Messages in this thread Patch in this message | | | Date | Mon, 8 Jun 2009 15:40:07 +0800 | Subject | [PATCH v3] printk: add halt_delay parameter for printk delay in halt phase | From | Dave Young <> |
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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; + + 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 */ --- linux-2.6.orig/Documentation/kernel-parameters.txt 2009-05-28 08:40:42.000000000 +0800 +++ linux-2.6/Documentation/kernel-parameters.txt 2009-06-08 14:06:47.000000000 +0800 @@ -1897,6 +1897,11 @@ and is between 256 and 4096 characters. printk.time= Show timing data prefixed to each printk message line Format: <bool> (1/Y/y=enable, 0/N/n=disable)
+ printk.halt_delay= + Milliseconds to delay each printk during + halt/poweroff/restart phase. + Format: <ushort> + processor.max_cstate= [HW,ACPI] Limit processor to maximum C-state max_cstate=9 overrides any DMI blacklist limit.
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