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Message-ID: <20081011145823.GA14062@elte.hu> Date: Sat, 11 Oct 2008 16:58:23 +0200 From: Ingo Molnar <mingo@...e.hu> To: Jens Axboe <jens.axboe@...cle.com> Cc: Tejun Heo <tj@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, Yinghai Lu <yinghai@...nel.org> Subject: Re: [bug] latest -git boot hang * Jens Axboe <jens.axboe@...cle.com> wrote: > On Sat, Oct 11 2008, Ingo Molnar wrote: > > > > * Jens Axboe <jens.axboe@...cle.com> wrote: > > > > > On Sat, Oct 11 2008, Ingo Molnar wrote: > > > > > > > > * Tejun Heo <tj@...nel.org> wrote: > > > > > > > > > > It does sound like perhaps the option should be hidden more, if it's > > > > > > really only reasonably enabled for some very specialized distro > > > > > > debuggers, not normal kernel people. > > > > > > > > > > Yeap, if fedora didn't work, I think it should be hidden. Do we > > > > > already have place to hide things like this? > > > > > > > > in my local testing i'm using simple annotations like the one attached > > > > further below. Any objections against sending my BROKEN_BOOT_ALLOWED kit > > > > upstream, and merge my annotations for various kernel features that > > > > break a generic distro bootup? > > > > > > > > Right now i have about 40 such annotations for -tip testing: > > > > > > > > fs/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > fs/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > security/selinux/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > security/smack/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > security/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/net/appletalk/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/net/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/media/video/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/scsi/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/watchdog/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/watchdog/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/ide/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/i2c/busses/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/block/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/video/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/video/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/video/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/video/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/video/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/video/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/video/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/video/console/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/video/console/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/mtd/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > drivers/isdn/icn/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > lib/Kconfig.kgdb: depends on BROKEN_BOOT_ALLOWED > > > > lib/Kconfig.debug: depends on BROKEN_BOOT_ALLOWED > > > > lib/Kconfig.debug: depends on BROKEN_BOOT_ALLOWED > > > > arch/x86/Kconfig.debug: depends on BROKEN_BOOT_ALLOWED > > > > arch/x86/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > arch/x86/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > arch/x86/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > arch/x86/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > arch/x86/Kconfig: # depends on BROKEN_BOOT_ALLOWED > > > > arch/x86/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > arch/x86/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > arch/x86/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > arch/x86/Kconfig: depends on BROKEN_BOOT_ALLOWED > > > > arch/x86/Kconfig.cpu: depends on BROKEN_BOOT_ALLOWED > > > > > > > > and note the stark contrast to CONFIG_BROKEN - sometimes a given > > > > functionality is really not meant to be enabled on a generic system. > > > > > > > > Ingo > > > > > > > > ----------------> > > > > Subject: qa: no ext devt > > > > From: Ingo Molnar <mingo@...e.hu> > > > > Date: Fri Oct 10 22:54:57 CEST 2008 > > > > > > > > Signed-off-by: Ingo Molnar <mingo@...e.hu> > > > > --- > > > > lib/Kconfig.debug | 2 ++ > > > > 1 file changed, 2 insertions(+) > > > > > > > > Index: linux/lib/Kconfig.debug > > > > =================================================================== > > > > --- linux.orig/lib/Kconfig.debug > > > > +++ linux/lib/Kconfig.debug > > > > @@ -670,6 +670,8 @@ config DEBUG_BLOCK_EXT_DEVT > > > > bool "Force extended block device numbers and spread them" > > > > depends on DEBUG_KERNEL > > > > depends on BLOCK > > > > + depends on BROKEN_BOOT_ALLOWED > > > > + select BROKEN_BOOT > > > > default n > > > > help > > > > Conventionally, block device numbers are allocated from > > > > > > What is BROKEN_BOOT_ALLOWED? Honestly, I'd prefer to just put an extra > > > 2-3 line paragraph in the help entry, saying that it's quite possible > > > that current distros wont boot with this testing code enabled. Since > > > it default to 'n', people should read the entry before turning it on > > > anyway. > > > > well, the extra BROKEN_BOOT_ALLOWED helps my automated test-setup to > > decide whether a .config that it's testing (either sent by a reporter or > > generated randomly) can be booted. > > > > If CONFIG_BROKEN_BOOT_ALLOWED=y, then i allow config options that can > > break the bootup. In that case, and _if_ such a possibly-boot-breaking > > config option is enabled, CONFIG_BROKEN_BOOT is set - which my scripts > > detect. > > > > This gives the test harness the highest flexibility and annotates those > > kernel features / drivers which can result in a (possibly) broken > > bootup. The scripts cannot read help entries. > > OK, makes sense to me then, thanks. I was afraid it was some user > exposed parameter, in which case it sounded... interesting :-) > > For users, we just need to expand the help entry a bit. We could perhaps rename it to: CONFIG_ALLOW_NON_GENERIC_FEATURES=y ? It's usually things like ISA drivers or very specific hardware support that falls into this category - none of our major features or drivers, so you should not be worried about any limitation effects of such a feature. The help text does not help me much in that case, it was not me who enabled that option, i just want to use a .config from some other person and want to reproduce a bugreport. I do that almost on a daily basis. And this CONFIG_ALLOW_NON_GENERIC_FEATURES=y option could even be exposed to users. I have three first-hand usecases for it: First usecase: when i get a .config from a tester and want to test-boot it on a box, i dont want to spend hours of .config bisection just to find out that it has a driver enabled that is known to break generic boxes. Yes, this has happened to me in the past. The second usecase where i utilize it is random kernel testing: there randconfig is what enables drivers, not me, so the help text does not help much. Third usecase: where i just accidentally enable something i should not have enabled. It's nice to have tools around that can protect me from such mistakes. This too has happened to me. So i find it very convenient that i can just disable CONFIG_ALLOW_NON_GENERIC_FEATURES - which automatically disables all possibly-broken functionality. Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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