Messages in this thread Patch in this message | | | Date | Tue, 2 Jun 2009 17:54:52 +0800 | Subject | [PATCH] 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.
halt_delay 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 | 21 +++++++++++++++++++++ lib/Kconfig.debug | 10 ++++++++++ 2 files changed, 31 insertions(+)
--- linux-2.6.orig/kernel/printk.c 2009-04-09 16:23:03.000000000 +0800 +++ linux-2.6/kernel/printk.c 2009-06-02 17:45:54.000000000 +0800 @@ -250,6 +250,26 @@ static inline void boot_delay_msec(void) } #endif
+#ifdef CONFIG_HALT_PRINTK_DELAY +/* msecs delay after each halt/poweroff/restart phase printk */ +static unsigned int halt_delay; + +static inline void halt_delay_msec(void) +{ + if (halt_delay == 0 || !(system_state == SYSTEM_HALT + || system_state == SYSTEM_POWER_OFF + || system_state == SYSTEM_RESTART)) + return; + + mdelay(halt_delay); +} + +module_param(halt_delay, int, S_IRUGO | S_IWUSR); +#else +static inline void halt_delay_msec(void) +{ +} +#endif /* * Commands to do_syslog: * @@ -649,6 +669,7 @@ 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/lib/Kconfig.debug 2009-05-12 11:27:22.000000000 +0800 +++ linux-2.6/lib/Kconfig.debug 2009-06-02 17:50:15.000000000 +0800 @@ -647,6 +647,16 @@ config BOOT_PRINTK_DELAY BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect what it believes to be lockup conditions.
+config HALT_PRINTK_DELAY + bool "Delay halt/poweroff/restart printk message by N milliseconds" + depends on DEBUG_KERNEL && PRINTK && SYSFS + default n + help + This build option allows you to read kernel messages in + halt/poweroff/restart phase by inserting a short delay after + each one. The delay is specified in milliseconds on the + module parameter: /sys/module/printk/halt_delay. + config RCU_TORTURE_TEST tristate "torture tests for RCU" depends on DEBUG_KERNEL
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