path: root/lib/Kconfig.debug
diff options
authorRandy Dunlap <rdunlap@xenotime.net>2007-10-16 01:23:46 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-16 09:42:49 -0700
commitbfe8df3d314bddf30758bd738e0087e80964760c (patch)
treed04db4fb2592e2d416073681903f05f5b30f204b /lib/Kconfig.debug
parentConsolidate PTRACE_DETACH (diff)
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 '')
1 files changed, 18 insertions, 0 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 396c38b3cb69..7d16e6433302 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -413,6 +413,24 @@ config FORCED_INLINING
become the default in the future, until then this option is there to
test gcc for this.
+ bool "Delay each boot printk message by N milliseconds"
+ help
+ This build option allows you to read kernel boot messages
+ by inserting a short delay after each one. The delay is
+ specified in milliseconds on the kernel command line,
+ using "boot_delay=N".
+ It is likely that you would also need to use "lpj=M" to preset
+ the "loops per jiffie" value.
+ See a previous boot log for the "lpj" value to use for your
+ system, and then set "lpj=M" before setting "boot_delay=N".
+ NOTE: Using this option may adversely affect SMP systems.
+ I.e., processors other than the first one may not boot up.
+ BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect
+ what it believes to be lockup conditions.
tristate "torture tests for RCU"
depends on DEBUG_KERNEL