lockdep: update lockdep_recursion on graph_lock

With the introduction of ftrace, it is possible to recurse into
the lockdep functions via the mcount call. To prevent possible
lockups, updating the lockdep_recursion counter on grabbing the internal
lockdep_lock should prevent deadlocks.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 90a440cbd6de..65548eff029e 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -82,6 +82,8 @@ static int graph_lock(void)
                 __raw_spin_unlock(&lockdep_lock);
                 return 0;
         }
+        /* prevent any recursions within lockdep from causing deadlocks */
+        current->lockdep_recursion++;
         return 1;
 }
 
@@ -90,6 +92,7 @@ static inline int graph_unlock(void)
         if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
                 return DEBUG_LOCKS_WARN_ON(1);
 
+        current->lockdep_recursion--;
         __raw_spin_unlock(&lockdep_lock);
         return 0;
 }