On 19/07/2021 21:52, Ben Pfaff wrote:
On Fri, Jul 16, 2021 at 02:42:32PM +0100, [email protected] wrote:
From: Anton Ivanov <[email protected]>
If we are not obtaining any useful information out of the poll(),
such as is a fd busy or not, we do not need to do a poll() if
an immediate_wake() has been requested.
This cuts out all the pollfd hash additions, forming the poll
arguments and the actual poll() after a call to
poll_immediate_wake()
Signed-off-by: Anton Ivanov <[email protected]>
Thanks for v3.
I believe that the existing code here properly handles the pathological
case where the current time is less than 0. This is a case that I have
seen happen on real systems that have a real-time clock with a bad
current time and do not have proper support for a monotonic clock. I
believe that your new code does not properly handle this case, because
it treats all times less than 0 as immediate. I think that you can fix
it by comparing against LLONG_MIN rather than zero.
In that case, we should set poll_immediate_wake to be LLONG_MIN as well, right?
In poll-loop, I would move
COVERAGE_INC(poll_zero_timeout);
inside the new statement that is already conditional on timeout_when ==
LLONG_MIN.
I don't like the new assumption in time_poll() that n_pollfds == 0 means
we're waking immediately.
We can do everything on timeout. That is more consistent.
As far as assumptions go, it is equivalent on Unixes, because the number of fds is
always > 1. This is because you always get 1 fd from the signal pipe.
The code on Windows has that assumption already.
Thanks,
Ben.
--
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/
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