On Tue, Sep 22, 2015 at 8:58 AM, Junio C Hamano <gitster@xxxxxxxxx> wrote:
> Eric Sunshine <sunshine@xxxxxxxxxxxxxx> writes:
>
>>> while (1) {
>>> nr = read(fd, buf, len);
>>> - if ((nr < 0) && (errno == EAGAIN || errno == EINTR))
>>> - continue;
>>> + if (nr < 0) {
>>> + if (errno == EINTR)
>>> + continue;
>>> + if (errno == EAGAIN || errno == EWOULDBLOCK) {
>>> + struct pollfd pfd;
>>> + int i;
>>> + pfd.events = POLLIN;
>>> + pfd.fd = fd;
>>> + i = poll(&pfd, 1, 100);
>>
>> Why is this poll() using a timeout? Isn't that still a busy wait of
>> sorts (even if less aggressive)?
>
True. Maybe we could have just a warning for now?
if (errno == EAGAIN) {
warning("Using xread with a non blocking fd");
continue; /* preserve previous behavior */
}
I think I am going to drop this patch off the main series and spin it out
as an extra patch as the discussion is a bit unclear to me at the moment
where we're heading.
> Good point. If we _were_ to have this kind of "hiding issues under
> the rug and continuing without issues" approach, I do not think we
> would need timeout for this poll(2). The caller accepted that it is
> willing to wait until we read up to len (which is capped, though) by
> not calling the nonblocking variant.
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