Wake up join list within thread EC context. (#4471)

* Wake up join list within thread EC context.

* Consume items from join list so that they are not re-executed.

If `rb_fiber_scheduler_unblock` raises an exception, it can result in a
segfault if `rb_threadptr_join_list_wakeup` is not within a valid EC. This
change moves `rb_threadptr_join_list_wakeup` into the thread's top level EC
which initially caused an infinite loop because on exception will retry. We
explicitly remove items from the thread's join list to avoid this situation.

* Verify the required scheduler interface.

* Test several scheduler hooks methods with broken `unblock` implementation.

4 files changed, 66 insertions, 2 deletions

diff --git a/test/fiber/scheduler.rb b/test/fiber/scheduler.rb
index 69299b04e6..c844200935 100644
--- a/test/fiber/scheduler.rb
+++ b/test/fiber/scheduler.rb
@@ -230,3 +230,11 @@ class Scheduler
     end.value
   end
 end
+
+class BrokenUnblockScheduler < Scheduler
+  def unblock(blocker, fiber)
+    super
+
+    raise "Broken unblock!"
+  end
+end
diff --git a/test/fiber/test_scheduler.rb b/test/fiber/test_scheduler.rb
index eeb0d67ec5..f0f5b79f36 100644
--- a/test/fiber/test_scheduler.rb
+++ b/test/fiber/test_scheduler.rb
@@ -66,9 +66,23 @@ class TestFiberScheduler < Test::Unit::TestCase
     RUBY
   end
 
-  def test_optional_close
+  def test_minimal_interface
+    scheduler = Object.new
+
+    def scheduler.block
+    end
+
+    def scheduler.unblock
+    end
+
+    def scheduler.io_wait
+    end
+
+    def scheduler.kernel_sleep
+    end
+
     thread = Thread.new do
-      Fiber.set_scheduler Object.new
+      Fiber.set_scheduler scheduler
     end
 
     thread.join
diff --git a/test/fiber/test_sleep.rb b/test/fiber/test_sleep.rb
index e882766345..844369740f 100644
--- a/test/fiber/test_sleep.rb
+++ b/test/fiber/test_sleep.rb
@@ -43,4 +43,26 @@ class TestFiberSleep < Test::Unit::TestCase
 
     assert_operator seconds, :>=, 2, "actual: %p" % seconds
   end
+
+  def test_broken_sleep
+    thread = Thread.new do
+      Thread.current.report_on_exception = false
+
+      scheduler = Scheduler.new
+
+      def scheduler.kernel_sleep(duration = nil)
+        raise "Broken sleep!"
+      end
+
+      Fiber.set_scheduler scheduler
+
+      Fiber.schedule do
+        sleep 0
+      end
+    end
+
+    assert_raise(RuntimeError) do
+      thread.join
+    end
+  end
 end
diff --git a/test/fiber/test_thread.rb b/test/fiber/test_thread.rb
index 5fc80f0e6c..b7323d7237 100644
--- a/test/fiber/test_thread.rb
+++ b/test/fiber/test_thread.rb
@@ -42,4 +42,24 @@ class TestFiberThread < Test::Unit::TestCase
 
     assert_equal :done, thread.value
   end
+
+  def test_broken_unblock
+    thread = Thread.new do
+      Thread.current.report_on_exception = false
+
+      scheduler = BrokenUnblockScheduler.new
+
+      Fiber.set_scheduler scheduler
+
+      Fiber.schedule do
+        Thread.new{}.join
+      end
+
+      scheduler.run
+    end
+
+    assert_raise(RuntimeError) do
+      thread.join
+    end
+  end
 end