Eliminate phase unlock for case where we are not going to wait

1 files changed, 6 insertions, 2 deletions

diff --git a/libbuild2/context.ixx b/libbuild2/context.ixx
index 46fe4f7..73601d4 100644
--- a/libbuild2/context.ixx
+++ b/libbuild2/context.ixx
@@ -56,8 +56,12 @@ namespace build2
   inline void wait_guard::
   wait ()
   {
-    phase_unlock u (*ctx, phase);
-    ctx->sched.wait (start_count, *task_count);
+    if (task_count->load (memory_order_acquire) > start_count)
+    {
+      phase_unlock u (*ctx, phase);
+      ctx->sched.wait (start_count, *task_count);
+    }
+
     task_count = nullptr;
   }
 }