perf top: Don't stop if no kernel symtab is found
[linux-2.6.git] / kernel / lockdep.c
index 8bbeef9..63437d0 100644 (file)
 #include <linux/hash.h>
 #include <linux/ftrace.h>
 #include <linux/stringify.h>
+#include <linux/bitops.h>
+#include <linux/gfp.h>
 
 #include <asm/sections.h>
 
 #include "lockdep_internals.h"
 
 #define CREATE_TRACE_POINTS
-#include <trace/events/lockdep.h>
+#include <trace/events/lock.h>
 
 #ifdef CONFIG_PROVE_LOCKING
 int prove_locking = 1;
@@ -72,11 +74,11 @@ module_param(lock_stat, int, 0644);
  * to use a raw spinlock - we really dont want the spinlock
  * code to recurse back into the lockdep code...
  */
-static raw_spinlock_t lockdep_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
+static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
 
 static int graph_lock(void)
 {
-       __raw_spin_lock(&lockdep_lock);
+       arch_spin_lock(&lockdep_lock);
        /*
         * Make sure that if another CPU detected a bug while
         * walking the graph we dont change it (while the other
@@ -84,7 +86,7 @@ static int graph_lock(void)
         * dropped already)
         */
        if (!debug_locks) {
-               __raw_spin_unlock(&lockdep_lock);
+               arch_spin_unlock(&lockdep_lock);
                return 0;
        }
        /* prevent any recursions within lockdep from causing deadlocks */
@@ -94,11 +96,11 @@ static int graph_lock(void)
 
 static inline int graph_unlock(void)
 {
-       if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
+       if (debug_locks && !arch_spin_is_locked(&lockdep_lock))
                return DEBUG_LOCKS_WARN_ON(1);
 
        current->lockdep_recursion--;
-       __raw_spin_unlock(&lockdep_lock);
+       arch_spin_unlock(&lockdep_lock);
        return 0;
 }
 
@@ -110,7 +112,7 @@ static inline int debug_locks_off_graph_unlock(void)
 {
        int ret = debug_locks_off();
 
-       __raw_spin_unlock(&lockdep_lock);
+       arch_spin_unlock(&lockdep_lock);
 
        return ret;
 }
@@ -139,7 +141,13 @@ static inline struct lock_class *hlock_class(struct held_lock *hlock)
 }
 
 #ifdef CONFIG_LOCK_STAT
-static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], lock_stats);
+static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS],
+                     cpu_lock_stats);
+
+static inline u64 lockstat_clock(void)
+{
+       return local_clock();
+}
 
 static int lock_point(unsigned long points[], unsigned long ip)
 {
@@ -157,12 +165,12 @@ static int lock_point(unsigned long points[], unsigned long ip)
        return i;
 }
 
-static void lock_time_inc(struct lock_time *lt, s64 time)
+static void lock_time_inc(struct lock_time *lt, u64 time)
 {
        if (time > lt->max)
                lt->max = time;
 
-       if (time < lt->min || !lt->min)
+       if (time < lt->min || !lt->nr)
                lt->min = time;
 
        lt->total += time;
@@ -171,8 +179,15 @@ static void lock_time_inc(struct lock_time *lt, s64 time)
 
 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
 {
-       dst->min += src->min;
-       dst->max += src->max;
+       if (!src->nr)
+               return;
+
+       if (src->max > dst->max)
+               dst->max = src->max;
+
+       if (src->min < dst->min || !dst->nr)
+               dst->min = src->min;
+
        dst->total += src->total;
        dst->nr += src->nr;
 }
@@ -185,7 +200,7 @@ struct lock_class_stats lock_stats(struct lock_class *class)
        memset(&stats, 0, sizeof(struct lock_class_stats));
        for_each_possible_cpu(cpu) {
                struct lock_class_stats *pcs =
-                       &per_cpu(lock_stats, cpu)[class - lock_classes];
+                       &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
 
                for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
                        stats.contention_point[i] += pcs->contention_point[i];
@@ -212,7 +227,7 @@ void clear_lock_stats(struct lock_class *class)
 
        for_each_possible_cpu(cpu) {
                struct lock_class_stats *cpu_stats =
-                       &per_cpu(lock_stats, cpu)[class - lock_classes];
+                       &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
 
                memset(cpu_stats, 0, sizeof(struct lock_class_stats));
        }
@@ -222,23 +237,23 @@ void clear_lock_stats(struct lock_class *class)
 
 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
 {
-       return &get_cpu_var(lock_stats)[class - lock_classes];
+       return &get_cpu_var(cpu_lock_stats)[class - lock_classes];
 }
 
 static void put_lock_stats(struct lock_class_stats *stats)
 {
-       put_cpu_var(lock_stats);
+       put_cpu_var(cpu_lock_stats);
 }
 
 static void lock_release_holdtime(struct held_lock *hlock)
 {
        struct lock_class_stats *stats;
-       s64 holdtime;
+       u64 holdtime;
 
        if (!lock_stat)
                return;
 
-       holdtime = sched_clock() - hlock->holdtime_stamp;
+       holdtime = lockstat_clock() - hlock->holdtime_stamp;
 
        stats = get_lock_stats(hlock_class(hlock));
        if (hlock->read)
@@ -366,11 +381,22 @@ static int save_trace(struct stack_trace *trace)
 
        save_stack_trace(trace);
 
