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>

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 90a440cbd6de32786150a9f865d800d02fa76b4b..65548eff029e4d61360d5a29626bce3f64ffaae1 100644 (file)
--- 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;
 }