Fix timeout for no metadata run session

.github/workflows/ubuntu-ci.yml

@@ -156,21 +156,51 @@ jobs:
           # The tests establish real XRCE sessions, so an Agent has to be running before colcon test starts
           # The Agent must not pick up the implementation under test as its own middleware
           RMW_IMPLEMENTATION=rmw_fastrtps_cpp ros2 run micro_ros_agent micro_ros_agent udp4 --port 8888 -d -v4 &
+          agent_pid=$!
           sleep 1
 
           colcon test \
             --event-handlers console_direct+ \
             --return-code-on-test-failure \
             --packages-select $TESTED_PACKAGES
 
+          # Kill Agent so the next step can start its own Agent
+          kill $agent_pid
+
+      - name: Ensure wait set stability (rmw_wait)
+        # test_wait.cpp asserts on wall clock timings, so it is the part of the suite most
+        # exposed to flakiness, so it is repeated 100 times in a random order
+        run: |
+          . /opt/ros/$ROS_DISTRO/setup.bash
+          . install/local_setup.bash
+
+          RMW_IMPLEMENTATION=rmw_fastrtps_cpp ros2 run micro_ros_agent micro_ros_agent udp4 --port 8888 -d -v4 &
+          agent_pid=$!
+          sleep 1
+
+          # --gtest_shuffle reseeds on every iteration and prints the seed it used
+          ./build/rmw_microxrcedds/test/test-wait \
+            --gtest_repeat=100 \
+            --gtest_shuffle
+
+          kill $agent_pid
+
       - name: Static memory report
         # Kept separate from the test step so it still runs when a test fails,
         # but needs the build to succeed
         if: ${{ !cancelled() && steps.build.outcome == 'success' }}
         run: |
           . /opt/ros/$ROS_DISTRO/setup.bash
+          . install/local_setup.bash
+
+          RMW_IMPLEMENTATION=rmw_fastrtps_cpp ros2 run micro_ros_agent micro_ros_agent udp4 --port 8888 -d -v4 &
+          agent_pid=$!
+          sleep 1
+
           ./build/rmw_microxrcedds/test/test-sizes 2> memanalisys_out
 
+          kill $agent_pid
+
       - name: Test results
         if: ${{ !cancelled() }}
         run: |

rmw_microxrcedds_c/src/rmw_microros_internal/types.h

@@ -252,7 +252,9 @@ typedef struct rmw_uxrce_guard_condition_t
 {
   rmw_uxrce_mempool_item_t mem;
 
-  bool hasTriggered;
+  // Polled by rmw_wait and can be written from arbitrary threads
+  // by rmw_trigger_guard_condition, needs 'volatile'
+  volatile bool hasTriggered;
 
   rmw_guard_condition_t rmw_guard_condition;
 } rmw_uxrce_guard_condition_t;

rmw_microxrcedds_c/src/rmw_wait.c

@@ -18,9 +18,25 @@
 #include <rmw/rmw.h>
 #include <rmw/time.h>
 #include <uxr/client/core/session/session.h>
+#include <uxr/client/util/time.h>
 
 #include "./rmw_microros_internal/utils.h"
 
+#define RMW_UXRCE_MAX_SESSION_WAIT_SLICE_MS 10
+
+static bool rmw_uxrce_any_guard_condition_triggered(
+  const rmw_guard_conditions_t * guard_conditions)
+{
+  for (size_t i = 0; guard_conditions && i < guard_conditions->guard_condition_count; ++i) {
+    rmw_uxrce_guard_condition_t * custom_guard_condition =
+      (rmw_uxrce_guard_condition_t *)guard_conditions->guard_conditions[i];
+    if (NULL != custom_guard_condition && custom_guard_condition->hasTriggered) {
+      return true;
+    }
+  }
+  return false;
+}
+
 rmw_ret_t
 rmw_wait(
   rmw_subscriptions_t * subscriptions,
@@ -88,34 +104,58 @@ rmw_wait(
 
   // Count sessions to be ran
   uint8_t available_contexts = 0;
+  uint8_t available_sessions = 0;
   item = session_memory.allocateditems;
   while (item != NULL) {
     rmw_context_impl_t * custom_context = (rmw_context_impl_t *)item->data;
     available_contexts += custom_context->need_to_be_ran ? 1 : 0;
+    available_sessions++;
     item = item->next;
   }
 
