
+                    promise.set_value();
+                });
+
+        // One second sleep to make the `wait_set.wait` check `triggered_condition` in the above thread
+        std::this_thread::sleep_for(std::chrono::seconds(1));
+        triggered_condition.trigger_value = true;
+        wait_set.wake_up();
+
+        // Expecting get notification after wake_up, otherwise output error within 5 seconds.
+        future.wait_for(std::chrono::seconds(5));
+        EXPECT_EQ(ReturnCode_t::RETCODE_OK, ret);
+        EXPECT_EQ(1u, conditions.size());
+        EXPECT_NE(conditions.cend(), std::find(conditions.cbegin(), conditions.cend(), &triggered_condition));
+
+        // Wake up the `wait_set` to make sure the thread exit
+        wait_set.wake_up();
+        wait_conditions.join();
+
+        wait_set.will_be_deleted(triggered_condition);
+        wait_set.will_be_deleted(second_simulator_condition);
+    }
+}
+
 int main(
         int argc,
         char** argv)