Drop FOLLY_HAVE_STD_THIS_THREAD_SLEEP_FOR

[folly.git] / folly / futures / DrivableExecutor.h

diff --git a/folly/futures/DrivableExecutor.h b/folly/futures/DrivableExecutor.h
index 6364bf0c5279efc1fa12580c90131e8ca7597971..a33d2d6f6b9340bd51fd5a991b109db1ee859f75 100644 (file)
--- a/folly/futures/DrivableExecutor.h
+++ b/folly/futures/DrivableExecutor.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -36,11 +36,19 @@ namespace folly {
  * These will be most helpful in tests, for instance if you need to pump a mock
  * EventBase until Futures complete.
  */
+
 class DrivableExecutor : public virtual Executor {
  public:
   virtual ~DrivableExecutor() = default;
 
   // Make progress on this Executor's work.
+  //
+  // Drive *must not* busy wait if there is no work to do.  Instead,
+  // sleep (using a semaphore or similar) until at least one event is
+  // processed.
+  // I.e. make_future().via(foo).then(...).getVia(DrivableExecutor)
+  // must not spin, even though nothing happens on the drivable
+  // executor.
   virtual void drive() = 0;
 };