checkpatch: validate signature styles and To: and Cc: lines
[linux-2.6.git] / kernel / lockdep.c
index 367f724..3956f51 100644 (file)
@@ -146,7 +146,7 @@ static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS],
 
 static inline u64 lockstat_clock(void)
 {
-       return cpu_clock(smp_processor_id());
+       return local_clock();
 }
 
 static int lock_point(unsigned long points[], unsigned long ip)
@@ -431,20 +431,7 @@ static struct stack_trace lockdep_init_trace = {
 /*
  * Various lockdep statistics:
  */
-atomic_t chain_lookup_hits;
-atomic_t chain_lookup_misses;
-atomic_t hardirqs_on_events;
-atomic_t hardirqs_off_events;
-atomic_t redundant_hardirqs_on;
-atomic_t redundant_hardirqs_off;
-atomic_t softirqs_on_events;
-atomic_t softirqs_off_events;
-atomic_t redundant_softirqs_on;
-atomic_t redundant_softirqs_off;
-atomic_t nr_unused_locks;
-atomic_t nr_cyclic_checks;
-atomic_t nr_find_usage_forwards_checks;
-atomic_t nr_find_usage_backwards_checks;
+DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
 #endif
 
 /*
@@ -503,6 +490,18 @@ void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
        usage[i] = '\0';
 }
 
+static int __print_lock_name(struct lock_class *class)
+{
+       char str[KSYM_NAME_LEN];
+       const char *name;
+
+       name = class->name;
+       if (!name)
+               name = __get_key_name(class->key, str);
+
+       return printk("%s", name);
+}
+
 static void print_lock_name(struct lock_class *class)
 {
        char str[KSYM_NAME_LEN], usage[LOCK_USAGE_CHARS];
@@ -583,9 +582,6 @@ static int static_obj(void *obj)
        unsigned long start = (unsigned long) &_stext,
                      end   = (unsigned long) &_end,
                      addr  = (unsigned long) obj;
-#ifdef CONFIG_SMP
-       int i;
-#endif
 
        /*
         * static variable?
@@ -596,24 +592,16 @@ static int static_obj(void *obj)
        if (arch_is_kernel_data(addr))
                return 1;
 
-#ifdef CONFIG_SMP
        /*
-        * percpu var?
+        * in-kernel percpu var?
         */
-       for_each_possible_cpu(i) {
-               start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
-               end   = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
-                                       + per_cpu_offset(i);
-
-               if ((addr >= start) && (addr < end))
-                       return 1;
-       }
-#endif
+       if (is_kernel_percpu_address(addr))
+               return 1;
 
        /*
-        * module var?
+        * module static or percpu var?
         */
-       return is_module_address(addr);
+       return is_module_address(addr) || is_module_percpu_address(addr);
 }
 
 /*
@@ -663,6 +651,16 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
        }
 #endif
 
+       if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
+               debug_locks_off();
+               printk(KERN_ERR
+                       "BUG: looking up invalid subclass: %u\n", subclass);
+               printk(KERN_ERR
+                       "turning off the locking correctness validator.\n");
+               dump_stack();
+               return NULL;
+       }
+
        /*
         * Static locks do not have their class-keys yet - for them the key
         * is the lock object itself:
@@ -759,7 +757,7 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
                return NULL;
        }
        class = lock_classes + nr_lock_classes++;
-       debug_atomic_inc(&nr_unused_locks);
+       debug_atomic_inc(nr_unused_locks);
        class->key = key;
        class->name = lock->name;
        class->subclass = subclass;
@@ -798,7 +796,9 @@ out_unlock_set:
        raw_local_irq_restore(flags);
 
        if (!subclass || force)
-               lock->class_cache = class;
+               lock->class_cache[0] = class;
+       else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
+               lock->class_cache[subclass] = class;
 
        if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
                return NULL;
@@ -829,7 +829,8 @@ static struct lock_list *alloc_list_entry(void)
  * Add a new dependency to the head of the list:
  */
 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
-                           struct list_head *head, unsigned long ip, int distance)
+                           struct list_head *head, unsigned long ip,
+                           int distance, struct stack_trace *trace)
 {
        struct lock_list *entry;
        /*
@@ -840,11 +841,9 @@ static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
        if (!entry)
                return 0;
 
