3 files changed, 53 insertions, 1 deletions
diff --git a/src/vlib/main.h b/src/vlib/main.h
index 20b8b464e34..a2ed9ba69f9 100644
--- a/src/vlib/main.h
+++ b/src/vlib/main.h
@@ -96,7 +96,7 @@ typedef struct vlib_main_t
   u64 cpu_time_main_loop_start;
 
   /* Incremented once for each main loop. */
-  u32 main_loop_count;
+  volatile u32 main_loop_count;
 
   /* Count of vectors processed this main loop. */
   u32 main_loop_vectors_processed;
diff --git a/src/vlib/threads.c b/src/vlib/threads.c
index 07e1d79cf4c..26b9e7f8d56 100644
--- a/src/vlib/threads.c
+++ b/src/vlib/threads.c
@@ -1390,6 +1390,18 @@ vlib_worker_thread_initial_barrier_sync_and_release (vlib_main_t * vm)
   *vlib_worker_threads->wait_at_barrier = 0;
 }
 
+/**
+ * Return true if the wroker thread barrier is held
+ */
+u8
+vlib_worker_thread_barrier_held (void)
+{
+  if (vec_len (vlib_mains) < 2)
+    return (1);
+
+  return (*vlib_worker_threads->wait_at_barrier == 1);
+}
+
 void
 vlib_worker_thread_barrier_sync_int (vlib_main_t * vm, const char *func_name)
 {
@@ -1586,6 +1598,41 @@ vlib_worker_thread_barrier_release (vlib_main_t * vm)
 
 }
 
+/**
+ * Wait until each of the workers has been once around the track
+ */
+void
+vlib_worker_wait_one_loop (void)
+{
+  ASSERT (vlib_get_thread_index () == 0);
+
+  if (vec_len (vlib_mains) < 2)
+    return;
+
+  if (vlib_worker_thread_barrier_held ())
+    return;
+
+  u32 *counts = 0;
+  u32 ii;
+
+  vec_validate (counts, vec_len (vlib_mains) - 1);
+
+  /* record the current loop counts */
+  vec_foreach_index (ii, vlib_mains)
+    counts[ii] = vlib_mains[ii]->main_loop_count;
+
+  /* spin until each changes, apart from the main thread, or we'd be
+   * a while */
+  for (ii = 1; ii < vec_len (counts); ii++)
+    {
+      while (counts[ii] == vlib_mains[ii]->main_loop_count)
+	CLIB_PAUSE ();
+    }
+
+  vec_free (counts);
+  return;
+}
+
 /*
  * Check the frame queue to see if any frames are available.
  * If so, pull the packets off the frames and put them to
diff --git a/src/vlib/threads.h b/src/vlib/threads.h
index 312323c096d..2088c5b8b7a 100644
--- a/src/vlib/threads.h
+++ b/src/vlib/threads.h
@@ -206,8 +206,13 @@ u32 vlib_frame_queue_main_init (u32 node_index, u32 frame_queue_nelts);
 void vlib_worker_thread_barrier_sync_int (vlib_main_t * vm,
 					  const char *func_name);
 void vlib_worker_thread_barrier_release (vlib_main_t * vm);
+u8 vlib_worker_thread_barrier_held (void);
 void vlib_worker_thread_initial_barrier_sync_and_release (vlib_main_t * vm);
 void vlib_worker_thread_node_refork (void);
+/**
+ * Wait until each of the workers has been once around the track
+ */
+void vlib_worker_wait_one_loop (void);
 
 static_always_inline uword
 vlib_get_thread_index (void)