git: af949c590bd8 - main - Disable stack gap for ntpd during build.

[Jessica Clarke]

> On 21 May 2021, at 15:11, Marcin Wojtas <mw at semihalf.com> wrote:
> 
> Hi Jess
> 
> pt., 21 maj 2021 o 15:39 Jessica Clarke <jrtc27 at freebsd.org> napisał(a):
>> 
>> On 21 May 2021, at 14:34, Marcin Wojtas <mw at FreeBSD.org> wrote:
>>> 
>>> The branch main has been updated by mw:
>>> 
>>> URL: https://cgit.FreeBSD.org/src/commit/?id=af949c590bd8a00a5973b5875d7e0fa6832ea64a
>>> 
>>> commit af949c590bd8a00a5973b5875d7e0fa6832ea64a
>>> Author:     Marcin Wojtas <mw at FreeBSD.org>
>>> AuthorDate: 2021-05-21 09:29:22 +0000
>>> Commit:     Marcin Wojtas <mw at FreeBSD.org>
>>> CommitDate: 2021-05-21 13:33:06 +0000
>>> 
>>>   Disable stack gap for ntpd during build.
>>> 
>>>   When starting, ntpd calls setrlimit(2) to limit maximum size of its
>>>   stack. The stack limit chosen by ntpd is 200K, so when stack gap
>>>   is enabled, the stack gap is larger than this limit, which results
>>>   in ntpd crashing.
>> 
>> Isn’t the bug that the unusable gap counts as usage?
>> 
>> Jess
>> 
> 
> An alternative solution was submitted
> (https://reviews.freebsd.org/D29832), so that to extend the limit for
> ntpd, but eventually it was recommended to simple disable the stack
> gap for it until it's fixed upstream (see the last comment in the
> linked revision).

That’s my point, there is nothing to “fix” upstream. NTPD uses less than 200K
of stack, thus it is perfectly reasonable for it to set its limit to that. The
fact that FreeBSD decides to count an arbitrary, non-deterministic amount of
additional unusable virtual address space towards that limit is not its fault,
but a bug in FreeBSD that needs to be fixed as it’s entirely unreasonable for
applications to have to account for that.

Jess