+       /*
+        * Some daft arches put -1 at the end to indicate its a full trace.
+        *
+        * <rant> this is buggy anyway, since it takes a whole extra entry so a
+        * complete trace that maxes out the entries provided will be reported
+        * as incomplete, friggin useless </rant>
+        */
+       if (trace->nr_entries != 0 &&
+           trace->entries[trace->nr_entries-1] == ULONG_MAX)
+               trace->nr_entries--;
+
        trace->max_entries = trace->nr_entries;
 
        nr_stack_trace_entries += trace->nr_entries;
 
-       if (nr_stack_trace_entries == MAX_STACK_TRACE_ENTRIES) {
+       if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
                if (!debug_locks_off_graph_unlock())
                        return 0;
 
@@ -388,20 +414,6 @@ unsigned int nr_hardirq_chains;
 unsigned int nr_softirq_chains;
 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
 /*
@@ -419,23 +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_cyclic_check_recursions;
-atomic_t nr_find_usage_forwards_checks;
-atomic_t nr_find_usage_forwards_recursions;
-atomic_t nr_find_usage_backwards_checks;
-atomic_t nr_find_usage_backwards_recursions;
+DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
 #endif
 
 /*
@@ -494,6 +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];
@@ -551,58 +559,6 @@ static void lockdep_print_held_locks(struct task_struct *curr)
        }
 }
 
-static void print_lock_class_header(struct lock_class *class, int depth)
-{
-       int bit;
-
-       printk("%*s->", depth, "");
-       print_lock_name(class);
-       printk(" ops: %lu", class->ops);
-       printk(" {\n");
-
-       for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
-               if (class->usage_mask & (1 << bit)) {
-                       int len = depth;
-
-                       len += printk("%*s   %s", depth, "", usage_str[bit]);
-                       len += printk(" at:\n");
-                       print_stack_trace(class->usage_traces + bit, len);
-               }
-       }
-       printk("%*s }\n", depth, "");
-
-       printk("%*s ... key      at: ",depth,"");
-       print_ip_sym((unsigned long)class->key);
-}
-
-/*
- * printk all lock dependencies starting at <entry>:
- */
-static void __used
-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;
-
-       print_lock_class_header(class, depth);
-
-       list_for_each_entry(entry, &class->locks_after, entry) {
-               if (DEBUG_LOCKS_WARN_ON(!entry->class))
-                       return;
-
-               print_lock_dependencies(entry->class, depth + 1);
-
-               printk("%*s ... acquired at:\n",depth,"");
-               print_stack_trace(&entry->trace, 2);
-               printk("\n");
-       }
-}
-
 static void print_kernel_version(void)
 {
        printk("%s %.*s\n", init_utsname()->release,
@@ -626,9 +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?
@@ -636,24 +589,19 @@ static int static_obj(void *obj)
        if ((addr >= start) && (addr < end))
                return 1;
 
-#ifdef CONFIG_SMP
+       if (arch_is_kernel_data(addr))
+               return 1;
+
        /*
-        * 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);
 }
 
 /*
@@ -703,6 +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:
@@ -799,7 +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;
@@ -838,7 +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;
@@ -869,7 +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;
        /*
@@ -880,11 +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
@@ -898,22 +857,203 @@ static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
 }
 
