09.09.2020, 07:13, "Andriy Gapon" <a...@freebsd.org>:
> On 09/09/2020 00:50, Alexander V. Chernikov wrote:
>> 08.09.2020, 21:03, "Andriy Gapon" <a...@freebsd.org>:
>>> On 22/08/2020 00:34, Alexander V. Chernikov wrote:
>>>> Author: melifaro
>>>> Date: Fri Aug 21 21:34:52 2020
>>>> New Revision: 364465
>>>> URL: https://svnweb.freebsd.org/changeset/base/364465
>>>>
>>>> Log:
>>>> Make net.fibs growable.
>>>>
>>>> Allow to dynamically grow the amount of fibs in each vnet.
>>>>
>>>> This change alters current behavior. Currently, if one defines
>>>> ROUTETABLES > 1 in the kernel config, each vnet will be created
>>>> with the number of fibs defined in the kernel config.
>>>> After this commit vnets will be created with fibs=1.
>>>>
>>>> Dynamic net.fibs is not compatible with net.add_addr_allfibs.
>>>> The plan is to deprecate the latter and make
>>>> net.add_addr_allfibs=0 default behaviour.
>>>>
>>>> Reviewed by: glebius
>>>> Relnotes: yes
>>>> Differential Revision: https://reviews.freebsd.org/D26062
>>>
>>> I wonder why no one reported a problem that I am seeing after upgrading
>>> past
>>> this revision. Maybe because I do have net.fibs=2 in my loader.conf?
>> Hi Andriy,
>>
>> Does r365475 fix the problem for you?
>> CTLFLAG_RWTUN flag got slipped through the cracks somewhere :-(
>
> I am not sure that it does, I haven't tried it, but I agree with Ryan's
> comment.
It should.
> In general, I would keep CTLFLAG_RWTUN as the knob is a tunable indeed and
> some
> tools query that flag.
Thanks for the suggestion, I've updated the params to include CTLFLAG_NOFETCH
in r365517.
> So, I would like to re-iterate my earlier suggestion to use CTLFLAG_NOFETCH
> paired with explicit TUNABLE_INT_FETCH (which seems to be there already).
>
>>> The problem -- unfortunately I only have a screenshot -- but it's a page
>>> fault
>>> trap in this call chain:
>>> sysctl_register_all -> sysctl_load_tunable_by_oid_locked -> sysctl_fibs ->
>>> _sx_xlock.
>>>
>>> The crash is on the RTABLES_LOCK() line.
>>> And it's kind of obvious why.
>>>
>>> The tunables, including net.fibs which is declared as RWTUN, are set at
>>> SI_SUB_TUNABLES stage, but RTABLES_LOCK_INIT() is not called until
>>> SI_SUB_PROTO_DOMAIN much later. In other words, sysctal_fibs can be called
>>> earlier than vnet_rtables_init.
>>>
>>> I think that the best way to handle the problem would be to add
>>> CTLFLAG_NOFETCH
>>> to the sysctl declaration and then to add -- if necessary at all -- an
>>> explicit
>>> query of the kenv.
>>>
>>> --
>>> Andriy Gapon
>
> --
> Andriy Gapon
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