Fix data race in GetInstance

isergeyam · isergeyam · commit 87488f13387a · 2020-09-08T19:31:58.000+03:00
diff --git a/src/Singleton/Conceptual/ThreadSafe/main.cc b/src/Singleton/Conceptual/ThreadSafe/main.cc
@@ -112,13 +112,10 @@ std::mutex Singleton::mutex_;
      */
 Singleton *Singleton::GetInstance(const std::string& value)
 {
+    std::lock_guard<std::mutex> lock(mutex_);
     if (pinstance_ == nullptr)
     {
-        std::lock_guard<std::mutex> lock(mutex_);
-        if (pinstance_ == nullptr)
-        {
-            pinstance_ = new Singleton(value);
-        }
+        pinstance_ = new Singleton(value);
     }
     return pinstance_;
 }

Original file line number	Diff line number	Diff line change
`@@ -112,13 +112,10 @@ std::mutex Singleton::mutex_;`
`112`	`112`	`*/`
`113`	`113`	`Singleton *Singleton::GetInstance(const std::string& value)`
`114`	`114`	`{`
	`115`	`+ std::lock_guard<std::mutex> lock(mutex_);`
`115`	`116`	`if (pinstance_ == nullptr)`
`116`	`117`	`{`
`117`		`- std::lock_guard<std::mutex> lock(mutex_);`
`118`		`- if (pinstance_ == nullptr)`
`119`		`- {`
`120`		`- pinstance_ = new Singleton(value);`
`121`		`- }`
	`118`	`+ pinstance_ = new Singleton(value);`
`122`	`119`	`}`
`123`	`120`	`return pinstance_;`
`124`	`121`	`}`