Date: Wed, 9 Sep 2020 09:13:45 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: "Alexander V. Chernikov" <melifaro@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r364465 - in head/sys: conf net net/route Message-ID: <05bfa3f4-8c95-3ad4-80b5-c5e48cd6370d@FreeBSD.org> In-Reply-To: <93541599601730@mail.yandex.ru> References: <202008212134.07LLYq3K071532@repo.freebsd.org> <69399f59-4eca-ee29-7230-678a02cf6eff@FreeBSD.org> <93541599601730@mail.yandex.ru>
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On 09/09/2020 00:50, Alexander V. Chernikov wrote: > 08.09.2020, 21:03, "Andriy Gapon" <avg@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. In general, I would keep CTLFLAG_RWTUN as the knob is a tunable indeed and some tools query that flag. 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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