-       if (!save_trace(&entry->trace))
-               return 0;
-
        entry->class = this;
        entry->distance = distance;
+       entry->trace = *trace;
        /*
         * Since we never remove from the dependency list, the list can
         * be walked lockless by other CPUs, it's only allocation
@@ -1066,6 +1065,56 @@ print_circular_bug_entry(struct lock_list *target, int depth)
        return 0;
 }
 
+static void
+print_circular_lock_scenario(struct held_lock *src,
+                            struct held_lock *tgt,
+                            struct lock_list *prt)
+{
+       struct lock_class *source = hlock_class(src);
+       struct lock_class *target = hlock_class(tgt);
+       struct lock_class *parent = prt->class;
+
+       /*
+        * A direct locking problem where unsafe_class lock is taken
+        * directly by safe_class lock, then all we need to show
+        * is the deadlock scenario, as it is obvious that the
+        * unsafe lock is taken under the safe lock.
+        *
+        * But if there is a chain instead, where the safe lock takes
+        * an intermediate lock (middle_class) where this lock is
+        * not the same as the safe lock, then the lock chain is
+        * used to describe the problem. Otherwise we would need
+        * to show a different CPU case for each link in the chain
+        * from the safe_class lock to the unsafe_class lock.
+        */
+       if (parent != source) {
+               printk("Chain exists of:\n  ");
+               __print_lock_name(source);
+               printk(" --> ");
+               __print_lock_name(parent);
+               printk(" --> ");
+               __print_lock_name(target);
+               printk("\n\n");
+       }
+
+       printk(" Possible unsafe locking scenario:\n\n");
+       printk("       CPU0                    CPU1\n");
+       printk("       ----                    ----\n");
+       printk("  lock(");
+       __print_lock_name(target);
+       printk(");\n");
+       printk("                               lock(");
+       __print_lock_name(parent);
+       printk(");\n");
+       printk("                               lock(");
+       __print_lock_name(target);
+       printk(");\n");
+       printk("  lock(");
+       __print_lock_name(source);
+       printk(");\n");
+       printk("\n *** DEADLOCK ***\n\n");
+}
+
 /*
  * When a circular dependency is detected, print the
  * header first:
@@ -1109,6 +1158,7 @@ static noinline int print_circular_bug(struct lock_list *this,
 {
        struct task_struct *curr = current;
        struct lock_list *parent;
+       struct lock_list *first_parent;
        int depth;
 
        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
@@ -1122,6 +1172,7 @@ static noinline int print_circular_bug(struct lock_list *this,
        print_circular_bug_header(target, depth, check_src, check_tgt);
 
        parent = get_lock_parent(target);
+       first_parent = parent;
 
        while (parent) {
                print_circular_bug_entry(parent, --depth);
@@ -1129,6 +1180,9 @@ static noinline int print_circular_bug(struct lock_list *this,
        }
 
        printk("\nother info that might help us debug this:\n\n");
+       print_circular_lock_scenario(check_src, check_tgt,
+                                    first_parent);
+
        lockdep_print_held_locks(curr);
 
        printk("\nstack backtrace:\n");
@@ -1216,7 +1270,7 @@ check_noncircular(struct lock_list *root, struct lock_class *target,
 {
        int result;
 
-       debug_atomic_inc(&nr_cyclic_checks);
+       debug_atomic_inc(nr_cyclic_checks);
 
        result = __bfs_forwards(root, target, class_equal, target_entry);
 
@@ -1253,7 +1307,7 @@ find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
 {
        int result;
 
-       debug_atomic_inc(&nr_find_usage_forwards_checks);
+       debug_atomic_inc(nr_find_usage_forwards_checks);
 
        result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
 
@@ -1276,7 +1330,7 @@ find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
 {
        int result;
 
-       debug_atomic_inc(&nr_find_usage_backwards_checks);
+       debug_atomic_inc(nr_find_usage_backwards_checks);
 
        result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
 
@@ -1327,7 +1381,7 @@ print_shortest_lock_dependencies(struct lock_list *leaf,
                printk("\n");
 
                if (depth == 0 && (entry != root)) {
-                       printk("lockdep:%s bad BFS generated tree\n", __func__);
+                       printk("lockdep:%s bad path found in chain graph\n", __func__);
                        break;
                }
 
