X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=folly%2Ffutures%2Fdetail%2FCore.h;h=7516885264c2c68deff2e6dd17fb74f6cb9315c1;hb=dda657cc57624ebea01a96a54fed2c0c86b398fe;hp=4bdc5ef4755e05f20ef761420d1510fdb2e966ba;hpb=714633903be94edc55af06571738d3ad0343b925;p=folly.git

diff --git a/folly/futures/detail/Core.h b/folly/futures/detail/Core.h
index 4bdc5ef4..75168852 100644
--- a/folly/futures/detail/Core.h
+++ b/folly/futures/detail/Core.h
@@ -22,7 +22,7 @@
 #include <vector>
 
 #include <folly/Optional.h>
-#include <folly/SmallLocks.h>
+#include <folly/MicroSpinLock.h>
 
 #include <folly/futures/Try.h>
 #include <folly/futures/Promise.h>
@@ -68,19 +68,27 @@ enum class State : uint8_t {
 /// migrate between threads, though this usually happens within the API code.
 /// For example, an async operation will probably make a Promise, grab its
 /// Future, then move the Promise into another thread that will eventually
-/// fulfil it. With executors and via, this gets slightly more complicated at
+/// fulfill it. With executors and via, this gets slightly more complicated at
 /// first blush, but it's the same principle. In general, as long as the user
 /// doesn't access a Future or Promise object from more than one thread at a
 /// time there won't be any problems.
 template<typename T>
 class Core {
+  static_assert(!std::is_void<T>::value,
+                "void futures are not supported. Use Unit instead.");
  public:
   /// This must be heap-constructed. There's probably a way to enforce that in
   /// code but since this is just internal detail code and I don't know how
   /// off-hand, I'm punting.
-  Core() {}
+  Core() : result_(), fsm_(State::Start), attached_(2) {}
+
+  explicit Core(Try<T>&& t)
+    : result_(std::move(t)),
+      fsm_(State::OnlyResult),
+      attached_(1) {}
+
   ~Core() {
-    assert(attached_ == 0);
+    DCHECK(attached_ == 0);
   }
 
   // not copyable
@@ -122,7 +130,8 @@ class Core {
   template <typename F>
   class LambdaBufHelper {
    public:
-    explicit LambdaBufHelper(F&& func) : func_(std::forward<F>(func)) {}
+    template <typename FF>
+    explicit LambdaBufHelper(FF&& func) : func_(std::forward<FF>(func)) {}
     void operator()(Try<T>&& t) {
       SCOPE_EXIT { this->~LambdaBufHelper(); };
       func_(std::move(t));
@@ -140,7 +149,7 @@ class Core {
 
       // Move the lambda into the Core if it fits
       if (sizeof(LambdaBufHelper<F>) <= lambdaBufSize) {
-        auto funcLoc = static_cast<LambdaBufHelper<F>*>((void*)lambdaBuf_);
+        auto funcLoc = reinterpret_cast<LambdaBufHelper<F>*>(&lambdaBuf_);
         new (funcLoc) LambdaBufHelper<F>(std::forward<F>(func));
         callback_ = std::ref(*funcLoc);
       } else {
@@ -198,7 +207,7 @@ class Core {
 
   /// Called by a destructing Future (in the Future thread, by definition)
   void detachFuture() {
-    activateNoDeprecatedWarning();
+    activate();
     detachOne();
   }
 
@@ -206,28 +215,39 @@ class Core {
   void detachPromise() {
     // detachPromise() and setResult() should never be called in parallel
     // so we don't need to protect this.
-    if (!result_) {
-      setResult(Try<T>(exception_wrapper(BrokenPromise())));
+    if (UNLIKELY(!result_)) {
+      setResult(Try<T>(exception_wrapper(BrokenPromise(typeid(T).name()))));
     }
     detachOne();
   }
 
   /// May call from any thread
-  void deactivate() DEPRECATED {
-    active_ = false;
+  void deactivate() {
+    active_.store(false, std::memory_order_release);
   }
 
