What does poll() do with a timeout of 0?

Question

I\'m looking at the poll() man page, and it tells me the behavior of poll() when positive and negative values are passed in for the timeout parameter.

Answer 1

As I see it, waiting for a timeout means "having" a timeout. This way I would expect that poll() actually checks the file descriptors, and then waits if no one is ready to a timeout of 0 milliseconds (no wait at all). But the case is that it will just signal if a fd is available.

I also checked linux source code and to my knowledge, this is the way it works: first calculates the "future" waiting point, then checks the file descriptors, then if none available, waits for the timeout specified time.

Regards,