@@ -1338,6 +1392,62 @@ print_shortest_lock_dependencies(struct lock_list *leaf,
        return;
 }
 
+static void
+print_irq_lock_scenario(struct lock_list *safe_entry,
+                       struct lock_list *unsafe_entry,
+                       struct lock_class *prev_class,
+                       struct lock_class *next_class)
+{
+       struct lock_class *safe_class = safe_entry->class;
+       struct lock_class *unsafe_class = unsafe_entry->class;
+       struct lock_class *middle_class = prev_class;
+
+       if (middle_class == safe_class)
+               middle_class = next_class;
+
+       /*
+        * A direct locking problem where unsafe_class lock is taken
+        * directly by safe_class lock, then all we need to show
+        * is the deadlock scenario, as it is obvious that the
+        * unsafe lock is taken under the safe lock.
+        *
+        * But if there is a chain instead, where the safe lock takes
+        * an intermediate lock (middle_class) where this lock is
+        * not the same as the safe lock, then the lock chain is
+        * used to describe the problem. Otherwise we would need
+        * to show a different CPU case for each link in the chain
+        * from the safe_class lock to the unsafe_class lock.
+        */
+       if (middle_class != unsafe_class) {
+               printk("Chain exists of:\n  ");
+               __print_lock_name(safe_class);
+               printk(" --> ");
+               __print_lock_name(middle_class);
+               printk(" --> ");
+               __print_lock_name(unsafe_class);
+               printk("\n\n");
+       }
+
+       printk(" Possible interrupt unsafe locking scenario:\n\n");
+       printk("       CPU0                    CPU1\n");
+       printk("       ----                    ----\n");
+       printk("  lock(");
+       __print_lock_name(unsafe_class);
+       printk(");\n");
+       printk("                               local_irq_disable();\n");
+       printk("                               lock(");
+       __print_lock_name(safe_class);
+       printk(");\n");
+       printk("                               lock(");
+       __print_lock_name(middle_class);
+       printk(");\n");
+       printk("  <Interrupt>\n");
+       printk("    lock(");
+       __print_lock_name(safe_class);
+       printk(");\n");
+       printk("\n *** DEADLOCK ***\n\n");
+}
+
 static int
 print_bad_irq_dependency(struct task_struct *curr,
                         struct lock_list *prev_root,
@@ -1389,6 +1499,9 @@ print_bad_irq_dependency(struct task_struct *curr,
        print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
 
        printk("\nother info that might help us debug this:\n\n");
+       print_irq_lock_scenario(backwards_entry, forwards_entry,
+                               hlock_class(prev), hlock_class(next));
+
        lockdep_print_held_locks(curr);
 
        printk("\nthe dependencies between %s-irq-safe lock", irqclass);
@@ -1552,6 +1665,26 @@ static inline void inc_chains(void)
 
 #endif
 
+static void
+print_deadlock_scenario(struct held_lock *nxt,
+                            struct held_lock *prv)
+{
+       struct lock_class *next = hlock_class(nxt);
+       struct lock_class *prev = hlock_class(prv);
+
+       printk(" Possible unsafe locking scenario:\n\n");
+       printk("       CPU0\n");
+       printk("       ----\n");
+       printk("  lock(");
+       __print_lock_name(prev);
+       printk(");\n");
+       printk("  lock(");
+       __print_lock_name(next);
+       printk(");\n");
+       printk("\n *** DEADLOCK ***\n\n");
+       printk(" May be due to missing lock nesting notation\n\n");
+}
+
 static int
 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
                   struct held_lock *next)
@@ -1570,6 +1703,7 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
        print_lock(prev);
 
        printk("\nother info that might help us debug this:\n");
+       print_deadlock_scenario(next, prev);
        lockdep_print_held_locks(curr);
 
        printk("\nstack backtrace:\n");
@@ -1646,12 +1780,20 @@ check_deadlock(struct task_struct *curr, struct held_lock *next,
  */
 static int
 check_prev_add(struct task_struct *curr, struct held_lock *prev,
-              struct held_lock *next, int distance)
+              struct held_lock *next, int distance, int trylock_loop)
 {
        struct lock_list *entry;
        int ret;
        struct lock_list this;
        struct lock_list *uninitialized_var(target_entry);
+       /*
+        * Static variable, serialized by the graph_lock().
+        *
+        * We use this static variable to save the stack trace in case
+        * we call into this function multiple times due to encountering
+        * trylocks in the held lock stack.
+        */
+       static struct stack_trace trace;
 
