lockdep: Introduce lockdep_assert_held()

Add a lockdep helper to validate that we indeed are the owner
of a lock.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 43 insertions, 0 deletions

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 12aabfcb45f6..a6d5e5e4d084 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -296,6 +296,10 @@ extern void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 extern void lock_release(struct lockdep_map *lock, int nested,
                          unsigned long ip);
 
+#define lockdep_is_held(lock)   lock_is_held(&(lock)->dep_map)
+
+extern int lock_is_held(struct lockdep_map *lock);
+
 extern void lock_set_class(struct lockdep_map *lock, const char *name,
                            struct lock_class_key *key, unsigned int subclass,
                            unsigned long ip);
@@ -314,6 +318,8 @@ extern void lockdep_trace_alloc(gfp_t mask);
 
 #define lockdep_depth(tsk)      (debug_locks ? (tsk)->lockdep_depth : 0)
 
+#define lockdep_assert_held(l)  WARN_ON(debug_locks && !lockdep_is_held(l))
+
 #else /* !LOCKDEP */
 
 static inline void lockdep_off(void)
@@ -358,6 +364,8 @@ struct lock_class_key { };
 
 #define lockdep_depth(tsk)      (0)
 
+#define lockdep_assert_held(l)                  do { } while (0)
+
 #endif /* !LOCKDEP */
 
 #ifdef CONFIG_LOCK_STAT
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 4b6cebe8ab31..28914a509914 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3059,6 +3059,19 @@ __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
         check_chain_key(curr);
 }
 
+static int __lock_is_held(struct lockdep_map *lock)
+{
+        struct task_struct *curr = current;
+        int i;
+
+        for (i = 0; i < curr->lockdep_depth; i++) {
+                if (curr->held_locks[i].instance == lock)
+                        return 1;
+        }
+
+        return 0;
+}
+
 /*
  * Check whether we follow the irq-flags state precisely:
  */
@@ -3160,6 +3173,26 @@ void lock_release(struct lockdep_map *lock, int nested,
 }
 EXPORT_SYMBOL_GPL(lock_release);
 
+int lock_is_held(struct lockdep_map *lock)
+{
+        unsigned long flags;
+        int ret = 0;
+
+        if (unlikely(current->lockdep_recursion))
+                return ret;
+
+        raw_local_irq_save(flags);
+        check_flags(flags);
+
+        current->lockdep_recursion = 1;
+        ret = __lock_is_held(lock);
+        current->lockdep_recursion = 0;
+        raw_local_irq_restore(flags);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(lock_is_held);
+
 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
 {
         current->lockdep_reclaim_gfp = gfp_mask;
diff --git a/kernel/sched.c b/kernel/sched.c
index 1b59e265273b..2c75f7daa439 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6609,6 +6609,8 @@ int cond_resched_lock(spinlock_t *lock)
         int resched = should_resched();
         int ret = 0;
 
+        lockdep_assert_held(lock);
+
         if (spin_needbreak(lock) || resched) {
                 spin_unlock(lock);
                 if (resched)