-  // There is no context that contais any of the wait set entities. Nothing to wait here.
-  if (available_contexts != 0) {
-    int32_t per_session_timeout =
-      (timeout.i32 == UXR_TIMEOUT_INF) ? UXR_TIMEOUT_INF :
-      (int32_t)((float)timeout.i32 / (float)available_contexts);
-
+  // Ensure spinning at least once, even if the timeout is 0
+  bool data_available = false;
+  item = session_memory.allocateditems;
+  while (item != NULL) {
+    rmw_context_impl_t * custom_context = (rmw_context_impl_t *)item->data;
+    if (custom_context->need_to_be_ran) {
+      data_available |= uxr_run_session_until_data(&custom_context->session, 0);
+    } else {
+      uxr_run_session_timeout(&custom_context->session, 0);
+    }
+    item = item->next;
+  }
+  bool guard_condition_triggered = rmw_uxrce_any_guard_condition_triggered(guard_conditions);
+
+  if (available_sessions != 0 && !data_available && !guard_condition_triggered &&
+    timeout.i32 != 0)
+  {
+    // An infinite timeout is handled as a deadline that never expires, so that guard conditions
+    // are still polled between slices instead of blocking inside a single XRCE receive.
+    const int64_t deadline = (timeout.i32 == UXR_TIMEOUT_INF) ?
+      INT64_MAX : uxr_millis() + timeout.i32;
+
+    // Sessions are serviced round-robin in bounded slices, so that no session monopolises the
+    // wait, guard conditions are polled between slices and the deadline is not overshot.
     item = session_memory.allocateditems;
-    while (item != NULL) {
+    int64_t now = uxr_millis();
+    while (!data_available && !guard_condition_triggered && now < deadline) {
       rmw_context_impl_t * custom_context = (rmw_context_impl_t *)item->data;
+      const int64_t remaining = deadline - now;
+      const int32_t slice = (remaining < RMW_UXRCE_MAX_SESSION_WAIT_SLICE_MS) ?
+        (int32_t)remaining : RMW_UXRCE_MAX_SESSION_WAIT_SLICE_MS;
+
       if (custom_context->need_to_be_ran) {
-        uxr_run_session_until_data(&custom_context->session, per_session_timeout);
+        // If at least one context needs to be ran, the other sessions are not serviced
+        data_available = uxr_run_session_until_data(&custom_context->session, slice);
+      } else if (available_contexts == 0) {
+        // No wait set entity belongs to any session, keep every session's metatraffic alive
+        uxr_run_session_timeout(&custom_context->session, slice);
       }
-      item = item->next;
-    }
-  } else {
-    // Spin with no blocking to handle session metatraffic
-    item = session_memory.allocateditems;
-    while (item != NULL) {
-      rmw_context_impl_t * custom_context = (rmw_context_impl_t *)item->data;
-      uxr_run_session_timeout(&custom_context->session, 0);
-      item = item->next;
+
+      guard_condition_triggered = rmw_uxrce_any_guard_condition_triggered(guard_conditions);
+      item = (item->next == NULL) ? session_memory.allocateditems : item->next;
+      now = uxr_millis();
     }
   }
 
@@ -161,7 +201,7 @@ rmw_wait(
   for (size_t i = 0; guard_conditions && i < guard_conditions->guard_condition_count; ++i) {
     rmw_uxrce_guard_condition_t * custom_guard_condition =
       (rmw_uxrce_guard_condition_t *)guard_conditions->guard_conditions[i];
-    if (custom_guard_condition->hasTriggered == false) {
+    if (NULL == custom_guard_condition || custom_guard_condition->hasTriggered == false) {
       guard_conditions->guard_conditions[i] = NULL;
     } else {
       custom_guard_condition->hasTriggered = false;

rmw_microxrcedds_c/test/CMakeLists.txt

@@ -57,4 +57,5 @@ rmw_test(test-reqres      test_reqres.cpp)
 rmw_test(test-topic       test_topic.cpp)
 rmw_test(test-rmw         test_rmw.cpp)
 rmw_test(test-sizes       test_sizes.cpp)
-rmw_test(test-guardcond   test_guard_condition.cpp)
+rmw_test(test-guardcond   test_guard_condition.cpp)
+rmw_test(test-wait        test_wait.cpp)