locking/lockdep: Introduce lock_class_cache_is_registered()

This patch does not change any functionality but makes the
lockdep_reset_lock() function easier to read.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: johannes.berg@intel.com
Cc: tj@kernel.org
Link: https://lkml.kernel.org/r/20181207011148.251812-11-bvanassche@acm.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index b5c8fcb..81388d0 100644 (file)
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4201,13 +4201,33 @@ void lockdep_free_key_range(void *start, unsigned long size)
         */
 }
 
-void lockdep_reset_lock(struct lockdep_map *lock)
+/*
+ * Check whether any element of the @lock->class_cache[] array refers to a
+ * registered lock class. The caller must hold either the graph lock or the
+ * RCU read lock.
+ */
+static bool lock_class_cache_is_registered(struct lockdep_map *lock)
 {
        struct lock_class *class;
        struct hlist_head *head;
-       unsigned long flags;
        int i, j;
-       int locked;
+
+       for (i = 0; i < CLASSHASH_SIZE; i++) {
+               head = classhash_table + i;
+               hlist_for_each_entry_rcu(class, head, hash_entry) {
+                       for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
+                               if (lock->class_cache[j] == class)
+                                       return true;
+               }
+       }
+       return false;
+}
+
+void lockdep_reset_lock(struct lockdep_map *lock)
+{
+       struct lock_class *class;
+       unsigned long flags;
+       int j, locked;
 
        raw_local_irq_save(flags);
 
@@ -4227,24 +4247,14 @@ void lockdep_reset_lock(struct lockdep_map *lock)
         * be gone.
         */
        locked = graph_lock();
-       for (i = 0; i < CLASSHASH_SIZE; i++) {
-               head = classhash_table + i;
-               hlist_for_each_entry_rcu(class, head, hash_entry) {
-                       int match = 0;
-
-                       for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
-                               match |= class == lock->class_cache[j];
-
-                       if (unlikely(match)) {
-                               if (debug_locks_off_graph_unlock()) {
-                                       /*
-                                        * We all just reset everything, how did it match?
-                                        */
-                                       WARN_ON(1);
-                               }
-                               goto out_restore;
-                       }
+       if (unlikely(lock_class_cache_is_registered(lock))) {
+               if (debug_locks_off_graph_unlock()) {
+                       /*
+                        * We all just reset everything, how did it match?
+                        */
+                       WARN_ON(1);
                }
+               goto out_restore;
        }
        if (locked)
                graph_unlock();