   /// May call from any thread
-  void activate() DEPRECATED {
-    activateNoDeprecatedWarning();
+  void activate() {
+    active_.store(true, std::memory_order_release);
+    maybeCallback();
   }
 
   /// May call from any thread
-  bool isActive() { return active_; }
+  bool isActive() { return active_.load(std::memory_order_acquire); }
 
   /// Call only from Future thread
-  void setExecutor(Executor* x) {
+  void setExecutor(Executor* x, int8_t priority = Executor::MID_PRI) {
+    if (!executorLock_.try_lock()) {
+      executorLock_.lock();
+    }
+    executor_ = x;
+    priority_ = priority;
+    executorLock_.unlock();
+  }
+
+  void setExecutorNoLock(Executor* x, int8_t priority = Executor::MID_PRI) {
     executor_ = x;
+    priority_ = priority;
   }
 
   Executor* getExecutor() {
@@ -236,39 +256,57 @@ class Core {
 
   /// Call only from Future thread
   void raise(exception_wrapper e) {
-    std::lock_guard<decltype(interruptLock_)> guard(interruptLock_);
+    if (!interruptLock_.try_lock()) {
+      interruptLock_.lock();
+    }
     if (!interrupt_ && !hasResult()) {
       interrupt_ = folly::make_unique<exception_wrapper>(std::move(e));
       if (interruptHandler_) {
         interruptHandler_(*interrupt_);
       }
     }
+    interruptLock_.unlock();
+  }
+
+  std::function<void(exception_wrapper const&)> getInterruptHandler() {
+    if (!interruptHandlerSet_.load(std::memory_order_acquire)) {
+      return nullptr;
+    }
+    if (!interruptLock_.try_lock()) {
+      interruptLock_.lock();
+    }
+    auto handler = interruptHandler_;
+    interruptLock_.unlock();
+    return handler;
   }
 
   /// Call only from Promise thread
   void setInterruptHandler(std::function<void(exception_wrapper const&)> fn) {
-    std::lock_guard<decltype(interruptLock_)> guard(interruptLock_);
+    if (!interruptLock_.try_lock()) {
+      interruptLock_.lock();
+    }
     if (!hasResult()) {
       if (interrupt_) {
         fn(*interrupt_);
       } else {
-        interruptHandler_ = std::move(fn);
+        setInterruptHandlerNoLock(std::move(fn));
       }
     }
+    interruptLock_.unlock();
   }
 
- protected:
-  void activateNoDeprecatedWarning() {
-    active_ = true;
-    maybeCallback();
+  void setInterruptHandlerNoLock(
+      std::function<void(exception_wrapper const&)> fn) {
+    interruptHandlerSet_.store(true, std::memory_order_relaxed);
+    interruptHandler_ = std::move(fn);
   }
 
+ protected:
   void maybeCallback() {
     FSM_START(fsm_)
       case State::Armed:
-        if (active_) {
-          FSM_UPDATE2(fsm_, State::Done, []{},
-                                         std::bind(&Core::doCallback, this));
+        if (active_.load(std::memory_order_acquire)) {
+          FSM_UPDATE2(fsm_, State::Done, []{}, [this]{ this->doCallback(); });
         }
         FSM_BREAK
 
