Reset blocked operations after fork

lib/async/scheduler.rb

@@ -685,6 +685,7 @@ def process_fork
 			@children = nil
 			@selector = nil
 			@timers = nil
+			@blocked = 0
 
 			# Close the scheduler:
 			Fiber.set_scheduler(nil)

releases.md

@@ -1,5 +1,9 @@
 # Releases
 
+## Unreleased
+
+  - Fixed scheduler cleanup after forking while other fibers are blocked.
+
 ## v2.43.0
 
   - Propagate cancellation causes through task trees so child tasks observe the original cancellation cause.

test/process/fork.rb

@@ -44,5 +44,28 @@
 				Process.waitpid(pid) if pid
 			end
 		end
+
+		it "can fork while another fiber is blocked" do
+			r, w = IO.pipe
+			queue = Thread::Queue.new
+
+			Async do |task|
+				blocked_task = task.async do
+					queue.pop
+				end
+
+				pid = Process.fork do
+					# Child process:
+					w.write("hello")
+				end
+
+				# Parent process:
+				w.close
+				expect(r.read).to be == "hello"
+			ensure
+				blocked_task&.stop
+				Process.waitpid(pid) if pid
+			end
+		end
 	end
 end