Make blockingWait fibers compatible

Summary: This will make it easy to use coro primitives from fibers code.

Reviewed By: lewissbaker

Differential Revision: D9932012

fbshipit-source-id: cd0524ccfee7bee9405f29ddaa3533084b18b38b

folly/experimental/coro/BlockingWait.h

@@ -17,6 +17,7 @@
 
 #include <folly/Try.h>
 #include <folly/experimental/coro/Traits.h>
+#include <folly/fibers/Baton.h>
 #include <folly/synchronization/Baton.h>
 
 #include <cassert>
@@ -64,7 +65,7 @@ class BlockingWaitPromiseBase {
   }
 
  private:
-  folly::Baton<> baton_;
+  folly::fibers::Baton baton_;
 };
 
 template <typename T>

folly/experimental/coro/test/BlockingWaitTest.cpp

@@ -22,6 +22,8 @@
 #include <folly/experimental/coro/Baton.h>
 #include <folly/experimental/coro/BlockingWait.h>
 #include <folly/experimental/coro/Utils.h>
+#include <folly/fibers/FiberManager.h>
+#include <folly/fibers/FiberManagerMap.h>
 #include <folly/portability/GTest.h>
 
 #include <memory>
@@ -224,4 +226,22 @@ TEST(BlockingWait, moveCountingAwaitableReady) {
   EXPECT_GE(4, result.count_);
 }
 
+TEST(BlockingWait, WaitInFiber) {
+  SimplePromise<int> promise;
+  folly::EventBase evb;
+  auto& fm = folly::fibers::getFiberManager(evb);
+
+  auto future =
+      fm.addTaskFuture([&] { return folly::coro::blockingWait(promise); });
+
+  evb.loopOnce();
+  EXPECT_FALSE(future.isReady());
+
+  promise.emplace(42);
+
+  evb.loopOnce();
+  EXPECT_TRUE(future.isReady());
+  EXPECT_EQ(42, std::move(future).get());
+}
+
 #endif

folly/fibers/Baton-inl.h

@@ -34,7 +34,7 @@ class Baton::FiberWaiter : public Baton::Waiter {
   Fiber* fiber_{nullptr};
 };
 
-inline Baton::Baton() : Baton(NO_WAITER) {
+inline Baton::Baton() noexcept : Baton(NO_WAITER) {
   assert(Baton(NO_WAITER).futex_.futex == static_cast<uint32_t>(NO_WAITER));
   assert(Baton(POSTED).futex_.futex == static_cast<uint32_t>(POSTED));
   assert(Baton(TIMEOUT).futex_.futex == static_cast<uint32_t>(TIMEOUT));

folly/fibers/Baton.h

@@ -48,9 +48,9 @@ class Baton {
     virtual ~Waiter() {}
   };
 
-  Baton();
+  Baton() noexcept;
 
-  ~Baton() {}
+  ~Baton() noexcept = default;
 
   bool ready() const {
     auto state = waiter_.load();