ASP.NET MVC thread context switching overhead

Question

I would like to know if an asynchronous implementation like the one I will show below generates a context switch problem.

public async  Task<JsonResult> Get() 
{
    var data = await GetDataAsync();
    return data;
}

public async Task<string> GetDataAsync() 
{
     return  await getDataWcfAsync();
}

public async Task<string> getDataWcfAsync()
{
    return  await getcfAsync();
}

I see a warning as shown in the screenshot.

What does this warning refer to?