[PATCH] detect soft lockups
This patch adds a new kernel debug feature: CONFIG_DETECT_SOFTLOCKUP.
When enabled then per-CPU watchdog threads are started, which try to run
once per second. If they get delayed for more than 10 seconds then a
callback from the timer interrupt detects this condition and prints out a
warning message and a stack dump (once per lockup incident). The feature
is otherwise non-intrusive, it doesnt try to unlock the box in any way, it
only gets the debug info out, automatically, and on all CPUs affected by
the lockup.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-Off-By: Matthias Urlichs <smurf@smurf.noris.de>
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 299f7f3..3754c9a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -46,6 +46,25 @@
13 => 8 KB
12 => 4 KB
+config DETECT_SOFTLOCKUP
+ bool "Detect Soft Lockups"
+ depends on DEBUG_KERNEL
+ default y
+ help
+ Say Y here to enable the kernel to detect "soft lockups",
+ which are bugs that cause the kernel to loop in kernel
+ mode for more than 10 seconds, without giving other tasks a
+ chance to run.
+
+ When a soft-lockup is detected, the kernel will print the
+ current stack trace (which you should report), but the
+ system will stay locked up. This feature has negligible
+ overhead.
+
+ (Note that "hard lockups" are separate type of bugs that
+ can be detected via the NMI-watchdog, on platforms that
+ support it.)
+
config SCHEDSTATS
bool "Collect scheduler statistics"
depends on DEBUG_KERNEL && PROC_FS