 /*
+ * For good efficiency of modular, we use power of 2
+ */
+#define MAX_CIRCULAR_QUEUE_SIZE                4096UL
+#define CQ_MASK                                (MAX_CIRCULAR_QUEUE_SIZE-1)
+
+/*
+ * The circular_queue and helpers is used to implement the
+ * breadth-first search(BFS)algorithem, by which we can build
+ * the shortest path from the next lock to be acquired to the
+ * previous held lock if there is a circular between them.
+ */
+struct circular_queue {
+       unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
+       unsigned int  front, rear;
+};
+
+static struct circular_queue lock_cq;
+
+unsigned int max_bfs_queue_depth;
+
+static unsigned int lockdep_dependency_gen_id;
+
+static inline void __cq_init(struct circular_queue *cq)
+{
+       cq->front = cq->rear = 0;
+       lockdep_dependency_gen_id++;
+}
+
+static inline int __cq_empty(struct circular_queue *cq)
+{
+       return (cq->front == cq->rear);
+}
+
+static inline int __cq_full(struct circular_queue *cq)
+{
+       return ((cq->rear + 1) & CQ_MASK) == cq->front;
+}
+
+static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
+{
+       if (__cq_full(cq))
+               return -1;
+
+       cq->element[cq->rear] = elem;
+       cq->rear = (cq->rear + 1) & CQ_MASK;
+       return 0;
+}
+
+static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
+{
+       if (__cq_empty(cq))
+               return -1;
+
+       *elem = cq->element[cq->front];
+       cq->front = (cq->front + 1) & CQ_MASK;
+       return 0;
+}
+
+static inline unsigned int  __cq_get_elem_count(struct circular_queue *cq)
+{
+       return (cq->rear - cq->front) & CQ_MASK;
+}
+
+static inline void mark_lock_accessed(struct lock_list *lock,
+                                       struct lock_list *parent)
+{
+       unsigned long nr;
+
+       nr = lock - list_entries;
+       WARN_ON(nr >= nr_list_entries);
+       lock->parent = parent;
+       lock->class->dep_gen_id = lockdep_dependency_gen_id;
+}
+
+static inline unsigned long lock_accessed(struct lock_list *lock)
+{
+       unsigned long nr;
+
+       nr = lock - list_entries;
+       WARN_ON(nr >= nr_list_entries);
+       return lock->class->dep_gen_id == lockdep_dependency_gen_id;
+}
+
+static inline struct lock_list *get_lock_parent(struct lock_list *child)
+{
+       return child->parent;
+}
+
+static inline int get_lock_depth(struct lock_list *child)
+{
+       int depth = 0;
+       struct lock_list *parent;
+
+       while ((parent = get_lock_parent(child))) {
+               child = parent;
+               depth++;
+       }
+       return depth;
+}
+
+static int __bfs(struct lock_list *source_entry,
+                void *data,
+                int (*match)(struct lock_list *entry, void *data),
+                struct lock_list **target_entry,
+                int forward)
+{
+       struct lock_list *entry;
+       struct list_head *head;
+       struct circular_queue *cq = &lock_cq;
+       int ret = 1;
+
+       if (match(source_entry, data)) {
+               *target_entry = source_entry;
+               ret = 0;
+               goto exit;
+       }
+
+       if (forward)
+               head = &source_entry->class->locks_after;
+       else
+               head = &source_entry->class->locks_before;
+
+       if (list_empty(head))
+               goto exit;
+
+       __cq_init(cq);
+       __cq_enqueue(cq, (unsigned long)source_entry);
+
+       while (!__cq_empty(cq)) {
+               struct lock_list *lock;
+
+               __cq_dequeue(cq, (unsigned long *)&lock);
+
+               if (!lock->class) {
+                       ret = -2;
+                       goto exit;
+               }
+
+               if (forward)
+                       head = &lock->class->locks_after;
+               else
+                       head = &lock->class->locks_before;
+
+               list_for_each_entry(entry, head, entry) {
+                       if (!lock_accessed(entry)) {
+                               unsigned int cq_depth;
+                               mark_lock_accessed(entry, lock);
+                               if (match(entry, data)) {
+                                       *target_entry = entry;
+                                       ret = 0;
+                                       goto exit;
+                               }
+
+                               if (__cq_enqueue(cq, (unsigned long)entry)) {
+                                       ret = -1;
+                                       goto exit;
+                               }
+                               cq_depth = __cq_get_elem_count(cq);
+                               if (max_bfs_queue_depth < cq_depth)
+                                       max_bfs_queue_depth = cq_depth;
+                       }
+               }
+       }
+exit:
+       return ret;
+}
+
+static inline int __bfs_forwards(struct lock_list *src_entry,
+                       void *data,
+                       int (*match)(struct lock_list *entry, void *data),
+                       struct lock_list **target_entry)
+{
+       return __bfs(src_entry, data, match, target_entry, 1);
+
+}
+
+static inline int __bfs_backwards(struct lock_list *src_entry,
+                       void *data,
+                       int (*match)(struct lock_list *entry, void *data),
+                       struct lock_list **target_entry)
+{
+       return __bfs(src_entry, data, match, target_entry, 0);
+
+}
+
+/*
  * Recursive, forwards-direction lock-dependency checking, used for
  * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
  * checking.
- *
- * (to keep the stackframe of the recursive functions small we
- *  use these global variables, and we also mark various helper
- *  functions as noinline.)
  */
-static struct held_lock *check_source, *check_target;
 
 /*
  * Print a dependency chain entry (this is only done when a deadlock
  * has been detected):
  */
 static noinline int
-print_circular_bug_entry(struct lock_list *target, unsigned int depth)
+print_circular_bug_entry(struct lock_list *target, int depth)
 {
        if (debug_locks_silent)
                return 0;
@@ -925,16 +1065,68 @@ print_circular_bug_entry(struct lock_list *target, unsigned 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:
  */
 static noinline int
-print_circular_bug_header(struct lock_list *entry, unsigned int depth)
+print_circular_bug_header(struct lock_list *entry, unsigned int depth,
+                       struct held_lock *check_src,
+                       struct held_lock *check_tgt)
 {
        struct task_struct *curr = current;
 
-       if (!debug_locks_off_graph_unlock() || debug_locks_silent)
+       if (debug_locks_silent)
                return 0;
 
        printk("\n=======================================================\n");
@@ -943,9 +1135,9 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth)
        printk(  "-------------------------------------------------------\n");
        printk("%s/%d is trying to acquire lock:\n",
                curr->comm, task_pid_nr(curr));
-       print_lock(check_source);
+       print_lock(check_src);
        printk("\nbut task is already holding lock:\n");
-       print_lock(check_target);
+       print_lock(check_tgt);
        printk("\nwhich lock already depends on the new lock.\n\n");
        printk("\nthe existing dependency chain (in reverse order) is:\n");
 
@@ -954,21 +1146,43 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth)
        return 0;
 }
 
-static noinline int print_circular_bug_tail(void)
+static inline int class_equal(struct lock_list *entry, void *data)
+{
+       return entry->class == data;
+}
+
+static noinline int print_circular_bug(struct lock_list *this,
+                               struct lock_list *target,
+                               struct held_lock *check_src,
+                               struct held_lock *check_tgt)
 {
        struct task_struct *curr = current;
-       struct lock_list this;
+       struct lock_list *parent;
+       struct lock_list *first_parent;
+       int depth;
 
-       if (debug_locks_silent)
+       if (!debug_locks_off_graph_unlock() || debug_locks_silent)
                return 0;
 
-       this.class = hlock_class(check_source);
-       if (!save_trace(&this.trace))
+       if (!save_trace(&this->trace))
                return 0;
 
-       print_circular_bug_entry(&this, 0);
+       depth = get_lock_depth(target);
+
+       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);
+               parent = get_lock_parent(parent);
+       }
 
        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");
@@ -977,74 +1191,70 @@ static noinline int print_circular_bug_tail(void)
        return 0;
 }
 
-#define RECURSION_LIMIT 40
-
-static int noinline print_infinite_recursion_bug(void)
+static noinline int print_bfs_bug(int ret)
 {
        if (!debug_locks_off_graph_unlock())
                return 0;
 
