More elaborate exception handling. Fixes puma#2699.

lib/puma/server.rb

@@ -356,7 +356,10 @@ def handle_servers
                 pool << client
               end
             end
-          rescue Object => e
+          rescue IOError, Errno::EBADF
+            # In the case that any of the sockets are unexpectedly close.
+            raise
+          rescue StandardError => e
             @events.unknown_error e, nil, "Listen loop"
           end
         end

test/config/broken_io.rb

@@ -0,0 +1,9 @@
+require 'objspace'
+
+app do |env|
+  ios = ObjectSpace.each_object(IO).to_a.select {|io| io.is_a?(TCPServer)}
+
+  ios.each(&:close)
+
+  [200, [], [ios.inspect]]
+end

test/test_broken_io.rb

@@ -0,0 +1,28 @@
+require_relative "helper"
+require_relative "helpers/integration"
+
+class TestBrokenIO < TestIntegration
+  def wait_for(pattern)
+    while line = @server.gets
+      if line =~ pattern
+        return true
+      end
+    end
+  end
+
+  def test_broken_io
+    @tcp_port = UniquePort.call
+
+    cli_server "-b tcp://#{HOST}:#{@tcp_port} -C test/config/broken_io.rb test/rackup/hello.ru"
+
+    # Invoke a request which must be rejected
+    stdout_str, status = Open3.capture2("curl #{HOST}:#{@tcp_port}")
+
+    Process.kill :INT , @pid
+
+    wait_for(/Goodbye/)
+
+    @server.close
+    @server = nil
+  end
+end