Ensure portability/Windows.h is included before OpenSSL headers

[folly.git] / folly / Singleton.h

diff --git a/folly/Singleton.h b/folly/Singleton.h
index c4640aff40d5b4e41b54f37302ce1e5284e7bed5..c8cbea9f56fd09f38b0edf525824ef9b36717e80 100644 (file)
--- a/folly/Singleton.h
+++ b/folly/Singleton.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.
@@ -71,6 +71,15 @@
 // Where create and destroy are functions, Singleton<T>::CreateFunc
 // Singleton<T>::TeardownFunc.
 //
+// For example, if you need to pass arguments to your class's constructor:
+//   class X {
+//    public:
+//      X(int a1, std::string a2);
+//    // ...
+//   }
+// Make your singleton like this:
+//   folly::Singleton<X> singleton_x([]() { return new X(42, "foo"); });
+//
 // The above examples detail a situation where an expensive singleton is loaded
 // on-demand (thus only if needed).  However if there is an expensive singleton
 // that will likely be needed, and initialization takes a potentially long time,
@@ -103,14 +112,15 @@
 
 #pragma once
 #include <folly/Baton.h>
+#include <folly/Demangle.h>
 #include <folly/Exception.h>
+#include <folly/Executor.h>
 #include <folly/Hash.h>
 #include <folly/Memory.h>
 #include <folly/RWSpinLock.h>
-#include <folly/Demangle.h>
-#include <folly/Executor.h>
-#include <folly/experimental/ReadMostlySharedPtr.h>
+#include <folly/Synchronized.h>
 #include <folly/detail/StaticSingletonManager.h>
+#include <folly/experimental/ReadMostlySharedPtr.h>
 
 #include <algorithm>
 #include <atomic>
@@ -338,7 +348,7 @@ class SingletonVault {
     }
   };
 
-  explicit SingletonVault(Type type = Type::Relaxed) : type_(type) {}
+  explicit SingletonVault(Type type = Type::Strict) : type_(type) {}
 
   // Destructor is only called by unit tests to check destroyInstances.
   ~SingletonVault();
@@ -400,9 +410,7 @@ class SingletonVault {
 
   // For testing; how many registered and living singletons we have.
   size_t registeredSingletonCount() const {
-    RWSpinLock::ReadHolder rh(&mutex_);
-
-    return singletons_.size();
+    return singletons_.rlock()->size();
   }
 
   /**
@@ -412,10 +420,10 @@ class SingletonVault {
   bool eagerInitComplete() const;
 
   size_t livingSingletonCount() const {
-    RWSpinLock::ReadHolder rh(&mutex_);
+    auto singletons = singletons_.rlock();
 
     size_t ret = 0;
-    for (const auto& p : singletons_) {
+    for (const auto& p : *singletons) {
       if (p.second->hasLiveInstance()) {
         ++ret;
       }
@@ -461,13 +469,20 @@ class SingletonVault {
     Quiescing,
   };
 
+  struct State {
+    SingletonVaultState state{SingletonVaultState::Running};
+    bool registrationComplete{false};
+  };
+
   // Each singleton in the vault can be in two states: dead
   // (registered but never created), living (CreateFunc returned an instance).
 
-  void stateCheck(SingletonVaultState expected,
-                  const char* msg="Unexpected singleton state change") {
-    if (expected != state_) {
-        throw std::logic_error(msg);
+  static void stateCheck(
+      SingletonVaultState expected,
+      const State& state,
+      const char* msg = "Unexpected singleton state change") {
+    if (expected != state.state) {
+      throw std::logic_error(msg);
     }
   }
 
@@ -487,15 +502,17 @@ class SingletonVault {
   typedef std::unordered_map<detail::TypeDescriptor,
                              detail::SingletonHolderBase*,
                              detail::TypeDescriptorHasher> SingletonMap;
+  folly::Synchronized<SingletonMap> singletons_;
+  folly::Synchronized<std::unordered_set<detail::SingletonHolderBase*>>
+      eagerInitSingletons_;
+  folly::Synchronized<std::vector<detail::TypeDescriptor>> creationOrder_;
+
+  // Using SharedMutexReadPriority is important here, because we want to make
+  // sure we don't block nested singleton creation happening concurrently with
+  // destroyInstances().
+  folly::Synchronized<State, folly::SharedMutexReadPriority> state_;
 
-  mutable folly::RWSpinLock mutex_;
-  SingletonMap singletons_;
-  std::unordered_set<detail::SingletonHolderBase*> eagerInitSingletons_;
-  std::vector<detail::TypeDescriptor> creation_order_;
-  SingletonVaultState state_{SingletonVaultState::Running};
-  bool registrationComplete_{false};
-  folly::RWSpinLock stateMutex_;
-  Type type_{Type::Relaxed};
+  Type type_;
 };
 
 // This is the wrapper class that most users actually interact with.