From: Yedidya Feldblum <yfeldblum@fb.com>
Date: Sat, 7 Oct 2017 01:04:56 +0000 (-0700)
Subject: Let EventBase::runInEventBaseThreadAndWait consume its argument
X-Git-Tag: v2017.10.09.00~1
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=662b86a949f85dfcbf966a346dba8306710eabcb;p=folly.git

Let EventBase::runInEventBaseThreadAndWait consume its argument

Summary:
[Folly] Let `EventBase::runInEventBaseThreadAndWait` consume its argument.

Likewise `EventBase::runImmediatelyOrRunInEventBaseThreadAndWait`.

And enforce that the function is destructed before returning, so that, in the case of a wrapped lambda, all captured objects' destructors run before returning from the function.

Reviewed By: elsteveogrande

Differential Revision: D5994106

fbshipit-source-id: 816c9431a85a3d41e4fda321065614f4c18f0697
---

diff --git a/folly/io/async/EventBase.cpp b/folly/io/async/EventBase.cpp
index 7ef3c8a3..56f92c8d 100644
--- a/folly/io/async/EventBase.cpp
+++ b/folly/io/async/EventBase.cpp
@@ -566,7 +566,7 @@ bool EventBase::runInEventBaseThread(Func fn) {
   return true;
 }
 
-bool EventBase::runInEventBaseThreadAndWait(FuncRef fn) {
+bool EventBase::runInEventBaseThreadAndWait(Func fn) {
   if (inRunningEventBaseThread()) {
     LOG(ERROR) << "EventBase " << this << ": Waiting in the event loop is not "
                << "allowed";
@@ -574,18 +574,20 @@ bool EventBase::runInEventBaseThreadAndWait(FuncRef fn) {
   }
 
   Baton<> ready;
-  runInEventBaseThread([&] {
+  runInEventBaseThread([&ready, fn = std::move(fn)]() mutable {
     SCOPE_EXIT {
       ready.post();
     };
-    fn();
+    // A trick to force the stored functor to be executed and then destructed
+    // before posting the baton and waking the waiting thread.
+    copy(std::move(fn))();
   });
   ready.wait();
 
   return true;
 }
 
-bool EventBase::runImmediatelyOrRunInEventBaseThreadAndWait(FuncRef fn) {
+bool EventBase::runImmediatelyOrRunInEventBaseThreadAndWait(Func fn) {
   if (isInEventBaseThread()) {
     fn();
     return true;
diff --git a/folly/io/async/EventBase.h b/folly/io/async/EventBase.h
index fff75adb..ee7ceca7 100644
--- a/folly/io/async/EventBase.h
+++ b/folly/io/async/EventBase.h
@@ -127,7 +127,6 @@ class EventBase : private boost::noncopyable,
                   public DrivableExecutor {
  public:
   using Func = folly::Function<void()>;
-  using FuncRef = folly::FunctionRef<void()>;
 
   /**
    * A callback interface to use with runInLoop()
@@ -417,7 +416,7 @@ class EventBase : private boost::noncopyable,
    * Like runInEventBaseThread, but the caller waits for the callback to be
    * executed.
    */
-  bool runInEventBaseThreadAndWait(FuncRef fn);
+  bool runInEventBaseThreadAndWait(Func fn);
 
   /*
    * Like runInEventBaseThreadAndWait, except if the caller is already in the
@@ -430,7 +429,7 @@ class EventBase : private boost::noncopyable,
    * Like runInEventBaseThreadAndWait, except if the caller is already in the
    * event base thread, the functor is simply run inline.
    */
-  bool runImmediatelyOrRunInEventBaseThreadAndWait(FuncRef fn);
+  bool runImmediatelyOrRunInEventBaseThreadAndWait(Func fn);
 
   /**
    * Set the maximum desired latency in us and provide a callback which will be