[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>

1 files changed, 17 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index dec5827c7742..5fb31bede103 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -176,6 +176,23 @@ extern void trap_init(void);
 extern void update_process_times(int user);
 extern void scheduler_tick(void);
 
+#ifdef CONFIG_DETECT_SOFTLOCKUP
+extern void softlockup_tick(struct pt_regs *regs);
+extern void spawn_softlockup_task(void);
+extern void touch_softlockup_watchdog(void);
+#else
+static inline void softlockup_tick(struct pt_regs *regs)
+{
+}
+static inline void spawn_softlockup_task(void)
+{
+}
+static inline void touch_softlockup_watchdog(void)
+{
+}
+#endif
+
+
 /* Attach to any functions which should be ignored in wchan output. */
 #define __sched         __attribute__((__section__(".sched.text")))
 /* Is this address in the __sched functions? */