[PATCH] lockdep: better lock debugging

Generic lock debugging:

 - generalized lock debugging framework. For example, a bug in one lock
   subsystem turns off debugging in all lock subsystems.

 - got rid of the caller address passing (__IP__/__IP_DECL__/etc.) from
   the mutex/rtmutex debugging code: it caused way too much prototype
   hackery, and lockdep will give the same information anyway.

 - ability to do silent tests

 - check lock freeing in vfree too.

 - more finegrained debugging options, to allow distributions to
   turn off more expensive debugging features.

There's no separate 'held mutexes' list anymore - but there's a 'held locks'
stack within lockdep, which unifies deadlock detection across all lock
classes.  (this is independent of the lockdep validation stuff - lockdep first
checks whether we are holding a lock already)

Here are the current debugging options:

CONFIG_DEBUG_MUTEXES=y
CONFIG_DEBUG_LOCK_ALLOC=y

which do:

 config DEBUG_MUTEXES
          bool "Mutex debugging, basic checks"

 config DEBUG_LOCK_ALLOC
         bool "Detect incorrect freeing of live mutexes"

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 11 insertions, 5 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index d5e3707..48c1faa 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -30,6 +30,7 @@
 #include <linux/capability.h>
 #include <linux/completion.h>
 #include <linux/kernel_stat.h>
+#include <linux/debug_locks.h>
 #include <linux/security.h>
 #include <linux/notifier.h>
 #include <linux/profile.h>
@@ -3142,12 +3143,13 @@ void fastcall add_preempt_count(int val)
 	/*
 	 * Underflow?
 	 */
-	BUG_ON((preempt_count() < 0));
+	if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
+		return;
 	preempt_count() += val;
 	/*
 	 * Spinlock count overflowing soon?
 	 */
-	BUG_ON((preempt_count() & PREEMPT_MASK) >= PREEMPT_MASK-10);
+	DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >= PREEMPT_MASK-10);
 }
 EXPORT_SYMBOL(add_preempt_count);
 
@@ -3156,11 +3158,15 @@ void fastcall sub_preempt_count(int val)
 	/*
 	 * Underflow?
 	 */
-	BUG_ON(val > preempt_count());
+	if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
+		return;
 	/*
 	 * Is the spinlock portion underflowing?
 	 */
-	BUG_ON((val < PREEMPT_MASK) && !(preempt_count() & PREEMPT_MASK));
+	if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
+			!(preempt_count() & PREEMPT_MASK)))
+		return;
+
 	preempt_count() -= val;
 }
 EXPORT_SYMBOL(sub_preempt_count);
@@ -4690,7 +4696,7 @@ void show_state(void)
 	} while_each_thread(g, p);
 
 	read_unlock(&tasklist_lock);
-	mutex_debug_show_all_locks();
+	debug_show_all_locks();
 }
 
 /**