Hi,
I am trying to embed libuv into another event loop. After the watcher queue is modified uv_backend_timeout() should return 0 so that uv_run can be called again immediately to add the fds to the poll set. Otherwise, the embed thread can't be notified of events on these fds. Electron has solved this with an ugly hack:
electron/node@693b350#diff-2f99e28360b27d4873b9a7678227d11c

I think if uv_backend_timeout() would return 0 in this case, it would be feasible to embed libuv without relying on custom patches.