-       WARN_ON(1);
+       WARN(1, "lockdep bfs error:%d\n", ret);
 
        return 0;
 }
 
-unsigned long __lockdep_count_forward_deps(struct lock_class *class,
-                                          unsigned int depth)
+static int noop_count(struct lock_list *entry, void *data)
 {
-       struct lock_list *entry;
-       unsigned long ret = 1;
+       (*(unsigned long *)data)++;
+       return 0;
+}
 
-       if (lockdep_dependency_visit(class, depth))
-               return 0;
+unsigned long __lockdep_count_forward_deps(struct lock_list *this)
+{
+       unsigned long  count = 0;
+       struct lock_list *uninitialized_var(target_entry);
 
-       /*
-        * Recurse this class's dependency list:
-        */
-       list_for_each_entry(entry, &class->locks_after, entry)
-               ret += __lockdep_count_forward_deps(entry->class, depth + 1);
+       __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
 
-       return ret;
+       return count;
 }
-
 unsigned long lockdep_count_forward_deps(struct lock_class *class)
 {
        unsigned long ret, flags;
+       struct lock_list this;
+
+       this.parent = NULL;
+       this.class = class;
 
        local_irq_save(flags);
-       __raw_spin_lock(&lockdep_lock);
-       ret = __lockdep_count_forward_deps(class, 0);
-       __raw_spin_unlock(&lockdep_lock);
+       arch_spin_lock(&lockdep_lock);
+       ret = __lockdep_count_forward_deps(&this);
+       arch_spin_unlock(&lockdep_lock);
        local_irq_restore(flags);
 
        return ret;
 }
 
-unsigned long __lockdep_count_backward_deps(struct lock_class *class,
-                                           unsigned int depth)
+unsigned long __lockdep_count_backward_deps(struct lock_list *this)
 {
-       struct lock_list *entry;
-       unsigned long ret = 1;
+       unsigned long  count = 0;
+       struct lock_list *uninitialized_var(target_entry);
 
-       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);
+       __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
 
-       return ret;
+       return count;
 }
 
 unsigned long lockdep_count_backward_deps(struct lock_class *class)
 {
        unsigned long ret, flags;
+       struct lock_list this;
+
+       this.parent = NULL;
+       this.class = class;
 
        local_irq_save(flags);
-       __raw_spin_lock(&lockdep_lock);
-       ret = __lockdep_count_backward_deps(class, 0);
-       __raw_spin_unlock(&lockdep_lock);
+       arch_spin_lock(&lockdep_lock);
+       ret = __lockdep_count_backward_deps(&this);
+       arch_spin_unlock(&lockdep_lock);
        local_irq_restore(flags);
 
        return ret;
@@ -1055,29 +1265,16 @@ unsigned long lockdep_count_backward_deps(struct lock_class *class)
  * lead to <target>. Print an error and return 0 if it does.
  */
 static noinline int
-check_noncircular(struct lock_class *source, unsigned int depth)
+check_noncircular(struct lock_list *root, struct lock_class *target,
+               struct lock_list **target_entry)
 {
-       struct lock_list *entry;
+       int result;
 
-       if (lockdep_dependency_visit(source, depth))
-               return 1;
+       debug_atomic_inc(nr_cyclic_checks);
 
-       debug_atomic_inc(&nr_cyclic_check_recursions);
-       if (depth > max_recursion_depth)
-               max_recursion_depth = depth;
-       if (depth >= RECURSION_LIMIT)
-               return print_infinite_recursion_bug();
-       /*
-        * Check this lock's dependency list:
-        */
-       list_for_each_entry(entry, &source->locks_after, entry) {
-               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))
-                       return print_circular_bug_entry(entry, depth+1);
-       }
-       return 1;
+       result = __bfs_forwards(root, target, class_equal, target_entry);
+
+       return result;
 }
 
 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
@@ -1086,103 +1283,177 @@ check_noncircular(struct lock_class *source, unsigned int depth)
  * proving that two subgraphs can be connected by a new dependency
  * without creating any illegal irq-safe -> irq-unsafe lock dependency.
  */
-static enum lock_usage_bit find_usage_bit;
-static struct lock_class *forwards_match, *backwards_match;
+
+static inline int usage_match(struct lock_list *entry, void *bit)
+{
+       return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
+}
+
+
 
 /*
  * Find a node in the forwards-direction dependency sub-graph starting
- * at <source> that matches <find_usage_bit>.
+ * at @root->class that matches @bit.
  *
- * Return 2 if such a node exists in the subgraph, and put that node
- * into <forwards_match>.
+ * Return 0 if such a node exists in the subgraph, and put that node
+ * into *@target_entry.
  *
- * Return 1 otherwise and keep <forwards_match> unchanged.
- * Return 0 on error.
+ * Return 1 otherwise and keep *@target_entry unchanged.
+ * Return <0 on error.
  */
-static noinline int
-find_usage_forwards(struct lock_class *source, unsigned int depth)
+static int
+find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
+                       struct lock_list **target_entry)
 {
-       struct lock_list *entry;
-       int ret;
+       int result;
 
-       if (lockdep_dependency_visit(source, depth))
-               return 1;
+       debug_atomic_inc(nr_find_usage_forwards_checks);
 
-       if (depth > max_recursion_depth)
-               max_recursion_depth = depth;
-       if (depth >= RECURSION_LIMIT)
-               return print_infinite_recursion_bug();
+       result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
 
