rcu: Integrate rcu_dereference_check() message into lockdep

Make rcu_dereference_check() print the list of held locks in
addition to the stack dump to ease debugging.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1266887105-1528-3-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 18 insertions, 0 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index c62ec14609b9..672c436946ce 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3809,3 +3809,21 @@ void lockdep_sys_exit(void)
                 lockdep_print_held_locks(curr);
         }
 }
+
+void lockdep_rcu_dereference(const char *file, const int line)
+{
+        struct task_struct *curr = current;
+
+        if (!debug_locks_off())
+                return;
+        printk("\n==============================================\n");
+        printk(  "[ BUG: Unsafe rcu_dereference_check() usage! ]\n");
+        printk(  "----------------------------------------------\n");
+        printk("%s:%d invoked rcu_dereference_check() without protection!\n",
+                        file, line);
+        printk("\nother info that might help us debug this:\n\n");
+        lockdep_print_held_locks(curr);
+        printk("\nstack backtrace:\n");
+        dump_stack();
+}
+EXPORT_SYMBOL_GPL(lockdep_rcu_dereference);