nearly-tickless-tinc

[Loïc Grenié]

2011/6/1 Guus Sliepen <guus at tinc-vpn.org>:
> On Wed, Jun 01, 2011 at 10:15:26AM +0200, Loïc Grenié wrote:
>
>> >>     However, once again, if pselect() is not available or not compatible or
>> >>   whatever it can be emulated with a select:
>> >
>> > Yes. You can add a check in configure.in for pselect(), and add the necessary
>> > #ifdefs to ensure it automatically selects the right thing.
>>
>>      What do you think about the racy "glibc pselect" ? Right now I do
>>   not test for it. It is probably possible to test for it using
>> syscall(2), either
>>   at compile time or at runtime.
>
> Well, it is not so critical, and the problem is only with kernels that are more
> than five years old.

    tincd is not tickless anyway: there is a tick for keepalive, that means that
  signal handling will be at most delayed.

> If you really want, you could add a runtime check using the uname() function.

     I do not "really" want. If you think it's not critical, I'm happy
to leave it
  that way.

>> > Looks good! If you can add the configure.in checks, and write a description for
>> > your patch, I can commit it to the git repository without any changes :)
>>
>>        We'll see ! Right now I have hijacked timespec and tv_nsec in net.c
>>   -- when not using pselect() -- to streamline mail_loop source code -- it's
>>   probably not very good software engineering. What do you prefer ?
>
> Hm, in this case it is better to explicitly use #ifdef ... #else ... #endif in
> the main loop, instead of #defining tinc_pselect and friends. With the former
> it is more clear what happens.

     Here you go !

    It is probably a good idea to also change time comparison: with this
  patch "now" is evaluated after pselect(), thus with code like this:

timeout = now+1;
[... pselect() lasting 1s ... ]
if (timeout < now) {
    contional code
}

  conditional code will not get executed. It would be if comparison were
  timeout <= now (the instruction "next_event++;" in the patch would
  also disappear). I can take care of it.

         Thanks,

                Loïc