-       debug_atomic_inc(&nr_find_usage_forwards_checks);
-       if (source->usage_mask & (1 << find_usage_bit)) {
-               forwards_match = source;
-               return 2;
-       }
-
-       /*
-        * Check this lock's dependency list:
-        */
-       list_for_each_entry(entry, &source->locks_after, entry) {
-               debug_atomic_inc(&nr_find_usage_forwards_recursions);
-               ret = find_usage_forwards(entry->class, depth+1);
-               if (ret == 2 || ret == 0)
-                       return ret;
-       }
-       return 1;
+       return result;
 }
 
 /*
  * Find a node in the backwards-direction dependency sub-graph starting
- * at <source> that matches <find_usage_bit>.
+ * at @root->class that matches @bit.
  *
- * Return 2 if such a node exists in the subgraph, and put that node
- * into <backwards_match>.
+ * Return 0 if such a node exists in the subgraph, and put that node
+ * into *@target_entry.
  *
- * Return 1 otherwise and keep <backwards_match> unchanged.
- * Return 0 on error.
+ * Return 1 otherwise and keep *@target_entry unchanged.
+ * Return <0 on error.
  */
-static noinline int
-find_usage_backwards(struct lock_class *source, unsigned int depth)
+static int
+find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
+                       struct lock_list **target_entry)
 {
-       struct lock_list *entry;
-       int ret;
+       int result;
 
-       if (lockdep_dependency_visit(source, depth))
-               return 1;
+       debug_atomic_inc(nr_find_usage_backwards_checks);
 
-       if (!__raw_spin_is_locked(&lockdep_lock))
-               return DEBUG_LOCKS_WARN_ON(1);
+       result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
 
-       if (depth > max_recursion_depth)
-               max_recursion_depth = depth;
-       if (depth >= RECURSION_LIMIT)
-               return print_infinite_recursion_bug();
+       return result;
+}
 
-       debug_atomic_inc(&nr_find_usage_backwards_checks);
-       if (source->usage_mask & (1 << find_usage_bit)) {
-               backwards_match = source;
-               return 2;
-       }
+static void print_lock_class_header(struct lock_class *class, int depth)
+{
+       int bit;
 
-       if (!source && debug_locks_off_graph_unlock()) {
-               WARN_ON(1);
-               return 0;
+       printk("%*s->", depth, "");
+       print_lock_name(class);
+       printk(" ops: %lu", class->ops);
+       printk(" {\n");
+
+       for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
+               if (class->usage_mask & (1 << bit)) {
+                       int len = depth;
+
+                       len += printk("%*s   %s", depth, "", usage_str[bit]);
+                       len += printk(" at:\n");
+                       print_stack_trace(class->usage_traces + bit, len);
+               }
        }
+       printk("%*s }\n", depth, "");
+
+       printk("%*s ... key      at: ",depth,"");
+       print_ip_sym((unsigned long)class->key);
+}
+
+/*
+ * printk the shortest lock dependencies from @start to @end in reverse order:
+ */
+static void __used
+print_shortest_lock_dependencies(struct lock_list *leaf,
+                               struct lock_list *root)
+{
+       struct lock_list *entry = leaf;
+       int depth;
+
+       /*compute depth from generated tree by BFS*/
+       depth = get_lock_depth(leaf);
+
+       do {
+               print_lock_class_header(entry->class, depth);
+               printk("%*s ... acquired at:\n", depth, "");
+               print_stack_trace(&entry->trace, 2);
+               printk("\n");
+
+               if (depth == 0 && (entry != root)) {
+                       printk("lockdep:%s bad path found in chain graph\n", __func__);
+                       break;
+               }
+
+               entry = get_lock_parent(entry);
+               depth--;
+       } while (entry && (depth >= 0));
+
+       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;
 
        /*
-        * Check this lock's dependency list:
-        */
-       list_for_each_entry(entry, &source->locks_before, entry) {
-               debug_atomic_inc(&nr_find_usage_backwards_recursions);
-               ret = find_usage_backwards(entry->class, depth+1);
-               if (ret == 2 || ret == 0)
-                       return ret;
-       }
-       return 1;
+        * 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,
+                        struct lock_list *next_root,
+                        struct lock_list *backwards_entry,
+                        struct lock_list *forwards_entry,
                         struct held_lock *prev,
                         struct held_lock *next,
                         enum lock_usage_bit bit1,
@@ -1215,26 +1486,35 @@ print_bad_irq_dependency(struct task_struct *curr,
 
        printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
                irqclass);
-       print_lock_name(backwards_match);
+       print_lock_name(backwards_entry->class);
        printk("\n... which became %s-irq-safe at:\n", irqclass);
 
-       print_stack_trace(backwards_match->usage_traces + bit1, 1);
+       print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
 
        printk("\nto a %s-irq-unsafe lock:\n", irqclass);
-       print_lock_name(forwards_match);
+       print_lock_name(forwards_entry->class);
        printk("\n... which became %s-irq-unsafe at:\n", irqclass);
        printk("...");
 
-       print_stack_trace(forwards_match->usage_traces + bit2, 1);
+       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 %s-irq-safe lock's dependencies:\n", irqclass);
-       print_lock_dependencies(backwards_match, 0);
+       printk("\nthe dependencies between %s-irq-safe lock", irqclass);
+       printk(" and the holding lock:\n");
+       if (!save_trace(&prev_root->trace))
+               return 0;
+       print_shortest_lock_dependencies(backwards_entry, prev_root);
 
