lockdep: handle chains involving classes defined in modules

Solve this by marking the classes as unused and not printing information
about the unused classes.

Reported-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Rabin Vincent <rabin@rab.in>
Acked-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 4 insertions, 0 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 410c3365ad8f..ab933fecd2a1 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3176,6 +3176,7 @@ static void zap_class(struct lock_class *class)
         list_del_rcu(&class->hash_entry);
         list_del_rcu(&class->lock_entry);
 
+        class->key = NULL;
 }
 
 static inline int within(const void *addr, void *start, unsigned long size)
diff --git a/kernel/lockdep_proc.c b/kernel/lockdep_proc.c
index 6252ff799d19..fa19aee604c2 100644
--- a/kernel/lockdep_proc.c
+++ b/kernel/lockdep_proc.c
@@ -201,6 +201,9 @@ static int lc_show(struct seq_file *m, void *v)
 
         for (i = 0; i < chain->depth; i++) {
                 class = lock_chain_get_class(chain, i);
+                if (!class->key)
+                        continue;
+
                 seq_printf(m, "[%p] ", class->key);
                 print_name(m, class);
                 seq_puts(m, "\n");