        /*
         * Prove that the new <prev> -> <next> dependency would not
@@ -1699,20 +1841,23 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
                }
        }
 
+       if (!trylock_loop && !save_trace(&trace))
+               return 0;
+
        /*
         * Ok, all validations passed, add the new lock
         * to the previous lock's dependency list:
         */
        ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
                               &hlock_class(prev)->locks_after,
-                              next->acquire_ip, distance);
+                              next->acquire_ip, distance, &trace);
 
        if (!ret)
                return 0;
 
        ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
                               &hlock_class(next)->locks_before,
-                              next->acquire_ip, distance);
+                              next->acquire_ip, distance, &trace);
        if (!ret)
                return 0;
 
@@ -1742,6 +1887,7 @@ static int
 check_prevs_add(struct task_struct *curr, struct held_lock *next)
 {
        int depth = curr->lockdep_depth;
+       int trylock_loop = 0;
        struct held_lock *hlock;
 
        /*
@@ -1767,7 +1913,8 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
                 * added:
                 */
                if (hlock->read != 2) {
-                       if (!check_prev_add(curr, hlock, next, distance))
+                       if (!check_prev_add(curr, hlock, next,
+                                               distance, trylock_loop))
                                return 0;
                        /*
                         * Stop after the first non-trylock entry,
@@ -1790,6 +1937,7 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
                if (curr->held_locks[depth].irq_context !=
                                curr->held_locks[depth-1].irq_context)
                        break;
+               trylock_loop = 1;
        }
        return 1;
 out_bug:
@@ -1825,7 +1973,7 @@ static inline int lookup_chain_cache(struct task_struct *curr,
        struct list_head *hash_head = chainhashentry(chain_key);
        struct lock_chain *chain;
        struct held_lock *hlock_curr, *hlock_next;
-       int i, j, n, cn;
+       int i, j;
 
        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                return 0;
@@ -1836,7 +1984,7 @@ static inline int lookup_chain_cache(struct task_struct *curr,
        list_for_each_entry(chain, hash_head, entry) {
                if (chain->chain_key == chain_key) {
 cache_hit:
-                       debug_atomic_inc(&chain_lookup_hits);
+                       debug_atomic_inc(chain_lookup_hits);
                        if (very_verbose(class))
                                printk("\nhash chain already cached, key: "
                                        "%016Lx tail class: [%p] %s\n",
@@ -1885,15 +2033,9 @@ cache_hit:
        }
        i++;
        chain->depth = curr->lockdep_depth + 1 - i;
-       cn = nr_chain_hlocks;
-       while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
-               n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
-               if (n == cn)
-                       break;
-               cn = n;
-       }
-       if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
-               chain->base = cn;
+       if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
+               chain->base = nr_chain_hlocks;
+               nr_chain_hlocks += chain->depth;
                for (j = 0; j < chain->depth - 1; j++, i++) {
                        int lock_id = curr->held_locks[i].class_idx - 1;
                        chain_hlocks[chain->base + j] = lock_id;
@@ -1901,7 +2043,7 @@ cache_hit:
                chain_hlocks[chain->base + j] = class - lock_classes;
        }
        list_add_tail_rcu(&chain->entry, hash_head);
-       debug_atomic_inc(&chain_lookup_misses);
+       debug_atomic_inc(chain_lookup_misses);
        inc_chains();
 
        return 1;
@@ -2010,6 +2152,24 @@ static void check_chain_key(struct task_struct *curr)
 #endif
 }
 
