svn commit: r364465 - in head/sys: conf net net/route

Alexander V. Chernikov melifaro at freebsd.org
Tue Sep 8 21:50:41 UTC 2020


08.09.2020, 21:03, "Andriy Gapon" <avg at 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 :-(

> 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


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