missing status line with windows client/server

missing status line with windows client/server

[James Rizzo]

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We are seeing an issue with windows fio using the client/server model where
it often doesn’t display the ongoing status line during a run.  I’ve been
looking into this and found that when the issue occurs,
fio_handle_clients->poll() is returning revents with POLLIN set for an fd
that has nothing pending.  This later results in a hang in
fio_handle_clients->
fio_handle_client()->fio_net_recv_cmd()->fio_recv_data()->recv() because
recv() is called with wait=true.

Looking at the poll() function in os/windows/posix, it appears that
fds[i].revents only ever gets set, never cleared(except in the
INVALID_SOCKET case).

I’ve experimented with the following change, and it appears to work as
expected.  Can you confirm this issue and, if so, whether this is the
appropriate fix?

int poll(struct pollfd fds[], nfds_t nfds, int timeout)
{
...
    FD_ZERO(&readfds);
    FD_ZERO(&writefds);
    FD_ZERO(&exceptfds);

    for (i = 0; i < nfds; i++) {
        fds[i].revents = 0;                   //  <<< add this line to clear
the revents before they are set below
        if (fds[i].fd == INVALID_SOCKET) {
            fds[i].revents = 0;               //  <<< assuming above is
correct, this line can be deleted
            continue;
        }

Thanks,
Jim

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