+static void
+print_usage_bug_scenario(struct held_lock *lock)
+{
+       struct lock_class *class = hlock_class(lock);
+
+       printk(" Possible unsafe locking scenario:\n\n");
+       printk("       CPU0\n");
+       printk("       ----\n");
+       printk("  lock(");
+       __print_lock_name(class);
+       printk(");\n");
+       printk("  <Interrupt>\n");
+       printk("    lock(");
+       __print_lock_name(class);
+       printk(");\n");
+       printk("\n *** DEADLOCK ***\n\n");
+}
+
 static int
 print_usage_bug(struct task_struct *curr, struct held_lock *this,
                enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
@@ -2038,6 +2198,8 @@ print_usage_bug(struct task_struct *curr, struct held_lock *this,
 
        print_irqtrace_events(curr);
        printk("\nother info that might help us debug this:\n");
+       print_usage_bug_scenario(this);
+
        lockdep_print_held_locks(curr);
 
        printk("\nstack backtrace:\n");
@@ -2072,6 +2234,10 @@ print_irq_inversion_bug(struct task_struct *curr,
                        struct held_lock *this, int forwards,
                        const char *irqclass)
 {
+       struct lock_list *entry = other;
+       struct lock_list *middle = NULL;
+       int depth;
+
        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
                return 0;
 
@@ -2090,6 +2256,25 @@ print_irq_inversion_bug(struct task_struct *curr,
        printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
 
        printk("\nother info that might help us debug this:\n");
+
+       /* Find a middle lock (if one exists) */
+       depth = get_lock_depth(other);
+       do {
+               if (depth == 0 && (entry != root)) {
+                       printk("lockdep:%s bad path found in chain graph\n", __func__);
+                       break;
+               }
+               middle = entry;
+               entry = get_lock_parent(entry);
+               depth--;
+       } while (entry && entry != root && (depth >= 0));
+       if (forwards)
+               print_irq_lock_scenario(root, other,
+                       middle ? middle->class : root->class, other->class);
+       else
+               print_irq_lock_scenario(other, root,
+                       middle ? middle->class : other->class, root->class);
+
        lockdep_print_held_locks(curr);
 
        printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
@@ -2283,6 +2468,9 @@ mark_held_locks(struct task_struct *curr, enum mark_type mark)
 
                BUG_ON(usage_bit >= LOCK_USAGE_STATES);
 
+               if (hlock_class(hlock)->key == &__lockdep_no_validate__)
+                       continue;
+
                if (!mark_lock(curr, hlock, usage_bit))
                        return 0;
        }
@@ -2291,45 +2479,27 @@ mark_held_locks(struct task_struct *curr, enum mark_type mark)
 }
 
 /*
- * Debugging helper: via this flag we know that we are in
- * 'early bootup code', and will warn about any invalid irqs-on event:
- */
-static int early_boot_irqs_enabled;
-
-void early_boot_irqs_off(void)
-{
-       early_boot_irqs_enabled = 0;
-}
-
-void early_boot_irqs_on(void)
-{
-       early_boot_irqs_enabled = 1;
-}
-
-/*
  * Hardirqs will be enabled:
  */
-void trace_hardirqs_on_caller(unsigned long ip)
+static void __trace_hardirqs_on_caller(unsigned long ip)
 {
        struct task_struct *curr = current;
 
-       time_hardirqs_on(CALLER_ADDR0, ip);
-
-       if (unlikely(!debug_locks || current->lockdep_recursion))
-               return;
-
-       if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
+       if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
                return;
 
        if (unlikely(curr->hardirqs_enabled)) {
-               debug_atomic_inc(&redundant_hardirqs_on);
+               /*
+                * Neither irq nor preemption are disabled here
+                * so this is racy by nature but losing one hit
+                * in a stat is not a big deal.
+                */
+               __debug_atomic_inc(redundant_hardirqs_on);
                return;
        }
        /* we'll do an OFF -> ON transition: */
        curr->hardirqs_enabled = 1;
 
