On Mon, Oct 8, 2012 at 3:37 PM, Kees Cook <keesc...@chromium.org> wrote: > On Mon, Oct 8, 2012 at 3:29 PM, Paul E. McKenney > <paul...@linux.vnet.ibm.com> wrote: >> On Mon, Oct 08, 2012 at 03:07:24PM -0700, Kees Cook wrote: >>> On Sun, Oct 7, 2012 at 6:04 PM, Paul E. McKenney >>> <paul...@linux.vnet.ibm.com> wrote: >>> > On Sun, Oct 07, 2012 at 04:18:54PM -0400, Dave Jones wrote: >>> >> On Sun, Oct 07, 2012 at 09:30:29AM -0700, Paul E. McKenney wrote: >>> >> >>> >> > > I think Kconfig is mostly what distro would like to use the thing is >>> >> > > the Kconfig text needs to be there upfront when its merged, not two >>> >> > > months later, since then it too late for a distro to notice. >>> >> > > >>> >> > > I'd bet most distros would read the warnings, but in a lot of cases >>> >> > > the warning don't exist until its too late. >>> >> > >>> >> > In the case of CONFIG_RCU_USER_QS you are quite right, the warning >>> >> > should have been there from the beginning and was not. I suppose you >>> >> > could argue that the warning was not sufficiently harsh in the case of >>> >> > CONFIG_RCU_FAST_NO_HZ, but either way it did get ignored: >>> >> >>> >> Maybe if we had a universally agreed upon tag for kconfig, like >>> >> "distro recommendation: N" that would make things obvious, and also allow >>> >> those of us unfortunate enough to maintain distro kernels to have >>> >> something >>> >> to easily grep for. This would also catch the case when you eventually >>> >> (hopefully) >>> >> flip from an N to a Y. >>> >> >>> >> There will likely still be some distros that will decide they know better >>> >> (and I'm pretty sure eventually I'll find reason to do so myself), but >>> >> it at least >>> >> gives the feature maintainer the "I told you so" clause. >>> >> >>> >> Something we do quite often for our in-development kernels is enable >>> >> something >>> >> that's shiny, new and unproven, and then when we branch for a release, >>> >> we turn >>> >> it back off. It would be great if a lot of this kind of thing could be >>> >> more automated. >>> > >>> > One approach would be to have CONFIG_DISTRO, so that experimental >>> > features could use "depends on !DISTRO", but also to have multiple >>> > "BLEEDING" symbols. For example, given a CONFIG_DISTRO_BLEEDING_HPC >>> > and CONFIG_DISTRO_BLEEDING_RT, CONFIG_RCU_USER_QS might eventually >>> > use the following clause: >>> > >>> > depends on !DISTRO || DISTRO_BLEEDING_HPC || DISTRO_BLEEDING_RT >>> > >>> > A normal distro would define DISTRO, a distro looking to provide >>> > bleeding-edge >>> > HPC or real-time features would also define DISTRO_BLEEDING_HPC or >>> > DISTRO_BLEEDING_RT, respectively. >>> > >>> > Does that make sense, or am I being overly naive? >>> >>> I think we should avoid any global configs that disable things. We'll >>> just end up in the same place with distros again. >> >> So you believe that we should taint the kernel or splat on boot to >> warn distros off of features that might not be ready for 100 million >> users? Or do you have some other approach in mind? > > Personally, I think taint+printk seems like the right way to go.
Actually, I think printk is sufficient. I don't want kernel taint to become the new CONFIG_EXPERIMENTAL. :) -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
