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SubjectRe: [PATCH v2] printk: add halt_delay parameter for printk delay in halt phase

* 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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