1 files changed, 239 insertions, 56 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index d38a64362973..1aa91fd6b06e 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -124,6 +124,15 @@ static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
 unsigned long nr_lock_classes;
 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
 
+static inline struct lock_class *hlock_class(struct held_lock *hlock)
+{
+        if (!hlock->class_idx) {
+                DEBUG_LOCKS_WARN_ON(1);
+                return NULL;
+        }
+        return lock_classes + hlock->class_idx - 1;
+}
+
 #ifdef CONFIG_LOCK_STAT
 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], lock_stats);
 
@@ -222,7 +231,7 @@ static void lock_release_holdtime(struct held_lock *hlock)
 
         holdtime = sched_clock() - hlock->holdtime_stamp;
 
-        stats = get_lock_stats(hlock->class);
+        stats = get_lock_stats(hlock_class(hlock));
         if (hlock->read)
                 lock_time_inc(&stats->read_holdtime, holdtime);
         else
@@ -372,6 +381,19 @@ unsigned int nr_process_chains;
 unsigned int max_lockdep_depth;
 unsigned int max_recursion_depth;
 
+static unsigned int lockdep_dependency_gen_id;
+
+static bool lockdep_dependency_visit(struct lock_class *source,
+                                     unsigned int depth)
+{
+        if (!depth)
+                lockdep_dependency_gen_id++;
+        if (source->dep_gen_id == lockdep_dependency_gen_id)
+                return true;
+        source->dep_gen_id = lockdep_dependency_gen_id;
+        return false;
+}
+
 #ifdef CONFIG_DEBUG_LOCKDEP
 /*
  * We cannot printk in early bootup code. Not even early_printk()
@@ -505,7 +527,7 @@ static void print_lockdep_cache(struct lockdep_map *lock)
 
 static void print_lock(struct held_lock *hlock)
 {
-        print_lock_name(hlock->class);
+        print_lock_name(hlock_class(hlock));
         printk(", at: ");
         print_ip_sym(hlock->acquire_ip);
 }
@@ -558,6 +580,9 @@ static void print_lock_dependencies(struct lock_class *class, int depth)
 {
         struct lock_list *entry;
 
+        if (lockdep_dependency_visit(class, depth))
+                return;
+
         if (DEBUG_LOCKS_WARN_ON(depth >= 20))
                 return;
 
@@ -932,7 +957,7 @@ static noinline int print_circular_bug_tail(void)
         if (debug_locks_silent)
                 return 0;
 
-        this.class = check_source->class;
+        this.class = hlock_class(check_source);
         if (!save_trace(&this.trace))
                 return 0;
 
@@ -959,6 +984,67 @@ static int noinline print_infinite_recursion_bug(void)
         return 0;
 }
 
+unsigned long __lockdep_count_forward_deps(struct lock_class *class,
+                                           unsigned int depth)
+{
+        struct lock_list *entry;
+        unsigned long ret = 1;
+
+        if (lockdep_dependency_visit(class, depth))
+                return 0;
+
+        /*
+         * Recurse this class's dependency list:
+         */
+        list_for_each_entry(entry, &class->locks_after, entry)
+                ret += __lockdep_count_forward_deps(entry->class, depth + 1);
+
+        return ret;
+}
+
+unsigned long lockdep_count_forward_deps(struct lock_class *class)
+{
+        unsigned long ret, flags;
+
+        local_irq_save(flags);
+        __raw_spin_lock(&lockdep_lock);
+        ret = __lockdep_count_forward_deps(class, 0);
+        __raw_spin_unlock(&lockdep_lock);
+        local_irq_restore(flags);
+
+        return ret;
+}
+
+unsigned long __lockdep_count_backward_deps(struct lock_class *class,
+                                            unsigned int depth)
+{
+        struct lock_list *entry;
+        unsigned long ret = 1;
+
+        if (lockdep_dependency_visit(class, depth))
+                return 0;
+        /*
+         * Recurse this class's dependency list:
+         */
+        list_for_each_entry(entry, &class->locks_before, entry)
+                ret += __lockdep_count_backward_deps(entry->class, depth + 1);
+
+        return ret;
+}
+
+unsigned long lockdep_count_backward_deps(struct lock_class *class)
+{
+        unsigned long ret, flags;
+
+        local_irq_save(flags);
+        __raw_spin_lock(&lockdep_lock);
+        ret = __lockdep_count_backward_deps(class, 0);
+        __raw_spin_unlock(&lockdep_lock);
+        local_irq_restore(flags);
+
+        return ret;
+}
+
 /*
  * Prove that the dependency graph starting at <entry> can not
  * lead to <target>. Print an error and return 0 if it does.
@@ -968,6 +1054,9 @@ check_noncircular(struct lock_class *source, unsigned int depth)
 {
         struct lock_list *entry;
 
