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authorRandy Dunlap <rdunlap@xenotime.net>2007-10-16 12:23:46 +0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-16 20:42:49 +0400
commitbfe8df3d314bddf30758bd738e0087e80964760c (patch)
treed04db4fb2592e2d416073681903f05f5b30f204b /include/linux/jiffies.h
parent1bcf548293aef19b0797348332cf1dfbf2116cef (diff)
downloadlinux-bfe8df3d314bddf30758bd738e0087e80964760c.tar.xz
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 <rdunlap@xenotime.net> Signed-off-by: Dave Jones <davej@redhat.com> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/jiffies.h')
-rw-r--r--include/linux/jiffies.h2
1 files changed, 2 insertions, 0 deletions
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