@@ -278,19 +316,46 @@ class Core {
   }
 
   void doCallback() {
-    // TODO(5306911) we should probably try/catch around the callback
-
-    RequestContext::setContext(context_);
-
-    // TODO(6115514) semantic race on reading executor_ and setExecutor()
     Executor* x = executor_;
+    int8_t priority;
     if (x) {
-      ++attached_; // keep Core alive until executor did its thing
-      x->add([this]() mutable {
-        SCOPE_EXIT { detachOne(); };
+      if (!executorLock_.try_lock()) {
+        executorLock_.lock();
+      }
+      x = executor_;
+      priority = priority_;
+      executorLock_.unlock();
+    }
+
+    if (x) {
+      // keep Core alive until executor did its thing
+      ++attached_;
+      try {
+        if (LIKELY(x->getNumPriorities() == 1)) {
+          x->add([this]() mutable {
+            SCOPE_EXIT { detachOne(); };
+            RequestContext::setContext(context_);
+            SCOPE_EXIT { callback_ = {}; };
+            callback_(std::move(*result_));
+          });
+        } else {
+          x->addWithPriority([this]() mutable {
+            SCOPE_EXIT { detachOne(); };
+            RequestContext::setContext(context_);
+            SCOPE_EXIT { callback_ = {}; };
+            callback_(std::move(*result_));
+          }, priority);
+        }
+      } catch (...) {
+        --attached_; // Account for extra ++attached_ before try
+        RequestContext::setContext(context_);
+        result_ = Try<T>(exception_wrapper(std::current_exception()));
+        SCOPE_EXIT { callback_ = {}; };
         callback_(std::move(*result_));
-      });
+      }
     } else {
+      RequestContext::setContext(context_);
+      SCOPE_EXIT { callback_ = {}; };
       callback_(std::move(*result_));
     }
   }
@@ -304,75 +369,99 @@ class Core {
     }
   }
 
-  FSM<State> fsm_ {State::Start};
-  std::atomic<unsigned char> attached_ {2};
+  // lambdaBuf occupies exactly one cache line
+  static constexpr size_t lambdaBufSize = 8 * sizeof(void*);
+  typename std::aligned_storage<lambdaBufSize>::type lambdaBuf_;
+  // place result_ next to increase the likelihood that the value will be
+  // contained entirely in one cache line
+  folly::Optional<Try<T>> result_;
+  std::function<void(Try<T>&&)> callback_ {nullptr};
+  FSM<State> fsm_;
+  std::atomic<unsigned char> attached_;
   std::atomic<bool> active_ {true};
+  std::atomic<bool> interruptHandlerSet_ {false};
   folly::MicroSpinLock interruptLock_ {0};
-  folly::Optional<Try<T>> result_ {};
-  std::function<void(Try<T>&&)> callback_ {nullptr};
-  static constexpr size_t lambdaBufSize = 8 * sizeof(void*);
-  char lambdaBuf_[lambdaBufSize];
+  folly::MicroSpinLock executorLock_ {0};
+  int8_t priority_ {-1};
+  Executor* executor_ {nullptr};
   std::shared_ptr<RequestContext> context_ {nullptr};
-  std::atomic<Executor*> executor_ {nullptr};
   std::unique_ptr<exception_wrapper> interrupt_ {};
   std::function<void(exception_wrapper const&)> interruptHandler_ {nullptr};
 };
 
 template <typename... Ts>
-struct VariadicContext {
-  VariadicContext() : total(0), count(0) {}
-  Promise<std::tuple<Try<Ts>... > > p;
-  std::tuple<Try<Ts>... > results;
-  size_t total;
-  std::atomic<size_t> count;
+struct CollectAllVariadicContext {
+  CollectAllVariadicContext() {}
+  template <typename T, size_t I>
+  inline void setPartialResult(Try<T>& t) {
+    std::get<I>(results) = std::move(t);
+  }
+  ~CollectAllVariadicContext() {
+    p.setValue(std::move(results));
+  }
+  Promise<std::tuple<Try<Ts>...>> p;
+  std::tuple<Try<Ts>...> results;
   typedef Future<std::tuple<Try<Ts>...>> type;
 };
 