+        if (lockdep_dependency_visit(source, depth))
+                return 1;
+
         debug_atomic_inc(&nr_cyclic_check_recursions);
         if (depth > max_recursion_depth)
                 max_recursion_depth = depth;
@@ -977,7 +1066,7 @@ check_noncircular(struct lock_class *source, unsigned int depth)
          * Check this lock's dependency list:
          */
         list_for_each_entry(entry, &source->locks_after, entry) {
-                if (entry->class == check_target->class)
+                if (entry->class == hlock_class(check_target))
                         return print_circular_bug_header(entry, depth+1);
                 debug_atomic_inc(&nr_cyclic_checks);
                 if (!check_noncircular(entry->class, depth+1))
@@ -1011,6 +1100,9 @@ find_usage_forwards(struct lock_class *source, unsigned int depth)
         struct lock_list *entry;
         int ret;
 
+        if (lockdep_dependency_visit(source, depth))
+                return 1;
+
         if (depth > max_recursion_depth)
                 max_recursion_depth = depth;
         if (depth >= RECURSION_LIMIT)
@@ -1050,6 +1142,9 @@ find_usage_backwards(struct lock_class *source, unsigned int depth)
         struct lock_list *entry;
         int ret;
 
+        if (lockdep_dependency_visit(source, depth))
+                return 1;
+
         if (!__raw_spin_is_locked(&lockdep_lock))
                 return DEBUG_LOCKS_WARN_ON(1);
 
@@ -1064,6 +1159,11 @@ find_usage_backwards(struct lock_class *source, unsigned int depth)
                 return 2;
         }
 
+        if (!source && debug_locks_off_graph_unlock()) {
+                WARN_ON(1);
+                return 0;
+        }
+
         /*
          * Check this lock's dependency list:
          */
@@ -1103,9 +1203,9 @@ print_bad_irq_dependency(struct task_struct *curr,
         printk("\nand this task is already holding:\n");
         print_lock(prev);
         printk("which would create a new lock dependency:\n");
-        print_lock_name(prev->class);
+        print_lock_name(hlock_class(prev));
         printk(" ->");
-        print_lock_name(next->class);
+        print_lock_name(hlock_class(next));
         printk("\n");
 
         printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
@@ -1146,12 +1246,12 @@ check_usage(struct task_struct *curr, struct held_lock *prev,
 
         find_usage_bit = bit_backwards;
         /* fills in <backwards_match> */
-        ret = find_usage_backwards(prev->class, 0);
+        ret = find_usage_backwards(hlock_class(prev), 0);
         if (!ret || ret == 1)
                 return ret;
 
         find_usage_bit = bit_forwards;
-        ret = find_usage_forwards(next->class, 0);
+        ret = find_usage_forwards(hlock_class(next), 0);
         if (!ret || ret == 1)
                 return ret;
         /* ret == 2 */
@@ -1272,18 +1372,32 @@ check_deadlock(struct task_struct *curr, struct held_lock *next,
                struct lockdep_map *next_instance, int read)
 {
         struct held_lock *prev;
+        struct held_lock *nest = NULL;
         int i;
 
