Running multiple instances of Tornado gives ioloop is already running error

This is how my code looks like, (have excluded some details that aren't really relevant)

from multiprocessing.pool import ThreadPool as Pool

class GetUsers(BaseTask):
    def foo(self):
        pool = Pool()
        try:
            pool.map(self.bar, users)
        finally:
            pool.close()
            pool.join()

    def bar(self, users):
        uuid = users[0]
        ioloopInstance = ioloop.IOLoop().instance()
        isInExperiment = self.isInExperiment(uuid, ioloopInstance)
        log.info(str(uuid)+str(isInExperiment))

    def isInExperiment(self, uuid, ioloop):
        isInExpTag_response =ioloop.run_sync(lambda: self.
                                             fetch_isInExperiment_response(uuid))
        if len(isInExpTag_response.body) > 0:
            return True
        return False

    @gen.coroutine
    def fetch_isInExperiment_response(self, uuid):
        response = yield baz
        raise gen.Return(response)

When I run this, I get ioloop is already running error. I feel that this is because several process running are trying to access the same instance of Tornado and so this error is seen. I have tried reading the documentation of tornado and seen other resources online trying to tackle the same error, but could not find anything helpful.

Can anyone please help me out?