2 files changed, 90 insertions, 0 deletions

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 066ba4157541..c5b6b5830acf 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -255,6 +255,7 @@ struct held_lock {
         unsigned int check:1;       /* see lock_acquire() comment */
         unsigned int hardirqs_off:1;
         unsigned int references:12;                                     /* 32 bits */
+        unsigned int pin_count;
 };
 
 /*
@@ -354,6 +355,9 @@ extern void lockdep_set_current_reclaim_state(gfp_t gfp_mask);
 extern void lockdep_clear_current_reclaim_state(void);
 extern void lockdep_trace_alloc(gfp_t mask);
 
+extern void lock_pin_lock(struct lockdep_map *lock);
+extern void lock_unpin_lock(struct lockdep_map *lock);
+
 # define INIT_LOCKDEP                           .lockdep_recursion = 0, .lockdep_reclaim_gfp = 0,
 
 #define lockdep_depth(tsk)      (debug_locks ? (tsk)->lockdep_depth : 0)
@@ -368,6 +372,9 @@ extern void lockdep_trace_alloc(gfp_t mask);
 
 #define lockdep_recursing(tsk)  ((tsk)->lockdep_recursion)
 
+#define lockdep_pin_lock(l)             lock_pin_lock(&(l)->dep_map)
+#define lockdep_unpin_lock(l)   lock_unpin_lock(&(l)->dep_map)
+
 #else /* !CONFIG_LOCKDEP */
 
 static inline void lockdep_off(void)
@@ -420,6 +427,9 @@ struct lock_class_key { };
 
 #define lockdep_recursing(tsk)                  (0)
 
+#define lockdep_pin_lock(l)                             do { (void)(l); } while (0)
+#define lockdep_unpin_lock(l)                   do { (void)(l); } while (0)
+
 #endif /* !LOCKDEP */
 
 #ifdef CONFIG_LOCK_STAT
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index a266d5165b63..18f9f434d17e 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3157,6 +3157,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
         hlock->waittime_stamp = 0;
         hlock->holdtime_stamp = lockstat_clock();
 #endif
+        hlock->pin_count = 0;
 
         if (check && !mark_irqflags(curr, hlock))
                 return 0;
@@ -3403,6 +3404,8 @@ found_it:
         if (hlock->instance == lock)
                 lock_release_holdtime(hlock);
 
+        WARN(hlock->pin_count, "releasing a pinned lock\n");
+
         if (hlock->references) {
                 hlock->references--;
                 if (hlock->references) {
@@ -3459,6 +3462,49 @@ static int __lock_is_held(struct lockdep_map *lock)
         return 0;
 }
 
+static void __lock_pin_lock(struct lockdep_map *lock)
+{
+        struct task_struct *curr = current;
+        int i;
+
+        if (unlikely(!debug_locks))
+                return;
+
+        for (i = 0; i < curr->lockdep_depth; i++) {
+                struct held_lock *hlock = curr->held_locks + i;
+
+                if (match_held_lock(hlock, lock)) {
+                        hlock->pin_count++;
+                        return;
+                }
+        }
+
+        WARN(1, "pinning an unheld lock\n");
+}
+
+static void __lock_unpin_lock(struct lockdep_map *lock)
+{
+        struct task_struct *curr = current;
+        int i;
+
+        if (unlikely(!debug_locks))
+                return;
+
+        for (i = 0; i < curr->lockdep_depth; i++) {
+                struct held_lock *hlock = curr->held_locks + i;
+
+                if (match_held_lock(hlock, lock)) {
+                        if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
+                                return;
+
+                        hlock->pin_count--;
+                        return;
+                }
+        }
+
+        WARN(1, "unpinning an unheld lock\n");
+}
+
 /*
  * Check whether we follow the irq-flags state precisely:
  */
@@ -3582,6 +3628,40 @@ int lock_is_held(struct lockdep_map *lock)
 }
 EXPORT_SYMBOL_GPL(lock_is_held);
 
+void lock_pin_lock(struct lockdep_map *lock)
+{
+        unsigned long flags;
+
+        if (unlikely(current->lockdep_recursion))
+                return;
+
+        raw_local_irq_save(flags);
+        check_flags(flags);
+
+        current->lockdep_recursion = 1;
+        __lock_pin_lock(lock);
+        current->lockdep_recursion = 0;
+        raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_pin_lock);
+
+void lock_unpin_lock(struct lockdep_map *lock)
+{
+        unsigned long flags;
+
+        if (unlikely(current->lockdep_recursion))
+                return;
+
+        raw_local_irq_save(flags);
+        check_flags(flags);
+
+        current->lockdep_recursion = 1;
+        __lock_unpin_lock(lock);
+        current->lockdep_recursion = 0;
+        raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_unpin_lock);
+
 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
 {
         current->lockdep_reclaim_gfp = gfp_mask;