         for (i = 0; i < curr->lockdep_depth; i++) {
                 prev = curr->held_locks + i;
-                if (prev->class != next->class)
+
+                if (prev->instance == next->nest_lock)
+                        nest = prev;
+
+                if (hlock_class(prev) != hlock_class(next))
                         continue;
+
                 /*
                  * Allow read-after-read recursion of the same
                  * lock class (i.e. read_lock(lock)+read_lock(lock)):
                  */
                 if ((read == 2) && prev->read)
                         return 2;
+
+                /*
+                 * We're holding the nest_lock, which serializes this lock's
+                 * nesting behaviour.
+                 */
+                if (nest)
+                        return 2;
+
                 return print_deadlock_bug(curr, prev, next);
         }
         return 1;
@@ -1329,7 +1443,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
          */
         check_source = next;
         check_target = prev;
-        if (!(check_noncircular(next->class, 0)))
+        if (!(check_noncircular(hlock_class(next), 0)))
                 return print_circular_bug_tail();
 
         if (!check_prev_add_irq(curr, prev, next))
@@ -1353,8 +1467,8 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
          *  chains - the second one will be new, but L1 already has
          *  L2 added to its dependency list, due to the first chain.)
          */
-        list_for_each_entry(entry, &prev->class->locks_after, entry) {
-                if (entry->class == next->class) {
+        list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
+                if (entry->class == hlock_class(next)) {
                         if (distance == 1)
                                 entry->distance = 1;
                         return 2;
@@ -1365,26 +1479,28 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
          * Ok, all validations passed, add the new lock
          * to the previous lock's dependency list:
          */
-        ret = add_lock_to_list(prev->class, next->class,
-                               &prev->class->locks_after, next->acquire_ip, distance);
+        ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
+                               &hlock_class(prev)->locks_after,
+                               next->acquire_ip, distance);
 
         if (!ret)
                 return 0;
 
-        ret = add_lock_to_list(next->class, prev->class,
-                               &next->class->locks_before, next->acquire_ip, distance);
+        ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
+                               &hlock_class(next)->locks_before,
+                               next->acquire_ip, distance);
         if (!ret)
                 return 0;
 
         /*
          * Debugging printouts:
          */
-        if (verbose(prev->class) || verbose(next->class)) {
+        if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
                 graph_unlock();
                 printk("\n new dependency: ");
-                print_lock_name(prev->class);
+                print_lock_name(hlock_class(prev));
                 printk(" => ");
-                print_lock_name(next->class);
+                print_lock_name(hlock_class(next));
                 printk("\n");
                 dump_stack();
                 return graph_lock();
@@ -1481,7 +1597,7 @@ static inline int lookup_chain_cache(struct task_struct *curr,
                                      struct held_lock *hlock,
                                      u64 chain_key)
 {
-        struct lock_class *class = hlock->class;
+        struct lock_class *class = hlock_class(hlock);
         struct list_head *hash_head = chainhashentry(chain_key);
         struct lock_chain *chain;
         struct held_lock *hlock_curr, *hlock_next;
@@ -1554,7 +1670,7 @@ cache_hit:
         if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
                 chain->base = cn;
                 for (j = 0; j < chain->depth - 1; j++, i++) {
-                        int lock_id = curr->held_locks[i].class - lock_classes;
+                        int lock_id = curr->held_locks[i].class_idx - 1;
                         chain_hlocks[chain->base + j] = lock_id;
                 }
                 chain_hlocks[chain->base + j] = class - lock_classes;
@@ -1650,7 +1766,7 @@ static void check_chain_key(struct task_struct *curr)
                         WARN_ON(1);
                         return;
                 }
-                id = hlock->class - lock_classes;
+                id = hlock->class_idx - 1;
                 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
                         return;
 
