Messages in this thread |  | | Date | Sun, 7 Jun 2009 16:32:21 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH v2] printk: add halt_delay parameter for printk delay in halt phase |
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* 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> > --- > kernel/printk.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > --- linux-2.6.orig/kernel/printk.c 2009-06-03 10:16:55.000000000 +0800 > +++ linux-2.6/kernel/printk.c 2009-06-03 10:32:43.000000000 +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; > + > + mdelay(halt_delay); > +} > + > +module_param(halt_delay, ushort, S_IRUGO | S_IWUSR); > + > /* > * Commands to do_syslog: > * > @@ -649,6 +665,7 @@ asmlinkage int vprintk(const char *fmt, > char *p; > > boot_delay_msec(); > + halt_delay_msec(); > > preempt_disable(); > /* This stops the holder of console_sem just where we want him */
Looks nice now - but please also add a description to Documentation/kernel-parameters.txt.
Thanks,
Ingo
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