Fix copyright lines

[folly.git] / folly / futures / detail / FSM.h

diff --git a/folly/futures/detail/FSM.h b/folly/futures/detail/FSM.h
index 0d4ffbed462c9dfb2865ac31df5354a6a392b019..04c57d118c4daf11fca35ee335cc041f67e8e127 100644 (file)
--- a/folly/futures/detail/FSM.h
+++ b/folly/futures/detail/FSM.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 Facebook, Inc.
+ * Copyright 2014-present Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,16 +18,19 @@
 
 #include <atomic>
 #include <mutex>
-#include <folly/SmallLocks.h>
 
-namespace folly { namespace detail {
+#include <folly/MicroSpinLock.h>
+
+namespace folly {
+namespace futures {
+namespace detail {
 
 /// Finite State Machine helper base class.
 /// Inherit from this.
 /// For best results, use an "enum class" for Enum.
 template <class Enum>
 class FSM {
-private:
+ private:
   // I am not templatizing this because folly::MicroSpinLock needs to be
   // zero-initialized (or call init) which isn't generic enough for something
   // that behaves like std::mutex. :(
@@ -40,11 +43,11 @@ private:
   // An optimization would be to use a static conditional on the Enum type.
   std::atomic<Enum> state_;
 
-public:
+ public:
   explicit FSM(Enum startState) : state_(startState) {}
 
-  Enum getState() const {
-    return state_.load(std::memory_order_relaxed);
+  Enum getState() const noexcept {
+    return state_.load(std::memory_order_acquire);
   }
 
   /// Atomically do a state transition with accompanying action.
@@ -52,10 +55,16 @@ public:
   /// @returns true on success, false and action unexecuted otherwise
   template <class F>
   bool updateState(Enum A, Enum B, F const& action) {
-    std::lock_guard<Mutex> lock(mutex_);
-    if (state_ != A) return false;
+    if (!mutex_.try_lock()) {
+      mutex_.lock();
+    }
+    if (state_.load(std::memory_order_acquire) != A) {
+      mutex_.unlock();
+      return false;
+    }
     action();
-    state_ = B;
+    state_.store(B, std::memory_order_release);
+    mutex_.unlock();
     return true;
   }
 
@@ -119,5 +128,6 @@ public:
 #define FSM_BREAK done = true; break;
 #define FSM_END }}}
 
-
-}} // folly::detail
+} // namespace detail
+} // namespace futures
+} // namespace folly