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

[Dave Young]

On Sun, Jun 7, 2009 at 10:32 PM, Ingo Molnar<mingo@xxxxxxx> wrote:
>
> * Dave Young <hidave.darkstar@xxxxxxxxx> 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@xxxxxxxxx>
>> ---
>> kernel/printk.c | Â 16 ++++++++++++++++
>> 1 file changed, 16 insertions(+)
>>
>> --- linux-2.6.orig/kernel/printk.c  Â2009-06-03 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)
>> Â}
>> Â#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)
>> +{
>> + Â Â if (unlikely(halt_delay == 0 || !(system_state == SYSTEM_HALT
>> + Â Â Â Â Â Â Â Â Â Â Â Â Â Â || system_state == SYSTEM_POWER_OFF
>> + Â Â Â Â Â Â Â Â Â Â Â Â Â Â || system_state == SYSTEM_RESTART)))
>> + Â Â Â Â Â Â return;
>> +
>> + Â Â mdelay(halt_delay);
>> +}
>> +
>> +module_param(halt_delay, ushort, S_IRUGO | S_IWUSR);
>> +
>> Â/*
>> Â * Commands to do_syslog:
>> Â *
>> @@ -649,6 +665,7 @@ asmlinkage int vprintk(const char *fmt,
>> Â Â Â char *p;
>>
>> Â Â Â boot_delay_msec();
>> + Â Â halt_delay_msec();
>>
>> Â Â Â preempt_disable();
>> Â Â Â /* 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.

Oops, will add in v3

>
> Thanks,
>
> Â Â Â ÂIngo
>



-- 
Regards
dave
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