-       printk("\nthe %s-irq-unsafe lock's dependencies:\n", irqclass);
-       print_lock_dependencies(forwards_match, 0);
+       printk("\nthe dependencies between the lock to be acquired");
+       printk(" and %s-irq-unsafe lock:\n", irqclass);
+       if (!save_trace(&next_root->trace))
+               return 0;
+       print_shortest_lock_dependencies(forwards_entry, next_root);
 
        printk("\nstack backtrace:\n");
        dump_stack();
@@ -1248,19 +1528,30 @@ check_usage(struct task_struct *curr, struct held_lock *prev,
            enum lock_usage_bit bit_forwards, const char *irqclass)
 {
        int ret;
+       struct lock_list this, that;
+       struct lock_list *uninitialized_var(target_entry);
+       struct lock_list *uninitialized_var(target_entry1);
 
-       find_usage_bit = bit_backwards;
-       /* fills in <backwards_match> */
-       ret = find_usage_backwards(hlock_class(prev), 0);
-       if (!ret || ret == 1)
+       this.parent = NULL;
+
+       this.class = hlock_class(prev);
+       ret = find_usage_backwards(&this, bit_backwards, &target_entry);
+       if (ret < 0)
+               return print_bfs_bug(ret);
+       if (ret == 1)
                return ret;
 
-       find_usage_bit = bit_forwards;
-       ret = find_usage_forwards(hlock_class(next), 0);
-       if (!ret || ret == 1)
+       that.parent = NULL;
+       that.class = hlock_class(next);
+       ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
+       if (ret < 0)
+               return print_bfs_bug(ret);
+       if (ret == 1)
                return ret;
-       /* ret == 2 */
-       return print_bad_irq_dependency(curr, prev, next,
+
+       return print_bad_irq_dependency(curr, &this, &that,
+                       target_entry, target_entry1,
+                       prev, next,
                        bit_backwards, bit_forwards, irqclass);
 }
 
@@ -1374,6 +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)
@@ -1392,6 +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");
@@ -1468,10 +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
@@ -1482,10 +1804,13 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
         * We are using global variables to control the recursion, to
         * keep the stackframe size of the recursive functions low:
         */
-       check_source = next;
-       check_target = prev;
-       if (!(check_noncircular(hlock_class(next), 0)))
-               return print_circular_bug_tail();
+       this.class = hlock_class(next);
+       this.parent = NULL;
+       ret = check_noncircular(&this, hlock_class(prev), &target_entry);
+       if (unlikely(!ret))
+               return print_circular_bug(&this, target_entry, next, prev);
+       else if (unlikely(ret < 0))
+               return print_bfs_bug(ret);
 
        if (!check_prev_add_irq(curr, prev, next))
                return 0;
@@ -1516,20 +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;
 
@@ -1559,6 +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;
 
        /*
@@ -1584,7 +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,
@@ -1607,6 +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:
@@ -1642,7 +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;
@@ -1653,7 +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",
@@ -1702,15 +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;
@@ -1718,7 +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;
@@ -1827,6 +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)
@@ -1855,6 +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");
@@ -1884,10 +2229,15 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
  * print irq inversion bug:
  */
 static int
-print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
+print_irq_inversion_bug(struct task_struct *curr,
+                       struct lock_list *root, struct lock_list *other,
                        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;
 
@@ -1902,17 +2252,35 @@ print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
                printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
        else
                printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
-       print_lock_name(other);
+       print_lock_name(other->class);
        printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
 
        printk("\nother info that might help us debug this:\n");
-       lockdep_print_held_locks(curr);
 
-       printk("\nthe first lock's dependencies:\n");
-       print_lock_dependencies(hlock_class(this), 0);
+       /* 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 second lock's dependencies:\n");
-       print_lock_dependencies(other, 0);
+       printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
+       if (!save_trace(&root->trace))
+               return 0;
+       print_shortest_lock_dependencies(other, root);
 
        printk("\nstack backtrace:\n");
        dump_stack();
@@ -1929,14 +2297,19 @@ check_usage_forwards(struct task_struct *curr, struct held_lock *this,
                     enum lock_usage_bit bit, const char *irqclass)
 {
        int ret;
-
-       find_usage_bit = bit;
-       /* fills in <forwards_match> */
-       ret = find_usage_forwards(hlock_class(this), 0);
-       if (!ret || ret == 1)
+       struct lock_list root;
+       struct lock_list *uninitialized_var(target_entry);
+
+       root.parent = NULL;
+       root.class = hlock_class(this);
+       ret = find_usage_forwards(&root, bit, &target_entry);
+       if (ret < 0)
+               return print_bfs_bug(ret);
+       if (ret == 1)
                return ret;
 
-       return print_irq_inversion_bug(curr, forwards_match, this, 1, irqclass);
+       return print_irq_inversion_bug(curr, &root, target_entry,
+                                       this, 1, irqclass);
 }
 
 /*
@@ -1948,14 +2321,19 @@ check_usage_backwards(struct task_struct *curr, struct held_lock *this,
                      enum lock_usage_bit bit, const char *irqclass)
 {
        int ret;
-
-       find_usage_bit = bit;
-       /* fills in <backwards_match> */
-       ret = find_usage_backwards(hlock_class(this), 0);
-       if (!ret || ret == 1)
+       struct lock_list root;
+       struct lock_list *uninitialized_var(target_entry);
+
+       root.parent = NULL;
+       root.class = hlock_class(this);
+       ret = find_usage_backwards(&root, bit, &target_entry);
+       if (ret < 0)
+               return print_bfs_bug(ret);
+       if (ret == 1)
                return ret;
 
-       return print_irq_inversion_bug(curr, backwards_match, this, 0, irqclass);
+       return print_irq_inversion_bug(curr, &root, target_entry,
+                                       this, 0, irqclass);
 }
 
 void print_irqtrace_events(struct task_struct *curr)
@@ -2098,22 +2476,6 @@ 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)
@@ -2125,11 +2487,16 @@ void trace_hardirqs_on_caller(unsigned long 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: */
@@ -2156,7 +2523,7 @@ 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);
 }
 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 
@@ -2188,9 +2555,9 @@ 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);
 