@@ -1695,7 +1811,7 @@ print_usage_bug(struct task_struct *curr, struct held_lock *this,
         print_lock(this);
 
         printk("{%s} state was registered at:\n", usage_str[prev_bit]);
-        print_stack_trace(this->class->usage_traces + prev_bit, 1);
+        print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
 
         print_irqtrace_events(curr);
         printk("\nother info that might help us debug this:\n");
@@ -1714,7 +1830,7 @@ static inline int
 valid_state(struct task_struct *curr, struct held_lock *this,
             enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
 {
-        if (unlikely(this->class->usage_mask & (1 << bad_bit)))
+        if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
                 return print_usage_bug(curr, this, bad_bit, new_bit);
         return 1;
 }
@@ -1753,7 +1869,7 @@ print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
         lockdep_print_held_locks(curr);
 
         printk("\nthe first lock's dependencies:\n");
-        print_lock_dependencies(this->class, 0);
+        print_lock_dependencies(hlock_class(this), 0);
 
         printk("\nthe second lock's dependencies:\n");
         print_lock_dependencies(other, 0);
@@ -1776,7 +1892,7 @@ check_usage_forwards(struct task_struct *curr, struct held_lock *this,
 
         find_usage_bit = bit;
         /* fills in <forwards_match> */
-        ret = find_usage_forwards(this->class, 0);
+        ret = find_usage_forwards(hlock_class(this), 0);
         if (!ret || ret == 1)
                 return ret;
 
@@ -1795,7 +1911,7 @@ check_usage_backwards(struct task_struct *curr, struct held_lock *this,
 
         find_usage_bit = bit;
         /* fills in <backwards_match> */
-        ret = find_usage_backwards(this->class, 0);
+        ret = find_usage_backwards(hlock_class(this), 0);
         if (!ret || ret == 1)
                 return ret;
 
@@ -1861,7 +1977,7 @@ static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
                                 LOCK_ENABLED_HARDIRQS_READ, "hard-read"))
                         return 0;
 #endif
-                if (hardirq_verbose(this->class))
+                if (hardirq_verbose(hlock_class(this)))
                         ret = 2;
                 break;
         case LOCK_USED_IN_SOFTIRQ:
@@ -1886,7 +2002,7 @@ static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
                                 LOCK_ENABLED_SOFTIRQS_READ, "soft-read"))
                         return 0;
 #endif
-                if (softirq_verbose(this->class))
+                if (softirq_verbose(hlock_class(this)))
                         ret = 2;
                 break;
         case LOCK_USED_IN_HARDIRQ_READ:
@@ -1899,7 +2015,7 @@ static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
                 if (!check_usage_forwards(curr, this,
                                           LOCK_ENABLED_HARDIRQS, "hard"))
                         return 0;
-                if (hardirq_verbose(this->class))
+                if (hardirq_verbose(hlock_class(this)))
                         ret = 2;
                 break;
         case LOCK_USED_IN_SOFTIRQ_READ:
@@ -1912,7 +2028,7 @@ static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
                 if (!check_usage_forwards(curr, this,
                                           LOCK_ENABLED_SOFTIRQS, "soft"))
                         return 0;
-                if (softirq_verbose(this->class))
+                if (softirq_verbose(hlock_class(this)))
                         ret = 2;
                 break;
         case LOCK_ENABLED_HARDIRQS:
@@ -1938,7 +2054,7 @@ static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
                                    LOCK_USED_IN_HARDIRQ_READ, "hard-read"))
                         return 0;
 #endif
-                if (hardirq_verbose(this->class))
+                if (hardirq_verbose(hlock_class(this)))
                         ret = 2;
                 break;
         case LOCK_ENABLED_SOFTIRQS:
@@ -1964,7 +2080,7 @@ static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
                                    LOCK_USED_IN_SOFTIRQ_READ, "soft-read"))
                         return 0;
 #endif
-                if (softirq_verbose(this->class))
+                if (softirq_verbose(hlock_class(this)))
                         ret = 2;
                 break;
         case LOCK_ENABLED_HARDIRQS_READ:
@@ -1979,7 +2095,7 @@ static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
                                            LOCK_USED_IN_HARDIRQ, "hard"))
                         return 0;
 #endif
-                if (hardirq_verbose(this->class))
+                if (hardirq_verbose(hlock_class(this)))
                         ret = 2;
                 break;
         case LOCK_ENABLED_SOFTIRQS_READ:
@@ -1994,7 +2110,7 @@ static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
                                            LOCK_USED_IN_SOFTIRQ, "soft"))
                         return 0;
 #endif
-                if (softirq_verbose(this->class))
+                if (softirq_verbose(hlock_class(this)))
                         ret = 2;
                 break;
         default:
@@ -2310,7 +2426,7 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
          * If already set then do not dirty the cacheline,
          * nor do any checks:
          */
-        if (likely(this->class->usage_mask & new_mask))
+        if (likely(hlock_class(this)->usage_mask & new_mask))
                 return 1;
 
