Multiple failures in em_http_request adapter when synchrony is enabled.

[phdavis1027]

I wrote the following specs in spec/acceptance/em_http_request/em_http_request_spec.rb, which all failed due to timeout:

      if defined?(EventMachine::Synchrony)
      # ...
                it "should call `headers` before processing stream" do
            stub_request(:get, "www.example.com").to_return(body: "abc", headers: { 'needle': 'found' })
            headers_called = nil
            EM.run do
              EM.add_timer(1) { raise "Timeout: callbacks never fired" }
              fiber = Fiber.new do
                http = EM::HttpRequest.new("http://www.example.com").get
                http.stream { |*|
                  expect(headers_called).to eq('found')
                  EM.stop
                }
                http.headers { |h|
                  expect(headers_called).to be_nil
                  headers_called = h['needle']
                }
              end
              fiber.resume
            end
          end

          it "should call `stream` callback at all" do
            stub_request(:get, "www.example.com").to_return(body: "abc")
            stream_called = false
            EM.run do
              EM.add_timer(1) { EM.stop }
              fiber = Fiber.new do
                http = EM::HttpRequest.new("http://www.example.com").get
                http.stream { |*| stream_called = true }
              end
              fiber.resume
            end
            expect(stream_called).to eq(true)
          end

          it "should call `headers` callback at all" do
            stub_request(:get, "www.example.com").to_return(body: "abc", headers: { "X-DEBUG": "Hello, World!" })
            EM.run do
              EM.add_timer(1) { EM.stop }
              fiber = Fiber.new do
                http = EM::HttpRequest.new("http://www.example.com").get
                http.headers { |h| expect(h['X-DEBUG'].to eq('Hello, World!')) }
              end
              fiber.resume
            end
            expect(stream_called).to eq(true)
          end

I ran them like this:

bundle exec rspec -r em-synchrony spec/acceptance/em_http_request/em_http_request_spec.rb -e "should call"

against tip of master.

Worth noting: when I just cloned the repo fresh and ran bundle exec rspec I got dozens of failures and multiple sluggish tests which together ran so slowly that I could not let them all finish. Don't know why.

I'm on Fedora 42, MRI 3.4.7