@@ -2214,7 +2581,7 @@ void trace_softirqs_on(unsigned long ip)
                return;
 
        if (curr->softirqs_enabled) {
-               debug_atomic_inc(&redundant_softirqs_on);
+               debug_atomic_inc(redundant_softirqs_on);
                return;
        }
 
@@ -2224,7 +2591,7 @@ void trace_softirqs_on(unsigned long ip)
        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
@@ -2254,10 +2621,10 @@ 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)
@@ -2437,7 +2804,7 @@ 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();
@@ -2462,7 +2829,7 @@ 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())
@@ -2492,7 +2859,11 @@ 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
@@ -2524,19 +2895,23 @@ 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:
  */
 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
                          int trylock, int read, int check, int hardirqs_off,
-                         struct lockdep_map *nest_lock, unsigned long ip)
+                         struct lockdep_map *nest_lock, unsigned long ip,
+                         int references)
 {
        struct task_struct *curr = current;
        struct lock_class *class = NULL;
        struct held_lock *hlock;
        unsigned int depth, id;
        int chain_head = 0;
+       int class_idx;
        u64 chain_key;
 
        if (!prove_locking)
@@ -2548,25 +2923,20 @@ 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)
@@ -2584,10 +2954,24 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
        if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
                return 0;
 
+       class_idx = class - lock_classes + 1;
+
+       if (depth) {
+               hlock = curr->held_locks + depth - 1;
+               if (hlock->class_idx == class_idx && nest_lock) {
+                       if (hlock->references)
+                               hlock->references++;
+                       else
+                               hlock->references = 2;
+
+                       return 1;
+               }
+       }
+
        hlock = curr->held_locks + depth;
        if (DEBUG_LOCKS_WARN_ON(!class))
                return 0;
-       hlock->class_idx = class - lock_classes + 1;
+       hlock->class_idx = class_idx;
        hlock->acquire_ip = ip;
        hlock->instance = lock;
        hlock->nest_lock = nest_lock;
@@ -2595,9 +2979,10 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
        hlock->read = read;
        hlock->check = check;
        hlock->hardirqs_off = !!hardirqs_off;
+       hlock->references = references;
 #ifdef CONFIG_LOCK_STAT
        hlock->waittime_stamp = 0;
-       hlock->holdtime_stamp = sched_clock();
+       hlock->holdtime_stamp = lockstat_clock();
 #endif
 
        if (check == 2 && !mark_irqflags(curr, hlock))
@@ -2703,6 +3088,30 @@ static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
        return 1;
 }
 
+static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
+{
+       if (hlock->instance == lock)
+               return 1;
+
+       if (hlock->references) {
+               struct lock_class *class = lock->class_cache[0];
+
+               if (!class)
+                       class = look_up_lock_class(lock, 0);
+
+               if (DEBUG_LOCKS_WARN_ON(!class))
+                       return 0;
+
+               if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
+                       return 0;
+
+               if (hlock->class_idx == class - lock_classes + 1)
+                       return 1;
+       }
+
+       return 0;
+}
+
 static int
 __lock_set_class(struct lockdep_map *lock, const char *name,
                 struct lock_class_key *key, unsigned int subclass,
@@ -2726,7 +3135,7 @@ __lock_set_class(struct lockdep_map *lock, const char *name,
                 */
                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
                        break;
-               if (hlock->instance == lock)
+               if (match_held_lock(hlock, lock))
                        goto found_it;
                prev_hlock = hlock;
        }
@@ -2745,7 +3154,8 @@ found_it:
                if (!__lock_acquire(hlock->instance,
                        hlock_class(hlock)->subclass, hlock->trylock,
                                hlock->read, hlock->check, hlock->hardirqs_off,
-                               hlock->nest_lock, hlock->acquire_ip))
+                               hlock->nest_lock, hlock->acquire_ip,
+                               hlock->references))
                        return 0;
        }
 
@@ -2784,20 +3194,34 @@ lock_release_non_nested(struct task_struct *curr,
                 */
                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
                        break;
-               if (hlock->instance == lock)
+               if (match_held_lock(hlock, lock))
                        goto found_it;
                prev_hlock = hlock;
        }
        return print_unlock_inbalance_bug(curr, lock, ip);
 
 found_it:
-       lock_release_holdtime(hlock);
+       if (hlock->instance == lock)
+               lock_release_holdtime(hlock);
+
+       if (hlock->references) {
+               hlock->references--;
+               if (hlock->references) {
+                       /*
+                        * We had, and after removing one, still have
+                        * references, the current lock stack is still
+                        * valid. We're done!
+                        */
+                       return 1;
+               }
+       }
 
        /*
         * We have the right lock to unlock, 'hlock' points to it.
         * Now we remove it from the stack, and add back the other
         * entries (if any), recalculating the hash along the way:
         */
+
        curr->lockdep_depth = i;
        curr->curr_chain_key = hlock->prev_chain_key;
 
@@ -2806,7 +3230,8 @@ found_it:
                if (!__lock_acquire(hlock->instance,
                        hlock_class(hlock)->subclass, hlock->trylock,
                                hlock->read, hlock->check, hlock->hardirqs_off,
-                               hlock->nest_lock, hlock->acquire_ip))
+                               hlock->nest_lock, hlock->acquire_ip,
+                               hlock->references))
                        return 0;
        }
 