-template <typename... Ts, typename THead, typename... Fs>
-typename std::enable_if<sizeof...(Fs) == 0, void>::type
-whenAllVariadicHelper(VariadicContext<Ts...> *ctx, THead&& head, Fs&&... tail) {
-  head.setCallback_([ctx](Try<typename THead::value_type>&& t) {
-    std::get<sizeof...(Ts) - sizeof...(Fs) - 1>(ctx->results) = std::move(t);
-    if (++ctx->count == ctx->total) {
-      ctx->p.setValue(std::move(ctx->results));
-      delete ctx;
+template <typename... Ts>
+struct CollectVariadicContext {
+  CollectVariadicContext() {}
+  template <typename T, size_t I>
+  inline void setPartialResult(Try<T>& t) {
+    if (t.hasException()) {
+       if (!threw.exchange(true)) {
+         p.setException(std::move(t.exception()));
+       }
+     } else if (!threw) {
+       std::get<I>(results) = std::move(t);
+     }
+  }
+  ~CollectVariadicContext() {
+    if (!threw.exchange(true)) {
+      p.setValue(unwrap(std::move(results)));
     }
-  });
+  }
+  Promise<std::tuple<Ts...>> p;
+  std::tuple<folly::Try<Ts>...> results;
+  std::atomic<bool> threw {false};
+  typedef Future<std::tuple<Ts...>> type;
+
+ private:
+  template <typename... Ts2>
+  static std::tuple<Ts...> unwrap(std::tuple<folly::Try<Ts>...>&& o,
+                                  Ts2&&... ts2) {
+    static_assert(sizeof...(ts2) <
+                  std::tuple_size<std::tuple<folly::Try<Ts>...>>::value,
+                  "Non-templated unwrap should be used instead");
+    assert(std::get<sizeof...(ts2)>(o).hasValue());
+
+    return unwrap(std::move(o),
+                  std::forward<Ts2>(ts2)...,
+                  std::move(*std::get<sizeof...(ts2)>(o)));
+  }
+
+  static std::tuple<Ts...> unwrap(std::tuple<folly::Try<Ts>...>&& /* o */,
+                                  Ts&&... ts) {
+    return std::tuple<Ts...>(std::forward<Ts>(ts)...);
+  }
+};
+
+template <template <typename...> class T, typename... Ts>
+void collectVariadicHelper(const std::shared_ptr<T<Ts...>>& /* ctx */) {
+  // base case
 }
 
-template <typename... Ts, typename THead, typename... Fs>
-typename std::enable_if<sizeof...(Fs) != 0, void>::type
-whenAllVariadicHelper(VariadicContext<Ts...> *ctx, THead&& head, Fs&&... tail) {
+template <template <typename ...> class T, typename... Ts,
+          typename THead, typename... TTail>
+void collectVariadicHelper(const std::shared_ptr<T<Ts...>>& ctx,
+                           THead&& head, TTail&&... tail) {
   head.setCallback_([ctx](Try<typename THead::value_type>&& t) {
-    std::get<sizeof...(Ts) - sizeof...(Fs) - 1>(ctx->results) = std::move(t);
-    if (++ctx->count == ctx->total) {
-      ctx->p.setValue(std::move(ctx->results));
-      delete ctx;
-    }
+    ctx->template setPartialResult<typename THead::value_type,
+                                   sizeof...(Ts) - sizeof...(TTail) - 1>(t);
   });
   // template tail-recursion
-  whenAllVariadicHelper(ctx, std::forward<Fs>(tail)...);
+  collectVariadicHelper(ctx, std::forward<TTail>(tail)...);
 }
 
-template <typename T>
-struct WhenAllContext {
-  WhenAllContext() : count(0) {}
-  Promise<std::vector<Try<T> > > p;
-  std::vector<Try<T> > results;
-  std::atomic<size_t> count;
-};
-
-template <typename T>
-struct WhenAnyContext {
-  explicit WhenAnyContext(size_t n) : done(false), ref_count(n) {};
-  Promise<std::pair<size_t, Try<T>>> p;
-  std::atomic<bool> done;
-  std::atomic<size_t> ref_count;
-  void decref() {
-    if (--ref_count == 0) {
-      delete this;
-    }
-  }
-};
-
 }} // folly::detail