         if (!graph_lock())
@@ -2318,14 +2434,14 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
         /*
          * Make sure we didnt race:
          */
-        if (unlikely(this->class->usage_mask & new_mask)) {
+        if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
                 graph_unlock();
                 return 1;
         }
 
-        this->class->usage_mask |= new_mask;
+        hlock_class(this)->usage_mask |= new_mask;
 
-        if (!save_trace(this->class->usage_traces + new_bit))
+        if (!save_trace(hlock_class(this)->usage_traces + new_bit))
                 return 0;
 
         switch (new_bit) {
@@ -2405,7 +2521,7 @@ EXPORT_SYMBOL_GPL(lockdep_init_map);
  */
 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
                           int trylock, int read, int check, int hardirqs_off,
-                          unsigned long ip)
+                          struct lockdep_map *nest_lock, unsigned long ip)
 {
         struct task_struct *curr = current;
         struct lock_class *class = NULL;
@@ -2459,10 +2575,12 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
                 return 0;
 
         hlock = curr->held_locks + depth;
-
-        hlock->class = class;
+        if (DEBUG_LOCKS_WARN_ON(!class))
+                return 0;
+        hlock->class_idx = class - lock_classes + 1;
         hlock->acquire_ip = ip;
         hlock->instance = lock;
+        hlock->nest_lock = nest_lock;
         hlock->trylock = trylock;
         hlock->read = read;
         hlock->check = check;
@@ -2574,6 +2692,55 @@ static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
         return 1;
 }
 
+static int
+__lock_set_subclass(struct lockdep_map *lock,
+                    unsigned int subclass, unsigned long ip)
+{
+        struct task_struct *curr = current;
+        struct held_lock *hlock, *prev_hlock;
+        struct lock_class *class;
+        unsigned int depth;
+        int i;
+
+        depth = curr->lockdep_depth;
+        if (DEBUG_LOCKS_WARN_ON(!depth))
+                return 0;
+
+        prev_hlock = NULL;
+        for (i = depth-1; i >= 0; i--) {
+                hlock = curr->held_locks + i;
+                /*
+                 * We must not cross into another context:
+                 */
+                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
+                        break;
+                if (hlock->instance == lock)
+                        goto found_it;
+                prev_hlock = hlock;
+        }
+        return print_unlock_inbalance_bug(curr, lock, ip);
+
+found_it:
+        class = register_lock_class(lock, subclass, 0);
+        hlock->class_idx = class - lock_classes + 1;
+
+        curr->lockdep_depth = i;
+        curr->curr_chain_key = hlock->prev_chain_key;
+
+        for (; i < depth; i++) {
+                hlock = curr->held_locks + i;
+                if (!__lock_acquire(hlock->instance,
+                        hlock_class(hlock)->subclass, hlock->trylock,
+                                hlock->read, hlock->check, hlock->hardirqs_off,
+                                hlock->nest_lock, hlock->acquire_ip))
+                        return 0;
+        }
+
+        if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
+                return 0;
+        return 1;
+}
+
 /*
  * Remove the lock to the list of currently held locks in a
  * potentially non-nested (out of order) manner. This is a
@@ -2624,9 +2791,9 @@ found_it:
         for (i++; i < depth; i++) {
                 hlock = curr->held_locks + i;
                 if (!__lock_acquire(hlock->instance,
-                        hlock->class->subclass, hlock->trylock,
+                        hlock_class(hlock)->subclass, hlock->trylock,
                                 hlock->read, hlock->check, hlock->hardirqs_off,
-                                hlock->acquire_ip))
+                                hlock->nest_lock, hlock->acquire_ip))
                         return 0;
         }
 