@@ -2836,7 +3261,7 @@ static int lock_release_nested(struct task_struct *curr,
        /*
         * Is the unlock non-nested:
         */
-       if (hlock->instance != lock)
+       if (hlock->instance != lock || hlock->references)
                return lock_release_non_nested(curr, lock, ip);
        curr->lockdep_depth--;
 
@@ -2881,6 +3306,21 @@ __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++) {
+               struct held_lock *hlock = curr->held_locks + i;
+
+               if (match_held_lock(hlock, lock))
+                       return 1;
+       }
+
+       return 0;
+}
+
 /*
  * Check whether we follow the irq-flags state precisely:
  */
@@ -2947,8 +3387,6 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 {
        unsigned long flags;
 
-       trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
-
        if (unlikely(current->lockdep_recursion))
                return;
 
@@ -2956,8 +3394,9 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
        check_flags(flags);
 
        current->lockdep_recursion = 1;
+       trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
        __lock_acquire(lock, subclass, trylock, read, check,
-                      irqs_disabled_flags(flags), nest_lock, ip);
+                      irqs_disabled_flags(flags), nest_lock, ip, 0);
        current->lockdep_recursion = 0;
        raw_local_irq_restore(flags);
 }
@@ -2968,20 +3407,39 @@ void lock_release(struct lockdep_map *lock, int nested,
 {
        unsigned long flags;
 
-       trace_lock_release(lock, nested, ip);
-
        if (unlikely(current->lockdep_recursion))
                return;
 
        raw_local_irq_save(flags);
        check_flags(flags);
        current->lockdep_recursion = 1;
+       trace_lock_release(lock, ip);
        __lock_release(lock, nested, ip);
        current->lockdep_recursion = 0;
        raw_local_irq_restore(flags);
 }
 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;
@@ -3041,7 +3499,7 @@ __lock_contended(struct lockdep_map *lock, unsigned long ip)
                 */
                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
                        break;
-               if (hlock->instance == lock)
+               if (match_held_lock(hlock, lock))
                        goto found_it;
                prev_hlock = hlock;
        }
@@ -3049,7 +3507,10 @@ __lock_contended(struct lockdep_map *lock, unsigned long ip)
        return;
 
 found_it:
-       hlock->waittime_stamp = sched_clock();
+       if (hlock->instance != lock)
+               return;
+
+       hlock->waittime_stamp = lockstat_clock();
 
        contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
        contending_point = lock_point(hlock_class(hlock)->contending_point,
@@ -3072,8 +3533,7 @@ __lock_acquired(struct lockdep_map *lock, unsigned long ip)
        struct held_lock *hlock, *prev_hlock;
        struct lock_class_stats *stats;
        unsigned int depth;
-       u64 now;
-       s64 waittime = 0;
+       u64 now, waittime = 0;
        int i, cpu;
 
        depth = curr->lockdep_depth;
@@ -3088,7 +3548,7 @@ __lock_acquired(struct lockdep_map *lock, unsigned long ip)
                 */
                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
                        break;
-               if (hlock->instance == lock)
+               if (match_held_lock(hlock, lock))
                        goto found_it;
                prev_hlock = hlock;
        }
@@ -3096,14 +3556,17 @@ __lock_acquired(struct lockdep_map *lock, unsigned long ip)
        return;
 
 found_it:
+       if (hlock->instance != lock)
+               return;
+
        cpu = smp_processor_id();
        if (hlock->waittime_stamp) {
-               now = sched_clock();
+               now = lockstat_clock();
                waittime = now - hlock->waittime_stamp;
                hlock->holdtime_stamp = now;
        }
 
-       trace_lock_acquired(lock, ip, waittime);
+       trace_lock_acquired(lock, ip);
 
        stats = get_lock_stats(hlock_class(hlock));
        if (waittime) {
@@ -3124,8 +3587,6 @@ void lock_contended(struct lockdep_map *lock, unsigned long ip)
 {
        unsigned long flags;
 
-       trace_lock_contended(lock, ip);
-
        if (unlikely(!lock_stat))
                return;
 
@@ -3135,6 +3596,7 @@ void lock_contended(struct lockdep_map *lock, unsigned long ip)
        raw_local_irq_save(flags);
        check_flags(flags);
        current->lockdep_recursion = 1;
+       trace_lock_contended(lock, ip);
        __lock_contended(lock, ip);
        current->lockdep_recursion = 0;
        raw_local_irq_restore(flags);
@@ -3273,7 +3735,12 @@ 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;
@@ -3326,7 +3793,12 @@ void __init lockdep_info(void)
                sizeof(struct list_head) * CLASSHASH_SIZE +
                sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
                sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
-               sizeof(struct list_head) * CHAINHASH_SIZE) / 1024);
+               sizeof(struct list_head) * CHAINHASH_SIZE
+#ifdef CONFIG_PROVE_LOCKING
+               + sizeof(struct circular_queue)
+#endif
+               ) / 1024
+               );
 
        printk(" per task-struct memory footprint: %lu bytes\n",
                sizeof(struct held_lock) * MAX_LOCK_DEPTH);
@@ -3484,7 +3956,7 @@ 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");
@@ -3492,12 +3964,6 @@ 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)
@@ -3515,3 +3981,25 @@ void lockdep_sys_exit(void)
                lockdep_print_held_locks(curr);
        }
 }
+
+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");
+       printk("%s:%d invoked rcu_dereference_check() without protection!\n",
+                       file, line);
+       printk("\nother info that might help us debug this:\n\n");
+       printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
+       lockdep_print_held_locks(curr);
+       printk("\nstack backtrace:\n");
+       dump_stack();
+}
+EXPORT_SYMBOL_GPL(lockdep_rcu_dereference);