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 <[email protected]>
---
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 */
* Dave Young <[email protected]> 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 <[email protected]>
> ---
> 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
On Sun, Jun 7, 2009 at 10:32 PM, Ingo Molnar<[email protected]> wrote:
>
> * Dave Young <[email protected]> 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 <[email protected]>
>> ---
>> 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.
Oops, will add in v3
>
> Thanks,
>
> Ingo
>
--
Regards
dave