From f13c24bd6699a77e7d8f7c8bfacc7bd8f7284ee6 Mon Sep 17 00:00:00 2001
From: Nat Goodspeed <nat@lindenlab.com>
Date: Wed, 6 Apr 2016 10:57:20 -0400
Subject: [PATCH 1/2] Launch client fibers on alternate thread.

---
 examples/asio/autoecho.cpp | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/examples/asio/autoecho.cpp b/examples/asio/autoecho.cpp
index 0d3cb3c6..2f46d97c 100644
--- a/examples/asio/autoecho.cpp
+++ b/examples/asio/autoecho.cpp
@@ -236,19 +236,19 @@ int main( int argc, char* argv[]) {
         // server
         boost::fibers::fiber f(
             server, boost::ref( io_svc) );
-        // client
-        const unsigned iterations = 20;
-        const unsigned clients = 3;
-        boost::fibers::barrier barrier(clients);
-        for (unsigned c = 0; c < clients; ++c) {
-            boost::fibers::fiber(
-                client, boost::ref( io_svc), boost::ref( barrier),
-                iterations ).detach();
-        }
         // run io_service in two threads
         std::thread t([&io_svc](){
                     boost::fibers::use_scheduling_algorithm< boost::fibers::asio::round_robin >( io_svc);
                     print( "Thread ", thread_names.lookup(), ": started");
+                    // client
+                    const unsigned iterations = 20;
+                    const unsigned clients = 3;
+                    boost::fibers::barrier barrier(clients);
+                    for (unsigned c = 0; c < clients; ++c) {
+                        boost::fibers::fiber(
+                            client, boost::ref( io_svc), boost::ref( barrier),
+                            iterations ).detach();
+                    }
                     io_svc.run();
                     print( "Thread ", thread_names.lookup(), ": stopping");
                 });

From 9b3559dd4946d82249bf3b857e1c78895161bb37 Mon Sep 17 00:00:00 2001
From: Nat Goodspeed <nat@lindenlab.com>
Date: Wed, 6 Apr 2016 12:03:30 -0400
Subject: [PATCH 2/2] Remove 'yield_hop' and the whole allow_hop_ mechanism.

Given the necessity for fibers::asio::round_robin to share its ready queue
among all threads calling io_service::run() on the same io_service instance,
the capability to allow hop (or not) in the fibers::asio::yield mechanism is
redundant.
---
 doc/callbacks.qbk              |  4 ++--
 examples/asio/detail/yield.hpp | 14 +++-----------
 examples/asio/yield.hpp        | 17 +++++------------
 3 files changed, 10 insertions(+), 25 deletions(-)

diff --git a/doc/callbacks.qbk b/doc/callbacks.qbk
index 05e6760b..3788044e 100644
--- a/doc/callbacks.qbk
+++ b/doc/callbacks.qbk
@@ -184,7 +184,7 @@ and `future` for two reasons:
 `boost::fibers::asio::yield` is a completion token of this kind. `yield` is an
 instance of `yield_t`:
 
-[fibers_asio_yield]
+[fibers_asio_yield_t]
 
 `yield_t` is in fact only a placeholder, a way to trigger Boost.Asio
 customization. It can bind a
@@ -195,7 +195,7 @@ for use by the actual handler.
 In fact there are two canonical instances of `yield_t` [mdash] `yield` and
 `yield_hop`:
 
-[fibers_asio_yield_and_hop]
+[fibers_asio_yield]
 
 We'll get to the differences between these shortly.
 
diff --git a/examples/asio/detail/yield.hpp b/examples/asio/detail/yield.hpp
index 29077c08..973673cb 100644
--- a/examples/asio/detail/yield.hpp
+++ b/examples/asio/detail/yield.hpp
@@ -87,18 +87,10 @@ public:
         * yt_.ec_ = ec;
         // If ctx_ is still active, e.g. because the async operation
         // immediately called its callback (this method!) before the asio
-        // async function called async_result_base::get(), we must neither
-        // migrate it nor set it ready.
+        // async function called async_result_base::get(), we must not set it
+        // ready.
         if ( fibers::context::active() != ctx_ ) {
-            // Are we permitted to wake up the suspended fiber on this thread, the
-            // thread that called the completion handler?
-            if ( ( ! ctx_->is_context( fibers::type::pinned_context) ) && yt_.allow_hop_) {
-                // We must not migrate a pinned_context to another thread. If this
-                // isn't a pinned_context, and the application passed yield_hop
-                // rather than yield, migrate this fiber to the running thread.
-                fibers::context::active()->migrate( ctx_);
-            }
-            // either way, wake the fiber
+            // wake the fiber
             fibers::context::active()->set_ready( ctx_);
         }
     }
diff --git a/examples/asio/yield.hpp b/examples/asio/yield.hpp
index 09e3aa63..b40f0295 100644
--- a/examples/asio/yield.hpp
+++ b/examples/asio/yield.hpp
@@ -18,12 +18,10 @@ namespace boost {
 namespace fibers {
 namespace asio {
 
-//[fibers_asio_yield
+//[fibers_asio_yield_t
 class yield_t {
 public:
-    yield_t( bool hop) :
-        allow_hop_( hop) {
-    }
+    yield_t() = default;
 
     /**
      * @code
@@ -46,17 +44,12 @@ public:
 //private:
     // ptr to bound error_code instance if any
     boost::system::error_code   *   ec_{ nullptr };
-    // allow calling fiber to "hop" to another thread if it could resume more
-    // quickly that way
-    bool                            allow_hop_;
 };
 //]
 
-//[fibers_asio_yield_and_hop
-// canonical instance with allow_hop_ == false
-thread_local yield_t yield{ false };
-// canonical instance with allow_hop_ == true
-thread_local yield_t yield_hop{ true };
+//[fibers_asio_yield
+// canonical instance
+thread_local yield_t yield{};
 //]
 
 }}}