-       if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
-               return;
        if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
                return;
        /*
@@ -2349,7 +2519,22 @@ void trace_hardirqs_on_caller(unsigned long ip)
 
        curr->hardirq_enable_ip = ip;
        curr->hardirq_enable_event = ++curr->irq_events;
-       debug_atomic_inc(&hardirqs_on_events);
+       debug_atomic_inc(hardirqs_on_events);
+}
+
+void trace_hardirqs_on_caller(unsigned long ip)
+{
+       time_hardirqs_on(CALLER_ADDR0, ip);
+
+       if (unlikely(!debug_locks || current->lockdep_recursion))
+               return;
+
+       if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+               return;
+
+       current->lockdep_recursion = 1;
+       __trace_hardirqs_on_caller(ip);
+       current->lockdep_recursion = 0;
 }
 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 
@@ -2381,9 +2566,9 @@ void trace_hardirqs_off_caller(unsigned long ip)
                curr->hardirqs_enabled = 0;
                curr->hardirq_disable_ip = ip;
                curr->hardirq_disable_event = ++curr->irq_events;
-               debug_atomic_inc(&hardirqs_off_events);
+               debug_atomic_inc(hardirqs_off_events);
        } else
-               debug_atomic_inc(&redundant_hardirqs_off);
+               debug_atomic_inc(redundant_hardirqs_off);
 }
 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 
@@ -2400,24 +2585,25 @@ void trace_softirqs_on(unsigned long ip)
 {
        struct task_struct *curr = current;
 
-       if (unlikely(!debug_locks))
+       if (unlikely(!debug_locks || current->lockdep_recursion))
                return;
 
        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                return;
 
        if (curr->softirqs_enabled) {
-               debug_atomic_inc(&redundant_softirqs_on);
+               debug_atomic_inc(redundant_softirqs_on);
                return;
        }
 
+       current->lockdep_recursion = 1;
        /*
         * We'll do an OFF -> ON transition:
         */
        curr->softirqs_enabled = 1;
        curr->softirq_enable_ip = ip;
        curr->softirq_enable_event = ++curr->irq_events;
-       debug_atomic_inc(&softirqs_on_events);
+       debug_atomic_inc(softirqs_on_events);
        /*
         * We are going to turn softirqs on, so set the
         * usage bit for all held locks, if hardirqs are
@@ -2425,6 +2611,7 @@ void trace_softirqs_on(unsigned long ip)
         */
        if (curr->hardirqs_enabled)
                mark_held_locks(curr, SOFTIRQ);
+       current->lockdep_recursion = 0;
 }
 
 /*
@@ -2434,7 +2621,7 @@ void trace_softirqs_off(unsigned long ip)
 {
        struct task_struct *curr = current;
 
-       if (unlikely(!debug_locks))
+       if (unlikely(!debug_locks || current->lockdep_recursion))
                return;
 
        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
@@ -2447,10 +2634,10 @@ void trace_softirqs_off(unsigned long ip)
                curr->softirqs_enabled = 0;
                curr->softirq_disable_ip = ip;
                curr->softirq_disable_event = ++curr->irq_events;
-               debug_atomic_inc(&softirqs_off_events);
+               debug_atomic_inc(softirqs_off_events);
                DEBUG_LOCKS_WARN_ON(!softirq_count());
        } else
-               debug_atomic_inc(&redundant_softirqs_off);
+               debug_atomic_inc(redundant_softirqs_off);
 }
 
 static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
@@ -2630,7 +2817,7 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
        if (!graph_lock())
                return 0;
        /*
-        * Make sure we didnt race:
+        * Make sure we didn't race:
         */
        if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
                graph_unlock();
@@ -2655,7 +2842,7 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
                        return 0;
                break;
        case LOCK_USED:
-               debug_atomic_dec(&nr_unused_locks);
+               debug_atomic_dec(nr_unused_locks);
                break;
        default:
                if (!debug_locks_off_graph_unlock())
@@ -2685,7 +2872,11 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
 void lockdep_init_map(struct lockdep_map *lock, const char *name,
                      struct lock_class_key *key, int subclass)
 {
-       lock->class_cache = NULL;
+       int i;
+
+       for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
+               lock->class_cache[i] = NULL;
+
 #ifdef CONFIG_LOCK_STAT
        lock->cpu = raw_smp_processor_id();
 #endif
@@ -2717,6 +2908,8 @@ void lockdep_init_map(struct lockdep_map *lock, const char *name,
 }
 EXPORT_SYMBOL_GPL(lockdep_init_map);
 
