2 files changed, 189 insertions, 9 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 8bbeef996c76..93dc70d18cdf 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -897,6 +897,79 @@ static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
         return 1;
 }
 
+static struct circular_queue  lock_cq;
+static int __search_shortest_path(struct lock_list *source_entry,
+                                struct lock_class *target,
+                                struct lock_list **target_entry,
+                                int forward)
+{
+        struct lock_list *entry;
+        struct circular_queue *cq = &lock_cq;
+        int ret = 1;
+
+        __cq_init(cq);
+
+        mark_lock_accessed(source_entry, NULL);
+        if (source_entry->class == target) {
+                *target_entry = source_entry;
+                ret = 0;
+                goto exit;
+        }
+
+        __cq_enqueue(cq, (unsigned long)source_entry);
+
+        while (!__cq_empty(cq)) {
+                struct lock_list *lock;
+                struct list_head *head;
+
+                __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)) {
+                                mark_lock_accessed(entry, lock);
+                                if (entry->class == target) {
+                                        *target_entry = entry;
+                                        ret = 0;
+                                        goto exit;
+                                }
+
+                                if (__cq_enqueue(cq, (unsigned long)entry)) {
+                                        ret = -1;
+                                        goto exit;
+                                }
+                        }
+                }
+        }
+exit:
+        return ret;
+}
+
+static inline int __search_forward_shortest_path(struct lock_list *src_entry,
+                                struct lock_class *target,
+                                struct lock_list **target_entry)
+{
+        return __search_shortest_path(src_entry, target, target_entry, 1);
+
+}
+
+static inline int __search_backward_shortest_path(struct lock_list *src_entry,
+                                struct lock_class *target,
+                                struct lock_list **target_entry)
+{
+        return __search_shortest_path(src_entry, target, target_entry, 0);
+
+}
+
 /*
  * Recursive, forwards-direction lock-dependency checking, used for
  * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
@@ -934,7 +1007,7 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth)
 {
         struct task_struct *curr = current;
 
-        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
+        if (debug_locks_silent)
                 return 0;
 
         printk("\n=======================================================\n");
@@ -954,19 +1027,41 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth)
         return 0;
 }
 
-static noinline int print_circular_bug_tail(void)
+static noinline int print_circular_bug(void)
 {
         struct task_struct *curr = current;
         struct lock_list this;
+        struct lock_list *target;
+        struct lock_list *parent;
+        int result;
+        unsigned long 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))
                 return 0;
 
-        print_circular_bug_entry(&this, 0);
+        result = __search_forward_shortest_path(&this,
+                                                hlock_class(check_target),
+                                                &target);
+        if (result) {
+                printk("\n%s:search shortest path failed:%d\n", __func__,
+                        result);
+                return 0;
+        }
+
+        depth = get_lock_depth(target);
+
+        print_circular_bug_header(target, depth);
+
+        parent = get_lock_parent(target);
+
+        while (parent) {
+                print_circular_bug_entry(parent, --depth);
+                parent = get_lock_parent(parent);
+        }
 
         printk("\nother info that might help us debug this:\n\n");
         lockdep_print_held_locks(curr);
@@ -1072,14 +1167,15 @@ check_noncircular(struct lock_class *source, unsigned int depth)
          */
         list_for_each_entry(entry, &source->locks_after, entry) {
                 if (entry->class == hlock_class(check_target))
-                        return print_circular_bug_header(entry, depth+1);
+                        return 2;
                 debug_atomic_inc(&nr_cyclic_checks);
-                if (!check_noncircular(entry->class, depth+1))
-                        return print_circular_bug_entry(entry, depth+1);
+                if (check_noncircular(entry->class, depth+1) == 2)
+                        return 2;
         }
         return 1;
 }
 
+
 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
 /*
  * Forwards and backwards subgraph searching, for the purposes of
@@ -1484,8 +1580,9 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
          */
         check_source = next;
         check_target = prev;
-        if (!(check_noncircular(hlock_class(next), 0)))
-                return print_circular_bug_tail();
+        if (check_noncircular(hlock_class(next), 0) == 2)
+                return print_circular_bug();
+
 
         if (!check_prev_add_irq(curr, prev, next))
                 return 0;
diff --git a/kernel/lockdep_internals.h b/kernel/lockdep_internals.h
index 699a2ac3a0d7..6f48d37d5be2 100644
--- a/kernel/lockdep_internals.h
+++ b/kernel/lockdep_internals.h
@@ -136,3 +136,86 @@ extern atomic_t nr_find_usage_backwards_recursions;
 # define debug_atomic_dec(ptr)          do { } while (0)
 # define debug_atomic_read(ptr)         0
 #endif
+
+/* 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.
+ * */
+#define  MAX_CIRCULAR_QUE_SIZE      4096UL
+struct circular_queue{
+        unsigned long element[MAX_CIRCULAR_QUE_SIZE];
+        unsigned int  front, rear;
+};
+
+#define LOCK_ACCESSED           1UL
+#define LOCK_ACCESSED_MASK      (~LOCK_ACCESSED)
+
+static inline void __cq_init(struct circular_queue *cq)
+{
+        cq->front = cq->rear = 0;
+}
+
+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)%MAX_CIRCULAR_QUE_SIZE)  == 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)%MAX_CIRCULAR_QUE_SIZE;
+        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)%MAX_CIRCULAR_QUE_SIZE;
+        return 0;
+}
+
+static inline int __cq_get_elem_count(struct circular_queue *cq)
+{
+        return (cq->rear - cq->front)%MAX_CIRCULAR_QUE_SIZE;
+}
+
+static inline void mark_lock_accessed(struct lock_list *lock,
+                                        struct lock_list *parent)
+{
+        lock->parent = (void *) parent + LOCK_ACCESSED;
+}
+
+static inline unsigned long lock_accessed(struct lock_list *lock)
+{
+        return (unsigned long)lock->parent & LOCK_ACCESSED;
+}
+
+static inline struct lock_list *get_lock_parent(struct lock_list *child)
+{
+        return (struct lock_list *)
+                ((unsigned long)child->parent & LOCK_ACCESSED_MASK);
+}
+
+static inline unsigned long get_lock_depth(struct lock_list *child)
+{
+        unsigned long depth = 0;
+        struct lock_list *parent;
+
+        while ((parent = get_lock_parent(child))) {
+                child = parent;
+                depth++;
+        }
+        return depth;
+}