From bfe8df3d314bddf30758bd738e0087e80964760c Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Tue, 16 Oct 2007 01:23:46 -0700 Subject: slow down printk during boot Optionally add a boot delay after each kernel printk() call, crudely measured in milliseconds, with a maximum delay of 10 seconds per printk. Enable CONFIG_BOOT_PRINTK_DELAY=y and then add (e.g.): "lpj=loops_per_jiffy boot_delay=100" to the kernel command line. It has been useful in cases like "during boot, my machine just reboots or the screen goes black" by slowing down printk, (and adding initcall_debug), we can usually see the last thing that happened before the lights went out which is usually a valuable clue. [akpm@linux-foundation.org: not all architectures implement CONFIG_HZ] [akpm@linux-foundation.org: fix lots of stuff] [bunk@stusta.de: kernel/printk.c: make 2 variables static] [heiko.carstens@de.ibm.com: fix slow down printk on boot compile error] Signed-off-by: Randy Dunlap Signed-off-by: Dave Jones Signed-off-by: Adrian Bunk Signed-off-by: Heiko Carstens Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/jiffies.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/jiffies.h') diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h index e757a74b9d17..8b080024bbc1 100644 --- a/include/linux/jiffies.h +++ b/include/linux/jiffies.h @@ -148,6 +148,8 @@ static inline u64 get_jiffies_64(void) */ #define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1) +extern unsigned long preset_lpj; + /* * We want to do realistic conversions of time so we need to use the same * values the update wall clock code uses as the jiffies size. This value -- cgit v1.2.3-59-g8ed1b