+struct lock_class_key __lockdep_no_validate__;
+
 /*
  * This gets called for every mutex_lock*()/spin_lock*() operation.
  * We maintain the dependency maps and validate the locking attempt:
@@ -2743,25 +2936,20 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                return 0;
 
-       if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
-               debug_locks_off();
-               printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
-               printk("turning off the locking correctness validator.\n");
-               dump_stack();
-               return 0;
-       }
+       if (lock->key == &__lockdep_no_validate__)
+               check = 1;
 
-       if (!subclass)
-               class = lock->class_cache;
+       if (subclass < NR_LOCKDEP_CACHING_CLASSES)
+               class = lock->class_cache[subclass];
        /*
-        * Not cached yet or subclass?
+        * Not cached?
         */
        if (unlikely(!class)) {
                class = register_lock_class(lock, subclass, 0);
                if (!class)
                        return 0;
        }
-       debug_atomic_inc((atomic_t *)&class->ops);
+       atomic_inc((atomic_t *)&class->ops);
        if (very_verbose(class)) {
                printk("\nacquire class [%p] %s", class->key, class->name);
                if (class->name_version > 1)
@@ -2919,7 +3107,7 @@ static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
                return 1;
 
        if (hlock->references) {
-               struct lock_class *class = lock->class_cache;
+               struct lock_class *class = lock->class_cache[0];
 
                if (!class)
                        class = look_up_lock_class(lock, 0);
@@ -3238,7 +3426,7 @@ void lock_release(struct lockdep_map *lock, int nested,
        raw_local_irq_save(flags);
        check_flags(flags);
        current->lockdep_recursion = 1;
-       trace_lock_release(lock, nested, ip);
+       trace_lock_release(lock, ip);
        __lock_release(lock, nested, ip);
        current->lockdep_recursion = 0;
        raw_local_irq_restore(flags);
@@ -3251,7 +3439,7 @@ int lock_is_held(struct lockdep_map *lock)
        int ret = 0;
 
        if (unlikely(current->lockdep_recursion))
-               return ret;
+               return 1; /* avoid false negative lockdep_assert_held() */
 
        raw_local_irq_save(flags);
        check_flags(flags);
@@ -3391,7 +3579,7 @@ found_it:
                hlock->holdtime_stamp = now;
        }
 
-       trace_lock_acquired(lock, ip, waittime);
+       trace_lock_acquired(lock, ip);
 
        stats = get_lock_stats(hlock_class(hlock));
        if (waittime) {
@@ -3560,7 +3748,12 @@ void lockdep_reset_lock(struct lockdep_map *lock)
                if (list_empty(head))
                        continue;
                list_for_each_entry_safe(class, next, head, hash_entry) {
-                       if (unlikely(class == lock->class_cache)) {
+                       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())
                                        WARN_ON(1);
                                goto out_restore;
@@ -3776,7 +3969,7 @@ EXPORT_SYMBOL_GPL(debug_show_all_locks);
  * Careful: only use this function if you are sure that
  * the task cannot run in parallel!
  */
-void __debug_show_held_locks(struct task_struct *task)
+void debug_show_held_locks(struct task_struct *task)
 {
        if (unlikely(!debug_locks)) {
                printk("INFO: lockdep is turned off.\n");
@@ -3784,12 +3977,6 @@ void __debug_show_held_locks(struct task_struct *task)
        }
        lockdep_print_held_locks(task);
 }
-EXPORT_SYMBOL_GPL(__debug_show_held_locks);
-
-void debug_show_held_locks(struct task_struct *task)
-{
-               __debug_show_held_locks(task);
-}
 EXPORT_SYMBOL_GPL(debug_show_held_locks);
 
 void lockdep_sys_exit(void)
@@ -3812,8 +3999,11 @@ void lockdep_rcu_dereference(const char *file, const int line)
 {
        struct task_struct *curr = current;
 
+#ifndef CONFIG_PROVE_RCU_REPEATEDLY
        if (!debug_locks_off())
                return;
+#endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
+       /* Note: the following can be executed concurrently, so be careful. */
        printk("\n===================================================\n");
        printk(  "[ INFO: suspicious rcu_dereference_check() usage. ]\n");
        printk(  "---------------------------------------------------\n");