Messages in this thread | | | Date | Tue, 9 Jun 2009 00:02:53 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH v3] printk: add halt_delay parameter for printk delay in halt phase |
| |
* Andrew Morton <akpm@linux-foundation.org> wrote:
> On Mon, 8 Jun 2009 19:15:01 +0200 > Ingo Molnar <mingo@elte.hu> wrote: > > > > questions: is it possible for interrupts to be disabled at this > > > time? If so, can we get an NMI watchdog hit? > > > > no, we generally turn off the nmi watchdog during shutdown, > > disable the lapic and io-apic, etc. > > Is x86 the only architecture which implements an NMI watchdog?
Sparc64 does too IIRC.
> > > Is the softlockup detector still running and if so, can it > > > trigger? > > > > in (non-emergency) reboot, last i checked, we stopped all other > > CPUs first, and then killed the current one. There's no chance > > for the watchdog thread to run. > > OK, but... See below. > > > Anyway ... you seem to be uncomfortable about this patch - > > should i delay it for now to let it all play out? We are close > > to the merge window. > > I'm OK - I'm just bouncing ideas and questions off you guys, to > make sure that we've thought this through all the way. > > Here's another: why is it a boot option rather than a > runtime-tunable? A /proc tweakable is generally preferable because > it avoids the oh-crap-i-forgot-to-edit-grub.conf thing. And we > could perhaps then remove all those system_state tests: userspace > sets printk_delay immediately prior to running halt/reboot/etc? > > Plus the feature becomes more general - perhaps there are use > cases where people want to slow down printks, such as: kernel goes > oops, data scrolls off, serial console/netconsole unavailable. > pause_on_oops is supposed to help here but last time I tried it, > it kinda didn't work, plus pause_on_oops doesn't solve the > data-scrolled-off problem. > > Thirdly, if we do this as a general /proc/printk_delay thing, > perhaps it can be consolidated with the existing boot_delay= > implementation.
Consolidatig with the existing boot delay implementation was one of my first suggestions.
The /proc thing definitely makes sense - the boot option was just symmetry to the existing boot-delay approach.
I've unapplied this patch - i agree that it needs a bit more work and i dont want to hold up other changes in the core/printk branch.
Ingo
| |