Question about socket timeouts

[John Baldwin]

On Friday, August 23, 2013 9:53:12 am Davide Italiano wrote:
> On Fri, Aug 23, 2013 at 3:45 PM, John Baldwin <jhb at freebsd.org> wrote:
> > On Friday, August 23, 2013 2:27:58 am Vitja Makarov wrote:
> >> 2013/8/22 John Baldwin <jhb at freebsd.org>:
> >> > On Thursday, August 22, 2013 12:18:48 am Vitja Makarov wrote:
> >> >> 2013/8/21 John Baldwin <jhb at freebsd.org>:
> >> >> > On Monday, August 19, 2013 11:13:02 pm Daniel Eischen wrote:
> >> >> >> On Mon, 19 Aug 2013, Adrian Chadd wrote:
> >> >> >>
> >> >> >> > Yes! Please file a PR!
> >> >> >>
> >> >> >> This sorta implies that both are acceptable (although,
> >> >> >> the Linux behavior seems more desirable).
> >> >> >>
> >> >> >>    http://austingroupbugs.net/view.php?id=369
> >> >> >
> >> >> > No, that says "round up", so it does mean that the requested timeout
> >> >> > should be the minimum amount slept.  tvtohz() does this.  Really odd
> >> >> > that the socket code is using its own version of this rather than
> >> >> > tvtohz().
> >> >> >
> >> >> > Oh, I bet this just predates tvtohz().  Interesting that it keeps 
getting
> >> >> > bug fixes in its history that simply using tvtohz() would have 
solved.
> >> >> >
> >> >> > Try this:
> >> >> >
> >> >> > Index: uipc_socket.c
> >> >> > ===================================================================
> >> >> > --- uipc_socket.c       (revision 254570)
> >> >> > +++ uipc_socket.c       (working copy)
> >> >> > @@ -2699,21 +2699,16 @@ sosetopt(struct socket *so, struct sockopt 
*sopt)
> >> >> >                         if (error)
> >> >> >                                 goto bad;
> >> >> >
> >> >> > -                       /* assert(hz > 0); */
> >> >> >                         if (tv.tv_sec < 0 || tv.tv_sec > INT_MAX / 
hz ||
> >> >> >                             tv.tv_usec < 0 || tv.tv_usec >= 1000000) 
{
> >> >> >                                 error = EDOM;
> >> >> >                                 goto bad;
> >> >> >                         }
> >> >> > -                       /* assert(tick > 0); */
> >> >> > -                       /* assert(ULONG_MAX - INT_MAX >= 1000000); 
*/
> >> >> > -                       val = (u_long)(tv.tv_sec * hz) + tv.tv_usec 
/ tick;
> >> >> > -                       if (val > INT_MAX) {
> >> >> > +                       val = tvtohz(&tv);
> >> >> > +                       if (val == INT_MAX) {
> >> >> >                                 error = EDOM;
> >> >> >                                 goto bad;
> >> >> >                         }
> >> >> > -                       if (val == 0 && tv.tv_usec != 0)
> >> >> > -                               val = 1;
> >> >> >
> >> >> >                         switch (sopt->sopt_name) {
> >> >> >                         case SO_SNDTIMEO:
> >> >> >
> >> >>
> >> >> That must help. But I want to see the issue solved in the next
> >> >> release. I can't apply patch to the production system. Btw in
> >> >> production environment we have kern.hz set to 1000 so it's not a
> >> >> problem there.
> >> >
> >> > Can you test this in some way in a test environment?
> >> >
> >>
> >> Ok, sorry for posting out of the list.
> >>
> >> Simple test program is attached. Without your patch timeout expires in
> >> about 20ms. With it it's ~40ms.
> >>
> >> 40 instead of 30 is beacuse of odd tick added by tvtohz().
> >
> > Ok, thanks.  tvtohz() will be good to MFC (and I will do that), but for
> > HEAD I think we can fix this to use a precise timeout.  I've cc'd davide@
> > so he can take a look at that.
> >
> > --
> > John Baldwin
> 
> Hi,
> I think I can switch this code to new timeout KPI, but this will
> require the timeout field of 'struct sockbuf' to be changed from 'int'
> to 'sbintime_t' which breaks binary compatibility. Do you have any
> strong objections about this? If any, I would like this to happen ABI
> freeze, so it looks like this is the right moment.

This should be fine to change now, it just can't be MFC'd (which we can't
do anyway).

-- 
John Baldwin