From 6cf4cd30fc40660978b14c118db081da529b7a88 Mon Sep 17 00:00:00 2001
From: Bi Xue <bixue@fb.com>
Date: Mon, 26 Jun 2017 12:19:40 -0700
Subject: [PATCH 1/1] Fix SharedPromise::isFulfilled doesn't get back correct
 value when it's running in a different thread of SharedPromise::setValue

Summary: The implementation of `SharedPromise::isFulfilled` return `hasValue_` directly without taking a lock. `isFulfilled` can be accessed concurrently, but `hasValue_` is not synchronized. Adding a lock fix the issue.

Reviewed By: yfeldblum

Differential Revision: D5319030

fbshipit-source-id: a94b12ed277aa64254680ae84cb18946226cceea
---
 folly/futures/SharedPromise-inl.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/folly/futures/SharedPromise-inl.h b/folly/futures/SharedPromise-inl.h
index 185062ac..9def3bc6 100644
--- a/folly/futures/SharedPromise-inl.h
+++ b/folly/futures/SharedPromise-inl.h
@@ -131,6 +131,7 @@ void SharedPromise<T>::setTry(Try<T>&& t) {
 
 template <class T>
 bool SharedPromise<T>::isFulfilled() {
+  std::lock_guard<std::mutex> g(mutex_);
   return hasValue_;
 }
 
-- 
2.34.1