Messages in this thread | | | Date | Tue, 24 Jun 2014 23:35:09 +0100 | From | Ken Moffat <> | Subject | Re: CONFIG_UEVENT_HELPER default |
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On Tue, Jun 24, 2014 at 12:55:26PM -0700, Andy Lutomirski wrote: > On 06/24/2014 11:33 AM, Greg KH wrote: > > On Tue, Jun 24, 2014 at 11:30:05AM -0700, Michael Marineau wrote: > >> On Jun 24, 2014 11:23 AM, "Alan Stern" <stern@rowland.harvard.edu> wrote: > >>> > >>> Michael and Greg: > >>> > >>> The help text for CONFIG_UEVENT_HELPER says (among other things): > >>> > >>> This should not be used today, because usual systems create > >>> many events at bootup or device discovery in a very short time > >>> frame. > >>> > >>> If it shouldn't be used, why does it default to 'y'? > >>> > >>> Alan Stern > >>> > >> > >> To introduce the option but not change the default behavior. (yet?) I don't > >> really have an opinion one way or the other, I just defaulted to being > >> conservative. > > > > Yes, being conservative is good as turning this off with older systems > > (like the pathological Fedora 3 system that some kernel developers still > > use for testing), would result in a non-booting box. So if you know > > that your system is "new enough", it's safe to turn off, but if you have > > a doubt, leave it on to be safe. > > As far as I know, there's no real requirement that a defconfig kernel be > able to boot old userspace. We want an oldconfig kernel to be able to > boot old userspace, but changing the default won't affect that. > > For example, a defconfig kernel won't boot opensuse 9. > > --Andy
I noticed this help message yesterday, and decided that I almost-certainly did NOT want it (that system is about 6 weeks old, with then-current releases of everything). But I was not able to complete the kernel build because of other problems (possibly related to gcc-4.9.1) and I have other things to do at the moment. All of which means that I can not, for the moment, review what will happen if I let this option get enabled.
Two things about this default concern me:
(i.) I got the option with 'make oldconfig' and, after reading the help, made a decision. But, in the absence of other problems, and if the help text is correct, it looks as if a kernel built after accepting the default 'Y' here with recent userspace might grind to a halt after "successfully" booting? That sounds slightly better than "fails to boot", but only slightly. Maybe the problem needs a lot of modules, or is it something like "it will hang for a minute, then boot" ?
(ii.) I understand that people continue to use ancient userspace, and for that the 'Y' option is needed. Using ancient userspace is a worthwhile thing for _somebody_ to try. But where is the line between "you need to enable this" and "enabling this might be a really bad idea" ? Maybe a specific version of udev ?
ĸen -- Nanny Ogg usually went to bed early. After all, she was an old lady. Sometimes she went to bed as early as 6 a.m. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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