Messages in this thread | | | Date | Mon, 8 Jun 2009 16:37:35 +0800 | Subject | Re: [PATCH v3] printk: add halt_delay parameter for printk delay in halt phase | From | Dave Young <> |
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On Mon, Jun 8, 2009 at 4:14 PM, Ingo Molnar<mingo@elte.hu> wrote: > > * Dave Young <hidave.darkstar@gmail.com> wrote: > >> Add a halt_delay module parameter in printk.c used to read the >> printk messages in halt/poweroff/restart phase, delay each printk >> messages by halt_delay milliseconds. It is useful for debugging if >> there's no other way to dump kernel messages that time. >> >> The halt_delay max value is 65535, default value is 0, change it >> by: >> >> echo xxx > /sys/module/printk/parameters/halt_delay >> >> Signed-off-by: Dave Young <hidave.darkstar@gmail.com> >> --- >> Documentation/kernel-parameters.txt | 5 +++++ >> kernel/printk.c | 17 +++++++++++++++++ >> 2 files changed, 22 insertions(+) >> >> --- linux-2.6.orig/kernel/printk.c 2009-06-08 13:55:35.000000000 +0800 >> +++ linux-2.6/kernel/printk.c 2009-06-08 13:56:23.000000000 +0800 >> @@ -250,6 +250,22 @@ static inline void boot_delay_msec(void) >> } >> #endif >> >> +/* msecs delay after each halt/poweroff/restart phase printk, >> + unsigned short is enough for delay in milliseconds */ >> +static unsigned short halt_delay; >> + >> +static inline void halt_delay_msec(void) >> +{ >> + if (unlikely(halt_delay == 0 || !(system_state == SYSTEM_HALT >> + || system_state == SYSTEM_POWER_OFF >> + || system_state == SYSTEM_RESTART))) >> + return; > > This is a tiny bit ugly (and goes into the vprintf path) but i can > see no other way either - a system_state > SYSTEM_RUNNING check > would needlessly include the suspend-to-disk state (which we dont > want to include here).
Can we move suspend-to-disk before halt state?
> > In theory we could turn system_state into a bitmask and have a > print_delay_mask check instead of these flags ... but that is a far > wider change and i'm not sure it's a net step forwards. > > I've applied your patch to tip:core/printk with small edits to the > changelog - Linus & Andrew is Cc:ed, should they have any > objections. > > Ingo >
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