/// 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
void detachPromise() {
// detachPromise() and setResult() should never be called in parallel
// so we don't need to protect this.
- if (!result_) {
+ if (UNLIKELY(!result_)) {
setResult(Try<T>(exception_wrapper(BrokenPromise())));
}
detachOne();
/// May call from any thread
void deactivate() {
- active_ = false;
+ active_.store(false, std::memory_order_release);
}
/// May call from any thread
void activate() {
- active_ = true;
+ 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, int8_t priority) {
- folly::MSLGuard g(executorLock_);
+ 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() {
- folly::MSLGuard g(executorLock_);
return executor_;
}
/// Call only from Future thread
void raise(exception_wrapper e) {
- folly::MSLGuard 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() {
- folly::MSLGuard guard(interruptLock_);
- return interruptHandler_;
+ 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) {
- folly::MSLGuard 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();
+ }
+
+ 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_) {
+ if (active_.load(std::memory_order_acquire)) {
FSM_UPDATE2(fsm_, State::Done, []{}, [this]{ this->doCallback(); });
}
FSM_BREAK
}
void doCallback() {
- RequestContext::setContext(context_);
-
- // TODO(6115514) semantic race on reading executor_ and setExecutor()
- Executor* x;
+ Executor* x = executor_;
int8_t priority;
- {
- folly::MSLGuard g(executorLock_);
+ if (x) {
+ if (!executorLock_.try_lock()) {
+ executorLock_.lock();
+ }
x = executor_;
priority = priority_;
+ executorLock_.unlock();
}
if (x) {
- ++attached_; // keep Core alive until executor did its thing
+ // 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_);
callback_(std::move(*result_));
});
} else {
x->addWithPriority([this]() mutable {
SCOPE_EXIT { detachOne(); };
+ RequestContext::setContext(context_);
callback_(std::move(*result_));
}, priority);
}
} catch (...) {
+ --attached_; // Account for extra ++attached_ before try
+ RequestContext::setContext(context_);
result_ = Try<T>(exception_wrapper(std::current_exception()));
callback_(std::move(*result_));
}
} else {
+ RequestContext::setContext(context_);
callback_(std::move(*result_));
}
}
}
}
- 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*);
+ char lambdaBuf_[lambdaBufSize];
+ // 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::MicroSpinLock executorLock_ {0};
int8_t priority_ {-1};
Executor* executor_ {nullptr};
- folly::Optional<Try<T>> result_ {};
- std::function<void(Try<T>&&)> callback_ {nullptr};
- static constexpr size_t lambdaBufSize = 8 * sizeof(void*);
- char lambdaBuf_[lambdaBufSize];
std::shared_ptr<RequestContext> context_ {nullptr};
std::unique_ptr<exception_wrapper> interrupt_ {};
std::function<void(exception_wrapper const&)> interruptHandler_ {nullptr};
};
template <typename... Ts>
-struct VariadicContext {
- VariadicContext() {}
- ~VariadicContext() {
+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;
+ 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
-collectAllVariadicHelper(std::shared_ptr<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);
- });
+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.value());
+ }
+ }
+ ~CollectVariadicContext() {
+ if (!threw.exchange(true)) {
+ p.setValue(std::move(results));
+ }
+ }
+ Promise<std::tuple<Ts...>> p;
+ std::tuple<Ts...> results;
+ std::atomic<bool> threw {false};
+ typedef Future<std::tuple<Ts...>> type;
+};
+
+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
-collectAllVariadicHelper(std::shared_ptr<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);
+ ctx->template setPartialResult<typename THead::value_type,
+ sizeof...(Ts) - sizeof...(TTail) - 1>(t);
});
// template tail-recursion
- collectAllVariadicHelper(ctx, std::forward<Fs>(tail)...);
+ collectVariadicHelper(ctx, std::forward<TTail>(tail)...);
}
}} // folly::detail
projects / folly.git / blobdiff