@@ -2669,7 +2836,7 @@ static int lock_release_nested(struct task_struct *curr,
 
 #ifdef CONFIG_DEBUG_LOCKDEP
         hlock->prev_chain_key = 0;
-        hlock->class = NULL;
+        hlock->class_idx = 0;
         hlock->acquire_ip = 0;
         hlock->irq_context = 0;
 #endif
@@ -2738,18 +2905,36 @@ static void check_flags(unsigned long flags)
 #endif
 }
 
+void
+lock_set_subclass(struct lockdep_map *lock,
+                  unsigned int subclass, unsigned long ip)
+{
+        unsigned long flags;
+
+        if (unlikely(current->lockdep_recursion))
+                return;
+
+        raw_local_irq_save(flags);
+        current->lockdep_recursion = 1;
+        check_flags(flags);
+        if (__lock_set_subclass(lock, subclass, ip))
+                check_chain_key(current);
+        current->lockdep_recursion = 0;
+        raw_local_irq_restore(flags);
+}
+
+EXPORT_SYMBOL_GPL(lock_set_subclass);
+
 /*
  * We are not always called with irqs disabled - do that here,
  * and also avoid lockdep recursion:
  */
 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
-                          int trylock, int read, int check, unsigned long ip)
+                          int trylock, int read, int check,
+                          struct lockdep_map *nest_lock, unsigned long ip)
 {
         unsigned long flags;
 
-        if (unlikely(!lock_stat && !prove_locking))
-                return;
-
         if (unlikely(current->lockdep_recursion))
                 return;
 
@@ -2758,7 +2943,7 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 
         current->lockdep_recursion = 1;
         __lock_acquire(lock, subclass, trylock, read, check,
-                       irqs_disabled_flags(flags), ip);
+                       irqs_disabled_flags(flags), nest_lock, ip);
         current->lockdep_recursion = 0;
         raw_local_irq_restore(flags);
 }
@@ -2770,9 +2955,6 @@ void lock_release(struct lockdep_map *lock, int nested,
 {
         unsigned long flags;
 
-        if (unlikely(!lock_stat && !prove_locking))
-                return;
-
         if (unlikely(current->lockdep_recursion))
                 return;
 
@@ -2845,9 +3027,9 @@ __lock_contended(struct lockdep_map *lock, unsigned long ip)
 found_it:
         hlock->waittime_stamp = sched_clock();
 
-        point = lock_contention_point(hlock->class, ip);
+        point = lock_contention_point(hlock_class(hlock), ip);
 
-        stats = get_lock_stats(hlock->class);
+        stats = get_lock_stats(hlock_class(hlock));
         if (point < ARRAY_SIZE(stats->contention_point))
                 stats->contention_point[i]++;
         if (lock->cpu != smp_processor_id())
@@ -2893,7 +3075,7 @@ found_it:
                 hlock->holdtime_stamp = now;
         }
 
-        stats = get_lock_stats(hlock->class);
+        stats = get_lock_stats(hlock_class(hlock));
         if (waittime) {
                 if (hlock->read)
                         lock_time_inc(&stats->read_waittime, waittime);
@@ -2988,6 +3170,7 @@ static void zap_class(struct lock_class *class)
         list_del_rcu(&class->hash_entry);
         list_del_rcu(&class->lock_entry);
 
+        class->key = NULL;
 }
 
 static inline int within(const void *addr, void *start, unsigned long size)