Date: Mon, 03 Nov 2014 19:05:37 +0800 From: Julian Elischer <julian@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com>, Mateusz Guzik <mjguzik@gmail.com>, Tiwei Bie <btw@mail.ustc.edu.cn>, freebsd-hackers@freebsd.org Subject: Re: [maybe spam] Re: [PATCH] Finish the task 'sysctl reporting current working directory' Message-ID: <54576181.5010405@freebsd.org> In-Reply-To: <20141103104052.GL53947@kib.kiev.ua> References: <1414987325-23280-1-git-send-email-btw@mail.ustc.edu.cn> <20141103051908.GC29497@dft-labs.eu> <20141103064052.GA1739@freebsd> <5457394E.4050905@freebsd.org> <20141103084129.GF29497@dft-labs.eu> <20141103090940.GI53947@kib.kiev.ua> <20141103102005.GI29497@dft-labs.eu> <20141103104052.GL53947@kib.kiev.ua>
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On 11/3/14, 6:40 PM, Konstantin Belousov wrote: > On Mon, Nov 03, 2014 at 11:20:05AM +0100, Mateusz Guzik wrote: >> On Mon, Nov 03, 2014 at 11:09:40AM +0200, Konstantin Belousov wrote: >>> On Mon, Nov 03, 2014 at 09:41:29AM +0100, Mateusz Guzik wrote: >>>> On Mon, Nov 03, 2014 at 04:14:06PM +0800, Julian Elischer wrote: >>>>> why are you using a fixed sysctl MIB number? >>>>> I thought we were moving towards dynamic sysctls when we add new ones. >>>>> >>>> We are? KERN_PROC_* seems to be a complete list with SIGTRAMP added last >>>> year. >>>> >>>> I guess we can do it with OID_AUTO, if there will be any need we can >>>> switch it back to a static var. >>> I am very curious how would you make kern.proc.cwd auto, while >>> still using kern.proc leaf. And more important question is, why ? >> Unclear what you mean. I just tested with marking it OID_AUTO and it >> works. > Typical caller of other sysctls from kern.proc family does > (slightly edited code from libunwind): > > int mib[4], error, ret; > size_t len, len1; > > len = 0; > mib[0] = CTL_KERN; > mib[1] = KERN_PROC; > mib[2] = KERN_PROC_VMMAP; > mib[3] = pid; > >> Userspace code does sysctlbyname to look it up and sysctl + mib[3] = pid to >> call, no problems that I can see. > Yes, but currently userspace does not need to do this dance (for other > kern.proc sysctls). > >> I'm not a fan of this because of the need for lookup for what is a >> compiled in and always available sysctl. >> >> I only said we can do OID_AUTO because of Julian's complaint. Was about >> to do some search for apparent agreement to not add more static sysctls, >> but your reply suggests there was no such thing. > It is reasonable to not manage allocation of oids for things which are > hard or impossible to statically manage, e.g. the leafs from dynamically > loaded modules, or leafs describing the device tree on the machine, > where structure of the tree depends on the local conditions. > > Trying to enforce this rule for oids where only static tree is used > only complicates life for consumers without any benefits for code > clarity or extensibility. > >> That said, I prefer static version. > Agree. I withdraw my comment.. :-) > >
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